Bug 796429

Cloning to krb5. We want to change the default location for tools such as kinit to /run/user/<username>/krb5cc as well.


+++ This bug was initially created as a clone of Bug #786993 +++

+++ This bug was initially created as a clone of Bug #786957 +++

I know we are late for this as a security feature, but I have been running with this for a while and I think it is the right thing to do.

Change sssd default to put the cc file in /run/user.  If this is accepted we will have to change rpc.gssd to look in this new location.

If you want I will write up a feature page for this.

--- Additional comment from sgallagh on 2012-02-02 13:54:31 EST ---

It's probably too late for a feature submission, but can you open a dialog with the rpc.gssd folks about changing this? Find out whether it can be done within the F17 alpha timeframe (read: by Feb 13).

--- Additional comment from dwalsh on 2012-02-02 15:44:31 EST ---

Steve how much work would it be to get rpc.gssd to search /run/user/USERNAME/
before searching /tmp?

--- Additional comment from nalin on 2012-02-02 17:09:17 EST ---

As Stephen and Simo have noted elsewhere, when we do that we might as well have SSSD drop the unique-suffix-via-mkstemp() logic, as it's only being done to avoid a DoS that's possible in a shared /tmp, and not to ensure that ccaches are per-session.

At any rate, rpc.gssd would want to be able to search the ccache with a name along the lines of "DIR:/run/user/$LOGIN/blahblah" or "FILE:/run/user/$LOGIN/blahblah", depending on whether the agreed-upon location was a directory or a file (the exact name under /run/user/$LOGIN is not set yet).  The libraries should know the specifics of how to deal with the contents of the ccache, so long as rpc.gssd tells them to look there.

--- Additional comment from steved on 2012-02-03 11:39:19 EST ---

(In reply to comment #1)
> Steve how much work would it be to get rpc.gssd to search /run/user/USERNAME/
> before searching /tmp?
Changing the default path probably will not be too bad but getting the user name might be a bit time consuming since uids are passed up from the kernel. Doing that uid to username conversion very time consuming... 

/run/usr/<uid>/ would be better from rpc.gssd's perceptive

--- Additional comment from sgallagh on 2012-02-03 15:18:25 EST ---

This would be very easy to accomplish from SSSD's perspective, but I defer to Dan to tell us how feasible this is from SELinux's (and systemd's) point of view. I got the impression that /var/run/user/username was automatically created (and its permissions managed) by systemd.

--- Additional comment from ssorce on 2012-02-03 18:49:11 EST ---

(In reply to comment #3)
> (In reply to comment #1)
> > Steve how much work would it be to get rpc.gssd to search /run/user/USERNAME/
> > before searching /tmp?
> Changing the default path probably will not be too bad but getting the user
> name might be a bit time consuming since uids are passed up from the kernel.
> Doing that uid to username conversion very time consuming... 
> 
> /run/usr/<uid>/ would be better from rpc.gssd's perceptive

Maybe we can have a symlink with the userid.

--- Additional comment from bfields on 2012-02-06 07:58:14 EST ---

The kernel can't pass up any uids, all it has to pass up is a gss init_sec_context token, which svcgssd uses the gss/krb5 libraries to turn into some kind of gss name, which is mapped to numeric id's by libnfsidmap--see nfs-utils/utils/gssd/svcgssd_proc.c:get_ids().  (I don't really know if that's the best way to do it, but that's how it works right now.)

So if there's an easy way to map the gss name to the right form then getting the username shouldn't be too bad....

But it still might be simplest if we could continue doing the lookup by id.

--- Additional comment from ssorce on 2012-02-06 08:27:39 EST ---

Bruce,
I think you are describing the case of a NFS server.
Ccaches are used in the case of an NFS client. In that case the uid is the only information the kernel has about the process trying to access a specific mount point.
In gss-proxy I can do the uid->name lookup (which is very fast with either nscd or sssd+memcache patches so I don't think you should worry too much about the speed of that lookup.

HTH,
Simo

--- Additional comment from bfields on 2012-02-06 08:45:43 EST ---

(In reply to comment #7)
> Bruce,
> I think you are describing the case of a NFS server.
> Ccaches are used in the case of an NFS client. In that case the uid is the only
> information the kernel has about the process trying to access a specific mount
> point.

Bah, you're right, sorry for not following carefully!

> In gss-proxy I can do the uid->name lookup (which is very fast with either nscd
> or sssd+memcache patches so I don't think you should worry too much about the
> speed of that lookup.

OK.

--- Additional comment from updates on 2012-02-22 09:36:22 EST ---

sssd-1.8.0-5.fc17.beta3 has been submitted as an update for Fedora 17.
https://admin.fedoraproject.org/updates/sssd-1.8.0-5.fc17.beta3

--- Additional comment from sgallagh on 2012-02-22 09:41:58 EST ---

Sorry, selected the wrong BZ for this update. It has now been correct.

But you're at least now aware that the SSSD side of this change is now in updates-testing. Please look into the nfs-utils changes ASAP.