Merge commit 'ae733129' into oauth2client v3.0.0android-p-preview-5android-p-preview-4

Initial commitcd  of oauth2client v3.0.0 with history.

Added:
- Android.bp
- MODULE_LICENSE_APACHE2
- NOTICE
- METADATA

Bug: b/80314772
Test: pip uninstall oauth2client and complied acloud.
Change-Id: Id17fea7b8b7bbe6e28a208a37cbfe509bc7a6af4

38 files changed, 9499 insertions, 0 deletions

diff --git a/oauth2client/Android.bp b/oauth2client/Android.bp
new file mode 100644
index 0000000..7818920
--- /dev/null
+++ b/oauth2client/Android.bp
@@ -0,0 +1,38 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+python_library {
+    name: "py-oauth2client",
+    host_supported: true,
+    srcs: [
+        "*.py",
+        "contrib/*.py",
+        "contrib/django_util/*.py",
+    ],
+    version: {
+        py2: {
+            enabled: true,
+        },
+        py3: {
+            enabled: true,
+        },
+    },
+    libs: [
+        "py-httplib2",
+        "py-pyasn1",
+        "py-pyasn1-modules",
+        "py-rsa",
+        "py-six",
+    ],
+    pkg_path: "oauth2client",
+}
diff --git a/oauth2client/__init__.py b/oauth2client/__init__.py
new file mode 100644
index 0000000..28384bb
--- /dev/null
+++ b/oauth2client/__init__.py
@@ -0,0 +1,23 @@
+# Copyright 2015 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Client library for using OAuth2, especially with Google APIs."""
+
+__version__ = '3.0.0'
+
+GOOGLE_AUTH_URI = 'https://accounts.google.com/o/oauth2/v2/auth'
+GOOGLE_DEVICE_URI = 'https://accounts.google.com/o/oauth2/device/code'
+GOOGLE_REVOKE_URI = 'https://accounts.google.com/o/oauth2/revoke'
+GOOGLE_TOKEN_URI = 'https://www.googleapis.com/oauth2/v4/token'
+GOOGLE_TOKEN_INFO_URI = 'https://www.googleapis.com/oauth2/v3/tokeninfo'
diff --git a/oauth2client/_helpers.py b/oauth2client/_helpers.py
new file mode 100644
index 0000000..cb959c5
--- /dev/null
+++ b/oauth2client/_helpers.py
@@ -0,0 +1,105 @@
+# Copyright 2015 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Helper functions for commonly used utilities."""
+
+import base64
+import json
+
+import six
+
+
+def _parse_pem_key(raw_key_input):
+    """Identify and extract PEM keys.
+
+    Determines whether the given key is in the format of PEM key, and extracts
+    the relevant part of the key if it is.
+
+    Args:
+        raw_key_input: The contents of a private key file (either PEM or
+                       PKCS12).
+
+    Returns:
+        string, The actual key if the contents are from a PEM file, or
+        else None.
+    """
+    offset = raw_key_input.find(b'-----BEGIN ')
+    if offset != -1:
+        return raw_key_input[offset:]
+
+
+def _json_encode(data):
+    return json.dumps(data, separators=(',', ':'))
+
+
+def _to_bytes(value, encoding='ascii'):
+    """Converts a string value to bytes, if necessary.
+
+    Unfortunately, ``six.b`` is insufficient for this task since in
+    Python2 it does not modify ``unicode`` objects.
+
+    Args:
+        value: The string/bytes value to be converted.
+        encoding: The encoding to use to convert unicode to bytes. Defaults
+                  to "ascii", which will not allow any characters from ordinals
+                  larger than 127. Other useful values are "latin-1", which
+                  which will only allows byte ordinals (up to 255) and "utf-8",
+                  which will encode any unicode that needs to be.
+
+    Returns:
+        The original value converted to bytes (if unicode) or as passed in
+        if it started out as bytes.
+
+    Raises:
+        ValueError if the value could not be converted to bytes.
+    """
+    result = (value.encode(encoding)
+              if isinstance(value, six.text_type) else value)
+    if isinstance(result, six.binary_type):
+        return result
+    else:
+        raise ValueError('{0!r} could not be converted to bytes'.format(value))
+
+
+def _from_bytes(value):
+    """Converts bytes to a string value, if necessary.
+
+    Args:
+        value: The string/bytes value to be converted.
+
+    Returns:
+        The original value converted to unicode (if bytes) or as passed in
+        if it started out as unicode.
+
+    Raises:
+        ValueError if the value could not be converted to unicode.
+    """
+    result = (value.decode('utf-8')
+              if isinstance(value, six.binary_type) else value)
+    if isinstance(result, six.text_type):
+        return result
+    else:
+        raise ValueError(
+            '{0!r} could not be converted to unicode'.format(value))
+
+
+def _urlsafe_b64encode(raw_bytes):
+    raw_bytes = _to_bytes(raw_bytes, encoding='utf-8')
+    return base64.urlsafe_b64encode(raw_bytes).rstrip(b'=')
+
+
+def _urlsafe_b64decode(b64string):
+    # Guard against unicode strings, which base64 can't handle.
+    b64string = _to_bytes(b64string)
+    padded = b64string + b'=' * (4 - len(b64string) % 4)
+    return base64.urlsafe_b64decode(padded)
diff --git a/oauth2client/_openssl_crypt.py b/oauth2client/_openssl_crypt.py
new file mode 100644
index 0000000..77fac74
--- /dev/null
+++ b/oauth2client/_openssl_crypt.py
@@ -0,0 +1,136 @@
+# Copyright 2015 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""OpenSSL Crypto-related routines for oauth2client."""
+
+from OpenSSL import crypto
+
+from oauth2client import _helpers
+
+
+class OpenSSLVerifier(object):
+    """Verifies the signature on a message."""
+
+    def __init__(self, pubkey):
+        """Constructor.
+
+        Args:
+            pubkey: OpenSSL.crypto.PKey, The public key to verify with.
+        """
+        self._pubkey = pubkey
+
+    def verify(self, message, signature):
+        """Verifies a message against a signature.
+
+        Args:
+        message: string or bytes, The message to verify. If string, will be
+                 encoded to bytes as utf-8.
+        signature: string or bytes, The signature on the message. If string,
+                   will be encoded to bytes as utf-8.
+
+        Returns:
+            True if message was signed by the private key associated with the
+            public key that this object was constructed with.
+        """
+        message = _helpers._to_bytes(message, encoding='utf-8')
+        signature = _helpers._to_bytes(signature, encoding='utf-8')
+        try:
+            crypto.verify(self._pubkey, signature, message, 'sha256')
+            return True
+        except crypto.Error:
+            return False
+
+    @staticmethod
+    def from_string(key_pem, is_x509_cert):
+        """Construct a Verified instance from a string.
+
+        Args:
+            key_pem: string, public key in PEM format.
+            is_x509_cert: bool, True if key_pem is an X509 cert, otherwise it
+                          is expected to be an RSA key in PEM format.
+
+        Returns:
+            Verifier instance.
+
+        Raises:
+            OpenSSL.crypto.Error: if the key_pem can't be parsed.
+        """
+        key_pem = _helpers._to_bytes(key_pem)
+        if is_x509_cert:
+            pubkey = crypto.load_certificate(crypto.FILETYPE_PEM, key_pem)
+        else:
+            pubkey = crypto.load_privatekey(crypto.FILETYPE_PEM, key_pem)
+        return OpenSSLVerifier(pubkey)
+
+
+class OpenSSLSigner(object):
+    """Signs messages with a private key."""
+
+    def __init__(self, pkey):
+        """Constructor.
+
+        Args:
+            pkey: OpenSSL.crypto.PKey (or equiv), The private key to sign with.
+        """
+        self._key = pkey
+
+    def sign(self, message):
+        """Signs a message.
+
+        Args:
+            message: bytes, Message to be signed.
+
+        Returns:
+            string, The signature of the message for the given key.
+        """
+        message = _helpers._to_bytes(message, encoding='utf-8')
+        return crypto.sign(self._key, message, 'sha256')
+
+    @staticmethod
+    def from_string(key, password=b'notasecret'):
+        """Construct a Signer instance from a string.
+
+        Args:
+            key: string, private key in PKCS12 or PEM format.
+            password: string, password for the private key file.
+
+        Returns:
+            Signer instance.
+
+        Raises:
+            OpenSSL.crypto.Error if the key can't be parsed.
+        """
+        key = _helpers._to_bytes(key)
+        parsed_pem_key = _helpers._parse_pem_key(key)
+        if parsed_pem_key:
+            pkey = crypto.load_privatekey(crypto.FILETYPE_PEM, parsed_pem_key)
+        else:
+            password = _helpers._to_bytes(password, encoding='utf-8')
+            pkey = crypto.load_pkcs12(key, password).get_privatekey()
+        return OpenSSLSigner(pkey)
+
+
+def pkcs12_key_as_pem(private_key_bytes, private_key_password):
+    """Convert the contents of a PKCS#12 key to PEM using pyOpenSSL.
+
+    Args:
+        private_key_bytes: Bytes. PKCS#12 key in DER format.
+        private_key_password: String. Password for PKCS#12 key.
+
+    Returns:
+        String. PEM contents of ``private_key_bytes``.
+    """
+    private_key_password = _helpers._to_bytes(private_key_password)
+    pkcs12 = crypto.load_pkcs12(private_key_bytes, private_key_password)
+    return crypto.dump_privatekey(crypto.FILETYPE_PEM,
+                                  pkcs12.get_privatekey())
diff --git a/oauth2client/_pure_python_crypt.py b/oauth2client/_pure_python_crypt.py
new file mode 100644
index 0000000..2c5d43a
--- /dev/null
+++ b/oauth2client/_pure_python_crypt.py
@@ -0,0 +1,184 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Pure Python crypto-related routines for oauth2client.
+
+Uses the ``rsa``, ``pyasn1`` and ``pyasn1_modules`` packages
+to parse PEM files storing PKCS#1 or PKCS#8 keys as well as
+certificates.
+"""
+
+from pyasn1.codec.der import decoder
+from pyasn1_modules import pem
+from pyasn1_modules.rfc2459 import Certificate
+from pyasn1_modules.rfc5208 import PrivateKeyInfo
+import rsa
+import six
+
+from oauth2client import _helpers
+
+
+_PKCS12_ERROR = r"""\
+PKCS12 format is not supported by the RSA library.
+Either install PyOpenSSL, or please convert .p12 format
+to .pem format:
+    $ cat key.p12 | \
+    >   openssl pkcs12 -nodes -nocerts -passin pass:notasecret | \
+    >   openssl rsa > key.pem
+"""
+
+_POW2 = (128, 64, 32, 16, 8, 4, 2, 1)
+_PKCS1_MARKER = ('-----BEGIN RSA PRIVATE KEY-----',
+                 '-----END RSA PRIVATE KEY-----')
+_PKCS8_MARKER = ('-----BEGIN PRIVATE KEY-----',
+                 '-----END PRIVATE KEY-----')
+_PKCS8_SPEC = PrivateKeyInfo()
+
+
+def _bit_list_to_bytes(bit_list):
+    """Converts an iterable of 1's and 0's to bytes.
+
+    Combines the list 8 at a time, treating each group of 8 bits
+    as a single byte.
+    """
+    num_bits = len(bit_list)
+    byte_vals = bytearray()
+    for start in six.moves.xrange(0, num_bits, 8):
+        curr_bits = bit_list[start:start + 8]
+        char_val = sum(val * digit
+                       for val, digit in zip(_POW2, curr_bits))
+        byte_vals.append(char_val)
+    return bytes(byte_vals)
+
+
+class RsaVerifier(object):
+    """Verifies the signature on a message.
+
+    Args:
+        pubkey: rsa.key.PublicKey (or equiv), The public key to verify with.
+    """
+
+    def __init__(self, pubkey):
+        self._pubkey = pubkey
+
+    def verify(self, message, signature):
+        """Verifies a message against a signature.
+
+        Args:
+            message: string or bytes, The message to verify. If string, will be
+                     encoded to bytes as utf-8.
+            signature: string or bytes, The signature on the message. If
+                       string, will be encoded to bytes as utf-8.
+
+        Returns:
+            True if message was signed by the private key associated with the
+            public key that this object was constructed with.
+        """
+        message = _helpers._to_bytes(message, encoding='utf-8')
+        try:
+            return rsa.pkcs1.verify(message, signature, self._pubkey)
+        except (ValueError, rsa.pkcs1.VerificationError):
+            return False
+
+    @classmethod
+    def from_string(cls, key_pem, is_x509_cert):
+        """Construct an RsaVerifier instance from a string.
+
+        Args:
+            key_pem: string, public key in PEM format.
+            is_x509_cert: bool, True if key_pem is an X509 cert, otherwise it
+                          is expected to be an RSA key in PEM format.
+
+        Returns:
+            RsaVerifier instance.
+
+        Raises:
+            ValueError: if the key_pem can't be parsed. In either case, error
+                        will begin with 'No PEM start marker'. If
+                        ``is_x509_cert`` is True, will fail to find the
+                        "-----BEGIN CERTIFICATE-----" error, otherwise fails
+                        to find "-----BEGIN RSA PUBLIC KEY-----".
+        """
+        key_pem = _helpers._to_bytes(key_pem)
+        if is_x509_cert:
+            der = rsa.pem.load_pem(key_pem, 'CERTIFICATE')
+            asn1_cert, remaining = decoder.decode(der, asn1Spec=Certificate())
+            if remaining != b'':
+                raise ValueError('Unused bytes', remaining)
+
+            cert_info = asn1_cert['tbsCertificate']['subjectPublicKeyInfo']
+            key_bytes = _bit_list_to_bytes(cert_info['subjectPublicKey'])
+            pubkey = rsa.PublicKey.load_pkcs1(key_bytes, 'DER')
+        else:
+            pubkey = rsa.PublicKey.load_pkcs1(key_pem, 'PEM')
+        return cls(pubkey)
+
+
+class RsaSigner(object):
+    """Signs messages with a private key.
+
+    Args:
+        pkey: rsa.key.PrivateKey (or equiv), The private key to sign with.
+    """
+
+    def __init__(self, pkey):
+        self._key = pkey
+
+    def sign(self, message):
+        """Signs a message.
+
+        Args:
+            message: bytes, Message to be signed.
+
+        Returns:
+            string, The signature of the message for the given key.
+        """
+        message = _helpers._to_bytes(message, encoding='utf-8')
+        return rsa.pkcs1.sign(message, self._key, 'SHA-256')
+
+    @classmethod
+    def from_string(cls, key, password='notasecret'):
+        """Construct an RsaSigner instance from a string.
+
+        Args:
+            key: string, private key in PEM format.
+            password: string, password for private key file. Unused for PEM
+                      files.
+
+        Returns:
+            RsaSigner instance.
+
+        Raises:
+            ValueError if the key cannot be parsed as PKCS#1 or PKCS#8 in
+            PEM format.
+        """
+        key = _helpers._from_bytes(key)  # pem expects str in Py3
+        marker_id, key_bytes = pem.readPemBlocksFromFile(
+            six.StringIO(key), _PKCS1_MARKER, _PKCS8_MARKER)
+
+        if marker_id == 0:
+            pkey = rsa.key.PrivateKey.load_pkcs1(key_bytes,
+                                                 format='DER')
+        elif marker_id == 1:
+            key_info, remaining = decoder.decode(
+                key_bytes, asn1Spec=_PKCS8_SPEC)
+            if remaining != b'':
+                raise ValueError('Unused bytes', remaining)
+            pkey_info = key_info.getComponentByName('privateKey')
+            pkey = rsa.key.PrivateKey.load_pkcs1(pkey_info.asOctets(),
+                                                 format='DER')
+        else:
+            raise ValueError('No key could be detected.')
+
+        return cls(pkey)
diff --git a/oauth2client/_pycrypto_crypt.py b/oauth2client/_pycrypto_crypt.py
new file mode 100644
index 0000000..fd2ce0c
--- /dev/null
+++ b/oauth2client/_pycrypto_crypt.py
@@ -0,0 +1,124 @@
+# Copyright 2015 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""pyCrypto Crypto-related routines for oauth2client."""
+
+from Crypto.Hash import SHA256
+from Crypto.PublicKey import RSA
+from Crypto.Signature import PKCS1_v1_5
+from Crypto.Util.asn1 import DerSequence
+
+from oauth2client import _helpers
+
+
+class PyCryptoVerifier(object):
+    """Verifies the signature on a message."""
+
+    def __init__(self, pubkey):
+        """Constructor.
+
+        Args:
+            pubkey: OpenSSL.crypto.PKey (or equiv), The public key to verify
+            with.
+        """
+        self._pubkey = pubkey
+
+    def verify(self, message, signature):
+        """Verifies a message against a signature.
+
+        Args:
+            message: string or bytes, The message to verify. If string, will be
+                     encoded to bytes as utf-8.
+            signature: string or bytes, The signature on the message.
+
+        Returns:
+            True if message was signed by the private key associated with the
+            public key that this object was constructed with.
+        """
+        message = _helpers._to_bytes(message, encoding='utf-8')
+        return PKCS1_v1_5.new(self._pubkey).verify(
+            SHA256.new(message), signature)
+
+    @staticmethod
+    def from_string(key_pem, is_x509_cert):
+        """Construct a Verified instance from a string.
+
+        Args:
+            key_pem: string, public key in PEM format.
+            is_x509_cert: bool, True if key_pem is an X509 cert, otherwise it
+                          is expected to be an RSA key in PEM format.
+
+        Returns:
+            Verifier instance.
+        """
+        if is_x509_cert:
+            key_pem = _helpers._to_bytes(key_pem)
+            pemLines = key_pem.replace(b' ', b'').split()
+            certDer = _helpers._urlsafe_b64decode(b''.join(pemLines[1:-1]))
+            certSeq = DerSequence()
+            certSeq.decode(certDer)
+            tbsSeq = DerSequence()
+            tbsSeq.decode(certSeq[0])
+            pubkey = RSA.importKey(tbsSeq[6])
+        else:
+            pubkey = RSA.importKey(key_pem)
+        return PyCryptoVerifier(pubkey)
+
+
+class PyCryptoSigner(object):
+    """Signs messages with a private key."""
+
+    def __init__(self, pkey):
+        """Constructor.
+
+        Args:
+            pkey, OpenSSL.crypto.PKey (or equiv), The private key to sign with.
+        """
+        self._key = pkey
+
+    def sign(self, message):
+        """Signs a message.
+
+        Args:
+            message: string, Message to be signed.
+
+        Returns:
+            string, The signature of the message for the given key.
+        """
+        message = _helpers._to_bytes(message, encoding='utf-8')
+        return PKCS1_v1_5.new(self._key).sign(SHA256.new(message))
+
+    @staticmethod
+    def from_string(key, password='notasecret'):
+        """Construct a Signer instance from a string.
+
+        Args:
+            key: string, private key in PEM format.
+            password: string, password for private key file. Unused for PEM
+                      files.
+
+        Returns:
+            Signer instance.
+
+        Raises:
+            NotImplementedError if the key isn't in PEM format.
+        """
+        parsed_pem_key = _helpers._parse_pem_key(_helpers._to_bytes(key))
+        if parsed_pem_key:
+            pkey = RSA.importKey(parsed_pem_key)
+        else:
+            raise NotImplementedError(
+                'No key in PEM format was detected. This implementation '
+                'can only use the PyCrypto library for keys in PEM '
+                'format.')
+        return PyCryptoSigner(pkey)
diff --git a/oauth2client/client.py b/oauth2client/client.py
new file mode 100644
index 0000000..8956443
--- /dev/null
+++ b/oauth2client/client.py
@@ -0,0 +1,2133 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""An OAuth 2.0 client.
+
+Tools for interacting with OAuth 2.0 protected resources.
+"""
+
+import collections
+import copy
+import datetime
+import json
+import logging
+import os
+import shutil
+import socket
+import sys
+import tempfile
+
+import six
+from six.moves import http_client
+from six.moves import urllib
+
+import oauth2client
+from oauth2client import _helpers
+from oauth2client import clientsecrets
+from oauth2client import transport
+from oauth2client import util
+
+
+__author__ = 'jcgregorio@google.com (Joe Gregorio)'
+
+HAS_OPENSSL = False
+HAS_CRYPTO = False
+try:
+    from oauth2client import crypt
+    HAS_CRYPTO = True
+    HAS_OPENSSL = crypt.OpenSSLVerifier is not None
+except ImportError:  # pragma: NO COVER
+    pass
+
+
+logger = logging.getLogger(__name__)
+
+# Expiry is stored in RFC3339 UTC format
+EXPIRY_FORMAT = '%Y-%m-%dT%H:%M:%SZ'
+
+# Which certs to use to validate id_tokens received.
+ID_TOKEN_VERIFICATION_CERTS = 'https://www.googleapis.com/oauth2/v1/certs'
+# This symbol previously had a typo in the name; we keep the old name
+# around for now, but will remove it in the future.
+ID_TOKEN_VERIFICATON_CERTS = ID_TOKEN_VERIFICATION_CERTS
+
+# Constant to use for the out of band OAuth 2.0 flow.
+OOB_CALLBACK_URN = 'urn:ietf:wg:oauth:2.0:oob'
+
+# The value representing user credentials.
+AUTHORIZED_USER = 'authorized_user'
+
+# The value representing service account credentials.
+SERVICE_ACCOUNT = 'service_account'
+
+# The environment variable pointing the file with local
+# Application Default Credentials.
+GOOGLE_APPLICATION_CREDENTIALS = 'GOOGLE_APPLICATION_CREDENTIALS'
+# The ~/.config subdirectory containing gcloud credentials. Intended
+# to be swapped out in tests.
+_CLOUDSDK_CONFIG_DIRECTORY = 'gcloud'
+# The environment variable name which can replace ~/.config if set.
+_CLOUDSDK_CONFIG_ENV_VAR = 'CLOUDSDK_CONFIG'
+
+# The error message we show users when we can't find the Application
+# Default Credentials.
+ADC_HELP_MSG = (
+    'The Application Default Credentials are not available. They are '
+    'available if running in Google Compute Engine. Otherwise, the '
+    'environment variable ' +
+    GOOGLE_APPLICATION_CREDENTIALS +
+    ' must be defined pointing to a file defining the credentials. See '
+    'https://developers.google.com/accounts/docs/'
+    'application-default-credentials for more information.')
+
+_WELL_KNOWN_CREDENTIALS_FILE = 'application_default_credentials.json'
+
+# The access token along with the seconds in which it expires.
+AccessTokenInfo = collections.namedtuple(
+    'AccessTokenInfo', ['access_token', 'expires_in'])
+
+DEFAULT_ENV_NAME = 'UNKNOWN'
+
+# If set to True _get_environment avoid GCE check (_detect_gce_environment)
+NO_GCE_CHECK = os.environ.setdefault('NO_GCE_CHECK', 'False')
+
+# Timeout in seconds to wait for the GCE metadata server when detecting the
+# GCE environment.
+try:
+    GCE_METADATA_TIMEOUT = int(
+        os.environ.setdefault('GCE_METADATA_TIMEOUT', '3'))
+except ValueError:  # pragma: NO COVER
+    GCE_METADATA_TIMEOUT = 3
+
+_SERVER_SOFTWARE = 'SERVER_SOFTWARE'
+_GCE_METADATA_HOST = '169.254.169.254'
+_METADATA_FLAVOR_HEADER = 'Metadata-Flavor'
+_DESIRED_METADATA_FLAVOR = 'Google'
+
+# Expose utcnow() at module level to allow for
+# easier testing (by replacing with a stub).
+_UTCNOW = datetime.datetime.utcnow
+
+# NOTE: These names were previously defined in this module but have been
+#       moved into `oauth2client.transport`,
+clean_headers = transport.clean_headers
+MemoryCache = transport.MemoryCache
+REFRESH_STATUS_CODES = transport.REFRESH_STATUS_CODES
+
+
+class SETTINGS(object):
+    """Settings namespace for globally defined values."""
+    env_name = None
+
+
+class Error(Exception):
+    """Base error for this module."""
+
+
+class FlowExchangeError(Error):
+    """Error trying to exchange an authorization grant for an access token."""
+
+
+class AccessTokenRefreshError(Error):
+    """Error trying to refresh an expired access token."""
+
+
+class HttpAccessTokenRefreshError(AccessTokenRefreshError):
+    """Error (with HTTP status) trying to refresh an expired access token."""
+    def __init__(self, *args, **kwargs):
+        super(HttpAccessTokenRefreshError, self).__init__(*args)
+        self.status = kwargs.get('status')
+
+
+class TokenRevokeError(Error):
+    """Error trying to revoke a token."""
+
+
+class UnknownClientSecretsFlowError(Error):
+    """The client secrets file called for an unknown type of OAuth 2.0 flow."""
+
+
+class AccessTokenCredentialsError(Error):
+    """Having only the access_token means no refresh is possible."""
+
+
+class VerifyJwtTokenError(Error):
+    """Could not retrieve certificates for validation."""
+
+
+class NonAsciiHeaderError(Error):
+    """Header names and values must be ASCII strings."""
+
+
+class ApplicationDefaultCredentialsError(Error):
+    """Error retrieving the Application Default Credentials."""
+
+
+class OAuth2DeviceCodeError(Error):
+    """Error trying to retrieve a device code."""
+
+
+class CryptoUnavailableError(Error, NotImplementedError):
+    """Raised when a crypto library is required, but none is available."""
+
+
+def _parse_expiry(expiry):
+    if expiry and isinstance(expiry, datetime.datetime):
+        return expiry.strftime(EXPIRY_FORMAT)
+    else:
+        return None
+
+
+class Credentials(object):
+    """Base class for all Credentials objects.
+
+    Subclasses must define an authorize() method that applies the credentials
+    to an HTTP transport.
+
+    Subclasses must also specify a classmethod named 'from_json' that takes a
+    JSON string as input and returns an instantiated Credentials object.
+    """
+
+    NON_SERIALIZED_MEMBERS = frozenset(['store'])
+
+    def authorize(self, http):
+        """Take an httplib2.Http instance (or equivalent) and authorizes it.
+
+        Authorizes it for the set of credentials, usually by replacing
+        http.request() with a method that adds in the appropriate headers and
+        then delegates to the original Http.request() method.
+
+        Args:
+            http: httplib2.Http, an http object to be used to make the refresh
+                  request.
+        """
+        raise NotImplementedError
+
+    def refresh(self, http):
+        """Forces a refresh of the access_token.
+
+        Args:
+            http: httplib2.Http, an http object to be used to make the refresh
+                  request.
+        """
+        raise NotImplementedError
+
+    def revoke(self, http):
+        """Revokes a refresh_token and makes the credentials void.
+
+        Args:
+            http: httplib2.Http, an http object to be used to make the revoke
+                  request.
+        """
+        raise NotImplementedError
+
+    def apply(self, headers):
+        """Add the authorization to the headers.
+
+        Args:
+            headers: dict, the headers to add the Authorization header to.
+        """
+        raise NotImplementedError
+
+    def _to_json(self, strip, to_serialize=None):
+        """Utility function that creates JSON repr. of a Credentials object.
+
+        Args:
+            strip: array, An array of names of members to exclude from the
+                   JSON.
+            to_serialize: dict, (Optional) The properties for this object
+                          that will be serialized. This allows callers to
+                          modify before serializing.
+
+        Returns:
+            string, a JSON representation of this instance, suitable to pass to
+            from_json().
+        """
+        curr_type = self.__class__
+        if to_serialize is None:
+            to_serialize = copy.copy(self.__dict__)
+        else:
+            # Assumes it is a str->str dictionary, so we don't deep copy.
+            to_serialize = copy.copy(to_serialize)
+        for member in strip:
+            if member in to_serialize:
+                del to_serialize[member]
+        to_serialize['token_expiry'] = _parse_expiry(
+            to_serialize.get('token_expiry'))
+        # Add in information we will need later to reconstitute this instance.
+        to_serialize['_class'] = curr_type.__name__
+        to_serialize['_module'] = curr_type.__module__
+        for key, val in to_serialize.items():
+            if isinstance(val, bytes):
+                to_serialize[key] = val.decode('utf-8')
+            if isinstance(val, set):
+                to_serialize[key] = list(val)
+        return json.dumps(to_serialize)
+
+    def to_json(self):
+        """Creating a JSON representation of an instance of Credentials.
+
+        Returns:
+            string, a JSON representation of this instance, suitable to pass to
+            from_json().
+        """
+        return self._to_json(self.NON_SERIALIZED_MEMBERS)
+
+    @classmethod
+    def new_from_json(cls, json_data):
+        """Utility class method to instantiate a Credentials subclass from JSON.
+
+        Expects the JSON string to have been produced by to_json().
+
+        Args:
+            json_data: string or bytes, JSON from to_json().
+
+        Returns:
+            An instance of the subclass of Credentials that was serialized with
+            to_json().
+        """
+        json_data_as_unicode = _helpers._from_bytes(json_data)
+        data = json.loads(json_data_as_unicode)
+        # Find and call the right classmethod from_json() to restore
+        # the object.
+        module_name = data['_module']
+        try:
+            module_obj = __import__(module_name)
+        except ImportError:
+            # In case there's an object from the old package structure,
+            # update it
+            module_name = module_name.replace('.googleapiclient', '')
+            module_obj = __import__(module_name)
+
+        module_obj = __import__(module_name,
+                                fromlist=module_name.split('.')[:-1])
+        kls = getattr(module_obj, data['_class'])
+        return kls.from_json(json_data_as_unicode)
+
+    @classmethod
+    def from_json(cls, unused_data):
+        """Instantiate a Credentials object from a JSON description of it.
+
+        The JSON should have been produced by calling .to_json() on the object.
+
+        Args:
+            unused_data: dict, A deserialized JSON object.
+
+        Returns:
+            An instance of a Credentials subclass.
+        """
+        return Credentials()
+
+
+class Flow(object):
+    """Base class for all Flow objects."""
+    pass
+
+
+class Storage(object):
+    """Base class for all Storage objects.
+
+    Store and retrieve a single credential. This class supports locking
+    such that multiple processes and threads can operate on a single
+    store.
+    """
+    def __init__(self, lock=None):
+        """Create a Storage instance.
+
+        Args:
+            lock: An optional threading.Lock-like object. Must implement at
+                  least acquire() and release(). Does not need to be
+                  re-entrant.
+        """
+        self._lock = lock
+
+    def acquire_lock(self):
+        """Acquires any lock necessary to access this Storage.
+
+        This lock is not reentrant.
+        """
+        if self._lock is not None:
+            self._lock.acquire()
+
+    def release_lock(self):
+        """Release the Storage lock.
+
+        Trying to release a lock that isn't held will result in a
+        RuntimeError in the case of a threading.Lock or multiprocessing.Lock.
+        """
+        if self._lock is not None:
+            self._lock.release()
+
+    def locked_get(self):
+        """Retrieve credential.
+
+        The Storage lock must be held when this is called.
+
+        Returns:
+            oauth2client.client.Credentials
+        """
+        raise NotImplementedError
+
+    def locked_put(self, credentials):
+        """Write a credential.
+
+        The Storage lock must be held when this is called.
+
+        Args:
+            credentials: Credentials, the credentials to store.
+        """
+        raise NotImplementedError
+
+    def locked_delete(self):
+        """Delete a credential.
+
+        The Storage lock must be held when this is called.
+        """
+        raise NotImplementedError
+
+    def get(self):
+        """Retrieve credential.
+
+        The Storage lock must *not* be held when this is called.
+
+        Returns:
+            oauth2client.client.Credentials
+        """
+        self.acquire_lock()
+        try:
+            return self.locked_get()
+        finally:
+            self.release_lock()
+
+    def put(self, credentials):
+        """Write a credential.
+
+        The Storage lock must be held when this is called.
+
+        Args:
+            credentials: Credentials, the credentials to store.
+        """
+        self.acquire_lock()
+        try:
+            self.locked_put(credentials)
+        finally:
+            self.release_lock()
+
+    def delete(self):
+        """Delete credential.
+
+        Frees any resources associated with storing the credential.
+        The Storage lock must *not* be held when this is called.
+
+        Returns:
+            None
+        """
+        self.acquire_lock()
+        try:
+            return self.locked_delete()
+        finally:
+            self.release_lock()
+
+
+def _update_query_params(uri, params):
+    """Updates a URI with new query parameters.
+
+    Args:
+        uri: string, A valid URI, with potential existing query parameters.
+        params: dict, A dictionary of query parameters.
+
+    Returns:
+        The same URI but with the new query parameters added.
+    """
+    parts = urllib.parse.urlparse(uri)
+    query_params = dict(urllib.parse.parse_qsl(parts.query))
+    query_params.update(params)
+    new_parts = parts._replace(query=urllib.parse.urlencode(query_params))
+    return urllib.parse.urlunparse(new_parts)
+
+
+class OAuth2Credentials(Credentials):
+    """Credentials object for OAuth 2.0.
+
+    Credentials can be applied to an httplib2.Http object using the authorize()
+    method, which then adds the OAuth 2.0 access token to each request.
+
+    OAuth2Credentials objects may be safely pickled and unpickled.
+    """
+
+    @util.positional(8)
+    def __init__(self, access_token, client_id, client_secret, refresh_token,
+                 token_expiry, token_uri, user_agent, revoke_uri=None,
+                 id_token=None, token_response=None, scopes=None,
+                 token_info_uri=None):
+        """Create an instance of OAuth2Credentials.
+
+        This constructor is not usually called by the user, instead
+        OAuth2Credentials objects are instantiated by the OAuth2WebServerFlow.
+
+        Args:
+            access_token: string, access token.
+            client_id: string, client identifier.
+            client_secret: string, client secret.
+            refresh_token: string, refresh token.
+            token_expiry: datetime, when the access_token expires.
+            token_uri: string, URI of token endpoint.
+            user_agent: string, The HTTP User-Agent to provide for this
+                        application.
+            revoke_uri: string, URI for revoke endpoint. Defaults to None; a
+                        token can't be revoked if this is None.
+            id_token: object, The identity of the resource owner.
+            token_response: dict, the decoded response to the token request.
+                            None if a token hasn't been requested yet. Stored
+                            because some providers (e.g. wordpress.com) include
+                            extra fields that clients may want.
+            scopes: list, authorized scopes for these credentials.
+          token_info_uri: string, the URI for the token info endpoint. Defaults
+                          to None; scopes can not be refreshed if this is None.
+
+        Notes:
+            store: callable, A callable that when passed a Credential
+                   will store the credential back to where it came from.
+                   This is needed to store the latest access_token if it
+                   has expired and been refreshed.
+        """
+        self.access_token = access_token
+        self.client_id = client_id
+        self.client_secret = client_secret
+        self.refresh_token = refresh_token
+        self.store = None
+        self.token_expiry = token_expiry
+        self.token_uri = token_uri
+        self.user_agent = user_agent
+        self.revoke_uri = revoke_uri
+        self.id_token = id_token
+        self.token_response = token_response
+        self.scopes = set(util.string_to_scopes(scopes or []))
+        self.token_info_uri = token_info_uri
+
+        # True if the credentials have been revoked or expired and can't be
+        # refreshed.
+        self.invalid = False
+
+    def authorize(self, http):
+        """Authorize an httplib2.Http instance with these credentials.
+
+        The modified http.request method will add authentication headers to
+        each request and will refresh access_tokens when a 401 is received on a
+        request. In addition the http.request method has a credentials
+        property, http.request.credentials, which is the Credentials object
+        that authorized it.
+
+        Args:
+            http: An instance of ``httplib2.Http`` or something that acts
+                  like it.
+
+        Returns:
+            A modified instance of http that was passed in.
+
+        Example::
+
+            h = httplib2.Http()
+            h = credentials.authorize(h)
+
+        You can't create a new OAuth subclass of httplib2.Authentication
+        because it never gets passed the absolute URI, which is needed for
+        signing. So instead we have to overload 'request' with a closure
+        that adds in the Authorization header and then calls the original
+        version of 'request()'.
+        """
+        transport.wrap_http_for_auth(self, http)
+        return http
+
+    def refresh(self, http):
+        """Forces a refresh of the access_token.
+
+        Args:
+            http: httplib2.Http, an http object to be used to make the refresh
+                  request.
+        """
+        self._refresh(http.request)
+
+    def revoke(self, http):
+        """Revokes a refresh_token and makes the credentials void.
+
+        Args:
+            http: httplib2.Http, an http object to be used to make the revoke
+                  request.
+        """
+        self._revoke(http.request)
+
+    def apply(self, headers):
+        """Add the authorization to the headers.
+
+        Args:
+            headers: dict, the headers to add the Authorization header to.
+        """
+        headers['Authorization'] = 'Bearer ' + self.access_token
+
+    def has_scopes(self, scopes):
+        """Verify that the credentials are authorized for the given scopes.
+
+        Returns True if the credentials authorized scopes contain all of the
+        scopes given.
+
+        Args:
+            scopes: list or string, the scopes to check.
+
+        Notes:
+            There are cases where the credentials are unaware of which scopes
+            are authorized. Notably, credentials obtained and stored before
+            this code was added will not have scopes, AccessTokenCredentials do
+            not have scopes. In both cases, you can use refresh_scopes() to
+            obtain the canonical set of scopes.
