Initial commit

Signed-off-by: Christian Dupuis <cd@atomist.com>

registry/registry.go

@@ -0,0 +1,83 @@
+/*
+ * Copyright © 2022 Docker, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package registry
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/docker/cli/cli/command"
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/daemon"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/opencontainers/go-digest"
+	"github.com/pkg/errors"
+)
+
+// DigestForImage retrieves the layer digests from either a local or remote image
+func DigestForImage(dockerCli command.Cli, image string) ([]digest.Digest, error) {
+	digests := make([]digest.Digest, 0)
+
+	limg, _, err := dockerCli.Client().ImageInspectWithRaw(context.Background(), image)
+	if err == nil {
+		for _, l := range limg.RootFS.Layers {
+			parsed, _ := digest.Parse(l)
+			digests = append(digests, parsed)
+		}
+		return digests, nil
+	}
+
+	ref, err := name.ParseReference(image)
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to parse reference: %s", image)
+	}
+
+	// check local daemon first
+	img, err := daemon.Image(ref)
+	if err != nil {
+		// image doesn't exist in daemon; try remote
+		index, _ := remote.Index(ref, remote.WithAuthFromKeychain(authn.DefaultKeychain))
+		if index != nil {
+			m, _ := index.IndexManifest()
+			for _, manifest := range m.Manifests {
+				ref, _ = name.ParseReference(fmt.Sprintf("%s@%s", ref.Context(), manifest.Digest))
+				if manifest.Platform.OS == "linux" && manifest.Platform.Architecture == "amd64" {
+					break
+				}
+			}
+		}
+
+		desc, err := remote.Get(ref, remote.WithAuthFromKeychain(authn.DefaultKeychain))
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to pull image: %s", image)
+		} else if desc != nil {
+			img, _ = desc.Image()
+		}
+	}
+
+	if img != nil {
+		layers, _ := img.Layers()
+		for _, layer := range layers {
+			d, _ := layer.DiffID()
+			parsed, _ := digest.Parse(d.String())
+			digests = append(digests, parsed)
+		}
+	}
+
+	return digests, nil
+}