Add an exportable option to default-plugins

[kshinn]

Addresses issue #108

This simply adds and exportable parameter to the EcdsaKeyPair class to allow the key to be exported.

[matheus23]

With the provided fix, I can successfully export the key, however it exports it in pkcs8 format. There doesn't seem to be a symmetrical way to import this key material. The import function uses the jwk format instead of a raw format. In order to make this change useful, we would need to also add an importFromRaw type of method to this class. This may start to diverge from the original intent of these classes.

The export function hard-codes the pkcs8 format:

ts-ucan/packages/default-plugins/src/p256/keypair.ts

Lines 73 to 76 in 4b1be87

	const arrayBuffer = await webcrypto.subtle.exportKey(
	"pkcs8",
	this.keypair.privateKey
	)

Perhaps it makes sense to change it to jwk. It's not really a breaking change, because you weren't able to export P-256 keys previously at all, anyways.

[matheus23]

It is weird that it wouldn't match the RSA export format though (which is also pkcs8).

[kshinn]

To me, it looks like ed25519 is the only plugin with a full / symmetric import-export support. The p256 looks asymmetric (import is jwk, export is pkcs8). RSA only looks to export and doesn't have an import. As part of this PR, I could revamp both p256 and RSA to have an import and export based on pkcs8. What do you think?

[matheus23]

Sounds good. I'll leave it up to you to whether it's going to be JWK or PCKS8 :) ✌️

[kshinn]

Ok, I did a pass and got symmetric import / export functionality for all of the plugins. I tried to reuse where I could, but realized a lot of the import type functions are there for other purposes (usually in the process of signing or verifying a message). I went with JWK where it was available (p256 and rsa). Ed25519 is using a different library and doesn't appear to support JWK, but I it was the easiest to get working with the existing format.

[matheus23]

@kshinn is there a reason why you removed the uint8arrays dependency?
Buffer is only available in nodejs, and this project also targets working in browsers, so relying on Buffer is a no-go for its goals, unfortunately.

[kshinn]

Oops, that wasn't supposed to commit to this branch. I'll return the dependency. Long story short: I'm trying to make this library work in a constrained nodejs setting (total size needs to be as small as possible). I'm trying to eliminate some of the polyfills and work directly with node libs to do this.

But this is unrelated to the changes I'm making here and I didn't see that they leaked in. I will undo those changes in this branch.

[matheus23]

Putting this on approve, because I trust you to fix the last nit before we merge :)

[matheus23]

Thanks for your work, this looks good to me :)