Improved Tinyboard anti-bot/spam filter. See large comment in inc/config.php for details.

inc/anti-bot.php

@@ -12,8 +12,7 @@ if(realpath($_SERVER['SCRIPT_FILENAME']) == str_replace('\\', '/', __FILE__)) {
 $hidden_inputs_twig = array();
 
 class AntiBot {
-	public $inputs = array(), $index = 0;
+	public $salt, $inputs = array(), $index = 0;
-	private $salt;
 	
 	public static function randomString($length, $uppercase = false, $special_chars = false) {
 		$chars = 'abcdefghijklmnopqrstuvwxyz0123456789';
@@ -90,12 +89,14 @@ class AntiBot {
 				$this->inputs[$name] = (string)rand(0, 100);
 			} else {
 				// Obscure value
-				$this->inputs[$name] = $this->randomString(rand(5, 100));
+				$this->inputs[$name] = $this->randomString(rand(5, 100), true, true);
 			}
 		}
 	}
 	
 	public function html($count = false) {
+		global $config;
+		
 		$elements = array(
 			'<input type="hidden" name="%name%" value="%value%">',
 			'<input type="hidden" value="%value%" name="%name%">',
@@ -110,7 +111,11 @@ class AntiBot {
 		
 		$html = '';
 		
-		if($count == 0) {
+		if($count === false) {
+			$count = rand(1, count($this->inputs) / 15);
+		}
+		
+		if($count === true) {
 			// all elements
 			$inputs = array_slice($this->inputs, $this->index);
 		} else {
@@ -134,7 +139,10 @@ class AntiBot {
 				$value = $this->make_confusing($value);
 			else
 				$value = utf8tohtml($value);
-				
+			
+			if(strpos($element, 'textarea') === false)
+				$value = str_replace('"', '&quot;', $value);
+			
 			$element = str_replace('%value%', $value, $element);
 			
 			$html .= $element;
@@ -162,36 +170,42 @@ class AntiBot {
 		// Use SHA1 for the hash
 		return sha1($hash . $this->salt);
 	}
-};;
-
-
-function hiddenInputs(array $salt, $print_the_rest = false) {
-	global $hidden_inputs_twig;
-	
-	$salt_str = implode(':', $salt);
-	
-	if(!isset($hidden_inputs_twig[$salt_str]))
-		$hidden_inputs_twig[$salt_str] = new AntiBot($salt);
-	
-	if($print_the_rest)
-		return $hidden_inputs_twig[$salt_str]->html(0);
-	else
-		return $hidden_inputs_twig[$salt_str]->html(rand(1, 5));
 }
 
-function hiddenInputsHash(array $salt) {
+function _create_antibot($board, $thread) {
-	global $hidden_inputs_twig;
+	global $config;
 	
-	$salt_str = implode(':', $salt);
+	$antibot = new AntiBot(array($board, $thread));
 	
-	if(!isset($hidden_inputs_twig[$salt_str]))
+	query('DELETE FROM `antispam` WHERE `expires` < UNIX_TIMESTAMP()') or error(db_error($query));
-		$hidden_inputs_twig[$salt_str] = new AntiBot($salt);
 	
-	return $hidden_inputs_twig[$salt_str]->hash();
+	if($thread)
+		$query = prepare('UPDATE `antispam` SET `expires` = UNIX_TIMESTAMP() + :expires WHERE `board` = :board AND `thread` = :thread');
+	else
+		$query = prepare('UPDATE `antispam` SET `expires` = UNIX_TIMESTAMP() + :expires WHERE `board` = :board AND `thread` IS NULL');
+	
+	$query->bindValue(':board', $board);
+	if($thread)
+		$query->bindValue(':thread', $thread);
+	$query->bindValue(':expires', $config['spam']['hidden_inputs_expire']);
+	$query->execute() or error(db_error($query));
+	
+	$query = prepare('INSERT INTO `antispam` VALUES (:board, :thread, CRC32(:hash), UNIX_TIMESTAMP(), NULL, 0)');
+	$query->bindValue(':board', $board);
+	$query->bindValue(':thread', $thread);
+	$query->bindValue(':hash', $antibot->hash());
+	$query->execute() or error(db_error($query));
+	
+	if($query->rowCount() == 0) {
+		// there was no database entry for this hash. most likely expired.
+		return true;
+	}
+	
+	return $antibot;
 }
 
