dnsupdater/main.go

package main

import (
	"encoding/json"
	"fmt"
	"github.com/robfig/cron"
	log "github.com/sirupsen/logrus"
	"github.com/urfave/cli"
	"gopkg.in/src-d/go-git.v4"
	"gopkg.in/src-d/go-git.v4/plumbing/object"
	githttp "gopkg.in/src-d/go-git.v4/plumbing/transport/http"
	"io/ioutil"
	"net/http"
	"net/smtp"
	"os"
	"os/signal"
	"path"
	"regexp"
	"strconv"
	"strings"
	"syscall"
	"time"
)

type Configuration struct {
	RepositoryUrl string `json:"url"`
	Username      string `json:"name"`
	Email         string `json:"email"`
	GitLogin      string `json:"login"`
	GitPassword   string `json:"password"`
}

var (
	configPath   string
	scheduleSpec string
)

var version = "master"
var commit = "unknown"
var date = "unknown"

func main() {

	app := cli.NewApp()
	app.Name = "watchtower"
	app.Version = version + " - " + commit + " - " + date
	app.Usage = "Automatically update running Docker containers"
	app.Before = before
	app.Action = start
	app.Flags = []cli.Flag{

		cli.StringFlag{
			Name:   "config, C",
			Usage:  "path to config file",
			Value:  "/config/conf.json",
			EnvVar: "CONFIG_PATH",
		},
		cli.IntFlag{
			Name:   "interval, i",
			Usage:  "poll interval (in seconds)",
			Value:  300,
			EnvVar: "DNSUPDATER_POLL_INTERVAL",
		},
		cli.StringFlag{
			Name:   "schedule, s",
			Usage:  "the cron expression which defines when to update",
			EnvVar: "DNSUPDATER_SCHEDULE",
		},
	}

	if err := app.Run(os.Args); err != nil {
		log.Fatal(err)
	}
}

func before(c *cli.Context) error {
	if c.GlobalBool("debug") {
		log.SetLevel(log.DebugLevel)
	}

	pollingSet := c.IsSet("interval")
	cronSet := c.IsSet("schedule")

	if pollingSet && cronSet {
		log.Fatal("Only schedule or interval can be defined, not both.")
	} else if cronSet {
		scheduleSpec = c.String("schedule")
	} else {
		scheduleSpec = "@every " + strconv.Itoa(c.Int("interval")) + "s"
	}
	return nil
}

func start(c *cli.Context) error {
	tryLockSem := make(chan bool, 1)
	tryLockSem <- true

	cron := cron.New()
	err := cron.AddFunc(
		scheduleSpec,
		func() {
			select {
			case v := <-tryLockSem:
				defer func() { tryLockSem <- v }()
				if err := update(c); err != nil {
					log.Println(err)
					SendStatusMail(fmt.Sprintf("Error during update process : %s", err))
				}
			default:
				log.Debug("Skipped another update already running.")
			}

			nextRuns := cron.Entries()
			if len(nextRuns) > 0 {
				log.Debug("Scheduled next run: " + nextRuns[0].Next.String())
			}
		})

	if err != nil {
		return err
	}

	log.Info("First run: " + cron.Entries()[0].Schedule.Next(time.Now()).String())
	cron.Start()

	// Graceful shut-down on SIGINT/SIGTERM
	interrupt := make(chan os.Signal, 1)
	signal.Notify(interrupt, os.Interrupt)
	signal.Notify(interrupt, syscall.SIGTERM)

	<-interrupt
	cron.Stop()
	log.Info("Waiting for running update to be finished...")
	<-tryLockSem
	os.Exit(1)
	return nil
}

func update(c *cli.Context) error {
	Info("Running dnsupdater...")

	configPath = c.String("config")

	if confPathExists, _ := exists(configPath); !confPathExists {
		configPath = "./data";
	}

	file, _ := os.Open(path.Join(configPath, "conf.json"))
	defer file.Close()
	decoder := json.NewDecoder(file)
	configuration := Configuration{}
	err := decoder.Decode(&configuration)

	Info("Repository : %s", configuration.RepositoryUrl)
	Info("Name : %s", configuration.Username)
	Info("Email : %s", configuration.Email)
	Info("GitLogin : %s", configuration.GitLogin)


	err = os.RemoveAll(path.Join(configPath, "data"))
	if err != nil {
		return err
	}

