listfunds: add "redeemscript" field.

You'd need this if you ever wanted to make your own PSBT.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: `listfunds` now has a `redeemscript` field for p2sh-wrapped outputs.

doc/lightning-listfunds.7

@@ -35,6 +35,8 @@ appended)
 .IP \[bu]
 \fIscriptpubkey\fR (the ScriptPubkey of the output, in hex)
 .IP \[bu]
+\fIredeemscript\fR (the redeemscript of the output, in hex, only if it's p2sh-wrapped)
+.IP \[bu]
 \fIstatus\fR (whether \fIunconfirmed\fR, \fIconfirmed\fR, or \fIspent\fR)
 .IP \[bu]
 \fIreserved\fR (whether this is UTXO is currently reserved for an in-flight tx)

doc/lightning-listfunds.7.md

@@ -28,6 +28,7 @@ Each entry in *outputs* will include:
     appended)
 -   *address*
 -   *scriptpubkey* (the ScriptPubkey of the output, in hex)
+-   *redeemscript* (the redeemscript of the output, in hex, only if it's p2sh-wrapped)
 -   *status* (whether *unconfirmed*, *confirmed*, or *spent*)
 -   *reserved* (whether this is UTXO is currently reserved for an in-flight tx)
 

wallet/walletrpc.c

@@ -868,6 +868,14 @@ static void json_add_utxo(struct json_stream *response,
 	json_add_amount_sat_compat(response, utxo->amount,
 				   "value", "amount_msat");
 
+	if (utxo->is_p2sh) {
+		struct pubkey key;
+		bip32_pubkey(wallet->bip32_base, &key, utxo->keyindex);
+
+		json_add_hex_talarr(response, "redeemscript",
+				    bitcoin_redeem_p2sh_p2wpkh(tmpctx, &key));
+	}
+
 	json_add_hex_talarr(response, "scriptpubkey", utxo->scriptPubkey);
 	out = encode_scriptpubkey_to_addr(tmpctx, chainparams,
 					  utxo->scriptPubkey);