sha256.c

/* sha256.c - Functions to compute SHA256 and SHA224 message digest of files or
   memory blocks according to the NIST specification FIPS-180-2.

   Copyright (C) 2005-2006, 2008-2016 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* Written by David Madore, considerably copypasting from
   Scott G. Miller's sha1.c
*/

#include "sha256.h"

#include <stdalign.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#ifdef WORDS_BIGENDIAN
# define SWAP(n) (n)
#else
# define SWAP(n) \
    (((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
#endif

#define BLOCKSIZE 32768
#if BLOCKSIZE % 64 != 0
# error "invalid BLOCKSIZE"
#endif

/* This array contains the bytes used to pad the buffer to the next
   64-byte boundary.  */
static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ...  */ };


/*
  Takes a pointer to a 256 bit block of data (eight 32 bit ints) and
  initializes it to the start constants of the SHA256 algorithm.  This
  must be called before using hash in the call to sha256_hash
*/
void
sha256_init_ctx (struct sha256_ctx *ctx)
{
  ctx->state[0] = 0x6a09e667UL;
  ctx->state[1] = 0xbb67ae85UL;
  ctx->state[2] = 0x3c6ef372UL;
  ctx->state[3] = 0xa54ff53aUL;
  ctx->state[4] = 0x510e527fUL;
  ctx->state[5] = 0x9b05688cUL;
  ctx->state[6] = 0x1f83d9abUL;
  ctx->state[7] = 0x5be0cd19UL;

  ctx->total[0] = ctx->total[1] = 0;
  ctx->buflen = 0;
}

void
sha224_init_ctx (struct sha256_ctx *ctx)
{
  ctx->state[0] = 0xc1059ed8UL;
  ctx->state[1] = 0x367cd507UL;
  ctx->state[2] = 0x3070dd17UL;
  ctx->state[3] = 0xf70e5939UL;
  ctx->state[4] = 0xffc00b31UL;
  ctx->state[5] = 0x68581511UL;
  ctx->state[6] = 0x64f98fa7UL;
  ctx->state[7] = 0xbefa4fa4UL;

  ctx->total[0] = ctx->total[1] = 0;
  ctx->buflen = 0;
}

/* Copy the value from v into the memory location pointed to by *cp,
   If your architecture allows unaligned access this is equivalent to
   * (uint32_t *) cp = v  */
static void
set_uint32 (char *cp, uint32_t v)
{
  memcpy (cp, &v, sizeof v);
}

/* Put result from CTX in first 32 bytes following RESBUF.  The result
   must be in little endian byte order.  */
void *
sha256_read_ctx (const struct sha256_ctx *ctx, void *resbuf)
{
  int i;
  char *r = resbuf;

  for (i = 0; i < 8; i++)
    set_uint32 (r + i * sizeof ctx->state[0], SWAP (ctx->state[i]));

  return resbuf;
}

void *
sha224_read_ctx (const struct sha256_ctx *ctx, void *resbuf)
{
  int i;
  char *r = resbuf;

  for (i = 0; i < 7; i++)
    set_uint32 (r + i * sizeof ctx->state[0], SWAP (ctx->state[i]));

  return resbuf;
}

/* Process the remaining bytes in the internal buffer and the usual
   prolog according to the standard and write the result to RESBUF.  */
static void
sha256_conclude_ctx (struct sha256_ctx *ctx)
{
  /* Take yet unprocessed bytes into account.  */
  size_t bytes = ctx->buflen;
  size_t size = (bytes < 56) ? 64 / 4 : 64 * 2 / 4;

  /* Now count remaining bytes.  */
  ctx->total[0] += bytes;
  if (ctx->total[0] < bytes)
    ++ctx->total[1];

  /* Put the 64-bit file length in *bits* at the end of the buffer.
     Use set_uint32 rather than a simple assignment, to avoid risk of
     unaligned access.  */
  set_uint32 ((char *) &ctx->buffer[size - 2],
              SWAP ((ctx->total[1] << 3) | (ctx->total[0] >> 29)));
  set_uint32 ((char *) &ctx->buffer[size - 1],
              SWAP (ctx->total[0] << 3));

  memcpy (&((char *) ctx->buffer)[bytes], fillbuf, (size - 2) * 4 - bytes);

