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Testcase Reduction for Non-Preprocessed C and C++
C-Reduce takes a C or C++ file that triggers a bug in a compiler (or other tool that processes source code) and turns it into the smallest possible test case that still triggers the bug. Most often, we try to reduce code that has already been preprocessed. This post is about how to reduce non-preprocessed…
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A Few Pictures
Paris was very quiet on Saturday and people on the street looked tired, having (like us) stayed up most of the night watching the news, listening to sirens, and worrying about things. Today was sunny and warm and things seemed more normal; plenty of folks out jogging, sitting in parks, other usual weekend activities.
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Classic Bug Reports
A bug report is sometimes entertaining either because of the personalities involved or because of the bug itself. Here are a collection of links into public bug trackers; I learned about most of these in a recent Twitter thread. GCC’s magnum opus, its War and Peace, is Bug 323: optimized code gives strange floating point…
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API Fuzzing vs. File Fuzzing: A Cautionary Tale
Libraries that provide APIs should be rock solid, and so should file parsers. Although we can use fuzzing to ensure the solidity of both kinds of software, there are some big differences in how we do that. A file parser should be fully robust: it isn’t allowed to crash even if presented with a corrupted…
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Comments on a Formal Verification of PolarSSL
The C language has given the world many enduring gifts such as buffer overflows, uninitialized variables, and use-after-free errors. Since rewriting a code base in some other language is not easy, we’re often stuck trying to eliminate bugs in legacy C before they bite us, and of course bugs in network-facing code sometimes bite us…
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Secret Coders
Although I’m not sure that I’ve mentioned it here before, I’m a pretty big comic book nerd. So I was psyched when, late last year, Gene Luen Yang mailed me asking if I’d like a review copy of his upcoming graphic novel. I love Gene’s Avatar comics, which I had been reading with my kids,…
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Sabbatical at TrustInSoft
At the beginning of September I started at TrustInSoft, a Paris-based startup where I’ll be working for the next 10 months. I’ll post later about what I’m doing here, for now a bit about the company. TrustInSoft was founded by Pascal Cuoq, Fabrice Derepas, and Benjamin Monate: computer science researchers who (among others) created the…
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A Few Synthesizing Superoptimizer Results
For this post, I crippled Souper by disabling its path conditions and limiting the depth of harvested expressions to two LLVM instructions. The first goal was to create a nice easy burn-in test for Souper’s instruction synthesizer, which uses a variant of this method; the second goal was to see if depth-limited, path-condition-free expressions would…
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Nibble Sort Denouement
Back in January my nibble sort contest resulted in entries that dramatically exceeded my expectations. Since then I’ve been trying to write up a post explaining the various strategies that people used and since you don’t care about my excuses I won’t tell you them, but I never got it written. However! I want to…
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Defending Against Compiler-Based Backdoors
Scotty Bauer (a Utah grad student), Pascal Cuoq, and I have an article in the latest PoC||GTFO about introducing a backdoor into sudo using a compiler bug. In other words, the C code implementing sudo does not contain a backdoor, but a backdoor appears when sudo is built using a particular compiler version (clang 3.3,…