findme

Overview

Overall difficulty for me (From 1-10 stars): ★☆☆☆☆☆☆☆☆☆

Background

Author: Geoffrey Njogu

Description

Help us test the form by submiting the username as test and password as test!

The website running here.

Enumeration

Home page:

In here, we see there’s a login page!

Let’s try test:test:

Nope. We need to try test:test!:

Now, what I would like to do is fire up Burp Suite, and proxying ALL the HTTP traffics.

Burp Suite HTTP history:

When we click the “test” button, it’ll send a POST request to /login, with parameter username and password.

If we’re authenticated, it’ll redirect us to /next-page/id=cGljb0NURntwcm94aWVzX2Fs.

/next-page/id=cGljb0NURntwcm94aWVzX2Fs:

In this page, it has a JavaScript code:

setTimeout(function () {
   // after 2 seconds
   window.location = "/next-page/id=bF90aGVfd2F5X2UzMWJiNzZkfQ==";
}, 0.5)

After 2 seconds, it’ll set the window object’s location attribute to /next-page/id=bF90aGVfd2F5X2UzMWJiNzZkfQ==, which is redirecting us to that page.

/next-page/id=bF90aGVfd2F5X2UzMWJiNzZkfQ==:

Then, it’ll redirect us to /home.

Hmm… I wonder what are those id GET parameter’s value:

cGljb0NURntwcm94aWVzX2FsbF90aGVfd2F5X2UzMWJiNzZkfQ==

In that string, there’s a = character, which is a base64 encoding’s padding string.

Armed with above information, we can base64 decode it:

┌[siunam♥earth]-(~/ctf/picoCTF-2023)-[2023.03.15|19:57:49(HKT)]
└> echo 'cGljb0NURntwcm94aWVzX2FsbF90aGVfd2F5X2UzMWJiNzZkfQ==' | base64 -d
picoCTF{proxies_all_the_way_e31bb76d}

Boom! We got the flag!

Flag: picoCTF{proxies_all_the_way_e31bb76d}

Conclusion

What we’ve learned:

Proxying HTTP Traffics