libcrypt/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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 /* Written by Ulrich Drepper <drepper@redhat.com>, 2007.  */
  21
  22 #ifdef HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 #include <endian.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <sys/types.h>
  30
  31 #include "sha256.h"
  32
  33 #if __BYTE_ORDER == __LITTLE_ENDIAN
  34 # ifdef _LIBC
  35 #  include <byteswap.h>
  36 #  define SWAP(n) bswap_32 (n)
  37 # else
  38 #  define SWAP(n) \
  39     (((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
  40 # endif
  41 #else
  42 # define SWAP(n) (n)
  43 #endif
  44
  45
  46 /* This array contains the bytes used to pad the buffer to the next
  47    64-byte boundary.  (FIPS 180-2:5.1.1)  */
  48 static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ...  */ };
  49
  50
  51 /* Constants for SHA256 from FIPS 180-2:4.2.2.  */
  52 static const uint32_t K[64] =
  53   {
  54     0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
  55     0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
  56     0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
  57     0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
  58     0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
  59     0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
  60     0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
  61     0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
  62     0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
  63     0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
  64     0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
  65     0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
  66     0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
  67     0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
  68     0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
  69     0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
  70   };
  71
  72
  73 /* Process LEN bytes of BUFFER, accumulating context into CTX.
  74    It is assumed that LEN % 64 == 0.  */
  75 static void
  76 sha256_process_block (const void *buffer, size_t len, struct sha256_ctx *ctx)
  77 {
  78   const uint32_t *words = buffer;
  79   size_t nwords = len / sizeof (uint32_t);
  80   uint32_t a = ctx->H[0];
  81   uint32_t b = ctx->H[1];
  82   uint32_t c = ctx->H[2];
  83   uint32_t d = ctx->H[3];
  84   uint32_t e = ctx->H[4];
  85   uint32_t f = ctx->H[5];
  86   uint32_t g = ctx->H[6];
  87   uint32_t h = ctx->H[7];
  88
  89   /* First increment the byte count.  FIPS 180-2 specifies the possible
  90      length of the file up to 2^64 bits.  Here we only compute the
  91      number of bytes.  Do a double word increment.  */
  92   ctx->total[0] += len;
  93   if (ctx->total[0] < len)
  94     ++ctx->total[1];
  95
  96   /* Process all bytes in the buffer with 64 bytes in each round of
  97      the loop.  */
  98   while (nwords > 0)
  99     {
 100       uint32_t W[64];
 101       uint32_t a_save = a;
 102       uint32_t b_save = b;
 103       uint32_t c_save = c;
 104       uint32_t d_save = d;
 105       uint32_t e_save = e;
 106       uint32_t f_save = f;
 107       uint32_t g_save = g;
 108       uint32_t h_save = h;
 109
 110       /* Operators defined in FIPS 180-2:4.1.2.  */
 111 #define _Ch(x, y, z) ((x & y) ^ (~x & z))
 112 #define _Maj(x, y, z) ((x & y) ^ (x & z) ^ (y & z))
 113 #define _S0(x) (CYCLIC (x, 2) ^ CYCLIC (x, 13) ^ CYCLIC (x, 22))
 114 #define _S1(x) (CYCLIC (x, 6) ^ CYCLIC (x, 11) ^ CYCLIC (x, 25))
 115 #define _R0(x) (CYCLIC (x, 7) ^ CYCLIC (x, 18) ^ (x >> 3))
 116 #define _R1(x) (CYCLIC (x, 17) ^ CYCLIC (x, 19) ^ (x >> 10))
 117
 118       /* It is unfortunate that C does not provide an operator for
 119          cyclic rotation.  Hope the C compiler is smart enough.  */
 120 #define CYCLIC(w, s) ((w >> s) | (w << (32 - s)))
 121
 122       /* Compute the message schedule according to FIPS 180-2:6.2.2 step 2.  */
 123       for (unsigned int t = 0; t < 16; ++t)
 124         {
 125           W[t] = SWAP (*words);
 126           ++words;
 127         }
 128       for (unsigned int t = 16; t < 64; ++t)
 129         W[t] = _R1 (W[t - 2]) + W[t - 7] + _R0 (W[t - 15]) + W[t - 16];
 130
 131       /* The actual computation according to FIPS 180-2:6.2.2 step 3.  */
 132       for (unsigned int t = 0; t < 64; ++t)
 133         {
 134           uint32_t T1 = h + _S1 (e) + _Ch (e, f, g) + K[t] + W[t];
 135           uint32_t T2 = _S0 (a) + _Maj (a, b, c);
 136           h = g;
 137           g = f;
 138           f = e;
 139           e = d + T1;
 140           d = c;
 141           c = b;
 142           b = a;
 143           a = T1 + T2;
 144         }
 145
 146       /* Add the starting values of the context according to FIPS 180-2:6.2.2
 147          step 4.  */
 148       a += a_save;
 149       b += b_save;
 150       c += c_save;
 151       d += d_save;
 152       e += e_save;
 153       f += f_save;
 154       g += g_save;
 155       h += h_save;
 156
 157       /* Prepare for the next round.  */
 158       nwords -= 16;
 159     }
 160
 161   /* Put checksum in context given as argument.  */
 162   ctx->H[0] = a;
 163   ctx->H[1] = b;
 164   ctx->H[2] = c;
 165   ctx->H[3] = d;
 166   ctx->H[4] = e;
 167   ctx->H[5] = f;
 168   ctx->H[6] = g;
 169   ctx->H[7] = h;
 170 }
 171
 172
 173 /* Initialize structure containing state of computation.
