X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/fadf2b0fe1240f607fc91d65d6831621262afeb1..c3d4b399c57e711f0cd87c2178f873a688323967:/services/api/app/models/link.rb

diff --git a/services/api/app/models/link.rb b/services/api/app/models/link.rb
index af3918551e..6321145045 100644
--- a/services/api/app/models/link.rb
+++ b/services/api/app/models/link.rb
@@ -10,6 +10,7 @@ class Link < ArvadosModel
   after_destroy :maybe_invalidate_permissions_cache
   attr_accessor :head_kind, :tail_kind
   validate :name_link_has_valid_name
+  validate :name_link_owner_is_tail
 
   api_accessible :user, extend: :common do |t|
     t.add :tail_uuid
@@ -50,22 +51,9 @@ class Link < ArvadosModel
     # Administrators can grant permissions
     return true if current_user.is_admin
 
-    # All users can grant permissions on objects they own
-    head_obj = self.class.
-      resource_class_for_uuid(self.head_uuid).
-      where('uuid=?',head_uuid).
-      first
-    if head_obj
-      return true if head_obj.owner_uuid == current_user.uuid
-    end
-
-    # Users with "can_grant" permission on an object can grant
-    # permissions on that object
-    has_grant_permission = self.class.
-      where('link_class=? AND name=? AND tail_uuid=? AND head_uuid=?',
-            'permission', 'can_grant', current_user.uuid, self.head_uuid).
-      count > 0
-    return true if has_grant_permission
+    # All users can grant permissions on objects they own or can manage
+    head_obj = ArvadosModel.find_by_uuid(head_uuid)
+    return true if current_user.can?(manage: head_obj)
 
     # Default = deny.
     false
@@ -92,4 +80,39 @@ class Link < ArvadosModel
       true
     end
   end
+
+  def name_link_owner_is_tail
+    if link_class == 'name'
+      self.owner_uuid = tail_uuid
+      ensure_owner_uuid_is_permitted
+    end
+  end
+
+  # A user is permitted to create, update or modify a permission link
+  # if and only if they have "manage" permission on the destination
+  # object.
+  # All other links are treated as regular ArvadosModel objects.
+  #
+  def ensure_owner_uuid_is_permitted
+    if link_class == 'permission'
+      ob = ArvadosModel.find_by_uuid(head_uuid)
+      raise PermissionDeniedError unless current_user.can?(manage: ob)
+      # All permission links should be owned by the system user.
+      self.owner_uuid = system_user_uuid
+      return true
+    else
+      super
+    end
+  end
+
+  # A user can give all other users permissions on folders.
+  def skip_uuid_read_permission_check
+    skipped_attrs = super
+    if link_class == "permission" and
+        (ArvadosModel.resource_class_for_uuid(head_uuid) == Group) and
+        (ArvadosModel.resource_class_for_uuid(tail_uuid) == User)
+      skipped_attrs << "tail_uuid"
+    end
+    skipped_attrs
+  end
 end