I have a fork of Imagr here:
https://github.com/gregneagle/imagr that implements HTTP Basic and Digest authentication for the workflows.plist.
Imagr requests the workflow.plist.
Server responds with 401 Authentication Required.
Imagr displays a credentials dialog.
User enters credentials.
Imagr re-requests the workflow.plist with the provided creds.
Server validates the credentials with whatever mechanism it wants -- this could be backed by LDAP or AD, or whatever mechanism you can implement on your web server.
I would like some people to kick it around a bit before I make a Pull Request to Graham.
Note: you don't have to go to the effort of building a new NBI, etc. To test the new functionality, you can just run Imagr locally from Xcode, and use `defaults write com.grahamgilbert.Imagr serverurl <a workflows.plist url that requires authentication>` to point it at a testing URL.
-Greg