Elements PSBT / test fixup

bitcoin/psbt.c

@@ -257,13 +257,29 @@ void psbt_input_set_wit_utxo(struct wally_psbt *psbt, size_t in,
 
 	assert(in < psbt->num_inputs);
 	assert(tal_bytelen(scriptPubkey) > 0);
-	wally_err = wally_tx_output_init(amt.satoshis, /* Raw: type conv */
-					 scriptPubkey,
-					 tal_bytelen(scriptPubkey),
-					 &tx_out);
+	if (is_elements(chainparams)) {
+		u8 value[9];
+		wally_err =
+			wally_tx_confidential_value_from_satoshi(amt.satoshis, /* Raw: wally API */
+								 value,
+								 sizeof(value));
+		assert(wally_err == WALLY_OK);
+		wally_err =
+			wally_tx_elements_output_init(scriptPubkey,
+						      tal_bytelen(scriptPubkey),
+						      chainparams->fee_asset_tag,
+						      ELEMENTS_ASSET_LEN,
+						      value, sizeof(value),
+						      NULL, 0, NULL, 0,
+						      NULL, 0, &tx_out);
+
+	} else
+		wally_err = wally_tx_output_init(amt.satoshis, /* Raw: type conv */
+						 scriptPubkey,
+						 tal_bytelen(scriptPubkey),
+						 &tx_out);
 	assert(wally_err == WALLY_OK);
-	wally_err = wally_psbt_input_set_witness_utxo(&psbt->inputs[in],
-						      &tx_out);
+	wally_err = wally_psbt_input_set_witness_utxo(&psbt->inputs[in], &tx_out);
 	assert(wally_err == WALLY_OK);
 }
 
@@ -292,6 +308,57 @@ void psbt_elements_input_set_asset(struct wally_psbt *psbt, size_t in,
 		abort();
 }
 
+void psbt_elements_normalize_fees(struct wally_psbt *psbt)
+{
+	struct amount_asset asset;
+	size_t fee_output_idx = psbt->num_outputs;
+
+	if (!is_elements(chainparams))
+		return;
+
+	/* Elements requires that every input value is accounted for,
+	 * including the fees */
+	struct amount_sat total_in = AMOUNT_SAT(0), val;
+	for (size_t i = 0; i < psbt->num_inputs; i++) {
+		val = psbt_input_get_amount(psbt, i);
+		if (!amount_sat_add(&total_in, total_in, val))
+			return;
+	}
+	for (size_t i = 0; i < psbt->num_outputs; i++) {
+		asset = wally_tx_output_get_amount(&psbt->tx->outputs[i]);
+		if (elements_wtx_output_is_fee(psbt->tx, i)) {
+			if (fee_output_idx == psbt->num_outputs) {
+				fee_output_idx = i;
+				continue;
+			}
+			/* We already have at least one fee output,
+			 * remove this one */
+			psbt_rm_output(psbt, i--);
+			continue;
+		}
+		if (!amount_asset_is_main(&asset))
+			continue;
+
+		if (!amount_sat_sub(&total_in, total_in,
+				    amount_asset_to_sat(&asset)))
+			return;
+	}
+
+	if (amount_sat_eq(total_in, AMOUNT_SAT(0)))
+		return;
+
+	/* We need to add a fee output */
+	if (fee_output_idx == psbt->num_outputs) {
+		psbt_append_output(psbt, NULL, total_in);
+	} else {
+		u64 sats = total_in.satoshis; /* Raw: wally API */
+		struct wally_tx_output *out = &psbt->tx->outputs[fee_output_idx];
+		if (wally_tx_confidential_value_from_satoshi(
+			sats, out->value, out->value_len) != WALLY_OK)
+			return;
+	}
+}
+
 bool psbt_has_input(struct wally_psbt *psbt,
 		    struct bitcoin_txid *txid,
 		    u32 outnum)

bitcoin/psbt.h

@@ -69,6 +69,14 @@ bool psbt_is_finalized(const struct wally_psbt *psbt);
 void psbt_txid(const struct wally_psbt *psbt, struct bitcoin_txid *txid,
 	       struct wally_tx **wtx);
 
+/* psbt_elements_normalize_fees - Figure out the fee output for a PSET
+ *
+ * Adds a fee output if not present, or updates it to include the diff
+ * between inputs - outputs. Unlike bitcoin, elements requires every
+ * satoshi to be accounted for in an output.
+ */
+void psbt_elements_normalize_fees(struct wally_psbt *psbt);
+
 struct wally_tx *psbt_finalize(struct wally_psbt *psbt, bool finalize_in_place);
 
 /* psbt_make_key - Create a new, proprietary c-lightning key

bitcoin/tx.c

@@ -98,11 +98,16 @@ int bitcoin_tx_add_multi_outputs(struct bitcoin_tx *tx,
 	return tx->wtx->num_outputs;
 }
 
