CRI: Retrieve image spec on client

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>

image.go

@@ -64,6 +64,8 @@ type Image interface {
 	Metadata() images.Image
 	// Platform returns the platform match comparer. Can be nil.
 	Platform() platforms.MatchComparer
+	// Spec returns the OCI image spec for a given image.
+	Spec(ctx context.Context) (ocispec.Image, error)
 }
 
 type usageOptions struct {
@@ -279,6 +281,26 @@ func (i *image) IsUnpacked(ctx context.Context, snapshotterName string) (bool, e
 	return false, nil
 }
 
+func (i *image) Spec(ctx context.Context) (ocispec.Image, error) {
+	var ociImage ocispec.Image
+
+	desc, err := i.Config(ctx)
+	if err != nil {
+		return ociImage, fmt.Errorf("get image config descriptor: %w", err)
+	}
+
+	blob, err := content.ReadBlob(ctx, i.ContentStore(), desc)
+	if err != nil {
+		return ociImage, fmt.Errorf("read image config from content store: %w", err)
+	}
+
+	if err := json.Unmarshal(blob, &ociImage); err != nil {
+		return ociImage, fmt.Errorf("unmarshal image config %s: %w", blob, err)
+	}
+
+	return ociImage, nil
+}
+
 // UnpackConfig provides configuration for the unpack of an image
 type UnpackConfig struct {
 	// ApplyOpts for applying a diff to a snapshotter

pkg/cri/store/image/image.go

@@ -18,12 +18,10 @@ package image
 
 import (
 	"context"
-	"encoding/json"
 	"fmt"
 	"sync"
 
 	"github.com/containerd/containerd"
-	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/pkg/cri/util"
 
@@ -132,15 +130,12 @@ func getImage(ctx context.Context, i containerd.Image) (*Image, error) {
 	if err != nil {
 		return nil, fmt.Errorf("get image config descriptor: %w", err)
 	}
+
 	id := desc.Digest.String()
 
-	rb, err := content.ReadBlob(ctx, i.ContentStore(), desc)
+	spec, err := i.Spec(ctx)
 	if err != nil {
-		return nil, fmt.Errorf("read image config from content store: %w", err)
-	}
-	var ociimage imagespec.Image
-	if err := json.Unmarshal(rb, &ociimage); err != nil {
-		return nil, fmt.Errorf("unmarshal image config %s: %w", rb, err)
+		return nil, fmt.Errorf("failed to read get image spec: %w", err)
 	}
 
 	return &Image{
@@ -148,7 +143,7 @@ func getImage(ctx context.Context, i containerd.Image) (*Image, error) {
 		References: []string{i.Name()},
 		ChainID:    chainID.String(),
 		Size:       size,
-		ImageSpec:  ociimage,
+		ImageSpec:  spec,
 	}, nil
 }