syncthing/lib/upgrade/upgrade_supported.go
Jakob Borg 718b1ce2b7
chore(discovery,upgrade): use regular TLS certificate verification (#9673)
This changes the two remaining instances where we use insecure HTTPS to
use standard HTTPS certificate verification.

When we introduced these things, almost a decade ago, HTTPS certificates
were expensive and annoying to get, much of the web was still HTTP, and
many devices seemed to not have up-to-date CA bundles.

Nowadays _all_ of the web is HTTPS and I'm skeptical that any device can
work well without understanding LetsEncrypt certificates in particular.

Our current discovery servers use hardcoded certificates which has
several issues:
- Not great for security if it leaks as there is no way to rotate it
- Not great for infrastructure flexibility as we can't use many load
balancer or TLS termination services
- The certificate is a very oddball ECDSA-SHA384 type certificate which
has higher CPU cost than a more regular certificate, which has real
effects on our infrastructure

Using normal TLS certificates here improves these things.

I expect there will be some very few devices out there for which this
doesn't work. For the foreseeable future they can simply change the
config to use the old URLs and parameters -- it'll be years before we
can retire those entirely.

For the upgrade client this simply seems like better hygiene. While our
releases are signed anyway, protecting the metadata exchange is _better_
and, again, I doubt many clients will fail this today.
2024-09-11 09:29:19 +02:00

