Update embedded Docker reference, if any, in copy.Image

Add EmbbeddedDockerReference to types.ManifestUpdateOptions, and use it
in copy.Image.  Pushing signed schema1 images to a different location
is impossible (skopeo users can use --remove-signatures), but signing an
unsigned schema1 image while pushing it does work.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

copy/copy.go

@@ -143,6 +143,10 @@ func Image(policyContext *signature.PolicyContext, destRef, srcRef types.ImageRe
 	canModifyManifest := len(sigs) == 0
 	manifestUpdates := types.ManifestUpdateOptions{}
 
+	if err := updateEmbeddedDockerReference(&manifestUpdates, dest, src, canModifyManifest); err != nil {
+		return err
+	}
+
 	if err := determineManifestConversion(&manifestUpdates, src, destSupportedManifestMIMETypes, canModifyManifest); err != nil {
 		return err
 	}
@@ -206,6 +210,33 @@ func Image(policyContext *signature.PolicyContext, destRef, srcRef types.ImageRe
 	return nil
 }
 
+// updateEmbeddedDockerReference handles the Docker reference embedded in Docker schema1 manifests.
+func updateEmbeddedDockerReference(manifestUpdates *types.ManifestUpdateOptions, dest types.ImageDestination, src types.Image, canModifyManifest bool) error {
+	manifestRef, err := src.EmbeddedDockerReference()
+	if err != nil {
+		return fmt.Errorf("Error parsing source image for embedded Docker reference: %v", err)
+	}
+	if manifestRef == nil {
+		return nil // No embedded manifest
+	}
+
+	destRef := dest.Reference().DockerReference()
+	if destRef == nil {
+		return nil // Destination does not care about Docker references
+	}
+
+	if destRef.String() == manifestRef.String() {
+		return nil // The reference matches
+	}
+
+	if !canModifyManifest {
+		return fmt.Errorf("Copying a schema1 image with embedded Docker reference %s to %s (Docker reference %s) would invalidate existing signatures. Explicitly enable signature removal to proceed anyway",
+			manifestRef.String(), transports.ImageName(dest.Reference()), destRef.String())
+	}
+	manifestUpdates.EmbeddedDockerReference = destRef
+	return nil
+}
+
 // copyLayers copies layers from src/rawSource to dest, using and updating manifestUpdates if necessary and canModifyManifest.
 // If src.UpdatedImageNeedsLayerDiffIDs(manifestUpdates) will be true, it needs to be true by the time this function is called.
 func copyLayers(manifestUpdates *types.ManifestUpdateOptions, dest types.ImageDestination, src types.Image, rawSource types.ImageSource,

image/docker_schema1.go

@@ -178,6 +178,14 @@ func (m *manifestSchema1) UpdatedImage(options types.ManifestUpdateOptions) (typ
 			copy.FSLayers[(len(options.LayerInfos)-1)-i].BlobSum = info.Digest
 		}
 	}
+	if options.EmbeddedDockerReference != nil {
+		copy.Name = options.EmbeddedDockerReference.Name()
+		if tagged, isTagged := options.EmbeddedDockerReference.(reference.NamedTagged); isTagged {
+			copy.Tag = tagged.Tag()
+		} else {
+			copy.Tag = ""
+		}
+	}
 
 	switch options.ManifestMIMEType {
 	case "": // No conversion, OK

image/docker_schema2.go

@@ -168,6 +168,7 @@ func (m *manifestSchema2) UpdatedImage(options types.ManifestUpdateOptions) (typ
 			copy.LayersDescriptors[i].URLs = info.URLs
 		}
 	}
+	// Ignore options.EmbeddedDockerReference: it may be set when converting from schema1 to schema2, but we really don't care.
 
 	switch options.ManifestMIMEType {
 	case "": // No conversion, OK

types/types.go

@@ -219,8 +219,9 @@ type Image interface {
 
 // ManifestUpdateOptions is a way to pass named optional arguments to Image.UpdatedManifest
 type ManifestUpdateOptions struct {
-	LayerInfos       []BlobInfo // Complete BlobInfos (size+digest+urls) which should replace the originals, in order (the root layer first, and then successive layered layers)
-	ManifestMIMEType string
+	LayerInfos              []BlobInfo // Complete BlobInfos (size+digest+urls) which should replace the originals, in order (the root layer first, and then successive layered layers)
+	EmbeddedDockerReference reference.Named
+	ManifestMIMEType        string
 	// The values below are NOT requests to modify the image; they provide optional context which may or may not be used.
 	InformationOnly ManifestUpdateInformation
 }