Re: [GNAP] Review of draft-ietf-gnap-core-protocol-00

[Francis Pouatcha <[e-mail]>]

Hello Fabian,

I am sorry for the delayed reply, but very busy working on those decentralized use cases where tokens a produced on the user device.


Like we can see in this thread, it is not obvious to have those use cases considered in GNAP (as the GNAP charter mentions reliance on HTTP based AS).

If the role of an AS is to produce an authorization, a user device hosted AS can be build, but the negotiation process will be different from the one defined by GNAP. Means interaction protocol will need more than just HTTP.

The biggest challenge we are facing on user device produced auth tokens is on how to preserve those crypto keys held on user device from malware, loss of device...

For the moment keeping focus of GNAP on (http) server-based production of token looks like a good decision.

I will review the draft sometime as soon as possible and provide my feedback.

Best regards,

/Francis

________________________________
From: TXAuth <[e-mail]> on behalf of Fabien Imbault <[e-mail]>
Sent: Friday, February 5, 2021 3:41 PM
To: Adrian Gropper <[e-mail]>
Cc: Tom Jones <[e-mail]>; txauth gnap <[e-mail]>; Justin Richer <[e-mail]>
Subject: Re: [GNAP] Review of draft-ietf-gnap-core-protocol-00

Hi Adrian,

We would be glad to get your expertise on that. Not sure DIDComm is essential yet, so far I see it personally as something to look into, especially for use cases when we want to reach out to a RO. I agree with the potential issues.

I have a few ideas on how to implement privacy, but it's quite involved in terms of crypto (again using Ristretto groups :-)).

Of course there will be a question of priority in the features we plan to implement. I guess we should aim for a first publication without the parts which are blurry, and take the time to prototype the rest.

Cheers
Fabien

Le ven. 5 févr. 2021 à 21:19, Adrian Gropper <[e-mail]<mailto:[e-mail]>> a écrit :
There are privacy implications as well as the cost of processing spam. A service endpoint associated with a DID can be presumed to be a public broadcast. Any party can attempt to send a message or an authorization request to that service endpoint. The operator of that service, typically the DID controller, will bear the cost and risk of processing the message. They may request a bond be posted by the party responding to the "broadcast" in order to mitigate spam and phishing. They may also require that the party seeking to communicate offer credentials, which poses a privacy risk to that party in the form of phishing "broadcasts" via DIDs and lures that lead to DIDs.

In my role as invited expert on privacy to some W3C WGs and, to some extent, DIF WGs, I have not managed to understand the privacy engineering and implications in DIDcomm. I will try harder if DIDcomm has an essential role with GNAP and I can understand it in the self-sovereign or fiduciary authorization server context. Does it?

Adrian

On Fri, Feb 5, 2021 at 1:08 PM Fabien Imbault <[e-mail]<mailto:[e-mail]>> wrote:
Probably (and to be honest even for industrial users I find it complex), but alternatives are not ready for prime time either.
Maybe some day DIDComm could be useful as a basic block, what we suggest is to first use that as a potential interaction (and there's already a lot of questions that arise just from that).

Fabien

On Fri, Feb 5, 2021 at 6:55 PM Tom Jones <[e-mail]<mailto:[e-mail]>> wrote:
No, you didn't misunderstand me. It's just that the ux for that is not acceptable to retail users. As long as gnap sticks to industrial users you should do fine.

thx ..Tom (mobile)

On Fri, Feb 5, 2021, 7:56 AM Fabien Imbault <[e-mail]<mailto:[e-mail]>> wrote:
Targeting existing browsers and types of applications (web, pwa, mobile, etc.) seems like a reasonable option for an industrial standard. Improving security, privacy, ease of use and interoperability (including decentralized identity as well) should be good enough objectives.
Plus from our previous discussions, I was under the impression you were fine with the approach of deploying the AS on the phone as a loopback, for mobile apps. Did I miss something?

Cheers,
Fabien

Le ven. 5 févr. 2021 à 16:33, Tom Jones <[e-mail]<mailto:[e-mail]>> a écrit :
If you mean can GNAP work on old fashioned apps running with existing browsers and existing identity providers, then yes, i guess you are ok.

If you want to work on apps where the user is in control of authn and authz, then no, GNAP cannot work. It is not alone in that OIDC wont work there either.

Be the change you want to see in the world ..tom


On Fri, Feb 5, 2021 at 3:19 AM Fabien Imbault <[e-mail]<mailto:[e-mail]>> wrote:
Hi Tom,

Thanks, your responses made it clearer for me what you expect from an AS deployed on a mobile.

