csaw21

Writeups for CSAW 2021 CTF

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Ninja

Writeup by: GoProSlowYo and solved by jrozner

Team: OnlyFeet

Writeup URL: GitHub


Hey guys come checkout this website i made to test my ninja-coding skills.

http://web.chal.csaw.io:5000

Initial Research

There’s an input box and after a few seconds of playing with input we find that we have Server Side Template Injection (SSTI).

We entered:


Server-Side Template Injection

Finding the Right SSTI Payload

There’s some filters on the server-side that seem to be filtering some of the payload so we need to bypass it with some special techniques.

You can find great examples and help at the Filter Bypass section of the PayloadAllTheThings:


We should URL encode that and then send it off. In this example I used Zeds Attack Proxy.

Exploiting Server-Side Template Injection using Zed Attack Proxy and Getting the Flag

Victory

Submit the flag and claim the points:

flag{m0mmy_s33_1m_4_r34l_n1nj4}