[Openid-specs-fapi] A simpler signing solution

[Dave Tonge]

I've pushed some example code for the some of the different signing
mechanisms here: https://github.com/davidgtonge/http-signing

I'll add a bit more analysis.
But my main issue with the OBE approach is the unnecessary complexity.

For example compare this file:
https://github.com/davidgtonge/http-signing/blob/main/src/obe.js
With this one:
https://github.com/davidgtonge/http-signing/blob/main/src/dpop-plus.js

This is just the signing rather than the verification.

The question to my mind is will PSD2 API initiatives in Europe adopt the
OBE profile. I'm not sure that OBUK will. Do you know if Berlin Group will?

Dave

On Thu, 29 Oct 2020 at 15:33, Francis Pouatcha <Francis.Pouatcha at adorsys.com>
wrote:

>
> ------------------------------
> *From:* Dave Tonge <dave.tonge at momentumft.co.uk>
> *Sent:* Thursday, October 29, 2020 10:09 AM
> *To:* FAPI Working Group List <openid-specs-fapi at lists.openid.net>
> *Cc:* Francis Pouatcha <Francis.Pouatcha at adorsys.com>; Brian Campbell <
> bcampbell at pingidentity.com>
> *Subject:* Re: [Openid-specs-fapi] A simpler signing solution
>
> Hi Francis, Brian
>
> I am proposing that we define a new mechanism for http signing in the FAPI
> WG.
> Obviously it should use existing standards where at all applicable.
>
> As discussed on the call, it would be good to come up with a document that
> we can present to the WG.
> It seems that we have two options at the moment:
>
> *1. Build on the OBE spec*
> *2. Build on dPOP*
>
> At first I was leaning towards option 1, but after further review of the
> OBE spec I personally am very much leaning towards option 2. I think the
> OBE spec is not fit for purpose, it adds lots of unnecessary complexity
> just because its trying to join draft-cavage and  an earlier version of the
> UK OpenBanking signing spec together. I may try and show some worked
> examples as I think my suggestion will result in a small http payload even
> if some header values are repeated.
>
> I do believe the payload size is less interesting here than
> interoperability. I prefer we look at how to simplify  the current OBE
> draft.
>
> @Brian Campbell <bcampbell at pingidentity.com> -> reply inline bellow:
>
> On Thu, 29 Oct 2020 at 14:12, Brian Campbell via Openid-specs-fapi <
> openid-specs-fapi at lists.openid.net> wrote:
>
>
> On Thu, Oct 29, 2020 at 5:10 AM Francis Pouatcha <
> Francis.Pouatcha at adorsys.com> wrote:
>
> I agree with Dave we shall not define a new signature mechanism.
>
>
> As I understood the message that started this thread and the discussion
> about it during the call yesterday, Dave is very much proposing that we
> define a new mechanism. Maybe there's some semantic difference or
> miscommunication here but I'm confused by your statement.
>
> I think having compatibility with OBE is essential.
>
>
>
> As for the replacement of RFC3230 with
> https://datatracker.ietf.org/doc/draft-ietf-httpbis-digest-headers/,
> adding a signature header field to indicate the mechanism used to digest
> the http body might solve the problem.
>
>
> What problem? I just wanted to note that there was work underway to
> update/obsolete RFC3230 as it seemed relevant given Dave's initial proposal
> relied on RFC3230. But I don't understand what problem you're suggesting
> would be introduced by the new document or how that would solve it.
>
> No problem. Like elaborated in
> https://bitbucket.org/openid/fapi/issues/297/open-banking-europe-jws-profile-for#comment-59040544 the
> field "sigD"."pars" can be  used to indicate canonicalization and digest
> rules for body. Giving implementor a choice on how to process the http body.
>
> <https://bitbucket.org/openid/fapi/issues/297/open-banking-europe-jws-profile-for#comment-59040544>
> Open Banking Europe JWS PROFILE for OpenBanking
> <https://bitbucket.org/openid/fapi/issues/297/open-banking-europe-jws-profile-for#comment-59040544>
> This JWS profile consolidate the work done at ETSI \\(JADes\\) and the
> Internet Draft draft-cavage-http-signatures-10 and Signing HTTP Messages.
> This issue will be used to collect details associated with referencing that
> work in the FAPI profiles for the purpose of addressing non repudiation.
> bitbucket.org
>
>
> I am a bit concerned (or rather just don't really understand the
> implications of) about RFC3230 and it's successor digesting the "instance"
> or "representation" of the resource as opposed to the payload of the
> message itself. But as far as I can tell RFC3230 and
> https://datatracker.ietf.org/doc/draft-ietf-httpbis-digest-headers/ are
> the same in this regard but just use different language to describe it.
>
>
> Yes.
>
> /Francis
>
>

-- 
Dave Tonge
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