moving to scripts
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eneller
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# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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from cryptography import utils
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from cryptography.exceptions import InvalidTag, UnsupportedAlgorithm, _Reasons
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from cryptography.hazmat.primitives import ciphers
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from cryptography.hazmat.primitives.ciphers import modes
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@utils.register_interface(ciphers.CipherContext)
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@utils.register_interface(ciphers.AEADCipherContext)
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@utils.register_interface(ciphers.AEADEncryptionContext)
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@utils.register_interface(ciphers.AEADDecryptionContext)
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class _CipherContext(object):
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_ENCRYPT = 1
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_DECRYPT = 0
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_MAX_CHUNK_SIZE = 2 ** 30 - 1
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def __init__(self, backend, cipher, mode, operation):
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self._backend = backend
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self._cipher = cipher
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self._mode = mode
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self._operation = operation
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self._tag = None
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if isinstance(self._cipher, ciphers.BlockCipherAlgorithm):
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self._block_size_bytes = self._cipher.block_size // 8
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else:
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self._block_size_bytes = 1
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ctx = self._backend._lib.EVP_CIPHER_CTX_new()
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ctx = self._backend._ffi.gc(
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ctx, self._backend._lib.EVP_CIPHER_CTX_free
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)
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registry = self._backend._cipher_registry
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try:
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adapter = registry[type(cipher), type(mode)]
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except KeyError:
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raise UnsupportedAlgorithm(
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"cipher {} in {} mode is not supported "
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"by this backend.".format(
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cipher.name, mode.name if mode else mode
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),
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_Reasons.UNSUPPORTED_CIPHER,
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)
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evp_cipher = adapter(self._backend, cipher, mode)
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if evp_cipher == self._backend._ffi.NULL:
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msg = "cipher {0.name} ".format(cipher)
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if mode is not None:
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msg += "in {0.name} mode ".format(mode)
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msg += (
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"is not supported by this backend (Your version of OpenSSL "
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"may be too old. Current version: {}.)"
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).format(self._backend.openssl_version_text())
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raise UnsupportedAlgorithm(msg, _Reasons.UNSUPPORTED_CIPHER)
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if isinstance(mode, modes.ModeWithInitializationVector):
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iv_nonce = self._backend._ffi.from_buffer(
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mode.initialization_vector
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)
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elif isinstance(mode, modes.ModeWithTweak):
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iv_nonce = self._backend._ffi.from_buffer(mode.tweak)
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elif isinstance(mode, modes.ModeWithNonce):
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iv_nonce = self._backend._ffi.from_buffer(mode.nonce)
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elif isinstance(cipher, modes.ModeWithNonce):
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iv_nonce = self._backend._ffi.from_buffer(cipher.nonce)
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else:
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iv_nonce = self._backend._ffi.NULL
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# begin init with cipher and operation type
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res = self._backend._lib.EVP_CipherInit_ex(
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ctx,
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evp_cipher,
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self._backend._ffi.NULL,
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self._backend._ffi.NULL,
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self._backend._ffi.NULL,
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operation,
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)
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self._backend.openssl_assert(res != 0)
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# set the key length to handle variable key ciphers
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res = self._backend._lib.EVP_CIPHER_CTX_set_key_length(
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ctx, len(cipher.key)
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)
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self._backend.openssl_assert(res != 0)
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if isinstance(mode, modes.GCM):
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res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
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ctx,
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self._backend._lib.EVP_CTRL_AEAD_SET_IVLEN,
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len(iv_nonce),
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self._backend._ffi.NULL,
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)
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self._backend.openssl_assert(res != 0)
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if mode.tag is not None:
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res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
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ctx,
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self._backend._lib.EVP_CTRL_AEAD_SET_TAG,
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len(mode.tag),
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mode.tag,
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)
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self._backend.openssl_assert(res != 0)
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self._tag = mode.tag
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# pass key/iv
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res = self._backend._lib.EVP_CipherInit_ex(
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ctx,
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self._backend._ffi.NULL,
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self._backend._ffi.NULL,
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self._backend._ffi.from_buffer(cipher.key),
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iv_nonce,
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operation,
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)
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# Check for XTS mode duplicate keys error
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errors = self._backend._consume_errors()
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lib = self._backend._lib
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if res == 0 and (
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(
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lib.CRYPTOGRAPHY_OPENSSL_111D_OR_GREATER
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and errors[0]._lib_reason_match(
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lib.ERR_LIB_EVP, lib.EVP_R_XTS_DUPLICATED_KEYS
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)
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)
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or (
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lib.Cryptography_HAS_PROVIDERS
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and errors[0]._lib_reason_match(
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lib.ERR_LIB_PROV, lib.PROV_R_XTS_DUPLICATED_KEYS
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)
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)
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):
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raise ValueError("In XTS mode duplicated keys are not allowed")
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self._backend.openssl_assert(res != 0, errors=errors)
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# We purposely disable padding here as it's handled higher up in the
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# API.
