---
-- The VNC library provides some basic functionality needed in order to
-- communicate with VNC servers, and derivates such as Tight- or Ultra-
-- VNC.
--
-- Summary
-- -------
-- The library currently supports the VNC Authentication security type only.
-- This security type is supported by default in VNC, TightVNC and
-- "Remote Desktop Sharing" in eg. Ubuntu. For servers that do not support
-- this authentication security type the login method will fail.
--
-- Overview
-- --------
-- The library contains the following classes:
--
-- o VNC
-- - This class contains the core functions needed to communicate with VNC
--
-- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html
-- @author "Patrik Karlsson <patrik@cqure.net>"
-- Version 0.1
-- Created 07/07/2010 - v0.1 - created by Patrik Karlsson <patrik@cqure.net>
local bin = require "bin"
local match = require "match"
local nmap = require "nmap"
local stdnse = require "stdnse"
local string = require "string"
local table = require "table"
_ENV = stdnse.module("vnc", stdnse.seeall)
local HAVE_SSL, openssl = pcall(require,'openssl')
VNC = {
-- We currently support version 3.8 of the protocol only
versions = {
["RFB 003.003\n"] = "3.3",
["RFB 003.007\n"] = "3.7",
["RFB 003.008\n"] = "3.8",
-- Mac Screen Sharing, could probably be used to fingerprint OS
["RFB 003.889\n"] = "3.889",
},
sectypes = {
INVALID = 0,
NONE = 1,
VNCAUTH = 2,
RA2 = 5,
RA2NE = 6,
TIGHT = 16,
ULTRA = 17,
TNS = 18,
VENCRYPT = 19,
GTK_VNC_SASL = 20,
MD5 = 21,
COLIN_DEAN_XVP = 22,
MAC_OSX_SECTYPE_30 = 30,
MAC_OSX_SECTYPE_35 = 35,
},
-- Security types are fetched from the rfbproto.pdf
sectypes_str = {
[0] = "Invalid security type",
[1] = "None",
[2] = "VNC Authentication",
[5] = "RA2",
[6] = "RA2ne",
[16]= "Tight",
[17]= "Ultra",
[18]= "TLS",
[19]= "VeNCrypt",
[20]= "GTK-VNC SASL",
[21]= "MD5 hash authentication",
[22]= "Colin Dean xvp",
-- Mac OS X screen sharing uses 30 and 35
[30]= "Mac OS X security type (30)",
[35]= "Mac OS X security type (35)",
},
new = function(self, host, port)
local o = {
host = host,
port = port,
socket = nmap.new_socket(),
cli_version = nmap.registry.args['vnc-brute.version'] or "RFB 003.889\n"
}
setmetatable(o, self)
self.__index = self
return o
end,
--- Connects the VNC socket
connect = function(self)
if ( not(HAVE_SSL) ) then
return false, "The VNC module requires OpenSSL support"
end
return self.socket:connect(self.host, self.port, "tcp")
end,
--- Disconnects the VNC socket
disconnect = function(self)
return self.socket:close()
end,
--- Performs the VNC handshake and determines
-- o The RFB Protocol to use
-- o The supported authentication security types
--
-- @return status, true on success, false on failure
-- @return error string containing error message if status is false
handshake = function(self)
local status, data = self.socket:receive_buf(match.numbytes(12), true)
local vncsec = {
count = 1,
types = {}
}
if ( not(status) ) then
return status, "ERROR: VNC:handshake failed to receive protocol version"
end
self.protover = VNC.versions[data]
if ( not(self.protover) ) then
stdnse.print_debug("ERROR: VNC:handshake unsupported version (%s)", data:sub(1,11))
return false, ("Unsupported version (%s)"):format(data:sub(1,11))
end
status = self.socket:send( self.cli_version )
if ( not(status) ) then
stdnse.print_debug("ERROR: VNC:handshake failed to send client version")
return false, "ERROR: VNC:handshake failed"
end
local function process_error()
local status, tmp = self.socket:receive_buf(match.numbytes(4), true)
if( not(status) ) then
return false, "VNC:handshake failed to retrieve error message"
end
local len = select(2, bin.unpack(">I", tmp))
local status, err = self.socket:receive_buf(match.numbytes(len), true)
if( not(status) ) then
return false, "VNC:handshake failed to retrieve error message"
end
return false, err
end
if ( self.protover == "3.3" ) then
local status, tmp = self.socket:receive_buf(match.numbytes(4), true)
if( not(status) ) then
