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-rw-r--r--src/crypto.cpp234
1 files changed, 234 insertions, 0 deletions
diff --git a/src/crypto.cpp b/src/crypto.cpp
new file mode 100644
index 0000000..2397d7c
--- /dev/null
+++ b/src/crypto.cpp
@@ -0,0 +1,234 @@
+#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_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);
+ 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 + 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);
+ std::memset(o_pad, 0, sizeof(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);
+ std::memset(key_schedule, 0, sizeof(key_schedule));
+ std::memset(input_block, 0, sizeof(AES_BLOCK_LENGTH));
+}
+
+
+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]);
+ }
+ }
+ std::memset(key_schedule, 0, sizeof(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);
+}
+
+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 * 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);
+}