description = [[
Listens for Dropbox LanSync information broadcasts.

The Dropbox LanSync protocol broadcasts an opaque set of host and share
identifiers. It does this every twenty seconds.
]]

author = "Ron Bowes, Mak Kolybabi, Andrew Orr, Russ Tait Milne"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"broadcast", "safe"}

require("json")
require("shortport")
require("stdnse")
require("tab")
require("target")

local DROPBOX_BROADCAST_PERIOD = 20
local DROPBOX_PORT = 17500

prerule = function()
	return true
end

action = function()
	-- Start listening for broadcasts.
	local sock = nmap.new_socket("udp")
	sock:set_timeout(2 * DROPBOX_BROADCAST_PERIOD * 1000)
	local status, result = sock:bind(nil, DROPBOX_PORT)
	if not status then
		stdnse.print_debug(1, "Could not bind on port %d: %s", DROPBOX_PORT, result)
		sock:close()
		return
	end

	-- Keep track of the IDs we've already seen.
	local ids = {}

	-- Initialize the output table.
	results = tab.new(6)
	tab.addrow(
		results,
		'displayname',
		'ip',
		'port',
		'version',
		'host_int',
		'namespaces'
	)

	local status, result = sock:receive()
	while status do
		-- Parse JSON.
		local status, info = json.parse(result)
		if status then
			-- Get IP address of broadcasting host.
			local status, _, _, ip, _ = sock:get_info()
			if not status then
				stdnse.print_debug(1, "Failed to get socket info.")
				break
			end
			stdnse.print_debug(1, "Received broadcast from host %s (%s).", info.displayname, ip)

			-- Check if we've already seen this ID.
			if ids[info.host_int] then
				break
			end
			ids[info.host_int] = true

			-- Add host scan list.
			if target.ALLOW_NEW_TARGETS then
				target.add(ip)
			end

			-- Add host to list.
			for _, key1 in pairs({"namespaces", "version"}) do
				for key2, val in pairs(info[key1]) do
					info[key1][key2] = tostring(info[key1][key2])
				end
			end
			tab.addrow(
				results,
				info.displayname,
				ip,
				info.port,
				stdnse.strjoin(".", info.version),
				info.host_int,
				stdnse.strjoin(", ", info.namespaces)
			)

			stdnse.print_debug(1, "Added host %s.", info.displayname)
		end

		status, result = sock:receive()
	end

	sock:close()

	-- If no broadcasts received, don't output anything.
	if table.maxn(ids) == 0 then
		 return
	end

	-- Format table, without trailing newline.
	results = tab.dump(results)
	results = results:sub(1, #results - 1)

	return "\n" .. results
end