440 lines
10 KiB
Go

// Copyright (C) 2014 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
//go:build !noupgrade && !ios
// +build !noupgrade,!ios
package upgrade
import (
"archive/tar"
"archive/zip"
"bytes"
"compress/gzip"
"encoding/json"
"errors"
"fmt"
"io"
"net/http"
"os"
"path"
"path/filepath"
"runtime"
"sort"
"strings"
"time"
"github.com/shirou/gopsutil/v4/host"
"github.com/syncthing/syncthing/lib/dialer"
"github.com/syncthing/syncthing/lib/signature"
"golang.org/x/net/http2"
)
const DisabledByCompilation = false
const (
// Current binary size hovers around 10 MB. We give it some room to grow
// and say that we never expect the binary to be larger than 64 MB.
maxBinarySize = 64 << 20 // 64 MiB
// The max expected size of the signature file.
maxSignatureSize = 10 << 10 // 10 KiB
// We set the same limit on the archive. The binary will compress and we
// include some other stuff - currently the release archive size is
// around 6 MB.
maxArchiveSize = maxBinarySize
// When looking through the archive for the binary and signature, stop
// looking once we've searched this many files.
maxArchiveMembers = 100
// Archive reads, or metadata checks, that take longer than this will be
// rejected.
readTimeout = 30 * time.Minute
// The limit on the size of metadata that we accept.
maxMetadataSize = 10 << 20 // 10 MiB
)
var upgradeClient = &http.Client{
Timeout: readTimeout,
Transport: &http.Transport{
DialContext: dialer.DialContext,
Proxy: http.ProxyFromEnvironment,
},
}
var osVersion string
func init() {
_ = http2.ConfigureTransport(upgradeClient.Transport.(*http.Transport))
osVersion, _ = host.KernelVersion()
osVersion = strings.TrimSpace(osVersion)
}
func insecureGet(url, version string) (*http.Response, error) {
req, err := http.NewRequest(http.MethodGet, url, nil)
if err != nil {
return nil, err
}
req.Header.Set("User-Agent", fmt.Sprintf(`syncthing %s (%s %s-%s)`, version, runtime.Version(), runtime.GOOS, runtime.GOARCH))
if osVersion != "" {
req.Header.Set("Syncthing-Os-Version", osVersion)
}
return upgradeClient.Do(req)
}
// FetchLatestReleases returns the latest releases. The "current" parameter
// is used for setting the User-Agent only.
func FetchLatestReleases(releasesURL, current string) []Release {
resp, err := insecureGet(releasesURL, current)
if err != nil {
l.Infoln("Couldn't fetch release information:", err)
return nil
}
if resp.StatusCode > 299 {
l.Infoln("API call returned HTTP error:", resp.Status)
return nil
}
var rels []Release
err = json.NewDecoder(io.LimitReader(resp.Body, maxMetadataSize)).Decode(&rels)
if err != nil {
l.Infoln("Fetching release information:", err)
}
resp.Body.Close()
return rels
}
type SortByRelease []Release
func (s SortByRelease) Len() int {
return len(s)
}
func (s SortByRelease) Swap(i, j int) {
s[i], s[j] = s[j], s[i]
}
func (s SortByRelease) Less(i, j int) bool {
return CompareVersions(s[i].Tag, s[j].Tag) > 0
}
func LatestRelease(releasesURL, current string, upgradeToPreReleases bool) (Release, error) {
rels := FetchLatestReleases(releasesURL, current)
return SelectLatestRelease(rels, current, upgradeToPreReleases)
}
func SelectLatestRelease(rels []Release, current string, upgradeToPreReleases bool) (Release, error) {
if len(rels) == 0 {
return Release{}, ErrNoVersionToSelect
}
// Sort the releases, lowest version number first
sort.Sort(sort.Reverse(SortByRelease(rels)))
var selected Release
for _, rel := range rels {
if CompareVersions(rel.Tag, current) == MajorNewer {
// We've found a new major version. That's fine, but if we've
// already found a minor upgrade that is acceptable we should go
// with that one first and then revisit in the future.
if selected.Tag != "" && CompareVersions(selected.Tag, current) == Newer {
return selected, nil
}
}
if rel.Prerelease && !upgradeToPreReleases {
l.Debugln("skipping pre-release", rel.Tag)
continue
}
expectedReleases := releaseNames(rel.Tag)
nextAsset:
for _, asset := range rel.Assets {
assetName := path.Base(asset.Name)
// Check for the architecture
for _, expRel := range expectedReleases {
if strings.HasPrefix(assetName, expRel) {
l.Debugln("selected", rel.Tag)
selected = rel
break nextAsset
}
}
}
}
if selected.Tag == "" {
return Release{}, ErrNoReleaseDownload
}
return selected, nil
}
// Upgrade to the given release, saving the previous binary with a ".old" extension.
func upgradeTo(binary string, rel Release) error {
expectedReleases := releaseNames(rel.Tag)
for _, asset := range rel.Assets {
assetName := path.Base(asset.Name)
l.Debugln("considering release", assetName)
for _, expRel := range expectedReleases {
if strings.HasPrefix(assetName, expRel) {
return upgradeToURL(assetName, binary, asset.URL)
}
}
}
return ErrNoReleaseDownload
}
// Upgrade to the given release, saving the previous binary with a ".old" extension.
