Edit File: ciphers.py
# This file is dual licensed under the terms of the Apache License, Version # 2.0, and the BSD License. See the LICENSE file in the root of this repository # for complete details. from __future__ import absolute_import, division, print_function from cryptography import utils from cryptography.exceptions import InvalidTag, UnsupportedAlgorithm, _Reasons from cryptography.hazmat.primitives import ciphers from cryptography.hazmat.primitives.ciphers import modes @utils.register_interface(ciphers.CipherContext) @utils.register_interface(ciphers.AEADCipherContext) @utils.register_interface(ciphers.AEADEncryptionContext) @utils.register_interface(ciphers.AEADDecryptionContext) class _CipherContext(object): _ENCRYPT = 1 _DECRYPT = 0 _MAX_CHUNK_SIZE = 2 ** 30 - 1 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, ciphers.BlockCipherAlgorithm): self._block_size_bytes = self._cipher.block_size // 8 else: self._block_size_bytes = 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 {} in {} 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: msg = "cipher {0.name} ".format(cipher) if mode is not None: msg += "in {0.name} mode ".format(mode) msg += ( "is not supported by this backend (Your version of OpenSSL " "may be too old. Current version: {}.)" ).format(self._backend.openssl_version_text()) raise UnsupportedAlgorithm(msg, _Reasons.UNSUPPORTED_CIPHER) if isinstance(mode, modes.ModeWithInitializationVector): iv_nonce = self._backend._ffi.from_buffer( mode.initialization_vector ) elif isinstance(mode, modes.ModeWithTweak): iv_nonce = self._backend._ffi.from_buffer(mode.tweak) elif isinstance(mode, modes.ModeWithNonce): iv_nonce = self._backend._ffi.from_buffer(mode.nonce) elif isinstance(cipher, modes.ModeWithNonce): iv_nonce = self._backend._ffi.from_buffer(cipher.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, ) self._backend.openssl_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) ) self._backend.openssl_assert(res != 0) if isinstance(mode, modes.GCM): res = self._backend._lib.EVP_CIPHER_CTX_ctrl( ctx, self._backend._lib.EVP_CTRL_AEAD_SET_IVLEN, len(iv_nonce), self._backend._ffi.NULL, ) self._backend.openssl_assert(res != 0) if mode.tag is not None: res = self._backend._lib.EVP_CIPHER_CTX_ctrl( ctx, self._backend._lib.EVP_CTRL_AEAD_SET_TAG, len(mode.tag), mode.tag, ) self._backend.openssl_assert(res != 0) self._tag = mode.tag # pass key/iv res = self._backend._lib.EVP_CipherInit_ex( ctx, self._backend._ffi.NULL, self._backend._ffi.NULL, self._backend._ffi.from_buffer(cipher.key), iv_nonce, operation, ) self._backend.openssl_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): buf = bytearray(len(data) + self._block_size_bytes - 1) n = self.update_into(data, buf) return bytes(buf[:n]) def update_into(self, data, buf): total_data_len = len(data) if len(buf) < (total_data_len + self._block_size_bytes - 1): raise ValueError( "buffer must be at least {} bytes for this " "payload".format(len(data) + self._block_size_bytes - 1) ) data_processed = 0 total_out = 0 outlen = self._backend._ffi.new("int *") baseoutbuf = self._backend._ffi.from_buffer(buf) baseinbuf = self._backend._ffi.from_buffer(data) while data_processed != total_data_len: outbuf = baseoutbuf + total_out inbuf = baseinbuf + data_processed inlen = min(self._MAX_CHUNK_SIZE, total_data_len - data_processed) res = self._backend._lib.EVP_CipherUpdate( self._ctx, outbuf, outlen, inbuf, inlen ) self._backend.openssl_assert(res != 0) data_processed += inlen total_out += outlen[0] return total_out def finalize(self): if ( self._operation == self._DECRYPT and isinstance(self._mode, modes.ModeWithAuthenticationTag) and self.tag is None ): raise ValueError( "Authentication tag must be provided when decrypting." ) buf = self._backend._ffi.new("unsigned char[]", self._block_size_bytes) 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, modes.GCM): raise InvalidTag self._backend.openssl_assert( errors[0]._lib_reason_match( self._backend._lib.ERR_LIB_EVP, self._backend._lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH, ), errors=errors, ) raise ValueError( "The length of the provided data is not a multiple of " "the block length." ) if ( isinstance(self._mode, modes.GCM) and self._operation == self._ENCRYPT ): tag_buf = self._backend._ffi.new( "unsigned char[]", self._block_size_bytes ) res = self._backend._lib.EVP_CIPHER_CTX_ctrl( self._ctx, self._backend._lib.EVP_CTRL_AEAD_GET_TAG, self._block_size_bytes, tag_buf, ) self._backend.openssl_assert(res != 0) self._tag = self._backend._ffi.buffer(tag_buf)[:] res = self._backend._lib.EVP_CIPHER_CTX_cleanup(self._ctx) self._backend.openssl_assert(res == 1) return self._backend._ffi.buffer(buf)[: outlen[0]] def finalize_with_tag(self, tag): if len(tag) < self._mode._min_tag_length: raise ValueError( "Authentication tag must be {} bytes or longer.".format( self._mode._min_tag_length ) ) res = self._backend._lib.EVP_CIPHER_CTX_ctrl( self._ctx, self._backend._lib.EVP_CTRL_AEAD_SET_TAG, len(tag), tag ) self._backend.openssl_assert(res != 0) self._tag = tag return self.finalize() 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, self._backend._ffi.from_buffer(data), len(data), ) self._backend.openssl_assert(res != 0) tag = utils.read_only_property("_tag")