Fix panic in kubectl cp command

pkg/kubectl/cmd/cp/cp.go

@@ -307,7 +307,7 @@ func (o *CopyOptions) copyFromPod(src, dest fileSpec) error {
 	// remove extraneous path shortcuts - these could occur if a path contained extra "../"
 	// and attempted to navigate beyond "/" in a remote filesystem
 	prefix = stripPathShortcuts(prefix)
-	return untarAll(reader, dest.File, prefix)
+	return o.untarAll(reader, dest.File, prefix)
 }
 
 // stripPathShortcuts removes any leading or trailing "../" from a given path
@@ -418,7 +418,7 @@ func clean(fileName string) string {
 	return path.Clean(string(os.PathSeparator) + fileName)
 }
 
-func untarAll(reader io.Reader, destFile, prefix string) error {
+func (o *CopyOptions) untarAll(reader io.Reader, destFile, prefix string) error {
 	entrySeq := -1
 
 	// TODO: use compression here?
@@ -433,6 +433,12 @@ func untarAll(reader io.Reader, destFile, prefix string) error {
 		}
 		entrySeq++
 		mode := header.FileInfo().Mode()
+		// all the files will start with the prefix, which is the directory where
+		// they were located on the pod, we need to strip down that prefix, but
+		// if the prefix is missing it means the tar was tempered with
+		if !strings.HasPrefix(header.Name, prefix) {
+			return fmt.Errorf("tar contents corrupted")
+		}
 		outFileName := path.Join(destFile, clean(header.Name[len(prefix):]))
 		baseName := path.Dir(outFileName)
 		if err := os.MkdirAll(baseName, 0755); err != nil {
@@ -457,8 +463,16 @@ func untarAll(reader io.Reader, destFile, prefix string) error {
 		}
 
 		if mode&os.ModeSymlink != 0 {
-			err := os.Symlink(header.Linkname, outFileName)
-			if err != nil {
+			linkname := header.Linkname
+			// error is returned if linkname can't be made relative to destFile,
+			// but relative can end up being ../dir that's why we also need to
+			// verify if relative path is the same after Clean-ing
+			relative, err := filepath.Rel(destFile, linkname)
+			if path.IsAbs(linkname) && (err != nil || relative != stripPathShortcuts(relative)) {
+				fmt.Fprintf(o.IOStreams.ErrOut, "warning: link %q is pointing to %q which is outside target destination, skipping\n", outFileName, header.Linkname)
+				continue
+			}
+			if err := os.Symlink(linkname, outFileName); err != nil {
 				return err
 			}
 		} else {

pkg/kubectl/cmd/cp/cp_test.go

@@ -191,27 +191,33 @@ func TestStripPathShortcuts(t *testing.T) {
 	}
 }
 
-func TestTarUntar(t *testing.T) {
-	dir, err := ioutil.TempDir("", "input")
-	dir2, err2 := ioutil.TempDir("", "output")
-	if err != nil || err2 != nil {
-		t.Errorf("unexpected error: %v | %v", err, err2)
+func checkErr(t *testing.T, err error) {
+	if err != nil {
+		t.Errorf("unexpected error: %v", err)
 		t.FailNow()
 	}
+}
+
+func TestTarUntar(t *testing.T) {
+	dir, err := ioutil.TempDir("", "input")
+	checkErr(t, err)
+	dir2, err := ioutil.TempDir("", "output")
+	checkErr(t, err)
+	dir3, err := ioutil.TempDir("", "dir")
+	checkErr(t, err)
+
 	dir = dir + "/"
 	defer func() {
-		if err := os.RemoveAll(dir); err != nil {
-			t.Errorf("Unexpected error cleaning up: %v", err)
-		}
-		if err := os.RemoveAll(dir2); err != nil {
-			t.Errorf("Unexpected error cleaning up: %v", err)
-		}
+		os.RemoveAll(dir)
+		os.RemoveAll(dir2)
+		os.RemoveAll(dir3)
 	}()
 
