Hi,

I've been looking into enabling SPNEGO for our CAS server and have a
question relating to the CAS 3.4.12 + SPNEGO thread in
cas-u...@lists.jasig.org.

As the SPNEGO module works currently it puts itself as a layer before
the username/password authentication, sending an empty
401/Authorization: Negotiate response. If negotiation fails, say if the
kerberos tickets are expired, the login will fall back to
username/password which is nice.

But, browsers that are not explicitely configured to allow negotiation
for our server will just stop on the 401 response, not try a negotiation
and hence not fall back to username/password.

This makes the SPNEGO module somewhat useless for anything other than a
tightly controlled intranet environment where you have control over all
clients, which is not very internetish.

A work-around for this is to lay an additional layer in the login flow
and check for a user-agent header that in some manner indicates that the
browser is under sysadmin control and configured to use negotiation.
This works, but places additional burden on maintenance for all browsers
which user-agents must be maintained if we want to keep the original
version information in them.


So, my question is if there is any particular reason why the SPNEGO
module not rather amends the normal 200 username/password response with
401 Authorization: Negotiate headers then do a separate, empty response
before the username/password? 

As far as I can see this would mean that unconfigured clients would work
just fine with username/password while configured clients will try a
negotiation.

Or am I missing something?

Best regards,
/Fredrik

-- 
Fredrik Jönsson, M.Sc.              Email:  f...@kth.se
System architect                    Phone:  +46 8 790 66 03
Kungliga tekniska högskolan (KTH)   Mobile: +46 73 595 66 03
KTH/UF/ITA/Infosys


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