Update tag validation

Fixes #536

endpoints/api/tag.py

@@ -8,6 +8,7 @@ from endpoints.api import (resource, nickname, require_repo_read, require_repo_w
 from endpoints.api.image import image_view
 from data import model
 from auth.auth_context import get_authenticated_user
+from util.names import TAG_ERROR, TAG_REGEX
 
 
 @resource('/v1/repository/<repopath:repository>/tag/')
@@ -85,6 +86,10 @@ class RepositoryTag(RepositoryParamResource):
   @validate_json_request('MoveTag')
   def put(self, namespace, repository, tag):
     """ Change which image a tag points to or create a new tag."""
+
+    if not TAG_REGEX.match(tag):
+      abort(400, TAG_ERROR)
+
     image_id = request.get_json()['image']
     image = model.image.get_repo_image(namespace, repository, image_id)
     if not image: