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|
# 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.
from __future__ import absolute_import, division, print_function
from collections import namedtuple
from cryptography import utils
from cryptography.exceptions import (
InternalError, InvalidTag, UnsupportedAlgorithm, _Reasons
)
from cryptography.hazmat.backends.interfaces import (
CipherBackend, HMACBackend, HashBackend, PBKDF2HMACBackend
)
from cryptography.hazmat.bindings.commoncrypto.binding import Binding
from cryptography.hazmat.primitives import constant_time, interfaces
from cryptography.hazmat.primitives.ciphers.algorithms import (
AES, ARC4, Blowfish, CAST5, TripleDES
)
from cryptography.hazmat.primitives.ciphers.modes import (
CBC, CFB, CFB8, CTR, ECB, GCM, OFB
)
HashMethods = namedtuple(
"HashMethods", ["ctx", "hash_init", "hash_update", "hash_final"]
)
@utils.register_interface(CipherBackend)
@utils.register_interface(HashBackend)
@utils.register_interface(HMACBackend)
@utils.register_interface(PBKDF2HMACBackend)
class Backend(object):
"""
CommonCrypto API wrapper.
"""
name = "commoncrypto"
def __init__(self):
self._binding = Binding()
self._ffi = self._binding.ffi
self._lib = self._binding.lib
self._cipher_registry = {}
self._register_default_ciphers()
self._hash_mapping = {
"md5": HashMethods(
"CC_MD5_CTX *", self._lib.CC_MD5_Init,
self._lib.CC_MD5_Update, self._lib.CC_MD5_Final
),
"sha1": HashMethods(
"CC_SHA1_CTX *", self._lib.CC_SHA1_Init,
self._lib.CC_SHA1_Update, self._lib.CC_SHA1_Final
),
"sha224": HashMethods(
"CC_SHA256_CTX *", self._lib.CC_SHA224_Init,
self._lib.CC_SHA224_Update, self._lib.CC_SHA224_Final
),
"sha256": HashMethods(
"CC_SHA256_CTX *", self._lib.CC_SHA256_Init,
self._lib.CC_SHA256_Update, self._lib.CC_SHA256_Final
),
"sha384": HashMethods(
"CC_SHA512_CTX *", self._lib.CC_SHA384_Init,
self._lib.CC_SHA384_Update, self._lib.CC_SHA384_Final
),
"sha512": HashMethods(
"CC_SHA512_CTX *", self._lib.CC_SHA512_Init,
self._lib.CC_SHA512_Update, self._lib.CC_SHA512_Final
),
}
self._supported_hmac_algorithms = {
"md5": self._lib.kCCHmacAlgMD5,
"sha1": self._lib.kCCHmacAlgSHA1,
"sha224": self._lib.kCCHmacAlgSHA224,
"sha256": self._lib.kCCHmacAlgSHA256,
"sha384": self._lib.kCCHmacAlgSHA384,
"sha512": self._lib.kCCHmacAlgSHA512,
}
self._supported_pbkdf2_hmac_algorithms = {
"sha1": self._lib.kCCPRFHmacAlgSHA1,
"sha224": self._lib.kCCPRFHmacAlgSHA224,
"sha256": self._lib.kCCPRFHmacAlgSHA256,
"sha384": self._lib.kCCPRFHmacAlgSHA384,
"sha512": self._lib.kCCPRFHmacAlgSHA512,
}
def hash_supported(self, algorithm):
return algorithm.name in self._hash_mapping
def hmac_supported(self, algorithm):
return algorithm.name in self._supported_hmac_algorithms
def create_hash_ctx(self, algorithm):
return _HashContext(self, algorithm)
def create_hmac_ctx(self, key, algorithm):
return _HMACContext(self, key, algorithm)
def cipher_supported(self, cipher, mode):
return (type(cipher), type(mode)) in self._cipher_registry
