lib/md5-stream.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) 1995-1997, 1999-2001, 2005-2006, 2008-2025 Free Software
   4    Foundation, Inc.
   5    This file is part of the GNU C Library.
   6
   7    This file is free software: you can redistribute it and/or modify
   8    it under the terms of the GNU Lesser General Public License as
   9    published by the Free Software Foundation; either version 2.1 of the
  10    License, or (at your option) any later version.
  11
  12    This file 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
  15    GNU Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public License
  18    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  19
  20 /* Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.  */
  21
  22 #include <config.h>
  23
  24 /* Specification.  */
  25 #include "md5.h"
  26
  27 #include <stdlib.h>
  28
  29 #if USE_UNLOCKED_IO
  30 # include "unlocked-io.h"
  31 #endif
  32
  33 #include "af_alg.h"
  34
  35 #ifdef _LIBC
  36 # include <endian.h>
  37 # if __BYTE_ORDER == __BIG_ENDIAN
  38 #  define WORDS_BIGENDIAN 1
  39 # endif
  40 /* We need to keep the namespace clean so define the MD5 function
  41    protected using leading __ .  */
  42 # define md5_init_ctx __md5_init_ctx
  43 # define md5_process_block __md5_process_block
  44 # define md5_process_bytes __md5_process_bytes
  45 # define md5_finish_ctx __md5_finish_ctx
  46 # define md5_stream __md5_stream
  47 #endif
  48
  49 #define BLOCKSIZE 32768
  50 #if BLOCKSIZE % 64 != 0
  51 # error "invalid BLOCKSIZE"
  52 #endif
  53
  54 /* Compute MD5 message digest for bytes read from STREAM.  The
  55    resulting message digest number will be written into the 16 bytes
  56    beginning at RESBLOCK.  */
  57 int
  58 md5_stream (FILE *stream, void *resblock)
  59 {
  60   switch (afalg_stream (stream, "md5", resblock, MD5_DIGEST_SIZE))
  61     {
  62     case 0: return 0;
  63     case -EIO: return 1;
  64     }
  65
  66   char *buffer = malloc (BLOCKSIZE + 72);
  67   if (!buffer)
  68     return 1;
  69
  70   struct md5_ctx ctx;
  71   md5_init_ctx (&ctx);
  72   size_t sum;
  73
  74   /* Iterate over full file contents.  */
  75   while (1)
  76     {
  77       /* We read the file in blocks of BLOCKSIZE bytes.  One call of the
  78          computation function processes the whole buffer so that with the
  79          next round of the loop another block can be read.  */
  80       size_t n;
  81       sum = 0;
  82
  83       /* Read block.  Take care for partial reads.  */
  84       while (1)
  85         {
  86           /* Either process a partial fread() from this loop,
  87              or the fread() in afalg_stream may have gotten EOF.
  88              We need to avoid a subsequent fread() as EOF may
  89              not be sticky.  For details of such systems, see:
  90              https://sourceware.org/bugzilla/show_bug.cgi?id=1190  */
  91           if (feof (stream))
  92             goto process_partial_block;
  93
  94           n = fread (buffer + sum, 1, BLOCKSIZE - sum, stream);
  95
  96           sum += n;
  97
  98           if (sum == BLOCKSIZE)
  99             break;
 100
 101           if (n == 0)
 102             {
 103               /* Check for the error flag IFF N == 0, so that we don't
 104                  exit the loop after a partial read due to e.g., EAGAIN
 105                  or EWOULDBLOCK.  */
 106               if (ferror (stream))
 107                 {
 108                   free (buffer);
 109                   return 1;
 110                 }
 111               goto process_partial_block;
 112             }
 113         }
 114
 115       /* Process buffer with BLOCKSIZE bytes.  Note that
 116          BLOCKSIZE % 64 == 0
 117        */
 118       md5_process_block (buffer, BLOCKSIZE, &ctx);
 119     }
 120
 121 process_partial_block:
 122
 123   /* Process any remaining bytes.  */
 124   if (sum > 0)
 125     md5_process_bytes (buffer, sum, &ctx);
 126
 127   /* Construct result in desired memory.  */
 128   md5_finish_ctx (&ctx, resblock);
 129   free (buffer);
 130   return 0;
 131 }