+        """
+        scopes = util.string_to_scopes(scopes)
+        return set(scopes).issubset(self.scopes)
+
+    def retrieve_scopes(self, http):
+        """Retrieves the canonical list of scopes for this access token.
+
+        Gets the scopes from the OAuth2 provider.
+
+        Args:
+            http: httplib2.Http, an http object to be used to make the refresh
+                  request.
+
+        Returns:
+            A set of strings containing the canonical list of scopes.
+        """
+        self._retrieve_scopes(http.request)
+        return self.scopes
+
+    @classmethod
+    def from_json(cls, json_data):
+        """Instantiate a Credentials object from a JSON description of it.
+
+        The JSON should have been produced by calling .to_json() on the object.
+
+        Args:
+            json_data: string or bytes, JSON to deserialize.
+
+        Returns:
+            An instance of a Credentials subclass.
+        """
+        data = json.loads(_helpers._from_bytes(json_data))
+        if (data.get('token_expiry') and
+                not isinstance(data['token_expiry'], datetime.datetime)):
+            try:
+                data['token_expiry'] = datetime.datetime.strptime(
+                    data['token_expiry'], EXPIRY_FORMAT)
+            except ValueError:
+                data['token_expiry'] = None
+        retval = cls(
+            data['access_token'],
+            data['client_id'],
+            data['client_secret'],
+            data['refresh_token'],
+            data['token_expiry'],
+            data['token_uri'],
+            data['user_agent'],
+            revoke_uri=data.get('revoke_uri', None),
+            id_token=data.get('id_token', None),
+            token_response=data.get('token_response', None),
+            scopes=data.get('scopes', None),
+            token_info_uri=data.get('token_info_uri', None))
+        retval.invalid = data['invalid']
+        return retval
+
+    @property
+    def access_token_expired(self):
+        """True if the credential is expired or invalid.
+
+        If the token_expiry isn't set, we assume the token doesn't expire.
+        """
+        if self.invalid:
+            return True
+
+        if not self.token_expiry:
+            return False
+
+        now = _UTCNOW()
+        if now >= self.token_expiry:
+            logger.info('access_token is expired. Now: %s, token_expiry: %s',
+                        now, self.token_expiry)
+            return True
+        return False
+
+    def get_access_token(self, http=None):
+        """Return the access token and its expiration information.
+
+        If the token does not exist, get one.
+        If the token expired, refresh it.
+        """
+        if not self.access_token or self.access_token_expired:
+            if not http:
+                http = transport.get_http_object()
+            self.refresh(http)
+        return AccessTokenInfo(access_token=self.access_token,
+                               expires_in=self._expires_in())
+
+    def set_store(self, store):
+        """Set the Storage for the credential.
+
+        Args:
+            store: Storage, an implementation of Storage object.
+                   This is needed to store the latest access_token if it
+                   has expired and been refreshed. This implementation uses
+                   locking to check for updates before updating the
+                   access_token.
+        """
+        self.store = store
+
+    def _expires_in(self):
+        """Return the number of seconds until this token expires.
+
+        If token_expiry is in the past, this method will return 0, meaning the
+        token has already expired.
+
+        If token_expiry is None, this method will return None. Note that
+        returning 0 in such a case would not be fair: the token may still be
+        valid; we just don't know anything about it.
+        """
+        if self.token_expiry:
+            now = _UTCNOW()
+            if self.token_expiry > now:
+                time_delta = self.token_expiry - now
+                # TODO(orestica): return time_delta.total_seconds()
+                # once dropping support for Python 2.6
+                return time_delta.days * 86400 + time_delta.seconds
+            else:
+                return 0
+
+    def _updateFromCredential(self, other):
+        """Update this Credential from another instance."""
+        self.__dict__.update(other.__getstate__())
+
+    def __getstate__(self):
+        """Trim the state down to something that can be pickled."""
+        d = copy.copy(self.__dict__)
+        del d['store']
+        return d
+
+    def __setstate__(self, state):
+        """Reconstitute the state of the object from being pickled."""
+        self.__dict__.update(state)
+        self.store = None
+
+    def _generate_refresh_request_body(self):
+        """Generate the body that will be used in the refresh request."""
+        body = urllib.parse.urlencode({
+            'grant_type': 'refresh_token',
+            'client_id': self.client_id,
+            'client_secret': self.client_secret,
+            'refresh_token': self.refresh_token,
+        })
+        return body
+
+    def _generate_refresh_request_headers(self):
+        """Generate the headers that will be used in the refresh request."""
+        headers = {
+            'content-type': 'application/x-www-form-urlencoded',
+        }
+
+        if self.user_agent is not None:
+            headers['user-agent'] = self.user_agent
+
+        return headers
+
+    def _refresh(self, http_request):
+        """Refreshes the access_token.
+
+        This method first checks by reading the Storage object if available.
+        If a refresh is still needed, it holds the Storage lock until the
+        refresh is completed.
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make the
+                          refresh request.
+
+        Raises:
+            HttpAccessTokenRefreshError: When the refresh fails.
+        """
+        if not self.store:
+            self._do_refresh_request(http_request)
+        else:
+            self.store.acquire_lock()
+            try:
+                new_cred = self.store.locked_get()
+
+                if (new_cred and not new_cred.invalid and
+                        new_cred.access_token != self.access_token and
+                        not new_cred.access_token_expired):
+                    logger.info('Updated access_token read from Storage')
+                    self._updateFromCredential(new_cred)
+                else:
+                    self._do_refresh_request(http_request)
+            finally:
+                self.store.release_lock()
+
+    def _do_refresh_request(self, http_request):
+        """Refresh the access_token using the refresh_token.
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make the
+                          refresh request.
+
+        Raises:
+            HttpAccessTokenRefreshError: When the refresh fails.
+        """
+        body = self._generate_refresh_request_body()
+        headers = self._generate_refresh_request_headers()
+
+        logger.info('Refreshing access_token')
+        resp, content = http_request(
+            self.token_uri, method='POST', body=body, headers=headers)
+        content = _helpers._from_bytes(content)
+        if resp.status == http_client.OK:
+            d = json.loads(content)
+            self.token_response = d
+            self.access_token = d['access_token']
+            self.refresh_token = d.get('refresh_token', self.refresh_token)
+            if 'expires_in' in d:
+                delta = datetime.timedelta(seconds=int(d['expires_in']))
+                self.token_expiry = delta + _UTCNOW()
+            else:
+                self.token_expiry = None
+            if 'id_token' in d:
+                self.id_token = _extract_id_token(d['id_token'])
+            else:
+                self.id_token = None
+            # On temporary refresh errors, the user does not actually have to
+            # re-authorize, so we unflag here.
+            self.invalid = False
+            if self.store:
+                self.store.locked_put(self)
+        else:
+            # An {'error':...} response body means the token is expired or
+            # revoked, so we flag the credentials as such.
+            logger.info('Failed to retrieve access token: %s', content)
+            error_msg = 'Invalid response {0}.'.format(resp['status'])
+            try:
+                d = json.loads(content)
+                if 'error' in d:
+                    error_msg = d['error']
+                    if 'error_description' in d:
+                        error_msg += ': ' + d['error_description']
+                    self.invalid = True
+                    if self.store is not None:
+                        self.store.locked_put(self)
+            except (TypeError, ValueError):
+                pass
+            raise HttpAccessTokenRefreshError(error_msg, status=resp.status)
+
+    def _revoke(self, http_request):
+        """Revokes this credential and deletes the stored copy (if it exists).
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make the
+                          revoke request.
+        """
+        self._do_revoke(http_request, self.refresh_token or self.access_token)
+
+    def _do_revoke(self, http_request, token):
+        """Revokes this credential and deletes the stored copy (if it exists).
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make the
+                          refresh request.
+            token: A string used as the token to be revoked. Can be either an
+                   access_token or refresh_token.
+
+        Raises:
+            TokenRevokeError: If the revoke request does not return with a
+                              200 OK.
+        """
+        logger.info('Revoking token')
+        query_params = {'token': token}
+        token_revoke_uri = _update_query_params(self.revoke_uri, query_params)
+        resp, content = http_request(token_revoke_uri)
+        if resp.status == http_client.OK:
+            self.invalid = True
+        else:
+            error_msg = 'Invalid response {0}.'.format(resp.status)
+            try:
+                d = json.loads(_helpers._from_bytes(content))
+                if 'error' in d:
+                    error_msg = d['error']
+            except (TypeError, ValueError):
+                pass
+            raise TokenRevokeError(error_msg)
+
+        if self.store:
+            self.store.delete()
+
+    def _retrieve_scopes(self, http_request):
+        """Retrieves the list of authorized scopes from the OAuth2 provider.
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make the
+                          revoke request.
+        """
+        self._do_retrieve_scopes(http_request, self.access_token)
+
+    def _do_retrieve_scopes(self, http_request, token):
+        """Retrieves the list of authorized scopes from the OAuth2 provider.
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make the
+                          refresh request.
+            token: A string used as the token to identify the credentials to
+                   the provider.
+
+        Raises:
+            Error: When refresh fails, indicating the the access token is
+                   invalid.
+        """
+        logger.info('Refreshing scopes')
+        query_params = {'access_token': token, 'fields': 'scope'}
+        token_info_uri = _update_query_params(self.token_info_uri,
+                                              query_params)
+        resp, content = http_request(token_info_uri)
+        content = _helpers._from_bytes(content)
+        if resp.status == http_client.OK:
+            d = json.loads(content)
+            self.scopes = set(util.string_to_scopes(d.get('scope', '')))
+        else:
+            error_msg = 'Invalid response {0}.'.format(resp.status)
+            try:
+                d = json.loads(content)
+                if 'error_description' in d:
+                    error_msg = d['error_description']
+            except (TypeError, ValueError):
+                pass
+            raise Error(error_msg)
+
+
+class AccessTokenCredentials(OAuth2Credentials):
+    """Credentials object for OAuth 2.0.
+
+    Credentials can be applied to an httplib2.Http object using the
+    authorize() method, which then signs each request from that object
+    with the OAuth 2.0 access token. This set of credentials is for the
+    use case where you have acquired an OAuth 2.0 access_token from
+    another place such as a JavaScript client or another web
+    application, and wish to use it from Python. Because only the
+    access_token is present it can not be refreshed and will in time
+    expire.
+
+    AccessTokenCredentials objects may be safely pickled and unpickled.
+
+    Usage::
+
+        credentials = AccessTokenCredentials('<an access token>',
+            'my-user-agent/1.0')
+        http = httplib2.Http()
+        http = credentials.authorize(http)
+
+    Raises:
+        AccessTokenCredentialsExpired: raised when the access_token expires or
+                                       is revoked.
+    """
+
+    def __init__(self, access_token, user_agent, revoke_uri=None):
+        """Create an instance of OAuth2Credentials
+
+        This is one of the few types if Credentials that you should contrust,
+        Credentials objects are usually instantiated by a Flow.
+
+        Args:
+            access_token: string, access token.
+            user_agent: string, The HTTP User-Agent to provide for this
+                        application.
+            revoke_uri: string, URI for revoke endpoint. Defaults to None; a
+                        token can't be revoked if this is None.
+        """
+        super(AccessTokenCredentials, self).__init__(
+            access_token,
+            None,
+            None,
+            None,
+            None,
+            None,
+            user_agent,
+            revoke_uri=revoke_uri)
+
+    @classmethod
+    def from_json(cls, json_data):
+        data = json.loads(_helpers._from_bytes(json_data))
+        retval = AccessTokenCredentials(
+            data['access_token'],
+            data['user_agent'])
+        return retval
+
+    def _refresh(self, http_request):
+        raise AccessTokenCredentialsError(
+            'The access_token is expired or invalid and can\'t be refreshed.')
+
+    def _revoke(self, http_request):
+        """Revokes the access_token and deletes the store if available.
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make the
+                          revoke request.
+        """
+        self._do_revoke(http_request, self.access_token)
+
+
+def _detect_gce_environment():
+    """Determine if the current environment is Compute Engine.
+
+    Returns:
+        Boolean indicating whether or not the current environment is Google
+        Compute Engine.
+    """
+    # NOTE: The explicit ``timeout`` is a workaround. The underlying
+    #       issue is that resolving an unknown host on some networks will take
+    #       20-30 seconds; making this timeout short fixes the issue, but
+    #       could lead to false negatives in the event that we are on GCE, but
+    #       the metadata resolution was particularly slow. The latter case is
+    #       "unlikely".
+    connection = six.moves.http_client.HTTPConnection(
+        _GCE_METADATA_HOST, timeout=GCE_METADATA_TIMEOUT)
+
+    try:
+        headers = {_METADATA_FLAVOR_HEADER: _DESIRED_METADATA_FLAVOR}
+        connection.request('GET', '/', headers=headers)
+        response = connection.getresponse()
+        if response.status == http_client.OK:
+            return (response.getheader(_METADATA_FLAVOR_HEADER) ==
+                    _DESIRED_METADATA_FLAVOR)
+    except socket.error:  # socket.timeout or socket.error(64, 'Host is down')
+        logger.info('Timeout attempting to reach GCE metadata service.')
+        return False
+    finally:
+        connection.close()
+
+
+def _in_gae_environment():
+    """Detects if the code is running in the App Engine environment.
+
+    Returns:
+        True if running in the GAE environment, False otherwise.
+    """
+    if SETTINGS.env_name is not None:
+        return SETTINGS.env_name in ('GAE_PRODUCTION', 'GAE_LOCAL')
+
+    try:
+        import google.appengine  # noqa: unused import
+    except ImportError:
+        pass
+    else:
+        server_software = os.environ.get(_SERVER_SOFTWARE, '')
+        if server_software.startswith('Google App Engine/'):
+            SETTINGS.env_name = 'GAE_PRODUCTION'
+            return True
+        elif server_software.startswith('Development/'):
+            SETTINGS.env_name = 'GAE_LOCAL'
+            return True
+
+    return False
+
+
+def _in_gce_environment():
+    """Detect if the code is running in the Compute Engine environment.
+
+    Returns:
+        True if running in the GCE environment, False otherwise.
+    """
+    if SETTINGS.env_name is not None:
+        return SETTINGS.env_name == 'GCE_PRODUCTION'
+
+    if NO_GCE_CHECK != 'True' and _detect_gce_environment():
+        SETTINGS.env_name = 'GCE_PRODUCTION'
+        return True
+    return False
+
+
+class GoogleCredentials(OAuth2Credentials):
+    """Application Default Credentials for use in calling Google APIs.
+
+    The Application Default Credentials are being constructed as a function of
+    the environment where the code is being run.
+    More details can be found on this page:
+    https://developers.google.com/accounts/docs/application-default-credentials
+
+    Here is an example of how to use the Application Default Credentials for a
+    service that requires authentication::
+
+        from googleapiclient.discovery import build
+        from oauth2client.client import GoogleCredentials
+
+        credentials = GoogleCredentials.get_application_default()
+        service = build('compute', 'v1', credentials=credentials)
+
+        PROJECT = 'bamboo-machine-422'
+        ZONE = 'us-central1-a'
+        request = service.instances().list(project=PROJECT, zone=ZONE)
+        response = request.execute()
+
+        print(response)
+    """
+
+    NON_SERIALIZED_MEMBERS = (
+        frozenset(['_private_key']) |
+        OAuth2Credentials.NON_SERIALIZED_MEMBERS)
+    """Members that aren't serialized when object is converted to JSON."""
+
+    def __init__(self, access_token, client_id, client_secret, refresh_token,
+                 token_expiry, token_uri, user_agent,
+                 revoke_uri=oauth2client.GOOGLE_REVOKE_URI):
+        """Create an instance of GoogleCredentials.
+
+        This constructor is not usually called by the user, instead
+        GoogleCredentials objects are instantiated by
+        GoogleCredentials.from_stream() or
+        GoogleCredentials.get_application_default().
+
+        Args:
+            access_token: string, access token.
+            client_id: string, client identifier.
+            client_secret: string, client secret.
+            refresh_token: string, refresh token.
+            token_expiry: datetime, when the access_token expires.
+            token_uri: string, URI of token endpoint.
+            user_agent: string, The HTTP User-Agent to provide for this
+                        application.
+            revoke_uri: string, URI for revoke endpoint. Defaults to
+                        oauth2client.GOOGLE_REVOKE_URI; a token can't be
+                        revoked if this is None.
+        """
+        super(GoogleCredentials, self).__init__(
+            access_token, client_id, client_secret, refresh_token,
+            token_expiry, token_uri, user_agent, revoke_uri=revoke_uri)
+
+    def create_scoped_required(self):
+        """Whether this Credentials object is scopeless.
+
+        create_scoped(scopes) method needs to be called in order to create
+        a Credentials object for API calls.
+        """
+        return False
+
+    def create_scoped(self, scopes):
+        """Create a Credentials object for the given scopes.
+
+        The Credentials type is preserved.
+        """
+        return self
+
+    @classmethod
+    def from_json(cls, json_data):
+        # TODO(issue 388): eliminate the circularity that is the reason for
+        #                  this non-top-level import.
+        from oauth2client import service_account
+        data = json.loads(_helpers._from_bytes(json_data))
+
+        # We handle service_account.ServiceAccountCredentials since it is a
+        # possible return type of GoogleCredentials.get_application_default()
+        if (data['_module'] == 'oauth2client.service_account' and
+                data['_class'] == 'ServiceAccountCredentials'):
+            return service_account.ServiceAccountCredentials.from_json(data)
+        elif (data['_module'] == 'oauth2client.service_account' and
+                data['_class'] == '_JWTAccessCredentials'):
+            return service_account._JWTAccessCredentials.from_json(data)
+
+        token_expiry = _parse_expiry(data.get('token_expiry'))
+        google_credentials = cls(
+            data['access_token'],
+            data['client_id'],
+            data['client_secret'],
+            data['refresh_token'],
+            token_expiry,
+            data['token_uri'],
+            data['user_agent'],
+            revoke_uri=data.get('revoke_uri', None))
+        google_credentials.invalid = data['invalid']
+        return google_credentials
+
+    @property
+    def serialization_data(self):
+        """Get the fields and values identifying the current credentials."""
+        return {
+            'type': 'authorized_user',
+            'client_id': self.client_id,
+            'client_secret': self.client_secret,
+            'refresh_token': self.refresh_token
+        }
+
+    @staticmethod
+    def _implicit_credentials_from_gae():
+        """Attempts to get implicit credentials in Google App Engine env.
+
+        If the current environment is not detected as App Engine, returns None,
+        indicating no Google App Engine credentials can be detected from the
+        current environment.
+
+        Returns:
+            None, if not in GAE, else an appengine.AppAssertionCredentials
+            object.
+        """
+        if not _in_gae_environment():
+            return None
+
+        return _get_application_default_credential_GAE()
+
+    @staticmethod
+    def _implicit_credentials_from_gce():
+        """Attempts to get implicit credentials in Google Compute Engine env.
+
+        If the current environment is not detected as Compute Engine, returns
+        None, indicating no Google Compute Engine credentials can be detected
+        from the current environment.
+
+        Returns:
+            None, if not in GCE, else a gce.AppAssertionCredentials object.
+        """
+        if not _in_gce_environment():
+            return None
+
+        return _get_application_default_credential_GCE()
+
+    @staticmethod
+    def _implicit_credentials_from_files():
+        """Attempts to get implicit credentials from local credential files.
+
+        First checks if the environment variable GOOGLE_APPLICATION_CREDENTIALS
+        is set with a filename and then falls back to a configuration file (the
+        "well known" file) associated with the 'gcloud' command line tool.
+
+        Returns:
+            Credentials object associated with the
+            GOOGLE_APPLICATION_CREDENTIALS file or the "well known" file if
+            either exist. If neither file is define, returns None, indicating
+            no credentials from a file can detected from the current
+            environment.
+        """
+        credentials_filename = _get_environment_variable_file()
+        if not credentials_filename:
+            credentials_filename = _get_well_known_file()
+            if os.path.isfile(credentials_filename):
+                extra_help = (' (produced automatically when running'
+                              ' "gcloud auth login" command)')
+            else:
+                credentials_filename = None
+        else:
+            extra_help = (' (pointed to by ' + GOOGLE_APPLICATION_CREDENTIALS +
+                          ' environment variable)')
+
+        if not credentials_filename:
+            return
+
+        # If we can read the credentials from a file, we don't need to know
+        # what environment we are in.
+        SETTINGS.env_name = DEFAULT_ENV_NAME
+
+        try:
+            return _get_application_default_credential_from_file(
+                credentials_filename)
+        except (ApplicationDefaultCredentialsError, ValueError) as error:
+            _raise_exception_for_reading_json(credentials_filename,
+                                              extra_help, error)
+
+    @classmethod
+    def _get_implicit_credentials(cls):
+        """Gets credentials implicitly from the environment.
+
+        Checks environment in order of precedence:
+        - Environment variable GOOGLE_APPLICATION_CREDENTIALS pointing to
+          a file with stored credentials information.
+        - Stored "well known" file associated with `gcloud` command line tool.
+        - Google App Engine (production and testing)
+        - Google Compute Engine production environment.
+
+        Raises:
+            ApplicationDefaultCredentialsError: raised when the credentials
+                                                fail to be retrieved.
+        """
+        # Environ checks (in order).
+        environ_checkers = [
+            cls._implicit_credentials_from_files,
+            cls._implicit_credentials_from_gae,
+            cls._implicit_credentials_from_gce,
+        ]
+
+        for checker in environ_checkers:
+            credentials = checker()
+            if credentials is not None:
+                return credentials
+
+        # If no credentials, fail.
+        raise ApplicationDefaultCredentialsError(ADC_HELP_MSG)
+
+    @staticmethod
+    def get_application_default():
+        """Get the Application Default Credentials for the current environment.
+
+        Raises:
+            ApplicationDefaultCredentialsError: raised when the credentials
+                                                fail to be retrieved.
+        """
+        return GoogleCredentials._get_implicit_credentials()
+
+    @staticmethod
+    def from_stream(credential_filename):
+        """Create a Credentials object by reading information from a file.
+
+        It returns an object of type GoogleCredentials.
+
+        Args:
+            credential_filename: the path to the file from where the
+                                 credentials are to be read
+
+        Raises:
+            ApplicationDefaultCredentialsError: raised when the credentials
+                                                fail to be retrieved.
+        """
+        if credential_filename and os.path.isfile(credential_filename):
+            try:
+                return _get_application_default_credential_from_file(
+                    credential_filename)
+            except (ApplicationDefaultCredentialsError, ValueError) as error:
+                extra_help = (' (provided as parameter to the '
+                              'from_stream() method)')
+                _raise_exception_for_reading_json(credential_filename,
+                                                  extra_help,
+                                                  error)
+        else:
+            raise ApplicationDefaultCredentialsError(
+                'The parameter passed to the from_stream() '
+                'method should point to a file.')
+
+
+def _save_private_file(filename, json_contents):
+    """Saves a file with read-write permissions on for the owner.
+
+    Args:
+        filename: String. Absolute path to file.
+        json_contents: JSON serializable object to be saved.
+    """
+    temp_filename = tempfile.mktemp()
+    file_desc = os.open(temp_filename, os.O_WRONLY | os.O_CREAT, 0o600)
+    with os.fdopen(file_desc, 'w') as file_handle:
+        json.dump(json_contents, file_handle, sort_keys=True,
+                  indent=2, separators=(',', ': '))
+    shutil.move(temp_filename, filename)
+
+
+def save_to_well_known_file(credentials, well_known_file=None):
+    """Save the provided GoogleCredentials to the well known file.
+
+    Args:
+        credentials: the credentials to be saved to the well known file;
+                     it should be an instance of GoogleCredentials
+        well_known_file: the name of the file where the credentials are to be
+                         saved; this parameter is supposed to be used for
+                         testing only
+    """
+    # TODO(orestica): move this method to tools.py
+    # once the argparse import gets fixed (it is not present in Python 2.6)
+
+    if well_known_file is None:
+        well_known_file = _get_well_known_file()
+
+    config_dir = os.path.dirname(well_known_file)
+    if not os.path.isdir(config_dir):
+        raise OSError(
+            'Config directory does not exist: {0}'.format(config_dir))
+
+    credentials_data = credentials.serialization_data
+    _save_private_file(well_known_file, credentials_data)
+
+
+def _get_environment_variable_file():
+    application_default_credential_filename = (
+        os.environ.get(GOOGLE_APPLICATION_CREDENTIALS, None))
+
+    if application_default_credential_filename:
+        if os.path.isfile(application_default_credential_filename):
+            return application_default_credential_filename
+        else:
+            raise ApplicationDefaultCredentialsError(
+                'File ' + application_default_credential_filename +
+                ' (pointed by ' +
+                GOOGLE_APPLICATION_CREDENTIALS +
+                ' environment variable) does not exist!')
+
+
+def _get_well_known_file():
+    """Get the well known file produced by command 'gcloud auth login'."""
+    # TODO(orestica): Revisit this method once gcloud provides a better way
+    # of pinpointing the exact location of the file.
+    default_config_dir = os.getenv(_CLOUDSDK_CONFIG_ENV_VAR)
+    if default_config_dir is None:
+        if os.name == 'nt':
+            try:
+                default_config_dir = os.path.join(os.environ['APPDATA'],
+                                                  _CLOUDSDK_CONFIG_DIRECTORY)
+            except KeyError:
+                # This should never happen unless someone is really
+                # messing with things.
+                drive = os.environ.get('SystemDrive', 'C:')
+                default_config_dir = os.path.join(drive, '\\',
+                                                  _CLOUDSDK_CONFIG_DIRECTORY)
+        else:
+            default_config_dir = os.path.join(os.path.expanduser('~'),
+                                              '.config',
+                                              _CLOUDSDK_CONFIG_DIRECTORY)
+
+    return os.path.join(default_config_dir, _WELL_KNOWN_CREDENTIALS_FILE)
+
+
+def _get_application_default_credential_from_file(filename):
+    """Build the Application Default Credentials from file."""
+    # read the credentials from the file
+    with open(filename) as file_obj:
+        client_credentials = json.load(file_obj)
+
+    credentials_type = client_credentials.get('type')
+    if credentials_type == AUTHORIZED_USER:
+        required_fields = set(['client_id', 'client_secret', 'refresh_token'])
+    elif credentials_type == SERVICE_ACCOUNT:
+        required_fields = set(['client_id', 'client_email', 'private_key_id',
+                               'private_key'])
+    else:
+        raise ApplicationDefaultCredentialsError(
+            "'type' field should be defined (and have one of the '" +
+            AUTHORIZED_USER + "' or '" + SERVICE_ACCOUNT + "' values)")
+
+    missing_fields = required_fields.difference(client_credentials.keys())
+
+    if missing_fields:
+        _raise_exception_for_missing_fields(missing_fields)
+
+    if client_credentials['type'] == AUTHORIZED_USER:
+        return GoogleCredentials(
+            access_token=None,
+            client_id=client_credentials['client_id'],
+            client_secret=client_credentials['client_secret'],
+            refresh_token=client_credentials['refresh_token'],
+            token_expiry=None,
+            token_uri=oauth2client.GOOGLE_TOKEN_URI,
+            user_agent='Python client library')
+    else:  # client_credentials['type'] == SERVICE_ACCOUNT
+        from oauth2client import service_account
+        return service_account._JWTAccessCredentials.from_json_keyfile_dict(
+            client_credentials)
+
+
+def _raise_exception_for_missing_fields(missing_fields):
+    raise ApplicationDefaultCredentialsError(
+        'The following field(s) must be defined: ' + ', '.join(missing_fields))
+
+
+def _raise_exception_for_reading_json(credential_file,
+                                      extra_help,
+                                      error):
+    raise ApplicationDefaultCredentialsError(
+        'An error was encountered while reading json file: ' +
+        credential_file + extra_help + ': ' + str(error))
+
+
+def _get_application_default_credential_GAE():
+    from oauth2client.contrib.appengine import AppAssertionCredentials
+
+    return AppAssertionCredentials([])
+
+
+def _get_application_default_credential_GCE():
+    from oauth2client.contrib.gce import AppAssertionCredentials
+
+    return AppAssertionCredentials()
+
+
+class AssertionCredentials(GoogleCredentials):
+    """Abstract Credentials object used for OAuth 2.0 assertion grants.
+
+    This credential does not require a flow to instantiate because it
+    represents a two legged flow, and therefore has all of the required
+    information to generate and refresh its own access tokens. It must
+    be subclassed to generate the appropriate assertion string.
+
+    AssertionCredentials objects may be safely pickled and unpickled.
+    """
+
+    @util.positional(2)
+    def __init__(self, assertion_type, user_agent=None,
+                 token_uri=oauth2client.GOOGLE_TOKEN_URI,
+                 revoke_uri=oauth2client.GOOGLE_REVOKE_URI,
+                 **unused_kwargs):
+        """Constructor for AssertionFlowCredentials.
+
+        Args:
+            assertion_type: string, assertion type that will be declared to the
+                            auth server
+            user_agent: string, The HTTP User-Agent to provide for this
+                        application.
+            token_uri: string, URI for token endpoint. For convenience defaults
+                       to Google's endpoints but any OAuth 2.0 provider can be
+                       used.
+            revoke_uri: string, URI for revoke endpoint.
+        """
+        super(AssertionCredentials, self).__init__(
+            None,
+            None,
+            None,
+            None,
+            None,
+            token_uri,
+            user_agent,
+            revoke_uri=revoke_uri)
+        self.assertion_type = assertion_type
+
+    def _generate_refresh_request_body(self):
+        assertion = self._generate_assertion()
+
+        body = urllib.parse.urlencode({
+            'assertion': assertion,
+            'grant_type': 'urn:ietf:params:oauth:grant-type:jwt-bearer',
+        })
+
+        return body
+
+    def _generate_assertion(self):
+        """Generate assertion string to be used in the access token request."""
+        raise NotImplementedError
+
+    def _revoke(self, http_request):
+        """Revokes the access_token and deletes the store if available.
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make the
+                          revoke request.
+        """
+        self._do_revoke(http_request, self.access_token)
+
+    def sign_blob(self, blob):
+        """Cryptographically sign a blob (of bytes).
+
+        Args:
+            blob: bytes, Message to be signed.
+
+        Returns:
+            tuple, A pair of the private key ID used to sign the blob and
+            the signed contents.
+        """
+        raise NotImplementedError('This method is abstract.')
+
+
+def _require_crypto_or_die():
+    """Ensure we have a crypto library, or throw CryptoUnavailableError.
+
+    The oauth2client.crypt module requires either PyCrypto or PyOpenSSL
+    to be available in order to function, but these are optional
+    dependencies.
+    """
+    if not HAS_CRYPTO:
+        raise CryptoUnavailableError('No crypto library available')
+
+
+@util.positional(2)
+def verify_id_token(id_token, audience, http=None,
+                    cert_uri=ID_TOKEN_VERIFICATION_CERTS):
+    """Verifies a signed JWT id_token.
+
+    This function requires PyOpenSSL and because of that it does not work on
+    App Engine.
+
+    Args:
+        id_token: string, A Signed JWT.
+        audience: string, The audience 'aud' that the token should be for.
+        http: httplib2.Http, instance to use to make the HTTP request. Callers
+              should supply an instance that has caching enabled.
+        cert_uri: string, URI of the certificates in JSON format to
+                  verify the JWT against.
+
+    Returns:
+        The deserialized JSON in the JWT.
+
+    Raises:
+        oauth2client.crypt.AppIdentityError: if the JWT fails to verify.
+        CryptoUnavailableError: if no crypto library is available.
+    """
+    _require_crypto_or_die()
+    if http is None:
+        http = transport.get_cached_http()
+
+    resp, content = http.request(cert_uri)
+    if resp.status == http_client.OK:
+        certs = json.loads(_helpers._from_bytes(content))
+        return crypt.verify_signed_jwt_with_certs(id_token, certs, audience)
+    else:
+        raise VerifyJwtTokenError('Status code: {0}'.format(resp.status))
+
+
+def _extract_id_token(id_token):
+    """Extract the JSON payload from a JWT.
+
+    Does the extraction w/o checking the signature.
+
+    Args:
+        id_token: string or bytestring, OAuth 2.0 id_token.
+
+    Returns:
+        object, The deserialized JSON payload.
+    """
+    if type(id_token) == bytes:
+        segments = id_token.split(b'.')
+    else:
+        segments = id_token.split(u'.')
+
+    if len(segments) != 3:
+        raise VerifyJwtTokenError(
+            'Wrong number of segments in token: {0}'.format(id_token))
+
+    return json.loads(
+        _helpers._from_bytes(_helpers._urlsafe_b64decode(segments[1])))
+
+
+def _parse_exchange_token_response(content):
+    """Parses response of an exchange token request.
+
+    Most providers return JSON but some (e.g. Facebook) return a
+    url-encoded string.
+
+    Args:
+        content: The body of a response
+
+    Returns:
+        Content as a dictionary object. Note that the dict could be empty,
+        i.e. {}. That basically indicates a failure.
+    """
+    resp = {}
+    content = _helpers._from_bytes(content)
+    try:
+        resp = json.loads(content)
+    except Exception:
+        # different JSON libs raise different exceptions,
+        # so we just do a catch-all here
+        resp = dict(urllib.parse.parse_qsl(content))
+
+    # some providers respond with 'expires', others with 'expires_in'
+    if resp and 'expires' in resp:
+        resp['expires_in'] = resp.pop('expires')
+
+    return resp
+
+
+@util.positional(4)
+def credentials_from_code(client_id, client_secret, scope, code,
+                          redirect_uri='postmessage', http=None,
+                          user_agent=None,
+                          token_uri=oauth2client.GOOGLE_TOKEN_URI,
+                          auth_uri=oauth2client.GOOGLE_AUTH_URI,
+                          revoke_uri=oauth2client.GOOGLE_REVOKE_URI,
+                          device_uri=oauth2client.GOOGLE_DEVICE_URI,
+                          token_info_uri=oauth2client.GOOGLE_TOKEN_INFO_URI):
+    """Exchanges an authorization code for an OAuth2Credentials object.
+
+    Args:
+        client_id: string, client identifier.
+        client_secret: string, client secret.
+        scope: string or iterable of strings, scope(s) to request.
+        code: string, An authorization code, most likely passed down from
+              the client
+        redirect_uri: string, this is generally set to 'postmessage' to match
+                      the redirect_uri that the client specified
+        http: httplib2.Http, optional http instance to use to do the fetch
+        token_uri: string, URI for token endpoint. For convenience defaults
+                   to Google's endpoints but any OAuth 2.0 provider can be
+                   used.
+        auth_uri: string, URI for authorization endpoint. For convenience
+                  defaults to Google's endpoints but any OAuth 2.0 provider
+                  can be used.
+        revoke_uri: string, URI for revoke endpoint. For convenience
+                    defaults to Google's endpoints but any OAuth 2.0 provider
+                    can be used.
+        device_uri: string, URI for device authorization endpoint. For
+                    convenience defaults to Google's endpoints but any OAuth
+                    2.0 provider can be used.
+
+    Returns:
+        An OAuth2Credentials object.
+
+    Raises:
+        FlowExchangeError if the authorization code cannot be exchanged for an
+        access token
+    """
+    flow = OAuth2WebServerFlow(client_id, client_secret, scope,
+                               redirect_uri=redirect_uri,
+                               user_agent=user_agent, auth_uri=auth_uri,
+                               token_uri=token_uri, revoke_uri=revoke_uri,
+                               device_uri=device_uri,
+                               token_info_uri=token_info_uri)
+
+    credentials = flow.step2_exchange(code, http=http)
+    return credentials
+
+
+@util.positional(3)
+def credentials_from_clientsecrets_and_code(filename, scope, code,
+                                            message=None,
+                                            redirect_uri='postmessage',
+                                            http=None,
+                                            cache=None,
+                                            device_uri=None):
+    """Returns OAuth2Credentials from a clientsecrets file and an auth code.
+
+    Will create the right kind of Flow based on the contents of the
+    clientsecrets file or will raise InvalidClientSecretsError for unknown
+    types of Flows.
+
+    Args:
+        filename: string, File name of clientsecrets.
+        scope: string or iterable of strings, scope(s) to request.
+        code: string, An authorization code, most likely passed down from
+              the client
+        message: string, A friendly string to display to the user if the
+                 clientsecrets file is missing or invalid. If message is
+                 provided then sys.exit will be called in the case of an error.
+                 If message in not provided then
+                 clientsecrets.InvalidClientSecretsError will be raised.
+        redirect_uri: string, this is generally set to 'postmessage' to match
+                      the redirect_uri that the client specified
+        http: httplib2.Http, optional http instance to use to do the fetch
+        cache: An optional cache service client that implements get() and set()
+               methods. See clientsecrets.loadfile() for details.
+        device_uri: string, OAuth 2.0 device authorization endpoint
+
+    Returns:
+        An OAuth2Credentials object.
+
+    Raises:
+        FlowExchangeError: if the authorization code cannot be exchanged for an
+                           access token
+        UnknownClientSecretsFlowError: if the file describes an unknown kind
+                                       of Flow.
+        clientsecrets.InvalidClientSecretsError: if the clientsecrets file is
+                                                 invalid.
