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Replace sephereon/PEX presentation definitions with web5 js VCs implementation #112

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merged 7 commits into from
Dec 7, 2023

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kirahsapong
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This PR addresses #25

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changeset-bot bot commented Dec 5, 2023

🦋 Changeset detected

Latest commit: b96056a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages
Name Type
@tbdex/protocol Patch
@tbdex/http-client Patch
@tbdex/http-server Patch

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@kirahsapong
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kirahsapong commented Dec 5, 2023

One note is this PR now explicitly types our offering's get requiredClaims in response to this error. TS threw this after replacing sphereon's PresentationDefinitionV2 type import with that from Web5

The inferred type of 'requiredClaims' cannot be named without a reference to '.pnpm/@[email protected]/node_modules/@sphereon/pex-models'. This is likely not portable. A type annotation is necessary.

It seems like this might be due to conflicting package deps but we've removed the dep from our protocols package. Haven't run into this before so any thoughts from others v welcome!

For added info: Here's where Web5 import/exports sphereon's type PresentationDefinitionV2

@KendallWeihe
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explicitly types our offering's get requiredClaims

I believe the issue is because PresentationDefinitionV2 is a type alias in web5-js; see here.

So I'm guessing the TypeScript compiler is replacing the type reference w/ @sphereon/pex-models, but that's not what is defined as the OfferingData.requiredClaims type from here

So yeah... it's an odd ball out, in that it's the only get() method with an explicit return type, but I guess that's okay.

The other option is, we could change web5-js's presentation-exchange.ts to not do a type alias, and just directly export the sphereon type, so change this (how it currently is)...

import type { PresentationDefinitionV2 as PexPresDefV2 } from '@sphereon/pex-models';

//...

export type PresentationDefinitionV2 = PexPresDefV2

to this...

import type { PresentationDefinitionV2 } from '@sphereon/pex-models';
export type { PresentationDefinitionV2 } from '@sphereon/pex-models';

If we keep it as-is, then I would classify this as technical debt, albeit it's an extremely small amount of debt. The other option is, I think we should include a comment above the get requiredClaims() accessor explaining what's going on here (maybe with a link to this comment).

@@ -77,9 +74,9 @@ export class Rfq extends Message<'rfq'> {
* @throws if rfq's claims do not fulfill the offering's requirements
*/
async verifyClaims(offering: Offering | ResourceModel<'offering'>) {
const { areRequiredCredentialsPresent } = pex.evaluateCredentials(offering.data.requiredClaims, this.claims)
const requiredCredentialsPresent = PresentationExchange.selectCredentials(this.claims, offering.data.requiredClaims)
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This is a nit-pick, but variable name is slightly misleading IMO, could do either one of these...

Suggested change
const requiredCredentialsPresent = PresentationExchange.selectCredentials(this.claims, offering.data.requiredClaims)
const requiredCredentialsPresent = PresentationExchange.selectCredentials(this.claims, offering.data.requiredClaims).length > 0

And then update the if () condition below like this

    if (!requiredCredentialsPresent) {
      throw new Error(`claims do not fulfill the offering's requirements`)
    }

Or, could do...

Suggested change
const requiredCredentialsPresent = PresentationExchange.selectCredentials(this.claims, offering.data.requiredClaims)
const credentials = PresentationExchange.selectCredentials(this.claims, offering.data.requiredClaims)

and then keep the if () condition as-is (I think I prefer this way)

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yeah good callout, totes agree.

@@ -77,9 +74,9 @@ export class Rfq extends Message<'rfq'> {
* @throws if rfq's claims do not fulfill the offering's requirements
*/
async verifyClaims(offering: Offering | ResourceModel<'offering'>) {
const { areRequiredCredentialsPresent } = pex.evaluateCredentials(offering.data.requiredClaims, this.claims)
const credentials = PresentationExchange.selectCredentials(this.claims, offering.data.requiredClaims)
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does this method return credentials or error encapsulated in an object?

