RC3 CTF - 100 - Who's a good boy - Web

Information#

Version#

By	Version	Comment
noraj	1.0	Creation

CTF#

• Name : RC3 CTF 2016
• Website : http://ctf.rc3.club/
• Type : Online
• Format : Jeopardy
• CTF Time : link

Description#

You’re trying to see the cute dog pictures on ctf.rc3.club. But every time you click on one of them, it brings you to a bad gateway.

https://ctf.rc3.club:3000/

-- Your friendly neighborhood webadmin

Solution#

We can see that one of the image is not like all others:

[...]
<img class="phil me up"
src="http://admissions.vanderbilt.edu/insidedores/manage/wp-content/uploads/doge-pattern-27481-2880x1800.jpg">
<h4>the absolute mostest?</p>
<img class="philarydufflebag"
src="http://admissions.vanderbilt.edu/insidedores/doge/this-aint-the-RC3-flag-we're-getting-there-though.jpg">
<h4>CTF flags!!1!</p>
<img class="guys the flag is!"
src="http://admissions.vanderbilt.edu/insidedores/manage/wp-content/uploads/doge-pattern-27481-2880x1800.jpg">
<h4>Find the Phil</p>
[...]

But this image doesn't exist, and is not cached in the WayBackMachine.

Each image has a different class:

<img class="why hello there"
<img class="try not to get too distracted"
<img class="or infuriated"
<img class="don't give up, you can do it!"
<img class="hey, by the way"
<img class="have you ever"
<img class="heard of phil"
<img class="phil's a good name"
<img class="philly phil phil"
<img class="philthy phil"
<img class="now if only there was a way to philter out this nonsense"
<img class="phil likes phalgs?"
<img class="phil's gone phishing"
<img class ="philet-o-phish"
<img class= "philament"
<img class = "philanthropy"
<img class="phil me up"
<img class="philarydufflebag"
<img class="guys the flag is!"
<img class="phil pills r phor phil's phlegm"
<img class="not phil nor phlag"
<img class=i like scary philms"
<img class=phillllllyy"
<img class= philadelphia"
<img class="fill me up with dreams of phil"
<img class="still not phil"
<img class="also not phil"
<img class="not phil"

See what is the mess in the css:

[...]
.philarydufflebag{

/*hiya*/
/*compress your frontend*/
/*here's a flag :)*/
flag:RC3-2016-CanineSS
}

Flag was not well hidden: RC3-2016-CanineSS.