251 lines
8.2 KiB
Python
251 lines
8.2 KiB
Python
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# -*- coding: utf-8 -*-
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#
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# Copyright 2014 Google Inc. All rights reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Crypto-related routines for oauth2client."""
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import json
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import logging
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import time
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from oauth2client import _helpers
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from oauth2client import _pure_python_crypt
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RsaSigner = _pure_python_crypt.RsaSigner
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RsaVerifier = _pure_python_crypt.RsaVerifier
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CLOCK_SKEW_SECS = 300 # 5 minutes in seconds
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AUTH_TOKEN_LIFETIME_SECS = 300 # 5 minutes in seconds
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MAX_TOKEN_LIFETIME_SECS = 86400 # 1 day in seconds
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logger = logging.getLogger(__name__)
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class AppIdentityError(Exception):
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"""Error to indicate crypto failure."""
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def _bad_pkcs12_key_as_pem(*args, **kwargs):
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raise NotImplementedError('pkcs12_key_as_pem requires OpenSSL.')
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try:
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from oauth2client import _openssl_crypt
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OpenSSLSigner = _openssl_crypt.OpenSSLSigner
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OpenSSLVerifier = _openssl_crypt.OpenSSLVerifier
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pkcs12_key_as_pem = _openssl_crypt.pkcs12_key_as_pem
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except ImportError: # pragma: NO COVER
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OpenSSLVerifier = None
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OpenSSLSigner = None
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pkcs12_key_as_pem = _bad_pkcs12_key_as_pem
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try:
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from oauth2client import _pycrypto_crypt
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PyCryptoSigner = _pycrypto_crypt.PyCryptoSigner
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PyCryptoVerifier = _pycrypto_crypt.PyCryptoVerifier
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except ImportError: # pragma: NO COVER
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PyCryptoVerifier = None
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PyCryptoSigner = None
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if OpenSSLSigner:
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Signer = OpenSSLSigner
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Verifier = OpenSSLVerifier
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elif PyCryptoSigner: # pragma: NO COVER
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Signer = PyCryptoSigner
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Verifier = PyCryptoVerifier
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else: # pragma: NO COVER
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Signer = RsaSigner
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Verifier = RsaVerifier
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def make_signed_jwt(signer, payload, key_id=None):
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"""Make a signed JWT.
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See http://self-issued.info/docs/draft-jones-json-web-token.html.
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Args:
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signer: crypt.Signer, Cryptographic signer.
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payload: dict, Dictionary of data to convert to JSON and then sign.
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key_id: string, (Optional) Key ID header.
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Returns:
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string, The JWT for the payload.
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"""
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header = {'typ': 'JWT', 'alg': 'RS256'}
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if key_id is not None:
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header['kid'] = key_id
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segments = [
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_helpers._urlsafe_b64encode(_helpers._json_encode(header)),
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_helpers._urlsafe_b64encode(_helpers._json_encode(payload)),
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]
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signing_input = b'.'.join(segments)
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signature = signer.sign(signing_input)
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segments.append(_helpers._urlsafe_b64encode(signature))
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logger.debug(str(segments))
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return b'.'.join(segments)
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def _verify_signature(message, signature, certs):
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"""Verifies signed content using a list of certificates.
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Args:
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message: string or bytes, The message to verify.
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signature: string or bytes, The signature on the message.
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certs: iterable, certificates in PEM format.
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Raises:
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AppIdentityError: If none of the certificates can verify the message
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against the signature.
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"""
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for pem in certs:
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verifier = Verifier.from_string(pem, is_x509_cert=True)
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if verifier.verify(message, signature):
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return
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# If we have not returned, no certificate confirms the signature.
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raise AppIdentityError('Invalid token signature')
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def _check_audience(payload_dict, audience):
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"""Checks audience field from a JWT payload.
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Does nothing if the passed in ``audience`` is null.
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Args:
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payload_dict: dict, A dictionary containing a JWT payload.
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audience: string or NoneType, an audience to check for in
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the JWT payload.
