Compiled | TryHackme | Writeup

Original article published on Medium - SiapaHeker

Challenge Overview

Strings can only help you so far.

Download the task file and get started. The binary can also be found in the AttackBox inside the /root/Rooms/Compiled/ directory.

Note: The binary will not execute if using the AttackBox. However, you can still solve the challenge.

Answer the questions below

What is the password?

First, i downloaded the given file, then ran it in terminal

Run test

This file asks for a password. Then I used the **strings **command to find several interesting strings.

Strings output

The output contained that following strings, These strings looked suspicious, so I opened the binary in IDA to inspect the decompiled code.

Ida decompiled code

The relevant part of the code is shown below:

__isoc99_scanf("DoYouEven%sCTF", s1);

if ((strcmp(s1, "__dso_handle") < 0 ||
     strcmp(s1, "__dso_handle") > 0) &&
    !strcmp(s1, "_init"))
{
    printf("Correct!");
}

From the decompiled code, the program compares the input stored in **s1 **with two strings, **__dso_handle **and _init.

strcmp(s1, "__dso_handle") < 0 ||
strcmp(s1, "__dso_handle") > 0

That first condition is equivalent to checking that s1 is not equal to __dso_handle.

and the second condition is only true when s1 is exactly equal to _init.

!strcmp(s1, "_init")

Therefore, the only value that satisfies the condition is _init. Then the password is DoYouEven_init

Password input