security server for oc and opensecurity

local cryptKey = {1, 2, 3, 4, 5}
local modemPort = 199



local component = require("component")
local event = require("event")
local modem = component.modem
local ser = require ("serialization")
local term = require("term")

local function convert( chars, dist, inv )
  return string.char( ( string.byte( chars ) - 32 + ( inv and -dist or dist ) ) % 95 + 32 )
end


local function crypt(str,k,inv)
  local enc= "";
  for i=1,#str do
    if(#str-k[5] >= i or not inv)then
      for inc=0,3 do
    if(i%4 == inc)then
      enc = enc .. convert(string.sub(str,i,i),k[inc+1],inv);
      break;
    end
      end
    end
  end
  if(not inv)then
    for i=1,k[5] do
      enc = enc .. string.char(math.random(32,126));
    end
  end
  return enc;
end

--// exportstring( string )
--// returns a "Lua" portable version of the string
local function exportstring( s )
    s = string.format( "%q",s )
    -- to replace
    s = string.gsub( s,"\\\n","\\n" )
    s = string.gsub( s,"\r","\\r" )
    s = string.gsub( s,string.char(26),"\"..string.char(26)..\"" )
    return s
end
--// The Save Function
function saveTable(  tbl,filename )
    local charS,charE = "   ","\n"
    local file,err
    -- create a pseudo file that writes to a string and return the string
    if not filename then
        file =  { write = function( self,newstr ) self.str = self.str..newstr end, str = "" }
        charS,charE = "",""
    -- write table to tmpfile
    elseif filename == true or filename == 1 then
        charS,charE,file = "","",io.tmpfile()
    -- write table to file
    -- use io.open here rather than io.output, since in windows when clicking on a file opened with io.output will create an error
    else
        file,err = io.open( filename, "w" )
        if err then return _,err end
    end
    -- initiate variables for save procedure
    local tables,lookup = { tbl },{ [tbl] = 1 }
    file:write( "return {"..charE )
    for idx,t in ipairs( tables ) do
        if filename and filename ~= true and filename ~= 1 then
            file:write( "-- Table: {"..idx.."}"..charE )
        end
        file:write( "{"..charE )
        local thandled = {}
        for i,v in ipairs( t ) do
            thandled[i] = true
            -- escape functions and userdata
            if type( v ) ~= "userdata" then
                -- only handle value
                if type( v ) == "table" then
                    if not lookup[v] then
                        table.insert( tables, v )
                        lookup[v] = #tables
                    end
                    file:write( charS.."{"..lookup[v].."},"..charE )
                elseif type( v ) == "function" then
                    file:write( charS.."loadstring("..exportstring(string.dump( v )).."),"..charE )
                else
                    local value =  ( type( v ) == "string" and exportstring( v ) ) or tostring( v )
                    file:write(  charS..value..","..charE )
                end
            end
        end
        for i,v in pairs( t ) do
            -- escape functions and userdata
            if (not thandled[i]) and type( v ) ~= "userdata" then
                -- handle index
                if type( i ) == "table" then
                    if not lookup[i] then
                        table.insert( tables,i )
                        lookup[i] = #tables
                    end
                    file:write( charS.."[{"..lookup[i].."}]=" )
                else
                    local index = ( type( i ) == "string" and "["..exportstring( i ).."]" ) or string.format( "[%d]",i )
                    file:write( charS..index.."=" )
                end
                -- handle value
                if type( v ) == "table" then
                    if not lookup[v] then
                        table.insert( tables,v )
                        lookup[v] = #tables
                    end
                    file:write( "{"..lookup[v].."},"..charE )
                elseif type( v ) == "function" then
                    file:write( "loadstring("..exportstring(string.dump( v )).."),"..charE )
                else
                    local value =  ( type( v ) == "string" and exportstring( v ) ) or tostring( v )
                    file:write( value..","..charE )
                end
            end
        end
        file:write( "},"..charE )
    end
    file:write( "}" )
    -- Return Values
    -- return stringtable from string
    if not filename then
        -- set marker for stringtable
        return file.str.."--|"
    -- return stringttable from file
    elseif filename == true or filename == 1 then
        file:seek ( "set" )
        -- no need to close file, it gets closed and removed automatically
        -- set marker for stringtable
        return file:read( "*a" ).."--|"
    -- close file and return 1
    else
        file:close()
        return 1
    end
end

--// The Load Function
function loadTable( sfile )
    local tables, err, _
    -- catch marker for stringtable
    if string.sub( sfile,-3,-1 ) == "--|" then
        tables,err = loadstring( sfile )
    else
        tables,err = loadfile( sfile )
    end
    if err then return _,err
    end
    tables = tables()
    for idx = 1,#tables do
        local tolinkv,tolinki = {},{}
        for i,v in pairs( tables[idx] ) do
            if type( v ) == "table" and tables[v[1]] then
                table.insert( tolinkv,{ i,tables[v[1]] } )
            end
            if type( i ) == "table" and tables[i[1]] then
                table.insert( tolinki,{ i,tables[i[1]] } )
            end
        end
        -- link values, first due to possible changes of indices
        for _,v in ipairs( tolinkv ) do
            tables[idx][v[1]] = v[2]
        end
        -- link indices
        for _,v in ipairs( tolinki ) do
            tables[idx][v[2]],tables[idx][v[1]] =  tables[idx][v[1]],nil
        end
    end
    return tables[1]
end


term.clear()
print("Security server")
print("---------------------------------------------------------------------------")

local userTable = loadTable("userlist.txt")
local doorTable = loadTable("doorlist.txt")
if userTable == nil then
  userTable = {}
end
if doorTable == nil then
  doorTable = {}
end

function checkUser(user)
  for key, value in pairs(userTable) do
    if value.name == user then
      return true, not value.blocked, tonumber(value.level)
    end
  end
  return false
end

function checkLevel(id)
  for key, value in pairs(doorTable) do
    if key == id then
      return tonumber(value)
    end
  end
  return 0
end

while true do
  if modem.isOpen(modemPort) == false then
    modem.open(modemPort)
  end

  local _, _, from, port, _, command, msg = event.pull("modem_message")
  local data = crypt(msg, cryptKey, true)
  term.write(from .. ":" .. port .. ":" .. command)
  if command == "updateuser" then
    userTable = ser.unserialize(data)
    term.write("\n")
    saveTable(userTable, "userlist.txt")
  elseif command == "setlevel" then
    term.write(" " .. data .. "\n")
    doorTable[from] = data
    saveTable(doorTable, "doorlist.txt")
  elseif command == "checkuser" then
    term.write(":" .. data .. ":")
    local cu, isBlocked, level = checkUser(data)
    if cu == true then          -- user found
      if isBlocked == false then
    data = crypt("false", cryptKey)
    term.write("blocked\n")
    modem.send(from, port, data)
      else
    local cl = checkLevel(from)
    if cl > level then
      data = crypt("false", cryptKey)
      term.write("level too low\n")
      modem.send(from, port, data)
    else
      data = crypt("true", cryptKey)
      term.write("ok\n")
      modem.send(from, port, data)
    end
      end
    else
      data = crypt("false", cryptKey)
      term.write("not found\n")
      modem.send(from, port, data)
    end
  end
end