cannot get super user access when changing encryption passphrase

[anarcat]

I know there has been multiple reports of this in the past (#1, #2, #21) but this is again a problem on Android 7 (fairphone OS "saibon" 15.02). The phone is rooted and I have the root permissions ("Root access: apps only" in Settings -> Developer options). I get prompted to grant super user access to the app, and I do, permanently. Yet it still fails with the error:

Cannot get superuser access, exiting

... when I tap the "Change encryption password" button in the app's UI. It seems that the fixes for #2 need to be updated again here.

Or is there a way to do this without the app, I would be happy as well... As specified elsewhere, using a root shell you can change the encryption password separately using:

vdc cryptfs changepw password <current_PIN> password <new_passphrase>

This is similar to the problem with Cryptfs Password, see nelenkov/cryptfs-password-manager#20

I can also confirm that the enforcement of a limited number of unlock attempts is not working either.

[anarcat]

I ended up using this app with the manual encryption setup process.