BOLT 12 Proof of Payment

[TheBlueMatt]

We currently don't support proof of payment for sent BOLT 12 payments because the user needs the Bolt12Invoice in the PaymentSent Event. This will require a bit of involvement, we'll need to store the Bolt12Invoice in the ChannelMonitorUpdates for sent payments so we can restore them if the ChannelManager is stale on reload. When we do this we should also include DNSSECProof objects from #3179 so that we get BIP 353 proof of payment too. cc @jkczyz

[jkczyz]

IIUC, for BOLT11 payments, the onus is on the user to maintain a copy of the invoice. Any reason why we wouldn't do the same for BOLT12 payments? It would require using manually_handle_bolt12_invoices.

[TheBlueMatt]

Because using manually_handle_bolt12_invoices requires a bunch of work, but PoP is something we should encourage all our users to maintain. If we want to require manually_handle_bolt12_invoices for PoP IMO we should completely remove support for !manually_handle_bolt12_invoices.

[vincenzopalazzo]

Just for proof of payment do you think that would be a nice idea to pop out the invoice through an event? and then also together with the payment completed notification?

For payment proof what you need is that at some point you can get the invoice somewhere.

Not sure if the case that I described is included with the manually_handle_bolt12_invoices, I need to look more inside the code for it

[TheBlueMatt]

Yea, we could have a separate event for it, but its definitely nicer for the user if we provide it all in one go, and I'm not sure its that much work to do so, just a question of piping the invoice through a few state machine states and popping it back out when we get the preimage.

[vincenzopalazzo]

Since I am already going down this proof of payment rabbit hole in other projects, and Jeff isn’t looking into it yet, I could explore this task a bit further.