xcb: Soundness issue with base::Error

[Qwaz]

Original issue report: https://github.com/rtbo/rust-xcb/issues/93

[Shnatsel]

Thanks!

[psychon]

Sorry for highjacking this PR, but I do not think this warrants a separate issue/PR.
I am exaggerating, but almost all of xcb is unsafe. Here are some examples that are easier to trigger accidentally than what this PR is about:

• interpret some bytes coming from the X11 server as any type you like: https://github.com/rtbo/rust-xcb/issues/95
• Out-of-bounds read for sending bytes to the server: https://github.com/rtbo/rust-xcb/issues/94
• a "safe" version of mem::transmute (with some limits on the types, but not enough): https://github.com/rtbo/rust-xcb/issues/78
• I'm not sure if this even counts, but here is an old issue about a NULL pointer dereference in safe rust: https://github.com/rtbo/rust-xcb/issues/64

[psychon]

I'm not looking for these on purpose. I am just reading some code /(edit: some code using xcb, not the source code of xcb itself) and wonder "why doesn't this return a Result?". This one is is a call to std::str::from_utf8_unchecked with a comment next to it saying "should we check what comes from X?". Yes, you should, and you should not simply assume that the data is fine.
https://github.com/rtbo/rust-xcb/issues/96

(Side note: X11 atoms are specified to use latin1)

[Shnatsel]

@psychon thank your for investigating the xcb crate and reporting the issues upstream! Could you add a bit more detail to the upstream report - that atoms are specified to use latin1, what exactly is the problem with the current approach, and what should be done instead? I am not sure the issue is actionable for the maintainers as-is.

[psychon]

Done, I hope. I also improved my other report there slightly, explaining that bool can only have values 0 and 1.

I am not sure the issue is actionable for the maintainers as-is.

Well, according to its README, I would think that the xcb crate is unmaintained. At its very top:

Maintainance request

I've been very happy to work on this project, but I don't have the possibility anymore to maintain these bindings to the level the Rust community deserves. I can't spend as much time on it as I used to, and I'm not using neither Rust nor XCB anymore, so I clearly can't improve the bindings with the latest Rust features. Person with motivation and good knowledge of Rust and XCB may contact me per email.