Add option for giving amountless invoice but specify amount for the proxy invoice

[benthecarman]

It would be nice to be able to pass an amountless invoice and receive an invoice with an amount.

My use case here is having a semi trusted 3rd party storing pre-created invoices for the user and then giving them to lnproxy to create an invoice with the correct parameters.

[lnproxy]

That should be simple to add. Any preference for a parameter name for the spec https://github.com/lnproxy/spec ?

I'm curious about the use case though, if this semi-trusted party is creating proxy invoices on your behalf they could presumably have them point to any destination right? Similar trust model as a something like https://github.com/nbd-wtf/satdress except it's more difficult to figure out if the semi-trusted party is behaving badly. Or am I missing something?

[benthecarman]

Any preference for a parameter name for the spec lnproxy/spec ?

Probably just amount_msats

I'm curious about the use case though ...

I am not sure how satdress works but the idea is to be able to load up a bunch of invoices that can later be served out on something like an lnurl, using the wrapped version for privacy and so it can work for lnurl by settings the desc_hash and amount

[lnproxy]

I love the idea of pregenerating invoices. Completely removes the requirement of having to use tor to communicate with the semi-trusted party. I'll work on this today.

[lnproxy]

satdress does what you want but has to talk to your node each time it needs an invoice. This might be interesting for you: nbd-wtf/satdress#42

[lnproxy]

I've thought about this carefully and have decided not to add it to the main code base.

Trusting thee relay with zero amount invoices misses the point of a tool like lnproxy in the first place. If you're ok with trusting a third party, it would be much better, in terms of both payment success and fee costs, to simply use a custodial wallet and withdraw periodically.

I don't want lnproxy to be a trusted third party. The whole point is that anyone can run a rely and you don't have to trust them.

This line of thinking has even inspired me to remove a "feature" I had been supporting up to now: lnproxy will no longer accept zero-amount invoices. Only invoices with amounts can be relayed trustlessly.