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<?php |
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declare(strict_types=1); |
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namespace SimpleSAML\Module\webauthn\WebAuthn; |
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use CBOR\Decoder; |
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use CBOR\Normalized; |
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use CBOR\OtherObject; |
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use CBOR\StringStream; |
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use CBOR\Tag; |
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use SimpleSAML\Utils\HTTP as HTTPHelper; |
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/** |
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* FIDO2/WebAuthn Authentication Processing filter |
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* |
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* Filter for registering or authenticating with a FIDO2/WebAuthn token after |
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* having authenticated with the primary authsource. |
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* |
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* @author Stefan Winter <[email protected]> |
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* @package SimpleSAMLphp |
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*/ |
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abstract class WebAuthnAbstractEvent |
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{ |
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public const PRESENCE_LEVEL_PRESENT = 1; |
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public const PRESENCE_LEVEL_VERIFIED = 4; |
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public const PRESENCE_LEVEL_NONE = 0; |
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/** |
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* The SHA256 hash of the clientDataJSON |
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* |
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* @var string |
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*/ |
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protected string $clientDataHash; |
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/** |
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* the authenticator's signature counter |
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* |
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* @var int |
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*/ |
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protected int $counter; |
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/** |
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* the authenticator's signature algorithm |
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* |
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* @var int |
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*/ |
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protected int $algo; |
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/** |
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* UV or UP bit? |
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*/ |
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protected int $presenceLevel; |
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/** |
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* A string buffer to hold debug information in case we need it. |
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* |
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* @var string |
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*/ |
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protected string $debugBuffer = ''; |
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/** |
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* A string buffer to hold raw validation data in case we want to look at it. |
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* |
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* @var string |
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*/ |
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protected string $validateBuffer = ''; |
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/** |
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* the type of event requested. This is to be set in child class constructors |
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* before calling the parent's. |
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* |
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* @var string |
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*/ |
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protected string $eventType; |
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/** |
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* The rpIdHash, available once validated during constructor of base class |
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*/ |
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protected string $rpIdHash; |
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/** |
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* the credential ID for this event (either the one that gets registered, or |
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* the one that gets used to authenticate) |
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* |
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* To be set by the constructors of the child classes. |
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* |
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* @var string |
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*/ |
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protected string $credentialId; |
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/** |
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* the credential binary data for this event (either the one that gets |
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* registered, or the one that gets used to authenticate) |
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* |
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* To be set by the constructors of the child classes. |
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* |
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* @var string |
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*/ |
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protected string $credential; |
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/** |
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* Initialize the event object. |
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* |
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* Validates and parses the configuration. |
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* |
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* @param string $pubkeyCredType PublicKeyCredential.type |
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* @param string $scope the scope of the event |
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* @param string $challenge the challenge which was used to trigger this event |
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* @param string $authData the authData / authenticatorData structure which is present in all types of events |
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* @param string $clientDataJSON the client data JSON string which is present in all types of events |
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* @param bool $debugMode shall we collect and output some extensive debugging information along the way? |
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*/ |
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public function __construct( |
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string $pubkeyCredType, |
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protected string $scope, |
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protected string $challenge, |
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string $authData, |
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string $clientDataJSON, |
