Bug in 2.0.8.1_beta_2024-05-07 With SSH Fingerprinting

I have just upgraded to 2.0.8.1_beta_2024-05-07 and found that my SFTP (SSH) targets no longer work. When the backup runs they report an error with the fingerprint. When I edit the configuration, go to Destination, and click “Test Connection” I get this rather unhelpful message:

"The host key has changed, please check with the server administrator if this is correct, otherwise you could be the victim of a MAN-IN-THE-MIDDLE attack. Do you want to REPLACE your CURRENT host key “ssh-ed25519 32 36:D5:82:12:8F:DF:6D:15:43:31:9D:3D:A6:C0:22:32” with the REPORTED host key: ssh-ed25519 256 36:D5:82:12:8F:DF:6D:15:43:31:9D:3D:A6:C0:22:32? "

So there might be a bug introduced into the fingerprint comparison, because they sure look the same to me. I do note the key length change, though since nothing has changed on the destination ends, this might be something with how Duplicati processes keys or fingerprints. I see that this update included a lot of library updates so it may not even be Duplicati code that has changed.

When I click Accept to the “new” key then everything works as expected, but note that it is unclear whether I then have to click on “5. Options” so I can click “Save” or not. I did, and it worked, but it’s a clunk in the interface.

Correct. Details below.

It’s not a bug introduced, it’s a bug fixed in the SSH.NET library that now correctly reports length in bits.

Everything else looks the same because the problem was from the previous SSH.NET saying 32 bytes.

2.0.8.1 update may request SSH/SFTP ssh-ed25519 host key reverification has the recent investigation.

1 Like

Thank you for the follow up, and glad that it’s a known thing.

Another known thing is that Advanced options on screen 2 may disappear on editing that job again.
If you run into this, going as you’re going, please confirm the problem and move option to screen 5.