 function checkSpam(array $extra_salt = array()) {
-	global $config;
+	global $config, $pdo;
 	
 	if(!isset($_POST['hash']))
 		return true;
@@ -231,6 +245,25 @@ function checkSpam(array $extra_salt = array()) {
 	// Use SHA1 for the hash
 	$_hash = sha1($_hash . $extra_salt);
 	
-	return $hash != $_hash;
+	if($hash != $_hash)
+		return true;
+	
+	$query = prepare('UPDATE `antispam` SET `passed` = `passed` + 1 WHERE `hash` = CRC32(:hash)');
+	$query->bindValue(':hash', $hash);
+	$query->execute() or error(db_error($query));
+	if($query->rowCount() == 0) {
+		// there was no database entry for this hash. most likely expired.
+		return true;
+	}
+	
+	$query = prepare('SELECT `passed` FROM `antispam` WHERE `hash` = CRC32(:hash)');
+	$query->bindValue(':hash', $hash);
+	$query->execute() or error(db_error($query));
+	$passed = $query->fetchColumn(0);
+	
+	if($passed > $config['spam']['hidden_inputs_max_pass'])
+		return true;
+	
+	return false;
 }
 

inc/config.php

@@ -170,9 +170,33 @@
 	// Skip checking certain IP addresses against blacklists (for troubleshooting or whatever)
 	$config['dnsbl_exceptions'][] = '127.0.0.1';
 	
-	// Spam filter
+	/*
+	 * Introduction to Tinyboard's spam filter:
+	 *
+	 * In simple terms, whenever a posting form on a page is generated (which happens whenever a
+	 * post is made), Tinyboard will add a random amount of hidden, obscure fields to it to
+	 * confuse bots and upset hackers. These fields and their respective obscure values are
+	 * validated upon posting with a 160-bit "hash". That hash can only be used as many times
+	 * as you specify; otherwise, flooding bots could just keep reusing the same hash.
+	 * Once a new set of inputs (and the hash) are generated, old hashes for the same thread
+	 * and board are set to expire. Because you have to reload the page to get the new set
+	 * of inputs and hash, if they expire too quickly and more than one person is viewing the
+	 * page at a given time, Tinyboard would return false positives (depending on how long the
+	 * user sits on the page before posting). If your imageboard is quite fast/popular, set
+	 * $config['spam']['hidden_inputs_max_pass'] and $config['spam']['hidden_inputs_expire'] to
+	 * something higher to avoid false positives.
+	 *
+	 * See also: http://tinyboard.org/docs/?p=Your_request_looks_automated
+	 *
+	 */
+	
+	// Number of hidden fields to generate
 	$config['spam']['hidden_inputs_min'] = 4;
 	$config['spam']['hidden_inputs_max'] = 12;
+	// How many times can a "hash" be used to post?
+	$config['spam']['hidden_inputs_max_pass'] = 30;
+	// How soon after regeneration do hashes expire (in seconds)?
+	$config['spam']['hidden_inputs_expire'] = 60 * 60 * 2; // two hours
 	// These are fields used to confuse the bots. Make sure they aren't actually used by Tinyboard, or it won't work.
 	$config['spam']['hidden_input_names'] = array(
 		'user',

inc/functions.php

@@ -13,7 +13,6 @@ require_once 'inc/display.php';
 require_once 'inc/template.php';
 require_once 'inc/database.php';
 require_once 'inc/events.php';
-require_once 'inc/anti-bot.php';
 require_once 'inc/lib/gettext/gettext.inc';
 
 // the user is not currently logged in as a moderator
@@ -210,6 +209,11 @@ function _syslog($priority, $message) {
 	}
 }
 
