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/* simple program to insert a md5sum into application data area of */
/* an iso9660 image */
/* Copyright 2001 Red Hat, Inc. */
/* Michael Fulbright msf@redhat.com */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "md5.h"
#define APPDATA_OFFSET 883
#define SIZE_OFFSET 84
/* number of sectors to ignore at end of iso when computing sum */
#define SKIPSECTORS 15
#define MAX(x, y) ((x > y) ? x : y)
#define MIN(x, y) ((x < y) ? x : y)
/* finds primary volume descriptor and returns info from it */
/* mediasum must be a preallocated buffer at least 33 bytes long */
int parsepvd(int isofd, char *mediasum, long long *isosize) {
unsigned char buf[2048];
long long offset;
unsigned char *p;
if (lseek(isofd, (off_t)(16L * 2048L), SEEK_SET) == -1)
return ((long long)-1);
offset = (16L * 2048L);
for (;1;) {
read(isofd, buf, 2048);
if (buf[0] == 1)
/* found primary volume descriptor */
break;
else if (buf[0] == 255)
/* hit end and didn't find primary volume descriptor */
return ((long long)-1);
offset += 2048L;
}
/* read out md5sum */
#if 0
memcpy(mediasum, buf + APPDATA_OFFSET + 13, 32);
mediasum[32] = '\0';
for (p=mediasum; *p; p++)
if (*p != ' ')
break;
/* if the md5sum was all spaces, we didn't find md5sum */
if (!*p)
return -1;
#endif
/* get isosize */
*isosize = (buf[SIZE_OFFSET]*0x1000000+buf[SIZE_OFFSET+1]*0x10000 +
buf[SIZE_OFFSET+2]*0x100 + buf[SIZE_OFFSET+3]) * 2048LL;
return offset;
}
int main(int argc, char **argv) {
int isofd;
int nread;
int i;
int dirty;
int pvd_offset;
int forceit;
long long isosize;
unsigned char md5sum[16];
unsigned int total;
unsigned char *fname;
unsigned char buf[2048];
unsigned char orig_appdata[512];
unsigned char new_appdata[512];
unsigned char mediasum[33], computedsum[33];
char md5str[40];
MD5_CTX md5ctx;
if (argc < 2) {
printf("Usage: implantisomd5 [-f] <isofilename>\n\n");
exit(1);
}
if (!strncmp(argv[1] , "-f", 3)) {
forceit = 1;
fname = argv[2];
} else {
forceit = 0;
fname = argv[1];
}
isofd = open(fname, O_RDWR);
if (isofd < 0) {
fprintf(stderr, "Error - Unable to open file %s\n\n", fname);
exit(1);
}
pvd_offset = parsepvd(isofd, mediasum, &isosize);
if (pvd_offset < 0) {
fprintf(stderr, "Could not find primary volumne!\n\n");
exit(1);
}
lseek(isofd, pvd_offset + APPDATA_OFFSET, SEEK_SET);
nread = read(isofd, orig_appdata, 512);
if (!forceit) {
dirty = 0;
for (i=0; i < 512; i++)
if (orig_appdata[i] != ' ')
dirty = 1;
if (dirty) {
fprintf(stderr, "Application data has been used - not implanting md5sum!\n");
exit(1);
}
}
lseek(isofd, 0L, SEEK_SET);
MD5_Init(&md5ctx);
total = 0;
/* read up to 15 sectors from end, due to problems reading last few */
/* sectors on burned CDs */
while (total < isosize - SKIPSECTORS*2048) {
nread = read(isofd, buf, 2048);
if (nread <= 0)
break;
MD5_Update(&md5ctx, buf, nread);
total = total + nread;
}
MD5_Final(md5sum, &md5ctx);
*md5str = '\0';
for (i=0; i<16; i++) {
char tmpstr[4];
snprintf (tmpstr, 4, "%02x", md5sum[i]);
strcat(md5str, tmpstr);
}
printf("Inserting md5sum into iso image...\n");
printf("md5 = %s\n", md5str);
/* memcpy(new_appdata, orig_appdata, 512); */
memset(new_appdata, ' ', 512);
memcpy(new_appdata, "ISO MD5SUM = ", 13);
memcpy(new_appdata+13, md5str, 33);
memcpy(new_appdata+47, "THIS IS NOT THE SAME AS RUNNING MD5SUM ON THIS ISO!!", 51);
i = lseek(isofd, pvd_offset + APPDATA_OFFSET, SEEK_SET);
if (i<0)
printf("seek failed\n");
i = write(isofd, new_appdata, 512);
if (i<0) {
printf("write failed %d\n", i);
perror("");
}
close(isofd);
printf("Done!\n");
}
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