Refactor updater API (#767)

* Moved updater business logic in updater package

* Moved updater business logic in updater package

* Added infrastructure for generic updater procedure

* Factored fetchInfo function to retrieve information about the latest update

* Inlined Updater.fetchInfo method

* Renamed updater_macos -> updater_darwin and removed build flag

Author: cmaglie

Diff for: main.go

@@ -22,7 +22,6 @@ import (
 	_ "embed"
 	"encoding/json"
 	"flag"
-	"io/ioutil"
 	"os"
 	"runtime"
 	"runtime/debug"
@@ -149,39 +148,15 @@ func main() {
 		ConfigDir:        configDir,
 	}
 
-	// If the executable is temporary, copy it to the full path, then restart
 	if src, err := os.Executable(); err != nil {
 		panic(err)
-	} else if strings.Contains(src, "-temp") {
-		newPath := updater.RemoveTempSuffixFromPath(src)
-		if err := copyExe(src, newPath); err != nil {
-			log.Println("Copy error: ", err)
-			panic(err)
-		}
-		Systray.RestartWith(newPath)
+	} else if restartPath := updater.Start(src); restartPath != "" {
+		Systray.RestartWith(restartPath)
 	} else {
-		// Otherwise copy to a path with -temp suffix
-		if err := copyExe(src, updater.AddTempSuffixToPath(src)); err != nil {
-			panic(err)
-		}
 		Systray.Start()
 	}
 }
 
-func copyExe(from, to string) error {
-	data, err := ioutil.ReadFile(from)
-	if err != nil {
-		log.Println("Cannot read file: ", from)
-		return err
-	}
-	err = ioutil.WriteFile(to, data, 0755)
-	if err != nil {
-		log.Println("Cannot write file: ", to)
-		return err
-	}
-	return nil
-}
-
 func loop() {
 	if *hibernate {
 		return

Diff for: update.go

@@ -30,40 +30,16 @@
 package main
 
 import (
-	"os"
-
 	"github.com/arduino/arduino-create-agent/updater"
 	"github.com/gin-gonic/gin"
 )
 
 func updateHandler(c *gin.Context) {
-
-	path, err := os.Executable()
-
-	if err != nil {
-		c.JSON(500, gin.H{"error": err.Error()})
-		return
-	}
-
-	var up = &updater.Updater{
-		CurrentVersion: version,
-		APIURL:         *updateURL,
-		BinURL:         *updateURL,
-		DiffURL:        "",
-		Dir:            "update/",
-		CmdName:        *appName,
-	}
-
-	err = up.BackgroundRun()
-
+	restartPath, err := updater.CheckForUpdates(version, *updateURL, *updateURL, *appName)
 	if err != nil {
 		c.JSON(500, gin.H{"error": err.Error()})
 		return
 	}
-
-	path = updater.AddTempSuffixToPath(path)
-
 	c.JSON(200, gin.H{"success": "Please wait a moment while the agent reboots itself"})
-
-	Systray.RestartWith(path)
+	Systray.RestartWith(restartPath)
 }

Diff for: updater/updater.go

@@ -16,121 +16,54 @@
 package updater
 
 import (
-	"bytes"
-	"compress/gzip"
 	"crypto/sha256"
 	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"net/http"
-	"os"
-	"path/filepath"
 	"runtime"
-	"strings"
 
-	"github.com/kr/binarydist"
 	log "github.com/sirupsen/logrus"
-	"gopkg.in/inconshreveable/go-update.v0"
 )
 
-// Update protocol:
-//
-//   GET hk.heroku.com/hk/linux-amd64.json
-//
-//   200 ok
-//   {
-//       "Version": "2",
-//       "Sha256": "..." // base64
-//   }
-//
-// then
-//
-//   GET hkpatch.s3.amazonaws.com/hk/1/2/linux-amd64
-//
-//   200 ok
-//   [bsdiff data]
-//
-// or
-//
-//   GET hkdist.s3.amazonaws.com/hk/2/linux-amd64.gz
-//
-//   200 ok
-//   [gzipped executable data]
-//
-//
+// Start checks if an update has been downloaded and if so returns the path to the
+// binary to be executed to perform the update. If no update has been downloaded
+// it returns an empty string.
+func Start(src string) string {
+	return start(src)
+}
+
+// CheckForUpdates checks if there is a new version of the binary available and
+// if so downloads it.
+func CheckForUpdates(currentVersion string, updateAPIURL, updateBinURL string, cmdName string) (string, error) {
+	return checkForUpdates(currentVersion, updateAPIURL, updateBinURL, cmdName)
+}
 
 const (
 	plat = runtime.GOOS + "-" + runtime.GOARCH
 )
 
