toolsmith #114: WireEdit and Deep Packet Modification

PCAPs or it didn't happen, right? 



Introduction
Packet heads, this toolsmith is for you. Social media to the rescue. Packet Watcher (jinq102030) Tweeted using the #toolsmith hashtag to say that WireEdit would make a great toolsmith topic. Right you are, sir! Thank you. Many consider Wireshark the eponymous tool for packet analysis; it was only my second toolsmith topic almost ten years ago in November 2006. I wouldn't dream of conducting network forensic analysis without NetworkMiner (August 2008) or CapLoader (October 2015). Then there's Xplico, Security Onion, NST, Hex, the list goes on and on...
Time to add a new one. Ever want to more easily edit those packets? Me too. Enter WireEdit, a comparatively new player in the space. Michael Sukhar (@wirefloss) wrote and maintains WireEdit, the first universal WYSIWYG (what you see is what you get) packet editor. Michael identifies WireEdit as a huge productivity booster for anybody working with network packets, in a manner similar to other industry groundbreaking WYSIWIG tools.

In Michael's own words: "Network packets are complex data structures built and manipulated by applying complex but, in most cases, well known rules. Manipulating packets with C/C++, or even Python, requires programming skills not everyone possesses and often lots of time, even if one has to change a single bit value. The other existing packet editors support editing of low stack layers like IPv4, TCP/UDP, etc, because the offsets of specific fields from the beginning of the packet are either fixed or easily calculated. The application stack layers supported by those pre-WireEdit tools are usually the text based ones, like SIP, HTTP, etc. This is because no magic is required to edit text. WireEdit's main innovation is that it allows editing binary encoded application layers in a WYSIWYG mode."

I've typically needed to edit packets to anonymize or reduce captures, but why else would one want to edit packets?
1) Sanitization: Often, PCAPs contain sensitive data. To date, there has been no easy mechanism to “sanitize” a PCAP, which, in turn, makes traces hard to share.
2) Security testing: Engineers often want to vary or manipulate packets to see how the network stack reacts to it. To date, that task is often accomplished via programmatic means.
WireEdit allows you to do so in just a few clicks.

Michael describes a demo video he published in April 2015, where he edits the application layer of the SS7 stack (GSM MAP packets). GSM MAP is the protocol responsible for much of the application logic in “classic” mobile networks, and is still widely deployed. The packet he edits carries an SMS text message, and the layer he edits is way up the stack and binary encoded. Michael describes the message displayed as a text, but notes that if looking at the binary of the packet, you wouldn’t find it there due to complex encoding. If you choose to decode in order to edit the text, your only option is to look up the offset of the appropriate bytes in Wireshark or a similar tool, and try to edit the bytes directly.
This often completely breaks the packet and Michael proudly points out that he's not aware of any tool allowing to such editing in WYSIWYG mode. Nor am I, and I enjoyed putting WireEdit through a quick validation of my own.

Test Plan

I conceived a test plan to modify a PCAP of normal web browsing traffic with web application attacks written in to the capture with WireEdit. Before editing the capture, I'd run it through a test harness to validate that no rules were triggered resulting in any alerts, thus indicating that the capture was clean. The test harness was a Snort 2.9.8.0 instance I'd implemented on a new Ubuntu 14.04 LTS, configured with Snort VRT and Emerging Threats emerging-web_server and emerging-web_specific_apps rules enabled. To keep our analysis all in the family I took a capture while properly browsing the OpenBSD entry for tcpdump.
A known good request for such a query would, in text, as a URL, look like:
http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man8/tcpdump.8?query=tcpdump&sec=8
Conversely, if I were to pass a cross-site scripting attack (I did not, you do not) via this same URL and one of the available parameters, in text, it might look something like:
http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man8/tcpdump.8?query=tcpdump&sec=8%22onmouseover%3Dalert(1337)%2F%2F
Again though, my test plan was one where I wasn't conducting any actual attacks against any website, and instead used WireEdit to "maliciously" modify the packet capture from a normal browsing session. I would then parsed it with Snort to validate that the related web application security rules fired correctly.
This in turn would validate WireEdit's capabilities as a WYSIWYG PCAP editor as you'll see in the walk-though. Such a testing scenario is a very real method for testing the efficacy of your IDS for web application attack detection, assuming it utilized a Snort-based rule set.

