elements,pset: populate elements specific data for PSBTs

PSETs have a bit different requirements. The witness_utxo needs
the asset tag + values, and these should also be added to the PSET
struct separately as well. To do this, we create a new 'init' method for
elements inputs, which takes care of the elements specific things.

bitcoin/chainparams.h

@@ -9,6 +9,8 @@
 #include <common/bip32.h>
 #include <stdbool.h>
 
+#define ELEMENTS_ASSET_LEN 33
+
 struct chainparams {
 	const char *network_name;
 	const char *bip173_name;

bitcoin/psbt.c

@@ -267,6 +267,16 @@ bool psbt_input_set_partial_sig(struct wally_psbt *psbt, size_t in,
 					 sizeof(sig->s.data)) == WALLY_OK;
 }
 
+static void psbt_input_set_witness_utxo(struct wally_psbt *psbt, size_t in,
+					struct wally_tx_output *txout)
+{
+	int wally_err;
+	assert(psbt->num_inputs > in);
+	wally_err = wally_psbt_input_set_witness_utxo(&psbt->inputs[in],
+						      txout);
+	assert(wally_err == WALLY_OK);
+}
+
 void psbt_input_set_prev_utxo(struct wally_psbt *psbt, size_t in,
 			      const u8 *scriptPubkey, struct amount_sat amt)
 {
@@ -274,7 +284,6 @@ void psbt_input_set_prev_utxo(struct wally_psbt *psbt, size_t in,
 	int wally_err;
 	u8 *scriptpk;
 
-	assert(psbt->num_inputs > in);
 	if (scriptPubkey) {
 		assert(is_p2wsh(scriptPubkey, NULL) || is_p2wpkh(scriptPubkey, NULL)
 		       || is_p2sh(scriptPubkey, NULL));
@@ -293,10 +302,34 @@ void psbt_input_set_prev_utxo(struct wally_psbt *psbt, size_t in,
 					       tal_bytelen(scriptpk),
 					       &prev_out);
 	assert(wally_err == WALLY_OK);
-	wally_err = wally_psbt_input_set_witness_utxo(&psbt->inputs[in],
+	psbt_input_set_witness_utxo(psbt, in, prev_out);
-						      prev_out);
+}
+
+static void psbt_input_set_elements_prev_utxo(struct wally_psbt *psbt,
+					      size_t in,
+					      const u8 *scriptPubkey,
+					      struct amount_asset *asset,
+					      const u8 *nonce)
+{
+	struct wally_tx_output *prev_out;
+	int wally_err;
+
+	u8 *prefixed_value = amount_asset_extract_value(psbt, asset);
+
+	wally_err =
+		wally_tx_elements_output_init_alloc(scriptPubkey,
+					            tal_bytelen(scriptPubkey),
+						    asset->asset,
+						    sizeof(asset->asset),
+						    prefixed_value,
+						    tal_bytelen(prefixed_value),
+						    nonce,
+						    tal_bytelen(nonce),
+						    NULL, 0,
+						    NULL, 0,
+					            &prev_out);
 	assert(wally_err == WALLY_OK);
-	tal_steal(psbt, psbt->inputs[in].witness_utxo);
+	psbt_input_set_witness_utxo(psbt, in, prev_out);
 }
 
 void psbt_input_set_prev_utxo_wscript(struct wally_psbt *psbt, size_t in,
@@ -316,6 +349,76 @@ void psbt_input_set_prev_utxo_wscript(struct wally_psbt *psbt, size_t in,
 	psbt_input_set_prev_utxo(psbt, in, scriptPubkey, amt);
 }
 
