I verified the test plan * on 20.04 using lightdm 1.30.0-0ubuntu4~20.04.1 from focal-proposed
* on 20.10 using lightdm 1.30.0-0ubuntu4~20.10.1 from groovy-proposed ** Tags removed: verification-needed verification-needed-focal verification-needed-groovy ** Tags added: verification-done verification-done-focal verification-done-groovy -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to lightdm in Ubuntu. https://bugs.launchpad.net/bugs/1921655 Title: lightdm-guest-session ICEauthority error Status in Ubuntu MATE: New Status in lightdm package in Ubuntu: Fix Released Status in lightdm source package in Focal: Fix Committed Status in lightdm source package in Groovy: Fix Committed Status in lightdm source package in Hirsute: Fix Released Bug description: [Impact] If you enable the guest session feature on e.g. Ubuntu MATE, you are met by an error message when trying to enter a guest session: "Could not update file ICEauthority file /run/user/XXX/ICEauthority" Even if it's not always a fatal error (the login may succeed after a few minutes), the user experience is really bad, and you are inclined to conclude that you are completely blocked from using the feature. The proposed fix adds a rule to the lightdm-guest-session AppArmor profile and prevents the error from happening. [Test Plan] On an updated Ubuntu MATE installation: * Enable guest session sudo sh -c 'printf "[Seat:*]\nallow-guest=true\n" >/etc/lightdm/lightdm.conf.d/50-enable-guest.conf' * Install lightdm from {focal,groovy}-proposed * Reboot You should now be able to enter a guest session without being stopped by the ICEauthority error. [Where problems could occur] This one-liner is a harmless change. The guest session is run in an unconfined mode since Ubuntu 16.10. That's why the feature is disabled by default. So if the additional rule would be wrong somehow (which I have no reason to believe), it wouldn't break the AppArmor security layer for the simple reason that it's already broken to begin with. [Original description] Hello I ran into trouble to start the lightdm-guest-session in linux mint (cinnamon). ## How to reproduce: - boot linux mint (20.02) or ubuntu mate (20.04) I haven't tested other distros but I think others are also affected. - enable guest user session - try to login as guest user ## Error logs: ### Error Message: ` Could not update file ICEauthority file /run/user/XXX/ICEauthority` ### aa-notify: ``` Profile: /usr/lib/lightdm/lightdm-guest-session Operation: open Name: /proc/8125/uid_map Denied: w Logfile: /var/log/kern.log Profile: /usr/lib/lightdm/lightdm-guest-session Operation: open Name: /proc/8125/setgroups Denied: w Logfile: /var/log/kern.log Profile: /usr/lib/lightdm/lightdm-guest-session Operation: open Name: /proc/8125/gid_map Denied: w Logfile: /var/log/kern.log Profile: /usr/lib/lightdm/lightdm-guest-session Operation: open Name: /proc/8624/fd/ Denied: r Logfile: /var/log/kern.log ``` ### dmesg: ``` [ 218.831289] audit: type=1400 audit(1616864450.287:76): apparmor="DENIED" operation="sendmsg" profile="/usr/lib/lightdm/lightdm-guest-session" name="/run/systemd/journal/dev-log" pid=3916 comm="cinnamon-sessio" requested_mask="w" denied_mask="w" fsuid=999 ouid=0 [ 1157.263045] audit: type=1400 audit(1616865388.720:1084): apparmor="DENIED" operation="open" profile="/usr/lib/lightdm/lightdm-guest-session" name="/proc/9899/fd/" pid=9899 comm="gpg-agent" requested_mask="r" denied_mask="r" fsuid=999 #ouid=0 [ 1157.899223] audit: type=1400 audit(1616865389.356:1085): apparmor="DENIED" operation="open" profile="/usr/lib/lightdm/lightdm-guest-session" name="/proc/1/cgroup" pid=9840 comm="cinnamon-sessio" requested_mask="r" denied_mask="r" fsuid=999 ouid=0 [ 1157.899445] audit: type=1400 audit(1616865389.360:1086): apparmor="DENIED" operation="sendmsg" profile="/usr/lib/lightdm/lightdm-guest-session" name="/run/systemd/journal/dev-log" pid=9840 comm="cinnamon-sessio" requested_mask="w" denied_mask="w" fsuid=999 ouid=0 [ 1157.903410] audit: type=1400 audit(1616865389.364:1087): apparmor="DENIED" operation="link" profile="/usr/lib/lightdm/lightdm-guest-session" name="/run/user/999/ICEauthority-l" pid=9840 comm="cinnamon-sessio" requested_mask="l" denied_mask="l" fsuid=999 ouid=999 target="/run/user/999/ICEauthority-c" ``` ## Solutions: ### bad but common work around Solutions I found in different forums were to move lightdm-guest-session into complain mode like this: `aa-complain /usr/lib/lightdm/lightdm-guest-session` ### maybe better sollution: My fix would be to add this to `/etc/apparmor.d/lightdm-guest-session`: ``` ... /usr/lib/lightdm/lightdm-guest-session { ... owner /run/user/[0-9]*/ICEauthority-? l,` ... } ``` I honestly have no clue about apparmor and I'm unsure where to post this but I hope this maybe helps some other people in the future. 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