Testing

On my Ubuntu Snort server VM I ran sudo tcpdump -i eth0 -w toolsmith.pcap while browsing http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man8/tcpdump.8?query=tcpdump&sec=8.
Next, I ran sudo snort -c /etc/snort/snort.conf -r toolsmith.pcap against the clean, unmodified PCAP to validate that no alerts were received, results noted in Figure 1.

Figure 1: No alerts triggered via initial OpenBSD browsing PCAP

I then dragged the capture (407 packets) over to my Windows host running WireEdit.
Now wait for it, because this is a lot to grasp in short period of time regarding using WireEdit.
In the WireEdit UI, click the Open icon, then select the PCAP you wish to edit, and...that's it, you're ready to edit. :-) WireEdit tagged packet #9 with the pre-requisite GET request marker I was interest in so expanded that packet, and drilled down to the HTTP: GET descriptor and the Request-URI under Request-Line. More massive complexity, here take notes because it's gonna be rough. I right-clicked the Request-URI, selected Edit PDU, and edited the PDU with a cross-site scripting (JavaScript) payload (URL encoded) as part of the GET request. I told you, really difficult right? Figure 2 shows just how easy it really is.

Figure 2: Using WireEdit to modify Request-URI with XSS payload

I then saved the edited PCAP as toolsmithXSS.pcap and dragged it back over to my Snort server and re-ran it through Snort. The once clean, pristine PCAP elicited an entirely different response from Snort this time. Figure 3 tells no lies.

Figure 3: XSS ET Snort alert fires

Perfect, in what was literally a :30 second edit with WireEdit, I validated that my ten minute Snort setup catches cross-site scripting attempts with at least one rule. And no websites were actually harmed in the making of this test scenario, just a quick tweak with WireEdit.
That was fun, let's do it again, this time with a SQL injection payload. Continuing with toolsmithXSS.pcap I jumped to the GET request in frame 203 as it included a request for a different query and again edited the Request-URI with an attack specific for MySQL as seen in Figure 4.

I saved this PCAP modification as toolsmithXSS_SQLi.pcap and returned to the Snort server for yet another happy trip Snort Rule Lane. As Figure 5 represents, we had an even better result this time.  

Figure 5: WireEdited PCAP trigger multiple SQL injection alerts

In addition to the initial XSS alert firing again, this time we collected four alerts for:

• ET WEB_SERVER MYSQL SELECT CONCAT SQL Injection Attempt
• ET WEB_SERVER SELECT USER SQL Injection Attempt in URI
• ET WEB_SERVER Possible SQL Injection Attempt UNION SELECT
• ET WEB_SERVER Possible SQL Injection Attempt SELECT FROM

That's a big fat "hell, yes" for WireEdit.
Still with me that I never actually executed these attacks? I just edited the PCAP with WireEdit and fed it back to the Snort beast. Imagine a PCAP like being optimized for the OWASP Top 10 and being added to your security test library, and you didn't need to conduct any actual web application attacks. Thanks WireEdit!

Conclusion

WireEdit is beautifully documented, with a great Quickstart. Peruse the WireEdit website and FAQ, and watch the available videos. The next time you need to edit packets, you'll be well armed and ready to do so with WireEdit, and you won't be pulling your hair out trying to accomplish it quickly, effectively, and correctly. WireEdit my a huge leap from not known to me to the top five on my favorite tools list. WireEdit is everything it is claimed to be. Outstanding.
Ping me via email or Twitter if you have questions: russ at holisticinfosec dot org or @holisticinfosec.

ACK

Thanks to Michael Sukhar for WireEdit and Packet Watcher for the great suggestion.

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toolsmith: Network Security Toolkit (NST) - Packet Analysis Personified

Prerequisites

Virtualization software if you don’t wish to run NST as a LiveCD or install to dedicated hardware.

