From 66dda32da2ff27bcadfc323e30d40f635cdf9d88 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Fri, 19 Feb 2021 14:52:01 +1030
Subject: [PATCH] common/shutdown_scriptpubkey: extract shutdown scriptpubkey
 test.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 common/Makefile                |  1 +
 common/shutdown_scriptpubkey.c | 10 ++++++++++
 common/shutdown_scriptpubkey.h | 21 +++++++++++++++++++++
 lightningd/Makefile            |  1 +
 lightningd/channel_control.c   | 17 ++---------------
 5 files changed, 35 insertions(+), 15 deletions(-)
 create mode 100644 common/shutdown_scriptpubkey.c
 create mode 100644 common/shutdown_scriptpubkey.h

diff --git a/common/Makefile b/common/Makefile
index b72c6695c..dfc7ab9cc 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -71,6 +71,7 @@ COMMON_SRC_NOGEN :=				\
 	common/read_peer_msg.c			\
 	common/route.c				\
 	common/setup.c				\
+	common/shutdown_scriptpubkey.c		\
 	common/socket_close.c			\
 	common/sphinx.c				\
 	common/status.c				\
diff --git a/common/shutdown_scriptpubkey.c b/common/shutdown_scriptpubkey.c
new file mode 100644
index 000000000..8c7bcee24
--- /dev/null
+++ b/common/shutdown_scriptpubkey.c
@@ -0,0 +1,10 @@
+#include <bitcoin/script.h>
+#include <common/shutdown_scriptpubkey.h>
+
+bool valid_shutdown_scriptpubkey(const u8 *scriptpubkey)
+{
+	return is_p2pkh(scriptpubkey, NULL)
+		|| is_p2sh(scriptpubkey, NULL)
+		|| is_p2wpkh(scriptpubkey, NULL)
+		|| is_p2wsh(scriptpubkey, NULL);
+}
diff --git a/common/shutdown_scriptpubkey.h b/common/shutdown_scriptpubkey.h
new file mode 100644
index 000000000..1e70e91fd
--- /dev/null
+++ b/common/shutdown_scriptpubkey.h
@@ -0,0 +1,21 @@
+#ifndef LIGHTNING_COMMON_SHUTDOWN_SCRIPTPUBKEY_H
+#define LIGHTNING_COMMON_SHUTDOWN_SCRIPTPUBKEY_H
+#include "config.h"
+#include <ccan/short_types/short_types.h>
+
+/* BOLT #2:
+ *
+ * 1. `OP_DUP` `OP_HASH160` `20` 20-bytes `OP_EQUALVERIFY` `OP_CHECKSIG`
+ *   (pay to pubkey hash), OR
+ * 2. `OP_HASH160` `20` 20-bytes `OP_EQUAL` (pay to script hash), OR
+ * 3. `OP_0` `20` 20-bytes (version 0 pay to witness pubkey), OR
+ * 4. `OP_0` `32` 32-bytes (version 0 pay to witness script hash)
+ *
+ * A receiving node:
+ *...
+ *  - if the `scriptpubkey` is not in one of the above forms:
+ *    - SHOULD fail the connection.
+ */
+bool valid_shutdown_scriptpubkey(const u8 *scriptpubkey);
+
+#endif /* LIGHTNING_COMMON_SHUTDOWN_SCRIPTPUBKEY_H */
diff --git a/lightningd/Makefile b/lightningd/Makefile
index 497a01801..287ffb873 100644
--- a/lightningd/Makefile
+++ b/lightningd/Makefile
@@ -120,6 +120,7 @@ LIGHTNINGD_COMMON_OBJS :=			\
 	common/pseudorand.o			\
 	common/random_select.o			\
 	common/setup.o				\
+	common/shutdown_scriptpubkey.o		\
 	common/sphinx.o				\
 	common/status_wire.o			\
 	common/timeout.o			\
diff --git a/lightningd/channel_control.c b/lightningd/channel_control.c
index 6775b645f..de2109baf 100644
--- a/lightningd/channel_control.c
+++ b/lightningd/channel_control.c
@@ -12,6 +12,7 @@
 #include <common/memleak.h>
 #include <common/per_peer_state.h>
 #include <common/psbt_open.h>
+#include <common/shutdown_scriptpubkey.h>
 #include <common/timeout.h>
 #include <common/tx_roles.h>
 #include <common/utils.h>
@@ -237,21 +238,7 @@ static void peer_got_shutdown(struct channel *channel, const u8 *msg)
 	tal_free(channel->shutdown_scriptpubkey[REMOTE]);
 	channel->shutdown_scriptpubkey[REMOTE] = scriptpubkey;
 
-	/* BOLT #2:
-	 *
-	 * 1. `OP_DUP` `OP_HASH160` `20` 20-bytes `OP_EQUALVERIFY` `OP_CHECKSIG`
-	 *   (pay to pubkey hash), OR
-	 * 2. `OP_HASH160` `20` 20-bytes `OP_EQUAL` (pay to script hash), OR
-	 * 3. `OP_0` `20` 20-bytes (version 0 pay to witness pubkey), OR
-	 * 4. `OP_0` `32` 32-bytes (version 0 pay to witness script hash)
-	 *
-	 * A receiving node:
-	 *...
-	 *  - if the `scriptpubkey` is not in one of the above forms:
-	 *    - SHOULD fail the connection.
-	 */
-	if (!is_p2pkh(scriptpubkey, NULL) && !is_p2sh(scriptpubkey, NULL)
-	    && !is_p2wpkh(scriptpubkey, NULL) && !is_p2wsh(scriptpubkey, NULL)) {
+	if (!valid_shutdown_scriptpubkey(scriptpubkey)) {
 		channel_fail_permanent(channel,
 				       REASON_PROTOCOL,
 				       "Bad shutdown scriptpubkey %s",