initial commit: start implementing the crypto primitives

include/axolotl/crypto.hh

+#include <cstdint>
+
+namespace axolotl {
+
+
+struct Curve25519PublicKey {
+    static const int LENGTH = 32;
+    std::uint8_t public_key[32];
+};
+
+
+struct Curve25519KeyPair : public Curve25519PublicKey {
+    std::uint8_t private_key[32];
+};
+
+
+Curve25519KeyPair generate_key(
+    std::uint8_t const * random_32_bytes
+);
+
+
+const std::size_t CURVE25519_SHARED_SECRET_LENGTH = 16;
+
+
+void curve25519_shared_secret(
+    Curve25519KeyPair const & our_key,
+    Curve25519PublicKey const & their_key,
+    std::uint8_t * output
+);
+
+
+struct Aes256Key {
+    static const int LENGTH = 32;
+    std::uint8_t key[32];
+};
+
+
+struct Aes256Iv {
+    static const int LENGTH = 16;
+    std::uint8_t iv[16];
+};
+
+
+std::size_t aes_pkcs_7_padded_length(
+    std::size_t input_length
+);
+
+
+void aes_pkcs_7_padding(
+    std::uint8_t const * input, std::size_t input_length,
+    std::uint8_t * output
+);
+
+
+void aes_encrypt_cbc(
+    Aes256Key const & key,
+    Aes256Iv const & iv,
+    std::uint8_t const * input, std::size_t input_length,
+    std::uint8_t * output
+);
+
+
+void aes_decrypt_cbc(
+    Aes256Key const & key,
+    Aes256Iv const & iv,
+    std::uint8_t const * input, std::size_t input_length,
+    std::uint8_t * output
+);
+
+
+const std::size_t HMAC_SHA256_OUTPUT_LENGTH = 32;
+
+
+void 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
+);
+
+
+void 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
+);
+
+} // namespace axolotl

src/crypto.cpp

+#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);
+}

src/libs.cpp

+extern "C" {
+#include "crypto-algorithms/sha256.c"
+#include "crypto-algorithms/aes.c"
+#include "curve25519-donna/curve25519-donna.c"
+}

tests/test_crypto.cpp

+#include "axolotl/crypto.hh"
+
+#include <cstring>
+#include <iostream>
+#include <iomanip>
+#include <cstdlib>
+
+std::ostream & print_hex(
+    std::ostream & os,
+    std::uint8_t const * data,
+    std::size_t length
+) {
+    for (std::size_t i = 0; i < length; i++) {
+        std::cerr << std::setw(2) << std::setfill('0') << std::right
+            << std::hex << (int) data[i];
+    }
+    return os;
+}
+
+char const * TEST_CASE;
+
+void assert_equals(
+    std::uint8_t *expected,
+    std::uint8_t *actual,
+    std::size_t length
+) {
+    if (std::memcmp(expected, actual, length)) {
+        std::cerr << "FAILED :" << TEST_CASE << std::endl;
+        print_hex(std::cerr << "Expected: ", expected, length) << std::endl;
+        print_hex(std::cerr << "Actual:   ", actual, length) << std::endl;
+        std::exit(1);
+    }
+}
+
+
+int main() {
+
+
+
+
+{ /* HDKF Test Case 1 */
+
+TEST_CASE = "HDKF Test Case 1";
+
+std::uint8_t input[22] = {
+    0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
+    0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
+    0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b
+};
+
+std::uint8_t salt[13] = {
+    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+    0x08, 0x09, 0x0a, 0x0b, 0x0c
+};
+
+std::uint8_t info[10] = {
+    0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
+    0xf8, 0xf9
+};
+
+std::uint8_t hmac_expected_output[32] = {
+    0x07, 0x77, 0x09, 0x36, 0x2c, 0x2e, 0x32, 0xdf,
+    0x0d, 0xdc, 0x3f, 0x0d, 0xc4, 0x7b, 0xba, 0x63,
+    0x90, 0xb6, 0xc7, 0x3b, 0xb5, 0x0f, 0x9c, 0x31,
+    0x22, 0xec, 0x84, 0x4a, 0xd7, 0xc2, 0xb3, 0xe5,
+};
+
+std::uint8_t hmac_actual_output[32] = {};
+
+axolotl::hmac_sha256(
+    salt, 0 * sizeof(salt),
+    input, 0 * sizeof(input),
+    hmac_actual_output
+);
+
+assert_equals(hmac_expected_output, hmac_actual_output, 32);
+
+std::uint8_t hkdf_expected_output[42] {
+    0x3c, 0xb2, 0x5f, 0x25, 0xfa, 0xac, 0xd5, 0x7a,
+    0x90, 0x43, 0x4f, 0x64, 0xd0, 0x36, 0x2f, 0x2a,
+    0x2d, 0x2d, 0x0a, 0x90, 0xcf, 0x1a, 0x5a, 0x4c,
+    0x5d, 0xb0, 0x2d, 0x56, 0xec, 0xc4, 0xc5, 0xbf,
+    0x34, 0x00, 0x72, 0x08, 0xd5, 0xb8, 0x87, 0x18,
+    0x58, 0x65
+};
+
+std::uint8_t hkdf_actual_output[42] = {};
+
+axolotl::hkdf_sha256(
+    input, sizeof(input),
+    salt, sizeof(salt),
+    info, sizeof(info),
+    hkdf_actual_output, sizeof(hkdf_actual_output)
+);
+
+assert_equals(hkdf_expected_output, hkdf_actual_output, 42);
+
+} /* HDKF Test Case 1 */
+
+}