Introduction

As I write this I’m on the way back from SANS Network Security in Las Vegas where I’d spent two days deeply entrenched analyzing packet captures during the lab portion of the GSE exam. During preparation for this exam I’d used a variety of VM-based LiveCD distributions to study and practice, amongst them Security Onion. There are three distributions I run as VMs that are always on immediate standby in my toolkit. They are, in no particular order, Doug Burk’s brilliant Security Onion, Kevin Johnson’s SamuraiWTF, and Back Track 5 R3. Security Onion and SamuraiWTF have both been toolsmith topics for good reason; I’ve not covered Back Track only because it would seem so cliché. I will tell you that I am extremely fond of Security Onion and consider it indispensable. As such, I hesitated to cover the Network Security Toolkit (NST) when I first learned of it while preparing for the lab, feeling as if it might violate some code of loyalty I felt to Doug and Security Onion. Weird I know, and the truth is Doug would be one of the first to tell you that the more tools made available to defenders the better. NST represents a number of core principles inherent to toolsmith and the likes of Security Onion. NST is comprehensive and convenient and allows the analyst almost immediate and useful results. NST is an excellent learning tool and allows beginners and experts much success in discovering more about their network environments. NST is also an inclusive, open project that grows with help from an interested and engaged community. The simple truth is Security Onion and NST represent different approaches to complex problems. We all have a community to serve and the same goals at heart, so I got over my hesitation and reached out to the NST project leads.

The Network Security Toolkit is the brainchild of Paul Blankenbaker and Ron Henderson and is a Linux distribution that includes a vast collection of best-of-breed open source network security applications useful to the network security professional. In the early days of NST Paul and Ron found that they needed a common user interface and unified methodology for ease of access and efficiency in automating the configuration process. Ron’s background in network computing and Paul’s in software development lead to what is now referred to as the NST WUI (Web User Interface). Given the wide range of open source networking tools with corresponding command line interface that differ from one application to the next, this was no small feat. The NST WUI now provides a means to allow easy access and a common look-and-feel for many popular network security tools, giving the novice the ability to point and click while also providing advanced users (security analysts, ethical hackers) options to work directly with command line console output.
According to Ron, one of the most beneficial tool enhancements that NST has to offer for the network and security administrator is the Single-Tap and Multi-Tap Network Packet Capture interface. Essentially, adding a web-based front-end to Wireshark, Tcpdump, and Snort for packet capture analysis and decode has made it easy to perform these tasks using a web browser. With the new NST v2.16.0-4104 release they took it a step forward and integrated CloudShark technology into the NST WUI for collaborative packet capture analysis, sharing and management.
Ron is also fond of the Network Interface Bandwidth monitor.  This tool is an interactive dynamic SVG/AJAX enabled application integrated into the NST WUI for monitoring Network Bandwidth
usage on each configured network interface in pseudo real-time. He designed this application with the controls of a standard digital oscilloscope in mind.
Ron is also proud of NST’s ability to Geolocate network entities. We’ll further explore using NST’s current repertoire of available network entities that can geolocated with their associated application, as well as Ron’s other favorites mentioned above.

Paul also shared something I enjoyed as acronyms are so common in our trade. He mentioned that the NST distribution can be used in many situations. One of his personal favorites is related to the FIRST Robotics Competition (FRC) which occurs each year. FIRST for Paul is For Inspiration and Recognition of Science and Technology where I am more accustomed to its use as Forum for Incident Response and Security Teams. Paul mentors FIRST team 868, the TechHounds at the Carmel high school in Indiana, where in FRC competitions, teams have used NST (or could use) during a hectic FRC build season:

·      Quickly identity which network components involved with operating the robot are "alive"

o   From the WUI menu: Security -> Active Scanners -> ARP Scan (arp-scan)

·         Observe how much network traffic increases or decreases as we adjust the IP based robot camera settings

o   From the WUI menu: Network -> Monitors -> Network Interface Bandwidth Monitor

·         Capture packets between the robot and the controlling computer

·         Scan the area for WIFI traffic and use this information to pick frequencies for robot communications that are not heavily used

·         Set up a Subversion and Trac server for managing source code through the build season.

o   From the WUI menu: System -> File System Management -> Subversion Manager

·         Teach the benefits of scripting and automating tasks

·         Provide an environment that can be expanded and customized

While Paul and team have used NST for robotics, it’s quite clear how their use case bullet list applies to the incident responder and network security analyst. 

Installing NST

NST, as an ISO, can be run as LiveCD, installed to dedicated hardware, and also as a virtual machine. If you intend to take advantage of the Multi-Tap Network Packet Capture interface feature with your NST installation set up as a centralized, aggregating sensor then you’ll definitely want to utilize dedicated hardware with multiple network interfaces. As an example, Figure 1 displays using NST to capture network and port address translation traffic across a firewall boundary.

