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# 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.exceptions import InvalidTag _ENCRYPT = 1 _DECRYPT = 0 def _aead_cipher_name(cipher): from cryptography.hazmat.primitives.ciphers.aead import ( AESCCM, AESGCM, ChaCha20Poly1305, ) if isinstance(cipher, ChaCha20Poly1305): return b"chacha20-poly1305" elif isinstance(cipher, AESCCM): return "aes-{}-ccm".format(len(cipher._key) * 8).encode("ascii") else: assert isinstance(cipher, AESGCM) return "aes-{}-gcm".format(len(cipher._key) * 8).encode("ascii") def _aead_setup(backend, cipher_name, key, nonce, tag, tag_len, operation): evp_cipher = backend._lib.EVP_get_cipherbyname(cipher_name) backend.openssl_assert(evp_cipher != backend._ffi.NULL) ctx = backend._lib.EVP_CIPHER_CTX_new() ctx = backend._ffi.gc(ctx, backend._lib.EVP_CIPHER_CTX_free) res = backend._lib.EVP_CipherInit_ex( ctx, evp_cipher, backend._ffi.NULL, backend._ffi.NULL, backend._ffi.NULL, int(operation == _ENCRYPT), ) backend.openssl_assert(res != 0) res = backend._lib.EVP_CIPHER_CTX_set_key_length(ctx, len(key)) backend.openssl_assert(res != 0) res = backend._lib.EVP_CIPHER_CTX_ctrl( ctx, backend._lib.EVP_CTRL_AEAD_SET_IVLEN, len(nonce), backend._ffi.NULL, ) backend.openssl_assert(res != 0) if operation == _DECRYPT: res = backend._lib.EVP_CIPHER_CTX_ctrl( ctx, backend._lib.EVP_CTRL_AEAD_SET_TAG, len(tag), tag ) backend.openssl_assert(res != 0) elif cipher_name.endswith(b"-ccm"): res = backend._lib.EVP_CIPHER_CTX_ctrl( ctx, backend._lib.EVP_CTRL_AEAD_SET_TAG, tag_len, backend._ffi.NULL ) backend.openssl_assert(res != 0) nonce_ptr = backend._ffi.from_buffer(nonce) key_ptr = backend._ffi.from_buffer(key) res = backend._lib.EVP_CipherInit_ex( ctx, backend._ffi.NULL, backend._ffi.NULL, key_ptr, nonce_ptr, int(operation == _ENCRYPT), ) backend.openssl_assert(res != 0) return ctx def _set_length(backend, ctx, data_len): intptr = backend._ffi.new("int *") res = backend._lib.EVP_CipherUpdate( ctx, backend._ffi.NULL, intptr, backend._ffi.NULL, data_len ) backend.openssl_assert(res != 0) def _process_aad(backend, ctx, associated_data): outlen = backend._ffi.new("int *") res = backend._lib.EVP_CipherUpdate( ctx, backend._ffi.NULL, outlen, associated_data, len(associated_data) ) backend.openssl_assert(res != 0) def _process_data(backend, ctx, data): outlen = backend._ffi.new("int *") buf = backend._ffi.new("unsigned char[]", len(data)) res = backend._lib.EVP_CipherUpdate(ctx, buf, outlen, data, len(data)) backend.openssl_assert(res != 0) return backend._ffi.buffer(buf, outlen[0])[:] def _encrypt(backend, cipher, nonce, data, associated_data, tag_length): from cryptography.hazmat.primitives.ciphers.aead import AESCCM cipher_name = _aead_cipher_name(cipher) ctx = _aead_setup( backend, cipher_name, cipher._key, nonce, None, tag_length, _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): _set_length(backend, ctx, len(data)) _process_aad(backend, ctx, associated_data) processed_data = _process_data(backend, ctx, data) outlen = backend._ffi.new("int *") res = backend._lib.EVP_CipherFinal_ex(ctx, backend._ffi.NULL, outlen) backend.openssl_assert(res != 0) backend.openssl_assert(outlen[0] == 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)[:] return processed_data + tag def _decrypt(backend, cipher, nonce, data, associated_data, tag_length): from cryptography.hazmat.primitives.ciphers.aead import AESCCM if len(data) < tag_length: raise InvalidTag tag = data[-tag_length:] data = data[:-tag_length] cipher_name = _aead_cipher_name(cipher) ctx = _aead_setup( backend, cipher_name, cipher._key, nonce, tag, tag_length, _DECRYPT ) # 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): _set_length(backend, ctx, len(data)) _process_aad(backend, ctx, associated_data) # 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)) res = backend._lib.EVP_CipherUpdate(ctx, buf, outlen, data, len(data)) if res != 1: backend._consume_errors() raise InvalidTag processed_data = backend._ffi.buffer(buf, outlen[0])[:] else: processed_data = _process_data(backend, ctx, data) outlen = backend._ffi.new("int *") res = backend._lib.EVP_CipherFinal_ex(ctx, backend._ffi.NULL, outlen) if res == 0: backend._consume_errors() raise InvalidTag return processed_data