#51 WIP network interface controller
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Mikayla
225
scada-common/network.lua
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225
scada-common/network.lua
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--
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-- Network Communications
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--
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local md5 = require("lockbox.digest.md5")
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local sha256 = require("lockbox.digest.sha2_256")
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local pbkdf2 = require("lockbox.kdf.pbkdf2")
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local hmac = require("lockbox.mac.hmac")
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local stream = require("lockbox.util.stream")
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local array = require("lockbox.util.array")
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local comms = require("scada-common.comms")
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local log = require("scada-common.log")
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local util = require("scada-common.util")
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local network = {}
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local c_eng = {
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key = nil,
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hmac = nil
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}
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-- initialize message authentication system
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---@param passkey string facility passkey
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---@return integer init_time milliseconds init took
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function network.init_mac(passkey)
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local start = util.time_ms()
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local key_deriv = pbkdf2()
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-- setup PBKDF2
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key_deriv.setPassword(passkey)
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key_deriv.setSalt("pepper")
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key_deriv.setIterations(32)
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key_deriv.setBlockLen(8)
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key_deriv.setDKeyLen(16)
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key_deriv.setPRF(hmac().setBlockSize(64).setDigest(sha256))
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key_deriv.finish()
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c_eng.key = array.fromHex(key_deriv.asHex())
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-- initialize HMAC
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c_eng.hmac = hmac()
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c_eng.hmac.setBlockSize(64)
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c_eng.hmac.setDigest(md5)
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c_eng.hmac.setKey(c_eng.key)
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local init_time = util.time_ms() - start
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log.info("network.init_mac completed in " .. init_time .. "ms")
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return init_time
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end
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-- generate HMAC of message
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---@nodiscard
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---@param message string initial value concatenated with ciphertext
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local function compute_hmac(message)
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local start = util.time_ms()
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c_eng.hmac.init()
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c_eng.hmac.update(stream.fromString(message))
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c_eng.hmac.finish()
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local hash = c_eng.hmac.asHex()
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log.debug("compute_hmac(): hmac-md5 = " .. util.strval(hash) .. " (took " .. (util.time_ms() - start) .. "ms)")
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return hash
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end
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-- NIC: Network Interface Controller<br>
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-- utilizes HMAC-MD5 for message authentication, if enabled
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---@param modem table modem to use
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function network.nic(modem)
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local self = {
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connected = (modem ~= nil),
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channels = {}
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}
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---@class nic
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---@field open function
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---@field isOpen function
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---@field close function
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---@field closeAll function
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---@field isWireless function
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---@field getNameLocal function
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---@field getNamesRemote function
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---@field isPresentRemote function
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---@field getTypeRemote function
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---@field hasTypeRemote function
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---@field getMethodsRemote function
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---@field callRemote function
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local public = {}
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-- connect to a modem peripheral
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---@param reconnected_modem table
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function public.connect(reconnected_modem)
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modem = reconnected_modem
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self.connected = true
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-- open previously opened channels
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for _, channel in ipairs(self.channels) do
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modem.open(channel)
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end
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-- link all public functions except for transmit
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for key, func in pairs(modem) do
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if key ~= "transmit" and key ~= "open" and key ~= "close" and key ~= "closeAll" then public[key] = func end
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end
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end
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-- flag this NIC as no longer having a connected modem (usually do to peripheral disconnect)
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function public.disconnect() self.connected = false end
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-- check if this NIC has a connected modem
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---@nodiscard
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function public.connected() return self.connected end
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-- check if a peripheral is this modem
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---@nodiscard
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---@param device table
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function public.is_modem(device) return device == modem end
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-- wrap modem functions, then create custom transmit
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public.connect(modem)
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function public.open(channel)
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if self.connected then
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modem.open(channel)
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local already_open = false
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for i = 1, #self.channels do
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if self.channels[i] == channel then
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already_open = true
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break
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end
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end
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if not already_open then
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table.insert(self.channels, channel)
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end
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end
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end
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function public.close(channel)
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if self.connected then
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modem.close(channel)
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for i = 1, #self.channels do
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if self.channels[i] == channel then
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table.remove(self.channels, i)
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return
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end
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end
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end
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end
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function public.closeAll()
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if self.connected then
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modem.closeAll()
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self.channels = {}
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end
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end
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-- send a packet, with message authentication if configured
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---@param dest_channel integer destination channel
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---@param local_channel integer local channel
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---@param packet scada_packet packet raw_sendable
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function public.transmit(dest_channel, local_channel, packet)
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if self.connected then
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if c_eng.hmac ~= nil then
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local start = util.time_ms()
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local message = textutils.serialize(packet.raw_verifiable(), { allow_repetitions = true, compact = true })
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local computed_hmac = compute_hmac(message)
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packet.set_mac(computed_hmac)
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log.debug("crypto.modem.transmit: data processing took " .. (util.time_ms() - start) .. "ms")
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end
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modem.transmit(dest_channel, local_channel, packet.raw_sendable())
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end
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end
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-- parse in a modem message as a network packet
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---@nodiscard
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---@param side string modem side
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---@param sender integer sender channel
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---@param reply_to integer reply channel
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---@param message any packet sent with or without message authentication
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---@param distance integer transmission distance
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---@return scada_packet|nil packet received packet if valid and passed authentication check
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function public.receive(side, sender, reply_to, message, distance)
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local packet = nil
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if self.connected then
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local s_packet = comms.scada_packet()
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-- parse packet as generic SCADA packet
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s_packet.receive(side, sender, reply_to, message, distance)
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if s_packet.is_valid() then
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if c_eng.hmac ~= nil then
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local start = util.time_ms()
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local packet_hmac = s_packet.mac()
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local computed_hmac = compute_hmac(textutils.serialize(s_packet.raw_verifiable(), { allow_repetitions = true, compact = true }))
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if packet_hmac == computed_hmac then
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log.debug("crypto.modem.receive: HMAC verified in " .. (util.time_ms() - start) .. "ms")
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packet = s_packet
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else
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log.debug("crypto.modem.receive: HMAC failed verification in " .. (util.time_ms() - start) .. "ms")
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end
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else
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packet = s_packet
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end
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end
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end
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return packet
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end
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return public
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end
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return network
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