How to add Stack Canaries to Rust executables?

Question

I'm trying to harden some executables in a project I'm working on. To test, I'm using a hello world program, and checking it with checksec , which reports that there are no canaries. I'm very new to Rust, and the lack of information on Google makes me feel I'm missing something obvious.

With GCC, it's a simple compiler flag: -fstack-protector-all . The closest thing I've found for LLVM is safe stack . However, that doesn't seem to be recognized by the Rust compiler when I try to pass it through to LLVM. For example:

rustc -C llvm-args="-fsanitize=safe-stack" -C link-arg="-fsanitize=safe-stack" test.rust

Results in

rustc: Unknown command line argument '-fsanitize=safe-stack'. Try: 'rustc -help' rustc: Did you mean '-spp-no-call'?

I'm using Rust 1.23.0. I'm trying to add these canaries not just on x86_64, but also on armeabi-v7a, in case that's relevant.

Answer 1

Currently, this isn't supported:

We updated LLVM so there's support for this [safe stack attribute] in our LLVM, and I think that turning this on by default probably wants some investigation and likely an RFC first, so I'm going to close this for now.

-- alexcrichton https://github.com/rust-lang/rust/issues/26612

I'm not able to find an RFC for this feature.

Answer 2

You cannot use LLVM's SafeStack right now.

-fsanitize=safe-stack is a Clang command line option, not necessarily an LLVM one. This likely explains why you get the error you do.

SafeStack support was originally brought up in issue 26612 , but enabling it was deferred until more investigation could be performed.

Since SafeStack is a sanitizer, the next thing to follow would be issue 39699 , the tracking issue for more sanitizers. Only a few sanitizers and platforms are currently supported. It might be as "simple" as adding it to a list and creating a PR to enable it.

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That being said, I believe Rust does have some amount of stack protection. For example, this recent issue talks about how some upcoming changes to glibc are going to affect Rust's stack guard calculations.