I spent the last weeks traveling to Singapore and Miami to present my Xenpwn research about double fetch vulnerabilities in paravirtualized devices at Infiltrate and Syscan360. You can find my slides here. Both conferences had great organization, very technical talks and a cool audience. In the following I want to give a short recap of some of the talks I liked the most:
Sean Heelan – Automatic Root-Cause Identification for Crashing Executions (Infiltrate)
Sean Heelan talked about his work on automated root cause analysis. The goal of this research is to give a human researcher a detailed analysis of the potential root causes (in the form of violated predicates) that triggered a crash during a fuzzing run. Sean summarizes the core idea of his research much better than I would be able to in his blog post, which also contains a link to his slides. I’m always a big fan of his talks because he is one of the few peoples working in the intersection between the academic program verification community and the IT security industry.
As part of my research on the security of paravirtualized devices, I reported a number of vulnerabilities to the Xen security team, which were patched today. All of them are double fetch vulnerabilities affecting the different backend components used for paravirtualized devices. While the severity and impact of these bugs varies heavily and is dependent on a lot of external factors, I would recommend patching them as soon as possible. In the rest of this blog post I’ll give a short teaser about my research with full details coming out in the first quarter of 2016 .
This post is a short wrap-up of our Troopers talk about the research we did on IBM’s General Parallel File System. If you are interested in all the technical details take a look at our slides or the video recording. We will also give an updated version of this talk at the PHDays conference in Moscow next month.
The IBM General Parallel File System is a distributed file system used in large scale enterprise environments, high performance clusters as well as some of the worlds largest super computers. It is considered by many in the industry to be the most feature rich and production hardened distributed file system currently available. GPFS has a long and really interesting history, going back to the Tiger Shark file system created by IBM 1993.
Last week Matthias and I went to Singapore to teach our workshop on Hypervisor Exploitation at SyScan. After a very unpleasant Lufthansa strike (which made us arrive late in Singapore) and two intense workshop days, we were free to attend the “last” SyScan. There are few IT security conferences that have such a great reputation in the community and so we had high expectations, which were definitely not disappointed. This year had a lot of really interesting talks so I will just summarize some of the ones I liked the most.
In my last blog post, I gave an overview about recent vulnerabilities discovered in the x86 emulation layer of Xen. While both of the discussed vulnerabilities only allow for guest privilege escalation, the complexity of the involved code seemed to indicate that even more interesting bugs could be discovered. So I spent some time searching for memory corruption issues and discovered a very interesting bug that resulted in XSA 123 . This post gives an overview about the root cause of the bug and a short description of exploitation challenges. A follow-up post will describe possible exploitation strategies in more detail.
Developing a secure and feature rich hypervisor is no easy task. Recently, the open source Xen hypervisor was affected by two interesting vulnerabilities involving its x86 emulation code: XSA 110 and XSA 105. Both bugs show that the attack surface of hypervisors is often larger than expected. XSA 105 was originally reported) by Andrei Lutas from BitDefender. The patch adds missing privilege checks to the emulation routines of several critical system instructions including LGDT and LIDT. The vulnerable code can be reached from unprivileged user code running inside hardware virtual machine (HVM) guests and can be used to escalate guest privileges. XSA 110 was reported by Jan Beulich from SUSE and concerns insufficient checks when emulating long jumps, calls or returns.
As every year some of us used the holidays to visit the Chaos Communication Congress to socialize with like-minded people and to hear interesting talks.
I mean what other reasons than learning about security might exist to leave behind all your lovely in-laws you’ve been sharing some relative’s house with the days before … 😉
Here is a short recap of some of the talks we found most interesting:
Mining for Bugs with Graph Database Queries by Fabian Yamaguchi Video
One of my favorite talks at this years congress was about the open source tool joern, a code analysis platform for C/C++ applications. Fabian, the main author of joern, presented his work on vulnerability discovery in large code bases. One of the key points of his work is robustness, meaning that the resulting tools should produce meaningful results in large and noisy real world projects even if this results in a loss of accuracy. The second important point is that tools should assist human auditors, not replace them, which seems to be one of the more interesting current research directions (see also this paper). At its core joern combines standard compiler technology with modern graph databases to offer auditors a powerful way to search for certain code constructs. To do this joern parses source code into an AST (Abstract Syntax Tree) and creates the corresponding CFG (Control Flow Graph), as well as a Data Dependency Graph (PDG) for all functions. This creates the Code Property Graph which combines all three representation forms into a single unified layer.
The Code Property Graph is stored inside a graph database (joern uses neo4j), which can be queried using a powerful graph traversal language named gremlin (https://github.com/tinkerpop/gremlin/wiki). The combination of gremlin with some wrapper tools included in joern gives an auditor the possibility to construct powerful search queries against the code base. Fabian presented different queries he used to search for vulnerabilities in the VLC video player, as well as the Linux kernel that resulted in really impressive results (and a high number of discovered vulnerabilities). Joern is definitely a tool you should check out and I’m looking forward to more impressive research by its author.
– Felix
One interesting observation we make when testing complex environments is that at the bottom of huge technology stacks, there is usually a handful of shell scripts doing interesting stuff. More often than not these helper scripts are started as part of cron jobs running as root and perform basic administrative tasks like compressing and copying log files or deleting leftover files in temporary directories. Of course, these high privileges make them an interesting target for privilege escalation attacks and one class of vulnerability we reliably encounter in shell scripts is unsafe handling of globbing or filename expansions.
The below post was originally written on February 9th as a little educational exercise & follow-up to my BinDiff post. (This research was actually triggered by a relative asking about that strange Fritz!Box vulnerability he heard about on the radio). Once we realized the full potential of the bug we decided against publishing the post and contacted several parties instead. Amongst others this contributed to the German BSI press release. Given the cat is out of the bag now anyway, we see no reason to hold it back. We will further take this as an opportunity to lay out our basic vulnerability disclosure principles in a future post. This topic will also be discussed in the panel “Ethics of Security Work & Research” at Troopers
When teaching courses on topics like Reverse Engineering or Malware Analysis we always emphasize the need to minimize unneeded work. Because reversing an unknown binary is a time consuming and complex process, tools that simplify the RE process are invaluable when working under time pressure. In this blogpost series I will present multiple tools and techniques that can help to reverse an unknown binary. Please note that these articles do not contain cutting edge research but rather target at newcomers. However, I hope to also provide some useful and interesting information for moreexperienced practitioners.
