[Discussion] Username characters restrictions in Debian

[sanal]

Even though POSIX recommendation of username characters are very limited, Debian allows most of the characters (except few) in username with a patch in shadow package.

What is the reasoning for allowing non-POSIX characters in username? Asking this to understand the impact, if we remove the Debian patch in shadow package.

Thanks,
-Sanal

[Aki]

Hello,
There's no package names shadow in Debian repository ? What is the package your are referring to ?

[Random_Troll]

https://systemd.io/USER_NAMES/ explain the various limitations for the current release. Note that Debian is actually more restrictive than POSIX, not less.

[sanal]

@Aki
https://packages.debian.org/source/bullseye/shadow
https://salsa.debian.org/debian/shadow/ ... _usernames

[fabien]

What is the reasoning for allowing non-POSIX characters in username?

See /usr/share/doc/passwd/changelog.Debian.gz

shadow (1:4.0.3-9) unstable; urgency=low
[...]
* I can't come up with a good justification as to why characters other
than ':'s and '\0's should be disallowed in group and usernames (other
than '-' as the leading character). Thus, the maintenance tools don't
anymore. closes: #79682, #166798, #171179
[...]
-- Karl Ramm <kcr@debian.org> Wed, 20 Aug 2003 02:06:50 -0400

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=79682

[kent_dorfman766]

I liken the question to "how far can I push the envelope" with things that mature professionals intuitively know that you should not do.

Cannot tell you how often I get into arguments at companies where they push back when I request they use a file naming convention that fits in 7bit ascii, no spaces, dashes, or special characters, and the inference of a space should be an undersore, or the case where folks won't use ISO most-to-least specific date/time formats such as yyyymmdd-hhmmss so items can be sorted properly.

keep your user names as lower latin char letters and numbers using the following RE: [a-z][a-z0-9]{0,15}

Always use the most portable least common denominator!

[Aki]

@sanal

@Aki
https://packages.debian.org/source/bullseye/shadow

Yes, of course. I was searching for a binary package :wink:

[sanal]

What is the reasoning for allowing non-POSIX characters in username?

See /usr/share/doc/passwd/changelog.Debian.gz

shadow (1:4.0.3-9) unstable; urgency=low
[...]
* I can't come up with a good justification as to why characters other
than ':'s and '\0's should be disallowed in group and usernames (other
than '-' as the leading character). Thus, the maintenance tools don't
anymore. closes: #79682, #166798, #171179
[...]
-- Karl Ramm <kcr@debian.org> Wed, 20 Aug 2003 02:06:50 -0400

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=79682

As shell interprets few special characters (/, `, ;, etc) of username different way, think we need to relook at this patch to add the restrictions at least for few special characters in username.