Figure 1: Multi-Tap Network Packet Capture Across A Firewall Boundary - NAT/PAT Traffic

Once booted into NST you can navigate from Applications to System Tools to Install NST to Hard Drive in order to execute a dedicated installation.

Keep in mind that when virtualizing you could enable multiple NICs to leverage multi-tap, but your performance will be limited as you’d likely do so on a host system with one NIC.

Using NST

NST use centers around the WUI; access it via Firefox on the NST installation at http://127.0.0.1/nstwui/main.cgi. 

The first time you login, you’ll be immediately reminded to change the default password (nst2003). After doing so, log back in and select Tools -> Network Widgets -> IPv4 Address. Once you know what the IP address is you can opt to use NST WUI from another browser. My session as an example: https://192.168.153.132/nstwui/index.cgi.

Per Ron’s above mentioned tool enhancements, let’s explore Single-Tap Network Packet Capture (I’m running NST as a VM). Click Network -> Protocol Analyzers -> Single-Tap Network Packet Capture where you’ll be presented with a number of options regarding how you’d like to configure the capture. You can choose define the likes of duration, file size, and packet count or select predefined short or long capture sessions as seen in Figure 2.

Figure 2: Configure a Single-Tap capture with NST

If you accepted defaults for capture storage location you can click Browse and find the results of your efforts in /var/nst/wuiout/wireshark. Now here’s where the cool comes in. CloudShark (yep, Wireshark in the cloud) allows you to “secure, share, and analyze capture files anywhere, on any device” via either cloudshark.org or a CloudShark appliance. Please note that capture files uploaded to cloudshark.org are not secured by default and can be viewed by anyone who knows the correct URL. You’ll need an appliance or CloudShark Enterprise to secure and manage captures. That aside the premise of CloudShark is appealing and NST integrates CloudShark directly. From the Tools menu select Network Widgets then CloudShark Upload Manager. I’d already upload malicious.pcap as seen in Figure 3.

Figure 3: CloudShark tightly integrated with NST

Users need only click on View Network Packet Captures in the upload manager and they’ll be directed right to the CloudShark instance of their uploaded capture as seen in Figure 4.

Figure 4: Capture results displayed via CloudShark

Many of the features you’d expect from a local instance of Wireshark are available to the analyst, including graphs, conversations, protocol decodes, and follow stream.

NST also includes the Network Interface Bandwidth Monitor. Select Network -> Monitors -> Network Interface Bandwidth Monitor. A bandwidth monitor for any interface present on your NST instance will be available to you (eth0 and lo on my VM) as seen in Figure 5.

Figure 5: NST’s Network Interface Bandwidth Monitor

You can see the +100 kbps spikes I generated against eth0 with a quick NMAP scan as an example.

NST’s geolocation capabilities are many, but be sure to setup the NST system to geolocate data first. I uploaded a multiple host PCAP (P2P traffic) via Network Packet Capture Manager, clicked the A (attach) button under Action and was them redirected back to Network -> Protocol Analyzers -> Single-Tap Network Packet Capture. I then chose to use the Text-Based Protocol Analyzer Decode option as described on the NST Wiki and clicked the Hosts – Google Maps button. This particular capture gave NST a lot of work to do as it includes thousands of IPs but the resulting geolocated visualization as seen in Figure 6 is well worth it.

Figure 6: P2P bot visually geolocated via NST

If we had page space available to show you the whole world you’d see that the entire globe is represented by this bot, but I’m only showing you North America and Europe.

As discussed in recent OSINT-related toolsmiths, there’s even an NST OSINT feature called theHarvester found under Security -> Information Search -> theHarvester. Information gathering with theHarvester includes e-mail accounts, user names, hostnames, and domains from different public internet sources.

So many features, so little time. Pick an item from the menu and drill in. There’s a ton of documentation under the Docs menu too, including the NST Wiki, so you have no excuses not to jump in head first.

In Conclusion

NST is one of those offerings where the few pages dedicated to it in toolsmith don’t do it justice. NST is incredibly feature rich, and literally invites the user to explore while the hours sneak by unnoticed. The NST WUI has created a learning environment I will be incorporating into my network security analysis teaching regimens. New to network security analysis or a salty old hand, NST is a worthy addition to your tool collection.

Ping me via email if you have questions (russ at holisticinfosec dot org).

Cheers…until next month.

Acknowledgements

Paul Blankenbaker and Ron Henderson, NST project leads