def create_symmetric_encryption_ctx(self, cipher, mode):
if isinstance(mode, GCM):
return _GCMCipherContext(
self, cipher, mode, self._lib.kCCEncrypt
)
else:
return _CipherContext(self, cipher, mode, self._lib.kCCEncrypt)
def create_symmetric_decryption_ctx(self, cipher, mode):
if isinstance(mode, GCM):
return _GCMCipherContext(
self, cipher, mode, self._lib.kCCDecrypt
)
else:
return _CipherContext(self, cipher, mode, self._lib.kCCDecrypt)
def pbkdf2_hmac_supported(self, algorithm):
return algorithm.name in self._supported_pbkdf2_hmac_algorithms
def derive_pbkdf2_hmac(self, algorithm, length, salt, iterations,
key_material):
alg_enum = self._supported_pbkdf2_hmac_algorithms[algorithm.name]
buf = self._ffi.new("char[]", length)
res = self._lib.CCKeyDerivationPBKDF(
self._lib.kCCPBKDF2,
key_material,
len(key_material),
salt,
len(salt),
alg_enum,
iterations,
buf,
length
)
self._check_response(res)
return self._ffi.buffer(buf)[:]
def _register_cipher_adapter(self, cipher_cls, cipher_const, mode_cls,
mode_const):
if (cipher_cls, mode_cls) in self._cipher_registry:
raise ValueError("Duplicate registration for: {0} {1}.".format(
cipher_cls, mode_cls)
)
self._cipher_registry[cipher_cls, mode_cls] = (cipher_const,
mode_const)
def _register_default_ciphers(self):
for mode_cls, mode_const in [
(CBC, self._lib.kCCModeCBC),
(ECB, self._lib.kCCModeECB),
(CFB, self._lib.kCCModeCFB),
(CFB8, self._lib.kCCModeCFB8),
(OFB, self._lib.kCCModeOFB),
(CTR, self._lib.kCCModeCTR),
(GCM, self._lib.kCCModeGCM),
]:
self._register_cipher_adapter(
AES,
self._lib.kCCAlgorithmAES128,
mode_cls,
mode_const
)
for mode_cls, mode_const in [
(CBC, self._lib.kCCModeCBC),
(CFB, self._lib.kCCModeCFB),
(CFB8, self._lib.kCCModeCFB8),
(OFB, self._lib.kCCModeOFB),
]:
self._register_cipher_adapter(
TripleDES,
self._lib.kCCAlgorithm3DES,
mode_cls,
mode_const
)
for mode_cls, mode_const in [
(CBC, self._lib.kCCModeCBC),
(ECB, self._lib.kCCModeECB),
(CFB, self._lib.kCCModeCFB),
(OFB, self._lib.kCCModeOFB)
]:
self._register_cipher_adapter(
Blowfish,
self._lib.kCCAlgorithmBlowfish,
mode_cls,
mode_const
)
for mode_cls, mode_const in [
(CBC, self._lib.kCCModeCBC),
(ECB, self._lib.kCCModeECB),
(CFB, self._lib.kCCModeCFB),
(OFB, self._lib.kCCModeOFB),
(CTR, self._lib.kCCModeCTR)
]:
self._register_cipher_adapter(
CAST5,
self._lib.kCCAlgorithmCAST,
mode_cls,
mode_const
)
self._register_cipher_adapter(
ARC4,
self._lib.kCCAlgorithmRC4,
type(None),
self._lib.kCCModeRC4
)
def _check_response(self, response):
if response == self._lib.kCCSuccess:
return
elif response == self._lib.kCCAlignmentError:
# This error is not currently triggered due to a bug filed as
# rdar://15589470
raise ValueError(
"The length of the provided data is not a multiple of "
"the block length."
)
else:
raise InternalError(
"The backend returned an unknown error, consider filing a bug."
" Code: {0}.".format(response)
)
def _release_cipher_ctx(ctx):
"""
Called by the garbage collector and used to safely dereference and
release the context.
