I have a need to setup an FTP server for many users to upload and download files.
The users are not consistent in their chosen protocol, some use FTP, some FTPS, some SFTP.
I would like to setup a server to provide this preferably using some Virtual Hosting arrangement that does not involve setting up system accounts for individual users. While the software for FTPS and FTP to enable this is readily available SFTP (the subsystem of SSH) does not appear to have many equivalents.
I have a single RedHat EL machine provisioned for this purpose.
In my experience, you are forced to use PAM to authenticate users using SSH. You may want to look into pam_pwdfile if you wish to keep things simple for storing users and create a /etc/pam.d/ssh file accordingly.
You probably want to create SFTP-only chrooted accesses for your users, OpenSSHv5 allows you to do so very simply with ChrootDirectory (quick example here).