FOAF+SSL Login

<?php

function getAuthFromDelegatedFOAFSSL() {
	/*
	* Settings for the IdP. The following two variables may change with
	* another IdP.
	*/
    $sigalg = "rsa-sha1";
    $idp_certificate = "foafssl.org-cert.pem";
    
    $webid = "";
    
	/* Reconstructs the signed message: the URI except the 'sig' parameter */
    $full_uri = ((isset($_SERVER["HTTPS"]) && ($_SERVER["HTTPS"] == "on")) ? "https" : "http")
        . "://" . $_SERVER["HTTP_HOST"]
        . ($_SERVER["SERVER_PORT"] != ((isset($_SERVER["HTTPS"]) && ($_SERVER["HTTPS"] == "on")) ? 443 : 80) ? ":".$_SERVER["SERVER_PORT"] : "")
        . $_SERVER["REQUEST_URI"];
    
    $signed_info = substr($full_uri, 0, -5-strlen(urlencode(isset($_GET["sig"]) ? $_GET["sig"] : NULL)));
    
	/* Extracts the signature */
    $signature = base64_decode(isset($_GET["sig"]) ? $_GET["sig"] : NULL);
    
	/* Only rsa-sha1 is supported at the moment. */
    if ($sigalg == "rsa-sha1") {
		/*
		 * Loads the trusted certificate of the IdP: its public key is used to
		 * verify the integrity of the signed assertion.
		 */
        $fp = fopen($idp_certificate, "r");
        $cert = fread($fp, 8192);
        fclose($fp);
        
        $pubkeyid = openssl_get_publickey($cert);
        
/* Verifies the signature */
        $verified = openssl_verify($signed_info, $signature, $pubkeyid);
        if ($verified == 1) {
        // The verification was successful.
            setAuthenticatedWebID($_GET['webid']);
        }
        elseif ($verified == 0) {
        // The signature didn't match.
            unsetAuthenticatedWebID();
        }
        else {
        // Error during the verification.
            unsetAuthenticatedWebID();
        }
        
        openssl_free_key($pubkeyid);
    } else {
    // Unsupported signature algorithm.
        unsetAuthenticatedWebID();
    }
}

?>