Vulnerable Program

vuln.c

#include<stdio.h>
#include<unistd.h>
 
void a();
void b();
void c();
 
void a()
{
    char *dummy[] = {NULL,"dummy"};
    execve("/bin/sh",dummy,NULL);
    perror("execve");
}
void b()
{
    printf("\nHello World\n");
}
void c()
{
    char buf[512];
    printf("Address of a(): %p\n", a);
    printf("Addres of buf: %p\n",buf);
    printf("uid is:%u\teuid is:%u\n",getuid(),geteuid());
    read(0,buf,1024);
}
int main()
{
    c();
    return 0;
}

1. Remove the lines
   printf("You just entered\n");
   puts(bug);

No need for that.

1. Instead of "Reading input...\n", make it print the current uid.
2. Make the binary setuid; also add the command line commands to make it uid as comments at the start of the c program so that you can use it for reference. When run the binary should run as root.