/nselib/mssql.lua

---
-- MSSQL Library supporting a very limited subset of operations.
--
-- The library was designed and tested against Microsoft SQL Server 2005.
-- However, it should work with versions 7.0, 2000, 2005, 2008 and 2012. 
-- Only a minimal amount of parsers have been added for tokens, column types
-- and column data in order to support the first scripts.
-- 
-- The code has been implemented based on traffic analysis and the following
-- documentation:
-- * SSRP Protocol Specification: http://msdn.microsoft.com/en-us/library/cc219703.aspx
-- * TDS Protocol Specification: http://msdn.microsoft.com/en-us/library/dd304523.aspx
-- * TDS Protocol Documentation: http://www.freetds.org/tds.html.
-- * The JTDS source code: http://jtds.sourceforge.net/index.html.
--
-- * SSRP: Class that handles communication over the SQL Server Resolution Protocol, used for identifying instances on a host.
-- * ColumnInfo: Class containing parsers for column types which are present before the row data in all query response packets. The column information contains information relevant to the data type used to hold the data eg. precision, character sets, size etc.
-- * ColumnData: Class containing parsers for the actual column information.
-- * Token: Class containing parsers for tokens returned in all TDS responses. A server response may hold one or more tokens with information from the server. Each token has a type which has a number of type specific fields.
-- * QueryPacket: Class used to hold a query and convert it to a string suitable for transmission over a socket.
-- * LoginPacket: Class used to hold login specific data which can easily be converted to a string suitable for transmission over a socket.
-- * PreLoginPacket: Class used to (partially) implement the TDS PreLogin packet
-- * TDSStream: Class that handles communication over the Tabular Data Stream protocol used by SQL serve. It is used to transmit the the Query- and Login-packets to the server.
-- * Helper: Class which facilitates the use of the library by through action oriented functions with descriptive names.
-- * Util: A "static" class containing mostly character and type conversion functions.
--
-- The following sample code illustrates how scripts can use the Helper class
-- to interface the library:
--
-- <code>
-- local helper = mssql.Helper:new()
-- status, result = helper:Connect( host, port )
-- status, result = helper:Login( username, password, "temdpb", host.ip )
-- status, result = helper:Query( "SELECT name FROM master..syslogins" )
-- helper:Disconnect()
-- </code>
--
-- The following sample code illustrates how scripts can use the Helper class
-- with pre-discovered instances (e.g. by <code>ms-sql-discover</code> or <code>broadcast-ms-sql-discover</code>):
--
-- <code>
-- local instance = mssql.Helper.GetDiscoveredInstances( host, port )
-- if ( instance ) then
--   local helper = mssql.Helper:new()
--   status, result = helper:ConnectEx( instance )
--   status, result = helper:LoginEx( instance )
--   status, result = helper:Query( "SELECT name FROM master..syslogins" )
--   helper:Disconnect()
-- end
-- </code>
--
-- Known limitations:
-- * The library does not support SSL. The foremost reason being the akward choice of implementation where the SSL handshake is performed within the TDS data block. By default, servers support connections over non SSL connections though. 
-- * Version 7 and ONLY version 7 of the protocol is supported. This should cover Microsoft SQL Server 7.0 and later.
-- * TDS Responses contain one or more response tokens which are parsed based on their type. The supported tokens are listed in the <code>TokenType</code> table and their respective parsers can be found in the <code>Token</code> class. Note that some token parsers are not fully implemented and simply move the offset the right number of bytes to continue processing of the response.
-- * The library only supports a limited subsets of datatypes and will abort execution and return an error if it detects an unsupported type. The supported data types are listed in the <code>DataTypes</code> table. In order to add additional data types a parser function has to be added to both the <code>ColumnInfo</code> and <code>ColumnData</code> class.
-- * No functionality for languages, localization or characted codepages has been considered or implemented.
-- * The library does database authentication only. No OS authentication or use of the integrated security model is supported.
-- * Queries using SELECT, INSERT, DELETE and EXEC of procedures have been tested while developing scripts.
--
-- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html
--
-- @author "Patrik Karlsson <patrik@cqure.net>, Chris Woodbury"
-- 
-- @args mssql.username The username to use to connect to SQL Server instances.
--		This username is used by scripts taking actions that require
--		authentication (e.g. <code>ms-sql-query</code>) This username (and its
--		associated password) takes precedence over any credentials discovered
--		by the <code>ms-sql-brute</code> and <code>ms-sql-empty-password</code>
--		scripts.
--
-- @args mssql.password The password for <code>mssql.username</code>. If this
--		argument is not given but <code>mssql.username</code>, a blank password
--		is used.
--
-- @args mssql.instance-name The name of the instance to connect to.
--
-- @args mssql.instance-port The port of the instance to connect to.
--
-- @args mssql.instance-all Targets all SQL server instances discovered
--       throught the browser service.
--
-- @args mssql.domain The domain against which to perform integrated
--       authentication. When set, the scripts assume integrated authentication
--       should be performed, rather than the default sql login.
--
-- @args mssql.protocol The protocol to use to connect to the instance. The
--       protocol may be either <code>NP</code>,<code>Named Pipes</code> or
--       <code>TCP</code>.
--
-- @args mssql.timeout How long to wait for SQL responses. This is a number
--		followed by <code>ms</code> for milliseconds, <code>s</code> for
--		seconds, <code>m</code> for minutes, or <code>h</code> for hours.
--		Default: <code>30s</code>.
--
-- @args mssql.scanned-ports-only If set, the script will only connect
--			to ports that were included in the Nmap scan. This may result in
--			instances not being discovered, particularly if UDP port 1434 is not
--			included. Additionally, instances that are found to be running on
--			ports that were not scanned (e.g. if 1434/udp is in the scan and the
--			SQL Server Browser service on that port reports an instance
--			listening on 43210/tcp, which was not scanned) will be reported but
--			will not be stored for use by other ms-sql-* scripts.

local bin = require "bin"
local bit = require "bit"
local math = require "math"
local match = require "match"
local nmap = require "nmap"
local os = require "os"
local shortport = require "shortport"
local smb = require "smb"
local smbauth = require "smbauth"
local stdnse = require "stdnse"
local strbuf = require "strbuf"
local string = require "string"
local table = require "table"
_ENV = stdnse.module("mssql", stdnse.seeall)

-- Created 01/17/2010 - v0.1 - created by Patrik Karlsson <patrik@cqure.net>
-- Revised 03/28/2010 - v0.2 - fixed incorrect token types. added 30 seconds timeout
-- Revised 01/23/2011 - v0.3 - fixed parsing error in discovery code with patch
--							   from Chris Woodbury
-- Revised 02/01/2011 - v0.4 - numerous changes and additions to support new
--							   functionality in ms-sql- scripts and to be more
--							   robust in parsing and handling data. (Chris Woodbury)
-- Revised 02/19/2011 - v0.5 - numerous changes in script, library behaviour
-- 								* huge improvements in version detection
--								* added support for named pipes
--								* added support for integrated NTLMv1 authentication
--
--								(Patrik Karlsson, Chris Woodbury)
-- Revised 08/19/2012 - v0.6 - added multiple data types
-- 								* added detection and handling of null values when processing query responses from the server
--								* added DoneProc response token support
--
--								(Tom Sellers)
-- Updated 10/01/2012 - v0.7 - added support for 2012 and later service packs for 2005, 2008 and 2008 R2 (Rob Nicholls)

local HAVE_SSL, openssl = pcall(require, "openssl")

do
  namedpipes = smb.namedpipes
  local arg = stdnse.get_script_args( "mssql.timeout" ) or "30s"
  
  local timeout, err = stdnse.parse_timespec(arg)
  if not timeout then
    error(err)
  end
  MSSQL_TIMEOUT = timeout
  
  SCANNED_PORTS_ONLY = false
  if ( stdnse.get_script_args( "mssql.scanned-ports-only" ) ) then
  	SCANNED_PORTS_ONLY = true
  end
end


-- *************************************
-- Informational Classes
-- ************************************* 

--- SqlServerInstanceInfo class
SqlServerInstanceInfo =
{
	instanceName = nil,
	version = nil,
	serverName = nil,
	isClustered = nil,
	host = nil,
	port = nil,
	pipeName = nil,

	new = function(self,o)
		o = o or {}
        setmetatable(o, self)
        self.__index = self
		return o
    end,
    
    -- Compares two SqlServerInstanceInfo objects and determines whether they
    -- refer to the same SQL Server instance, judging by a combination of host,
    -- port, named pipe information and instance name.
    __eq = function( self, other )
    	local areEqual
    	if ( not (self.host and other.host) ) then
    		-- if they don't both have host information, we certainly can't say
    		-- whether they're the same
    		areEqual = false
    	else
    		areEqual = (self.host.ip == other.host.ip)
    	end
    	
    	if (self.port and other.port) then
    		areEqual = areEqual and ( other.port.number == self.port.number and
    									other.port.protocol == self.port.protocol ) 
    	elseif (self.pipeName and other.pipeName) then
    		areEqual = areEqual and (self.pipeName == other.pipeName)
    	elseif (self.instanceName and other.instanceName) then
    		areEqual = areEqual and (self.instanceName == other.instanceName)
    	else
    		-- if we have neither port nor named pipe info nor instance names,
    		-- we can't say whether they're the same
    		areEqual = false
    	end
    	
    	return areEqual
    end,
    
    --- Merges the data from one SqlServerInstanceInfo object into another. Each
    --  field in the first object is populated with the data from that field in
    --  second object if the first object's field is nil OR if <code>overwrite</code>
    --  is set to true. A special case is made for the <code>version</code> field,
    --  which is only overwritten in the second object has more reliable version
    --  information. The second object is not modified.
    Merge = function( self, other, overwrite )
    	local mergeFields = { "host", "port", "instanceName", "version", "isClustered", "pipeName" }
    	for _, fieldname in ipairs( mergeFields ) do
    		-- Add values from other only if self doesn't have a value, or if overwrite is true
    		if ( other[ fieldname ] ~= nil and (overwrite or self[ fieldname ] == nil) ) then
    			self[ fieldname ] = other[ fieldname ]
    		end
    	end
    	if (self.version and self.version.source == "SSRP" and 
    		other.version and other.version.Source == "SSNetLib") then
    			self.version = other.version
    	end
    end,
    
    --- Returns a name for the instance, based on the available information. This
    --  may take one of the following forms:
    --  * HOST\INSTANCENAME
    --  * PIPENAME
    --  * HOST:PORT
    GetName = function( self )
    	if (self.instanceName) then
    		return string.format( "%s\\%s", self.host.ip or self.serverName or "[nil]", self.instanceName or "[nil]" )
    	elseif (self.pipeName) then
    		return string.format( "%s", self.pipeName )
    	else
    		return string.format( "%s:%s",  self.host.ip or self.serverName or "[nil]", (self.port and self.port.number) or "[nil]" )
    	end
    end,
    
    --- Sets whether the instance is in a cluster
    --
    --	@param self
    -- 	@param isClustered Boolean true or the string "Yes" are interpreted as true;
    --				all other values are interpreted as false.
    SetIsClustered = function( self, isClustered )
    	self.isClustered = (isClustered == true) or (isClustered == "Yes")
    end,
    
    --- Indicates whether this instance has networking protocols enabled, such
    --  that scripts could attempt to connect to it.
    HasNetworkProtocols = function( self )
    	return (self.pipeName ~= nil) or (self.port and self.port.number)
    end,
}


--- SqlServerVersionInfo class
SqlServerVersionInfo = 
{
	versionNumber = "",		-- The full version string (e.g. "9.00.2047.00") 
	major = nil,			-- The major version (e.g. 9)
	minor = nil,			-- The minor version (e.g. 0)
	build = nil,			-- The build number (e.g. 2047)
	subBuild = nil,			-- The sub-build number (e.g. 0)
	productName = nil,		-- The prodcut name (e.g. "SQL Server 2005")
	brandedVersion = nil,	-- The branded version of the product (e.g. "2005")
	servicePackLevel = nil,	-- The service pack leve (e.g. "SP1")
	patched = nil,			-- Whether patches have been applied since SP installation (true/false/nil)
	source = nil,			-- The source of the version info (e.g. "SSRP", "SSNetLib")

	new = function(self,o)
		o = o or {}
        setmetatable(o, self)
        self.__index = self
		return o
    end,
	
	--- Sets the version using a version number string.
	--
	-- @param versionNumber a version number string (e.g. "9.00.1399.00")
	-- @param source a string indicating the source of the version info (e.g. "SSRP", "SSNetLib")
	SetVersionNumber = function(self, versionNumber, source)
		local major, minor, revision, subBuild
		if versionNumber:match( "^%d+%.%d+%.%d+.%d+" ) then
			major, minor, revision, subBuild = versionNumber:match( "^(%d+)%.(%d+)%.(%d+)" )
		elseif versionNumber:match( "^%d+%.%d+%.%d+" ) then
			major, minor, revision = versionNumber:match( "^(%d+)%.(%d+)%.(%d+)" )
		else
			stdnse.print_debug( 1, "%s: SetVersionNumber: versionNumber is not in correct format: %s", "MSSQL", versionNumber or "nil" )
		end

		self:SetVersion( major, minor, revision, subBuild, source )
	end,
	
	--- Sets the version using the individual numeric components of the version
	--  number.
	--
	-- @param source a string indicating the source of the version info (e.g. "SSRP", "SSNetLib")
	SetVersion = function(self, major, minor, build, subBuild, source)
		self.source = source
		-- make sure our version numbers all end up as valid numbers
		self.major, self.minor, self.build, self.subBuild = 
			tonumber( major or 0 ), tonumber( minor or 0 ), tonumber( build or 0 ), tonumber( subBuild or 0 )
		
		self.versionNumber = string.format( "%u.%02u.%u.%02u", self.major, self.minor, self.build, self.subBuild )
		
		self:_ParseVersionInfo()
	end,
		
	--- Using the version number, determines the product version
	_InferProductVersion = function(self)
		
		local VERSION_LOOKUP_TABLE = {
			["^6%.0"] = "6.0", ["^6%.5"] = "6.5", ["^7%.0"] = "7.0", 
			["^8%.0"] = "2000",	["^9%.0"] = "2005",	["^10%.0"] = "2008",
			["^10%.50"] = "2008 R2", ["^11%.0"] = "2012",
		}
		
		local product = ""
	
		for m, v in pairs(VERSION_LOOKUP_TABLE) do
			if ( self.versionNumber:match(m) ) then
				product = v
				self.brandedVersion = product
				break
			end
		end
		
		self.productName = ("Microsoft SQL Server %s"):format(product)
		
	end,
	
	
	--- Returns a lookup table that maps revision numbers to service pack levels for
	--  the applicable SQL Server version (e.g. { {1600, "RTM"}, {2531, "SP1"} }).
	_GetSpLookupTable = function(self)
	
