Fusion address reuse

[markblundeberg]

Some fusions have been happening with reused output addresses.

Clues:

• The fusions are happening around the same time (within a day or so) but not exactly at the same time.
• Not because multiple copies of wallet open.

[markblundeberg]

I strongly suspect that this can happen when the electron server connection is down but the connection to fusion server is still good:

• When fusions finish, they unreserve addresses in order to not bloat the reserved-address data structure. The unreserved addresses will then get tried again as candidates, but, normally this is no problem because now the address has an associated transaction so they will be skipped.
• If there is a connection issue, then the wallet will have a stale view of coins and then addresses will be tried again.

Mitigations:

• Don't fuse when wallet is not synced (good idea anyway for other reasons!).
• Be more careful about unreserving.

[cculianu]

Hmm your theory seems plausible.