+    """
+    flow = flow_from_clientsecrets(filename, scope, message=message,
+                                   cache=cache, redirect_uri=redirect_uri,
+                                   device_uri=device_uri)
+    credentials = flow.step2_exchange(code, http=http)
+    return credentials
+
+
+class DeviceFlowInfo(collections.namedtuple('DeviceFlowInfo', (
+        'device_code', 'user_code', 'interval', 'verification_url',
+        'user_code_expiry'))):
+    """Intermediate information the OAuth2 for devices flow."""
+
+    @classmethod
+    def FromResponse(cls, response):
+        """Create a DeviceFlowInfo from a server response.
+
+        The response should be a dict containing entries as described here:
+
+        http://tools.ietf.org/html/draft-ietf-oauth-v2-05#section-3.7.1
+        """
+        # device_code, user_code, and verification_url are required.
+        kwargs = {
+            'device_code': response['device_code'],
+            'user_code': response['user_code'],
+        }
+        # The response may list the verification address as either
+        # verification_url or verification_uri, so we check for both.
+        verification_url = response.get(
+            'verification_url', response.get('verification_uri'))
+        if verification_url is None:
+            raise OAuth2DeviceCodeError(
+                'No verification_url provided in server response')
+        kwargs['verification_url'] = verification_url
+        # expires_in and interval are optional.
+        kwargs.update({
+            'interval': response.get('interval'),
+            'user_code_expiry': None,
+        })
+        if 'expires_in' in response:
+            kwargs['user_code_expiry'] = (
+                _UTCNOW() +
+                datetime.timedelta(seconds=int(response['expires_in'])))
+        return cls(**kwargs)
+
+
+def _oauth2_web_server_flow_params(kwargs):
+    """Configures redirect URI parameters for OAuth2WebServerFlow."""
+    params = {
+        'access_type': 'offline',
+        'response_type': 'code',
+    }
+
+    params.update(kwargs)
+
+    # Check for the presence of the deprecated approval_prompt param and
+    # warn appropriately.
+    approval_prompt = params.get('approval_prompt')
+    if approval_prompt is not None:
+        logger.warning(
+            'The approval_prompt parameter for OAuth2WebServerFlow is '
+            'deprecated. Please use the prompt parameter instead.')
+
+        if approval_prompt == 'force':
+            logger.warning(
+                'approval_prompt="force" has been adjusted to '
+                'prompt="consent"')
+            params['prompt'] = 'consent'
+            del params['approval_prompt']
+
+    return params
+
+
+class OAuth2WebServerFlow(Flow):
+    """Does the Web Server Flow for OAuth 2.0.
+
+    OAuth2WebServerFlow objects may be safely pickled and unpickled.
+    """
+
+    @util.positional(4)
+    def __init__(self, client_id,
+                 client_secret=None,
+                 scope=None,
+                 redirect_uri=None,
+                 user_agent=None,
+                 auth_uri=oauth2client.GOOGLE_AUTH_URI,
+                 token_uri=oauth2client.GOOGLE_TOKEN_URI,
+                 revoke_uri=oauth2client.GOOGLE_REVOKE_URI,
+                 login_hint=None,
+                 device_uri=oauth2client.GOOGLE_DEVICE_URI,
+                 token_info_uri=oauth2client.GOOGLE_TOKEN_INFO_URI,
+                 authorization_header=None,
+                 **kwargs):
+        """Constructor for OAuth2WebServerFlow.
+
+        The kwargs argument is used to set extra query parameters on the
+        auth_uri. For example, the access_type and prompt
+        query parameters can be set via kwargs.
+
+        Args:
+            client_id: string, client identifier.
+            client_secret: string client secret.
+            scope: string or iterable of strings, scope(s) of the credentials
+                   being requested.
+            redirect_uri: string, Either the string 'urn:ietf:wg:oauth:2.0:oob'
+                          for a non-web-based application, or a URI that
+                          handles the callback from the authorization server.
+            user_agent: string, HTTP User-Agent to provide for this
+                        application.
+            auth_uri: string, URI for authorization endpoint. For convenience
+                      defaults to Google's endpoints but any OAuth 2.0 provider
+                      can be used.
+            token_uri: string, URI for token endpoint. For convenience
+                       defaults to Google's endpoints but any OAuth 2.0
+                       provider can be used.
+            revoke_uri: string, URI for revoke endpoint. For convenience
+                        defaults to Google's endpoints but any OAuth 2.0
+                        provider can be used.
+            login_hint: string, Either an email address or domain. Passing this
+                        hint will either pre-fill the email box on the sign-in
+                        form or select the proper multi-login session, thereby
+                        simplifying the login flow.
+            device_uri: string, URI for device authorization endpoint. For
+                        convenience defaults to Google's endpoints but any
+                        OAuth 2.0 provider can be used.
+            authorization_header: string, For use with OAuth 2.0 providers that
+                                  require a client to authenticate using a
+                                  header value instead of passing client_secret
+                                  in the POST body.
+            **kwargs: dict, The keyword arguments are all optional and required
+                      parameters for the OAuth calls.
+        """
+        # scope is a required argument, but to preserve backwards-compatibility
+        # we don't want to rearrange the positional arguments
+        if scope is None:
+            raise TypeError("The value of scope must not be None")
+        self.client_id = client_id
+        self.client_secret = client_secret
+        self.scope = util.scopes_to_string(scope)
+        self.redirect_uri = redirect_uri
+        self.login_hint = login_hint
+        self.user_agent = user_agent
+        self.auth_uri = auth_uri
+        self.token_uri = token_uri
+        self.revoke_uri = revoke_uri
+        self.device_uri = device_uri
+        self.token_info_uri = token_info_uri
+        self.authorization_header = authorization_header
+        self.params = _oauth2_web_server_flow_params(kwargs)
+
+    @util.positional(1)
+    def step1_get_authorize_url(self, redirect_uri=None, state=None):
+        """Returns a URI to redirect to the provider.
+
+        Args:
+            redirect_uri: string, Either the string 'urn:ietf:wg:oauth:2.0:oob'
+                          for a non-web-based application, or a URI that
+                          handles the callback from the authorization server.
+                          This parameter is deprecated, please move to passing
+                          the redirect_uri in via the constructor.
+            state: string, Opaque state string which is passed through the
+                   OAuth2 flow and returned to the client as a query parameter
+                   in the callback.
+
+        Returns:
+            A URI as a string to redirect the user to begin the authorization
+            flow.
+        """
+        if redirect_uri is not None:
+            logger.warning((
+                'The redirect_uri parameter for '
+                'OAuth2WebServerFlow.step1_get_authorize_url is deprecated. '
+                'Please move to passing the redirect_uri in via the '
+                'constructor.'))
+            self.redirect_uri = redirect_uri
+
+        if self.redirect_uri is None:
+            raise ValueError('The value of redirect_uri must not be None.')
+
+        query_params = {
+            'client_id': self.client_id,
+            'redirect_uri': self.redirect_uri,
+            'scope': self.scope,
+        }
+        if state is not None:
+            query_params['state'] = state
+        if self.login_hint is not None:
+            query_params['login_hint'] = self.login_hint
+        query_params.update(self.params)
+        return _update_query_params(self.auth_uri, query_params)
+
+    @util.positional(1)
+    def step1_get_device_and_user_codes(self, http=None):
+        """Returns a user code and the verification URL where to enter it
+
+        Returns:
+            A user code as a string for the user to authorize the application
+            An URL as a string where the user has to enter the code
+        """
+        if self.device_uri is None:
+            raise ValueError('The value of device_uri must not be None.')
+
+        body = urllib.parse.urlencode({
+            'client_id': self.client_id,
+            'scope': self.scope,
+        })
+        headers = {
+            'content-type': 'application/x-www-form-urlencoded',
+        }
+
+        if self.user_agent is not None:
+            headers['user-agent'] = self.user_agent
+
+        if http is None:
+            http = transport.get_http_object()
+
+        resp, content = http.request(self.device_uri, method='POST', body=body,
+                                     headers=headers)
+        content = _helpers._from_bytes(content)
+        if resp.status == http_client.OK:
+            try:
+                flow_info = json.loads(content)
+            except ValueError as exc:
+                raise OAuth2DeviceCodeError(
+                    'Could not parse server response as JSON: "{0}", '
+                    'error: "{1}"'.format(content, exc))
+            return DeviceFlowInfo.FromResponse(flow_info)
+        else:
+            error_msg = 'Invalid response {0}.'.format(resp.status)
+            try:
+                error_dict = json.loads(content)
+                if 'error' in error_dict:
+                    error_msg += ' Error: {0}'.format(error_dict['error'])
+            except ValueError:
+                # Couldn't decode a JSON response, stick with the
+                # default message.
+                pass
+            raise OAuth2DeviceCodeError(error_msg)
+
+    @util.positional(2)
+    def step2_exchange(self, code=None, http=None, device_flow_info=None):
+        """Exchanges a code for OAuth2Credentials.
+
+        Args:
+            code: string, a dict-like object, or None. For a non-device
+                  flow, this is either the response code as a string, or a
+                  dictionary of query parameters to the redirect_uri. For a
+                  device flow, this should be None.
+            http: httplib2.Http, optional http instance to use when fetching
+                  credentials.
+            device_flow_info: DeviceFlowInfo, return value from step1 in the
+                              case of a device flow.
+
+        Returns:
+            An OAuth2Credentials object that can be used to authorize requests.
+
+        Raises:
+            FlowExchangeError: if a problem occurred exchanging the code for a
+                               refresh_token.
+            ValueError: if code and device_flow_info are both provided or both
+                        missing.
+        """
+        if code is None and device_flow_info is None:
+            raise ValueError('No code or device_flow_info provided.')
+        if code is not None and device_flow_info is not None:
+            raise ValueError('Cannot provide both code and device_flow_info.')
+
+        if code is None:
+            code = device_flow_info.device_code
+        elif not isinstance(code, (six.string_types, six.binary_type)):
+            if 'code' not in code:
+                raise FlowExchangeError(code.get(
+                    'error', 'No code was supplied in the query parameters.'))
+            code = code['code']
+
+        post_data = {
+            'client_id': self.client_id,
+            'code': code,
+            'scope': self.scope,
+        }
+        if self.client_secret is not None:
+            post_data['client_secret'] = self.client_secret
+        if device_flow_info is not None:
+            post_data['grant_type'] = 'http://oauth.net/grant_type/device/1.0'
+        else:
+            post_data['grant_type'] = 'authorization_code'
+            post_data['redirect_uri'] = self.redirect_uri
+        body = urllib.parse.urlencode(post_data)
+        headers = {
+            'content-type': 'application/x-www-form-urlencoded',
+        }
+        if self.authorization_header is not None:
+            headers['Authorization'] = self.authorization_header
+        if self.user_agent is not None:
+            headers['user-agent'] = self.user_agent
+
+        if http is None:
+            http = transport.get_http_object()
+
+        resp, content = http.request(self.token_uri, method='POST', body=body,
+                                     headers=headers)
+        d = _parse_exchange_token_response(content)
+        if resp.status == http_client.OK and 'access_token' in d:
+            access_token = d['access_token']
+            refresh_token = d.get('refresh_token', None)
+            if not refresh_token:
+                logger.info(
+                    'Received token response with no refresh_token. Consider '
+                    "reauthenticating with prompt='consent'.")
+            token_expiry = None
+            if 'expires_in' in d:
+                delta = datetime.timedelta(seconds=int(d['expires_in']))
+                token_expiry = delta + _UTCNOW()
+
+            extracted_id_token = None
+            if 'id_token' in d:
+                extracted_id_token = _extract_id_token(d['id_token'])
+
+            logger.info('Successfully retrieved access token')
+            return OAuth2Credentials(
+                access_token, self.client_id, self.client_secret,
+                refresh_token, token_expiry, self.token_uri, self.user_agent,
+                revoke_uri=self.revoke_uri, id_token=extracted_id_token,
+                token_response=d, scopes=self.scope,
+                token_info_uri=self.token_info_uri)
+        else:
+            logger.info('Failed to retrieve access token: %s', content)
+            if 'error' in d:
+                # you never know what those providers got to say
+                error_msg = (str(d['error']) +
+                             str(d.get('error_description', '')))
+            else:
+                error_msg = 'Invalid response: {0}.'.format(str(resp.status))
+            raise FlowExchangeError(error_msg)
+
+
+@util.positional(2)
+def flow_from_clientsecrets(filename, scope, redirect_uri=None,
+                            message=None, cache=None, login_hint=None,
+                            device_uri=None):
+    """Create a Flow from a clientsecrets file.
+
+    Will create the right kind of Flow based on the contents of the
+    clientsecrets file or will raise InvalidClientSecretsError for unknown
+    types of Flows.
+
+    Args:
+        filename: string, File name of client secrets.
+        scope: string or iterable of strings, scope(s) to request.
+        redirect_uri: string, Either the string 'urn:ietf:wg:oauth:2.0:oob' for
+                      a non-web-based application, or a URI that handles the
+                      callback from the authorization server.
+        message: string, A friendly string to display to the user if the
+                 clientsecrets file is missing or invalid. If message is
+                 provided then sys.exit will be called in the case of an error.
+                 If message in not provided then
+                 clientsecrets.InvalidClientSecretsError will be raised.
+        cache: An optional cache service client that implements get() and set()
+               methods. See clientsecrets.loadfile() for details.
+        login_hint: string, Either an email address or domain. Passing this
+                    hint will either pre-fill the email box on the sign-in form
+                    or select the proper multi-login session, thereby
+                    simplifying the login flow.
+        device_uri: string, URI for device authorization endpoint. For
+                    convenience defaults to Google's endpoints but any
+                    OAuth 2.0 provider can be used.
+
+    Returns:
+        A Flow object.
+
+    Raises:
+        UnknownClientSecretsFlowError: if the file describes an unknown kind of
+                                       Flow.
+        clientsecrets.InvalidClientSecretsError: if the clientsecrets file is
+                                                 invalid.
+    """
+    try:
+        client_type, client_info = clientsecrets.loadfile(filename,
+                                                          cache=cache)
+        if client_type in (clientsecrets.TYPE_WEB,
+                           clientsecrets.TYPE_INSTALLED):
+            constructor_kwargs = {
+                'redirect_uri': redirect_uri,
+                'auth_uri': client_info['auth_uri'],
+                'token_uri': client_info['token_uri'],
+                'login_hint': login_hint,
+            }
+            revoke_uri = client_info.get('revoke_uri')
+            if revoke_uri is not None:
+                constructor_kwargs['revoke_uri'] = revoke_uri
+            if device_uri is not None:
+                constructor_kwargs['device_uri'] = device_uri
+            return OAuth2WebServerFlow(
+                client_info['client_id'], client_info['client_secret'],
+                scope, **constructor_kwargs)
+
+    except clientsecrets.InvalidClientSecretsError as e:
+        if message is not None:
+            if e.args:
+                message = ('The client secrets were invalid: '
+                           '\n{0}\n{1}'.format(e, message))
+            sys.exit(message)
+        else:
+            raise
+    else:
+        raise UnknownClientSecretsFlowError(
+            'This OAuth 2.0 flow is unsupported: {0!r}'.format(client_type))
diff --git a/oauth2client/clientsecrets.py b/oauth2client/clientsecrets.py
new file mode 100644
index 0000000..4b43e66
--- /dev/null
+++ b/oauth2client/clientsecrets.py
@@ -0,0 +1,174 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities for reading OAuth 2.0 client secret files.
+
+A client_secrets.json file contains all the information needed to interact with
+an OAuth 2.0 protected service.
+"""
+
+import json
+
+import six
+
+__author__ = 'jcgregorio@google.com (Joe Gregorio)'
+
+# Properties that make a client_secrets.json file valid.
+TYPE_WEB = 'web'
+TYPE_INSTALLED = 'installed'
+
+VALID_CLIENT = {
+    TYPE_WEB: {
+        'required': [
+            'client_id',
+            'client_secret',
+            'redirect_uris',
+            'auth_uri',
+            'token_uri',
+        ],
+        'string': [
+            'client_id',
+            'client_secret',
+        ],
+    },
+    TYPE_INSTALLED: {
+        'required': [
+            'client_id',
+            'client_secret',
+            'redirect_uris',
+            'auth_uri',
+            'token_uri',
+        ],
+        'string': [
+            'client_id',
+            'client_secret',
+        ],
+    },
+}
+
+
+class Error(Exception):
+    """Base error for this module."""
+
+
+class InvalidClientSecretsError(Error):
+    """Format of ClientSecrets file is invalid."""
+
+
+def _validate_clientsecrets(clientsecrets_dict):
+    """Validate parsed client secrets from a file.
+
+    Args:
+        clientsecrets_dict: dict, a dictionary holding the client secrets.
+
+    Returns:
+        tuple, a string of the client type and the information parsed
+        from the file.
+    """
+    _INVALID_FILE_FORMAT_MSG = (
+        'Invalid file format. See '
+        'https://developers.google.com/api-client-library/'
+        'python/guide/aaa_client_secrets')
+
+    if clientsecrets_dict is None:
+        raise InvalidClientSecretsError(_INVALID_FILE_FORMAT_MSG)
+    try:
+        (client_type, client_info), = clientsecrets_dict.items()
+    except (ValueError, AttributeError):
+        raise InvalidClientSecretsError(
+            _INVALID_FILE_FORMAT_MSG + ' '
+            'Expected a JSON object with a single property for a "web" or '
+            '"installed" application')
+
+    if client_type not in VALID_CLIENT:
+        raise InvalidClientSecretsError(
+            'Unknown client type: {0}.'.format(client_type))
+
+    for prop_name in VALID_CLIENT[client_type]['required']:
+        if prop_name not in client_info:
+            raise InvalidClientSecretsError(
+                'Missing property "{0}" in a client type of "{1}".'.format(
+                    prop_name, client_type))
+    for prop_name in VALID_CLIENT[client_type]['string']:
+        if client_info[prop_name].startswith('[['):
+            raise InvalidClientSecretsError(
+                'Property "{0}" is not configured.'.format(prop_name))
+    return client_type, client_info
+
+
+def load(fp):
+    obj = json.load(fp)
+    return _validate_clientsecrets(obj)
+
+
+def loads(s):
+    obj = json.loads(s)
+    return _validate_clientsecrets(obj)
+
+
+def _loadfile(filename):
+    try:
+        with open(filename, 'r') as fp:
+            obj = json.load(fp)
+    except IOError as exc:
+        raise InvalidClientSecretsError('Error opening file', exc.filename,
+                                        exc.strerror, exc.errno)
+    return _validate_clientsecrets(obj)
+
+
+def loadfile(filename, cache=None):
+    """Loading of client_secrets JSON file, optionally backed by a cache.
+
+    Typical cache storage would be App Engine memcache service,
+    but you can pass in any other cache client that implements
+    these methods:
+
+    * ``get(key, namespace=ns)``
+    * ``set(key, value, namespace=ns)``
+
+    Usage::
+
+        # without caching
+        client_type, client_info = loadfile('secrets.json')
+        # using App Engine memcache service
+        from google.appengine.api import memcache
+        client_type, client_info = loadfile('secrets.json', cache=memcache)
+
+    Args:
+        filename: string, Path to a client_secrets.json file on a filesystem.
+        cache: An optional cache service client that implements get() and set()
+        methods. If not specified, the file is always being loaded from
+                 a filesystem.
+
+    Raises:
+        InvalidClientSecretsError: In case of a validation error or some
+                                   I/O failure. Can happen only on cache miss.
+
+    Returns:
+        (client_type, client_info) tuple, as _loadfile() normally would.
+        JSON contents is validated only during first load. Cache hits are not
+        validated.
+    """
+    _SECRET_NAMESPACE = 'oauth2client:secrets#ns'
+
+    if not cache:
+        return _loadfile(filename)
+
+    obj = cache.get(filename, namespace=_SECRET_NAMESPACE)
+    if obj is None:
+        client_type, client_info = _loadfile(filename)
+        obj = {client_type: client_info}
+        cache.set(filename, obj, namespace=_SECRET_NAMESPACE)
+
+    return next(six.iteritems(obj))
diff --git a/oauth2client/contrib/__init__.py b/oauth2client/contrib/__init__.py
new file mode 100644
index 0000000..ecfd06c
--- /dev/null
+++ b/oauth2client/contrib/__init__.py
@@ -0,0 +1,6 @@
+"""Contributed modules.
+
+Contrib contains modules that are not considered part of the core oauth2client
+library but provide additional functionality. These modules are intended to
+make it easier to use oauth2client.
+"""
diff --git a/oauth2client/contrib/_appengine_ndb.py b/oauth2client/contrib/_appengine_ndb.py
new file mode 100644
index 0000000..c863e8f
--- /dev/null
+++ b/oauth2client/contrib/_appengine_ndb.py
@@ -0,0 +1,163 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Google App Engine utilities helper.
+
+Classes that directly require App Engine's ndb library. Provided
+as a separate module in case of failure to import ndb while
+other App Engine libraries are present.
+"""
+
+import logging
+
+from google.appengine.ext import ndb
+
+from oauth2client import client
+
+
+NDB_KEY = ndb.Key
+"""Key constant used by :mod:`oauth2client.contrib.appengine`."""
+
+NDB_MODEL = ndb.Model
+"""Model constant used by :mod:`oauth2client.contrib.appengine`."""
+
+_LOGGER = logging.getLogger(__name__)
+
+
+class SiteXsrfSecretKeyNDB(ndb.Model):
+    """NDB Model for storage for the sites XSRF secret key.
+
+    Since this model uses the same kind as SiteXsrfSecretKey, it can be
+    used interchangeably. This simply provides an NDB model for interacting
+    with the same data the DB model interacts with.
+
+    There should only be one instance stored of this model, the one used
+    for the site.
+    """
+    secret = ndb.StringProperty()
+
+    @classmethod
+    def _get_kind(cls):
+        """Return the kind name for this class."""
+        return 'SiteXsrfSecretKey'
+
+
+class FlowNDBProperty(ndb.PickleProperty):
+    """App Engine NDB datastore Property for Flow.
+
+    Serves the same purpose as the DB FlowProperty, but for NDB models.
+    Since PickleProperty inherits from BlobProperty, the underlying
+    representation of the data in the datastore will be the same as in the
+    DB case.
+
+    Utility property that allows easy storage and retrieval of an
+    oauth2client.Flow
+    """
+
+    def _validate(self, value):
+        """Validates a value as a proper Flow object.
+
+        Args:
+            value: A value to be set on the property.
+
+        Raises:
+            TypeError if the value is not an instance of Flow.
+        """
+        _LOGGER.info('validate: Got type %s', type(value))
+        if value is not None and not isinstance(value, client.Flow):
+            raise TypeError(
+                'Property {0} must be convertible to a flow '
+                'instance; received: {1}.'.format(self._name, value))
+
+
+class CredentialsNDBProperty(ndb.BlobProperty):
+    """App Engine NDB datastore Property for Credentials.
+
+    Serves the same purpose as the DB CredentialsProperty, but for NDB
+    models. Since CredentialsProperty stores data as a blob and this
+    inherits from BlobProperty, the data in the datastore will be the same
+    as in the DB case.
+
+    Utility property that allows easy storage and retrieval of Credentials
+    and subclasses.
+    """
+
+    def _validate(self, value):
+        """Validates a value as a proper credentials object.
+
+        Args:
+            value: A value to be set on the property.
+
+        Raises:
+            TypeError if the value is not an instance of Credentials.
+        """
+        _LOGGER.info('validate: Got type %s', type(value))
+        if value is not None and not isinstance(value, client.Credentials):
+            raise TypeError(
+                'Property {0} must be convertible to a credentials '
+                'instance; received: {1}.'.format(self._name, value))
+
+    def _to_base_type(self, value):
+        """Converts our validated value to a JSON serialized string.
+
+        Args:
+            value: A value to be set in the datastore.
+
+        Returns:
+            A JSON serialized version of the credential, else '' if value
+            is None.
+        """
+        if value is None:
+            return ''
+        else:
+            return value.to_json()
+
+    def _from_base_type(self, value):
+        """Converts our stored JSON string back to the desired type.
+
+        Args:
+            value: A value from the datastore to be converted to the
+                   desired type.
+
+        Returns:
+            A deserialized Credentials (or subclass) object, else None if
+            the value can't be parsed.
+        """
+        if not value:
+            return None
+        try:
+            # Uses the from_json method of the implied class of value
+            credentials = client.Credentials.new_from_json(value)
+        except ValueError:
+            credentials = None
+        return credentials
+
+
+class CredentialsNDBModel(ndb.Model):
+    """NDB Model for storage of OAuth 2.0 Credentials
+
+    Since this model uses the same kind as CredentialsModel and has a
+    property which can serialize and deserialize Credentials correctly, it
+    can be used interchangeably with a CredentialsModel to access, insert
+    and delete the same entities. This simply provides an NDB model for
+    interacting with the same data the DB model interacts with.
+
+    Storage of the model is keyed by the user.user_id().
+    """
+    credentials = CredentialsNDBProperty()
+
+    @classmethod
+    def _get_kind(cls):
+        """Return the kind name for this class."""
+        return 'CredentialsModel'
diff --git a/oauth2client/contrib/_fcntl_opener.py b/oauth2client/contrib/_fcntl_opener.py
new file mode 100644
index 0000000..ae6c85b
--- /dev/null
+++ b/oauth2client/contrib/_fcntl_opener.py
@@ -0,0 +1,81 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import errno
+import fcntl
+import time
+
+from oauth2client.contrib import locked_file
+
+
+class _FcntlOpener(locked_file._Opener):
+    """Open, lock, and unlock a file using fcntl.lockf."""
+
+    def open_and_lock(self, timeout, delay):
+        """Open the file and lock it.
+
+        Args:
+            timeout: float, How long to try to lock for.
+            delay: float, How long to wait between retries
+
+        Raises:
+            AlreadyLockedException: if the lock is already acquired.
+            IOError: if the open fails.
+            CredentialsFileSymbolicLinkError: if the file is a symbolic
+                                              link.
+        """
+        if self._locked:
+            raise locked_file.AlreadyLockedException(
+                'File {0} is already locked'.format(self._filename))
+        start_time = time.time()
+
+        locked_file.validate_file(self._filename)
+        try:
+            self._fh = open(self._filename, self._mode)
+        except IOError as e:
+            # If we can't access with _mode, try _fallback_mode and
+            # don't lock.
+            if e.errno in (errno.EPERM, errno.EACCES):
+                self._fh = open(self._filename, self._fallback_mode)
+                return
+
+        # We opened in _mode, try to lock the file.
+        while True:
+            try:
+                fcntl.lockf(self._fh.fileno(), fcntl.LOCK_EX)
+                self._locked = True
+                return
+            except IOError as e:
+                # If not retrying, then just pass on the error.
+                if timeout == 0:
+                    raise
+                if e.errno != errno.EACCES:
+                    raise
+                # We could not acquire the lock. Try again.
+                if (time.time() - start_time) >= timeout:
+                    locked_file.logger.warn('Could not lock %s in %s seconds',
+                                            self._filename, timeout)
+                    if self._fh:
+                        self._fh.close()
+                    self._fh = open(self._filename, self._fallback_mode)
+                    return
+                time.sleep(delay)
+
+    def unlock_and_close(self):
+        """Close and unlock the file using the fcntl.lockf primitive."""
+        if self._locked:
+            fcntl.lockf(self._fh.fileno(), fcntl.LOCK_UN)
+        self._locked = False
+        if self._fh:
+            self._fh.close()
diff --git a/oauth2client/contrib/_metadata.py b/oauth2client/contrib/_metadata.py
new file mode 100644
index 0000000..10e6a69
--- /dev/null
+++ b/oauth2client/contrib/_metadata.py
@@ -0,0 +1,123 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Provides helper methods for talking to the Compute Engine metadata server.
+
+See https://cloud.google.com/compute/docs/metadata
+"""
+
+import datetime
+import json
+
+import httplib2
+from six.moves import http_client
+from six.moves.urllib import parse as urlparse
+
+from oauth2client import _helpers
+from oauth2client import client
+from oauth2client import util
+
+
+METADATA_ROOT = 'http://metadata.google.internal/computeMetadata/v1/'
+METADATA_HEADERS = {'Metadata-Flavor': 'Google'}
+
+
+def get(http_request, path, root=METADATA_ROOT, recursive=None):
+    """Fetch a resource from the metadata server.
+
+    Args:
+        path: A string indicating the resource to retrieve. For example,
+            'instance/service-accounts/defualt'
+        http_request: A callable that matches the method
+            signature of httplib2.Http.request. Used to make the request to the
+            metadataserver.
+        root: A string indicating the full path to the metadata server root.
+        recursive: A boolean indicating whether to do a recursive query of
+            metadata. See
+            https://cloud.google.com/compute/docs/metadata#aggcontents
+
+    Returns:
+        A dictionary if the metadata server returns JSON, otherwise a string.
+
+    Raises:
+        httplib2.Httplib2Error if an error corrured while retrieving metadata.
+    """
+    url = urlparse.urljoin(root, path)
+    url = util._add_query_parameter(url, 'recursive', recursive)
+
+    response, content = http_request(
+        url,
+        headers=METADATA_HEADERS
+    )
+
+    if response.status == http_client.OK:
+        decoded = _helpers._from_bytes(content)
+        if response['content-type'] == 'application/json':
+            return json.loads(decoded)
+        else:
+            return decoded
+    else:
+        raise httplib2.HttpLib2Error(
+            'Failed to retrieve {0} from the Google Compute Engine'
+            'metadata service. Response:\n{1}'.format(url, response))
+
+
+def get_service_account_info(http_request, service_account='default'):
+    """Get information about a service account from the metadata server.
+
+    Args:
+        service_account: An email specifying the service account for which to
+            look up information. Default will be information for the "default"
+            service account of the current compute engine instance.
+        http_request: A callable that matches the method
+            signature of httplib2.Http.request. Used to make the request to the
+            metadata server.
+    Returns:
+         A dictionary with information about the specified service account,
+         for example:
+
+            {
+                'email': '...',
+                'scopes': ['scope', ...],
+                'aliases': ['default', '...']
+            }
+    """
+    return get(
+        http_request,
+        'instance/service-accounts/{0}/'.format(service_account),
+        recursive=True)
+
+
+def get_token(http_request, service_account='default'):
+    """Fetch an oauth token for the
+
+    Args:
+        service_account: An email specifying the service account this token
+            should represent. Default will be a token for the "default" service
+            account of the current compute engine instance.
+        http_request: A callable that matches the method
+            signature of httplib2.Http.request. Used to make the request to the
+            metadataserver.
+
+    Returns:
+         A tuple of (access token, token expiration), where access token is the
+         access token as a string and token expiration is a datetime object
+         that indicates when the access token will expire.
+    """
+    token_json = get(
+        http_request,
+        'instance/service-accounts/{0}/token'.format(service_account))
+    token_expiry = client._UTCNOW() + datetime.timedelta(
+        seconds=token_json['expires_in'])
+    return token_json['access_token'], token_expiry
diff --git a/oauth2client/contrib/_win32_opener.py b/oauth2client/contrib/_win32_opener.py
new file mode 100644
index 0000000..34b4f48
--- /dev/null
+++ b/oauth2client/contrib/_win32_opener.py
@@ -0,0 +1,106 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import errno
+import time
+
+import pywintypes
+import win32con
+import win32file
+
+from oauth2client.contrib import locked_file
+
+
+class _Win32Opener(locked_file._Opener):
+    """Open, lock, and unlock a file using windows primitives."""
+
+    # Error #33:
+    #  'The process cannot access the file because another process'
+    FILE_IN_USE_ERROR = 33
+
+    # Error #158:
+    #  'The segment is already unlocked.'
+    FILE_ALREADY_UNLOCKED_ERROR = 158
+
+    def open_and_lock(self, timeout, delay):
+        """Open the file and lock it.
+
+        Args:
+            timeout: float, How long to try to lock for.
+            delay: float, How long to wait between retries
+
+        Raises:
+            AlreadyLockedException: if the lock is already acquired.
+            IOError: if the open fails.
+            CredentialsFileSymbolicLinkError: if the file is a symbolic
+                                              link.
+        """
+        if self._locked:
+            raise locked_file.AlreadyLockedException(
+                'File {0} is already locked'.format(self._filename))
+        start_time = time.time()
+
+        locked_file.validate_file(self._filename)
+        try:
+            self._fh = open(self._filename, self._mode)
+        except IOError as e:
+            # If we can't access with _mode, try _fallback_mode
+            # and don't lock.
+            if e.errno == errno.EACCES:
+                self._fh = open(self._filename, self._fallback_mode)
+                return
+
+        # We opened in _mode, try to lock the file.
+        while True:
+            try:
+                hfile = win32file._get_osfhandle(self._fh.fileno())
+                win32file.LockFileEx(
+                    hfile,
+                    (win32con.LOCKFILE_FAIL_IMMEDIATELY |
+                     win32con.LOCKFILE_EXCLUSIVE_LOCK), 0, -0x10000,
+                    pywintypes.OVERLAPPED())
+                self._locked = True
+                return
+            except pywintypes.error as e:
+                if timeout == 0:
+                    raise
+
+                # If the error is not that the file is already
+                # in use, raise.
+                if e[0] != _Win32Opener.FILE_IN_USE_ERROR:
+                    raise
+
+                # We could not acquire the lock. Try again.
+                if (time.time() - start_time) >= timeout:
+                    locked_file.logger.warn('Could not lock %s in %s seconds',
+                                            self._filename, timeout)
+                    if self._fh:
+                        self._fh.close()
+                    self._fh = open(self._filename, self._fallback_mode)
+                    return
+                time.sleep(delay)
+
+    def unlock_and_close(self):
+        """Close and unlock the file using the win32 primitive."""
+        if self._locked:
+            try:
+                hfile = win32file._get_osfhandle(self._fh.fileno())
+                win32file.UnlockFileEx(hfile, 0, -0x10000,
+                                       pywintypes.OVERLAPPED())
+            except pywintypes.error as e:
+                if e[0] != _Win32Opener.FILE_ALREADY_UNLOCKED_ERROR:
+                    raise
+        self._locked = False
+        if self._fh:
+            self._fh.close()
diff --git a/oauth2client/contrib/appengine.py b/oauth2client/contrib/appengine.py
new file mode 100644
index 0000000..661105e
--- /dev/null
+++ b/oauth2client/contrib/appengine.py
@@ -0,0 +1,913 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities for Google App Engine
+
+Utilities for making it easier to use OAuth 2.0 on Google App Engine.
+"""
+
+import cgi
+import json
+import logging
+import os
+import pickle
+import threading
+
+from google.appengine.api import app_identity
+from google.appengine.api import memcache
+from google.appengine.api import users
+from google.appengine.ext import db
+from google.appengine.ext.webapp.util import login_required
+import httplib2
+import webapp2 as webapp
+
+import oauth2client
+from oauth2client import client
+from oauth2client import clientsecrets
+from oauth2client import util
+from oauth2client.contrib import xsrfutil
+
+# This is a temporary fix for a Google internal issue.
+try:
+    from oauth2client.contrib import _appengine_ndb
+except ImportError:  # pragma: NO COVER
+    _appengine_ndb = None
+
+
+__author__ = 'jcgregorio@google.com (Joe Gregorio)'
+
+logger = logging.getLogger(__name__)
+
+OAUTH2CLIENT_NAMESPACE = 'oauth2client#ns'
+
+XSRF_MEMCACHE_ID = 'xsrf_secret_key'
+
+if _appengine_ndb is None:  # pragma: NO COVER
+    CredentialsNDBModel = None
+    CredentialsNDBProperty = None
+    FlowNDBProperty = None
+    _NDB_KEY = None
+    _NDB_MODEL = None
+    SiteXsrfSecretKeyNDB = None
+else:
+    CredentialsNDBModel = _appengine_ndb.CredentialsNDBModel
+    CredentialsNDBProperty = _appengine_ndb.CredentialsNDBProperty
+    FlowNDBProperty = _appengine_ndb.FlowNDBProperty
+    _NDB_KEY = _appengine_ndb.NDB_KEY
+    _NDB_MODEL = _appengine_ndb.NDB_MODEL
+    SiteXsrfSecretKeyNDB = _appengine_ndb.SiteXsrfSecretKeyNDB
+
+
+def _safe_html(s):
+    """Escape text to make it safe to display.
+
+    Args:
+        s: string, The text to escape.
+
+    Returns:
+        The escaped text as a string.
+    """
+    return cgi.escape(s, quote=1).replace("'", '&#39;')
+
+
+class SiteXsrfSecretKey(db.Model):
+    """Storage for the sites XSRF secret key.
+
+    There will only be one instance stored of this model, the one used for the
+    site.
+    """
+    secret = db.StringProperty()
+
+
+def _generate_new_xsrf_secret_key():
+    """Returns a random XSRF secret key."""
+    return os.urandom(16).encode("hex")
+
+
+def xsrf_secret_key():
+    """Return the secret key for use for XSRF protection.
+
+    If the Site entity does not have a secret key, this method will also create
+    one and persist it.
+
+    Returns:
+        The secret key.
+    """
+    secret = memcache.get(XSRF_MEMCACHE_ID, namespace=OAUTH2CLIENT_NAMESPACE)
+    if not secret:
+        # Load the one and only instance of SiteXsrfSecretKey.