I think we're on the right path to meet the rest of your concerns. There are already a few items on these:
- privacy preserving techniques have been discussed and are likely to be included (I think). It's been recognized as a core concern
- not exactly sure the meaning you give to discovery here (it's already been used in the WG but with a different meaning I believe). The request or the continuation api provide entry points to pay attention to.

Is that enough for your use case ? Do you need something else ? (like SSE?)

Cheers
Fabien

Le jeu. 4 févr. 2021 à 22:10, Tom Jones <[e-mail]<mailto:[e-mail]>> a écrit :
discovery is the prime problem.  What causes the wallet/AS to wake up and pay attention. How does the RP know what to ask for without violating user privacy rights?

CHAPI would be ok i guess, but that requires cred man to be fixed. Not sure if it fixes discovery or privacy even then.

Be the change you want to see in the world ..tom


On Thu, Feb 4, 2021 at 12:45 PM Justin Richer <[e-mail]<mailto:[e-mail]>> wrote:
Tom, what additional functionality do you see that a browser would need to support in order for GNAP to be adopted? For the elements of the core protocol today, nothing is needed to change within the browsers — everything is built on existing functions. GNAP uses browsers as a tool, and I would argue depends on them even less so than OAuth 2 does. Extensions could use browser functionality, like using CHAPI to pass interaction elements, but the core protocol functions on vanilla browsers today.

 — Justin

On Feb 4, 2021, at 3:20 PM, Tom Jones <[e-mail]<mailto:[e-mail]>> wrote:

i assumed that the wallet (aka AS) needed to be a native app, not a PWA (which can come from a traditional web server).
There are folks, lke Kim C, who are working on a PWA, but i agree the blocks there seem to be large.
THe blocks on a native app are simple, easy to describe, and easy to ask the browser guys to fix. Not sure if they care tho.
I have trouble seeing a path to GNAP adoption for retail customers w/o some browser support.
That's why i am mostly silent here.

Be the change you want to see in the world ..tom


On Thu, Feb 4, 2021 at 11:43 AM Fabien Imbault <[e-mail]<mailto:[e-mail]>> wrote:
Fair enough. But loopback limits a lot what you can do... Just for debug it's a pain.
But as soon as you try more, it's a bit crazy. Fun to test ipv6 (luckily supported by my ISP) and ddns. But it feels really hacky.
Also deployment is a pain, compared to a traditional webserver.

Le jeu. 4 févr. 2021 à 20:20, Tom Jones <[e-mail]<mailto:[e-mail]>> a écrit :
doesn't work very well on windows uwp. works fine on smartphones
Be the change you want to see in the world ..tom


On Thu, Feb 4, 2021 at 11:18 AM Justin Richer <[e-mail]<mailto:[e-mail]>> wrote:
OK, thanks — in that case, there are no changes at all to GNAP, which is already HTTP driven. The harder parts tend to be where you can’t (or don’t want to) use something like that.

 — Justin

On Feb 4, 2021, at 2:16 PM, Tom Jones <[e-mail]<mailto:[e-mail]>> wrote:

yes, loopback

Be the change you want to see in the world ..tom


On Thu, Feb 4, 2021 at 11:01 AM Justin Richer <[e-mail]<mailto:[e-mail]>> wrote:
Tom, can you expand on how exactly the back-channel  communication works between on-device components? Do you use HTTP locally?

Thanks,
 — Justin

On Feb 4, 2021, at 1:03 PM, Tom Jones <[e-mail]<mailto:[e-mail]>> wrote:

Justin's analysis of use of the front channel is misleading.
It could equally be argued that what i have done is installed an AS on the phone and the communications with it & the PR is back channel.
Basically the point is that the old OIDC paradigms are no longer valid.
Be the change you want to see in the world ..tom


On Thu, Feb 4, 2021 at 7:47 AM Fabien Imbault <[e-mail]<mailto:[e-mail]>> wrote:
Yes, issue (#168) message based interaction / DIDComm is a tentative alternative mecanism for the interaction part. Not sure how that would work in details though, prototyping will probably help here.
Token delivery through continuation seems fine to me. The client will probably have to wait for the next polling before it receives a token issued as the result of an asynchronous interaction, but that's not a big issue.

But the AS on the phone seems like a harder nut to crack, at least at first sight. I think that would be awesome, but it gives me headaches, so I think I'll work on easier stuff right now ;-)

Fabien

On Thu, Feb 4, 2021 at 4:30 PM Justin Richer <[e-mail]<mailto:[e-mail]>> wrote:
One of the biggest drawbacks of the current app-centric approaches in OIDC (self-issued OP, or SIOP) is that they depend on using the front channel and browser redirects to pass everything, which is something that GNAP is deliberately getting away from by starting in the back channel.

