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Diffstat (limited to 'src/cryptography/hazmat/backends/commoncrypto/ciphers.py')
| -rw-r--r-- | src/cryptography/hazmat/backends/commoncrypto/ciphers.py | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/src/cryptography/hazmat/backends/commoncrypto/ciphers.py b/src/cryptography/hazmat/backends/commoncrypto/ciphers.py new file mode 100644 index 00000000..d94746c6 --- /dev/null +++ b/src/cryptography/hazmat/backends/commoncrypto/ciphers.py @@ -0,0 +1,201 @@ +# 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 cryptography import utils +from cryptography.exceptions import ( + InvalidTag, UnsupportedAlgorithm, _Reasons +) +from cryptography.hazmat.primitives import constant_time, interfaces +from cryptography.hazmat.primitives.ciphers.modes import ( + CFB, CFB8, CTR, OFB +) + + +@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, self._backend._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_cipher_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_cipher_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_cipher_response(res) + self._backend._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, self._backend._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_cipher_response(res) + + res = self._backend._lib.CCCryptorGCMAddIV( + self._ctx[0], + mode.initialization_vector, + len(mode.initialization_vector) + ) + self._backend._check_cipher_response(res) + # CommonCrypto has a bug where calling update without at least one + # call to authenticate_additional_data will result in null byte output + # for ciphertext. The following empty byte string call prevents the + # issue, which is present in at least 10.8 and 10.9. + # Filed as rdar://18314544 + self.authenticate_additional_data(b"") + + 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_cipher_response(res) + return self._backend._ffi.buffer(buf)[:] + + def finalize(self): + # CommonCrypto has a yet another bug where you must make at least one + # call to update. If you pass just AAD and call finalize without a call + # to update you'll get null bytes for tag. The following update call + # prevents this issue, which is present in at least 10.8 and 10.9. + # Filed as rdar://18314580 + self.update(b"") + 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 = self._backend._lib.CCCryptorGCMFinal( + self._ctx[0], tag_buf, tag_len + ) + self._backend._check_cipher_response(res) + self._backend._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_cipher_response(res) + + tag = utils.read_only_property("_tag") |