Re: [OAUTH-WG] New Version Notification for draft-fett-oauth-dpop-03.txt

[Rob Otto <[e-mail]>]

Hi Torsten - thanks for the reply.

Responses in line.

Grüsse
Rob

On Fri, 22 Nov 2019 at 07:59, Torsten Lodderstedt <torsten=
[e-mail]> wrote:

> Hi Rob,
>
> > On 22. Nov 2019, at 15:52, Rob Otto <robotto=
> [e-mail]> wrote:
> >
> > Hi everyone
> >
> > I'd agree with this. I'm looking at DPOP as an alternative and
> ultimately simpler way to accomplish what we can already do with MTLS-bound
> Access Tokens, for use cases such as the ones we address in Open Banking;
> these are API transactions that demand a high level of assurance and as
> such we absolutely must have a mechanism to constrain those tokens to the
> intended bearer. Requiring MTLS across the ecosystem, however, adds
> significant overhead in terms of infrastructural complexity and is always
> going to limit the extent to which such a model can scale.
>
> I would like to unterstand why mTLS adds “significant overhead in terms of
> infrastructural complexity”. Can you please dig into details?
>

I guess it's mostly that every RS-endpoint (or what sits in front of it)
has to have a mechanism for accepting/terminating mTLS, managing roots of
trust, validating/OCSP, etc and then passing the certificates downstream as
headers. None of it is necessarily difficult or impossible to do in
isolation, but I meet many many people every week who simply don't know how
to do any of this stuff. And these are typically "network people", for want
of a better word. There are quite a few SaaS API management and edge
solutions out there that don't even support mTLS at all. You also have the
difficulty in handling a combination of MTLS and non-MTLS traffic to the
same endpoints. Again, it's possible to do, but far from straightforward.



>
> Our experience so far: It can be a headache to set up in a microservice
> architecture with TLS terminating proxies but once it runs it’s ok. On the
> other side, it’s easy to use for client developers and it combines client
> authentication and sender constraining nicely.
>

I do think its an elegant solution, don't get me wrong. It's just that
there are plenty of moving parts that you need to get right and that can be
a challenge, particularly in large, complex environments.



>
> >
> > DPOP, to me, appears to be a rather more elegant way of solving the same
> problem, with the benefit of significantly reducing the complexity of (and
> dependency on) the transport layer. I would not argue, however, that it is
> meant to be a solution intended for ubiquitous adoption across all
> OAuth-protected API traffic. Clients still need to manage private keys
> under this model and my experience is that there is typically a steep
> learning curve for developers to negotiate any time you introduce a
> requirement to hold and use keys within  an application.
>
> My experience is most developer don’t even get the URL right (in the
> signature and the value used on the receiving end). So the total cost of
> ownership is increased by numerous support inquiries.
>
I'll not comment, at the risk of offending developers :)

>
> best regards,
> Torsten.
>
> >
> > I guess I'm with Justin - let's look at DPOP as an alternative to
> MTLS-bound tokens for high-assurance use cases, at least initially, without
> trying to make it solve every problem.
> >
> > Best regards
> > Rob
> >
> >
> > On Fri, 22 Nov 2019 at 07:24, Justin Richer <[e-mail]> wrote:
> > I’m going to +1 Dick and Annabelle’s question about the scope here. That
> was the one major thing that struck me during the DPoP discussions in
> Singapore yesterday: we don’t seem to agree on what DPoP is for. Some
> (including the authors, it seems) see it as a quick point-solution to a
> specific use case. Others see it as a general PoP mechanism.
> >
> > If it’s the former, then it should be explicitly tied to one specific
> set of things. If it’s the latter, then it needs to be expanded.
> >
> > I’ll repeat what I said at the mic line: My take is that we should
> explicitly narrow down DPoP so that it does exactly one thing and solves
> one narrow use case. And for a general solution? Let’s move that discussion
> into the next major revision of the protocol where we’ll have a bit more
> running room to figure things out..
> >
> >  — Justin
> >
> >> On Nov 22, 2019, at 3:13 PM, Dick Hardt <[e-mail]> wrote:
> >>
> >>
> >>
> >> On Fri, Nov 22, 2019 at 3:08 PM Neil Madden <[e-mail]>
> wrote:
> >> On 22 Nov 2019, at 01:42, Richard Backman, Annabelle <
> [e-mail]> wrote:
> >>> There are key distribution challenges with that if you are doing
> validation at the RS, but validation at the RS using either approach means
> you’ve lost protection against replay by the RS. This brings us back to a
> core question: what threats are in scope for DPoP, and in what contexts?
> >>
> >> Agreed, but validation at the RS is premature optimisation in many
> cases. And if you do need protection against that the client can even
> append a confirmation key as a caveat and retrospectively upgrade a bearer
> token to a pop token. They can even do transfer of ownership by creating
> copies of the original token bound to other certificates/public keys.
> >>
> >> While validation at the RS may be an optimization in many cases, it is
> still a requirement for deployments.
> >>
> >> I echo Annabelle's last question: what threats are in scope (and out of
> scope) for DPoP?
> >>
> >>
> >> _______________________________________________
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> >> [e-mail]
> >> https://www.ietf.org/mailman/listinfo/oauth
> >
> > _______________________________________________
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> >
> >
> > --
> >
> > Rob Otto
> > EMEA Field CTO/Solutions Architect
> > [e-mail]
> >
> > c: [phone]
> > Connect with us:
>
>
> >
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>

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Rob Otto
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[e-mail]

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