---
-- Informix Library supporting a very limited subset of Informix operations
--
-- Summary
-- -------
-- Informix supports both The Open Group Distributed Relational Database
-- Architecture (DRDA) protocol, and their own. This library attempts to
-- implement a basic subset of operations. It currently supports;
--   o Authentication using plain-text usernames and passwords
--   o Simple SELECT, INSERT and UPDATE queries, possible more ...
--
-- Overview
-- --------
-- The library contains the following classes:
--
--   o Packet.*
--		- The Packet classes contain specific packets and function to serialize
--        them to strings that can be sent over the wire. Each class may also
--        contain a function to parse the servers response.
--
--   o ColMetaData
--      - A class holding the meta data for each column
--
--  o Comm
--		- Implements a number of functions to handle communication over the
--        the Socket class.
--
--	o Helper
--		- A helper class that provides easy access to the rest of the library
--
--   o Socket
--      - This is a copy of the DB2Socket class which provides fundamental 
--        buffering
--
-- In addition the library contains the following tables with decoder functions
--
--  o MetaDataDecoders
--     - Contains functions to decode the column metadata per data type 
--
--  o DataTypeDecoders
--     - Contains function to decode each data-type in the query resultset
--
--  o MessageDecoders
--     - Contains a decoder for each supported protocol message
--
-- Example
-- -------
-- The following sample code illustrates how scripts can use the Helper class
-- to interface the library:
--
-- <code>
--	helper 	= informix.Helper:new( host, port, "on_demo" )
--	status, err = helper:Connect()
--	status, res = helper:Login("informix", "informix")
--	status, err = helper:Close()
-- </code>
--
-- Additional information
-- ----------------------
-- The implementation is based on analysis of packet dumps and has been tested
-- against:
-- 
-- x IBM Informix Dynamic Server Express Edition v11.50 32-bit on Ubuntu
-- x IBM Informix Dynamic Server xxx 32-bit on Windows 2003
--
-- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html
-- @author "Patrik Karlsson <patrik@cqure.net>"
--
-- @args informix.instance specifies the Informix instance to connect to

--
-- Version 0.1
-- Created 07/23/2010 - v0.1 - created by Patrik Karlsson <patrik@cqure.net>
-- Revised 07/28/2010 - v0.2 - added support for SELECT, INSERT and UPDATE
--							   queries
--

local bin = require "bin"
local nmap = require "nmap"
local stdnse = require "stdnse"
local table = require "table"
_ENV = stdnse.module("informix", stdnse.seeall)

-- A bunch of constants
Constants =
{
	-- A subset of supported messages
	Message = {
		SQ_COMMAND = 0x01,
		SQ_PREPARE = 0x02,
		SQ_ID = 0x04,
		SQ_DESCRIBE = 0x08,
		SQ_EOT = 0x0c,
		SQ_ERR = 0x0d,
		SQ_TUPLE = 0x0e,
		SQ_DONE = 0x0f,
		SQ_DBLIST = 0x1a,
		SQ_DBOPEN = 0x24,
		SQ_EXIT = 0x38,
		SQ_INFO = 0x51,
		SQ_PROTOCOLS = 0x7e,
	},
	
	-- A subset of supported data types
	DataType = {
		CHAR = 0x00,
		SMALLINT = 0x01,
		INT = 0x02,
		FLOAT = 0x03,
		SERIAL = 0x06,
		DATE = 0x07,
		DATETIME = 0x0a,
		VARCHAR = 0x0d,
	},
	
	-- These were the ones I ran into when developing :-)
	ErrorMsg = {
		[-201] = "A syntax error has occurred.",
		[-206] = "The specified table is not in the database.",
		[-208] = "Memory allocation failed during query processing.",
		[-258] = "System error - invalid statement id received by the sqlexec process.",
		[-217] = "Column (%s) not found in any table in the query (or SLV is undefined).",
		[-310] = "Table (%s) already exists in database.",
		[-363] = "CURSOR not on SELECT statement.",
		[-555] = "Cannot use a select or any of the database statements in a multi-query prepare.",
		[-664] = "Wrong number of arguments to system function(%s).",
		[-761] = "INFORMIXSERVER does not match either DBSERVERNAME or DBSERVERALIASES.",
		[-951] = "Incorrect password or user is not known on the database server.",
		[-329] = "Database not found or no system permission.",
		[-9628] = "Type (%s) not found.",
		[-23101] = "Unable to load locale categories.",
	}
}

-- A socket implementation that provides fundamental buffering and allows for
-- reading of an exact number of bytes, instead of atleast ...
Socket =
{	
	new = function(self, socket)
		local o = {}
       	setmetatable(o, self)
        self.__index = self
		o.Socket = socket or nmap.new_socket()
		o.Buffer = nil
		return o
	end,
	

	--- Establishes a connection.
	--
	-- @param hostid Hostname or IP address.
	-- @param port Port number.
	-- @param protocol <code>"tcp"</code>, <code>"udp"</code>, or
	-- @return Status (true or false).
	-- @return Error code (if status is false).
	connect = function( self, hostid, port, protocol )
		-- Some Informix server seem to take a LOT of time to respond?!
		local status = self.Socket:set_timeout(20000)
		return self.Socket:connect( hostid, port, protocol )
	end,
	
	--- Closes an open connection.
	--
	-- @return Status (true or false).
	-- @return Error code (if status is false).
	close = function( self )
		return self.Socket:close()
	end,
	
