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, 2011 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 #  define SWAP64(n) bswap_64 (n)
  38 # else
  39 #  define SWAP(n) \
  40     (((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
  41 #  define SWAP64(n) \
  42   (((n) << 56)                                  \
  43    | (((n) & 0xff00) << 40)                     \
  44    | (((n) & 0xff0000) << 24)                   \
  45    | (((n) & 0xff000000) << 8)                  \
  46    | (((n) >> 8) & 0xff000000)                  \
  47    | (((n) >> 24) & 0xff0000)                   \
  48    | (((n) >> 40) & 0xff00)                     \
  49    | ((n) >> 56))
  50 # endif
  51 #else
  52 # define SWAP(n) (n)
  53 # define SWAP64(n) (n)
  54 #endif
  55
  56
  57 /* This array contains the bytes used to pad the buffer to the next
  58    64-byte boundary.  (FIPS 180-2:5.1.1)  */
  59 static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ...  */ };
  60
  61
  62 /* Constants for SHA256 from FIPS 180-2:4.2.2.  */
  63 static const uint32_t K[64] =
  64   {
  65     0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
  66     0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
  67     0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
  68     0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
  69     0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
  70     0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
  71     0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
  72     0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
  73     0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
  74     0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
  75     0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
  76     0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
  77     0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
  78     0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
  79     0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
  80     0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
  81   };
  82
  83
  84 /* Process LEN bytes of BUFFER, accumulating context into CTX.
  85    It is assumed that LEN % 64 == 0.  */
  86 static void
  87 sha256_process_block (const void *buffer, size_t len, struct sha256_ctx *ctx)
  88 {
  89   const uint32_t *words = buffer;
  90   size_t nwords = len / sizeof (uint32_t);
  91   uint32_t a = ctx->H[0];
  92   uint32_t b = ctx->H[1];
  93   uint32_t c = ctx->H[2];
  94   uint32_t d = ctx->H[3];
  95   uint32_t e = ctx->H[4];
  96   uint32_t f = ctx->H[5];
  97   uint32_t g = ctx->H[6];
  98   uint32_t h = ctx->H[7];
  99
 100   /* First increment the byte count.  FIPS 180-2 specifies the possible
 101      length of the file up to 2^64 bits.  Here we only compute the
 102      number of bytes.  */
 103   ctx->total64 += len;
 104
 105   /* Process all bytes in the buffer with 64 bytes in each round of
 106      the loop.  */
 107   while (nwords > 0)
 108     {
 109       uint32_t W[64];
 110       uint32_t a_save = a;
 111       uint32_t b_save = b;
 112       uint32_t c_save = c;
 113       uint32_t d_save = d;
 114       uint32_t e_save = e;
 115       uint32_t f_save = f;
 116       uint32_t g_save = g;
 117       uint32_t h_save = h;
 118
 119       /* Operators defined in FIPS 180-2:4.1.2.  */
 120 #define Ch(x, y, z) ((x & y) ^ (~x & z))
 121 #define Maj(x, y, z) ((x & y) ^ (x & z) ^ (y & z))
 122 #define S0(x) (CYCLIC (x, 2) ^ CYCLIC (x, 13) ^ CYCLIC (x, 22))
 123 #define S1(x) (CYCLIC (x, 6) ^ CYCLIC (x, 11) ^ CYCLIC (x, 25))
 124 #define R0(x) (CYCLIC (x, 7) ^ CYCLIC (x, 18) ^ (x >> 3))
 125 #define R1(x) (CYCLIC (x, 17) ^ CYCLIC (x, 19) ^ (x >> 10))
 126
 127       /* It is unfortunate that C does not provide an operator for
 128          cyclic rotation.  Hope the C compiler is smart enough.  */
 129 #define CYCLIC(w, s) ((w >> s) | (w << (32 - s)))
 130
 131       /* Compute the message schedule according to FIPS 180-2:6.2.2 step 2.  */
 132       for (unsigned int t = 0; t < 16; ++t)
 133         {
 134           W[t] = SWAP (*words);
 135           ++words;
 136         }
 137       for (unsigned int t = 16; t < 64; ++t)
 138         W[t] = R1 (W[t - 2]) + W[t - 7] + R0 (W[t - 15]) + W[t - 16];
 139
 140       /* The actual computation according to FIPS 180-2:6.2.2 step 3.  */
 141       for (unsigned int t = 0; t < 64; ++t)
 142         {
 143           uint32_t T1 = h + S1 (e) + Ch (e, f, g) + K[t] + W[t];
 144           uint32_t T2 = S0 (a) + Maj (a, b, c);
 145           h = g;
 146           g = f;
 147           f = e;
 148           e = d + T1;
 149           d = c;
 150           c = b;
 151           b = a;
 152           a = T1 + T2;
 153         }
 154
 155       /* Add the starting values of the context according to FIPS 180-2:6.2.2
 156          step 4.  */
 157       a += a_save;
 158       b += b_save;
 159       c += c_save;
 160       d += d_save;
 161       e += e_save;
 162       f += f_save;
 163       g += g_save;
 164       h += h_save;
 165
 166       /* Prepare for the next round.  */
 167       nwords -= 16;
 168     }
 169
 170   /* Put checksum in context given as argument.  */
 171   ctx->H[0] = a;
 172   ctx->H[1] = b;
 173   ctx->H[2] = c;
 174   ctx->H[3] = d;
 175   ctx->H[4] = e;
 176   ctx->H[5] = f;
 177   ctx->H[6] = g;
 178   ctx->H[7] = h;
 179 }
 180
 181
 182 /* Initialize structure containing state of computation.
