o [NSE] Added a new library for ASN.1 parsing and adapted the SNMP library to

make use of it. Added 5 scripts that use the new libraries:
  - snmp-netstat shows listening and connected sockets
  - snmp-processes shows process information including name, pid, path and 
    parameters
  - snmp-win32-services shows the names of running Windows services
  - snmp-win32-shares shows the names and path of Windows shares
  - snmp-win32-software shows a list of installed Windows software
  - snmp-win32-users shows a list of local Windows users

scripts/snmp-win32-software.nse

@@ -0,0 +1,147 @@
+description = [[
+Attempts to enumerate installed software through SNMP
+]]
+
+---
+-- @output
+-- | snmp-win32-software:  
+-- |   Apache Tomcat 5.5 (remove only); 2007-09-15 15:13:18
+-- |   Microsoft Internationalized Domain Names Mitigation APIs; 2007-09-15 15:13:18
+-- |   Security Update for Windows Media Player (KB911564); 2007-09-15 15:13:18
+-- |   Security Update for Windows Server 2003 (KB924667-v2); 2007-09-15 15:13:18
+-- |   Security Update for Windows Media Player 6.4 (KB925398); 2007-09-15 15:13:18
+-- |   Security Update for Windows Server 2003 (KB925902); 2007-09-15 15:13:18
+-- |_  Windows Internet Explorer 7; 2007-09-15 15:13:18
+
+author = "Patrik Karlsson"
+license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
+categories = {"default", "discovery", "safe"}
+dependencies = {"snmp-brute"}
+
+-- Version 0.2
+-- Created 01/15/2010 - v0.1 - created by Patrik Karlsson <patrik@cqure.net>
+-- Revised 01/19/2010 - v0.2 - fixed loop that would occure if a mib did not exist
+
+require "shortport"
+require "snmp"
+
+portrule = shortport.portnumber(161, "udp", {"open", "open|filtered"})
+
+
+--- Walks the MIB Tree
+--
+-- @param socket socket already connected to the server
+-- @base_oid string containing the base object ID to walk
+-- @return table containing <code>oid</code> and <code>value</code>
+function snmp_walk( socket, base_oid )
+	
+	local catch = function() socket:close()	end
+	local try = nmap.new_try(catch)	
+
+	local snmp_table = {}
+	local oid = base_oid
+	
+	while ( true ) do
+		
+		local value, response, snmpdata, options, item = nil, nil, nil, {}, {}
+		options.reqId = 28428 -- unnecessary?
+		payload = snmp.encode( snmp.buildPacket( snmp.buildGetNextRequest(options, oid) ) )
+
+		try(socket:send(payload))
+		response = try( socket:receive_bytes(1) )
+	
+		snmpdata = snmp.fetchResponseValues( response )
+		
+		value = snmpdata[1][1]
+		oid  = snmpdata[1][2]
+		
+		if not oid:match( base_oid ) or base_oid == oid then
+			break
+		end
+		
+		item.oid = oid
+		item.value = value
+		
+		table.insert( snmp_table, item )
+		
+	end
+
+	socket:close()
+	snmp_table.baseoid = base_oid
+
+	return snmp_table
+	
+end
+
+--- Gets a value for the specified oid
+--
+-- @param tbl table containing <code>oid</code> and <code>value</code>
+-- @param oid string containing the object id for which the value should be extracted
+-- @return value of relevant type or nil if oid was not found
+function get_value_from_table( tbl, oid )
+	
+	for _, v in ipairs( tbl ) do
+		if v.oid == oid then
+			return v.value
+		end
+	end
+	
+	return nil
+end
+
+--- Processes the table and creates the script output
+--
+-- @param tbl table containing <code>oid</code> and <code>value</code>
+-- @return table suitable for <code>stdnse.format_output</code>
+function process_answer( tbl )
+	
+	local sw_name = "1.3.6.1.2.1.25.6.3.1.2"
+	local sw_date = "1.3.6.1.2.1.25.6.3.1.5"
+	local new_tbl = {}
+	
+	for _, v in ipairs( tbl ) do
+		
+		if ( v.oid:match("^" .. sw_name) ) then
+			local objid = v.oid:gsub( "^" .. sw_name, sw_date) 
+			local install_date = get_value_from_table( tbl, objid )
+			local sw_item
+			
+			local _, year, month, day, hour, min, sec = bin.unpack( ">SCCCCC", install_date )
+			install_date = ("%02d-%02d-%02d %02d:%02d:%02d"):format( year, month, day, hour, min, sec )	
+
+			sw_item = ("%s; %s"):format(v.value ,install_date)
+			table.insert( new_tbl, sw_item )
+		end
+	
+	end
+	
+	table.sort( new_tbl )
+	return new_tbl
+	
+end
+
+
+action = function(host, port)
+
+	local socket = nmap.new_socket()
+	local catch = function() socket:close()	end
+	local try = nmap.new_try(catch)	
+	local data, snmpoid = nil, "1.3.6.1.2.1.25.6.3.1"
+	local sw = {}
+
+	socket:set_timeout(5000)
+	try(socket:connect(host.ip, port.number, "udp"))
+	
+	sw = snmp_walk( socket, snmpoid )
+
+	if ( sw == nil ) or ( #sw == 0 ) then
+		return
+	end
+		
+	sw = process_answer( sw )
+
+	nmap.set_port_state(host, port, "open")
+
+	return stdnse.format_output( true, sw )
+end
+