Disable grab download resume

This is to mitigate cases like #4296

By default grab tries to resume the download if the file name determined from either the url or from content-type headers already exists. This makes things go side ways, if the existing file is smaller than the new one, the old content would still be there and only the "extra" new bytes would get written. I.e. the download would be "resumed". 🤦

This is probably not a fix for the root cause in #4296 as the only way I've been able to make grab fail with `bad content length` is by crafting a custom http server that maliciously borks `Content-Length` header.

This is a minimal possible fix that we can easily backport. @twz123 is already working on bigger refactoring of autopilot download functionality that gets rid of grab. Grab seems to bring more (bad) surprises than real benefits. In the end, we just download files and we should pretty much always just replace them. No need for full library dependecy for that.

Signed-off-by: Jussi Nummelin <jnummelin@mirantis.com>

pkg/autopilot/controller/signal/common/download.go

@@ -32,6 +32,8 @@ type DownloadManifest struct {
 	apdl.Config
 
 	SuccessState string
+	// A hook that will be called after the download itself is done succesfully
+	AfterTransferSuccess func() error
 }
 
 type DownloadManifestBuilder interface {
@@ -90,7 +92,12 @@ func (r *downloadController) Reconcile(ctx context.Context, req cr.Request) (cr.
 
 	} else {
 		logger.Infof("Download of '%s' successful", manifest.URL)
-
+		// When download is successful, run the post-download hook
+		if manifest.AfterTransferSuccess != nil {
+			if err := manifest.AfterTransferSuccess(); err != nil {
+				return cr.Result{}, fmt.Errorf("failed to run post-download hook: %w", err)
+			}
+		}
 		// When the download is complete move the status to the success state
 		signalData.Status = apsigv2.NewStatus(manifest.SuccessState)
 	}

pkg/autopilot/controller/signal/k0s/download.go

@@ -16,6 +16,8 @@ package k0s
 
 import (
 	"crypto/sha256"
+	"os"
+	"path/filepath"
 
 	apcomm "github.com/k0sproject/k0s/pkg/autopilot/common"
 	apdel "github.com/k0sproject/k0s/pkg/autopilot/controller/delegate"
@@ -88,6 +90,13 @@ func (b downloadManifestBuilderK0s) Build(signalNode crcli.Object, signalData ap
 			ExpectedHash: signalData.Command.K0sUpdate.Sha256,
 			Hasher:       sha256.New(),
 			DownloadDir:  b.k0sBinaryDir,
+			Filename:     filepath.Join(b.k0sBinaryDir, "k0s.tmp"),
+		},
+		// After the download is done, we need to rename the file to the correct name
+		AfterTransferSuccess: func() error {
+			src := filepath.Join(b.k0sBinaryDir, "k0s.tmp")
+			dst := filepath.Join(b.k0sBinaryDir, "k0s")
+			return os.Rename(src, dst)
 		},
 		SuccessState: Cordoning,
 	}

pkg/autopilot/download/downloader.go

@@ -34,6 +34,7 @@ type Config struct {
 	ExpectedHash string
 	Hasher       hash.Hash
 	DownloadDir  string
+	Filename     string
 }
 
 type downloader struct {
@@ -72,6 +73,15 @@ func (d *downloader) Download(ctx context.Context) error {
 		dlreq.SetChecksum(d.config.Hasher, expectedHash, true)
 	}
 
+	// We're never really resuming downloads, so disable this feature.
+	// This also allows to re-download the file if it's already present.
+	dlreq.NoResume = true
+
+	if d.config.Filename != "" {
+		d.logger.Infof("Setting filename to %s", d.config.Filename)
+		dlreq.Filename = d.config.Filename
+	}
+
 	client := grab.NewClient()
 	// Set user agent to mitigate 403 errors from GitHub
 	// See https://github.com/cavaliergopher/grab/issues/104