		-- Service pack lookup tables: 
		-- For instances where a revised service pack was released (e.g. 2000 SP3a), we will include the
		-- build number for the original SP and the build number for the revision. However, leaving it
		-- like this would make it appear that subsequent builds were a patched version of the revision
		-- (e.g. a patch applied to 2000 SP3 that increased the build number to 780 would get displayed
		-- as "SP3a+", when it was actually SP3+). To avoid this, we will include an additional fake build
		-- number that combines the two.
		local SP_LOOKUP_TABLE_6_5 = { {201, "RTM"}, {213, "SP1"}, {240, "SP2"}, {258, "SP3"}, {281, "SP4"},
			{415, "SP5"}, {416, "SP5a"}, {417, "SP5/SP5a"}, }
		
		local SP_LOOKUP_TABLE_7 = { {623, "RTM"}, {699, "SP1"}, {842, "SP2"}, {961, "SP3"}, {1063, "SP4"}, }
		
		local SP_LOOKUP_TABLE_2000 = { {194, "RTM"}, {384, "SP1"}, {532, "SP2"}, {534, "SP2"}, {760, "SP3"},
			{766, "SP3a"}, {767, "SP3/SP3a"}, {2039, "SP4"}, }
		
		local SP_LOOKUP_TABLE_2005 = { {1399, "RTM"}, {2047, "SP1"}, {3042, "SP2"}, {4035, "SP3"}, {5000, "SP4"}, }
		
		local SP_LOOKUP_TABLE_2008 = { {1600, "RTM"}, {2531, "SP1"}, {4000, "SP2"}, {5500, "SP3"}, }
		
		local SP_LOOKUP_TABLE_2008R2 = { {1600, "RTM"}, {2500, "SP1"}, {4000, "SP2"}, }

		local SP_LOOKUP_TABLE_2012 = { {2100, "RTM"}, }
	
	
		if ( not self.brandedVersion ) then
			self:_InferProductVersion()
		end
		
		local spLookupTable
		if self.brandedVersion == "6.5" then spLookupTable = SP_LOOKUP_TABLE_6_5
			elseif self.brandedVersion == "7.0" then spLookupTable = SP_LOOKUP_TABLE_7
			elseif self.brandedVersion == "2000" then spLookupTable = SP_LOOKUP_TABLE_2000
			elseif self.brandedVersion == "2005" then spLookupTable = SP_LOOKUP_TABLE_2005
			elseif self.brandedVersion == "2008" then spLookupTable = SP_LOOKUP_TABLE_2008
			elseif self.brandedVersion == "2008 R2" then spLookupTable = SP_LOOKUP_TABLE_2008R2
			elseif self.brandedVersion == "2012" then spLookupTable = SP_LOOKUP_TABLE_2012
		end
		
		return spLookupTable
	
	end,
	
	
	--- Processes version data to determine (if possible) the product version,
	--  service pack level and patch status.
	_ParseVersionInfo = function(self)
	
		local spLookupTable = self:_GetSpLookupTable()
		
		if spLookupTable then
			
			local spLookupItr = 0
			-- Loop through the service pack levels until we find one whose revision
			-- number is the same as or lower than our revision number.
			while spLookupItr < #spLookupTable do
				spLookupItr = spLookupItr + 1
				
				if (spLookupTable[ spLookupItr ][1] == self.build ) then
					spLookupItr = spLookupItr
					break
				elseif (spLookupTable[ spLookupItr ][1] > self.build ) then
					-- The target revision number is lower than the first release
					if spLookupItr == 1 then
						self.servicePackLevel = "Pre-RTM"
					else
						-- we went too far - it's the previous SP, but with patches applied
						spLookupItr = spLookupItr - 1
					end
					break
				end
			end
			
			-- Now that we've identified the proper service pack level:
			if self.servicePackLevel ~= "Pre-RTM" then
				self.servicePackLevel = spLookupTable[ spLookupItr ][2]
				
				if ( spLookupTable[ spLookupItr ][1] == self.build ) then
					self.patched = false
				else
					self.patched = true
				end
			end
			
			-- Clean up some of our inferences. If the source of our revision number
			-- was the SSRP (SQL Server Browser) response, we need to recognize its
			-- limitations:
			--  * Versions of SQL Server prior to 2005 are reported with the RTM build
			--    number, regardless of the actual version (e.g. SQL Server 2000 is
			--    always 8.00.194).
			--  * Versions of SQL Server starting with 2005 (and going through at least
			--    2008) do better but are still only reported with the build number as
			--    of the last service pack (e.g. SQL Server 2005 SP3 with patches is
			--    still reported as 9.00.4035.00). 
			if ( self.source == "SSRP" ) then
				self.patched = nil
				
				if ( self.major <= 8 ) then
					self.servicePackLevel = nil
				end
			end
		end
		
		return true
	end,
	
	---
	ToString = function(self)
		local friendlyVersion = strbuf.new()
		if self.productName then
			friendlyVersion:concatbuf( self.productName )
			if self.servicePackLevel then
				friendlyVersion:concatbuf( " " )
				friendlyVersion:concatbuf( self.servicePackLevel )
			end
			if self.patched then
				friendlyVersion:concatbuf( "+" )
			end
		end
		
		return friendlyVersion:dump()
	end,
	
	--- Uses the information in this SqlServerVersionInformation object to
	--  populate the version information in an Nmap port table for a SQL Server
	--  TCP listener.
	--  
	--  @param self A SqlServerVersionInformation object
	--  @param port An Nmap port table corresponding to the instance
	PopulateNmapPortVersion = function(self, port)
		
		port.service = "ms-sql-s"
		port.version = port.version or {}
		port.version.name = "ms-sql-s"
		port.version.product = self.productName
		
		local versionString = strbuf.new()
		if self.source ~= "SSRP" then
			versionString:concatbuf( self.versionNumber )
			if self.servicePackLevel then
				versionString:concatbuf( "; " )
				versionString:concatbuf( self.servicePackLevel )
			end
			if self.patched then
				versionString:concatbuf( "+" )
			end
			port.version.version = versionString:dump()
		end
		
		return port
	end,
}


-- *************************************
-- SSRP (SQL Server Resolution Protocol)
-- ************************************* 
SSRP = 
{
	PORT = { number = 1434, protocol = "udp" },
	DEBUG_ID = "MSSQL-SSRP",
	
	MESSAGE_TYPE =
	{
		ClientBroadcast 		= 0x02,
		ClientUnicast			= 0x03,
		ClientUnicastInstance	= 0x04,
		ClientUnicastDAC		= 0x0F,
		ServerResponse			= 0x05,
	},
	
	--- Parses an SSRP string and returns a table containing one or more
	--  SqlServerInstanceInfo objects created from the parsed string.
	_ParseSsrpString = function( host, ssrpString )
		-- It would seem easier to just capture (.-;;) repeateadly, since
		-- each instance ends with ";;", but ";;" can also occur within the
		-- data, signifying an empty field (e.g. "...bv;;@COMPNAME;;tcp;1433;;...").
		-- So, instead, we'll split up the string ahead of time.
		-- See the SSRP specification for more details.
		
		local instanceStrings = {}
		local firstInstanceEnd, instanceString
		repeat
			firstInstanceEnd = ssrpString:find( ";ServerName;(.-);InstanceName;(.-);IsClustered;(.-);" )
			if firstInstanceEnd then
				instanceString = ssrpString:sub( 1, firstInstanceEnd )
				ssrpString = ssrpString:sub( firstInstanceEnd + 1 )
			else
				instanceString = ssrpString
			end
			
			table.insert( instanceStrings, instanceString )
		until (not firstInstanceEnd)
		stdnse.print_debug( 2, "%s: SSRP Substrings:\n  %s", SSRP.DEBUG_ID, stdnse.strjoin( "\n  ", instanceStrings ) )
		
		local instances = {}
		for _, instanceString in ipairs( instanceStrings ) do
	  		local instance = SqlServerInstanceInfo:new()
	  		local version = SqlServerVersionInfo:new()
	  		instance.version = version
	  		
	  		instance.host = host
	  		instance.serverName = instanceString:match( "ServerName;(.-);")
	  		instance.instanceName = instanceString:match( "InstanceName;(.-);")
	  		instance:SetIsClustered( instanceString:match( "IsClustered;(.-);") )
	  		version:SetVersionNumber( instanceString:match( "Version;(.-);"), "SSRP" )
	  		
	  		local tcpPort = tonumber( instanceString:match( ";tcp;(.-);") )
	  		if tcpPort then instance.port = {number = tcpPort, protocol = "tcp"} end 
	  		
	  		local pipeName = instanceString:match( ";np;(.-);")
	  		local status, pipeSubPath = namedpipes.get_pipe_subpath( pipeName )
	    	if status then
	    		pipeName = namedpipes.make_pipe_name( host.ip, pipeSubPath )
	    	elseif pipeName ~= nil then
				stdnse.print_debug( 1, "%s: Invalid pipe name:\n%s", SSRP.DEBUG_ID, pipeName )
	    	end
	    	instance.pipeName = pipeName
			
			table.insert( instances, instance )
		end
		
		return instances
	end,
	
	---
	_ProcessResponse = function( host, responseData )
		local instances

		local pos, messageType, dataLength = 1, nil, nil
		pos, messageType, dataLength = bin.unpack("<CS", responseData, 1)
		-- extract the response data (i.e. everything after the 3-byte header)
		responseData = responseData:sub(4)
		stdnse.print_debug( 2, "%s: SSRP Data: %s", SSRP.DEBUG_ID, responseData )
		if ( messageType ~= SSRP.MESSAGE_TYPE.ServerResponse or
			 dataLength ~= responseData:len() ) then
			
			stdnse.print_debug( 2, "%s: Invalid SSRP response. Type: 0x%02x, Length: %d, Actual length: %d",
				SSRP.DEBUG_ID, messageType, dataLength, responseData:len() )
		else
			instances = SSRP._ParseSsrpString( host, responseData )
		end
		
		return instances
	end,
	
	---	Attempts to retrieve information about SQL Server instances by querying
	--	the SQL Server Browser service on a host.
	--
	--	@param host A host table for the target host
	--	@param port (Optional) A port table for the target SQL Server Browser service
	--	@return (status, result) If status is true, result is a table of
	--		SqlServerInstanceInfo objects. If status is false, result is an
	--		error message. 
	DiscoverInstances = function( host, port )
		port = port or SSRP.PORT
		
		if ( SCANNED_PORTS_ONLY and nmap.get_port_state( host, port ) == nil ) then
			stdnse.print_debug( 2, "%s: Discovery disallowed: scanned-ports-only is set and port %d was not scanned", SSRP.DEBUG_ID, port.number )
			return false, "Discovery disallowed: scanned-ports-only"
		end
		
		local socket = nmap.new_socket("udp")
		socket:set_timeout(5000)
		
		if ( port.number ~= SSRP.PORT.number ) then
			stdnse.print_debug( 1, "%s: DiscoverInstances() called with non-standard port (%d)", SSRP.DEBUG_ID, port.number )
		end
		
		local status, err = socket:connect( host, port )
		if ( not(status) ) then	return false, err end
		status, err = socket:send( bin.pack( "C", SSRP.MESSAGE_TYPE.ClientUnicast ) )
		if ( not(status) ) then	return false, err end
		
		local responseData, instances_host
		status, responseData = socket:receive()
		if ( not(status) ) then	return false, responseData
		else
			instances_host = SSRP._ProcessResponse( host, responseData )
		end
		socket:close()
		
		return status, instances_host
	end,
	
	
	---	Attempts to retrieve information about SQL Server instances by querying
	--	the SQL Server Browser service on a broadcast domain.
	--
	--	@param host A host table for the broadcast specification
	--	@param port (Optional) A port table for the target SQL Server Browser service
	--	@return (status, result) If status is true, result is a table of
	--		tables containing SqlServerInstanceInfo objects. The top-level table
	--		is indexed by IP address. If status is false, result is an
	--		error message. 
	DiscoverInstances_Broadcast = function( host, port )
		port = port or SSRP.PORT
		
		local socket = nmap.new_socket("udp")
		socket:set_timeout(5000)
		local instances_all = {}
		
		if ( port.number ~= SSRP.PORT.number ) then
			stdnse.print_debug( 1, "%S: DiscoverInstances_Broadcast() called with non-standard port (%d)", SSRP.DEBUG_ID, port.number )
		end
		
		local status, err = socket:sendto(host, port, bin.pack( "C", SSRP.MESSAGE_TYPE.ClientBroadcast ))
		if ( not(status) ) then	return false, err end
		
		while ( status ) do
			local responseData
			status, responseData = socket:receive()
			if ( status ) then
				local remoteIp, _
				status, _, _, remoteIp, _ = socket:get_info()
				local instances_host = SSRP._ProcessResponse( {ip = remoteIp, name = ""}, responseData )
				instances_all[ remoteIp ] = instances_host
			end
		end
		socket:close()
		
		return true, instances_all
	end,
}



-- *************************
-- TDS (Tabular Data Stream)
-- *************************

-- TDS packet types
PacketType =
{
	Query = 0x01,
	Response = 0x04,
	Login = 0x10,
	NTAuthentication = 0x11,
	PreLogin = 0x12,
}

-- TDS response token types
TokenType = 
{
	ReturnStatus         = 0x79,
	TDS7Results          = 0x81,
	ErrorMessage         = 0xAA,
	InformationMessage   = 0xAB,
	LoginAcknowledgement = 0xAD,
	Row                  = 0xD1,
	OrderBy              = 0xA9,
	EnvironmentChange    = 0xE3,
	NTLMSSP_CHALLENGE    = 0xed,
	Done                 = 0xFD,
	DoneProc             = 0xFE,
	DoneInProc           = 0xFF,
}

