computercraft/packages/lns_server.lua

settings.define("lns_server.modem_location", {
    description = "Modem location",
    type = "string",
    default = "right"
})
modem_location = settings.get("lns_server.modem_location")

settings.define("lns_server.rednet_hostname", {
    description = "Rednet hostname",
    type = "string",
    default = "test"
})

settings.define("lns_server.require_auth", {
    description = "Require authentication",
    type = "boolean",
    default = false
})
require_auth = settings.get("lns_server.require_auth")

settings.define("lns_server.auth_group", {
    description = "Authentication group",
    type = "string",
    default = "admin"
})
local auth_group = settings.get("lns_server.auth_group")

settings.define("lns_server.auth_server", {
    description = "Authentication server",
    type = "string",
    default = "auth.box"
})
auth_server = settings.get("lns_server.auth_server")

settings.define("lns_server.log_level", {
    description = "Log Level",
    type = "string",
    default = "info"
})
log_level = settings.get("lns_server.log_level")

rednet.host("lns", settings.get("lns_server.rednet_hostname"))
rednet.open(modem_location)

local data = {}


function log(str)
    io.write("[" .. os.time() .. "] " .. str .. "\n")
end

function log_debug(str)
    if log_level == "debug" then
        log(str)
    end
end

function save_data()
    db = fs.open("lns.db", "w")
    db.write(textutils.serialize(data))
    db.close()
end

function load_data()
    if fs.exists("lns.db") then
        db = fs.open("lns.db", "r")
        db_contents = db.readAll()
        db.close()

        data = textutils.unserialize(db_contents)
    end
end

function split (inputstr, sep)
    if sep == nil then
       sep = "%s"
    end
    local t={}
    for str in string.gmatch(inputstr, "([^"..sep.."]+)") do
       table.insert(t, str)
    end
    return t
 end

 function check_user_in_group(username, group)
    local package = {
        ["action"] = "check_group",
        ["username"] = username,
        ["group"] = group
    }

    local authID = data[auth_server]
    rednet.send(authID, package, "auth")

    while true do
        id, msg = rednet.receive("auth")
        if id == authID then
            if msg == "invalid request" then
                io.write("Invalid request\n")
                return false
            elseif msg == true then
                return true
            else
                return false
            end
        end
    end
end


load_data()

while true do
    client_id, msg = rednet.receive("lns")
    request = msg

    if request.action == nil or request.hostname == nil then
        rednet.send(client_id, "invalid request", "lns")
    end

    if request.action == "lookup" then

        -- check if hostname in data
        if request.hostname == nil then
            rednet.send(client_id, nil, "lns")
            log("Sent nil to " .. client_id)
        else
            rednet.send(client_id, data[request.hostname], "lns")
            log("Sent " .. request.hostname .. " to " .. client_id)
        end
    end
    
    if request.action == "reload" then
        load_data()
        rednet.send(client_id, "ok", "lns")
        log("Reloaded data")
    end

    if request.action == "register" then

        local auth_passed = false
        if require_auth then
            local authID = data[auth_server]
            if request.token == nil then
                rednet.send(client_id, "invalid auth", "lns")
            elseif authID ~= nil then
                rednet.send(authID, {
                    ["action"] = "token",
                    ["token"] = request.token
                }, "auth")

                local responseServerID = nil
                while responseServerID ~= authID do
                    responseServerID, auth_response = rednet.receive("auth")
                end
                
                local errorPos, errorEnd = string.find(auth_response, "invalid")
                if errorPos then
                    log("Error: " .. auth_response)
                else
                    if check_user_in_group(auth_response, auth_group) then
                        auth_passed = true
                    else
                        rednet.send(client_id, "invalid auth", "lns")
                    end
                end
            else
                log("Error: Auth server not found to " .. client_id)
            end
        else
            auth_passed = true
        end

        if auth_passed then
            data[request.hostname] = client_id
            log("Registered " .. request.hostname .. " as " .. client_id)
            save_data()
            rednet.send(client_id, "ok", "lns")
        else
            rednet.send(client_id, "auth required", "lns")
        end
    end
end