1 files changed, 181 insertions, 0 deletions
diff --git a/updater/downloader.go b/updater/downloader.go
new file mode 100644
index 00000000..ea3ee9d4
--- /dev/null
+++ b/updater/downloader.go
@@ -0,0 +1,181 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package updater
+
+import (
+	"crypto/hmac"
+	"errors"
+	"fmt"
+	"golang.org/x/crypto/blake2b"
+	"golang.zx2c4.com/wireguard/windows/version"
+	"hash"
+	"io"
+	"net/http"
+	"os"
+	"path"
+	"sync/atomic"
+)
+
+type DownloadProgress struct {
+	Activity        string
+	BytesDownloaded uint64
+	BytesTotal      uint64
+	Error           error
+	Complete        bool
+}
+
+type progressHashWatcher struct {
+	dp        *DownloadProgress
+	c         chan DownloadProgress
+	hashState hash.Hash
+}
+
+func (pm *progressHashWatcher) Write(p []byte) (int, error) {
+	bytes := len(p)
+	pm.dp.BytesDownloaded += uint64(bytes)
+	pm.c <- *pm.dp
+	pm.hashState.Write(p)
+	return bytes, nil
+}
+
+type UpdateFound struct {
+	name string
+	hash [blake2b.Size256]byte
+}
+
+func CheckForUpdate() (*UpdateFound, error) {
+	request, err := http.NewRequest(http.MethodGet, latestVersionURL, nil)
+	if err != nil {
+		return nil, err
+	}
+	request.Header.Add("User-Agent", version.UserAgent())
+	response, err := http.DefaultClient.Do(request)
+	if err != nil {
+		return nil, err
+	}
+	defer response.Body.Close()
+	var fileList [1024 * 512] /* 512 KiB */ byte
+	bytesRead, err := response.Body.Read(fileList[:])
+	if err != nil && (err != io.EOF || bytesRead == 0) {
+		return nil, err
+	}
+	files, err := readFileList(fileList[:bytesRead])
+	if err != nil {
+		return nil, err
+	}
+	return findCandidate(files)
+}
+
+var updateInProgress = uint32(0)
+
+func DownloadVerifyAndExecute() (progress chan DownloadProgress) {
+	progress = make(chan DownloadProgress, 128)
+	progress <- DownloadProgress{Activity: "Initializing"}
+
+	if !atomic.CompareAndSwapUint32(&updateInProgress, 0, 1) {
+		progress <- DownloadProgress{Error: errors.New("An update is already in progress")}
+		return
+	}
+
+	go func() {
+		defer atomic.StoreUint32(&updateInProgress, 0)
+
+		progress <- DownloadProgress{Activity: "Rechecking for update"}
+		update, err := CheckForUpdate()
+		if err != nil {
+			progress <- DownloadProgress{Error: err}
+			return
+		}
+		if update == nil {
+			progress <- DownloadProgress{Error: errors.New("No update was found when re-checking for updates")}
+			return
+		}
+
+		progress <- DownloadProgress{Activity: "Creating update file"}
+		updateDir, err := msiSaveDirectory()
+		if err != nil {
+			progress <- DownloadProgress{Error: err}
+			return
+		}
+		// Clean up old updates the brutal way:
+		os.RemoveAll(updateDir)
+
+		err = os.MkdirAll(updateDir, 0700)
+		if err != nil {
+			progress <- DownloadProgress{Error: err}
+			return
+		}
+		destinationFilename := path.Join(updateDir, update.name)
+		unverifiedDestinationFilename := destinationFilename + ".unverified"
+		out, err := os.Create(unverifiedDestinationFilename)
+		if err != nil {
+			progress <- DownloadProgress{Error: err}
+			return
+		}
+		defer func() {
+			if out != nil {
+				out.Seek(0, io.SeekStart)
+				out.Truncate(0)
+				out.Close()
+				os.Remove(unverifiedDestinationFilename)
+			}
+		}()
+
+		dp := DownloadProgress{Activity: "Downloading update"}
+		progress <- dp
+		request, err := http.NewRequest(http.MethodGet, fmt.Sprintf(msiURL, update.name), nil)
+		if err != nil {
+			progress <- DownloadProgress{Error: err}
+			return
+		}
+		request.Header.Add("User-Agent", version.UserAgent())
+		request.Header.Set("Accept-Encoding", "identity")
+		response, err := http.DefaultClient.Do(request)
+		if err != nil {
+			progress <- DownloadProgress{Error: err}
+			return
+		}
+		defer response.Body.Close()
+		if response.ContentLength >= 0 {
+			dp.BytesTotal = uint64(response.ContentLength)
+			progress <- dp
+		}
+		hasher, err := blake2b.New256(nil)
+		if err != nil {
+			progress <- DownloadProgress{Error: err}
+			return
+		}
+		pm := &progressHashWatcher{&dp, progress, hasher}
+		_, err = io.Copy(out, io.TeeReader(io.LimitReader(response.Body, 1024*1024*100 /* 100 MiB */), pm))
+		if err != nil {
+			progress <- DownloadProgress{Error: err}
+			return
+		}
+		if !hmac.Equal(hasher.Sum(nil), update.hash[:]) {
+			progress <- DownloadProgress{Error: errors.New("The downloaded update has the wrong hash")}
+			return
+		}
+		out.Close()
+		out = nil
+		err = os.Rename(unverifiedDestinationFilename, destinationFilename)
+		if err != nil {
+			os.Remove(unverifiedDestinationFilename)
+			progress <- DownloadProgress{Error: err}
+			return
+		}
+		progress <- DownloadProgress{Activity: "Installing update"}
+		err = runMsi(destinationFilename)
+		os.Remove(unverifiedDestinationFilename)
+		if err != nil {
+			progress <- DownloadProgress{Error: err}
+			return
+		}
+
+		progress <- DownloadProgress{Complete: true}
+	}()
+
+	return progress
+}