-- SQL Server/Sybase data types
DataTypes = 
{
	SQLTEXT       = 0x23,
	GUIDTYPE      = 0x24,
	SYBINTN       = 0x26,
	SYBINT2       = 0x34,
	SYBINT4       = 0x38,
	SYBDATETIME   = 0x3D,
	NTEXTTYPE     = 0x63,
	BITNTYPE      = 0x68,
	DECIMALNTYPE  = 0x6A,
	NUMERICNTYPE  = 0x6C,
	FLTNTYPE      = 0x6D,
	MONEYNTYPE    = 0x6E,
	SYBDATETIMN   = 0x6F,
	XSYBVARBINARY = 0xA5,
	XSYBVARCHAR   = 0xA7,
	BIGBINARYTYPE = 0xAD,
	BIGCHARTYPE   = 0xAF,
	XSYBNVARCHAR  = 0xE7,
	SQLNCHAR      = 0xEF,
}

-- SQL Server login error codes
-- See http://msdn.microsoft.com/en-us/library/ms131024.aspx
LoginErrorType = 
{
	AccountLockedOut						= 15113,
	NotAssociatedWithTrustedConnection		= 18452,	-- This probably means that the server is set for Windows authentication only
	InvalidUsernameOrPassword				= 18456,
	PasswordChangeFailed_PasswordNotAllowed	= 18463,
	PasswordChangeFailed_PasswordTooShort	= 18464,
	PasswordChangeFailed_PasswordTooLong	= 18465,
	PasswordChangeFailed_PasswordNotComplex	= 18466,
	PasswordChangeFailed_PasswordFilter		= 18467,
	PasswordChangeFailed_UnexpectedError	= 18468,
	PasswordExpired							= 18487,
	PasswordMustChange						= 18488,
}

LoginErrorMessage = {}
for i, v in pairs(LoginErrorType) do
	LoginErrorMessage[v] = i
end

-- "static" ColumInfo parser class
ColumnInfo = 
{

	Parse =
	{

		[DataTypes.SQLTEXT] = function( data, pos )
			local colinfo = {}
			local tmp
			
			pos, colinfo.unknown, colinfo.codepage, colinfo.flags, colinfo.charset = bin.unpack("<ISSC", data, pos )

			pos, colinfo.tablenamelen = bin.unpack("s", data, pos )
			pos, colinfo.tablename		= bin.unpack("A" .. (colinfo.tablenamelen * 2), data, pos)
			pos, colinfo.msglen			  = bin.unpack("<C", data, pos )
			pos, tmp = bin.unpack("A" .. (colinfo.msglen * 2), data, pos)

			colinfo.text = Util.FromWideChar(tmp)

			return pos, colinfo
		end,

		[DataTypes.GUIDTYPE] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.SYBINTN](data, pos)
		end,

		[DataTypes.SYBINTN] = function( data, pos )
			local colinfo = {}
			local tmp

			pos, colinfo.unknown, colinfo.msglen = bin.unpack("<CC", data, pos)
			pos, tmp = bin.unpack("A" .. (colinfo.msglen * 2), data, pos )
			colinfo.text = Util.FromWideChar(tmp)

			return pos, colinfo
		end,

		[DataTypes.SYBINT2] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.SYBDATETIME](data, pos)
		end,

		[DataTypes.SYBINT4] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.SYBDATETIME](data, pos)
		end,

		[DataTypes.SYBDATETIME] = function( data, pos )
			local colinfo = {}
			local tmp
		
			pos, colinfo.msglen = bin.unpack("C", data, pos)
			pos, tmp = bin.unpack("A" .. (colinfo.msglen * 2), data, pos )
			colinfo.text = Util.FromWideChar(tmp)
	
			return pos, colinfo
		end,

		[DataTypes.NTEXTTYPE] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.SQLTEXT](data, pos)
		end,

		[DataTypes.BITNTYPE] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.SYBINTN](data, pos)
		end,

		[DataTypes.DECIMALNTYPE] = function( data, pos )
			local colinfo = {}
			local tmp

			pos, colinfo.unknown, colinfo.precision, colinfo.scale = bin.unpack("<CCC", data, pos)
			pos, colinfo.msglen = bin.unpack("<C",data,pos)
			pos, tmp = bin.unpack("A" .. (colinfo.msglen * 2), data, pos )
			colinfo.text = Util.FromWideChar(tmp)

			return pos, colinfo
		end,

		[DataTypes.NUMERICNTYPE] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.DECIMALNTYPE](data, pos)
		end,

		[DataTypes.FLTNTYPE] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.SYBINTN](data, pos)
		end,

		[DataTypes.MONEYNTYPE] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.SYBINTN](data, pos)
		end,

		[DataTypes.SYBDATETIMN] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.SYBINTN](data, pos)
		end,

		[DataTypes.XSYBVARBINARY] = function( data, pos )
			local colinfo = {}
			local tmp

			pos, colinfo.lts, colinfo.msglen = bin.unpack("<SC", data, pos)
			pos, tmp = bin.unpack("A" .. (colinfo.msglen * 2), data, pos )
			colinfo.text = Util.FromWideChar(tmp)
			
			return pos, colinfo
		end,

		[DataTypes.XSYBVARCHAR] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.XSYBNVARCHAR](data, pos)
		end,

		[DataTypes.BIGBINARYTYPE] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.XSYBVARBINARY](data, pos)
		end,

		[DataTypes.BIGCHARTYPE] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.XSYBNVARCHAR](data, pos)
		end,

		[DataTypes.XSYBNVARCHAR] = function( data, pos )
			local colinfo = {}
			local tmp

			pos, colinfo.lts, colinfo.codepage, colinfo.flags, colinfo.charset, 
			colinfo.msglen = bin.unpack("<SSSCC", data, pos )
			pos, tmp = bin.unpack("A" .. (colinfo.msglen * 2), data, pos)
			colinfo.text = Util.FromWideChar(tmp)

			return pos, colinfo
		end,

		[DataTypes.SQLNCHAR] = function( data, pos )
			return ColumnInfo.Parse[DataTypes.XSYBNVARCHAR](data, pos)
		end,
  
	}
	
}

-- "static" ColumData parser class
ColumnData = 
{
	Parse = {

		[DataTypes.SQLTEXT] = function( data, pos )
			local len, coldata
			
			-- The first len value is the size of the meta data block
			-- for non-null values this seems to be 0x10 / 16 bytes
			pos, len = bin.unpack( "<C", data, pos )

			if ( len == 0 ) then
				return pos, 'Null'
			end

			-- Skip over the text update time and date values, we don't need them
			-- We may come back add parsing for this information.
			pos = pos + len 

			-- skip a label, should be 'dummyTS'
			pos = pos + 8

			-- extract the actual data
			pos, len = bin.unpack( "<I", data, pos )
			pos, coldata = bin.unpack( "A"..len, data, pos )

			return pos, coldata
		end,

		[DataTypes.GUIDTYPE] = function( data, pos )
			local len, coldata, index, nextdata
			local hex = {}
			pos, len = bin.unpack("C", data, pos)
			
			if ( len == 0 ) then
				return pos, 'Null'
				
			elseif ( len == 16 ) then
				
				-- Return the first 8 bytes
				for index=1, 8 do
					pos, hex[index] = bin.unpack("H", data, pos)
				end
				
				-- reorder the bytes
				coldata = hex[4] .. hex[3] .. hex[2] .. hex[1]
				coldata = coldata .. '-' .. hex[6] .. hex[5]
				coldata = coldata .. '-' .. hex[8] .. hex[7]
				
				pos, nextdata = bin.unpack("H2", data, pos)
				coldata = coldata .. '-' .. nextdata		 
				
				pos, nextdata = bin.unpack("H6", data, pos)
				coldata = coldata .. '-' .. nextdata
			 
			else
				 stdnse.print_debug("Unhandled length (%d) for GUIDTYPE", len)
				return pos + len, 'Unsupported Data'
			end	

			return pos, coldata
		end,	
		
		[DataTypes.SYBINTN] = function( data, pos )
			local len, num
			pos, len = bin.unpack("C", data, pos)

      if ( len == 0 ) then
        return pos, 'Null'
			elseif ( len == 1 ) then
				return bin.unpack("C", data, pos)
			elseif ( len == 2 ) then
				return bin.unpack("<s", data, pos)
			elseif ( len == 4 ) then
				return bin.unpack("<i", data, pos)
			elseif ( len == 8 ) then
				return bin.unpack("<l", data, pos)
			else
				return -1, ("Unhandled length (%d) for SYBINTN"):format(len)
			end

			return -1, "Error"
		end,
		
		[DataTypes.SYBINT2] = function( data, pos )
			local num
			pos, num = bin.unpack("<S", data, pos)
			
			return pos, num
		end,
		
		[DataTypes.SYBINT4] = function( data, pos )
			local num
			pos, num = bin.unpack("<I", data, pos)
			
			return pos, num
		end,

		[DataTypes.SYBDATETIME] = function( data, pos )
			local hi, lo, result_seconds, result
			local tds_epoch, system_epoch, tds_offset_seconds

			pos, hi, lo = bin.unpack("<iI", data, pos)

			tds_epoch = os.time( {year = 1900, month = 1, day = 1, hour = 00, min = 00, sec = 00, isdst = nil} )
			-- determine the offset between the tds_epoch and the local system epoch
			system_epoch       = os.time( os.date("*t", 0))
			tds_offset_seconds = os.difftime(tds_epoch,system_epoch)
 
			result_seconds = (hi*24*60*60) + (lo/300)

			result = os.date("!%b %d, %Y %H:%M:%S", tds_offset_seconds + result_seconds )
			return pos, result
		end,
 
		[DataTypes.NTEXTTYPE] = function( data, pos )
			local len, coldata

			-- The first len value is the size of the meta data block
			pos, len = bin.unpack( "<C", data, pos )

			if ( len == 0 ) then
				return pos, 'Null'
			end

			-- Skip over the text update time and date values, we don't need them
			-- We may come back add parsing for this information.
			pos = pos + len 

			-- skip a label, should be 'dummyTS'
			pos = pos + 8

			-- extract the actual data
			pos, len = bin.unpack( "<I", data, pos )
			pos, coldata = bin.unpack( "A"..len, data, pos )

			return pos, Util.FromWideChar(coldata)
		end,
   
		[DataTypes.BITNTYPE] = function( data, pos )
			return ColumnData.Parse[DataTypes.SYBINTN](data, pos)
		end,

		[DataTypes.DECIMALNTYPE] = function( precision, scale, data, pos )
			local len, sign, format_string, coldata

			pos, len = bin.unpack("<C", data, pos)

			if ( len == 0 ) then
				return pos, 'Null'
			end

			pos, sign = bin.unpack("<C", data, pos)

			-- subtract 1 from data len to account for sign byte
			len = len - 1

			if ( len == 2 ) then
				pos, coldata = bin.unpack("<S", data, pos)
			elseif ( len == 4 ) then
				pos, coldata =	bin.unpack("<I", data, pos)
			elseif ( len == 8 ) then
				pos, coldata =	bin.unpack("<L", data, pos)
			else
				stdnse.print_debug("Unhandled length (%d) for DECIMALNTYPE", len)
				return pos + len, 'Unsupported Data'
			end

			if ( sign == 0 ) then
				coldata = coldata * -1
			end
			
			coldata = coldata * (10^-scale)
			-- format the return information to reduce truncation by lua
			format_string = string.format("%%.%if", scale)
			coldata = string.format(format_string,coldata)
			
			return pos, coldata
		end,
		
		[DataTypes.NUMERICNTYPE] = function( precision, scale, data, pos )
			return ColumnData.Parse[DataTypes.DECIMALNTYPE]( precision, scale, data, pos )
		end,
 
		[DataTypes.SYBDATETIME] = function( data, pos )
			local hi, lo, result_seconds, result
			local tds_epoch, system_epoch, tds_offset_seconds

			pos, hi, lo = bin.unpack("<iI", data, pos)

			tds_epoch = os.time( {year = 1900, month = 1, day = 1, hour = 00, min = 00, sec = 00, isdst = nil} )
			-- determine the offset between the tds_epoch and the local system epoch
			system_epoch       = os.time( os.date("*t", 0))
			tds_offset_seconds = os.difftime(tds_epoch,system_epoch)
 
			result_seconds = (hi*24*60*60) + (lo/300)

			result = os.date("!%b %d, %Y %H:%M:%S", tds_offset_seconds + result_seconds )
			return pos, result
		end,
 
		[DataTypes.BITNTYPE] = function( data, pos )
			return ColumnData.Parse[DataTypes.SYBINTN](data, pos)
		end,

		[DataTypes.NTEXTTYPE] = function( data, pos )
		local len, coldata

			-- The first len value is the size of the meta data block
			pos, len = bin.unpack( "<C", data, pos )

			if ( len == 0 ) then
				return pos, 'Null'
			end

			-- Skip over the text update time and date values, we don't need them
			-- We may come back add parsing for this information.
			pos = pos + len 

			-- skip a label, should be 'dummyTS'
			pos = pos + 8

			-- extract the actual data
			pos, len = bin.unpack( "<I", data, pos )
			pos, coldata = bin.unpack( "A"..len, data, pos )

			return pos, Util.FromWideChar(coldata)
		end,

		[DataTypes.FLTNTYPE] = function( data, pos )
			local len, coldata
			pos, len = bin.unpack("<C", data, pos)

			if ( len == 0 ) then
				return pos, 'Null'
			elseif ( len == 4 ) then
				pos, coldata = bin.unpack("f", data, pos)
			elseif ( len == 8 ) then
				pos, coldata = bin.unpack("<d", data, pos)
			end

			return pos, coldata
		end,

		[DataTypes.MONEYNTYPE] = function( data, pos )
			local len, value, coldata, hi, lo
			pos, len = bin.unpack("C", data, pos)

			if ( len == 0 ) then
				return pos, 'Null'
			elseif (	len == 4 ) then
				--type smallmoney
				pos, value =	bin.unpack("<i", data, pos)
			elseif ( len == 8 ) then
				-- type money
				pos, hi,lo = bin.unpack("<II", data, pos)
				value = ( hi * 4294967296 ) + lo
			else
				return -1, ("Unhandled length (%d) for MONEYNTYPE"):format(len)
			end

