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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::Auxiliary
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  include Msf::Auxiliary::Report
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  include Msf::Exploit::Capture
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  include Msf::Auxiliary::UDPScanner
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  include Msf::Auxiliary::DRDoS
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  def initialize
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    super(
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      'Name'        => 'Memcached Stats Amplification Scanner',
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      'Description' => %q(
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          This module can be used to discover Memcached servers which expose the
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          unrestricted UDP port 11211. A basic "stats" request is executed to check
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          if an amplification attack is possible against a third party.
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      ),
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      'Author'      =>
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        [
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          'Marek Majkowski', # Cloudflare blog and base payload
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          'xistence <xistence[at]0x90.nl>', # Metasploit scanner module
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          'Jon Hart <[email protected]>', # Metasploit scanner module
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        ],
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      'License'     => MSF_LICENSE,
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      'DisclosureDate' => 'Feb 27 2018',
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      'References'  =>
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          [
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            ['URL', 'https://blog.cloudflare.com/memcrashed-major-amplification-attacks-from-port-11211/'],
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            ['CVE', '2018-1000115']
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          ]
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    )
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    register_options([
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      Opt::RPORT(11211)
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    ])
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  end
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  def build_probe
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    # Memcached stats probe, per https://github.com/memcached/memcached/blob/master/doc/protocol.txt
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    @memcached_probe ||= [
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      rand(2**16), # random request ID
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      0, # sequence number
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      1, # number of datagrams in this sequence
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      0, # reserved; must be 0
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      "stats\r\n"
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    ].pack("nnnna*")
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  end
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  def scanner_process(data, shost, sport)
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    # Check the response data for a "STAT" response
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    if data =~ /\x0d\x0aSTAT\x20/
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      @results[shost] ||= []
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      @results[shost] << data
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    end
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  end
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  # Called after the scan block
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  def scanner_postscan(batch)
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    @results.keys.each do |host|
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      response_map = { @memcached_probe => @results[host] }
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      report_service(
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        host: host,
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        proto: 'udp',
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        port: rport,
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        name: 'memcached'
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      )
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      peer = "#{host}:#{rport}"
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      vulnerable, proof = prove_amplification(response_map)
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      what = 'memcached stats amplification'
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      if vulnerable
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        print_good("#{peer} - Vulnerable to #{what}: #{proof}")
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        report_vuln(
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          host: host,
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          port: rport,
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          proto: 'udp',
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          name: what,
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          refs: references
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        )
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      else
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        vprint_status("#{peer} - Not vulnerable to #{what}: #{proof}")
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      end
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    end
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  end
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end
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