1 # -*- coding: utf-8 -*- 2 # 3 # Copyright 2014 Google Inc. All rights reserved. 4 # 5 # Licensed under the Apache License, Version 2.0 (the "License"); 6 # you may not use this file except in compliance with the License. 7 # You may obtain a copy of the License at 8 # 9 # http://www.apache.org/licenses/LICENSE-2.0 10 # 11 # Unless required by applicable law or agreed to in writing, software 12 # distributed under the License is distributed on an "AS IS" BASIS, 13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 # See the License for the specific language governing permissions and 15 # limitations under the License. 16 """Crypto-related routines for oauth2client.""" 17 18 import json 19 import logging 20 import time 21 22 from oauth2client import _helpers 23 from oauth2client import _pure_python_crypt 24 25 26 RsaSigner = _pure_python_crypt.RsaSigner 27 RsaVerifier = _pure_python_crypt.RsaVerifier 28 29 CLOCK_SKEW_SECS = 300 # 5 minutes in seconds 30 AUTH_TOKEN_LIFETIME_SECS = 300 # 5 minutes in seconds 31 MAX_TOKEN_LIFETIME_SECS = 86400 # 1 day in seconds 32 33 logger = logging.getLogger(__name__) 34 35 36 class AppIdentityError(Exception): 37 """Error to indicate crypto failure.""" 38 39 40 def _bad_pkcs12_key_as_pem(*args, **kwargs): 41 raise NotImplementedError('pkcs12_key_as_pem requires OpenSSL.') 42 43 44 try: 45 from oauth2client import _openssl_crypt 46 OpenSSLSigner = _openssl_crypt.OpenSSLSigner 47 OpenSSLVerifier = _openssl_crypt.OpenSSLVerifier 48 pkcs12_key_as_pem = _openssl_crypt.pkcs12_key_as_pem 49 except ImportError: # pragma: NO COVER 50 OpenSSLVerifier = None 51 OpenSSLSigner = None 52 pkcs12_key_as_pem = _bad_pkcs12_key_as_pem 53 54 try: 55 from oauth2client import _pycrypto_crypt 56 PyCryptoSigner = _pycrypto_crypt.PyCryptoSigner 57 PyCryptoVerifier = _pycrypto_crypt.PyCryptoVerifier 58 except ImportError: # pragma: NO COVER 59 PyCryptoVerifier = None 60 PyCryptoSigner = None 61 62 63 if OpenSSLSigner: 64 Signer = OpenSSLSigner 65 Verifier = OpenSSLVerifier 66 elif PyCryptoSigner: # pragma: NO COVER 67 Signer = PyCryptoSigner 68 Verifier = PyCryptoVerifier 69 else: # pragma: NO COVER 70 Signer = RsaSigner 71 Verifier = RsaVerifier 72 73 74 def make_signed_jwt(signer, payload, key_id=None): 75 """Make a signed JWT. 76 77 See http://self-issued.info/docs/draft-jones-json-web-token.html. 78 79 Args: 80 signer: crypt.Signer, Cryptographic signer. 81 payload: dict, Dictionary of data to convert to JSON and then sign. 82 key_id: string, (Optional) Key ID header. 83 84 Returns: 85 string, The JWT for the payload. 86 """ 87 header = {'typ': 'JWT', 'alg': 'RS256'} 88 if key_id is not None: 89 header['kid'] = key_id 90 91 segments = [ 92 _helpers._urlsafe_b64encode(_helpers._json_encode(header)), 93 _helpers._urlsafe_b64encode(_helpers._json_encode(payload)), 94 ] 95 signing_input = b'.'.join(segments) 96 97 signature = signer.sign(signing_input) 98 segments.append(_helpers._urlsafe_b64encode(signature)) 99 100 logger.debug(str(segments)) 101 102 return b'.'.join(segments) 103 104 105 def _verify_signature(message, signature, certs): 106 """Verifies signed content using a list of certificates. 107 108 Args: 109 message: string or bytes, The message to verify. 110 signature: string or bytes, The signature on the message. 111 certs: iterable, certificates in PEM format. 112 113 Raises: 114 AppIdentityError: If none of the certificates can verify the message 115 against the signature. 116 """ 117 for pem in certs: 118 verifier = Verifier.from_string(pem, is_x509_cert=True) 119 if verifier.verify(message, signature): 120 return 121 122 # If we have not returned, no certificate confirms the signature. 123 raise AppIdentityError('Invalid token signature') 124 125 126 def _check_audience(payload_dict, audience): 127 """Checks audience field from a JWT payload. 128 129 Does nothing if the passed in ``audience`` is null. 130 131 Args: 132 payload_dict: dict, A dictionary containing a JWT payload. 133 audience: string or NoneType, an audience to check for in 134 the JWT payload. 