 	files := []struct {
 		name     string
 		nameList []string
 		data     string
+		omitted  bool
 		fileType FileType
 	}{
 		{
@@ -236,7 +242,24 @@ func TestTarUntar(t *testing.T) {
 		},
 		{
 			name:     "gakki",
+			data:     "tmp/gakki",
+			fileType: SymLink,
+		},
+		{
+			name:     "relative_to_dest",
+			data:     path.Join(dir2, "foo"),
+			fileType: SymLink,
+		},
+		{
+			name:     "tricky_relative",
+			data:     path.Join(dir3, "xyz"),
+			omitted:  true,
+			fileType: SymLink,
+		},
+		{
+			name:     "absolute_path",
 			data:     "/tmp/gakki",
+			omitted:  true,
 			fileType: SymLink,
 		},
 		{
@@ -268,13 +291,15 @@ func TestTarUntar(t *testing.T) {
 		}
 	}
 
+	opts := NewCopyOptions(genericclioptions.NewTestIOStreamsDiscard())
+
 	writer := &bytes.Buffer{}
 	if err := makeTar(dir, dir, writer); err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
 
 	reader := bytes.NewBuffer(writer.Bytes())
-	if err := untarAll(reader, dir2, ""); err != nil {
+	if err := opts.untarAll(reader, dir2, ""); err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
 
@@ -286,7 +311,12 @@ func TestTarUntar(t *testing.T) {
 			cmpFileData(t, filePath, file.data)
 		} else if file.fileType == SymLink {
 			dest, err := os.Readlink(filePath)
-
+			if file.omitted {
+				if err != nil && strings.Contains(err.Error(), "no such file or directory") {
+					continue
+				}
+				t.Fatalf("expected to omit symlink for %s", filePath)
+			}
 			if err != nil {
 				t.Fatalf("unexpected error: %v", err)
 			}
@@ -304,6 +334,38 @@ func TestTarUntar(t *testing.T) {
 	}
 }
 
+func TestTarUntarWrongPrefix(t *testing.T) {
+	dir, err := ioutil.TempDir("", "input")
+	checkErr(t, err)
+	dir2, err := ioutil.TempDir("", "output")
+	checkErr(t, err)
+
+	dir = dir + "/"
+	defer func() {
+		os.RemoveAll(dir)
+		os.RemoveAll(dir2)
+	}()
+
+	filepath := path.Join(dir, "foo")
+	if err := os.MkdirAll(path.Dir(filepath), 0755); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	createTmpFile(t, filepath, "sample data")
+
+	opts := NewCopyOptions(genericclioptions.NewTestIOStreamsDiscard())
+
+	writer := &bytes.Buffer{}
+	if err := makeTar(dir, dir, writer); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	reader := bytes.NewBuffer(writer.Bytes())
+	err = opts.untarAll(reader, dir2, "verylongprefix-showing-the-tar-was-tempered-with")
+	if err == nil || !strings.Contains(err.Error(), "tar contents corrupted") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
 // TestCopyToLocalFileOrDir tests untarAll in two cases :
 // 1: copy pod file to local file
 // 2: copy pod file into local directory
@@ -376,7 +438,8 @@ func TestCopyToLocalFileOrDir(t *testing.T) {
 			}
 			defer srcTarFile.Close()
 
-			if err := untarAll(srcTarFile, destPath, getPrefix(srcFilePath)); err != nil {
+			opts := NewCopyOptions(genericclioptions.NewTestIOStreamsDiscard())
+			if err := opts.untarAll(srcTarFile, destPath, getPrefix(srcFilePath)); err != nil {
 				t.Errorf("unexpected error: %v", err)
 				t.FailNow()
 			}
@@ -503,7 +566,8 @@ func TestBadTar(t *testing.T) {
 		t.FailNow()
 	}
 
-	if err := untarAll(&buf, dir, "/prefix"); err != nil {
+	opts := NewCopyOptions(genericclioptions.NewTestIOStreamsDiscard())
+	if err := opts.untarAll(&buf, dir, "/prefix"); err != nil {
 		t.Errorf("unexpected error: %v ", err)
 		t.FailNow()
 	}