+static void
+psbt_input_set_elements_prev_utxo_wscript(struct wally_psbt *psbt,
+					  size_t in,
+					  const u8 *wscript,
+					  struct amount_asset *asset,
+					  const u8 *nonce)
+{
+	int wally_err;
+	const u8 *scriptPubkey;
+
+	if (wscript) {
+		scriptPubkey = scriptpubkey_p2wsh(psbt, wscript);
+		wally_err = wally_psbt_input_set_witness_script(
+				&psbt->inputs[in],
+				cast_const(u8 *, wscript),
+				tal_bytelen(wscript));
+		assert(wally_err == WALLY_OK);
+	} else
+		scriptPubkey = NULL;
+
+	psbt_input_set_elements_prev_utxo(psbt, in, scriptPubkey,
+					  asset, nonce);
+}
+
+void psbt_elements_input_init_witness(struct wally_psbt *psbt, size_t in,
+				      const u8 *witscript,
+				      struct amount_asset *asset,
+				      const u8 *nonce)
+{
+	psbt_input_set_elements_prev_utxo_wscript(
+			psbt, in, witscript,
+			asset, nonce);
+
+	if (asset->value > 0)
+		wally_psbt_elements_input_set_value(&psbt->inputs[in],
+						    asset->value);
+
+	/* PSET expects an asset tag without the prefix */
+	if (wally_psbt_elements_input_set_asset(&psbt->inputs[in],
+					    asset->asset + 1,
+					    ELEMENTS_ASSET_LEN - 1) != WALLY_OK)
+		abort();
+}
+
+void psbt_elements_input_init(struct wally_psbt *psbt, size_t in,
+			      const u8 *scriptPubkey,
+			      struct amount_asset *asset,
+			      const u8 *nonce)
+{
+	psbt_input_set_elements_prev_utxo(psbt, in,
+					  scriptPubkey,
+					  asset, nonce);
+
+	if (asset->value > 0) {
+		if (wally_psbt_elements_input_set_value(
+					&psbt->inputs[in],
+					asset->value) != WALLY_OK)
+			abort();
+
+	}
+
+	/* PSET expects an asset tag without the prefix */
+	/* FIXME: Verify that we're sending unblinded asset tag */
+	if (wally_psbt_elements_input_set_asset(
+					&psbt->inputs[in],
+					asset->asset + 1,
+					ELEMENTS_ASSET_LEN - 1) != WALLY_OK)
+		abort();
+}
+
 bool psbt_input_set_redeemscript(struct wally_psbt *psbt, size_t in,
 				 const u8 *redeemscript)
 {
@@ -333,7 +436,10 @@ struct amount_sat psbt_input_get_amount(struct wally_psbt *psbt,
 	struct amount_sat val;
 	assert(in < psbt->num_inputs);
 	if (psbt->inputs[in].witness_utxo) {
-		val.satoshis = psbt->inputs[in].witness_utxo->satoshi; /* Raw: type conversion */
+		struct amount_asset amt_asset =
+			wally_tx_output_get_amount(psbt->inputs[in].witness_utxo);
+		assert(amount_asset_is_main(&amt_asset));
+		val = amount_asset_to_sat(&amt_asset);
 	} else if (psbt->inputs[in].non_witness_utxo) {
 		int idx = psbt->tx->inputs[in].index;
 		struct wally_tx *prev_tx = psbt->inputs[in].non_witness_utxo;

bitcoin/psbt.h

@@ -10,6 +10,7 @@ struct wally_tx_output;
 struct wally_psbt;
 struct wally_psbt_input;
 struct wally_tx;
+struct amount_asset;
 struct amount_sat;
 struct bitcoin_signature;
 struct pubkey;
@@ -55,10 +56,21 @@ WARN_UNUSED_RESULT bool psbt_input_set_partial_sig(struct wally_psbt *psbt, size
 						   const struct pubkey *pubkey,
 						   const struct bitcoin_signature *sig);
 
-void psbt_input_set_prev_utxo(struct wally_psbt *psbt, size_t in,
+void psbt_input_set_prev_utxo(struct wally_psbt *psbt,
-			      const u8 *wscript, struct amount_sat amt);
+			      size_t in,
+			      const u8 *wscript,
+			      struct amount_sat amt);
 void psbt_input_set_prev_utxo_wscript(struct wally_psbt *psbt, size_t in,
-			              const u8 *wscript, struct amount_sat amt);
+			              const u8 *wscript,
+				      struct amount_sat amt);
+void psbt_elements_input_init(struct wally_psbt *psbt, size_t in,
+			      const u8 *scriptPubkey,
+			      struct amount_asset *asset,
+			      const u8 *nonce);
+void psbt_elements_input_init_witness(struct wally_psbt *psbt, size_t in,
+				      const u8 *witscript,
+				      struct amount_asset *asset,
+				      const u8 *nonce);
 bool psbt_input_set_redeemscript(struct wally_psbt *psbt, size_t in,
 				 const u8 *redeemscript);
 struct amount_sat psbt_input_get_amount(struct wally_psbt *psbt,

bitcoin/tx.c

@@ -207,18 +207,51 @@ int bitcoin_tx_add_input(struct bitcoin_tx *tx, const struct bitcoin_txid *txid,
 
