feat: Optionally force convert to OCI media types on push

This enables support for stricter registries, such as zot, as well as enabling
users to move to a future without vendor specific Docker media types.

README.md

@@ -62,6 +62,11 @@ mindthegap push image-bundle --image-bundle <path/to/images.tar> \
 
 All images in the image bundle tar file will be pushed to the target OCI registry.
 
+Some registries (e.g. [zot](https://zotregistry.dev/) are strict about what media types they support. If you are pushing
+to a registry that only accepts OCI media types, then specify the `--force-oci-media-types` flag. This will internally
+convert any images that currently use Docker media types (`application/vnd.docker.*`) to OCI compatible media types
+(`application/vnd.oci.*`). Using the images via any container runtime does not change.
+
 #### Serving an image bundle
 
 **_This command is deprecated - see [Serving a bundle](#serving-a-bundle-supports-both-image-or-helm-chart)_**

cmd/mindthegap/push/bundle/bundle.go

@@ -16,8 +16,12 @@ import (
 	"github.com/google/go-containerregistry/pkg/authn"
 	"github.com/google/go-containerregistry/pkg/logs"
 	"github.com/google/go-containerregistry/pkg/name"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/empty"
+	"github.com/google/go-containerregistry/pkg/v1/mutate"
 	"github.com/google/go-containerregistry/pkg/v1/remote"
 	"github.com/google/go-containerregistry/pkg/v1/remote/transport"
+	mediatypes "github.com/google/go-containerregistry/pkg/v1/types"
 	"github.com/spf13/cobra"
 	"github.com/thediveo/enumflag/v2"
 	"golang.org/x/sync/errgroup"
@@ -59,6 +63,7 @@ func NewCommand(out output.Output, bundleCmdName string) *cobra.Command {
 		ecrLifecyclePolicy            string
 		onExistingTag                 = Overwrite
 		imagePushConcurrency          int
+		forceOCIMediaTypes            bool
 	)
 
 	cmd := &cobra.Command{
@@ -219,6 +224,7 @@ func NewCommand(out output.Output, bundleCmdName string) *cobra.Command {
 					onExistingTag,
 					imagePushConcurrency,
 					out,
+					forceOCIMediaTypes,
 					prePushFuncs...,
 				)
 				if err != nil {
@@ -289,6 +295,8 @@ func NewCommand(out output.Output, bundleCmdName string) *cobra.Command {
 	cmd.Flags().
 		IntVar(&imagePushConcurrency, "image-push-concurrency", 1, "Image push concurrency")
 
+	cmd.Flags().BoolVar(&forceOCIMediaTypes, "force-oci-media-types", false, "force OCI media types")
+
 	return cmd
 }
 
@@ -301,6 +309,7 @@ func pushImages(
 	onExistingTag onExistingTagMode,
 	imagePushConcurrency int,
 	out output.Output,
+	forceOCIMediaTypes bool,
 	prePushFuncs ...prePushFunc,
 ) error {
 	puller, err := remote.NewPuller(destRemoteOpts...)
@@ -379,7 +388,9 @@ func pushImages(
 					case Skip:
 						// If tag exists already then do nothing.
 						if _, exists := existingImageTags[imageTag]; exists {
-							pushFn = func(_ name.Reference, _ []remote.Option, _ name.Reference, _ []remote.Option) error {
+							pushFn = func(
+								_ name.Reference, _ []remote.Option, _ name.Reference, _ []remote.Option, _ bool,
+							) error {
 								return nil
 							}
 						}
@@ -391,7 +402,7 @@ func pushImages(
 						}
 					}
 
-					if err := pushFn(srcImage, sourceRemoteOpts, destImage, destRemoteOpts); err != nil {
+					if err := pushFn(srcImage, sourceRemoteOpts, destImage, destRemoteOpts, forceOCIMediaTypes); err != nil {
 						return err
 					}
 
@@ -418,12 +429,20 @@ func pushTag(
 	sourceRemoteOpts []remote.Option,
 	destImage name.Reference,
 	destRemoteOpts []remote.Option,
+	forceOCIMediaTypes bool,
 ) error {
 	idx, err := remote.Index(srcImage, sourceRemoteOpts...)
 	if err != nil {
 		return err
 	}
 
+	if forceOCIMediaTypes {
+		idx, err = convertToOCIIndex(idx, srcImage, sourceRemoteOpts)
+		if err != nil {
+			return fmt.Errorf("failed to convert index to OCI format: %w", err)
+		}
+	}
+
 	return remote.WriteIndex(destImage, idx, destRemoteOpts...)
 }
 
@@ -518,3 +537,78 @@ func getExistingImages(
 
 	return existingTags, nil
 }
+
+func convertToOCIIndex(
+	originalIndex v1.ImageIndex,
+	srcImage name.Reference,
+	sourceRemoteOpts []remote.Option,
+) (v1.ImageIndex, error) {
+	originalMediaType, err := originalIndex.MediaType()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get media type of image index: %w", err)
+	}
+
+	if originalMediaType == mediatypes.OCIImageIndex {
+		return originalIndex, nil
+	}
+
+	var ociIdx v1.ImageIndex = empty.Index
+	ociIdx = mutate.IndexMediaType(ociIdx, mediatypes.OCIImageIndex)
+
+	originalIdx, err := originalIndex.IndexManifest()
+	if err != nil {
+		return nil, fmt.Errorf("failed to read original image index manifest: %w", err)
+	}
+
+	for i := range originalIdx.Manifests {
+		manifest := originalIdx.Manifests[i]
+		manifest.MediaType = mediatypes.OCIManifestSchema1
+
+		digestRef, err := name.NewDigest(fmt.Sprintf("%s@%s", srcImage.Context().Name(), manifest.Digest.String()))
+		if err != nil {
+			return nil, fmt.Errorf("failed to create digest reference: %w", err)
+		}
+
+		imgDesc, err := remote.Get(digestRef, sourceRemoteOpts...)
+		if err != nil {
+			return nil, fmt.Errorf("failed to get image %q: %w", digestRef, err)
+		}
+
+		img, err := imgDesc.Image()
+		if err != nil {
+			return nil, fmt.Errorf("failed to convert image descriptor for %q to image: %w", digestRef, err)
+		}
+
+		ociImg := empty.Image
+		ociImg = mutate.MediaType(ociImg, mediatypes.OCIManifestSchema1)
+		ociImg = mutate.ConfigMediaType(ociImg, mediatypes.OCIConfigJSON)
+		layers, err := img.Layers()
+		if err != nil {
+			return nil, fmt.Errorf("failed to get layers for image %q: %w", digestRef, err)
+		}
+
+		for _, layer := range layers {
+			ociImg, err = mutate.Append(ociImg, mutate.Addendum{
+				Layer:     layer,
+				MediaType: mediatypes.OCILayer,
+			})
+			if err != nil {
+				return nil, fmt.Errorf("failed to append layer to image %q: %w", digestRef, err)
+			}
+		}
+
+		ociImgDigest, err := ociImg.Digest()
+		if err != nil {
+			return nil, fmt.Errorf("failed to get digest for image %q: %w", digestRef, err)
+		}
+
+		manifest.Digest = ociImgDigest
+
+		ociIdx = mutate.AppendManifests(ociIdx, mutate.IndexAddendum{
+			Add:        ociImg,
+			Descriptor: manifest,
+		})
+	}
+
+	return ociIdx, nil
+}

images/manifest.go

@@ -5,6 +5,7 @@ package images
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/google/go-containerregistry/pkg/name"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
@@ -145,7 +146,17 @@ func indexForSinglePlatformImage(
 			},
 		},
 	)
-	index = mutate.IndexMediaType(index, types.DockerManifestList)
+
+	imgMediaType, err := img.MediaType()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get image media type for image %q: %w", ref, err)
+	}
+	idxMediaType := types.OCIImageIndex
+	if strings.Contains(string(imgMediaType), types.DockerVendorPrefix) {
+		idxMediaType = types.DockerManifestList
+	}
+
+	index = mutate.IndexMediaType(index, idxMediaType)
 
 	if len(platforms) == 0 {
 		return index, nil

test/e2e/imagebundle/helpers/helpers.go

@@ -25,6 +25,7 @@ import (
 	"github.com/google/go-containerregistry/pkg/name"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/google/go-containerregistry/pkg/v1/types"
 	"github.com/onsi/ginkgo/v2"
 	"github.com/onsi/gomega"
 	"github.com/onsi/gomega/gstruct"
@@ -189,6 +190,7 @@ func ValidateImageIsAvailable(
 	port int,
 	registryPath, image, tag string,
 	platforms []*v1.Platform,
+	forceOCIMediaTypes bool,
 	opts ...remote.Option,
 ) {
 	t.Helper()
@@ -205,6 +207,9 @@ func ValidateImageIsAvailable(
 
 	manifest, err := idx.IndexManifest()
 	gomega.ExpectWithOffset(1, err).NotTo(gomega.HaveOccurred())
+	if forceOCIMediaTypes {
+		gomega.ExpectWithOffset(1, manifest.MediaType).To(gomega.Equal(types.OCIImageIndex))
+	}
 
 	gomega.ExpectWithOffset(1, manifest.Manifests).To(gomega.HaveLen(len(platforms)))
 

test/e2e/imagebundle/push_bundle_test.go

@@ -57,6 +57,7 @@ var _ = Describe("Push Bundle", func() {
 			registryScheme string,
 			registryPath string,
 			registryInsecure bool,
+			forceOCIMediaTypes bool,
 		) {
 			registryCACertFile := ""
 			registryCertFile := ""
@@ -113,6 +114,10 @@ var _ = Describe("Push Bundle", func() {
 				args = append(args, "--to-registry-ca-cert-file", registryCACertFile)
 			}
 
