krb5 library missing functions for collections

[Simo Sorce]

On Mon, 2019-07-22 at 20:10 +0000, Charles Hedrick wrote:
> The problem is that the code in rpc.gssd works as followers:
> 
> * get the default credential from the collection
> * fail unless it’s username at DOMAIN
> 
> If you replace the initial step by code telling it explicitly to get 
> username at DOMAIN then it works just fine, assuming that the user
> actually has such a credential. Which they will. GSSAPI is perfectly
> capable of looking for a specific credential if you tell it to. It’s
> just that the code doesn’t do it that way. To avoid building my own
> copy of rpc.gssd, I use a loadable library to interpose code around
> GSSAPI that supplies the right argument.

rpc.gssd does this because it cannot know what the right credential
name is in all situations.

In very controlled environments it is indeed username + @REALM and the
realm is known, but in other cases it is not.
For example a personal laptop where the username is 'joe' and no
default realm is set and someone doing kinit jdoe at WORK.REALM then
walking into an NFS mount.

I guess the nfs-utils folks may accept a patch to rpc.gssd where an
option can be given to assume a specific form for the user's principal
name to look for, but that can't be the default as it would break
current uses.

HTH,
Simo.

-- 
Simo Sorce
RHEL Crypto Team
Red Hat, Inc