f - grind_signatures

Author: jkczyz

lightning/src/ln/funding.rs

@@ -143,7 +143,13 @@ impl FundingTxInput {
 	/// [`TxIn::sequence`]: bitcoin::TxIn::sequence
 	/// [`set_sequence`]: Self::set_sequence
 	pub fn new_p2wpkh(prevtx: Transaction, vout: u32) -> Result<Self, ()> {
-		let witness_weight = Weight::from_wu(P2WPKH_WITNESS_WEIGHT);
+		let witness_weight = Weight::from_wu(P2WPKH_WITNESS_WEIGHT)
+			- if cfg!(feature = "grind_signatures") {
+				// Guarantees a low R signature
+				Weight::from_wu(1)
+			} else {
+				Weight::ZERO
+			};
 		FundingTxInput::new(prevtx, vout, witness_weight, Script::is_p2wpkh)
 	}
 

lightning/src/util/test_utils.rs

@@ -2226,10 +2226,16 @@ impl TestWalletSource {
 					utxo.output.value,
 					EcdsaSighashType::All,
 				)?;
+				#[cfg(not(feature = "grind_signatures"))]
 				let signature = self.secp.sign_ecdsa(
 					&secp256k1::Message::from_digest(sighash.to_byte_array()),
 					&self.secret_key,
 				);
+				#[cfg(feature = "grind_signatures")]
+				let signature = self.secp.sign_ecdsa_low_r(
+					&secp256k1::Message::from_digest(sighash.to_byte_array()),
+					&self.secret_key,
+				);
 				let bitcoin_sig =
 					bitcoin::ecdsa::Signature { signature, sighash_type: EcdsaSighashType::All };
 				tx.input[i].witness =