File syn_sha256.c¶

File List > src > syntropic > util > syn_sha256.c
#if __has_include("syn_config.h")
#include "syn_config.h"
#endif

#if !defined(SYN_USE_SHA256) || SYN_USE_SHA256

#include "syn_assert.h"
#include "syn_pack.h"
#include "syn_sha256.h"

#include <string.h>

/* ── Constants ──────────────────────────────────────────────────────────── */

static const uint32_t H_INIT[8] = {0x6a09e667u, 0xbb67ae85u, 0x3c6ef372u, 0xa54ff53au,
                                   0x510e527fu, 0x9b05688cu, 0x1f83d9abu, 0x5be0cd19u};

static const uint32_t K[64] = {
    0x428a2f98u, 0x71374491u, 0xb5c0fbcfu, 0xe9b5dba5u, 0x3956c25bu, 0x59f111f1u, 0x923f82a4u,
    0xab1c5ed5u, 0xd807aa98u, 0x12835b01u, 0x243185beu, 0x550c7dc3u, 0x72be5d74u, 0x80deb1feu,
    0x9bdc06a7u, 0xc19bf174u, 0xe49b69c1u, 0xefbe4786u, 0x0fc19dc6u, 0x240ca1ccu, 0x2de92c6fu,
    0x4a7484aau, 0x5cb0a9dcu, 0x76f988dau, 0x983e5152u, 0xa831c66du, 0xb00327c8u, 0xbf597fc7u,
    0xc6e00bf3u, 0xd5a79147u, 0x06ca6351u, 0x14292967u, 0x27b70a85u, 0x2e1b2138u, 0x4d2c6dfcu,
    0x53380d13u, 0x650a7354u, 0x766a0abbu, 0x81c2c92eu, 0x92722c85u, 0xa2bfe8a1u, 0xa81a664bu,
    0xc24b8b70u, 0xc76c51a3u, 0xd192e819u, 0xd6990624u, 0xf40e3585u, 0x106aa070u, 0x19a4c116u,
    0x1e376c08u, 0x2748774cu, 0x34b0bcb5u, 0x391c0cb3u, 0x4ed8aa4au, 0x5b9cca4fu, 0x682e6ff3u,
    0x748f82eeu, 0x78a5636fu, 0x84c87814u, 0x8cc70208u, 0x90befffau, 0xa4506cebu, 0xbef9a3f7u,
    0xc67178f2u};

/* ── Bit operations (FIPS 180-4 §4.1.2) ───────────────────────────────── */

static inline uint32_t rotr(uint32_t x, unsigned n)
{
    return (x >> n) | (x << (32u - n));
}

static inline uint32_t ch(uint32_t x, uint32_t y, uint32_t z)
{
    return (x & y) ^ (~x & z);
}

static inline uint32_t maj(uint32_t x, uint32_t y, uint32_t z)
{
    return (x & y) ^ (x & z) ^ (y & z);
}

static inline uint32_t sigma0(uint32_t x)
{
    return rotr(x, 2) ^ rotr(x, 13) ^ rotr(x, 22);
}

static inline uint32_t sigma1(uint32_t x)
{
    return rotr(x, 6) ^ rotr(x, 11) ^ rotr(x, 25);
}

static inline uint32_t gamma0(uint32_t x)
{
    return rotr(x, 7) ^ rotr(x, 18) ^ (x >> 3);
}

static inline uint32_t gamma1(uint32_t x)
{
    return rotr(x, 17) ^ rotr(x, 19) ^ (x >> 10);
}

/* ── Block transform ────────────────────────────────────────────────────── */

static void sha256_transform(uint32_t state[8], const uint8_t block[64])
{
    uint32_t W[64];
    uint32_t a, b, c, d, e, f, g, h;
    unsigned i;

    /* Prepare message schedule */
    for (i = 0; i < 16; i++) {
        W[i] = syn_peek_u32(block, i * 4);
    }
    for (i = 16; i < 64; i++) {
        W[i] = gamma1(W[i - 2]) + W[i - 7] + gamma0(W[i - 15]) + W[i - 16];
    }

