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Diffstat (limited to 'google/auth/crypt/_python_rsa.py')
| -rw-r--r-- | google/auth/crypt/_python_rsa.py | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/google/auth/crypt/_python_rsa.py b/google/auth/crypt/_python_rsa.py new file mode 100644 index 0000000..ec30dd0 --- /dev/null +++ b/google/auth/crypt/_python_rsa.py @@ -0,0 +1,173 @@ +# Copyright 2016 Google LLC +# +# 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 RSA cryptography implementation. + +Uses the ``rsa``, ``pyasn1`` and ``pyasn1_modules`` packages +to parse PEM files storing PKCS#1 or PKCS#8 keys as well as +certificates. There is no support for p12 files. +""" + +from __future__ import absolute_import + +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 google.auth import _helpers +from google.auth.crypt import base + +_POW2 = (128, 64, 32, 16, 8, 4, 2, 1) +_CERTIFICATE_MARKER = b"-----BEGIN CERTIFICATE-----" +_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 1s and 0s to bytes. + + Combines the list 8 at a time, treating each group of 8 bits + as a single byte. + + Args: + bit_list (Sequence): Sequence of 1s and 0s. + + Returns: + bytes: The decoded bytes. + """ + 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 six.moves.zip(_POW2, curr_bits)) + byte_vals.append(char_val) + return bytes(byte_vals) + + +class RSAVerifier(base.Verifier): + """Verifies RSA cryptographic signatures using public keys. + + Args: + public_key (rsa.key.PublicKey): The public key used to verify + signatures. + """ + + def __init__(self, public_key): + self._pubkey = public_key + + @_helpers.copy_docstring(base.Verifier) + def verify(self, message, signature): + message = _helpers.to_bytes(message) + try: + return rsa.pkcs1.verify(message, signature, self._pubkey) + except (ValueError, rsa.pkcs1.VerificationError): + return False + + @classmethod + def from_string(cls, public_key): + """Construct an Verifier instance from a public key or public + certificate string. + + Args: + public_key (Union[str, bytes]): The public key in PEM format or the + x509 public key certificate. + + Returns: + google.auth.crypt._python_rsa.RSAVerifier: The constructed verifier. + + Raises: + ValueError: If the public_key can't be parsed. + """ + public_key = _helpers.to_bytes(public_key) + is_x509_cert = _CERTIFICATE_MARKER in public_key + + # If this is a certificate, extract the public key info. + if is_x509_cert: + der = rsa.pem.load_pem(public_key, "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(public_key, "PEM") + return cls(pubkey) + + +class RSASigner(base.Signer, base.FromServiceAccountMixin): + """Signs messages with an RSA private key. + + Args: + private_key (rsa.key.PrivateKey): The private key to sign with. + key_id (str): Optional key ID used to identify this private key. This + can be useful to associate the private key with its associated + public key or certificate. + """ + + def __init__(self, private_key, key_id=None): + self._key = private_key + self._key_id = key_id + + @property + @_helpers.copy_docstring(base.Signer) + def key_id(self): + return self._key_id + + @_helpers.copy_docstring(base.Signer) + def sign(self, message): + message = _helpers.to_bytes(message) + return rsa.pkcs1.sign(message, self._key, "SHA-256") + + @classmethod + def from_string(cls, key, key_id=None): + """Construct an Signer instance from a private key in PEM format. + + Args: + key (str): Private key in PEM format. + key_id (str): An optional key id used to identify the private key. + + Returns: + google.auth.crypt.Signer: The constructed signer. + + 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 Python 3 + marker_id, key_bytes = pem.readPemBlocksFromFile( + six.StringIO(key), _PKCS1_MARKER, _PKCS8_MARKER + ) + + # Key is in pkcs1 format. + if marker_id == 0: + private_key = rsa.key.PrivateKey.load_pkcs1(key_bytes, format="DER") + # Key is in pkcs8. + elif marker_id == 1: + key_info, remaining = decoder.decode(key_bytes, asn1Spec=_PKCS8_SPEC) + if remaining != b"": + raise ValueError("Unused bytes", remaining) + private_key_info = key_info.getComponentByName("privateKey") + private_key = rsa.key.PrivateKey.load_pkcs1( + private_key_info.asOctets(), format="DER" + ) + else: + raise ValueError("No key could be detected.") + + return cls(private_key, key_id=key_id) |