Re: [pgAdmin4][Patch] - RM 5457 - Kerberos Authentication - Phase 1

On Sun, 3 Jan 2021 at 17:31, Stephen Frost <sfrost(at)snowman(dot)net> wrote:

> Greetings,
>
> * Dave Page (dpage(at)pgadmin(dot)org) wrote:
> > On Sat, 2 Jan 2021 at 15:59, Stephen Frost <sfrost(at)snowman(dot)net> wrote:
> > > * Dave Page (dpage(at)pgadmin(dot)org) wrote:
> > > > On Sat, 2 Jan 2021 at 15:41, Stephen Frost <sfrost(at)snowman(dot)net>
> wrote:
> > > > > * Khushboo Vashi (khushboo(dot)vashi(at)enterprisedb(dot)com) wrote:
> > > > > > Please find the attached patch to support Kerberos
> Authentication in
> > > > > > pgAdmin RM 5457.
> > > > > >
> > > > > > The patch introduces a new pluggable option for Kerberos
> > > authentication,
> > > > > > using SPNEGO to forward kerberos tickets through a browser which
> will
> > > > > > bypass the login page entirely if the Kerberos Authentication
> > > succeeds.
> > > > >
> > > > > I've taken a (very short) look at this as it's certainly something
> that
> > > > > I'm interested in and glad to see work is being done on it.
> > > > >
> > > > > I notice that 'delegated_creds' is being set but it's unclear to
> me how
> > > > > they're actually being used (if at all), which is a very important
> part
> > > > > of Kerberos.
> > > > >
> > > > > What's commonly done with mod_auth_kerb/mod_auth_gss is that the
> > > > > delegated credentials are stored on the filesystem in a temporary
> > > > > directory and then an environment variable is set to signal to
> libpq /
> > > > > the Kerberos libraries that the delegated credentials can be found
> in
> > > > > the temporary file. I don't see any of that happening in this
> patch-
> > > is
> > > > > that already handled in some way? If not, what's the plan for
> making
> > > > > that work? Also important is to make sure that this approach will
> work
> > > > > for constrainted delegation implementations.
> > > >
> > > > Phase 1 of this project (which this patch aims to implement) is to
> handle
> > > > Kerberos logins to pgAdmin when running in server mode (as we’ve
> already
> > > > done for LDAP, except KRB authenticated users don’t see a login page
> of
> > > > course). Phase 2 will add support for logging into the PostgreSQL
> > > servers -
> > > > I believe that is where we’ll need to handle delegated credentials,
> > > correct?
> > >
> > > Yes, though I sure hope there isn't a plan to release just 'phase 1'
> > > since that would imply that the user is still sending their password to
> > > pgAdmin in some form that pgAdmin then turns around and impersonates
> the
> > > user, basically completely against how Kerberos auth should be working
> > > in this kind of a intermediate service arrangement.
> > >
> > > In other words, if just 'phase 1' is released, it'd probably be CVE
> > > worthy right out of the gate...
> >
> > It wouldn’t impersonate the user at all, it would just work as it does
> now,
> > requiring the user to supply a username/password for scram/md5/ldap etc,
> or
> > a cert for SSL auth. Connection to a PostgreSQL server which required gss
> > or sspi simply wouldn’t work (unless the service account under which the
> > pgAdmin server is running has a valid ticket through other means).
>
> That *is* impersonating the user..
>
> Kerberized services really should *not* be accepting a cleartext
> password to use to authenticate as the user against another service,
> which is why I'd strongly recommend against releasing with just
> 'phase 1' done.. or at least heavily caveat'ing it that this isn't
> actually real Kerberos support but is just an intermediate step that no
> one should really deploy...

By that argument, one should not be able to login to a kerberised SSH
server and then use a mail client to access Gmail (or for that matter, the
web interface), neither should one be able to login to a Postgres server
using Kerberos, and then use a non-kerberised FDW.

Why aren’t those cases CVE worthy?
--
--
Dave Page
https://pgsnake.blogspot.com

EDB Postgres
https://www.enterprisedb.com