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protected bool $debugMode = false, |
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) { |
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$this->presenceLevel = self::PRESENCE_LEVEL_NONE; |
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$this->debugBuffer .= "PublicKeyCredential.type: $pubkeyCredType<br/>"; |
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/** |
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* This is not a required validation as per spec. Still odd that Firefox returns |
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* "undefined" even though its own API spec says it will send "public-key". |
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*/ |
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switch ($pubkeyCredType) { |
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case "public-key": |
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$this->pass("Key Type OK"); |
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break; |
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case "undefined": |
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$this->warn("Key Type 'undefined' - Firefox or Yubikey issue?"); |
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break; |
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default: |
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$this->fail("Unknown Key Type: " . $_POST['type']); |
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break; |
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} |
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/** |
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* eventType is already set by child constructor, otherwise the function |
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* will fail because of the missing type) |
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*/ |
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$this->clientDataHash = $this->verifyClientDataJSON($clientDataJSON); |
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$this->counter = $this->validateAuthData($authData); |
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} |
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/** |
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* @return int |
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*/ |
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public function getCounter(): int |
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{ |
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return $this->counter; |
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} |
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/** |
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* @return string |
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*/ |
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public function getCredential(): string |
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{ |
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return $this->credential; |
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} |
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/** |
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* @return int |
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*/ |
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public function getAlgo(): int |
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{ |
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return $this->algo; |
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} |
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/** |
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* @return int |
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*/ |
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public function getPresenceLevel(): int |
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{ |
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return $this->presenceLevel; |
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} |
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/** |
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* @return string |
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*/ |
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public function getCredentialId(): string |
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{ |
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return $this->credentialId; |
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} |
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/** |
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* @return string |
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*/ |
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public function getDebugBuffer(): string |
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{ |
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return $this->debugBuffer; |
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} |
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/** |
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* @return string |
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*/ |
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public function getValidateBuffer(): string |
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{ |
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return $this->validateBuffer; |
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} |
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/** |
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* The base64url decode function differs slightly from base64. Thanks. |
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* |
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* taken from https://gist.github.com/nathggns/6652997 |
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* |
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* @param string $data the base64url-encoded source string |
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* @return string the decoded string |
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*/ |
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public static function base64urlDecode(string $data): string |
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{ |
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return base64_decode(strtr($data, '-_', '+/')); |
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} |
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/** |
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* this function validates the content of clientDataJSON. |
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* I.e. it performs |
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* - for a REGistration session |
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* - the validation steps 2 through 8 of the validation |
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* - the parts of step 14 that relate to clientDataJSON |
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* - for a AUTHentication session |
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* - the validation steps 6 through 11 of the validation |
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* - the parts of step 15 that relate to clientDataJSON |
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* |
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* @param string $clientDataJSON the incoming data |
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* |
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* @return string |
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*/ |
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private function verifyClientDataJSON(string $clientDataJSON): string |
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{ |
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/** |
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* §7.1 STEP 2 + 3 : convert to JSON and dissect JSON into PHP associative array |
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* §7.2 STEP 6 + 7 : convert to JSON and dissect JSON into PHP associative array |
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*/ |