	--- Opposed to the <code>socket:receive_bytes</code> function, that returns
	-- at least x bytes, this function returns the amount of bytes requested.
	--
	-- @param count of bytes to read
	-- @return true on success, false on failure
	-- @return data containing bytes read from the socket
	-- 		   err containing error message if status is false
	recv = function( self, count )
		local status, data
	
		self.Buffer = self.Buffer or ""
	
		if ( #self.Buffer < count ) then
			status, data = self.Socket:receive_bytes( count - #self.Buffer )
			if ( not(status) or #data < count - #self.Buffer ) then
				return false, data
			end
			self.Buffer = self.Buffer .. data
		end
			
		data = self.Buffer:sub( 1, count )
		self.Buffer = self.Buffer:sub( count + 1)
	
		return true, data	
	end,
	
	--- Sends data over the socket
	--
	-- @return Status (true or false).
	-- @return Error code (if status is false).
	send = function( self, data )
		return self.Socket:send( data )
	end,
}

-- The ColMetaData class
ColMetaData = {
	
	---Creates a new ColMetaData instance
	--
	-- @return object a new instance of ColMetaData
	new = function(self)
		local o = {}
       	setmetatable(o, self)
        self.__index = self
		return o
	end,
	
	--- Sets the datatype
	--
	-- @param typ number containing the datatype
	setType = function( self, typ ) self.type = typ end,
	
	--- Sets the name
	--
	-- @param name string containing the name
	setName = function( self, name) self.name = name end,


	--- Sets the length
	--
	-- @param len number containing the length of the column
	setLength = function( self, len ) self.len = len end,
	
	--- Gets the column type
	--
	-- @return typ the column type
	getType = function( self ) return self.type end,

	--- Gets the column name
	--
	-- @return name the column name
	getName = function( self ) return self.name end,
	
	--- Gets the column length
	--
	-- @return len the column length
	getLength = function( self ) return self.len end,
}

Packet  = {}

-- MetaData decoders used to decode the information for each data type in the
-- meta data returned by the server
--
-- The decoders, should be self explanatory 
MetaDataDecoders = {
	
	[Constants.DataType.INT] = function( data )
		local col_md = ColMetaData:new( )
		local pos = 19
		
		if ( #data < pos ) then	return false, "Failed to decode meta data for data type INT" end
		
		local _, len = bin.unpack(">S", data, pos)
		col_md:setLength(len)
		col_md:setType( Constants.DataType.INT )
		
		return true, col_md
	end,

	[Constants.DataType.CHAR] = function( data )
		local status, col_md = MetaDataDecoders[Constants.DataType.INT]( data )
		if( not(status) ) then
			return false, "Failed to decode metadata for data type CHAR"
		end
		col_md:setType( Constants.DataType.CHAR )
		
		return true, col_md
	end,

	[Constants.DataType.VARCHAR] = function( data )
		local status, col_md = MetaDataDecoders[Constants.DataType.INT]( data )
		if( not(status) ) then return false, "Failed to decode metadata for data type CHAR"	end
		col_md:setType( Constants.DataType.VARCHAR )
		
		return true, col_md
	end,

	[Constants.DataType.SMALLINT] = function( data )
		local status, col_md = MetaDataDecoders[Constants.DataType.INT]( data )
		if( not(status) ) then return false, "Failed to decode metadata for data type SMALLINT"	end
		col_md:setType( Constants.DataType.SMALLINT )
				
		return true, col_md
	end,

	[Constants.DataType.SERIAL] = function( data )
		local status, col_md = MetaDataDecoders[Constants.DataType.INT]( data )
		if( not(status) ) then return false, "Failed to decode metadata for data type SMALLINT"	end
		col_md:setType( Constants.DataType.SERIAL )
				
		return true, col_md
	end,

	[Constants.DataType.DATETIME] = function( data )
		local status, col_md = MetaDataDecoders[Constants.DataType.INT]( data )
		if( not(status) ) then return false, "Failed to decode metadata for data type DATETIME"	end
		col_md:setType( Constants.DataType.DATETIME )
		col_md:setLength(10)
		
		return true, col_md
	end,

	[Constants.DataType.FLOAT] = function( data )
		local status, col_md = MetaDataDecoders[Constants.DataType.INT]( data )
		if( not(status) ) then return false, "Failed to decode metadata for data type DATETIME"	end
		col_md:setType( Constants.DataType.FLOAT )
		
		return true, col_md
	end,
	
	[Constants.DataType.DATE] = function( data )
		local status, col_md = MetaDataDecoders[Constants.DataType.INT]( data )
		if( not(status) ) then return false, "Failed to decode metadata for data type DATETIME"	end
		col_md:setType( Constants.DataType.DATE )
		
		return true, col_md
	end,
		
		
}

-- DataType decoders used to decode result set returned from the server
-- This class is still incomplete and some decoders just adjust the offset
-- position rather than decode the value.
--
-- The decoders, should be self explanatory 
DataTypeDecoders = {
	
	[Constants.DataType.INT] = function( data, pos )
		return bin.unpack(">i", data, pos)
	end,

	[Constants.DataType.FLOAT] = function( data, pos )
		return bin.unpack(">d", data, pos)
	end,

