GHSA-875x-g8p7-5w27

### Summary

The ProfileBasedRequestOptionsBuilder method returns allowedCredentials without any credentials if no username was found.

### Details

When WebAuthn is used as the first or only authentication method, an attacker can enumerate usernames based on the absence of the `allowedCredentials` property in the assertion options response. This allows enumeration of valid or invalid usernames.

#### Proposal how to resolve it: ``` return $this->publicKeyCredentialRequestOptionsFactory->create( $this->profile, count($allowedCredentials) <= 0 ? self::getRandomCredentials(): $allowedCredentials, $optionsRequest->userVerification, $extensions );

private static function getRandomCredentials(): array { $credentialSources = []; for ($i = 0; $i <= rand(0,1); $i++) { $credentialSources[] = new PublicKeyCredentialSource( random_bytes(32), "public-key", [], "basic", new EmptyTrustPath(), Uuid::v7(), random_bytes(77), Uuid::v7()->__toString(), rand(0, 6000), null ); } return array_map( static fn (PublicKeyCredentialSource $credential): PublicKeyCredentialDescriptor => $credential->getPublicKeyCredentialDescriptor(), $credentialSources ); } ```

### PoC

curl https://example.com/assertion/options \ -H 'content-type: application/json' \ --data-raw '{"username":"NotMeRandomUsername123"}'

### Impact

By knowing which usernames are valid, attackers can focus their efforts on a smaller set of potential targets, increasing the efficiency and likelihood of successful attacks.