blob: 70bef8c184f92bc39c4778a1277d7990ab240ffe [file] [log] [blame]
# -*- 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._helpers import _from_bytes
from oauth2client._helpers import _json_encode
from oauth2client._helpers import _to_bytes
from oauth2client._helpers import _urlsafe_b64decode
from oauth2client._helpers import _urlsafe_b64encode
from oauth2client._pure_python_crypt import RsaSigner
from oauth2client._pure_python_crypt import 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._openssl_crypt import OpenSSLVerifier
from oauth2client._openssl_crypt import OpenSSLSigner
from oauth2client._openssl_crypt import 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._pycrypto_crypt import PyCryptoVerifier
from oauth2client._pycrypto_crypt import PyCryptoSigner
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 = [
_urlsafe_b64encode(_json_encode(header)),
_urlsafe_b64encode(_json_encode(payload)),
]
signing_input = b'.'.join(segments)
signature = signer.sign(signing_input)
segments.append(_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: %s' %
(payload_dict,))
if audience_in_payload != audience:
raise AppIdentityError('Wrong recipient, %s != %s: %s' %
(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: %s' % (payload_dict,))
expiration = payload_dict.get('exp')
if expiration is None:
raise AppIdentityError('No exp field in token: %s' % (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: %s' %
(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, %d < %d: %s' %
(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, %d > %d: %s' %
(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 = _to_bytes(jwt)
if jwt.count(b'.') != 2:
raise AppIdentityError(
'Wrong number of segments in token: %s' % (jwt,))
header, payload, signature = jwt.split(b'.')
message_to_sign = header + b'.' + payload
signature = _urlsafe_b64decode(signature)
# Parse token.
payload_bytes = _urlsafe_b64decode(payload)
try:
payload_dict = json.loads(_from_bytes(payload_bytes))
except:
raise AppIdentityError('Can\'t parse token: %s' % (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