elements: Extract the real value from the transactions

If we are handling an elements transaction the value is not stored in the
satoshi field, rather it is stored in the `value` field which is prefixed with
a version (0x01) and is counted in `asset` units.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

bitcoin/tx.c

@@ -14,6 +14,13 @@
 
 #define SEGREGATED_WITNESS_FLAG 0x1
 
+static u8 bitcoin_asset[] =
+    {
+	0x01, 0x5c, 0xe7, 0xb9, 0x63, 0xd3, 0x7f, 0x8f, 0x2d, 0x51, 0xca,
+	0xfb, 0xba, 0x92, 0x8a, 0xaa, 0x9e, 0x22, 0x0b, 0x8b, 0xbc, 0x66,
+	0x05, 0x71, 0x49, 0x9c, 0x03, 0x62, 0x8a, 0x38, 0x51, 0xb8, 0xce,
+    };
+
 int bitcoin_tx_add_output(struct bitcoin_tx *tx, const u8 *script,
 			  struct amount_sat amount)
 {
@@ -86,8 +93,22 @@ bool bitcoin_tx_check(const struct bitcoin_tx *tx)
 void bitcoin_tx_output_set_amount(struct bitcoin_tx *tx, int outnum,
 				  struct amount_sat amount)
 {
+	u64 satoshis = amount.satoshis; /* Raw: low-level helper */
+	struct wally_tx_output *output = &tx->wtx->outputs[outnum];
 	assert(outnum < tx->wtx->num_outputs);
-	tx->wtx->outputs[outnum].satoshi = amount.satoshis; /* Raw: low-level helper */
+	if (is_elements) {
+		u8 raw[9];
+		be64 rawu64;
+		output->asset = bitcoin_asset;
+		output->asset_len = sizeof(bitcoin_asset);
+		output->value_len = 9;
+		raw[0] = 0x01; /* Value version 01 */
+		rawu64 = cpu_to_be64(satoshis);
+		memcpy(raw+1, &rawu64, 8);
+		output->satoshi = UINT64_MAX;
+	} else {
+		output->satoshi = satoshis;
+	}
 }
 
 const u8 *bitcoin_tx_output_get_script(const tal_t *ctx,
@@ -109,8 +130,25 @@ struct amount_sat bitcoin_tx_output_get_amount(const struct bitcoin_tx *tx,
 					       int outnum)
 {
 	struct amount_sat amount;
+	struct wally_tx_output *output;
+	u64 satoshis;
 	assert(outnum < tx->wtx->num_outputs);
-	amount.satoshis = tx->wtx->outputs[outnum].satoshi; /* Raw: helper */
+	output = &tx->wtx->outputs[outnum];
+
+	if (is_elements && !memeq(output->asset, output->asset_len,
+				  bitcoin_asset, sizeof(bitcoin_asset))) {
+		/* If this is an asset based tx, and we don't know the asset
+		 * type, i.e., it's not bitcoin, return a 0 amount */
+		satoshis = 0;
+	} else if (is_elements) {
+		be64 raw;
+		memcpy(&raw, output->value + 1, sizeof(raw));
+		satoshis = be64_to_cpu(raw);
+	}else {
+		satoshis = tx->wtx->outputs[outnum].satoshi;
+	}
+
+	amount.satoshis = satoshis; /* Raw: helper */
 	return amount;
 }
 

hsmd/hsmd.c

@@ -603,6 +603,8 @@ static struct io_plan *init_hsm(struct io_conn *conn,
 	/* Once we have read the init message we know which params the master
 	 * will use */
 	c->chainparams = chainparams_by_chainhash(&chain_hash);
+	is_elements = c->chainparams->is_elements;
+
 	maybe_create_new_hsm();
 	load_hsm();