improved image OCI conversion

cmd/build.go

@@ -190,7 +190,7 @@ func build(cmd *cobra.Command, _ []string) error {
 	}
 
 	// pull the base image
-	baseImg, err := containerutil.Pull(cmd.Context(), baseImage)
+	baseImg, err := containerutil.Get(cmd.Context(), baseImage)
 	if err != nil {
 		return err
 	}

pkg/containerutil/append.go

@@ -3,14 +3,15 @@ package containerutil
 import (
 	"context"
 	"fmt"
+	"path/filepath"
+	"strings"
+
 	"github.com/chainguard-dev/go-apk/pkg/fs"
 	"github.com/go-logr/logr"
 	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/types"
-	"path/filepath"
-	"strings"
 )
 
 const MagicImageScratch = "scratch"
@@ -88,7 +89,7 @@ func (ib *Image) Append(ctx context.Context, fs fs.FullFS, platform *v1.Platform
 	if mt, err := ib.baseImage.MediaType(); err == nil {
 		log.V(1).Info("detected base image media type", "mediaType", mt)
 	}
-	baseImage := mutate.MediaType(ib.baseImage, types.OCIManifestSchema1)
+	baseImage := ib.baseImage
 
 	// append our layer
 	layers := []mutate.Addendum{

pkg/containerutil/get.go

@@ -0,0 +1,46 @@
+package containerutil
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/djcass44/ci-tools/pkg/ociutil"
+	"github.com/go-logr/logr"
+	"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/remote"
+)
+
+func Get(ctx context.Context, ref string) (v1.Image, error) {
+	log := logr.FromContextOrDiscard(ctx).WithValues("ref", ref)
+	log.Info("getting image")
+
+	if ref == MagicImageScratch {
+		return empty.Image, nil
+	}
+
+	remoteRef, err := name.ParseReference(ref)
+	if err != nil {
+		return nil, fmt.Errorf("parsing name %s: %w", ref, err)
+	}
+
+	// fetch the image without actually
+	// pulling it
+	rmt, err := remote.Get(remoteRef, remote.WithContext(ctx), remote.WithAuthFromKeychain(ociutil.KeyChain(ociutil.Auth{})))
+	if err != nil {
+		return nil, fmt.Errorf("getting %s: %w", ref, err)
+	}
+
+	img, err := rmt.Image()
+	if err != nil {
+		return nil, err
+	}
+
+	// normalise the image
+	img, err = NormaliseImage(ctx, img)
+	if err != nil {
+		return nil, fmt.Errorf("normalising %s: %w", ref, err)
+	}
+	return img, nil
+}

pkg/containerutil/get_test.go

@@ -0,0 +1,32 @@
+package containerutil
+
+import (
+	"context"
+	"testing"
+
+	"github.com/go-logr/logr"
+	"github.com/go-logr/logr/testr"
+	"github.com/google/go-containerregistry/pkg/v1/empty"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGet(t *testing.T) {
+	ctx := logr.NewContext(context.TODO(), testr.NewWithOptions(t, testr.Options{Verbosity: 10}))
+
+	t.Run("real image", func(t *testing.T) {
+		img, err := Get(ctx, "busybox")
+		assert.NoError(t, err)
+		size, err := img.Size()
+		assert.NoError(t, err)
+		assert.NotZero(t, size)
+	})
+	t.Run("scratch image", func(t *testing.T) {
+		img, err := Get(ctx, "scratch")
+		assert.NoError(t, err)
+		size, err := img.Size()
+		assert.NoError(t, err)
+		assert.NotZero(t, size)
+
+		assert.Equal(t, empty.Image, img)
+	})
+}

pkg/containerutil/mutate.go

@@ -0,0 +1,106 @@
+package containerutil
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/go-logr/logr"
+	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/tarball"
+	"github.com/google/go-containerregistry/pkg/v1/types"
+)
+
+// Drops docker specific properties
+// See: https://github.com/opencontainers/image-spec/blob/main/config.md
+func toOCIV1Config(config v1.Config) v1.Config {
+	return v1.Config{
+		User:         config.User,
+		ExposedPorts: config.ExposedPorts,
+		Env:          config.Env,
+		Entrypoint:   config.Entrypoint,
+		Cmd:          config.Cmd,
+		Volumes:      config.Volumes,
+		WorkingDir:   config.WorkingDir,
+		Labels:       config.Labels,
+		StopSignal:   config.StopSignal,
+	}
+}
+
+func toOCIV1ConfigFile(cf *v1.ConfigFile) *v1.ConfigFile {
+	return &v1.ConfigFile{
+		Created:      cf.Created,
+		Author:       cf.Author,
+		Architecture: cf.Architecture,
+		OS:           cf.OS,
+		OSVersion:    cf.OSVersion,
+		History:      cf.History,
+		RootFS:       cf.RootFS,
+		Config:       toOCIV1Config(cf.Config),
+	}
+}
+
+// NormaliseImage mutates the provided v1.Image to be OCI compliant v1.Image.
+//
+// Check image-spec to see which properties are ported and which are dropped.
+// https://github.com/opencontainers/image-spec/blob/main/config.md
+func NormaliseImage(ctx context.Context, base v1.Image) (v1.Image, error) {
+	log := logr.FromContextOrDiscard(ctx)
+	log.V(1).Info("normalising base image")
+	// get the original manifest
+	m, err := base.Manifest()
+	if err != nil {
+		return nil, err
+	}
+	// convert config
+	cfg, err := base.ConfigFile()
+	if err != nil {
+		return nil, err
+	}
+	cfg = toOCIV1ConfigFile(cfg)
+
+	layers, err := base.Layers()
+	if err != nil {
+		return nil, err
+	}
+
+	newLayers := []v1.Layer{}
+
+	// go through each layer and convert it to
+	// OCI format
+	for _, layer := range layers {
+		mediaType, err := layer.MediaType()
+		if err != nil {
+			return nil, err
+		}
+		log.V(2).Info("checking layer", "mediaType", mediaType)
+		switch mediaType {
+		case types.DockerLayer:
+			layer, err = tarball.LayerFromOpener(layer.Compressed, tarball.WithMediaType(types.OCILayer))
+			if err != nil {
+				return nil, fmt.Errorf("building layer: %w", err)
+			}
+		case types.DockerUncompressedLayer:
+			layer, err = tarball.LayerFromOpener(layer.Uncompressed, tarball.WithMediaType(types.OCIUncompressedLayer))
+			if err != nil {
+				return nil, fmt.Errorf("building layer: %w", err)
+			}
+		}
+		newLayers = append(newLayers, layer)
+	}
+
+	base, err = mutate.AppendLayers(empty.Image, newLayers...)
+	if err != nil {
+		return nil, err
+	}
+
+	base = mutate.MediaType(base, types.OCIManifestSchema1)
+	base = mutate.ConfigMediaType(base, types.OCIConfigJSON)
+	base = mutate.Annotations(base, m.Annotations).(v1.Image)
+	base, err = mutate.ConfigFile(base, cfg)
+	if err != nil {
+		return nil, err
+	}
+	return base, nil
+}