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#include "axolotl/crypto.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_BLOCK_LENGTH = 32;
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
) {
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::memset(hmac_key, 0, SHA256_BLOCK_LENGTH);
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] ^= 0x5C;
}
::sha256_init(context);
::sha256_update(context, i_pad, SHA256_BLOCK_LENGTH);
std::memset(i_pad, 0, sizeof(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];
std::memcpy(o_pad, hmac_key, SHA256_BLOCK_LENGTH);
for (std::size_t i = 0; i < SHA256_BLOCK_LENGTH; ++i) {
o_pad[i] ^= 0x36;
}
::SHA256_CTX final_context;
::sha256_init(&final_context);
::sha256_update(&final_context, o_pad, SHA256_BLOCK_LENGTH);
::sha256_final(context, o_pad);
::sha256_update(&final_context, o_pad, SHA256_BLOCK_LENGTH);
::sha256_final(&final_context, output);
std::memset(o_pad, 0, sizeof(o_pad));
}
} // namespace
axolotl::Curve25519KeyPair 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
);
return key_pair;
}
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_pkcs_7_padded_length(
std::size_t input_length
) {
return input_length + AES_BLOCK_LENGTH - input_length % AES_BLOCK_LENGTH;
}
void axolotl::aes_pkcs_7_padding(
std::uint8_t const * input, std::size_t input_length,
std::uint8_t * output
) {
std::memcpy(output, input, input_length);
std::size_t padded_length = axolotl::aes_pkcs_7_padded_length(input_length);
std::uint8_t padding = padded_length - input_length;
for (std::size_t i = input_length; i < padded_length; ++i) {
output[i] = padding;
}
}
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);
for (std::size_t i = 0; i < input_length; i += AES_BLOCK_LENGTH) {
xor_block<AES_BLOCK_LENGTH>(input_block, &input[i]);
::aes_encrypt(input_block, &output[i], key_schedule, 256);
std::memcpy(input_block, &output[i], AES_BLOCK_LENGTH);
}
std::memset(key_schedule, 0, sizeof(key_schedule));
std::memset(input_block, 0, sizeof(AES_BLOCK_LENGTH));
}
void 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]);
}
}
std::memset(key_schedule, 0, sizeof(key_schedule));
}
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);
std::memset(hmac_key, 0, sizeof(hmac_key));
}
void axolotl::hkdf_sha256(
std::uint8_t const * input, std::size_t input_length,
std::uint8_t const * info, std::size_t info_length,
std::uint8_t const * salt, std::size_t salt_length,
std::uint8_t * output, std::size_t output_length
) {
::SHA256_CTX context;
std::uint8_t extract_key[SHA256_BLOCK_LENGTH];
std::uint8_t expand_key[SHA256_BLOCK_LENGTH];
std::uint8_t step_result[SHA256_BLOCK_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, extract_key);
hmac_sha256_init(&context, extract_key);
::sha256_update(&context, input, input_length);
hmac_sha256_final(&context, extract_key, expand_key);
/* Extract */
hmac_sha256_init(&context, expand_key);
::sha256_update(&context, info, info_length);
::sha256_update(&context, &iteration, 1);
hmac_sha256_final(&context, expand_key, step_result);
while (bytes_remaining > SHA256_BLOCK_LENGTH) {
std::memcpy(output, step_result, SHA256_BLOCK_LENGTH);
output += SHA256_BLOCK_LENGTH;
bytes_remaining -= SHA256_BLOCK_LENGTH;
iteration ++;
hmac_sha256_init(&context, expand_key);
::sha256_update(&context, step_result, SHA256_BLOCK_LENGTH);
::sha256_update(&context, info, info_length);
::sha256_update(&context, &iteration, 1);
hmac_sha256_final(&context, expand_key, step_result);
}
std::memcpy(output, step_result, bytes_remaining);
}
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