/*
 *  Copyright (C) 2017 - This file is part of libecc project
 *
 *  Authors:
 *      Ryad BENADJILA <ryadbenadjila@gmail.com>
 *      Arnaud EBALARD <arnaud.ebalard@ssi.gouv.fr>
 *      Jean-Pierre FLORI <jean-pierre.flori@ssi.gouv.fr>
 *
 *  Contributors:
 *      Nicolas VIVET <nicolas.vivet@ssi.gouv.fr>
 *      Karim KHALFALLAH <karim.khalfallah@ssi.gouv.fr>
 *
 *  This software is licensed under a dual BSD and GPL v2 license.
 *  See LICENSE file at the root folder of the project.
 */
#include <libecc/lib_ecc_config.h>
#ifdef WITH_HASH_SHA256

#include <libecc/hash/sha256.h>

/* SHA-2 core processing */
ATTRIBUTE_WARN_UNUSED_RET static int sha256_process(sha256_context *ctx,
                           const u8 data[SHA256_BLOCK_SIZE])
{
        u32 a, b, c, d, e, f, g, h;
        u32 W[64];
        unsigned int i;
        int ret;

        MUST_HAVE((data != NULL), ret, err);
        SHA256_HASH_CHECK_INITIALIZED(ctx, ret, err);

        /* Init our inner variables */
        a = ctx->sha256_state[0];
        b = ctx->sha256_state[1];
        c = ctx->sha256_state[2];
        d = ctx->sha256_state[3];
        e = ctx->sha256_state[4];
        f = ctx->sha256_state[5];
        g = ctx->sha256_state[6];
        h = ctx->sha256_state[7];

        for (i = 0; i < 16; i++) {
                GET_UINT32_BE(W[i], data, 4 * i);
                SHA2CORE_SHA256(a, b, c, d, e, f, g, h, W[i], K_SHA256[i]);
        }

        for (i = 16; i < 64; i++) {
                SHA2CORE_SHA256(a, b, c, d, e, f, g, h, UPDATEW_SHA256(W, i),
                                K_SHA256[i]);
        }

        /* Update state */
        ctx->sha256_state[0] += a;
        ctx->sha256_state[1] += b;
        ctx->sha256_state[2] += c;
        ctx->sha256_state[3] += d;
        ctx->sha256_state[4] += e;
        ctx->sha256_state[5] += f;
        ctx->sha256_state[6] += g;
        ctx->sha256_state[7] += h;

        ret = 0;

err:
        return ret;
}

/* Init hash function */
int sha256_init(sha256_context *ctx)
{
        int ret;

        MUST_HAVE((ctx != NULL), ret, err);

        ctx->sha256_total = 0;
        ctx->sha256_state[0] = 0x6A09E667;
        ctx->sha256_state[1] = 0xBB67AE85;
        ctx->sha256_state[2] = 0x3C6EF372;
        ctx->sha256_state[3] = 0xA54FF53A;
        ctx->sha256_state[4] = 0x510E527F;
        ctx->sha256_state[5] = 0x9B05688C;
        ctx->sha256_state[6] = 0x1F83D9AB;
        ctx->sha256_state[7] = 0x5BE0CD19;

        /* Tell that we are initialized */
        ctx->magic = SHA256_HASH_MAGIC;

        ret = 0;

err:
        return ret;
}

/* Update hash function */
int sha256_update(sha256_context *ctx, const u8 *input, u32 ilen)
{
        const u8 *data_ptr = input;
        u32 remain_ilen = ilen;
        u16 fill;
        u8 left;
        int ret;

        MUST_HAVE((input != NULL) || (ilen == 0), ret, err);
        SHA256_HASH_CHECK_INITIALIZED(ctx, ret, err);

        /* Nothing to process, return */
        if (ilen == 0) {
                ret = 0;
                goto err;
        }

