SSH not working after upgrading to 19.07.5 (non-default shell )

[weka]

I was running 19.07.3 on my router, and I could easily ssh into the box using an SSH key. Now I upgraded to 19.07.5 and SSH is not working any more, neither using password authentication, nor using an SSH key.

I tried removing the package dropbear, deleting the provided public key, reinstalling dropbear, letting opk overwrite any existing file. Then I added a complete new dropbear instance, choosing password authentication and allowing root to login using password. Then I even changed root's password to "123456" temporarily, to eliminate any typing errors.

But still no deal:

ssh root@10.20.30.40
root@10.20.30.40's password: 
Connection to 10.20.30.40 closed.

What is wrong in 19.07.5, compared to 19.07.3? Why does this dropbear version not accept any connection?

Once I accidentally hit ENTER without typing in the password, which leads to this dialog:

ssh root@10.20.30.40
root@10.20.30.40's password: 
Permission denied, please try again.

So, typing in the password is closing the connection, while typing in no password is answered by "permission denied".

Can someone explain this?

[vgaetera]

You are not using a custom login shell, are you?

Check the logs.

[ergamus]

Both of my devices still have SSH access available after upgrading to 19.07.5, with the same configuration as before.

Append -vv to the ssh command, it might reveal more. Be careful, it might contain a hash of your key in the output, if you use one.

[weka]

YES, YES, YES! Silly me!

I forgot to install bash after upgrading.

Boing! (That was the sound of my head hitting the table...)

Sorry for the unnecessary disturbance!