Type of `CryptoKey.algorithm` is incomplete, making usage of `SubtleCrypto` difficult

[LiraNuna]

Search Terms:

cryptokey algorithm

Code

function sign(key: CryptoKey, message: ArrayBuffer): Promise<ArrayBuffer> {
    return crypto.subtle.sign(
        key.algorithm,
        key,
        message,
    );
}

Expected behavior:
CryptoKey.algorithm is an appropriate way to pass the key algorithm to subtle methods such as sign and encrypt. However, the original definition of the type CryptoKey defines the type of algorithm as KeyAlgorithm which misses extra attributes that could be there.

Therefor the expected behavior is for the code to now have a type error and compile correctly. Maybe the correct type for CryptoKey should be

interface CryptoKey {
    readonly algorithm: RsaKeyAlgorithm | EcKeyAlgorithm | AesKeyAlgorithm | HmacKeyAlgorithm | DhKeyAlgorithm;
    readonly extractable: boolean;
    readonly type: string;
    readonly usages: string[];
}

I am not sure how to fully test such a change, since modifying lib.es6.d.ts locally and running tsc produces the same message.

Actual behavior:
The following type error:

Argument of type 'KeyAlgorithm' is not assignable to parameter of type 'string | RsaPssParams | EcdsaParams | AesCmacParams'.
  Type 'KeyAlgorithm' is not assignable to type 'AesCmacParams'.
  Property 'length' is missing in type 'KeyAlgorithm'. (2345)

Playground Link: Playground link

Related Issues: Unknown

[mhegazy]

PRs welcomed. You can find more information about contributing lib.d.ts fixes at https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md#contributing-libdts-fixes.

[LiraNuna]

I tried giving this a go but it required me to go down into a rabbit hole I was not able to fully grok.
My proposed changes did not fix the issue and therefor I'm not sure what a "correct" solution may look like.

[LiraNuna]

This issue has been open for 4 months without much progress. I've been trying to address this issue myself but I do not have the knowledge necessary to contribute to lib.d.ts even with the instructions (especially since this depends on Edge?).

Is there any plan to address this? This makes WebCrypto quite unusable on TypeScript.

[jiripudil]

Hello, I'm currently enhancing the Web Crypto API types and I have mixed feelings about this issue. While I agree that it might be useful to have a more specific set of types for CryptoKey.algorithm, I don't understand the motivation.

CryptoKey.algorithm is an appropriate way to pass the key algorithm to subtle methods such as sign and encrypt

This is what confuses me the most because I can't agree with it. More often than not, SubtleCrypto methods require a different set of properties from those contained in KeyAlgorithm: commonly additional details such as initialization vectors are required, while some information in KeyAlgorithm such as key length is excessive because that's just information about the key, not parameters of the crypto operation.

[LiraNuna]

This is what confuses me the most because I can't agree with it. More often than not, SubtleCrypto methods require a different set of properties from those contained in KeyAlgorithm

Sure, I agree with that. For that, wouldn't you want to use {...key.algorithm, more: rest} which will have similar issues?

because that's just information about the key

For some reason, WebCrypto requires the information on the key alongside the key.

[jakebailey]

This was fixed in #37464.