Added wallet keypath to PSBT for local output of closing transaction.

Author: ksedgwic

closingd/closingd.c

@@ -36,6 +36,8 @@ static struct bitcoin_tx *close_tx(const tal_t *ctx,
 				   const struct chainparams *chainparams,
 				   struct per_peer_state *pps,
 				   const struct channel_id *channel_id,
+				   u32 local_wallet_index,
+				   const struct ext_key *local_wallet_ext_key,
 				   u8 *scriptpubkey[NUM_SIDES],
 				   const struct bitcoin_txid *funding_txid,
 				   unsigned int funding_txout,
@@ -69,6 +71,7 @@ static struct bitcoin_tx *close_tx(const tal_t *ctx,
 	/* FIXME: We need to allow this! */
 	tx = create_close_tx(ctx,
 			     chainparams,
+			     local_wallet_index, local_wallet_ext_key,
 			     scriptpubkey[LOCAL], scriptpubkey[REMOTE],
 			     funding_wscript,
 			     funding_txid,
@@ -135,6 +138,8 @@ static void send_offer(struct per_peer_state *pps,
 		       const struct channel_id *channel_id,
 		       const struct pubkey funding_pubkey[NUM_SIDES],
 		       const u8 *funding_wscript,
+		       u32 local_wallet_index,
+		       const struct ext_key *local_wallet_ext_key,
 		       u8 *scriptpubkey[NUM_SIDES],
 		       const struct bitcoin_txid *funding_txid,
 		       unsigned int funding_txout,
@@ -156,6 +161,8 @@ static void send_offer(struct per_peer_state *pps,
 	 *     #3](03-transactions.md#closing-transaction).
 	 */
 	tx = close_tx(tmpctx, chainparams, pps, channel_id,
+		      local_wallet_index,
+		      local_wallet_ext_key,
 		      scriptpubkey,
 		      funding_txid,
 		      funding_txout,
@@ -215,6 +222,8 @@ receive_offer(struct per_peer_state *pps,
 	      const struct channel_id *channel_id,
 	      const struct pubkey funding_pubkey[NUM_SIDES],
 	      const u8 *funding_wscript,
+	      u32 local_wallet_index,
+	      const struct ext_key *local_wallet_ext_key,
 	      u8 *scriptpubkey[NUM_SIDES],
 	      const struct bitcoin_txid *funding_txid,
 	      unsigned int funding_txout,
@@ -269,6 +278,8 @@ receive_offer(struct per_peer_state *pps,
 	 *     - MUST fail the connection.
 	 */
 	tx = close_tx(tmpctx, chainparams, pps, channel_id,
+		      local_wallet_index,
+		      local_wallet_ext_key,
 		      scriptpubkey,
 		      funding_txid,
 		      funding_txout,
@@ -300,6 +311,8 @@ receive_offer(struct per_peer_state *pps,
 		 *   - MAY eliminate its own output.
 		 */
 		trimmed = close_tx(tmpctx, chainparams, pps, channel_id,
+				   local_wallet_index,
+				   local_wallet_ext_key,
 				   scriptpubkey,
 				   funding_txid,
 				   funding_txout,
@@ -506,6 +519,8 @@ int main(int argc, char *argv[])
 	struct amount_sat min_fee_to_accept, commitment_fee, offer[NUM_SIDES];
 	struct feerange feerange;
 	enum side opener;
+	u32 local_wallet_index;
+	struct ext_key local_wallet_ext_key;
 	u8 *scriptpubkey[NUM_SIDES], *funding_wscript;
 	u64 fee_negotiation_step;
 	u8 fee_negotiation_step_unit;
@@ -533,6 +548,8 @@ int main(int argc, char *argv[])
 				    &our_dust_limit,
 				    &min_fee_to_accept, &commitment_fee,
 				    &offer[LOCAL],
+				    &local_wallet_index,
+				    &local_wallet_ext_key,
 				    &scriptpubkey[LOCAL],
 				    &scriptpubkey[REMOTE],
 				    &fee_negotiation_step,
@@ -590,6 +607,8 @@ int main(int argc, char *argv[])
 		if (whose_turn == LOCAL) {
 			send_offer(pps, chainparams,
 				   &channel_id, funding_pubkey, funding_wscript,
+				   local_wallet_index,
+				   &local_wallet_ext_key,
 				   scriptpubkey, &funding_txid, funding_txout,
 				   funding, out, opener,
 				   our_dust_limit,
@@ -610,6 +629,8 @@ int main(int argc, char *argv[])
 				= receive_offer(pps, chainparams,
 						&channel_id, funding_pubkey,
 						funding_wscript,
+						local_wallet_index,
+						&local_wallet_ext_key,
 						scriptpubkey, &funding_txid,
 						funding_txout, funding,
 						out, opener,
@@ -641,6 +662,8 @@ int main(int argc, char *argv[])
 						    fee_negotiation_step_unit);
 			send_offer(pps, chainparams, &channel_id,
 				   funding_pubkey, funding_wscript,
+				   local_wallet_index,
+				   &local_wallet_ext_key,
 				   scriptpubkey, &funding_txid, funding_txout,
 				   funding, out, opener,
 				   our_dust_limit,
@@ -656,6 +679,8 @@ int main(int argc, char *argv[])
 				= receive_offer(pps, chainparams, &channel_id,
 						funding_pubkey,
 						funding_wscript,
+						local_wallet_index,
+						&local_wallet_ext_key,
 						scriptpubkey, &funding_txid,
 						funding_txout, funding,
 						out, opener,

