/* ec_dh.c - TinyCrypt implementation of EC-DH */

/*
    Copyright (c) 2014, Kenneth MacKay
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:
 *  * Redistributions of source code must retain the above copyright notice,
      this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright notice,
      this list of conditions and the following disclaimer in the documentation
      and/or other materials provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    POSSIBILITY OF SUCH DAMAGE.
*/

/*
    Copyright (C) 2017 by Intel Corporation, All Rights Reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:

      - Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.

      - Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.

      - Neither the name of Intel Corporation nor the names of its contributors
      may be used to endorse or promote products derived from this software
      without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    POSSIBILITY OF SUCH DAMAGE.
*/
#include <tinycrypt/constants.h>
#include <tinycrypt/ecc.h>
#include <tinycrypt/ecc_dh.h>
#include <string.h>

#if default_RNG_defined
    static uECC_RNG_Function g_rng_function = &default_CSPRNG;
#else
    static uECC_RNG_Function g_rng_function = 0;
#endif

int uECC_make_key_with_d(uint8_t* public_key, uint8_t* private_key,
                         unsigned int* d, uECC_Curve curve)
{
    uECC_word_t _private[NUM_ECC_WORDS];
    uECC_word_t _public[NUM_ECC_WORDS * 2];
    /*  This function is designed for test purposes-only (such as validating NIST
        test vectors) as it uses a provided value for d instead of generating
        it uniformly at random. */
    memcpy (_private, d, NUM_ECC_BYTES);

    /* Computing public-key from private: */
    if (EccPoint_compute_public_key(_public, _private, curve))
    {
        /* Converting buffers to correct bit order: */
        uECC_vli_nativeToBytes(private_key,
                               BITS_TO_BYTES(curve->num_n_bits),
                               _private);
        uECC_vli_nativeToBytes(public_key,
                               curve->num_bytes,
                               _public);
        uECC_vli_nativeToBytes(public_key + curve->num_bytes,
                               curve->num_bytes,
                               _public + curve->num_words);
        /* erasing temporary buffer used to store secret: */
        memset(_private, 0, NUM_ECC_BYTES);
        return 1;
    }

    return 0;
}

int uECC_make_key(uint8_t* public_key, uint8_t* private_key, uECC_Curve curve)
{
    uECC_word_t _random[NUM_ECC_WORDS * 2];
    uECC_word_t _private[NUM_ECC_WORDS];
    uECC_word_t _public[NUM_ECC_WORDS * 2];
    uECC_word_t tries;

    for (tries = 0; tries < uECC_RNG_MAX_TRIES; ++tries)
    {
        /* Generating _private uniformly at random: */
        uECC_RNG_Function rng_function = uECC_get_rng();

        if (!rng_function ||
                !rng_function((uint8_t*)_random, 2 * NUM_ECC_WORDS*uECC_WORD_SIZE))
        {
            return 0;
        }

        /* computing modular reduction of _random (see FIPS 186.4 B.4.1): */
        uECC_vli_mmod(_private, _random, curve->n, BITS_TO_WORDS(curve->num_n_bits));

        /* Computing public-key from private: */
        if (EccPoint_compute_public_key(_public, _private, curve))
        {
            /* Converting buffers to correct bit order: */
            uECC_vli_nativeToBytes(private_key,
                                   BITS_TO_BYTES(curve->num_n_bits),
                                   _private);
            uECC_vli_nativeToBytes(public_key,
                                   curve->num_bytes,
                                   _public);
            uECC_vli_nativeToBytes(public_key + curve->num_bytes,
                                   curve->num_bytes,
                                   _public + curve->num_words);
            /* erasing temporary buffer that stored secret: */
            memset(_private, 0, NUM_ECC_BYTES);
            return 1;
        }
    }

    return 0;
}

int uECC_shared_secret(const uint8_t* public_key, const uint8_t* private_key,
                       uint8_t* secret, uECC_Curve curve)
{
    uECC_word_t _public[NUM_ECC_WORDS * 2];
    uECC_word_t _private[NUM_ECC_WORDS];
    uECC_word_t tmp[NUM_ECC_WORDS];
    uECC_word_t* p2[2] = {_private, tmp};
    uECC_word_t* initial_Z = 0;
    uECC_word_t carry;
    wordcount_t num_words = curve->num_words;
    wordcount_t num_bytes = curve->num_bytes;
    int r;
    /* Converting buffers to correct bit order: */
    uECC_vli_bytesToNative(_private,
                           private_key,
                           BITS_TO_BYTES(curve->num_n_bits));
    uECC_vli_bytesToNative(_public,
                           public_key,
                           num_bytes);
    uECC_vli_bytesToNative(_public + num_words,
                           public_key + num_bytes,
                           num_bytes);
    /*  Regularize the bitcount for the private key so that attackers cannot use a
        side channel attack to learn the number of leading zeros. */
    carry = regularize_k(_private, _private, tmp, curve);

    /*  If an RNG function was specified, try to get a random initial Z value to
        improve protection against side-channel attacks. */
    if (g_rng_function)
    {
        if (!uECC_generate_random_int(p2[carry], curve->p, num_words))
        {
            r = 0;
            goto clear_and_out;
        }

        initial_Z = p2[carry];
    }

    EccPoint_mult(_public, _public, p2[!carry], initial_Z, curve->num_n_bits + 1,
                  curve);
    uECC_vli_nativeToBytes(secret, num_bytes, _public);
    r = !EccPoint_isZero(_public, curve);
clear_and_out:
    /* erasing temporary buffer used to store secret: */
    memset(p2, 0, sizeof(p2));
    /*__asm volatile("" :: "g"(p2) : "memory");*/
    memset(tmp, 0, sizeof(tmp));
    /*__asm volatile("" :: "g"(tmp) : "memory");*/
    memset(_private, 0, sizeof(_private));
    /*__asm volatile("" :: "g"(_private) : "memory");*/
    return r;
}
