Created attachment 370212 [details]
Gdm in Ubuntu 17.10 (ipdated 03-18-2018) with "û"

Hi,

I have a bug since the recent updates on pre-release Ubuntu 18.04 (post 10th March):
https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1758563

When the user password contains a non US character, as French  circumflex accent like "û", access is denied even if password entered is correct and I stay blocked in a loop at gdm login screen - error message (translated from French): "Sorry, it doesn't work, please try again".

Even after modifying it on recovery mode with passwd without û, it stays blocked. Only way to solve it is to reinstall.

Graphic card: [AMD/ATI] Cape Verde XT [Radeon HD 7770/8760 / R7 250X]
Kernel driver in use: radeon
Kernel modules: radeon, amdgpu

gdm and login field :

Debian Stretch						3.22.3		Type "u with circumflex accent" = û
Ubuntu 17.10 updated 03-18-18		3.26.1		Type "u with circumflex accent" = û			Type Euro Symbol = €
Ubuntu 18.04 > 10th March 2018		3.27.92		Type "u with circumflex accent" = u			Type Euro Symbol = I have to check

Steps to reproduce :

I did a fresh and new install with 18.04 daily iso from 21st March, formatting / and /home with following user password:

Ubuntu42

At startup, I could log successfully both on Xorg and Wayland sessions. Then I modified and tested those passwords, with all of them I could again boot and connect, on Xorg and Wayland:
ArchLinux43
LinuxMint@28
KDENeon=51
Fedora_1984

But the last one made me blocked at the gdm login screen:

Debianû74

Here unable to modify it on recovery session, error message in French: "erreur de manipulation du jeton d'authentification".

Also unable to launch terminal: CTRl Alt F1 refreshes the screen, but F2, F3... F12 freezes it! I only can update in chroot with lie USB.

I had to again format and reinstall, with a password without any circumflex accent.

How and when I discovered it :

On 10th March, I ran since many weeks the alpha version of Ubuntu 18.04, with a password having a "û" inside, which had always worked fine. I did an update, cumulating the last 3 weeks before.

On next startup, when I typed my password, both on Xorg and Wayland sessions, no error message but no desktop, nothing appeared but a few seconds later I was back on login screen.

I could well log in on terminal (Ctrl Alt F2) or chroot with a live USB, and do the last updates in the next days, but nothing changed.

On console, if I ran "startx" I got the message "timeout in locking authority file" and "fatal server error: cannot open log file ./local/share/xorg/Xorg.0.log

Both / and /home were not full - more than 60% space available, verified with df -Th ; echo ; df -Ti

I tried to reinstall Ubuntu with daily live of 15th March, formatting / but not /home as it was protected by ecryptfs and I didn't save some files, using same user name and password, still blocked.

So I copied the /home and .Private folders to another disk to try later recover them, reinstall again, formatting both / and /home, always with my usual password having a "û" (I verified French language, keyboard with French activated, upper case, symbols... OK).

This time, again both for Xorg or Wayland sessions, at gdm login I did not success to connect, I got an error message "Désolé ça n'a pas fonctionné, veuillez réessayer",

I tried to modify the password in recovery mode, with no special characters nor accents, but still blocked at gdm. And no terminal available with Ctrl Alt F2...

On 23rd March, I re-reinstalled all Ubuntu, formatting / and /home, this time with daily iso from 21st March, but with a modification: to avoid any misconfiguration with languages on live USB, I chose a very easy password, only with normal letters and numbers.

On startup, yes, finally I could log at gdm on default Xorg session and enter desktop !

I went to my user configuration, changed to put my usual password (with an "û"), and bam, back to the future, still blocked at gdm screen on restart, either on Xorg or Wayland, Ctr Alt F2 not working.

It made me understand that the bug came from a special character in my password, then I tried the different ones explained on top of this report to discover it was "û".


I also updated a laptop to Ubuntu 17.10, the password with "û" is well accepted, like in my previous home computer.

It's only since the 10th March update that it fails...