Server error codes

[Mykhailo-Sichkaruk]

Proposal

It would be great if server lib had codes for errors. There are such error codes for frontend - https://github.com/MasterKale/SimpleWebAuthn/pull/367 .

Consider example -

• you want to run some logic if counter is lower than expected,
• and you want to run another logic if origin mismathes
• else rethrow

I want to it to look like this in my code:

			try {
				const verification = await verifyAuthenticationResponse({
				...
				});
			} catch (error: WebAuthnError) {
			        if (error.code === 'COUNTER_TOO_LOW') {
			            // logout user
			            // delete passkey
			        } else if (error.code === 'ORIGIN_MISMATCH'){
			            throw new Error('I'm a teapot');
                                } else {
                                    throw error;
                                }
			}

Just say what do you think about it generally and we can start discussing implementation details. I want to contribute.

---

P.S.: thank you for such great library

[MasterKale]

Hello @Mykhailo-Sichkaruk, thanks for the suggestion! This is a great idea, I see how it'd be nice to bring some order to the many more errors that @simplewebauthn/server might raise. I'll begin thinking about this and try to implement a custom error like @simplewebauthn/browser's WebAuthnError from #367 like you called out... 🤔

[Mykhailo-Sichkaruk]

Thanks for considering this feature 😊 I'm also thinking how we can improve error handling

I have a related idea: grouping errors to handle not just one error but set of related errors.

For example, a PublicKeyError category could group all public key-related issues, such as:

• PublicKeyMissingAlgError
• PublicKeyInvalidAlgError
• other

This could be implemented with inheritance:

class PublicKeyError extends WebAuthnError {}
class PublicKeyInvalidAlgError extends PublicKeyError {}

Or, alternatively, using a list of error codes:

const PublicKeyErrors = ['public_key_invalid_alg', 'public_key_missing_alg', ...];

This can help not only in handling errors, but also in understanding for users of the lib how errors relate to each other and how they should be handled.