Ubuntu - changing another users file permissions

Question

I have setup Ubuntu as a development web server - however I am experiencing problems with file permissions. I have 2 users, user1 and user2, and they both have been put into the group www-data.

I have uploaded a new file with user1 so the file is owned by user1 and the www-data group.

At present if user2 wants to modify the permissions on that file to say 777 - they cannot.

Is there a way to allow any users within a group to be able to modifiy permissions etc.. on this file? I have tried changing umask to 002 and a few other combinations that were suggested without luck.

Answer 1

From chmod(2) --

   The effective UID of the calling process must match the  owner  of  the
   file,  or  the  process  must  be  privileged  (Linux: it must have the
   CAP_FOWNER capability).

However, user2 (with write permissions on the directory) could create a copy of the file, set its permissions, then replace the original file with the copy.