Exactly, so at the moment only the following are affected: - impish - jammy
I've added a few comments to the arctica-greeter repo and issued a pull request that basically reverts the commit that introduced the weakness. However this still needs to be reviewed by the maintainers -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to lightdm in Ubuntu. https://bugs.launchpad.net/bugs/1948339 Title: Logon screen can be bypassed using various shortcuts Status in Ubuntu MATE: New Status in arctica-greeter package in Ubuntu: New Status in lightdm package in Ubuntu: New Status in mate-settings-daemon package in Ubuntu: New Bug description: Hi, my little daughter discovered a logon screen bypass in Ubuntu Mate 21.10 after hitting the keyboard for a while. It turns out that several keyboard shortcuts are allowed while Ubuntu Mate is locked (arctica-greeter): - Mod4 + S (mate-search-tool) - Mod4 + E (Open Caja / File Explorer) - CTRL + Shift + Esc (mate-system-monitor) - PRNT (Screenshot) All of the mentioned shortcuts could be used to spawn a file explorer (Caja) or various other binaries as user "lightdm", who owns the logon screen. Although an interactive terminal like mate-terminal, xterm, lxterm etc. could not be opened directly, there are various options to run commands as the lightdm user, for example by creating a shell script using "caja", and execute it directly using the GUI. I've attached Proof-of-Concept GIFs for all shortcuts mentioned above. There might be additional shortcuts that could be used to achieve the same, however I'm not aware about every shortcut that is configured, but I suppose that the root cause is located somewhere in arctica- greeter, rather than within every single binary launched by shortcuts. The bug was reproduced on a fresh installation of Ubuntu Mate 21.10. I haven't tested other versions of Ubuntu Mate yet. Please find additional version details below: $ apt-cache policy lightdm lightdm: Installed: 1.30.0-0ubuntu4 Candidate: 1.30.0-0ubuntu4 Version table: *** 1.30.0-0ubuntu4 500 500 http://de.archive.ubuntu.com/ubuntu impish/universe amd64 Packages 100 /var/lib/dpkg/status $ apt-cache policy arctica-greeter arctica-greeter: Installed: 0.99.1.5-2nmu1 Candidate: 0.99.1.5-2nmu1 Version table: *** 0.99.1.5-2nmu1 500 500 http://de.archive.ubuntu.com/ubuntu impish/universe amd64 Packages 100 /var/lib/dpkg/status Thanks, Basti To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-mate/+bug/1948339/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
