sudo-rs: Partial password reveal is possible after timeout

Summary

If a user begins entering a password but does not press return for an extended period, a password timeout may occur. When this happens, the keystrokes that were entered are echoed back to the console.

Example

Using sudo-rs:

geiger@cerberus:~$ sudo -s
[sudo: authenticate] Password: sudo-rs: timed out
geiger@cerberus:~$ testtesttest

"testtesttest" was entered at the password prompt but not confirmed by pressing return and then waiting for the timeout.

Impact

This could reveal partial password information, possibly exposing history files when not carefully handled by the user and on screen, usable for Social Engineering or Pass-By attacks.

Versions affected

Passwords timeouts were added in sudo-rs 0.2.7 (with a default set to 5 minutes).

Credits

This issue was discovered and reported by @DevLaTron.