signature: fix signatures for p2sh inputs.

The subscript in this case is the redeemscript, not the input script.

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

check-commit-sig.c

@@ -28,7 +28,7 @@ int main(int argc, char *argv[])
 	OpenCommitSig *cs2;
 	struct bitcoin_tx *anchor, *commit;
 	struct sha256_double txid;
-	u8 *tx_arr;
+	u8 *tx_arr, *subscript;
 	size_t *inmap, *outmap;
 	struct pubkey pubkey1, pubkey2;
 	struct bitcoin_signature sig1, sig2;
@@ -58,6 +58,10 @@ int main(int argc, char *argv[])
 	if (!testnet)
 		errx(1, "Private key '%s' not on testnet!", argv[4]);
 
+	/* Pubkey well-formed? */
+	if (!proto_to_pubkey(o2->anchor->pubkey, &pubkey2))
+		errx(1, "Invalid anchor-2 key");
+
 	/* Get the transaction ID of the anchor. */
 	anchor = anchor_tx_create(ctx, o1, o2, &inmap, &outmap);
 	if (!anchor)
@@ -79,19 +83,17 @@ int main(int argc, char *argv[])
 	 * is overkill: if their signature and pubkey signed the commit txin,
 	 * we're happy. */
 	sig1.stype = SIGHASH_ALL;
-	sign_tx_input(ctx, commit, 0, anchor->output[outmap[0]].script,
-		      anchor->output[outmap[0]].script_length, privkey,
-		      &sig1.sig);
+	subscript = bitcoin_redeem_2of2(ctx, &pubkey1, &pubkey2);
+	sign_tx_input(ctx, commit, 0, subscript, tal_count(subscript),
+		      privkey, &sig1.sig);
 
-	/* Signatures and pubkeys well-formed? */
+	/* Signatures well-formed? */
 	if (!proto_to_signature(cs2->sig, &sig2.sig))
 		errx(1, "Invalid commit-sig-2");
 	sig2.stype = SIGHASH_ALL;
-	if (!proto_to_pubkey(o2->anchor->pubkey, &pubkey2))
-		errx(1, "Invalid anchor-2 key");
 
 	/* Combined signatures must validate correctly. */
-	if (!check_2of2_sig(commit, 0, &anchor->output[outmap[0]],
+	if (!check_2of2_sig(commit, 0, subscript, tal_count(subscript),
 			    &pubkey1, &pubkey2, &sig1, &sig2))
 		errx(1, "Signature failed");
 

open-commit-sig.c

@@ -32,7 +32,8 @@ int main(int argc, char *argv[])
 	size_t *inmap, *outmap;
 	EC_KEY *privkey;
 	bool testnet;
-	struct pubkey pubkey;
+	struct pubkey pubkey1, pubkey2;
+	u8 *subscript;
 
 	err_set_progname(argv[0]);
 
@@ -49,7 +50,7 @@ int main(int argc, char *argv[])
 	o1 = pkt_from_file(argv[1], PKT__PKT_OPEN)->open;
 	o2 = pkt_from_file(argv[2], PKT__PKT_OPEN)->open;
 
-	privkey = key_from_base58(argv[3], strlen(argv[3]), &testnet, &pubkey);
+	privkey = key_from_base58(argv[3], strlen(argv[3]), &testnet, &pubkey1);
 	if (!privkey)
 		errx(1, "Invalid private key '%s'", argv[3]);
 	if (!testnet)
@@ -74,9 +75,14 @@ int main(int argc, char *argv[])
 		     (long long)o1->commitment_fee,
 		     (long long)o2->commitment_fee);
 
+	/* Their pubkey must be valid */
+	if (!proto_to_pubkey(o2->anchor->pubkey, &pubkey2))
+		errx(1, "Invalid public open-channel-file2");
+
 	/* Sign it for them. */
-	sign_tx_input(ctx, commit, 0, anchor->output[outmap[0]].script,
-		      anchor->output[outmap[0]].script_length, privkey, &sig);
+	subscript = bitcoin_redeem_2of2(ctx, &pubkey1, &pubkey2);
+	sign_tx_input(ctx, commit, 0, subscript, tal_count(subscript),
+		      privkey, &sig);
 
 	pkt = open_commit_sig_pkt(ctx, &sig);
 	if (!write_all(STDOUT_FILENO, pkt,

signature.c

@@ -137,7 +137,7 @@ out:
 }
 
 bool check_2of2_sig(struct bitcoin_tx *tx, size_t input_num,
-		    const struct bitcoin_tx_output *output,
+		    const u8 *redeemscript, size_t redeemscript_len,
 		    const struct pubkey *key1, const struct pubkey *key2,
 		    const struct bitcoin_signature *sig1,
 		    const struct bitcoin_signature *sig2)
@@ -145,9 +145,8 @@ bool check_2of2_sig(struct bitcoin_tx *tx, size_t input_num,
 	struct sha256_double hash;
 	assert(input_num < tx->input_count);
 
-	assert(is_p2sh(output->script, output->script_length));
-	sha256_tx_one_input(tx, input_num,
-			    output->script, output->script_length, &hash);
+	sha256_tx_one_input(tx, input_num, redeemscript, redeemscript_len,
+			    &hash);
 
 	/* We only use SIGHASH_ALL for the moment. */
 	if (sig1->stype != SIGHASH_ALL || sig2->stype != SIGHASH_ALL)

signature.h

@@ -35,7 +35,7 @@ bool sign_tx_input(const tal_t *ctx, struct bitcoin_tx *tx,
 		   EC_KEY *privkey, struct signature *sig);
 
 bool check_2of2_sig(struct bitcoin_tx *tx, size_t input_num,
-		    const struct bitcoin_tx_output *spending,
+		    const u8 *redeemscript, size_t redeemscript_len,
 		    const struct pubkey *key1, const struct pubkey *key2,
 		    const struct bitcoin_signature *sig1,
 		    const struct bitcoin_signature *sig2);