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@nitro-neal nitro-neal Dec 6, 2023

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  /**
   * Selects credentials that satisfy a given presentation definition.
   *
   * @param {string[]} vcJwts The list of Verifiable Credentials to select from.
   * @param {PresentationDefinitionV2} presentationDefinition The Presentation Definition to match against.
   * @return {string[]} selectedVcJwts A list of Verifiable Credentials that satisfy the Presentation Definition.
   */
  public static selectCredentials(
    vcJwts: string[],
    presentationDefinition: PresentationDefinitionV2
  ): string[] {
    this.resetPex();
    const selectResults: SelectResults = this.pex.selectFrom(presentationDefinition, vcJwts);
    return selectResults.verifiableCredential as string[] ?? [];
  }
  

it retuns the list of Verifiable Credentials that can satisfy the Presentation Definition.

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actually might be helpful to return the error. this way we can surface it back up to the caller

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I propose we use exceptions for error cases. Two benefits I can think of:

  1. The return type is scoped to the semantic use case, which makes naming more cohesive and self-evident (ex. List<Credentials> as opposed to SelectCredentialsResponse (which would include a credentials and errors arrays))
  2. By decoupling the error from the type, we have flexibility to introduce deeper call stacks abstracted behind the selectCredentials down the road, which could bubble-up exceptions, rather than having to then concern ourselves with passing errors up the callstack in return types

The counter argument is it makes the consumer have to use try/catch which can become verbose, but it isn't much more verbose than the subsequent if (selectCredentialsResponse.errors?.length) { ...

@@ -50,8 +50,6 @@
},
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i think this PR necessitates a version bump - would you be able to do that? the readme has a section on how to add a changeset and automatically bump the version.

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automagic nice!

@nitro-neal
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This is merged in now - TBD54566975/web5-js#336

@kirahsapong
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kirahsapong commented Dec 6, 2023

Took another look at this and wondered why we verify all claims submitted including those that aren't needed to satisfy our PD? Would it make sense to only verify those claims that satisfy the PD?

Current:

  async verifyClaims(offering: Offering | ResourceModel<'offering'>) {
    const credentials = PresentationExchange.selectCredentials(this.claims, offering.data.requiredClaims)

    if (!credentials.length) {
      throw new Error(`claims do not fulfill the offering's requirements`)
    }

    for (let claim of this.claims) {
      await VerifiableCredential.verify(claim)
    }
  }

Proposed:

  async verifyClaims(offering: Offering | ResourceModel<'offering'>) {
    const credentials = PresentationExchange.selectCredentials(this.claims, offering.data.requiredClaims)

    if (!credentials.length) {
      throw new Error(`claims do not fulfill the offering's requirements`)
    }

    for (let credential of credentials) {
      await VerifiableCredential.verify(credential)
    }
  }

@mistermoe @jiyoontbd @KendallWeihe

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Would it make sense to only verify those claims that satisfy the PD?

Yeah, I think so! @jiyoontbd can you think of an instance where we need to verify claims which are not defined in the Offering? That is, the Offering has N-number of claim requirements, and the RFQ has (N+M)-number of requirements, and we need to verify all N+M of them?

@jiyoontbd
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@KendallWeihe @kirahsapong that makes sense to me! The API is a bit different now that we're using web5/credentials, which allows us to get back the credentials that meet the requirements, so i don't see why we should verify all incoming claims from the RFQ.

As long as the credential we get back from PresentationExchange.selectCredentials(..) is the credential(s) from the RFQ.claims that happen to meet the requirements, I'm good with this new approach!

@@ -64,7 +65,9 @@ export class Offering extends Resource<'offering'> {
}

/** Articulates the claim(s) required when submitting an RFQ for this offering. */
get requiredClaims() {
// TODO: Remove type annotation once type alias replaced with direct export in @web5/credentials
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I think this is good to go now, right? Do we have to wait on a release to be cut? If so, and that may be some time, then I'm cool with leaving this comment, opening and issue, and going ahead with a merge here

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this lgtm! barring if we can go ahead and use the latest @web5/credentials change

@kirahsapong kirahsapong merged commit 5631d32 into main Dec 7, 2023
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@kirahsapong kirahsapong deleted the ksap/replace-pex-impl branch December 7, 2023 17:07
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5 participants