Path traversal in `rio-vt` Kitty graphics protocol handler allows out-of-bounds file delete (and read)

The Kitty graphics protocol handler in rio-vt builds a filesystem path from an attacker-controlled APC escape sequence and, for the temp-file medium, only checks that the path *contains the substring* "tty-graphics-protocol" before it opens, reads, and remove_files it. There is no .. rejection and no canonicalization, so a path containing the marker substring plus .. escapes the terminal's temp directory (path traversal, CWE-22/CWE-23).

Because a terminal renders whatever arrives on the PTY (ssh output, a cat'd file, CI logs), untrusted output can delete a file outside the temp area and cause its bytes to be read back in.

Details

The sink is create_graphic_data() in src/ansi/kitty_graphics_protocol.rs, in the TransmissionMedium::TempFile branch, reachable through the public API rio_vt::ansi::kitty_graphics_protocol::parse. The path is the base64 APC payload of an a=t,t=t command, and the guard is:

let path = Path::new(path_str);
if !path.is_file() { return Err(GraphicError::FileNotFound); }       // literal path, resolves `..`
// reject /proc/ /sys/ /dev/ (lowercased substring)
if cmd.medium == TransmissionMedium::TempFile
    && !path_str.contains("tty-graphics-protocol") {                 // SUBSTRING, not a component
    return Err(GraphicError::InvalidData);
}
// ...
let mut file = File::open(path)...;          // reads file bytes
if cmd.medium == TransmissionMedium::TempFile {
    let _ = std::fs::remove_file(path);      // deletes the file
}

This affects any terminal emulator or application built on rio-vt (e.g. the Rio terminal) that renders attacker-influenced output: an out-of-bounds file is deleted, and its contents are read into the process.

The fix

Fixed in rio-vt 0.5.29 (Rio 0.5.29) by PR #1998. For the temp-file medium the parent directory is resolved with canonicalize before any check, the resolved entry must lie inside a temp directory (temp_dir(), /tmp or /dev/shm) and contain the marker, and the delete goes through unlinkat on a handle to the validated directory, so neither .. nor a swapped symlink can redirect it. Path checks for the file medium also run on the file actually opened.