That said, once a request is kicked off in GNAP, the interaction and fulfillment can happen through any number of means. Part of the work that’s being done with the “interaction” section is going to help facilitate this, and I think that there are some other potential branches here.

Token delivery is where things get extra weird though — we are explicitly not delivering tokens in the front channel in the core of GNAP, we’re using the response from the continuation API. One idea (that isn’t particularly well thought out and hasn’t been implemented at all) is to have an extension declare an alternative response from the “continue” section that’s defined today, which points to the GNPA continuation API. If an extension defines some alternative way to deliver tokens, that could live alongside a continuation API and the client could indicate support for it in its initial request.

In any event, alternative interaction and delivery methods are important, and even if we aren’t going to support every last one of them directly, the protocol design should at least be aware of them.

 — Justin

On Feb 4, 2021, at 8:35 AM, Fabien Imbault <[e-mail]<mailto:[e-mail]>> wrote:

Hi Tom,

Sure, any experience on that would be greatly appreciated, we're calling for help here (the point being that I suspect what they're doing is not trivial).

Fabien

On Thu, Feb 4, 2021 at 2:21 PM Tom Jones <[e-mail]<mailto:[e-mail]>> wrote:
I've had such an app working for over a year. There are issues which are being addressed by the browser Interaction team of oidc.

thx ..Tom (mobile)

On Thu, Feb 4, 2021, 3:12 AM Fabien Imbault <[e-mail]<mailto:[e-mail]>> wrote:
Hi Francis,

I've tried a few things with regards to using the AS on a phone, but it's really quite complex.

Making that run on a phone comes with quite a bit of trouble. The most difficult part if that we'd need to use a secure element, but just installing and hosting a http server securely is not a standard setup at all. I suggest interested people step in to work on this, as we already have a lot of work for the (more usual) server case and already handle a privacy preserving scheme.

Please let us know what you think.

Cheers,
Fabien

On Tue, Nov 24, 2020 at 5:55 AM Fabien Imbault <[e-mail]<mailto:[e-mail]>> wrote:
Hi Francis,

I've thought a bit more to what you said. I think I'll give it a try as a separate experiment (in code, not in theory). Not that I would expect it to be included in GNAP, but I kind of like the idea :-)

The direct impact for GNAP would be to think about multiple ASs.

Will let you know.

Fabien


Le mer. 18 nov. 2020 à 13:06, Francis Pouatcha <[e-mail]<mailto:[e-mail]>> a écrit :
It would be nice if the protocol was designed at many layers of abstraction.


  *   The first layer shall design abstract protocol flows, without specification of the mode and mechanism of interaction.
  *   The second layer can instantiate the first layer for dedicated interaction. Here we can talk http, we can define interactions that presume server based token generation, we can define interaction that run on user device based token generation.

This is also the fundament of the structure I proposed for the spec (https://github.com/ietf-wg-gnap/gnap-core-protocol/issues/30).

/Francis

________________________________
From: Fabien Imbault <[e-mail]<mailto:[e-mail]>>
Sent: Wednesday, November 18, 2020 6:35 AM
To: Francis Pouatcha <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>; Dick Hardt <[e-mail]<mailto:[e-mail]>>; Tom Jones <[e-mail]<mailto:[e-mail]>>; Denis <[e-mail]<mailto:[e-mail]>>; Justin Richer <[e-mail]<mailto:[e-mail]>>
Subject: Re: [GNAP] Review of draft-ietf-gnap-core-protocol-00

Would make sense, but not so easy as we rely heavily on HTTP. Hence the discussion about deep links and so on.

An alternative might be provided by wasm/wasi (running a local sandbox on your phone, for your own AS), but it's really early stage. This also poses another question that Denis has put forward, i.e. how do we handle the multiple AS scenario (likely to occur then).

Fabien

On Wed, Nov 18, 2020 at 12:16 PM Francis Pouatcha <[e-mail]<mailto:[e-mail]>> wrote:
We are drifting away from the original problem space.

  *   My original mention was about the "POST" request, that subsumes that the "AS" is a "Server". Designing a new protocol, we cannot afford this limitation.
  *   I just mentioned SIOP to show a known and closed example? Let us not focus on the device local discovery scheme (like openid:) for now.
  *   As capability of holding private keys on user device evolves, server-based issuing of token will be fading out giving way to device local generation of token.

While designing GNAP, let us assume the AS-Role can be exercised on a user device and design the protocol to honor that.

