crypt/sha256.c

   1 /* Functions to compute SHA256 message digest of files or memory blocks.
   2    according to the definition of SHA256 in FIPS 180-2.
   3    Copyright (C) 2007 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 /* Written by Ulrich Drepper <drepper@redhat.com>, 2007.  */
  22
  23 #ifdef HAVE_CONFIG_H
  24 # include <config.h>
  25 #endif
  26
  27 #include <endian.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include <sys/types.h>
  31
  32 #include "sha256.h"
  33
  34 #if __BYTE_ORDER == __LITTLE_ENDIAN
  35 # ifdef _LIBC
  36 #  include <byteswap.h>
  37 #  define SWAP(n) bswap_32 (n)
  38 # else
  39 #  define SWAP(n) \
  40     (((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
  41 # endif
  42 #else
  43 # define SWAP(n) (n)
  44 #endif
  45
  46
  47 /* This array contains the bytes used to pad the buffer to the next
  48    64-byte boundary.  (FIPS 180-2:5.1.1)  */
  49 static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ...  */ };
  50
  51
  52 /* Constants for SHA256 from FIPS 180-2:4.2.2.  */
  53 static const uint32_t K[64] =
  54   {
  55     0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
  56     0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
  57     0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
  58     0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
  59     0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
  60     0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
  61     0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
  62     0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
  63     0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
  64     0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
  65     0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
  66     0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
  67     0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
  68     0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
  69     0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
  70     0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
  71   };
  72
  73
  74 /* Process LEN bytes of BUFFER, accumulating context into CTX.
  75    It is assumed that LEN % 64 == 0.  */
  76 static void
  77 sha256_process_block (const void *buffer, size_t len, struct sha256_ctx *ctx)
  78 {
  79   const uint32_t *words = buffer;
  80   size_t nwords = len / sizeof (uint32_t);
  81   uint32_t a = ctx->H[0];
  82   uint32_t b = ctx->H[1];
  83   uint32_t c = ctx->H[2];
  84   uint32_t d = ctx->H[3];
  85   uint32_t e = ctx->H[4];
  86   uint32_t f = ctx->H[5];
  87   uint32_t g = ctx->H[6];
  88   uint32_t h = ctx->H[7];
  89
  90   /* First increment the byte count.  FIPS 180-2 specifies the possible
  91      length of the file up to 2^64 bits.  Here we only compute the
  92      number of bytes.  Do a double word increment.  */
  93   ctx->total[0] += len;
  94   if (ctx->total[0] < len)
  95     ++ctx->total[1];
  96
  97   /* Process all bytes in the buffer with 64 bytes in each round of
  98      the loop.  */
  99   while (nwords > 0)
 100     {
 101       uint32_t W[64];
 102       uint32_t a_save = a;
 103       uint32_t b_save = b;
 104       uint32_t c_save = c;
 105       uint32_t d_save = d;
 106       uint32_t e_save = e;
 107       uint32_t f_save = f;
 108       uint32_t g_save = g;
 109       uint32_t h_save = h;
 110
 111       /* Operators defined in FIPS 180-2:4.1.2.  */
 112 #define Ch(x, y, z) ((x & y) ^ (~x & z))
 113 #define Maj(x, y, z) ((x & y) ^ (x & z) ^ (y & z))
 114 #define S0(x) (CYCLIC (x, 2) ^ CYCLIC (x, 13) ^ CYCLIC (x, 22))
 115 #define S1(x) (CYCLIC (x, 6) ^ CYCLIC (x, 11) ^ CYCLIC (x, 25))
 116 #define R0(x) (CYCLIC (x, 7) ^ CYCLIC (x, 18) ^ (x >> 3))
 117 #define R1(x) (CYCLIC (x, 17) ^ CYCLIC (x, 19) ^ (x >> 10))
 118
 119       /* It is unfortunate that C does not provide an operator for
 120          cyclic rotation.  Hope the C compiler is smart enough.  */
 121 #define CYCLIC(w, s) ((w >> s) | (w << (32 - s)))
 122
 123       /* Compute the message schedule according to FIPS 180-2:6.2.2 step 2.  */
 124       for (unsigned int t = 0; t < 16; ++t)
 125         {
 126           W[t] = SWAP (*words);
 127           ++words;
 128         }
 129       for (unsigned int t = 16; t < 64; ++t)
 130         W[t] = R1 (W[t - 2]) + W[t - 7] + R0 (W[t - 15]) + W[t - 16];
 131
 132       /* The actual computation according to FIPS 180-2:6.2.2 step 3.  */
 133       for (unsigned int t = 0; t < 64; ++t)
 134         {
 135           uint32_t T1 = h + S1 (e) + Ch (e, f, g) + K[t] + W[t];
 136           uint32_t T2 = S0 (a) + Maj (a, b, c);
 137           h = g;
 138           g = f;
 139           f = e;
 140           e = d + T1;
 141           d = c;
 142           c = b;
 143           b = a;
 144           a = T1 + T2;
 145         }
 146
 147       /* Add the starting values of the context according to FIPS 180-2:6.2.2
 148          step 4.  */
 149       a += a_save;
 150       b += b_save;
 151       c += c_save;
 152       d += d_save;
 153       e += e_save;
 154       f += f_save;
 155       g += g_save;
 156       h += h_save;
 157
 158       /* Prepare for the next round.  */
 159       nwords -= 16;
 160     }
 161
 162   /* Put checksum in context given as argument.  */
 163   ctx->H[0] = a;
 164   ctx->H[1] = b;
 165   ctx->H[2] = c;
 166   ctx->H[3] = d;
 167   ctx->H[4] = e;
 168   ctx->H[5] = f;
 169   ctx->H[6] = g;
 170   ctx->H[7] = h;
 171 }
 172
 173
 174 /* Initialize structure containing state of computation.
