Typescript JWK Key return type issues

[HiskiRobo]

Describe the bug
Currently all return values regarding Keys are typed under the Key interface.

This causes that no Key type specific parameters can be accessed (for example EC Key crv value) in the return values regarding keys.

*To Reproduce

// fill with EC type public / private key
const ecTypeKey = 'EC KEY';
const key = JWK.asKey(ecTypeKey);
// This will cause an error: Property 'crv' does not exist on type 'Key'.
console.log(key.crv);

Expected behaviour
Should return proper Key sub type, so parameters can be accessed

Environment:

• jose version: [e.g. v1.22.2]
• node version: [e.g. v13.3.0]

Additional context

• This should be implemented to all return values regarding Key type (JWE.completeDecrypt, etc)

[panva]

The types can't possibly know the kty from a string or a buffer... They do know when you pass in a JWK formatted object.

const key = jose.JWK.asKey({ kty: 'EC', x: 'foo', y: 'bar', d: 'foo', crv: 'P-256' })

key.crv

Please come forth with a proposal for an improvement, otherwise i'm not seeing one other than - if you know the key type contained by the string, cast the value to e.g. JWK.ECKey, otherwise, don’t access these attributes.

const key = jose.JWK.asKey('EC KEY') as jose.JWK.ECKey

key.crv

[HiskiRobo]

How about creating a mixed key type for the situation when they actual key type cannot be inferred:

interface MixedKey extends Key {
    e?: string;
    n?: string;
    d?: string;
    p?: string;
    q?: string;
    dp?: string;
    dq?: string;
    qi?: string;
    crv?: ECCurve | OKPCurve;
    x?: string;
    y?: string;
    k?: string;
  }

And in asKey:

  function asKey(key: KeyObject | KeyInput, parameters?: KeyParameters): MixedKey;
  function asKey(jwk: JWKOctKey): OctKey;
  function asKey(jwk: JWKRSAKey, options?: ImportOptions): RSAKey;
  function asKey(jwk: JWKECKey): ECKey;
  function asKey(jwk: JWKOKPKey): OKPKey;

And in CompleteDecrypt

  interface completeDecrypt {
    cleartext: Buffer;
    key: JWK.MixedKey;
    cek: JWK.OctKey;
    aad?: string;
    header?: object;
    unprotected?: object;
    protected?: object;
  }

[panva]

Well, i can do one of two things. Your UndefinedKeyType idea doesn't sit well with me.

Easiest is to add this to JWK.Key

 [key: string]: any;

or add all of these to JWK.Key and then undefine them for the respective types.

  crv?: ECCurve | OKPCurve;
  d?: string;
  dp?: string;
  dq?: string;
  e?: string;
  k?: string;
  n?: string;
  p?: string;
  q?: string;
  qi?: string;
  x?: string;
  y?: string;

[HiskiRobo]

Nice solution in the commit! This can be closed. Thanks!

[panva]

This branch will land with the next 13.x node release. Planned for the 18th