	[Constants.DataType.DATE] = function( data, pos )
		return pos + 4, "DATE"
	end,

	[Constants.DataType.SERIAL] = function( data, pos )
		return bin.unpack(">I", data, pos)
	end,

	[Constants.DataType.SMALLINT] = function( data, pos )
		return bin.unpack(">s", data, pos)
	end,

	[Constants.DataType.CHAR] = function( data, pos, len )
		local pos, ret = bin.unpack("A" .. len, data, pos)
		return pos, Util.ifxToLuaString( ret )		
	end,

	[Constants.DataType.VARCHAR] = function( data, pos, len )
		local pos, len = bin.unpack("C", data, pos)
		local ret
				
		pos, ret = bin.unpack("A" .. len, data, pos)		
		return pos, Util.ifxToLuaString( ret )
	end,
	
	[Constants.DataType.DATETIME] = function( data, pos )
		return pos + 10, "DATETIME"
	end,
	
}


-- The MessageDecoders class "holding" the Response Decoders
MessageDecoders = {
	
	--- Decodes the SQ_ERR error message
	--
	-- @param socket already connected to the Informix database server
	-- @return status true on success, false on failure
	-- @return errmsg, Informix error message or decoding error message if
	--         status is false
	[Constants.Message.SQ_ERR] = function( socket )
		local status, data = socket:recv(8)
		local _, svcerr, oserr, errmsg, str, len, pos

		if( not(status) ) then return false, "Failed to decode error response"	end
		
		pos, svcerr, oserr, _, len = bin.unpack(">ssss", data )
		
		if( len and len > 0 ) then
			status, data = socket:recv(len)
			if( not(status) ) then return false, "Failed to decode error response"	end
			_, str = bin.unpack("A" .. len, data)
		end
		
		status, data = socket:recv(2)
		
		errmsg = Constants.ErrorMsg[svcerr]
		if ( errmsg and str ) then
			errmsg = errmsg:format(str)
		end
		return false, errmsg or ("Informix returned an error (svcerror: %d, oserror: %d)"):format( svcerr, oserr )
	end,
	
	--- Decodes the SQ_PROTOCOLS message
	--
	-- @param socket already connected to the Informix database server
	-- @return status true on success, false on failure
	-- @return err error message if status is false
	[Constants.Message.SQ_PROTOCOLS] = function( socket )
		local status, data
		local len, _
				
		status, data = socket:recv(2)
		if( not(status) ) then return false, "Failed to decode SQ_PROTOCOLS response" end
		_, len = bin.unpack(">S", data )

		-- read the remaining data
		return socket:recv(len + 2)
	end,
	
	--- Decodes the SQ_EOT message
	--
	-- @return status, always true
	[Constants.Message.SQ_EOT] = function( socket )		
		return true
	end,
	
	--- Decodes the SQ_DONE message
	--
	-- @param socket already connected to the Informix database server
	-- @return status true on success, false on failure
	-- @return err error message if status is false
	[Constants.Message.SQ_DONE] = function( socket )
		local status, data = socket:recv(2)
		local _, len, tmp
		if( not(status) ) then return false, "Failed to decode SQ_DONE response" end
		_, len = bin.unpack(">S", data )
		
		-- For some *@#! reason the SQ_DONE packet sometimes contains an
		-- length exeeding the length of the packet by one. Attempt to
		-- detect this and fix.
		status, data = socket:recv( len )
		_, tmp = bin.unpack(">S", data, len - 2)
		return socket:recv( (tmp == 0) and 3 or 4 )
	end,
	
	--- Decodes the metadata for a result set
	--
	-- @param socket already connected to the Informix database server
	-- @return status true on success, false on failure
	-- @return column_meta table containing the metadata
	[Constants.Message.SQ_DESCRIBE] = function( socket )
		local status, data = socket:recv(14)
		local pos, cols, col_type, col_name, col_len, col_md, stmt_id
		local coldesc_len, x
		local column_meta = {}
		
		if( not(status) ) then return false, "Failed to decode SQ_DESCRIBE response" end
		pos, cols, coldesc_len = bin.unpack(">SS", data, 11)
		pos, stmt_id = bin.unpack(">S", data, 3)

		if ( cols <= 0 ) then
			-- We can end up here if we executed a CREATE, UPDATE OR INSERT statement
			local tmp
			status, data = socket:recv(2)
			if( not(status) ) then return false, "Failed to decode SQ_DESCRIBE response" end

			pos, tmp = bin.unpack(">S", data)
			
			-- This was the result of a CREATE or UPDATE statement
			if ( tmp == 0x0f ) then
				status, data = socket:recv(26)
			-- This was the result of a INSERT statement
			elseif( tmp == 0x5e ) then
				status, data = socket:recv(46)
			end
			return true
		end

		status, data = socket:recv(6)
		if( not(status) ) then return false, "Failed to decode SQ_DESCRIBE response" end

		for i=1, cols do

			status, data = socket:recv(2)
			if( not(status) ) then return false, "Failed to decode SQ_DESCRIBE response" end
			pos, col_type = bin.unpack("C", data, 2)

			if ( MetaDataDecoders[col_type] ) then

				status, data = socket:recv(20)
				if( not(status) ) then
					return false, "Failed to read column meta data"
				end
				
				status, col_md = MetaDataDecoders[col_type]( data )
				if ( not(status) ) then
					return false, col_md
				end
			else
				return false, ("No metadata decoder for column type: %d"):format(col_type)
			end
			
