create-close-tx: create a mutual close tx from the close sigs.

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

Makefile

@@ -3,7 +3,7 @@
 # Needs to have oneof support: Ubuntu vivid's is too old :(
 PROTOCC:=protoc-c
 
-PROGRAMS := open-channel open-anchor-scriptsigs leak-anchor-sigs open-commit-sig check-commit-sig check-anchor-scriptsigs get-anchor-depth create-steal-tx create-commit-spend-tx close-channel
+PROGRAMS := open-channel open-anchor-scriptsigs leak-anchor-sigs open-commit-sig check-commit-sig check-anchor-scriptsigs get-anchor-depth create-steal-tx create-commit-spend-tx close-channel create-close-tx
 
 HELPER_OBJS := base58.o lightning.pb-c.o shadouble.o pkt.o bitcoin_script.o permute_tx.o signature.o bitcoin_tx.o bitcoin_address.o anchor.o commit_tx.o pubkey.o opt_bits.o close_tx.o
 

create-close-tx.c

@@ -0,0 +1,109 @@
+/* My example:
+ * ./create-close-tx A-anchor.tx A-open.pb B-open.pb A-close.pb B-close-complete.pb > A-close.tx
+ */
+#include <ccan/crypto/shachain/shachain.h>
+#include <ccan/short_types/short_types.h>
+#include <ccan/tal/tal.h>
+#include <ccan/opt/opt.h>
+#include <ccan/str/hex/hex.h>
+#include <ccan/err/err.h>
+#include <ccan/read_write_all/read_write_all.h>
+#include "lightning.pb-c.h"
+#include "anchor.h"
+#include "base58.h"
+#include "pkt.h"
+#include "bitcoin_script.h"
+#include "permute_tx.h"
+#include "signature.h"
+#include "pubkey.h"
+#include "close_tx.h"
+#include <openssl/ec.h>
+#include <unistd.h>
+
+int main(int argc, char *argv[])
+{
+	const tal_t *ctx = tal_arr(NULL, char, 0);
+	OpenChannel *o1, *o2;
+	struct bitcoin_tx *anchor, *close_tx;
+	struct sha256_double anchor_txid;
+	struct bitcoin_signature sig1, sig2;
+	struct pubkey pubkey1, pubkey2;
+	u8 *redeemscript, *p2sh, *tx_arr;
+	char *tx_hex;
+	CloseChannel *close;
+	CloseChannelComplete *closecomplete;
+	size_t i;
+
+	err_set_progname(argv[0]);
+
+	/* FIXME: Take update.pbs to adjust channel */
+	opt_register_noarg("--help|-h", opt_usage_and_exit,
+			   "<anchor-tx> <open-channel-file1> <open-channel-file2> <close-protobuf> <close-complete-protobuf>\n"
+			   "Create the close transaction from the signatures",
+			   "Print this message.");
+
+ 	opt_parse(&argc, argv, opt_log_stderr_exit);
+
+	if (argc != 6)
+		opt_usage_exit_fail("Expected 5 arguments");
+
+	anchor = bitcoin_tx_from_file(ctx, argv[1]);
+	o1 = pkt_from_file(argv[2], PKT__PKT_OPEN)->open;
+	o2 = pkt_from_file(argv[3], PKT__PKT_OPEN)->open;
+	close = pkt_from_file(argv[4], PKT__PKT_CLOSE)->close;
+	closecomplete = pkt_from_file(argv[5], PKT__PKT_CLOSE_COMPLETE)->close_complete;
+
+	bitcoin_txid(anchor, &anchor_txid);
+
+	/* Pubkeys well-formed? */
+	if (!proto_to_pubkey(o1->anchor->pubkey, &pubkey1))
+		errx(1, "Invalid anchor-1 key");
+	if (!proto_to_pubkey(o2->anchor->pubkey, &pubkey2))
+		errx(1, "Invalid anchor-2 key");
+	
+	/* This is what the anchor pays to; figure out which output. */
+	redeemscript = bitcoin_redeem_2of2(ctx, &pubkey1, &pubkey2);
+
+	/* This is the scriptPubKey commit tx will have */
+	p2sh = scriptpubkey_p2sh(ctx, redeemscript);
+
+	for (i = 0; i < anchor->output_count; i++) {
+		if (anchor->output[i].script_length != tal_count(p2sh))
+			continue;
+		if (memcmp(anchor->output[i].script, p2sh, tal_count(p2sh)) == 0)
+			break;
+	}
+	if (i == anchor->output_count)
+		errx(1, "No matching output in %s", argv[1]);
+
+	/* Now create the close tx to spend 2/2 output of anchor. */
+	close_tx = create_close_tx(ctx, o1, o2, &anchor_txid, i);
+
+	/* Signatures well-formed? */
+	sig1.stype = sig2.stype = SIGHASH_ALL;
+	if (!proto_to_signature(close->sig, &sig1.sig))
+		errx(1, "Invalid close-packet");
+	if (!proto_to_signature(closecomplete->sig, &sig2.sig))
+		errx(1, "Invalid closecomplete-packet");
+
+	/* Combined signatures must validate correctly. */
+	if (!check_2of2_sig(close_tx, 0, redeemscript, tal_count(redeemscript),
+			    &pubkey1, &pubkey2, &sig1, &sig2))
+		errx(1, "Signature failed");
+
+	/* Create p2sh input for close_tx */
+	close_tx->input[0].script = scriptsig_p2sh_2of2(close_tx, &sig1, &sig2,
+						      &pubkey1, &pubkey2);
+	close_tx->input[0].script_length = tal_count(close_tx->input[0].script);
+
+	/* Print it out in hex. */
+	tx_arr = linearize_tx(ctx, close_tx);
+	tx_hex = tal_arr(tx_arr, char, hex_str_size(tal_count(tx_arr)));
+	hex_encode(tx_arr, tal_count(tx_arr), tx_hex, tal_count(tx_hex));
+
+	if (!write_all(STDOUT_FILENO, tx_hex, strlen(tx_hex)))
+		err(1, "Writing out transaction");
+
+	tal_free(ctx);
+	return 0;
+}