+        model = SiteXsrfSecretKey.get_or_insert(key_name='site')
+        if not model.secret:
+            model.secret = _generate_new_xsrf_secret_key()
+            model.put()
+        secret = model.secret
+        memcache.add(XSRF_MEMCACHE_ID, secret,
+                     namespace=OAUTH2CLIENT_NAMESPACE)
+
+    return str(secret)
+
+
+class AppAssertionCredentials(client.AssertionCredentials):
+    """Credentials object for App Engine Assertion Grants
+
+    This object will allow an App Engine application to identify itself to
+    Google and other OAuth 2.0 servers that can verify assertions. It can be
+    used for the purpose of accessing data stored under an account assigned to
+    the App Engine application itself.
+
+    This credential does not require a flow to instantiate because it
+    represents a two legged flow, and therefore has all of the required
+    information to generate and refresh its own access tokens.
+    """
+
+    @util.positional(2)
+    def __init__(self, scope, **kwargs):
+        """Constructor for AppAssertionCredentials
+
+        Args:
+            scope: string or iterable of strings, scope(s) of the credentials
+                   being requested.
+            **kwargs: optional keyword args, including:
+            service_account_id: service account id of the application. If None
+                                or unspecified, the default service account for
+                                the app is used.
+        """
+        self.scope = util.scopes_to_string(scope)
+        self._kwargs = kwargs
+        self.service_account_id = kwargs.get('service_account_id', None)
+        self._service_account_email = None
+
+        # Assertion type is no longer used, but still in the
+        # parent class signature.
+        super(AppAssertionCredentials, self).__init__(None)
+
+    @classmethod
+    def from_json(cls, json_data):
+        data = json.loads(json_data)
+        return AppAssertionCredentials(data['scope'])
+
+    def _refresh(self, http_request):
+        """Refreshes the access_token.
+
+        Since the underlying App Engine app_identity implementation does its
+        own caching we can skip all the storage hoops and just to a refresh
+        using the API.
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make the
+                          refresh request.
+
+        Raises:
+            AccessTokenRefreshError: When the refresh fails.
+        """
+        try:
+            scopes = self.scope.split()
+            (token, _) = app_identity.get_access_token(
+                scopes, service_account_id=self.service_account_id)
+        except app_identity.Error as e:
+            raise client.AccessTokenRefreshError(str(e))
+        self.access_token = token
+
+    @property
+    def serialization_data(self):
+        raise NotImplementedError('Cannot serialize credentials '
+                                  'for Google App Engine.')
+
+    def create_scoped_required(self):
+        return not self.scope
+
+    def create_scoped(self, scopes):
+        return AppAssertionCredentials(scopes, **self._kwargs)
+
+    def sign_blob(self, blob):
+        """Cryptographically sign a blob (of bytes).
+
+        Implements abstract method
+        :meth:`oauth2client.client.AssertionCredentials.sign_blob`.
+
+        Args:
+            blob: bytes, Message to be signed.
+
+        Returns:
+            tuple, A pair of the private key ID used to sign the blob and
+            the signed contents.
+        """
+        return app_identity.sign_blob(blob)
+
+    @property
+    def service_account_email(self):
+        """Get the email for the current service account.
+
+        Returns:
+            string, The email associated with the Google App Engine
+            service account.
+        """
+        if self._service_account_email is None:
+            self._service_account_email = (
+                app_identity.get_service_account_name())
+        return self._service_account_email
+
+
+class FlowProperty(db.Property):
+    """App Engine datastore Property for Flow.
+
+    Utility property that allows easy storage and retrieval of an
+    oauth2client.Flow
+    """
+
+    # Tell what the user type is.
+    data_type = client.Flow
+
+    # For writing to datastore.
+    def get_value_for_datastore(self, model_instance):
+        flow = super(FlowProperty, self).get_value_for_datastore(
+            model_instance)
+        return db.Blob(pickle.dumps(flow))
+
+    # For reading from datastore.
+    def make_value_from_datastore(self, value):
+        if value is None:
+            return None
+        return pickle.loads(value)
+
+    def validate(self, value):
+        if value is not None and not isinstance(value, client.Flow):
+            raise db.BadValueError(
+                'Property {0} must be convertible '
+                'to a FlowThreeLegged instance ({1})'.format(self.name, value))
+        return super(FlowProperty, self).validate(value)
+
+    def empty(self, value):
+        return not value
+
+
+class CredentialsProperty(db.Property):
+    """App Engine datastore Property for Credentials.
+
+    Utility property that allows easy storage and retrieval of
+    oauth2client.Credentials
+    """
+
+    # Tell what the user type is.
+    data_type = client.Credentials
+
+    # For writing to datastore.
+    def get_value_for_datastore(self, model_instance):
+        logger.info("get: Got type " + str(type(model_instance)))
+        cred = super(CredentialsProperty, self).get_value_for_datastore(
+            model_instance)
+        if cred is None:
+            cred = ''
+        else:
+            cred = cred.to_json()
+        return db.Blob(cred)
+
+    # For reading from datastore.
+    def make_value_from_datastore(self, value):
+        logger.info("make: Got type " + str(type(value)))
+        if value is None:
+            return None
+        if len(value) == 0:
+            return None
+        try:
+            credentials = client.Credentials.new_from_json(value)
+        except ValueError:
+            credentials = None
+        return credentials
+
+    def validate(self, value):
+        value = super(CredentialsProperty, self).validate(value)
+        logger.info("validate: Got type " + str(type(value)))
+        if value is not None and not isinstance(value, client.Credentials):
+            raise db.BadValueError(
+                'Property {0} must be convertible '
+                'to a Credentials instance ({1})'.format(self.name, value))
+        return value
+
+
+class StorageByKeyName(client.Storage):
+    """Store and retrieve a credential to and from the App Engine datastore.
+
+    This Storage helper presumes the Credentials have been stored as a
+    CredentialsProperty or CredentialsNDBProperty on a datastore model class,
+    and that entities are stored by key_name.
+    """
+
+    @util.positional(4)
+    def __init__(self, model, key_name, property_name, cache=None, user=None):
+        """Constructor for Storage.
+
+        Args:
+            model: db.Model or ndb.Model, model class
+            key_name: string, key name for the entity that has the credentials
+            property_name: string, name of the property that is a
+                           CredentialsProperty or CredentialsNDBProperty.
+            cache: memcache, a write-through cache to put in front of the
+                   datastore. If the model you are using is an NDB model, using
+                   a cache will be redundant since the model uses an instance
+                   cache and memcache for you.
+            user: users.User object, optional. Can be used to grab user ID as a
+                  key_name if no key name is specified.
+        """
+        super(StorageByKeyName, self).__init__()
+
+        if key_name is None:
+            if user is None:
+                raise ValueError('StorageByKeyName called with no '
+                                 'key name or user.')
+            key_name = user.user_id()
+
+        self._model = model
+        self._key_name = key_name
+        self._property_name = property_name
+        self._cache = cache
+
+    def _is_ndb(self):
+        """Determine whether the model of the instance is an NDB model.
+
+        Returns:
+            Boolean indicating whether or not the model is an NDB or DB model.
+        """
+        # issubclass will fail if one of the arguments is not a class, only
+        # need worry about new-style classes since ndb and db models are
+        # new-style
+        if isinstance(self._model, type):
+            if _NDB_MODEL is not None and issubclass(self._model, _NDB_MODEL):
+                return True
+            elif issubclass(self._model, db.Model):
+                return False
+
+        raise TypeError(
+            'Model class not an NDB or DB model: {0}.'.format(self._model))
+
+    def _get_entity(self):
+        """Retrieve entity from datastore.
+
+        Uses a different model method for db or ndb models.
+
+        Returns:
+            Instance of the model corresponding to the current storage object
+            and stored using the key name of the storage object.
+        """
+        if self._is_ndb():
+            return self._model.get_by_id(self._key_name)
+        else:
+            return self._model.get_by_key_name(self._key_name)
+
+    def _delete_entity(self):
+        """Delete entity from datastore.
+
+        Attempts to delete using the key_name stored on the object, whether or
+        not the given key is in the datastore.
+        """
+        if self._is_ndb():
+            _NDB_KEY(self._model, self._key_name).delete()
+        else:
+            entity_key = db.Key.from_path(self._model.kind(), self._key_name)
+            db.delete(entity_key)
+
+    @db.non_transactional(allow_existing=True)
+    def locked_get(self):
+        """Retrieve Credential from datastore.
+
+        Returns:
+            oauth2client.Credentials
+        """
+        credentials = None
+        if self._cache:
+            json = self._cache.get(self._key_name)
+            if json:
+                credentials = client.Credentials.new_from_json(json)
+        if credentials is None:
+            entity = self._get_entity()
+            if entity is not None:
+                credentials = getattr(entity, self._property_name)
+                if self._cache:
+                    self._cache.set(self._key_name, credentials.to_json())
+
+        if credentials and hasattr(credentials, 'set_store'):
+            credentials.set_store(self)
+        return credentials
+
+    @db.non_transactional(allow_existing=True)
+    def locked_put(self, credentials):
+        """Write a Credentials to the datastore.
+
+        Args:
+            credentials: Credentials, the credentials to store.
+        """
+        entity = self._model.get_or_insert(self._key_name)
+        setattr(entity, self._property_name, credentials)
+        entity.put()
+        if self._cache:
+            self._cache.set(self._key_name, credentials.to_json())
+
+    @db.non_transactional(allow_existing=True)
+    def locked_delete(self):
+        """Delete Credential from datastore."""
+
+        if self._cache:
+            self._cache.delete(self._key_name)
+
+        self._delete_entity()
+
+
+class CredentialsModel(db.Model):
+    """Storage for OAuth 2.0 Credentials
+
+    Storage of the model is keyed by the user.user_id().
+    """
+    credentials = CredentialsProperty()
+
+
+def _build_state_value(request_handler, user):
+    """Composes the value for the 'state' parameter.
+
+    Packs the current request URI and an XSRF token into an opaque string that
+    can be passed to the authentication server via the 'state' parameter.
+
+    Args:
+        request_handler: webapp.RequestHandler, The request.
+        user: google.appengine.api.users.User, The current user.
+
+    Returns:
+        The state value as a string.
+    """
+    uri = request_handler.request.url
+    token = xsrfutil.generate_token(xsrf_secret_key(), user.user_id(),
+                                    action_id=str(uri))
+    return uri + ':' + token
+
+
+def _parse_state_value(state, user):
+    """Parse the value of the 'state' parameter.
+
+    Parses the value and validates the XSRF token in the state parameter.
+
+    Args:
+        state: string, The value of the state parameter.
+        user: google.appengine.api.users.User, The current user.
+
+    Returns:
+        The redirect URI, or None if XSRF token is not valid.
+    """
+    uri, token = state.rsplit(':', 1)
+    if xsrfutil.validate_token(xsrf_secret_key(), token, user.user_id(),
+                               action_id=uri):
+        return uri
+    else:
+        return None
+
+
+class OAuth2Decorator(object):
+    """Utility for making OAuth 2.0 easier.
+
+    Instantiate and then use with oauth_required or oauth_aware
+    as decorators on webapp.RequestHandler methods.
+
+    ::
+
+        decorator = OAuth2Decorator(
+            client_id='837...ent.com',
+            client_secret='Qh...wwI',
+            scope='https://www.googleapis.com/auth/plus')
+
+        class MainHandler(webapp.RequestHandler):
+            @decorator.oauth_required
+            def get(self):
+                http = decorator.http()
+                # http is authorized with the user's Credentials and can be
+                # used in API calls
+
+    """
+
+    def set_credentials(self, credentials):
+        self._tls.credentials = credentials
+
+    def get_credentials(self):
+        """A thread local Credentials object.
+
+        Returns:
+            A client.Credentials object, or None if credentials hasn't been set
+            in this thread yet, which may happen when calling has_credentials
+            inside oauth_aware.
+        """
+        return getattr(self._tls, 'credentials', None)
+
+    credentials = property(get_credentials, set_credentials)
+
+    def set_flow(self, flow):
+        self._tls.flow = flow
+
+    def get_flow(self):
+        """A thread local Flow object.
+
+        Returns:
+            A credentials.Flow object, or None if the flow hasn't been set in
+            this thread yet, which happens in _create_flow() since Flows are
+            created lazily.
+        """
+        return getattr(self._tls, 'flow', None)
+
+    flow = property(get_flow, set_flow)
+
+    @util.positional(4)
+    def __init__(self, client_id, client_secret, scope,
+                 auth_uri=oauth2client.GOOGLE_AUTH_URI,
+                 token_uri=oauth2client.GOOGLE_TOKEN_URI,
+                 revoke_uri=oauth2client.GOOGLE_REVOKE_URI,
+                 user_agent=None,
+                 message=None,
+                 callback_path='/oauth2callback',
+                 token_response_param=None,
+                 _storage_class=StorageByKeyName,
+                 _credentials_class=CredentialsModel,
+                 _credentials_property_name='credentials',
+                 **kwargs):
+        """Constructor for OAuth2Decorator
+
+        Args:
+            client_id: string, client identifier.
+            client_secret: string client secret.
+            scope: string or iterable of strings, scope(s) of the credentials
+                   being requested.
+            auth_uri: string, URI for authorization endpoint. For convenience
+                      defaults to Google's endpoints but any OAuth 2.0 provider
+                      can be used.
+            token_uri: string, URI for token endpoint. For convenience defaults
+                       to Google's endpoints but any OAuth 2.0 provider can be
+                       used.
+            revoke_uri: string, URI for revoke endpoint. For convenience
+                        defaults to Google's endpoints but any OAuth 2.0
+                        provider can be used.
+            user_agent: string, User agent of your application, default to
+                        None.
+            message: Message to display if there are problems with the
+                     OAuth 2.0 configuration. The message may contain HTML and
+                     will be presented on the web interface for any method that
+                     uses the decorator.
+            callback_path: string, The absolute path to use as the callback
+                           URI. Note that this must match up with the URI given
+                           when registering the application in the APIs
+                           Console.
+            token_response_param: string. If provided, the full JSON response
+                                  to the access token request will be encoded
+                                  and included in this query parameter in the
+                                  callback URI. This is useful with providers
+                                  (e.g. wordpress.com) that include extra
+                                  fields that the client may want.
+            _storage_class: "Protected" keyword argument not typically provided
+                            to this constructor. A storage class to aid in
+                            storing a Credentials object for a user in the
+                            datastore. Defaults to StorageByKeyName.
+            _credentials_class: "Protected" keyword argument not typically
+                                provided to this constructor. A db or ndb Model
+                                class to hold credentials. Defaults to
+                                CredentialsModel.
+            _credentials_property_name: "Protected" keyword argument not
+                                        typically provided to this constructor.
+                                        A string indicating the name of the
+                                        field on the _credentials_class where a
+                                        Credentials object will be stored.
+                                        Defaults to 'credentials'.
+            **kwargs: dict, Keyword arguments are passed along as kwargs to
+                      the OAuth2WebServerFlow constructor.
+        """
+        self._tls = threading.local()
+        self.flow = None
+        self.credentials = None
+        self._client_id = client_id
+        self._client_secret = client_secret
+        self._scope = util.scopes_to_string(scope)
+        self._auth_uri = auth_uri
+        self._token_uri = token_uri
+        self._revoke_uri = revoke_uri
+        self._user_agent = user_agent
+        self._kwargs = kwargs
+        self._message = message
+        self._in_error = False
+        self._callback_path = callback_path
+        self._token_response_param = token_response_param
+        self._storage_class = _storage_class
+        self._credentials_class = _credentials_class
+        self._credentials_property_name = _credentials_property_name
+
+    def _display_error_message(self, request_handler):
+        request_handler.response.out.write('<html><body>')
+        request_handler.response.out.write(_safe_html(self._message))
+        request_handler.response.out.write('</body></html>')
+
+    def oauth_required(self, method):
+        """Decorator that starts the OAuth 2.0 dance.
+
+        Starts the OAuth dance for the logged in user if they haven't already
+        granted access for this application.
+
+        Args:
+            method: callable, to be decorated method of a webapp.RequestHandler
+                    instance.
+        """
+
+        def check_oauth(request_handler, *args, **kwargs):
+            if self._in_error:
+                self._display_error_message(request_handler)
+                return
+
+            user = users.get_current_user()
+            # Don't use @login_decorator as this could be used in a
+            # POST request.
+            if not user:
+                request_handler.redirect(users.create_login_url(
+                    request_handler.request.uri))
+                return
+
+            self._create_flow(request_handler)
+
+            # Store the request URI in 'state' so we can use it later
+            self.flow.params['state'] = _build_state_value(
+                request_handler, user)
+            self.credentials = self._storage_class(
+                self._credentials_class, None,
+                self._credentials_property_name, user=user).get()
+
+            if not self.has_credentials():
+                return request_handler.redirect(self.authorize_url())
+            try:
+                resp = method(request_handler, *args, **kwargs)
+            except client.AccessTokenRefreshError:
+                return request_handler.redirect(self.authorize_url())
+            finally:
+                self.credentials = None
+            return resp
+
+        return check_oauth
+
+    def _create_flow(self, request_handler):
+        """Create the Flow object.
+
+        The Flow is calculated lazily since we don't know where this app is
+        running until it receives a request, at which point redirect_uri can be
+        calculated and then the Flow object can be constructed.
+
+        Args:
+            request_handler: webapp.RequestHandler, the request handler.
+        """
+        if self.flow is None:
+            redirect_uri = request_handler.request.relative_url(
+                self._callback_path)  # Usually /oauth2callback
+            self.flow = client.OAuth2WebServerFlow(
+                self._client_id, self._client_secret, self._scope,
+                redirect_uri=redirect_uri, user_agent=self._user_agent,
+                auth_uri=self._auth_uri, token_uri=self._token_uri,
+                revoke_uri=self._revoke_uri, **self._kwargs)
+
+    def oauth_aware(self, method):
+        """Decorator that sets up for OAuth 2.0 dance, but doesn't do it.
+
+        Does all the setup for the OAuth dance, but doesn't initiate it.
+        This decorator is useful if you want to create a page that knows
+        whether or not the user has granted access to this application.
+        From within a method decorated with @oauth_aware the has_credentials()
+        and authorize_url() methods can be called.
+
+        Args:
+            method: callable, to be decorated method of a webapp.RequestHandler
+                    instance.
+        """
+
+        def setup_oauth(request_handler, *args, **kwargs):
+            if self._in_error:
+                self._display_error_message(request_handler)
+                return
+
+            user = users.get_current_user()
+            # Don't use @login_decorator as this could be used in a
+            # POST request.
+            if not user:
+                request_handler.redirect(users.create_login_url(
+                    request_handler.request.uri))
+                return
+
+            self._create_flow(request_handler)
+
+            self.flow.params['state'] = _build_state_value(request_handler,
+                                                           user)
+            self.credentials = self._storage_class(
+                self._credentials_class, None,
+                self._credentials_property_name, user=user).get()
+            try:
+                resp = method(request_handler, *args, **kwargs)
+            finally:
+                self.credentials = None
+            return resp
+        return setup_oauth
+
+    def has_credentials(self):
+        """True if for the logged in user there are valid access Credentials.
+
+        Must only be called from with a webapp.RequestHandler subclassed method
+        that had been decorated with either @oauth_required or @oauth_aware.
+        """
+        return self.credentials is not None and not self.credentials.invalid
+
+    def authorize_url(self):
+        """Returns the URL to start the OAuth dance.
+
+        Must only be called from with a webapp.RequestHandler subclassed method
+        that had been decorated with either @oauth_required or @oauth_aware.
+        """
+        url = self.flow.step1_get_authorize_url()
+        return str(url)
+
+    def http(self, *args, **kwargs):
+        """Returns an authorized http instance.
+
+        Must only be called from within an @oauth_required decorated method, or
+        from within an @oauth_aware decorated method where has_credentials()
+        returns True.
+
+        Args:
+            *args: Positional arguments passed to httplib2.Http constructor.
+            **kwargs: Positional arguments passed to httplib2.Http constructor.
+        """
+        return self.credentials.authorize(httplib2.Http(*args, **kwargs))
+
+    @property
+    def callback_path(self):
+        """The absolute path where the callback will occur.
+
+        Note this is the absolute path, not the absolute URI, that will be
+        calculated by the decorator at runtime. See callback_handler() for how
+        this should be used.
+
+        Returns:
+            The callback path as a string.
+        """
+        return self._callback_path
+
+    def callback_handler(self):
+        """RequestHandler for the OAuth 2.0 redirect callback.
+
+        Usage::
+
+            app = webapp.WSGIApplication([
+                ('/index', MyIndexHandler),
+                ...,
+                (decorator.callback_path, decorator.callback_handler())
+            ])
+
+        Returns:
+            A webapp.RequestHandler that handles the redirect back from the
+            server during the OAuth 2.0 dance.
+        """
+        decorator = self
+
+        class OAuth2Handler(webapp.RequestHandler):
+            """Handler for the redirect_uri of the OAuth 2.0 dance."""
+
+            @login_required
+            def get(self):
+                error = self.request.get('error')
+                if error:
+                    errormsg = self.request.get('error_description', error)
+                    self.response.out.write(
+                        'The authorization request failed: {0}'.format(
+                            _safe_html(errormsg)))
+                else:
+                    user = users.get_current_user()
+                    decorator._create_flow(self)
+                    credentials = decorator.flow.step2_exchange(
+                        self.request.params)
+                    decorator._storage_class(
+                        decorator._credentials_class, None,
+                        decorator._credentials_property_name,
+                        user=user).put(credentials)
+                    redirect_uri = _parse_state_value(
+                        str(self.request.get('state')), user)
+                    if redirect_uri is None:
+                        self.response.out.write(
+                            'The authorization request failed')
+                        return
+
+                    if (decorator._token_response_param and
+                            credentials.token_response):
+                        resp_json = json.dumps(credentials.token_response)
+                        redirect_uri = util._add_query_parameter(
+                            redirect_uri, decorator._token_response_param,
+                            resp_json)
+
+                    self.redirect(redirect_uri)
+
+        return OAuth2Handler
+
+    def callback_application(self):
+        """WSGI application for handling the OAuth 2.0 redirect callback.
+
+        If you need finer grained control use `callback_handler` which returns
+        just the webapp.RequestHandler.
+
+        Returns:
+            A webapp.WSGIApplication that handles the redirect back from the
+            server during the OAuth 2.0 dance.
+        """
+        return webapp.WSGIApplication([
+            (self.callback_path, self.callback_handler())
+        ])
+
+
+class OAuth2DecoratorFromClientSecrets(OAuth2Decorator):
+    """An OAuth2Decorator that builds from a clientsecrets file.
+
+    Uses a clientsecrets file as the source for all the information when
+    constructing an OAuth2Decorator.
+
+    ::
+
+        decorator = OAuth2DecoratorFromClientSecrets(
+            os.path.join(os.path.dirname(__file__), 'client_secrets.json')
+            scope='https://www.googleapis.com/auth/plus')
+
+        class MainHandler(webapp.RequestHandler):
+            @decorator.oauth_required
+            def get(self):
+                http = decorator.http()
+                # http is authorized with the user's Credentials and can be
+                # used in API calls
+
+    """
+
+    @util.positional(3)
+    def __init__(self, filename, scope, message=None, cache=None, **kwargs):
+        """Constructor
+
+        Args:
+            filename: string, File name of client secrets.
+            scope: string or iterable of strings, scope(s) of the credentials
+                   being requested.
+            message: string, A friendly string to display to the user if the
+                     clientsecrets file is missing or invalid. The message may
+                     contain HTML and will be presented on the web interface
+                     for any method that uses the decorator.
+            cache: An optional cache service client that implements get() and
+                   set()
+            methods. See clientsecrets.loadfile() for details.
+            **kwargs: dict, Keyword arguments are passed along as kwargs to
+                      the OAuth2WebServerFlow constructor.
+        """
+        client_type, client_info = clientsecrets.loadfile(filename,
+                                                          cache=cache)
+        if client_type not in (clientsecrets.TYPE_WEB,
+                               clientsecrets.TYPE_INSTALLED):
+            raise clientsecrets.InvalidClientSecretsError(
+                "OAuth2Decorator doesn't support this OAuth 2.0 flow.")
+
+        constructor_kwargs = dict(kwargs)
+        constructor_kwargs.update({
+            'auth_uri': client_info['auth_uri'],
+            'token_uri': client_info['token_uri'],
+            'message': message,
+        })
+        revoke_uri = client_info.get('revoke_uri')
+        if revoke_uri is not None:
+            constructor_kwargs['revoke_uri'] = revoke_uri
+        super(OAuth2DecoratorFromClientSecrets, self).__init__(
+            client_info['client_id'], client_info['client_secret'],
+            scope, **constructor_kwargs)
+        if message is not None:
+            self._message = message
+        else:
+            self._message = 'Please configure your application for OAuth 2.0.'
+
+
+@util.positional(2)
+def oauth2decorator_from_clientsecrets(filename, scope,
+                                       message=None, cache=None):
+    """Creates an OAuth2Decorator populated from a clientsecrets file.
+
+    Args:
+        filename: string, File name of client secrets.
+        scope: string or list of strings, scope(s) of the credentials being
+               requested.
+        message: string, A friendly string to display to the user if the
+                 clientsecrets file is missing or invalid. The message may
+                 contain HTML and will be presented on the web interface for
+                 any method that uses the decorator.
+        cache: An optional cache service client that implements get() and set()
+               methods. See clientsecrets.loadfile() for details.
+
+    Returns: An OAuth2Decorator
+    """
+    return OAuth2DecoratorFromClientSecrets(filename, scope,
+                                            message=message, cache=cache)
diff --git a/oauth2client/contrib/devshell.py b/oauth2client/contrib/devshell.py
new file mode 100644
index 0000000..b8bb978
--- /dev/null
+++ b/oauth2client/contrib/devshell.py
@@ -0,0 +1,146 @@
+# Copyright 2015 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""OAuth 2.0 utitilies for Google Developer Shell environment."""
+
+import datetime
+import json
+import os
+import socket
+
+from oauth2client import _helpers
+from oauth2client import client
+
+DEVSHELL_ENV = 'DEVSHELL_CLIENT_PORT'
+
+
+class Error(Exception):
+    """Errors for this module."""
+    pass
+
+
+class CommunicationError(Error):
+    """Errors for communication with the Developer Shell server."""
+
+
+class NoDevshellServer(Error):
+    """Error when no Developer Shell server can be contacted."""
+
+# The request for credential information to the Developer Shell client socket
+# is always an empty PBLite-formatted JSON object, so just define it as a
+# constant.
+CREDENTIAL_INFO_REQUEST_JSON = '[]'
+
+
+class CredentialInfoResponse(object):
+    """Credential information response from Developer Shell server.
+
+    The credential information response from Developer Shell socket is a
+    PBLite-formatted JSON array with fields encoded by their index in the
+    array:
+
+    * Index 0 - user email
+    * Index 1 - default project ID. None if the project context is not known.
+    * Index 2 - OAuth2 access token. None if there is no valid auth context.
+    * Index 3 - Seconds until the access token expires. None if not present.
+    """
+
+    def __init__(self, json_string):
+        """Initialize the response data from JSON PBLite array."""
+        pbl = json.loads(json_string)
+        if not isinstance(pbl, list):
+            raise ValueError('Not a list: ' + str(pbl))
+        pbl_len = len(pbl)
+        self.user_email = pbl[0] if pbl_len > 0 else None
+        self.project_id = pbl[1] if pbl_len > 1 else None
+        self.access_token = pbl[2] if pbl_len > 2 else None
+        self.expires_in = pbl[3] if pbl_len > 3 else None
+
+
+def _SendRecv():
+    """Communicate with the Developer Shell server socket."""
+
+    port = int(os.getenv(DEVSHELL_ENV, 0))
+    if port == 0:
+        raise NoDevshellServer()
+
+    sock = socket.socket()
+    sock.connect(('localhost', port))
+
+    data = CREDENTIAL_INFO_REQUEST_JSON
+    msg = '{0}\n{1}'.format(len(data), data)
+    sock.sendall(_helpers._to_bytes(msg, encoding='utf-8'))
+
+    header = sock.recv(6).decode()
+    if '\n' not in header:
+        raise CommunicationError('saw no newline in the first 6 bytes')
+    len_str, json_str = header.split('\n', 1)
+    to_read = int(len_str) - len(json_str)
+    if to_read > 0:
+        json_str += sock.recv(to_read, socket.MSG_WAITALL).decode()
+
+    return CredentialInfoResponse(json_str)
+
+
+class DevshellCredentials(client.GoogleCredentials):
+    """Credentials object for Google Developer Shell environment.
+
+    This object will allow a Google Developer Shell session to identify its
+    user to Google and other OAuth 2.0 servers that can verify assertions. It
+    can be used for the purpose of accessing data stored under the user
+    account.
+
+    This credential does not require a flow to instantiate because it
+    represents a two legged flow, and therefore has all of the required
+    information to generate and refresh its own access tokens.
+    """
+
+    def __init__(self, user_agent=None):
+        super(DevshellCredentials, self).__init__(
+            None,  # access_token, initialized below
+            None,  # client_id
+            None,  # client_secret
+            None,  # refresh_token
+            None,  # token_expiry
+            None,  # token_uri
+            user_agent)
+        self._refresh(None)
+
+    def _refresh(self, http_request):
+        self.devshell_response = _SendRecv()
+        self.access_token = self.devshell_response.access_token
+        expires_in = self.devshell_response.expires_in
+        if expires_in is not None:
+            delta = datetime.timedelta(seconds=expires_in)
+            self.token_expiry = client._UTCNOW() + delta
+        else:
+            self.token_expiry = None
+
+    @property
+    def user_email(self):
+        return self.devshell_response.user_email
+
+    @property
+    def project_id(self):
+        return self.devshell_response.project_id
+
+    @classmethod
+    def from_json(cls, json_data):
+        raise NotImplementedError(
+            'Cannot load Developer Shell credentials from JSON.')
+
+    @property
+    def serialization_data(self):
+        raise NotImplementedError(
+            'Cannot serialize Developer Shell credentials.')
diff --git a/oauth2client/contrib/dictionary_storage.py b/oauth2client/contrib/dictionary_storage.py
new file mode 100644
index 0000000..6ee333f
--- /dev/null
+++ b/oauth2client/contrib/dictionary_storage.py
@@ -0,0 +1,65 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Dictionary storage for OAuth2 Credentials."""
+
+from oauth2client import client
+
+
+class DictionaryStorage(client.Storage):
+    """Store and retrieve credentials to and from a dictionary-like object.
+
+    Args:
+        dictionary: A dictionary or dictionary-like object.
+        key: A string or other hashable. The credentials will be stored in
+             ``dictionary[key]``.
+        lock: An optional threading.Lock-like object. The lock will be
+              acquired before anything is written or read from the
+              dictionary.
+    """
+
+    def __init__(self, dictionary, key, lock=None):
+        """Construct a DictionaryStorage instance."""
+        super(DictionaryStorage, self).__init__(lock=lock)
+        self._dictionary = dictionary
+        self._key = key
+
+    def locked_get(self):
+        """Retrieve the credentials from the dictionary, if they exist.
+
+        Returns: A :class:`oauth2client.client.OAuth2Credentials` instance.
+        """
+        serialized = self._dictionary.get(self._key)
+
+        if serialized is None:
+            return None
+
+        credentials = client.OAuth2Credentials.from_json(serialized)
+        credentials.set_store(self)
+
+        return credentials
+
+    def locked_put(self, credentials):
+        """Save the credentials to the dictionary.
+
+        Args:
+            credentials: A :class:`oauth2client.client.OAuth2Credentials`
+                         instance.
+        """
+        serialized = credentials.to_json()
+        self._dictionary[self._key] = serialized
+
+    def locked_delete(self):
+        """Remove the credentials from the dictionary, if they exist."""
+        self._dictionary.pop(self._key, None)
diff --git a/oauth2client/contrib/django_util/__init__.py b/oauth2client/contrib/django_util/__init__.py
new file mode 100644
index 0000000..5449e32
--- /dev/null
+++ b/oauth2client/contrib/django_util/__init__.py
@@ -0,0 +1,477 @@
+# Copyright 2015 Google Inc.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities for the Django web framework.
+
+Provides Django views and helpers the make using the OAuth2 web server
+flow easier. It includes an ``oauth_required`` decorator to automatically
+ensure that user credentials are available, and an ``oauth_enabled`` decorator
+to check if the user has authorized, and helper shortcuts to create the
+authorization URL otherwise.
+
+There are two basic use cases supported. The first is using Google OAuth as the
+primary form of authentication, which is the simpler approach recommended
+for applications without their own user system.
+
+The second use case is adding Google OAuth credentials to an
+existing Django model containing a Django user field. Most of the
+configuration is the same, except for `GOOGLE_OAUTH_MODEL_STORAGE` in
+settings.py. See "Adding Credentials To An Existing Django User System" for
+usage differences.
+
+Only Django versions 1.8+ are supported.
+
+Configuration
+===============
+
+To configure, you'll need a set of OAuth2 web application credentials from
+`Google Developer's Console <https://console.developers.google.com/project/_/apiui/credential>`.
+
+Add the helper to your INSTALLED_APPS:
+
+.. code-block:: python
+   :caption: settings.py
+   :name: installed_apps
+
+    INSTALLED_APPS = (
+        # other apps
+        "django.contrib.sessions.middleware"
+        "oauth2client.contrib.django_util"
+    )
+
+This helper also requires the Django Session Middleware, so
+``django.contrib.sessions.middleware`` should be in INSTALLED_APPS as well.
+
+Add the client secrets created earlier to the settings. You can either
+specify the path to the credentials file in JSON format
+
+.. code-block:: python
+   :caption:  settings.py
+   :name: secrets_file
+
+   GOOGLE_OAUTH2_CLIENT_SECRETS_JSON=/path/to/client-secret.json
+
+Or, directly configure the client Id and client secret.
+
+
+.. code-block:: python
+   :caption: settings.py
+   :name: secrets_config
+
+   GOOGLE_OAUTH2_CLIENT_ID=client-id-field
+   GOOGLE_OAUTH2_CLIENT_SECRET=client-secret-field
+
+By default, the default scopes for the required decorator only contains the
+``email`` scopes. You can change that default in the settings.
+
+.. code-block:: python
+   :caption: settings.py
+   :name: scopes
+
+   GOOGLE_OAUTH2_SCOPES = ('email', 'https://www.googleapis.com/auth/calendar',)
+
+By default, the decorators will add an `oauth` object to the Django request
+object, and include all of its state and helpers inside that object. If the
+`oauth` name conflicts with another usage, it can be changed
+
+.. code-block:: python
+   :caption: settings.py
+   :name: request_prefix
+
+   # changes request.oauth to request.google_oauth
+   GOOGLE_OAUTH2_REQUEST_ATTRIBUTE = 'google_oauth'
+
+Add the oauth2 routes to your application's urls.py urlpatterns.
+
+.. code-block:: python
+   :caption: urls.py
+   :name: urls
+
+   from oauth2client.contrib.django_util.site import urls as oauth2_urls
+
+   urlpatterns += [url(r'^oauth2/', include(oauth2_urls))]
+
+To require OAuth2 credentials for a view, use the `oauth2_required` decorator.
+This creates a credentials object with an id_token, and allows you to create
+an `http` object to build service clients with. These are all attached to the
+request.oauth
+
+.. code-block:: python
+   :caption: views.py
+   :name: views_required
+
+   from oauth2client.contrib.django_util.decorators import oauth_required
+
+   @oauth_required
+   def requires_default_scopes(request):
+      email = request.oauth.credentials.id_token['email']
+      service = build(serviceName='calendar', version='v3',
+                    http=request.oauth.http,
+                   developerKey=API_KEY)
+      events = service.events().list(calendarId='primary').execute()['items']
+      return HttpResponse("email: {0} , calendar: {1}".format(
+                           email,str(events)))
+      return HttpResponse(
+          "email: {0} , calendar: {1}".format(email, str(events)))
+
+To make OAuth2 optional and provide an authorization link in your own views.
+
+.. code-block:: python
+   :caption: views.py
+   :name: views_enabled2
+
+   from oauth2client.contrib.django_util.decorators import oauth_enabled
+
+   @oauth_enabled
+   def optional_oauth2(request):
+       if request.oauth.has_credentials():
+           # this could be passed into a view
+           # request.oauth.http is also initialized
+           return HttpResponse("User email: {0}".format(
+               request.oauth.credentials.id_token['email']))
+       else:
+           return HttpResponse(
+               'Here is an OAuth Authorize link: <a href="{0}">Authorize'
+               '</a>'.format(request.oauth.get_authorize_redirect()))
+
+If a view needs a scope not included in the default scopes specified in
+the settings, you can use [incremental auth](https://developers.google.com/identity/sign-in/web/incremental-auth)
+and specify additional scopes in the decorator arguments.
