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

[Filip Skokan <[e-mail]>]

Rob, I agree that managing roots of trust, validating/OCSP etc is not
"easy" per se, but the MTLS setup gets really simple with the Self-Signed
Certificate Mutual-TLS Method
<https://tools.ietf.org/html/draft-ietf-oauth-mtls-17#section-2.2> and we
made sure combined traffic is simple to signal by the AS and simple to
detect and use by clients using the mtls_endpoint_aliases discovery
metadata.

S pozdravem,
*Filip Skokan*


On Fri, 22 Nov 2019 at 09:10, Rob Otto <robotto=
[e-mail]> wrote:

> 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=
>> 40pingidentity.com@dmarc..ietf.org <[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]
>> <[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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>> >
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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
> EMEA Field CTO/Solutions Architect
> [e-mail]
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