-bool elements_tx_output_is_fee(const struct bitcoin_tx *tx, int outnum)
+bool elements_wtx_output_is_fee(const struct wally_tx *tx, int outnum)
 {
-	assert(outnum < tx->wtx->num_outputs);
+	assert(outnum < tx->num_outputs);
 	return chainparams->is_elements &&
-	       tx->wtx->outputs[outnum].script_len == 0;
+		tx->outputs[outnum].script_len == 0;
+}
+
+bool elements_tx_output_is_fee(const struct bitcoin_tx *tx, int outnum)
+{
+	return elements_wtx_output_is_fee(tx->wtx, outnum);
 }
 
 struct amount_sat bitcoin_tx_compute_fee_w_inputs(const struct bitcoin_tx *tx,

bitcoin/tx.h

@@ -210,6 +210,11 @@ bool bitcoin_tx_check(const struct bitcoin_tx *tx);
  */
 void bitcoin_tx_finalize(struct bitcoin_tx *tx);
 
+/**
+ * Returns true if the given outnum is a fee output
+ */
+bool elements_wtx_output_is_fee(const struct wally_tx *tx, int outnum);
+
 /**
  * Returns true if the given outnum is a fee output
  */

plugins/multifundchannel.c

@@ -1362,9 +1362,10 @@ perform_funding_tx_finalize(struct multifundchannel_command *mfc)
 			/* Funding outpoint.  */
 			struct multifundchannel_destination *dest;
 			dest = deck[outnum];
-			(void) psbt_append_output(mfc->psbt,
+			(void) psbt_insert_output(mfc->psbt,
 						  dest->funding_script,
-						  dest->amount);
+						  dest->amount,
+						  outnum);
 			dest->outnum = outnum;
 			tal_append_fmt(&content, "%s: %s",
 				       type_to_string(tmpctx, struct node_id,
@@ -1375,9 +1376,10 @@ perform_funding_tx_finalize(struct multifundchannel_command *mfc)
 		} else {
 			/* Change output.  */
 			assert(mfc->change_needed);
-			(void) psbt_append_output(mfc->psbt,
+			(void) psbt_insert_output(mfc->psbt,
 						  mfc->change_scriptpubkey,
-						  mfc->change_amount);
+						  mfc->change_amount,
+						  outnum);
 			tal_append_fmt(&content, "change: %s",
 				       type_to_string(tmpctx,
 						      struct amount_sat,
@@ -1386,30 +1388,7 @@ perform_funding_tx_finalize(struct multifundchannel_command *mfc)
 	}
 
 	/* Elements requires a fee output.  */
-	if (chainparams->is_elements) {
-		struct amount_sat inputs = AMOUNT_SAT(0);
-		struct amount_sat outputs = AMOUNT_SAT(0);
-		struct amount_sat fees;
-		for (size_t i = 0; i < mfc->psbt->num_inputs; ++i)
-			if (!amount_sat_add(&inputs,
-					    inputs,
-					    psbt_input_get_amount(mfc->psbt,
-								  i)))
-				plugin_err(mfc->cmd->plugin,
-					   "Overflow while adding inputs");
-		for (size_t i = 0; i < mfc->psbt->num_outputs; ++i)
-			if (!amount_sat_add(&outputs,
-					    outputs,
-					    psbt_output_get_amount(mfc->psbt,
-								   i)))
-				plugin_err(mfc->cmd->plugin,
-					   "Overflow while adding outputs");
-		if (!amount_sat_sub(&fees, inputs, outputs))
-			fees = AMOUNT_SAT(0);
-		/* If there is any fee at all, add the fee output.  */
-		if (!amount_sat_eq(fees, AMOUNT_SAT(0)))
-			(void) psbt_append_output(mfc->psbt, NULL, fees);
-	}
+	psbt_elements_normalize_fees(mfc->psbt);
 
 	/* Generate the TXID.  */
 	mfc->txid = tal(mfc, struct bitcoin_txid);

plugins/txprepare.c

@@ -191,6 +191,10 @@ static struct command_result *finish_txprepare(struct command *cmd,
 		psbt_add_output(txp->psbt, out, i);
 	}
 
