[39620] in Kerberos
Re: krb5ccmachine
daemon@ATHENA.MIT.EDU (Simo Sorce via Kerberos)
Mon Apr 27 14:25:11 2026
Message-ID: <dc229c433d8b8df49db5fd947d415531fbadc20d.camel@redhat.com>
To: Marek =?UTF-8?Q?Gre=C5=A1ko?= <marek.gresko@protonmail.com>
Cc: kerberos@mit.edu
Date: Mon, 27 Apr 2026 14:23:51 -0400
In-Reply-To: <7uYlNDUvFSY5hD4DQSn67uoKVLT07fiPNKBinyxa6Gtg1sljpPsp9L0OV5NSMzGrRgVCZzDfC3eALGaTBJ32uOOigmLDDKcPC5IIhZ6e6KU=@protonmail.com>
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From: Simo Sorce via Kerberos <kerberos@mit.edu>
Reply-To: Simo Sorce <simo@redhat.com>
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On Mon, 2026-04-27 at 18:12 +0000, Marek Greško wrote:
> Great analysis. I found out there are some ways of configuring gssd in /etc/nfs.conf. Mys current config for it states:
>
> use-gss-proxy=1
>
> There are available options
>
> # cred-cache-directory=
> # use-memcache=0
>
> Would not one of these options solve my problem?
memcache may be worth a try, the only issue is that a process restart
means loosing the cache and having to go back to the KDC to acquire a
new TGT, but that shouldn't be a big deal.
> I think the memory cache woudl be better. Are there any culprits I am not aware of not to do it like this?
The memory cache is a cache collection and could lead to some
interesting issues, but it may be worth a try.
> If the second option with cred directory is used, what is the recommended diretory in Fedora to use? Should I use /var/lib/nfs?
Any directory that is accessible by rpc.gssd and is not world writable
will not cause selinux issues will be fine, given your users never
litter /tmp with ccaches. In fact an otherwise empty directory will
speed up some operations when rpc.gssd decided to "scan" the ccache
directory for user caches.
> Thanks
>
> Marek
>
>
> Odoslané pomocou bezpečného emailu Proton Mail.
>
> pondelok 27. apríla 2026, 19:33, Simo Sorce via Kerberos <kerberos@mit.edu> napísal/a:
>
> > Gssproxy never stores caches in /tmp, that file is more likely created
> > by rpc.gssd the NFS Client daemon that handles GSSAPI authentication.
> >
> > rpc.gssd is sadly stuck in time and forces the use of the FILE: ccache
> > through most of its code, which is why we intercept it with gssproxy
> > for some operations with user ccaches only.
> >
> > HTH,
> > Simo.
> >
> > On Mon, 2026-04-27 at 17:02 +0000, Marek Greško via Kerberos wrote:
> > > Hello,
> > >
> > > so for klist it seems it is generated by gssproxy, because there is nfs/ ticket.
> > >
> > > Regarding gssproxy.conf I have the file /etc/gssproxy/99-network-fs-clients.conf containing:
> > >
> > > [service/network-fs-clients]
> > > mechs = krb5
> > > cred_store = keytab:/etc/krb5.keytab
> > > cred_store = ccache:FILE:/var/lib/gssproxy/clients/krb5cc_%U
> > > cred_store = client_keytab:/var/lib/gssproxy/clients/%U.keytab
> > > cred_usage = initiate
> > > allow_any_uid = yes
> > > trusted = yes
> > > euid = 0
> > > min_lifetime = 60
> > >
> > > But apparently it is not using the path. I also did not find how to specify path for machine ccache. Even better, if I could convince machine ccache to be also stored in KCM. Is it possible?
> > >
> > > Thanks
> > >
> > > Marek
> > >
> > >
> > >
> > >
> > > Odoslané pomocou bezpečného emailu Proton Mail.
> > >
> > > pondelok 27. apríla 2026, 16:19, Christian, Mark <mark.christian@intel.com> napísal/a:
> > >
> > > > On Mon, 2026-04-27 at 04:38 +0000, Marek Greško wrote:
> > > > > Hello,
> > > > >
> > > > > the
> > > > > kinit -c /tmp/krb5ccmachine_EXAMPLE.COM
> > > > > asks for password. Which password? What should I expect thereafter to
> > > > > happen?
> > > >
> > > > Sorry I meant for you to use klist, not kinit:
> > > >
> > > > % klist -c /tmp/krb5ccmachine_EXAMPLE.COM
> > > >
> > > > >
> > > > > I also asked AI to help me on the original issue. It thinks it is
> > > > > related to gssproxy and most probably it is right. It stated there is
> > > > > not nuch to do and I should accept the current state. But I feel a
> > > > > little bit unhappy, since it creates file with predictable name in
> > > > > the /tmp and it could be a security risk.
> > > >
> > > > see man gssproxy.conf for details on howto configure the location of
> > > > cred_store / ccache.
> > > >
> > > > Mark
> > > >
> > > >
> > > > >
> > > > > Thanks
> > > > >
> > > > > Marek
> > > > >
> > > > >
> > > > >
> > > > > Odoslané pomocou bezpečného emailu Proton Mail.
> > > > >
> > > > > piatok 24. apríla 2026, 16:02, Christian, Mark
> > > > > <mark.christian@intel.com> napísal/a:
> > > > >
> > > > > > On Fri, 2026-04-24 at 10:44 +0000, Marek Greško via Kerberos wrote:
> > > > > > > Hello,
> > > > > > >
> > > > > > > I have configured kerberos client on Fedora 43. I configured
> > > > > > > kerberos
> > > > > > > to use KCM: ccache. Users ccaches are in KCM, but I always see
> > > > > > > the
> > > > > > > file /tmp/krb5ccmachine_EXAMPLE.COM created. Why is this file
> > > > > > > created?
> > > > > >
> > > > > > Perhaps related to your kerberos NFS configuration? Inspect the
> > > > > > cache,
> > > > > > kinit -c /tmp/krb5ccmachine_EXAMPLE.COM, doing so might clue you
> > > > > > in.
> > > > > >
> > > > > > Mark
> > > > > >
> > > > > > > What mechanism does not use KCM and how could it be convinced to
> > > > > > > do
> > > > > > > so?
> > > > > > >
> > > > > > > Thanks
> > > > > > >
> > > > > > > Marek
> > > > > > > ________________________________________________
> > > > > > > Kerberos mailing list Kerberos@mit.edu
> > > > > > > https://mailman.mit.edu/mailman/listinfo/kerberos
> > > > > >
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> > > > > >
> > > >
> > > > ________________________________________________
> > > > Kerberos mailing list Kerberos@mit.edu
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> > > >
> > >
> > > ________________________________________________
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> > > https://mailman.mit.edu/mailman/listinfo/kerberos
> >
> > --
> > Simo Sorce
> > Distinguished Engineer
> > RHEL Crypto Team
> > Red Hat, Inc
> >
> >
> > ________________________________________________
> > Kerberos mailing list Kerberos@mit.edu
> > https://mailman.mit.edu/mailman/listinfo/kerberos
> >
--
Simo Sorce
Distinguished Engineer
RHEL Crypto Team
Red Hat, Inc
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