Revert: 064309df1a "peer: signature in commit_info is always valid."

It's not quite true: if we offer the anchor, we have a commitinfo
without their signature yet.  So make it a pointer again.  Since we
always allocate struct commit_info with talz, it starts as a NULL
pointer.

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

daemon/packets.c

@@ -141,10 +141,12 @@ void queue_pkt_anchor(struct peer *peer)
 	}
 
 	/* Sign their commit sig */
-	peer->them.commit->sig.stype = SIGHASH_ALL;
+	peer->them.commit->sig = tal(peer->them.commit,
+				     struct bitcoin_signature);
+	peer->them.commit->sig->stype = SIGHASH_ALL;
 	peer_sign_theircommit(peer, peer->them.commit->tx,
-			      &peer->them.commit->sig.sig);
-	a->commit_sig = signature_to_proto(a, &peer->them.commit->sig.sig);
+			      &peer->them.commit->sig->sig);
+	a->commit_sig = signature_to_proto(a, &peer->them.commit->sig->sig);
 
 	queue_pkt(peer, PKT__PKT_OPEN_ANCHOR, a);
 }
@@ -158,10 +160,12 @@ void queue_pkt_open_commit_sig(struct peer *peer)
 	dump_tx("Creating sig for:", peer->them.commit->tx);
 	dump_key("Using key:", &peer->us.commitkey);
 
-	peer->them.commit->sig.stype = SIGHASH_ALL;
+	peer->them.commit->sig = tal(peer->them.commit,
+				     struct bitcoin_signature);
+	peer->them.commit->sig->stype = SIGHASH_ALL;
 	peer_sign_theircommit(peer, peer->them.commit->tx,
-			      &peer->them.commit->sig.sig);
-	s->sig = signature_to_proto(s, &peer->them.commit->sig.sig);
+			      &peer->them.commit->sig->sig);
+	s->sig = signature_to_proto(s, &peer->them.commit->sig->sig);
 
 	queue_pkt(peer, PKT__PKT_OPEN_COMMIT_SIG, s);
 }
@@ -314,8 +318,9 @@ void queue_pkt_commit(struct peer *peer)
 	 */
 	assert(ci->prev->cstate->changes != ci->cstate->changes);
 
-	ci->sig.stype = SIGHASH_ALL;
-	peer_sign_theircommit(peer, ci->tx, &ci->sig.sig);
+	ci->sig = tal(ci, struct bitcoin_signature);
+	ci->sig->stype = SIGHASH_ALL;
+	peer_sign_theircommit(peer, ci->tx, &ci->sig->sig);
 
 	/* Switch to the new commitment. */
 	peer->them.commit = ci;
@@ -324,7 +329,7 @@ void queue_pkt_commit(struct peer *peer)
 	
 	/* Now send message */
 	update_commit__init(u);
-	u->sig = signature_to_proto(u, &ci->sig.sig);
+	u->sig = signature_to_proto(u, &ci->sig->sig);
 	u->ack = peer_outgoing_ack(peer);
 
 	queue_pkt(peer, PKT__PKT_UPDATE_COMMIT, u);
@@ -344,7 +349,7 @@ void queue_pkt_revocation(struct peer *peer)
 	assert(!peer->us.commit->prev->revocation_preimage);
 
 	/* We have their signature on the current one, right? */
-	memcheck(&peer->us.commit->sig, sizeof(peer->us.commit->sig));
+	assert(peer->us.commit->sig);
 
 	peer->us.commit->prev->revocation_preimage
 		= tal(peer->us.commit->prev, struct sha256);
@@ -477,8 +482,10 @@ static Pkt *check_and_save_commit_sig(struct peer *peer,
 				      struct commit_info *ci,
 				      const Signature *pb)
 {
-	ci->sig.stype = SIGHASH_ALL;
-	if (!proto_to_signature(pb, &ci->sig.sig))
+	assert(!ci->sig);
+	ci->sig = tal(ci, struct bitcoin_signature);
+	ci->sig->stype = SIGHASH_ALL;
+	if (!proto_to_signature(pb, &ci->sig->sig))
 		return pkt_err(peer, "Malformed signature");
 
 	/* Their sig should sign our commit tx. */
@@ -487,7 +494,7 @@ static Pkt *check_and_save_commit_sig(struct peer *peer,
 			  NULL, 0,
 			  peer->anchor.witnessscript,
 			  &peer->them.commitkey,
-			  &ci->sig))
+			  ci->sig))
 		return pkt_err(peer, "Bad signature");
 
 	return NULL;

daemon/peer.c

@@ -1294,7 +1294,7 @@ const struct bitcoin_tx *bitcoin_commit(struct peer *peer)
 
 	peer->us.commit->tx->input[0].witness
 		= bitcoin_witness_2of2(peer->us.commit->tx->input,
-				       &peer->us.commit->sig,
+				       peer->us.commit->sig,
 				       &sig,
 				       &peer->them.commitkey,
 				       &peer->us.commitkey);

daemon/peer.h

@@ -61,8 +61,8 @@ struct commit_info {
 	struct bitcoin_tx *tx;
 	/* Channel state for this tx. */
 	struct channel_state *cstate;
-	/* Other side's signature for this commit tx. */
-	struct bitcoin_signature sig;
+	/* Other side's signature for last commit tx (if known) */
+	struct bitcoin_signature *sig;
 	/* Map for permutation: see commit_tx.c */
 	int *map;
 	/* Revocation preimage (if known). */