1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
|
# Copyright 2017 Google Inc.
#
# 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.
"""ECDSA (ES256) verifier and signer that use the ``cryptography`` library.
"""
from cryptography import utils
import cryptography.exceptions
from cryptography.hazmat import backends
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import ec
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.primitives.asymmetric.utils import decode_dss_signature
from cryptography.hazmat.primitives.asymmetric.utils import encode_dss_signature
import cryptography.x509
from google.auth import _helpers
from google.auth.crypt import base
_CERTIFICATE_MARKER = b"-----BEGIN CERTIFICATE-----"
_BACKEND = backends.default_backend()
_PADDING = padding.PKCS1v15()
class ES256Verifier(base.Verifier):
"""Verifies ECDSA cryptographic signatures using public keys.
Args:
public_key (
cryptography.hazmat.primitives.asymmetric.ec.ECDSAPublicKey):
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):
# First convert (r||s) raw signature to ASN1 encoded signature.
sig_bytes = _helpers.to_bytes(signature)
if len(sig_bytes) != 64:
return False
r = (
int.from_bytes(sig_bytes[:32], byteorder="big")
if _helpers.is_python_3()
else utils.int_from_bytes(sig_bytes[:32], byteorder="big")
)
s = (
int.from_bytes(sig_bytes[32:], byteorder="big")
if _helpers.is_python_3()
else utils.int_from_bytes(sig_bytes[32:], byteorder="big")
)
asn1_sig = encode_dss_signature(r, s)
message = _helpers.to_bytes(message)
try:
self._pubkey.verify(asn1_sig, message, ec.ECDSA(hashes.SHA256()))
return True
except (ValueError, cryptography.exceptions.InvalidSignature):
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:
Verifier: The constructed verifier.
Raises:
ValueError: If the public key can't be parsed.
"""
public_key_data = _helpers.to_bytes(public_key)
if _CERTIFICATE_MARKER in public_key_data:
cert = cryptography.x509.load_pem_x509_certificate(
public_key_data, _BACKEND
)
pubkey = cert.public_key()
else:
pubkey = serialization.load_pem_public_key(public_key_data, _BACKEND)
return cls(pubkey)
class ES256Signer(base.Signer, base.FromServiceAccountMixin):
"""Signs messages with an ECDSA private key.
Args:
private_key (
cryptography.hazmat.primitives.asymmetric.ec.ECDSAPrivateKey):
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)
asn1_signature = self._key.sign(message, ec.ECDSA(hashes.SHA256()))
# Convert ASN1 encoded signature to (r||s) raw signature.
(r, s) = decode_dss_signature(asn1_signature)
return (
(r.to_bytes(32, byteorder="big") + s.to_bytes(32, byteorder="big"))
if _helpers.is_python_3()
else (utils.int_to_bytes(r, 32) + utils.int_to_bytes(s, 32))
)
@classmethod
def from_string(cls, key, key_id=None):
"""Construct a RSASigner from a private key in PEM format.
Args:
key (Union[bytes, str]): Private key in PEM format.
key_id (str): An optional key id used to identify the private key.
Returns:
google.auth.crypt._cryptography_rsa.RSASigner: The
constructed signer.
Raises:
ValueError: If ``key`` is not ``bytes`` or ``str`` (unicode).
UnicodeDecodeError: If ``key`` is ``bytes`` but cannot be decoded
into a UTF-8 ``str``.
ValueError: If ``cryptography`` "Could not deserialize key data."
"""
key = _helpers.to_bytes(key)
private_key = serialization.load_pem_private_key(
key, password=None, backend=_BACKEND
)
return cls(private_key, key_id=key_id)
|
