alg-sha256.c

/* Functions to compute SHA256 message digest of files or memory blocks.
   according to the definition of SHA256 in FIPS 180-2.
   Copyright (C) 2007-2017 Free Software Foundation, Inc.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License
   as published by the Free Software Foundation; either version 2.1 of
   the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see
   <https://www.gnu.org/licenses/>.  */

/* Written by Ulrich Drepper <drepper@redhat.com>, 2007.  */

#include "crypt-port.h"
#include "alg-sha256.h"
#include "byteorder.h"

#if INCLUDE_sha256

/* Constants for SHA256 from FIPS 180-2:4.2.2.  */
static const 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
};


/* Process LEN bytes of BUFFER, accumulating context into CTX.
   It is assumed that LEN % 64 == 0.  */
static void
sha256_process_block (const void *buffer, size_t len, struct sha256_ctx *ctx)
{
  unsigned int t;
  const unsigned char *p = buffer;
  size_t nwords = len / sizeof (uint32_t);
  uint32_t a = ctx->H[0];
  uint32_t b = ctx->H[1];
  uint32_t c = ctx->H[2];
  uint32_t d = ctx->H[3];
  uint32_t e = ctx->H[4];
  uint32_t f = ctx->H[5];
  uint32_t g = ctx->H[6];
  uint32_t h = ctx->H[7];

  /* First increment the byte count.  FIPS 180-2 specifies the possible
     length of the file up to 2^64 bits.  Here we only compute the
     number of bytes.  */
  ctx->total += len;

  /* Process all bytes in the buffer with 64 bytes in each round of
     the loop.  */
  while (nwords > 0)
    {
      uint32_t W[64];
      uint32_t a_save = a;
      uint32_t b_save = b;
      uint32_t c_save = c;
      uint32_t d_save = d;
      uint32_t e_save = e;
      uint32_t f_save = f;
      uint32_t g_save = g;
      uint32_t h_save = h;

      /* Operators defined in FIPS 180-2:4.1.2.  */
#define Ch(x, y, z) ((x & y) ^ (~x & z))
#define Maj(x, y, z) ((x & y) ^ (x & z) ^ (y & z))
#define S0(x) (CYCLIC (x, 2) ^ CYCLIC (x, 13) ^ CYCLIC (x, 22))
#define S1(x) (CYCLIC (x, 6) ^ CYCLIC (x, 11) ^ CYCLIC (x, 25))
#define R0(x) (CYCLIC (x, 7) ^ CYCLIC (x, 18) ^ (x >> 3))
#define R1(x) (CYCLIC (x, 17) ^ CYCLIC (x, 19) ^ (x >> 10))

      /* It is unfortunate that C does not provide an operator for
         cyclic rotation.  Hope the C compiler is smart enough.  */
#define CYCLIC(w, s) ((w >> s) | (w << (32 - s)))

      /* Compute the message schedule according to FIPS 180-2:6.2.2 step 2.  */
      for (t = 0; t < 16; ++t)
        {
          W[t] = be32_to_cpu (p);
          p += 4;
        }
      for (t = 16; t < 64; ++t)
        W[t] = R1 (W[t - 2]) + W[t - 7] + R0 (W[t - 15]) + W[t - 16];

      /* The actual computation according to FIPS 180-2:6.2.2 step 3.  */
      for (t = 0; t < 64; ++t)
        {
          uint32_t T1 = h + S1 (e) + Ch (e, f, g) + K[t] + W[t];
          uint32_t T2 = S0 (a) + Maj (a, b, c);
          h = g;
          g = f;
          f = e;
          e = d + T1;
          d = c;
          c = b;
          b = a;
          a = T1 + T2;
        }

      /* Add the starting values of the context according to FIPS 180-2:6.2.2
         step 4.  */
      a += a_save;
      b += b_save;
      c += c_save;
      d += d_save;
      e += e_save;
      f += f_save;
      g += g_save;
      h += h_save;