closingd/closingd_wire.csv

@@ -1,4 +1,5 @@
 #include <bitcoin/tx.h>
+#include <common/bip32.h>
 #include <common/channel_id.h>
 #include <common/cryptomsg.h>
 #include <common/htlc_wire.h>
@@ -20,6 +21,8 @@ msgdata,closingd_init,our_dust_limit,amount_sat,
 msgdata,closingd_init,min_fee_satoshi,amount_sat,
 msgdata,closingd_init,fee_limit_satoshi,amount_sat,
 msgdata,closingd_init,initial_fee_satoshi,amount_sat,
+msgdata,closingd_init,local_wallet_index,u32,
+msgdata,closingd_init,local_wallet_ext_key,ext_key,
 msgdata,closingd_init,local_scriptpubkey_len,u16,
 msgdata,closingd_init,local_scriptpubkey,u8,local_scriptpubkey_len
 msgdata,closingd_init,remote_scriptpubkey_len,u16,

closingd/closingd_wiregen.c

@@ -5,8 +5,39 @@
 #include <assert.h>
 #include <common/utils.h>
 
+static void add_keypath_item_to_last_output(struct bitcoin_tx *tx,
+					    u32 index,
+					    const struct ext_key *ext) {
+	// Skip if there is no wallet keypath for this output.
+	if (index == UINT32_MAX)
+		return;
+
+	size_t outndx = tx->psbt->num_outputs - 1;
+	struct wally_map *map_in = &tx->psbt->outputs[outndx].keypaths;
+
+	u8 fingerprint[BIP32_KEY_FINGERPRINT_LEN];
+	if (bip32_key_get_fingerprint(
+		    (struct ext_key *) ext, fingerprint, sizeof(fingerprint)) != WALLY_OK) {
+		abort();
+	}
+
+	u32 path[1];
+	path[0] = index;
+
+	tal_wally_start();
+	if (wally_map_add_keypath_item(map_in,
+				       ext->pub_key, sizeof(ext->pub_key),
+				       fingerprint, sizeof(fingerprint),
+				       path, 1) != WALLY_OK) {
+		abort();
+	}
+	tal_wally_end(tx->psbt);
+}
+
 struct bitcoin_tx *create_close_tx(const tal_t *ctx,
 				   const struct chainparams *chainparams,
+				   u32 local_wallet_index,
+				   const struct ext_key *local_wallet_ext_key,
 				   const u8 *our_script,
 				   const u8 *their_script,
 				   const u8 *funding_wscript,
@@ -47,6 +78,7 @@ struct bitcoin_tx *create_close_tx(const tal_t *ctx,
 		script = tal_dup_talarr(tx, u8, our_script);
 		/* One output is to us. */
 		bitcoin_tx_add_output(tx, script, NULL, to_us);
+		add_keypath_item_to_last_output(tx, local_wallet_index, local_wallet_ext_key);
 		num_outputs++;
 	}
 