-var errHashMismatch = errors.New("new file hash mismatch after patch")
-var errDiffURLUndefined = errors.New("DiffURL is not defined, I cannot fetch and apply patch, reverting to full bin")
-var up = update.New()
-
-// AddTempSuffixToPath adds the "-temp" suffix to the path to an executable file (a ".exe" extension is replaced with "-temp.exe")
-func AddTempSuffixToPath(path string) string {
-	if filepath.Ext(path) == "exe" {
-		path = strings.Replace(path, ".exe", "-temp.exe", -1)
-	} else {
-		path = path + "-temp"
+func fetchInfo(updateAPIURL string, cmdName string) (*availableUpdateInfo, error) {
+	r, err := fetch(updateAPIURL + cmdName + "/" + plat + ".json")
+	if err != nil {
+		return nil, err
 	}
+	defer r.Close()
 
-	return path
-}
-
-// RemoveTempSuffixFromPath removes "-temp" suffix from the path to an executable file (a "-temp.exe" extension is replaced with ".exe")
-func RemoveTempSuffixFromPath(path string) string {
-	return strings.Replace(path, "-temp", "", -1)
-}
-
-// Updater is the configuration and runtime data for doing an update.
-//
-// Note that ApiURL, BinURL and DiffURL should have the same value if all files are available at the same location.
-//
-// Example:
-//
-//	updater := &selfupdate.Updater{
-//		CurrentVersion: version,
-//		ApiURL:         "http://updates.yourdomain.com/",
-//		BinURL:         "http://updates.yourdownmain.com/",
-//		DiffURL:        "http://updates.yourdomain.com/",
-//		Dir:            "update/",
-//		CmdName:        "myapp", // app name
-//	}
-//	if updater != nil {
-//		go updater.BackgroundRun()
-//	}
-type Updater struct {
-	CurrentVersion string // Currently running version.
-	APIURL         string // Base URL for API requests (json files).
-	CmdName        string // Command name is appended to the ApiURL like http://apiurl/CmdName/. This represents one binary.
-	BinURL         string // Base URL for full binary downloads.
-	DiffURL        string // Base URL for diff downloads.
-	Dir            string // Directory to store selfupdate state.
-	Info           struct {
-		Version string
-		Sha256  []byte
+	var res availableUpdateInfo
+	if err := json.NewDecoder(r).Decode(&res); err != nil {
+		return nil, err
+	}
+	if len(res.Sha256) != sha256.Size {
+		return nil, errors.New("bad cmd hash in info")
 	}
+	return &res, nil
 }
 
-// BackgroundRun starts the update check and apply cycle.
-func (u *Updater) BackgroundRun() error {
-	os.MkdirAll(u.getExecRelativeDir(u.Dir), 0777)
-	if err := up.CanUpdate(); err != nil {
-		log.Println(err)
-		return err
-	}
-	//self, err := os.Executable()
-	//if err != nil {
-	// fail update, couldn't figure out path to self
-	//return
-	//}
-	// TODO(bgentry): logger isn't on Windows. Replace w/ proper error reports.
-	if err := u.update(); err != nil {
-		return err
-	}
-	return nil
+type availableUpdateInfo struct {
+	Version string
+	Sha256  []byte
 }
 
