Black Magic Exploitation

CTF's, Exploits, and Black Magic

RC3 2015 ~ Goal!: Web 100


Another baby CTF question. It was very simple, even though it did throw me off quite a bit… We are given a link: When visiting the site all it had was a gif of some guys playing soccer


Maybe we should look at the source?


<img src="goal.gif" alt="goal"/>


No helpful data in there. I tried doing a quick directory search such as /flag, /.git, and /admin and none of those worked. I also tried looking at the metadeta

exiftool goal.gif

ExifTool Version Number         : 9.46
File Name                       : goal.gif
Directory                       : .
File Size                       : 3.0 MB
File Modification Date/Time     : 2015:11:21 12:06:36-08:00
File Access Date/Time           : 2015:11:21 12:06:36-08:00
File Inode Change Date/Time     : 2015:11:21 12:06:36-08:00
File Permissions                : rw-r-----
File Type                       : GIF
MIME Type                       : image/gif
GIF Version                     : 89a
Image Width                     : 407
Image Height                    : 211
Has Color Map                   : Yes
Color Resolution Depth          : 7
Bits Per Pixel                  : 7
Background Color                : 121
Animation Iterations            : Infinite
Frame Count                     : 78
Duration                        : 4.68 s
Image Size                      : 407x211

Nothing showed up there either. Luckily I always keep Burp Suite and Zap Proxy up. Let’s look at the request. I opened my Burp, searched for the ip address, searched for the page, and looked at the request.


User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:42.0) Gecko/20100101 Firefox/42.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive

Everything looks normal there. Now let’s look at the response from the web server.


HTTP/1.1 200 OK
Date: Sat, 21 Nov 2015 20:07:23 GMT
Server: Apache
Flag: RC3-SOCCER-8675309
Vary: Accept-Encoding
Content-Length: 95
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Content-Type: text/html; charset=UTF-8


<img src="goal.gif" alt="goal"/>


We see something very interesting here. There’s a section called “Flag” with the value: RC3-SOCCER-8675309. Finally we have the flag: RC3-SOCCER-8675309