# 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 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: bytes) -> bytes:
buf = bytearray(len(data) + self._block_size_bytes - 1)
n = self.update_into(data, buf)
return bytes(buf[:n])
def update_into(self, data: bytes, buf) -> int:
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, require_writable=True)
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
)
if res == 0 and isinstance(self._mode, modes.XTS):
raise ValueError(
"In XTS mode you must supply at least a full block in the "
"first update call. For AES this is 16 bytes."
)
else:
self._backend.openssl_assert(res != 0)
data_processed += inlen
total_out += outlen[0]
return total_out
def finalize(self) -> bytes:
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,
)
or (
self._backend._lib.Cryptography_HAS_PROVIDERS
and errors[0]._lib_reason_match(
self._backend._lib.ERR_LIB_PROV,
self._backend._lib.PROV_R_WRONG_FINAL_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_reset(self._ctx)
self._backend.openssl_assert(res == 1)
return self._backend._ffi.buffer(buf)[: outlen[0]]
def finalize_with_tag(self, tag: bytes) -> bytes:
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: bytes) -> None:
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")