Best regards,
/Francis
________________________________
From: TXAuth <[e-mail]<mailto:[e-mail]>> on behalf of Dick Hardt <[e-mail]<mailto:[e-mail]>>
Sent: Tuesday, November 17, 2020 1:28 PM
To: Tom Jones <[e-mail]<mailto:[e-mail]>>
Cc: Fabien Imbault <[e-mail]<mailto:[e-mail]>>; Denis <[e-mail]<mailto:[e-mail]>>; GNAP Mailing List <[e-mail]<mailto:[e-mail]>>; Justin Richer <[e-mail]<mailto:[e-mail]>>
Subject: Re: [GNAP] Review of draft-ietf-gnap-core-protocol-00

Got it.

So web apps invoke a openid: deep link and hope there is an app to handle the openid: scheme? ... and that it is the user's wallet rather than some malware that has registered openid: on the mobile device?

A native app can attempt to open a deep link associated with an app, and will fail if the app is not there. If the app is there, it will be opened, so this can't be used to silently test if an app is present, but it does allow a native app to provide an alternative experience if an app is not present. I don't think this works with custom schemes ... and I don't know how it could work from a web app on the phone with the current Safari APIs.

Apple warns against using custom schemes [1] ... but perhaps they can be convinced to make openid: a managed scheme similar to mailto:, tel:, sms:, facetime: ?

[1] https://developer.apple.com/documentation/xcode/allowing_apps_and_websites_to_link_to_your_content/defining_a_custom_url_scheme_for_your_app


[https://mailfoogae.appspot.com/t?sender=aZGljay5oYXJkdEBnbWFpbC5jb20%3D&type=zerocontent&guid=011490be-d3a0-4b2c-8abb-e51175e3ae19]ᐧ

On Tue, Nov 17, 2020 at 10:06 AM Tom Jones <[e-mail]<mailto:[e-mail]>> wrote:
You are - that is not standard which is opeind://
This is the one step that still needs to be optimized for SIOP to have good UX.
Peace ..tom


On Tue, Nov 17, 2020 at 9:59 AM Dick Hardt <[e-mail]<mailto:[e-mail]>> wrote:
Hi Tom

I watched your video (I watched at 2X speed)

Looks like the employment website app that is using localhost:8765 to communicate with the wallet. Am I correct?

/Dick
[https://mailfoogae.appspot.com/t?sender=aZGljay5oYXJkdEBnbWFpbC5jb20%3D&type=zerocontent&guid=11a62ce6-9b4a-4d5f-86c5-d2c114395aee]ᐧ

On Tue, Nov 17, 2020 at 9:46 AM Tom Jones <[e-mail]<mailto:[e-mail]>> wrote:
Well, here's a demo. Note that in this case the AS is not online all of the time, so it is really implicit flow and the OIDC id-token comes from the siop device directly.
(whether this is front-channel or back channel is no longer an interesting question.)
Now if an always-on AS is required, that is possible, but probably beyond the scope of this effort and would require something like an agent-in-the-sky (with diamonds).
here is the link to the 9 min video   https://youtu.be/Tq4hw7X5SW0<https://urldefense.us/v2/url?u=https-3A__youtu.be_Tq4hw7X5SW0&d=DwMFaQ&c=2plI3hXH8ww3j2g8pV19QHIf4SmK_I-Eol_p9P0CttE&r=D5lnfoa2MVZWELqVbbz71ooelbP7rVGCjGDSBNvUpYQ&m=ixsudGSr_dhG-SLiatb4Sz9FWslmywnYyZAOLgZxhl8&s=jdLLy0G1JTQCAOBZ6PeUgI0kiCtVJXrru0VToYWlNZ8&e=>
Peace ..tom


On Tue, Nov 17, 2020 at 9:20 AM Justin Richer <[e-mail]<mailto:[e-mail]>> wrote:
Ultimately, in most situations like these in the real world, the hurdle isn’t technical compatibility so much as it is trust compatibility. The RP (client) needs to have some incentive to trust the assertions and identity information that’s coming from the AS. The same is true for an RS trusting tokens from the AS. The hard question is less “how” to do that (which SSI answers), but more “why” to do that (which SSI doesn’t answer very well, because it’s a hard question).

