checksum.c

   1 /*
   2    Copyright (C) Andrew Tridgell 1996
   3    Copyright (C) Paul Mackerras 1996
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software
  17    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18 */
  19
  20 #include "rsync.h"
  21
  22 int csum_length=2; /* initial value */
  23
  24 #define CSUM_CHUNK 64
  25
  26 int checksum_seed = 0;
  27 extern int remote_version;
  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,int len)
  34 {
  35     int 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,int len,char *sum)
  53 {
  54         int i;
  55         static char *buf1;
  56         static int len1;
  57         struct mdfour m;
  58
  59         if (len > len1) {
  60                 if (buf1) free(buf1);
  61                 buf1 = (char *)malloc(len+4);
  62                 len1 = len;
  63                 if (!buf1) out_of_memory("get_checksum2");
  64         }
  65
  66         mdfour_begin(&m);
  67
  68         memcpy(buf1,buf,len);
  69         if (checksum_seed) {
  70                 SIVAL(buf1,len,checksum_seed);
  71                 len += 4;
  72         }
  73
  74         for(i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK) {
  75                 mdfour_update(&m, (uchar *)(buf1+i), CSUM_CHUNK);
  76         }
  77         /*
  78          * Prior to version 27 an incorrect MD4 checksum was computed
  79          * by failing to call mdfour_tail() for block sizes that
  80          * are multiples of 64.  This is fixed by calling mdfour_update()
  81          * even when there are no more bytes.
  82          */
  83         if (len - i > 0 || remote_version >= 27) {
  84                 mdfour_update(&m, (uchar *)(buf1+i), (len-i));
  85         }
  86
  87         mdfour_result(&m, (uchar *)sum);
  88 }
  89
  90
  91 void file_checksum(char *fname,char *sum,OFF_T size)
  92 {
  93         OFF_T i;
  94         struct map_struct *buf;
  95         int fd;
  96         OFF_T len = size;
  97         char tmpchunk[CSUM_CHUNK];
  98         struct mdfour m;
  99
 100         memset(sum,0,MD4_SUM_LENGTH);
 101
 102         fd = do_open(fname, O_RDONLY, 0);
 103         if (fd == -1) return;
 104
 105         buf = map_file(fd,size);
 106
 107         mdfour_begin(&m);
 108
 109         for(i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK) {
 110                 memcpy(tmpchunk, map_ptr(buf,i,CSUM_CHUNK), CSUM_CHUNK);
 111                 mdfour_update(&m, (uchar *)tmpchunk, CSUM_CHUNK);
 112         }
 113
 114         /*
 115          * Prior to version 27 an incorrect MD4 checksum was computed
 116          * by failing to call mdfour_tail() for block sizes that
 117          * are multiples of 64.  This is fixed by calling mdfour_update()
 118          * even when there are no more bytes.
 119          */
 120         if (len - i > 0) {
 121                 memcpy(tmpchunk, map_ptr(buf,i,len-i), len-i);
 122         }
 123         if (len - i > 0 || remote_version >= 27) {
 124                 mdfour_update(&m, (uchar *)tmpchunk, (len-i));
 125         }
 126
 127         mdfour_result(&m, (uchar *)sum);
 128
 129         close(fd);
 130         unmap_file(buf);
 131 }
 132
 133
 134 static int sumresidue;
 135 static char sumrbuf[CSUM_CHUNK];
 136 static struct mdfour md;
 137
 138 void sum_init(void)
 139 {
 140         char s[4];
 141         mdfour_begin(&md);
 142         sumresidue=0;
 143         SIVAL(s,0,checksum_seed);
 144         sum_update(s,4);
 145 }
 146
 147 /**
 148  * Feed data into an MD4 accumulator, md.  The results may be
 149  * retrieved using sum_end().  md is used for different purposes at
 150  * different points during execution.
 151  *
 152  * @todo Perhaps get rid of md and just pass in the address each time.
 153  * Very slightly clearer and slower.
 154  **/
 155 void sum_update(char *p, int len)
 156 {
 157         int i;
 158         if (len + sumresidue < CSUM_CHUNK) {
 159                 memcpy(sumrbuf+sumresidue, p, len);
 160                 sumresidue += len;
 161                 return;
 162         }
 163
 164         if (sumresidue) {
 165                 i = MIN(CSUM_CHUNK-sumresidue,len);
 166                 memcpy(sumrbuf+sumresidue,p,i);
 167                 mdfour_update(&md, (uchar *)sumrbuf, (i+sumresidue));
 168                 len -= i;
 169                 p += i;
 170         }
 171
 172         for(i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK) {
 173                 memcpy(sumrbuf,p+i,CSUM_CHUNK);
 174                 mdfour_update(&md, (uchar *)sumrbuf, CSUM_CHUNK);
 175         }
 176
 177         if (len - i > 0) {
 178                 sumresidue = len-i;
 179                 memcpy(sumrbuf,p+i,sumresidue);
 180         } else {
 181                 sumresidue = 0;
 182         }
 183 }
 184
 185 void sum_end(char *sum)
 186 {
 187         if (sumresidue || remote_version >= 27) {
 188                 mdfour_update(&md, (uchar *)sumrbuf, sumresidue);
 189         }
 190
 191         mdfour_result(&md, (uchar *)sum);
 192 }