4 ms·

I think Rust has to mature some more. As far as I know, it is currently not possible to implement constant-time functions using stable Rust.

by whyever 11y ago

simcop2387 11y ago
That's been the consensus I've seen from the group working on Octavo, a rust crypto library. http://lukasz.niemier.pl/octavo/octavo/index.html http://lukasz.niemier.pl/octavo/octavo/index.html It's a possible future goal of the project to end up API compatible to OpenSSL to do just what the GP was saying. I think the constant time functions are the biggest reason it can't happen yet, though there's probably more I'm just not aware of.
deleted 11y ago
[deleted]
masklinn 11y ago
> As far as I know, it is currently not possible to implement constant-time functions using stable Rust. For those wondering, that's because asm! is not stabilised and the stabilisation path for it is unclear[0], there's also been a proposal for an alternative asm![1], Rust otherwise relies on LLVM and Brian Anderson reported[2] having > been told by LLVM folks that getting LLVM to do constant time code generation is essentially hopeless, and it should just be written in asm. Nadeko[3] aims to do exactly that, but because of the above only works on nightly. [0] an RFC was created then retracted[4] for discussions on internals[5] [1] https://github.com/rust-lang/rfcs/pull/129/files https://github.com/rust-lang/rfcs/pull/129/files [2] http://rust-dev.1092773.n5.nabble.com/Rust-crypto-highlights-td11192.html#message11198 http://rust-dev.1092773.n5.nabble.com/Rust-crypto-highlights... [3] https://github.com/klutzy/nadeko https://github.com/klutzy/nadeko [4] https://github.com/rust-lang/rfcs/issues/1274 https://github.com/rust-lang/rfcs/issues/1274 [5] https://internals.rust-lang.org/t/stabilization-path-for-asm/2610 https://internals.rust-lang.org/t/stabilization-path-for-asm...
- ori_b 11y ago
  Why do you need asm! for it? .s files exist, and as far as I understand, are easy to link to.
  - masklinn 11y ago
    I'm not sure composition would work so you'd have to code every constant-time function entirely in assembler. And now I wonder why there isn't already such a project, surely the number of necessarily constant-time functions is relatively low? Constant-time equality (of byte sequences), constant time conditional (`a if b else c`), constant-time comparison (<=) and maybe constant-time bytes copy?

I think Rust has to mature some more. As far as I know, it is currently not possible to implement constant-time functions using stable Rust.

by whyever 11y ago

I think Rust has to mature some more. As far as I know, it is currently not possible to implement constant-time functions using stable Rust.

simcop2387 11y ago

That's been the consensus I've seen from the group working on Octavo, a rust crypto library. http://lukasz.niemier.pl/octavo/octavo/index.html http://lukasz.niemier.pl/octavo/octavo/index.html It's a possible future goal of the project to end up API compatible to OpenSSL to do just what the GP was saying. I think the constant time functions are the biggest reason it can't happen yet, though there's probably more I'm just not aware of.

deleted 11y ago

[deleted]

masklinn 11y ago

> As far as I know, it is currently not possible to implement constant-time functions using stable Rust. For those wondering, that's because asm! is not stabilised and the stabilisation path for it is unclear[0], there's also been a proposal for an alternative asm![1], Rust otherwise relies on LLVM and Brian Anderson reported[2] having > been told by LLVM folks that getting LLVM to do constant time code generation is essentially hopeless, and it should just be written in asm. Nadeko[3] aims to do exactly that, but because of the above only works on nightly. [0] an RFC was created then retracted[4] for discussions on internals[5] [1] https://github.com/rust-lang/rfcs/pull/129/files https://github.com/rust-lang/rfcs/pull/129/files [2] http://rust-dev.1092773.n5.nabble.com/Rust-crypto-highlights-td11192.html#message11198 http://rust-dev.1092773.n5.nabble.com/Rust-crypto-highlights... [3] https://github.com/klutzy/nadeko https://github.com/klutzy/nadeko [4] https://github.com/rust-lang/rfcs/issues/1274 https://github.com/rust-lang/rfcs/issues/1274 [5] https://internals.rust-lang.org/t/stabilization-path-for-asm/2610 https://internals.rust-lang.org/t/stabilization-path-for-asm...

ori_b 11y ago
Why do you need asm! for it? .s files exist, and as far as I understand, are easy to link to.
- masklinn 11y ago
  I'm not sure composition would work so you'd have to code every constant-time function entirely in assembler. And now I wonder why there isn't already such a project, surely the number of necessarily constant-time functions is relatively low? Constant-time equality (of byte sequences), constant time conditional (`a if b else c`), constant-time comparison (<=) and maybe constant-time bytes copy?