containerimage: support SOURCE_DATE_EPOCH for CreatedAt

Fix issue 3167

Signed-off-by: Akihiro Suda <[email protected]>

client/client_test.go

@@ -179,6 +179,7 @@ func TestIntegration(t *testing.T) {
 		testSourceDateEpochReset,
 		testSourceDateEpochLocalExporter,
 		testSourceDateEpochTarExporter,
+		testSourceDateEpochImageExporter,
 		testAttestationBundle,
 		testSBOMScan,
 		testSBOMScanSingleRef,
@@ -2683,6 +2684,60 @@ func testSourceDateEpochTarExporter(t *testing.T, sb integration.Sandbox) {
 	checkAllReleasable(t, c, sb, true)
 }
 
+func testSourceDateEpochImageExporter(t *testing.T, sb integration.Sandbox) {
+	integration.SkipIfDockerd(t, sb, "image exporter")
+
+	requiresLinux(t)
+	c, err := New(sb.Context(), sb.Address())
+	require.NoError(t, err)
+
+	busybox := llb.Image("busybox:latest")
+	st := llb.Scratch()
+
+	run := func(cmd string) {
+		st = busybox.Run(llb.Shlex(cmd), llb.Dir("/wd")).AddMount("/wd", st)
+	}
+
+	run(`sh -c "echo -n first > foo"`)
+	run(`sh -c "echo -n second > bar"`)
+
+	def, err := st.Marshal(sb.Context())
+	require.NoError(t, err)
+
+	name := strings.ToLower(path.Base(t.Name()))
+	tm := time.Date(2015, time.October, 21, 7, 28, 0, 0, time.UTC)
+
+	_, err = c.Solve(sb.Context(), def, SolveOpt{
+		FrontendAttrs: map[string]string{
+			"build-arg:SOURCE_DATE_EPOCH": fmt.Sprintf("%d", tm.Unix()),
+		},
+		Exports: []ExportEntry{
+			{
+				Type: ExporterImage,
+				Attrs: map[string]string{
+					"name": name,
+				},
+			},
+		},
+	}, nil)
+	require.NoError(t, err)
+
+	if cdAddress := sb.ContainerdAddress(); cdAddress != "" {
+		ctx := namespaces.WithNamespace(sb.Context(), "buildkit")
+		client, err := newContainerd(cdAddress)
+		require.NoError(t, err)
+		defer client.Close()
+
+		img, err := client.GetImage(ctx, name)
+		require.NoError(t, err)
+		require.Equal(t, tm, img.Metadata().CreatedAt)
+
+		// TODO: mount and validate the snapshots
+	}
+
+	checkAllReleasable(t, c, sb, true)
+}
+
 func testFrontendMetadataReturn(t *testing.T, sb integration.Sandbox) {
 	requiresLinux(t)
 	c, err := New(sb.Context(), sb.Address())

exporter/containerimage/export.go

@@ -241,9 +241,13 @@ func (e *imageExporterInstance) Export(ctx context.Context, src *exporter.Source
 		for _, targetName := range targetNames {
 			if e.opt.Images != nil && e.store {
 				tagDone := progress.OneOff(ctx, "naming to "+targetName)
+				tm := time.Now()
+				if e.opts.Epoch != nil {
+					tm = *e.opts.Epoch
+				}
 				img := images.Image{
 					Target:    *desc,
-					CreatedAt: time.Now(),
+					CreatedAt: tm,
 				}
 				sfx := []string{""}
 				if nameCanonical {