FTP access error from Safari in iOS / macOS after updating OS

I have a ProFTPd Server where the users can access to files using links dynamically generated in a website. The link URL follows the pattern ftp://user:password@host/path/to/file

With the new iOS 11 and new macOS, users cannot access the FTP server. They get a "don't have permission to open" error.

Surprisingly, on a Mac, hovering over the link and using contextual menu->“download attached file” will download the file.

Any iPhone or Mac running previous OS versions can download the files normally.

Looking through FTP logs confirms credentials are not sent by Safari.

Using any other browser (Chrome, Firefox) works fine as well.

Forcing users to an external app is not an option.

Any idea?

EDIT: I have tpcdump the connection and I see that Safari changes request user and password to: user-> anonymous pass-> [email protected]

So the FTP server rejects the connection to a anonymous user.

Solution 1:

Consider switching to anonymous FTP, or HTTPS or SFTP.

Apple has been making a concerted effort to make sure credentials and other possibly private info never traverses the network in the clear. For example they removed the command-line FTP and Telnet clients from macOS as of High Sierra (10.13), since those protocols are insecure.

Anonymous FTP might work since it doesn’t send credentials. HTTPS or SFTP might work since those are secure.