src/md5.c

   1 /* Functions to compute MD5 message digest of files or memory blocks.
   2    according to the definition of MD5 in RFC 1321 from April 1992.
   3    Copyright (C) 1995, 1996, 1997, 1999, 2000, 2002, 2003, 2004,
   4                  2005, 2006 Free Software Foundation, Inc.
   5    This file is part of the GNU Emacs.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU General Public License as
   9    published by the Free Software Foundation; either version 2 of the
  10    License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public
  18    License along with the GNU C Library; see the file COPYING.  If not,
  19    write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  20    Boston, MA 02110-1301, USA.  */
  21
  22 /* Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.  */
  23
  24 #ifdef HAVE_CONFIG_H
  25 # include <config.h>
  26 #endif
  27
  28 #include <sys/types.h>
  29
  30 #if STDC_HEADERS || defined _LIBC
  31 # include <stdlib.h>
  32 # include <string.h>
  33 #else
  34 # ifndef HAVE_MEMCPY
  35 #  define memcpy(d, s, n) bcopy ((s), (d), (n))
  36 # endif
  37 #endif
  38
  39 #ifdef _LIBC
  40 # include <endian.h>
  41 # if __BYTE_ORDER == __BIG_ENDIAN
  42 #  define WORDS_BIG_ENDIAN 1
  43 # endif
  44 /* We need to keep the namespace clean so define the MD5 function
  45    protected using leading __ .  */
  46 # define md5_init_ctx __md5_init_ctx
  47 # define md5_process_block __md5_process_block
  48 # define md5_process_bytes __md5_process_bytes
  49 # define md5_finish_ctx __md5_finish_ctx
  50 # define md5_read_ctx __md5_read_ctx
  51 # define md5_stream __md5_stream
  52 # define md5_buffer __md5_buffer
  53 #endif
  54
  55 #include "md5.h"
  56
  57 #ifdef WORDS_BIG_ENDIAN
  58 # define SWAP(n)                                                        \
  59     (((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
  60 #else
  61 # define SWAP(n) (n)
  62 #endif
  63
  64
  65 /* This array contains the bytes used to pad the buffer to the next
  66    64-byte boundary.  (RFC 1321, 3.1: Step 1)  */
  67 static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ...  */ };
  68
  69
  70 /* Initialize structure containing state of computation.
  71    (RFC 1321, 3.3: Step 3)  */
  72 void
  73 md5_init_ctx (ctx)
  74      struct md5_ctx *ctx;
  75 {
  76   ctx->A = 0x67452301;
  77   ctx->B = 0xefcdab89;
  78   ctx->C = 0x98badcfe;
  79   ctx->D = 0x10325476;
  80
  81   ctx->total[0] = ctx->total[1] = 0;
  82   ctx->buflen = 0;
  83 }
  84
  85 /* Put result from CTX in first 16 bytes following RESBUF.  The result
  86    must be in little endian byte order.
  87
  88    IMPORTANT: On some systems it is required that RESBUF is correctly
  89    aligned for a 32 bits value.  */
  90 void *
  91 md5_read_ctx (ctx, resbuf)
  92      const struct md5_ctx *ctx;
  93      void *resbuf;
  94 {
  95   ((md5_uint32 *) resbuf)[0] = SWAP (ctx->A);
  96   ((md5_uint32 *) resbuf)[1] = SWAP (ctx->B);
  97   ((md5_uint32 *) resbuf)[2] = SWAP (ctx->C);
  98   ((md5_uint32 *) resbuf)[3] = SWAP (ctx->D);
  99
 100   return resbuf;
 101 }
 102
 103 /* Process the remaining bytes in the internal buffer and the usual
 104    prolog according to the standard and write the result to RESBUF.
