Soundness bug

[eduardosm]

Getting a segmentation fault is as easy as:

fn main() {
    let b = cbox::CBox::<str>::new(std::ptr::null_mut());
    println!("{}", b);
}

This allows to de-reference arbitrary raw pointers.

[elichai]

You can also get it to double free just as easily:

use cbox::*;
fn main() {
    let p = vec![1, 2, 3].as_mut_ptr();
    let semibox: CSemiBox<'static, str> = CSemiBox::new(p as _);
    drop(semibox);
    println!("Hello World")
}

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=23b843114b14d79ebb418975c2474dd1

[elichai]

You can also create UB via invalid UTF-8:

fn main() {
    let mut vec = vec![139,50];
    let p = vec.as_mut_ptr();
    let cbox: CBox<str> = CBox::new(p as _);
    let s: &str = cbox.deref();
    println!("Hello World: {:?}", s);
}

[elichai]

Anyhow this is a fun library :)
But it was written 5 years ago... so IMO the bug is in any library that is still maintained/used that uses a library that was last maintained before Rust 1.10 came out