Re: Support for multiple GSS libs

[Nicolas Williams <Nicolas.Williams@ubsw.com>]

On Wed, Nov 07, 2001 at 11:05:23PM +0000, Simon Wilkinson wrote:
> On Wednesday 07 November 2001 22:37, Douglas E. Engert wrote:
> > Another problem is that the GSSAPI does not define how delegated
> > credentials are to be saved. It is left up to the implementation to provide
> > extra implementation specific routines to handle the delegated credentials.
> > The gss_krb5_* and Kerberos routines are called to do this from the openssh
> > for the Kerberos credentials, where there is a
> > ssh_gssapi_krb5_storecreds().
> 
> There's actually two points where the GSSAPI doesn't provide the necessary 
> hooks. The first, as you have noted, is in storing delegated credentials. The 
> second is in checking to see if the given principal is allowed to connect as
> a particular user (the kuserok check). Both of these are implemented by means 
> of a mechanism dependent switch, and some helper code, within the OpenSSH GSS
> patch.  

With respect to the userok() check, the named-keys-in-auth_keys patch I
posted helps: instead of relying on the krb5 or GSI specific userok()
you can rely on authorized_keys.

This is how GSS-API was meant to be used in authorization: get the
initiator's name, export it, compare it to an ACL built using the
import_name/canon_name/export_name functions.

My named-keys-in-auth_keys patch gets pretty close to that... And
authorized_keys is way superior to .k5login...

> The code is in ssh_gssapi_do_child() and ssh_gssapi_userok() within 
> gss_serv.c. Fortunately, these complications appear to be server only.

Well, the initiator might want to authorize the aceptor too.
Say, if you have Kerberos principal name canonicalization.

> Cheers,
> 
> Simon.


Cheers,

Nico
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