I currently have chroot users whos home directories contain both an 'upload' directory and a 'download' directory.

Originally the permissions on the upload directory where

 chown user:sftpadmin upload
 chmod 370 upload

and the permissions on the download directory where

 chown user:sftpadmin download
 chmod 570 dowload

The purpose of the sftpadmins group is for service accounts that are a member of this group would be able to place/retrieve files for the user from the respective directories.

Now we have a request to allow the users the ability to delete files in the download directory after they are finished with them. However the only option I can come up with to accomplish this is setting the permissions on the download dir to 

`chmod 770 download`

However this would grant the chroot'ed users the ability to write any file to this directory, which I would like to avoid.

Is there any combination of permissions I can set that would allow them the ability to read, download, and delete the files in the directory, without allowing them to write files to the download directory?