Source code for oauth2client.crypt

# -*- 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
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# 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__)

[docs]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
[docs]def make_signed_jwt(signer, payload, key_id=None): """Make a signed JWT. See 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))
[docs]def verify_signed_jwt_with_certs(jwt, certs, audience=None): """Verify a JWT against public certs. See 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