528 lines
16 KiB
Python
528 lines
16 KiB
Python
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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 __future__ import annotations
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import typing
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from cryptography.exceptions import InvalidTag
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if typing.TYPE_CHECKING:
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from cryptography.hazmat.backends.openssl.backend import Backend
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from cryptography.hazmat.primitives.ciphers.aead import (
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AESCCM,
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AESGCM,
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AESOCB3,
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AESSIV,
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ChaCha20Poly1305,
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)
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_AEADTypes = typing.Union[
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AESCCM, AESGCM, AESOCB3, AESSIV, ChaCha20Poly1305
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]
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def _is_evp_aead_supported_cipher(
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backend: Backend, cipher: _AEADTypes
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) -> bool:
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"""
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Checks whether the given cipher is supported through
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EVP_AEAD rather than the normal OpenSSL EVP_CIPHER API.
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"""
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from cryptography.hazmat.primitives.ciphers.aead import ChaCha20Poly1305
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return backend._lib.Cryptography_HAS_EVP_AEAD and isinstance(
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cipher, ChaCha20Poly1305
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)
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def _aead_cipher_supported(backend: Backend, cipher: _AEADTypes) -> bool:
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if _is_evp_aead_supported_cipher(backend, cipher):
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return True
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else:
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cipher_name = _evp_cipher_cipher_name(cipher)
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if backend._fips_enabled and cipher_name not in backend._fips_aead:
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return False
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# SIV isn't loaded through get_cipherbyname but instead a new fetch API
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# only available in 3.0+. But if we know we're on 3.0+ then we know
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# it's supported.
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if cipher_name.endswith(b"-siv"):
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return backend._lib.CRYPTOGRAPHY_OPENSSL_300_OR_GREATER == 1
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else:
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return (
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backend._lib.EVP_get_cipherbyname(cipher_name)
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!= backend._ffi.NULL
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)
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def _aead_create_ctx(
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backend: Backend,
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cipher: _AEADTypes,
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key: bytes,
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):
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if _is_evp_aead_supported_cipher(backend, cipher):
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return _evp_aead_create_ctx(backend, cipher, key)
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else:
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return _evp_cipher_create_ctx(backend, cipher, key)
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def _encrypt(
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backend: Backend,
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cipher: _AEADTypes,
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nonce: bytes,
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data: bytes,
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associated_data: typing.List[bytes],
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tag_length: int,
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ctx: typing.Any = None,
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) -> bytes:
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if _is_evp_aead_supported_cipher(backend, cipher):
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return _evp_aead_encrypt(
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backend, cipher, nonce, data, associated_data, tag_length, ctx
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)
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else:
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return _evp_cipher_encrypt(
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backend, cipher, nonce, data, associated_data, tag_length, ctx
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)
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def _decrypt(
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backend: Backend,
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cipher: _AEADTypes,
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nonce: bytes,
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data: bytes,
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associated_data: typing.List[bytes],
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tag_length: int,
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ctx: typing.Any = None,
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) -> bytes:
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if _is_evp_aead_supported_cipher(backend, cipher):
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return _evp_aead_decrypt(
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backend, cipher, nonce, data, associated_data, tag_length, ctx
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)
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else:
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return _evp_cipher_decrypt(
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backend, cipher, nonce, data, associated_data, tag_length, ctx
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)
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def _evp_aead_create_ctx(
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backend: Backend,
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cipher: _AEADTypes,
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key: bytes,
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tag_len: typing.Optional[int] = None,
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):
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aead_cipher = _evp_aead_get_cipher(backend, cipher)
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assert aead_cipher is not None
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key_ptr = backend._ffi.from_buffer(key)
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tag_len = (
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backend._lib.EVP_AEAD_DEFAULT_TAG_LENGTH
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if tag_len is None
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else tag_len
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)
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ctx = backend._lib.Cryptography_EVP_AEAD_CTX_new(
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aead_cipher, key_ptr, len(key), tag_len
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)
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backend.openssl_assert(ctx != backend._ffi.NULL)
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ctx = backend._ffi.gc(ctx, backend._lib.EVP_AEAD_CTX_free)
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return ctx
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def _evp_aead_get_cipher(backend: Backend, cipher: _AEADTypes):
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from cryptography.hazmat.primitives.ciphers.aead import (
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ChaCha20Poly1305,
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)
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# Currently only ChaCha20-Poly1305 is supported using this API
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assert isinstance(cipher, ChaCha20Poly1305)
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return backend._lib.EVP_aead_chacha20_poly1305()
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def _evp_aead_encrypt(
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backend: Backend,
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cipher: _AEADTypes,
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nonce: bytes,
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data: bytes,
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associated_data: typing.List[bytes],
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tag_length: int,
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ctx: typing.Any,
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) -> bytes:
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assert ctx is not None
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aead_cipher = _evp_aead_get_cipher(backend, cipher)
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assert aead_cipher is not None
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out_len = backend._ffi.new("size_t *")
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# max_out_len should be in_len plus the result of
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# EVP_AEAD_max_overhead.