			if ( i<cols ) then
				status, data = socket:recv(6)
				if( not(status) ) then return false, "Failed to decode SQ_DESCRIBE response" end
			end
			
			col_md:setType( col_type )
			table.insert( column_meta, col_md )
		end
		
		status, data = socket:recv( ( coldesc_len % 2 ) == 0 and coldesc_len or coldesc_len + 1 )
		if( not(status) ) then return false, "Failed to decode SQ_DESCRIBE response" end
		pos = 1
		
		for i=1, cols do
			local col_name
			pos, col_name = bin.unpack("z", data, pos)
			column_meta[i]:setName( col_name )
		end
				
		status, data = socket:recv(2)
		if( not(status) ) then return false, "Failed to decode SQ_DESCRIBE response" end
	
		pos, data = bin.unpack(">S", data)
		if( data == Constants.Message.SQ_DONE ) then
			status, data = socket:recv(26)
		else
			status, data = socket:recv(10)
		end
		return true, { metadata = column_meta, stmt_id = stmt_id }
	end,
	
	--- Processes the result from a query
	--
	-- @param socket already connected to the Informix database server
	-- @param info table containing the following fields:
	--        <code>metadata</code> as recieved from <code>SQ_DESCRIBE</code>
	--        <code>rows</code> containing already retrieved rows
	--        <code>id</code> containing the statement id as sent to SQ_ID
	-- @return status true on success, false on failure
	-- @return rows table containing the resulting columns and rows as:
	--         { { col, col2, col3 } }
	--         or error message if status is false
	[Constants.Message.SQ_TUPLE] = function( socket, info )
		local status, data
		local row = {}
		local count = 1

		if ( not( info.rows ) ) then info.rows = {} end

		while (true) do
			local pos = 1
		
			status, data = socket:recv(6)
			if( not(status) ) then return false, "Failed to read column data" end
			
			local _, total_len = bin.unpack(">I", data, 3)
			status, data = socket:recv( ( total_len % 2 == 0 ) and total_len or total_len + 1)
			if( not(status) ) then return false, "Failed to read column data" end

			row = {}
			for _, col in ipairs(info.metadata) do
				local typ, len, name = col:getType(), col:getLength(), col:getName()
				local val
								
				if( DataTypeDecoders[typ] ) then
					pos, val = DataTypeDecoders[typ]( data, pos, len )
				else
					return false, ("No data type decoder for type: 0x%d"):format(typ)
				end
				table.insert( row, val )
			end

			status, data = socket:recv(2)
			
			local _, flags = bin.unpack(">S", data)

			count = count + 1
			table.insert( info.rows, row )

			-- Check if we're done
			if ( Constants.Message.SQ_DONE == flags ) then
				break
			end
			
			-- If there's more data we need to send a new SQ_ID packet
			if ( flags == Constants.Message.SQ_EOT ) then 
				local status, tmp = socket:send( tostring(Packet.SQ_ID:new( info.id, nil, "continue" ) ) )
				local pkt_type
								
				status, tmp = socket:recv( 2 )
				pos, pkt_type = bin.unpack(">S", tmp) 
				
				return MessageDecoders[pkt_type]( socket, info )
			end
			
		end
		
		-- read the remaining data
		status, data = socket:recv( 26 )
		if( not(status) ) then return false, "Failed to read column data" end
		
		-- signal finnish reading
		status, data = socket:send( tostring(Packet.SQ_ID:new( info.id, nil, "end" ) ) )
		status, data = socket:recv( 2 )
		
		return true, info
		
	end,
	
	--- Decodes a SQ_DBLIST response
	--
	-- @param socket already connected to the Informix database server
	-- @return status true on success, false on failure
	-- @return databases array of database names
	[Constants.Message.SQ_DBLIST] = function( socket )
	
		local status, data, pos, len, db
		local databases = {}
		
		while( true ) do
			status, data = socket:recv(2)
			if ( not(status) ) then return false, "Failed to parse SQ_DBLIST response" end
		
			pos, len = bin.unpack(">S", data)
			if ( 0 == len ) then break end
		
			status, data = socket:recv(len)
			if ( not(status) ) then return false, "Failed to parse SQ_DBLIST response" end
			
			pos, db = bin.unpack("A" .. len, data )
			table.insert( databases, db )
			
			if ( len %2 == 1 ) then
				socket:recv(1)
				if ( not(status) ) then return false, "Failed to parse SQ_DBLIST response" end
			end
		end
		
		-- read SQ_EOT
		status, data = socket:recv(2)
				
		return true, databases
	end,
	
	[Constants.Message.SQ_EXIT] = function( socket )
		local status, data = socket:recv(2)
		if ( not(status) ) then return false, "Failed to parse SQ_EXIT response" end
		
		return true
	end
	
	
} 

-- Packet used to request a list of available databases
Packet.SQ_DBLIST =
{
	--- Creates a new Packet.SQ_DBLIST instance
	--
	-- @return object new instance of Packet.SQ_DBLIST		
	new = function( self )
		local o = {}
       	setmetatable(o, self)
        self.__index = self
   		return o
	end,
	
	--- Converts the class to a string suitable to send over the socket
	--
	-- @return string containing the packet data				
	__tostring = function(self)
		return bin.pack(">SS", Constants.Message.SQ_DBLIST, Constants.Message.SQ_EOT)
	end
	
