Skip to main content

So, How will you work with a Proxy on NTLM...?

Most SharePoint environments today are using NTLM (the default) as the authentication protocol. NTLM authentication is a challenge-response scheme, consisting of three messages, commonly referred to as Type 1 (negotiation), Type 2 (challenge) and Type 3 (authentication). For more information on NTLM go to http://en.wikipedia.org/wiki/NTLM as discussion over NTLM and its working in out of scope for this post.
The problem with setting up Web Proxies (Paros, Burp etc) is that they work fine with other types of authentication (Custom, Basic) but where there's NTLM is used the chain breaks between the proxy and the server resulting in non function of the application.
As soon as the proxy wants to connect to the server it gets the following '401:Unauthorized' response:
HTTP/1.1 401 Unauthorized Server: Microsoft-IIS/7.5 WWW-Authenticate: NTLM X-Powered-By: ASP.NET MicrosoftSharePointTeamServices: 14.0.0.4762 Date: Sat, 04 Sep 2010 06:38:22 GMT Content-Length: 0

You can't capture requests/responses through the proxies at all. I was also facing the same problem. Ronnie suggested me to use a tool which will sit between the proxy and application server. Which will handle all the NTLM communications between the proxy and the server...cool! The tool is called NTLMaps and can be downloaded here: http://ntlmaps.sourceforge.net/
'NTLM Authorization Proxy Server' (NTLMAPS) is a proxy software that allows you to authenticate via an MS Proxy Server using the proprietary NTLM protocol
Now the scenario was like this:

How to setup the chain:
1. Set the proxy server address in your browser to any port, lets say-localhost:8080

2. Set the Local proxy setting in the Web Proxy (Paros) as the same as you did for the browser so that the can communicate with each other on same port- localhost:8080
3. In Connection section of the Paros set the Outgoing proxy port no. as 5865. By default, the NTLMAPS tool runs on the same port. Now Paros will forward all requests obtained by browser to NTLMAPS at 5865.


4. Now start the NTLMAPS tool:

5. Now go to your browser and access the application. You will be able to capture request -response as usual as if you were working with custom authentications! The tool does the NTLM communications for you in the background without your knowing. You can see the communications also on the screen:



Happy Pentesting ! :)

Comments

Popular posts from this blog

Ardilla- New tool for finding SQL Injection and XSS

Three Researchers -- MIT's Adam Kiezun , Stanford's Philip Guo , and Syracuse University's Karthick Jayaraman -- has developed a new tool ' Ardilla ' that automatically finds and exploits SQL injection and cross-site scripting vulnerabilities in Web applications. It creates inputs that pinpoint bugs in Web applications and then generates SQL injection and XSS attacks. But for now Ardilla is for PHP -based Web app only. The researchers say Ardilla found 68 never-before found vulnerabilities in five different PHP applications using the tool -- 23 SQL injection and 45 XSS flaws. More information is awaited. For their attack generation techniques refer to their document at: http://www.cs.washington.edu/homes/mernst/pubs/create-attacks-tr054.pdf

Combining power of Fiddler with Burp

Both are pretty powerful tools when it comes to intercept and modify http communications. But at some point of time, they become even more powerful combo if tied with each other. They complement each other. In a recent pentest I came across a similar situation where in Burp was not able to intercept a specific kind of traffic and Fiddler came to rescue. The application was designed to upload video. The initial communication was straight forward, I mean logging into application, filling up the video details etc. And all these were easily captured by Burp except the point where you hit the Upload Video and it connects to a different server and surprisingly it was not captured by Burp, not sure why, even after repeated attempts. So, I fired Fiddler to see if the it sees this request. But it's a;ways to play with requests using Burp due to it's various functionalities like, Intruder, Repeaters etc. But it was necessary to capture this request in Burp. So the below steps can be

File Upload through Null Byte Injection

Sometimes, during file upload we come across situation wherein there would be check on the file extension at the client side as well as server side too. If the application does allow only .jpeg extension to be uploaded, the client side java script checks for the extension of the file before passing the request. We all know that how easily this can be defeated. Some applications, checks for the extension at the server side also. That's not easy to bypass. However there are some ways with which it still can be bypassed. Most of server side scripts are written in high level languages such as Php, Java etc who still use some C/C++ libraries to read the file name and contents. That leads to the problem. In C/C++ a line ends with /00 or which is called Null Byte. So whenever the interpreter sees a null byte at the end of the a string, it stops reading thinking it has reached at the end of the string. This can be used for the bypass. It works for many servers, specially php servers. T