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self._backend._lib.EVP_CIPHER_CTX_set_padding(ctx, 0)
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self._ctx = ctx
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def update(self, data: bytes) -> bytes:
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buf = bytearray(len(data) + self._block_size_bytes - 1)
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n = self.update_into(data, buf)
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return bytes(buf[:n])
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def update_into(self, data: bytes, buf) -> int:
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total_data_len = len(data)
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if len(buf) < (total_data_len + self._block_size_bytes - 1):
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raise ValueError(
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"buffer must be at least {} bytes for this "
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"payload".format(len(data) + self._block_size_bytes - 1)
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)
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data_processed = 0
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total_out = 0
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outlen = self._backend._ffi.new("int *")
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baseoutbuf = self._backend._ffi.from_buffer(buf)
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baseinbuf = self._backend._ffi.from_buffer(data)
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while data_processed != total_data_len:
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outbuf = baseoutbuf + total_out
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inbuf = baseinbuf + data_processed
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inlen = min(self._MAX_CHUNK_SIZE, total_data_len - data_processed)
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res = self._backend._lib.EVP_CipherUpdate(
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self._ctx, outbuf, outlen, inbuf, inlen
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)
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if res == 0 and isinstance(self._mode, modes.XTS):
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self._backend._consume_errors()
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raise ValueError(
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"In XTS mode you must supply at least a full block in the "
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"first update call. For AES this is 16 bytes."
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)
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else:
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self._backend.openssl_assert(res != 0)
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data_processed += inlen
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total_out += outlen[0]
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return total_out
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def finalize(self) -> bytes:
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if (
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self._operation == self._DECRYPT
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and isinstance(self._mode, modes.ModeWithAuthenticationTag)
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and self.tag is None
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):
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raise ValueError(
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"Authentication tag must be provided when decrypting."
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)
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buf = self._backend._ffi.new("unsigned char[]", self._block_size_bytes)
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outlen = self._backend._ffi.new("int *")
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res = self._backend._lib.EVP_CipherFinal_ex(self._ctx, buf, outlen)
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if res == 0:
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errors = self._backend._consume_errors()
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if not errors and isinstance(self._mode, modes.GCM):
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raise InvalidTag
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self._backend.openssl_assert(
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errors[0]._lib_reason_match(
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self._backend._lib.ERR_LIB_EVP,
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self._backend._lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH,
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)
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or (
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self._backend._lib.Cryptography_HAS_PROVIDERS
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and errors[0]._lib_reason_match(
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self._backend._lib.ERR_LIB_PROV,
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self._backend._lib.PROV_R_WRONG_FINAL_BLOCK_LENGTH,
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)
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),
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errors=errors,
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)
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raise ValueError(
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"The length of the provided data is not a multiple of "
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"the block length."
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)
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if (
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isinstance(self._mode, modes.GCM)
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and self._operation == self._ENCRYPT
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):
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tag_buf = self._backend._ffi.new(
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"unsigned char[]", self._block_size_bytes
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)
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res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
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self._ctx,
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self._backend._lib.EVP_CTRL_AEAD_GET_TAG,
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self._block_size_bytes,
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tag_buf,
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)
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self._backend.openssl_assert(res != 0)
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self._tag = self._backend._ffi.buffer(tag_buf)[:]
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res = self._backend._lib.EVP_CIPHER_CTX_reset(self._ctx)
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self._backend.openssl_assert(res == 1)
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return self._backend._ffi.buffer(buf)[: outlen[0]]
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def finalize_with_tag(self, tag: bytes) -> bytes:
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tag_len = len(tag)
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if tag_len < self._mode._min_tag_length:
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raise ValueError(
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"Authentication tag must be {} bytes or longer.".format(
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self._mode._min_tag_length
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)
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)
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elif tag_len > self._block_size_bytes:
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raise ValueError(
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"Authentication tag cannot be more than {} bytes.".format(
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self._block_size_bytes
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)
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)
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res = self._backend._lib.EVP_CIPHER_CTX_ctrl(
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self._ctx, self._backend._lib.EVP_CTRL_AEAD_SET_TAG, len(tag), tag
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)
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self._backend.openssl_assert(res != 0)
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self._tag = tag
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return self.finalize()
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def authenticate_additional_data(self, data: bytes) -> None:
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outlen = self._backend._ffi.new("int *")
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res = self._backend._lib.EVP_CipherUpdate(
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self._ctx,
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self._backend._ffi.NULL,
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outlen,
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self._backend._ffi.from_buffer(data),
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len(data),
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)
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self._backend.openssl_assert(res != 0)
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tag = utils.read_only_property("_tag")
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