Incorporate low-R values into estimate signature size

Author: benthecarman

lightning/src/chain/keysinterface.rs

@@ -60,6 +60,11 @@ use crate::util::invoice::construct_invoice_preimage;
 #[derive(Hash, Copy, Clone, PartialEq, Eq, Debug)]
 pub struct KeyMaterial(pub [u8; 32]);
 
+#[cfg(feature = "grind_signatures")]
+const ECDSA_SIGNATURE_SIZE: usize = 72;
+#[cfg(not(feature = "grind_signatures"))]
+const ECDSA_SIGNATURE_SIZE: usize = 73;
+
 /// Information about a spendable output to a P2WSH script.
 ///
 /// See [`SpendableOutputDescriptor::DelayedPaymentOutput`] for more details on how to spend this.
@@ -85,9 +90,9 @@ pub struct DelayedPaymentOutputDescriptor {
 }
 impl DelayedPaymentOutputDescriptor {
 	/// The maximum length a well-formed witness spending one of these should have.
-	// Calculated as 1 byte length + 73 byte signature, 1 byte empty vec push, 1 byte length plus
+	// Calculated as 1 byte length + ECDSA signature, 1 byte empty vec push, 1 byte length plus
 	// redeemscript push length.
-	pub const MAX_WITNESS_LENGTH: usize = 1 + 73 + 1 + chan_utils::REVOKEABLE_REDEEMSCRIPT_MAX_LENGTH + 1;
+	pub const MAX_WITNESS_LENGTH: usize = 1 + ECDSA_SIGNATURE_SIZE + 1 + chan_utils::REVOKEABLE_REDEEMSCRIPT_MAX_LENGTH + 1;
 }
 
 impl_writeable_tlv_based!(DelayedPaymentOutputDescriptor, {
@@ -117,9 +122,9 @@ pub struct StaticPaymentOutputDescriptor {
 }
 impl StaticPaymentOutputDescriptor {
 	/// The maximum length a well-formed witness spending one of these should have.
-	// Calculated as 1 byte legnth + 73 byte signature, 1 byte empty vec push, 1 byte length plus
+	// Calculated as 1 byte legnth + ECDSA signature, 1 byte empty vec push, 1 byte length plus
 	// redeemscript push length.
-	pub const MAX_WITNESS_LENGTH: usize = 1 + 73 + 34;
+	pub const MAX_WITNESS_LENGTH: usize = 1 + ECDSA_SIGNATURE_SIZE + 34;
 }
 impl_writeable_tlv_based!(StaticPaymentOutputDescriptor, {
 	(0, outpoint, required),
@@ -1209,7 +1214,7 @@ impl KeysManager {
 						sequence: Sequence::ZERO,
 						witness: Witness::new(),
 					});
-					witness_weight += 1 + 73 + 34;
+					witness_weight += 1 + ECDSA_SIGNATURE_SIZE + 34;
 					input_value += output.value;
 					if !output_set.insert(*outpoint) { return Err(()); }
 				}