[bug] password_only passthrough not working

[e2489]

Description of the bug

The password_only strategy for passthrough is not working as intended. If you fill in the password in attribute mapping, the login accepts any password and logs you in, even if it's wrong. If you leave the password blank in attribute mapping, any password (including the correct one) gives you "Oops! Invalid account".

Step by step instructions to reproduce the bug

• Add the SFTP backend, add the passthrough middleware, and select password_only
• Fill in the SFTP information
• Attempt to log in to the SFTP server with the password

Can you replicate that error from the demo?

Can't test the backend

Observed behavior

It either logs you in with any password, or doesn't log you in at all.

Expected behavior

I fill in attribute mapping, they type the given password for the specified SFTP user, and it logs them in. If the password is wrong, it doesn't.