/usr/lib/python2.7/dist-packages/keystoneclient/middleware/memcache_crypt.py is in python-keystoneclient 1:0.7.1-ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 | # Copyright 2010-2013 OpenStack Foundation
#
# 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.
"""
Utilities for memcache encryption and integrity check.
Data should be serialized before entering these functions. Encryption
has a dependency on the pycrypto. If pycrypto is not available,
CryptoUnavailableError will be raised.
This module will not be called unless signing or encryption is enabled
in the config. It will always validate signatures, and will decrypt
data if encryption is enabled. It is not valid to mix protection
modes.
"""
import base64
import functools
import hashlib
import hmac
import math
import os
import six
import sys
# make sure pycrypto is available
try:
from Crypto.Cipher import AES
except ImportError:
AES = None
HASH_FUNCTION = hashlib.sha384
DIGEST_LENGTH = HASH_FUNCTION().digest_size
DIGEST_SPLIT = DIGEST_LENGTH // 3
DIGEST_LENGTH_B64 = 4 * int(math.ceil(DIGEST_LENGTH / 3.0))
class InvalidMacError(Exception):
"""raise when unable to verify MACed data.
This usually indicates that data had been expectedly modified in memcache.
"""
pass
class DecryptError(Exception):
"""raise when unable to decrypt encrypted data.
"""
pass
class CryptoUnavailableError(Exception):
"""raise when Python Crypto module is not available.
"""
pass
def assert_crypto_availability(f):
"""Ensure Crypto module is available."""
@functools.wraps(f)
def wrapper(*args, **kwds):
if AES is None:
raise CryptoUnavailableError()
return f(*args, **kwds)
return wrapper
if sys.version_info >= (3, 3):
constant_time_compare = hmac.compare_digest
else:
def constant_time_compare(first, second):
"""Returns True if both string inputs are equal, otherwise False.
This function should take a constant amount of time regardless of
how many characters in the strings match.
"""
if len(first) != len(second):
return False
result = 0
if six.PY3 and isinstance(first, bytes) and isinstance(second, bytes):
for x, y in zip(first, second):
result |= x ^ y
else:
for x, y in zip(first, second):
result |= ord(x) ^ ord(y)
return result == 0
def derive_keys(token, secret, strategy):
"""Derives keys for MAC and ENCRYPTION from the user-provided
secret. The resulting keys should be passed to the protect and
unprotect functions.
As suggested by NIST Special Publication 800-108, this uses the
first 128 bits from the sha384 KDF for the obscured cache key
value, the second 128 bits for the message authentication key and
the remaining 128 bits for the encryption key.
This approach is faster than computing a separate hmac as the KDF
for each desired key.
"""
digest = hmac.new(secret, token + strategy, HASH_FUNCTION).digest()
return {'CACHE_KEY': digest[:DIGEST_SPLIT],
'MAC': digest[DIGEST_SPLIT: 2 * DIGEST_SPLIT],
'ENCRYPTION': digest[2 * DIGEST_SPLIT:],
'strategy': strategy}
def sign_data(key, data):
"""Sign the data using the defined function and the derived key."""
mac = hmac.new(key, data, HASH_FUNCTION).digest()
return base64.b64encode(mac)
@assert_crypto_availability
def encrypt_data(key, data):
"""Encrypt the data with the given secret key.
Padding is n bytes of the value n, where 1 <= n <= blocksize.
"""
iv = os.urandom(16)
cipher = AES.new(key, AES.MODE_CBC, iv)
padding = 16 - len(data) % 16
return iv + cipher.encrypt(data + six.int2byte(padding) * padding)
@assert_crypto_availability
def decrypt_data(key, data):
"""Decrypt the data with the given secret key."""
iv = data[:16]
cipher = AES.new(key, AES.MODE_CBC, iv)
try:
result = cipher.decrypt(data[16:])
except Exception:
raise DecryptError('Encrypted data appears to be corrupted.')
# Strip the last n padding bytes where n is the last value in
# the plaintext
return result[:-1 * six.byte2int([result[-1]])]
def protect_data(keys, data):
"""Given keys and serialized data, returns an appropriately
protected string suitable for storage in the cache.
"""
if keys['strategy'] == b'ENCRYPT':
data = encrypt_data(keys['ENCRYPTION'], data)
encoded_data = base64.b64encode(data)
signature = sign_data(keys['MAC'], encoded_data)
return signature + encoded_data
def unprotect_data(keys, signed_data):
"""Given keys and cached string data, verifies the signature,
decrypts if necessary, and returns the original serialized data.
"""
# cache backends return None when no data is found. We don't mind
# that this particular special value is unsigned.
if signed_data is None:
return None
# First we calculate the signature
provided_mac = signed_data[:DIGEST_LENGTH_B64]
calculated_mac = sign_data(
keys['MAC'],
signed_data[DIGEST_LENGTH_B64:])
# Then verify that it matches the provided value
if not constant_time_compare(provided_mac, calculated_mac):
raise InvalidMacError('Invalid MAC; data appears to be corrupted.')
data = base64.b64decode(signed_data[DIGEST_LENGTH_B64:])
# then if necessary decrypt the data
if keys['strategy'] == b'ENCRYPT':
data = decrypt_data(keys['ENCRYPTION'], data)
return data
def get_cache_key(keys):
"""Given keys generated by derive_keys(), returns a base64
encoded value suitable for use as a cache key in memcached.
"""
return base64.b64encode(keys['CACHE_KEY'])
|