			-- the datatype allows for 4 decimal places after the period to support various currency types.
			-- forcing to string to avoid truncation
			coldata = string.format("%.4f",value/10000)

			return pos, coldata
		end,

		[DataTypes.SYBDATETIMN] = function( data, pos )
			local len, coldata

			pos, len = bin.unpack( "<C", data, pos )

			if ( len == 0 ) then
				return pos, 'Null'
			elseif ( len == 4 ) then
				-- format is smalldatetime
				local days, mins
				pos, days, mins = bin.unpack("<SS", data, pos)
				
				local tds_epoch = os.time( {year = 1900, month = 1, day = 1, hour = 00, min = 00, sec = 00, isdst = nil} )
				-- determine the offset between the tds_epoch and the local system epoch
				local system_epoch			 = os.time( os.date("*t", 0))
				local tds_offset_seconds = os.difftime(tds_epoch,system_epoch)

				local result_seconds = (days*24*60*60) + (mins*60)
				coldata = os.date("!%b %d, %Y %H:%M:%S", tds_offset_seconds + result_seconds )
				
				return pos,coldata
				
			elseif ( len == 8 ) then
				-- format is datetime
				return ColumnData.Parse[DataTypes.SYBDATETIME](data, pos)
			else
				return -1, ("Unhandled length (%d) for SYBDATETIMN"):format(len)
			end
		 
		end,

		[DataTypes.XSYBVARBINARY] = function( data, pos )
			local len, coldata

			pos, len = bin.unpack( "<S", data, pos )

			if ( len == 65535 ) then
				return pos, 'Null'
			else
				pos, coldata = bin.unpack( "A"..len, data, pos )
				return pos, "0x" .. select(2, bin.unpack("H"..coldata:len(), coldata ) )
			end

			return -1, "Error"
		end,
  
		[DataTypes.XSYBVARCHAR] = function( data, pos )
			local len, coldata

			pos, len = bin.unpack( "<S", data, pos )
			if ( len == 65535 ) then
				return pos, 'Null'
			end

			pos, coldata = bin.unpack( "A"..len, data, pos )

			return pos, coldata
		end,

		[DataTypes.BIGBINARYTYPE] = function( data, pos )
			return ColumnData.Parse[DataTypes.XSYBVARBINARY](data, pos)
		end,

		[DataTypes.BIGCHARTYPE] = function( data, pos )
			return ColumnData.Parse[DataTypes.XSYBVARCHAR](data, pos)
		end,

		[DataTypes.XSYBNVARCHAR] = function( data, pos )
			local len, coldata

			pos, len = bin.unpack( "<S", data, pos )
			if ( len == 65535 ) then
				return pos, 'Null'
			end
			pos, coldata = bin.unpack( "A"..len, data, pos )

			return pos, Util.FromWideChar(coldata)
		end,

		[DataTypes.SQLNCHAR] = function( data, pos )
			return ColumnData.Parse[DataTypes.XSYBNVARCHAR](data, pos)
		end,

	}
}

-- "static" Token parser class
Token = 
{

	Parse = {
		--- Parse error message tokens
		--
		-- @param data string containing "raw" data
		-- @param pos number containing offset into data
		-- @return pos number containing new offset after parse
		-- @return token table containing token specific fields
		[TokenType.ErrorMessage] = function( data, pos )
			local token = {}
			local tmp

			token.type = TokenType.ErrorMessage
			pos, token.size, token.errno, token.state, token.severity, token.errlen = bin.unpack( "<SICCS", data, pos )
			pos, tmp = bin.unpack("A" .. (token.errlen * 2), data, pos )
			token.error = Util.FromWideChar(tmp)
			pos, token.srvlen = bin.unpack("C", data, pos)
			pos, tmp = bin.unpack("A" .. (token.srvlen * 2), data, pos )
			token.server = Util.FromWideChar(tmp)
			pos, token.proclen = bin.unpack("C", data, pos)
			pos, tmp = bin.unpack("A" .. (token.proclen * 2), data, pos )
			token.proc = Util.FromWideChar(tmp)
			pos, token.lineno = bin.unpack("<S", data, pos)

			return pos, token
		end,
		
		--- Parse environment change tokens
		-- (This function is not implemented and simply moves the pos offset)
		--
		-- @param data string containing "raw" data
		-- @param pos number containing offset into data
		-- @return pos number containing new offset after parse
		-- @return token table containing token specific fields		
		[TokenType.EnvironmentChange] = function( data, pos )
			local token = {}
			local tmp
			
			token.type = TokenType.EnvironmentChange
			pos, token.size = bin.unpack("<S", data, pos)
		
			return pos + token.size, token
		end,
	
		--- Parse information message tokens
		--
		-- @param data string containing "raw" data
		-- @param pos number containing offset into data
		-- @return pos number containing new offset after parse
		-- @return token table containing token specific fields		
		[TokenType.InformationMessage] = function( data, pos )
			local pos, token = Token.Parse[TokenType.ErrorMessage]( data, pos )
			token.type = TokenType.InformationMessage
			return pos, token
		end,
	
		--- Parse login acknowledgment tokens
		--
		-- @param data string containing "raw" data
		-- @param pos number containing offset into data
		-- @return pos number containing new offset after parse
		-- @return token table containing token specific fields			
		[TokenType.LoginAcknowledgement] = function( data, pos )
			local token = {}
			local _
			
			token.type = TokenType.LoginAcknowledgement
			pos, token.size, _, _, _, _, token.textlen = bin.unpack( "<SCCCSC", data, pos )
			pos, token.text = bin.unpack("A" .. token.textlen * 2, data, pos)
			pos, token.version = bin.unpack("<I", data, pos )

			return pos, token
		end,
	
		--- Parse done tokens
		--
		-- @param data string containing "raw" data
		-- @param pos number containing offset into data
		-- @return pos number containing new offset after parse
		-- @return token table containing token specific fields			
		[TokenType.Done] = function( data, pos )
			local token = {}
			
			token.type = TokenType.Done
			pos, token.flags, token.operation, token.rowcount = bin.unpack( "<SSI", data, pos )
			
			return pos, token
		end,

		--- Parses a DoneProc token recieved after executing a SP
		--
		-- @param data string containing "raw" data
		-- @param pos number containing offset into data
		-- @return pos number containing new offset after parse
		-- @return token table containing token specific fields				
		[TokenType.DoneProc] = function( data, pos )
			local token
			pos, token = Token.Parse[TokenType.Done]( data, pos )
			token.type = TokenType.DoneProc
			
			return pos, token
		end,

		
		--- Parses a DoneInProc token recieved after executing a SP
		--
		-- @param data string containing "raw" data
		-- @param pos number containing offset into data
		-- @return pos number containing new offset after parse
		-- @return token table containing token specific fields				
		[TokenType.DoneInProc] = function( data, pos )
			local token
			pos, token = Token.Parse[TokenType.Done]( data, pos )
			token.type = TokenType.DoneInProc
			
			return pos, token
		end,
		
		--- Parses a ReturnStatus token
		--
		-- @param data string containing "raw" data
		-- @param pos number containing offset into data
		-- @return pos number containing new offset after parse
		-- @return token table containing token specific fields	
		[TokenType.ReturnStatus] = function( data, pos )
			local token = {}
			
			pos, token.value = bin.unpack("<i", data, pos)
			token.type = TokenType.ReturnStatus
			return pos, token
		end,
		
		--- Parses a OrderBy token
		--
		-- @param data string containing "raw" data
		-- @param pos number containing offset into data
		-- @return pos number containing new offset after parse
		-- @return token table containing token specific fields						
		[TokenType.OrderBy] = function( data, pos )
			local token = {}
			
			pos, token.size = bin.unpack("<S", data, pos)
			token.type = TokenType.OrderBy
			return pos + token.size, token
		end,

		
		--- Parse TDS result tokens
		--
		-- @param data string containing "raw" data
		-- @param pos number containing offset into data
		-- @return pos number containing new offset after parse
		-- @return token table containing token specific fields			
		[TokenType.TDS7Results] = function( data, pos )
			local token = {}
			local _

			token.type = TokenType.TDS7Results
			pos, token.count = bin.unpack( "<S", data, pos )
			token.colinfo = {}

			for i=1, token.count do
				local colinfo = {}
				local usertype, flags, ttype

				pos, usertype, flags, ttype = bin.unpack("<SSC", data, pos )
				if ( not(ColumnInfo.Parse[ttype]) ) then
					return -1, ("Unhandled data type: 0x%X"):format(ttype)
				end

				pos, colinfo = ColumnInfo.Parse[ttype]( data, pos )
				colinfo.usertype = usertype
				colinfo.flags = flags
				colinfo.type = ttype
				
				table.insert( token.colinfo, colinfo )
			end
			return pos, token
		end,
		
		
		[TokenType.NTLMSSP_CHALLENGE] = function(data, pos)
			local pos, len, ntlmssp, msgtype = bin.unpack("<SA8I", data, pos)
			local NTLMSSP_CHALLENGE = 2

			if ( ntlmssp ~= "NTLMSSP\0" or msgtype ~= NTLMSSP_CHALLENGE ) then
				return -1, "Failed to process NTLMSSP Challenge"
			end
			
			local ntlm_challenge = data:sub( 28, 35 )
			pos = pos + len - 13
			return pos, ntlm_challenge
		end,
	},
	
	--- Parses the first token at positions pos
	--
	-- @param data string containing "raw" data
	-- @param pos number containing offset into data
	-- @return pos number containing new offset after parse or -1 on error
	-- @return token table containing token specific fields	or error message on error		
	ParseToken = function( data, pos )
		local ttype
		pos, ttype = bin.unpack("C", data, pos)
		if ( not(Token.Parse[ttype]) ) then
			stdnse.print_debug( 1, "%s: No parser for token type 0x%X", "MSSQL", ttype )
			return -1, ("No parser for token type: 0x%X"):format( ttype )
		end
			
		return Token.Parse[ttype](data, pos)
	end,
	
}


--- QueryPacket class
QueryPacket = 
{
	new = function(self,o)
		o = o or {}
        setmetatable(o, self)
        self.__index = self
		return o
    end,
	
	SetQuery = function( self, query )
		self.query = query
	end,
	
	--- Returns the query packet as string
	--
	-- @return string containing the authentication packet
	ToString = function( self )
		return PacketType.Query, Util.ToWideChar( self.query )
	end,
	
}


--- PreLoginPacket class
PreLoginPacket = 
{
	-- TDS pre-login option types
	OPTION_TYPE = {
		Version = 0x00,
		Encryption = 0x01,
		InstOpt = 0x02,
		ThreadId = 0x03,
		MARS = 0x04,
		Terminator = 0xFF,
	},
	
	
	versionInfo = nil,
	_requestEncryption = 0,
	_instanceName = "",
	_threadId = 0, -- Dummy value; will be filled in later
	_requestMars = nil,

	new = function(self,o)
		o = o or {}
        setmetatable(o, self)
        self.__index = self
		return o
    end,
	
	--- Sets the client version (default = 9.00.1399.00)
	--
	-- @param versionInfo A SqlServerVersionInfo object with the client version information
	SetVersion = function(self, versionInfo)
		self._versionInfo = versionInfo
	end,
	
	--- Sets whether to request encryption (default = false)
	--
	-- @param requestEncryption A boolean indicating whether encryption will be requested
	SetRequestEncryption = function(self, requestEncryption)
		if requestEncryption then
			self._requestEncryption = 1
		else
			self._requestEncryption = 0
		end
	end,
	
	--- Sets whether to request MARS support (default = undefined)
	--
	-- @param requestMars A boolean indicating whether MARS support will be requested
	SetRequestMars = function(self, requestMars)
		if requestMars then
			self._requestMars = 1
		else
			self._requestMars = 0
		end
	end,

	--- Sets the instance name of the target
	--
	-- @param instanceName A string containing the name of the instance	
	SetInstanceName = function(self, instanceName)
		self._instanceName = instanceName or ""
	end,
	
	--- Returns the pre-login packet as a byte string
	--
	-- @return byte string containing the pre-login packet
	ToBytes = function(self)
		-- Lengths for the values of TDS pre-login option fields
		local OPTION_LENGTH_CLIENT = {
			[PreLoginPacket.OPTION_TYPE.Version] = 6,
			[PreLoginPacket.OPTION_TYPE.Encryption] = 1,
			[PreLoginPacket.OPTION_TYPE.InstOpt] = -1,
			[PreLoginPacket.OPTION_TYPE.ThreadId] = 4,
			[PreLoginPacket.OPTION_TYPE.MARS] = 1,
			[PreLoginPacket.OPTION_TYPE.Terminator] = 0,
		}
	
		local data, optionLength, optionType = "", 0, 0
		local offset = 1 -- Terminator
		offset = offset + 5 -- Version
		offset = offset + 5 -- Encryption
		offset = offset + 5 -- InstOpt
		offset = offset + 5 -- ThreadId
		if self._requestMars then offset = offset + 3 end -- MARS
		
		if not self.versionInfo then
			self.versionInfo = SqlServerVersionInfo:new()
			self.versionInfo:SetVersionNumber( "9.00.1399.00" )
		end
		
		optionType = PreLoginPacket.OPTION_TYPE.Version
		optionLength = OPTION_LENGTH_CLIENT[ optionType ]
		data = data .. bin.pack( ">CSS", optionType, offset, optionLength )
		offset = offset + optionLength
		
		optionType = PreLoginPacket.OPTION_TYPE.Encryption
		optionLength = OPTION_LENGTH_CLIENT[ optionType ]
		data = data .. bin.pack( ">CSS", optionType, offset, optionLength )
		offset = offset + optionLength
		
		optionType = PreLoginPacket.OPTION_TYPE.InstOpt
		optionLength = #self._instanceName + 1 --(string length + null-terminator)
		data = data .. bin.pack( ">CSS", optionType, offset, optionLength )
		offset = offset + optionLength
		
		optionType = PreLoginPacket.OPTION_TYPE.ThreadId
		optionLength = OPTION_LENGTH_CLIENT[ optionType ]
		data = data .. bin.pack( ">CSS", optionType, offset, optionLength )
		offset = offset + optionLength
		
		if self.requestMars then
			optionType = PreLoginPacket.OPTION_TYPE.MARS
			optionLength = OPTION_LENGTH_CLIENT[ optionType ]
			data = data .. bin.pack( ">CSS", optionType, offset, optionLength )
			offset = offset + optionLength
		end
		
		data = data .. bin.pack( "C", PreLoginPacket.OPTION_TYPE.Terminator )
		
