Authentication without username

With Webauthn, it is possible to authenticate a user without username. This behavior implies several constraints:

1. During the registration of the authenticator, a Resident Key must have been asked,

2. The user verification is required,

3. The list of allowed authenticators must be empty

In case of failure, you should continue with the standard authentication process i.e. by asking the username of the user.

The Easy Way

Selection criteria for the registration of the authenticator:

use Webauthn\AuthenticatorSelectionCriteria;
use Webauthn\PublicKeyCredentialCreationOptions;

$authenticatorSelectionCriteria = new AuthenticatorSelectionCriteria(
    AuthenticatorSelectionCriteria::AUTHENTICATOR_ATTACHMENT_NO_PREFERENCE,
    true,                                                                   // Resident key required
    AuthenticatorSelectionCriteria::USER_VERIFICATION_REQUIREMENT_REQUIRED, // User verification required
    AuthenticatorSelectionCriteria::RESIDENT_KEY_REQUIREMENT_REQUIRED
);

The Request Options:

<?php

use Webauthn\PublicKeyCredentialRequestOptions;

$ublicKeyCredentialRequestOptions = $server->generatePublicKeyCredentialRequestOptions(
    PublicKeyCredentialRequestOptions::USER_VERIFICATION_REQUIREMENT_REQUIRED,
);

The Hard Way

Selection criteria for the registration of the authenticator:

$authenticatorSelectionCriteria = new AuthenticatorSelectionCriteria(
    AuthenticatorSelectionCriteria::AUTHENTICATOR_ATTACHMENT_NO_PREFERENCE,
    true,                                                                   // Resident key required
    AuthenticatorSelectionCriteria::USER_VERIFICATION_REQUIREMENT_REQUIRED, // User verification required
    AuthenticatorSelectionCriteria::RESIDENT_KEY_REQUIREMENT_REQUIRED
);

$publicKeyCredentialCreationOptions = new PublicKeyCredentialCreationOptions(
    $rpEntity,
    $userEntity,
    $challenge,
    $publicKeyCredentialParametersList,
    $timeout,
    $excludedPublicKeyDescriptors,
    $authenticatorSelectionCriteria
);

The Request Options:

// Public Key Credential Request Options
$publicKeyCredentialRequestOptions = new PublicKeyCredentialRequestOptions(
    random_bytes(32),
    60000, 
    'foo.example.com',
    [],
    PublicKeyCredentialRequestOptions::USER_VERIFICATION_REQUIREMENT_REQUIRED
);

The Symfony Way

The bundle configuration should have a profile with the constraints listed above:

webauthn:
    credential_repository: '…'
    user_repository: '…'
    creation_profiles:
        default:
            rp:
                name: 'My application'
                id: 'example.com'
            authenticator_selection_criteria:
                require_resident_key: true
                user_verification: !php/const Webauthn\AuthenticatorSelectionCriteria::USER_VERIFICATION_REQUIREMENT_REQUIRED
                resident_key: !php/const Webauthn\AuthenticatorSelectionCriteria::RESIDENT_KEY_REQUIREMENT_REQUIRED
    request_profiles:
        default:
            rp_id: 'example.com'
            user_verification: !php/const Webauthn\AuthenticatorSelectionCriteria::USER_VERIFICATION_REQUIREMENT_REQUIRED