+function create_antibot($board, $thread = null) {
+	require_once 'inc/anti-bot.php';
+	
+	return _create_antibot($board, $thread);
+}
 
 function rebuildThemes($action) {
 	// List themes
@@ -1175,6 +1179,7 @@ function buildIndex() {
 		$content['pages'] = $pages;
 		$content['pages'][$page-1]['selected'] = true;
 		$content['btn'] = getPageButtons($content['pages']);
+		$content['antibot'] = create_antibot($board['uri']);
 		file_write($filename, Element('index.html', $content));
 		
 		if(isset($md5) && $md5 == md5_file($filename)) {
@@ -1492,6 +1497,7 @@ function buildThread($id, $return=false, $mod=false) {
 		'config' => $config,
 		'id' => $id,
 		'mod' => $mod,
+		'antibot' => $mod ? false : create_antibot($board['uri'], $id),
 		'boardlist' => createBoardlist($mod),
 		'return' => ($mod ? '?' . $board['url'] . $config['file_index'] : $config['root'] . $board['uri'] . '/' . $config['file_index'])
 	));

inc/template.php

@@ -24,7 +24,7 @@ function load_twig() {
 	
 	$loader = new Twig_Loader_Filesystem($config['dir']['template']);
 	$loader->setPaths($config['dir']['template']);
-	$twig = new Twig_Environment($loader, Array(
+	$twig = new Twig_Environment($loader, array(
 		'autoescape' => false,
 		'cache' => "{$config['dir']['template']}/cache",
 		'debug' => ($config['debug'] ? true : false),

install.php

@@ -1,7 +1,7 @@
 <?php
 
 // Installation/upgrade file	
-define('VERSION', 'v0.9.6-dev-1');
+define('VERSION', 'v0.9.6-dev-2');
 
 require 'inc/functions.php';
 
@@ -174,6 +174,17 @@ if(file_exists($config['has_installed'])) {
 				CHANGE  `uri`  `uri` VARCHAR( 50 ) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
 				CHANGE  `title`  `title` TINYTEXT CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
 				CHANGE  `subtitle`  `subtitle` TINYTEXT CHARACTER SET utf8 COLLATE utf8_general_ci NULL") or error(db_error());
+		case 'v0.9.6-dev-1':
+			query("CREATE TABLE IF NOT EXISTS `antispam` (
+				  `board` varchar(255) NOT NULL,
+				  `thread` int(11) DEFAULT NULL,
+				  `hash` bigint(20) NOT NULL,
+				  `created` int(11) NOT NULL,
+				  `expires` int(11) DEFAULT NULL,
+				  `passed` smallint(6) NOT NULL,
+				  PRIMARY KEY (`hash`),
+				  KEY `board` (`board`,`thread`)
+				) ENGINE=MyISAM DEFAULT CHARSET=utf8;");
 		case false:
 			// Update version number
 			file_write($config['has_installed'], VERSION);

install.sql

@@ -228,6 +228,23 @@ CREATE TABLE IF NOT EXISTS `cites` (
   KEY `post` (`board`,`post`)
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8;
 
+-- --------------------------------------------------------
+
+--
+-- Table structure for table `antispam`
+--
+
+CREATE TABLE IF NOT EXISTS `antispam` (
+  `board` varchar(255) NOT NULL,
+  `thread` int(11) DEFAULT NULL,
+  `hash` bigint(20) NOT NULL,
+  `created` int(11) NOT NULL,
+  `expires` int(11) DEFAULT NULL,
+  `passed` smallint(6) NOT NULL,
+  PRIMARY KEY (`hash`),
+  KEY `board` (`board`,`thread`)
+) ENGINE=MyISAM DEFAULT CHARSET=utf8;
+
 
 /*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
 /*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;

mod.php

@@ -9,7 +9,7 @@ require 'inc/mod.php';
 
 if (get_magic_quotes_gpc()) {
 	function strip_array($var) {
-		return is_array($var) ? array_map("strip_array", $var) : stripslashes($var);
+		return is_array($var) ? array_map('strip_array', $var) : stripslashes($var);
 	}
 	