}

-- Packet used to open the database
Packet.SQ_DBOPEN =
{
	
	--- Creates a new Packet.SQ_DBOPEN instance
	--
	-- @param database string containing the name of the database to open
	-- @return object new instance of Packet.SQ_DBOPEN		
	new = function( self, database )
		local o = {}
       	setmetatable(o, self)
        self.__index = self
		o.database = database
   		return o
	end,
	
	--- Converts the class to a string suitable to send over the socket
	--
	-- @return string containing the packet data				
	__tostring = function(self)
		return bin.pack(">SSASS", Constants.Message.SQ_DBOPEN, #self.database,
		 				Util.padToOdd(self.database), 0x00,
		 				Constants.Message.SQ_EOT)
	end
	
}

-- This packet is "a mess" and requires further analysis
Packet.SQ_ID = 
{
	--- Creates a new Packet.SQ_ID instance
	--
	-- @param id number containing the statement identifier
	-- @param s1 number unknown, should be 0 on first call and 1 when more data is requested
	-- @return object new instance of Packet.SQ_ID		
	new = function( self, id, id2, mode )
		local o = {}
       	setmetatable(o, self)
        self.__index = self
		o.id = ("_ifxc%.13d"):format( id2 or 0 )
		o.seq = id
		o.mode = mode
   		return o
	end,
	
	--- Converts the class to a string suitable to send over the socket
	--
	-- @return string containing the packet data				
	__tostring = function(self)
		if ( self.mode == "continue" ) then
			return bin.pack( ">SSSSSS",  Constants.Message.SQ_ID, self.seq, 0x0009, 0x1000, 0x0000, Constants.Message.SQ_EOT )
		elseif ( self.mode == "end" ) then
			return bin.pack( ">SSSS", Constants.Message.SQ_ID, self.seq, 0x000a, Constants.Message.SQ_EOT)
		else
			return bin.pack(">SSSSASSSSSSS", Constants.Message.SQ_ID, self.seq, 0x0003, #self.id, self.id, 
							0x0006, 0x0004, self.seq, 0x0009, 0x1000, 0x0000, Constants.Message.SQ_EOT )
		end
	end
	
}

Packet.SQ_INFO =
{

	-- The default parameters
	DEFAULT_PARAMETERS = {
		[1] = { ["DBTEMP"] = "/tmp" },
		[2] = { ["SUBQCACHESZ"] = "10" },
	},

	--- Creates a new Packet.SQ_INFO instance
	--
	-- @param params containing any additional parameters to use
	-- @return object new instance of Packet.SQ_INFO	
	new = function( self, params )
		local o = {}
		local params = params or Packet.SQ_INFO.DEFAULT_PARAMETERS
       	setmetatable(o, self)
        self.__index = self
		o.parameters = {}

		for _, v in ipairs( params ) do
			for k2, v2 in pairs(v) do
				o:addParameter( k2, v2 )
			end
		end
   		return o
	end,
	
	addParameter = function( self, key, value )
		table.insert( self.parameters, { [key] = value } )
	end,
	
	paramToString = function( self, key, value )
		return bin.pack(">SASA", #key, Util.padToOdd(key), #value, Util.padToOdd( value ) )
	end,
	
	--- Converts the class to a string suitable to send over the socket
	--
	-- @return string containing the packet data				
	__tostring = function( self )
		local params = ""
		local data
		
		for _, v in ipairs( self.parameters ) do
			for k2, v2 in pairs( v ) do
				params = params .. self:paramToString( k2, v2 )
			end
		end
		
		data = bin.pack(">SSSSS", Constants.Message.SQ_INFO, 0x0006, #params + 6, 0x000c, 0x0004 )
		data = data .. params .. bin.pack(">SSS", 0x0000, 0x0000, Constants.Message.SQ_EOT)
		return data
	end
}

-- Performs protocol negotiation?
Packet.SQ_PROTOCOLS = 
{
	-- hex-encoded data to send as protocol negotiation
	data = "0007fffc7ffc3c8c8a00000c",

	--- Creates a new Packet.SQ_PROTOCOLS instance
	--
	-- @return object new instance of Packet.SQ_PROTOCOLS	
	new = function( self )
		local o = {}
       	setmetatable(o, self)
        self.__index = self
   		return o
	end,

	--- Converts the class to a string suitable to send over the socket
	--
	-- @return string containing the packet data			
	__tostring = function(self)
		return bin.pack(">SH", Constants.Message.SQ_PROTOCOLS, self.data)
	end
	
}

-- Packet used to execute SELECT Queries
Packet.SQ_PREPARE = 
{
	
	--- Creates a new Packet.SQ_PREPARE instance
	--
	-- @param query string containing the query to execute
	-- @return object new instance of Packet.SQ_PREPARE
	new = function( self, query )
		local o = {}
       	setmetatable(o, self)
        self.__index = self
		o.query = Util.padToEven(query)
   		return o
	end,
	
	--- Converts the class to a string suitable to send over the socket
	--
	-- @return string containing the packet data	
	__tostring = function(self)
		return bin.pack(">SIACSSS", Constants.Message.SQ_PREPARE, #self.query, self.query, 0, 0x0016, 0x0031, Constants.Message.SQ_EOT)
	end
	
