Problem - Kevin Tafuro

eturn 4;
}
/* get entry point : here we assume ELF example */
entry = elf_get_entry(buf);
if (!entry) {
fprintf(stderr, "Invalid ELF header\n");
munmap(buf, sb.st_size);
close(fd);
return 5;
}
/* these are offsets from the entry point */
offset += entry;
key_offset += entry;
printf("Encrypting %d bytes at 0x%X with %d bytes at 0x%X\n",
len, offset, key_len, key_offset);
/* Because we're using RC4, encryption and decryption are the same operation */
spc_smc_decrypt(buf + offset, len, buf + key_offset, key_len);
/* mem-unmap the file */
msync(buf, sb.st_size, MS_SYNC);
munmap(buf, sb.st_size);
close(fd);
return 0;
}
This program incorporates an ELF file-header parser in the elf_get_entry( ) routine.
The program header table entries of the ELF header are searched for the loadable
segment containing the entry point. This is done to translate the entry point
virtual address into an offset from the start of the file. This is necessary because the
offsets generated by the SPC_SMC_OFFSET macro are relative to the program entry point
(_start).
The following code provides an example of using the code we’ve presented in this
recipe. The program decrypts itself at runtime, using bogus_routine( ) as a key for
decrypting test_routine( ).
#include
#include
SPC_SMC_START_BLOCK(test)
int test_routine(void) {
int x;
for (x = 0; x < 10; x++) printf("decrpyted!\n");
return x;
}
SPC_SMC_END_BLOCK(test)
SPC_SMC_START_KEY(test)
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Using Self-Modifying Code | 697