+
+.. code-block:: python
+   :caption: views.py
+   :name: views_required_additional_scopes
+
+   @oauth_enabled(scopes=['https://www.googleapis.com/auth/drive'])
+   def drive_required(request):
+       if request.oauth.has_credentials():
+           service = build(serviceName='drive', version='v2',
+                http=request.oauth.http,
+                developerKey=API_KEY)
+           events = service.files().list().execute()['items']
+           return HttpResponse(str(events))
+       else:
+           return HttpResponse(
+               'Here is an OAuth Authorize link: <a href="{0}">Authorize'
+               '</a>'.format(request.oauth.get_authorize_redirect()))
+
+
+To provide a callback on authorization being completed, use the
+oauth2_authorized signal:
+
+.. code-block:: python
+   :caption: views.py
+   :name: signals
+
+   from oauth2client.contrib.django_util.signals import oauth2_authorized
+
+   def test_callback(sender, request, credentials, **kwargs):
+       print("Authorization Signal Received {0}".format(
+               credentials.id_token['email']))
+
+   oauth2_authorized.connect(test_callback)
+
+Adding Credentials To An Existing Django User System
+=====================================================
+
+As an alternative to storing the credentials in the session, the helper
+can be configured to store the fields on a Django model. This might be useful
+if you need to use the credentials outside the context of a user request. It
+also prevents the need for a logged in user to repeat the OAuth flow when
+starting a new session.
+
+To use, change ``settings.py``
+
+.. code-block:: python
+   :caption:  settings.py
+   :name: storage_model_config
+
+   GOOGLE_OAUTH2_STORAGE_MODEL = {
+       'model': 'path.to.model.MyModel',
+       'user_property': 'user_id',
+       'credentials_property': 'credential'
+    }
+
+Where ``path.to.model`` class is the fully qualified name of a
+``django.db.model`` class containing a ``django.contrib.auth.models.User``
+field with the name specified by `user_property` and a
+:class:`oauth2client.contrib.django_util.models.CredentialsField` with the name
+specified by `credentials_property`. For the sample configuration given,
+our model would look like
+
+.. code-block:: python
+   :caption: models.py
+   :name: storage_model_model
+
+   from django.contrib.auth.models import User
+   from oauth2client.contrib.django_util.models import CredentialsField
+
+   class MyModel(models.Model):
+       #  ... other fields here ...
+       user = models.OneToOneField(User)
+       credential = CredentialsField()
+"""
+
+import importlib
+
+import django.conf
+from django.core import exceptions
+from django.core import urlresolvers
+import httplib2
+from six.moves.urllib import parse
+
+from oauth2client import clientsecrets
+from oauth2client.contrib import dictionary_storage
+from oauth2client.contrib.django_util import storage
+
+GOOGLE_OAUTH2_DEFAULT_SCOPES = ('email',)
+GOOGLE_OAUTH2_REQUEST_ATTRIBUTE = 'oauth'
+
+
+def _load_client_secrets(filename):
+    """Loads client secrets from the given filename.
+
+    Args:
+        filename: The name of the file containing the JSON secret key.
+
+    Returns:
+        A 2-tuple, the first item containing the client id, and the second
+        item containing a client secret.
+    """
+    client_type, client_info = clientsecrets.loadfile(filename)
+
+    if client_type != clientsecrets.TYPE_WEB:
+        raise ValueError(
+            'The flow specified in {} is not supported, only the WEB flow '
+            'type  is supported.'.format(client_type))
+    return client_info['client_id'], client_info['client_secret']
+
+
+def _get_oauth2_client_id_and_secret(settings_instance):
+    """Initializes client id and client secret based on the settings.
+
+    Args:
+        settings_instance: An instance of ``django.conf.settings``.
+
+    Returns:
+        A 2-tuple, the first item is the client id and the second
+         item is the client secret.
+    """
+    secret_json = getattr(settings_instance,
+                          'GOOGLE_OAUTH2_CLIENT_SECRETS_JSON', None)
+    if secret_json is not None:
+        return _load_client_secrets(secret_json)
+    else:
+        client_id = getattr(settings_instance, "GOOGLE_OAUTH2_CLIENT_ID",
+                            None)
+        client_secret = getattr(settings_instance,
+                                "GOOGLE_OAUTH2_CLIENT_SECRET", None)
+        if client_id is not None and client_secret is not None:
+            return client_id, client_secret
+        else:
+            raise exceptions.ImproperlyConfigured(
+                "Must specify either GOOGLE_OAUTH2_CLIENT_SECRETS_JSON, or "
+                "both GOOGLE_OAUTH2_CLIENT_ID and "
+                "GOOGLE_OAUTH2_CLIENT_SECRET in settings.py")
+
+
+def _get_storage_model():
+    """This configures whether the credentials will be stored in the session
+    or the Django ORM based on the settings. By default, the credentials
+    will be stored in the session, unless `GOOGLE_OAUTH2_STORAGE_MODEL`
+    is found in the settings. Usually, the ORM storage is used to integrate
+    credentials into an existing Django user system.
+
+    Returns:
+        A tuple containing three strings, or None. If
+        ``GOOGLE_OAUTH2_STORAGE_MODEL`` is configured, the tuple
+        will contain the fully qualifed path of the `django.db.model`,
+        the name of the ``django.contrib.auth.models.User`` field on the
+        model, and the name of the
+        :class:`oauth2client.contrib.django_util.models.CredentialsField`
+        field on the model. If Django ORM storage is not configured,
+        this function returns None.
+    """
+    storage_model_settings = getattr(django.conf.settings,
+                                     'GOOGLE_OAUTH2_STORAGE_MODEL', None)
+    if storage_model_settings is not None:
+        return (storage_model_settings['model'],
+                storage_model_settings['user_property'],
+                storage_model_settings['credentials_property'])
+    else:
+        return None, None, None
+
+
+class OAuth2Settings(object):
+    """Initializes Django OAuth2 Helper Settings
+
+    This class loads the OAuth2 Settings from the Django settings, and then
+    provides those settings as attributes to the rest of the views and
+    decorators in the module.
+
+    Attributes:
+      scopes: A list of OAuth2 scopes that the decorators and views will use
+              as defaults.
+      request_prefix: The name of the attribute that the decorators use to
+                    attach the UserOAuth2 object to the Django request object.
+      client_id: The OAuth2 Client ID.
+      client_secret: The OAuth2 Client Secret.
+    """
+
+    def __init__(self, settings_instance):
+        self.scopes = getattr(settings_instance, 'GOOGLE_OAUTH2_SCOPES',
+                              GOOGLE_OAUTH2_DEFAULT_SCOPES)
+        self.request_prefix = getattr(settings_instance,
+                                      'GOOGLE_OAUTH2_REQUEST_ATTRIBUTE',
+                                      GOOGLE_OAUTH2_REQUEST_ATTRIBUTE)
+        self.client_id, self.client_secret = \
+            _get_oauth2_client_id_and_secret(settings_instance)
+
+        if ('django.contrib.sessions.middleware.SessionMiddleware'
+           not in settings_instance.MIDDLEWARE_CLASSES):
+            raise exceptions.ImproperlyConfigured(
+                  'The Google OAuth2 Helper requires session middleware to '
+                  'be installed. Edit your MIDDLEWARE_CLASSES setting'
+                  ' to include \'django.contrib.sessions.middleware.'
+                  'SessionMiddleware\'.')
+        (self.storage_model, self.storage_model_user_property,
+         self.storage_model_credentials_property) = _get_storage_model()
+
+
+oauth2_settings = OAuth2Settings(django.conf.settings)
+
+_CREDENTIALS_KEY = 'google_oauth2_credentials'
+
+
+def get_storage(request):
+    """ Gets a Credentials storage object provided by the Django OAuth2 Helper
+    object.
+
+    Args:
+        request: Reference to the current request object.
+
+    Returns:
+       An :class:`oauth2.client.Storage` object.
+    """
+    storage_model = oauth2_settings.storage_model
+    user_property = oauth2_settings.storage_model_user_property
+    credentials_property = oauth2_settings.storage_model_credentials_property
+
+    if storage_model:
+        module_name, class_name = storage_model.rsplit('.', 1)
+        module = importlib.import_module(module_name)
+        storage_model_class = getattr(module, class_name)
+        return storage.DjangoORMStorage(storage_model_class,
+                                        user_property,
+                                        request.user,
+                                        credentials_property)
+    else:
+        # use session
+        return dictionary_storage.DictionaryStorage(
+            request.session, key=_CREDENTIALS_KEY)
+
+
+def _redirect_with_params(url_name, *args, **kwargs):
+    """Helper method to create a redirect response with URL params.
+
+    This builds a redirect string that converts kwargs into a
+    query string.
+
+    Args:
+        url_name: The name of the url to redirect to.
+        kwargs: the query string param and their values to build.
+
+    Returns:
+        A properly formatted redirect string.
+    """
+    url = urlresolvers.reverse(url_name, args=args)
+    params = parse.urlencode(kwargs, True)
+    return "{0}?{1}".format(url, params)
+
+
+def _credentials_from_request(request):
+    """Gets the authorized credentials for this flow, if they exist."""
+    # ORM storage requires a logged in user
+    if (oauth2_settings.storage_model is None or
+            request.user.is_authenticated()):
+        return get_storage(request).get()
+    else:
+        return None
+
+
+class UserOAuth2(object):
+    """Class to create oauth2 objects on Django request objects containing
+    credentials and helper methods.
+    """
+
+    def __init__(self, request, scopes=None, return_url=None):
+        """Initialize the Oauth2 Object.
+
+        Args:
+            request: Django request object.
+            scopes: Scopes desired for this OAuth2 flow.
+            return_url: The url to return to after the OAuth flow is complete,
+                 defaults to the request's current URL path.
+        """
+        self.request = request
+        self.return_url = return_url or request.get_full_path()
+        if scopes:
+            self._scopes = set(oauth2_settings.scopes) | set(scopes)
+        else:
+            self._scopes = set(oauth2_settings.scopes)
+
+    def get_authorize_redirect(self):
+        """Creates a URl to start the OAuth2 authorization flow."""
+        get_params = {
+            'return_url': self.return_url,
+            'scopes': self._get_scopes()
+        }
+
+        return _redirect_with_params('google_oauth:authorize', **get_params)
+
+    def has_credentials(self):
+        """Returns True if there are valid credentials for the current user
+        and required scopes."""
+        credentials = _credentials_from_request(self.request)
+        return (credentials and not credentials.invalid and
+                credentials.has_scopes(self._get_scopes()))
+
+    def _get_scopes(self):
+        """Returns the scopes associated with this object, kept up to
+         date for incremental auth."""
+        if _credentials_from_request(self.request):
+            return (self._scopes |
+                    _credentials_from_request(self.request).scopes)
+        else:
+            return self._scopes
+
+    @property
+    def scopes(self):
+        """Returns the scopes associated with this OAuth2 object."""
+        # make sure previously requested custom scopes are maintained
+        # in future authorizations
+        return self._get_scopes()
+
+    @property
+    def credentials(self):
+        """Gets the authorized credentials for this flow, if they exist."""
+        return _credentials_from_request(self.request)
+
+    @property
+    def http(self):
+        """Helper method to create an HTTP client authorized with OAuth2
+        credentials."""
+        if self.has_credentials():
+            return self.credentials.authorize(httplib2.Http())
+        return None
diff --git a/oauth2client/contrib/django_util/apps.py b/oauth2client/contrib/django_util/apps.py
new file mode 100644
index 0000000..86676b9
--- /dev/null
+++ b/oauth2client/contrib/django_util/apps.py
@@ -0,0 +1,32 @@
+# Copyright 2015 Google Inc.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Application Config For Django OAuth2 Helper.
+
+Django 1.7+ provides an
+[applications](https://docs.djangoproject.com/en/1.8/ref/applications/)
+API so that Django projects can introspect on installed applications using a
+stable API. This module exists to follow that convention.
+"""
+
+import sys
+
+# Django 1.7+ only supports Python 2.7+
+if sys.hexversion >= 0x02070000:  # pragma: NO COVER
+    from django.apps import AppConfig
+
+    class GoogleOAuth2HelperConfig(AppConfig):
+        """ App Config for Django Helper"""
+        name = 'oauth2client.django_util'
+        verbose_name = "Google OAuth2 Django Helper"
diff --git a/oauth2client/contrib/django_util/decorators.py b/oauth2client/contrib/django_util/decorators.py
new file mode 100644
index 0000000..e62e171
--- /dev/null
+++ b/oauth2client/contrib/django_util/decorators.py
@@ -0,0 +1,145 @@
+# Copyright 2015 Google Inc.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Decorators for Django OAuth2 Flow.
+
+Contains two decorators, ``oauth_required`` and ``oauth_enabled``.
+
+``oauth_required`` will ensure that a user has an oauth object containing
+credentials associated with the request, and if not, redirect to the
+authorization flow.
+
+``oauth_enabled`` will attach the oauth2 object containing credentials if it
+exists. If it doesn't, the view will still render, but helper methods will be
+attached to start the oauth2 flow.
+"""
+
+from django import shortcuts
+import django.conf
+from six import wraps
+from six.moves.urllib import parse
+
+from oauth2client.contrib import django_util
+
+
+def oauth_required(decorated_function=None, scopes=None, **decorator_kwargs):
+    """ Decorator to require OAuth2 credentials for a view.
+
+
+    .. code-block:: python
+       :caption: views.py
+       :name: views_required_2
+
+
+       from oauth2client.django_util.decorators import oauth_required
+
+       @oauth_required
+       def requires_default_scopes(request):
+          email = request.credentials.id_token['email']
+          service = build(serviceName='calendar', version='v3',
+                       http=request.oauth.http,
+                       developerKey=API_KEY)
+          events = service.events().list(
+                                    calendarId='primary').execute()['items']
+          return HttpResponse(
+              "email: {0}, calendar: {1}".format(email, str(events)))
+
+    Args:
+        decorated_function: View function to decorate, must have the Django
+           request object as the first argument.
+        scopes: Scopes to require, will default.
+        decorator_kwargs: Can include ``return_url`` to specify the URL to
+           return to after OAuth2 authorization is complete.
+
+    Returns:
+        An OAuth2 Authorize view if credentials are not found or if the
+        credentials are missing the required scopes. Otherwise,
+        the decorated view.
+    """
+    def curry_wrapper(wrapped_function):
+        @wraps(wrapped_function)
+        def required_wrapper(request, *args, **kwargs):
+            if not (django_util.oauth2_settings.storage_model is None or
+                    request.user.is_authenticated()):
+                redirect_str = '{0}?next={1}'.format(
+                    django.conf.settings.LOGIN_URL,
+                    parse.quote(request.path))
+                return shortcuts.redirect(redirect_str)
+
+            return_url = decorator_kwargs.pop('return_url',
+                                              request.get_full_path())
+            user_oauth = django_util.UserOAuth2(request, scopes, return_url)
+            if not user_oauth.has_credentials():
+                return shortcuts.redirect(user_oauth.get_authorize_redirect())
+            setattr(request, django_util.oauth2_settings.request_prefix,
+                    user_oauth)
+            return wrapped_function(request, *args, **kwargs)
+
+        return required_wrapper
+
+    if decorated_function:
+        return curry_wrapper(decorated_function)
+    else:
+        return curry_wrapper
+
+
+def oauth_enabled(decorated_function=None, scopes=None, **decorator_kwargs):
+    """ Decorator to enable OAuth Credentials if authorized, and setup
+    the oauth object on the request object to provide helper functions
+    to start the flow otherwise.
+
+    .. code-block:: python
+       :caption: views.py
+       :name: views_enabled3
+
+       from oauth2client.django_util.decorators import oauth_enabled
+
+       @oauth_enabled
+       def optional_oauth2(request):
+           if request.oauth.has_credentials():
+               # this could be passed into a view
+               # request.oauth.http is also initialized
+               return HttpResponse("User email: {0}".format(
+                                   request.oauth.credentials.id_token['email'])
+           else:
+               return HttpResponse('Here is an OAuth Authorize link:
+               <a href="{0}">Authorize</a>'.format(
+                   request.oauth.get_authorize_redirect()))
+
+
+    Args:
+        decorated_function: View function to decorate.
+        scopes: Scopes to require, will default.
+        decorator_kwargs: Can include ``return_url`` to specify the URL to
+           return to after OAuth2 authorization is complete.
+
+    Returns:
+         The decorated view function.
+    """
+    def curry_wrapper(wrapped_function):
+        @wraps(wrapped_function)
+        def enabled_wrapper(request, *args, **kwargs):
+            return_url = decorator_kwargs.pop('return_url',
+                                              request.get_full_path())
+            user_oauth = django_util.UserOAuth2(request, scopes, return_url)
+            setattr(request, django_util.oauth2_settings.request_prefix,
+                    user_oauth)
+            return wrapped_function(request, *args, **kwargs)
+
+        return enabled_wrapper
+
+    if decorated_function:
+        return curry_wrapper(decorated_function)
+    else:
+        return curry_wrapper
diff --git a/oauth2client/contrib/django_util/models.py b/oauth2client/contrib/django_util/models.py
new file mode 100644
index 0000000..87e1da7
--- /dev/null
+++ b/oauth2client/contrib/django_util/models.py
@@ -0,0 +1,75 @@
+# Copyright 2016 Google Inc.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Contains classes used for the Django ORM storage."""
+
+import base64
+import pickle
+
+from django.db import models
+from django.utils import encoding
+
+import oauth2client
+
+
+class CredentialsField(models.Field):
+    """Django ORM field for storing OAuth2 Credentials."""
+
+    def __init__(self, *args, **kwargs):
+        if 'null' not in kwargs:
+            kwargs['null'] = True
+        super(CredentialsField, self).__init__(*args, **kwargs)
+
+    def get_internal_type(self):
+        return 'BinaryField'
+
+    def from_db_value(self, value, expression, connection, context):
+        """Overrides ``models.Field`` method. This converts the value
+        returned from the database to an instance of this class.
+        """
+        return self.to_python(value)
+
+    def to_python(self, value):
+        """Overrides ``models.Field`` method. This is used to convert
+        bytes (from serialization etc) to an instance of this class"""
+        if value is None:
+            return None
+        elif isinstance(value, oauth2client.client.Credentials):
+            return value
+        else:
+            return pickle.loads(base64.b64decode(encoding.smart_bytes(value)))
+
+    def get_prep_value(self, value):
+        """Overrides ``models.Field`` method. This is used to convert
+        the value from an instances of this class to bytes that can be
+        inserted into the database.
+        """
+        if value is None:
+            return None
+        else:
+            return encoding.smart_text(base64.b64encode(pickle.dumps(value)))
+
+    def value_to_string(self, obj):
+        """Convert the field value from the provided model to a string.
+
+        Used during model serialization.
+
+        Args:
+            obj: db.Model, model object
+
+        Returns:
+            string, the serialized field value
+        """
+        value = self._get_val_from_obj(obj)
+        return self.get_prep_value(value)
diff --git a/oauth2client/contrib/django_util/signals.py b/oauth2client/contrib/django_util/signals.py
new file mode 100644
index 0000000..e9356b4
--- /dev/null
+++ b/oauth2client/contrib/django_util/signals.py
@@ -0,0 +1,28 @@
+# Copyright 2015 Google Inc.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Signals for Google OAuth2 Helper.
+
+This module contains signals for Google OAuth2 Helper. Currently it only
+contains one, which fires when an OAuth2 authorization flow has completed.
+"""
+
+import django.dispatch
+
+"""Signal that fires when  OAuth2 Flow has completed.
+It passes the Django request object and the OAuth2 credentials object to the
+ receiver.
+"""
+oauth2_authorized = django.dispatch.Signal(
+    providing_args=["request", "credentials"])
diff --git a/oauth2client/contrib/django_util/site.py b/oauth2client/contrib/django_util/site.py
new file mode 100644
index 0000000..631f79b
--- /dev/null
+++ b/oauth2client/contrib/django_util/site.py
@@ -0,0 +1,26 @@
+# Copyright 2015 Google Inc.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Contains Django URL patterns used for OAuth2 flow."""
+
+from django.conf import urls
+
+from oauth2client.contrib.django_util import views
+
+urlpatterns = [
+    urls.url(r'oauth2callback/', views.oauth2_callback, name="callback"),
+    urls.url(r'oauth2authorize/', views.oauth2_authorize, name="authorize")
+]
+
+urls = (urlpatterns, "google_oauth", "google_oauth")
diff --git a/oauth2client/contrib/django_util/storage.py b/oauth2client/contrib/django_util/storage.py
new file mode 100644
index 0000000..5682919
--- /dev/null
+++ b/oauth2client/contrib/django_util/storage.py
@@ -0,0 +1,81 @@
+# Copyright 2015 Google Inc.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Contains a storage module that stores credentials using the Django ORM."""
+
+from oauth2client import client
+
+
+class DjangoORMStorage(client.Storage):
+    """Store and retrieve a single credential to and from the Django datastore.
+
+    This Storage helper presumes the Credentials
+    have been stored as a CredentialsField
+    on a db model class.
+    """
+
+    def __init__(self, model_class, key_name, key_value, property_name):
+        """Constructor for Storage.
+
+        Args:
+            model: string, fully qualified name of db.Model model class.
+            key_name: string, key name for the entity that has the credentials
+            key_value: string, key value for the entity that has the
+               credentials.
+            property_name: string, name of the property that is an
+                           CredentialsProperty.
+        """
+        super(DjangoORMStorage, self).__init__()
+        self.model_class = model_class
+        self.key_name = key_name
+        self.key_value = key_value
+        self.property_name = property_name
+
+    def locked_get(self):
+        """Retrieve stored credential from the Django ORM.
+
+        Returns:
+            oauth2client.Credentials retrieved from the Django ORM, associated
+             with the ``model``, ``key_value``->``key_name`` pair used to query
+             for the model, and ``property_name`` identifying the
+             ``CredentialsProperty`` field, all of which are defined in the
+             constructor for this Storage object.
+
+        """
+        query = {self.key_name: self.key_value}
+        entities = self.model_class.objects.filter(**query)
+        if len(entities) > 0:
+            credential = getattr(entities[0], self.property_name)
+            if getattr(credential, 'set_store', None) is not None:
+                credential.set_store(self)
+            return credential
+        else:
+            return None
+
+    def locked_put(self, credentials):
+        """Write a Credentials to the Django datastore.
+
+        Args:
+            credentials: Credentials, the credentials to store.
+        """
+        entity, _ = self.model_class.objects.get_or_create(
+            **{self.key_name: self.key_value})
+
+        setattr(entity, self.property_name, credentials)
+        entity.save()
+
+    def locked_delete(self):
+        """Delete Credentials from the datastore."""
+        query = {self.key_name: self.key_value}
+        self.model_class.objects.filter(**query).delete()
diff --git a/oauth2client/contrib/django_util/views.py b/oauth2client/contrib/django_util/views.py
new file mode 100644
index 0000000..4d8ae03
--- /dev/null
+++ b/oauth2client/contrib/django_util/views.py
@@ -0,0 +1,190 @@
+# Copyright 2015 Google Inc.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""This module contains the views used by the OAuth2 flows.
+
+Their are two views used by the OAuth2 flow, the authorize and the callback
+view. The authorize view kicks off the three-legged OAuth flow, and the
+callback view validates the flow and if successful stores the credentials
+in the configured storage."""
+
+import hashlib
+import json
+import os
+import pickle
+
+from django import http
+from django import shortcuts
+from django.conf import settings
+from django.core import urlresolvers
+from django.shortcuts import redirect
+from six.moves.urllib import parse
+
+from oauth2client import client
+from oauth2client.contrib import django_util
+from oauth2client.contrib.django_util import get_storage
+from oauth2client.contrib.django_util import signals
+
+_CSRF_KEY = 'google_oauth2_csrf_token'
+_FLOW_KEY = 'google_oauth2_flow_{0}'
+
+
+def _make_flow(request, scopes, return_url=None):
+    """Creates a Web Server Flow
+
+    Args:
+        request: A Django request object.
+        scopes: the request oauth2 scopes.
+        return_url: The URL to return to after the flow is complete. Defaults
+            to the path of the current request.
+
+    Returns:
+        An OAuth2 flow object that has been stored in the session.
+    """
+    # Generate a CSRF token to prevent malicious requests.
+    csrf_token = hashlib.sha256(os.urandom(1024)).hexdigest()
+
+    request.session[_CSRF_KEY] = csrf_token
+
+    state = json.dumps({
+        'csrf_token': csrf_token,
+        'return_url': return_url,
+    })
+
+    flow = client.OAuth2WebServerFlow(
+        client_id=django_util.oauth2_settings.client_id,
+        client_secret=django_util.oauth2_settings.client_secret,
+        scope=scopes,
+        state=state,
+        redirect_uri=request.build_absolute_uri(
+            urlresolvers.reverse("google_oauth:callback")))
+
+    flow_key = _FLOW_KEY.format(csrf_token)
+    request.session[flow_key] = pickle.dumps(flow)
+    return flow
+
+
+def _get_flow_for_token(csrf_token, request):
+    """ Looks up the flow in session to recover information about requested
+    scopes.
+
+    Args:
+        csrf_token: The token passed in the callback request that should
+            match the one previously generated and stored in the request on the
+            initial authorization view.
+
+    Returns:
+        The OAuth2 Flow object associated with this flow based on the
+        CSRF token.
+    """
+    flow_pickle = request.session.get(_FLOW_KEY.format(csrf_token), None)
+    return None if flow_pickle is None else pickle.loads(flow_pickle)
+
+
+def oauth2_callback(request):
+    """ View that handles the user's return from OAuth2 provider.
+
+    This view verifies the CSRF state and OAuth authorization code, and on
+    success stores the credentials obtained in the storage provider,
+    and redirects to the return_url specified in the authorize view and
+    stored in the session.
+
+    Args:
+        request: Django request.
+
+    Returns:
+         A redirect response back to the return_url.
+    """
+    if 'error' in request.GET:
+        reason = request.GET.get(
+            'error_description', request.GET.get('error', ''))
+        return http.HttpResponseBadRequest(
+            'Authorization failed {0}'.format(reason))
+
+    try:
+        encoded_state = request.GET['state']
+        code = request.GET['code']
+    except KeyError:
+        return http.HttpResponseBadRequest(
+            'Request missing state or authorization code')
+
+    try:
+        server_csrf = request.session[_CSRF_KEY]
+    except KeyError:
+        return http.HttpResponseBadRequest(
+            'No existing session for this flow.')
+
+    try:
+        state = json.loads(encoded_state)
+        client_csrf = state['csrf_token']
+        return_url = state['return_url']
+    except (ValueError, KeyError):
+        return http.HttpResponseBadRequest('Invalid state parameter.')
+
+    if client_csrf != server_csrf:
+        return http.HttpResponseBadRequest('Invalid CSRF token.')
+
+    flow = _get_flow_for_token(client_csrf, request)
+
+    if not flow:
+        return http.HttpResponseBadRequest('Missing Oauth2 flow.')
+
+    try:
+        credentials = flow.step2_exchange(code)
+    except client.FlowExchangeError as exchange_error:
+        return http.HttpResponseBadRequest(
+            'An error has occurred: {0}'.format(exchange_error))
+
+    get_storage(request).put(credentials)
+
+    signals.oauth2_authorized.send(sender=signals.oauth2_authorized,
+                                   request=request, credentials=credentials)
+
+    return shortcuts.redirect(return_url)
+
+
+def oauth2_authorize(request):
+    """ View to start the OAuth2 Authorization flow.
+
+     This view starts the OAuth2 authorization flow. If scopes is passed in
+     as a  GET URL parameter, it will authorize those scopes, otherwise the
+     default scopes specified in settings. The return_url can also be
+     specified as a GET parameter, otherwise the referer header will be
+     checked, and if that isn't found it will return to the root path.
+
+    Args:
+       request: The Django request object.
+
+    Returns:
+         A redirect to Google OAuth2 Authorization.
+    """
+    return_url = request.GET.get('return_url', None)
+
+    # Model storage (but not session storage) requires a logged in user
+    if django_util.oauth2_settings.storage_model:
+        if not request.user.is_authenticated():
+            return redirect('{0}?next={1}'.format(
+                settings.LOGIN_URL, parse.quote(request.get_full_path())))
+        # This checks for the case where we ended up here because of a logged
+        # out user but we had credentials for it in the first place
+        elif get_storage(request).get() is not None:
+            return redirect(return_url)
+
+    scopes = request.GET.getlist('scopes', django_util.oauth2_settings.scopes)
+
+    if not return_url:
+        return_url = request.META.get('HTTP_REFERER', '/')
+    flow = _make_flow(request=request, scopes=scopes, return_url=return_url)
+    auth_url = flow.step1_get_authorize_url()
+    return shortcuts.redirect(auth_url)
diff --git a/oauth2client/contrib/flask_util.py b/oauth2client/contrib/flask_util.py
new file mode 100644
index 0000000..47c3df1
--- /dev/null
+++ b/oauth2client/contrib/flask_util.py
@@ -0,0 +1,556 @@
+# Copyright 2015 Google Inc.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities for the Flask web framework
+
+Provides a Flask extension that makes using OAuth2 web server flow easier.
+The extension includes views that handle the entire auth flow and a
+``@required`` decorator to automatically ensure that user credentials are
+available.
+
+
+Configuration
+=============
+
+To configure, you'll need a set of OAuth2 web application credentials from the
+`Google Developer's Console <https://console.developers.google.com/project/_/\
+apiui/credential>`__.
+
+.. code-block:: python
+
+    from oauth2client.contrib.flask_util import UserOAuth2
+
+    app = Flask(__name__)
+
+    app.config['SECRET_KEY'] = 'your-secret-key'
+
+    app.config['GOOGLE_OAUTH2_CLIENT_SECRETS_FILE'] = 'client_secrets.json'
+
+    # or, specify the client id and secret separately
+    app.config['GOOGLE_OAUTH2_CLIENT_ID'] = 'your-client-id'
+    app.config['GOOGLE_OAUTH2_CLIENT_SECRET'] = 'your-client-secret'
+
+    oauth2 = UserOAuth2(app)
+
+
+Usage
+=====
+
+Once configured, you can use the :meth:`UserOAuth2.required` decorator to
+ensure that credentials are available within a view.
+
+.. code-block:: python
+   :emphasize-lines: 3,7,10
+
+    # Note that app.route should be the outermost decorator.
+    @app.route('/needs_credentials')
+    @oauth2.required
+    def example():
+        # http is authorized with the user's credentials and can be used
+        # to make http calls.
+        http = oauth2.http()
+
+        # Or, you can access the credentials directly
+        credentials = oauth2.credentials
+
+If you want credentials to be optional for a view, you can leave the decorator
+off and use :meth:`UserOAuth2.has_credentials` to check.
+
+.. code-block:: python
+   :emphasize-lines: 3
+
+    @app.route('/optional')
+    def optional():
+        if oauth2.has_credentials():
+            return 'Credentials found!'
+        else:
+            return 'No credentials!'
+
+
+When credentials are available, you can use :attr:`UserOAuth2.email` and
+:attr:`UserOAuth2.user_id` to access information from the `ID Token
+<https://developers.google.com/identity/protocols/OpenIDConnect?hl=en>`__, if
+available.
+
+.. code-block:: python
+   :emphasize-lines: 4
+
+    @app.route('/info')
+    @oauth2.required
+    def info():
+        return "Hello, {} ({})".format(oauth2.email, oauth2.user_id)
+
+
+URLs & Trigging Authorization
+=============================
+
+The extension will add two new routes to your application:
+
+    * ``"oauth2.authorize"`` -> ``/oauth2authorize``
+    * ``"oauth2.callback"`` -> ``/oauth2callback``
+
+When configuring your OAuth2 credentials on the Google Developer's Console, be
+sure to add ``http[s]://[your-app-url]/oauth2callback`` as an authorized
+callback url.
+
+Typically you don't not need to use these routes directly, just be sure to
+decorate any views that require credentials with ``@oauth2.required``. If
+needed, you can trigger authorization at any time by redirecting the user
+to the URL returned by :meth:`UserOAuth2.authorize_url`.
+
+.. code-block:: python
+   :emphasize-lines: 3
+
+    @app.route('/login')
+    def login():
+        return oauth2.authorize_url("/")
+
+
+Incremental Auth
+================
+
+This extension also supports `Incremental Auth <https://developers.google.com\
+/identity/protocols/OAuth2WebServer?hl=en#incrementalAuth>`__. To enable it,
+configure the extension with ``include_granted_scopes``.
+
+.. code-block:: python
+
+    oauth2 = UserOAuth2(app, include_granted_scopes=True)
+
+Then specify any additional scopes needed on the decorator, for example:
+
+.. code-block:: python
+   :emphasize-lines: 2,7
+
+    @app.route('/drive')
+    @oauth2.required(scopes=["https://www.googleapis.com/auth/drive"])
+    def requires_drive():
+        ...
+
+    @app.route('/calendar')
+    @oauth2.required(scopes=["https://www.googleapis.com/auth/calendar"])
+    def requires_calendar():
+        ...
+
+The decorator will ensure that the the user has authorized all specified scopes
+before allowing them to access the view, and will also ensure that credentials
+do not lose any previously authorized scopes.
+
+
+Storage
+=======
+
+By default, the extension uses a Flask session-based storage solution. This
+means that credentials are only available for the duration of a session. It
+also means that with Flask's default configuration, the credentials will be
+visible in the session cookie. It's highly recommended to use database-backed
+session and to use https whenever handling user credentials.
+
+If you need the credentials to be available longer than a user session or
+available outside of a request context, you will need to implement your own
+:class:`oauth2client.Storage`.
+"""
+
+from functools import wraps
+import hashlib
+import json
+import os
+import pickle
+
+try:
+    from flask import Blueprint
+    from flask import _app_ctx_stack
+    from flask import current_app
+    from flask import redirect
+    from flask import request
+    from flask import session
+    from flask import url_for
+except ImportError:  # pragma: NO COVER
+    raise ImportError('The flask utilities require flask 0.9 or newer.')
+
+import httplib2
+import six.moves.http_client as httplib
+
+from oauth2client import client
+from oauth2client import clientsecrets
+from oauth2client.contrib import dictionary_storage
+
+
+__author__ = 'jonwayne@google.com (Jon Wayne Parrott)'
+
+_DEFAULT_SCOPES = ('email',)
+_CREDENTIALS_KEY = 'google_oauth2_credentials'
+_FLOW_KEY = 'google_oauth2_flow_{0}'
+_CSRF_KEY = 'google_oauth2_csrf_token'
+
+
+def _get_flow_for_token(csrf_token):
+    """Retrieves the flow instance associated with a given CSRF token from
+    the Flask session."""
+    flow_pickle = session.pop(
+        _FLOW_KEY.format(csrf_token), None)
+
+    if flow_pickle is None:
+        return None
+    else:
+        return pickle.loads(flow_pickle)
+
+
+class UserOAuth2(object):
+    """Flask extension for making OAuth 2.0 easier.
+
+    Configuration values:
+
+        * ``GOOGLE_OAUTH2_CLIENT_SECRETS_FILE`` path to a client secrets json
+          file, obtained from the credentials screen in the Google Developers
+          console.
+        * ``GOOGLE_OAUTH2_CLIENT_ID`` the oauth2 credentials' client ID. This
+          is only needed if ``GOOGLE_OAUTH2_CLIENT_SECRETS_FILE`` is not
+          specified.
+        * ``GOOGLE_OAUTH2_CLIENT_SECRET`` the oauth2 credentials' client
+          secret. This is only needed if ``GOOGLE_OAUTH2_CLIENT_SECRETS_FILE``
+          is not specified.
+
+    If app is specified, all arguments will be passed along to init_app.
+
+    If no app is specified, then you should call init_app in your application
+    factory to finish initialization.
+    """
+
+    def __init__(self, app=None, *args, **kwargs):
+        self.app = app
+        if app is not None:
+            self.init_app(app, *args, **kwargs)
+
+    def init_app(self, app, scopes=None, client_secrets_file=None,
+                 client_id=None, client_secret=None, authorize_callback=None,
+                 storage=None, **kwargs):
+        """Initialize this extension for the given app.
+
+        Arguments:
+            app: A Flask application.
+            scopes: Optional list of scopes to authorize.
+            client_secrets_file: Path to a file containing client secrets. You
+                can also specify the GOOGLE_OAUTH2_CLIENT_SECRETS_FILE config
+                value.
+            client_id: If not specifying a client secrets file, specify the
+                OAuth2 client id. You can also specify the
+                GOOGLE_OAUTH2_CLIENT_ID config value. You must also provide a
+                client secret.
+            client_secret: The OAuth2 client secret. You can also specify the
+                GOOGLE_OAUTH2_CLIENT_SECRET config value.
+            authorize_callback: A function that is executed after successful
+                user authorization.
+            storage: A oauth2client.client.Storage subclass for storing the
+                credentials. By default, this is a Flask session based storage.
+            kwargs: Any additional args are passed along to the Flow
+                constructor.
+        """
+        self.app = app
+        self.authorize_callback = authorize_callback
+        self.flow_kwargs = kwargs
+
+        if storage is None:
+            storage = dictionary_storage.DictionaryStorage(
+                session, key=_CREDENTIALS_KEY)
+        self.storage = storage
+
+        if scopes is None:
+            scopes = app.config.get('GOOGLE_OAUTH2_SCOPES', _DEFAULT_SCOPES)
+        self.scopes = scopes
+
+        self._load_config(client_secrets_file, client_id, client_secret)
+
+        app.register_blueprint(self._create_blueprint())
+
+    def _load_config(self, client_secrets_file, client_id, client_secret):
+        """Loads oauth2 configuration in order of priority.
