- personal software technology blog

Tonight I am trying to install WebScarab so I can complete the webgoat tutorials (at least some of them).

I have to back track and install java on my laptop to run the installer (java jdk - web scarab - web goat is the stack so far).

I'd like to work through WebGoat and get to SQL injection attacks - I'd like to be able to see what that looks like, basically because this xkcd comic is hilarious:

Ack:  webgoat died in java 6 with this exception from the installer:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at com.izforge.izpack.panels.ShortcutPanel.isValidated(ShortcutPanel.jav
at com.izforge.izpack.installer.InstallerFrame.navigateNext(InstallerFra
at com.izforge.izpack.installer.InstallerFrame$NavigationHandler.actionP

Easily solved - simply go to \Prgram Files\WebScarab and launch the webscarab.jar by hand - the only thing this stops is the shortcuts being created. So now I'm wondering about the wisdom of going with Java 6 AWT with this tool that is from 2007, but I'll give it  a go.

Now I am running WebScarab, I decided to also install Wireshark to have around.  Already had Firebug installed too.

So I just tested and webscarab appears to be working.  It appears to be nicer than tcpmon from axis.  I'm going to try it out - editing a request on-the-fly seems like a nice feature for debugging issues.

First Attack Vector - HTTP Splitting

Okay, so I am just working through the HTTP splitting attack - this is using carriage return and line feeds to inject fake responses.

This can obviously be avoided by filtering input characters to exclude control characters.  An important concern for internationalization.

I think the key idea is to fool the browser into doing a 302 redirect with a parameter that can contain an encoded line feed and "HTTP/1.1 200 OK" header.  When the server writes out the Location: header for the redirect, we end up simulating a 200 OK on a new line.  The browser interprets this as a second response and you can inject whatever content you like - add an accurate content-length and the browser renders it and whats more stops at the end of your content.

Example:  (see also

Content-Length: 0

HTTP/1.1 200 OK
Content-Type: text/html
Content-Length: 21

One arranges for a 302 to happen where a parameter has a value like:


This ends up rendering a response like:

HTTP/1.1 302 Found 
Date: Tue, 14 Dec 2010 11:11:07 GMT
Server: Apache/1.3.29 (Unix) mod_ssl/2.8.16 OpenSSL/0.9.7c
Content-length: 0
HTTP/1.1 200 OK
Content-length: 22 
<html>Hacked</html> of 302 headers....

This attack vector supports others (cache poisoning for example uses a future Last-Modified header with this vector to fool browsers into caching a attack site).  In a sense this attack is not "pure" - it relies on browsers being "naive" and starting processing of the second response in the middle of the 302 response.  Less than satisfying....

One thought is that many companies protect request parameters but not response ones - we could attack from within a company by setting funny values in these parameters too on the server responses.  That would be more interesting to protect against....