}

-- Packet used to execute commands other than SELECT
Packet.SQ_COMMAND = 
{
	
	--- Creates a new Packet.SQ_COMMAND instance
	--
	-- @param query string containing the query to execute
	-- @return object new instance of Packet.SQ_COMMAND
	new = function( self, query )
		local o = {}
       	setmetatable(o, self)
        self.__index = self
		o.query = Util.padToEven(query)
   		return o
	end,
	
	--- Converts the class to a string suitable to send over the socket
	--
	-- @return string containing the packet data	
	__tostring = function(self)
		return bin.pack(">SIACSSSS", Constants.Message.SQ_COMMAND, #self.query, self.query, 0, 0x0016, 0x0007, 0x000b, Constants.Message.SQ_EOT)
	end
	
}

Packet.SQ_EXIT = {

	--- Creates a new Packet.SQ_EXIT instance
	--
	-- @return object new instance of Packet.SQ_EXIT
	new = function( self )
		local o = {}
       	setmetatable(o, self)
        self.__index = self
   		return o
	end,
	
	--- Converts the class to a string suitable to send over the socket
	--
	-- @return string containing the packet data	
	__tostring = function(self)
		return bin.pack(">S", Constants.Message.SQ_EXIT)
	end
	
}

-- The Utility Class
Util = 
{
	--- Converts a connection parameter to string
	--
	-- @param param string containing the parameter name
	-- @param value string containing the parameter value
	-- @return string containing the encoded parameter as string
	paramToString = function( param, value )
		return bin.pack(">PP", param, value )
	end,
	
	--- Pads a string to an even number of characters
	--
	-- @param str the string to pad
	-- @param pad the character to pad with
	-- @return result the padded string
	padToEven = function( str, pad )
		return (#str % 2 == 1) and str or str .. ( pad and pad or "\0")
	end,

	--- Pads a string to an odd number of characters
	--
	-- @param str the string to pad
	-- @param pad the character to pad with
	-- @return result the padded string	
	padToOdd = function( str, pad )
		return (#str % 2 == 0) and str or str .. ( pad and pad or "\0")
	end,
	
	--- Formats a table to suitable script output
	--
	-- @param info as returned from ExecutePrepare
	-- @return table suitable for use by <code>stdnse.format_output</code>
	formatTable = function( info )
		local header, row = "", ""
		local result = {}
		local metadata = info.metadata
		local rows = info.rows
		
		if ( info.error ) then
			table.insert(result, info.error)
			return result
		end
		
		if ( info.info ) then
			table.insert(result, info.info)
			return result
		end
		
		if ( not(metadata) ) then return "" end
		
		for i=1, #metadata do
			if ( metadata[i]:getType() == Constants.DataType.CHAR and metadata[i]:getLength() < 50) then
				header = header .. ("%-" .. metadata[i]:getLength() .. "s "):format(metadata[i]:getName())
			else
				header = header .. metadata[i]:getName() 
				if ( i<#metadata ) then
					header = header .. "\t"
				end
			end
		end
		table.insert( result, header )

		for j=1, #rows do
			row = ""
			for i=1, #metadata do
				row = row .. rows[j][i] .. " "
				if ( metadata[i]:getType() ~= Constants.DataType.CHAR and i<#metadata and metadata[i]:getLength() < 50 ) then	row = row .. "\t" end
			end
			table.insert( result, row )
		end
		
		return result
	end,

	-- Removes trailing nulls
	--
	-- @param str containing the informix string
	-- @return ret the string with any trailing nulls removed
	ifxToLuaString = function( str )
		local ret
		
		if ( not(str) ) then return "" end
		
		if ( str:sub(-1, -1 ) ~= "\0" ) then
			return str
		end

	  	for i=1, #str do
	   		if ( str:sub(-i,-i) == "\0" ) then 
	    		ret = str:sub(1, -i - 1) 
	   		else
	    		break
	   		end
	  	end

		return ret
	end,
}

-- The connection Class, used to connect and authenticate to the server
-- Currently only supports plain-text authentication
--
-- The unknown portions in the __tostring method have been derived from Java
-- code connecting to Informix using JDBC.
Packet.Connect = {
	
	-- default parameters sent using JDBC
	DEFAULT_PARAMETERS = {
		[1] = { ['LOCKDOWN'] = 'no' },
		[2] = { ['DBDATE'] = 'Y4MD-' },
		[3] = { ['SINGLELEVEL'] = 'no' },
		[4] = { ['NODEFDAC'] = 'no' },
		[5] = { ['CLNT_PAM_CAPABLE'] = '1' },
		[6] = { ['SKALL'] = '0' },
		[7] = { ['LKNOTIFY'] = 'yes' },
		[8] = { ['SKSHOW'] = '0' },
		[9] = { ['IFX_UPDDESC'] = '1' },
		[10] = { ['DBPATH'] = '.' },
		[11] = { ['CLIENT_LOCALE'] = 'en_US.8859-1' },
		[12] = { ['SKINHIBIT'] = '0' },
	},
	
	--- Creates a new Connection packet
	--
	-- @param username string containing the username for authentication
	-- @param password string containing the password for authentication
	-- @param instance string containing the instance to connect to
	-- @return a new Packet.Connect instance
	new = function(self, username, password, instance, parameters)
		local o = {}
       	setmetatable(o, self)
        self.__index = self
		o.username = username and username .. "\0"
		o.password = password and password .. "\0"
		o.instance = instance and instance .. "\0"
		o.parameters = parameters
		return o
	end,

