| Current Path : /usr/share/nmap/nselib/ |
| Current File : //usr/share/nmap/nselib/vnc.lua |
---
-- 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
--
-- o VNCSocket
-- - This is a copy of the DB2Socket class which provides fundamental buffering
--
--
-- @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>
module(... or "vnc", package.seeall)
require "bin"
local HAVE_SSL = false
if pcall(require,'openssl') then
HAVE_SSL = true
end
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 = {}
setmetatable(o, self)
self.__index = self
o.host = host
o.port = port
o.vncsocket = VNCSocket:new()
o.cli_version = nmap.registry.args['vnc-brute.version'] or "RFB 003.889\n"
return o
end,
--- Connects the VNC socket
connect = function(self)
local data, status, msg
if ( not(HAVE_SSL) ) then
return false, "The VNC module requires OpenSSL support"
end
status, msg = self.vncsocket:connect(self.host, self.port, "tcp")
return status, msg
end,
--- Disconnects the VNC socket
disconnect = function(self)
self.vncsocket: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.vncsocket:recv( 12 )
local vncsec = {}
local tmp
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.vncsocket: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
if ( self.protover == "3.3" ) then
vncsec.count = 1
vncsec.types = {}
status, tmp = self.vncsocket:recv(4)
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
local len, err
status, tmp = self.vncsocket:recv(4)
if( not(status) ) then
return false, "VNC:handshake failed to retrieve error message"
end
len = select(2, bin.unpack(">I", tmp) )
status, err = self.vncsocket:recv(len)
if( not(status) ) then
return false, "VNC:handshake failed to retrieve error message"
end
return false, err
end
else
status, tmp = self.vncsocket:recv(1)
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
local len, err
status, tmp = self.vncsocket:recv(4)
if( not(status) ) then
return false, "VNC:handshake failed to retrieve error message"
end
len = select(2, bin.unpack(">I", tmp) )
status, err = self.vncsocket:recv(len)
if( not(status) ) then
return false, "VNC:handshake failed to retrieve error message"
end
return false, err
end
status, tmp = self.vncsocket:recv(vncsec.count)
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.types = {}
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 )
local _, bitstr
local newpass = ""
if ( #password < 8 ) then
for i=1, (8 - #password) do
password = password .. string.char(0x00)
end
end
for i=1, 8 do
_, 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 )
local status, result
local chall, resp, key
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
status = self.vncsocket:send( bin.pack("C", VNC.sectypes.VNCAUTH) )
if ( not(status) ) then
return false, "Failed to select authentication type"
end
status, chall = self.vncsocket:recv( 16 )
if ( not(status) ) then
return false, "Failed to receive authentication challenge"
end
key = self:createVNCDESKey(password)
resp = openssl.encrypt("des-ecb", key, nil, chall, false )
status = self.vncsocket:send( resp )
if ( not(status) ) then
return false, "Failed to send authentication response to server"
end
status, result = self.vncsocket:recv(4)
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,
}
VNCSocket =
{
retries = 3,
new = function(self)
local o = {}
setmetatable(o, self)
self.__index = self
o.Socket = nmap.new_socket()
o.Buffer = nil
return o
end,
--- Establishes a connection.
--
-- @param hostid Hostname or IP address.
-- @param port Port number.
-- @param protocol <code>"tcp"</code>, <code>"udp"</code>, or
-- @return Status (true or false).
-- @return Error code (if status is false).
connect = function( self, hostid, port, protocol )
-- VNC servers sometimes take a long time to respond 10seconds seems ok
self.Socket:set_timeout(10000)
return self.Socket:connect( hostid, port, protocol )
end,
--- Closes an open connection.
--
-- @return Status (true or false).
-- @return Error code (if status is false).
close = function( self )
return self.Socket:close()
end,
--- Opposed to the <code>socket:receive_bytes</code> function, that returns
-- at least x bytes, this function returns the amount of bytes requested.
--
-- @param count of bytes to read
-- @return true on success, false on failure
-- @return data containing bytes read from the socket
-- err containing error message if status is false
recv = function( self, count )
local status, data
self.Buffer = self.Buffer or ""
if ( #self.Buffer < count ) then
status, data = self.Socket:receive_bytes( count - #self.Buffer )
if ( not(status) ) then
return false, data
end
self.Buffer = self.Buffer .. data
end
data = self.Buffer:sub( 1, count )
self.Buffer = self.Buffer:sub( count + 1)
return true, data
end,
--- Sends data over the socket
--
-- @return Status (true or false).
-- @return Error code (if status is false).
send = function( self, data )
return self.Socket:send( data )
end,
}
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