 	$_GET = strip_array($_GET);
@@ -1698,6 +1698,10 @@ if(!$mod) {
 			$query->bindValue(':board', $board['uri']);
 			$query->execute() or error(db_error($query));
 			
+			$query = prepare("DELETE FROM `antispam` WHERE `board` = :board");
+			$query->bindValue(':board', $board['uri']);
+			$query->execute() or error(db_error($query));
+			
 			$_board = $board;
 			
 			rebuildThemes('boards');
@@ -2209,7 +2213,6 @@ if(!$mod) {
 		$page['pages'][$page_no-1]['selected'] = true;
 		$page['btn'] = getPageButtons($page['pages'], true);
 		$page['mod'] = true;
-		
 		echo Element('index.html', $page);
 	} elseif(preg_match('/^\/' . $regex['board'] . $regex['res'] . $regex['page'] . '$/', $query, $matches)) {
 		// View thread
@@ -2354,7 +2357,8 @@ if(!$mod) {
 		if(!openBoard($boardName))
 			error($config['error']['noboard']);
 		
-		if(!hasPermission($config['mod']['delete'], $boardName)) error($config['error']['noaccess']);
+		if(!hasPermission($config['mod']['delete'], $boardName))
+			error($config['error']['noaccess']);
 		
 		$post = &$matches[2];
 		

post.php

@@ -5,11 +5,12 @@
  */
 
 require 'inc/functions.php';
+require 'inc/anti-bot.php';
 
 // Fix for magic quotes
 if (get_magic_quotes_gpc()) {
 	function strip_array($var) {
-		return is_array($var) ? array_map("strip_array", $var) : stripslashes($var);
+		return is_array($var) ? array_map('strip_array', $var) : stripslashes($var);
 	}
 	
 	$_GET = strip_array($_GET);
@@ -192,7 +193,26 @@ if(isset($_POST['delete'])) {
 		}
 	}
 	
-	if(checkSpam(array($board['uri'], isset($post['thread']) && !($config['quick_reply'] && isset($_POST['quick-reply'])) ? $post['thread'] : null)))
+	if($post['mod'] = isset($_POST['mod']) && $_POST['mod']) {
+		require 'inc/mod.php';
+		if(!$mod) {
+			// Liar. You're not a mod.
+			error($config['error']['notamod']);
+		}
+		
+		$post['sticky'] = $post['op'] && isset($_POST['sticky']);
+		$post['locked'] = $post['op'] && isset($_POST['lock']);
+		$post['raw'] = isset($_POST['raw']);
+		
+		if($post['sticky'] && !hasPermission($config['mod']['sticky'], $board['uri']))
+			error($config['error']['noaccess']);
+		if($post['locked'] && !hasPermission($config['mod']['lock'], $board['uri']))
+			error($config['error']['noaccess']);
+		if($post['raw'] && !hasPermission($config['mod']['rawhtml'], $board['uri']))
+			error($config['error']['noaccess']);
+	}
+	
+	if(!$post['mod'] && checkSpam(array($board['uri'], isset($post['thread']) && !($config['quick_reply'] && isset($_POST['quick-reply'])) ? $post['thread'] : null)))
 		error($config['error']['spam']);
 	
 	if($config['robot_enable'] && $config['robot_mute']) {
@@ -239,25 +259,6 @@ if(isset($_POST['delete'])) {
 		}
 	}
 	
-	if($post['mod'] = isset($_POST['mod']) && $_POST['mod']) {
-		require 'inc/mod.php';
-		if(!$mod) {
-			// Liar. You're not a mod.
-			error($config['error']['notamod']);
-		}
-		
-		$post['sticky'] = $post['op'] && isset($_POST['sticky']);
-		$post['locked'] = $post['op'] && isset($_POST['lock']);
-		$post['raw'] = isset($_POST['raw']);
-		
-		if($post['sticky'] && !hasPermission($config['mod']['sticky'], $board['uri']))
-			error($config['error']['noaccess']);
-		if($post['locked'] && !hasPermission($config['mod']['lock'], $board['uri']))
-			error($config['error']['noaccess']);
-		if($post['raw'] && !hasPermission($config['mod']['rawhtml'], $board['uri']))
-			error($config['error']['noaccess']);
-	}
-	
 	if(!hasPermission($config['mod']['bypass_field_disable'], $board['uri'])) {
 		if($config['field_disable_name'])
 			$_POST['name'] = $config['anonymous']; // "forced anonymous"