	--- Adds the default set of parameters
	addDefaultParameters = function( self )
		for _, v in ipairs( self.DEFAULT_PARAMETERS ) do
			for k2, v2 in pairs( v ) do
				self:addParameter( k2, v2 )
			end
		end		
	end,

	--- Adds a parameter to the connection packet
	--
	-- @param param string containing the parameter name
	-- @param value string containing the parameter value
	-- @return status, always true
	addParameter = function( self, param, value )
		local tbl = {}
		tbl[param] = value
		table.insert( self.parameters, tbl )
		
		return true
	end,
		
	--- Retrieves the OS error code
	--
	-- @return oserror number containing the OS error code
	getOsError = function( self ) return self.oserror end,

	--- Retrieves the Informix service error
	--
	-- @return svcerror number containing the service error
	getSvcError = function( self ) return self.svcerror end,

	--- Retrieves the Informix error message
	--
	-- @return errmsg string containing the "mapped" error message
	getErrMsg = function( self ) return self.errmsg end,
	
	--- Reads and decodes the response to the connect packet from the server.
	-- The function will return true even if the response contains an Informix
	-- error. In order to verify if the connection was successful, check for OS
	-- or service errors using the getSvcError and getOsError methods.
	--
	-- @param socket already connected to the server
	-- @return status true on success, false on failure
	-- @return err msg if status is false
	readResponse = function( self, socket )
		local status, data = socket:recv( 2 )
		local len, pos, tmp
		
		if ( not(status) ) then	return false, data	end
		pos, len = bin.unpack(">S", data)
		status, data = socket:recv( len - 2 )
		if ( not(status) ) then	return false, data	end
	
		pos = 13
		pos, tmp = bin.unpack(">S", data, pos)
		pos = pos + tmp
		
		pos, tmp = bin.unpack(">S", data, pos)
		
		if ( 108 ~= tmp ) then
			return false, "Connect recieved unexpected response"
		end
		
		pos = pos + 12
		-- version
		pos, len = bin.unpack(">S", data, pos)
		pos, self.version = bin.unpack("A" .. len, data, pos)

		-- serial
		pos, len = bin.unpack(">S", data, pos)
		pos, self.serial = bin.unpack("A" .. len, data, pos)
		
		-- applid
		pos, len = bin.unpack(">S", data, pos)
		pos, self.applid = bin.unpack("A" .. len, data, pos)
			
		-- skip 14 bytes ahead
		pos = pos + 14

		-- do some more skipping
		pos, tmp = bin.unpack(">S", data, pos)
		pos = pos + tmp
		
		-- do some more skipping
		pos, tmp = bin.unpack(">S", data, pos)
		pos = pos + tmp
		
		-- skip another 24 bytes
		pos = pos + 24
		pos, tmp = bin.unpack(">S", data, pos)
		
		if ( tmp ~= 102 ) then
			return false, "Connect recieved unexpected response"
		end
		
		pos = pos + 6
		pos, self.svcerror = bin.unpack(">s", data, pos)
		pos, self.oserror = bin.unpack(">s", data, pos )
		
		if ( self.svcerror ~= 0 ) then
			self.errmsg = Constants.ErrorMsg[self.svcerror] or ("Unknown error %d occured"):format( self.svcerror )
		end
		
		return true
	end,
	
	--- Converts the class to a string suitable to send over the socket
	--
	-- @return string containing the packet data
	__tostring = function( self )
		local data
		local unknown = [[
						013c0000006400650000003d0006494545454d00006c73716c65786563000000
						00000006392e32383000000c524453235230303030303000000573716c690000
						00013300000000000000000001
		]]
		
		local unknown2 = [[
						6f6c0000000000000000003d746c697463700000000000010068000b
						00000003
		]]
		
		local unknown3 = [[
						00000000000000000000006a
		]]
		
		local unknown4 = [[ 007f ]]

		if ( not(self.parameters) ) then
			self.parameters = {}
			self:addDefaultParameters()
		end
				
		data = bin.pack(">HPPHPHS", unknown, self.username, self.password, unknown2, self.instance, unknown3, #self.parameters ) 

		if ( self.parameters ) then
			for _, v in ipairs( self.parameters ) do
				for k2, v2 in pairs( v ) do
					data = data .. Util.paramToString( k2 .. "\0", v2 .. "\0" )
				end
			end
		end
		
		data = data .. bin.pack("H", unknown4)
		data = bin.pack(">S", #data + 2) .. data
				
		return data
	end,
	
	
}

-- The communication class
Comm = 
{
	--- Creates a new Comm instance
	--
	-- @param socket containing a buffered socket connected to the server
	-- @return a new Comm instance
	new = function(self, socket)
		local o = {}
       	setmetatable(o, self)
        self.__index = self
		o.socket = socket
		return o
	end,
	
	--- Sends and packet and attempts to handle the response
	--
	-- @param packets an instance of a Packet.* class
	-- @param info any additional info to pass as the second parameter to the
	--        decoder
	-- @return status true on success, false on failure
	-- @return data returned from the ResponseDecoder
	exchIfxPacket = function( self, packet, info )	
		local _, typ
		local status, data = self.socket:send( tostring(packet) )
		if ( not(status) ) then	return false, data	end

		status, data = self.socket:recv( 2 )
		_, typ = bin.unpack(">S", data)

		if ( MessageDecoders[typ] ) then
			status, data = MessageDecoders[typ]( self.socket, info )
		else
			return false, ("Unsupported data returned from server (type: 0x%x)"):format(typ)
		end
		
		return status, data
	end
	
}

-- The Helper class providing easy access to the other db functionality
Helper = {
	