  /* Process last bytes.  */
  sha256_process_block (ctx->buffer, size * 4, ctx);
}

void *
sha256_finish_ctx (struct sha256_ctx *ctx, void *resbuf)
{
  sha256_conclude_ctx (ctx);
  return sha256_read_ctx (ctx, resbuf);
}

void *
sha224_finish_ctx (struct sha256_ctx *ctx, void *resbuf)
{
  sha256_conclude_ctx (ctx);
  return sha224_read_ctx (ctx, resbuf);
}

/* Compute SHA256 message digest for bytes read from STREAM.  The
   resulting message digest number will be written into the 32 bytes
   beginning at RESBLOCK.  */
int
sha256_stream (FILE *stream, void *resblock)
{
  struct sha256_ctx ctx;
  size_t sum;

  char *buffer = malloc (BLOCKSIZE + 72);
  if (!buffer)
    return 1;

  /* Initialize the computation context.  */
  sha256_init_ctx (&ctx);

  /* Iterate over full file contents.  */
  while (1)
    {
      /* We read the file in blocks of BLOCKSIZE bytes.  One call of the
         computation function processes the whole buffer so that with the
         next round of the loop another block can be read.  */
      size_t n;
      sum = 0;

      /* Read block.  Take care for partial reads.  */
      while (1)
        {
          n = fread (buffer + sum, 1, BLOCKSIZE - sum, stream);

          sum += n;

          if (sum == BLOCKSIZE)
            break;

          if (n == 0)
            {
              /* Check for the error flag IFF N == 0, so that we don't
                 exit the loop after a partial read due to e.g., EAGAIN
                 or EWOULDBLOCK.  */
              if (ferror (stream))
                {
                  free (buffer);
                  return 1;
                }
              goto process_partial_block;
            }

          /* We've read at least one byte, so ignore errors.  But always
             check for EOF, since feof may be true even though N > 0.
             Otherwise, we could end up calling fread after EOF.  */
          if (feof (stream))
            goto process_partial_block;
        }

      /* Process buffer with BLOCKSIZE bytes.  Note that
                        BLOCKSIZE % 64 == 0
       */
      sha256_process_block (buffer, BLOCKSIZE, &ctx);
    }

 process_partial_block:;

  /* Process any remaining bytes.  */
  if (sum > 0)
    sha256_process_bytes (buffer, sum, &ctx);

  /* Construct result in desired memory.  */
  sha256_finish_ctx (&ctx, resblock);
  free (buffer);
  return 0;
}

/* FIXME: Avoid code duplication */
int
sha224_stream (FILE *stream, void *resblock)
{
  struct sha256_ctx ctx;
  size_t sum;

  char *buffer = malloc (BLOCKSIZE + 72);
  if (!buffer)
    return 1;

  /* Initialize the computation context.  */
  sha224_init_ctx (&ctx);

  /* Iterate over full file contents.  */
  while (1)
    {
      /* We read the file in blocks of BLOCKSIZE bytes.  One call of the
         computation function processes the whole buffer so that with the
         next round of the loop another block can be read.  */
      size_t n;
      sum = 0;

      /* Read block.  Take care for partial reads.  */
      while (1)
        {
          n = fread (buffer + sum, 1, BLOCKSIZE - sum, stream);

          sum += n;

          if (sum == BLOCKSIZE)
            break;

          if (n == 0)
            {
              /* Check for the error flag IFF N == 0, so that we don't
                 exit the loop after a partial read due to e.g., EAGAIN
                 or EWOULDBLOCK.  */
              if (ferror (stream))
                {
                  free (buffer);
                  return 1;
                }
              goto process_partial_block;
            }