"""
if ctx[0] != backend._ffi.NULL:
res = backend._lib.CCCryptorRelease(ctx[0])
backend._check_response(res)
ctx[0] = backend._ffi.NULL
@utils.register_interface(interfaces.CipherContext)
class _CipherContext(object):
def __init__(self, backend, cipher, mode, operation):
self._backend = backend
self._cipher = cipher
self._mode = mode
self._operation = operation
# There is a bug in CommonCrypto where block ciphers do not raise
# kCCAlignmentError when finalizing if you supply non-block aligned
# data. To work around this we need to keep track of the block
# alignment ourselves, but only for alg+mode combos that require
# block alignment. OFB, CFB, and CTR make a block cipher algorithm
# into a stream cipher so we don't need to track them (and thus their
# block size is effectively 1 byte just like OpenSSL/CommonCrypto
# treat RC4 and other stream cipher block sizes).
# This bug has been filed as rdar://15589470
self._bytes_processed = 0
if (isinstance(cipher, interfaces.BlockCipherAlgorithm) and not
isinstance(mode, (OFB, CFB, CFB8, CTR))):
self._byte_block_size = cipher.block_size // 8
else:
self._byte_block_size = 1
registry = self._backend._cipher_registry
try:
cipher_enum, mode_enum = registry[type(cipher), type(mode)]
except KeyError:
raise UnsupportedAlgorithm(
"cipher {0} in {1} mode is not supported "
"by this backend.".format(
cipher.name, mode.name if mode else mode),
_Reasons.UNSUPPORTED_CIPHER
)
ctx = self._backend._ffi.new("CCCryptorRef *")
ctx = self._backend._ffi.gc(ctx, _release_cipher_ctx)
if isinstance(mode, interfaces.ModeWithInitializationVector):
iv_nonce = mode.initialization_vector
elif isinstance(mode, interfaces.ModeWithNonce):
iv_nonce = mode.nonce
else:
iv_nonce = self._backend._ffi.NULL
if isinstance(mode, CTR):
mode_option = self._backend._lib.kCCModeOptionCTR_BE
else:
mode_option = 0
res = self._backend._lib.CCCryptorCreateWithMode(
operation,
mode_enum, cipher_enum,
self._backend._lib.ccNoPadding, iv_nonce,
cipher.key, len(cipher.key),
self._backend._ffi.NULL, 0, 0, mode_option, ctx)
self._backend._check_response(res)
self._ctx = ctx
def update(self, data):
# Count bytes processed to handle block alignment.
self._bytes_processed += len(data)
buf = self._backend._ffi.new(
"unsigned char[]", len(data) + self._byte_block_size - 1)
outlen = self._backend._ffi.new("size_t *")
res = self._backend._lib.CCCryptorUpdate(
self._ctx[0], data, len(data), buf,
len(data) + self._byte_block_size - 1, outlen)
self._backend._check_response(res)
return self._backend._ffi.buffer(buf)[:outlen[0]]
def finalize(self):
# Raise error if block alignment is wrong.
if self._bytes_processed % self._byte_block_size:
raise ValueError(
"The length of the provided data is not a multiple of "
"the block length."
)
buf = self._backend._ffi.new("unsigned char[]", self._byte_block_size)
outlen = self._backend._ffi.new("size_t *")
res = self._backend._lib.CCCryptorFinal(
self._ctx[0], buf, len(buf), outlen)
self._backend._check_response(res)
_release_cipher_ctx(self._ctx)
return self._backend._ffi.buffer(buf)[:outlen[0]]
@utils.register_interface(interfaces.AEADCipherContext)
@utils.register_interface(interfaces.AEADEncryptionContext)
class _GCMCipherContext(object):
def __init__(self, backend, cipher, mode, operation):
self._backend = backend
self._cipher = cipher
self._mode = mode
self._operation = operation
self._tag = None
registry = self._backend._cipher_registry
try:
cipher_enum, mode_enum = registry[type(cipher), type(mode)]
except KeyError:
raise UnsupportedAlgorithm(
"cipher {0} in {1} mode is not supported "
"by this backend.".format(
cipher.name, mode.name if mode else mode),
_Reasons.UNSUPPORTED_CIPHER
)
ctx = self._backend._ffi.new("CCCryptorRef *")
ctx = self._backend._ffi.gc(ctx, _release_cipher_ctx)
self._ctx = ctx