 105
 106    IMPORTANT: On some systems it is required that RESBUF is correctly
 107    aligned for a 32 bits value.  */
 108 void *
 109 md5_finish_ctx (ctx, resbuf)
 110      struct md5_ctx *ctx;
 111      void *resbuf;
 112 {
 113   /* Take yet unprocessed bytes into account.  */
 114   md5_uint32 bytes = ctx->buflen;
 115   size_t pad;
 116
 117   /* Now count remaining bytes.  */
 118   ctx->total[0] += bytes;
 119   if (ctx->total[0] < bytes)
 120     ++ctx->total[1];
 121
 122   pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
 123   memcpy (&ctx->buffer[bytes], fillbuf, pad);
 124
 125   /* Put the 64-bit file length in *bits* at the end of the buffer.  */
 126   *(md5_uint32 *) &ctx->buffer[bytes + pad] = SWAP (ctx->total[0] << 3);
 127   *(md5_uint32 *) &ctx->buffer[bytes + pad + 4] = SWAP ((ctx->total[1] << 3) |
 128                                                         (ctx->total[0] >> 29));
 129
 130   /* Process last bytes.  */
 131   md5_process_block (ctx->buffer, bytes + pad + 8, ctx);
 132
 133   return md5_read_ctx (ctx, resbuf);
 134 }
 135
 136 /* Compute MD5 message digest for bytes read from STREAM.  The
 137    resulting message digest number will be written into the 16 bytes
 138    beginning at RESBLOCK.  */
 139 int
 140 md5_stream (stream, resblock)
 141      FILE *stream;
 142      void *resblock;
 143 {
 144   /* Important: BLOCKSIZE must be a multiple of 64.  */
 145 #define BLOCKSIZE 4096
 146   struct md5_ctx ctx;
 147   char buffer[BLOCKSIZE + 72];
 148   size_t sum;
 149
 150   /* Initialize the computation context.  */
 151   md5_init_ctx (&ctx);
 152
 153   /* Iterate over full file contents.  */
 154   while (1)
 155     {
 156       /* We read the file in blocks of BLOCKSIZE bytes.  One call of the
 157          computation function processes the whole buffer so that with the
 158          next round of the loop another block can be read.  */
 159       size_t n;
 160       sum = 0;
 161
 162       /* Read block.  Take care for partial reads.  */
 163       do
 164         {
 165           n = fread (buffer + sum, 1, BLOCKSIZE - sum, stream);
 166
 167           sum += n;
 168         }
 169       while (sum < BLOCKSIZE && n != 0);
 170       if (n == 0 && ferror (stream))
 171         return 1;
 172
 173       /* If end of file is reached, end the loop.  */
 174       if (n == 0)
 175         break;
 176
 177       /* Process buffer with BLOCKSIZE bytes.  Note that
 178                         BLOCKSIZE % 64 == 0
 179        */
 180       md5_process_block (buffer, BLOCKSIZE, &ctx);
 181     }
 182
 183   /* Add the last bytes if necessary.  */
 184   if (sum > 0)
 185     md5_process_bytes (buffer, sum, &ctx);
 186
 187   /* Construct result in desired memory.  */
 188   md5_finish_ctx (&ctx, resblock);
 189   return 0;
 190 }
 191
 192 /* Compute MD5 message digest for LEN bytes beginning at BUFFER.  The
 193    result is always in little endian byte order, so that a byte-wise
 194    output yields to the wanted ASCII representation of the message
 195    digest.  */
 196 void *
 197 md5_buffer (buffer, len, resblock)
 198      const char *buffer;
 199      size_t len;
 200      void *resblock;
 201 {
 202   struct md5_ctx ctx;
 203
 204   /* Initialize the computation context.  */
 205   md5_init_ctx (&ctx);
 206
 207   /* Process whole buffer but last len % 64 bytes.  */
 208   md5_process_bytes (buffer, len, &ctx);
 209
 210   /* Put result in desired memory area.  */
 211   return md5_finish_ctx (&ctx, resblock);
 212 }
 213
 214
 215 void
 216 md5_process_bytes (buffer, len, ctx)
 217      const void *buffer;
 218      size_t len;
 219      struct md5_ctx *ctx;
 220 {
 221   /* const void aligned_buffer = buffer; */
 222
 223   /* When we already have some bits in our internal buffer concatenate
 224      both inputs first.  */
 225   if (ctx->buflen != 0)
 226     {
 227       size_t left_over = ctx->buflen;
 228       size_t add = 128 - left_over > len ? len : 128 - left_over;
 229
 230       /* Only put full words in the buffer.  */
 231       add -= add % __alignof__ (md5_uint32);
 232
 233       memcpy (&ctx->buffer[left_over], buffer, add);
 234       ctx->buflen += add;
 235
 236       if (ctx->buflen > 64)
 237         {
 238           md5_process_block (ctx->buffer, ctx->buflen & ~63, ctx);
 239
 240           ctx->buflen &= 63;
 241           /* The regions in the following copy operation cannot overlap.  */
 242           memcpy (ctx->buffer, &ctx->buffer[(left_over + add) & ~63],
 243                   ctx->buflen);
 244         }
 245
 246       buffer = (const char *) buffer + add;
 247       len -= add;
 248     }
 249
 250   /* Process available complete blocks.  */
 251   if (len > 64)
 252     {
 253       md5_process_block (buffer, len & ~63, ctx);
 254       buffer = (const char *) buffer + (len & ~63);
 255       len &= 63;
 256     }
 257
 258   /* Move remaining bytes in internal buffer.  */
 259   if (len > 0)
 260     {
 261       size_t left_over = ctx->buflen;
 262
 263       memcpy (&ctx->buffer[left_over], buffer, len);
 264       left_over += len;
 265       if (left_over >= 64)
 266         {
 267           md5_process_block (ctx->buffer, 64, ctx);
 268           left_over -= 64;
 269           memcpy (ctx->buffer, &ctx->buffer[64], left_over);
 270         }
 271       ctx->buflen = left_over;
 272     }
 273 }
 274
 275
 276 /* These are the four functions used in the four steps of the MD5 algorithm
 277    and defined in the RFC 1321.  The first function is a little bit optimized
 278    (as found in Colin Plumbs public domain implementation).  */
 279 /* #define FF(b, c, d) ((b & c) | (~b & d)) */
 280 #define FF(b, c, d) (d ^ (b & (c ^ d)))
 281 #define FG(b, c, d) FF (d, b, c)
 282 #define FH(b, c, d) (b ^ c ^ d)
 283 #define FI(b, c, d) (c ^ (b | ~d))
 284
 285 /* Process LEN bytes of BUFFER, accumulating context into CTX.
