feat(plugin): Ports file mode preservation for tarballs from v3

This is a port of #5428 and readds a unit test for the `Extract` method

Signed-off-by: Taylor Thomas <taylor.thomas@microsoft.com>

pkg/plugin/installer/http_installer.go

@@ -187,7 +187,7 @@ func (g *TarGzExtractor) Extract(buffer *bytes.Buffer, targetDir string) error {
 				return err
 			}
 		case tar.TypeReg:
-			outFile, err := os.Create(path)
+			outFile, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, os.FileMode(header.Mode))
 			if err != nil {
 				return err
 			}

pkg/plugin/installer/http_installer_test.go

@@ -16,9 +16,14 @@ limitations under the License.
 package installer // import "helm.sh/helm/v3/pkg/plugin/installer"
 
 import (
+	"archive/tar"
 	"bytes"
+	"compress/gzip"
 	"encoding/base64"
+	"io/ioutil"
 	"os"
+	"path/filepath"
+	"syscall"
 	"testing"
 
 	"github.com/pkg/errors"
@@ -177,3 +182,87 @@ func TestHTTPInstallerUpdate(t *testing.T) {
 		t.Error("update method not implemented for http installer")
 	}
 }
+
+func TestExtract(t *testing.T) {
+	source := "https://repo.localdomain/plugins/fake-plugin-0.0.1.tar.gz"
+
+	tempDir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Set the umask to default open permissions so we can actually test
+	oldmask := syscall.Umask(0000)
+	defer func() {
+		syscall.Umask(oldmask)
+	}()
+
+	// Write a tarball to a buffer for us to extract
+	var tarbuf bytes.Buffer
+	tw := tar.NewWriter(&tarbuf)
+	var files = []struct {
+		Name, Body string
+		Mode       int64
+	}{
+		{"plugin.yaml", "plugin metadata", 0600},
+		{"README.md", "some text", 0777},
+	}
+	for _, file := range files {
+		hdr := &tar.Header{
+			Name:     file.Name,
+			Typeflag: tar.TypeReg,
+			Mode:     file.Mode,
+			Size:     int64(len(file.Body)),
+		}
+		if err := tw.WriteHeader(hdr); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := tw.Write([]byte(file.Body)); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := tw.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	var buf bytes.Buffer
+	gz := gzip.NewWriter(&buf)
+	if _, err := gz.Write(tarbuf.Bytes()); err != nil {
+		t.Fatal(err)
+	}
+	gz.Close()
+	// END tarball creation
+
+	extr, err := NewExtractor(source)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err = extr.Extract(&buf, tempDir); err != nil {
+		t.Errorf("Did not expect error but got error: %v", err)
+	}
+
+	pluginYAMLFullPath := filepath.Join(tempDir, "plugin.yaml")
+	if info, err := os.Stat(pluginYAMLFullPath); err != nil {
+		if os.IsNotExist(err) {
+			t.Errorf("Expected %s to exist but doesn't", pluginYAMLFullPath)
+		} else {
+			t.Error(err)
+		}
+	} else if info.Mode().Perm() != 0600 {
+		t.Errorf("Expected %s to have 0600 mode it but has %o", pluginYAMLFullPath, info.Mode().Perm())
+	}
+
+	readmeFullPath := filepath.Join(tempDir, "README.md")
+	if info, err := os.Stat(readmeFullPath); err != nil {
+		if os.IsNotExist(err) {
+			t.Errorf("Expected %s to exist but doesn't", readmeFullPath)
+		} else {
+			t.Error(err)
+		}
+	} else if info.Mode().Perm() != 0777 {
+		t.Errorf("Expected %s to have 0777 mode it but has %o", readmeFullPath, info.Mode().Perm())
+	}
+
+}