          /* We've read at least one byte, so ignore errors.  But always
             check for EOF, since feof may be true even though N > 0.
             Otherwise, we could end up calling fread after EOF.  */
          if (feof (stream))
            goto process_partial_block;
        }

      /* Process buffer with BLOCKSIZE bytes.  Note that
                        BLOCKSIZE % 64 == 0
       */
      sha256_process_block (buffer, BLOCKSIZE, &ctx);
    }

 process_partial_block:;

  /* Process any remaining bytes.  */
  if (sum > 0)
    sha256_process_bytes (buffer, sum, &ctx);

  /* Construct result in desired memory.  */
  sha224_finish_ctx (&ctx, resblock);
  free (buffer);
  return 0;
}

/* Compute SHA512 message digest for LEN bytes beginning at BUFFER.  The
   result is always in little endian byte order, so that a byte-wise
   output yields to the wanted ASCII representation of the message
   digest.  */
void *
sha256_buffer (const char *buffer, size_t len, void *resblock)
{
  struct sha256_ctx ctx;

  /* Initialize the computation context.  */
  sha256_init_ctx (&ctx);

  /* Process whole buffer but last len % 64 bytes.  */
  sha256_process_bytes (buffer, len, &ctx);

  /* Put result in desired memory area.  */
  return sha256_finish_ctx (&ctx, resblock);
}

void *
sha224_buffer (const char *buffer, size_t len, void *resblock)
{
  struct sha256_ctx ctx;

  /* Initialize the computation context.  */
  sha224_init_ctx (&ctx);

  /* Process whole buffer but last len % 64 bytes.  */
  sha256_process_bytes (buffer, len, &ctx);

  /* Put result in desired memory area.  */
  return sha224_finish_ctx (&ctx, resblock);
}

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)
    {
      size_t left_over = ctx->buflen;
      size_t add = 128 - left_over > len ? len : 128 - left_over;

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

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

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

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

  /* Process available complete blocks.  */
  if (len >= 64)
    {
#if !_STRING_ARCH_unaligned
# define UNALIGNED_P(p) ((uintptr_t) (p) % alignof (uint32_t) != 0)
      if (UNALIGNED_P (buffer))
        while (len > 64)
          {
            sha256_process_block (memcpy (ctx->buffer, buffer, 64), 64, ctx);
            buffer = (const char *) buffer + 64;
            len -= 64;
          }
      else
#endif
        {
          sha256_process_block (buffer, len & ~63, ctx);
          buffer = (const char *) buffer + (len & ~63);
          len &= 63;
        }
    }

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

      memcpy (&((char *) 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[16], left_over);
        }
      ctx->buflen = left_over;
    }
}

/* --- Code below is the primary difference between sha1.c and sha256.c --- */

/* SHA256 round constants */
#define K(I) sha256_round_constants[I]
static const uint32_t sha256_round_constants[64] = {
  0x428a2f98UL, 0x71374491UL, 0xb5c0fbcfUL, 0xe9b5dba5UL,
  0x3956c25bUL, 0x59f111f1UL, 0x923f82a4UL, 0xab1c5ed5UL,
  0xd807aa98UL, 0x12835b01UL, 0x243185beUL, 0x550c7dc3UL,
  0x72be5d74UL, 0x80deb1feUL, 0x9bdc06a7UL, 0xc19bf174UL,
  0xe49b69c1UL, 0xefbe4786UL, 0x0fc19dc6UL, 0x240ca1ccUL,
  0x2de92c6fUL, 0x4a7484aaUL, 0x5cb0a9dcUL, 0x76f988daUL,
  0x983e5152UL, 0xa831c66dUL, 0xb00327c8UL, 0xbf597fc7UL,
  0xc6e00bf3UL, 0xd5a79147UL, 0x06ca6351UL, 0x14292967UL,
  0x27b70a85UL, 0x2e1b2138UL, 0x4d2c6dfcUL, 0x53380d13UL,
  0x650a7354UL, 0x766a0abbUL, 0x81c2c92eUL, 0x92722c85UL,
  0xa2bfe8a1UL, 0xa81a664bUL, 0xc24b8b70UL, 0xc76c51a3UL,
  0xd192e819UL, 0xd6990624UL, 0xf40e3585UL, 0x106aa070UL,
  0x19a4c116UL, 0x1e376c08UL, 0x2748774cUL, 0x34b0bcb5UL,
  0x391c0cb3UL, 0x4ed8aa4aUL, 0x5b9cca4fUL, 0x682e6ff3UL,
  0x748f82eeUL, 0x78a5636fUL, 0x84c87814UL, 0x8cc70208UL,
  0x90befffaUL, 0xa4506cebUL, 0xbef9a3f7UL, 0xc67178f2UL,
};

