math/src/sha256.c

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/// A SHA-256 implementation.
/*! \file */

#include "epid/member/tiny/math/sha256.h"

#include "epid/member/tiny/stdlib/tiny_stdlib.h"

static void sha256_compress(unsigned int* iv, const uint8_t* data);

void tc_sha256_init(sha256_state* s) {
  /*
   * Setting the initial state values.
   * These values correspond to the first 32 bits of the fractional parts
   * of the square roots of the first 8 primes: 2, 3, 5, 7, 11, 13, 17
   * and 19.
   */
  (void)memset((uint8_t*)s, 0x00, sizeof(*s));
  s->iv[0] = 0x6a09e667;
  s->iv[1] = 0xbb67ae85;
  s->iv[2] = 0x3c6ef372;
  s->iv[3] = 0xa54ff53a;
  s->iv[4] = 0x510e527f;
  s->iv[5] = 0x9b05688c;
  s->iv[6] = 0x1f83d9ab;
  s->iv[7] = 0x5be0cd19;
}

void tc_sha256_update(sha256_state* s, const uint8_t* data, size_t datalen) {
  while (datalen-- > 0) {
    s->leftover[s->leftover_offset++] = *(data++);
    if (s->leftover_offset >= SHA256_BLOCK_SIZE) {
      sha256_compress(s->iv, s->leftover);
      s->leftover_offset = 0;
      s->bits_hashed += (SHA256_BLOCK_SIZE << 3);
    }
  }
}

void tc_sha256_final(uint8_t* digest, sha256_state* s) {
  unsigned int i;

  s->bits_hashed += (s->leftover_offset << 3);

  s->leftover[s->leftover_offset++] = 0x80; /* always room for one byte */
  if (s->leftover_offset > (sizeof(s->leftover) - 8)) {
    /* there is not room for all the padding in this block */
    (void)memset(s->leftover + s->leftover_offset, 0x00,
                 sizeof(s->leftover) - s->leftover_offset);
    sha256_compress(s->iv, s->leftover);
    s->leftover_offset = 0;
  }

  /* add the padding and the length in big-Endian format */
  (void)memset(s->leftover + s->leftover_offset, 0x00,
               sizeof(s->leftover) - 8 - s->leftover_offset);
  s->leftover[sizeof(s->leftover) - 1] = (uint8_t)(s->bits_hashed);
  s->leftover[sizeof(s->leftover) - 2] = (uint8_t)(s->bits_hashed >> 8);
  s->leftover[sizeof(s->leftover) - 3] = (uint8_t)(s->bits_hashed >> 16);
  s->leftover[sizeof(s->leftover) - 4] = (uint8_t)(s->bits_hashed >> 24);
  s->leftover[sizeof(s->leftover) - 5] = (uint8_t)(s->bits_hashed >> 32);
  s->leftover[sizeof(s->leftover) - 6] = (uint8_t)(s->bits_hashed >> 40);
  s->leftover[sizeof(s->leftover) - 7] = (uint8_t)(s->bits_hashed >> 48);
  s->leftover[sizeof(s->leftover) - 8] = (uint8_t)(s->bits_hashed >> 56);

  /* hash the padding and length */
  sha256_compress(s->iv, s->leftover);

  /* copy the iv out to digest */
  for (i = 0; i < SHA256_STATE_BLOCKS; ++i) {
    unsigned int t = *((unsigned int*)&s->iv[i]);
    *digest++ = (uint8_t)(t >> 24);
    *digest++ = (uint8_t)(t >> 16);
    *digest++ = (uint8_t)(t >> 8);
    *digest++ = (uint8_t)(t);
  }

  /* destroy the current state */
  (void)memset(s, 0, sizeof(*s));
}

/*
 * Initializing SHA-256 Hash constant words K.
 * These values correspond to the first 32 bits of the fractional parts of the
 * cube roots of the first 64 primes between 2 and 311.
 */
static const unsigned int k256[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};

static unsigned int ROTR(unsigned int a, unsigned int n) {
  return (((a) >> n) | ((a) << (32 - n)));
}

#define Sigma0(a) (ROTR((a), 2) ^ ROTR((a), 13) ^ ROTR((a), 22))
#define Sigma1(a) (ROTR((a), 6) ^ ROTR((a), 11) ^ ROTR((a), 25))
#define sigma0(a) (ROTR((a), 7) ^ ROTR((a), 18) ^ ((a) >> 3))
#define sigma1(a) (ROTR((a), 17) ^ ROTR((a), 19) ^ ((a) >> 10))

#define Ch(a, b, c) (((a) & (b)) ^ ((~(a)) & (c)))
#define Maj(a, b, c) (((a) & (b)) ^ ((a) & (c)) ^ ((b) & (c)))

static unsigned int BigEndian(const uint8_t** c) {
  unsigned int n = 0;

  n = (((unsigned int)(*((*c)++))) << 24);
  n |= ((unsigned int)(*((*c)++)) << 16);
  n |= ((unsigned int)(*((*c)++)) << 8);
  n |= ((unsigned int)(*((*c)++)));
  return n;
}

static void sha256_compress(unsigned int* iv, const uint8_t* data) {
  unsigned int a, b, c, d, e, f, g, h;
  unsigned int s0, s1;
  unsigned int t1, t2;
  unsigned int work_space[16];
  unsigned int n;
  unsigned int i;

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

  for (i = 0; i < 16; ++i) {
    n = BigEndian(&data);
    t1 = work_space[i] = n;
    t1 += h + Sigma1(e) + Ch(e, f, g) + k256[i];
    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;
  }

  for (; i < 64; ++i) {
    s0 = work_space[(i + 1) & 0x0f];
    s0 = sigma0(s0);
    s1 = work_space[(i + 14) & 0x0f];
    s1 = sigma1(s1);

    t1 = work_space[i & 0xf] += s0 + s1 + work_space[(i + 9) & 0xf];
    t1 += h + Sigma1(e) + Ch(e, f, g) + k256[i];
    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;
  }

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