CVE-2023-42456

Sudo-rs, a memory safe implementation of sudo and su, allows users to not
have to enter authentication at every sudo attempt, but instead only
requiring authentication every once in a while in every terminal or process
group. Only once a configurable timeout has passed will the user have to
re-authenticate themselves. Supporting this functionality is a set of
session files (timestamps) for each user, stored in /var/run/sudo-rs/ts.
These files are named according to the username from which the sudo attempt
is made (the origin user). An issue was discovered in versions prior to
0.2.1 where usernames containing the . and / characters could result in
the corruption of specific files on the filesystem. As usernames are
generally not limited by the characters they can contain, a username
appearing to be a relative path can be constructed. For example we could
add a user to the system containing the username ../../../../bin/cp. When
logged in as a user with that name, that user could run sudo -K to clear
their session record file. The session code then constructs the path to the
session file by concatenating the username to the session file storage
directory, resulting in a resolved path of /bin/cp. The code then clears
that file, resulting in the cp binary effectively being removed from the
system. An attacker needs to be able to login as a user with a constructed
username. Given that such a username is unlikely to exist on an existing
system, they will also need to be able to create the users with the
constructed usernames. The issue is patched in version 0.2.1 of sudo-rs.
Sudo-rs now uses the uid for the user instead of their username for
determining the filename. Note that an upgrade to this version will result
in existing session files being ignored and users will be forced to
re-authenticate. It also fully eliminates any possibility of path
traversal, given that uids are always integer values. The sudo -K and
sudo -k commands can run, even if a user has no sudo access. As a
workaround, make sure that one’s system does not contain any users with a
specially crafted username. While this is the case and while untrusted
users do not have the ability to create arbitrary users on the system, one
should not be able to exploit this issue.