/**
 * Copyright (c) 2015 - 2018, Nordic Semiconductor ASA
 * 
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, 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.
 * 
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 * 
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 * 
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 * 
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA 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.
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 */
#include <stdlib.h>
#include "sha256.h"
#include "sdk_errors.h"
#include "sdk_common.h"


#define ROTLEFT(a,b) (((a) << (b)) | ((a) >> (32 - (b))))
#define ROTRIGHT(a,b) (((a) >> (b)) | ((a) << (32 - (b))))

#define CH(x,y,z) (((x) & (y)) ^ (~(x) & (z)))
#define MAJ(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
#define EP0(x) (ROTRIGHT(x,2) ^ ROTRIGHT(x,13) ^ ROTRIGHT(x,22))
#define EP1(x) (ROTRIGHT(x,6) ^ ROTRIGHT(x,11) ^ ROTRIGHT(x,25))
#define SIG0(x) (ROTRIGHT(x,7) ^ ROTRIGHT(x,18) ^ ((x) >> 3))
#define SIG1(x) (ROTRIGHT(x,17) ^ ROTRIGHT(x,19) ^ ((x) >> 10))


static const uint32_t k[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
};


/**@brief Function for calculating the hash of a 64-byte section of data.
 *
 * @param[in,out] ctx   Hash instance.
 * @param[in]     data  Aray with data to be hashed. Assumed to be 64 bytes long.
 */
void sha256_transform(sha256_context_t *ctx, const uint8_t * data)
{
    uint32_t a, b, c, d, e, f, g, h, i, j, t1, t2, m[64];

    for (i = 0, j = 0; i < 16; ++i, j += 4)
        m[i] = (data[j] << 24) | (data[j + 1] << 16) | (data[j + 2] << 8) | (data[j + 3]);
    for ( ; i < 64; ++i)
        m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];

    a = ctx->state[0];
    b = ctx->state[1];
    c = ctx->state[2];
    d = ctx->state[3];
    e = ctx->state[4];
    f = ctx->state[5];
    g = ctx->state[6];
    h = ctx->state[7];

    for (i = 0; i < 64; ++i) {
        t1 = h + EP1(e) + CH(e,f,g) + k[i] + m[i];
        t2 = EP0(a) + MAJ(a,b,c);
        h = g;
        g = f;
        f = e;
        e = d + t1;
        d = c;
        c = b;
        b = a;
        a = t1 + t2;
    }

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


ret_code_t sha256_init(sha256_context_t *ctx)
{
    VERIFY_PARAM_NOT_NULL(ctx);

    ctx->datalen = 0;
    ctx->bitlen = 0;
    ctx->state[0] = 0x6a09e667;
    ctx->state[1] = 0xbb67ae85;
    ctx->state[2] = 0x3c6ef372;
    ctx->state[3] = 0xa54ff53a;
    ctx->state[4] = 0x510e527f;
    ctx->state[5] = 0x9b05688c;
    ctx->state[6] = 0x1f83d9ab;
    ctx->state[7] = 0x5be0cd19;

    return NRF_SUCCESS;
}


ret_code_t sha256_update(sha256_context_t *ctx, const uint8_t * data, size_t len)
{
    VERIFY_PARAM_NOT_NULL(ctx);
    if (((len > 0) && (data == NULL)))
    {
        return NRF_ERROR_NULL;
    }

    uint32_t i;

    for (i = 0; i < len; ++i) {
        ctx->data[ctx->datalen] = data[i];
        ctx->datalen++;
        if (ctx->datalen == 64) {
            sha256_transform(ctx, ctx->data);
            ctx->bitlen += 512;
            ctx->datalen = 0;
        }
    }

    return NRF_SUCCESS;
}


ret_code_t sha256_final(sha256_context_t *ctx, uint8_t * hash, uint8_t le)
{
    uint32_t i;

    VERIFY_PARAM_NOT_NULL(ctx);
    VERIFY_PARAM_NOT_NULL(hash);

    i = ctx->datalen;

    // Pad whatever data is left in the buffer.
    if (ctx->datalen < 56) {
        ctx->data[i++] = 0x80;
        while (i < 56)
            ctx->data[i++] = 0x00;
    }
    else {
        ctx->data[i++] = 0x80;
        while (i < 64)
            ctx->data[i++] = 0x00;
        sha256_transform(ctx, ctx->data);
        memset(ctx->data, 0, 56);
    }

    // Append to the padding the total message's length in bits and transform.
    ctx->bitlen += (uint64_t)ctx->datalen * 8;
    ctx->data[63] = ctx->bitlen;
    ctx->data[62] = ctx->bitlen >> 8;
    ctx->data[61] = ctx->bitlen >> 16;
    ctx->data[60] = ctx->bitlen >> 24;
    ctx->data[59] = ctx->bitlen >> 32;
    ctx->data[58] = ctx->bitlen >> 40;
    ctx->data[57] = ctx->bitlen >> 48;
    ctx->data[56] = ctx->bitlen >> 56;
    sha256_transform(ctx, ctx->data);

    if (le)
    {
        for (i = 0; i < 4; ++i) {
            hash[i]      = (ctx->state[7] >> (i * 8)) & 0x000000ff;
            hash[i + 4]  = (ctx->state[6] >> (i * 8)) & 0x000000ff;
            hash[i + 8]  = (ctx->state[5] >> (i * 8)) & 0x000000ff;
            hash[i + 12] = (ctx->state[4] >> (i * 8)) & 0x000000ff;
            hash[i + 16] = (ctx->state[3] >> (i * 8)) & 0x000000ff;
            hash[i + 20] = (ctx->state[2] >> (i * 8)) & 0x000000ff;
            hash[i + 24] = (ctx->state[1] >> (i * 8)) & 0x000000ff;
            hash[i + 28] = (ctx->state[0] >> (i * 8)) & 0x000000ff;
        }
    }
    else
    {

        // Since this implementation uses little endian uint8_t ordering and SHA uses big endian,
        // reverse all the uint8_ts when copying the final state to the output hash.
        for (i = 0; i < 4; ++i) {
            hash[i]      = (ctx->state[0] >> (24 - i * 8)) & 0x000000ff;
            hash[i + 4]  = (ctx->state[1] >> (24 - i * 8)) & 0x000000ff;
            hash[i + 8]  = (ctx->state[2] >> (24 - i * 8)) & 0x000000ff;
            hash[i + 12] = (ctx->state[3] >> (24 - i * 8)) & 0x000000ff;
            hash[i + 16] = (ctx->state[4] >> (24 - i * 8)) & 0x000000ff;
            hash[i + 20] = (ctx->state[5] >> (24 - i * 8)) & 0x000000ff;
            hash[i + 24] = (ctx->state[6] >> (24 - i * 8)) & 0x000000ff;
            hash[i + 28] = (ctx->state[7] >> (24 - i * 8)) & 0x000000ff;
        }
    }

    return NRF_SUCCESS;
}