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 extern int checksum_seed;
  27 extern int protocol_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, 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         int32 i;
  55         static char *buf1;
  56         static int32 len1;
  57         struct mdfour m;
  58
  59         if (len > len1) {
  60                 if (buf1)
  61                         free(buf1);
  62                 buf1 = new_array(char, len+4);
  63                 len1 = len;
  64                 if (!buf1)
  65                         out_of_memory("get_checksum2");
  66         }
  67
  68         mdfour_begin(&m);
  69
  70         memcpy(buf1,buf,len);
  71         if (checksum_seed) {
  72                 SIVAL(buf1,len,checksum_seed);
  73                 len += 4;
  74         }
  75
  76         for(i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK) {
  77                 mdfour_update(&m, (uchar *)(buf1+i), CSUM_CHUNK);
  78         }
  79         /*
  80          * Prior to version 27 an incorrect MD4 checksum was computed
  81          * by failing to call mdfour_tail() for block sizes that
  82          * are multiples of 64.  This is fixed by calling mdfour_update()
  83          * even when there are no more bytes.
  84          */
  85         if (len - i > 0 || protocol_version >= 27) {
  86                 mdfour_update(&m, (uchar *)(buf1+i), (len-i));
  87         }
  88
  89         mdfour_result(&m, (uchar *)sum);
  90 }
  91
  92
  93 void file_checksum(char *fname,char *sum,OFF_T size)
  94 {
  95         OFF_T i;
  96         struct map_struct *buf;
  97         int fd;
  98         OFF_T len = size;
  99         struct mdfour m;
 100
 101         memset(sum,0,MD4_SUM_LENGTH);
 102
 103         fd = do_open(fname, O_RDONLY, 0);
 104         if (fd == -1)
 105                 return;
 106
 107         buf = map_file(fd, size, MAX_MAP_SIZE, CSUM_CHUNK);
 108
 109         mdfour_begin(&m);
 110
 111         for(i = 0; i + CSUM_CHUNK <= len; i += CSUM_CHUNK) {
 112                 mdfour_update(&m, (uchar *)map_ptr(buf, i, CSUM_CHUNK),
 113                               CSUM_CHUNK);
 114         }
 115
 116         /* Prior to version 27 an incorrect MD4 checksum was computed
 117          * by failing to call mdfour_tail() for block sizes that
 118          * are multiples of 64.  This is fixed by calling mdfour_update()
 119          * even when there are no more bytes. */
 120         if (len - i > 0 || protocol_version >= 27)
 121                 mdfour_update(&m, (uchar *)map_ptr(buf, i, len-i), len-i);
 122
 123         mdfour_result(&m, (uchar *)sum);
 124
 125         close(fd);
 126         unmap_file(buf);
 127 }
 128
 129
 130 static int32 sumresidue;
 131 static char sumrbuf[CSUM_CHUNK];
 132 static struct mdfour md;
 133
 134 void sum_init(int seed)
 135 {
 136         char s[4];
 137         mdfour_begin(&md);
 138         sumresidue = 0;
 139         SIVAL(s, 0, seed);
 140         sum_update(s, 4);
 141 }
 142
 143 /**
 144  * Feed data into an MD4 accumulator, md.  The results may be
 145  * retrieved using sum_end().  md is used for different purposes at
 146  * different points during execution.
 147  *
 148  * @todo Perhaps get rid of md and just pass in the address each time.
 149  * Very slightly clearer and slower.
 150  **/
 151 void sum_update(char *p, int32 len)
 152 {
 153         if (len + sumresidue < CSUM_CHUNK) {
 154                 memcpy(sumrbuf + sumresidue, p, len);
 155                 sumresidue += len;
 156                 return;
 157         }
 158
 159         if (sumresidue) {
 160                 int32 i = CSUM_CHUNK - sumresidue;
 161                 memcpy(sumrbuf + sumresidue, p, i);
 162                 mdfour_update(&md, (uchar *)sumrbuf, CSUM_CHUNK);
 163                 len -= i;
 164                 p += i;
 165         }
 166
 167         while (len >= CSUM_CHUNK) {
 168                 mdfour_update(&md, (uchar *)p, CSUM_CHUNK);
 169                 len -= CSUM_CHUNK;
 170                 p += CSUM_CHUNK;
 171         }
 172
 173         sumresidue = len;
 174         if (sumresidue)
 175                 memcpy(sumrbuf, p, sumresidue);
 176 }
 177
 178 void sum_end(char *sum)
 179 {
 180         if (sumresidue || protocol_version >= 27)
 181                 mdfour_update(&md, (uchar *)sumrbuf, sumresidue);
 182
 183         mdfour_result(&md, (uchar *)sum);
 184 }