 	if (input_wscript) {
 		/* Add the prev output's data into the PSBT struct */
-		psbt_input_set_prev_utxo_wscript(tx->psbt, i, input_wscript, amount);
+		if (is_elements(chainparams)) {
+			struct amount_asset asset;
+			/*FIXME: persist asset tags */
+			asset = amount_sat_to_asset(
+					&amount,
+					chainparams->fee_asset_tag);
+			psbt_elements_input_init_witness(tx->psbt, i,
+							 input_wscript,
+							 &asset, NULL);
+		} else
+			psbt_input_set_prev_utxo_wscript(tx->psbt, i,
+							 input_wscript,
+							 amount);
 	} else if (scriptPubkey) {
-		if (is_p2wsh(scriptPubkey, NULL) || is_p2wpkh(scriptPubkey, NULL) ||
+		if (is_p2wsh(scriptPubkey, NULL) ||
-			/* FIXME: assert that p2sh inputs are witness/are accompanied by a redeemscript+witnessscript */
+			is_p2wpkh(scriptPubkey, NULL) ||
+			/* FIXME: assert that p2sh inputs are
+			 * witness/are accompanied by a
+			 * redeemscript+witnessscript */
 			is_p2sh(scriptPubkey, NULL)) {
-			/* the only way to get here currently with a p2sh script is via a p2sh-p2wpkh script
+			/* the only way to get here currently with
+			 * a p2sh script is via a p2sh-p2wpkh script
 			 * that we've created ...*/
-			/* Relevant section from bip-0174, emphasis mine:
+			/* BIP0174:
-			 * ** Value: The entire transaction output in network serialization which the current input spends from.
+			 * ** Value: The entire transaction output in
-			 * This should only be present for inputs which spend segwit outputs, _including P2SH embedded ones._
+			 * network serialization which the
+			 * current input spends from.
+			 * This should only be present for
+			 * inputs which spend segwit outputs,
+			 * including P2SH embedded ones.
 			 */
-			psbt_input_set_prev_utxo(tx->psbt, i, scriptPubkey, amount);
+			if (is_elements(chainparams)) {
+				struct amount_asset asset;
+				/*FIXME: persist asset tags */
+				asset = amount_sat_to_asset(
+						&amount,
+						chainparams->fee_asset_tag);
+				/* FIXME: persist nonces */
+				psbt_elements_input_init(tx->psbt, i,
+							 scriptPubkey,
+							 &asset, NULL);
+			} else
+				psbt_input_set_prev_utxo(tx->psbt, i,
+							 scriptPubkey,
+							 amount);
 		}
 	}
 
@@ -722,10 +755,9 @@ wally_tx_output_get_amount(const struct wally_tx_output *output)
 	if (chainparams->is_elements) {
 		assert(output->asset_len == sizeof(amount.asset));
 		memcpy(&amount.asset, output->asset, sizeof(amount.asset));
-
+		/* We currently only support explicit value
-		/* We currently only support explicit value asset tags, others
+		 * asset tags, others are confidential, so
-		 * are confidential, so don't even try to assign a value to
+		 * don't even try to assign a value to it. */
-		 * it. */
 		if (output->asset[0] == 0x01) {
 			memcpy(&raw, output->value + 1, sizeof(raw));
 			amount.value = be64_to_cpu(raw);

wallet/db.c

@@ -1165,9 +1165,18 @@ void migrate_last_tx_to_psbt(struct lightningd *ld, struct db *db)
 		funding_wscript = bitcoin_redeem_2of2(stmt, &local_funding_pubkey,
 						      &remote_funding_pubkey);
 
-		psbt_input_set_prev_utxo_wscript(last_tx->psbt,
+		if (is_elements(chainparams)) {
-						 0, funding_wscript,
+			/*FIXME: persist asset tags */
-						 funding_sat);
+			struct amount_asset asset;
+			asset = amount_sat_to_asset(&funding_sat,
+						    chainparams->fee_asset_tag);
+			psbt_elements_input_init_witness(last_tx->psbt,
+							 0, funding_wscript,
+							 &asset, NULL);
+		} else
+			psbt_input_set_prev_utxo_wscript(last_tx->psbt,
+							 0, funding_wscript,
+							 funding_sat);
 
 		if (!db_column_signature(stmt, 5, &last_sig.s))
 			abort();