PHPCMS V9.6.3的后台漏洞分析

本文转载自查看原文 2019-03-13 14:07 2303 web漏洞分析

PHPCMS V9.6.3后台的漏洞分析

1、利用文件包含创建任意文件getshell

漏洞文件：\phpcmsv9\phpcms\modules\block\block_admin.php

漏洞产生点位于265~272行：

1 if (@file_put_contents($filepath,$str)) {
2                  ob_start();
3                  include $filepath;
4                  $html = ob_get_contents();
5                  ob_clean();
6                  @unlink($filepath);
7             }

可以看到使用file_put_contents函数将 $str 写入 $filepath 中并且包含该文件，查看$filepath和$str变量是否可控。

 1 public function public_view() {
 2         $id = isset($_GET['id']) && intval($_GET['id']) ? intval($_GET['id']) :  exit('0');
 3         if (!$data = $this->db->get_one(array('id'=>$id))) {
 4             showmessage(L('nofound'));
 5         }
 6         if ($data['type'] == 1) {
 7             exit('<script type="text/javascript">parent.showblock('.$id.', \''.str_replace("\r\n", '', $_POST['data']).'\')</script>');
 8         } elseif ($data['type'] == 2) {
 9             extract($data);
10             unset($data);
11             $title = isset($_POST['title']) ? $_POST['title'] : '';
12             $url = isset($_POST['url']) ? $_POST['url'] : '';
13             $thumb = isset($_POST['thumb']) ? $_POST['thumb'] : '';
14             $desc = isset($_POST['desc']) ? $_POST['desc'] : '';
15             $template = isset($_POST['template']) && trim($_POST['template']) ? trim($_POST['template']) : '';
16             $data = array();
17             foreach ($title as $key=>$v) {
18                 if (empty($v) || !isset($url[$key]) ||empty($url[$key])) continue;
19                 $data[$key] = array('title'=>$v, 'url'=>$url[$key], 'thumb'=>$thumb[$key], 'desc'=>str_replace(array(chr(13), chr(43)), array('<br />', '&nbsp;'), $desc[$key]));
20             }
21             $tpl = pc_base::load_sys_class('template_cache');
22             $str = $tpl->template_parse(new_stripslashes($template));
23             $filepath = CACHE_PATH.'caches_template'.DIRECTORY_SEPARATOR.'block'.DIRECTORY_SEPARATOR.'tmp_'.$id.'.php';
24             $dir = dirname($filepath);
25             if(!is_dir($dir)) {
26                 @mkdir($dir, 0777, true);
27             }

可以看到变量 $template 可控，跟进 new_stripslashes()函数：

/**
 * 返回经stripslashes处理过的字符串或数组
 * @param $string 需要处理的字符串或数组
 * @return mixed
 */
function new_stripslashes($string) {
    if(!is_array($string)) return stripslashes($string);
    foreach($string as $key => $val) $string[$key] = new_stripslashes($val);
    return $string;
}

template_parse()函数：

/**
     * 解析模板
     *
     * @param $str    模板内容
     * @return ture
     */
    public function template_parse($str) {
        $str = preg_replace ( "/\{template\s+(.+)\}/", "<?php include template(\\1); ?>", $str );
        $str = preg_replace ( "/\{include\s+(.+)\}/", "<?php include \\1; ?>", $str );
        $str = preg_replace ( "/\{php\s+(.+)\}/", "<?php \\1?>", $str );
        $str = preg_replace ( "/\{if\s+(.+?)\}/", "<?php if(\\1) { ?>", $str );
        $str = preg_replace ( "/\{else\}/", "<?php } else { ?>", $str );
        $str = preg_replace ( "/\{elseif\s+(.+?)\}/", "<?php } elseif (\\1) { ?>", $str );
        $str = preg_replace ( "/\{\/if\}/", "<?php } ?>", $str );
        //for 循环
        $str = preg_replace("/\{for\s+(.+?)\}/","<?php for(\\1) { ?>",$str);
        $str = preg_replace("/\{\/for\}/","<?php } ?>",$str);
        //++ --
        $str = preg_replace("/\{\+\+(.+?)\}/","<?php ++\\1; ?>",$str);
        $str = preg_replace("/\{\-\-(.+?)\}/","<?php ++\\1; ?>",$str);
        $str = preg_replace("/\{(.+?)\+\+\}/","<?php \\1++; ?>",$str);
        $str = preg_replace("/\{(.+?)\-\-\}/","<?php \\1--; ?>",$str);
        $str = preg_replace ( "/\{loop\s+(\S+)\s+(\S+)\}/", "<?php \$n=1;if(is_array(\\1)) foreach(\\1 AS \\2) { ?>", $str );
        $str = preg_replace ( "/\{loop\s+(\S+)\s+(\S+)\s+(\S+)\}/", "<?php \$n=1; if(is_array(\\1)) foreach(\\1 AS \\2 => \\3) { ?>", $str );
        $str = preg_replace ( "/\{\/loop\}/", "<?php \$n++;}unset(\$n); ?>", $str );
        $str = preg_replace ( "/\{([a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff:]*\(([^{}]*)\))\}/", "<?php echo \\1;?>", $str );
        $str = preg_replace ( "/\{\\$([a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff:]*\(([^{}]*)\))\}/", "<?php echo \\1;?>", $str );
        $str = preg_replace ( "/\{(\\$[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)\}/", "<?php echo \\1;?>", $str );
        $str = preg_replace_callback("/\{(\\$[a-zA-Z0-9_\[\]\'\"\$\x7f-\xff]+)\}/s",  array($this, 'addquote'),$str);
        $str = preg_replace ( "/\{([A-Z_\x7f-\xff][A-Z0-9_\x7f-\xff]*)\}/s", "<?php echo \\1;?>", $str );
        $str = preg_replace_callback("/\{pc:(\w+)\s+([^}]+)\}/i", array($this, 'pc_tag_callback'), $str);
        $str = preg_replace_callback("/\{\/pc\}/i", array($this, 'end_pc_tag'), $str);
        $str = "<?php defined('IN_PHPCMS') or exit('No permission resources.'); ?>" . $str;
        return $str;
    }

