[#505] morph/container: Verify signature of deleting container ID

Get all owner keys and verify container ID signature until first success. If
none of the keys match, then prohibit deletion. Thus, the delete operation
is only allowed to the owner of the container. With this approach, a
separate check for key ownership is not required.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/innerring/processors/container/process_container.go

@@ -96,8 +96,32 @@ func (cp *Processor) processContainerDelete(delete *containerEvent.Delete) {
 }
 
 func (cp *Processor) checkDeleteContainer(e *containerEvent.Delete) error {
+	cid := e.ContainerID()
+
+	// receive owner of the related container
+	cnr, err := cp.cnrClient.Get(cid)
+	if err != nil {
+		return fmt.Errorf("could not receive the container: %w", err)
+	}
+
+	// receive all owner keys
+	ownerKeys, err := cp.idClient.AccountKeys(cnr.OwnerID())
+	if err != nil {
+		return fmt.Errorf("could not received owner keys %s: %w", cnr.OwnerID(), err)
+	}
+
+	// verify signature
+	cidHash := sha256.Sum256(cid)
+	sig := e.Signature()
+
+	for _, ownerKey := range ownerKeys {
+		if ownerKey.Verify(sig, cidHash[:]) {
 			return nil
 		}
+	}
+
+	return errors.New("signature verification failed on all owner keys ")
+}
 
 func (cp *Processor) approveDeleteContainer(e *containerEvent.Delete) {
 	// FIXME: here we should try notary invoke