Exploit Exercises Nebula Level 19 - SemilleroSeguridadInformatica/Sem-Security GitHub Wiki

Exploit Exercises Nebula - Level 19

About

There is a flaw in the below program in how it operates.

To do this level, log in as level19 account with the password level19. Files for this level can be found in /home/flag19.

Source code

#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/stat.h>

int main(int argc, char **argv, char **envp)
{
  pid_t pid;
  char buf[256];
  struct stat statbuf;

  /* Get the parent's /proc entry, so we can verify its user id */

  snprintf(buf, sizeof(buf)-1, "/proc/%d", getppid());

  /* stat() it */

  if(stat(buf, &statbuf) == -1) {
      printf("Unable to check parent process\n");
      exit(EXIT_FAILURE);
  }

  /* check the owner id */

  if(statbuf.st_uid == 0) {
      /* If root started us, it is ok to start the shell */

      execve("/bin/sh", argv, envp);
      err(1, "Unable to execve");
  }

  printf("You are unauthorized to run this program\n");
}
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