Feature Request: Safe/reliable crypto.KeyObject and webcrypto.CryptoKey detection in userland

[mscdex]

Currently there are no public methods for checking for KeyObject and CryptoKey objects. Having reliable checks for these would be very nice to have for userland code that wants to support these types of objects in their code.

It seems there are already internal methods for achieving this, but I'm not sure why they are not currently exposed to userland. I was thinking maybe something like how Buffer handles this: KeyObject.isKeyObject() and CryptoKey.isCryptoKey(). The former is currently pretty easy to do in userland since it's just doing an instanceof check, but the latter checks "private" symbols, which is not as easy/ideal for userland (although I guess at least currently instanceof CryptoKey would work?). Either way, having these encapsulated in helper methods would help insulate changes to the checking logic, should it ever change.

[tniessen]

Re KeyObject: When I designed the new APIs, I intentionally did not expose that class directly. The only reason we did so eventually is such that users can rely on instanceof KeyObject.

[tniessen]

See #26200 and #26438.

[mscdex]

I still think it would be a good idea to expose static .is*() methods in case the method of detection should change in the future (e.g. instanceof to symbol check) as with Buffer.isBuffer() (where the detection method did change over time).

[panva]

Both instanceof crypto.KeyObject and instanceof crypto.webcrypto.CryptoKey work so long as the code doesn't run e.g. in a vm context.

I think exposing a symbol check function would be better.

[jasnell]

CryptoKey.isCryptoKey() is problematic because it extends the standard API in a non-standard way. As I suggest in @panva's PR, we could add both checks to KeyObject:

KeyObject.isKeyObject()
KeyObject.isCryptoKey()

Alternatively, we could add both to util/types

const { isKeyObject, isCryptoKey } = require('util/types');

isKeyObject(obj)
isCryptoKey(obj)

If the Node.js binary is built without crypto support, these would still exist but would always return false.

[mscdex]

I don't have a strong preference where the functions live, just that they're available in some sensible place.