Problem - Kevin Tafuro

phsz = *(unsigned short *) &buf[ELF_PHESZ_OFFSET];
phdr = &buf[phoff];
/* iterate through program headers */
for ( i = 0; i < phnum; i++, phdr += phsz ) {
p_vaddr = *(unsigned long *)&phdr[ELF_PH_VADDR_OFF];
p_filesz = *(unsigned long *)&phdr[ELF_PH_FILESZ_OFF];
/* if entry point is in this program segment */
if ( entry >= p_vaddr && entry < (p_vaddr + p_filesz) ) {
/* calculate offset of entry point */
p_offset = *(unsigned long *)&phdr[ELF_PH_OFFSET_OFF];
return( p_offset + (entry - p_vaddr) );
}
}
return 0;
}
int main(int argc, char *argv[ ]) {
unsigned long entry, offset, len, key_offset, key_len;
unsigned char *buf;
struct stat sb;
int fd;
if (argc < 6) {
printf("Usage: %s filename offset len key_offset key_len\n"
" filename: file to encrypt\n"
" offset: offset in file to start encryption\n"
" len: number of bytes to encrypt\n"
" key_offset: offset in file of key\n"
" key_len: number of bytes in key\n"
" Values are converted with strtol with base 0\n",
argv[0]);
return 1;
}
/* prepare the parameters */
offset = strtoul(argv[2], 0, 0);
len = strtoul(argv[3], 0, 0);
key_offset = strtoul(argv[4], 0, 0);
key_len = strtoul(argv[5], NULL, 0);
/* memory map the file so we can access it via pointers */
if (stat(argv[1], &sb)) {
fprintf(stderr, "Stat failed: %s\n", strerror(errno));
return 2;
}
if ((fd = open(argv[1], O_RDWR | O_EXCL)) < 0) {
fprintf(stderr, "Open failed: %s\n", strerror(errno));
return 3;
}
buf = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
if ((int)buf < 0) {
fprintf(stderr, "Open failed: %s\n", strerror(errno));
close(fd);
696 | Chapter 12: Anti-Tampering
This is the Title of the Book, eMatter Edition
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