Bypass Login Screen by replugging in external monitors

[yan]

I found a bug in ubuntu At the login screen

buster/sid
Linux 4.15.0-24-generic #26-Ubuntu SMP Wed Jun 13 08:44:47 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

I use my work laptop and today when I came back to office I connected both my external monitor.
1 HDMI cable and 1 Mini display port cable.

Then I realize one screen on the right had my login screen prompting for password and the left monitor was unlock, I was able to navigate the mouse and use the computer just fine. However all the keyboard input was sent to the password prompt.

I did the test a couple time and each time I was able to reproduce the issue.

#1: Lock the computer
#2: Disconnect both external monitor
#3: Reconnect external monitor ( my sequence was HDMI -> Display port )
#4: You've bypass the login screen.

When doing the demo to my colleague I was able to completely bypass the login screen on both screen and had complete mouse and keyboard input. At that time I was not able anymore to lock my session. I had to reboot the laptop.

Laptop model:
Manufacturer: LENOVO
Product Name: 20FN002VCA
Version: ThinkPad T460
---
ProblemType: Bug
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
DistroRelease: Ubuntu 18.04
InstallationDate: Installed on 2018-04-30 (104 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
Package: gdm3 3.28.2-0ubuntu1.3
PackageArchitecture: amd64
ProcEnviron:
 LANGUAGE=en_CA
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 4.15.0-30.32-generic 4.15.18
Tags: bionic
Uname: Linux 4.15.0-30-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

_MarkForUpload: True

[yan (nexandroid)]

When testing again, after the reboot I was able to bypass the login screen by just disconnecting both external monitor and had full access of the computer and input device.

[Daniel van Vugt (vanvugt)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please execute the following command only once, as it will automatically gather debugging information, in a terminal:

apport-collect 1786046

When reporting bugs in the future please use apport by using 'ubuntu-bug' and the name of the package affected. You can learn more about this functionality at https://wiki.ubuntu.com/ReportingBugs.

[yan (nexandroid)]

apport information

[yan (nexandroid)]

apport information

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Ihor Menshykov (ihor-ibm)]

I think my problem is related to this one. I couldn't include my `ubuntu-bug` debug info, because of a
`
ERROR: Could not import module, is a package upgrade in progress? Error: /usr/local/lib/libssl.so.1.1: version `OPENSSL_1_1_1' not found (required by /usr/lib/python3.6/lib-dynload/_ssl.cpython-36m-x86_64-linux-gnu.so)
`
bug that didn't go away even after installing a brand new openssl 3.0 from github. Quite ironic.

I've got 3 monitors always connected to a GPU and often after I let it rest for a while after locking the system with CTRL+L, when I'm trying to get it back on it first only shows a purle screen for like a minute on one monitor only. The rest of them go into sleep mode, then I turn them off and on and after some time the system unlocks without a password prompt, you're instantly thrown into the logged in user.

[Ihor Menshykov (ihor-ibm)]

That's on Ubuntu 18.04.2 LTS

[Seth Arnold (seth-arnold)]

> /usr/local/lib/libssl.so.1.1: version `OPENSSL_1_1_1' not found

It appears you may have a local install of openssl that is not compatible with other software on your system.

I hope this helps.

Thanks

[Ihor Menshykov (ihor-ibm)]

Well, it was v1.1.0e which is the latest one per Apt. The stuff that's in conflict seems to also be stock, not custom.