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Showing posts from November, 2015

Multi-Version Execution Defeats a Compiler-Bug-Based Backdoor

Cristian Cadar , Luís Pina , John Regehr What should you do if you’re worried that someone might have exploited a compiler bug to introduce a backdoor into code that you are running? One option is to find a bug-free compiler. Another is to run versions of the code produced by multiple compilers and to compare the results (of course, under the additional assumption that the same bug does not affect all the compilers). For some programs, such as those whose only effect is to produce a text file, comparing the output is easy. For others, such as servers, this is more difficult and specialized system support is required. Today we’ll look at using Varan the Unbelievable to defeat the sudo backdoor from the PoC||GTFO article. Varan is a multi-version execution system that exploits the fact that if you have some unused cores, running additional copies of a program can be cheap. Varan designates a leader process whose system call activity is recorded in a shared ring buffer, and on