		-- Now that the pre-login headers are done, write the data
		data = data .. bin.pack( ">CCSS", self.versionInfo.major, self.versionInfo.minor,
					self.versionInfo.build, self.versionInfo.subBuild )
		data = data .. bin.pack( "C", self._requestEncryption )
		data = data .. bin.pack( "z", self._instanceName )
		data = data .. bin.pack( "<I", self._threadId )
		if self.requestMars then
			data = data .. bin.pack( "C", self._requestMars )
		end
		
		return PacketType.PreLogin, data
	end,
	
	---	Reads a byte-string and creates a PreLoginPacket object from it. This is
	--	intended to handle the server's response to a pre-login request. 
	FromBytes = function( bytes )
		local OPTION_LENGTH_SERVER = {
			[PreLoginPacket.OPTION_TYPE.Version] = 6,
			[PreLoginPacket.OPTION_TYPE.Encryption] = 1,
			[PreLoginPacket.OPTION_TYPE.InstOpt] = -1,
			[PreLoginPacket.OPTION_TYPE.ThreadId] = 0, -- According to the TDS spec, this value should be empty from the server
			[PreLoginPacket.OPTION_TYPE.MARS] = 1,
			[PreLoginPacket.OPTION_TYPE.Terminator] = 0,
		}
		
		
		local status, pos = false, 1
		local preLoginPacket = PreLoginPacket:new()
		
		while true do
		
			local optionType, optionPos, optionLength, optionData, expectedOptionLength, _
			pos, optionType = bin.unpack("C", bytes, pos)
			if ( optionType == PreLoginPacket.OPTION_TYPE.Terminator ) then
				status = true
				break
			end
			expectedOptionLength = OPTION_LENGTH_SERVER[ optionType ]
			if ( not expectedOptionLength ) then
				stdnse.print_debug( 2, "%s: Unrecognized pre-login option type: %s", "MSSQL", optionType )
				expectedOptionLength = -1
			end
			
			pos, optionPos, optionLength = bin.unpack(">SS", bytes, pos)
			if not (optionPos and optionLength) then
				stdnse.print_debug( 2, "%s: Could not unpack optionPos and optionLength.", "MSSQL" )
				return false, "Invalid pre-login response"
			end
			
			optionPos = optionPos + 1 -- convert from 0-based index to 1-based index
			if ( (optionPos + optionLength) > (#bytes + 1) ) then
				stdnse.print_debug( 2, "%s: Pre-login response: pos+len for option type %s is beyond end of data.", "MSSQL", optionType )
				stdnse.print_debug( 2, "%s:   (optionPos: %s) (optionLength: %s)", "MSSQL", optionPos, optionLength )
				return false, "Invalid pre-login response"
			end
			
			
			if ( optionLength ~= expectedOptionLength and expectedOptionLength ~= -1 ) then
				stdnse.print_debug( 2, "%s: Option data is incorrect size in pre-login response. ", "MSSQL" )
				stdnse.print_debug( 2, "%s:   (optionType: %s) (optionLength: %s)", "MSSQL", optionType, optionLength )
				return false, "Invalid pre-login response"
			end
			optionData = bytes:sub( optionPos, optionPos + optionLength - 1 )
			if #optionData ~= optionLength then
				stdnse.print_debug( 2, "%s: Could not read sufficient bytes from version data.", "MSSQL" )
				return false, "Invalid pre-login response"
			end

			if ( optionType == PreLoginPacket.OPTION_TYPE.Version ) then
				local major, minor, build, subBuild, version
				major = string.byte( optionData:sub( 1, 1 ) )
				minor = string.byte( optionData:sub( 2, 2 ) )
				build = (string.byte( optionData:sub( 3, 3 ) ) * 256) + string.byte( optionData:sub( 4, 4 ) )
				subBuild = (string.byte( optionData:sub( 5, 5 ) ) * 256) + string.byte( optionData:sub( 6, 6 ) )
				
				version = SqlServerVersionInfo:new()
				version:SetVersion( major, minor, build, subBuild, "SSNetLib" )
				preLoginPacket.versionInfo = version
			elseif ( optionType == PreLoginPacket.OPTION_TYPE.Encryption ) then
				preLoginPacket:SetRequestEncryption( bin.unpack( "C", optionData ) )
			elseif ( optionType == PreLoginPacket.OPTION_TYPE.InstOpt ) then
				preLoginPacket:SetInstanceName( bin.unpack( "z", optionData ) )
			elseif ( optionType == PreLoginPacket.OPTION_TYPE.ThreadId ) then
				-- Do nothing. According to the TDS spec, this option is empty when sent from the server
			elseif ( optionType == PreLoginPacket.OPTION_TYPE.MARS ) then
				preLoginPacket:SetRequestMars( bin.unpack( "C", optionData ) )
			end
		end
		
		return status, preLoginPacket
	end,
}


--- LoginPacket class
LoginPacket = 
{
	
	-- options_1 possible values
	-- 0x80 enable warning messages if SET LANGUAGE issued
    -- 0x40 change to initial database must succeed
    -- 0x20 enable warning messages if USE <database> issued
    -- 0x10 enable BCP
    
	-- options_2 possible values
    -- 0x80 enable domain login security
	-- 0x40 "USER_SERVER - reserved" 
	-- 0x20 user type is "DQ login"
	-- 0x10 user type is "replication login"
	-- 0x08 "fCacheConnect"
	-- 0x04 "fTranBoundary"
    -- 0x02 client is an ODBC driver
    -- 0x01 change to initial language must succeed
	length = 0,
	version = 0x71000001, -- Version 7.1
	size = 0,
	cli_version = 7, -- From jTDS JDBC driver
	cli_pid = 0, -- Dummy value
	conn_id = 0,
	options_1 = 0xa0,
	options_2 = 0x03,
	sqltype_flag = 0,
	reserved_flag= 0,
	time_zone = 0,
	collation = 0,

	-- Strings
	client = "Nmap",
	username = nil,
	password = nil,
	app = "Nmap NSE",
	server = nil,
	library = "mssql.lua",
	locale = "",
	database = "master", --nil,
	MAC = string.char(0x00,0x00,0x00,0x00,0x00,0x00), -- should contain client MAC, jTDS uses all zeroes
	
	new = function(self,o)
		o = o or {}
        setmetatable(o, self)
        self.__index = self
		return o
    end,
	
	--- Sets the username used for authentication
	--
	-- @param username string containing the username to user for authentication
	SetUsername = function(self, username)
		self.username = username
	end,

	--- Sets the password used for authentication
	--
	-- @param password string containing the password to user for authentication	
	SetPassword = function(self, password)
		self.password = password
	end,
	
	--- Sets the database used in authentication
	--
	-- @param database string containing the database name
	SetDatabase = function(self, database)
		self.database = database
	end,

	--- Sets the server's name used in authentication
	--
	-- @param server string containing the name	or ip of the server
	SetServer = function(self, server)
		self.server = server
	end,
	
	SetDomain = function(self, domain)
		self.domain = domain
	end,
	
	--- Returns the authentication packet as string
	--
	-- @return string containing the authentication packet
	ToString = function(self)
		local data
		local offset = 86
		local ntlmAuth = not(not(self.domain))
		local authLen = 0
		
		self.cli_pid = math.random(100000)
		
		self.length = offset + 2 * ( self.client:len() + self.app:len() + self.server:len() + self.library:len() + self.database:len() )

		if ( ntlmAuth ) then
			authLen = 32 + #self.domain
			self.length = self.length + authLen
			self.options_2 = self.options_2 + 0x80
		else
			self.length = self.length + 2 * (self.username:len() + self.password:len())
		end
								
		data = bin.pack("<IIIIII", self.length, self.version, self.size, self.cli_version, self.cli_pid, self.conn_id )
		data = data .. bin.pack("CCCC", self.options_1, self.options_2, self.sqltype_flag, self.reserved_flag )
		data = data .. bin.pack("<II", self.time_zone, self.collation )
		
		-- offsets begin
		data = data .. bin.pack("<SS", offset, self.client:len() )
		offset = offset + self.client:len() * 2
		
		if ( not(ntlmAuth) ) then
			data = data .. bin.pack("<SS", offset, self.username:len() )

			offset = offset + self.username:len() * 2
			data = data .. bin.pack("<SS", offset, self.password:len() )
			offset = offset + self.password:len() * 2
		else
			data = data .. bin.pack("<SS", offset, 0 )
			data = data .. bin.pack("<SS", offset, 0 )
		end
		
		data = data .. bin.pack("<SS", offset, self.app:len() )
		offset = offset + self.app:len() * 2
		
		data = data .. bin.pack("<SS", offset, self.server:len() )
		offset = offset + self.server:len() * 2
		
		-- Offset to unused placeholder (reserved for future use in TDS spec)
		data = data .. bin.pack("<SS", 0, 0 )

		data = data .. bin.pack("<SS", offset, self.library:len() )
		offset = offset + self.library:len() * 2
		
		data = data .. bin.pack("<SS", offset, self.locale:len() )
		offset = offset + self.locale:len() * 2
		
		data = data .. bin.pack("<SS", offset, self.database:len() )
		offset = offset + self.database:len() * 2

		-- client MAC address, hardcoded to 00:00:00:00:00:00
		data = data .. bin.pack("A", self.MAC)
		
		-- offset to auth info
		data = data .. bin.pack("<S", offset)
		-- lenght of nt auth (should be 0 for sql auth)
		data = data .. bin.pack("<S", authLen)
		-- next position (same as total packet length)
		data = data .. bin.pack("<S", self.length)
		-- zero pad
		data = data .. bin.pack("<S", 0)
		
		-- Auth info wide strings
		data = data .. bin.pack("A", Util.ToWideChar(self.client) )
		if ( not(ntlmAuth) ) then
			data = data .. bin.pack("A", Util.ToWideChar(self.username) )
			data = data .. bin.pack("A", Auth.TDS7CryptPass(self.password) )
		end
		data = data .. bin.pack("A", Util.ToWideChar(self.app) )
		data = data .. bin.pack("A", Util.ToWideChar(self.server) )
		data = data .. bin.pack("A", Util.ToWideChar(self.library) )
		data = data .. bin.pack("A", Util.ToWideChar(self.locale) )
		data = data .. bin.pack("A", Util.ToWideChar(self.database) )

		if ( ntlmAuth ) then
			local NTLMSSP_NEGOTIATE = 1
			local flags = 0x0000b201
			local workstation = ""
			
			data = data .. "NTLMSSP\0"
			data = data .. bin.pack("<II", NTLMSSP_NEGOTIATE, flags)
			data = data .. bin.pack("<SSI", #self.domain, #self.domain, 32)
			data = data .. bin.pack("<SSI", #workstation, #workstation, 32)
			data = data .. bin.pack("A", self.domain:upper())
		end
		
		return PacketType.Login, data
	end,
	
}

NTAuthenticationPacket = {
	
	new = function(self, username, password, domain, nonce)
		local o = {}
        setmetatable(o, self)
		o.username = username
		o.domain = domain
		o.nonce = nonce
		o.password = password
		self.__index = self
		return o
    end,
	
	ToString = function(self)
		local ntlmssp = "NTLMSSP\0"
		local NTLMSSP_AUTH = 3
		local domain = Util.ToWideChar(self.domain:upper())
		local user = Util.ToWideChar(self.username)
		local hostname, sessionkey = "", ""
		local flags = 0x00008201		
		local ntlm_response = Auth.NtlmResponse(self.password, self.nonce)
		local lm_response = Auth.LmResponse(self.password, self.nonce)
		
		local domain_offset = 64
		local username_offset = domain_offset + #domain
		local lm_response_offset = username_offset + #user
		local ntlm_response_offset = lm_response_offset + #lm_response
		local hostname_offset = ntlm_response_offset + #ntlm_response
		local sessionkey_offset = hostname_offset + #hostname
		
		local data = bin.pack("<AISSI", ntlmssp, NTLMSSP_AUTH, #lm_response, #lm_response, lm_response_offset)
		data = data .. bin.pack("<SSI", #ntlm_response, #ntlm_response, ntlm_response_offset)
		data = data .. bin.pack("<SSI", #domain, #domain, domain_offset)
		data = data .. bin.pack("<SSI", #user, #user, username_offset)
		data = data .. bin.pack("<SSI", #hostname, #hostname, hostname_offset)
		data = data .. bin.pack("<SSI", #sessionkey, #sessionkey, sessionkey_offset)
		data = data .. bin.pack("<I", flags)
		data = data .. bin.pack("A", domain)
		data = data .. bin.pack("A", user )
		data = data .. lm_response .. ntlm_response
		
		return PacketType.NTAuthentication, data
	end,
	
}

-- Handles communication with SQL Server
TDSStream = {

	-- Status flag constants
	MESSAGE_STATUS_FLAGS = {
		Normal					= 0x0,
		EndOfMessage			= 0x1,
		IgnoreThisEvent			= 0x2,
		ResetConnection			= 0x4,
		ResetConnectionSkipTran	= 0x8,
	},

	_packetId = 0,
	_pipe = nil,
	_socket = nil,
	_name = nil,

	new = function(self,o)
		o = o or {}
        setmetatable(o, self)
        self.__index = self
		return o
    end,
    