135 136 Raises: 137 AppIdentityError: If there is no ``'aud'`` field in the payload 138 dictionary but there is an ``audience`` to check. 139 AppIdentityError: If the ``'aud'`` field in the payload dictionary 140 does not match the ``audience``. 141 """ 142 if audience is None: 143 return 144 145 audience_in_payload = payload_dict.get('aud') 146 if audience_in_payload is None: 147 raise AppIdentityError( 148 'No aud field in token: {0}'.format(payload_dict)) 149 if audience_in_payload != audience: 150 raise AppIdentityError('Wrong recipient, {0} != {1}: {2}'.format( 151 audience_in_payload, audience, payload_dict)) 152 153 154 def _verify_time_range(payload_dict): 155 """Verifies the issued at and expiration from a JWT payload. 156 157 Makes sure the current time (in UTC) falls between the issued at and 158 expiration for the JWT (with some skew allowed for via 159 ``CLOCK_SKEW_SECS``). 160 161 Args: 162 payload_dict: dict, A dictionary containing a JWT payload. 163 164 Raises: 165 AppIdentityError: If there is no ``'iat'`` field in the payload 166 dictionary. 167 AppIdentityError: If there is no ``'exp'`` field in the payload 168 dictionary. 169 AppIdentityError: If the JWT expiration is too far in the future (i.e. 170 if the expiration would imply a token lifetime 171 longer than what is allowed.) 172 AppIdentityError: If the token appears to have been issued in the 173 future (up to clock skew). 174 AppIdentityError: If the token appears to have expired in the past 175 (up to clock skew). 176 """ 177 # Get the current time to use throughout. 178 now = int(time.time()) 179 180 # Make sure issued at and expiration are in the payload. 181 issued_at = payload_dict.get('iat') 182 if issued_at is None: 183 raise AppIdentityError( 184 'No iat field in token: {0}'.format(payload_dict)) 185 expiration = payload_dict.get('exp') 186 if expiration is None: 187 raise AppIdentityError( 188 'No exp field in token: {0}'.format(payload_dict)) 189 190 # Make sure the expiration gives an acceptable token lifetime. 191 if expiration >= now + MAX_TOKEN_LIFETIME_SECS: 192 raise AppIdentityError( 193 'exp field too far in future: {0}'.format(payload_dict)) 194 195 # Make sure (up to clock skew) that the token wasn't issued in the future. 196 earliest = issued_at - CLOCK_SKEW_SECS 197 if now < earliest: 198 raise AppIdentityError('Token used too early, {0} < {1}: {2}'.format( 199 now, earliest, payload_dict)) 200 # Make sure (up to clock skew) that the token isn't already expired. 201 latest = expiration + CLOCK_SKEW_SECS 202 if now > latest: 203 raise AppIdentityError('Token used too late, {0} > {1}: {2}'.format( 204 now, latest, payload_dict)) 205 206 207 def verify_signed_jwt_with_certs(jwt, certs, audience=None): 208 """Verify a JWT against public certs. 209 210 See http://self-issued.info/docs/draft-jones-json-web-token.html. 211 212 Args: 213 jwt: string, A JWT. 214 certs: dict, Dictionary where values of public keys in PEM format. 215 audience: string, The audience, 'aud', that this JWT should contain. If 216 None then the JWT's 'aud' parameter is not verified. 217 218 Returns: 219 dict, The deserialized JSON payload in the JWT. 220 221 Raises: 222 AppIdentityError: if any checks are failed. 223 """ 224 jwt = _helpers._to_bytes(jwt) 225 226 if jwt.count(b'.') != 2: 227 raise AppIdentityError( 228 'Wrong number of segments in token: {0}'.format(jwt)) 229 230 header, payload, signature = jwt.split(b'.') 231 message_to_sign = header + b'.' + payload 232 signature = _helpers._urlsafe_b64decode(signature) 233 234 # Parse token. 235 payload_bytes = _helpers._urlsafe_b64decode(payload) 236 try: 237 payload_dict = json.loads(_helpers._from_bytes(payload_bytes)) 238 except: 239 raise AppIdentityError('Can\'t parse token: {0}'.format(payload_bytes)) 240 241 # Verify that the signature matches the message. 242 _verify_signature(message_to_sign, signature, certs.values()) 243 244 # Verify the issued at and created times in the payload. 245 _verify_time_range(payload_dict) 246 247 # Check audience. 248 _check_audience(payload_dict, audience) 249 250 return payload_dict 251
