kerberos and web authentication

[Benjamin Kaduk]

On Fri, Aug 21, 2020 at 08:04:24PM -0400, Rita wrote:
> hi
> 
> The webserver has DNS aliases but not multiple IPs. On a client level is it

(temporarily) forcing the name to resolve to just a single IP, e.g., via
/etc/hosts, would be one possible diagnostic measure.

> possible to disable the reverse lookup? I am not sure if its backed up a

See the 'rdns' keyword at
http://web.mit.edu/kerberos/krb5-latest/doc/admin/conf_files/krb5_conf.html#libdefaults

> pool of servers -- is there a way to find out from a client?

In general, no; one can make inferences from careful inspection of response
headers, request/response timing for exchanges that require server-side
state, and the like, but it may require some expertise to interpret the
results.

-Ben

> On Fri, Aug 21, 2020 at 7:30 PM Benjamin Kaduk <kaduk at mit.edu> wrote:
> 
> > On Thu, Aug 13, 2020 at 07:10:42AM -0400, Rita wrote:
> > > I created a user keytab. I use curl to authenticate against a web server.
> > > `curl -u : --negotitate` it works randomly (about 33% accuracy). I am
> > > trying to figure out if its a webserver issue or kerberos issue. Is there
> > > anything else I can do?
> >
> > There's (at least) a couple things that can come into play for this sort of
> > scenario (not least because HTTP Negotiate violates some fundamental
> > assumptions about message- vs. connection-oriented):
> >
> > Does the web server's hostname have multiple IP addresses in the DNS?  (Is
> > reverse DNS used for principal canonicalization by the krb5 library?  The
> > default is "yes" in many versions.)
> >
> > Does the web server have a pool of backend servers behind a load balancer?
> >
> > -Ben
> >
> 
> 
> -- 
> --- Get your facts first, then you can distort them as you please.--