Move signature <-> proto conversions to signature.c, check lower bit.

Make sure signature can be used by bitcoin.

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

pkt.c

@@ -47,37 +47,6 @@ void proto_to_sha256(const Sha256Hash *pb, struct sha256 *hash)
 	memcpy(hash->u.u8 + 24, &pb->d, 8);
 }
 
-Signature *signature_to_proto(const tal_t *ctx, const struct signature *sig)
-{
-	Signature *pb = tal(ctx, Signature);
-	signature__init(pb);
-
-	/* Kill me now... */
-	memcpy(&pb->r1, sig->r, 8);
-	memcpy(&pb->r2, sig->r + 8, 8);
-	memcpy(&pb->r3, sig->r + 16, 8);
-	memcpy(&pb->r4, sig->r + 24, 8);
-	memcpy(&pb->s1, sig->s, 8);
-	memcpy(&pb->s2, sig->s + 8, 8);
-	memcpy(&pb->s3, sig->s + 16, 8);
-	memcpy(&pb->s4, sig->s + 24, 8);
-
-	return pb;
-}
-
-void proto_to_signature(const Signature *pb, struct signature *sig)
-{
-	/* Kill me again. */
-	memcpy(sig->r, &pb->r1, 8);
-	memcpy(sig->r + 8, &pb->r2, 8);
-	memcpy(sig->r + 16, &pb->r3, 8);
-	memcpy(sig->r + 24, &pb->r4, 8);
-	memcpy(sig->s, &pb->s1, 8);
-	memcpy(sig->s + 8, &pb->s2, 8);
-	memcpy(sig->s + 16, &pb->s3, 8);
-	memcpy(sig->s + 24, &pb->s4, 8);
-}
-
 BitcoinPubkey *pubkey_to_proto(const tal_t *ctx,
 			       const struct bitcoin_compressed_pubkey *key)
 {

pkt.h

@@ -70,9 +70,7 @@ struct pkt *open_commit_sig_pkt(const tal_t *ctx, const struct signature *sig);
 Sha256Hash *sha256_to_proto(const tal_t *ctx, const struct sha256 *hash);
 void proto_to_sha256(const Sha256Hash *pb, struct sha256 *hash);
 
-Signature *signature_to_proto(const tal_t *ctx, const struct signature *sig);
-void proto_to_signature(const Signature *pb, struct signature *sig);
-
 BitcoinPubkey *pubkey_to_proto(const tal_t *ctx,
 			       const struct bitcoin_compressed_pubkey *key);
+
 #endif /* LIGHTNING_PKT_H */

signature.c

@@ -71,3 +71,40 @@ struct signature *sign_tx_input(const tal_t *ctx, struct bitcoin_tx *tx,
 
 	return sign_hash(ctx, privkey, &hash);
 }
+
+Signature *signature_to_proto(const tal_t *ctx, const struct signature *sig)
+{
+	Signature *pb = tal(ctx, Signature);
+	signature__init(pb);
+
+	assert((sig->s[31] & 1) == 0);
+
+	/* Kill me now... */
+	memcpy(&pb->r1, sig->r, 8);
+	memcpy(&pb->r2, sig->r + 8, 8);
+	memcpy(&pb->r3, sig->r + 16, 8);
+	memcpy(&pb->r4, sig->r + 24, 8);
+	memcpy(&pb->s1, sig->s, 8);
+	memcpy(&pb->s2, sig->s + 8, 8);
+	memcpy(&pb->s3, sig->s + 16, 8);
+	memcpy(&pb->s4, sig->s + 24, 8);
+
+	return pb;
+}
+
+bool proto_to_signature(const Signature *pb, struct signature *sig)
+{
+	/* Kill me again. */
+	memcpy(sig->r, &pb->r1, 8);
+	memcpy(sig->r + 8, &pb->r2, 8);
+	memcpy(sig->r + 16, &pb->r3, 8);
+	memcpy(sig->r + 24, &pb->r4, 8);
+	memcpy(sig->s, &pb->s1, 8);
+	memcpy(sig->s + 8, &pb->s2, 8);
+	memcpy(sig->s + 16, &pb->s3, 8);
+	memcpy(sig->s + 24, &pb->s4, 8);
+
+	/* S must be even */
+	return (sig->s[31] & 1) == 0;
+}
+

signature.h

@@ -3,6 +3,7 @@
 #include <ccan/short_types/short_types.h>
 #include <openssl/ecdsa.h>
 #include <ccan/tal/tal.h>
+#include "lightning.pb-c.h"
 
 enum sighash_type {
     SIGHASH_ALL = 1,
@@ -29,4 +30,8 @@ struct signature *sign_tx_input(const tal_t *ctx,
 				const u8 *subscript, size_t subscript_len,
 				EC_KEY *privkey);
 
+/* Convert to-from protobuf to internal representation. */
+Signature *signature_to_proto(const tal_t *ctx, const struct signature *sig);
+bool proto_to_signature(const Signature *pb, struct signature *sig);
+
 #endif /* LIGHTNING_SIGNATURE_H */