Cache chart layers without timestamp

This commit allows for the creation of a tar.gz archive of a chart
without a timestamp. Doing so ensures that charts with identical content
will have identical digests, which is important for storage in a
registry. Effort was made to ensure the functionality of `helm package`
was not affected.

Additionally, a unit test for the registry cache's StoreReference
function, to help track this bug.

Resolves #8212

Signed-off-by: Peter Engelbert <pmengelbert@gmail.com>

internal/experimental/registry/cache.go

@@ -288,7 +288,7 @@ func (cache *Cache) saveChartConfig(ch *chart.Chart) (*ocispec.Descriptor, bool,
 func (cache *Cache) saveChartContentLayer(ch *chart.Chart) (*ocispec.Descriptor, bool, error) {
 	destDir := filepath.Join(cache.rootDir, ".build")
 	os.MkdirAll(destDir, 0755)
-	tmpFile, err := chartutil.Save(ch, destDir)
+	tmpFile, err := chartutil.Save(ch, destDir, chartutil.WithoutTimestamp())
 	defer os.Remove(tmpFile)
 	if err != nil {
 		return nil, false, errors.Wrap(err, "failed to save")

pkg/action/chart_save_test.go

@@ -19,6 +19,7 @@ package action
 import (
 	"io/ioutil"
 	"testing"
+	"time"
 
 	"helm.sh/helm/v3/internal/experimental/registry"
 )
@@ -68,3 +69,48 @@ func TestChartSave(t *testing.T) {
 		t.Error(err)
 	}
 }
+
+func TestIdenticalDigests(t *testing.T) {
+	ref1String := "localhost:5000/test1:0.2.0"
+	ref2String := "localhost:5000/test2:0.2.0"
+
+	tmpDir, err := ioutil.TempDir("", "helm-digest-test")
+	if err != nil {
+		t.Error(err)
+	}
+
+	cache, err := registry.NewCache(
+		registry.CacheOptRoot(tmpDir),
+	)
+	if err != nil {
+		t.Error(err)
+	}
+
+	input := buildChart()
+
+	ref1, err := registry.ParseReference(ref1String)
+	if err != nil {
+		t.Error(err)
+	}
+
+	ref2, err := registry.ParseReference(ref2String)
+	if err != nil {
+		t.Error(err)
+	}
+
+	sum1, err := cache.StoreReference(ref1, input)
+	if err != nil {
+		t.Error(err)
+	}
+
+	time.Sleep(1 * time.Second)
+
+	sum2, err := cache.StoreReference(ref2, input)
+	if err != nil {
+		t.Error(err)
+	}
+
+	if a, b := string(sum1.Digest), string(sum2.Digest); a != b {
+		t.Fatalf("digest %s and digest %s do not match", a, b)
+	}
+}

pkg/chartutil/save.go

@@ -31,6 +31,22 @@ import (
 	"helm.sh/helm/v3/pkg/chart"
 )
 
+type (
+	saveConfig struct {
+		noTimestamp bool
+	}
+
+	// SaveOpt is an option for modifying the behavior of Save
+	SaveOpt func(*saveConfig)
+)
+
+// WithoutTimestamp provides the ability to save tar archives without a timestamp
+func WithoutTimestamp() SaveOpt {
+	return func(cfg *saveConfig) {
+		cfg.noTimestamp = true
+	}
+}
+
 var headerBytes = []byte("+aHR0cHM6Ly95b3V0dS5iZS96OVV6MWljandyTQo=")
 
 // SaveDir saves a chart as files in a directory.
@@ -99,7 +115,12 @@ func SaveDir(c *chart.Chart, dest string) error {
 // will generate /foo/bar-1.0.0.tgz.
 //
 // This returns the absolute path to the chart archive file.
-func Save(c *chart.Chart, outDir string) (string, error) {
+func Save(c *chart.Chart, outDir string, saveOpts ...SaveOpt) (string, error) {
+	config := new(saveConfig)
+	for _, fn := range saveOpts {
+		fn(config)
+	}
+
 	if err := c.Validate(); err != nil {
 		return "", errors.Wrap(err, "chart validation")
 	}
@@ -141,14 +162,19 @@ func Save(c *chart.Chart, outDir string) (string, error) {
 		}
 	}()
 