Still: it’s definitely a question about how to support this “AS on device” element. We’ve got the start of it more than OAuth2/OIDC have by allowing the bootstrap of the process from a starting call: the interaction and continuation URIs handed back by the AS don’t need to be the same URIs that the client starts with, so just like SIOP the process can start in HTTP and potentially move to other communication channels. A major difference is that we aren’t dependent on the assumption that the user will always be in a browser at some stage, and so the whole raft of front-channel messages that SIOP relies on doesn’t fly. That said, we’ve got an opportunity to more explicitly open up alternative communication channels here, and that’s something I’d like to see engineered, even if it’s an extension. I’d love to see a concrete proposal as to how that would work over specific protocols, starting with what we’ve got today.

 — Justin

On Nov 17, 2020, at 12:03 PM, Fabien Imbault <[e-mail]<mailto:[e-mail]>> wrote:

Hi Denis, hi Francis,

At some point integration with SSI (on the authentication side) will probably occur, including amongst other possibilities SIOP (since they work with OpenID a part of the work will probably be made easier).

That being said, Denis is right. It's not an AS. Technically it's entirely possible to rely on a decentralized wallet (for instance on your phone) and a centralized AS. I know of a few studies on how to decentralize the AS itself (for instance https://tools.ietf.org/html/draft-hardjono-oauth-decentralized-02).
Maybe it exists, but I'm still looking for real scenarios (or even architectures) where an AS is deployed directly on a phone, and under the sole authority of the RO, while being compatible with the rest of the world.

Cheers,
Fabien

On Tue, Nov 17, 2020 at 5:45 PM Denis <[e-mail]<mailto:[e-mail]>> wrote:
Hello  Francis,

See two comments in line.


B) Current Document

Roles description shall not hold any assumption on the physical structure of the party fulfilling the roles.
[FI] not sure what you mean
 [FP] for example, we assume the AS is a server! In most SSI based use cases, the AS will be running on the user device. See SIOP (https://identity.foundation/did-siop/).

I browsed through the two drafts, i.e. :

  *   Decentralized Identifiers (DIDs) v1.0 Core architecture, data model, and representations W3C Working Draft 08 November 2020
  *   Self-Issued OpenID Connect Provider DID Profile v0.1. DIF Working Group Draft

At no place within these two documents, it is possible to imagine that "the AS will be running on the user device".

From section 3 of the DIF Working Group Draft:

      "Unlike the OIDC Authorization Code Flow as per [OIDC.Core], the SIOP will not return an access token to the RP".

An Identity Wallet is not an AS.

Roles:
-> grant endpoint of the AS: Why is this a post request? This eliminates the chance of having user device hosted AS (no server).
[FI] what would you propose instead?
Would also be interested to understand better the deployment model when there is no server. That's something that was discussed several times but I'm still missing the underlying architecture and use case.
 [FP] See above (SIOP). There will be a lot of identity wallets operated on end user device.

See the above comment. Please, do not confuse an Identity Wallet with an Authentication Server (AS).

Denis

-> Resource Owner (RO) : Authorizes the request? Does it authorize the request or the access to a resource?
[FI] yes, we should make the wording clearer

Missing Section Interactions:
--> This section shall introduce the notion of interaction before we start listing interaction types.
[FI] yes

Interaction Types:
--> I prefer a classification with Redirect, Decoupled and Embedded is. In the draft, we have one redirect and 2 decouple interactions and nothing else.
[FI] this should be handled as a specific discussion item. As a reminder, how would you define embedded?

In practice there's at least these modes:
- redirect and redirect back
- redirect to different browser or device
- user code
- CIBA
[FP] This classification is limited.

  *   Redirect: same device, same or different user agents (browser, mobile app, desktop app, ...)
  *   Decoupled: different devices
  *   Embedded : RC carries RO authorization to AS


Resource Access Request vs. Resource Request
--> Both are mixed up. No clarification of the context of each section.
[FI] could you clarify what you'd expect.  Btw on this topic, there's a more general discussion on whether we should make a distinction or not.
[FP]: Here:

  *   Resource Access Request: Requesting Access to a resource. Response is an access token (or any type of grant)
  *   Resource Request: Request the resource. Response is the resource (or a corresponding execution)

Token Content Negotiation
--> Not expressed as such. This is central to GNAP and not represented enough  in the document.
[FI] right. This should be a specific discussion item.

Requesting "User" Information
we identify two types of users: RQ and RO. It will be better not to refer to a user in this draft, but either to a RQ or an RO.
[FI] yes that would avoid potential misunderstandings. Although in the end, people will translate RQ into user or end-user most of the time. Cf in definition, currently we have Requesting Party (RQ, aka "user")


Interaction Again
-> For each interaction type, we will have to describe the protocol flow and the nature and behavior of involved Roles (Parties), Elements, Requests.
[FI] yes

[FP] Will these and into tickets?

Best regards.
/Francis





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