Start Differentiating Credential Types

[suzannajiwani]

Added structure for additional credential types by moving existing code to a credential package and creating abstract classes for Credential and SecureAreaBoundCredential, with MdocCredential as the first implementation.

All tests pass + tested manually by provisioning and presenting in wallet and appholder.

[davidz25]

Looks like a great start! Comments inline!

[davidz25]

So, yeah, I think we should probably move credential creation into concrete Credential-derived classes and instead of Document.createCredential() it should just be Document.addCredential() and I think addCredential()'s only job would be to save the credential to disk ...

In this setup the application code would be something like this (for a contrived example where we're adding to mDL credentials - one for LoA Substantial, one for LoA High - one SD/JWT credentiat, and one mDL direct access credential.

val mdocCredential = MdocCredential.create(
  domain = "mDL_LoA_Substantial",
  validFrom = validFrom,
  validUntil = validUntil,
  secureArea = androidKeystoreSecureArea,
  createKeySettings = createKeySettings,
  asReplacementFor = null,
)
document.addCredential(mdocCredential)

val mdocCredentialLoAHigh = MdocCredential.create(
  domain = "mDL_LoA_High",
  validFrom = validFrom,
  validUntil = validUntil,
  secureArea = androidKeystoreSecureArea,
  createKeySettings = createKeySettingsForLoAHigh,
  asReplacementFor = null,
)
document.addCredential(mdocCredentialLoAHigh)

val sdjwtCredential = SdJwtCredential.create(
  domain = "sdjwt_LoA_Substantial",
  validFrom = validFrom,
  validUntil = validUntil,
  secureArea = androidKeystoreSecureArea,
  createKeySettings = createKeySettings,
  asReplacementFor = null,
)
document.addCredential(sdjwtCredential)

val mdocDirectAccessCredential = MdocDirectAccessCredential.create(
  domain = "mdoc_directAccess",
  validFrom = validFrom,
  validUntil = validUntil,
  asReplacementFor = null,
  /* some direct-access specific stuff */
)
document.addCredential(mdocDirectAccessCredential)

[suzannajiwani]

since credentials are so tied to the document they're associated with, I added the document to the create method so the usage would look like this instead:

val mdocCredentialLoAHigh = MdocCredential.create(
  domain = "mDL_LoA_High",
  secureArea = androidKeystoreSecureArea,
  createKeySettings = createKeySettingsForLoAHigh,
  asReplacementFor = null,
  document = document
)

with the document.addCredential implicitly in the Credential.create - lmk what you think

[davidz25]

Looks really great! Didn't have time to finish my review but here are some comments for what I did look at... might have some more comments on the next iteration!

[davidz25]

Thanks, this is almost ready. Mostly nits.

[davidz25]

I don't think this actually works since create() is protected. Use the constructor and then Document.addCredential() instead.

[suzannajiwani]

good point - I didn't check the samples to make sure it all works, but will before the next push

[davidz25]

LGTM, thanks!