可以看到并无对 $template 的有效过滤，从而导致 $str 可控。再看漏洞产生点，是将 $str 写入文件中包含该文件，然后再将该文件删除。那么可以构造payload:

<?php file_put_contents("phpinfo.php","<?php phpinfo();?>");

接下来寻找怎么利用该漏洞，在函数 public_view() 中，跟入get_one()函数：

/**
     * 获取单条记录查询
     * @param $data         需要查询的字段值[例`name`,`gender`,`birthday`]
     * @param $table         数据表
     * @param $where         查询条件
     * @param $order         排序方式    [默认按数据库默认方式排序]
     * @param $group         分组方式    [默认为空]
     * @return array/null    数据查询结果集,如果不存在，则返回空
     */
    public function get_one($data, $table, $where = '', $order = '', $group = '') {
        $where = $where == '' ? '' : ' WHERE '.$where;
        $order = $order == '' ? '' : ' ORDER BY '.$order;
        $group = $group == '' ? '' : ' GROUP BY '.$group;
        $limit = ' LIMIT 1';
        $field = explode( ',', $data);
        array_walk($field, array($this, 'add_special_char'));
        $data = implode(',', $field);

        $sql = 'SELECT '.$data.' FROM `'.$this->config['database'].'`.`'.$table.'`'.$where.$group.$order.$limit;
        $this->execute($sql);
        $res = $this->fetch_next();
        $this->free_result();
        return $res;
    }

可以看到是查询一条数据，其 sql 语句为: select * from phpcmsv9.block where id=$id limit 1; 并且需要返回一个数组。否则报错 nofound。因此需要先使用 add() 函数插入一条

数据并且 type 字段为 2，跟进 add() 函数：

 1 public function add() {
 2         $pos = isset($_GET['pos']) && trim($_GET['pos']) ? trim($_GET['pos']) : showmessage(L('illegal_operation'));
 3         if (isset($_POST['dosubmit'])) {
 4             $name = isset($_POST['name']) && trim($_POST['name']) ? trim($_POST['name']) : showmessage(L('illegal_operation'), HTTP_REFERER);
 5             $type = isset($_POST['type']) && intval($_POST['type']) ? intval($_POST['type']) : 1;
 6             //判断名称是否已经存在
 7             if ($this->db->get_one(array('name'=>$name))) {
 8                 showmessage(L('name').L('exists'), HTTP_REFERER);
 9             }
10             if ($id = $this->db->insert(array('name'=>$name, 'pos'=>$pos, 'type'=>$type, 'siteid'=>$this->siteid), true)) {
11                 //设置权限
12                 $priv = isset($_POST['priv']) ? $_POST['priv'] : '';
13                 if (!empty($priv)) {
14                     if (is_array($priv)) foreach ($priv as $v) {
15                         if (empty($v)) continue;
16                         $this->priv_db->insert(array('roleid'=>$v, 'blockid'=>$id, 'siteid'=>$this->siteid));
17                     }
18                 }
19                 showmessage(L('operation_success'), '?m=block&c=block_admin&a=block_update&id='.$id);
20             } else {
21                 showmessage(L('operation_failure'), HTTP_REFERER);
22             }
23         } else {
24             $show_header = $show_validator = true;
25             pc_base::load_sys_class('form');
26             $administrator = getcache('role', 'commons');
27             unset($administrator[1]);
28             include $this->admin_tpl('block_add_edit');
29         }
30     }