diff options
Diffstat (limited to 'src/cryptography/hazmat/backends/openssl/ciphers.py')
| -rw-r--r-- | src/cryptography/hazmat/backends/openssl/ciphers.py | 225 |
1 files changed, 225 insertions, 0 deletions
diff --git a/src/cryptography/hazmat/backends/openssl/ciphers.py b/src/cryptography/hazmat/backends/openssl/ciphers.py new file mode 100644 index 00000000..4ec2ac89 --- /dev/null +++ b/src/cryptography/hazmat/backends/openssl/ciphers.py @@ -0,0 +1,225 @@ +# 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 interfaces +from cryptography.hazmat.primitives.ciphers.modes import GCM + + +@utils.register_interface(interfaces.CipherContext) +@utils.register_interface(interfaces.AEADCipherContext) +@utils.register_interface(interfaces.AEADEncryptionContext) +class _CipherContext(object): + _ENCRYPT = 1 + _DECRYPT = 0 + + def __init__(self, backend, cipher, mode, operation): + self._backend = backend + self._cipher = cipher + self._mode = mode + self._operation = operation + self._tag = None + + if isinstance(self._cipher, interfaces.BlockCipherAlgorithm): + self._block_size = self._cipher.block_size + else: + self._block_size = 1 + + ctx = self._backend._lib.EVP_CIPHER_CTX_new() + ctx = self._backend._ffi.gc( + ctx, self._backend._lib.EVP_CIPHER_CTX_free + ) + + registry = self._backend._cipher_registry + try: + adapter = 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 + ) + + evp_cipher = adapter(self._backend, cipher, mode) + if evp_cipher == self._backend._ffi.NULL: + 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 + ) + + 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 + # begin init with cipher and operation type + res = self._backend._lib.EVP_CipherInit_ex(ctx, evp_cipher, + self._backend._ffi.NULL, + self._backend._ffi.NULL, + self._backend._ffi.NULL, + operation) + assert res != 0 + # set the key length to handle variable key ciphers + res = self._backend._lib.EVP_CIPHER_CTX_set_key_length( + ctx, len(cipher.key) + ) + assert res != 0 + if isinstance(mode, GCM): + res = self._backend._lib.EVP_CIPHER_CTX_ctrl( + ctx, self._backend._lib.EVP_CTRL_GCM_SET_IVLEN, + len(iv_nonce), self._backend._ffi.NULL + ) + assert res != 0 + if operation == self._DECRYPT: + res = self._backend._lib.EVP_CIPHER_CTX_ctrl( + ctx, self._backend._lib.EVP_CTRL_GCM_SET_TAG, + len(mode.tag), mode.tag + ) + assert res != 0 + + # pass key/iv + res = self._backend._lib.EVP_CipherInit_ex( + ctx, + self._backend._ffi.NULL, + self._backend._ffi.NULL, + cipher.key, + iv_nonce, + operation + ) + assert res != 0 + # We purposely disable padding here as it's handled higher up in the + # API. + self._backend._lib.EVP_CIPHER_CTX_set_padding(ctx, 0) + self._ctx = ctx + + def update(self, data): + # OpenSSL 0.9.8e has an assertion in its EVP code that causes it + # to SIGABRT if you call update with an empty byte string. This can be + # removed when we drop support for 0.9.8e (CentOS/RHEL 5). This branch + # should be taken only when length is zero and mode is not GCM because + # AES GCM can return improper tag values if you don't call update + # with empty plaintext when authenticating AAD for ...reasons. + if len(data) == 0 and not isinstance(self._mode, GCM): + return b"" + + buf = self._backend._ffi.new("unsigned char[]", + len(data) + self._block_size - 1) + outlen = self._backend._ffi.new("int *") + res = self._backend._lib.EVP_CipherUpdate(self._ctx, buf, outlen, data, + len(data)) + assert res != 0 + return self._backend._ffi.buffer(buf)[:outlen[0]] + + def finalize(self): + # OpenSSL 1.0.1 on Ubuntu 12.04 (and possibly other distributions) + # appears to have a bug where you must make at least one call to update + # even if you are only using authenticate_additional_data or the + # GCM tag will be wrong. An (empty) call to update resolves this + # and is harmless for all other versions of OpenSSL. + if isinstance(self._mode, GCM): + self.update(b"") + + buf = self._backend._ffi.new("unsigned char[]", self._block_size) + outlen = self._backend._ffi.new("int *") + res = self._backend._lib.EVP_CipherFinal_ex(self._ctx, buf, outlen) + if res == 0: + errors = self._backend._consume_errors() + + if not errors and isinstance(self._mode, GCM): + raise InvalidTag + + assert errors + + if errors[0][1:] == ( + self._backend._lib.ERR_LIB_EVP, + self._backend._lib.EVP_F_EVP_ENCRYPTFINAL_EX, + self._backend._lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH + ) or errors[0][1:] == ( + self._backend._lib.ERR_LIB_EVP, + self._backend._lib.EVP_F_EVP_DECRYPTFINAL_EX, + self._backend._lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH + ): + raise ValueError( + "The length of the provided data is not a multiple of " + "the block length." + ) + else: + raise self._backend._unknown_error(errors[0]) + + if (isinstance(self._mode, GCM) and + self._operation == self._ENCRYPT): + block_byte_size = self._block_size // 8 + tag_buf = self._backend._ffi.new( + "unsigned char[]", block_byte_size + ) + res = self._backend._lib.EVP_CIPHER_CTX_ctrl( + self._ctx, self._backend._lib.EVP_CTRL_GCM_GET_TAG, + block_byte_size, tag_buf + ) + assert res != 0 + self._tag = self._backend._ffi.buffer(tag_buf)[:] + + res = self._backend._lib.EVP_CIPHER_CTX_cleanup(self._ctx) + assert res == 1 + return self._backend._ffi.buffer(buf)[:outlen[0]] + + def authenticate_additional_data(self, data): + outlen = self._backend._ffi.new("int *") + res = self._backend._lib.EVP_CipherUpdate( + self._ctx, self._backend._ffi.NULL, outlen, data, len(data) + ) + assert res != 0 + + tag = utils.read_only_property("_tag") + + +@utils.register_interface(interfaces.CipherContext) +class _AESCTRCipherContext(object): + """ + This is needed to provide support for AES CTR mode in OpenSSL 0.9.8. It can + be removed when we drop 0.9.8 support (RHEL5 extended life ends 2020). + """ + def __init__(self, backend, cipher, mode): + self._backend = backend + + self._key = self._backend._ffi.new("AES_KEY *") + assert self._key != self._backend._ffi.NULL + res = self._backend._lib.AES_set_encrypt_key( + cipher.key, len(cipher.key) * 8, self._key + ) + assert res == 0 + self._ecount = self._backend._ffi.new("char[]", 16) + self._nonce = self._backend._ffi.new("char[16]", mode.nonce) + self._num = self._backend._ffi.new("unsigned int *", 0) + + def update(self, data): + buf = self._backend._ffi.new("unsigned char[]", len(data)) + self._backend._lib.AES_ctr128_encrypt( + data, buf, len(data), self._key, self._nonce, + self._ecount, self._num + ) + return self._backend._ffi.buffer(buf)[:] + + def finalize(self): + self._key = None + self._ecount = None + self._nonce = None + self._num = None + return b"" |