    /* Working variables */
    a = state[0];
    b = state[1];
    c = state[2];
    d = state[3];
    e = state[4];
    f = state[5];
    g = state[6];
    h = state[7];

    /* 64 rounds */
    for (i = 0; i < 64; i++) {
        uint32_t t1 = h + sigma1(e) + ch(e, f, g) + K[i] + W[i];
        uint32_t 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;
    }

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

/* ── API ────────────────────────────────────────────────────────────────── */

void syn_sha256_init(SYN_SHA256 *ctx)
{
    SYN_ASSERT(ctx != NULL);
    if (ctx == NULL) {
        return;
    }
    memcpy(ctx->state, H_INIT, sizeof(H_INIT));
    ctx->buf_len = 0;
    ctx->total_len_lo = 0;
    ctx->total_len_hi = 0;
}

void syn_sha256_update(SYN_SHA256 *ctx, const void *data, size_t len)
{
    SYN_ASSERT(ctx != NULL);
    if (ctx == NULL || data == NULL || len == 0)
        return;

    const uint8_t *p = (const uint8_t *)data;

    /* Track total length in bits (split into hi/lo for >4GB messages) */
    uint32_t len_bits_lo = (uint32_t)((uint64_t)len << 3);
    ctx->total_len_lo += len_bits_lo;
    if (ctx->total_len_lo < len_bits_lo) {
        ctx->total_len_hi++; /* carry */
    }
    ctx->total_len_hi += (uint32_t)((uint64_t)len >> 29);

    /* Fill partial buffer first */
    if (ctx->buf_len > 0) {
        uint32_t space = SYN_SHA256_BLOCK_SIZE - ctx->buf_len;
        uint32_t fill = (len < space) ? (uint32_t)len : space;
        memcpy(ctx->buf + ctx->buf_len, p, fill);
        ctx->buf_len += fill;
        p += fill;
        len -= fill;

        if (ctx->buf_len == SYN_SHA256_BLOCK_SIZE) {
            sha256_transform(ctx->state, ctx->buf);
            ctx->buf_len = 0;
        }
    }

    /* Process full blocks directly from input */
    while (len >= SYN_SHA256_BLOCK_SIZE) {
        sha256_transform(ctx->state, p);
        p += SYN_SHA256_BLOCK_SIZE;
        len -= SYN_SHA256_BLOCK_SIZE;
    }

    /* Buffer remaining bytes */
    if (len > 0) {
        memcpy(ctx->buf, p, len);
        ctx->buf_len = (uint32_t)len;
    }
}

void syn_sha256_final(SYN_SHA256 *ctx, uint8_t hash[SYN_SHA256_DIGEST_SIZE])
{
    SYN_ASSERT(ctx != NULL);
    SYN_ASSERT(hash != NULL);

    if (ctx == NULL || hash == NULL) {
        return;
    }

    /* Pad: append 0x80, then zeros, then 64-bit big-endian length */
    ctx->buf[ctx->buf_len++] = 0x80;

    if (ctx->buf_len > 56) {
        /* Not enough room for length — fill this block and process */
        memset(ctx->buf + ctx->buf_len, 0, SYN_SHA256_BLOCK_SIZE - ctx->buf_len);
        sha256_transform(ctx->state, ctx->buf);
        ctx->buf_len = 0;
    }

    /* Pad with zeros up to byte 56 */
    memset(ctx->buf + ctx->buf_len, 0, 56 - ctx->buf_len);

    /* Append 64-bit big-endian total length in bits */
    syn_poke_u32(ctx->total_len_hi, ctx->buf, 56);
    syn_poke_u32(ctx->total_len_lo, ctx->buf, 60);

    sha256_transform(ctx->state, ctx->buf);

    /* Produce big-endian digest */
    unsigned i;
    for (i = 0; i < 8; i++) {
        syn_poke_u32(ctx->state[i], hash, i * 4);
    }
}

#endif /* SYN_USE_SHA256 */