func upgradeToURL(archiveName, binary string, url string) error {
fname, err := readRelease(archiveName, filepath.Dir(binary), url)
if err != nil {
return err
}
defer os.Remove(fname)
old := binary + ".old"
os.Remove(old)
err = os.Rename(binary, old)
if err != nil {
return err
}
if err := os.Rename(fname, binary); err != nil {
os.Rename(old, binary)
return err
}
return nil
}
func readRelease(archiveName, dir, url string) (string, error) {
l.Debugf("loading %q", url)
req, err := http.NewRequest("GET", url, nil)
if err != nil {
return "", err
}
req.Header.Add("Accept", "application/octet-stream")
resp, err := upgradeClient.Do(req)
if err != nil {
return "", err
}
defer resp.Body.Close()
switch path.Ext(archiveName) {
case ".zip":
return readZip(archiveName, dir, io.LimitReader(resp.Body, maxArchiveSize))
default:
return readTarGz(archiveName, dir, io.LimitReader(resp.Body, maxArchiveSize))
}
}
func readTarGz(archiveName, dir string, r io.Reader) (string, error) {
gr, err := gzip.NewReader(r)
if err != nil {
return "", err
}
tr := tar.NewReader(gr)
var tempName string
var sig []byte
// Iterate through the files in the archive.
i := 0
for {
if i >= maxArchiveMembers {
break
}
i++
hdr, err := tr.Next()
if err == io.EOF {
// end of tar archive
break
}
if err != nil {
return "", err
}
if hdr.Size > maxBinarySize {
// We don't even want to try processing or skipping over files
// that are too large.
break
}
err = archiveFileVisitor(dir, &tempName, &sig, hdr.Name, tr)
if err != nil {
return "", err
}
if tempName != "" && sig != nil {
break
}
}
if err := verifyUpgrade(archiveName, tempName, sig); err != nil {
return "", err
}
return tempName, nil
}
func readZip(archiveName, dir string, r io.Reader) (string, error) {
body, err := io.ReadAll(r)
if err != nil {
return "", err
}
archive, err := zip.NewReader(bytes.NewReader(body), int64(len(body)))
if err != nil {
return "", err
}
var tempName string
var sig []byte
// Iterate through the files in the archive.
i := 0
for _, file := range archive.File {
if i >= maxArchiveMembers {
break
}
i++
if file.UncompressedSize64 > maxBinarySize {
// We don't even want to try processing or skipping over files
// that are too large.
break
}
inFile, err := file.Open()
if err != nil {
return "", err
}
err = archiveFileVisitor(dir, &tempName, &sig, file.Name, inFile)
inFile.Close()
if err != nil {
return "", err
}
if tempName != "" && sig != nil {
break
}
}
if err := verifyUpgrade(archiveName, tempName, sig); err != nil {
return "", err
}
return tempName, nil
}
// archiveFileVisitor is called for each file in an archive. It may set
// tempFile and signature.
func archiveFileVisitor(dir string, tempFile *string, signature *[]byte, archivePath string, filedata io.Reader) error {
var err error
filename := path.Base(archivePath)
archiveDir := path.Dir(archivePath)
l.Debugf("considering file %s", archivePath)
switch filename {
case "syncthing", "syncthing.exe":
archiveDirs := strings.Split(archiveDir, "/")
if len(archiveDirs) > 1 {
// Don't consider "syncthing" files found too deeply, as they may be
// other things.
return nil
}
l.Debugf("found upgrade binary %s", archivePath)
*tempFile, err = writeBinary(dir, io.LimitReader(filedata, maxBinarySize))
if err != nil {
return err
}
case "release.sig":
l.Debugf("found signature %s", archivePath)
*signature, err = io.ReadAll(io.LimitReader(filedata, maxSignatureSize))
if err != nil {
return err
}
}
return nil
}
func verifyUpgrade(archiveName, tempName string, sig []byte) error {
if tempName == "" {
return errors.New("no upgrade found")
}
if sig == nil {
return errors.New("no signature found")
}
l.Debugf("checking signature\n%s", sig)
fd, err := os.Open(tempName)
if err != nil {
return err
}
// Create a new reader that will serve reads from, in order:
//
// - the archive name ("syncthing-linux-amd64-v0.13.0-beta.4.tar.gz")
// followed by a newline
//
// - the temp file contents
//
// We then verify the release signature against the contents of this
// multireader. This ensures that it is not only a bonafide syncthing
// binary, but it is also of exactly the platform and version we expect.
mr := io.MultiReader(strings.NewReader(archiveName+"\n"), fd)
err = signature.Verify(SigningKey, sig, mr)
fd.Close()
if err != nil {
os.Remove(tempName)
return err
}
return nil
}
func writeBinary(dir string, inFile io.Reader) (filename string, err error) {
// Write the binary to a temporary file.
outFile, err := os.CreateTemp(dir, "syncthing")
if err != nil {
return "", err
}
_, err = io.Copy(outFile, inFile)
if err != nil {
os.Remove(outFile.Name())
return "", err
}
err = outFile.Close()
if err != nil {
os.Remove(outFile.Name())
return "", err
}
err = os.Chmod(outFile.Name(), os.FileMode(0o755))
if err != nil {
os.Remove(outFile.Name())
return "", err
}
return outFile.Name(), nil
}