    --- Establishes a connection to the SQL server.
    --	
    --	@param self A mssql.Helper object
    --	@param instanceInfo	A SqlServerInstanceInfo object for the instance to
    --		connect to.
    --	@param connectionPreference (Optional) A list containing one or both of
    --		the strings "TCP" and "Named Pipes", indicating which transport
    --		methods to try and in what order.
    --	@param smbOverrides (Optional) An overrides table for calls to the <code>smb</code>
    --		library (for use with named pipes).
	ConnectEx = function( self, instanceInfo, connectionPreference, smbOverrides )
		if ( self._socket ) then return false, "Already connected via TCP" end
		if ( self._pipe ) then return false, "Already connected via named pipes" end
		connectionPreference = connectionPreference or stdnse.get_script_args('mssql.protocol') or { "TCP", "Named Pipes" }
		if ( connectionPreference and 'string' == type(connectionPreference) ) then
			connectionPreference = { connectionPreference }
		end
		
		local status, result, connectionType, errorMessage
		stdnse.print_debug( 3, "%s: Connection preferences for %s: %s",
			"MSSQL", instanceInfo:GetName(), stdnse.strjoin( ", ", connectionPreference ) )
		
		for _, connectionType in ipairs( connectionPreference ) do
    		if connectionType == "TCP" then
    		
    			if not ( instanceInfo.port ) then
    				stdnse.print_debug( 3, "%s: Cannot connect to %s via TCP because port table is not set.",
    					"MSSQL", instanceInfo:GetName() )
    				result = "No TCP port for this instance"
    			else
    				status, result = self:Connect( instanceInfo.host, instanceInfo.port )
    				if status then return true end
    			end
    			
    		elseif connectionType == "Named Pipes" or connectionType == "NP" then
    		
    			if not ( instanceInfo.pipeName ) then
    				stdnse.print_debug( 3, "%s: Cannot connect to %s via named pipes because pipe name is not set.",
    					"MSSQL", instanceInfo:GetName() )
    				result = "No named pipe for this instance"
    			else
    				status, result = self:ConnectToNamedPipe( instanceInfo.host, instanceInfo.pipeName, smbOverrides )
    				if status then return true end
    			end
    		
    		else
    			stdnse.print_debug( 1, "%s: Unknown connection preference: %s", "MSSQL", connectionType )
				return false, ("ERROR: Unknown connection preference: %s"):format(connectionType)
    		end
    	
    		-- Handle any error messages 
    		if not status then
				if errorMessage then
					errorMessage = string.format( "%s, %s: %s", errorMessage, connectionType, result or "nil" )
				else
					errorMessage = string.format( "%s: %s", connectionType, result or "nil" )
				end	
			end
    	end
    	
    	if not errorMessage then
			errorMessage = string.format( "%s: None of the preferred connection types are available for %s\\%s",
    			"MSSQL", instanceInfo:GetName() )
		end
		
		return false, errorMessage
	end,
    
    --- Establishes a connection to the SQL server
	--
	-- @param host A host table for the target host
	-- @param pipePath The path to the named pipe of the target SQL Server
	--         (e.g. "\MSSQL$SQLEXPRESS\sql\query"). If nil, "\sql\query\" is used.
    --	@param smbOverrides (Optional) An overrides table for calls to the <code>smb</code>
    --		library (for use with named pipes).
	-- @return status: true on success, false on failure
	-- @return error_message: an error message, or nil
	ConnectToNamedPipe = function( self, host, pipePath, overrides )
		if ( self._socket ) then return false, "Already connected via TCP" end
		
		if ( SCANNED_PORTS_ONLY and smb.get_port( host ) == nil ) then
			stdnse.print_debug( 2, "%s: Connection disallowed: scanned-ports-only is set and no SMB port is available", "MSSQL" )
			return false, "Connection disallowed: scanned-ports-only"
		end
	
		pipePath = pipePath or "\\sql\\query"
		
		self._pipe = namedpipes.named_pipe:new()
		local status, result = self._pipe:connect( host, pipePath, overrides )
		if ( status ) then
			self._name = self._pipe.pipe
		else
			self._pipe = nil
		end
		
		return status, result
	end,

	--- Establishes a connection to the SQL server
	--
	-- @param host table containing host information
	-- @param port table containing port information
	-- @return status true on success, false on failure
	-- @return result containing error message on failure
	Connect = function( self, host, port )
		if ( self._pipe ) then return false, "Already connected via named pipes" end
		
		if ( SCANNED_PORTS_ONLY and nmap.get_port_state( host, port ) == nil ) then
			stdnse.print_debug( 2, "%s: Connection disallowed: scanned-ports-only is set and port %d was not scanned", "MSSQL", port.number )
			return false, "Connection disallowed: scanned-ports-only"
		end
	
		local status, result, lport, _
		
		self._socket = nmap.new_socket()

		-- Set the timeout to something realistic for connects
		self._socket:set_timeout( 5000 )
		status, result = self._socket:connect(host, port)
		
		if ( status ) then
			-- Sometimes a Query can take a long time to respond, so we set
			-- the timeout to 30 seconds. This shouldn't be a problem as the
			-- library attempt to decode the protocol and avoid reading past 
			-- the end of the input buffer. So the only time the timeout is
			-- triggered is when waiting for a response to a query.
			self._socket:set_timeout( MSSQL_TIMEOUT * 1000 )
	
			status, _, lport, _, _ = self._socket:get_info()
		end
		
		if ( not(status) ) then
			self._socket = nil
			stdnse.print_debug( 2, "%s: Socket connection failed on %s:%s", "MSSQL", host.ip, port.number )
			return false, "Socket connection failed"
		end
		self._name = string.format( "%s:%s", host.ip, port.number )
		
		return status, result
	end,

	--- Disconnects from the SQL Server
	--
	-- @return status true on success, false on failure
	-- @return result containing error message on failure
	Disconnect = function( self )
		if ( self._socket ) then
			local status, result = self._socket:close()
			self._socket = nil
			return status, result
		elseif ( self._pipe ) then
			local status, result = self._pipe:disconnect()
			self._pipe = nil
			return status, result
		else
			return false, "Not connected"
		end
	end,
	
	--- Sets the timeout for communication over the socket
	--
	-- @param timeout number containing the new socket timeout in ms
	SetTimeout = function( self, timeout )
		if ( self._socket ) then
			self._socket:set_timeout(timeout)
		else
			return false, "Not connected"
		end
	end,
	
	--- Gets the name of the name pipe, or nil
	GetNamedPipeName = function( self )
		if ( self._pipe ) then
			return self._pipe.name
		else
			return nil
		end
	end,
	
	--- Send a TDS request to the server
	--
	-- @param packetType A <code>PacketType</code>, indicating the type of TDS
	--		packet being sent.
	-- @param packetData A string containing the raw data to send to the server
	-- @return status true on success, false on failure
	-- @return result containing error message on failure
	Send = function( self, packetType, packetData )
		local packetLength = packetData:len() + 8 -- +8 for TDS header
		local messageStatus, spid, window = 1, 0, 0
	
	
		if ( packetType ~= PacketType.NTAuthentication ) then	self._packetId = self._packetId + 1 end
		local assembledPacket = bin.pack(">CCSSCCA", packetType, messageStatus, packetLength, spid, self._packetId, window, packetData )
		
		if ( self._socket ) then
			return self._socket:send( assembledPacket )
		elseif ( self._pipe ) then
			return self._pipe:send( assembledPacket )
		else
			return false, "Not connected"
		end
	end,

	--- Recieves responses from SQL Server
	-- The function continues to read and assemble a response until the server
	-- responds with the last response flag set
	--
	-- @return status true on success, false on failure
	-- @return result containing raw data contents or error message on failure
	-- @return errorDetail nil, or additional information about an error. In
	--		the case of named pipes, this will be an SMB error name (e.g. NT_STATUS_PIPE_DISCONNECTED)
	Receive = function( self )
		local status, result, errorDetail
		local combinedData, readBuffer = "", "" -- the buffer is solely for the benefit of TCP connections
		local tdsPacketAvailable = true
		
		if not ( self._socket or self._pipe ) then
			return false, "Not connected"
		end
		
		-- Large messages (e.g. result sets) can be split across multiple TDS
		-- packets from the server (which could themselves each be split across
		-- multiple TCP packets or SMB messages).
		while ( tdsPacketAvailable ) do
			local packetType, messageStatus, packetLength, spid, window
			local pos = 1
			
			if ( self._socket ) then
				-- If there is existing data in the readBuffer, see if there's
				-- enough to read the TDS headers for the next packet. If not,
				-- do another read so we have something to work with.
				if ( readBuffer:len() < 8 ) then
					status, result = self._socket:receive_bytes(8 - readBuffer:len())
					readBuffer = readBuffer .. result
				end
			elseif ( self._pipe ) then
				-- The named pipe takes care of all of its reassembly. We don't
				-- have to mess with buffers and repeatedly reading until we get
				-- the whole packet. We'll still write to readBuffer, though, so
				-- that the common logic can be reused.
				status, result, errorDetail = self._pipe:receive()
				readBuffer = result
			end
			
			if not ( status and readBuffer ) then return false, result, errorDetail end
			
			-- TDS packet validity check: packet at least as long as the TDS header
			if ( readBuffer:len() < 8 ) then
				stdnse.print_debug( 2, "%s: Receiving (%s): packet is invalid length", "MSSQL", self._name )
				return false, "Server returned invalid packet" 
			end
			
			-- read in the TDS headers
			pos, packetType, messageStatus, packetLength = bin.unpack(">CCS", readBuffer, pos )
			pos, spid, self._packetId, window = bin.unpack(">SCC", readBuffer, pos )
			
			-- TDS packet validity check: packet type is Response (0x4)
			if ( packetType ~= PacketType.Response ) then
				stdnse.print_debug( 2, "%s: Receiving (%s): Expected type 0x4 (response), but received type 0x%x",
					"MSSQL", self._name, packetType )
				return false, "Server returned invalid packet"
			end
			
			if ( self._socket ) then
				-- If we didn't previously read in enough data to complete this
				-- TDS packet, let's do so.
				while ( packetLength - readBuffer:len() > 0 ) do
					status, result = self._socket:receive()
					if not ( status and result ) then return false, result end
					readBuffer = readBuffer .. result
				end
			end
			
			-- We've read in an apparently valid TDS packet 
			local thisPacketData = readBuffer:sub( pos, packetLength )
			-- Append its data to that of any previous TDS packets
			combinedData = combinedData .. thisPacketData
			if ( self._socket ) then
				-- If we read in data beyond the end of this TDS packet, save it
				-- so that we can use it in the next loop.
				readBuffer = readBuffer:sub( packetLength + 1 )
			end
			
			-- TDS packet validity check: packet length matches length from header
			if ( packetLength ~= (thisPacketData:len() + 8) ) then
				stdnse.print_debug( 2, "%s: Receiving (%s): Header reports length %d, actual length is %d",
					"MSSQL", self._name, packetLength, thisPacketData:len()  )
				return false, "Server returned invalid packet" 
			end
			
			-- Check the status flags in the TDS packet to see if the message is
			-- continued in another TDS packet. 
			tdsPacketAvailable = (bit.band( messageStatus, TDSStream.MESSAGE_STATUS_FLAGS.EndOfMessage) ~= 
									TDSStream.MESSAGE_STATUS_FLAGS.EndOfMessage)
		end
		
		-- return only the data section ie. without the headers
		return status, combinedData
	end,
	
}

--- Helper class
Helper =
{
	new = function(self,o)
		o = o or {}
        setmetatable(o, self)
        self.__index = self
		return o
    end,
	
	--- Establishes a connection to the SQL server
	--
	-- @param host table containing host information
	-- @param port table containing port information
	-- @return status true on success, false on failure
	-- @return result containing error message on failure
	ConnectEx = function( self, instanceInfo )
		local status, result
		self.stream = TDSStream:new()
		status, result = self.stream:ConnectEx( instanceInfo )
		if ( not(status) ) then
			return false, result
		end

		return true
	end,
	
	--- Establishes a connection to the SQL server
	--
	-- @param host table containing host information
	-- @param port table containing port information
	-- @return status true on success, false on failure
	-- @return result containing error message on failure
	Connect = function( self, host, port )
		local status, result
		self.stream = TDSStream:new()
		status, result = self.stream:Connect(host, port)
		if ( not(status) ) then
			return false, result
		end

		return true
	end,
	
	---	Returns true if discovery has been performed to detect
	--	SQL Server instances on the given host
	WasDiscoveryPerformed = function( host )
		local mutex = nmap.mutex( "discovery_performed for " .. host.ip )
		mutex( "lock" )
		nmap.registry.mssql = nmap.registry.mssql or {}
		nmap.registry.mssql.discovery_performed = nmap.registry.mssql.discovery_performed or {}
		
		local wasPerformed = nmap.registry.mssql.discovery_performed[ host.ip ] or false
		mutex( "done" )
		
		return wasPerformed
	end,
	
	--- Adds an instance to the list of instances kept in the Nmap registry for
	--	shared use by SQL Server scripts. If the registry already contains the
	--	instance, any new information is merged into the existing instance info.
	--	This may happen, for example, when an instance is discovered via named
	--	pipes, but the same instance has already been discovered via SSRP; this
	--	will prevent duplicates, where possible.
	AddOrMergeInstance = function( newInstance )
		local instanceExists
		
		nmap.registry.mssql = nmap.registry.mssql or {}
		nmap.registry.mssql.instances = nmap.registry.mssql.instances or {}
  		nmap.registry.mssql.instances[ newInstance.host.ip ] = nmap.registry.mssql.instances[ newInstance.host.ip ] or {}
  		
  		for _, existingInstance in ipairs( nmap.registry.mssql.instances[ newInstance.host.ip ] ) do
  			if existingInstance == newInstance then
  				existingInstance:Merge( newInstance )
  				instanceExists = true
  				break
  			end
  		end
  		
  		if not instanceExists then
  			table.insert( nmap.registry.mssql.instances[ newInstance.host.ip ], newInstance )
  		end
	end,
	