+			if forceOCIMediaTypes {
+				args = append(args, "--force-oci-media-types")
+			}
+
 			cmd.SetArgs(args)
 
 			Expect(cmd.Execute()).To(Succeed())
@@ -136,6 +141,7 @@ var _ = Describe("Push Bundle", func() {
 					OS:           "linux",
 					Architecture: runtime.GOARCH,
 				}},
+				forceOCIMediaTypes,
 				remote.WithTransport(testRoundTripper),
 			)
 
@@ -150,6 +156,7 @@ var _ = Describe("Push Bundle", func() {
 				registryScheme string,
 				registryPath string,
 				registryInsecure bool,
+				forceOCIMediaTypes bool,
 			) {
 				helpers.CreateBundle(
 					GinkgoT(),
@@ -158,21 +165,22 @@ var _ = Describe("Push Bundle", func() {
 					"linux/"+runtime.GOARCH,
 				)
 
-				runTest(registryHost, registryScheme, registryPath, registryInsecure)
+				runTest(registryHost, registryScheme, registryPath, registryInsecure, forceOCIMediaTypes)
 			},
 
-			Entry("Without TLS", "127.0.0.1", "", "", true),
+			Entry("Without TLS", "127.0.0.1", "", "", true, false),
 
-			Entry("With TLS", helpers.GetFirstNonLoopbackIP(GinkgoT()).String(), "", "", false),
+			Entry("With TLS", helpers.GetFirstNonLoopbackIP(GinkgoT()).String(), "", "", false, false),
 
-			Entry("With Insecure TLS", helpers.GetFirstNonLoopbackIP(GinkgoT()).String(), "", "", true),
+			Entry("With Insecure TLS", helpers.GetFirstNonLoopbackIP(GinkgoT()).String(), "", "", true, false),
 
 			Entry(
 				"With http registry",
 				helpers.GetFirstNonLoopbackIP(GinkgoT()).String(),
 				"http",
 				"",
 				true,
+				false,
 			),
 
 			Entry(
@@ -181,9 +189,19 @@ var _ = Describe("Push Bundle", func() {
 				"http",
 				"",
 				false,
+				false,
+			),
+
+			Entry(
+				"With Subpath",
+				helpers.GetFirstNonLoopbackIP(GinkgoT()).String(),
+				"",
+				"/nested/path/for/registry",
+				false,
+				false,
 			),
 
-			Entry("With Subpath", helpers.GetFirstNonLoopbackIP(GinkgoT()).String(), "", "/nested/path/for/registry", false),
+			Entry("With force OCI media types", helpers.GetFirstNonLoopbackIP(GinkgoT()).String(), "", "", false, true),
 		)
 
 		It("Bundle does not exist", func() {
@@ -221,7 +239,7 @@ var _ = Describe("Push Bundle", func() {
 			})
 
 			It("Success", func() {
-				runTest(helpers.GetFirstNonLoopbackIP(GinkgoT()).String(), "", "", false)
+				runTest(helpers.GetFirstNonLoopbackIP(GinkgoT()).String(), "", "", false, false)
 			})
 
 			Context("With headers from Docker config", func() {
@@ -242,7 +260,7 @@ var _ = Describe("Push Bundle", func() {
 				})
 
 				It("Success", func() {
-					runTest(helpers.GetFirstNonLoopbackIP(GinkgoT()).String(), "", "", false)
+					runTest(helpers.GetFirstNonLoopbackIP(GinkgoT()).String(), "", "", false, false)
 				})
 			})
 		})

test/e2e/imagebundle/serve_bundle_test.go

@@ -82,6 +82,7 @@ var _ = Describe("Serve Bundle", func() {
 				OS:           "linux",
 				Architecture: runtime.GOARCH,
 			}},
+			false,
 		)
 
 		close(stopCh)
@@ -146,6 +147,7 @@ var _ = Describe("Serve Bundle", func() {
 				OS:           "linux",
 				Architecture: runtime.GOARCH,
 			}},
+			false,
 			remote.WithTransport(testRoundTripper),
 		)