Class: Rex::Proto::RFB::Client

Inherits:
Object
  • Object
show all
Defined in:
lib/rex/proto/rfb/client.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(sock, opts = {}) ⇒ Client

Returns a new instance of Client.


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# File 'lib/rex/proto/rfb/client.rb', line 22

def initialize(sock, opts = {})
  @sock = sock
  @opts = opts

  @banner = nil
  @majver = MajorVersions
  @minver = -1
  @auth_types = []
end

Instance Attribute Details

#auth_typesObject (readonly)

Returns the value of attribute auth_types


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# File 'lib/rex/proto/rfb/client.rb', line 250

def auth_types
  @auth_types
end

#errorObject (readonly)

Returns the value of attribute error


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# File 'lib/rex/proto/rfb/client.rb', line 250

def error
  @error
end

#majverObject (readonly)

Returns the value of attribute majver


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# File 'lib/rex/proto/rfb/client.rb', line 250

def majver
  @majver
end

#minverObject (readonly)

Returns the value of attribute minver


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# File 'lib/rex/proto/rfb/client.rb', line 250

def minver
  @minver
end

#view_onlyObject (readonly)

Returns the value of attribute view_only


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# File 'lib/rex/proto/rfb/client.rb', line 251

def view_only
  @view_only
end

Instance Method Details

#authenticate(password = nil) ⇒ Object


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# File 'lib/rex/proto/rfb/client.rb', line 90

def authenticate(password = nil)
  authenticate_with_user(nil, password)
end

#authenticate_with_type(type, username = nil, password = nil) ⇒ Object


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# File 'lib/rex/proto/rfb/client.rb', line 99

def authenticate_with_type(type, username = nil, password = nil)
  return false if not type

  # Authenticate.
  case type
  when AuthType::None
    # Nothing here.

  when AuthType::VNC
    return false if not negotiate_vnc_auth(password)

  when AuthType::ARD
    return false if not negotiate_ard_auth(username, password)

  end

  # Handle reading the security result message
  result = @sock.get_once(4)
  if not result
    @error = "Unable to read auth result"
    return false
  end

  result = result.unpack('N').first
  case result
  when 0
    return true

  when 1
    if @minver >= 8
      msg = read_error_message
      @error = "Authentication failed: #{msg}"
    else
      @error = "Authentication failed"
    end
  when 2
    @error = "Too many authentication attempts"
  else
    @error = "Unknown authentication result: #{result}"
  end

  false
end

#authenticate_with_user(username = nil, password = nil) ⇒ Object


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# File 'lib/rex/proto/rfb/client.rb', line 94

def authenticate_with_user(username = nil, password = nil)
  type = negotiate_authentication
  authenticate_with_type(type, username, password)
end

#connect(password = nil) ⇒ Object


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# File 'lib/rex/proto/rfb/client.rb', line 75

def connect(password = nil)
  return false if not handshake
  return false if not authenticate(password)
  return false if not send_client_init
  true
end

#handshakeObject


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# File 'lib/rex/proto/rfb/client.rb', line 40

def handshake
  @banner = @sock.get_once(12)
  if not @banner
    @error = "Unable to obtain banner from server"
    return false
  end

  # RFB Protocol Version 3.3 (1998-01)
  # RFB Protocol Version 3.7 (2003-08)
  # RFB Protocol Version 3.8 (2007-06)

  if @banner =~ /RFB ([0-9]{3})\.([0-9]{3})/
    maj = $1.to_i
    unless MajorVersions.include?(maj)
      @error = "Invalid major version number: #{maj}"
      return false
    end
  else
    @error = "Invalid RFB banner: #{@banner}"
    return false
  end

