From f0396df4492ac7b9590769ce5aae13f3b50c0dd3 Mon Sep 17 00:00:00 2001
From: Christian Decker <decker.christian@gmail.com>
Date: Mon, 6 May 2019 15:13:50 +0200
Subject: [PATCH] elements: Added small helper to compute the right signature
 hash

Depending on the network we end up with different signature hash algorithms,
so we just collect that decision in one place.

Signed-off-by: Christian Decker <decker.christian@gmail.com>
---
 bitcoin/signature.c | 39 +++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/bitcoin/signature.c b/bitcoin/signature.c
index 61dcfae73..6bd7bcd90 100644
--- a/bitcoin/signature.c
+++ b/bitcoin/signature.c
@@ -88,6 +88,32 @@ void sign_hash(const struct privkey *privkey,
 	assert(ok);
 }
 
+static void bitcoin_tx_hash_for_sig(const struct bitcoin_tx *tx, unsigned int in,
+				    const u8 *script,
+				    enum sighash_type sighash_type,
+				    struct sha256_double *dest)
+{
+	int ret;
+	u8 value[9];
+	u64 satoshis = tx->input_amounts[in]->satoshis /* Raw: sig-helper */;
+	int flags = WALLY_TX_FLAG_USE_WITNESS;
+
+	if (is_elements) {
+		ret = wally_tx_confidential_value_from_satoshi(satoshis, value, sizeof(value));
+		assert(ret == WALLY_OK);
+		ret = wally_tx_get_elements_signature_hash(
+		    tx->wtx, in, script, tal_bytelen(script), value,
+		    sizeof(value), sighash_type, flags, dest->sha.u.u8,
+		    sizeof(*dest));
+		assert(ret == WALLY_OK);
+	} else {
+		ret = wally_tx_get_btc_signature_hash(
+		    tx->wtx, in, script, tal_bytelen(script), satoshis,
+		    sighash_type, flags, dest->sha.u.u8, sizeof(*dest));
+		assert(ret == WALLY_OK);
+	}
+}
+
 void sign_tx_input(const struct bitcoin_tx *tx,
 		   unsigned int in,
 		   const u8 *subscript,
@@ -98,16 +124,12 @@ void sign_tx_input(const struct bitcoin_tx *tx,
 {
 	struct sha256_double hash;
 	bool use_segwit = witness_script != NULL;
-	int flags = use_segwit ? WALLY_TX_FLAG_USE_WITNESS : 0;
 	const u8 *script = use_segwit ? witness_script : subscript;
 
 	assert(sighash_type_valid(sighash_type));
 
 	sig->sighash_type = sighash_type;
-	wally_tx_get_btc_signature_hash(
-	    tx->wtx, in, script, tal_bytelen(script),
-	    tx->input_amounts[in]->satoshis /* Raw: low-level helper */,
-	    sighash_type, flags, hash.sha.u.u8, sizeof(hash));
+	bitcoin_tx_hash_for_sig(tx, in, script, sighash_type, &hash);
 
 	dump_tx("Signing", tx, in, subscript, key, &hash);
 	sign_hash(privkey, &hash, &sig->s);
@@ -133,7 +155,6 @@ bool check_tx_sig(const struct bitcoin_tx *tx, size_t input_num,
 {
 	struct sha256_double hash;
 	bool use_segwit = witness_script != NULL;
-	int flags = use_segwit ? WALLY_TX_FLAG_USE_WITNESS : 0;
 	const u8 *script = use_segwit ? witness_script : redeemscript;
 	bool ret;
 
@@ -146,10 +167,8 @@ bool check_tx_sig(const struct bitcoin_tx *tx, size_t input_num,
 	}
 	assert(input_num < tx->wtx->num_inputs);
 
-	wally_tx_get_btc_signature_hash(
-	    tx->wtx, input_num, script, tal_bytelen(script),
-	    tx->input_amounts[input_num]->satoshis /* Raw: low-level helper */,
-	    sig->sighash_type, flags, hash.sha.u.u8, sizeof(hash));
+	dump_tx("check_tx_sig", tx, input_num, script, key, &hash);
+	bitcoin_tx_hash_for_sig(tx, input_num, script, sig->sighash_type, &hash);
 
 	ret = check_signed_hash(&hash, &sig->s, key);
 	if (!ret)