	---	Gets a table containing SqlServerInstanceInfo objects discovered on
	--	the specified host (and port, if specified).
	--	
	--	@param host A host table for the target host
	--	@param port (Optional) If omitted, all of the instances for the host
	--		will be returned.
	--	@return A table containing SqlServerInstanceInfo objects, or nil
	GetDiscoveredInstances = function( host, port )
		nmap.registry.mssql = nmap.registry.mssql or {}
		nmap.registry.mssql.instances = nmap.registry.mssql.instances or {}
		nmap.registry.mssql.instances[ host.ip ] = nmap.registry.mssql.instances[ host.ip ] or {}
  		
		if ( not port ) then
			local instances = nmap.registry.mssql.instances[ host.ip ]
			if ( instances and #instances == 0 ) then instances = nil end
			return instances
		else
			for _, instance in ipairs( nmap.registry.mssql.instances[ host.ip ] ) do
	  			if ( instance.port and instance.port.number == port.number and
						instance.port.protocol == port.protocol ) then
	  				return { instance }
	  			end
	  		end
	
			return nil
		end
	end,

	--- Attempts to discover SQL Server instances using SSRP to query one or
	--	more (if <code>broadcast</code> is used) SQL Server Browser services.
	--	Any discovered instances are returned, as well as being stored for use
	--	by other scripts (see <code>mssql.Helper.GetDiscoveredInstances()</code>).
	--	
	--	@param host A host table for the target.
	--	@param port (Optional) A port table for the target port. If this is nil,
	--		the default SSRP port (UDP 1434) is used. 
	--	@param broadcast If true, this will be done with an SSRP broadcast, and
	--		<code>host</code> should contain the broadcast specification (e.g.
	--		ip = "255.255.255.255").
	--	@return (status, result) If status is true, result is a table of
	--		tables containing SqlServerInstanceInfo objects. The top-level table
	--		is indexed by IP address. If status is false, result is an
	--		error message. 
	DiscoverBySsrp = function( host, port, broadcast )
		
		if broadcast then
			local status, result = SSRP.DiscoverInstances_Broadcast( host, port )
			
			if not status then
				return status, result
			else
	  			for ipAddress, host in pairs( result ) do
		  			for _, instance in ipairs( host ) do
		  				Helper.AddOrMergeInstance( instance )
		  				-- Give some version info back to Nmap
		  				if ( instance.port and instance.version ) then
							instance.version:PopulateNmapPortVersion( instance.port )
							--nmap.set_port_version( instance.host, instance.port)
						end
		  			end
	  			end
	  			
				return true, result
			end
		else
			local status, result = SSRP.DiscoverInstances( host, port )
			
			if not status then
				return status, result
			else
	  			for _, instance in ipairs( result ) do
	  				Helper.AddOrMergeInstance( instance )
	  				-- Give some version info back to Nmap
	  				if ( instance.port and instance.version ) then
						instance.version:PopulateNmapPortVersion( instance.port )
						nmap.set_port_version( host, instance.port)
					end
	  			end
	  			
	  			local instances_all = {}
				instances_all[ host.ip ] = result
				return true, instances_all
			end
		end
	end,

	--- Attempts to discover a SQL Server instance listening on the specified
	--	port. If an instance is discovered, it is returned, as well as being 
	--	stored for use by other scripts (see <code>mssql.Helper.GetDiscoveredInstances()</code>).
	--
	--	@param host A host table for the target.
	--	@param port A port table for the target port.
	--	@return (status, result) If status is true, result is a table of
	--		SqlServerInstanceInfo objects. If status is false, result is an
	--		error message or nil.
	DiscoverByTcp = function( host, port )
		local version, instance, status
		-- Check to see if we've already discovered an instance on this port
		instance = Helper.GetDiscoveredInstances( host, port )
		if ( not instance ) then
			instance =  SqlServerInstanceInfo:new()
			instance.host = host
			instance.port = port
			
			status, version = Helper.GetInstanceVersion( instance )
			if ( status ) then
				Helper.AddOrMergeInstance( instance )
				-- The point of this wasn't to get the version, just to use the
				-- pre-login packet to determine whether there was a SQL Server on
				-- the port. However, since we have the version now, we'll store it.
				instance.version = version
				-- Give some version info back to Nmap
				if ( instance.port and instance.version ) then
					instance.version:PopulateNmapPortVersion( instance.port )
					nmap.set_port_version( host, instance.port)
				end
			end
		end
		
		return (instance ~= nil), { instance }
	end,

	---	Attempts to discover SQL Server instances listening on default named
	--	pipes. Any discovered instances are returned, as well as being stored
	--	for use by other scripts (see <code>mssql.Helper.GetDiscoveredInstances()</code>).
	--
	--	@param host A host table for the target.
	--	@param port A port table for the port to connect on for SMB
	--	@return (status, result) If status is true, result is a table of
	--		SqlServerInstanceInfo objects. If status is false, result is an
	--		error message or nil.
	DiscoverBySmb = function( host, port )
		local defaultPipes = {
			"\\sql\\query",
			"\\MSSQL$SQLEXPRESS\\sql\\query",
			"\\MSSQL$SQLSERVER\\sql\\query",
		}
		local tdsStream = TDSStream:new()
		local status, result, instances_host
		
		for _, pipeSubPath in ipairs( defaultPipes ) do
			status, result = tdsStream:ConnectToNamedPipe( host, pipeSubPath, nil )
			
			if status then
				instances_host = {}
				local instance = SqlServerInstanceInfo:new()
				instance.pipeName = tdsStream:GetNamedPipeName()
				tdsStream:Disconnect()
				instance.host = host
				
				Helper.AddOrMergeInstance( instance )
				table.insert( instances_host, instance )
			else
				stdnse.print_debug( 3, "DiscoverBySmb \n pipe: %s\n result: %s", pipeSubPath, tostring( result ) )
			end
		end
		
		return (instances_host ~= nil), instances_host
	end,
	
	--- Attempts to discover SQL Server instances by a variety of means.
	--	This function calls the three DiscoverBy functions, which perform the
	--	actual discovery. Any discovered instances can be retrieved using
	--	<code>mssql.Helper.GetDiscoveredInstances()</code>.
	--
	--	@param host Host table as received by the script action function
	Discover = function( host )
		nmap.registry.mssql = nmap.registry.mssql or {}
		nmap.registry.mssql.discovery_performed = nmap.registry.mssql.discovery_performed or {}
		nmap.registry.mssql.discovery_performed[ host.ip ] = false
		
		local mutex = nmap.mutex( "discovery_performed for " .. host.ip )
		mutex( "lock" )
		
		local sqlDefaultPort = nmap.get_port_state( host, {number = 1433, protocol = "tcp"} ) or {number = 1433, protocol = "tcp"}
		local sqlBrowserPort = nmap.get_port_state( host, {number = 1434, protocol = "udp"} ) or {number = 1434, protocol = "udp"}
		local smbPort
		 -- smb.get_port() will return nil if no SMB port was scanned OR if SMB ports were scanned but none was open
		local smbPortNumber = smb.get_port( host )
		if ( smbPortNumber ) then
			smbPort = nmap.get_port_state( host, {number = smbPortNumber, protocol = "tcp"} )
			-- There's no use in manually setting an SMB port; if no SMB port was
			-- scanned and found open, the SMB library won't work
		end
		-- if the user has specified ports, we'll check those too
		local targetInstancePorts = stdnse.get_script_args( "mssql.instance-port" )
		
		if ( sqlBrowserPort and sqlBrowserPort.state ~= "closed" ) then
			Helper.DiscoverBySsrp( host, sqlBrowserPort )
		end
		if ( sqlDefaultPort and sqlDefaultPort.state ~= "closed" ) then
			Helper.DiscoverByTcp( host, sqlDefaultPort )
		end
		if ( smbPort ) then
			Helper.DiscoverBySmb( host, smbPort )
		end
		if ( targetInstancePorts ) then
			if ( type( targetInstancePorts ) == "string" ) then
				targetInstancePorts = { targetInstancePorts }
			end
			for _, portNumber in ipairs( targetInstancePorts ) do
				portNumber = tonumber( portNumber )
				Helper.DiscoverByTcp( host, {number = portNumber, protocol = "tcp"} )
			end
		end
		
		nmap.registry.mssql.discovery_performed[ host.ip ] = true
		mutex( "done" )
	end,
	
	--- Returns all of the credentials available for the target instance,
	--	including any set by the <code>mssql.username</code> and <code>mssql.password</code>
	--	script arguments.
	--
	--	@param instanceInfo A SqlServerInstanceInfo object for the target instance
	--	@return A table of usernames mapped to passwords (i.e. <code>creds[ username ] = password</code>)
	GetLoginCredentials_All = function( instanceInfo )
		local credentials = instanceInfo.credentials or {}
		local credsExist = false
		for _, _ in pairs( credentials ) do
			credsExist = true
			break
		end
		if ( not credsExist ) then credentials = nil end
		
		if ( stdnse.get_script_args( "mssql.username" ) ) then
			credentials = credentials or {}
			local usernameArg = stdnse.get_script_args( "mssql.username" )
			local passwordArg = stdnse.get_script_args( "mssql.password" ) or ""
			credentials[ usernameArg ] = passwordArg
		end
		
		return credentials
	end,

	---	Returns a username-password set according to the following rules of
	--	precedence:
	--	* If the <code>mssql.username</code> and <code>mssql.password</code>
	--		script arguments were set, their values are used. (If the username
	--		argument was specified without the password argument, a blank
	--		password is used.)
	--	* If the password for the "sa" account has been discovered (e.g. by the
	--		<code>ms-sql-empty-password</code> or <code>ms-sql-brute</code>
	--		scripts), these credentials are used. 
	--	* If other credentials have been discovered, the first of these in the
	--		table are used.
	--	* Otherwise, nil is returned.
	--
	--	@param instanceInfo A SqlServerInstanceInfo object for the target instance
	--	@return (username, password)
	GetLoginCredentials = function( instanceInfo )
	
		-- First preference goes to any user-specified credentials
		local username = stdnse.get_script_args( "mssql.username" )
		local password = stdnse.get_script_args( "mssql.password" ) or ""
		
		-- Otherwise, use any valid credentials that have been discovered (e.g. by ms-sql-brute)
		if ( not(username) and instanceInfo.credentials ) then
			-- Second preference goes to the "sa" account
			if ( instanceInfo.credentials.sa ) then
				username = "sa"
				password = instanceInfo.credentials.sa
			else
				-- ok were stuck with some n00b account, just get the first one
				for user, pass in pairs( instanceInfo.credentials ) do
					username = user
					password = pass
					break
				end
			end
		end
		
		return username, password
	end,

	--- Disconnects from the SQL Server
	--
	-- @return status true on success, false on failure
	-- @return result containing error message on failure
	Disconnect = function( self )
		if ( not(self.stream) ) then
			return false, "Not connected to server"
		end
		
		self.stream:Disconnect()
		self.stream = nil
		
		return true
	end,
	
	--- Authenticates to SQL Server. If login fails, one of the following error
	--  messages will be returned:
	--  * "Password is expired"
	--  * "Must change password at next logon"
	--  * "Account is locked out"
	--  * "Login Failed"
	--
	-- @param username string containing the username for authentication
	-- @param password string containing the password for authentication
	-- @param database string containing the database to access
	-- @param servername string containing the name or ip of the remote server
	-- @return status true on success, false on failure
	-- @return result containing error message on failure
	-- @return errorDetail nil or a <code>LoginErrorType</code> value, if available
	Login = function( self, username, password, database, servername )
		local loginPacket = LoginPacket:new()
		local status, result, data, errorDetail, token
		local servername = servername or "DUMMY"
		local pos = 1
		local ntlmAuth = false
		
		if ( not self.stream ) then
			return false, "Not connected to server"
		end

		loginPacket:SetUsername(username)
		loginPacket:SetPassword(password)
		loginPacket:SetDatabase(database)
		loginPacket:SetServer(servername)
		
		local domain = stdnse.get_script_args("mssql.domain")
		if (domain) then
			if ( not(HAVE_SSL) ) then return false, "mssql: OpenSSL not present" end
			ntlmAuth = true
			-- if the domain was specified without an argument, set a default domain of "."
			if (domain == 1 or domain == true ) then
				domain = "."
			end
			loginPacket:SetDomain(domain) 
		end
		
		status, result = self.stream:Send( loginPacket:ToString() )
		if ( not(status) ) then
			return false, result
		end

		status, data, errorDetail = self.stream:Receive()
		if ( not(status) ) then
			-- When logging in via named pipes, SQL Server will sometimes
			-- disconnect the pipe if the login attempt failed (this only seems
			-- to happen with non-"sa") accounts. At this point, having
			-- successfully connected and sent a message, we can be reasonably
			-- comfortable that a disconnected pipe indicates a failed login. 
			if ( errorDetail == "NT_STATUS_PIPE_DISCONNECTED" ) then
				return false, "Bad username or password", LoginErrorType.InvalidUsernameOrPassword
			end
			return false, data
		end

		if ( ntlmAuth ) then
			local pos, nonce = Token.ParseToken( data, pos )
			local authpacket = NTAuthenticationPacket:new( username, password, domain, nonce )
			status, result = self.stream:Send( authpacket:ToString() )
			status, data = self.stream:Receive()
			if ( not(status) ) then
				return false, data
			end
		end

		while( pos < data:len() ) do
			pos, token = Token.ParseToken( data, pos )
			if ( -1 == pos ) then
				return false, token
			end
	
			if ( token.type == TokenType.ErrorMessage ) then
				local errorMessageLookup = {
					[LoginErrorType.AccountLockedOut] = "Account is locked out",
					[LoginErrorType.NotAssociatedWithTrustedConnection] = "User is not associated with a trusted connection (instance may allow Windows authentication only)",
					[LoginErrorType.InvalidUsernameOrPassword] = "Bad username or password",
					[LoginErrorType.PasswordExpired] = "Password is expired",
					[LoginErrorType.PasswordMustChange] = "Must change password at next logon",
				}
				local errorMessage = errorMessageLookup[ token.errno ] or string.format( "Login Failed (%s)", tostring(token.errno) )
				
				return false, errorMessage, token.errno
			elseif ( token.type == TokenType.LoginAcknowledgement ) then
				return true, "Login Success"
			end
		end

		return false, "Failed to process login response"
	end,
	
	--- Authenticates to SQL Server, using the credentials returned by
	--  Helper.GetLoginCredentials(). If the login is rejected by the server,
	--  the error code will be returned, as a number in the form of a 
	--  <code>mssql.LoginErrorType</code> (for which error messages can be 
	--  looked up in <code>mssql.LoginErrorMessage</code>).
	--
	-- @param instanceInfo a SqlServerInstanceInfo object for the instance to log into
	-- @param database string containing the database to access
	-- @param servername string containing the name or ip of the remote server
	-- @return status true on success, false on failure
	-- @return result containing error code or error message
	LoginEx = function( self, instanceInfo, database, servername )
		local servername = servername or instanceInfo.host.ip
		local username, password = Helper.GetLoginCredentials( instanceInfo )
		if ( not username ) then
			return false, "No login credentials"
		end
		
		return self:Login( username, password, database, servername )
	end,
	
	--- Performs a SQL query and parses the response
	--
	-- @param query string containing the SQL query
	-- @return status true on success, false on failure
	-- @return table containing a table of columns for each row
	--         or error message on failure
	Query = function( self, query )
	
		local queryPacket = QueryPacket:new()
		local status, result, data, token, colinfo, rows
		local pos = 1
			
		if ( nil == self.stream ) then
			return false, "Not connected to server"
		end
	
		queryPacket:SetQuery( query )		
		status, result = self.stream:Send( queryPacket:ToString() )
		if ( not(status) ) then
			return false, result
		end

		status, data = self.stream:Receive()
		if ( not(status) ) then
			return false, data
		end