  @minver = $2.to_i

  # Forces version 3 to be used. This adds support  for version 4 servers.
  # It may be necessary to hardcode minver as well.
  # TODO: Add support for Version 4.
  # Version 4 adds additional information to the packet regarding supported
  # authentication types.
  our_ver = "RFB %03d.%03d\n" % [3, @minver]
  @sock.put(our_ver)

  true
end

#negotiate_ard_auth(username = nil, password = nil) ⇒ Object


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# File 'lib/rex/proto/rfb/client.rb', line 216

def negotiate_ard_auth(username = nil, password = nil)
   generator = @sock.get_once(2)
   if not generator or generator.length != 2
     @error = "Unable to obtain ARD challenge: invalid generator value"
     return false
   end
   generator = generator.unpack("n").first

   key_length = @sock.get_once(2)
   if not key_length or key_length.length != 2
     @error = "Unable to obtain ARD challenge: invalid key length"
     return false
   end
   key_length = key_length.unpack("n").first

   prime_modulus = @sock.get_once(key_length)
   if not prime_modulus or prime_modulus.length != key_length
     @error = "Unable to obtain ARD challenge: invalid prime modulus"
     return false
   end

   peer_public_key = @sock.get_once(key_length)
   if not peer_public_key or peer_public_key.length != key_length
     @error = "Unable to obtain ARD challenge: invalid public key"
     return false
   end

   response = Cipher.encrypt_ard(username, password, generator, key_length, prime_modulus, peer_public_key)
   @sock.put(response)

   true
end

#negotiate_authenticationObject


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# File 'lib/rex/proto/rfb/client.rb', line 143

def negotiate_authentication
  # Authentication type negotiation is protocol version specific.
  if @minver < 7
    buf = @sock.get_once(4)
    if not buf
      @error = "Unable to obtain requested authentication method"
      return nil
    end
    @auth_types = buf.unpack('N')
    if not @auth_types or @auth_types.first == 0
      msg = read_error_message
      @error = "No authentication types available: #{msg}"
      return nil
    end
  else
    buf = @sock.get_once(1)
    if not buf
      @error = "Unable to obtain supported authentication method count"
      return nil
    end

    # first byte is number of security types
    num_types = buf.unpack("C").first
    if (num_types == 0)
      msg = read_error_message
      @error = "No authentication types available: #{msg}"
      return nil
    end

    buf = @sock.get_once(num_types)
    if not buf or buf.length != num_types
      @error = "Unable to read authentication types"
      return nil
    end

    @auth_types = buf.unpack("C*")
  end

  if not @auth_types or @auth_types.length < 1
    @error = "No authentication types found"
    return nil
  end

  # Select the one we prefer
  selected = nil
  selected ||= AuthType::None if @opts[:allow_none] and @auth_types.include? AuthType::None
  selected ||= AuthType::VNC if @auth_types.include? AuthType::VNC
  selected ||= AuthType::ARD if @auth_types.include? AuthType::ARD

  if not selected
    @error = "No supported authentication method found."
    return nil
  end

  # For 3.7 and later, clients must state which security-type to use
  @sock.put([selected].pack('C')) if @minver >= 7

  selected
end

#negotiate_vnc_auth(password = nil) ⇒ Object


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# File 'lib/rex/proto/rfb/client.rb', line 203

def negotiate_vnc_auth(password = nil)
  challenge = @sock.get_once(16)
  if not challenge or challenge.length != 16
    @error = "Unable to obtain VNC challenge"
    return false
  end

  response = Cipher.encrypt(challenge, password)
  @sock.put(response)

  true
end

#read_error_messageObject


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# File 'lib/rex/proto/rfb/client.rb', line 32

def read_error_message
  len = @sock.get_once(4)
  return 'Unknown error' if not len or len.length != 4

  len = len.unpack("N").first
  @sock.get_once(len)
end

#send_client_initObject


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# File 'lib/rex/proto/rfb/client.rb', line 82

def send_client_init
  if @opts[:exclusive]
    @sock.put("\x00") # do share.
  else
    @sock.put("\x01") # do share.
  end
end