#!/usr/bin/python2.4
# -*- coding: utf-8 -*-
#
# Copyright (C) 2011 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.
import base64
import hashlib
import logging
import time
from anyjson import simplejson
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):
pass
try:
from OpenSSL import crypto
class OpenSSLVerifier(object):
"""Verifies the signature on a message."""
def __init__(self, pubkey):
"""Constructor.
Args:
pubkey, OpenSSL.crypto.PKey, The public key to verify with.
"""
self._pubkey = pubkey
def verify(self, message, signature):
"""Verifies a message against a signature.
Args:
message: string, The message to verify.
signature: string, The signature on the message.
Returns:
True if message was signed by the private key associated with the public
key that this object was constructed with.
"""
try:
crypto.verify(self._pubkey, signature, message, 'sha256')
return True
except:
return False
@staticmethod
def from_string(key_pem, is_x509_cert):
"""Construct a Verified instance from a string.
Args:
key_pem: string, public key in PEM format.
is_x509_cert: bool, True if key_pem is an X509 cert, otherwise it is
expected to be an RSA key in PEM format.
Returns:
Verifier instance.
Raises:
OpenSSL.crypto.Error if the key_pem can't be parsed.
"""
if is_x509_cert:
pubkey = crypto.load_certificate(crypto.FILETYPE_PEM, key_pem)
else:
pubkey = crypto.load_privatekey(crypto.FILETYPE_PEM, key_pem)
return OpenSSLVerifier(pubkey)
class OpenSSLSigner(object):
"""Signs messages with a private key."""
def __init__(self, pkey):
"""Constructor.
Args:
pkey, OpenSSL.crypto.PKey (or equiv), The private key to sign with.
"""
self._key = pkey
def sign(self, message):
"""Signs a message.
Args:
message: string, Message to be signed.
Returns:
string, The signature of the message for the given key.
"""
return crypto.sign(self._key, message, 'sha256')
@staticmethod
def from_string(key, password='notasecret'):
"""Construct a Signer instance from a string.
Args:
key: string, private key in PKCS12 or PEM format.
password: string, password for the private key file.
Returns:
Signer instance.
Raises:
OpenSSL.crypto.Error if the key can't be parsed.
"""
if key.startswith('-----BEGIN '):
pkey = crypto.load_privatekey(crypto.FILETYPE_PEM, key)
else:
pkey = crypto.load_pkcs12(key, password).get_privatekey()
return OpenSSLSigner(pkey)
except ImportError:
OpenSSLVerifier = None
OpenSSLSigner = None
try:
from Crypto.PublicKey import RSA
from Crypto.Hash import SHA256
from Crypto.Signature import PKCS1_v1_5
class PyCryptoVerifier(object):
"""Verifies the signature on a message."""
def __init__(self, pubkey):
"""Constructor.
Args:
pubkey, OpenSSL.crypto.PKey (or equiv), The public key to verify with.
"""
self._pubkey = pubkey
def verify(self, message, signature):
"""Verifies a message against a signature.
Args:
message: string, The message to verify.
signature: string, The signature on the message.
Returns:
True if message was signed by the private key associated with the public
key that this object was constructed with.
"""
try:
return PKCS1_v1_5.new(self._pubkey).verify(
SHA256.new(message), signature)
except:
return False
@staticmethod
def from_string(key_pem, is_x509_cert):
"""Construct a Verified instance from a string.
Args:
key_pem: string, public key in PEM format.
is_x509_cert: bool, True if key_pem is an X509 cert, otherwise it is
expected to be an RSA key in PEM format.
Returns:
Verifier instance.
Raises:
NotImplementedError if is_x509_cert is true.
"""
if is_x509_cert:
raise NotImplementedError(
'X509 certs are not supported by the PyCrypto library. '
'Try using PyOpenSSL if native code is an option.')
else:
pubkey = RSA.importKey(key_pem)
return PyCryptoVerifier(pubkey)
class PyCryptoSigner(object):
"""Signs messages with a private key."""
def __init__(self, pkey):
"""Constructor.
Args:
pkey, OpenSSL.crypto.PKey (or equiv), The private key to sign with.
"""
self._key = pkey
def sign(self, message):
"""Signs a message.