+
+        Priority:
+            1. Config passed to the constructor or init_app.
+            2. Config passed via the GOOGLE_OAUTH2_CLIENT_SECRETS_FILE app
+               config.
+            3. Config passed via the GOOGLE_OAUTH2_CLIENT_ID and
+               GOOGLE_OAUTH2_CLIENT_SECRET app config.
+
+        Raises:
+            ValueError if no config could be found.
+        """
+        if client_id and client_secret:
+            self.client_id, self.client_secret = client_id, client_secret
+            return
+
+        if client_secrets_file:
+            self._load_client_secrets(client_secrets_file)
+            return
+
+        if 'GOOGLE_OAUTH2_CLIENT_SECRETS_FILE' in self.app.config:
+            self._load_client_secrets(
+                self.app.config['GOOGLE_OAUTH2_CLIENT_SECRETS_FILE'])
+            return
+
+        try:
+            self.client_id, self.client_secret = (
+                self.app.config['GOOGLE_OAUTH2_CLIENT_ID'],
+                self.app.config['GOOGLE_OAUTH2_CLIENT_SECRET'])
+        except KeyError:
+            raise ValueError(
+                'OAuth2 configuration could not be found. Either specify the '
+                'client_secrets_file or client_id and client_secret or set '
+                'the app configuration variables '
+                'GOOGLE_OAUTH2_CLIENT_SECRETS_FILE or '
+                'GOOGLE_OAUTH2_CLIENT_ID and GOOGLE_OAUTH2_CLIENT_SECRET.')
+
+    def _load_client_secrets(self, filename):
+        """Loads client secrets from the given filename."""
+        client_type, client_info = clientsecrets.loadfile(filename)
+        if client_type != clientsecrets.TYPE_WEB:
+            raise ValueError(
+                'The flow specified in {0} is not supported.'.format(
+                    client_type))
+
+        self.client_id = client_info['client_id']
+        self.client_secret = client_info['client_secret']
+
+    def _make_flow(self, return_url=None, **kwargs):
+        """Creates a Web Server Flow"""
+        # Generate a CSRF token to prevent malicious requests.
+        csrf_token = hashlib.sha256(os.urandom(1024)).hexdigest()
+
+        session[_CSRF_KEY] = csrf_token
+
+        state = json.dumps({
+            'csrf_token': csrf_token,
+            'return_url': return_url
+        })
+
+        kw = self.flow_kwargs.copy()
+        kw.update(kwargs)
+
+        extra_scopes = kw.pop('scopes', [])
+        scopes = set(self.scopes).union(set(extra_scopes))
+
+        flow = client.OAuth2WebServerFlow(
+            client_id=self.client_id,
+            client_secret=self.client_secret,
+            scope=scopes,
+            state=state,
+            redirect_uri=url_for('oauth2.callback', _external=True),
+            **kw)
+
+        flow_key = _FLOW_KEY.format(csrf_token)
+        session[flow_key] = pickle.dumps(flow)
+
+        return flow
+
+    def _create_blueprint(self):
+        bp = Blueprint('oauth2', __name__)
+        bp.add_url_rule('/oauth2authorize', 'authorize', self.authorize_view)
+        bp.add_url_rule('/oauth2callback', 'callback', self.callback_view)
+
+        return bp
+
+    def authorize_view(self):
+        """Flask view that starts the authorization flow.
+
+        Starts flow by redirecting the user to the OAuth2 provider.
+        """
+        args = request.args.to_dict()
+
+        # Scopes will be passed as mutliple args, and to_dict() will only
+        # return one. So, we use getlist() to get all of the scopes.
+        args['scopes'] = request.args.getlist('scopes')
+
+        return_url = args.pop('return_url', None)
+        if return_url is None:
+            return_url = request.referrer or '/'
+
+        flow = self._make_flow(return_url=return_url, **args)
+        auth_url = flow.step1_get_authorize_url()
+
+        return redirect(auth_url)
+
+    def callback_view(self):
+        """Flask view that handles the user's return from OAuth2 provider.
+
+        On return, exchanges the authorization code for credentials and stores
+        the credentials.
+        """
+        if 'error' in request.args:
+            reason = request.args.get(
+                'error_description', request.args.get('error', ''))
+            return ('Authorization failed: {0}'.format(reason),
+                    httplib.BAD_REQUEST)
+
+        try:
+            encoded_state = request.args['state']
+            server_csrf = session[_CSRF_KEY]
+            code = request.args['code']
+        except KeyError:
+            return 'Invalid request', httplib.BAD_REQUEST
+
+        try:
+            state = json.loads(encoded_state)
+            client_csrf = state['csrf_token']
+            return_url = state['return_url']
+        except (ValueError, KeyError):
+            return 'Invalid request state', httplib.BAD_REQUEST
+
+        if client_csrf != server_csrf:
+            return 'Invalid request state', httplib.BAD_REQUEST
+
+        flow = _get_flow_for_token(server_csrf)
+
+        if flow is None:
+            return 'Invalid request state', httplib.BAD_REQUEST
+
+        # Exchange the auth code for credentials.
+        try:
+            credentials = flow.step2_exchange(code)
+        except client.FlowExchangeError as exchange_error:
+            current_app.logger.exception(exchange_error)
+            content = 'An error occurred: {0}'.format(exchange_error)
+            return content, httplib.BAD_REQUEST
+
+        # Save the credentials to the storage.
+        self.storage.put(credentials)
+
+        if self.authorize_callback:
+            self.authorize_callback(credentials)
+
+        return redirect(return_url)
+
+    @property
+    def credentials(self):
+        """The credentials for the current user or None if unavailable."""
+        ctx = _app_ctx_stack.top
+
+        if not hasattr(ctx, _CREDENTIALS_KEY):
+            ctx.google_oauth2_credentials = self.storage.get()
+
+        return ctx.google_oauth2_credentials
+
+    def has_credentials(self):
+        """Returns True if there are valid credentials for the current user."""
+        if not self.credentials:
+            return False
+        # Is the access token expired? If so, do we have an refresh token?
+        elif (self.credentials.access_token_expired and
+                not self.credentials.refresh_token):
+            return False
+        else:
+            return True
+
+    @property
+    def email(self):
+        """Returns the user's email address or None if there are no credentials.
+
+        The email address is provided by the current credentials' id_token.
+        This should not be used as unique identifier as the user can change
+        their email. If you need a unique identifier, use user_id.
+        """
+        if not self.credentials:
+            return None
+        try:
+            return self.credentials.id_token['email']
+        except KeyError:
+            current_app.logger.error(
+                'Invalid id_token {0}'.format(self.credentials.id_token))
+
+    @property
+    def user_id(self):
+        """Returns the a unique identifier for the user
+
+        Returns None if there are no credentials.
+
+        The id is provided by the current credentials' id_token.
+        """
+        if not self.credentials:
+            return None
+        try:
+            return self.credentials.id_token['sub']
+        except KeyError:
+            current_app.logger.error(
+                'Invalid id_token {0}'.format(self.credentials.id_token))
+
+    def authorize_url(self, return_url, **kwargs):
+        """Creates a URL that can be used to start the authorization flow.
+
+        When the user is directed to the URL, the authorization flow will
+        begin. Once complete, the user will be redirected to the specified
+        return URL.
+
+        Any kwargs are passed into the flow constructor.
+        """
+        return url_for('oauth2.authorize', return_url=return_url, **kwargs)
+
+    def required(self, decorated_function=None, scopes=None,
+                 **decorator_kwargs):
+        """Decorator to require OAuth2 credentials for a view.
+
+        If credentials are not available for the current user, then they will
+        be redirected to the authorization flow. Once complete, the user will
+        be redirected back to the original page.
+        """
+
+        def curry_wrapper(wrapped_function):
+            @wraps(wrapped_function)
+            def required_wrapper(*args, **kwargs):
+                return_url = decorator_kwargs.pop('return_url', request.url)
+
+                requested_scopes = set(self.scopes)
+                if scopes is not None:
+                    requested_scopes |= set(scopes)
+                if self.has_credentials():
+                    requested_scopes |= self.credentials.scopes
+
+                requested_scopes = list(requested_scopes)
+
+                # Does the user have credentials and does the credentials have
+                # all of the needed scopes?
+                if (self.has_credentials() and
+                        self.credentials.has_scopes(requested_scopes)):
+                    return wrapped_function(*args, **kwargs)
+                # Otherwise, redirect to authorization
+                else:
+                    auth_url = self.authorize_url(
+                        return_url,
+                        scopes=requested_scopes,
+                        **decorator_kwargs)
+
+                    return redirect(auth_url)
+
+            return required_wrapper
+
+        if decorated_function:
+            return curry_wrapper(decorated_function)
+        else:
+            return curry_wrapper
+
+    def http(self, *args, **kwargs):
+        """Returns an authorized http instance.
+
+        Can only be called if there are valid credentials for the user, such
+        as inside of a view that is decorated with @required.
+
+        Args:
+            *args: Positional arguments passed to httplib2.Http constructor.
+            **kwargs: Positional arguments passed to httplib2.Http constructor.
+
+        Raises:
+            ValueError if no credentials are available.
+        """
+        if not self.credentials:
+            raise ValueError('No credentials available.')
+        return self.credentials.authorize(httplib2.Http(*args, **kwargs))
diff --git a/oauth2client/contrib/gce.py b/oauth2client/contrib/gce.py
new file mode 100644
index 0000000..f3a6ca1
--- /dev/null
+++ b/oauth2client/contrib/gce.py
@@ -0,0 +1,162 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities for Google Compute Engine
+
+Utilities for making it easier to use OAuth 2.0 on Google Compute Engine.
+"""
+
+import logging
+import warnings
+
+import httplib2
+
+from oauth2client import client
+from oauth2client.contrib import _metadata
+
+
+__author__ = 'jcgregorio@google.com (Joe Gregorio)'
+
+logger = logging.getLogger(__name__)
+
+_SCOPES_WARNING = """\
+You have requested explicit scopes to be used with a GCE service account.
+Using this argument will have no effect on the actual scopes for tokens
+requested. These scopes are set at VM instance creation time and
+can't be overridden in the request.
+"""
+
+
+class AppAssertionCredentials(client.AssertionCredentials):
+    """Credentials object for Compute Engine Assertion Grants
+
+    This object will allow a Compute Engine instance to identify itself to
+    Google and other OAuth 2.0 servers that can verify assertions. It can be
+    used for the purpose of accessing data stored under an account assigned to
+    the Compute Engine instance itself.
+
+    This credential does not require a flow to instantiate because it
+    represents a two legged flow, and therefore has all of the required
+    information to generate and refresh its own access tokens.
+
+    Note that :attr:`service_account_email` and :attr:`scopes`
+    will both return None until the credentials have been refreshed.
+    To check whether credentials have previously been refreshed use
+    :attr:`invalid`.
+    """
+
+    def __init__(self, email=None, *args, **kwargs):
+        """Constructor for AppAssertionCredentials
+
+        Args:
+            email: an email that specifies the service account to use.
+                   Only necessary if using custom service accounts
+                   (see https://cloud.google.com/compute/docs/access/create-enable-service-accounts-for-instances#createdefaultserviceaccount).
+        """
+        if 'scopes' in kwargs:
+            warnings.warn(_SCOPES_WARNING)
+            kwargs['scopes'] = None
+
+        # Assertion type is no longer used, but still in the
+        # parent class signature.
+        super(AppAssertionCredentials, self).__init__(None, *args, **kwargs)
+
+        self.service_account_email = email
+        self.scopes = None
+        self.invalid = True
+
+    @classmethod
+    def from_json(cls, json_data):
+        raise NotImplementedError(
+            'Cannot serialize credentials for GCE service accounts.')
+
+    def to_json(self):
+        raise NotImplementedError(
+            'Cannot serialize credentials for GCE service accounts.')
+
+    def retrieve_scopes(self, http):
+        """Retrieves the canonical list of scopes for this access token.
+
+        Overrides client.Credentials.retrieve_scopes. Fetches scopes info
+        from the metadata server.
+
+        Args:
+            http: httplib2.Http, an http object to be used to make the refresh
+                  request.
+
+        Returns:
+            A set of strings containing the canonical list of scopes.
+        """
+        self._retrieve_info(http.request)
+        return self.scopes
+
+    def _retrieve_info(self, http_request):
+        """Validates invalid service accounts by retrieving service account info.
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make the
+                          request to the metadata server
+        """
+        if self.invalid:
+            info = _metadata.get_service_account_info(
+                http_request,
+                service_account=self.service_account_email or 'default')
+            self.invalid = False
+            self.service_account_email = info['email']
+            self.scopes = info['scopes']
+
+    def _refresh(self, http_request):
+        """Refreshes the access_token.
+
+        Skip all the storage hoops and just refresh using the API.
+
+        Args:
+            http_request: callable, a callable that matches the method
+                          signature of httplib2.Http.request, used to make
+                          the refresh request.
+
+        Raises:
+            HttpAccessTokenRefreshError: When the refresh fails.
+        """
+        try:
+            self._retrieve_info(http_request)
+            self.access_token, self.token_expiry = _metadata.get_token(
+                http_request, service_account=self.service_account_email)
+        except httplib2.HttpLib2Error as e:
+            raise client.HttpAccessTokenRefreshError(str(e))
+
+    @property
+    def serialization_data(self):
+        raise NotImplementedError(
+            'Cannot serialize credentials for GCE service accounts.')
+
+    def create_scoped_required(self):
+        return False
+
+    def sign_blob(self, blob):
+        """Cryptographically sign a blob (of bytes).
+
+        This method is provided to support a common interface, but
+        the actual key used for a Google Compute Engine service account
+        is not available, so it can't be used to sign content.
+
+        Args:
+            blob: bytes, Message to be signed.
+
+        Raises:
+            NotImplementedError, always.
+        """
+        raise NotImplementedError(
+            'Compute Engine service accounts cannot sign blobs')
diff --git a/oauth2client/contrib/keyring_storage.py b/oauth2client/contrib/keyring_storage.py
new file mode 100644
index 0000000..f4f2e30
--- /dev/null
+++ b/oauth2client/contrib/keyring_storage.py
@@ -0,0 +1,98 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""A keyring based Storage.
+
+A Storage for Credentials that uses the keyring module.
+"""
+
+import threading
+
+import keyring
+
+from oauth2client import client
+
+
+__author__ = 'jcgregorio@google.com (Joe Gregorio)'
+
+
+class Storage(client.Storage):
+    """Store and retrieve a single credential to and from the keyring.
+
+    To use this module you must have the keyring module installed. See
+    <http://pypi.python.org/pypi/keyring/>. This is an optional module and is
+    not installed with oauth2client by default because it does not work on all
+    the platforms that oauth2client supports, such as Google App Engine.
+
+    The keyring module <http://pypi.python.org/pypi/keyring/> is a
+    cross-platform library for access the keyring capabilities of the local
+    system. The user will be prompted for their keyring password when this
+    module is used, and the manner in which the user is prompted will vary per
+    platform.
+
+    Usage::
+
+        from oauth2client import keyring_storage
+
+        s = keyring_storage.Storage('name_of_application', 'user1')
+        credentials = s.get()
+
+    """
+
+    def __init__(self, service_name, user_name):
+        """Constructor.
+
+        Args:
+            service_name: string, The name of the service under which the
+                          credentials are stored.
+            user_name: string, The name of the user to store credentials for.
+        """
+        super(Storage, self).__init__(lock=threading.Lock())
+        self._service_name = service_name
+        self._user_name = user_name
+
+    def locked_get(self):
+        """Retrieve Credential from file.
+
+        Returns:
+            oauth2client.client.Credentials
+        """
+        credentials = None
+        content = keyring.get_password(self._service_name, self._user_name)
+
+        if content is not None:
+            try:
+                credentials = client.Credentials.new_from_json(content)
+                credentials.set_store(self)
+            except ValueError:
+                pass
+
+        return credentials
+
+    def locked_put(self, credentials):
+        """Write Credentials to file.
+
+        Args:
+            credentials: Credentials, the credentials to store.
+        """
+        keyring.set_password(self._service_name, self._user_name,
+                             credentials.to_json())
+
+    def locked_delete(self):
+        """Delete Credentials file.
+
+        Args:
+            credentials: Credentials, the credentials to store.
+        """
+        keyring.set_password(self._service_name, self._user_name, '')
diff --git a/oauth2client/contrib/locked_file.py b/oauth2client/contrib/locked_file.py
new file mode 100644
index 0000000..0d28ebb
--- /dev/null
+++ b/oauth2client/contrib/locked_file.py
@@ -0,0 +1,234 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Locked file interface that should work on Unix and Windows pythons.
+
+This module first tries to use fcntl locking to ensure serialized access
+to a file, then falls back on a lock file if that is unavialable.
+
+Usage::
+
+    f = LockedFile('filename', 'r+b', 'rb')
+    f.open_and_lock()
+    if f.is_locked():
+      print('Acquired filename with r+b mode')
+      f.file_handle().write('locked data')
+    else:
+      print('Acquired filename with rb mode')
+    f.unlock_and_close()
+
+"""
+
+from __future__ import print_function
+
+import errno
+import logging
+import os
+import time
+
+from oauth2client import util
+
+
+__author__ = 'cache@google.com (David T McWherter)'
+
+logger = logging.getLogger(__name__)
+
+
+class CredentialsFileSymbolicLinkError(Exception):
+    """Credentials files must not be symbolic links."""
+
+
+class AlreadyLockedException(Exception):
+    """Trying to lock a file that has already been locked by the LockedFile."""
+    pass
+
+
+def validate_file(filename):
+    if os.path.islink(filename):
+        raise CredentialsFileSymbolicLinkError(
+            'File: {0} is a symbolic link.'.format(filename))
+
+
+class _Opener(object):
+    """Base class for different locking primitives."""
+
+    def __init__(self, filename, mode, fallback_mode):
+        """Create an Opener.
+
+        Args:
+            filename: string, The pathname of the file.
+            mode: string, The preferred mode to access the file with.
+            fallback_mode: string, The mode to use if locking fails.
+        """
+        self._locked = False
+        self._filename = filename
+        self._mode = mode
+        self._fallback_mode = fallback_mode
+        self._fh = None
+        self._lock_fd = None
+
+    def is_locked(self):
+        """Was the file locked."""
+        return self._locked
+
+    def file_handle(self):
+        """The file handle to the file. Valid only after opened."""
+        return self._fh
+
+    def filename(self):
+        """The filename that is being locked."""
+        return self._filename
+
+    def open_and_lock(self, timeout, delay):
+        """Open the file and lock it.
+
+        Args:
+            timeout: float, How long to try to lock for.
+            delay: float, How long to wait between retries.
+        """
+        pass
+
+    def unlock_and_close(self):
+        """Unlock and close the file."""
+        pass
+
+
+class _PosixOpener(_Opener):
+    """Lock files using Posix advisory lock files."""
+
+    def open_and_lock(self, timeout, delay):
+        """Open the file and lock it.
+
+        Tries to create a .lock file next to the file we're trying to open.
+
+        Args:
+            timeout: float, How long to try to lock for.
+            delay: float, How long to wait between retries.
+
+        Raises:
+            AlreadyLockedException: if the lock is already acquired.
+            IOError: if the open fails.
+            CredentialsFileSymbolicLinkError if the file is a symbolic link.
+        """
+        if self._locked:
+            raise AlreadyLockedException(
+                'File {0} is already locked'.format(self._filename))
+        self._locked = False
+
+        validate_file(self._filename)
+        try:
+            self._fh = open(self._filename, self._mode)
+        except IOError as e:
+            # If we can't access with _mode, try _fallback_mode and don't lock.
+            if e.errno == errno.EACCES:
+                self._fh = open(self._filename, self._fallback_mode)
+                return
+
+        lock_filename = self._posix_lockfile(self._filename)
+        start_time = time.time()
+        while True:
+            try:
+                self._lock_fd = os.open(lock_filename,
+                                        os.O_CREAT | os.O_EXCL | os.O_RDWR)
+                self._locked = True
+                break
+
+            except OSError as e:
+                if e.errno != errno.EEXIST:
+                    raise
+                if (time.time() - start_time) >= timeout:
+                    logger.warn('Could not acquire lock %s in %s seconds',
+                                lock_filename, timeout)
+                    # Close the file and open in fallback_mode.
+                    if self._fh:
+                        self._fh.close()
+                    self._fh = open(self._filename, self._fallback_mode)
+                    return
+                time.sleep(delay)
+
+    def unlock_and_close(self):
+        """Unlock a file by removing the .lock file, and close the handle."""
+        if self._locked:
+            lock_filename = self._posix_lockfile(self._filename)
+            os.close(self._lock_fd)
+            os.unlink(lock_filename)
+            self._locked = False
+            self._lock_fd = None
+        if self._fh:
+            self._fh.close()
+
+    def _posix_lockfile(self, filename):
+        """The name of the lock file to use for posix locking."""
+        return '{0}.lock'.format(filename)
+
+
+class LockedFile(object):
+    """Represent a file that has exclusive access."""
+
+    @util.positional(4)
+    def __init__(self, filename, mode, fallback_mode, use_native_locking=True):
+        """Construct a LockedFile.
+
+        Args:
+            filename: string, The path of the file to open.
+            mode: string, The mode to try to open the file with.
+            fallback_mode: string, The mode to use if locking fails.
+            use_native_locking: bool, Whether or not fcntl/win32 locking is
+                                used.
+        """
+        opener = None
+        if not opener and use_native_locking:
+            try:
+                from oauth2client.contrib._win32_opener import _Win32Opener
+                opener = _Win32Opener(filename, mode, fallback_mode)
+            except ImportError:
+                try:
+                    from oauth2client.contrib._fcntl_opener import _FcntlOpener
+                    opener = _FcntlOpener(filename, mode, fallback_mode)
+                except ImportError:
+                    pass
+
+        if not opener:
+            opener = _PosixOpener(filename, mode, fallback_mode)
+
+        self._opener = opener
+
+    def filename(self):
+        """Return the filename we were constructed with."""
+        return self._opener._filename
+
+    def file_handle(self):
+        """Return the file_handle to the opened file."""
+        return self._opener.file_handle()
+
+    def is_locked(self):
+        """Return whether we successfully locked the file."""
+        return self._opener.is_locked()
+
+    def open_and_lock(self, timeout=0, delay=0.05):
+        """Open the file, trying to lock it.
+
+        Args:
+            timeout: float, The number of seconds to try to acquire the lock.
+            delay: float, The number of seconds to wait between retry attempts.
+
+        Raises:
+            AlreadyLockedException: if the lock is already acquired.
+            IOError: if the open fails.
+        """
+        self._opener.open_and_lock(timeout, delay)
+
+    def unlock_and_close(self):
+        """Unlock and close a file."""
+        self._opener.unlock_and_close()
diff --git a/oauth2client/contrib/multiprocess_file_storage.py b/oauth2client/contrib/multiprocess_file_storage.py
new file mode 100644
index 0000000..e9e8c8c
--- /dev/null
+++ b/oauth2client/contrib/multiprocess_file_storage.py
@@ -0,0 +1,355 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Multiprocess file credential storage.
+
+This module provides file-based storage that supports multiple credentials and
+cross-thread and process access.
+
+This module supersedes the functionality previously found in `multistore_file`.
+
+This module provides :class:`MultiprocessFileStorage` which:
+    * Is tied to a single credential via a user-specified key. This key can be
+      used to distinguish between multiple users, client ids, and/or scopes.
+    * Can be safely accessed and refreshed across threads and processes.
+
+Process & thread safety guarantees the following behavior:
+    * If one thread or process refreshes a credential, subsequent refreshes
+      from other processes will re-fetch the credentials from the file instead
+      of performing an http request.
+    * If two processes or threads attempt to refresh concurrently, only one
+      will be able to acquire the lock and refresh, with the deadlock caveat
+      below.
+    * The interprocess lock will not deadlock, instead, the if a process can
+      not acquire the interprocess lock within ``INTERPROCESS_LOCK_DEADLINE``
+      it will allow refreshing the credential but will not write the updated
+      credential to disk, This logic happens during every lock cycle - if the
+      credentials are refreshed again it will retry locking and writing as
+      normal.
+
+Usage
+=====
+
+Before using the storage, you need to decide how you want to key the
+credentials. A few common strategies include:
+
+    * If you're storing credentials for multiple users in a single file, use
+      a unique identifier for each user as the key.
+    * If you're storing credentials for multiple client IDs in a single file,
+      use the client ID as the key.
+    * If you're storing multiple credentials for one user, use the scopes as
+      the key.
+    * If you have a complicated setup, use a compound key. For example, you
+      can use a combination of the client ID and scopes as the key.
+
+Create an instance of :class:`MultiprocessFileStorage` for each credential you
+want to store, for example::
+
+    filename = 'credentials'
+    key = '{}-{}'.format(client_id, user_id)
+    storage = MultiprocessFileStorage(filename, key)
+
+To store the credentials::
+
+    storage.put(credentials)
+
+If you're going to continue to use the credentials after storing them, be sure
+to call :func:`set_store`::
+
+    credentials.set_store(storage)
+
+To retrieve the credentials::
+
+    storage.get(credentials)
+
+"""
+
+import base64
+import json
+import logging
+import os
+import threading
+
+import fasteners
+from six import iteritems
+
+from oauth2client import _helpers
+from oauth2client import client
+
+
+#: The maximum amount of time, in seconds, to wait when acquire the
+#: interprocess lock before falling back to read-only mode.
+INTERPROCESS_LOCK_DEADLINE = 1
+
+logger = logging.getLogger(__name__)
+_backends = {}
+_backends_lock = threading.Lock()
+
+
+def _create_file_if_needed(filename):
+    """Creates the an empty file if it does not already exist.
+
+    Returns:
+        True if the file was created, False otherwise.
+    """
+    if os.path.exists(filename):
+        return False
+    else:
+        # Equivalent to "touch".
+        open(filename, 'a+b').close()
+        logger.info('Credential file {0} created'.format(filename))
+        return True
+
+
+def _load_credentials_file(credentials_file):
+    """Load credentials from the given file handle.
+
+    The file is expected to be in this format:
+
+        {
+            "file_version": 2,
+            "credentials": {
+                "key": "base64 encoded json representation of credentials."
+            }
+        }
+
+    This function will warn and return empty credentials instead of raising
+    exceptions.
+
+    Args:
+        credentials_file: An open file handle.
+
+    Returns:
+        A dictionary mapping user-defined keys to an instance of
+        :class:`oauth2client.client.Credentials`.
+    """
+    try:
+        credentials_file.seek(0)
+        data = json.load(credentials_file)
+    except Exception:
+        logger.warning(
+            'Credentials file could not be loaded, will ignore and '
+            'overwrite.')
+        return {}
+
+    if data.get('file_version') != 2:
+        logger.warning(
+            'Credentials file is not version 2, will ignore and '
+            'overwrite.')
+        return {}
+
+    credentials = {}
+
+    for key, encoded_credential in iteritems(data.get('credentials', {})):
+        try:
+            credential_json = base64.b64decode(encoded_credential)
+            credential = client.Credentials.new_from_json(credential_json)
+            credentials[key] = credential
+        except:
+            logger.warning(
+                'Invalid credential {0} in file, ignoring.'.format(key))
+
+    return credentials
+
+
+def _write_credentials_file(credentials_file, credentials):
+    """Writes credentials to a file.
+
+    Refer to :func:`_load_credentials_file` for the format.
+
+    Args:
+        credentials_file: An open file handle, must be read/write.
+        credentials: A dictionary mapping user-defined keys to an instance of
+            :class:`oauth2client.client.Credentials`.
+    """
+    data = {'file_version': 2, 'credentials': {}}
+
+    for key, credential in iteritems(credentials):
+        credential_json = credential.to_json()
+        encoded_credential = _helpers._from_bytes(base64.b64encode(
+            _helpers._to_bytes(credential_json)))
+        data['credentials'][key] = encoded_credential
+
+    credentials_file.seek(0)
+    json.dump(data, credentials_file)
+    credentials_file.truncate()
+
+
+class _MultiprocessStorageBackend(object):
+    """Thread-local backend for multiprocess storage.
+
+    Each process has only one instance of this backend per file. All threads
+    share a single instance of this backend. This ensures that all threads
+    use the same thread lock and process lock when accessing the file.
+    """
+
+    def __init__(self, filename):
+        self._file = None
+        self._filename = filename
+        self._process_lock = fasteners.InterProcessLock(
+            '{0}.lock'.format(filename))
+        self._thread_lock = threading.Lock()
+        self._read_only = False
+        self._credentials = {}
+
+    def _load_credentials(self):
+        """(Re-)loads the credentials from the file."""
+        if not self._file:
+            return
+
+        loaded_credentials = _load_credentials_file(self._file)
+        self._credentials.update(loaded_credentials)
+
+        logger.debug('Read credential file')
+
+    def _write_credentials(self):
+        if self._read_only:
+            logger.debug('In read-only mode, not writing credentials.')
+            return
+
+        _write_credentials_file(self._file, self._credentials)
+        logger.debug('Wrote credential file {0}.'.format(self._filename))
+
+    def acquire_lock(self):
+        self._thread_lock.acquire()
+        locked = self._process_lock.acquire(timeout=INTERPROCESS_LOCK_DEADLINE)
+
+        if locked:
+            _create_file_if_needed(self._filename)
+            self._file = open(self._filename, 'r+')
+            self._read_only = False
+
+        else:
+            logger.warn(
+                'Failed to obtain interprocess lock for credentials. '
+                'If a credential is being refreshed, other processes may '
+                'not see the updated access token and refresh as well.')
+            if os.path.exists(self._filename):
+                self._file = open(self._filename, 'r')
+            else:
+                self._file = None
+            self._read_only = True
+
+        self._load_credentials()
+
+    def release_lock(self):
+        if self._file is not None:
+            self._file.close()
+            self._file = None
+
+        if not self._read_only:
+            self._process_lock.release()
+
+        self._thread_lock.release()
+
+    def _refresh_predicate(self, credentials):
+        if credentials is None:
+            return True
+        elif credentials.invalid:
+            return True
+        elif credentials.access_token_expired:
+            return True
+        else:
+            return False
+
+    def locked_get(self, key):
+        # Check if the credential is already in memory.
+        credentials = self._credentials.get(key, None)
+
+        # Use the refresh predicate to determine if the entire store should be
+        # reloaded. This basically checks if the credentials are invalid
+        # or expired. This covers the situation where another process has
+        # refreshed the credentials and this process doesn't know about it yet.
+        # In that case, this process won't needlessly refresh the credentials.
+        if self._refresh_predicate(credentials):
+            self._load_credentials()
+            credentials = self._credentials.get(key, None)
+
+        return credentials
+
+    def locked_put(self, key, credentials):
+        self._load_credentials()
+        self._credentials[key] = credentials
+        self._write_credentials()
+
+    def locked_delete(self, key):
+        self._load_credentials()
+        self._credentials.pop(key, None)
+        self._write_credentials()
+
+
+def _get_backend(filename):
+    """A helper method to get or create a backend with thread locking.
+
+    This ensures that only one backend is used per-file per-process, so that
+    thread and process locks are appropriately shared.
+
+    Args:
+        filename: The full path to the credential storage file.
+
+    Returns:
+        An instance of :class:`_MultiprocessStorageBackend`.
+    """
+    filename = os.path.abspath(filename)
+
+    with _backends_lock:
+        if filename not in _backends:
+            _backends[filename] = _MultiprocessStorageBackend(filename)
+        return _backends[filename]
+
+
+class MultiprocessFileStorage(client.Storage):
+    """Multiprocess file credential storage.
+
+    Args:
+      filename: The path to the file where credentials will be stored.
+      key: An arbitrary string used to uniquely identify this set of
+          credentials. For example, you may use the user's ID as the key or
+          a combination of the client ID and user ID.
+    """
+    def __init__(self, filename, key):
+        self._key = key
+        self._backend = _get_backend(filename)
+
+    def acquire_lock(self):
+        self._backend.acquire_lock()
+
+    def release_lock(self):
+        self._backend.release_lock()
+
+    def locked_get(self):
+        """Retrieves the current credentials from the store.
+
+        Returns:
+            An instance of :class:`oauth2client.client.Credentials` or `None`.
+        """
+        credential = self._backend.locked_get(self._key)
+
+        if credential is not None:
+            credential.set_store(self)
+
+        return credential
+
+    def locked_put(self, credentials):
+        """Writes the given credentials to the store.
+
+        Args:
+            credentials: an instance of
+                :class:`oauth2client.client.Credentials`.
+        """
+        return self._backend.locked_put(self._key, credentials)
+
+    def locked_delete(self):
+        """Deletes the current credentials from the store."""
+        return self._backend.locked_delete(self._key)
diff --git a/oauth2client/contrib/multistore_file.py b/oauth2client/contrib/multistore_file.py
new file mode 100644
index 0000000..10f4cb4
--- /dev/null
+++ b/oauth2client/contrib/multistore_file.py
@@ -0,0 +1,505 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Multi-credential file store with lock support.
+
+This module implements a JSON credential store where multiple
+credentials can be stored in one file. That file supports locking
+both in a single process and across processes.
+
+The credential themselves are keyed off of:
+
+* client_id
+* user_agent
+* scope
+
+The format of the stored data is like so::
+
+    {
+      'file_version': 1,
+      'data': [
+          {
+              'key': {
+                  'clientId': '<client id>',
+                  'userAgent': '<user agent>',
+                  'scope': '<scope>'
+              },
+              'credential': {
+                  # JSON serialized Credentials.
+              }
+          }
+      ]
+    }
+
+"""
+
+import errno
+import json
+import logging
+import os
+import threading
+
+from oauth2client import client
+from oauth2client import util
+from oauth2client.contrib import locked_file
+
+__author__ = 'jbeda@google.com (Joe Beda)'
+
+logger = logging.getLogger(__name__)
+
+logger.warning(
+    'The oauth2client.contrib.multistore_file module has been deprecated and '
+    'will be removed in the next release of oauth2client. Please migrate to '
+    'multiprocess_file_storage.')
+
+# A dict from 'filename'->_MultiStore instances
+_multistores = {}
+_multistores_lock = threading.Lock()
+
+
+class Error(Exception):
+    """Base error for this module."""
+
+
+class NewerCredentialStoreError(Error):
+    """The credential store is a newer version than supported."""
+
+
+def _dict_to_tuple_key(dictionary):
+    """Converts a dictionary to a tuple that can be used as an immutable key.
+
+    The resulting key is always sorted so that logically equivalent
+    dictionaries always produce an identical tuple for a key.
+
+    Args:
+        dictionary: the dictionary to use as the key.
+
+    Returns:
+        A tuple representing the dictionary in it's naturally sorted ordering.
+    """
+    return tuple(sorted(dictionary.items()))
+
+
+@util.positional(4)
+def get_credential_storage(filename, client_id, user_agent, scope,
+                           warn_on_readonly=True):
+    """Get a Storage instance for a credential.
+
+    Args:
+        filename: The JSON file storing a set of credentials
+        client_id: The client_id for the credential
+        user_agent: The user agent for the credential
+        scope: string or iterable of strings, Scope(s) being requested
+        warn_on_readonly: if True, log a warning if the store is readonly
+
+    Returns:
+        An object derived from client.Storage for getting/setting the
+        credential.
+    """
+    # Recreate the legacy key with these specific parameters
+    key = {'clientId': client_id, 'userAgent': user_agent,
+           'scope': util.scopes_to_string(scope)}
+    return get_credential_storage_custom_key(
+        filename, key, warn_on_readonly=warn_on_readonly)
+
+
+@util.positional(2)
+def get_credential_storage_custom_string_key(filename, key_string,
+                                             warn_on_readonly=True):
+    """Get a Storage instance for a credential using a single string as a key.
+
+    Allows you to provide a string as a custom key that will be used for
+    credential storage and retrieval.
+
+    Args:
+        filename: The JSON file storing a set of credentials
+        key_string: A string to use as the key for storing this credential.
+        warn_on_readonly: if True, log a warning if the store is readonly
+
+    Returns:
+        An object derived from client.Storage for getting/setting the
+        credential.
+    """
+    # Create a key dictionary that can be used
+    key_dict = {'key': key_string}
+    return get_credential_storage_custom_key(
+        filename, key_dict, warn_on_readonly=warn_on_readonly)
+
+
+@util.positional(2)
+def get_credential_storage_custom_key(filename, key_dict,
+                                      warn_on_readonly=True):
+    """Get a Storage instance for a credential using a dictionary as a key.
+
+    Allows you to provide a dictionary as a custom key that will be used for
+    credential storage and retrieval.
+
+    Args:
+        filename: The JSON file storing a set of credentials
+        key_dict: A dictionary to use as the key for storing this credential.
+                  There is no ordering of the keys in the dictionary. Logically
+                  equivalent dictionaries will produce equivalent storage keys.
+        warn_on_readonly: if True, log a warning if the store is readonly
+
+    Returns:
+        An object derived from client.Storage for getting/setting the
+        credential.
