Strange behavior with mixed case host name/principal

[Jafar Aliev]

Ken, thank you for the fast response.

Your answer almost fulfills my request. I'll incorporate extra checks
in our playbooks to strict hostname cases.

One small splinter will remain: why kerberos lib indicates error with
exact host principal name that it has in keytab.

p.s. My old RHEL 7.9 setup also doesn't have this problem: it
lowercase hostname before requests for tickets.

On Fri, Apr 18, 2025 at 8:30 PM Ken Hornstein <kenh at cmf.nrl.navy.mil> wrote:
>
> >Workarounds with sshd_conf
> >GSSAPIStrictAcceptorCheck no
> >or krb5.conf
> >ignore_acceptor_hostname = true
> >work well, but I want to keep a strict hostname check.
>
> Why, exactly?  There are a few multi-homed situations where this
> can cause security issues but I don't think they apply here.
>
> There aren't wonderful solutions for this situation other than turning
> off strict acceptor checking.  The DNS is case-PRESERVING, but
> case-insensitive in lookup, so "SERVER" and "server" are treated as
> being identical when it comes to hostname lookup.  RFC 4120 recommends
> folding names to lowercase; that happens sometimes based on a particular
> Kerberos implementation (in MIT Kerberos that happens when the hostname
> is canonicalized in the function krb5_sname_to_principal() which is
> called by most higher-level APIs such as the GSSAPI).
>
> --Ken



-- 
Наилучшие пожелания,
Джафар Алиев
http://jafar.ru