 func fetch(url string) (io.ReadCloser, error) {
@@ -144,147 +77,3 @@ func fetch(url string) (io.ReadCloser, error) {
 	}
 	return resp.Body, nil
 }
-
-func verifySha(bin []byte, sha []byte) bool {
-	h := sha256.New()
-	h.Write(bin)
-	return bytes.Equal(h.Sum(nil), sha)
-}
-
-func (u *Updater) fetchAndApplyPatch(old io.Reader) ([]byte, error) {
-	if u.DiffURL == "" {
-		return nil, errDiffURLUndefined
-	}
-	r, err := fetch(u.DiffURL + u.CmdName + "/" + u.CurrentVersion + "/" + u.Info.Version + "/" + plat)
-	if err != nil {
-		return nil, err
-	}
-	defer r.Close()
-	var buf bytes.Buffer
-	err = binarydist.Patch(old, &buf, r)
-	return buf.Bytes(), err
-}
-
-func (u *Updater) fetchAndVerifyPatch(old io.Reader) ([]byte, error) {
-	bin, err := u.fetchAndApplyPatch(old)
-	if err != nil {
-		return nil, err
-	}
-	if !verifySha(bin, u.Info.Sha256) {
-		return nil, errHashMismatch
-	}
-	return bin, nil
-}
-
-func (u *Updater) fetchAndVerifyFullBin() ([]byte, error) {
-	bin, err := u.fetchBin()
-	if err != nil {
-		return nil, err
-	}
-	verified := verifySha(bin, u.Info.Sha256)
-	if !verified {
-		return nil, errHashMismatch
-	}
-	return bin, nil
-}
-
-func (u *Updater) fetchBin() ([]byte, error) {
-	r, err := fetch(u.BinURL + u.CmdName + "/" + u.Info.Version + "/" + plat + ".gz")
-	if err != nil {
-		return nil, err
-	}
-	defer r.Close()
-	buf := new(bytes.Buffer)
-	gz, err := gzip.NewReader(r)
-	if err != nil {
-		return nil, err
-	}
-	if _, err = io.Copy(buf, gz); err != nil {
-		return nil, err
-	}
-
-	return buf.Bytes(), nil
-}
-
-func (u *Updater) fetchInfo() error {
-	r, err := fetch(u.APIURL + u.CmdName + "/" + plat + ".json")
-	if err != nil {
-		return err
-	}
-	defer r.Close()
-	err = json.NewDecoder(r).Decode(&u.Info)
-	if err != nil {
-		return err
-	}
-	if len(u.Info.Sha256) != sha256.Size {
-		return errors.New("bad cmd hash in info")
-	}
-	return nil
-}
-
-func (u *Updater) getExecRelativeDir(dir string) string {
-	filename, _ := os.Executable()
-	path := filepath.Join(filepath.Dir(filename), dir)
-	return path
-}
-
-func (u *Updater) update() error {
-	path, err := os.Executable()
-	if err != nil {
-		return err
-	}
-
-	path = AddTempSuffixToPath(path)
-
-	old, err := os.Open(path)
-	if err != nil {
-		return err
-	}
-	defer old.Close()
-
-	err = u.fetchInfo()
-	if err != nil {
-		log.Println(err)
-		return err
-	}
-	if u.Info.Version == u.CurrentVersion {
-		return nil
-	}
-	bin, err := u.fetchAndVerifyPatch(old)
-	if err != nil {
-		switch err {
-		case errHashMismatch:
-			log.Println("update: hash mismatch from patched binary")
-		case errDiffURLUndefined:
-			log.Println("update: ", err)
-		default:
-			log.Println("update: patching binary, ", err)
-		}
-
-		bin, err = u.fetchAndVerifyFullBin()
-		if err != nil {
-			if err == errHashMismatch {
-				log.Println("update: hash mismatch from full binary")
-			} else {
-				log.Println("update: fetching full binary,", err)
-			}
-			return err
-		}
-	}
-
-	// close the old binary before installing because on windows
-	// it can't be renamed if a handle to the file is still open
-	old.Close()
-
-	up.TargetPath = path
-	err, errRecover := up.FromStream(bytes.NewBuffer(bin))
-	if errRecover != nil {
-		log.Errorf("update and recovery errors: %q %q", err, errRecover)
-		return fmt.Errorf("update and recovery errors: %q %q", err, errRecover)
-	}
-	if err != nil {
-		return err
-	}
-
-	return nil
-}