-	if err := writeTarContents(twriter, c, ""); err != nil {
+	var timestamp time.Time
+	if !config.noTimestamp {
+		timestamp = time.Now()
+	}
+
+	if err := writeTarContents(twriter, c, "", timestamp); err != nil {
 		rollback = true
 		return filename, err
 	}
 	return filename, nil
 }
 
-func writeTarContents(out *tar.Writer, c *chart.Chart, prefix string) error {
+func writeTarContents(out *tar.Writer, c *chart.Chart, prefix string, timestamp time.Time) error {
 	base := filepath.Join(prefix, c.Name())
 
 	// Pull out the dependencies of a v1 Chart, since there's no way
@@ -165,7 +191,7 @@ func writeTarContents(out *tar.Writer, c *chart.Chart, prefix string) error {
 	if err != nil {
 		return err
 	}
-	if err := writeToTar(out, filepath.Join(base, ChartfileName), cdata); err != nil {
+	if err := writeToTar(out, filepath.Join(base, ChartfileName), cdata, timestamp); err != nil {
 		return err
 	}
 
@@ -177,7 +203,7 @@ func writeTarContents(out *tar.Writer, c *chart.Chart, prefix string) error {
 			if err != nil {
 				return err
 			}
-			if err := writeToTar(out, filepath.Join(base, "Chart.lock"), ldata); err != nil {
+			if err := writeToTar(out, filepath.Join(base, "Chart.lock"), ldata, timestamp); err != nil {
 				return err
 			}
 		}
@@ -186,7 +212,7 @@ func writeTarContents(out *tar.Writer, c *chart.Chart, prefix string) error {
 	// Save values.yaml
 	for _, f := range c.Raw {
 		if f.Name == ValuesfileName {
-			if err := writeToTar(out, filepath.Join(base, ValuesfileName), f.Data); err != nil {
+			if err := writeToTar(out, filepath.Join(base, ValuesfileName), f.Data, timestamp); err != nil {
 				return err
 			}
 		}
@@ -197,7 +223,7 @@ func writeTarContents(out *tar.Writer, c *chart.Chart, prefix string) error {
 		if !json.Valid(c.Schema) {
 			return errors.New("Invalid JSON in " + SchemafileName)
 		}
-		if err := writeToTar(out, filepath.Join(base, SchemafileName), c.Schema); err != nil {
+		if err := writeToTar(out, filepath.Join(base, SchemafileName), c.Schema, timestamp); err != nil {
 			return err
 		}
 	}
@@ -205,7 +231,7 @@ func writeTarContents(out *tar.Writer, c *chart.Chart, prefix string) error {
 	// Save templates
 	for _, f := range c.Templates {
 		n := filepath.Join(base, f.Name)
-		if err := writeToTar(out, n, f.Data); err != nil {
+		if err := writeToTar(out, n, f.Data, timestamp); err != nil {
 			return err
 		}
 	}
@@ -213,14 +239,14 @@ func writeTarContents(out *tar.Writer, c *chart.Chart, prefix string) error {
 	// Save files
 	for _, f := range c.Files {
 		n := filepath.Join(base, f.Name)
-		if err := writeToTar(out, n, f.Data); err != nil {
+		if err := writeToTar(out, n, f.Data, timestamp); err != nil {
 			return err
 		}
 	}
 
 	// Save dependencies
 	for _, dep := range c.Dependencies() {
-		if err := writeTarContents(out, dep, filepath.Join(base, ChartsDir)); err != nil {
+		if err := writeTarContents(out, dep, filepath.Join(base, ChartsDir), timestamp); err != nil {
 			return err
 		}
 	}
@@ -228,13 +254,13 @@ func writeTarContents(out *tar.Writer, c *chart.Chart, prefix string) error {
 }
 
 // writeToTar writes a single file to a tar archive.
-func writeToTar(out *tar.Writer, name string, body []byte) error {
+func writeToTar(out *tar.Writer, name string, body []byte, timestamp time.Time) error {
 	// TODO: Do we need to create dummy parent directory names if none exist?
 	h := &tar.Header{
 		Name:    filepath.ToSlash(name),
 		Mode:    0644,
 		Size:    int64(len(body)),
-		ModTime: time.Now(),
+		ModTime: timestamp,
 	}
 	if err := out.WriteHeader(h); err != nil {
 		return err