certain usernames break config

[hyder365]

Calling sudo-rs with -u and a username that begins with an underscore seems to trip it up. Here I want to run a script, but only allow it without arguments.

sudo-rs -u _unpriv myscript

gives the error:

/etc/sudoers:37:13: expecting ')' but found '_'

Example config:

Cmnd_Alias BUILD = /usr/local/bin/myscript ""
myuser ALL=(_unpriv) NOPASSWD: BUILD`

[bjorn3]

This is what sudo-rs considers valid when parsing usernames:

A username consists of alphanumeric characters as well as "." and "-", but does not start with an underscore.

The actual parsing code:

sudo-rs/src/sudoers/tokens.rs

Lines 11 to 37 in 51f5235

	/// A username consists of alphanumeric characters as well as "." and "-", but does not start with an underscore.
	// See: https://systemd.io/USER_NAMES/
	impl Token for Username {
	fn construct(text: String) -> Result<Self, String> {
	// if a '$' occurs in a username, it has to be the final character
	if text.strip_suffix('$').unwrap_or(&text).contains('$') {
	return Err("embedded $ in username".to_string());
	}
	SudoString::new(text)
	.map_err(|e| e.to_string())
	.map(Username)
	}
	fn accept(c: char) -> bool {
	c.is_ascii_alphanumeric() || ".-_@$".contains(c)
	}
	fn accept_1st(c: char) -> bool {
	c != '_' && c != '@' && Self::accept(c)
	}
	const ALLOW_ESCAPE: bool = true;
	fn escaped(c: char) -> bool {
	matches!(c, '\\' | '"' | ',' | ':' | '=' | '!' | '(' | ')')
	}
	}

[squell]

Correct, underscores were not allowed to begin a username. It may be that that's too strict, an easy fix should be to remove c != '_' && on line 30 in tokens.rs.

I have a feeling we're going to see a lot of unexpected choices of user- and host-names in our issue tracker in the next few weeks; I welcome this, and thanks for opening an issue!