lightningd: export bitcoin_pubkey as bip32_pubkey.

We're going to need it.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/build_utxos.c

@@ -246,3 +246,20 @@ const struct utxo **build_utxos(const tal_t *ctx,
 
 	return tal_free(utxos);
 }
+
+bool bip32_pubkey(const struct ext_key *bip32_base,
+		  struct pubkey *pubkey, u32 index)
+{
+	struct ext_key ext;
+
+	assert(index < BIP32_INITIAL_HARDENED_CHILD);
+	if (bip32_key_from_parent(bip32_base, index,
+				  BIP32_FLAG_KEY_PUBLIC, &ext) != WALLY_OK)
+		return false;
+
+	if (!secp256k1_ec_pubkey_parse(secp256k1_ctx, &pubkey->pubkey,
+				       ext.pub_key, sizeof(ext.pub_key)))
+		return false;
+	return true;
+}
+

lightningd/build_utxos.h

@@ -13,4 +13,9 @@ const struct utxo **build_utxos(const tal_t *ctx,
 
 /* Once we've spent them, mark them confirmed. */
 void confirm_utxos(struct lightningd *ld, const struct utxo **utxos);
+
+struct ext_key;
+bool bip32_pubkey(const struct ext_key *bip32_base,
+		  struct pubkey *pubkey, u32 index);
+
 #endif /* LIGHTNING_LIGHTNINGD_BUILD_UTXOS_H */

lightningd/peer_control.c

@@ -36,22 +36,6 @@ static void destroy_peer(struct peer *peer)
 			     peer->condition);
 }
 
-static void bitcoin_pubkey(struct lightningd *ld,
-			   struct pubkey *pubkey, u32 index)
-{
-	struct ext_key ext;
-
-	assert(index < BIP32_INITIAL_HARDENED_CHILD);
-	assert(index < ld->bip32_max_index);
-	if (bip32_key_from_parent(ld->bip32_base, index,
-				  BIP32_FLAG_KEY_PUBLIC, &ext) != WALLY_OK)
-		fatal("BIP32 of %u failed", index);
-
-	if (!secp256k1_ec_pubkey_parse(secp256k1_ctx, &pubkey->pubkey,
-				       ext.pub_key, sizeof(ext.pub_key)))
-		fatal("Parse of BIP32 child %u pubkey failed", index);
-}
-
 void peer_set_condition(struct peer *peer, const char *fmt, ...)
 {
 	va_list ap;
@@ -591,8 +575,10 @@ static void opening_gen_funding(struct subdaemon *opening, const u8 *resp,
 		return;
 	}
 
-	if (fc->change)
-		bitcoin_pubkey(fc->peer->ld, &changekey, fc->change_keyindex);
+	if (fc->change
+	    && !bip32_pubkey(fc->peer->ld->bip32_base,
+			     &changekey, fc->change_keyindex))
+		fatal("Error deriving change key %u", fc->change_keyindex);
 
 	fc->funding_tx = funding_tx(fc, &outnum, fc->utxomap, fc->satoshi,
 				    &fc->local_fundingkey,