        /* Get what's left in our local buffer */
        left = (ctx->sha256_total & 0x3F);
        fill = (u16)(SHA256_BLOCK_SIZE - left);

        ctx->sha256_total += ilen;

        if ((left > 0) && (remain_ilen >= fill)) {
                /* Copy data at the end of the buffer */
                ret = local_memcpy(ctx->sha256_buffer + left, data_ptr, fill); EG(ret, err);
                ret = sha256_process(ctx, ctx->sha256_buffer); EG(ret, err);
                data_ptr += fill;
                remain_ilen -= fill;
                left = 0;
        }

        while (remain_ilen >= SHA256_BLOCK_SIZE) {
                ret = sha256_process(ctx, data_ptr); EG(ret, err);
                data_ptr += SHA256_BLOCK_SIZE;
                remain_ilen -= SHA256_BLOCK_SIZE;
        }

        if (remain_ilen > 0) {
                ret = local_memcpy(ctx->sha256_buffer + left, data_ptr, remain_ilen); EG(ret, err);
        }

        ret = 0;

err:
        return ret;
}

/* Finalize */
int sha256_final(sha256_context *ctx, u8 output[SHA256_DIGEST_SIZE])
{
        unsigned int block_present = 0;
        u8 last_padded_block[2 * SHA256_BLOCK_SIZE];
        int ret;

        MUST_HAVE((output != NULL), ret, err);
        SHA256_HASH_CHECK_INITIALIZED(ctx, ret, err);

        /* Fill in our last block with zeroes */
        ret = local_memset(last_padded_block, 0, sizeof(last_padded_block)); EG(ret, err);

        /* This is our final step, so we proceed with the padding */
        block_present = (ctx->sha256_total % SHA256_BLOCK_SIZE);
        if (block_present != 0) {
                /* Copy what's left in our temporary context buffer */
                ret = local_memcpy(last_padded_block, ctx->sha256_buffer,
                             block_present); EG(ret, err);
        }

        /* Put the 0x80 byte, beginning of padding  */
        last_padded_block[block_present] = 0x80;

        /* Handle possible additional block */
        if (block_present > (SHA256_BLOCK_SIZE - 1 - sizeof(u64))) {
                /* We need an additional block */
                PUT_UINT64_BE(8 * ctx->sha256_total, last_padded_block,
                              (2 * SHA256_BLOCK_SIZE) - sizeof(u64));
                ret = sha256_process(ctx, last_padded_block); EG(ret, err);
                ret = sha256_process(ctx, last_padded_block + SHA256_BLOCK_SIZE); EG(ret, err);
        } else {
                /* We do not need an additional block */
                PUT_UINT64_BE(8 * ctx->sha256_total, last_padded_block,
                              SHA256_BLOCK_SIZE - sizeof(u64));
                ret = sha256_process(ctx, last_padded_block); EG(ret, err);
        }

        /* Output the hash result */
        PUT_UINT32_BE(ctx->sha256_state[0], output, 0);
        PUT_UINT32_BE(ctx->sha256_state[1], output, 4);
        PUT_UINT32_BE(ctx->sha256_state[2], output, 8);
        PUT_UINT32_BE(ctx->sha256_state[3], output, 12);
        PUT_UINT32_BE(ctx->sha256_state[4], output, 16);
        PUT_UINT32_BE(ctx->sha256_state[5], output, 20);
        PUT_UINT32_BE(ctx->sha256_state[6], output, 24);
        PUT_UINT32_BE(ctx->sha256_state[7], output, 28);

        /* Tell that we are uninitialized */
        ctx->magic = WORD(0);

        ret = 0;

err:
        return ret;
}

int sha256_scattered(const u8 **inputs, const u32 *ilens,
                      u8 output[SHA256_DIGEST_SIZE])
{
        sha256_context ctx;
        int ret, pos = 0;

        MUST_HAVE((inputs != NULL) && (ilens != NULL) && (output != NULL), ret, err);

        ret = sha256_init(&ctx); EG(ret, err);

        while (inputs[pos] != NULL) {
                ret = sha256_update(&ctx, inputs[pos], ilens[pos]); EG(ret, err);
                pos += 1;
        }

        ret = sha256_final(&ctx, output);

err:
        return ret;
}

int sha256(const u8 *input, u32 ilen, u8 output[SHA256_DIGEST_SIZE])
{
        sha256_context ctx;
        int ret;

        ret = sha256_init(&ctx); EG(ret, err);
        ret = sha256_update(&ctx, input, ilen); EG(ret, err);
        ret = sha256_final(&ctx, output);

err:
        return ret;
}

#else /* WITH_HASH_SHA256 */

/*
 * Dummy definition to avoid the empty translation unit ISO C warning
 */
typedef int dummy;
#endif /* WITH_HASH_SHA256 */