 286    It is assumed that LEN % 64 == 0.  */
 287
 288 void
 289 md5_process_block (buffer, len, ctx)
 290      const void *buffer;
 291      size_t len;
 292      struct md5_ctx *ctx;
 293 {
 294   md5_uint32 correct_words[16];
 295   const md5_uint32 *words = buffer;
 296   size_t nwords = len / sizeof (md5_uint32);
 297   const md5_uint32 *endp = words + nwords;
 298   md5_uint32 A = ctx->A;
 299   md5_uint32 B = ctx->B;
 300   md5_uint32 C = ctx->C;
 301   md5_uint32 D = ctx->D;
 302
 303   /* First increment the byte count.  RFC 1321 specifies the possible
 304      length of the file up to 2^64 bits.  Here we only compute the
 305      number of bytes.  Do a double word increment.  */
 306   ctx->total[0] += len;
 307   if (ctx->total[0] < len)
 308     ++ctx->total[1];
 309
 310   /* Process all bytes in the buffer with 64 bytes in each round of
 311      the loop.  */
 312   while (words < endp)
 313     {
 314       md5_uint32 *cwp = correct_words;
 315       md5_uint32 A_save = A;
 316       md5_uint32 B_save = B;
 317       md5_uint32 C_save = C;
 318       md5_uint32 D_save = D;
 319
 320       /* First round: using the given function, the context and a constant
 321          the next context is computed.  Because the algorithms processing
 322          unit is a 32-bit word and it is determined to work on words in
 323          little endian byte order we perhaps have to change the byte order
 324          before the computation.  To reduce the work for the next steps
 325          we store the swapped words in the array CORRECT_WORDS.  */
 326
 327 #define OP(a, b, c, d, s, T)                                            \
 328       do                                                                \
 329         {                                                               \
 330           a += FF (b, c, d) + (*cwp++ = SWAP (*words)) + T;             \
 331           ++words;                                                      \
 332           CYCLIC (a, s);                                                \
 333           a += b;                                                       \
 334         }                                                               \
 335       while (0)
 336
 337       /* It is unfortunate that C does not provide an operator for
 338          cyclic rotation.  Hope the C compiler is smart enough.  */
 339 #define CYCLIC(w, s) (w = (w << s) | (w >> (32 - s)))
 340
 341       /* Before we start, one word to the strange constants.
 342          They are defined in RFC 1321 as
 343
 344          T[i] = (int) (4294967296.0 * fabs (sin (i))), i=1..64
 345        */
 346
 347       /* Round 1.  */
 348       OP (A, B, C, D,  7, 0xd76aa478);
 349       OP (D, A, B, C, 12, 0xe8c7b756);
 350       OP (C, D, A, B, 17, 0x242070db);
 351       OP (B, C, D, A, 22, 0xc1bdceee);
 352       OP (A, B, C, D,  7, 0xf57c0faf);
 353       OP (D, A, B, C, 12, 0x4787c62a);
 354       OP (C, D, A, B, 17, 0xa8304613);
 355       OP (B, C, D, A, 22, 0xfd469501);
 356       OP (A, B, C, D,  7, 0x698098d8);
 357       OP (D, A, B, C, 12, 0x8b44f7af);
 358       OP (C, D, A, B, 17, 0xffff5bb1);
 359       OP (B, C, D, A, 22, 0x895cd7be);
 360       OP (A, B, C, D,  7, 0x6b901122);
 361       OP (D, A, B, C, 12, 0xfd987193);
 362       OP (C, D, A, B, 17, 0xa679438e);
 363       OP (B, C, D, A, 22, 0x49b40821);
 364
 365       /* For the second to fourth round we have the possibly swapped words
 366          in CORRECT_WORDS.  Redefine the macro to take an additional first
 367          argument specifying the function to use.  */
