cannot log in with long username

[eoli3n]

We use ldap authentication with mail addresses as usernames.
So usernames are not posix and some are > 32 chars but are working.

Some of them fire a bug :
When trying to log, it doesn't asks for password, it just wait some seconds then reset to ask username.

I can't clearly identify which regex fire the bug or not but this one does
"<email address hidden>"

I reproduce it on ubuntu 18.04 and 20.04 daylibuild.

In auth.log, that line pops up when bug is started

"Mar 2 16:23:14 premier agetty[97945]: checkname failed: Operation not permitted"

[Steve Langasek (vorlon)]

What do you get on the affected system when you run 'getent passwd <email address hidden>'?

Is this reproducible with services other than a local console login?

The error message in your log is from agetty, not from pam.

[eoli3n (eoli3neoli3n)]

Nothing but i misexplained, bug isn't related to the fact that account exists or not.
Please try to enter in a tty that exact login :

'<email address hidden>'

It reset without asking for password, and the error line is added to auth.log

Then try :

'<email address hidden>'

It asks for password, even that account doesn't exists, and the error line isn't added

[eoli3n (eoli3neoli3n)]

All Ubuntu systems are affected.
That's not related to a personal configuration, booting live latest ubuntu let me reproduce this.

Its more clear on tty, as you see username field resets, but it's the same from ligthdm

So should i open a bug for agetty package instead ?

[Steve Langasek (vorlon)]

I am not able to reproduce this on an Ubuntu 19.10 system, either in a live environment or not, using '<email address hidden>' as a login on the console. In either case, I get a password prompt after the username prompt.

[Steve Langasek (vorlon)]

I also cannot reproduce the system you described on a 20.04 live system. Entering '<email address hidden>' as a login on the console does give a password prompt.

[eoli3n (eoli3neoli3n)]

Just retried with fresh download of this file :
http://cdimage.ubuntu.com/daily-live/current/focal-desktop-amd64.iso

I confirm that entering on tty3
<email address hidden>
(not just "user.")
does trigger the bug.

[eoli3n (eoli3neoli3n)]

By the way : <email address hidden> does not trigger the bug.

[Steve Langasek (vorlon)]

ok, sorry for misreading. will retest here.

[Steve Langasek (vorlon)]

There is a hard-coded limit of 42 characters in agetty, from util-linux. I don't know why this limit exists, but reassigning there.

[Steve Langasek (vorlon)]

for the record I don't find any hard-coded limit on username length in pam.