From 44d0c0920574c3169a0ebf6a03671332753a1c76 Mon Sep 17 00:00:00 2001 From: Mark Haines Date: Fri, 20 Feb 2015 21:32:56 +0000 Subject: initial commit: start implementing the crypto primitives --- src/crypto.cpp | 223 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 223 insertions(+) create mode 100644 src/crypto.cpp (limited to 'src/crypto.cpp') diff --git a/src/crypto.cpp b/src/crypto.cpp new file mode 100644 index 0000000..c1ef88a --- /dev/null +++ b/src/crypto.cpp @@ -0,0 +1,223 @@ +#include "axolotl/crypto.hh" +#include + +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 +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(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(&output[i], iv.iv); + } else { + xor_block(&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); +} -- cgit v1.2.3