Require a captcha for visitor submissions and for login.

Without the form field, the check was skipped. A solved captcha lasts 30 minutes in the session.
2026-09-25 21:54:14 +02:00
parent 1698680e24
commit 1468cf7138
8 changed files with 97 additions and 25 deletions
@@ -0,0 +1,72 @@
+<?php
+/*
+ * Google reCAPTCHA v2. The keys come from RECAPTCHA_SITE_KEY and
+ * RECAPTCHA_SECRET in .env. When the secret is missing or Google cannot
+ * be reached, every check fails (and the reason is logged), so a broken
+ * configuration never turns the captcha off.
+ */
+require_once(__DIR__ . '/config.lib.php');
+require_once(__DIR__ . '/html.lib.php');
+
+define('CAPTCHA_PASS_SECONDS', 30 * 60);
+
+function captcha_script() {
+  return '<script src="https://www.google.com/recaptcha/api.js" async defer></script>';
+}
+
+function captcha_widget() {
+  return '<div class="g-recaptcha" data-sitekey="'.form_value(config('RECAPTCHA_SITE_KEY')).'"></div>';
+}
+
+// Ask Google whether the captcha in this POST was solved
+function captcha_verify_response() {
+  $response = $_POST['g-recaptcha-response'] ?? '';
+  if (!is_string($response) || $response === '')
+    return FALSE;
+  $secret = (string)config('RECAPTCHA_SECRET');
+  if ($secret === '') {
+    error_log('xxx: RECAPTCHA_SECRET is not set, so every captcha check fails');
+    return FALSE;
+  }
+  $context = stream_context_create(array('http' => array(
+    'method'  => 'POST',
+    'header'  => "Content-Type: application/x-www-form-urlencoded\r\n",
+    'content' => http_build_query(array(
+      'secret'   => $secret,
+      'response' => $response,
+      'remoteip' => $_SERVER['REMOTE_ADDR'] ?? '',
+    )),
+    'timeout' => 10,
+  )));
+  $reply = @file_get_contents('https://www.google.com/recaptcha/api/siteverify', FALSE, $context);
+  if ($reply === FALSE) {
+    error_log('xxx: could not reach the reCAPTCHA server');
+    return FALSE;
+  }
+  $result = json_decode($reply);
+  return is_object($result) && !empty($result->success);
+}
+
+/*
+ * For story submissions: a solved captcha counts for CAPTCHA_PASS_SECONDS
+ * in this session, so the preview and the submit need only one captcha.
+ * captcha_used() ends the pass once a story is saved.
+ */
+function captcha_passed() {
+  return !empty($_SESSION['captcha_ok']) && $_SESSION['captcha_ok'] > time() - CAPTCHA_PASS_SECONDS;
+}
+
+function captcha_check() {
+  if (captcha_passed())
+    return TRUE;
+  if (captcha_verify_response()) {
+    $_SESSION['captcha_ok'] = time();
+    return TRUE;
+  }
+  return FALSE;
+}
+
+function captcha_used() {
+  unset($_SESSION['captcha_ok']);
+}
+?>