/* Round functions.  */
#define F2(A,B,C) ( ( A & B ) | ( C & ( A | B ) ) )
#define F1(E,F,G) ( G ^ ( E & ( F ^ G ) ) )

/* Process LEN bytes of BUFFER, accumulating context into CTX.
   It is assumed that LEN % 64 == 0.
   Most of this code comes from GnuPG's cipher/sha1.c.  */

void
sha256_process_block (const void *buffer, size_t len, struct sha256_ctx *ctx)
{
  const uint32_t *words = buffer;
  size_t nwords = len / sizeof (uint32_t);
  const uint32_t *endp = words + nwords;
  uint32_t x[16];
  uint32_t a = ctx->state[0];
  uint32_t b = ctx->state[1];
  uint32_t c = ctx->state[2];
  uint32_t d = ctx->state[3];
  uint32_t e = ctx->state[4];
  uint32_t f = ctx->state[5];
  uint32_t g = ctx->state[6];
  uint32_t h = ctx->state[7];
  uint32_t lolen = len;

  /* First increment the byte count.  FIPS PUB 180-2 specifies the possible
     length of the file up to 2^64 bits.  Here we only compute the
     number of bytes.  Do a double word increment.  */
  ctx->total[0] += lolen;
  ctx->total[1] += (len >> 31 >> 1) + (ctx->total[0] < lolen);

#define rol(x, n) (((x) << (n)) | ((x) >> (32 - (n))))
#define S0(x) (rol(x,25)^rol(x,14)^(x>>3))
#define S1(x) (rol(x,15)^rol(x,13)^(x>>10))
#define SS0(x) (rol(x,30)^rol(x,19)^rol(x,10))
#define SS1(x) (rol(x,26)^rol(x,21)^rol(x,7))

#define M(I) ( tm =   S1(x[(I-2)&0x0f]) + x[(I-7)&0x0f] \
                    + S0(x[(I-15)&0x0f]) + x[I&0x0f]    \
               , x[I&0x0f] = tm )

#define R(A,B,C,D,E,F,G,H,K,M)  do { t0 = SS0(A) + F2(A,B,C); \
                                     t1 = H + SS1(E)  \
                                      + F1(E,F,G)     \
                                      + K             \
                                      + M;            \
                                     D += t1;  H = t0 + t1; \
                               } while(0)

  while (words < endp)
    {
      uint32_t tm;
      uint32_t t0, t1;
      int t;
      /* FIXME: see sha1.c for a better implementation.  */
      for (t = 0; t < 16; t++)
        {
          x[t] = SWAP (*words);
          words++;
        }