Args:
message: string, Message to be signed.
Returns:
string, The signature of the message for the given key.
"""
return PKCS1_v1_5.new(self._key).sign(SHA256.new(message))
@staticmethod
def from_string(key, password='notasecret'):
"""Construct a Signer instance from a string.
Args:
key: string, private key in PEM format.
password: string, password for private key file. Unused for PEM files.
Returns:
Signer instance.
Raises:
NotImplementedError if they key isn't in PEM format.
"""
if key.startswith('-----BEGIN '):
pkey = RSA.importKey(key)
else:
raise NotImplementedError(
'PKCS12 format is not supported by the PyCrpto library. '
'Try converting to a "PEM" '
'(openssl pkcs12 -in xxxxx.p12 -nodes -nocerts > privatekey.pem) '
'or using PyOpenSSL if native code is an option.')
return PyCryptoSigner(pkey)
except ImportError:
PyCryptoVerifier = None
PyCryptoSigner = None
if OpenSSLSigner:
Signer = OpenSSLSigner
Verifier = OpenSSLVerifier
elif PyCryptoSigner:
Signer = PyCryptoSigner
Verifier = PyCryptoVerifier
else:
raise ImportError('No encryption library found. Please install either '
'PyOpenSSL, or PyCrypto 2.6 or later')
def _urlsafe_b64encode(raw_bytes):
return base64.urlsafe_b64encode(raw_bytes).rstrip('=')
def _urlsafe_b64decode(b64string):
# Guard against unicode strings, which base64 can't handle.
b64string = b64string.encode('ascii')
padded = b64string + '=' * (4 - len(b64string) % 4)
return base64.urlsafe_b64decode(padded)
def _json_encode(data):
return simplejson.dumps(data, separators = (',', ':'))
def make_signed_jwt(signer, payload):
"""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.
Returns:
string, The JWT for the payload.
"""
header = {'typ': 'JWT', 'alg': 'RS256'}
segments = [
_urlsafe_b64encode(_json_encode(header)),
_urlsafe_b64encode(_json_encode(payload)),
]
signing_input = '.'.join(segments)
signature = signer.sign(signing_input)
segments.append(_urlsafe_b64encode(signature))
logger.debug(str(segments))
return '.'.join(segments)
def verify_signed_jwt_with_certs(jwt, certs, audience):
"""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.
"""
segments = jwt.split('.')
if (len(segments) != 3):
raise AppIdentityError(
'Wrong number of segments in token: %s' % jwt)
signed = '%s.%s' % (segments[0], segments[1])
signature = _urlsafe_b64decode(segments[2])
# Parse token.
json_body = _urlsafe_b64decode(segments[1])
try:
parsed = simplejson.loads(json_body)
except:
raise AppIdentityError('Can\'t parse token: %s' % json_body)
# Check signature.
verified = False
for (keyname, pem) in certs.items():
verifier = Verifier.from_string(pem, True)
if (verifier.verify(signed, signature)):
verified = True
break
if not verified:
raise AppIdentityError('Invalid token signature: %s' % jwt)
# Check creation timestamp.
iat = parsed.get('iat')
if iat is None:
raise AppIdentityError('No iat field in token: %s' % json_body)
earliest = iat - CLOCK_SKEW_SECS
# Check expiration timestamp.
now = long(time.time())
exp = parsed.get('exp')
if exp is None:
raise AppIdentityError('No exp field in token: %s' % json_body)
if exp >= now + MAX_TOKEN_LIFETIME_SECS:
raise AppIdentityError(
'exp field too far in future: %s' % json_body)
latest = exp + CLOCK_SKEW_SECS
if now < earliest:
raise AppIdentityError('Token used too early, %d < %d: %s' %
(now, earliest, json_body))
if now > latest:
raise AppIdentityError('Token used too late, %d > %d: %s' %
(now, latest, json_body))
# Check audience.
if audience is not None:
aud = parsed.get('aud')
if aud is None:
raise AppIdentityError('No aud field in token: %s' % json_body)
if aud != audience:
raise AppIdentityError('Wrong recipient, %s != %s: %s' %
(aud, audience, json_body))
return parsed
