diff options
Diffstat (limited to 'src/crypto.cpp')
| -rw-r--r-- | src/crypto.cpp | 256 |
1 files changed, 256 insertions, 0 deletions
diff --git a/src/crypto.cpp b/src/crypto.cpp new file mode 100644 index 0000000..57f31cd --- /dev/null +++ b/src/crypto.cpp @@ -0,0 +1,256 @@ +/* Copyright 2015 OpenMarket Ltd + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +#include "axolotl/crypto.hh" +#include "axolotl/memory.hh" + +#include <cstring> + +extern "C" { + +int curve25519_donna( + uint8_t * output, + const uint8_t * secret, + const uint8_t * basepoint +); + +#include "crypto-algorithms/aes.h" +#include "crypto-algorithms/sha256.h" + +} + + +namespace { + +static const std::uint8_t CURVE25519_BASEPOINT[32] = {9}; +static const std::size_t AES_BLOCK_LENGTH = 16; +static const std::size_t SHA256_HASH_LENGTH = 32; +static const std::size_t SHA256_BLOCK_LENGTH = 64; +static const std::uint8_t HKDF_DEFAULT_SALT[32] = {}; + + +template<std::size_t block_size> +inline static void xor_block( + std::uint8_t * block, + std::uint8_t const * input +) { + for (std::size_t i = 0; i < block_size; ++i) { + block[i] ^= input[i]; + } +} + + +inline static void hmac_sha256_key( + std::uint8_t const * input_key, std::size_t input_key_length, + std::uint8_t * hmac_key +) { + std::memset(hmac_key, 0, SHA256_BLOCK_LENGTH); + if (input_key_length > SHA256_BLOCK_LENGTH) { + ::SHA256_CTX context; + ::sha256_init(&context); + ::sha256_update(&context, input_key, input_key_length); + ::sha256_final(&context, hmac_key); + } else { + std::memcpy(hmac_key, input_key, input_key_length); + } +} + + +inline void hmac_sha256_init( + ::SHA256_CTX * context, + std::uint8_t const * hmac_key +) { + std::uint8_t i_pad[SHA256_BLOCK_LENGTH]; + std::memcpy(i_pad, hmac_key, SHA256_BLOCK_LENGTH); + for (std::size_t i = 0; i < SHA256_BLOCK_LENGTH; ++i) { + i_pad[i] ^= 0x36; + } + ::sha256_init(context); + ::sha256_update(context, i_pad, SHA256_BLOCK_LENGTH); + axolotl::unset(i_pad); +} + + +inline void hmac_sha256_final( + ::SHA256_CTX * context, + std::uint8_t const * hmac_key, + std::uint8_t * output +) { + std::uint8_t o_pad[SHA256_BLOCK_LENGTH + SHA256_HASH_LENGTH]; + std::memcpy(o_pad, hmac_key, SHA256_BLOCK_LENGTH); + for (std::size_t i = 0; i < SHA256_BLOCK_LENGTH; ++i) { + o_pad[i] ^= 0x5C; + } + ::sha256_final(context, o_pad + SHA256_BLOCK_LENGTH); + ::SHA256_CTX final_context; + ::sha256_init(&final_context); + ::sha256_update(&final_context, o_pad, sizeof(o_pad)); + ::sha256_final(&final_context, output); + axolotl::unset(final_context); + axolotl::unset(o_pad); +} + +} // namespace + + +void axolotl::generate_key( + std::uint8_t const * random_32_bytes, + axolotl::Curve25519KeyPair & key_pair +) { + std::memcpy(key_pair.private_key, random_32_bytes, 32); + ::curve25519_donna( + key_pair.public_key, key_pair.private_key, CURVE25519_BASEPOINT + ); +} + + +void axolotl::curve25519_shared_secret( + axolotl::Curve25519KeyPair const & our_key, + axolotl::Curve25519PublicKey const & their_key, + std::uint8_t * output +) { + ::curve25519_donna(output, our_key.private_key, their_key.public_key); +} + + +std::size_t axolotl::aes_encrypt_cbc_length( + std::size_t input_length +) { + return input_length + AES_BLOCK_LENGTH - input_length % AES_BLOCK_LENGTH; +} + + +void axolotl::aes_encrypt_cbc( + axolotl::Aes256Key const & key, + axolotl::Aes256Iv const & iv, + std::uint8_t const * input, std::size_t input_length, + std::uint8_t * output +) { + std::uint32_t key_schedule[60]; + ::aes_key_setup(key.key, key_schedule, 256); + std::uint8_t input_block[AES_BLOCK_LENGTH]; + std::memcpy(input_block, iv.iv, AES_BLOCK_LENGTH); + while (input_length >= AES_BLOCK_LENGTH) { + xor_block<AES_BLOCK_LENGTH>(input_block, input); + ::aes_encrypt(input_block, output, key_schedule, 256); + std::memcpy(input_block, output, AES_BLOCK_LENGTH); + input += AES_BLOCK_LENGTH; + output += AES_BLOCK_LENGTH; + input_length -= AES_BLOCK_LENGTH; + } + std::size_t i = 0; + for (; i < input_length; ++i) { + input_block[i] ^= input[i]; + } + for (; i < AES_BLOCK_LENGTH; ++i) { + input_block[i] ^= AES_BLOCK_LENGTH - input_length; + } + ::aes_encrypt(input_block, output, key_schedule, 256); + axolotl::unset(key_schedule); + axolotl::unset(input_block); +} + + +std::size_t axolotl::aes_decrypt_cbc( + axolotl::Aes256Key const & key, + axolotl::Aes256Iv const & iv, + std::uint8_t const * input, std::size_t input_length, + std::uint8_t * output +) { + std::uint32_t key_schedule[60]; + ::aes_key_setup(key.key, key_schedule, 256); + for (std::size_t i = 0; i < input_length; i += AES_BLOCK_LENGTH) { + ::aes_decrypt(&input[i], &output[i], key_schedule, 256); + if (i == 0) { + xor_block<AES_BLOCK_LENGTH>(&output[i], iv.iv); + } else { + xor_block<AES_BLOCK_LENGTH>(&output[i], &input[i - AES_BLOCK_LENGTH]); + } + } + axolotl::unset(key_schedule); + std::size_t padding = output[input_length - 1]; + return (padding > input_length) ? std::size_t(-1) : (input_length - padding); +} + + +void axolotl::sha256( + std::uint8_t const * input, std::size_t input_length, + std::uint8_t * output +) { + ::SHA256_CTX context; + ::sha256_init(&context); + ::sha256_update(&context, input, input_length); + ::sha256_final(&context, output); + axolotl::unset(context); +} + +void axolotl::hmac_sha256( + std::uint8_t const * key, std::size_t key_length, + std::uint8_t const * input, std::size_t input_length, + std::uint8_t * output +) { + std::uint8_t hmac_key[SHA256_BLOCK_LENGTH]; + ::SHA256_CTX context; + hmac_sha256_key(key, key_length, hmac_key); + hmac_sha256_init(&context, hmac_key); + ::sha256_update(&context, input, input_length); + hmac_sha256_final(&context, hmac_key, output); + axolotl::unset(hmac_key); + axolotl::unset(context); +} + + +void axolotl::hkdf_sha256( + std::uint8_t const * input, std::size_t input_length, + std::uint8_t const * salt, std::size_t salt_length, + std::uint8_t const * info, std::size_t info_length, + std::uint8_t * output, std::size_t output_length +) { + ::SHA256_CTX context; + std::uint8_t hmac_key[SHA256_BLOCK_LENGTH]; + std::uint8_t step_result[SHA256_HASH_LENGTH]; + std::size_t bytes_remaining = output_length; + std::uint8_t iteration = 1; + if (!salt) { + salt = HKDF_DEFAULT_SALT; + salt_length = sizeof(HKDF_DEFAULT_SALT); + } + /* Expand */ + hmac_sha256_key(salt, salt_length, hmac_key); + hmac_sha256_init(&context, hmac_key); + ::sha256_update(&context, input, input_length); + hmac_sha256_final(&context, hmac_key, step_result); + hmac_sha256_key(step_result, SHA256_HASH_LENGTH, hmac_key); + + /* Extract */ + hmac_sha256_init(&context, hmac_key); + ::sha256_update(&context, info, info_length); + ::sha256_update(&context, &iteration, 1); + hmac_sha256_final(&context, hmac_key, step_result); + while (bytes_remaining > SHA256_HASH_LENGTH) { + std::memcpy(output, step_result, SHA256_HASH_LENGTH); + output += SHA256_HASH_LENGTH; + bytes_remaining -= SHA256_HASH_LENGTH; + iteration ++; + hmac_sha256_init(&context, hmac_key); + ::sha256_update(&context, step_result, SHA256_HASH_LENGTH); + ::sha256_update(&context, info, info_length); + ::sha256_update(&context, &iteration, 1); + hmac_sha256_final(&context, hmac_key, step_result); + } + std::memcpy(output, step_result, bytes_remaining); + axolotl::unset(context); + axolotl::unset(hmac_key); + axolotl::unset(step_result); +} |