/*
 * LITLS -- SHA-512 (FIPS 180-4 / RFC 6234)
 * Self-written implementation. Also provides the shared transform for SHA-384.
 */

#include "litls.h"
#include <string.h>

static const uint64_t K512[80] = {
    0x428a2f98d728ae22ULL, 0x7137449123ef65cdULL, 0xb5c0fbcfec4d3b2fULL, 0xe9b5dba58189dbbcULL, 0x3956c25bf348b538ULL,
    0x59f111f1b605d019ULL, 0x923f82a4af194f9bULL, 0xab1c5ed5da6d8118ULL, 0xd807aa98a3030242ULL, 0x12835b0145706fbeULL,
    0x243185be4ee4b28cULL, 0x550c7dc3d5ffb4e2ULL, 0x72be5d74f27b896fULL, 0x80deb1fe3b1696b1ULL, 0x9bdc06a725c71235ULL,
    0xc19bf174cf692694ULL, 0xe49b69c19ef14ad2ULL, 0xefbe4786384f25e3ULL, 0x0fc19dc68b8cd5b5ULL, 0x240ca1cc77ac9c65ULL,
    0x2de92c6f592b0275ULL, 0x4a7484aa6ea6e483ULL, 0x5cb0a9dcbd41fbd4ULL, 0x76f988da831153b5ULL, 0x983e5152ee66dfabULL,
    0xa831c66d2db43210ULL, 0xb00327c898fb213fULL, 0xbf597fc7beef0ee4ULL, 0xc6e00bf33da88fc2ULL, 0xd5a79147930aa725ULL,
    0x06ca6351e003826fULL, 0x142929670a0e6e70ULL, 0x27b70a8546d22ffcULL, 0x2e1b21385c26c926ULL, 0x4d2c6dfc5ac42aedULL,
    0x53380d139d95b3dfULL, 0x650a73548baf63deULL, 0x766a0abb3c77b2a8ULL, 0x81c2c92e47edaee6ULL, 0x92722c851482353bULL,
    0xa2bfe8a14cf10364ULL, 0xa81a664bbc423001ULL, 0xc24b8b70d0f89791ULL, 0xc76c51a30654be30ULL, 0xd192e819d6ef5218ULL,
    0xd69906245565a910ULL, 0xf40e35855771202aULL, 0x106aa07032bbd1b8ULL, 0x19a4c116b8d2d0c8ULL, 0x1e376c085141ab53ULL,
    0x2748774cdf8eeb99ULL, 0x34b0bcb5e19b48a8ULL, 0x391c0cb3c5c95a63ULL, 0x4ed8aa4ae3418acbULL, 0x5b9cca4f7763e373ULL,
    0x682e6ff3d6b2b8a3ULL, 0x748f82ee5defb2fcULL, 0x78a5636f43172f60ULL, 0x84c87814a1f0ab72ULL, 0x8cc702081a6439ecULL,
    0x90befffa23631e28ULL, 0xa4506cebde82bde9ULL, 0xbef9a3f7b2c67915ULL, 0xc67178f2e372532bULL, 0xca273eceea26619cULL,
    0xd186b8c721c0c207ULL, 0xeada7dd6cde0eb1eULL, 0xf57d4f7fee6ed178ULL, 0x06f067aa72176fbaULL, 0x0a637dc5a2c898a6ULL,
    0x113f9804bef90daeULL, 0x1b710b35131c471bULL, 0x28db77f523047d84ULL, 0x32caab7b40c72493ULL, 0x3c9ebe0a15c9bebcULL,
    0x431d67c49c100d4cULL, 0x4cc5d4becb3e42b6ULL, 0x597f299cfc657e2aULL, 0x5fcb6fab3ad6faecULL, 0x6c44198c4a475817ULL};

#define ROTR64(x, n)   (((x) >> (n)) | ((x) << (64 - (n))))
#define CH64(x, y, z)  (((x) & (y)) ^ (~(x) & (z)))
#define MAJ64(x, y, z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
#define EP0_64(x)      (ROTR64(x, 28) ^ ROTR64(x, 34) ^ ROTR64(x, 39))
#define EP1_64(x)      (ROTR64(x, 14) ^ ROTR64(x, 18) ^ ROTR64(x, 41))
#define SIG0_64(x)     (ROTR64(x, 1) ^ ROTR64(x, 8) ^ ((x) >> 7))
#define SIG1_64(x)     (ROTR64(x, 19) ^ ROTR64(x, 61) ^ ((x) >> 6))

void litls_sha512_transform_(litls_sha512_ctx *ctx) {
    uint64_t w[80];
    const uint8_t *d = ctx->data;

