include leading and trailing / in the userId regexp

Signed-off-by: Julien Veyssier <julien-nc@posteo.net>

Author: julien-nc

README.md

@@ -97,17 +97,17 @@ you can configure user_oidc to apply a regular expression to extract the user ID
 
 ```php
 'user_oidc' => [
-  'user_id_regexp' => 'u=([^,]+)'
+  'user_id_regexp' => '/u=([^,]+)/'
 ]
 ```
 
 This regular expression may or may not contain parenthesis. If it does, only the selected block will be extracted.
 Examples:
 
-* `'[a-zA-Z]+'`
+* `'/[a-zA-Z]+/'`
   * `'123-abc-123'` will give `'abc'`
   * `'123-abc-345-def'` will give `'abc'`
-* `'u=([^,]+)'`
+* `'/u=([^,]+)/'`
   * `'u=123'` will give `'123'`
   * `'anything,u=123,anything'` will give `'123'`
   * `'anything,u=123,anything,u=345'` will give `'123'`

lib/Service/SettingsService.php

@@ -46,8 +46,15 @@ public function setAllowMultipleUserBackEnds(bool $value): void {
 
 	public function parseUserId(string $userId): string {
 		$oidcSystemConfig = $this->config->getSystemValue('user_oidc', []);
-		if (isset($oidcSystemConfig['user_id_regexp']) && $oidcSystemConfig['user_id_regexp'] !== '') {
-			if (preg_match('/' . $oidcSystemConfig['user_id_regexp'] . '/', $userId, $matches) === 1) {
+		if (isset($oidcSystemConfig['user_id_regexp']) && is_string($oidcSystemConfig['user_id_regexp']) && $oidcSystemConfig['user_id_regexp'] !== '') {
+			// check that the regexp is valid
+			if (preg_match('/^\/.+\/[a-z]*$/', $oidcSystemConfig['user_id_regexp'], $matches) === 1) {
+				$this->logger->warning(
+					'Incorrect "user_id_regexp", it should start and end with a "/" and have optional trailing modifiers',
+					['regexp' => $oidcSystemConfig['user_id_regexp']],
+				);
+			}
+			if (preg_match($oidcSystemConfig['user_id_regexp'], $userId, $matches) === 1) {
 				return $matches[1] ?? $matches[0];
 			}
 		}