pkg/autopilot/download/downloader_test.go

@@ -0,0 +1,233 @@
+// Copyright 2021 k0s authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package download
+
+import (
+	"crypto/rand"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/cavaliergopher/grab/v3"
+	"github.com/fsnotify/fsnotify"
+	"github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+)
+
+type content struct {
+	content  string
+	checksum string
+}
+
+func TestDownloadWithGrab(t *testing.T) {
+	// go runServer()
+
+	tmp := t.TempDir()
+	dlPath := filepath.Join(tmp, "index.html")
+
+	go func() {
+		// Watch the file for changes
+		w, err := fsnotify.NewWatcher()
+		assert.NoError(t, err)
+		defer w.Close()
+		err = w.Add(tmp)
+		assert.NoError(t, err)
+		for {
+			select {
+			case event := <-w.Events:
+				t.Logf("event: %s -- %s", event.Op.String(), event.Name)
+			case err := <-w.Errors:
+				panic(err)
+			}
+		}
+	}()
+
+	// Dump some data to the file to make sure it will be overwritten
+	err := os.WriteFile(dlPath, []byte("foobar"), 0644)
+	assert.NoError(t, err)
+
+	url := "http://localhost:8888/index.html"
+	// Download should succeed and get "abc" as content
+	dlreq, err := grab.NewRequest(tmp, url)
+	assert.NoError(t, err)
+
+	// dlreq.NoResume = true
+
+	client := grab.NewClient()
+	resp := client.Do(dlreq)
+	<-resp.Done
+	assert.NoError(t, resp.Err())
+
+	data, err := getFileContent(dlPath)
+	assert.NoError(t, err)
+	assert.NotContains(t, data, "foobar")
+
+	// Now create the file again with more data than the previous download
+	// this way we can test if the download will overwrite the file entirely
+	randomData := make([]byte, 2048) // nginx index.html is 615 bytes
+	_, err = rand.Read(randomData)
+	assert.NoError(t, err)
+	err = os.WriteFile(dlPath, []byte("foobar"), 0644)
+	assert.NoError(t, err)
+
+	dlreq, err = grab.NewRequest(tmp, url)
+	dlreq.NoResume = true
+	assert.NoError(t, err)
+	client = grab.NewClient()
+	resp = client.Do(dlreq)
+	<-resp.Done
+	assert.NoError(t, resp.Err())
+
+	s, err := os.Stat(dlPath)
+	assert.NoError(t, err)
+	assert.Equal(t, int64(615), s.Size())
+
+	time.Sleep(5 * time.Second)
+}
+
+func TestDownloadRaw(t *testing.T) {
+	go runServer()
+
+	tmp := t.TempDir()
+	dlPath := filepath.Join(tmp, "foo.txt")
+
+	// Dump some data to the file to make sure it will be overwritten
+	err := os.WriteFile(dlPath, []byte("foobar"), 0644)
+	assert.NoError(t, err)
+
+	url := "http://localhost:8080/foo.txt"
+	// Download using plain http.Get
+	resp, err := http.Get(url)
+	assert.NoError(t, err)
+	defer resp.Body.Close()
+	// Dump all the data to file
+	f, err := os.Create(dlPath)
+	assert.NoError(t, err)
+	defer f.Close()
+	_, err = io.Copy(f, resp.Body)
+	assert.NoError(t, err)
+	// Check the content
+	data, err := getFileContent(dlPath)
+	assert.NoError(t, err)
+	assert.Equal(t, "abc", data)
+}
+
+func runServer() {
+	http.HandleFunc("/foo.txt", func(w http.ResponseWriter, r *http.Request) {
+		body := []byte("a")
+		// w.Header().Set("Content-Length", strconv.Itoa(len(body)))
+		if r.Method == http.MethodGet {
+			_, err := w.Write(body)
+			if err != nil {
+				logrus.Errorf("Failed to write response: %v", err)
+			}
+		}
+	})
+
+	http.ListenAndServe(":8080", nil)
+}
+
+// func TestDownload(t *testing.T) {
+
+// 	// content is a map of content and its checksum
+// 	// counter is used to switch between content
+// 	content := map[int]content{
+// 		0: {content: "a", checksum: "ca978112ca1bbdcafac231b39a23dc4da786eff8147c4e72b9807785afee48bb"},
+// 		1: {content: "bb", checksum: "961b6dd3ede3cb8ecbaacbd68de040cd78eb2ed5889130cceb4c49268ea4d506"},
+// 		// The next one has wrong checksum so it needs to fail
+// 		2: {content: "aaa", checksum: "961b6dd3ede3cb8ecbaacbd68de040cd78eb2ed5889130cceb4c49268ea4d506"},
+// 	}
+
+// 	counter := 0
+
+// 	http.HandleFunc("/foo.txt", func(w http.ResponseWriter, r *http.Request) {
+// 		// body := []byte(content[counter].content)
+// 		body := []byte("a")
+// 		w.Header().Set("Content-Length", strconv.Itoa(len(body)))
+// 		// w.Header().Set("Content-Length", "42")
+// 		// w.WriteHeader(http.StatusOK)
+
+// 		if r.Method == http.MethodGet {
+// 			_, err := w.Write(body)
+// 			if err != nil {
+// 				t.Errorf("Failed to write response: %v", err)
+// 			}
+
+// 			// increment the counter so next GET request will have different content
+// 			counter++
+// 		}
+// 	})
+
+// 	go func() {
+// 		assert.NoError(t, http.ListenAndServe(":8080", nil))
+// 	}()
+
+// 	tmp := t.TempDir()
+// 	dlPath := filepath.Join(tmp, "foo.txt")
+// 	url := "http://localhost:8080/foo.txt"
+// 	// Download should succeed and get "a" as content
+// 	err := dl(url, content[0].checksum, tmp)
+// 	assert.NoError(t, err)
+// 	data, err := getFileContent(dlPath)
+// 	assert.NoError(t, err)
+// 	assert.Equal(t, content[0].content, data)
+
+// 	// Write the file with different content and test if the download will overwrite it
+// 	os.WriteFile(dlPath, []byte("foobar"), 0644)
+
+// 	// Download should succeed and get "a" as content
+// 	err = dl(url, content[0].checksum, tmp)
+// 	assert.NoError(t, err)
+// 	data, err = getFileContent(dlPath)
+// 	assert.NoError(t, err)
+// 	assert.Equal(t, content[0].content, data)
+
+// 	// // Download should succeed and get "bb" as content
+// 	// err = dl(url, content[1].checksum, tmp)
+// 	// assert.NoError(t, err)
+// 	// data, err = getFileContent(dlPath)
+// 	// assert.NoError(t, err)
+// 	// assert.Equal(t, content[1].content, data)
+
+// 	// err = dl(url, content[2].checksum, tmp)
+// 	// assert.Error(t, err)
+
+// }
+
+// func dl(url, hash, dir string) error {
+// 	logger := logrus.New().WithField("component", "downloader")
+// 	config := Config{
+// 		URL:          url,
+// 		ExpectedHash: "",
+// 		DownloadDir:  dir,
+// 		Hasher:       sha256.New(),
+// 	}
+// 	d := NewDownloader(config, logger)
+// 	ctx, cancel := context.WithTimeout(context.Background(), 10000*time.Second)
+// 	defer cancel()
+
+// 	return d.Download(ctx)
+// }
+
+func getFileContent(path string) (string, error) {
+	content, err := os.ReadFile(path)
+	if err != nil {
+		return "", err
+	}
+	return string(content), nil
+}