 175    (FIPS 180-2:5.3.2)  */
 176 void
 177 __sha256_init_ctx (ctx)
 178      struct sha256_ctx *ctx;
 179 {
 180   ctx->H[0] = 0x6a09e667;
 181   ctx->H[1] = 0xbb67ae85;
 182   ctx->H[2] = 0x3c6ef372;
 183   ctx->H[3] = 0xa54ff53a;
 184   ctx->H[4] = 0x510e527f;
 185   ctx->H[5] = 0x9b05688c;
 186   ctx->H[6] = 0x1f83d9ab;
 187   ctx->H[7] = 0x5be0cd19;
 188
 189   ctx->total[0] = ctx->total[1] = 0;
 190   ctx->buflen = 0;
 191 }
 192
 193
 194 /* Process the remaining bytes in the internal buffer and the usual
 195    prolog according to the standard and write the result to RESBUF.
 196
 197    IMPORTANT: On some systems it is required that RESBUF is correctly
 198    aligned for a 32 bits value.  */
 199 void *
 200 __sha256_finish_ctx (ctx, resbuf)
 201      struct sha256_ctx *ctx;
 202      void *resbuf;
 203 {
 204   /* Take yet unprocessed bytes into account.  */
 205   uint32_t bytes = ctx->buflen;
 206   size_t pad;
 207
 208   /* Now count remaining bytes.  */
 209   ctx->total[0] += bytes;
 210   if (ctx->total[0] < bytes)
 211     ++ctx->total[1];
 212
 213   pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
 214   memcpy (&ctx->buffer[bytes], fillbuf, pad);
 215
 216   /* Put the 64-bit file length in *bits* at the end of the buffer.  */
 217   *(uint32_t *) &ctx->buffer[bytes + pad + 4] = SWAP (ctx->total[0] << 3);
 218   *(uint32_t *) &ctx->buffer[bytes + pad] = SWAP ((ctx->total[1] << 3) |
 219                                                   (ctx->total[0] >> 29));
 220
 221   /* Process last bytes.  */
 222   sha256_process_block (ctx->buffer, bytes + pad + 8, ctx);
 223
 224   /* Put result from CTX in first 32 bytes following RESBUF.  */
 225   for (unsigned int i = 0; i < 8; ++i)
 226     ((uint32_t *) resbuf)[i] = SWAP (ctx->H[i]);
 227
 228   return resbuf;
 229 }
 230
 231
 232 void
 233 __sha256_process_bytes (buffer, len, ctx)
 234      const void *buffer;
 235      size_t len;
 236      struct sha256_ctx *ctx;
 237 {
 238   /* When we already have some bits in our internal buffer concatenate
 239      both inputs first.  */
 240   if (ctx->buflen != 0)
 241     {
 242       size_t left_over = ctx->buflen;
 243       size_t add = 128 - left_over > len ? len : 128 - left_over;
 244
 245       memcpy (&ctx->buffer[left_over], buffer, add);
 246       ctx->buflen += add;
 247
 248       if (ctx->buflen > 64)
 249         {
 250           sha256_process_block (ctx->buffer, ctx->buflen & ~63, ctx);
 251
 252           ctx->buflen &= 63;
 253           /* The regions in the following copy operation cannot overlap.  */
 254           memcpy (ctx->buffer, &ctx->buffer[(left_over + add) & ~63],
 255                   ctx->buflen);
 256         }
 257
 258       buffer = (const char *) buffer + add;
 259       len -= add;
 260     }
 261
 262   /* Process available complete blocks.  */
 263   if (len >= 64)
 264     {
 265 #if !_STRING_ARCH_unaligned
 266 /* To check alignment gcc has an appropriate operator.  Other
 267    compilers don't.  */
 268 # if __GNUC__ >= 2
 269 #  define UNALIGNED_P(p) (((uintptr_t) p) % __alignof__ (uint32_t) != 0)
 270 # else
 271 #  define UNALIGNED_P(p) (((uintptr_t) p) % sizeof (uint32_t) != 0)
 272 # endif
 273       if (UNALIGNED_P (buffer))
 274         while (len > 64)
 275           {
 276             sha256_process_block (memcpy (ctx->buffer, buffer, 64), 64, ctx);
 277             buffer = (const char *) buffer + 64;
 278             len -= 64;
 279           }
 280       else
 281 #endif
 282         {
 283           sha256_process_block (buffer, len & ~63, ctx);
 284           buffer = (const char *) buffer + (len & ~63);
 285           len &= 63;
 286         }
 287     }
 288
 289   /* Move remaining bytes into internal buffer.  */
 290   if (len > 0)
 291     {
 292       size_t left_over = ctx->buflen;
 293
 294       memcpy (&ctx->buffer[left_over], buffer, len);
 295       left_over += len;
 296       if (left_over >= 64)
 297         {
 298           sha256_process_block (ctx->buffer, 64, ctx);
 299           left_over -= 64;
 300           memcpy (ctx->buffer, &ctx->buffer[64], left_over);
 301         }
 302       ctx->buflen = left_over;
 303     }
 304 }