remsec_server.lua

local event = require("event")
local component = require("component")
local thread = require("thread")
local term = require("term")
local debug = true
local gerti
local cfg
local data
local encrypt
local decrypt
local ok
local hash
local key
local iv
local timesHit
local attack_invalid
local attack_amount
local checksumtext
local commands = {[1] = "SET"}
ok, gerti = pcall(require, "GERTiClient")
if not ok then
  io.stderr:write("Could not load GERTi.")
  os.exit(1)
end
ok, cfg = pcall(require, "osu.config")
if not ok then
  io.stderr:write("Could not load config.")
  os.exit(1)
end
if not cfg.remsec.enabled then
  io.stderr:write("RemSec is disabled on this computer.")
  os.exit(1)
end
if gerti.getAddress() == nil then
  io.stderr:write("No connection to MNC.")
  os.exit(1)
end
local function containsKey(table, element)
  for key, _ in pairs(table) do
    if key == element then
      return true
    end
  end
  return false
end
key = cfg.remsec.key
iv = cfg.remsec.iv
attack_amount = cfg.remsec.attack_amount
attack_invalid = cfg.remsec.attack_invalid
checksumtext = cfg.remsec.checksumtext
local function containsValue(table, element)
  for _, value in pairs(table) do
    if value == element then
      return true
    end
  end
  return false
end
if not component.isAvailable("data") then
  io.stderr:write("Data card unavailable.")
  os.exit(1)
else
  data = component.data
  if not data.sha256 then
    io.stderr:write("SHA-256 not available.")
    os.exit(1)
  end
  if not data.encrypt then
    io.stderr:write("AES-128 encryption not available.")
    os.exit(1)
  end
  hash = data.sha256
  encrypt = function(text)
    if debug then
      print("DEBUG: Encrypting data")
    end
    encrypted = data.encrypt(tostring(text), tostring(key), tostring(iv))
    if debug then
      print("DEBUG: Done")
    end
    return encrypted
  end
  decrypt = function(binary)
    if debug then
      print("DEBUG: Decrypting data")
    end
    decrypted = data.decrypt(binary, tostring(key), tostring(iv))
    if debug then
      print("DEBUG: Done")
    end
    return decrypted
  end
end
local clients = {}
term.clear()
local addClient = thread.create(function()
  while true do
    local _, client, connectionID = event.pull("GERTConnectionID")
    clients[client] = gerti.openSocket(client, true, connectionID)
    print("Connected to computer "..client..".")
    clients[client]:write("CONNECT_SUCCESS")
  end
end)
local warnClosure = thread.create(function()
  while true do
    local _, client = event.pull("GERTConnectionClose")
    print("!! WARNING !! Client "..client.." has disconnected.")
  end
end)
local printData = thread.create(function()
  while true do
    local _, client = event.pull("GERTData")
    if debug then
      print("DEBUG: Received GERTData event")
    end
    if not containsKey(clients, client) then
      print("!! WARNING !! Message sent from nonexistent socket.")
    else
      text = clients[client]:read()
      if debug then
        print("DEBUG: Read from socket to computer "..client)
      end
      if decrypt(text[1]) == hash(checksumtext) then
        if debug then
          print("DEBUG: Decrypted hash and it is correct, waiting for data...")
        end
        _, client = event.pull("GERTData")
        if debug then
          print("DEBUG: Received second GERTData event")
        end
        text = clients[client]:read()
        if debug then
          print("DEBUG: Read from socket to computer "..client)
        end
        txt = decrypt(text[1])
        if containsValue(commands, txt:gmatch("%S+")():upper()) then
          command = txt:gmatch("%S+")():upper()
          if command == "SET" then
            _, var, newVal, pass = txt:gmatch("%S+")
            var = var:lower()
            if var == "key" then
              if pass == key then
                for num in pairs(clients) do
                  clients[num]:write("CHANGE_ENCRYPTION_KEY "..pass)
                end
                key = newVal
              else
                clients[client]:write("NEW_KEY_INVALID")
              end
            end
            if var == "iv" then
              if pass == iv then
                for num in pairs(clients) do
                  clients[num]:write(encrypt("CHANGE_ENCRYPTION_IV "..pass))
                end
                key = newVal
              else
                clients[client]:write("NEW_IV_INVALID")
              end
            end
          end
        else
          print("Received message from "..client..": "..txt)
          clients[client]:write(encrypt("MESSAGE_RECEIVED: "..decrypt(text[1])))
        end
      else
        print("!! CRITICAL !! Client "..client.." did not send correct checksum!")
        if attack_invalid then
          local timesHit = 0
          repeat
            clients[client]:write("REMSEC_INVALID_CLIENT")
            timesHit = timesHit + 1
          until timesHit == attack_amount
        end
        clients[client]:close()
      end
    end
  end
end)
local safeExit = thread.create(function()
  event.pull("interrupted")
  for num in pairs(clients) do
    clients[num]:write("DISCONNECT")
    clients[num]:close()
  end
end)
thread.waitForAny({addClient, printData, safeExit, warnClosure})
if printData:status() == "dead" then
  print("Fatal error!")
end
os.exit(0)