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Hi everyone,
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:
Continue reading “Infiltrate and Syscan 360”
Continue readingAs 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 .
Continue reading “Xen XSA 155: Double fetches in paravirtualized devices”
Continue readingThis 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.
Of course, this makes it an interesting target for security research. When looking at GPFS from an implementation point of view, the Linux version is made up of three different components: User space utilities and helper scripts, the mmfsd network daemon and multiple Linux kernel modules. We (Florian Grunow and me) spent some time analyzing the internals of these components and discovered critical vulnerabilities in all of them.
Continue reading “General Pr0ken Filesystem – Hacking IBM’s GPFS”
Continue readingLast 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.
Continue reading “Syscan 2015”
Continue readingIn 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.
Continue reading “Revisiting Xen’s x86 Emulation: Xen XSA 123”
Continue reading
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.
Continue reading “The Dangers of x86 Emulation: Xen XSA 110 and 105”
Continue readingAs 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:
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. Continue reading “Revisiting an Old Friend: Shell Globbing”
Continue readingThe 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
Fritz!Box is series of DSL and WLAN routers produced by AVM. They are extremely popular in Germany and are the uncontested market leader for private DSL customers. Recently, a significant number of Fritz!Box owners became victim of an attack that resulted in calls to expensive international numbers. The newspaper “Der Westen” reported about a case where phone calls valued over 4200€ were initiated from a compromised Fritz!Box. Few days later AVM published a security update for a large number of Fritz!Box models and urged customers to apply the patch as soon as possible.
However, no further details about the vulnerability were published. This blog post describes our analysis of the vulnerability that we performed directly after the first updates were released.
Continue reading “How to Own a Router – Fritz!Box AVM Vulnerability Analysis”
Continue readingWhen 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.
Continue reading “Reverse Engineering Tools Part 1: BinDiff”