templates/post_form.html

@@ -1,35 +1,35 @@
 <form name="post" onsubmit="return dopost(this);" enctype="multipart/form-data" action="{{ config.post_url }}" method="post">
-{{ hiddenInputs([board.uri, id]) }}
+{{ antibot.html() }}
 {% if id %}<input type="hidden" name="thread" value="{{ id }}">{% endif %}
-{{ hiddenInputs([board.uri, id]) }}
+{{ antibot.html() }}
 <input type="hidden" name="board" value="{{ board.uri }}">
-{{ hiddenInputs([board.uri, id]) }}
+{{ antibot.html() }}
 {% if mod %}<input type="hidden" name="mod" value="1">{% endif %}
 	<table>
 		{% if not config.field_disable_name or (mod and post.mod|hasPermission(config.mod.bypass_field_disable, board.uri)) %}<tr>
 			<th>
 				{% trans %}Name{% endtrans %}
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</th>
 			<td>
 				<input type="text" name="name" size="25" maxlength="50" autocomplete="off">
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</td>
 		</tr>{% endif %}
 		{% if not config.field_disable_email or (mod and post.mod|hasPermission(config.mod.bypass_field_disable, board.uri)) %}<tr>
 			<th>
 				{% trans %}Email{% endtrans %}
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</th>
 			<td>
 				<input type="text" name="email" size="25" maxlength="40" autocomplete="off">
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</td>
 		</tr>{% endif %}
 		<tr>
 			<th>
 				{% trans %}Subject{% endtrans %}
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</th>
 			<td>
 				<input style="float:left;" type="text" name="subject" size="25" maxlength="100" autocomplete="off">
@@ -39,22 +39,22 @@
 		<tr>
 			<th>
 				{% trans %}Comment{% endtrans %}
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</th>
 			<td>
 				<textarea name="body" id="body" rows="5" cols="35"></textarea>
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</td>
 		</tr>
 		{% if config.recaptcha %}
 		<tr>
 			<th>
 				{% trans %}Verification{% endtrans %}
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</th>
 			<td>
 				<script type="text/javascript" src="http://www.google.com/recaptcha/api/challenge?k={{ config.recaptcha_public }}"></script>
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</td>
 		</tr>
 		{% endif %}
@@ -64,18 +64,18 @@
 			</th>
 			<td>
 				<input type="file" name="file">
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</td>
 		</tr>
 		{% if config.enable_embedding %}
 		<tr>
 			<th>
 				{% trans %}Embed{% endtrans %}
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</th>
 			<td>
 				<input type="text" name="embed" size="30" maxlength="120" autocomplete="off">
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</td>
 		</tr>
 		{% endif %}
@@ -103,18 +103,17 @@
 		{% if not config.field_disable_password or (mod and post.mod|hasPermission(config.mod.bypass_field_disable, board.uri)) %}<tr>
 			<th>
 				{% trans %}Password{% endtrans %}
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</th>
 			<td>
 				<input type="password" name="password" size="12" maxlength="18" autocomplete="off"> 
 				<span class="unimportant">{% trans %}(For file deletion.){% endtrans %}</span>
-				{{ hiddenInputs([board.uri, id]) }}
+				{{ antibot.html() }}
 			</td>
 		</tr>{% endif %}
 	</table>
-{{ hiddenInputs([board.uri, id]) }}
+{{ antibot.html(true) }}
-<input type="hidden" name="hash" value="{{ hiddenInputsHash([board.uri, id]) }}">
+<input type="hidden" name="hash" value="{{ antibot.hash() }}">
-{{ hiddenInputs([board.uri, id], true) }}
 </form>
 
 <script type="text/javascript">{% raw %}