 368 #undef OP
 369 #define OP(f, a, b, c, d, k, s, T)                                      \
 370       do                                                                \
 371         {                                                               \
 372           a += f (b, c, d) + correct_words[k] + T;                      \
 373           CYCLIC (a, s);                                                \
 374           a += b;                                                       \
 375         }                                                               \
 376       while (0)
 377
 378       /* Round 2.  */
 379       OP (FG, A, B, C, D,  1,  5, 0xf61e2562);
 380       OP (FG, D, A, B, C,  6,  9, 0xc040b340);
 381       OP (FG, C, D, A, B, 11, 14, 0x265e5a51);
 382       OP (FG, B, C, D, A,  0, 20, 0xe9b6c7aa);
 383       OP (FG, A, B, C, D,  5,  5, 0xd62f105d);
 384       OP (FG, D, A, B, C, 10,  9, 0x02441453);
 385       OP (FG, C, D, A, B, 15, 14, 0xd8a1e681);
 386       OP (FG, B, C, D, A,  4, 20, 0xe7d3fbc8);
 387       OP (FG, A, B, C, D,  9,  5, 0x21e1cde6);
 388       OP (FG, D, A, B, C, 14,  9, 0xc33707d6);
 389       OP (FG, C, D, A, B,  3, 14, 0xf4d50d87);
 390       OP (FG, B, C, D, A,  8, 20, 0x455a14ed);
 391       OP (FG, A, B, C, D, 13,  5, 0xa9e3e905);
 392       OP (FG, D, A, B, C,  2,  9, 0xfcefa3f8);
 393       OP (FG, C, D, A, B,  7, 14, 0x676f02d9);
 394       OP (FG, B, C, D, A, 12, 20, 0x8d2a4c8a);
 395
 396       /* Round 3.  */
 397       OP (FH, A, B, C, D,  5,  4, 0xfffa3942);
 398       OP (FH, D, A, B, C,  8, 11, 0x8771f681);
 399       OP (FH, C, D, A, B, 11, 16, 0x6d9d6122);
 400       OP (FH, B, C, D, A, 14, 23, 0xfde5380c);
 401       OP (FH, A, B, C, D,  1,  4, 0xa4beea44);
 402       OP (FH, D, A, B, C,  4, 11, 0x4bdecfa9);
 403       OP (FH, C, D, A, B,  7, 16, 0xf6bb4b60);
 404       OP (FH, B, C, D, A, 10, 23, 0xbebfbc70);
 405       OP (FH, A, B, C, D, 13,  4, 0x289b7ec6);
 406       OP (FH, D, A, B, C,  0, 11, 0xeaa127fa);
 407       OP (FH, C, D, A, B,  3, 16, 0xd4ef3085);
 408       OP (FH, B, C, D, A,  6, 23, 0x04881d05);
 409       OP (FH, A, B, C, D,  9,  4, 0xd9d4d039);
 410       OP (FH, D, A, B, C, 12, 11, 0xe6db99e5);
 411       OP (FH, C, D, A, B, 15, 16, 0x1fa27cf8);
 412       OP (FH, B, C, D, A,  2, 23, 0xc4ac5665);
 413
 414       /* Round 4.  */
 415       OP (FI, A, B, C, D,  0,  6, 0xf4292244);
 416       OP (FI, D, A, B, C,  7, 10, 0x432aff97);
 417       OP (FI, C, D, A, B, 14, 15, 0xab9423a7);
 418       OP (FI, B, C, D, A,  5, 21, 0xfc93a039);
 419       OP (FI, A, B, C, D, 12,  6, 0x655b59c3);
 420       OP (FI, D, A, B, C,  3, 10, 0x8f0ccc92);
 421       OP (FI, C, D, A, B, 10, 15, 0xffeff47d);
 422       OP (FI, B, C, D, A,  1, 21, 0x85845dd1);
 423       OP (FI, A, B, C, D,  8,  6, 0x6fa87e4f);
 424       OP (FI, D, A, B, C, 15, 10, 0xfe2ce6e0);
 425       OP (FI, C, D, A, B,  6, 15, 0xa3014314);
 426       OP (FI, B, C, D, A, 13, 21, 0x4e0811a1);
 427       OP (FI, A, B, C, D,  4,  6, 0xf7537e82);
 428       OP (FI, D, A, B, C, 11, 10, 0xbd3af235);
 429       OP (FI, C, D, A, B,  2, 15, 0x2ad7d2bb);
 430       OP (FI, B, C, D, A,  9, 21, 0xeb86d391);
 431
 432       /* Add the starting values of the context.  */
 433       A += A_save;
 434       B += B_save;
 435       C += C_save;
 436       D += D_save;
 437     }
 438
 439   /* Put checksum in context given as argument.  */
 440   ctx->A = A;
 441   ctx->B = B;
 442   ctx->C = C;
 443   ctx->D = D;
 444 }
 445
 446 /* arch-tag: 60084f04-b434-42cb-9d2b-e91df01f4325
 447    (do not change this comment) */