Hi Torsten - thanks for the reply. Responses in line.
Grüsse Rob On Fri, 22 Nov 2019 at 07:59, Torsten Lodderstedt <torsten= [email protected]> wrote: > Hi Rob, > > > On 22. Nov 2019, at 15:52, Rob Otto <robotto= > [email protected]> 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 <[email protected]> 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 <[email protected]> wrote: > >> > >> > >> > >> On Fri, Nov 22, 2019 at 3:08 PM Neil Madden <[email protected]> > wrote: > >> On 22 Nov 2019, at 01:42, Richard Backman, Annabelle < > [email protected]> 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? > >> > >> > >> _______________________________________________ > >> OAuth mailing list > >> [email protected] > >> https://www.ietf.org/mailman/listinfo/oauth > > > > _______________________________________________ > > OAuth mailing list > > [email protected] > > https://www.ietf.org/mailman/listinfo/oauth > > > > > > -- > > > > Rob Otto > > EMEA Field CTO/Solutions Architect > > [email protected] > > > > c: +44 (0) 777 135 6092 > > Connect with us: > > > > > > > > CONFIDENTIALITY NOTICE: This email may contain confidential and > privileged material for the sole use of the intended recipient(s). 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