What is the secure way to isolate ftp server users on unix?
- by djs
I've read documentation for various ftp daemons and various long threads about the security implications of using a chroot environment for an ftp server when giving users write access. If you read the vsftpd documentation, in particular, it implies that using chroot_local_user is a security hazard, while not using it is not. There seems to be no coverage of the implications of allowing the user access to the entire filesystem (as permitted by their user and group membership), nor to the confusion this can create.
So, I'd like to understand what is the correct method to use in practice. Should an ftp server with authenticated write-access users provide a non-chroot environment, a chroot environment, or some other option? Given that Windows ftp daemons don't have the option to use chroot, they need to implement isolation otherwise. Do any unix ftp daemons do something similar?
