splice: Add plugin for magic “splice all” command

The command called “splice” can take a json payload or a ‘splice script’, process it into a list of ‘actions’ and then execute those actions.

These actions include or will include everything you would want to do with a splice:
* Splice into a channel
* Splice out of a channel
* Fund from wallet
* Deposit to wallet
* Send funds to bitcoin address

Changelog-Added: A new magic “splice” command is added that can take a ‘splice script’ or json payload and perform any complex splice across multiple channels merging the result into a single transaction. Some features are disabled and will be added in time.

common/addr.c

@@ -36,3 +36,79 @@ char *encode_scriptpubkey_to_addr(const tal_t *ctx,
 
 	return out;
 }
+
+static const char *segwit_addr_net_decode(int *witness_version,
+					  uint8_t *witness_program,
+					  size_t *witness_program_len,
+					  const char *addrz,
+					  const struct chainparams *chainparams)
+{
+	if (segwit_addr_decode(witness_version, witness_program,
+			       witness_program_len, chainparams->onchain_hrp,
+			       addrz))
+		return chainparams->onchain_hrp;
+	else
+		return NULL;
+}
+
+bool decode_scriptpubkey_from_addr(const tal_t *ctx,
+				   const struct chainparams *chainparams,
+				   const char *address,
+				   u8 **scriptpubkey)
+{
+	struct bitcoin_address destination;
+	int witness_version;
+	/* segwit_addr_net_decode requires a buffer of size 40, and will
+	 * not write to the buffer if the address is too long, so a buffer
+	 * of fixed size 40 will not overflow. */
+	uint8_t witness_program[40];
+	size_t witness_program_len;
+	const char *bech32;
+	u8 addr_version;
+
+	if (ripemd160_from_base58(&addr_version, &destination.addr,
+				  address, strlen(address))) {
+		if (addr_version == chainparams->p2pkh_version) {
+			*scriptpubkey = scriptpubkey_p2pkh(ctx, &destination);
+			return true;
+		} else if (addr_version == chainparams->p2sh_version) {
+			*scriptpubkey =
+			    scriptpubkey_p2sh_hash(ctx, &destination.addr);
+			return true;
+		} else {
+			return false;
+		}
+		/* Insert other parsers that accept pointer+len here. */
+		return false;
+	}
+
+	bech32 = segwit_addr_net_decode(&witness_version, witness_program,
+					&witness_program_len, address,
+					chainparams);
+	if (bech32) {
+		bool witness_ok;
+
+		if (witness_version == 0) {
+			witness_ok = (witness_program_len == 20 ||
+				       witness_program_len == 32);
+		} else if (witness_version == 1) {
+			witness_ok = (witness_program_len == 32);
+		} else {
+			witness_ok = true;
+		}
+
+		if (!witness_ok)
+			return false;
+
+		if (!streq(bech32, chainparams->onchain_hrp))
+			return false;
+
+		*scriptpubkey = scriptpubkey_witness_raw(ctx, witness_version,
+							 witness_program,
+							 witness_program_len);
+		return true;
+	}
+
+	/* Insert other parsers that accept null-terminated string here. */
+	return false;
+}

common/addr.h

@@ -8,4 +8,9 @@ char *encode_scriptpubkey_to_addr(const tal_t *ctx,
 				  const struct chainparams *chainparams,
 				  const u8 *scriptpubkey);
 
+bool decode_scriptpubkey_from_addr(const tal_t *ctx,
+				   const struct chainparams *chainparams,
+				   const char *address,
+				   u8 **scriptpubkey);
+
 #endif /* LIGHTNING_COMMON_ADDR_H */

common/channel_id.h

@@ -43,4 +43,7 @@ char *fmt_channel_id(const tal_t *ctx, const struct channel_id *channel_id);
 void towire_channel_id(u8 **pptr, const struct channel_id *channel_id);
 bool fromwire_channel_id(const u8 **cursor, size_t *max,
 			 struct channel_id *channel_id);
+
+char *fmt_channel_id(const tal_t *ctx, const struct channel_id *channel_id);
+
 #endif /* LIGHTNING_COMMON_CHANNEL_ID_H */

common/json_param.c

@@ -465,6 +465,22 @@ struct command_result *param_string(struct command *cmd, const char *name,
 	return NULL;
 }
 
+/* Extract a string or a json array */
+struct command_result *param_string_or_array(struct command *cmd, const char *name,
+					     const char * buffer, const jsmntok_t *tok,
+					     struct str_or_arr **result)
+{
+	*result = tal(cmd, struct str_or_arr);
+	(*result)->arr = NULL;
+	(*result)->str = NULL;
+	if (tok->type == JSMN_ARRAY) {
+		(*result)->arr = tok;
+		return NULL;
+	}
+
+	return param_string(cmd, name, buffer, tok, &(*result)->str);
+}
+
 struct command_result *param_invstring(struct command *cmd, const char *name,
 				       const char * buffer, const jsmntok_t *tok,
 				       const char **str)

common/json_param.h

@@ -198,6 +198,17 @@ struct command_result *param_string(struct command *cmd, const char *name,
 				    const char * buffer, const jsmntok_t *tok,
 				    const char **str);
 