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max_out_len = len(data) + backend._lib.EVP_AEAD_max_overhead(aead_cipher)
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out_buf = backend._ffi.new("uint8_t[]", max_out_len)
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data_ptr = backend._ffi.from_buffer(data)
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nonce_ptr = backend._ffi.from_buffer(nonce)
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aad = b"".join(associated_data)
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aad_ptr = backend._ffi.from_buffer(aad)
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res = backend._lib.EVP_AEAD_CTX_seal(
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ctx,
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out_buf,
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out_len,
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max_out_len,
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nonce_ptr,
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len(nonce),
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data_ptr,
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len(data),
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aad_ptr,
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len(aad),
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)
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backend.openssl_assert(res == 1)
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encrypted_data = backend._ffi.buffer(out_buf, out_len[0])[:]
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return encrypted_data
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def _evp_aead_decrypt(
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backend: Backend,
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cipher: _AEADTypes,
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nonce: bytes,
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data: bytes,
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associated_data: typing.List[bytes],
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tag_length: int,
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ctx: typing.Any,
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) -> bytes:
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if len(data) < tag_length:
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raise InvalidTag
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assert ctx is not None
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out_len = backend._ffi.new("size_t *")
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# max_out_len should at least in_len
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max_out_len = len(data)
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out_buf = backend._ffi.new("uint8_t[]", max_out_len)
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data_ptr = backend._ffi.from_buffer(data)
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nonce_ptr = backend._ffi.from_buffer(nonce)
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aad = b"".join(associated_data)
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aad_ptr = backend._ffi.from_buffer(aad)
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res = backend._lib.EVP_AEAD_CTX_open(
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ctx,
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out_buf,
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out_len,
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max_out_len,
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nonce_ptr,
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len(nonce),
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data_ptr,
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len(data),
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aad_ptr,
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len(aad),
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)
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if res == 0:
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backend._consume_errors()
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raise InvalidTag
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decrypted_data = backend._ffi.buffer(out_buf, out_len[0])[:]
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return decrypted_data
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_ENCRYPT = 1
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_DECRYPT = 0
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def _evp_cipher_cipher_name(cipher: _AEADTypes) -> bytes:
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from cryptography.hazmat.primitives.ciphers.aead import (
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AESCCM,
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AESGCM,
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AESOCB3,
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AESSIV,
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ChaCha20Poly1305,
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)
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if isinstance(cipher, ChaCha20Poly1305):
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return b"chacha20-poly1305"
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elif isinstance(cipher, AESCCM):
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return f"aes-{len(cipher._key) * 8}-ccm".encode("ascii")
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elif isinstance(cipher, AESOCB3):
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return f"aes-{len(cipher._key) * 8}-ocb".encode("ascii")
