Check local signtures explicitly in channel tx-generation tests

It appears the local signatures which are specified in the channel
transaction-generation tests were never checked directly (though
they were checked as a part of the overall fully-signed-transaction
tests).

Check them explicitly so that they can be updated for static remote
key.

Author: TheBlueMatt

lightning/src/ln/chan_utils.rs

@@ -567,6 +567,14 @@ impl LocalCommitmentTransaction {
 		}
 	}
 
+	#[cfg(test)]
+	/// Gets the local signature we will/would/have added to our transaction.
+	pub fn get_local_sig<T: secp256k1::Signing>(&self, funding_key: &SecretKey, funding_redeemscript: &Script, channel_value_satoshis: u64, secp_ctx: &Secp256k1<T>) -> secp256k1::Signature {
+		let sighash = hash_to_message!(&bip143::SighashComponents::new(&self.tx)
+			.sighash_all(&self.tx.input[0], funding_redeemscript, channel_value_satoshis)[..]);
+		secp_ctx.sign(&sighash, funding_key)
+	}
+
 	pub fn add_local_sig<T: secp256k1::Signing>(&mut self, funding_key: &SecretKey, funding_redeemscript: &Script, channel_value_satoshis: u64, secp_ctx: &Secp256k1<T>) {
 		if self.has_local_sig() { return; }
 		let sighash = hash_to_message!(&bip143::SighashComponents::new(&self.tx)

lightning/src/ln/channel.rs

@@ -4414,6 +4414,8 @@ mod tests {
 				secp_ctx.verify(&sighash, &their_signature, chan.their_funding_pubkey()).unwrap();
 
 				let mut localtx = LocalCommitmentTransaction::new_missing_local_sig(unsigned_tx.0.clone(), &their_signature, &PublicKey::from_secret_key(&secp_ctx, chan.local_keys.funding_key()), chan.their_funding_pubkey());
+				assert_eq!(Signature::from_der(&hex::decode($our_sig_hex).unwrap()[..]).unwrap(),
+					localtx.get_local_sig(chan.local_keys.funding_key(), &redeemscript, chan.channel_value_satoshis, &chan.secp_ctx));
 				localtx.add_local_sig(chan.local_keys.funding_key(), &redeemscript, chan.channel_value_satoshis, &chan.secp_ctx);
 
 				assert_eq!(serialize(localtx.with_valid_witness())[..],
@@ -4443,7 +4445,9 @@ mod tests {
 					assert!(preimage.is_some());
 				}
 
-				chan_utils::sign_htlc_transaction(&mut htlc_tx, &remote_signature, &preimage, &htlc, &keys.a_htlc_key, &keys.b_htlc_key, &keys.revocation_key, &keys.per_commitment_point, chan.local_keys.htlc_base_key(), &chan.secp_ctx).unwrap();
+				let our_signature = Signature::from_der(&hex::decode($our_sig_hex).unwrap()[..]).unwrap();
+				assert_eq!(our_signature,
+					chan_utils::sign_htlc_transaction(&mut htlc_tx, &remote_signature, &preimage, &htlc, &keys.a_htlc_key, &keys.b_htlc_key, &keys.revocation_key, &keys.per_commitment_point, chan.local_keys.htlc_base_key(), &chan.secp_ctx).unwrap().0);
 				assert_eq!(serialize(&htlc_tx)[..],
 						hex::decode($tx_hex).unwrap()[..]);
 			};