idea about modifying pam_krb5 use of krb5_verify_init_creds

[Will Fiveash]

On Sun, Jan 22, 2012 at 05:25:06PM -0800, Russ Allbery wrote:
> Will Fiveash <will.fiveash at oracle.com> writes:
> 
> > People may have addressed this already but for Solaris when one has
> > provisioned a krb5.keytab with a host princ and is using pam-krb5 in the
> > pam.conf auth stack, if the hostname changes the pam-krb5 will fail to
> > verify a user's initial krb cred unless there is a host service princ in
> > the krb5.keytab that matches the new hostname.  What I'm thinking would
> > be a better way for pam-krb5 to verify a user's initial krb cred is to
> > use a service princ found in the existing keytab and call
> > krb5_verify_init_creds() using that instead of using
> > krb5_sname_to_princ().  In fact, pam-krb5 could get a list of all unique
> > service princ names for the default realm in the keytab and call
> > krb5_verify_init_creds() in a loop until either one succeeds or they all
> > fail.  Thoughts?
> 
> My preference, rather than putting code into pam-krb5 to read the keytab,
> would be for there to be some way to tell krb5_verify_init_creds to
> internally switch to this behavior.

Yes, that sounds like a better approach.  I see from Greg's e-mail on
this thread that MIT has modified krb5_verify_init_creds() to use a
principal taken from the keytab to aquire a ticket for instead of
defaulting to krb5_sname_to_princ().

> This seems similar to, although distinct from, the discussion a while back
> (with patches by Luke Howard) to use principal canonicalization.

I will look for that, thanks.

-- 
Will Fiveash
Oracle Solaris Software Engineer
http://opensolaris.org/os/project/kerberos/
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