Tags: buffer-overflow segfault pwn
Rating:
Can you make this program crash?
`nc 0.cloud.chals.io 17289`
[crashme](https://github.com/Nightxade/ctf-writeups/blob/master/assets/CTFs/Cyber-Cooperative-CTF-2023/pwn/crashme)
[crashme.c](https://github.com/Nightxade/ctf-writeups/blob/master/assets/CTFs/Cyber-Cooperative-CTF-2023/pwn/crashme.c)
---
We're given an ELF binary, a C source file, and a service to connect to. Here's `crashme.c`:
```c
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(int argc, char *argv[]){
char buffer[32];
printf("Give me some data: \n");
fflush(stdout);
fgets(buffer, 64, stdin);
printf("You entered %s\n", buffer);
fflush(stdout);
return 0;
}
```
Seems like a very simple program. Simple programs require simple methods. `fgets()` can be vulnerable to buffer overflow, so why don't we try to send a large number of characters? I sent `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa` to the local program, which immediately resulted in a `Segmentation fault`.
This is what we need then! Send the same input to the program to get the flag:
flag{segfaults_a_hackers_best_friend}
