PHP审计之WeEngine审计

前言

审计该CMS加深一下对于MVC架构的php审计流程

梳理路由

打开代码看到index.php文件

if($_W['os'] == 'mobile' && (!empty($_GPC['i']) || !empty($_SERVER['QUERY_STRING']))) {
	header('Location: ./app/index.php?' . $_SERVER['QUERY_STRING']);
} else {
	header('Location: ./web/index.php?' . $_SERVER['QUERY_STRING']);
}

web端会跳转到/web/index.php，来看到web/index.php

if (($_W['setting']['copyright']['status'] == 1) && empty($_W['isfounder']) && $controller != 'cloud' && $controller != 'utility' && $controller != 'account') {
	$_W['siteclose'] = true;
	if ($controller == 'account' && $action == 'welcome') {
		template('account/welcome');
		exit;
	}
	if ($controller == 'user' && $action == 'login') {
		if (checksubmit()) {
			require _forward($controller, $action);
		}
		template('user/login');
		exit;
	}
	isetcookie('__session', '', -10000);
	message('站点已关闭，关闭原因：' . $_W['setting']['copyright']['reason'], url('account/welcome'), 'info');
}

这里$controller和$action接收是从bootstrap.inc.php

$controller = $_GPC['c'];
$action = $_GPC['a'];
$do = $_GPC['do'];

上面接收$controller和$action为account和welcome

调用template('account/welcome');

function template($filename, $flag = TEMPLATE_DISPLAY) {
	global $_W;
	$source = IA_ROOT . "/web/themes/{$_W['template']}/{$filename}.html";
	$compile = IA_ROOT . "/data/tpl/web/{$_W['template']}/{$filename}.tpl.php";
	if(!is_file($source)) {
		$source = IA_ROOT . "/web/themes/default/{$filename}.html";
		$compile = IA_ROOT . "/data/tpl/web/default/{$filename}.tpl.php";
	}
    ...

这段代码实际上就是加载一个模板渲染。

继续往下看

$controllers = array();
$handle = opendir(IA_ROOT . '/web/source/');
if(!empty($handle)) {
	while($dir = readdir($handle)) {
		if($dir != '.' && $dir != '..') {
			$controllers[] = $dir;
		}
	}
}
if(!in_array($controller, $controllers)) {
	$controller = 'account';
}
$init = IA_ROOT . "/web/source/{$controller}/__init.php";
if(is_file($init)) {
	require $init;
}

$actions = array();
$handle = opendir(IA_ROOT . '/web/source/' . $controller);
if(!empty($handle)) {
	while($dir = readdir($handle)) {
		if($dir != '.' && $dir != '..' && strexists($dir, '.ctrl.php')) {
			$dir = str_replace('.ctrl.php', '', $dir);
			$actions[] = $dir;
		}
	}
}
if(empty($actions)) {
	header('location: ?refresh');
}
if(!in_array($action, $actions)) {
	$action = $acl[$controller]['default'];
}
if(!in_array($action, $actions)) {
	$action = $actions[0];
}

遍历读取/web/source/,所有内容。

遍历读取/web/source/' . $controller，并且把内容中的.ctrl.php去掉。

if(is_array($acl[$controller]['direct']) && in_array($action, $acl[$controller]['direct'])) {
		require _forward($controller, $action);
	exit;

判断是否为数组并且判断$acl[$controller]['direct'],并且查看$action是否在$acl截取对应$controller的direct。

逻辑其实就是$acl中定义了大量的数组，如

'account' => array(
		'default' => 'welcome',
		'direct' => array(
			'welcome',
			'auth'
		)

$controller=account

direct=array(‘welcome’,’auth’)

direct这个数组对应的是account下面的路由

访问welcome的路由的访问策略即

/web/index.php?c=account&a=welcome

漏洞审计

定位到漏洞位置web/source/site/category.ctrl.php

定位到176行

if (!empty($navs)) {
		foreach ($navs as $row) {
			file_delete($row['icon']);
		}
		pdo_query("DELETE FROM ".tablename('site_nav')." WHERE id IN (".implode(',', array_keys($navs)).")");
	}

file_delete($row['icon']);,这里的$row['icon']是通过遍历$navs

$navs是通过一下这个sql语句查询得来的

$navs = pdo_fetchall("SELECT icon, id FROM ".tablename('site_nav')." WHERE id IN (SELECT nid FROM ".tablename('site_category')." WHERE id = {$id} OR parentid = '$id')", array(), 'id');

找看数据库中的这两个字段是否可控

site_nav数据库表中对应的数据是$nav变量内容，发现 $nav['icon'] 变量是从$_GPC['iconfile']来的，即参数可控。这里的 $nav['icon']变量，其实就是我们文章开头分析的传入 file_delete函数的参数

			if(!empty($nav_exist)) {
				pdo_update('site_nav', $nav, array('id' => $category['nid'], 'uniacid' => $_W['uniacid']));
			} else {
				pdo_insert('site_nav', $nav);

这里需要先把文件名插入到数据库中，然后调用该功能将文件上传，代码会从数据库从查找该文件名，然后删除对应文件。