+	/* If this is elements, we should normalize
+	 * the PSBT fee output */
+	psbt_elements_normalize_fees(txp->psbt);
+
 	utx = tal(NULL, struct unreleased_tx);
 	utx->psbt = tal_steal(utx, txp->psbt);
 	psbt_txid(txp->psbt, &utx->txid, &utx->tx);

tests/test_plugin.py

@@ -1488,8 +1488,10 @@ def test_coin_movement_notices(node_factory, bitcoind, chainparams):
         l2_wallet_mvts = [
             {'type': 'chain_mvt', 'credit': 2000000000, 'debit': 0, 'tag': 'deposit'},
             {'type': 'chain_mvt', 'credit': 0, 'debit': 0, 'tag': 'spend_track'},
-            {'type': 'chain_mvt', 'credit': 0, 'debit': 991900000, 'tag': 'withdrawal'},
-            {'type': 'chain_mvt', 'credit': 0, 'debit': 1000000000, 'tag': 'withdrawal'},
+            [
+                {'type': 'chain_mvt', 'credit': 0, 'debit': 991900000, 'tag': 'withdrawal'},
+                {'type': 'chain_mvt', 'credit': 0, 'debit': 1000000000, 'tag': 'withdrawal'},
+            ],
             {'type': 'chain_mvt', 'credit': 0, 'debit': 8100000, 'tag': 'chain_fees'},
             {'type': 'chain_mvt', 'credit': 991900000, 'debit': 0, 'tag': 'deposit'},
             {'type': 'chain_mvt', 'credit': 100001000, 'debit': 0, 'tag': 'deposit'},

tests/test_wallet.py

@@ -367,6 +367,8 @@ def test_txprepare(node_factory, bitcoind, chainparams):
     assert len(decode['vout']) == 3 if chainparams['feeoutput'] else 2
     # Change output pos is random.
     for vout in decode['vout']:
+        if vout['scriptPubKey']['type'] == 'fee':
+            continue
         if vout['scriptPubKey']['addresses'] == [addr]:
             changeout = vout
 
@@ -532,7 +534,7 @@ def test_fundpsbt(node_factory, bitcoind, chainparams):
         l1.rpc.fundpsbt(amount // 2, feerate, 0)
 
 
-def test_utxopsbt(node_factory, bitcoind):
+def test_utxopsbt(node_factory, bitcoind, chainparams):
     amount = 1000000
     l1 = node_factory.get_node()
 
@@ -548,7 +550,8 @@ def test_utxopsbt(node_factory, bitcoind):
     bitcoind.generate_block(1)
     wait_for(lambda: len(l1.rpc.listfunds()['outputs']) == len(outputs))
 
-    feerate = '7500perkw'
+    fee_val = 7500
+    feerate = '{}perkw'.format(fee_val)
 
     # Explicitly spend the first output above.
     funding = l1.rpc.utxopsbt(amount // 2, feerate, 0,
@@ -566,13 +569,19 @@ def test_utxopsbt(node_factory, bitcoind):
     assert 'reservations' not in funding
 
     # This should add 99 to the weight, but otherwise be identical except for locktime.
-    funding2 = l1.rpc.utxopsbt(amount // 2, feerate, 99,
+    start_weight = 99
+    funding2 = l1.rpc.utxopsbt(amount // 2, feerate, start_weight,
                                ['{}:{}'.format(outputs[0][0], outputs[0][1])],
                                reserve=False, locktime=bitcoind.rpc.getblockcount() + 1)
     psbt2 = bitcoind.rpc.decodepsbt(funding2['psbt'])
     assert psbt2['tx']['locktime'] == bitcoind.rpc.getblockcount() + 1
     assert psbt2['tx']['vin'] == psbt['tx']['vin']
-    assert psbt2['tx']['vout'] == psbt['tx']['vout']
+    if chainparams['elements']:
+        # elements includes the fee as an output
+        addl_fee = Millisatoshi(fee_val * start_weight // 1000 * 1000)
+        assert psbt2['tx']['vout'][0]['value'] == psbt['tx']['vout'][0]['value'] + addl_fee.to_btc()
+    else:
+        assert psbt2['tx']['vout'] == psbt['tx']['vout']
     assert funding2['excess_msat'] < funding['excess_msat']
     assert funding2['feerate_per_kw'] == 7500
     assert funding2['estimated_final_weight'] == funding['estimated_final_weight'] + 99
@@ -618,8 +627,6 @@ def test_utxopsbt(node_factory, bitcoind):
                     reservedok=True)
 
 
-@unittest.skipIf(TEST_NETWORK == 'liquid-regtest',
-                 "See ElementsProject/lightning#3998")
 def test_sign_and_send_psbt(node_factory, bitcoind, chainparams):
     """
     Tests for the sign + send psbt RPCs

wallet/reservation.c

@@ -280,6 +280,16 @@ static struct wally_psbt *psbt_using_utxos(const tal_t *ctx,
 				  NULL, redeemscript);
 
 		psbt_input_set_wit_utxo(psbt, i, scriptPubkey, utxos[i]->amount);
+		if (is_elements(chainparams)) {
+			struct amount_asset asset;
+			/* FIXME: persist asset tags */
+			asset = amount_sat_to_asset(&utxos[i]->amount,
+						    chainparams->fee_asset_tag);
+			/* FIXME: persist nonces */
+			psbt_elements_input_set_asset(psbt,
+						      psbt->num_inputs - 1,
+						      &asset);
+		}
 	}
 
 	return psbt;