+struct str_or_arr
+{
+	const char *str;
+	const jsmntok_t *arr;
+};
+
+/* Extract a string or a json array */
+struct command_result *param_string_or_array(struct command *cmd, const char *name,
+					     const char * buffer, const jsmntok_t *tok,
+					     struct str_or_arr **result);
+
 /* Extract an invoice string from a generic string, strip the `lightning:`
  * prefix from it if needed. */
 struct command_result *param_invstring(struct command *cmd, const char *name,

plugins/Makefile

@@ -50,13 +50,15 @@ PLUGIN_SPENDER_SRC :=				\
 	plugins/spender/main.c			\
 	plugins/spender/multifundchannel.c	\
 	plugins/spender/multiwithdraw.c		\
-	plugins/spender/openchannel.c
+	plugins/spender/openchannel.c		\
+	plugins/spender/splice.c
 PLUGIN_SPENDER_HEADER :=			\
 	plugins/spender/multifundchannel.h	\
 	plugins/spender/multiwithdraw.h		\
 	plugins/spender/fundchannel.h		\
 	plugins/spender/multifundchannel.h	\
-	plugins/spender/openchannel.h
+	plugins/spender/openchannel.h		\
+	plugins/spender/splice.h
 PLUGIN_SPENDER_OBJS := $(PLUGIN_SPENDER_SRC:.c=.o)
 
 PLUGIN_RECOVER_SRC := plugins/recover.c
@@ -153,6 +155,7 @@ PLUGIN_COMMON_OBJS :=				\
 	bitcoin/signature.o			\
 	bitcoin/tx.o				\
 	bitcoin/varint.o			\
+	common/addr.o				\
 	common/amount.o				\
 	common/autodata.o			\
 	common/coin_mvt.o			\
@@ -179,6 +182,7 @@ PLUGIN_COMMON_OBJS :=				\
 	common/psbt_open.o			\
 	common/pseudorand.o			\
 	common/random_select.o			\
+	common/splice_script.o			\
 	common/setup.o				\
 	common/status_levels.o			\
 	common/utils.o				\

plugins/spender/main.c

@@ -3,6 +3,7 @@
 #include <plugins/spender/multifundchannel.h>
 #include <plugins/spender/multiwithdraw.h>
 #include <plugins/spender/openchannel.h>
+#include <plugins/spender/splice.h>
 
 /*~ The spender plugin contains various commands that handle
  * spending from the onchain wallet.  */
@@ -27,6 +28,7 @@ int main(int argc, char **argv)
 	tal_expand(&commands, multiwithdraw_commands, num_multiwithdraw_commands);
 	tal_expand(&commands, fundchannel_commands, num_fundchannel_commands);
 	tal_expand(&commands, multifundchannel_commands, num_multifundchannel_commands);
+	tal_expand(&commands, splice_commands, num_splice_commands);
 	/* tal_expand(&commands, whatever_commands, num_whatever_commands); */
 
 	notifs = tal_arr(NULL, struct plugin_notification, 0);

plugins/spender/splice.h

@@ -0,0 +1,59 @@
+#ifndef LIGHTNING_PLUGINS_SPENDER_SPLICE_H
+#define LIGHTNING_PLUGINS_SPENDER_SPLICE_H
+#include "config.h"
+
+#include <plugins/libplugin.h>
+
+extern const struct plugin_command splice_commands[];
+extern const size_t num_splice_commands;
+
+enum splice_cmd_state {
+	SPLICE_CMD_NONE = 0,
+	SPLICE_CMD_INIT,
+	SPLICE_CMD_UPDATE,
+	SPLICE_CMD_UPDATE_NEEDS_CHANGES,
+	SPLICE_CMD_UPDATE_DONE,
+	SPLICE_CMD_RECVED_SIGS,
+	SPLICE_CMD_DONE,
+};
+
+struct splice_cmd_action_state {
+	enum splice_cmd_state state;
+};
+
+struct splice_cmd {
+	/* The plugin-level command.  */
+	struct command *cmd;
+	/* Script input by user */
+	const char *script;
+	/* The result of parsing the script or json */
+	struct splice_script_result **actions;
+	/* The states of actions at the same index */
+	struct splice_cmd_action_state **states;
+	/* The active psbt */
+	struct wally_psbt *psbt;
+	/* Output result but don't do any action */
+	bool dryrun;
+	/* Execute the splice and abort at the last moment */
+	bool wetrun;
+	/* Feerate queried from lightningd */
+	u32 feerate_per_kw;
+	/* Override max feerate */
+	bool force_feerate;
+	/* How many wallet inputs have we added to the psbt */
+	int wallet_inputs_to_signed;
+	/* Final result */
+	struct bitcoin_txid final_txid;
+	/* Has the fee been calculated yet */
+	bool fee_calculated;
+	/* The amount of sats provided by the user in the inital psbt */
+	struct amount_sat initial_funds;
+	/* The minimum sats that must go back into the wallet */
+	struct amount_sat emergency_sat;
+	/* A verbose debug log of all the splice states */
+	char *debug_log;
+	/* Counter used for more readable debug logs */
+	int debug_counter;
+};
+
+#endif /* LIGHTNING_PLUGINS_SPENDER_SPLICE_H */