Add phantom shared secret to HTLCPreviousHopData

This also fixes a bug where we were failing back phantom payments with the
wrong scid, causing them to never actually be failed backwards (L3022 in
channelmanager.rs)

This new field will be used in upcoming commit(s) to encrypt phantom payment failure
packets.

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 302760fef0a7581c2803b53f08c47f4e15638c8f..a6856b4119853e67435ab7f20d0bca4d261e8638 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -420,6 +420,7 @@ pub(crate) struct HTLCPreviousHopData {
        short_channel_id: u64,
        htlc_id: u64,
        incoming_packet_shared_secret: [u8; 32],
+       phantom_shared_secret: Option<[u8; 32]>,
 
        // This field is consumed by `claim_funds_from_hop()` when updating a force-closed backwards
        // channel with a preimage provided by the forward channel.
@@ -3014,17 +3015,18 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                                routing, incoming_shared_secret, payment_hash, amt_to_forward, outgoing_cltv_value },
                                                                                prev_funding_outpoint } => {
                                                                                        macro_rules! fail_forward {
-                                                                                               ($msg: expr, $err_code: expr, $err_data: expr) => {
+                                                                                               ($msg: expr, $err_code: expr, $err_data: expr, $phantom_ss: expr) => {
                                                                                                        {
                                                                                                                log_info!(self.logger, "Failed to accept/forward incoming HTLC: {}", $msg);
                                                                                                                let htlc_source = HTLCSource::PreviousHopData(HTLCPreviousHopData {
-                                                                                                                       short_channel_id: short_chan_id,
+                                                                                                                       short_channel_id: prev_short_channel_id,
                                                                                                                        outpoint: prev_funding_outpoint,
                                                                                                                        htlc_id: prev_htlc_id,
                                                                                                                        incoming_packet_shared_secret: incoming_shared_secret,
+                                                                                                                       phantom_shared_secret: $phantom_ss,
                                                                                                                });
                                                                                                                failed_forwards.push((htlc_source, payment_hash,
-                                                                                                                               HTLCFailReason::Reason { failure_code: $err_code, data: $err_data }
+                                                                                                                       HTLCFailReason::Reason { failure_code: $err_code, data: $err_data }
                                                                                                                ));
                                                                                                                continue;
                                                                                                        }
@@ -3041,26 +3043,26 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                                                        let next_hop = match onion_utils::decode_next_hop(phantom_shared_secret, &onion_packet.hop_data, onion_packet.hmac, payment_hash) {
                                                                                                                Ok(res) => res,
                                                                                                                Err(onion_utils::OnionDecodeErr::Malformed { err_msg, err_code }) => {
-                                                                                                                       fail_forward!(err_msg, err_code, Vec::new());
+                                                                                                                       fail_forward!(err_msg, err_code, Vec::new(), None);
                                                                                                                },
                                                                                                                Err(onion_utils::OnionDecodeErr::Relay { err_msg, err_code }) => {
-                                                                                                                       fail_forward!(err_msg, err_code, Vec::new());
+                                                                                                                       fail_forward!(err_msg, err_code, Vec::new(), Some(phantom_shared_secret));
                                                                                                                },
                                                                                                        };
                                                                                                        match next_hop {
                                                                                                                onion_utils::Hop::Receive(hop_data) => {
                                                                                                                        match self.construct_recv_pending_htlc_info(hop_data, incoming_shared_secret, payment_hash, amt_to_forward, outgoing_cltv_value, Some(phantom_shared_secret)) {
                                                                                                                                Ok(info) => phantom_receives.push((prev_short_channel_id, prev_funding_outpoint, vec![(info, prev_htlc_id)])),
-                                                                                                                               Err(ReceiveError { err_code, err_data, msg }) => fail_forward!(msg, err_code, err_data)
+                                                                                                                               Err(ReceiveError { err_code, err_data, msg }) => fail_forward!(msg, err_code, err_data, Some(phantom_shared_secret))
                                                                                                                        }
                                                                                                                },
                                                                                                                _ => panic!(),
                                                                                                        }
                                                                                                } else {
-                                                                                                       fail_forward!(format!("Unknown short channel id {} for forward HTLC", short_chan_id), 0x4000 | 10, Vec::new());
+                                                                                                       fail_forward!(format!("Unknown short channel id {} for forward HTLC", short_chan_id), 0x4000 | 10, Vec::new(), None);
                                                                                                }
                                                                                        } else {
-                                                                                               fail_forward!(format!("Unknown short channel id {} for forward HTLC", short_chan_id), 0x4000 | 10, Vec::new());
+                                                                                               fail_forward!(format!("Unknown short channel id {} for forward HTLC", short_chan_id), 0x4000 | 10, Vec::new(), None);
                                                                                        }
                                                                                },
                                                                        HTLCForwardInfo::FailHTLC { .. } => {
@@ -3093,6 +3095,8 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                                outpoint: prev_funding_outpoint,
                                                                                htlc_id: prev_htlc_id,
                                                                                incoming_packet_shared_secret: incoming_shared_secret,
+                                                                               // Phantom payments are only PendingHTLCRouting::Receive.
+                                                                               phantom_shared_secret: None,
                                                                        });
                                                                        match chan.get_mut().send_htlc(amt_to_forward, payment_hash, outgoing_cltv_value, htlc_source.clone(), onion_packet, &self.logger) {
                                                                                Err(e) => {
@@ -3224,6 +3228,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                                outpoint: prev_funding_outpoint,
                                                                                htlc_id: prev_htlc_id,
                                                                                incoming_packet_shared_secret: incoming_shared_secret,
+                                                                               phantom_shared_secret,
                                                                        },
                                                                        value: amt_to_forward,
                                                                        cltv_expiry,
@@ -3241,6 +3246,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                                                outpoint: prev_funding_outpoint,
                                                                                                htlc_id: $htlc.prev_hop.htlc_id,
                                                                                                incoming_packet_shared_secret: $htlc.prev_hop.incoming_packet_shared_secret,
+                                                                                               phantom_shared_secret,
                                                                                        }), payment_hash,
                                                                                        HTLCFailReason::Reason { failure_code: 0x4000 | 15, data: htlc_msat_height_data }
                                                                                ));
@@ -6073,6 +6079,7 @@ impl_writeable_tlv_based_enum!(PendingHTLCStatus, ;
 
 impl_writeable_tlv_based!(HTLCPreviousHopData, {
        (0, short_channel_id, required),
+       (1, phantom_shared_secret, option),
        (2, outpoint, required),
        (4, htlc_id, required),
        (6, incoming_packet_shared_secret, required)