res = self._backend._lib.CCCryptorCreateWithMode(
operation,
mode_enum, cipher_enum,
self._backend._lib.ccNoPadding,
self._backend._ffi.NULL,
cipher.key, len(cipher.key),
self._backend._ffi.NULL, 0, 0, 0, self._ctx)
self._backend._check_response(res)
res = self._backend._lib.CCCryptorGCMAddIV(
self._ctx[0],
mode.initialization_vector,
len(mode.initialization_vector)
)
self._backend._check_response(res)
def update(self, data):
buf = self._backend._ffi.new("unsigned char[]", len(data))
args = (self._ctx[0], data, len(data), buf)
if self._operation == self._backend._lib.kCCEncrypt:
res = self._backend._lib.CCCryptorGCMEncrypt(*args)
else:
res = self._backend._lib.CCCryptorGCMDecrypt(*args)
self._backend._check_response(res)
return self._backend._ffi.buffer(buf)[:]
def finalize(self):
tag_size = self._cipher.block_size // 8
tag_buf = self._backend._ffi.new("unsigned char[]", tag_size)
tag_len = self._backend._ffi.new("size_t *", tag_size)
res = backend._lib.CCCryptorGCMFinal(self._ctx[0], tag_buf, tag_len)
self._backend._check_response(res)
_release_cipher_ctx(self._ctx)
self._tag = self._backend._ffi.buffer(tag_buf)[:]
if (self._operation == self._backend._lib.kCCDecrypt and
not constant_time.bytes_eq(
self._tag[:len(self._mode.tag)], self._mode.tag
)):
raise InvalidTag
return b""
def authenticate_additional_data(self, data):
res = self._backend._lib.CCCryptorGCMAddAAD(
self._ctx[0], data, len(data)
)
self._backend._check_response(res)
@property
def tag(self):
return self._tag
@utils.register_interface(interfaces.HashContext)
class _HashContext(object):
def __init__(self, backend, algorithm, ctx=None):
self.algorithm = algorithm
self._backend = backend
if ctx is None:
try:
methods = self._backend._hash_mapping[self.algorithm.name]
except KeyError:
raise UnsupportedAlgorithm(
"{0} is not a supported hash on this backend.".format(
algorithm.name),
_Reasons.UNSUPPORTED_HASH
)
ctx = self._backend._ffi.new(methods.ctx)
res = methods.hash_init(ctx)
assert res == 1
self._ctx = ctx
def copy(self):
methods = self._backend._hash_mapping[self.algorithm.name]
new_ctx = self._backend._ffi.new(methods.ctx)
# CommonCrypto has no APIs for copying hashes, so we have to copy the
# underlying struct.
new_ctx[0] = self._ctx[0]
return _HashContext(self._backend, self.algorithm, ctx=new_ctx)
def update(self, data):
methods = self._backend._hash_mapping[self.algorithm.name]
res = methods.hash_update(self._ctx, data, len(data))
assert res == 1
def finalize(self):
methods = self._backend._hash_mapping[self.algorithm.name]
buf = self._backend._ffi.new("unsigned char[]",
self.algorithm.digest_size)
res = methods.hash_final(buf, self._ctx)
assert res == 1
return self._backend._ffi.buffer(buf)[:]
@utils.register_interface(interfaces.HashContext)
class _HMACContext(object):
def __init__(self, backend, key, algorithm, ctx=None):
self.algorithm = algorithm
self._backend = backend
if ctx is None:
ctx = self._backend._ffi.new("CCHmacContext *")
try:
alg = self._backend._supported_hmac_algorithms[algorithm.name]
except KeyError:
raise UnsupportedAlgorithm(
"{0} is not a supported HMAC hash on this backend.".format(
algorithm.name),
_Reasons.UNSUPPORTED_HASH
)
self._backend._lib.CCHmacInit(ctx, alg, key, len(key))
self._ctx = ctx
self._key = key
def copy(self):
copied_ctx = self._backend._ffi.new("CCHmacContext *")
# CommonCrypto has no APIs for copying HMACs, so we have to copy the
# underlying struct.
copied_ctx[0] = self._ctx[0]
return _HMACContext(
self._backend, self._key, self.algorithm, ctx=copied_ctx
)
def update(self, data):
self._backend._lib.CCHmacUpdate(self._ctx, data, len(data))
def finalize(self):
buf = self._backend._ffi.new("unsigned char[]",
self.algorithm.digest_size)
self._backend._lib.CCHmacFinal(self._ctx, buf)
return self._backend._ffi.buffer(buf)[:]
backend = Backend()
|