[Bug 1803993] Re: Password appears on the VT1 screen

[Balint Reczey]

It looks like systemd is changing the mode (see argument=3) on VT1 on
logouts.

#define         K_RAW           0x00
#define         K_XLATE         0x01
#define         K_MEDIUMRAW     0x02
#define         K_UNICODE       0x04
#define         K_OFF           0x04
#define KDGKBMODE       0x4B44  /* gets current keyboard mode */
#define KDSKBMODE       0x4B45  /* sets current keyboard mode */

test at test-Standard-PC-i440FX-PIIX-1996:~$ sudo sysdig evt.type=ioctl | grep  request=4B45
[sudo] password for test:
5657343 15:21:51.819076315 1 Xorg (1069) > ioctl fd=11(<f>/dev/tty1) request=4B45 argument=4
5657453 15:21:51.820019063 0 systemd-logind (575) > ioctl fd=22(<f>/dev/tty1) request=4B45 argument=3
5753055 15:21:52.771635876 0 systemd-logind (575) > ioctl fd=21(<f>/dev/tty1) request=4B45 argument=4
20723813 15:49:41.368621972 1 systemd (23717) > ioctl fd=3(<f>/dev/tty2) request=4B45 argument=3 
22605710 15:53:04.107253025 1 systemd-logind (575) > ioctl fd=23(<f>/dev/tty3) request=4B45 argument=4 
22612602 15:53:04.142057934 1 Xorg (24089) > ioctl fd=11(<f>/dev/tty3) request=4B45 argument=4 
24077108 15:53:28.705600119 0 Xorg (24089) > ioctl fd=11(<f>/dev/tty3) request=4B45 argument=4 
24077278 15:53:28.706353493 1 systemd-logind (575) > ioctl fd=24(<f>/dev/tty3) request=4B45 argument=3 
24626343 15:53:58.336589416 0 systemd-logind (575) > ioctl fd=22(<f>/dev/tty1) request=4B45 argument=3 
24804326 15:53:59.385872243 0 systemd-logind (575) > ioctl fd=21(<f>/dev/tty1) request=4B45 argument=4 
25515114 15:54:12.915072995 1 systemd-logind (575) > ioctl fd=23(<f>/dev/tty3) request=4B45 argument=4 
25520504 15:54:12.929480424 1 Xorg (25112) > ioctl fd=11(<f>/dev/tty3) request=4B45 argument=4 
26921037 15:54:46.872029874 1 Xorg (25112) > ioctl fd=11(<f>/dev/tty3) request=4B45 argument=4 
26921239 15:54:46.872654795 1 systemd-logind (575) > ioctl fd=24(<f>/dev/tty3) request=4B45 argument=3 
27104852 15:54:53.870639078 1 systemd-logind (575) > ioctl fd=23(<f>/dev/tty3) request=4B45 argument=4 
27112208 15:54:53.894217722 1 Xorg (25697) > ioctl fd=11(<f>/dev/tty3) request=4B45 argument=4 
28677455 15:55:44.581119464 0 Xorg (25697) > ioctl fd=11(<f>/dev/tty3) request=4B45 argument=4 
28678288 15:55:44.592966138 1 systemd-logind (575) > ioctl fd=24(<f>/dev/tty3) request=4B45 argument=3 


** Also affects: systemd (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1803993

Title:
  Password appears on the VT1 screen

Status in gdm3 package in Ubuntu:
  Confirmed
Status in plymouth package in Ubuntu:
  Confirmed
Status in systemd package in Ubuntu:
  New

Bug description:
  (continued from bug 1767918)

  This was found when an administrative error made /home directory
  inaccessible.  Any users that tried to login after that, were not able
  to (which is expected) but their password appears on the VT1 screen.
  Under normal circumstances, VT1 is not visible. But once the system
  was sent into this compromised mode, one can press ctrl+alt+F1 and
  then ctrl+alt+F2 and get a momentary glance at VT1. One can keep
  toggling between these key combinations in order to make out the
  password(s) on VT1.

  As a further test, I wanted to see if a non-super user could cause
  this condition, and it is in fact possible. As a regular user, I made
  their own home directory not writable and then removed ~/.config and
  logged out. Then logged in as that user again, and although that user
  can't login the system does go into that mode where passwords appear
  on VT1 and are viewable with the key combinations mentioned herein.
  Further, any other users that login will see no problem, but when they
  logon their passwords also appear on VT1 and are viewable.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: gdm3 3.28.3-0ubuntu18.04.3
  Uname: Linux 4.19.2-041902-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.5
  Architecture: amd64
  CurrentDesktop: ubuntu:GNOME
  Date: Mon Nov 19 08:32:59 2018
  InstallationDate: Installed on 2018-08-25 (85 days ago)
  InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: gdm3
  UpgradeStatus: No upgrade log present (probably fresh install)

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