Recovery not possible presumably because of GPG update
I'm using Déjà Dup 37.1-2fakesync1ubuntu0.1 on Ubuntu 18.04.2 to store encrypted backups on Google Drive regularly.
For several weeks I've been noticing that after entering my password, some work is done in the background (scanning, backing up, uploading, backing up, verifying), then the password dialogue is shown again. Clicking Forward on that dialogue just repeats this process. Once I had checked that new files are created in Drive as usual, I got used to just closing the dialogue.
Now I needed to recover an older version of a folder. Again, after some work ("preparing", the Details field is empty), the password dialogue appears over and over when clicking Forward. In addition, the folder is not being restored.
I tried to go through the process manually with Duplicity which showed me:
GPGError: GPG Failed, see log below:
===== Begin GnuPG log =====
gpg: AES encrypted data
gpg: encrypted with 1 passphrase
gpg: decryption failed: Bad session key
===== End GnuPG log =====
This could be due to a GPG version change as I made an update from 2.2.4-1ubuntu1.1 to the current 2.2.4-1ubuntu1.2 on 18 January according to the Apt logs. Déjà Dup itself has been updated from 37.1-2fakesync1 to the current version on 4 February. I don't remember for how long I'm getting these repeating password dialogs, but it could very well coincide with those dates.
The best I could find was a hint to reinitialise the backup, but I need to recover that folder, so it's not really an option. It's worth mentioning, though, that I when I set up a new backup in another folder, I could recover files from that.
I could try to manually downgrade GPG and/or Déjà Dup, but that's a lot of packages involved which in addition are not in the main repository anymore.
So my questions are:
- Is there any possibility to recover the folder?
- How should such issues be handled in the future? Basically destroying backups after some version change without providing a useful error message invalidates the whole point of a backup tool.