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elif isinstance(cipher, AESSIV):
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return f"aes-{len(cipher._key) * 8 // 2}-siv".encode("ascii")
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else:
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assert isinstance(cipher, AESGCM)
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return f"aes-{len(cipher._key) * 8}-gcm".encode("ascii")
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def _evp_cipher(cipher_name: bytes, backend: Backend):
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if cipher_name.endswith(b"-siv"):
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evp_cipher = backend._lib.EVP_CIPHER_fetch(
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backend._ffi.NULL,
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cipher_name,
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backend._ffi.NULL,
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)
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backend.openssl_assert(evp_cipher != backend._ffi.NULL)
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evp_cipher = backend._ffi.gc(evp_cipher, backend._lib.EVP_CIPHER_free)
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else:
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evp_cipher = backend._lib.EVP_get_cipherbyname(cipher_name)
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backend.openssl_assert(evp_cipher != backend._ffi.NULL)
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return evp_cipher
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def _evp_cipher_create_ctx(
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backend: Backend,
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cipher: _AEADTypes,
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key: bytes,
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):
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ctx = backend._lib.EVP_CIPHER_CTX_new()
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backend.openssl_assert(ctx != backend._ffi.NULL)
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ctx = backend._ffi.gc(ctx, backend._lib.EVP_CIPHER_CTX_free)
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cipher_name = _evp_cipher_cipher_name(cipher)
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evp_cipher = _evp_cipher(cipher_name, backend)
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key_ptr = backend._ffi.from_buffer(key)
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res = backend._lib.EVP_CipherInit_ex(
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ctx,
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evp_cipher,
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backend._ffi.NULL,
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key_ptr,
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backend._ffi.NULL,
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0,
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)
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backend.openssl_assert(res != 0)
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return ctx
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def _evp_cipher_aead_setup(
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backend: Backend,
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cipher_name: bytes,
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key: bytes,
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nonce: bytes,
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tag: typing.Optional[bytes],
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tag_len: int,
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operation: int,
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):
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evp_cipher = _evp_cipher(cipher_name, backend)
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ctx = backend._lib.EVP_CIPHER_CTX_new()
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ctx = backend._ffi.gc(ctx, backend._lib.EVP_CIPHER_CTX_free)
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res = backend._lib.EVP_CipherInit_ex(
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ctx,
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evp_cipher,
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backend._ffi.NULL,
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backend._ffi.NULL,
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backend._ffi.NULL,
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int(operation == _ENCRYPT),
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)
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backend.openssl_assert(res != 0)
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# CCM requires the IVLEN to be set before calling SET_TAG on decrypt
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res = backend._lib.EVP_CIPHER_CTX_ctrl(
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ctx,
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backend._lib.EVP_CTRL_AEAD_SET_IVLEN,
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len(nonce),
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backend._ffi.NULL,
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)
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backend.openssl_assert(res != 0)
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if operation == _DECRYPT:
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assert tag is not None
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_evp_cipher_set_tag(backend, ctx, tag)
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elif cipher_name.endswith(b"-ccm"):
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res = backend._lib.EVP_CIPHER_CTX_ctrl(
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ctx,
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backend._lib.EVP_CTRL_AEAD_SET_TAG,
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tag_len,
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backend._ffi.NULL,
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)
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backend.openssl_assert(res != 0)
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nonce_ptr = backend._ffi.from_buffer(nonce)
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key_ptr = backend._ffi.from_buffer(key)
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res = backend._lib.EVP_CipherInit_ex(
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ctx,
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backend._ffi.NULL,
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backend._ffi.NULL,
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key_ptr,
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nonce_ptr,
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int(operation == _ENCRYPT),
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)
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backend.openssl_assert(res != 0)
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return ctx
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def _evp_cipher_set_tag(backend, ctx, tag: bytes) -> None:
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tag_ptr = backend._ffi.from_buffer(tag)
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res = backend._lib.EVP_CIPHER_CTX_ctrl(
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ctx, backend._lib.EVP_CTRL_AEAD_SET_TAG, len(tag), tag_ptr
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)
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backend.openssl_assert(res != 0)
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def _evp_cipher_set_nonce_operation(
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backend, ctx, nonce: bytes, operation: int
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) -> None:
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nonce_ptr = backend._ffi.from_buffer(nonce)
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res = backend._lib.EVP_CipherInit_ex(
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ctx,
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backend._ffi.NULL,
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backend._ffi.NULL,
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backend._ffi.NULL,
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nonce_ptr,
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int(operation == _ENCRYPT),
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)
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backend.openssl_assert(res != 0)
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def _evp_cipher_set_length(backend: Backend, ctx, data_len: int) -> None:
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intptr = backend._ffi.new("int *")
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res = backend._lib.EVP_CipherUpdate(
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ctx, backend._ffi.NULL, intptr, backend._ffi.NULL, data_len
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)
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backend.openssl_assert(res != 0)
|
||
|
|
|
||
|
|
|
||
|
|
def _evp_cipher_process_aad(
|
||
|
|
backend: Backend, ctx, associated_data: bytes
|
||
|
|
) -> None:
|
||
|
|
outlen = backend._ffi.new("int *")
|
||
|
|
a_data_ptr = backend._ffi.from_buffer(associated_data)
|
||
|
|
res = backend._lib.EVP_CipherUpdate(
|
||
|
|
ctx, backend._ffi.NULL, outlen, a_data_ptr, len(associated_data)
|
||
|
|
)
|
||
|
|
backend.openssl_assert(res != 0)
|
||
|
|
|
||
|
|
|
||
|
|
def _evp_cipher_process_data(backend: Backend, ctx, data: bytes) -> bytes:
|
||
|
|
outlen = backend._ffi.new("int *")
|
||
|
|
buf = backend._ffi.new("unsigned char[]", len(data))
|
||
|
|
data_ptr = backend._ffi.from_buffer(data)
|
||
|
|
res = backend._lib.EVP_CipherUpdate(ctx, buf, outlen, data_ptr, len(data))
|
||
|
|
if res == 0:
|
||
|
|
# AES SIV can error here if the data is invalid on decrypt
|
||
|
|
backend._consume_errors()
|
||
|
|
raise InvalidTag
|
||
|
|
return backend._ffi.buffer(buf, outlen[0])[:]
|
||
|
|
|
||
|
|
|
||
|
|
def _evp_cipher_encrypt(
|
||
|
|
backend: Backend,
|
||
|
|
cipher: _AEADTypes,
|
||
|
|
nonce: bytes,
|
||
|
|
data: bytes,
|
||
|
|
associated_data: typing.List[bytes],
|
||
|
|
tag_length: int,
|
||
|
|
ctx: typing.Any = None,
|
||
|
|
) -> bytes:
|
||
|
|
from cryptography.hazmat.primitives.ciphers.aead import AESCCM, AESSIV
|
||
|
|
|
||
|
|
if ctx is None:
|
||
|
|
cipher_name = _evp_cipher_cipher_name(cipher)
|
||
|
|
ctx = _evp_cipher_aead_setup(
|
||
|
|
backend,
|
||
|
|
cipher_name,
|
||
|
|
cipher._key,
|
||
|
|
nonce,
|
||
|
|
None,
|
||
|
|
tag_length,
|
||
|
|
_ENCRYPT,
|
||
|
|
)
|
||
|
|
else:
|
||
|
|
_evp_cipher_set_nonce_operation(backend, ctx, nonce, _ENCRYPT)
|
||
|
|
|
||
|
|
# CCM requires us to pass the length of the data before processing
|
||
|
|
# anything.
|
||
|
|
# However calling this with any other AEAD results in an error
|
||
|
|
if isinstance(cipher, AESCCM):
|
||
|
|
_evp_cipher_set_length(backend, ctx, len(data))
|
||
|
|
|
||
|
|
for ad in associated_data:
|
||
|
|
_evp_cipher_process_aad(backend, ctx, ad)
|
||
|
|
processed_data = _evp_cipher_process_data(backend, ctx, data)
|
||
|
|
outlen = backend._ffi.new("int *")
