Stack Five

As opposed to executing an existing function in the binary, this time we’ll be introducing the concept of “shell code”, and being able to execute our own code.

Hints

  • Don’t feel like you have to write your own shellcode just yet – there’s plenty on the internet.
  • If you wish to debug your shellcode, be sure to make use of the breakpoint instruction. On i386 / x86_64, that’s 0xcc, and will cause a SIGTRAP.
  • Make sure you remove those breakpoints after you’re done.
/*  * phoenix/stack-five, by https://exploit.education  *  * Can you execve("/bin/sh", ...) ?  *  * What is green and goes to summer camp? A brussel scout.  */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h>  #define BANNER \  "Welcome to " LEVELNAME ", brought to you by https://exploit.education" char *gets(char *); void start_level() { char buffer[128]; gets(buffer); } int main(int argc, char **argv) { printf("%s\n", BANNER); start_level(); }