 183    (FIPS 180-2:5.3.2)  */
 184 void
 185 __sha256_init_ctx (ctx)
 186      struct sha256_ctx *ctx;
 187 {
 188   ctx->H[0] = 0x6a09e667;
 189   ctx->H[1] = 0xbb67ae85;
 190   ctx->H[2] = 0x3c6ef372;
 191   ctx->H[3] = 0xa54ff53a;
 192   ctx->H[4] = 0x510e527f;
 193   ctx->H[5] = 0x9b05688c;
 194   ctx->H[6] = 0x1f83d9ab;
 195   ctx->H[7] = 0x5be0cd19;
 196
 197   ctx->total64 = 0;
 198   ctx->buflen = 0;
 199 }
 200
 201
 202 /* Process the remaining bytes in the internal buffer and the usual
 203    prolog according to the standard and write the result to RESBUF.
 204
 205    IMPORTANT: On some systems it is required that RESBUF is correctly
 206    aligned for a 32 bits value.  */
 207 void *
 208 __sha256_finish_ctx (ctx, resbuf)
 209      struct sha256_ctx *ctx;
 210      void *resbuf;
 211 {
 212   /* Take yet unprocessed bytes into account.  */
 213   uint32_t bytes = ctx->buflen;
 214   size_t pad;
 215
 216   /* Now count remaining bytes.  */
 217   ctx->total64 += bytes;
 218
 219   pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
 220   memcpy (&ctx->buffer[bytes], fillbuf, pad);
 221
 222   /* Put the 64-bit file length in *bits* at the end of the buffer.  */
 223 #ifdef _STRING_ARCH_unaligned
 224   ctx->buffer64[(bytes + pad) / 8] = SWAP64 (ctx->total64 << 3);
 225 #else
 226   ctx->buffer32[(bytes + pad + 4) / 4] = SWAP (ctx->total[TOTAL64_low] << 3);
 227   ctx->buffer32[(bytes + pad) / 4] = SWAP ((ctx->total[TOTAL64_high] << 3) |
 228                                            (ctx->total[TOTAL64_low] >> 29));
 229 #endif
 230
 231   /* Process last bytes.  */
 232   sha256_process_block (ctx->buffer, bytes + pad + 8, ctx);
 233
 234   /* Put result from CTX in first 32 bytes following RESBUF.  */
 235   for (unsigned int i = 0; i < 8; ++i)
 236     ((uint32_t *) resbuf)[i] = SWAP (ctx->H[i]);
 237
 238   return resbuf;
 239 }
 240
 241
 242 void
 243 __sha256_process_bytes (buffer, len, ctx)
 244      const void *buffer;
 245      size_t len;
 246      struct sha256_ctx *ctx;
 247 {
 248   /* When we already have some bits in our internal buffer concatenate
 249      both inputs first.  */
 250   if (ctx->buflen != 0)
 251     {
 252       size_t left_over = ctx->buflen;
 253       size_t add = 128 - left_over > len ? len : 128 - left_over;
 254
 255       memcpy (&ctx->buffer[left_over], buffer, add);
 256       ctx->buflen += add;
 257
 258       if (ctx->buflen > 64)
 259         {
 260           sha256_process_block (ctx->buffer, ctx->buflen & ~63, ctx);
 261
 262           ctx->buflen &= 63;
 263           /* The regions in the following copy operation cannot overlap.  */
 264           memcpy (ctx->buffer, &ctx->buffer[(left_over + add) & ~63],
 265                   ctx->buflen);
 266         }
 267
 268       buffer = (const char *) buffer + add;
 269       len -= add;
 270     }
 271
 272   /* Process available complete blocks.  */
 273   if (len >= 64)
 274     {
 275 #if !_STRING_ARCH_unaligned
 276 /* To check alignment gcc has an appropriate operator.  Other
 277    compilers don't.  */
 278 # if __GNUC__ >= 2
 279 #  define UNALIGNED_P(p) (((uintptr_t) p) % __alignof__ (uint32_t) != 0)
 280 # else
 281 #  define UNALIGNED_P(p) (((uintptr_t) p) % sizeof (uint32_t) != 0)
 282 # endif
 283       if (UNALIGNED_P (buffer))
 284         while (len > 64)
 285           {
 286             sha256_process_block (memcpy (ctx->buffer, buffer, 64), 64, ctx);
 287             buffer = (const char *) buffer + 64;
 288             len -= 64;
 289           }
 290       else
 291 #endif
 292         {
 293           sha256_process_block (buffer, len & ~63, ctx);
 294           buffer = (const char *) buffer + (len & ~63);
 295           len &= 63;
 296         }
 297     }
 298
 299   /* Move remaining bytes into internal buffer.  */
 300   if (len > 0)
 301     {
 302       size_t left_over = ctx->buflen;
 303
 304       memcpy (&ctx->buffer[left_over], buffer, len);
 305       left_over += len;
 306       if (left_over >= 64)
 307         {
 308           sha256_process_block (ctx->buffer, 64, ctx);
 309           left_over -= 64;
 310           memcpy (ctx->buffer, &ctx->buffer[64], left_over);
 311         }
 312       ctx->buflen = left_over;
 313     }
 314 }