Re: [XCON] CPCP Issue 28: <pin> and <password>
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Re: [XCON] CPCP Issue 28: <pin> and <password>





Aki Niemi wrote:
Inline.

On Mon, 2004-09-13 at 20:14, ext Paul Kyzivat wrote:

By common usage today, it would be obtained because the initial connection is to an IVR that prompts for it. that dialog isn't really part of the conference. How the result of it gets back to the focus may need clarification.


Indeed, or how the call ends up in the IVR in the first place (more on
this below).


One possibility is that limited function voice only calls are directed at a different server - an IVR. It does its prompting to get a pin, and maybe conference id. Then it could:
- redirect the caller with a url to the focus that also embeds the pin.
In this case, the condition that checks the pin makes perfect sense.
The check is distinct from authentication, because the caller may
not be authenticated at all, or may be authenticated with an arbitrary
identity.

If the URL is secret (embeds the pin as you suggest) and the IVR is configured to redirect callers that entered the correct id/pin to that secret URL, why does there need to be a pin condition? Isn't the fact that the caller enters the focus using a secret URL enough?

Well, the pin wouldn't actually have to be *in* the url for the redirection to work. But it begins to look a lot like some of the alternatives to GRUU that were rejected.


A secret URL would perhaps serve the purpose. But it would have to be a different URL than the normal focus URL, which is often not a secret. That at least adds some complexity.

A middle ground is to pass the PIN as a URL parameter on the focus URL in the request URI. However this has problems if the focus URL is actually an AOR that has to be translated.

Seems like this approach is fraught with problems.

- act as a b2bua. In this case it can provide suitable authentication
  info which is chosen based on the pin. In this case no special
  conditions are needed - authorization can be based on the
  authenticated id provided by the b2bua.

I agree, this is one possibility. And it need not necessarily be a B2BUA either. Simple proxy authentication is enough in most cases where digest credentials can be used.

Well, in order to prompt for the pin it must first terminate the call itself. Once it has the pin it is too late to act as a proxy. It might be able to do something like send the focus a REFER/Replacing to accomplish the task without being a B2BUA. But then there would be need for some kind of conference rule to get the role for the conference participation from the REFER rather than by authenticating the called party. Is that already possible?


	Paul

Or, all calls can go directly to the focus. The authorization rules can be applied based on what authenticated identity is available, if any. If the call is going to be rejected, it can instead then be treated with an IVR that prompts for a pin. Then the rules are applied again with it.


Hmm... Do we in fact need another action defined, that redirects all
callers to an IVR if they call the focus without proper authenticated
identity?


I'm sure there are other ways to handle this stuff as well. But maybe these kinds of scenarios need to be explored to understand how the pin/password fits in with other authentication and authorization strategies.


You're probably right. It seems there is at least a concept here of an
"authentication service", that is able to provide authentication
information to the focus to be used in matching with the rule
conditions. An authenticated identity carried in for example as a
P-Asserted-Identity is an obvious example, but non-identity based
information could also be used, e.g., some SAML assertions described in
draft-tschofenig-sip-saml-00.txt.

But the <pin> condition is a poor attempt at that, especially as it is
trivially transformed into an equivalent <identiy> condition.

Say, instead of:

<conditions>
	<pin/>
</conditions>

you would have:

<conditions>
	<identity>
		<id>those_who_knew_the_PIN</id>
	</identity>
</conditions>

Cheers,
Aki


	Paul

Aki Niemi wrote:

Ok, I'll try.

There are different methods to access a conference. Some can readily
provide an identity to use in the conditions, others can't. Some require
that users are collectively authenticated using a passcode, others can
contain a random secret in the URI itself, or use specific
username/password pairs for this collective passcode.

If you have all of the above type accesses to a conference, and a single
set of rules, for which accesses does the condition apply to?

What if I want all PSTN-access allowed using a passcode, but all SIP
access only using authenticated identities, and *not* using a passcode?
I can't see a single <passcode> condition covering both of these
orthogonal cases.

That's why I proposed a separate ruleset for each access method. If you
have that, there's no need for the conditions you propose. For example,
if you've configured for a PSTN access to always prompt for a PIN, then
the only way ever anyone is ever going to get through using that access
is to know the PIN. (That would actually mean that you wouldn't
necessarily need any conditions at all...)

Another option is to assign a special identity for the PSTN-users in the
system (who've entered the PIN correctly), and use that in the
<identity> conditions. In other words, anyone who entered the PIN
correctly will get that authenticated identity assigned by the system.

This involves as much out-of-band configuration as setting the PIN and
configuring the PIN-prompt for it in the first place, and requires no
additional conditions to be defined.

Cheers,
Aki


On Mon, 2004-09-13 at 17:56, Khartabil Hisham (Nokia-TP-MSW/Helsinki) wrote:


Hi Aki,

I don't understand your argument here. The way PSTN users are
authorised to join a conference is through a PIN. The condition is if
they know the PIN, then they get in the conference. You cannot know
the user behind a PSTN number and therefore need an authorisation rule
based on PIN.

Perhaps I didn't fully understand your proposal, can you re-state?

Thanks,
Hisham



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