      /* Prepare for the next round.  */
      nwords -= 16;
    }

  /* Put checksum in context given as argument.  */
  ctx->H[0] = a;
  ctx->H[1] = b;
  ctx->H[2] = c;
  ctx->H[3] = d;
  ctx->H[4] = e;
  ctx->H[5] = f;
  ctx->H[6] = g;
  ctx->H[7] = h;
}


/* Initialize structure containing state of computation.
   (FIPS 180-2:5.3.2)  */
void
sha256_init_ctx (struct sha256_ctx *ctx)

{
  ctx->H[0] = 0x6a09e667;
  ctx->H[1] = 0xbb67ae85;
  ctx->H[2] = 0x3c6ef372;
  ctx->H[3] = 0xa54ff53a;
  ctx->H[4] = 0x510e527f;
  ctx->H[5] = 0x9b05688c;
  ctx->H[6] = 0x1f83d9ab;
  ctx->H[7] = 0x5be0cd19;

  ctx->total = 0;
  ctx->buflen = 0;
}


/* Process the remaining bytes in the internal buffer and the usual
   prolog according to the standard and write the result to RESBUF.  */
void *
sha256_finish_ctx (struct sha256_ctx *ctx, void *resbuf)
{
  /* Take yet unprocessed bytes into account.  */
  uint32_t bytes = ctx->buflen;
  size_t pad;
  unsigned int i;
  unsigned char *rp = resbuf;

  /* Now count remaining bytes.  */
  ctx->total += bytes;

  pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
  /* The first byte of padding should be 0x80 and the rest should be
     zero.  (FIPS 180-2:5.1.1) */
  ctx->buffer[bytes] = 0x80u;
  XCRYPT_SECURE_MEMSET (&ctx->buffer[bytes+1], pad-1);

  /* Put the 64-bit file length in big-endian *bits* at the end of the
     buffer.  */
  cpu_to_be64 (&ctx->buffer[bytes + pad], ctx->total << 3);

  /* Process last bytes.  */
  sha256_process_block (ctx->buffer, bytes + pad + 8, ctx);

  /* Put result from CTX in first 32 bytes following RESBUF.  */
  for (i = 0; i < 8; i++)
    cpu_to_be32 (rp + i*4, ctx->H[i]);

  XCRYPT_SECURE_MEMSET (ctx, sizeof (struct sha256_ctx));
  return resbuf;
}


void
sha256_process_bytes (const void *buffer, size_t len, struct sha256_ctx *ctx)
{
  /* When we already have some bits in our internal buffer concatenate
     both inputs first.  */
  if (ctx->buflen != 0)
    {
      uint32_t left_over = ctx->buflen;
      uint32_t add = 128 - left_over > len ? (uint32_t)len : 128 - left_over;

      memcpy (&ctx->buffer[left_over], buffer, add);
      ctx->buflen += add;

      if (ctx->buflen > 64)
        {
          sha256_process_block (ctx->buffer, ctx->buflen & ~63u, ctx);

          ctx->buflen &= 63;
          /* The regions in the following copy operation cannot overlap.  */
          memcpy (ctx->buffer, &ctx->buffer[(left_over + add) & ~63u],
                  ctx->buflen);
        }

      buffer = (const char *) buffer + add;
      len -= add;
    }

  /* Process available complete blocks.  */
  if (len > 64)
    {
      sha256_process_block (buffer, len & ~63u, ctx);
      buffer = (const char *) buffer + (len & ~63u);
      len &= 63;
    }

  /* Move remaining bytes into internal buffer.  */
  if (len > 0)
    {
      size_t left_over = ctx->buflen;

      memcpy (&ctx->buffer[left_over], buffer, len);
      left_over += len;
      if (left_over >= 64)
        {
          sha256_process_block (ctx->buffer, 64, ctx);
          left_over -= 64;
          memcpy (ctx->buffer, &ctx->buffer[64], left_over);
        }
      ctx->buflen = (uint32_t)left_over;
    }
}

#endif