	_, err = git.PlainClone(path.Join(configPath, "data"), false, &git.CloneOptions{
		URL:      configuration.RepositoryUrl,
		Progress: os.Stdout,
	})
	if err != nil {
		return err
	}

	currentIp, err := GetCurrentIp()
	if err != nil {
		return err
	}
	newIp, err := GetOutboundIP()
	if err != nil {
		return err
	}

	if currentIp == newIp {
		Info("Ip has not changed %s", currentIp)
		return nil
	}

	Info("Ip has changed %s -> %s", currentIp, newIp)
	SetCurrentIp(currentIp, newIp)

	repo, err := git.PlainOpen(path.Join(configPath, "data"))
	if err != nil {
		return err
	}
	w, err := repo.Worktree()
	if err != nil {
		return err
	}
	_, err = w.Add("templates/home_a.lua")
	if err != nil {
		return err
	}

	status, err := w.Status()
	if err != nil {
		return err
	}

	fmt.Println(status)
	_, err = w.Commit(fmt.Sprintf("Changement d'IP maison : %s -> %s", currentIp, newIp), &git.CommitOptions{
		Author: &object.Signature{
			Name:  configuration.Username,
			Email: configuration.Email,
			When:  time.Now().Local(),
		},
	})
	if err != nil {
		return err
	}

	err = repo.Push(&git.PushOptions{
		Auth: &githttp.BasicAuth{
			Username: configuration.GitLogin,
			Password: configuration.GitPassword,
		},
	})
	if err != nil {
		return err
	}

	SendStatusMail(fmt.Sprintf(`Home IP has changed : %s -> %s
Dns updated successfully`, currentIp, newIp))

	return nil
}

func SendStatusMail(messageText string) {
	// user we are authorizing as
	from := "laurent@lehouerou.net"

	// use we are sending email to
	to := "laurent@lehouerou.net"

	// server we are authorized to send email through
	host := "smtp.fastmail.com"

	// Create the authentication for the SendMail()
	// using PlainText, but other authentication methods are encouraged
	auth := smtp.PlainAuth("", from, "c9bd8fb8l4bhs2f8", host)

	// NOTE: Using the backtick here ` works like a heredoc, which is why all the
	// rest of the lines are forced to the beginning of the line, otherwise the
	// formatting is wrong for the RFC 822 style
	message := fmt.Sprintf(`To: "Laurent Le Houerou" <laurent@lehouerou.net>
From: "Laurent Le Houerou" <laurent@lehouerou.net>
Subject: DnsUpdater Status

%s
`,messageText)

	if err := smtp.SendMail(host+":587", auth, from, []string{to}, []byte(message)); err != nil {
		fmt.Println("Error SendMail: ", err)
	} else {
		fmt.Println("Email Sent!")
	}
}

func GetCurrentIp() (string, error) {
	b, err := ioutil.ReadFile(path.Join(configPath, "data/templates/home_a.lua"))
	if err != nil {
		return "", err
	}

	re := regexp.MustCompile("\"(.*?)\"")
	match := re.FindStringSubmatch(string(b))
	return match[1], nil
}

func SetCurrentIp(oldip string, newip string) error {
	b, err := ioutil.ReadFile(path.Join(configPath, "data/templates/home_a.lua"))
	if err != nil {
		return err
	}

	s := string(b)
	s = strings.Replace(s, oldip, newip, 1)
	ioutil.WriteFile(path.Join(configPath, "data/templates/home_a.lua"), []byte(s), 0644)
	return nil
}

func GetOutboundIP() (string, error) {
	url := "https://diagnostic.opendns.com/myip"
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return "", err
	}
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		return "", err
	}
	defer res.Body.Close()
	body, err := ioutil.ReadAll(res.Body)
	if err != nil {
		return "", err
	}
	return string(body), nil
}

func exists(path string) (bool, error) {
	_, err := os.Stat(path)
	if err == nil {
		return true, nil
	}
	if os.IsNotExist(err) {
		return false, nil
	}
	return true, err
}

func Info(format string, args ...interface{}) {
	fmt.Printf("\x1b[34;1m%s\x1b[0m\n", fmt.Sprintf(format, args...))
}