	--- Creates a new Helper instance
	--
	-- @param host table as passed to the action script function
	-- @param port table as passed to the action script function
	-- @param instance [optional] string containing the instance to connect to
	--        in case left empty it's populated by the informix.instance script
	--        argument.
	-- @return Helper instance
	new = function(self, host, port, instance)
		local o = {}
       	setmetatable(o, self)
        self.__index = self
		o.host = host
		o.port = port
		o.socket = Socket:new()
		o.instance = instance or "nmap_probe"
		return o
	end,
	
	--- Connects to the Informix server
	--
	-- @return true on success, false on failure
	-- @return err containing error message when status is false
	Connect = function( self )
		local status, data
		local conn, packet

		status, data = self.socket:connect( self.host.ip, self.port.number, "tcp" )

		if( not(status) ) then
			return status, data
		end
		
		self.comm = Comm:new( self.socket )
		
		return true
	end,

	--- Attempts to login to the Informix database server
	-- The optional parameters parameter takes any informix specific parameters
	-- used to connect to the database. In case it's ommited a set of default
	-- parameters are set. Parameters should be past as key, value pairs inside
	-- of a table array as the following example:
	-- 
	-- local params = {
	-- 		[1] = { ["PARAM1"] = "VALUE1" },
	--		[2] = { ["PARAM2"] = "VALUE2" },	
	-- }
	--
	-- @param username string containing the username for authentication
	-- @param password string containing the password for authentication
	-- @param parameters [optional] table of informix specific parameters
	-- @param database [optional] database to connect to
	-- @param retry [optional] used when autodetecting instance
	-- @return status true on success, false on failure
	-- @return err containing the error message if status is false 
	Login = function( self, username, password, parameters, database, retry )
		local conn, status, data, len, packet

		conn = Packet.Connect:new( username, password, self.instance, parameters )
	
		status, data = self.socket:send( tostring(conn) )
		if ( not(status) ) then	return false, "Helper.Login failed to send login request" end
		status = conn:readResponse( self.socket )
		if ( not(status) ) then	return false, "Helper.Login failed to read response" end
		
		if ( status and ( conn:getOsError() ~= 0  or conn:getSvcError() ~= 0 )  ) then
			-- Check if we didn't supply the correct instance name, if not attempt to
			-- reconnect using the instance name returned by the server
			if ( conn:getSvcError() == -761 and not(retry) ) then
				self.instance = conn.applid
				self:Close()
				self:Connect()
				return self:Login( username, password, parameters, database, 1 )
			end
			return false, conn:getErrMsg()
		end
		
		status, packet = self.comm:exchIfxPacket( Packet.SQ_PROTOCOLS:new() )
		if ( not(status) ) then	return false, packet end

		status, packet = self.comm:exchIfxPacket( Packet.SQ_INFO:new() )
		if ( not(status) ) then	return false, packet end
			
		-- If a database was supplied continue further protocol negotiation and
		-- attempt to open the database.
		if ( database ) then
			status, packet = self:OpenDatabase( database )
			if ( not(status) ) then	return false, packet end
		end
		
		return true
	end,
	
	--- Opens a database
	--
	-- @param database string containing the database name
	-- @return status true on success, false on failure
	-- @return err string containing the error message if status is false
	OpenDatabase = function( self, database )
		return self.comm:exchIfxPacket( Packet.SQ_DBOPEN:new( database ) )
	end,
	
	--- Attempts to retrieve a list of available databases
	--
	-- @return status true on success, false on failure
	-- @return databases array of database names or err on failure
	GetDatabases = function( self )
		return self.comm:exchIfxPacket( Packet.SQ_DBLIST:new() )
	end,
	
	Query = function( self, query )
		local status, metadata, data, res
		local id, seq = 0, 1
		local result = {}
		
		if ( type(query) == "string" ) then
			query = stdnse.strsplit(";%s*", query)
		end
		
		for _, q in ipairs( query ) do
			if ( q:upper():match("^%s*SELECT") ) then
				status, data = self.comm:exchIfxPacket( Packet.SQ_PREPARE:new( q ) )
				seq = seq + 1 
			else
				status, data = self.comm:exchIfxPacket( Packet.SQ_COMMAND:new( q .. ";" ) )
			end
		
			if( status and data ) then
				metadata = data.metadata
				status, data = self.comm:exchIfxPacket( Packet.SQ_ID:new( data.stmt_id, seq, "begin" ), { metadata = metadata, id = id, rows = nil, query=q }  )

				-- check if any rows were returned
				if ( not( data.rows ) ) then
					data = { query = q, info = "No rows returned" }
				end
				--if( not(status) ) then return false, data end
			elseif( not(status) ) then
				data = { query = q, ["error"] = "ERROR: " .. data }
			else
				data = { query = q, info = "No rows returned" }
			end
			table.insert( result, data )
		end
		
		return true, result
	end,
		
	--- Closes the connection to the server
	--
	-- @return status true on success, false on failure
	Close = function( self )
		local status, packet = self.comm:exchIfxPacket( Packet.SQ_EXIT:new() )
		return self.socket:close()
	end,
	
}

return _ENV;
