pytest: add dev hack for testing option_upfront_shutdown_script.

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

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - JSON API: `listforwards` now includes the time an HTLC was received and when it was resolved. Both are expressed as UNIX timestamps to facilitate parsing (Issue [#2491](https://github.com/ElementsProject/lightning/issues/2491), PR [#2528](https://github.com/ElementsProject/lightning/pull/2528))
 - JSON API: new plugin `invoice_payment` hook for intercepting invoices before they're paid.
 - plugin: the `connected` hook can now send an `error_message` to the rejected peer.
+- Protocol: we now enforce `option_upfront_shutdown_script` if a peer negotiates it.
 
 ### Changed
 

openingd/openingd.c

@@ -110,6 +110,17 @@ struct state {
 	const struct chainparams *chainparams;
 };
 
+static const u8 *dev_upfront_shutdown_script(const tal_t *ctx)
+{
+#if DEVELOPER
+	/* This is a hack, for feature testing */
+	const char *e = getenv("DEV_OPENINGD_UPFRONT_SHUTDOWN_SCRIPT");
+	if (e)
+		return tal_hexdata(ctx, e, strlen(e));
+#endif
+	return NULL;
+}
+
 /*~ If we can't agree on parameters, we fail to open the channel.  If we're
  * the funder, we need to tell lightningd, otherwise it never really notices. */
 static void negotiation_aborted(struct state *state, bool am_funder,
@@ -517,7 +528,8 @@ static u8 *funder_channel(struct state *state,
 				  &state->our_points.delayed_payment,
 				  &state->our_points.htlc,
 				  &state->first_per_commitment_point[LOCAL],
-				  channel_flags, NULL);
+				  channel_flags,
+				  dev_upfront_shutdown_script(tmpctx));
 	sync_crypto_write(&state->cs, PEER_FD, take(msg));
 
 	/* This is usually a very transient state... */
@@ -1080,7 +1092,7 @@ static u8 *fundee_channel(struct state *state, const u8 *open_channel_msg)
 				    &state->our_points.delayed_payment,
 				    &state->our_points.htlc,
 				    &state->first_per_commitment_point[LOCAL],
-				    NULL);
+				    dev_upfront_shutdown_script(tmpctx));
 
 	sync_crypto_write(&state->cs, PEER_FD, take(msg));
 

tests/test_closing.py

@@ -1491,3 +1491,56 @@ def test_shutdown(node_factory):
             raise Exception("Node {} has memory leaks: {}"
                             .format(l1.daemon.lightning_dir, leaks))
     l1.rpc.stop()
+
+
+@unittest.skipIf(not DEVELOPER, "needs to set upfront_shutdown_script")
+def test_option_upfront_shutdown_script(node_factory, bitcoind):
+    l1 = node_factory.get_node(start=False)
+    # Insist on upfront script we're not going to match.
+    l1.daemon.env["DEV_OPENINGD_UPFRONT_SHUTDOWN_SCRIPT"] = "76a91404b61f7dc1ea0dc99424464cc4064dc564d91e8988ac"
+    l1.start()
+
+    l2 = node_factory.get_node()
+    l1.rpc.connect(l2.info['id'], 'localhost', l2.port)
+    l1.fund_channel(l2, 1000000, False)
+
+    l1.rpc.close(l2.info['id'])
+
+    # l2 will close unilaterally when it dislikes shutdown script.
+    l1.daemon.wait_for_log(r'received ERROR.*scriptpubkey .* is not as agreed upfront \(76a91404b61f7dc1ea0dc99424464cc4064dc564d91e8988ac\)')
+
+    # Clear channel.
+    wait_for(lambda: len(bitcoind.rpc.getrawmempool()) != 0)
+    bitcoind.generate_block(1)
+    wait_for(lambda: [c['state'] for c in only_one(l1.rpc.listpeers()['peers'])['channels']] == ['ONCHAIN'])
+
+    # Works when l2 closes channel, too.
+    l1.rpc.connect(l2.info['id'], 'localhost', l2.port)
+    l1.fund_channel(l2, 1000000, False)
+
+    l2.rpc.close(l1.info['id'])
+
+    # l2 will close unilaterally when it dislikes shutdown script.
+    l1.daemon.wait_for_log(r'received ERROR.*scriptpubkey .* is not as agreed upfront \(76a91404b61f7dc1ea0dc99424464cc4064dc564d91e8988ac\)')
+
+    # Clear channel.
+    wait_for(lambda: len(bitcoind.rpc.getrawmempool()) != 0)
+    bitcoind.generate_block(1)
+    wait_for(lambda: [c['state'] for c in only_one(l1.rpc.listpeers()['peers'])['channels']] == ['ONCHAIN', 'ONCHAIN'])
+
+    # Figure out what address it will try to use.
+    keyidx = int(l1.db_query("SELECT val FROM vars WHERE name='bip32_max_index';")[0]['val'])
+
+    # Expect 1 for change address, 1 for the channel final address.
+    addr = l1.rpc.call('dev-listaddrs', [keyidx + 2])['addresses'][-1]
+
+    # Now, if we specify upfront and it's OK, all good.
+    l1.stop()
+    # We need to prepend the segwit version (0) and push opcode (14).
+    l1.daemon.env["DEV_OPENINGD_UPFRONT_SHUTDOWN_SCRIPT"] = '0014' + addr['bech32_redeemscript']
+    l1.start()
+
+    l1.rpc.connect(l2.info['id'], 'localhost', l2.port)
+    l1.rpc.fundchannel(l2.info['id'], 1000000)
+    l1.rpc.close(l2.info['id'])
+    wait_for(lambda: sorted([c['state'] for c in only_one(l1.rpc.listpeers()['peers'])['channels']]) == ['CLOSINGD_COMPLETE', 'ONCHAIN', 'ONCHAIN'])