|
||
|
|
# All AEADs we support besides OCB are streaming so they return nothing
|
||
|
|
# in finalization. OCB can return up to (16 byte block - 1) bytes so
|
||
|
|
# we need a buffer here too.
|
||
|
|
buf = backend._ffi.new("unsigned char[]", 16)
|
||
|
|
res = backend._lib.EVP_CipherFinal_ex(ctx, buf, outlen)
|
||
|
|
backend.openssl_assert(res != 0)
|
||
|
|
processed_data += backend._ffi.buffer(buf, outlen[0])[:]
|
||
|
|
tag_buf = backend._ffi.new("unsigned char[]", tag_length)
|
||
|
|
res = backend._lib.EVP_CIPHER_CTX_ctrl(
|
||
|
|
ctx, backend._lib.EVP_CTRL_AEAD_GET_TAG, tag_length, tag_buf
|
||
|
|
)
|
||
|
|
backend.openssl_assert(res != 0)
|
||
|
|
tag = backend._ffi.buffer(tag_buf)[:]
|
||
|
|
|
||
|
|
if isinstance(cipher, AESSIV):
|
||
|
|
# RFC 5297 defines the output as IV || C, where the tag we generate
|
||
|
|
# is the "IV" and C is the ciphertext. This is the opposite of our
|
||
|
|
# other AEADs, which are Ciphertext || Tag
|
||
|
|
backend.openssl_assert(len(tag) == 16)
|
||
|
|
return tag + processed_data
|
||
|
|
else:
|
||
|
|
return processed_data + tag
|
||
|
|
|
||
|
|
|
||
|
|
def _evp_cipher_decrypt(
|
||
|
|
backend: Backend,
|
||
|
|
cipher: _AEADTypes,
|
||
|
|
nonce: bytes,
|
||
|
|
data: bytes,
|
||
|
|
associated_data: typing.List[bytes],
|
||
|
|
tag_length: int,
|
||
|
|
ctx: typing.Any = None,
|
||
|
|
) -> bytes:
|
||
|
|
from cryptography.hazmat.primitives.ciphers.aead import AESCCM, AESSIV
|
||
|
|
|
||
|
|
if len(data) < tag_length:
|
||
|
|
raise InvalidTag
|
||
|
|
|
||
|
|
if isinstance(cipher, AESSIV):
|
||
|
|
# RFC 5297 defines the output as IV || C, where the tag we generate
|
||
|
|
# is the "IV" and C is the ciphertext. This is the opposite of our
|
||
|
|
# other AEADs, which are Ciphertext || Tag
|
||
|
|
tag = data[:tag_length]
|
||
|
|
data = data[tag_length:]
|
||
|
|
else:
|
||
|
|
tag = data[-tag_length:]
|
||
|
|
data = data[:-tag_length]
|
||
|
|
if ctx is None:
|
||
|
|
cipher_name = _evp_cipher_cipher_name(cipher)
|
||
|
|
ctx = _evp_cipher_aead_setup(
|
||
|
|
backend,
|
||
|
|
cipher_name,
|
||
|
|
cipher._key,
|
||
|
|
nonce,
|
||
|
|
tag,
|
||
|
|
tag_length,
|
||
|
|
_DECRYPT,
|
||
|
|
)
|
||
|
|
else:
|
||
|
|
_evp_cipher_set_nonce_operation(backend, ctx, nonce, _DECRYPT)
|
||
|
|
_evp_cipher_set_tag(backend, ctx, tag)
|
||
|
|
|
||
|
|
# CCM requires us to pass the length of the data before processing
|
||
|
|
# anything.
|
||
|
|
# However calling this with any other AEAD results in an error
|
||
|
|
if isinstance(cipher, AESCCM):
|
||
|
|
_evp_cipher_set_length(backend, ctx, len(data))
|
||
|
|
|
||
|
|
for ad in associated_data:
|
||
|
|
_evp_cipher_process_aad(backend, ctx, ad)
|
||
|
|
# CCM has a different error path if the tag doesn't match. Errors are
|
||
|
|
# raised in Update and Final is irrelevant.
|
||
|
|
if isinstance(cipher, AESCCM):
|
||
|
|
outlen = backend._ffi.new("int *")
|
||
|
|
buf = backend._ffi.new("unsigned char[]", len(data))
|
||
|
|
d_ptr = backend._ffi.from_buffer(data)
|
||
|
|
res = backend._lib.EVP_CipherUpdate(ctx, buf, outlen, d_ptr, len(data))
|
||
|
|
if res != 1:
|
||
|
|
backend._consume_errors()
|
||
|
|
raise InvalidTag
|
||
|
|
|
||
|
|
processed_data = backend._ffi.buffer(buf, outlen[0])[:]
|
||
|
|
else:
|
||
|
|
processed_data = _evp_cipher_process_data(backend, ctx, data)
|
||
|
|
outlen = backend._ffi.new("int *")
|
||
|
|
# OCB can return up to 15 bytes (16 byte block - 1) in finalization
|
||
|
|
buf = backend._ffi.new("unsigned char[]", 16)
|
||
|
|
res = backend._lib.EVP_CipherFinal_ex(ctx, buf, outlen)
|
||
|
|
processed_data += backend._ffi.buffer(buf, outlen[0])[:]
|
||
|
|
if res == 0:
|
||
|
|
backend._consume_errors()
|
||
|
|
raise InvalidTag
|
||
|
|
|
||
|
|
return processed_data
|