[systemd-devel] Github systemd issue 6237

[Jan Synacek]

On Mon, Jul 10, 2017 at 12:42 PM, Lennart Poettering
<lennart at poettering.net> wrote:
> Now, because this is so weakly defined, we hence do not follow POSIX
> rules, but filter out more that might be dangerous. Specifically:
>
> 1. We do not permit empty usernames
> 2. We don't permit the first character to be numeric
>    (This also filters out fully numeric user names)
> 3. We do not permit dots in usernames, neither at the beginning nor in
>    the middle.
> 4. We do not permit "-" at the beginning of usernames (something which
>    POSIX explicitly suggests, btw)
> 5. We require that the user name fits in the utmp user name field, so
>    that we can always log properly about it.

Is this documented somewhere? If not, it would be great to have it
documented. I'm pretty sure that this exact paragraph would be ok.

Cheers,
-- 
Jan Synacek
Software Engineer, Red Hat