		-- Iterate over tokens until we get to a rowtag
		while( pos < data:len() ) do
			local rowtag = select(2, bin.unpack("C", data, pos))
			
			if ( rowtag == TokenType.Row ) then
				break
			end
			
			pos, token = Token.ParseToken( data, pos )
			if ( -1 == pos ) then
				return false, token
			end
			if ( token.type == TokenType.ErrorMessage ) then
				return false, token.error
			elseif ( token.type == TokenType.TDS7Results ) then
				colinfo = token.colinfo
			end
		end


		rows = {}
	
		while(true) do
			local rowtag
			pos, rowtag = bin.unpack("C", data, pos )

			if ( rowtag ~= TokenType.Row ) then
				break
			end

			if ( rowtag == TokenType.Row and colinfo and #colinfo > 0 ) then
				local columns = {}
				
				for i=1, #colinfo do
					local val
				
					if ( ColumnData.Parse[colinfo[i].type] ) then
						if not ( colinfo[i].type == 106 or colinfo[i].type == 108) then
							pos, val = ColumnData.Parse[colinfo[i].type](data, pos)
						else
							-- decimal / numeric types need precision and scale passed.
							pos, val = ColumnData.Parse[colinfo[i].type]( colinfo[i].precision,  colinfo[i].scale, data, pos)
						end

						if ( -1 == pos ) then
							return false, val
						end
						table.insert(columns, val)
					else
						return false, ("unknown datatype=0x%X"):format(colinfo[i].type)
					end
				end
				table.insert(rows, columns)
			end
		end
		
		result = {}
		result.rows = rows
		result.colinfo = colinfo
		
		return true, result
	end,
	
	--- Attempts to connect to a SQL Server instance listening on a TCP port in
	--  order to determine the version of the SSNetLib DLL, which is an
	--  authoritative version number for the SQL Server instance itself.
	--
	-- @param instanceInfo An instance of SqlServerInstanceInfo
	-- @return status true on success, false on failure
	-- @return versionInfo an instance of mssql.SqlServerVersionInfo, or nil
	GetInstanceVersion = function( instanceInfo )
	
		if ( not instanceInfo.host or not (instanceInfo:HasNetworkProtocols()) ) then return false, nil end
		
		local status, response, version
		local tdsStream = TDSStream:new()

		status, response = tdsStream:ConnectEx( instanceInfo )
		
		if ( not status ) then
			stdnse.print_debug( 2, "%s: Connection to %s failed: %s", "MSSQL", instanceInfo:GetName(), response or "" )
			return false, "Connect failed"
		end
		
		local preLoginRequest = PreLoginPacket:new()
		preLoginRequest:SetInstanceName( instanceInfo.instanceName )
		
		tdsStream:SetTimeout( 5000 )
		tdsStream:Send( preLoginRequest:ToBytes() )
		
		-- read in any response we might get
		status, response = tdsStream:Receive()
		tdsStream:Disconnect()
		
		if status then
			local preLoginResponse
			status, preLoginResponse = PreLoginPacket.FromBytes( response )
			if status then
				version = preLoginResponse.versionInfo
			else
				stdnse.print_debug( 2, "%s: Parsing of pre-login packet from %s failed: %s",
					"MSSQL", instanceInfo:GetName(), preLoginResponse or "" )
				return false, "Parsing failed"
			end
		else
			stdnse.print_debug( 2, "%s: Receive for %s failed: %s", "MSSQL", instanceInfo:GetName(), response or "" )
			return false, "Receive failed"
		end
		
		return status, version
	end,
	
	--- Gets a table containing SqlServerInstanceInfo objects for the instances
	--	that should be run against, based on the script-args (e.g. <code>mssql.instance</code>)
	--
	--	@param host Host table as received by the script action function
	--	@param port (Optional) Port table as received by the script action function
	--	@return status True on success, false on failure
	--	@return instances If status is true, this will be a table with one or
	--		more SqlServerInstanceInfo objects. If status is false, this will be
	--		an error message.
	GetTargetInstances = function( host, port )
		if ( port ) then
			local status = true
			local instance = Helper.GetDiscoveredInstances( host, port )
			
			if ( not instance ) then
				status, instance = Helper.DiscoverByTcp( host, port )
			end
			if ( instance ) then
				return true, instance
			else
				return false, "No SQL Server instance detected on this port"
			end
		else
			local targetInstanceNames = stdnse.get_script_args( "mssql.instance-name" )
			local targetInstancePorts = stdnse.get_script_args( "mssql.instance-port" )
			local targetAllInstances = stdnse.get_script_args( "mssql.instance-all" )
			
			if ( targetInstanceNames and targetInstancePorts ) then
				return false, "Connections can be made either by instance name or port."
			end
			
			if ( targetAllInstances and ( targetInstanceNames or targetInstancePorts ) ) then
				return false, "All instances cannot be specified together with an instance name or port."
			end
			
			if ( not (targetInstanceNames or targetInstancePorts or targetAllInstances) ) then
				return false, "No instance(s) specified."
			end
			
			if ( not Helper.WasDiscoveryPerformed( host ) ) then
				stdnse.print_debug( 2, "%s: Discovery has not been performed prior to GetTargetInstances() call. Performing discovery now.", "MSSQL" )
				Helper.Discover( host )
			end
			
			local instanceList = Helper.GetDiscoveredInstances( host )
			if ( not instanceList ) then
				return false, "No instances found on target host"
			end
			
			local targetInstances = {}
			if ( targetAllInstances ) then
				targetInstances = instanceList
			else
				-- We want an easy way to look up whether an instance's name was
				-- in our target list. So, we'll make a table of { instanceName = true, ... }
				local temp = {}
				if ( targetInstanceNames ) then
					if ( type( targetInstanceNames ) == "string" ) then
						targetInstanceNames = { targetInstanceNames }
					end
					for _, instanceName in ipairs( targetInstanceNames ) do
						temp[ string.upper( instanceName ) ] = true
					end
				end
				targetInstanceNames = temp
				
				-- Do the same for the target ports 
				temp = {}
				if ( targetInstancePorts ) then
					if ( type( targetInstancePorts ) == "string" ) then
						targetInstancePorts = { targetInstancePorts }
					end
					for _, portNumber in ipairs( targetInstancePorts ) do
						portNumber = tonumber( portNumber )
						temp[portNumber] = true
					end
				end
				targetInstancePorts = temp
				
				for _, instance in ipairs( instanceList ) do
					if ( instance.instanceName and targetInstanceNames[ string.upper( instance.instanceName ) ] ) then
						table.insert( targetInstances, instance )
					elseif ( instance.port and targetInstancePorts[ tonumber( instance.port.number ) ] ) then
						table.insert( targetInstances, instance )
					end
				end
			end
			
			if ( #targetInstances > 0 ) then
				return true, targetInstances
			else
				return false, "Specified instance(s) not found on target host"
			end
		end
	end,
	
	--- Queries the SQL Browser service for the DAC port of the specified instance
	--  The DAC (Dedicated Admin Connection) port allows DBA's to connect to
	--  the database when normal connection attempts fail, for example, when
	--  the server is hanging, out of memory or other bad states.
	--
	--	@param host Host table as received by the script action function
	--  @param instanceName the instance name to probe for a DAC port
	--  @return number containing the DAC port on success or nil on failure
	DiscoverDACPort = function(host, instanceName)
		local socket = nmap.new_socket()
		socket:set_timeout(5000)

		if ( not(socket:connect(host, 1434, "udp")) ) then
			return false, "Failed to connect to sqlbrowser service"
		end
		
		if ( not(socket:send(bin.pack("Hz", "0F01", instanceName))) ) then
			socket:close()
			return false, "Failed to send request to sqlbrowser service"
		end
		
		local status, data = socket:receive_buf(match.numbytes(6), true)
		if ( not(status) ) then
			socket:close()
			return nil
		end
		socket:close()

		if ( #data < 6 ) then
			return nil
		end
		return select(2, bin.unpack("<S", data, 5))
	end,
	
	---	Returns a hostrule for standard SQL Server scripts, which will return
	--	true if one or more instances have been targeted with the <code>mssql.instance</code>
	--	script argument. However, if a previous script has failed to find any
	--	SQL Server instances on the host, the hostrule function will return
	--	false to keep further scripts from running unnecessarily on that host.
	--
	--	@return A hostrule function (use as <code>hostrule = mssql.GetHostrule_Standard()</code>)
	GetHostrule_Standard = function()
		return function( host )
			if ( stdnse.get_script_args( {"mssql.instance-all", "mssql.instance-name", "mssql.instance-port"} ) ~= nil ) then
				if ( Helper.WasDiscoveryPerformed( host ) ) then
					return Helper.GetDiscoveredInstances( host ) ~= nil
				else
					return true
				end
			else
				return false
			end
		end
	end,
	
	
	---	Returns a portrule for standard SQL Server scripts, which will run return
	--	true if BOTH of the following conditions are met:
	--	* The port has been identified as "ms-sql-s"
	--	* The <code>mssql.instance</code> script argument has NOT been used
	--
	--	@return A portrule function (use as <code>portrule = mssql.GetPortrule_Standard()</code>)
	GetPortrule_Standard = function()
		return function( host, port )
			return ( shortport.service( "ms-sql-s" )(host, port) and 
				 stdnse.get_script_args( {"mssql.instance-all", "mssql.instance-name", "mssql.instance-port"} ) == nil)
		end
	end,
}


Auth = {
	
	--- Encrypts a password using the TDS7 *ultra secure* XOR encryption
	--
	-- @param password string containing the password to encrypt
	-- @return string containing the encrypted password
	TDS7CryptPass = function(password)
		local xormask = 0x5a5a
		local result = ""
		
		for i=1, password:len() do
			local c = bit.bxor( string.byte( password:sub( i, i ) ), xormask )
			local m1= bit.band( bit.rshift( c, 4 ), 0x0F0F )
			local m2= bit.band( bit.lshift( c, 4 ), 0xF0F0 )
			result = result .. bin.pack("S", bit.bor( m1, m2 ) )
		end
		return result
	end,
	
	LmResponse = function( password, nonce )

		if ( not(HAVE_SSL) ) then
			stdnse.print_debug("ERROR: Nmap is missing OpenSSL")
			return
		end

		if(#password < 14) then
			password = password .. string.rep(string.char(0), 14 - #password)
		end

		password = password:upper()

		-- Take the first and second half of the password (note that if it's longer than 14 characters, it's truncated)
		local str1 = string.sub(password, 1, 7)
		local str2 = string.sub(password, 8, 14)

		-- Generate the keys
		local key1 = openssl.DES_string_to_key(str1)
		local key2 = openssl.DES_string_to_key(str2)

		local result = openssl.encrypt("DES", key1, nil, nonce) .. openssl.encrypt("DES", key2, nil, nonce)

		if(#result < 21) then
			result = result .. string.rep(string.char(0), 21 - #result)
		end

		str1 = string.sub(result, 1, 7)
		str2 = string.sub(result, 8, 14)
		local str3 = string.sub(result, 15, 21)

		key1 = openssl.DES_string_to_key(str1)
		key2 = openssl.DES_string_to_key(str2)
		local key3 = openssl.DES_string_to_key(str3)

		result = openssl.encrypt("DES", key1, nil, nonce) .. openssl.encrypt("DES", key2, nil, nonce) .. openssl.encrypt("DES", key3, nil, nonce)
		return result
	end,
	
	NtlmResponse = function( password, nonce )
		local lm_response, ntlm_response, mac_key = smbauth.get_password_response(nil, 
			nil, 
			nil, 
			password, 
			nil, 
			"v1", 
			nonce, 
			false
		)
		return ntlm_response
	end,	
}

--- "static" Utility class containing mostly conversion functions
Util = 
{
	--- Converts a string to a wide string
	--
	-- @param str string to be converted
	-- @return string containing a two byte representation of str where a zero
	--         byte character has been tagged on to each character.
	ToWideChar = function( str )
		return str:gsub("(.)", "%1" .. string.char(0x00) )
	end,
	
	
	--- Concerts a wide string to string
	--
	-- @param wstr containing the wide string to convert
	-- @return string with every other character removed
	FromWideChar = function( wstr )
		local str = ""
		if ( nil == wstr ) then
			return nil
		end
		for i=1, wstr:len(), 2 do
			str = str .. wstr:sub(i, i)
		end
		return str
	end,
	
	--- Takes a table as returned by Query and does some fancy formatting
	--  better suitable for <code>stdnse.output_result</code>
	--
	-- @param tbl as recieved by <code>Helper.Query</code>
	-- @param with_headers boolean true if output should contain column headers
	-- @return table suitable for <code>stdnse.output_result</code>
	FormatOutputTable = function ( tbl, with_headers )
		local new_tbl = {}
		local col_names = {}

		if ( not(tbl) ) then
			return
		end
		
		if ( with_headers and tbl.rows and #tbl.rows > 0 ) then
			local headers
			for k, v in pairs( tbl.colinfo ) do
				table.insert( col_names, v.text)
			end
			headers = stdnse.strjoin("\t", col_names)
			table.insert( new_tbl, headers)
			headers = headers:gsub("[^%s]", "=")
			table.insert( new_tbl, headers )
		end
		
		for _, v in ipairs( tbl.rows ) do
			table.insert( new_tbl, stdnse.strjoin("\t", v) )
		end

		return new_tbl
	end,
}

return _ENV;