storage: generate different imageID with partial layers

when an image using partial layers is pulled, generate a different
imageID that combines the digest of the TOC for the partial layers
since the partial pull didn't validate the diffID.

Signed-off-by: Giuseppe Scrivano <[email protected]>

storage/storage_dest.go

@@ -426,6 +426,7 @@ func (s *storageImageDestination) computeID(m manifest.Manifest) string {
 	// fill in the DiffIDs.  It's expected (but not enforced by us) that the number of
 	// diffIDs corresponds to the number of non-EmptyLayer entries in the history.
 	var diffIDs []digest.Digest
+	var tocDigests []digest.Digest
 	switch m := m.(type) {
 	case *manifest.Schema1:
 		// Build a list of the diffIDs we've generated for the non-throwaway FS layers,
@@ -442,16 +443,39 @@ func (s *storageImageDestination) computeID(m manifest.Manifest) string {
 			}
 			diffIDs = append([]digest.Digest{diffID}, diffIDs...)
 		}
-	case *manifest.Schema2, *manifest.OCI1:
-		// We know the ID calculation for these formats doesn't actually use the diffIDs,
-		// so we don't need to populate the diffID list.
+	case *manifest.Schema2:
+		// We know the ID calculation doesn't actually use the diffIDs, so we don't need to populate
+		// the diffID list.
+	case *manifest.OCI1:
+		for _, layer := range m.Layers {
+			toc, err := chunked.GetTOCDigest(layer.Annotations)
+			if err != nil {
+				logrus.Infof("error looking up annotation for layer %q: %v", layer.Digest, err)
+				continue
+			}
+			if toc != nil {
+				tocDigests = append(tocDigests, *toc)
+			}
+		}
 	default:
 		return ""
 	}
 	id, err := m.ImageID(diffIDs)
 	if err != nil {
 		return ""
 	}
+
+	// If the image is using any partial layer, let's generate a new image ID by combining the
+	// original image ID with the TOC digest of the partial layers.
+	if len(tocDigests) > 0 {
+		for _, d := range tocDigests {
+			id = id + "+" + string(d)
+		}
+		newID := digest.Canonical.Digester()
+		_, err = newID.Hash().Write([]byte(id))
+		id = newID.Digest().Hex()
+	}
+
 	return id
 }