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Raises:
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AppIdentityError: If there is no ``'aud'`` field in the payload
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dictionary but there is an ``audience`` to check.
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AppIdentityError: If the ``'aud'`` field in the payload dictionary
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does not match the ``audience``.
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"""
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if audience is None:
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return
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audience_in_payload = payload_dict.get('aud')
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if audience_in_payload is None:
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raise AppIdentityError(
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'No aud field in token: {0}'.format(payload_dict))
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if audience_in_payload != audience:
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raise AppIdentityError('Wrong recipient, {0} != {1}: {2}'.format(
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audience_in_payload, audience, payload_dict))
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def _verify_time_range(payload_dict):
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"""Verifies the issued at and expiration from a JWT payload.
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Makes sure the current time (in UTC) falls between the issued at and
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expiration for the JWT (with some skew allowed for via
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``CLOCK_SKEW_SECS``).
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Args:
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payload_dict: dict, A dictionary containing a JWT payload.
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Raises:
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AppIdentityError: If there is no ``'iat'`` field in the payload
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dictionary.
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AppIdentityError: If there is no ``'exp'`` field in the payload
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dictionary.
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AppIdentityError: If the JWT expiration is too far in the future (i.e.
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if the expiration would imply a token lifetime
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longer than what is allowed.)
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AppIdentityError: If the token appears to have been issued in the
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future (up to clock skew).
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AppIdentityError: If the token appears to have expired in the past
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(up to clock skew).
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"""
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# Get the current time to use throughout.
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now = int(time.time())
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# Make sure issued at and expiration are in the payload.
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issued_at = payload_dict.get('iat')
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if issued_at is None:
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raise AppIdentityError(
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'No iat field in token: {0}'.format(payload_dict))
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expiration = payload_dict.get('exp')
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if expiration is None:
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raise AppIdentityError(
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'No exp field in token: {0}'.format(payload_dict))
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# Make sure the expiration gives an acceptable token lifetime.
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if expiration >= now + MAX_TOKEN_LIFETIME_SECS:
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raise AppIdentityError(
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'exp field too far in future: {0}'.format(payload_dict))
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# Make sure (up to clock skew) that the token wasn't issued in the future.
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earliest = issued_at - CLOCK_SKEW_SECS
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if now < earliest:
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raise AppIdentityError('Token used too early, {0} < {1}: {2}'.format(
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now, earliest, payload_dict))
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# Make sure (up to clock skew) that the token isn't already expired.
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latest = expiration + CLOCK_SKEW_SECS
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if now > latest:
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raise AppIdentityError('Token used too late, {0} > {1}: {2}'.format(
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now, latest, payload_dict))
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def verify_signed_jwt_with_certs(jwt, certs, audience=None):
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"""Verify a JWT against public certs.
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See http://self-issued.info/docs/draft-jones-json-web-token.html.
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Args:
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jwt: string, A JWT.
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certs: dict, Dictionary where values of public keys in PEM format.
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audience: string, The audience, 'aud', that this JWT should contain. If
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None then the JWT's 'aud' parameter is not verified.
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Returns:
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dict, The deserialized JSON payload in the JWT.
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Raises:
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AppIdentityError: if any checks are failed.
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"""
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jwt = _helpers._to_bytes(jwt)
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if jwt.count(b'.') != 2:
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raise AppIdentityError(
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'Wrong number of segments in token: {0}'.format(jwt))
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header, payload, signature = jwt.split(b'.')
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message_to_sign = header + b'.' + payload
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signature = _helpers._urlsafe_b64decode(signature)
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# Parse token.
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payload_bytes = _helpers._urlsafe_b64decode(payload)
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try:
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payload_dict = json.loads(_helpers._from_bytes(payload_bytes))
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except:
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raise AppIdentityError('Can\'t parse token: {0}'.format(payload_bytes))
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# Verify that the signature matches the message.
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_verify_signature(message_to_sign, signature, certs.values())
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# Verify the issued at and created times in the payload.
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_verify_time_range(payload_dict)
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# Check audience.
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_check_audience(payload_dict, audience)
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return payload_dict
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