    for (int i = 0; i < 16; i++) {
        w[i] = ((uint64_t)d[i * 8] << 56) | ((uint64_t)d[i * 8 + 1] << 48) | ((uint64_t)d[i * 8 + 2] << 40) |
               ((uint64_t)d[i * 8 + 3] << 32) | ((uint64_t)d[i * 8 + 4] << 24) | ((uint64_t)d[i * 8 + 5] << 16) |
               ((uint64_t)d[i * 8 + 6] << 8) | (uint64_t)d[i * 8 + 7];
    }
    for (int i = 16; i < 80; i++) {
        w[i] = SIG1_64(w[i - 2]) + w[i - 7] + SIG0_64(w[i - 15]) + w[i - 16];
    }

    uint64_t a = ctx->state[0], b = ctx->state[1];
    uint64_t c = ctx->state[2], dd = ctx->state[3];
    uint64_t e = ctx->state[4], f = ctx->state[5];
    uint64_t g = ctx->state[6], h = ctx->state[7];

    for (int i = 0; i < 80; i++) {
        uint64_t t1 = h + EP1_64(e) + CH64(e, f, g) + K512[i] + w[i];
        uint64_t t2 = EP0_64(a) + MAJ64(a, b, c);
        h           = g;
        g           = f;
        f           = e;
        e           = dd + t1;
        dd          = c;
        c           = b;
        b           = a;
        a           = t1 + t2;
    }

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

void litls_sha512_init(litls_sha512_ctx *ctx) {
    ctx->datalen   = 0;
    ctx->bitlen[0] = 0;
    ctx->bitlen[1] = 0;
    ctx->state[0]  = 0x6a09e667f3bcc908ULL;
    ctx->state[1]  = 0xbb67ae8584caa73bULL;
    ctx->state[2]  = 0x3c6ef372fe94f82bULL;
    ctx->state[3]  = 0xa54ff53a5f1d36f1ULL;
    ctx->state[4]  = 0x510e527fade682d1ULL;
    ctx->state[5]  = 0x9b05688c2b3e6c1fULL;
    ctx->state[6]  = 0x1f83d9abfb41bd6bULL;
    ctx->state[7]  = 0x5be0cd19137e2179ULL;
}

void litls_sha512_update(litls_sha512_ctx *ctx, const uint8_t *data, size_t len) {
    for (size_t i = 0; i < len; i++) {
        ctx->data[ctx->datalen++] = data[i];
        if (ctx->datalen == 128) {
            litls_sha512_transform_(ctx);
            /* add 1024 bits to bitlen */
            ctx->bitlen[1] += 1024;
            if (ctx->bitlen[1] < 1024)
                ctx->bitlen[0]++;
            ctx->datalen = 0;
        }
    }
}

void litls_sha512_final(litls_sha512_ctx *ctx, uint8_t out[64]) {
    uint32_t i = ctx->datalen;

    ctx->data[i++] = 0x80;
    if (i > 112) {
        while (i < 128)
            ctx->data[i++] = 0;
        litls_sha512_transform_(ctx);
        i = 0;
    }
    while (i < 112)
        ctx->data[i++] = 0;

    /* total bits = bitlen + datalen * 8 */
    uint64_t total_lo = ctx->bitlen[1] + (uint64_t)ctx->datalen * 8;
    uint64_t total_hi = ctx->bitlen[0];
    if (total_lo < ctx->bitlen[1])
        total_hi++;

    /* store 128-bit length in big-endian */
    for (int j = 0; j < 8; j++) {
        ctx->data[112 + j] = (uint8_t)(total_hi >> (56 - j * 8));
        ctx->data[120 + j] = (uint8_t)(total_lo >> (56 - j * 8));
    }
    litls_sha512_transform_(ctx);

    for (int j = 0; j < 8; j++) {
        out[j * 8]     = (uint8_t)(ctx->state[j] >> 56);
        out[j * 8 + 1] = (uint8_t)(ctx->state[j] >> 48);
        out[j * 8 + 2] = (uint8_t)(ctx->state[j] >> 40);
        out[j * 8 + 3] = (uint8_t)(ctx->state[j] >> 32);
        out[j * 8 + 4] = (uint8_t)(ctx->state[j] >> 24);
        out[j * 8 + 5] = (uint8_t)(ctx->state[j] >> 16);
        out[j * 8 + 6] = (uint8_t)(ctx->state[j] >> 8);
        out[j * 8 + 7] = (uint8_t)(ctx->state[j]);
    }
}

void litls_sha512(const uint8_t *data, size_t len, uint8_t out[64]) {
    litls_sha512_ctx ctx;
    litls_sha512_init(&ctx);
    litls_sha512_update(&ctx, data, len);
    litls_sha512_final(&ctx, out);
}