common: pull out scriptPubkey address method

We're going to need this for P2WSH scripts. pull it out into
a common file plus adopt the sanity checks so that it will allow for
either P2WSH or P2WPKH (previously only encoded P2WPKH scripts)

common/Makefile

@@ -1,4 +1,5 @@
 COMMON_SRC_NOGEN :=				\
+	common/addr.c				\
 	common/amount.c				\
 	common/base32.c				\
 	common/bech32.c				\

common/addr.c

@@ -0,0 +1,22 @@
+#include "addr.h"
+#include <bitcoin/script.h>
+#include <common/bech32.h>
+
+/* Returns NULL if the script is not a P2WPKH or P2WSH */
+char *encode_scriptpubkey_to_addr(const tal_t *ctx,
+				   const char *hrp,
+				   const u8 *scriptPubkey)
+{
+	char *out;
+	size_t scriptLen = tal_bytelen(scriptPubkey);
+
+        /* Check that scriptPubkey is P2WSH or P2WPKH */
+	if (!is_p2wsh(scriptPubkey, NULL) && !is_p2wpkh(scriptPubkey, NULL))
+                return NULL;
+
+	out = tal_arr(ctx, char, 73 + strlen(hrp));
+	if (!segwit_addr_encode(out, hrp, 0, scriptPubkey + 2, scriptLen - 2))
+		return tal_free(out);
+
+	return out;
+}

common/addr.h

@@ -0,0 +1,12 @@
+#ifndef LIGHTNING_COMMON_ADDR_H
+#define LIGHTNING_COMMON_ADDR_H
+#include "config.h"
+#include <ccan/short_types/short_types.h>
+#include <ccan/tal/tal.h>
+
+/* Given a P2WSH or P2WPKH scriptPubkey, return a bech32 encoded address */
+char *encode_scriptpubkey_to_addr(const tal_t *ctx,
+                                  const char *hrp,
+                                  const u8 *scriptPubkey);
+
+#endif /* LIGHTNING_COMMON_ADDR_H */

lightningd/Makefile

@@ -14,6 +14,7 @@ default: lightningd-all
 
 # Common source we use.
 LIGHTNINGD_COMMON_OBJS :=			\
+	common/addr.o				\
 	common/amount.o				\
 	common/base32.o				\
 	common/bech32.o				\

lightningd/opening_control.c

@@ -2,6 +2,7 @@
 #include <bitcoin/privkey.h>
 #include <bitcoin/script.h>
 #include <ccan/tal/str/str.h>
+#include <common/addr.h>
 #include <common/channel_config.h>
 #include <common/funding_tx.h>
 #include <common/json_command.h>

wallet/walletrpc.c

@@ -2,6 +2,7 @@
 #include <bitcoin/base58.h>
 #include <bitcoin/script.h>
 #include <ccan/tal/str/str.h>
+#include <common/addr.h>
 #include <common/bech32.h>
 #include <common/json_command.h>
 #include <common/json_helpers.h>
@@ -419,26 +420,6 @@ encode_pubkey_to_addr(const tal_t *ctx,
 	return out;
 }
 
-/* Returns NULL if the script is not a P2WPKH */
-static char *
-encode_scriptpubkey_to_addr(const tal_t *ctx,
-			    const struct lightningd *ld,
-			    const u8 *scriptPubkey)
-{
-	char *out;
-	const char *hrp;
-	size_t scriptLen = tal_bytelen(scriptPubkey);
-	bool ok;
-	if (scriptLen != 22 || scriptPubkey[0] != 0x00 || scriptPubkey[1] != 0x14)
-		return NULL;
-	hrp = get_chainparams(ld)->bip173_name;
-	out = tal_arr(ctx, char, 73 + strlen(hrp));
-	ok = segwit_addr_encode(out, hrp, 0, scriptPubkey + 2, scriptLen - 2);
-	if (!ok)
-		return tal_free(out);
-	return out;
-}
-
 enum addrtype {
 	ADDR_P2SH_SEGWIT = 1,
 	ADDR_BECH32 = 2,
@@ -638,7 +619,8 @@ static struct command_result *json_listfunds(struct command *cmd,
 		        json_add_string(response, "address", out);
 		} else if (utxos[i]->scriptPubkey != NULL) {
 			out = encode_scriptpubkey_to_addr(
-			    cmd, cmd->ld, utxos[i]->scriptPubkey);
+			    cmd, get_chainparams(cmd->ld)->bip173_name,
+			    utxos[i]->scriptPubkey);
 			if (out)
 				json_add_string(response, "address", out);
 		}