pull: resolve the image config and set it on stored image (genuinetoo…

…ls#326)

Previously `pull` would not properly retain the image configuration
which contains the entrypoint, working directory, user, and more. This
resulted in broken images if they were pulled then subsequently pushed.

This commit fetches the image config, which must be done separately, and
then ensures that the configuration is set on the exported image into
the local img state store.

client/pull.go

@@ -9,8 +9,11 @@ import (
 	"github.com/moby/buildkit/cache"
 	"github.com/moby/buildkit/exporter"
 	imageexporter "github.com/moby/buildkit/exporter/containerimage"
+	"github.com/moby/buildkit/exporter/containerimage/exptypes"
 	"github.com/moby/buildkit/source"
 	"github.com/moby/buildkit/source/containerimage"
+	"github.com/moby/buildkit/util/imageutil"
+	"github.com/moby/buildkit/util/pull"
 )
 
 // Pull retrieves an image from a remote registry.
@@ -66,6 +69,22 @@ func (c *Client) Pull(ctx context.Context, image string) (*ListedImage, error) {
 	if err != nil {
 		return nil, err
 	}
+
+	// Fetch the configuration for the image. src.Resolve below fetches
+	// all the data layers but does NOT fetch the configuration. We need this
+	// to set it for export later.
+	_, configBytes, err := imageutil.Config(
+		ctx,
+		image,
+		pull.NewResolver(ctx, opt.RegistryHosts, sm, opt.ImageStore, source.ResolveModeDefault, image),
+		opt.ContentStore,
+		opt.LeaseManager,
+		nil,
+	)
+	if err != nil {
+		return nil, err
+	}
+
 	s, err := src.Resolve(ctx, identifier, sm)
 	if err != nil {
 		return nil, err
@@ -99,7 +118,13 @@ func (c *Client) Pull(ctx context.Context, image string) (*ListedImage, error) {
 	if err != nil {
 		return nil, err
 	}
-	if _, err := e.Export(ctx, exporter.Source{Ref: ref}); err != nil {
+	if _, err := e.Export(ctx, exporter.Source{
+		Ref: ref,
+		Metadata: map[string][]byte{
+			// This sets the image config to preserve entrypoint, workingdir, etc.
+			exptypes.ExporterImageConfigKey: configBytes,
+		},
+	}); err != nil {
 		return nil, err
 	}
 

pull_test.go

@@ -1,8 +1,11 @@
 package main
 
 import (
+	"encoding/json"
 	"strings"
 	"testing"
+
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
 func TestPullFromDefaultRegistry(t *testing.T) {
@@ -29,3 +32,19 @@ func TestPullIsInListOutput(t *testing.T) {
 		t.Fatalf("expected busybox:latest in ls output, got: %s", out)
 	}
 }
+
+func TestPullRetainsConfig(t *testing.T) {
+	// Test an official image,
+	run(t, "pull", "alpine")
+
+	out := run(t, "inspect", "alpine")
+
+	var image ocispec.Image
+	if err := json.Unmarshal([]byte(out), &image); err != nil {
+		t.Fatalf("error decoding JSON: %s", err)
+	}
+
+	if len(image.Config.Cmd) == 0 {
+		t.Fatal("image config should be populated")
+	}
+}