checksum.c

   1 /*
   2  * Routines to support checksumming of bytes.
   3  *
   4  * Copyright (C) 1996 Andrew Tridgell
   5  * Copyright (C) 1996 Paul Mackerras
   6  * Copyright (C) 2004-2008 Wayne Davison
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 3 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, visit the http://fsf.org website.
  20  */
  21
  22 #include "rsync.h"
  23
  24 extern int checksum_seed;
  25 extern int protocol_version;
  26
  27 int csum_length = SHORT_SUM_LENGTH; /* initial value */
  28
  29 /*
  30   a simple 32 bit checksum that can be upadted from either end
  31   (inspired by Mark Adler's Adler-32 checksum)
  32   */
  33 uint32 get_checksum1(char *buf1, int32 len)
  34 {
  35     int32 i;
  36     uint32 s1, s2;
  37     schar *buf = (schar *)buf1;
  38
  39     s1 = s2 = 0;
  40     for (i = 0; i < (len-4); i+=4) {
  41         s2 += 4*(s1 + buf[i]) + 3*buf[i+1] + 2*buf[i+2] + buf[i+3] +
  42           10*CHAR_OFFSET;
  43         s1 += (buf[i+0] + buf[i+1] + buf[i+2] + buf[i+3] + 4*CHAR_OFFSET);
  44     }
  45     for (; i < len; i++) {
  46         s1 += (buf[i]+CHAR_OFFSET); s2 += s1;
  47     }
  48     return (s1 & 0xffff) + (s2 << 16);
  49 }
  50
  51
  52 void get_checksum2(char *buf, int32 len, char *sum)
  53 {
  54         md_context m;
  55
  56         if (protocol_version >= 30) {
  57                 uchar seedbuf[4];
  58                 md5_begin(&m);
  59                 md5_update(&m, (uchar *)buf, len);
  60                 if (checksum_seed) {
  61                         SIVAL(seedbuf, 0, checksum_seed);
  62                         md5_update(&m, seedbuf, 4);
  63                 }
  64                 md5_result(&m, (uchar *)sum);
  65         } else {
  66                 int32 i;
  67                 static char *buf1;
  68                 static int32 len1;
  69
  70                 mdfour_begin(&m);
  71
  72                 if (len > len1) {
  73                         if (buf1)
  74                                 free(buf1);
  75                         buf1 = new_array(char, len+4);
  76                         len1 = len;
  77                         if (!buf1)
  78                                 out_of_memory("get_checksum2");
  79                 }
  80
  81                 memcpy(buf1, buf, len);
  82                 if (checksum_seed) {
  83                         SIVAL(buf1,len,checksum_seed);
  84                         len += 4;
  85                 }
  86
  87                 for (i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK)
  88                         mdfour_update(&m, (uchar *)(buf1+i), CSUM_CHUNK);
  89
  90                 /*
  91                  * Prior to version 27 an incorrect MD4 checksum was computed
  92                  * by failing to call mdfour_tail() for block sizes that
  93                  * are multiples of 64.  This is fixed by calling mdfour_update()
  94                  * even when there are no more bytes.
  95                  */
  96                 if (len - i > 0 || protocol_version >= 27)
  97                         mdfour_update(&m, (uchar *)(buf1+i), len-i);
  98
  99                 mdfour_result(&m, (uchar *)sum);
 100         }
 101 }
 102
 103 void file_checksum(char *fname, char *sum, OFF_T size)
 104 {
 105         struct map_struct *buf;
 106         OFF_T i, len = size;
 107         md_context m;
 108         int32 remainder;
 109         int fd;
 110
 111         memset(sum, 0, MAX_DIGEST_LEN);
 112
 113         fd = do_open(fname, O_RDONLY, 0);
 114         if (fd == -1)
 115                 return;
 116
 117         buf = map_file(fd, size, MAX_MAP_SIZE, CSUM_CHUNK);
 118
 119         if (protocol_version >= 30) {
 120                 md5_begin(&m);
 121
 122                 for (i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK) {
 123                         md5_update(&m, (uchar *)map_ptr(buf, i, CSUM_CHUNK),
 124                                    CSUM_CHUNK);
 125                 }
 126
 127                 remainder = (int32)(len - i);
 128                 if (remainder > 0)
 129                         md5_update(&m, (uchar *)map_ptr(buf, i, remainder), remainder);
 130
 131                 md5_result(&m, (uchar *)sum);
 132         } else {
 133                 mdfour_begin(&m);
 134
 135                 for (i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK) {
 136                         mdfour_update(&m, (uchar *)map_ptr(buf, i, CSUM_CHUNK),
 137                                       CSUM_CHUNK);
 138                 }
 139
 140                 /* Prior to version 27 an incorrect MD4 checksum was computed
 141                  * by failing to call mdfour_tail() for block sizes that
 142                  * are multiples of 64.  This is fixed by calling mdfour_update()
 143                  * even when there are no more bytes. */
 144                 remainder = (int32)(len - i);
 145                 if (remainder > 0 || protocol_version >= 27)
 146                         mdfour_update(&m, (uchar *)map_ptr(buf, i, remainder), remainder);
 147
 148                 mdfour_result(&m, (uchar *)sum);
 149         }
 150
 151         close(fd);
 152         unmap_file(buf);
 153 }
 154
 155 static int32 sumresidue;
 156 static md_context md;
 157
 158 void sum_init(int seed)
 159 {
 160         char s[4];
 161
 162         if (protocol_version >= 30)
 163                 md5_begin(&md);
 164         else {
 165                 mdfour_begin(&md);
 166                 sumresidue = 0;
 167                 SIVAL(s, 0, seed);
 168                 sum_update(s, 4);
 169         }
 170 }
 171
 172 /**
 173  * Feed data into an MD4 accumulator, md.  The results may be
 174  * retrieved using sum_end().  md is used for different purposes at
 175  * different points during execution.
 176  *
 177  * @todo Perhaps get rid of md and just pass in the address each time.
 178  * Very slightly clearer and slower.
 179  **/
 180 void sum_update(const char *p, int32 len)
 181 {
 182         if (protocol_version >= 30) {
 183                 md5_update(&md, (uchar *)p, len);
 184                 return;
 185         }
 186
 187         if (len + sumresidue < CSUM_CHUNK) {
 188                 memcpy(md.buffer + sumresidue, p, len);
 189                 sumresidue += len;
 190                 return;
 191         }
 192
 193         if (sumresidue) {
 194                 int32 i = CSUM_CHUNK - sumresidue;
 195                 memcpy(md.buffer + sumresidue, p, i);
 196                 mdfour_update(&md, (uchar *)md.buffer, CSUM_CHUNK);
 197                 len -= i;
 198                 p += i;
 199         }
 200
 201         while (len >= CSUM_CHUNK) {
 202                 mdfour_update(&md, (uchar *)p, CSUM_CHUNK);
 203                 len -= CSUM_CHUNK;
 204                 p += CSUM_CHUNK;
 205         }
 206
 207         sumresidue = len;
 208         if (sumresidue)
 209                 memcpy(md.buffer, p, sumresidue);
 210 }
 211
 212 int sum_end(char *sum)
 213 {
 214         if (protocol_version >= 30) {
 215                 md5_result(&md, (uchar *)sum);
 216                 return MD5_DIGEST_LEN;
 217         }
 218
 219         if (sumresidue || protocol_version >= 27)
 220                 mdfour_update(&md, (uchar *)md.buffer, sumresidue);
 221
 222         mdfour_result(&md, (uchar *)sum);
 223
 224         return MD4_DIGEST_LEN;
 225 }