Allow to specify `AbortSignal` in `startRegistration` and `startAuthentication`

[mahnunchik]

Describe the issue

There is no way to stop registration/authentication process. This is necessary when the user canceled an action in the UI, for example, pressed the back button.

Expected behavior

const controller = new AbortController();
startAuthentication({ signal: controller.signal});

// Cancel action
controller.abort();

Dependencies

• OS: all
• Browser: all
• Authenticator: all

SimpleWebAuthn Libraries

Latest version

Additional context

AbortController is used inside library but there is no option to specify it outside.

[MasterKale]

SimpleWebAuthn manages its own use of AbortController, what is an example of a scenario in which this is insufficient? You mention the user hitting the back button, are we talking a basic server-rendered website? A single-page app? If the browser doesn't cancel the WebAuthn call on a navigation event then I'm not sure how specifying a custom instance of an abort controller would be helpful here.

[mahnunchik]

I'm working on single-page app (web, electron). User can leave registration/authentication view (cancel action). Of course, after the timeout registration/authentication process will be cancelled, but it would be useful to be able to cancel it from the app.

[MasterKale]

I've created #449 that will offer a new WebAuthnAbortService import from @simplewebauthn/browser. This service singleton will have a cancelCeremony() method that can be called at any time to cancel any in-flight WebAuthn ceremony started with startRegistration() or startAuthentication().

Take a look and let me know if you think this will offer the escape hatch you're hoping for.

[mahnunchik]

This is exactly what I need for the current project.

[MasterKale]

WebAuthnAbortService.cancelCeremony() is now available as of @simplewebauthn/browser@8.3.0 ✌️

[martpet]

I would like to supply my own AbortSignal to startRegistration() as I want to reuse it in fetch calls to /options and /verify.