+    """
+    multistore = _get_multistore(filename, warn_on_readonly=warn_on_readonly)
+    key = _dict_to_tuple_key(key_dict)
+    return multistore._get_storage(key)
+
+
+@util.positional(1)
+def get_all_credential_keys(filename, warn_on_readonly=True):
+    """Gets all the registered credential keys in the given Multistore.
+
+    Args:
+        filename: The JSON file storing a set of credentials
+        warn_on_readonly: if True, log a warning if the store is readonly
+
+    Returns:
+        A list of the credential keys present in the file.  They are returned
+        as dictionaries that can be passed into
+        get_credential_storage_custom_key to get the actual credentials.
+    """
+    multistore = _get_multistore(filename, warn_on_readonly=warn_on_readonly)
+    multistore._lock()
+    try:
+        return multistore._get_all_credential_keys()
+    finally:
+        multistore._unlock()
+
+
+@util.positional(1)
+def _get_multistore(filename, warn_on_readonly=True):
+    """A helper method to initialize the multistore with proper locking.
+
+    Args:
+        filename: The JSON file storing a set of credentials
+        warn_on_readonly: if True, log a warning if the store is readonly
+
+    Returns:
+        A multistore object
+    """
+    filename = os.path.expanduser(filename)
+    _multistores_lock.acquire()
+    try:
+        multistore = _multistores.setdefault(
+            filename, _MultiStore(filename, warn_on_readonly=warn_on_readonly))
+    finally:
+        _multistores_lock.release()
+    return multistore
+
+
+class _MultiStore(object):
+    """A file backed store for multiple credentials."""
+
+    @util.positional(2)
+    def __init__(self, filename, warn_on_readonly=True):
+        """Initialize the class.
+
+        This will create the file if necessary.
+        """
+        self._file = locked_file.LockedFile(filename, 'r+', 'r')
+        self._thread_lock = threading.Lock()
+        self._read_only = False
+        self._warn_on_readonly = warn_on_readonly
+
+        self._create_file_if_needed()
+
+        # Cache of deserialized store. This is only valid after the
+        # _MultiStore is locked or _refresh_data_cache is called. This is
+        # of the form of:
+        #
+        # ((key, value), (key, value)...) -> OAuth2Credential
+        #
+        # If this is None, then the store hasn't been read yet.
+        self._data = None
+
+    class _Storage(client.Storage):
+        """A Storage object that can read/write a single credential."""
+
+        def __init__(self, multistore, key):
+            self._multistore = multistore
+            self._key = key
+
+        def acquire_lock(self):
+            """Acquires any lock necessary to access this Storage.
+
+            This lock is not reentrant.
+            """
+            self._multistore._lock()
+
+        def release_lock(self):
+            """Release the Storage lock.
+
+            Trying to release a lock that isn't held will result in a
+            RuntimeError.
+            """
+            self._multistore._unlock()
+
+        def locked_get(self):
+            """Retrieve credential.
+
+            The Storage lock must be held when this is called.
+
+            Returns:
+                oauth2client.client.Credentials
+            """
+            credential = self._multistore._get_credential(self._key)
+            if credential:
+                credential.set_store(self)
+            return credential
+
+        def locked_put(self, credentials):
+            """Write a credential.
+
+            The Storage lock must be held when this is called.
+
+            Args:
+                credentials: Credentials, the credentials to store.
+            """
+            self._multistore._update_credential(self._key, credentials)
+
+        def locked_delete(self):
+            """Delete a credential.
+
+            The Storage lock must be held when this is called.
+
+            Args:
+                credentials: Credentials, the credentials to store.
+            """
+            self._multistore._delete_credential(self._key)
+
+    def _create_file_if_needed(self):
+        """Create an empty file if necessary.
+
+        This method will not initialize the file. Instead it implements a
+        simple version of "touch" to ensure the file has been created.
+        """
+        if not os.path.exists(self._file.filename()):
+            old_umask = os.umask(0o177)
+            try:
+                open(self._file.filename(), 'a+b').close()
+            finally:
+                os.umask(old_umask)
+
+    def _lock(self):
+        """Lock the entire multistore."""
+        self._thread_lock.acquire()
+        try:
+            self._file.open_and_lock()
+        except (IOError, OSError) as e:
+            if e.errno == errno.ENOSYS:
+                logger.warn('File system does not support locking the '
+                            'credentials file.')
+            elif e.errno == errno.ENOLCK:
+                logger.warn('File system is out of resources for writing the '
+                            'credentials file (is your disk full?).')
+            elif e.errno == errno.EDEADLK:
+                logger.warn('Lock contention on multistore file, opening '
+                            'in read-only mode.')
+            elif e.errno == errno.EACCES:
+                logger.warn('Cannot access credentials file.')
+            else:
+                raise
+        if not self._file.is_locked():
+            self._read_only = True
+            if self._warn_on_readonly:
+                logger.warn('The credentials file (%s) is not writable. '
+                            'Opening in read-only mode. Any refreshed '
+                            'credentials will only be '
+                            'valid for this run.', self._file.filename())
+
+        if os.path.getsize(self._file.filename()) == 0:
+            logger.debug('Initializing empty multistore file')
+            # The multistore is empty so write out an empty file.
+            self._data = {}
+            self._write()
+        elif not self._read_only or self._data is None:
+            # Only refresh the data if we are read/write or we haven't
+            # cached the data yet. If we are readonly, we assume is isn't
+            # changing out from under us and that we only have to read it
+            # once. This prevents us from whacking any new access keys that
+            # we have cached in memory but were unable to write out.
+            self._refresh_data_cache()
+
+    def _unlock(self):
+        """Release the lock on the multistore."""
+        self._file.unlock_and_close()
+        self._thread_lock.release()
+
+    def _locked_json_read(self):
+        """Get the raw content of the multistore file.
+
+        The multistore must be locked when this is called.
+
+        Returns:
+            The contents of the multistore decoded as JSON.
+        """
+        assert self._thread_lock.locked()
+        self._file.file_handle().seek(0)
+        return json.load(self._file.file_handle())
+
+    def _locked_json_write(self, data):
+        """Write a JSON serializable data structure to the multistore.
+
+        The multistore must be locked when this is called.
+
+        Args:
+            data: The data to be serialized and written.
+        """
+        assert self._thread_lock.locked()
+        if self._read_only:
+            return
+        self._file.file_handle().seek(0)
+        json.dump(data, self._file.file_handle(),
+                  sort_keys=True, indent=2, separators=(',', ': '))
+        self._file.file_handle().truncate()
+
+    def _refresh_data_cache(self):
+        """Refresh the contents of the multistore.
+
+        The multistore must be locked when this is called.
+
+        Raises:
+            NewerCredentialStoreError: Raised when a newer client has written
+            the store.
+        """
+        self._data = {}
+        try:
+            raw_data = self._locked_json_read()
+        except Exception:
+            logger.warn('Credential data store could not be loaded. '
+                        'Will ignore and overwrite.')
+            return
+
+        version = 0
+        try:
+            version = raw_data['file_version']
+        except Exception:
+            logger.warn('Missing version for credential data store. It may be '
+                        'corrupt or an old version. Overwriting.')
+        if version > 1:
+            raise NewerCredentialStoreError(
+                'Credential file has file_version of {0}. '
+                'Only file_version of 1 is supported.'.format(version))
+
+        credentials = []
+        try:
+            credentials = raw_data['data']
+        except (TypeError, KeyError):
+            pass
+
+        for cred_entry in credentials:
+            try:
+                key, credential = self._decode_credential_from_json(cred_entry)
+                self._data[key] = credential
+            except:
+                # If something goes wrong loading a credential, just ignore it
+                logger.info('Error decoding credential, skipping',
+                            exc_info=True)
+
+    def _decode_credential_from_json(self, cred_entry):
+        """Load a credential from our JSON serialization.
+
+        Args:
+            cred_entry: A dict entry from the data member of our format
+
+        Returns:
+            (key, cred) where the key is the key tuple and the cred is the
+            OAuth2Credential object.
+        """
+        raw_key = cred_entry['key']
+        key = _dict_to_tuple_key(raw_key)
+        credential = None
+        credential = client.Credentials.new_from_json(
+            json.dumps(cred_entry['credential']))
+        return (key, credential)
+
+    def _write(self):
+        """Write the cached data back out.
+
+        The multistore must be locked.
+        """
+        raw_data = {'file_version': 1}
+        raw_creds = []
+        raw_data['data'] = raw_creds
+        for (cred_key, cred) in self._data.items():
+            raw_key = dict(cred_key)
+            raw_cred = json.loads(cred.to_json())
+            raw_creds.append({'key': raw_key, 'credential': raw_cred})
+        self._locked_json_write(raw_data)
+
+    def _get_all_credential_keys(self):
+        """Gets all the registered credential keys in the multistore.
+
+        Returns:
+            A list of dictionaries corresponding to all the keys currently
+            registered
+        """
+        return [dict(key) for key in self._data.keys()]
+
+    def _get_credential(self, key):
+        """Get a credential from the multistore.
+
+        The multistore must be locked.
+
+        Args:
+            key: The key used to retrieve the credential
+
+        Returns:
+            The credential specified or None if not present
+        """
+        return self._data.get(key, None)
+
+    def _update_credential(self, key, cred):
+        """Update a credential and write the multistore.
+
+        This must be called when the multistore is locked.
+
+        Args:
+            key: The key used to retrieve the credential
+            cred: The OAuth2Credential to update/set
+        """
+        self._data[key] = cred
+        self._write()
+
+    def _delete_credential(self, key):
+        """Delete a credential and write the multistore.
+
+        This must be called when the multistore is locked.
+
+        Args:
+            key: The key used to retrieve the credential
+        """
+        try:
+            del self._data[key]
+        except KeyError:
+            pass
+        self._write()
+
+    def _get_storage(self, key):
+        """Get a Storage object to get/set a credential.
+
+        This Storage is a 'view' into the multistore.
+
+        Args:
+            key: The key used to retrieve the credential
+
+        Returns:
+            A Storage object that can be used to get/set this cred
+        """
+        return self._Storage(self, key)
diff --git a/oauth2client/contrib/sqlalchemy.py b/oauth2client/contrib/sqlalchemy.py
new file mode 100644
index 0000000..7d9fd4b
--- /dev/null
+++ b/oauth2client/contrib/sqlalchemy.py
@@ -0,0 +1,173 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""OAuth 2.0 utilities for SQLAlchemy.
+
+Utilities for using OAuth 2.0 in conjunction with a SQLAlchemy.
+
+Configuration
+=============
+
+In order to use this storage, you'll need to create table
+with :class:`oauth2client.contrib.sqlalchemy.CredentialsType` column.
+It's recommended to either put this column on some sort of user info
+table or put the column in a table with a belongs-to relationship to
+a user info table.
+
+Here's an example of a simple table with a :class:`CredentialsType`
+column that's related to a user table by the `user_id` key.
+
+.. code-block:: python
+
+    from sqlalchemy import Column, ForeignKey, Integer
+    from sqlalchemy.ext.declarative import declarative_base
+    from sqlalchemy.orm import relationship
+
+    from oauth2client.contrib.sqlalchemy import CredentialsType
+
+
+    Base = declarative_base()
+
+
+    class Credentials(Base):
+        __tablename__ = 'credentials'
+
+        user_id = Column(Integer, ForeignKey('user.id'))
+        credentials = Column(CredentialsType)
+
+
+    class User(Base):
+        id = Column(Integer, primary_key=True)
+        # bunch of other columns
+        credentials = relationship('Credentials')
+
+
+Usage
+=====
+
+With tables ready, you are now able to store credentials in database.
+We will reuse tables defined above.
+
+.. code-block:: python
+
+    from sqlalchemy.orm import Session
+
+    from oauth2client.client import OAuth2Credentials
+    from oauth2client.contrib.sql_alchemy import Storage
+
+    session = Session()
+    user = session.query(User).first()
+    storage = Storage(
+        session=session,
+        model_class=Credentials,
+        # This is the key column used to identify
+        # the row that stores the credentials.
+        key_name='user_id',
+        key_value=user.id,
+        property_name='credentials',
+    )
+
+    # Store
+    credentials = OAuth2Credentials(...)
+    storage.put(credentials)
+
+    # Retrieve
+    credentials = storage.get()
+
+    # Delete
+    storage.delete()
+
+"""
+
+from __future__ import absolute_import
+
+import sqlalchemy.types
+
+from oauth2client import client
+
+
+class CredentialsType(sqlalchemy.types.PickleType):
+    """Type representing credentials.
+
+    Alias for :class:`sqlalchemy.types.PickleType`.
+    """
+
+
+class Storage(client.Storage):
+    """Store and retrieve a single credential to and from SQLAlchemy.
+    This helper presumes the Credentials
+    have been stored as a Credentials column
+    on a db model class.
+    """
+
+    def __init__(self, session, model_class, key_name,
+                 key_value, property_name):
+        """Constructor for Storage.
+
+        Args:
+            session: An instance of :class:`sqlalchemy.orm.Session`.
+            model_class: SQLAlchemy declarative mapping.
+            key_name: string, key name for the entity that has the credentials
+            key_value: key value for the entity that has the credentials
+            property_name: A string indicating which property on the
+                           ``model_class`` to store the credentials.
+                           This property must be a
+                           :class:`CredentialsType` column.
+        """
+        super(Storage, self).__init__()
+
+        self.session = session
+        self.model_class = model_class
+        self.key_name = key_name
+        self.key_value = key_value
+        self.property_name = property_name
+
+    def locked_get(self):
+        """Retrieve stored credential.
+
+        Returns:
+            A :class:`oauth2client.Credentials` instance or `None`.
+        """
+        filters = {self.key_name: self.key_value}
+        query = self.session.query(self.model_class).filter_by(**filters)
+        entity = query.first()
+
+        if entity:
+            credential = getattr(entity, self.property_name)
+            if credential and hasattr(credential, 'set_store'):
+                credential.set_store(self)
+            return credential
+        else:
+            return None
+
+    def locked_put(self, credentials):
+        """Write a credentials to the SQLAlchemy datastore.
+
+        Args:
+            credentials: :class:`oauth2client.Credentials`
+        """
+        filters = {self.key_name: self.key_value}
+        query = self.session.query(self.model_class).filter_by(**filters)
+        entity = query.first()
+
+        if not entity:
+            entity = self.model_class(**filters)
+
+        setattr(entity, self.property_name, credentials)
+        self.session.add(entity)
+
+    def locked_delete(self):
+        """Delete credentials from the SQLAlchemy datastore."""
+        filters = {self.key_name: self.key_value}
+        self.session.query(self.model_class).filter_by(**filters).delete()
diff --git a/oauth2client/contrib/xsrfutil.py b/oauth2client/contrib/xsrfutil.py
new file mode 100644
index 0000000..c03e679
--- /dev/null
+++ b/oauth2client/contrib/xsrfutil.py
@@ -0,0 +1,106 @@
+# Copyright 2014 the Melange authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Helper methods for creating & verifying XSRF tokens."""
+
+import base64
+import binascii
+import hmac
+import time
+
+from oauth2client import _helpers
+from oauth2client import util
+
+__authors__ = [
+    '"Doug Coker" <dcoker@google.com>',
+    '"Joe Gregorio" <jcgregorio@google.com>',
+]
+
+# Delimiter character
+DELIMITER = b':'
+
+# 1 hour in seconds
+DEFAULT_TIMEOUT_SECS = 60 * 60
+
+
+@util.positional(2)
+def generate_token(key, user_id, action_id='', when=None):
+    """Generates a URL-safe token for the given user, action, time tuple.
+
+    Args:
+        key: secret key to use.
+        user_id: the user ID of the authenticated user.
+        action_id: a string identifier of the action they requested
+                   authorization for.
+        when: the time in seconds since the epoch at which the user was
+              authorized for this action. If not set the current time is used.
+
+    Returns:
+        A string XSRF protection token.
+    """
+    digester = hmac.new(_helpers._to_bytes(key, encoding='utf-8'))
+    digester.update(_helpers._to_bytes(str(user_id), encoding='utf-8'))
+    digester.update(DELIMITER)
+    digester.update(_helpers._to_bytes(action_id, encoding='utf-8'))
+    digester.update(DELIMITER)
+    when = _helpers._to_bytes(str(when or int(time.time())), encoding='utf-8')
+    digester.update(when)
+    digest = digester.digest()
+
+    token = base64.urlsafe_b64encode(digest + DELIMITER + when)
+    return token
+
+
+@util.positional(3)
+def validate_token(key, token, user_id, action_id="", current_time=None):
+    """Validates that the given token authorizes the user for the action.
+
+    Tokens are invalid if the time of issue is too old or if the token
+    does not match what generateToken outputs (i.e. the token was forged).
+
+    Args:
+        key: secret key to use.
+        token: a string of the token generated by generateToken.
+        user_id: the user ID of the authenticated user.
+        action_id: a string identifier of the action they requested
+                   authorization for.
+
+    Returns:
+        A boolean - True if the user is authorized for the action, False
+        otherwise.
+    """
+    if not token:
+        return False
+    try:
+        decoded = base64.urlsafe_b64decode(token)
+        token_time = int(decoded.split(DELIMITER)[-1])
+    except (TypeError, ValueError, binascii.Error):
+        return False
+    if current_time is None:
+        current_time = time.time()
+    # If the token is too old it's not valid.
+    if current_time - token_time > DEFAULT_TIMEOUT_SECS:
+        return False
+
+    # The given token should match the generated one with the same time.
+    expected_token = generate_token(key, user_id, action_id=action_id,
+                                    when=token_time)
+    if len(token) != len(expected_token):
+        return False
+
+    # Perform constant time comparison to avoid timing attacks
+    different = 0
+    for x, y in zip(bytearray(token), bytearray(expected_token)):
+        different |= x ^ y
+    return not different
diff --git a/oauth2client/crypt.py b/oauth2client/crypt.py
new file mode 100644
index 0000000..1326098
--- /dev/null
+++ b/oauth2client/crypt.py
@@ -0,0 +1,250 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Crypto-related routines for oauth2client."""
+
+import json
+import logging
+import time
+
+from oauth2client import _helpers
+from oauth2client import _pure_python_crypt
+
+
+RsaSigner = _pure_python_crypt.RsaSigner
+RsaVerifier = _pure_python_crypt.RsaVerifier
+
+CLOCK_SKEW_SECS = 300  # 5 minutes in seconds
+AUTH_TOKEN_LIFETIME_SECS = 300  # 5 minutes in seconds
+MAX_TOKEN_LIFETIME_SECS = 86400  # 1 day in seconds
+
+logger = logging.getLogger(__name__)
+
+
+class AppIdentityError(Exception):
+    """Error to indicate crypto failure."""
+
+
+def _bad_pkcs12_key_as_pem(*args, **kwargs):
+    raise NotImplementedError('pkcs12_key_as_pem requires OpenSSL.')
+
+
+try:
+    from oauth2client import _openssl_crypt
+    OpenSSLSigner = _openssl_crypt.OpenSSLSigner
+    OpenSSLVerifier = _openssl_crypt.OpenSSLVerifier
+    pkcs12_key_as_pem = _openssl_crypt.pkcs12_key_as_pem
+except ImportError:  # pragma: NO COVER
+    OpenSSLVerifier = None
+    OpenSSLSigner = None
+    pkcs12_key_as_pem = _bad_pkcs12_key_as_pem
+
+try:
+    from oauth2client import _pycrypto_crypt
+    PyCryptoSigner = _pycrypto_crypt.PyCryptoSigner
+    PyCryptoVerifier = _pycrypto_crypt.PyCryptoVerifier
+except ImportError:  # pragma: NO COVER
+    PyCryptoVerifier = None
+    PyCryptoSigner = None
+
+
+if OpenSSLSigner:
+    Signer = OpenSSLSigner
+    Verifier = OpenSSLVerifier
+elif PyCryptoSigner:  # pragma: NO COVER
+    Signer = PyCryptoSigner
+    Verifier = PyCryptoVerifier
+else:  # pragma: NO COVER
+    Signer = RsaSigner
+    Verifier = RsaVerifier
+
+
+def make_signed_jwt(signer, payload, key_id=None):
+    """Make a signed JWT.
+
+    See http://self-issued.info/docs/draft-jones-json-web-token.html.
+
+    Args:
+        signer: crypt.Signer, Cryptographic signer.
+        payload: dict, Dictionary of data to convert to JSON and then sign.
+        key_id: string, (Optional) Key ID header.
+
+    Returns:
+        string, The JWT for the payload.
+    """
+    header = {'typ': 'JWT', 'alg': 'RS256'}
+    if key_id is not None:
+        header['kid'] = key_id
+
+    segments = [
+        _helpers._urlsafe_b64encode(_helpers._json_encode(header)),
+        _helpers._urlsafe_b64encode(_helpers._json_encode(payload)),
+    ]
+    signing_input = b'.'.join(segments)
+
+    signature = signer.sign(signing_input)
+    segments.append(_helpers._urlsafe_b64encode(signature))
+
+    logger.debug(str(segments))
+
+    return b'.'.join(segments)
+
+
+def _verify_signature(message, signature, certs):
+    """Verifies signed content using a list of certificates.
+
+    Args:
+        message: string or bytes, The message to verify.
+        signature: string or bytes, The signature on the message.
+        certs: iterable, certificates in PEM format.
+
+    Raises:
+        AppIdentityError: If none of the certificates can verify the message
+                          against the signature.
+    """
+    for pem in certs:
+        verifier = Verifier.from_string(pem, is_x509_cert=True)
+        if verifier.verify(message, signature):
+            return
+
+    # If we have not returned, no certificate confirms the signature.
+    raise AppIdentityError('Invalid token signature')
+
+
+def _check_audience(payload_dict, audience):
+    """Checks audience field from a JWT payload.
+
+    Does nothing if the passed in ``audience`` is null.
+
+    Args:
+        payload_dict: dict, A dictionary containing a JWT payload.
+        audience: string or NoneType, an audience to check for in
+                  the JWT payload.
+
+    Raises:
+        AppIdentityError: If there is no ``'aud'`` field in the payload
+                          dictionary but there is an ``audience`` to check.
+        AppIdentityError: If the ``'aud'`` field in the payload dictionary
+                          does not match the ``audience``.
+    """
+    if audience is None:
+        return
+
+    audience_in_payload = payload_dict.get('aud')
+    if audience_in_payload is None:
+        raise AppIdentityError(
+            'No aud field in token: {0}'.format(payload_dict))
+    if audience_in_payload != audience:
+        raise AppIdentityError('Wrong recipient, {0} != {1}: {2}'.format(
+            audience_in_payload, audience, payload_dict))
+
+
+def _verify_time_range(payload_dict):
+    """Verifies the issued at and expiration from a JWT payload.
+
+    Makes sure the current time (in UTC) falls between the issued at and
+    expiration for the JWT (with some skew allowed for via
+    ``CLOCK_SKEW_SECS``).
+
+    Args:
+        payload_dict: dict, A dictionary containing a JWT payload.
+
+    Raises:
+        AppIdentityError: If there is no ``'iat'`` field in the payload
+                          dictionary.
+        AppIdentityError: If there is no ``'exp'`` field in the payload
+                          dictionary.
+        AppIdentityError: If the JWT expiration is too far in the future (i.e.
+                          if the expiration would imply a token lifetime
+                          longer than what is allowed.)
+        AppIdentityError: If the token appears to have been issued in the
+                          future (up to clock skew).
+        AppIdentityError: If the token appears to have expired in the past
+                          (up to clock skew).
+    """
+    # Get the current time to use throughout.
+    now = int(time.time())
+
+    # Make sure issued at and expiration are in the payload.
+    issued_at = payload_dict.get('iat')
+    if issued_at is None:
+        raise AppIdentityError(
+            'No iat field in token: {0}'.format(payload_dict))
+    expiration = payload_dict.get('exp')
+    if expiration is None:
+        raise AppIdentityError(
+            'No exp field in token: {0}'.format(payload_dict))
+
+    # Make sure the expiration gives an acceptable token lifetime.
+    if expiration >= now + MAX_TOKEN_LIFETIME_SECS:
+        raise AppIdentityError(
+            'exp field too far in future: {0}'.format(payload_dict))
+
+    # Make sure (up to clock skew) that the token wasn't issued in the future.
+    earliest = issued_at - CLOCK_SKEW_SECS
+    if now < earliest:
+        raise AppIdentityError('Token used too early, {0} < {1}: {2}'.format(
+            now, earliest, payload_dict))
+    # Make sure (up to clock skew) that the token isn't already expired.
+    latest = expiration + CLOCK_SKEW_SECS
+    if now > latest:
+        raise AppIdentityError('Token used too late, {0} > {1}: {2}'.format(
+            now, latest, payload_dict))
+
+
+def verify_signed_jwt_with_certs(jwt, certs, audience=None):
+    """Verify a JWT against public certs.
+
+    See http://self-issued.info/docs/draft-jones-json-web-token.html.
+
+    Args:
+        jwt: string, A JWT.
+        certs: dict, Dictionary where values of public keys in PEM format.
+        audience: string, The audience, 'aud', that this JWT should contain. If
+                  None then the JWT's 'aud' parameter is not verified.
+
+    Returns:
+        dict, The deserialized JSON payload in the JWT.
+
+    Raises:
+        AppIdentityError: if any checks are failed.
+    """
+    jwt = _helpers._to_bytes(jwt)
+
+    if jwt.count(b'.') != 2:
+        raise AppIdentityError(
+            'Wrong number of segments in token: {0}'.format(jwt))
+
+    header, payload, signature = jwt.split(b'.')
+    message_to_sign = header + b'.' + payload
+    signature = _helpers._urlsafe_b64decode(signature)
+
+    # Parse token.
+    payload_bytes = _helpers._urlsafe_b64decode(payload)
+    try:
+        payload_dict = json.loads(_helpers._from_bytes(payload_bytes))
+    except:
+        raise AppIdentityError('Can\'t parse token: {0}'.format(payload_bytes))
+
+    # Verify that the signature matches the message.
+    _verify_signature(message_to_sign, signature, certs.values())
+
+    # Verify the issued at and created times in the payload.
+    _verify_time_range(payload_dict)
+
+    # Check audience.
+    _check_audience(payload_dict, audience)
+
+    return payload_dict
diff --git a/oauth2client/file.py b/oauth2client/file.py
new file mode 100644
index 0000000..feede11
--- /dev/null
+++ b/oauth2client/file.py
@@ -0,0 +1,106 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities for OAuth.
+
+Utilities for making it easier to work with OAuth 2.0
+credentials.
+"""
+
+import os
+import threading
+
+from oauth2client import client
+
+
+__author__ = 'jcgregorio@google.com (Joe Gregorio)'
+
+
+class CredentialsFileSymbolicLinkError(Exception):
+    """Credentials files must not be symbolic links."""
+
+
+class Storage(client.Storage):
+    """Store and retrieve a single credential to and from a file."""
+
+    def __init__(self, filename):
+        super(Storage, self).__init__(lock=threading.Lock())
+        self._filename = filename
+
+    def _validate_file(self):
+        if os.path.islink(self._filename):
+            raise CredentialsFileSymbolicLinkError(
+                'File: {0} is a symbolic link.'.format(self._filename))
+
+    def locked_get(self):
+        """Retrieve Credential from file.
+
+        Returns:
+            oauth2client.client.Credentials
+
+        Raises:
+            CredentialsFileSymbolicLinkError if the file is a symbolic link.
+        """
+        credentials = None
+        self._validate_file()
+        try:
+            f = open(self._filename, 'rb')
+            content = f.read()
+            f.close()
+        except IOError:
+            return credentials
+
+        try:
+            credentials = client.Credentials.new_from_json(content)
+            credentials.set_store(self)
+        except ValueError:
+            pass
+
+        return credentials
+
+    def _create_file_if_needed(self):
+        """Create an empty file if necessary.
+
+        This method will not initialize the file. Instead it implements a
+        simple version of "touch" to ensure the file has been created.
+        """
+        if not os.path.exists(self._filename):
+            old_umask = os.umask(0o177)
+            try:
+                open(self._filename, 'a+b').close()
+            finally:
+                os.umask(old_umask)
+
+    def locked_put(self, credentials):
+        """Write Credentials to file.
+
+        Args:
+            credentials: Credentials, the credentials to store.
+
+        Raises:
+            CredentialsFileSymbolicLinkError if the file is a symbolic link.
+        """
+        self._create_file_if_needed()
+        self._validate_file()
+        f = open(self._filename, 'w')
+        f.write(credentials.to_json())
+        f.close()
+
+    def locked_delete(self):
+        """Delete Credentials file.
+
+        Args:
+            credentials: Credentials, the credentials to store.
+        """
+        os.unlink(self._filename)
diff --git a/oauth2client/service_account.py b/oauth2client/service_account.py
new file mode 100644
index 0000000..bdcfd69
--- /dev/null
+++ b/oauth2client/service_account.py
@@ -0,0 +1,673 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""oauth2client Service account credentials class."""
+
+import base64
+import copy
+import datetime
+import json
+import time
+
+import oauth2client
+from oauth2client import _helpers
+from oauth2client import client
+from oauth2client import crypt
+from oauth2client import transport
+from oauth2client import util
+
+
+_PASSWORD_DEFAULT = 'notasecret'
+_PKCS12_KEY = '_private_key_pkcs12'
+_PKCS12_ERROR = r"""
+This library only implements PKCS#12 support via the pyOpenSSL library.
+Either install pyOpenSSL, or please convert the .p12 file
+to .pem format:
+    $ cat key.p12 | \
+    >   openssl pkcs12 -nodes -nocerts -passin pass:notasecret | \
+    >   openssl rsa > key.pem
+"""
+
+
+class ServiceAccountCredentials(client.AssertionCredentials):
+    """Service Account credential for OAuth 2.0 signed JWT grants.
+
+    Supports
+
+    * JSON keyfile (typically contains a PKCS8 key stored as
+      PEM text)
+    * ``.p12`` key (stores PKCS12 key and certificate)
+
+    Makes an assertion to server using a signed JWT assertion in exchange
+    for an access token.
+
+    This credential does not require a flow to instantiate because it
+    represents a two legged flow, and therefore has all of the required
+    information to generate and refresh its own access tokens.
+
+    Args:
+        service_account_email: string, The email associated with the
+                               service account.
+        signer: ``crypt.Signer``, A signer which can be used to sign content.
+        scopes: List or string, (Optional) Scopes to use when acquiring
+                an access token.
+        private_key_id: string, (Optional) Private key identifier. Typically
+                        only used with a JSON keyfile. Can be sent in the
+                        header of a JWT token assertion.
+        client_id: string, (Optional) Client ID for the project that owns the
+                   service account.
+        user_agent: string, (Optional) User agent to use when sending
+                    request.
+        token_uri: string, URI for token endpoint. For convenience defaults
+                   to Google's endpoints but any OAuth 2.0 provider can be
+                   used.
+        revoke_uri: string, URI for revoke endpoint.  For convenience defaults
+                   to Google's endpoints but any OAuth 2.0 provider can be
+                   used.
+        kwargs: dict, Extra key-value pairs (both strings) to send in the
+                payload body when making an assertion.
+    """
+
+    MAX_TOKEN_LIFETIME_SECS = 3600
+    """Max lifetime of the token (one hour, in seconds)."""
+
+    NON_SERIALIZED_MEMBERS = (
+        frozenset(['_signer']) |
+        client.AssertionCredentials.NON_SERIALIZED_MEMBERS)
+    """Members that aren't serialized when object is converted to JSON."""
+
+    # Can be over-ridden by factory constructors. Used for
+    # serialization/deserialization purposes.
+    _private_key_pkcs8_pem = None
+    _private_key_pkcs12 = None
+    _private_key_password = None
+
+    def __init__(self,
+                 service_account_email,
+                 signer,
+                 scopes='',
+                 private_key_id=None,
+                 client_id=None,
+                 user_agent=None,
+                 token_uri=oauth2client.GOOGLE_TOKEN_URI,
+                 revoke_uri=oauth2client.GOOGLE_REVOKE_URI,
+                 **kwargs):
+
+        super(ServiceAccountCredentials, self).__init__(
+            None, user_agent=user_agent, token_uri=token_uri,
+            revoke_uri=revoke_uri)
+
+        self._service_account_email = service_account_email
+        self._signer = signer
+        self._scopes = util.scopes_to_string(scopes)
+        self._private_key_id = private_key_id
+        self.client_id = client_id
+        self._user_agent = user_agent
+        self._kwargs = kwargs
+
+    def _to_json(self, strip, to_serialize=None):
+        """Utility function that creates JSON repr. of a credentials object.
+
+        Over-ride is needed since PKCS#12 keys will not in general be JSON
+        serializable.
+
+        Args:
+            strip: array, An array of names of members to exclude from the
+                   JSON.
+            to_serialize: dict, (Optional) The properties for this object
+                          that will be serialized. This allows callers to
+                          modify before serializing.
+
+        Returns:
+            string, a JSON representation of this instance, suitable to pass to
+            from_json().
+        """
+        if to_serialize is None:
+            to_serialize = copy.copy(self.__dict__)
+        pkcs12_val = to_serialize.get(_PKCS12_KEY)
+        if pkcs12_val is not None:
+            to_serialize[_PKCS12_KEY] = base64.b64encode(pkcs12_val)
+        return super(ServiceAccountCredentials, self)._to_json(
+            strip, to_serialize=to_serialize)
+
+    @classmethod
+    def _from_parsed_json_keyfile(cls, keyfile_dict, scopes,
+                                  token_uri=None, revoke_uri=None):
+        """Helper for factory constructors from JSON keyfile.
+
+        Args:
+            keyfile_dict: dict-like object, The parsed dictionary-like object
+                          containing the contents of the JSON keyfile.
+            scopes: List or string, Scopes to use when acquiring an
+                    access token.
+            token_uri: string, URI for OAuth 2.0 provider token endpoint.
+                       If unset and not present in keyfile_dict, defaults
+                       to Google's endpoints.
+            revoke_uri: string, URI for OAuth 2.0 provider revoke endpoint.
+                       If unset and not present in keyfile_dict, defaults
+                       to Google's endpoints.
+
+        Returns:
+            ServiceAccountCredentials, a credentials object created from
+            the keyfile contents.
+
+        Raises:
+            ValueError, if the credential type is not :data:`SERVICE_ACCOUNT`.
+            KeyError, if one of the expected keys is not present in
+                the keyfile.
+        """
+        creds_type = keyfile_dict.get('type')
+        if creds_type != client.SERVICE_ACCOUNT:
+            raise ValueError('Unexpected credentials type', creds_type,
+                             'Expected', client.SERVICE_ACCOUNT)
+
+        service_account_email = keyfile_dict['client_email']
+        private_key_pkcs8_pem = keyfile_dict['private_key']
+        private_key_id = keyfile_dict['private_key_id']
+        client_id = keyfile_dict['client_id']
+        if not token_uri:
+            token_uri = keyfile_dict.get('token_uri',
+                                         oauth2client.GOOGLE_TOKEN_URI)
+        if not revoke_uri:
+            revoke_uri = keyfile_dict.get('revoke_uri',
+                                          oauth2client.GOOGLE_REVOKE_URI)
+
+        signer = crypt.Signer.from_string(private_key_pkcs8_pem)
+        credentials = cls(service_account_email, signer, scopes=scopes,
+                          private_key_id=private_key_id,
+                          client_id=client_id, token_uri=token_uri,
+                          revoke_uri=revoke_uri)
+        credentials._private_key_pkcs8_pem = private_key_pkcs8_pem
+        return credentials
+
+    @classmethod
+    def from_json_keyfile_name(cls, filename, scopes='',
+                               token_uri=None, revoke_uri=None):
+
+        """Factory constructor from JSON keyfile by name.
+
+        Args:
+            filename: string, The location of the keyfile.
+            scopes: List or string, (Optional) Scopes to use when acquiring an
+                    access token.
+            token_uri: string, URI for OAuth 2.0 provider token endpoint.
+                       If unset and not present in the key file, defaults
+                       to Google's endpoints.
+            revoke_uri: string, URI for OAuth 2.0 provider revoke endpoint.
+                       If unset and not present in the key file, defaults
+                       to Google's endpoints.
+
+        Returns:
+            ServiceAccountCredentials, a credentials object created from
+            the keyfile.
+
+        Raises:
+            ValueError, if the credential type is not :data:`SERVICE_ACCOUNT`.
+            KeyError, if one of the expected keys is not present in
+                the keyfile.
+        """
+        with open(filename, 'r') as file_obj:
+            client_credentials = json.load(file_obj)
+        return cls._from_parsed_json_keyfile(client_credentials, scopes,
+                                             token_uri=token_uri,
+                                             revoke_uri=revoke_uri)
+
+    @classmethod
+    def from_json_keyfile_dict(cls, keyfile_dict, scopes='',
+                               token_uri=None, revoke_uri=None):
+        """Factory constructor from parsed JSON keyfile.
+
+        Args:
+            keyfile_dict: dict-like object, The parsed dictionary-like object
+                          containing the contents of the JSON keyfile.
+            scopes: List or string, (Optional) Scopes to use when acquiring an
+                    access token.
