Key backup seems to contain 0 room keys

[jryans]

When @BillCarsonFr was testing a new account between web <-> web or web <-> RiotX, we've observed that the new device doesn't find any message keys in the key backup e.g. the backup is empty:

• Create a new account with one device on web
• Create an encrypted room with some messages
• Add a new device (either web or RiotX)
• New device correctly receives key backup key via 4S secret sharing
• However, when the new device tries to restore for backup it doesn't contain any room keys

Questions:

• Is it just that there is some delay before web will add message keys to the backup...?
• Is it related to the malformed backup key (backup key stored in the wrong format #12970)? I would expect to see errors though if that were the issue...

[ara4n]

I think this is the same as the "online backup didn't seem to be working" at #12966

[dbkr]

Hmm - I can't repro this. We delay for up to 10s before backing up keys so if we were very fast it's possible you could have managed to log in before the key was backup up.

[jryans]

Since we can't reproduce, let's move this after release and retest.

[stevepdp]

I was able to reproduce this using the given steps.

Both clients: Firefox 95.0 (64-bit) snap on Ubuntu 21.10.

See: