RustEmbed generated `get` method allows for directory traversal when reading files from disk

Summary

When running in debug mode and the `debug-embed` (off by default) feature is not enabled, the generated `get` method does not check that the input path is a child of the folder given. This allows attackers to read arbitrary files in the file system if they have control over the filename given. The following code will print the contents of your `/etc/passwd` if adjusted with a correct number of `../`s depending on where it is run from. ```rust #[derive(rust_embed::RustEmbed)] #[folder = "src/"] pub struct Asset; fn main() { let d = Asset::get("../../../etc/passwd").unwrap().data; println!("{}", String::from_utf8_lossy(&d)); } ``` The flaw was corrected by canonicalizing the input filename and ensuring that it starts with the canonicalized folder path.