exporter: validate null config metadata from gateway

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
(cherry picked from commit ef536af15b2d351b8f0459022decc2a4955b1cb2)
(cherry picked from commit a8a6bc5180696624b18b5dc4ed4f9cf1a278ef27)

client/client_test.go

@@ -206,6 +206,7 @@ func TestIntegration(t *testing.T) {
 		testMultipleRecordsWithSameLayersCacheImportExport,
 		testExportLocalNoPlatformSplit,
 		testExportLocalNoPlatformSplitOverwrite,
+		testValidateNullConfig,
 	)
 }
 

client/validation_test.go

@@ -0,0 +1,50 @@
+package client
+
+import (
+	"context"
+	"io"
+	"testing"
+
+	"github.com/moby/buildkit/client/llb"
+	"github.com/moby/buildkit/frontend/gateway/client"
+	"github.com/moby/buildkit/util/testutil/integration"
+	"github.com/stretchr/testify/require"
+)
+
+func testValidateNullConfig(t *testing.T, sb integration.Sandbox) {
+	requiresLinux(t)
+
+	ctx := sb.Context()
+
+	c, err := New(ctx, sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	b := func(ctx context.Context, c client.Client) (*client.Result, error) {
+		def, err := llb.Scratch().Marshal(ctx)
+		if err != nil {
+			return nil, err
+		}
+
+		res, err := c.Solve(ctx, client.SolveRequest{
+			Evaluate:   true,
+			Definition: def.ToPB(),
+		})
+		if err != nil {
+			return nil, err
+		}
+		res.AddMeta("containerimage.config", []byte("null"))
+		return res, nil
+	}
+
+	_, err = c.Build(ctx, SolveOpt{
+		Exports: []ExportEntry{
+			{
+				Type:   ExporterOCI,
+				Output: fixedWriteCloser(nopWriteCloser{io.Discard}),
+			},
+		},
+	}, "", b, nil)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "invalid null image config for export")
+}

exporter/containerimage/writer.go

@@ -569,11 +569,20 @@ func parseHistoryFromConfig(dt []byte) ([]ocispecs.History, error) {
 }
 
 func patchImageConfig(dt []byte, descs []ocispecs.Descriptor, history []ocispecs.History, cache []byte, epoch *time.Time) ([]byte, error) {
+	var img ocispecs.Image
+	if err := json.Unmarshal(dt, &img); err != nil {
+		return nil, errors.Wrap(err, "invalid image config for export")
+	}
+
 	m := map[string]json.RawMessage{}
 	if err := json.Unmarshal(dt, &m); err != nil {
 		return nil, errors.Wrap(err, "failed to parse image config for patch")
 	}
 
+	if m == nil {
+		return nil, errors.Errorf("invalid null image config for export")
+	}
+
 	var rootFS ocispecs.RootFS
 	rootFS.Type = "layers"
 	for _, desc := range descs {