return false, "VNC:handshake failed to receive security data"
end
vncsec.types[1] = select(2, bin.unpack("I", tmp) )
self.vncsec = vncsec
-- do we have an invalid security type, if so we need to handle an
-- error condition
if ( vncsec.types[1] == 0 ) then
return process_error()
end
else
local status, tmp = self.socket:receive_buf(match.numbytes(1), true)
if ( not(status) ) then
stdnse.print_debug("ERROR: VNC:handshake failed to receive security data")
return false, "ERROR: VNC:handshake failed to receive security data"
end
vncsec.count = select(2, bin.unpack("C", tmp))
if ( vncsec.count == 0 ) then
return process_error()
end
status, tmp = self.socket:receive_buf(match.numbytes(vncsec.count), true)
if ( not(status) ) then
stdnse.print_debug("ERROR: VNC:handshake failed to receive security data")
return false, "ERROR: VNC:handshake failed to receive security data"
end
for i=1, vncsec.count do
table.insert( vncsec.types, select(2, bin.unpack("C", tmp, i) ) )
end
self.vncsec = vncsec
end
return true
end,
--- Creates the password bit-flip needed before DES encryption
--
-- @param password string containing the password to process
-- @return password string containing the processed password
createVNCDESKey = function( self, password )
if ( #password < 8 ) then
for i=1, (8 - #password) do
password = password .. string.char(0x00)
end
end
local newpass = ""
for i=1, 8 do
local _, bitstr = bin.unpack("B", password, i)
newpass = newpass .. bin.pack("B", bitstr:reverse())
end
return newpass
end,
--- Attempts to login to the VNC service
-- Currently the only supported auth sectype is VNC Authentication
--
-- @param username string, could be anything when VNCAuth is used
-- @param password string containing the password to use for authentication
-- @return status true on success, false on failure
-- @return err string containing error message when status is false
login = function( self, username, password )
if ( not(password) ) then
return false, "No password was supplied"
end
if ( not( self:supportsSecType( VNC.sectypes.VNCAUTH ) ) ) then
return false, "The server does not support the \"VNC Authentication\" security type."
end
-- Announce that we support VNC Authentication
local status = self.socket:send( bin.pack("C", VNC.sectypes.VNCAUTH) )
if ( not(status) ) then
return false, "Failed to select authentication type"
end
local status, chall = self.socket:receive_buf(match.numbytes(16), true)
if ( not(status) ) then
return false, "Failed to receive authentication challenge"
end
local key = self:createVNCDESKey(password)
local resp = openssl.encrypt("des-ecb", key, nil, chall, false )
status = self.socket:send( resp )
if ( not(status) ) then
return false, "Failed to send authentication response to server"
end
local status, result = self.socket:receive_buf(match.numbytes(4), true)
if ( not(status) ) then
return false, "Failed to retrieve authentication status from server"
end
if ( select(2, bin.unpack("I", result) ) ~= 0 ) then
return false, ("Authentication failed with password %s"):format(password)
end
return true, ""
end,
--- Returns all supported security types as a table of strings
--
-- @return table containing a string entry for each security type
getSecTypesAsStringTable = function( self )
local tmp = {}
for i=1, self.vncsec.count do
table.insert( tmp, VNC.sectypes_str[self.vncsec.types[i]] or ("Unknown security type (%d)"):format(self.vncsec.types[i]) )
end
return true, tmp
end,
--- Checks if the supplied security type is supported or not
--
-- @param sectype number containing the security type to check for
-- @return status true if supported, false if not supported
supportsSecType = function( self, sectype )
for i=1, self.vncsec.count do
if ( self.vncsec.types[i] == sectype ) then
return true
end
end
return false
end,
--- Returns the protocol version reported by the server
--
-- @param version string containing the version number
getProtocolVersion = function( self )
return self.protover
end,
}
return _ENV;
@KyuuKazami