Unix-style approach to web application testing

Author: dnet

SANS Institute accepted my GWAPT Gold Paper about Unix-style approach to web application testing, the paper is now published in the Reading Room.

The paper introduces several problems I’ve been facing while testing web applications, which converged in a common direction. Burp Suite is known by most and used by many professionals in this field, and while it’s extensible, writing such bits of software have a higher barrier of entry than the budgets of some project would allow for a one-off throwaway tool. Our solution, Piper is introduced through real-world examples to demonstrate its usage and the fact that it’s worth using it. I tried showing alternatives to each subset of the functionality to stimulate critical thinking in the minds of fellow penetration testers, since this tool is not a silver bullet either. By describing the landscape in a thorough manner, I hope everyone can learn to pick the best tool for the job, which might or might not be Piper.

The full Gold Paper can be downloaded from the website of SANS Institute:

Unix-style approach to web application testing

The accompanying code is available on GitHub. For those who prefer video content, only have 2 minutes, or find the whole idea too abstract, we made a short demonstration of the basic features below. If you’re interested in deeper internals, there’s also a longer, 45-minutes talk about it.


Wide open banking: PSD2 and us

Author: dnet

With the advent of PSD2 APIs, we had the opportunity to test some of them upon request from our clients. Although internet-facing APIs were already a thing thanks to smartphone apps, it seems that regulatory requirements and 3-way setups (customer, bank, provider) led to some surprises. Here are some of the things we found.

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Patching Android apps: what could possibly go wrong

Author: dnet

Many tools are timeless: a quality screwdriver will work in ten years just as fine as yesterday. Reverse engineering tools, on the other hand need constant maintenance as the technology we try to inspect with them is a moving target. We’ll show you how just a simple exercise in Android reverse engineering resulted in three patches in an already up-to-date tool.

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Evading Cisco AnyConnect blocking LAN connections

Author: dnet

Some VPNs allow split tunneling, however, Cisco AnyConnect and many other solutions offer a way for network administrators to forbid this. When that happens, connecting to the VPN seals off the client from the rest of the LAN. As it turns out, breaking this seal is not that hard, which can be useful for special cases like performing pentests over a VPN designed for average users.

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Self-defenseless – Exploring Kaspersky’s local attack surface

Author: b

I had the pleasure to present my research about the IPC mechanisms of Kaspersky products at the IV. EuskalHack conference this weekend. My main motivation for this research was to further explore the attack surface hidden behind the self-defense  mechanisms of endpoint security software, and I ended up with a local privilege escalation exploit that could be combined with an older self-defense bypass to make it work on default installations. I hope that the published information helps other curious people to dig even deeper and find more interesting pieces of code.

The presentation and some code examples are available on GitHub.

My local privilege-escalation exploit demo can be watched here:

The exploit code will be released at a later time on GitHub, so you can have some fun reconstructing it based on the slides ;)


Decrypting Eazfuscator.NET encrypted symbol names

Author: dnet

There are many obfuscators for different languages, and some of those offer reversible options for easier field debugging. Eazfuscator.NET is one of these and with a bit of reverse engineering, whole files can be restored with the original symbols once you have the password.

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Drop-by-Drop: Bleeding through libvips

Author: b

During a recent engagement we encountered a quite common web application feature: profile image uploads. One of the tools we used for the tests was the UploadScanner Burp Suite extension, that reported no vulnerabilities. However, we noticed that the profile picture of our test user showed seemingly random pixels. This reminded us to the Yahoobleed bugs published by Chris Evans  so we decided to investigate further.

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Our take on social engineering

Author: dnet

Like many other offensive IT security companies, we also offer social engineering assessments. And like in other areas of our portfolio, we try to steer client needs in a way that they order something that actually matters. This blog post summarizes what we experienced and how we see things in this field. While many things work the same way around the globe, the starting point is our feeling here in Hungary, where many people in the local IT security scene think social engineering means walking into buildings dressed as a pizza delivery guy and calling targets on the phone.

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The curious case of encrypted URL parameters

Author: dnet

As intra-app URLs used in web applications are generated and parsed by the same code base, there’s no external force pushing developers towards using a human-readable form of serialization. Sure, it’s easier to do debugging and development, but that’s why I used the word “external”. Many frameworks use custom encodings, but one of the most extreme things a developer can do in this regard is completely encrypting request parameters. We encountered such a setup during a recent web app security assessment, let’s see how it worked out.

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Snow cannon vs. unique snowflakes — testing registration forms

Author: dnet

Many of the web application tests we conducted had a registration form in the scope. In such cases, there’s usually a field that needs to be unique for each invocation, sometimes called username, in other cases, the e-mail address is used as such. However, launching the Scanner or Intruder of Burp Suite or a similar tool will send the same username over and over again, resulting in possible false negatives. We faced this problem long enough that we came up with a solution for it, and now you can use it too!

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