From: Matt Corallo Date: Mon, 14 Oct 2024 15:13:34 +0000 (+0000) Subject: Set `holder_commitment_point` to `Available` on upgrade X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=refs%2Fheads%2F2024-10-commitment-point-init;p=rust-lightning Set `holder_commitment_point` to `Available` on upgrade When we upgrade from LDK 0.0.123 or prior, we need to intialize `holder_commitment_point` with commitment point(s). In 1f7f3a366c9e62cff5a5025724b5b508255a89d7 we changed the point(s) which we fetch from both the current and next per-commitment-point (setting the value to `HolderCommitmentPoint::Available` on upgrade) to only fetching the current per-commitment-point (setting the value to `HolderCommitmentPoint::PendingNext` on upgrade). In `commitment_signed` handling, we expect the next per-commitment-point to be available (allowing us to `advance()` the `holder_commitment_point`), as it was included in the `revoke_and_ack` we most recently sent to our peer, so must've been available at that time. Sadly, these two interact negatively with each other - on upgrade, assuming the channel is at a steady state and there are no pending updates, we'll not make the next per-commitment-point available but if we receive a `commitment_signed` from our peer we'll assume it is. As a result, in debug mode, we'll hit an assertion failure, and in production mode we'll force-close the channel. Instead, here, we fix the upgrade logic to always upgrade directly to `HolderCommitmentPoint::Available`, making the next per-commitment-point available immediately. We also attempt to resolve the next per-commitment-point in `get_channel_reestablish`, allowing any channels which were upgraded to LDK 0.0.124 and are in this broken state to avoid the force-closure, as long as they don't receive a `commitment_signed` in the interim. --- diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs index 250704ea2..1972b4899 100644 --- a/lightning/src/ln/channel.rs +++ b/lightning/src/ln/channel.rs @@ -7142,6 +7142,12 @@ impl Channel where pub fn get_channel_reestablish(&mut self, logger: &L) -> msgs::ChannelReestablish where L::Target: Logger { assert!(self.context.channel_state.is_peer_disconnected()); assert_ne!(self.context.cur_counterparty_commitment_transaction_number, INITIAL_COMMITMENT_NUMBER); + // This is generally the first function which gets called on any given channel once we're + // up and running normally. Thus, we take this opportunity to attempt to resolve the + // `holder_commitment_point` to get any keys which we are currently missing. + self.context.holder_commitment_point.try_resolve_pending( + &self.context.holder_signer, &self.context.secp_ctx, logger, + ); // Prior to static_remotekey, my_current_per_commitment_point was critical to claiming // current to_remote balances. However, it no longer has any use, and thus is now simply // set to a dummy (but valid, as required by the spec) public key. @@ -9453,8 +9459,10 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch // TODO(async_signing): remove this expect with the Uninitialized variant let current = holder_signer.get_per_commitment_point(cur_holder_commitment_transaction_number, &secp_ctx) .expect("Must be able to derive the current commitment point upon channel restoration"); - HolderCommitmentPoint::PendingNext { - transaction_number: cur_holder_commitment_transaction_number, current, + let next = holder_signer.get_per_commitment_point(cur_holder_commitment_transaction_number - 1, &secp_ctx) + .expect("Must be able to derive the next commitment point upon channel restoration"); + HolderCommitmentPoint::Available { + transaction_number: cur_holder_commitment_transaction_number, current, next, } }, };