      R( a, b, c, d, e, f, g, h, K( 0), x[ 0] );
      R( h, a, b, c, d, e, f, g, K( 1), x[ 1] );
      R( g, h, a, b, c, d, e, f, K( 2), x[ 2] );
      R( f, g, h, a, b, c, d, e, K( 3), x[ 3] );
      R( e, f, g, h, a, b, c, d, K( 4), x[ 4] );
      R( d, e, f, g, h, a, b, c, K( 5), x[ 5] );
      R( c, d, e, f, g, h, a, b, K( 6), x[ 6] );
      R( b, c, d, e, f, g, h, a, K( 7), x[ 7] );
      R( a, b, c, d, e, f, g, h, K( 8), x[ 8] );
      R( h, a, b, c, d, e, f, g, K( 9), x[ 9] );
      R( g, h, a, b, c, d, e, f, K(10), x[10] );
      R( f, g, h, a, b, c, d, e, K(11), x[11] );
      R( e, f, g, h, a, b, c, d, K(12), x[12] );
      R( d, e, f, g, h, a, b, c, K(13), x[13] );
      R( c, d, e, f, g, h, a, b, K(14), x[14] );
      R( b, c, d, e, f, g, h, a, K(15), x[15] );
      R( a, b, c, d, e, f, g, h, K(16), M(16) );
      R( h, a, b, c, d, e, f, g, K(17), M(17) );
      R( g, h, a, b, c, d, e, f, K(18), M(18) );
      R( f, g, h, a, b, c, d, e, K(19), M(19) );
      R( e, f, g, h, a, b, c, d, K(20), M(20) );
      R( d, e, f, g, h, a, b, c, K(21), M(21) );
      R( c, d, e, f, g, h, a, b, K(22), M(22) );
      R( b, c, d, e, f, g, h, a, K(23), M(23) );
      R( a, b, c, d, e, f, g, h, K(24), M(24) );
      R( h, a, b, c, d, e, f, g, K(25), M(25) );
      R( g, h, a, b, c, d, e, f, K(26), M(26) );
      R( f, g, h, a, b, c, d, e, K(27), M(27) );
      R( e, f, g, h, a, b, c, d, K(28), M(28) );
      R( d, e, f, g, h, a, b, c, K(29), M(29) );
      R( c, d, e, f, g, h, a, b, K(30), M(30) );
      R( b, c, d, e, f, g, h, a, K(31), M(31) );
      R( a, b, c, d, e, f, g, h, K(32), M(32) );
      R( h, a, b, c, d, e, f, g, K(33), M(33) );
      R( g, h, a, b, c, d, e, f, K(34), M(34) );
      R( f, g, h, a, b, c, d, e, K(35), M(35) );
      R( e, f, g, h, a, b, c, d, K(36), M(36) );
      R( d, e, f, g, h, a, b, c, K(37), M(37) );
      R( c, d, e, f, g, h, a, b, K(38), M(38) );
      R( b, c, d, e, f, g, h, a, K(39), M(39) );
      R( a, b, c, d, e, f, g, h, K(40), M(40) );
      R( h, a, b, c, d, e, f, g, K(41), M(41) );
      R( g, h, a, b, c, d, e, f, K(42), M(42) );
      R( f, g, h, a, b, c, d, e, K(43), M(43) );
      R( e, f, g, h, a, b, c, d, K(44), M(44) );
      R( d, e, f, g, h, a, b, c, K(45), M(45) );
      R( c, d, e, f, g, h, a, b, K(46), M(46) );
      R( b, c, d, e, f, g, h, a, K(47), M(47) );
      R( a, b, c, d, e, f, g, h, K(48), M(48) );
      R( h, a, b, c, d, e, f, g, K(49), M(49) );
      R( g, h, a, b, c, d, e, f, K(50), M(50) );
      R( f, g, h, a, b, c, d, e, K(51), M(51) );
      R( e, f, g, h, a, b, c, d, K(52), M(52) );
      R( d, e, f, g, h, a, b, c, K(53), M(53) );
      R( c, d, e, f, g, h, a, b, K(54), M(54) );
      R( b, c, d, e, f, g, h, a, K(55), M(55) );
      R( a, b, c, d, e, f, g, h, K(56), M(56) );
      R( h, a, b, c, d, e, f, g, K(57), M(57) );
      R( g, h, a, b, c, d, e, f, K(58), M(58) );
      R( f, g, h, a, b, c, d, e, K(59), M(59) );
      R( e, f, g, h, a, b, c, d, K(60), M(60) );
      R( d, e, f, g, h, a, b, c, K(61), M(61) );
      R( c, d, e, f, g, h, a, b, K(62), M(62) );
      R( b, c, d, e, f, g, h, a, K(63), M(63) );

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