/* sha256.c - TinyCrypt SHA-256 crypto hash algorithm implementation */

/*
    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/sha256.h>
#include <tinycrypt/constants.h>
#include <tinycrypt/utils.h>

static void compress(unsigned int* iv, const uint8_t* data);

int tc_sha256_init(TCSha256State_t s)
{
    /* input sanity check: */
    if (s == (TCSha256State_t) 0)
    {
        return TC_CRYPTO_FAIL;
    }

    /*
        Setting the initial state values.
        These values correspond to the first 32 bits of the fractional parts
        of the square roots of the first 8 primes: 2, 3, 5, 7, 11, 13, 17
        and 19.
    */
    _set((uint8_t*) s, 0x00, sizeof(*s));
    s->iv[0] = 0x6a09e667;
    s->iv[1] = 0xbb67ae85;
    s->iv[2] = 0x3c6ef372;
    s->iv[3] = 0xa54ff53a;
    s->iv[4] = 0x510e527f;
    s->iv[5] = 0x9b05688c;
    s->iv[6] = 0x1f83d9ab;
    s->iv[7] = 0x5be0cd19;
    return TC_CRYPTO_SUCCESS;
}

int tc_sha256_update(TCSha256State_t s, const uint8_t* data, size_t datalen)
{
    /* input sanity check: */
    if (s == (TCSha256State_t) 0 ||
            data == (void*) 0)
    {
        return TC_CRYPTO_FAIL;
    }
    else if (datalen == 0)
    {
        return TC_CRYPTO_SUCCESS;
    }

    while (datalen-- > 0)
    {
        s->leftover[s->leftover_offset++] = *(data++);

        if (s->leftover_offset >= TC_SHA256_BLOCK_SIZE)
        {
            compress(s->iv, s->leftover);
            s->leftover_offset = 0;
            s->bits_hashed += (TC_SHA256_BLOCK_SIZE << 3);
        }
    }

    return TC_CRYPTO_SUCCESS;
}

int tc_sha256_final(uint8_t* digest, TCSha256State_t s)
{
    unsigned int i;

    /* input sanity check: */
    if (digest == (uint8_t*) 0 ||
            s == (TCSha256State_t) 0)
    {
        return TC_CRYPTO_FAIL;
    }

    s->bits_hashed += (s->leftover_offset << 3);
    s->leftover[s->leftover_offset++] = 0x80; /* always room for one byte */

    if (s->leftover_offset > (sizeof(s->leftover) - 8))
    {
        /* there is not room for all the padding in this block */
        _set(s->leftover + s->leftover_offset, 0x00,
             sizeof(s->leftover) - s->leftover_offset);
        compress(s->iv, s->leftover);
        s->leftover_offset = 0;
    }

    /* add the padding and the length in big-Endian format */
    _set(s->leftover + s->leftover_offset, 0x00,
         sizeof(s->leftover) - 8 - s->leftover_offset);
    s->leftover[sizeof(s->leftover) - 1] = (uint8_t)(s->bits_hashed);
    s->leftover[sizeof(s->leftover) - 2] = (uint8_t)(s->bits_hashed >> 8);
    s->leftover[sizeof(s->leftover) - 3] = (uint8_t)(s->bits_hashed >> 16);
    s->leftover[sizeof(s->leftover) - 4] = (uint8_t)(s->bits_hashed >> 24);
    s->leftover[sizeof(s->leftover) - 5] = (uint8_t)(s->bits_hashed >> 32);
    s->leftover[sizeof(s->leftover) - 6] = (uint8_t)(s->bits_hashed >> 40);
    s->leftover[sizeof(s->leftover) - 7] = (uint8_t)(s->bits_hashed >> 48);
    s->leftover[sizeof(s->leftover) - 8] = (uint8_t)(s->bits_hashed >> 56);
    /* hash the padding and length */
    compress(s->iv, s->leftover);

    /* copy the iv out to digest */
    for (i = 0; i < TC_SHA256_STATE_BLOCKS; ++i)
    {
        unsigned int t = *((unsigned int*) &s->iv[i]);
        *digest++ = (uint8_t)(t >> 24);
        *digest++ = (uint8_t)(t >> 16);
        *digest++ = (uint8_t)(t >> 8);
        *digest++ = (uint8_t)(t);
    }

    /* destroy the current state */
    _set(s, 0, sizeof(*s));
    return TC_CRYPTO_SUCCESS;
}

/*
    Initializing SHA-256 Hash constant words K.
    These values correspond to the first 32 bits of the fractional parts of the
    cube roots of the first 64 primes between 2 and 311.
*/
static const unsigned int k256[64] =
{
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
    0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
    0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
    0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
    0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
    0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
};

static inline unsigned int ROTR(unsigned int a, unsigned int n)
{
    return (((a) >> n) | ((a) << (32 - n)));
}

#define Sigma0(a)(ROTR((a), 2) ^ ROTR((a), 13) ^ ROTR((a), 22))
#define Sigma1(a)(ROTR((a), 6) ^ ROTR((a), 11) ^ ROTR((a), 25))
#define sigma0(a)(ROTR((a), 7) ^ ROTR((a), 18) ^ ((a) >> 3))
#define sigma1(a)(ROTR((a), 17) ^ ROTR((a), 19) ^ ((a) >> 10))

#define Ch(a, b, c)(((a) & (b)) ^ ((~(a)) & (c)))
#define Maj(a, b, c)(((a) & (b)) ^ ((a) & (c)) ^ ((b) & (c)))

static inline unsigned int BigEndian(const uint8_t** c)
{
    unsigned int n = 0;
    n = (((unsigned int)(*((*c)++))) << 24);
    n |= ((unsigned int)(*((*c)++)) << 16);
    n |= ((unsigned int)(*((*c)++)) << 8);
    n |= ((unsigned int)(*((*c)++)));
    return n;
}

static void compress(unsigned int* iv, const uint8_t* data)
{
    unsigned int a, b, c, d, e, f, g, h;
    unsigned int s0, s1;
    unsigned int t1, t2;
    unsigned int work_space[16];
    unsigned int n;
    unsigned int i;
    a = iv[0];
    b = iv[1];
    c = iv[2];
    d = iv[3];
    e = iv[4];
    f = iv[5];
    g = iv[6];
    h = iv[7];

    for (i = 0; i < 16; ++i)
    {
        n = BigEndian(&data);
        t1 = work_space[i] = n;
        t1 += h + Sigma1(e) + Ch(e, f, g) + k256[i];
        t2 = Sigma0(a) + Maj(a, b, c);
        h = g;
        g = f;
        f = e;
        e = d + t1;
        d = c;
        c = b;
        b = a;
        a = t1 + t2;
    }

    for ( ; i < 64; ++i)
    {
        s0 = work_space[(i+1)&0x0f];
        s0 = sigma0(s0);
        s1 = work_space[(i+14)&0x0f];
        s1 = sigma1(s1);
        t1 = work_space[i&0xf] += s0 + s1 + work_space[(i+9)&0xf];
        t1 += h + Sigma1(e) + Ch(e, f, g) + k256[i];
        t2 = Sigma0(a) + Maj(a, b, c);
        h = g;
        g = f;
        f = e;
        e = d + t1;
        d = c;
        c = b;
        b = a;
        a = t1 + t2;
    }

    iv[0] += a;
    iv[1] += b;
    iv[2] += c;
    iv[3] += d;
    iv[4] += e;
    iv[5] += f;
    iv[6] += g;
    iv[7] += h;
}