closingd/closingd_wiregen.h

@@ -13,6 +13,8 @@ struct pubkey;
  * input scriptsig. */
 struct bitcoin_tx *create_close_tx(const tal_t *ctx,
 				   const struct chainparams *chainparams,
+				   u32 local_wallet_index,
+				   const struct ext_key *local_wallet_ext_key,
 				   const u8 *our_script,
 				   const u8 *their_script,
 				   const u8 *funding_wscript,

common/close_tx.c

@@ -212,11 +212,26 @@ void marshal_single_input_tx(struct bitcoin_tx const *tx,
 
 	for (size_t ii = 0; ii < tx->wtx->num_outputs; ii++) {
 		OutputDescriptor *odesc = o_tp->add_output_descs();
+
+		// Add witness script
 		if (tx->psbt->outputs[ii].witness_script_len)
 			odesc->set_witscript(
 				(const char *)
 				tx->psbt->outputs[ii].witness_script,
 				tx->psbt->outputs[ii].witness_script_len);
+
+		// Add keypath
+		struct wally_map *mp = &tx->psbt->outputs[ii].keypaths;
+		if (mp->num_items == 1) {
+			const struct wally_map_item *ip = &mp->items[0];
+			size_t npath =
+				(ip->value_len - BIP32_KEY_FINGERPRINT_LEN) / sizeof(uint32_t);
+			uint32_t *path = (uint32_t *) (ip->value + BIP32_KEY_FINGERPRINT_LEN);
+			for (size_t jj = 0; jj < npath; ++jj) {
+				odesc->mutable_key_loc()->add_key_path(le32_to_cpu(path[jj]));
+			}
+		}
+
 	}
 }
 

common/close_tx.h

@@ -285,6 +285,32 @@ void peer_start_closingd(struct channel *channel,
 		return;
 	}
 
+	// Determine the wallet index for our output, UINT32_MAX if not found.
+	u32 local_wallet_index;
+	struct ext_key local_wallet_ext_key;
+	bool is_p2sh;
+	if (wallet_can_spend(
+		    ld->wallet,
+		    channel->shutdown_scriptpubkey[LOCAL],
+		    &local_wallet_index,
+		    &is_p2sh)) {
+		if (bip32_key_from_parent(
+			    ld->wallet->bip32_base,
+			    local_wallet_index,
+			    BIP32_FLAG_KEY_PUBLIC,
+			    &local_wallet_ext_key) != WALLY_OK) {
+			abort();
+		}
+	} else {
+		local_wallet_index = UINT32_MAX;
+		char *dummy_bip32 =
+			"tpubDAY5hwtonH4NE8zY46ZMFf6B6F3fqMis7cwfNihXXpAg6XzBZNo"
+			"HAdAzAZx2peoU8nTWFqvUncXwJ9qgE5VxcnUKxdut8F6mptVmKjfiwDQ";
+		if (bip32_key_from_base58(dummy_bip32, &local_wallet_ext_key) != WALLY_OK) {
+			abort();
+		}
+	}
+
 	initmsg = towire_closingd_init(tmpctx,
 				       chainparams,
 				       pps,
@@ -299,6 +325,8 @@ void peer_start_closingd(struct channel *channel,
 				       amount_msat_to_sat_round_down(their_msat),
 				       channel->our_config.dust_limit,
 				       minfee, feelimit, startfee,
+				       local_wallet_index,
+				       &local_wallet_ext_key,
 				       channel->shutdown_scriptpubkey[LOCAL],
 				       channel->shutdown_scriptpubkey[REMOTE],
 				       channel->closing_fee_negotiation_step,