 174    (FIPS 180-2:5.3.2)  */
 175 void
 176 __sha256_init_ctx (struct sha256_ctx *ctx)
 177 {
 178   ctx->H[0] = 0x6a09e667;
 179   ctx->H[1] = 0xbb67ae85;
 180   ctx->H[2] = 0x3c6ef372;
 181   ctx->H[3] = 0xa54ff53a;
 182   ctx->H[4] = 0x510e527f;
 183   ctx->H[5] = 0x9b05688c;
 184   ctx->H[6] = 0x1f83d9ab;
 185   ctx->H[7] = 0x5be0cd19;
 186
 187   ctx->total[0] = ctx->total[1] = 0;
 188   ctx->buflen = 0;
 189 }
 190
 191
 192 /* Process the remaining bytes in the internal buffer and the usual
 193    prolog according to the standard and write the result to RESBUF.
 194
 195    IMPORTANT: On some systems it is required that RESBUF is correctly
 196    aligned for a 32 bits value.  */
 197 void *
 198 __sha256_finish_ctx (struct sha256_ctx *ctx, void *resbuf)
 199 {
 200   /* Take yet unprocessed bytes into account.  */
 201   uint32_t bytes = ctx->buflen;
 202   size_t pad;
 203
 204   /* Now count remaining bytes.  */
 205   ctx->total[0] += bytes;
 206   if (ctx->total[0] < bytes)
 207     ++ctx->total[1];
 208
 209   pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
 210   memcpy (&ctx->buffer[bytes], fillbuf, pad);
 211
 212   /* Put the 64-bit file length in *bits* at the end of the buffer.  */
 213   *(uint32_t *) &ctx->buffer[bytes + pad + 4] = SWAP (ctx->total[0] << 3);
 214   *(uint32_t *) &ctx->buffer[bytes + pad] = SWAP ((ctx->total[1] << 3) |
 215                                                   (ctx->total[0] >> 29));
 216
 217   /* Process last bytes.  */
 218   sha256_process_block (ctx->buffer, bytes + pad + 8, ctx);
 219
 220   /* Put result from CTX in first 32 bytes following RESBUF.  */
 221   for (unsigned int i = 0; i < 8; ++i)
 222     ((uint32_t *) resbuf)[i] = SWAP (ctx->H[i]);
 223
 224   return resbuf;
 225 }
 226
 227
 228 void
 229 __sha256_process_bytes (const void *buffer, size_t len, struct sha256_ctx *ctx)
 230 {
 231   /* When we already have some bits in our internal buffer concatenate
 232      both inputs first.  */
 233   if (ctx->buflen != 0)
 234     {
 235       size_t left_over = ctx->buflen;
 236       size_t add = 128 - left_over > len ? len : 128 - left_over;
 237
 238       memcpy (&ctx->buffer[left_over], buffer, add);
 239       ctx->buflen += add;
 240
 241       if (ctx->buflen > 64)
 242         {
 243           sha256_process_block (ctx->buffer, ctx->buflen & ~63, ctx);
 244
 245           ctx->buflen &= 63;
 246           /* The regions in the following copy operation cannot overlap.  */
 247           memcpy (ctx->buffer, &ctx->buffer[(left_over + add) & ~63],
 248                   ctx->buflen);
 249         }
 250
 251       buffer = (const char *) buffer + add;
 252       len -= add;
 253     }
 254
 255   /* Process available complete blocks.  */
 256   if (len >= 64)
 257     {
 258 #if __GNUC__ >= 2
 259 # define UNALIGNED_P(p) (((uintptr_t) p) % __alignof__ (uint32_t) != 0)
 260 #else
 261 # define UNALIGNED_P(p) (((uintptr_t) p) % sizeof (uint32_t) != 0)
 262 #endif
 263       if (UNALIGNED_P (buffer))
 264         while (len > 64)
 265           {
 266             sha256_process_block (memcpy (ctx->buffer, buffer, 64), 64, ctx);
 267             buffer = (const char *) buffer + 64;
 268             len -= 64;
 269           }
 270       else
 271         {
 272           sha256_process_block (buffer, len & ~63, ctx);
 273           buffer = (const char *) buffer + (len & ~63);
 274           len &= 63;
 275         }
 276     }
 277
 278   /* Move remaining bytes into internal buffer.  */
 279   if (len > 0)
 280     {
 281       size_t left_over = ctx->buflen;
 282
 283       memcpy (&ctx->buffer[left_over], buffer, len);
 284       left_over += len;
 285       if (left_over >= 64)
 286         {
 287           sha256_process_block (ctx->buffer, 64, ctx);
 288           left_over -= 64;
 289           memcpy (ctx->buffer, &ctx->buffer[64], left_over);
 290         }
 291       ctx->buflen = left_over;
 292     }
 293 }