Martin Thomson said:
"Regarding client authentication, there are a number of
constraints on the solution that lead to the current choice. The most relevant
constraint is that there may be no prior relationship between LIS (network
operator) and device. In designing for arbitrary access networks, this
constraint
was considered important. This prevents use of pre-shared keys such as would
be required for digest/basic [1] [2].
Thus we come to the choice of IP address and return reachability.
I believe that the draft addresses the impact of this choice adequately; Section
9.3 seems most directly applicable here, but other places touch on this choice
where
it’s relevant. If you do not believe that there are relevant points that are
not brought up, I’d encourage you to send text."[BA] I understand that the IP
address is being used as an identifier. With respect to the lack of no prior
relationship between the access network and the device, presumably this is to
acommodate situations of anonymous access and/or no authentication (e.g.
non-authenticated Ethernet). If so, it might be useful to add a sentence to
that effect.
Regarding alternative identifiers, there is an extension
document that talks about use of alternative identifiers, and I do believe that
this particular point CAN be addressed in an extension. For those,
authentication (other than return reachability, if you consider that to be a
form of authentication) can be made a requirement.[BA] I'm trying to understand
how the mechanics of authentication could be accomodated. Since authentication
can't be required for authorization where an IP address is used for
identification, does this imply that a "407" response is not
permissible in that situation? Or is it just saying that if a 407 is returned
in that situation, then authorization needs to be provided? Does that imply
that a 407 could be returned in other situations (e.g. an alternative
identifier)? Just trying to understand the scope of the prohibition and how
implementations are expected to behave.
I’ll address the other more substantive point regarding identity
in PIDF-LO in another (longer) mail.
--Martin
[1] The document is clear on its use of digest/basic: the LIS
MUST NOT rely on it being used. That’s in recognition of the above constraint.
In other words, the LIS MUST NOT fail a request because the device did not
provide authentication. That doesn’t prevent it from being used in an
extension to the protocol.
[2] Of course, there are networks where the constraint might not
be applicable. For instance, access to the network could be restricted using
some
form of authentication. However, a device that accesses a LIS within those
networks must also be aware that it needs to present this same authentication
information when talking to a LIS. We cannot guarantee that a device will do
this, since compliance would need to be a prerequisite of network access;
designers
of future access networks might choose to add this to their network design.
From: Bernard Aboba
Sent: Tuesday, 9 June 2009 5:48 AM
To: ben(_at_)estacado(_dot_)net; ietf(_at_)ietf(_dot_)org
Subject: Re: Gen-ART LC Review
ofdraft-ietf-geopriv-http-location-delivery-14.txt
Mary
Barnes said:
"It
doesn't explicitly "forbid" the use of digest authn, but if it
can't depend
on client support, then it can't really base any decision on
it."
The question
isn't just about an authorization decision. There is also the issue about
what
the
LIS is supposed to do with client authentication information if it is
provided. How is
this
information reflected in the PIDF-LO that is returned in a HELD response?
Ben
Campbell said:
"The part I was trying to highlight was the lack of client device
authentication, not LIS authentication. If I read 9.1 right, it only
covers authentication of the LIS. I assume there is no expectation that
client devices present TLS certs to the LIS, right?"
There are multiple potential identities that a device (and a user of that
device) could assert and authenticate against.
Currently the document only talks about use of the IP address as an
identity, and says little about authentication.
However, the PIDF-LO objects that are returned in HELD responses contain
multiple identification fields. Currently the document says very
little about
how these fields are filled in. That leaves the protocol under-specified.
Issues of protocol behavior that are this basic shouldn't be left to an
"extensions" document.
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