Pierluigi Paganini
June 20, 2016
Early June the Tor Project announced a hardened version of the popular Tor Browser, the Tor Browser 6.5a1-hardened.
“A new hardened Tor Browser release is available. It can be found in the 6.5a1-hardened distribution directory and on the download page for hardened builds. This release features important security updates to Firefox.” states the announcement published by the Tor Project.
A group of researchers from the University of California, Irvine (UCI), composed of Mauro Conti, Stephen Crane, Tommaso Frassetto, Andrei Homescu, Georg Koppen, Per Larsen, Christopher Liebchen, Mike Perry, and Ahmad-Reza Sadeghi published an interesting paper entitled “Selfrando: Securing the Tor Browser against De-anonymization Exploits” that presents the recently introduced Selfrando feature.
The team also shared the Selfrando project on GitHub.
Selfrando is an enhanced and practical load-time randomization technique implemented for the Tor Browser that aims to defend Tor users against exploits.
The Selfrando will prevent intelligence agencies from de-anonymizing users through exploits. In the past, we discussed many cases where the FBI and law enforcement used exploits to unmask Tor users, including the case of the Playpen child pornography portal.
In the Playpen case, the FBI arrested Jay Michaud, a Vancouver public schools administration worker right after the law enforcement closed the popular child pornography site that was hosted on the dark web. The authorities used a specific exploit, known as network investigative technique (NIT), to track visitors of the Playpen bulletin board hidden service.
The FBI was able to harvest around 1300 IPs, and until the moment 137 people have been charged. The network investigative technique used by the FBI included computers in the UK, Chile, and Greece.
What is Selfrando?
Selfrando is a solution developed by the experts to significantly improve security over standard address space layout randomization (ASLR) techniques. The ASLR techniques are today used by Firefox and the most popular browsers, they were involved in protection from exploits leveraging buffer overflow vulnerabilities.
The team of researchers worked with the experts at the Tor Project to ensure that the Selfrando feature is fully compatible with AddressSanitizer (ASan), a compiler feature to detect memory corruption. The ASan technique is implemented in a hardened version of Tor Browser for test purposes, so the Tor Project decided to include Selfrando in the hardened releases of the Tor Browser.
The researchers demonstrated that the startup and performance overheads resulting from the implementation of the Selfrando technique are negligible (less than 1% overhead to running times).
Another interesting aspect of the feature is that it doesn’t need further development efforts, it doesn’t need too many changes to existing code.
Let me suggest to give a look to the report … it is simply amazing.
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