indieauth/index.php

<?php
/* Multi-user IndieAuth endpoint using server envvars from SSO
 * Based on https://github.com/inklings-io/selfauth
 */
require_once 'functions.php';
require_once 'config.php';

$error = null;

// Verification of codes.
$code = filter_input_regexp( INPUT_POST, 'code', '@^[0-9a-f]+:[0-9a-f]{64}:@' );
if ( ! is_null($code) ){
	$redirect_uri = filter_input( INPUT_POST, 'redirect_uri', FILTER_VALIDATE_URL );
	$client_id = filter_input( INPUT_POST, 'client_id', FILTER_VALIDATE_URL );

	if ( ! (
		is_string($code) &&
		is_string($redirect_uri) &&
		is_string($client_id)
	) ) {
		$error = 'Invalid request';
		http_response_code(400);
		include 'form.php';
		die();
	}

	$code_parts = explode(':', $code, 3);
	$suffix_parts = explode(':', base64_url_decode( $code_parts[2] ), 2 );
	$user = $suffix_parts[0];

	if ( ! verify_signed_code( APP_KEY, $user . $redirect_uri . $client_id, $code ) ) {
		$error = 'Invalid code';
		http_response_code(400);
		include 'form.php';
		die();
	}

	$response = array('me' => USER_URLS[$user]);

	$accept_header = $_SERVER['HTTP_ACCEPT'] ?: '*/*';

	if ( '' !== $suffix_parts[1] ) {
		$response['scope'] = $suffix_parts[1];
	}

	$json = get_q_value('application/json', $accept_header);
	$form = get_q_value('application/x-www-form-urlencoded', $accept_header);

	if ( 0 === $json && 0 === $form ){
		$error = 'Client does not accept JSON or Form encoded responses';
		http_response_code(406);
		include 'form.php';
		die();
	} elseif ( $json >= $form ){
		header('Content-Type: application/json');
		exit( json_encode($response) );
	} else {
		header('Content-Type: application/x-www-form-urlencoded');
		exit( http_build_query($response) );
	}
}

// No code submitted,
// Check login
$user = $_SERVER["REMOTE_USER"];
if ( is_null($user) ) {
	$error = 'Not logged in. Login on the <a href="https://auth.cool110.xyz/">SSO portal</a>';
	http_response_code(403);
	include 'form.php';
	die();
} elseif ( ! array_key_exists( $user, USER_URLS ) ){
	$error = 'Account not provisioned';
	http_response_code(403);
	include 'form.php';
	die();
}
// Filter client data
$me = filter_input( INPUT_GET, 'me', FILTER_VALIDATE_URL );
$client_id = filter_input( INPUT_GET, 'client_id', FILTER_VALIDATE_URL );
$redirect_uri = filter_input( INPUT_GET, 'redirect_uri', FILTER_VALIDATE_URL );
$state = filter_input_regexp( INPUT_GET, 'state', '@^[\x20-\x7E]*$@' );
$response_type = filter_input_regexp( INPUT_GET, 'response_type', '@^(id|code)?$@' );
$scope = filter_input_regexp( INPUT_GET, 'scope', '@^([\x21\x23-\x5B\x5D-\x7E]+( [\x21\x23-\x5B\x5D-\x7E]+)*)?$@' );

if ( ! is_string($client_id) ) {
	$error .= 'Invalid Client ID<br />';
}
if ( ! is_string($redirect_uri) ){
	$error .= 'Invalid redirect URI<br />';
}
if ( false === $state ) {
	$error .= 'Invalid state<br />';
}
if ( false === $response_type ) {
	$error .= 'Invalid response type<br />';
}

if ( $error ){
	http_response_code(400);
	include 'form.php';
	die();
}

$csrf_code = filter_input( INPUT_POST, '_csrf', FILTER_UNSAFE_RAW );
// If form submitted
if ( ! is_null($csrf_code) ) {
	if ( !verify_signed_code( APP_KEY, $client_id . $redirect_uri . $state, $csrf_code ) ){
		$error = 'Invalid CSFR code';
		http_response_code(400);
		include 'form.php';
		die();
	}

	$scope = filter_input_regexp( INPUT_POST, 'scopes', '@^[\x21\x23-\x5B\x5D-\x7E]+$@', FILTER_REQUIRE_ARRAY );
	if ( ! is_null($scope) ) {
		if ( false === $scope || in_array( false, $scope, true ) ) {
			$error = 'Provided scopes contain illegal characters';
		}
		$scope = implode( ' ', $scope );
	}

	$suffix = $user . ':' . $scope;
	$code = create_signed_code( APP_KEY, $user . $redirect_uri . $client_id, 5 * 60, $suffix );

	$final_redir = $redirect_uri;
	if ( strpos($redirect_uri, '?') === false ) {
		$final_redir .= '?';
	} else {
		$final_redir .= '&';
	}

	$parameters = array(
		'code' => $code,
		'me' => USER_URLS[$user]
    );
    if ( ! is_null($state) ) {
    	$parameters['state'] = $state;
    }
    $final_redir .= http_build_query($parameters);
    header('Location: ' . $final_redir, true, 302);
} else {
	$csrf_code = create_signed_code(APP_KEY, $client_id . $redirect_uri . $state, 2 * 60);
	include 'form.php';
}