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$this->debugBuffer .= "ClientDataJSON hash: " . hash("sha256", $clientDataJSON) . "<br/>"; |
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$clientData = json_decode($clientDataJSON, true); |
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$this->debugBuffer .= "<pre>" . /** @scrutinizer ignore-type */ print_r($clientData, true) . "</pre>"; |
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switch ($this->eventType) { |
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case "REG": |
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if ($clientData['type'] == "webauthn.create") { |
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/** |
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* §7.1 STEP 4 wheck for webauthn.create |
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*/ |
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$this->pass("Registration requested; type has expected value"); |
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} else { |
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$this->fail("REG requested, but did not receive webauthn.create."); |
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} |
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break; |
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case "AUTH": |
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if ($clientData['type'] == "webauthn.get") { |
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/** |
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* §7.2 STEP 8: check for webauthn.get |
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*/ |
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$this->pass("Authentication requested; type has expected value"); |
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} else { |
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$this->fail("AUTH requested, but did not receive webauthn.get."); |
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} |
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break; |
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default: |
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$this->fail("Unexpected operation " . $this->eventType); |
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break; |
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} |
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/** |
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* §7.1 STEP 5 : check if incoming challenge matches issued challenge |
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* §7.2 STEP 9 : check if incoming challenge matches issued challenge |
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*/ |
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if ($this->challenge == bin2hex(WebAuthnAbstractEvent::base64urlDecode($clientData['challenge']))) { |
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$this->pass("Challenge matches"); |
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} else { |
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$this->fail("Challenge does not match"); |
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} |
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/** |
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* §7.1 STEP 6 : check if incoming origin matches our hostname (taken from IdP metadata prefix) |
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* §7.2 STEP 10: check if incoming origin matches our hostname (taken from IdP metadata prefix) |
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*/ |
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$httpHeler = new HTTPHelper(); |
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$slash = strpos($httpHeler->getBaseURL(), '/', 8); |
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$expectedOrigin = ($slash !== false) ? substr($httpHeler->getBaseURL(), 0, $slash) : $slash; |
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if ($clientData['origin'] === $expectedOrigin) { |
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$this->pass("Origin matches"); |
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} else { |
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$this->fail("Origin does not match: " . $expectedOrigin); |
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} |
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/** |
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* §7.1 STEP 7 : optional tokenBinding check. The Yubikey does not make use of that option. |
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* §7.2 STEP 11: optional tokenBinding check. The Yubikey does not make use of that option. |
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*/ |
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if (!isset($clientData['tokenBinding'])) { |
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$this->pass("No optional token binding data to validate."); |
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} else { |
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$this->warn("Validation of the present token binding data not implemented, continuing without!"); |
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} |
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/** |
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* §7.1 STEP 8 : SHA-256 hashing the clientData |
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* §7.2 STEP 16: SHA-256 hashing the clientData |
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*/ |
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return hash("sha256", $clientDataJSON, true); |
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} |
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/** |
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* This function performs the required checks on the authData (REG) or authenticatorData (AUTH) structure |
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* |
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* I.e. it performs |
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* - for a REGistration session |
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* - the validation steps 10-12 of the validation |
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* - the parts of step 14 that relate to authData |
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* - for a AUTHentication session |
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* - the validation steps 12-14 of the validation |
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* - the parts of step 15 that relate to authData |
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* |
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* @param string $authData the authData / authenticatorData binary blob |
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* |
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* @return int the current counter value of the authenticator |
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*/ |
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private function validateAuthData(string $authData): int |
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{ |
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$this->debugBuffer .= "AuthData: <pre>"; |
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$this->debugBuffer .= print_r($authData, true); |
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$this->debugBuffer .= "</pre>"; |
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328
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/** |
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* §7.1 STEP 10: compare incoming RpId hash with expected value |
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* §7.2 STEP 12: compare incoming RpId hash with expected value |
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*/ |
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if (bin2hex(substr($authData, 0, 32)) == hash("sha256", $this->scope)) { |
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$this->pass("Relying Party hash correct."); |
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$this->rpIdHash = hash("sha256", $this->scope); |
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} else { |
336
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$this->fail("Mismatching Relying Party hash."); |
