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{ Category Archives } Software Correctness

Planning for Disaster

Alan Perlis once said: I think that it’s extraordinarily important that we in computer science keep fun in computing. When it started out, it was an awful lot of fun. Of course, the paying customers got shafted every now and then, and after a while we began to take their complaints seriously. We began to […]

Do Fiddly Buffer Overruns Matter?

by Pascal Cuoq and John Regehr Using tis-interpreter we found a “fiddly” buffer overrun in OpenSSL: it only goes a few bytes out of bounds and the bytes it writes have just been read from the same locations. Fiddly undefined behaviors are common and it can be hard to convince developers to fix them, especially […]

The Problem with Friendly C

I’ll assume you’re familiar with the Proposal for Friendly C and perhaps also Dan Bernstein’s recent call for a Boring C compiler. Both proposals are reactions to creeping exploitation of undefined behaviors as C/C++ compilers get better optimizers. In contrast, we want old code to just keep working, with latent bugs remaining latent. After publishing […]

Reducers are Fuzzers

A test case isn’t just a test case: it lives in the (generally extremely large) space of inputs for the software system you are testing. If we have a test case that triggers a bug, here’s one way we can look at it: The set of test cases triggering a bug is a useful notion […]

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

[This piece is jointly authored by Cristian Cadar, Luís Pina, and 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 […]

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 […]

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 […]

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 […]

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 […]

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, […]