MindShaRE: Using IO Ninja to Analyze NPFS

In this installment of our MindShaRE series, ZDI vulnerability researcher Michael DePlante describes how he uses the IO Ninja tool for reverse engineering and software analysis. According to its website, IO Ninja provides an “all-in-one terminal emulator, sniffer, and protocol analyzer.” The tool provides many options for researchers but can leave new users confused about where to begin. This blog provides a starting point for some of the most commonly used features. 

Looking at a new target can almost feel like meeting up with someone who’s selling their old car. I’m the type of person who would want to inspect the car for rust, rot, modifications, and other red flags before I waste the owner’s or my own time with a test drive. If the car isn’t super old, having an OBD reader (on-board diagnostics) may save you some time and money. After the initial inspection, a test drive can be critical to your decision. 

Much like checking out a used car, taking software for test drives as a researcher with the right tools is a wonderful way to find issues. In this blog post, I would like to highlight a tool that I have found incredibly handy to have in my lab – IO Ninja.

Lately, I have been interested in antivirus products, mainly looking for local privilege escalation vulnerabilities. After looking at several vendors including Avira, Bitdefender, ESET, Panda Security, Trend Micro, McAfee, and more, I started to notice that almost all of them utilize the Named Pipe Filesystem (NPFS). Furthermore, NPFS is used in many other product categories including virtualization, SCADA, license managers/updaters, etc.

I began doing some research and realized there were not many tools that let you locally sniff and connect to these named pipes easily in Windows. The Sysinternals suite has a tool called Pipelist and it works exactly as advertised. Pipelist can enumerate open pipes at runtime but can leave you in the dark about pipe connections that are opening and closing frequently. Another tool also in the Sysinternals suite called Process Explorer allows you to view open pipes but only shows them when you are actively monitoring a given process. IO Ninja fills the void with two great plugins it offers.

An Introduction to IO Ninja  

When you fire up IO Ninja and start a new session, you’re presented with an expansive list of plugins as shown below. I will be focusing on two of the plugins under the “File Systems” section in this blog: Pipe Monitor and Pipe Server.  

Before starting a new session, you may need to check the “Run as Administrator” box if the pipes you want to interact with require elevated privileges to read or write. You can inspect the permissions on a given pipe with the accesschk tool from the Sysinternals Suite:

The powerful Pipe Monitor plugin in IO Ninja allows you to record communication, as well as apply filters to the log. The Pipe Server plugin allows you to connect to the client side of a pipe. 

IO Ninja: Pipe Monitor

The following screenshot provides a look at the Pipe Monitor plugin that comes by default with IO Ninja.

In the above screenshot, I added a process filter (*chrome*) and started recording before I opened the application. You can also filter on a filename ( name of the pipe), PID, or file ID. After starting Chrome, data started flowing between several pipe instances. This is a terrific way to dynamically gather an understanding of what data is going through each pipe and when those pipes are opened and closed. I found this helpful when interacting with antivirus agents and wanted to know what pipes were being opened or closed based on certain actions from the user, such as performing a system scan or update. It can also be interesting to see the content going across the pipe, especially if it contains sensitive data and the pipe has a weak ACL.

It can also help a developer debug an application and find issues in real-time like unanswered pipe connections or permission issues as shown below. 

Using IO Ninja’s find text/bin feature to search for “cannot find”, I was able to identify several connections in the log below where the client side of a connection could not find the server side. In my experience, many applications make these unanswered connections out of the box.

What made this interesting was that the process updatesrv.exe, running as NT AUTHORITY\SYSTEM, tried to open the client side of a named pipe but failed with ERROR_FILE_NOT_FOUND. We can fill the void by creating our own server with the name it is looking for and then triggering the client connection by initiating an update within the user interface.

As a low privileged user, I am now able to send arbitrary data to a highly privileged process using the Pipe Server plugin. This could potentially result in a privilege escalation vulnerability, depending on how the privileged process handles the data I am sending it.

IO Ninja: Pipe Server

The Pipe Server plugin is powerful as it allows you to send data to specific client connections from the server side of a pipe. The GUI in IO Ninja allows you to select which conversation you’d like to interact with by selecting from a drop-down list of Client IDs. Just like with the Pipe Monitor plugin, you can apply filters to clean up the log. Below you’ll find a visual from the Pipe Server plugin after starting the server end of a pipe and getting a few client connections.  

In the bottom right of the previous image, you can see the handy packet library. Other related IO Ninja features include a built-in hex editor, file- and script-based transmission, and packet templating via the packet template editor.

The packet template editor allows you to create packet fields and script custom actions using the Jancy scripting language. Fields are visualized in the property grid as shown above on the bottom left-hand side of the image, where they can be edited. This feature makes it significantly easier to create and modify packets when compared to just using a hex editor.

Conclusion

This post only scratches the surface of what IO Ninja can do by highlighting just two of the plugins offered. The tool is scriptable and provides an IDE that encourages users to build, extend or modify existing plugins.  The plugins are open source and available in a link listed at the end of the blog. I hope that this post inspires you to take a closer look at NPFS as well as the IO Ninja tool and the other plugins it offers.

Keep an eye out for future blogs where I will go into more detail on vulnerabilities I have found in this area. Until then, you can follow me @izobashi and the team @thezdi on Twitter for the latest in exploit techniques and security patches.

Additional information about IO Ninja can be found on their website. All of IO Ninja’s plugins are open source and available here.

Additional References

If you are interested in learning more you can also check out the following resources which I found helpful.

Microsoft - Documentation: Named Pipes

Gil Cohen - Call the plumber: You have a leak in your named pipe

0xcsandker - Offensive Windows IPC Internals 1: Named Pipes