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} |
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$bitfield = substr($authData, 32, 1); |
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340
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/** |
341
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* §7.1 STEP 14 (authData part): no extensions were requested, so none are allowed to be present |
342
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* §7.2 STEP 15 (authData part): no extensions were requested, so none are allowed to be present |
343
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*/ |
344
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if ((128 & ord($bitfield)) > 0) { |
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// so we get Extensions. We typically ignore all, but the |
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// "credProtect" one may be interesting in the future. |
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$this->pass("ED: Extension Data included. Interesting bits may be extracted later."); |
348
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} else { |
349
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$this->pass("ED: Extension Data not present."); |
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} |
351
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352
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switch ($this->eventType) { |
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case "REG": |
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if ((64 & ord($bitfield)) > 0) { |
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$this->pass("AT: Attested Credential Data Included."); |
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} else { |
357
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$this->fail("AT: not present, but required during registration."); |
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} |
359
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// REG events parse their registration-related Extensions, if |
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// any, in the WebAuthnRegistrationEvent subclass |
361
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break; |
362
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case "AUTH": |
363
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if ((64 & ord($bitfield)) > 0) { |
364
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$this->fail("AT: Attested Credential Data Included."); |
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} else { |
366
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$this->pass("AT: not present, like it should be during an authentication."); |
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} |
368
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// AUTH events can also have extensions. Extensions, if any, |
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// would follow after the counter. We allow them to be present |
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// but don't currently do anything with them, so let's |
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// just make a useless extraction here as a reminder. |
372
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$extensionBytes = substr($authData, 37); |
373
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if (strlen($extensionBytes) > 0) { |
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// assign into variable and process if needed |
375
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|
|
$this->cborDecode($extensionBytes); |
376
|
|
|
} |
377
|
|
|
break; |
378
|
|
|
default: |
379
|
|
|
$this->fail("unknown type of operation!"); |
380
|
|
|
break; |
381
|
|
|
} |
382
|
|
|
|
383
|
|
|
/** |
384
|
|
|
* §7.1 STEP 11 + 12 : check user presence (this implementation does not insist on verification currently) |
385
|
|
|
* §7.2 STEP 13 + 14 : check user presence (this implementation does not insist on verification currently) |
386
|
|
|
*/ |
387
|
|
|
if ((4 & ord($bitfield)) > 0) { |
388
|
|
|
$this->presenceLevel = self::PRESENCE_LEVEL_VERIFIED; |
389
|
|
|
$this->pass("UV indicated: User is personally identified by the token."); |
390
|
|
|
} elseif ((1 & ord($bitfield)) > 0) { |
391
|
|
|
$this->presenceLevel = self::PRESENCE_LEVEL_PRESENT; |
392
|
|
|
$this->pass("UP indicated: someone is present and triggered the token."); |
393
|
|
|
} else { |
394
|
|
|
$this->fail("Neither UV nor UP asserted: user is possibly not present at computer."); |
395
|
|
|
} |
396
|
|
|
$counterBin = substr($authData, 33, 4); |
397
|
|
|
|
398
|
|
|
$counterDec = intval(bin2hex($counterBin), 16); |
399
|
|
|
$this->debugBuffer .= "Signature Counter: $counterDec<br/>"; |
400
|
|
|
return $counterDec; |
401
|
|
|
} |
402
|
|
|
|
403
|
|
|
/** |
404
|
|
|
* this function takes a binary CBOR blob and decodes it into an associative PHP array. |
405
|
|
|
* |
406
|
|
|
* @param string $rawData the binary CBOR blob |
407
|
|
|
* @return array the decoded CBOR data |
408
|
|
|
*/ |
409
|
|
|
protected function cborDecode(string $rawData): array |
410
|
|
|
{ |
411
|
|
|
$otherObjectManager = new OtherObject\OtherObjectManager(); |
412
|
|
|
$otherObjectManager->add(OtherObject\SimpleObject::class); |
413
|
|
|
$otherObjectManager->add(OtherObject\FalseObject::class); |
414
|
|
|
$otherObjectManager->add(OtherObject\TrueObject::class); |
415
|
|
|
$otherObjectManager->add(OtherObject\NullObject::class); |
416
|
|
|
$otherObjectManager->add(OtherObject\UndefinedObject::class); |
417
|
|
|
$otherObjectManager->add(OtherObject\HalfPrecisionFloatObject::class); |
418
|
|
|
$otherObjectManager->add(OtherObject\SinglePrecisionFloatObject::class); |
419
|
|
|
$otherObjectManager->add(OtherObject\DoublePrecisionFloatObject::class); |
420
|
|
|
|
421
|
|
|
$tagManager = new Tag\TagManager(); |
422
|
|
|
$tagManager->add(Tag\DatetimeTag::class); |
423
|
|
|
$tagManager->add(Tag\TimestampTag::class); |
424
|
|
|
$tagManager->add(Tag\UnsignedBigIntegerTag::class); |
425
|
|
|
$tagManager->add(Tag\NegativeBigIntegerTag::class); |
426
|
|
|
$tagManager->add(Tag\DecimalFractionTag::class); |
427
|
|
|
$tagManager->add(Tag\BigFloatTag::class); |
428
|
|
|
$tagManager->add(Tag\Base64UrlEncodingTag::class); |
429
|
|
|
$tagManager->add(Tag\Base64EncodingTag::class); |
430
|
|
|
$tagManager->add(Tag\Base16EncodingTag::class); |
431
|
|
|
|
432
|
|
|
$decoder = new Decoder($tagManager, $otherObjectManager); |
433
|
|
|
$stream = new StringStream($rawData); |
434
|
|
|
|
435
|
|
|
$finalData = $decoder->decode($stream); |
436
|
|
|
if ($finalData implements Normalized) { |
|
|
|
|
437
|
|
|
$finalData = $finalData->normalize(); |
438
|
|
|
} |
439
|
|
|
|
440
|
|
|
if ($finalData === null) { |
441
|
|
|
$this->fail("CBOR data decoding failed."); |
442
|
|
|
} |
443
|
|
|
return $finalData; |
444
|
|
|
} |
445
|
|
|
|
446
|
|
|
/** |
447
|
|
|
* @param string $text |
448
|
|
|
* @return void |
449
|
|
|
*/ |
450
|
|
|
protected function warn(string $text): void |
451
|
|
|
{ |
452
|
|
|
$this->validateBuffer .= "<span style='background-color:yellow;'>WARN: $text</span><br/>"; |
453
|
|
|
} |
454
|
|
|
|
455
|
|
|
/** |
456
|
|
|
* @param string $text |
457
|
|
|
* @throws \Exception |
458
|
|
|
* @return void |
459
|
|
|
*/ |
460
|
|
|
protected function fail(string $text): void |
461
|
|
|
{ |
462
|
|
|
$this->validateBuffer .= "<span style='background-color:red;'>FAIL: $text</span><br/>"; |
463
|
|
|
if ($this->debugMode === true) { |
464
|
|
|
echo $this->debugBuffer; |
465
|
|
|
echo $this->validateBuffer; |
466
|
|
|
} |
467
|
|
|
throw new \Exception($text); |
468
|
|
|
} |
469
|
|
|
|
470
|
|
|
/** |
471
|
|
|
* @param string $text |
472
|
|
|
* @return void |
473
|
|
|
*/ |
474
|
|
|
protected function pass(string $text): void |
475
|
|
|
{ |
476
|
|
|
$this->validateBuffer .= "<span style='background-color:green; color:white;'>PASS: $text</span><br/>"; |
477
|
|
|
} |
478
|
|
|
|
479
|
|
|
/** |
480
|
|
|
* @param string $text |
481
|
|
|
* @return void |
482
|
|
|
*/ |
483
|
|
|
protected function ignore(string $text): void |
484
|
|
|
{ |
485
|
|
|
$this->validateBuffer .= "<span style='background-color:blue; color:white;'>IGNORE: $text</span><br/>"; |
486
|
|
|
} |
487
|
|
|
} |
488
|
|
|
|