sha256.c

#include "sha256.h"
#include <stdio.h>
#include <string.h>

static 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};

void sha256_transform(SHA256_CTX* ctx, uint8_t block[]) {
    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] = block[j];
        m[i] = m[i] << 8 | block[j + 1];
        m[i] = m[i] << 8 | block[j + 2];
        m[i] = m[i] << 8 | block[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;
}

void sha256_init(SHA256_CTX* ctx) {
    ctx->datalen = 0;
    ctx->bitlen[0] = 0;
    ctx->bitlen[1] = 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;
}

void sha256_update(SHA256_CTX* ctx, uint8_t block[], uint32_t len) {
    uint32_t i;

    for (i = 0; i < len; ++i) {
        ctx->block[ctx->datalen] = block[i];
        ctx->datalen++;
        if (ctx->datalen == 64) {
            sha256_transform(ctx, ctx->block);
            DBL_INT_ADD(ctx->bitlen[0], ctx->bitlen[1], 512);
            ctx->datalen = 0;
        }
    }
}

void sha256_final(SHA256_CTX* ctx, uint8_t hash[]) {
    uint32_t i;

    i = ctx->datalen;

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

    /* Append to the padding the total message's length in bits and transform.*/
    DBL_INT_ADD(ctx->bitlen[0], ctx->bitlen[1], ctx->datalen * 8);
    ctx->block[63] = ctx->bitlen[0];
    ctx->block[62] = ctx->bitlen[0] >> 8;
    ctx->block[61] = ctx->bitlen[0] >> 16;
    ctx->block[60] = ctx->bitlen[0] >> 24;
    ctx->block[59] = ctx->bitlen[1];
    ctx->block[58] = ctx->bitlen[1] >> 8;
    ctx->block[57] = ctx->bitlen[1] >> 16;
    ctx->block[56] = ctx->bitlen[1] >> 24;
    sha256_transform(ctx, ctx->block);

    /* Since this implementation uses little endian byte ordering and SHA uses big endian,
    reverse all the bytes 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;
    }
}