I’m debugging a PHP script for the authentication of users, the users are authenticated via Firebase on the frontend, and each call to the backend contains this in the header;

Authorization: "Bearer eyJhbGciOiJSUzI1NiIsImtpZCI6IjU2OTFhMTk1Y..."

Here is my PHP code in the backend

    public static function checkLogin(){
        $headers = apache_request_headers();
        //var_dump($headers);

        // Get the public key
        $publicKey = file_get_contents('https://www.googleapis.com/robot/v1/metadata/x509/[email protected]');
        $publicKey = json_decode($publicKey, true);
        $k = array();
        foreach ($publicKey as $key => $value) {
            $k[] = $key;
        }
    
        // Get the bearer key from the header 
        if (isset($headers['Authorization']) ){
            $jwt = explode(' ', $headers['Authorization'])[1];
        } else if (isset($headers['authorization'])) {
            $jwt = explode(' ', $headers['authorization'])[1];
        }

        JWT::$leeway = 60;
        // HERE IS THE CRASH
        $decoded = JWT::decode($jwt, new Key($k[0], 'HS256'));

        
        
        $decoded_array = (array) $decoded;
        Utilities::debug($decoded_array);
        if ($decoded_array['exp'] > time() ) {
            return $decoded_array['exp'];
        }else {
            die(json_encode(array("error" => true, "status" => 401, "message" => "ACCESS DENIED.")));
        }

        
    }

I get this error, Fatal error: Uncaught UnexpectedValueException: Incorrect key for this algorithm in C:sourcesvendorfirebasephp-jwtsrcJWT.php on line <i>143</i>

I don’t see any ref of an algorithm in the frontend

Anyone have an idea of what’s wrong?

Ed