+            token_uri: string, URI for OAuth 2.0 provider token endpoint.
+                       If unset and not present in keyfile_dict, defaults
+                       to Google's endpoints.
+            revoke_uri: string, URI for OAuth 2.0 provider revoke endpoint.
+                       If unset and not present in keyfile_dict, defaults
+                       to Google's endpoints.
+
+        Returns:
+            ServiceAccountCredentials, a credentials object created from
+            the keyfile.
+
+        Raises:
+            ValueError, if the credential type is not :data:`SERVICE_ACCOUNT`.
+            KeyError, if one of the expected keys is not present in
+                the keyfile.
+        """
+        return cls._from_parsed_json_keyfile(keyfile_dict, scopes,
+                                             token_uri=token_uri,
+                                             revoke_uri=revoke_uri)
+
+    @classmethod
+    def _from_p12_keyfile_contents(cls, service_account_email,
+                                   private_key_pkcs12,
+                                   private_key_password=None, scopes='',
+                                   token_uri=oauth2client.GOOGLE_TOKEN_URI,
+                                   revoke_uri=oauth2client.GOOGLE_REVOKE_URI):
+        """Factory constructor from JSON keyfile.
+
+        Args:
+            service_account_email: string, The email associated with the
+                                   service account.
+            private_key_pkcs12: string, The contents of a PKCS#12 keyfile.
+            private_key_password: string, (Optional) Password for PKCS#12
+                                  private key. Defaults to ``notasecret``.
+            scopes: List or string, (Optional) Scopes to use when acquiring an
+                    access token.
+            token_uri: string, URI for token endpoint. For convenience defaults
+                       to Google's endpoints but any OAuth 2.0 provider can be
+                       used.
+            revoke_uri: string, URI for revoke endpoint. For convenience
+                        defaults to Google's endpoints but any OAuth 2.0
+                        provider can be used.
+
+        Returns:
+            ServiceAccountCredentials, a credentials object created from
+            the keyfile.
+
+        Raises:
+            NotImplementedError if pyOpenSSL is not installed / not the
+            active crypto library.
+        """
+        if private_key_password is None:
+            private_key_password = _PASSWORD_DEFAULT
+        if crypt.Signer is not crypt.OpenSSLSigner:
+            raise NotImplementedError(_PKCS12_ERROR)
+        signer = crypt.Signer.from_string(private_key_pkcs12,
+                                          private_key_password)
+        credentials = cls(service_account_email, signer, scopes=scopes,
+                          token_uri=token_uri, revoke_uri=revoke_uri)
+        credentials._private_key_pkcs12 = private_key_pkcs12
+        credentials._private_key_password = private_key_password
+        return credentials
+
+    @classmethod
+    def from_p12_keyfile(cls, service_account_email, filename,
+                         private_key_password=None, scopes='',
+                         token_uri=oauth2client.GOOGLE_TOKEN_URI,
+                         revoke_uri=oauth2client.GOOGLE_REVOKE_URI):
+
+        """Factory constructor from JSON keyfile.
+
+        Args:
+            service_account_email: string, The email associated with the
+                                   service account.
+            filename: string, The location of the PKCS#12 keyfile.
+            private_key_password: string, (Optional) Password for PKCS#12
+                                  private key. Defaults to ``notasecret``.
+            scopes: List or string, (Optional) Scopes to use when acquiring an
+                    access token.
+            token_uri: string, URI for token endpoint. For convenience defaults
+                       to Google's endpoints but any OAuth 2.0 provider can be
+                       used.
+            revoke_uri: string, URI for revoke endpoint. For convenience
+                        defaults to Google's endpoints but any OAuth 2.0
+                        provider can be used.
+
+        Returns:
+            ServiceAccountCredentials, a credentials object created from
+            the keyfile.
+
+        Raises:
+            NotImplementedError if pyOpenSSL is not installed / not the
+            active crypto library.
+        """
+        with open(filename, 'rb') as file_obj:
+            private_key_pkcs12 = file_obj.read()
+        return cls._from_p12_keyfile_contents(
+            service_account_email, private_key_pkcs12,
+            private_key_password=private_key_password, scopes=scopes,
+            token_uri=token_uri, revoke_uri=revoke_uri)
+
+    @classmethod
+    def from_p12_keyfile_buffer(cls, service_account_email, file_buffer,
+                                private_key_password=None, scopes='',
+                                token_uri=oauth2client.GOOGLE_TOKEN_URI,
+                                revoke_uri=oauth2client.GOOGLE_REVOKE_URI):
+        """Factory constructor from JSON keyfile.
+
+        Args:
+            service_account_email: string, The email associated with the
+                                   service account.
+            file_buffer: stream, A buffer that implements ``read()``
+                         and contains the PKCS#12 key contents.
+            private_key_password: string, (Optional) Password for PKCS#12
+                                  private key. Defaults to ``notasecret``.
+            scopes: List or string, (Optional) Scopes to use when acquiring an
+                    access token.
+            token_uri: string, URI for token endpoint. For convenience defaults
+                       to Google's endpoints but any OAuth 2.0 provider can be
+                       used.
+            revoke_uri: string, URI for revoke endpoint. For convenience
+                        defaults to Google's endpoints but any OAuth 2.0
+                        provider can be used.
+
+        Returns:
+            ServiceAccountCredentials, a credentials object created from
+            the keyfile.
+
+        Raises:
+            NotImplementedError if pyOpenSSL is not installed / not the
+            active crypto library.
+        """
+        private_key_pkcs12 = file_buffer.read()
+        return cls._from_p12_keyfile_contents(
+            service_account_email, private_key_pkcs12,
+            private_key_password=private_key_password, scopes=scopes,
+            token_uri=token_uri, revoke_uri=revoke_uri)
+
+    def _generate_assertion(self):
+        """Generate the assertion that will be used in the request."""
+        now = int(time.time())
+        payload = {
+            'aud': self.token_uri,
+            'scope': self._scopes,
+            'iat': now,
+            'exp': now + self.MAX_TOKEN_LIFETIME_SECS,
+            'iss': self._service_account_email,
+        }
+        payload.update(self._kwargs)
+        return crypt.make_signed_jwt(self._signer, payload,
+                                     key_id=self._private_key_id)
+
+    def sign_blob(self, blob):
+        """Cryptographically sign a blob (of bytes).
+
+        Implements abstract method
+        :meth:`oauth2client.client.AssertionCredentials.sign_blob`.
+
+        Args:
+            blob: bytes, Message to be signed.
+
+        Returns:
+            tuple, A pair of the private key ID used to sign the blob and
+            the signed contents.
+        """
+        return self._private_key_id, self._signer.sign(blob)
+
+    @property
+    def service_account_email(self):
+        """Get the email for the current service account.
+
+        Returns:
+            string, The email associated with the service account.
+        """
+        return self._service_account_email
+
+    @property
+    def serialization_data(self):
+        # NOTE: This is only useful for JSON keyfile.
+        return {
+            'type': 'service_account',
+            'client_email': self._service_account_email,
+            'private_key_id': self._private_key_id,
+            'private_key': self._private_key_pkcs8_pem,
+            'client_id': self.client_id,
+        }
+
+    @classmethod
+    def from_json(cls, json_data):
+        """Deserialize a JSON-serialized instance.
+
+        Inverse to :meth:`to_json`.
+
+        Args:
+            json_data: dict or string, Serialized JSON (as a string or an
+                       already parsed dictionary) representing a credential.
+
+        Returns:
+            ServiceAccountCredentials from the serialized data.
+        """
+        if not isinstance(json_data, dict):
+            json_data = json.loads(_helpers._from_bytes(json_data))
+
+        private_key_pkcs8_pem = None
+        pkcs12_val = json_data.get(_PKCS12_KEY)
+        password = None
+        if pkcs12_val is None:
+            private_key_pkcs8_pem = json_data['_private_key_pkcs8_pem']
+            signer = crypt.Signer.from_string(private_key_pkcs8_pem)
+        else:
+            # NOTE: This assumes that private_key_pkcs8_pem is not also
+            #       in the serialized data. This would be very incorrect
+            #       state.
+            pkcs12_val = base64.b64decode(pkcs12_val)
+            password = json_data['_private_key_password']
+            signer = crypt.Signer.from_string(pkcs12_val, password)
+
+        credentials = cls(
+            json_data['_service_account_email'],
+            signer,
+            scopes=json_data['_scopes'],
+            private_key_id=json_data['_private_key_id'],
+            client_id=json_data['client_id'],
+            user_agent=json_data['_user_agent'],
+            **json_data['_kwargs']
+        )
+        if private_key_pkcs8_pem is not None:
+            credentials._private_key_pkcs8_pem = private_key_pkcs8_pem
+        if pkcs12_val is not None:
+            credentials._private_key_pkcs12 = pkcs12_val
+        if password is not None:
+            credentials._private_key_password = password
+        credentials.invalid = json_data['invalid']
+        credentials.access_token = json_data['access_token']
+        credentials.token_uri = json_data['token_uri']
+        credentials.revoke_uri = json_data['revoke_uri']
+        token_expiry = json_data.get('token_expiry', None)
+        if token_expiry is not None:
+            credentials.token_expiry = datetime.datetime.strptime(
+                token_expiry, client.EXPIRY_FORMAT)
+        return credentials
+
+    def create_scoped_required(self):
+        return not self._scopes
+
+    def create_scoped(self, scopes):
+        result = self.__class__(self._service_account_email,
+                                self._signer,
+                                scopes=scopes,
+                                private_key_id=self._private_key_id,
+                                client_id=self.client_id,
+                                user_agent=self._user_agent,
+                                **self._kwargs)
+        result.token_uri = self.token_uri
+        result.revoke_uri = self.revoke_uri
+        result._private_key_pkcs8_pem = self._private_key_pkcs8_pem
+        result._private_key_pkcs12 = self._private_key_pkcs12
+        result._private_key_password = self._private_key_password
+        return result
+
+    def create_with_claims(self, claims):
+        """Create credentials that specify additional claims.
+
+        Args:
+            claims: dict, key-value pairs for claims.
+
+        Returns:
+            ServiceAccountCredentials, a copy of the current service account
+            credentials with updated claims to use when obtaining access
+            tokens.
+        """
+        new_kwargs = dict(self._kwargs)
+        new_kwargs.update(claims)
+        result = self.__class__(self._service_account_email,
+                                self._signer,
+                                scopes=self._scopes,
+                                private_key_id=self._private_key_id,
+                                client_id=self.client_id,
+                                user_agent=self._user_agent,
+                                **new_kwargs)
+        result.token_uri = self.token_uri
+        result.revoke_uri = self.revoke_uri
+        result._private_key_pkcs8_pem = self._private_key_pkcs8_pem
+        result._private_key_pkcs12 = self._private_key_pkcs12
+        result._private_key_password = self._private_key_password
+        return result
+
+    def create_delegated(self, sub):
+        """Create credentials that act as domain-wide delegation of authority.
+
+        Use the ``sub`` parameter as the subject to delegate on behalf of
+        that user.
+
+        For example::
+
+          >>> account_sub = 'foo@email.com'
+          >>> delegate_creds = creds.create_delegated(account_sub)
+
+        Args:
+            sub: string, An email address that this service account will
+                 act on behalf of (via domain-wide delegation).
+
+        Returns:
+            ServiceAccountCredentials, a copy of the current service account
+            updated to act on behalf of ``sub``.
+        """
+        return self.create_with_claims({'sub': sub})
+
+
+def _datetime_to_secs(utc_time):
+    # TODO(issue 298): use time_delta.total_seconds()
+    # time_delta.total_seconds() not supported in Python 2.6
+    epoch = datetime.datetime(1970, 1, 1)
+    time_delta = utc_time - epoch
+    return time_delta.days * 86400 + time_delta.seconds
+
+
+class _JWTAccessCredentials(ServiceAccountCredentials):
+    """Self signed JWT credentials.
+
+    Makes an assertion to server using a self signed JWT from service account
+    credentials.  These credentials do NOT use OAuth 2.0 and instead
+    authenticate directly.
+    """
+    _MAX_TOKEN_LIFETIME_SECS = 3600
+    """Max lifetime of the token (one hour, in seconds)."""
+
+    def __init__(self,
+                 service_account_email,
+                 signer,
+                 scopes=None,
+                 private_key_id=None,
+                 client_id=None,
+                 user_agent=None,
+                 token_uri=oauth2client.GOOGLE_TOKEN_URI,
+                 revoke_uri=oauth2client.GOOGLE_REVOKE_URI,
+                 additional_claims=None):
+        if additional_claims is None:
+            additional_claims = {}
+        super(_JWTAccessCredentials, self).__init__(
+            service_account_email,
+            signer,
+            private_key_id=private_key_id,
+            client_id=client_id,
+            user_agent=user_agent,
+            token_uri=token_uri,
+            revoke_uri=revoke_uri,
+            **additional_claims)
+
+    def authorize(self, http):
+        """Authorize an httplib2.Http instance with a JWT assertion.
+
+        Unless specified, the 'aud' of the assertion will be the base
+        uri of the request.
+
+        Args:
+            http: An instance of ``httplib2.Http`` or something that acts
+                  like it.
+        Returns:
+            A modified instance of http that was passed in.
+        Example::
+            h = httplib2.Http()
+            h = credentials.authorize(h)
+        """
+        transport.wrap_http_for_jwt_access(self, http)
+        return http
+
+    def get_access_token(self, http=None, additional_claims=None):
+        """Create a signed jwt.
+
+        Args:
+            http: unused
+            additional_claims: dict, additional claims to add to
+                the payload of the JWT.
+        Returns:
+            An AccessTokenInfo with the signed jwt
+        """
+        if additional_claims is None:
+            if self.access_token is None or self.access_token_expired:
+                self.refresh(None)
+            return client.AccessTokenInfo(
+              access_token=self.access_token, expires_in=self._expires_in())
+        else:
+            # Create a 1 time token
+            token, unused_expiry = self._create_token(additional_claims)
+            return client.AccessTokenInfo(
+              access_token=token, expires_in=self._MAX_TOKEN_LIFETIME_SECS)
+
+    def revoke(self, http):
+        """Cannot revoke JWTAccessCredentials tokens."""
+        pass
+
+    def create_scoped_required(self):
+        # JWTAccessCredentials are unscoped by definition
+        return True
+
+    def create_scoped(self, scopes, token_uri=oauth2client.GOOGLE_TOKEN_URI,
+                      revoke_uri=oauth2client.GOOGLE_REVOKE_URI):
+        # Returns an OAuth2 credentials with the given scope
+        result = ServiceAccountCredentials(self._service_account_email,
+                                           self._signer,
+                                           scopes=scopes,
+                                           private_key_id=self._private_key_id,
+                                           client_id=self.client_id,
+                                           user_agent=self._user_agent,
+                                           token_uri=token_uri,
+                                           revoke_uri=revoke_uri,
+                                           **self._kwargs)
+        if self._private_key_pkcs8_pem is not None:
+            result._private_key_pkcs8_pem = self._private_key_pkcs8_pem
+        if self._private_key_pkcs12 is not None:
+            result._private_key_pkcs12 = self._private_key_pkcs12
+        if self._private_key_password is not None:
+            result._private_key_password = self._private_key_password
+        return result
+
+    def refresh(self, http):
+        self._refresh(None)
+
+    def _refresh(self, http_request):
+        self.access_token, self.token_expiry = self._create_token()
+
+    def _create_token(self, additional_claims=None):
+        now = client._UTCNOW()
+        lifetime = datetime.timedelta(seconds=self._MAX_TOKEN_LIFETIME_SECS)
+        expiry = now + lifetime
+        payload = {
+            'iat': _datetime_to_secs(now),
+            'exp': _datetime_to_secs(expiry),
+            'iss': self._service_account_email,
+            'sub': self._service_account_email
+        }
+        payload.update(self._kwargs)
+        if additional_claims is not None:
+            payload.update(additional_claims)
+        jwt = crypt.make_signed_jwt(self._signer, payload,
+                                    key_id=self._private_key_id)
+        return jwt.decode('ascii'), expiry
diff --git a/oauth2client/tools.py b/oauth2client/tools.py
new file mode 100644
index 0000000..8947157
--- /dev/null
+++ b/oauth2client/tools.py
@@ -0,0 +1,256 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Command-line tools for authenticating via OAuth 2.0
+
+Do the OAuth 2.0 Web Server dance for a command line application. Stores the
+generated credentials in a common file that is used by other example apps in
+the same directory.
+"""
+
+from __future__ import print_function
+
+import logging
+import socket
+import sys
+
+from six.moves import BaseHTTPServer
+from six.moves import http_client
+from six.moves import input
+from six.moves import urllib
+
+from oauth2client import client
+from oauth2client import util
+
+
+__author__ = 'jcgregorio@google.com (Joe Gregorio)'
+__all__ = ['argparser', 'run_flow', 'message_if_missing']
+
+_CLIENT_SECRETS_MESSAGE = """WARNING: Please configure OAuth 2.0
+
+To make this sample run you will need to populate the client_secrets.json file
+found at:
+
+   {file_path}
+
+with information from the APIs Console <https://code.google.com/apis/console>.
+
+"""
+
+_FAILED_START_MESSAGE = """
+Failed to start a local webserver listening on either port 8080
+or port 8090. Please check your firewall settings and locally
+running programs that may be blocking or using those ports.
+
+Falling back to --noauth_local_webserver and continuing with
+authorization.
+"""
+
+_BROWSER_OPENED_MESSAGE = """
+Your browser has been opened to visit:
+
+    {address}
+
+If your browser is on a different machine then exit and re-run this
+application with the command-line parameter
+
+  --noauth_local_webserver
+"""
+
+_GO_TO_LINK_MESSAGE = """
+Go to the following link in your browser:
+
+    {address}
+"""
+
+
+def _CreateArgumentParser():
+    try:
+        import argparse
+    except ImportError:  # pragma: NO COVER
+        return None
+    parser = argparse.ArgumentParser(add_help=False)
+    parser.add_argument('--auth_host_name', default='localhost',
+                        help='Hostname when running a local web server.')
+    parser.add_argument('--noauth_local_webserver', action='store_true',
+                        default=False, help='Do not run a local web server.')
+    parser.add_argument('--auth_host_port', default=[8080, 8090], type=int,
+                        nargs='*', help='Port web server should listen on.')
+    parser.add_argument(
+        '--logging_level', default='ERROR',
+        choices=['DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL'],
+        help='Set the logging level of detail.')
+    return parser
+
+# argparser is an ArgumentParser that contains command-line options expected
+# by tools.run(). Pass it in as part of the 'parents' argument to your own
+# ArgumentParser.
+argparser = _CreateArgumentParser()
+
+
+class ClientRedirectServer(BaseHTTPServer.HTTPServer):
+    """A server to handle OAuth 2.0 redirects back to localhost.
+
+    Waits for a single request and parses the query parameters
+    into query_params and then stops serving.
+    """
+    query_params = {}
+
+
+class ClientRedirectHandler(BaseHTTPServer.BaseHTTPRequestHandler):
+    """A handler for OAuth 2.0 redirects back to localhost.
+
+    Waits for a single request and parses the query parameters
+    into the servers query_params and then stops serving.
+    """
+
+    def do_GET(self):
+        """Handle a GET request.
+
+        Parses the query parameters and prints a message
+        if the flow has completed. Note that we can't detect
+        if an error occurred.
+        """
+        self.send_response(http_client.OK)
+        self.send_header("Content-type", "text/html")
+        self.end_headers()
+        query = self.path.split('?', 1)[-1]
+        query = dict(urllib.parse.parse_qsl(query))
+        self.server.query_params = query
+        self.wfile.write(
+            b"<html><head><title>Authentication Status</title></head>")
+        self.wfile.write(
+            b"<body><p>The authentication flow has completed.</p>")
+        self.wfile.write(b"</body></html>")
+
+    def log_message(self, format, *args):
+        """Do not log messages to stdout while running as cmd. line program."""
+
+
+@util.positional(3)
+def run_flow(flow, storage, flags=None, http=None):
+    """Core code for a command-line application.
+
+    The ``run()`` function is called from your application and runs
+    through all the steps to obtain credentials. It takes a ``Flow``
+    argument and attempts to open an authorization server page in the
+    user's default web browser. The server asks the user to grant your
+    application access to the user's data. If the user grants access,
+    the ``run()`` function returns new credentials. The new credentials
+    are also stored in the ``storage`` argument, which updates the file
+    associated with the ``Storage`` object.
+
+    It presumes it is run from a command-line application and supports the
+    following flags:
+
+        ``--auth_host_name`` (string, default: ``localhost``)
+           Host name to use when running a local web server to handle
+           redirects during OAuth authorization.
+
+        ``--auth_host_port`` (integer, default: ``[8080, 8090]``)
+           Port to use when running a local web server to handle redirects
+           during OAuth authorization. Repeat this option to specify a list
+           of values.
+
+        ``--[no]auth_local_webserver`` (boolean, default: ``True``)
+           Run a local web server to handle redirects during OAuth
+           authorization.
+
+    The tools module defines an ``ArgumentParser`` the already contains the
+    flag definitions that ``run()`` requires. You can pass that
+    ``ArgumentParser`` to your ``ArgumentParser`` constructor::
+
+        parser = argparse.ArgumentParser(
+            description=__doc__,
+            formatter_class=argparse.RawDescriptionHelpFormatter,
+            parents=[tools.argparser])
+        flags = parser.parse_args(argv)
+
+    Args:
+        flow: Flow, an OAuth 2.0 Flow to step through.
+        storage: Storage, a ``Storage`` to store the credential in.
+        flags: ``argparse.Namespace``, (Optional) The command-line flags. This
+               is the object returned from calling ``parse_args()`` on
+               ``argparse.ArgumentParser`` as described above. Defaults
+               to ``argparser.parse_args()``.
+        http: An instance of ``httplib2.Http.request`` or something that
+              acts like it.
+
+    Returns:
+        Credentials, the obtained credential.
+    """
+    if flags is None:
+        flags = argparser.parse_args()
+    logging.getLogger().setLevel(getattr(logging, flags.logging_level))
+    if not flags.noauth_local_webserver:
+        success = False
+        port_number = 0
+        for port in flags.auth_host_port:
+            port_number = port
+            try:
+                httpd = ClientRedirectServer((flags.auth_host_name, port),
+                                             ClientRedirectHandler)
+            except socket.error:
+                pass
+            else:
+                success = True
+                break
+        flags.noauth_local_webserver = not success
+        if not success:
+            print(_FAILED_START_MESSAGE)
+
+    if not flags.noauth_local_webserver:
+        oauth_callback = 'http://{host}:{port}/'.format(
+            host=flags.auth_host_name, port=port_number)
+    else:
+        oauth_callback = client.OOB_CALLBACK_URN
+    flow.redirect_uri = oauth_callback
+    authorize_url = flow.step1_get_authorize_url()
+
+    if not flags.noauth_local_webserver:
+        import webbrowser
+        webbrowser.open(authorize_url, new=1, autoraise=True)
+        print(_BROWSER_OPENED_MESSAGE.format(address=authorize_url))
+    else:
+        print(_GO_TO_LINK_MESSAGE.format(address=authorize_url))
+
+    code = None
+    if not flags.noauth_local_webserver:
+        httpd.handle_request()
+        if 'error' in httpd.query_params:
+            sys.exit('Authentication request was rejected.')
+        if 'code' in httpd.query_params:
+            code = httpd.query_params['code']
+        else:
+            print('Failed to find "code" in the query parameters '
+                  'of the redirect.')
+            sys.exit('Try running with --noauth_local_webserver.')
+    else:
+        code = input('Enter verification code: ').strip()
+
+    try:
+        credential = flow.step2_exchange(code, http=http)
+    except client.FlowExchangeError as e:
+        sys.exit('Authentication has failed: {0}'.format(e))
+
+    storage.put(credential)
+    credential.set_store(storage)
+    print('Authentication successful.')
+
+    return credential
+
+
+def message_if_missing(filename):
+    """Helpful message to display if the CLIENT_SECRETS file is missing."""
+    return _CLIENT_SECRETS_MESSAGE.format(file_path=filename)
diff --git a/oauth2client/transport.py b/oauth2client/transport.py
new file mode 100644
index 0000000..8dbc60d
--- /dev/null
+++ b/oauth2client/transport.py
@@ -0,0 +1,245 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+
+import httplib2
+import six
+from six.moves import http_client
+
+from oauth2client._helpers import _to_bytes
+
+
+_LOGGER = logging.getLogger(__name__)
+# Properties present in file-like streams / buffers.
+_STREAM_PROPERTIES = ('read', 'seek', 'tell')
+
+# Google Data client libraries may need to set this to [401, 403].
+REFRESH_STATUS_CODES = (http_client.UNAUTHORIZED,)
+
+
+class MemoryCache(object):
+    """httplib2 Cache implementation which only caches locally."""
+
+    def __init__(self):
+        self.cache = {}
+
+    def get(self, key):
+        return self.cache.get(key)
+
+    def set(self, key, value):
+        self.cache[key] = value
+
+    def delete(self, key):
+        self.cache.pop(key, None)
+
+
+def get_cached_http():
+    """Return an HTTP object which caches results returned.
+
+    This is intended to be used in methods like
+    oauth2client.client.verify_id_token(), which calls to the same URI
+    to retrieve certs.
+
+    Returns:
+        httplib2.Http, an HTTP object with a MemoryCache
+    """
+    return _CACHED_HTTP
+
+
+def get_http_object():
+    """Return a new HTTP object.
+
+    Returns:
+        httplib2.Http, an HTTP object.
+    """
+    return httplib2.Http()
+
+
+def _initialize_headers(headers):
+    """Creates a copy of the headers.
+
+    Args:
+        headers: dict, request headers to copy.
+
+    Returns:
+        dict, the copied headers or a new dictionary if the headers
+        were None.
+    """
+    return {} if headers is None else dict(headers)
+
+
+def _apply_user_agent(headers, user_agent):
+    """Adds a user-agent to the headers.
+
+    Args:
+        headers: dict, request headers to add / modify user
+                 agent within.
+        user_agent: str, the user agent to add.
+
+    Returns:
+        dict, the original headers passed in, but modified if the
+        user agent is not None.
+    """
+    if user_agent is not None:
+        if 'user-agent' in headers:
+            headers['user-agent'] = (user_agent + ' ' + headers['user-agent'])
+        else:
+            headers['user-agent'] = user_agent
+
+    return headers
+
+
+def clean_headers(headers):
+    """Forces header keys and values to be strings, i.e not unicode.
+
+    The httplib module just concats the header keys and values in a way that
+    may make the message header a unicode string, which, if it then tries to
+    contatenate to a binary request body may result in a unicode decode error.
+
+    Args:
+        headers: dict, A dictionary of headers.
+
+    Returns:
+        The same dictionary but with all the keys converted to strings.
+    """
+    clean = {}
+    try:
+        for k, v in six.iteritems(headers):
+            if not isinstance(k, six.binary_type):
+                k = str(k)
+            if not isinstance(v, six.binary_type):
+                v = str(v)
+            clean[_to_bytes(k)] = _to_bytes(v)
+    except UnicodeEncodeError:
+        from oauth2client.client import NonAsciiHeaderError
+        raise NonAsciiHeaderError(k, ': ', v)
+    return clean
+
+
+def wrap_http_for_auth(credentials, http):
+    """Prepares an HTTP object's request method for auth.
+
+    Wraps HTTP requests with logic to catch auth failures (typically
+    identified via a 401 status code). In the event of failure, tries
+    to refresh the token used and then retry the original request.
+
+    Args:
+        credentials: Credentials, the credentials used to identify
+                     the authenticated user.
+        http: httplib2.Http, an http object to be used to make
+              auth requests.
+    """
+    orig_request_method = http.request
+
+    # The closure that will replace 'httplib2.Http.request'.
+    def new_request(uri, method='GET', body=None, headers=None,
+                    redirections=httplib2.DEFAULT_MAX_REDIRECTS,
+                    connection_type=None):
+        if not credentials.access_token:
+            _LOGGER.info('Attempting refresh to obtain '
+                         'initial access_token')
+            credentials._refresh(orig_request_method)
+
+        # Clone and modify the request headers to add the appropriate
+        # Authorization header.
+        headers = _initialize_headers(headers)
+        credentials.apply(headers)
+        _apply_user_agent(headers, credentials.user_agent)
+
+        body_stream_position = None
+        # Check if the body is a file-like stream.
+        if all(getattr(body, stream_prop, None) for stream_prop in
+               _STREAM_PROPERTIES):
+            body_stream_position = body.tell()
+
+        resp, content = orig_request_method(uri, method, body,
+                                            clean_headers(headers),
+                                            redirections, connection_type)
+
+        # A stored token may expire between the time it is retrieved and
+        # the time the request is made, so we may need to try twice.
+        max_refresh_attempts = 2
+        for refresh_attempt in range(max_refresh_attempts):
+            if resp.status not in REFRESH_STATUS_CODES:
+                break
+            _LOGGER.info('Refreshing due to a %s (attempt %s/%s)',
+                         resp.status, refresh_attempt + 1,
+                         max_refresh_attempts)
+            credentials._refresh(orig_request_method)
+            credentials.apply(headers)
+            if body_stream_position is not None:
+                body.seek(body_stream_position)
+
+            resp, content = orig_request_method(uri, method, body,
+                                                clean_headers(headers),
+                                                redirections, connection_type)
+
+        return resp, content
+
+    # Replace the request method with our own closure.
+    http.request = new_request
+
+    # Set credentials as a property of the request method.
+    setattr(http.request, 'credentials', credentials)
+
+
+def wrap_http_for_jwt_access(credentials, http):
+    """Prepares an HTTP object's request method for JWT access.
+
+    Wraps HTTP requests with logic to catch auth failures (typically
+    identified via a 401 status code). In the event of failure, tries
+    to refresh the token used and then retry the original request.
+
+    Args:
+        credentials: _JWTAccessCredentials, the credentials used to identify
+                     a service account that uses JWT access tokens.
+        http: httplib2.Http, an http object to be used to make
+              auth requests.
+    """
+    orig_request_method = http.request
+    wrap_http_for_auth(credentials, http)
+    # The new value of ``http.request`` set by ``wrap_http_for_auth``.
+    authenticated_request_method = http.request
+
+    # The closure that will replace 'httplib2.Http.request'.
+    def new_request(uri, method='GET', body=None, headers=None,
+                    redirections=httplib2.DEFAULT_MAX_REDIRECTS,
+                    connection_type=None):
+        if 'aud' in credentials._kwargs:
+            # Preemptively refresh token, this is not done for OAuth2
+            if (credentials.access_token is None or
+                    credentials.access_token_expired):
+                credentials.refresh(None)
+            return authenticated_request_method(uri, method, body,
+                                                headers, redirections,
+                                                connection_type)
+        else:
+            # If we don't have an 'aud' (audience) claim,
+            # create a 1-time token with the uri root as the audience
+            headers = _initialize_headers(headers)
+            _apply_user_agent(headers, credentials.user_agent)
+            uri_root = uri.split('?', 1)[0]
+            token, unused_expiry = credentials._create_token({'aud': uri_root})
+
+            headers['Authorization'] = 'Bearer ' + token
+            return orig_request_method(uri, method, body,
+                                       clean_headers(headers),
+                                       redirections, connection_type)
+
+    # Replace the request method with our own closure.
+    http.request = new_request
+
+
+_CACHED_HTTP = httplib2.Http(MemoryCache())
diff --git a/oauth2client/util.py b/oauth2client/util.py
new file mode 100644
index 0000000..e3ba62b
--- /dev/null
+++ b/oauth2client/util.py
@@ -0,0 +1,206 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Common utility library."""
+
+import functools
+import inspect
+import logging
+
+import six
+from six.moves import urllib
+
+
+__author__ = [
+    'rafek@google.com (Rafe Kaplan)',
+    'guido@google.com (Guido van Rossum)',
+]
+
+__all__ = [
+    'positional',
+    'POSITIONAL_WARNING',
+    'POSITIONAL_EXCEPTION',
+    'POSITIONAL_IGNORE',
+]
+
+logger = logging.getLogger(__name__)
+
+POSITIONAL_WARNING = 'WARNING'
+POSITIONAL_EXCEPTION = 'EXCEPTION'
+POSITIONAL_IGNORE = 'IGNORE'
+POSITIONAL_SET = frozenset([POSITIONAL_WARNING, POSITIONAL_EXCEPTION,
+                            POSITIONAL_IGNORE])
+
+positional_parameters_enforcement = POSITIONAL_WARNING
+
+
+def positional(max_positional_args):
+    """A decorator to declare that only the first N arguments my be positional.
+
+    This decorator makes it easy to support Python 3 style keyword-only
+    parameters. For example, in Python 3 it is possible to write::
+
+        def fn(pos1, *, kwonly1=None, kwonly1=None):
+            ...
+
+    All named parameters after ``*`` must be a keyword::
+
+        fn(10, 'kw1', 'kw2')  # Raises exception.
+        fn(10, kwonly1='kw1')  # Ok.
+
+    Example
+    ^^^^^^^
+
+    To define a function like above, do::
+
+        @positional(1)
+        def fn(pos1, kwonly1=None, kwonly2=None):
+            ...
+
+    If no default value is provided to a keyword argument, it becomes a
+    required keyword argument::
+
+        @positional(0)
+        def fn(required_kw):
+            ...
+
+    This must be called with the keyword parameter::
+
+        fn()  # Raises exception.
+        fn(10)  # Raises exception.
+        fn(required_kw=10)  # Ok.
+
+    When defining instance or class methods always remember to account for
+    ``self`` and ``cls``::
+
+        class MyClass(object):
+
+            @positional(2)
+            def my_method(self, pos1, kwonly1=None):
+                ...
+
+            @classmethod
+            @positional(2)
+            def my_method(cls, pos1, kwonly1=None):
+                ...
+
+    The positional decorator behavior is controlled by
+    ``util.positional_parameters_enforcement``, which may be set to
+    ``POSITIONAL_EXCEPTION``, ``POSITIONAL_WARNING`` or
+    ``POSITIONAL_IGNORE`` to raise an exception, log a warning, or do
+    nothing, respectively, if a declaration is violated.
+
+    Args:
+        max_positional_arguments: Maximum number of positional arguments. All
+                                  parameters after the this index must be
+                                  keyword only.
+
+    Returns:
+        A decorator that prevents using arguments after max_positional_args
+        from being used as positional parameters.
+
+    Raises:
+        TypeError: if a key-word only argument is provided as a positional
+                   parameter, but only if
+                   util.positional_parameters_enforcement is set to
+                   POSITIONAL_EXCEPTION.
+    """
+
+    def positional_decorator(wrapped):
+        @functools.wraps(wrapped)
+        def positional_wrapper(*args, **kwargs):
+            if len(args) > max_positional_args:
+                plural_s = ''
+                if max_positional_args != 1:
+                    plural_s = 's'
+                message = ('{function}() takes at most {args_max} positional '
+                           'argument{plural} ({args_given} given)'.format(
+                               function=wrapped.__name__,
+                               args_max=max_positional_args,
+                               args_given=len(args),
+                               plural=plural_s))
+                if positional_parameters_enforcement == POSITIONAL_EXCEPTION:
+                    raise TypeError(message)
+                elif positional_parameters_enforcement == POSITIONAL_WARNING:
+                    logger.warning(message)
+            return wrapped(*args, **kwargs)
+        return positional_wrapper
+
+    if isinstance(max_positional_args, six.integer_types):
+        return positional_decorator
+    else:
+        args, _, _, defaults = inspect.getargspec(max_positional_args)
+        return positional(len(args) - len(defaults))(max_positional_args)
+
+
+def scopes_to_string(scopes):
+    """Converts scope value to a string.
+
+    If scopes is a string then it is simply passed through. If scopes is an
+    iterable then a string is returned that is all the individual scopes
+    concatenated with spaces.
+
+    Args:
+        scopes: string or iterable of strings, the scopes.
+
+    Returns:
+        The scopes formatted as a single string.
+    """
+    if isinstance(scopes, six.string_types):
+        return scopes
+    else:
+        return ' '.join(scopes)
+
+
+def string_to_scopes(scopes):
+    """Converts stringifed scope value to a list.
+
+    If scopes is a list then it is simply passed through. If scopes is an
+    string then a list of each individual scope is returned.
+
+    Args:
+        scopes: a string or iterable of strings, the scopes.
+
+    Returns:
+        The scopes in a list.
+    """
+    if not scopes:
+        return []
+    if isinstance(scopes, six.string_types):
+        return scopes.split(' ')
+    else:
+        return scopes
+
+
+def _add_query_parameter(url, name, value):
+    """Adds a query parameter to a url.
+
+    Replaces the current value if it already exists in the URL.
+
+    Args:
+        url: string, url to add the query parameter to.
+        name: string, query parameter name.
+        value: string, query parameter value.
+
+    Returns:
+        Updated query parameter. Does not update the url if value is None.
+    """
+    if value is None:
+        return url
+    else:
+        parsed = list(urllib.parse.urlparse(url))
+        q = dict(urllib.parse.parse_qsl(parsed[4]))
+        q[name] = value
+        parsed[4] = urllib.parse.urlencode(q)
+        return urllib.parse.urlunparse(parsed)