Update incorrect_payment_amount generation/handling for BOLT uptd

ie dont generate them as they're a really obvious privacy leak.
Luckily we were already handling them the same aside from log
printing so don't have to touch anything there. I was lazy in
updating tests but it only effects log printing, so whatever.

Author: TheBlueMatt

src/ln/channelmanager.rs

@@ -212,16 +212,6 @@ impl MsgHandleErrInternal {
 	}
 }
 
-/// Pass to fail_htlc_backwwards to indicate the reason to fail the payment
-/// after a PaymentReceived event.
-#[derive(PartialEq)]
-pub enum PaymentFailReason {
-	/// Indicate the preimage for payment_hash is not known after a PaymentReceived event
-	PreimageUnknown,
-	/// Indicate the payment amount is incorrect ( received is < expected or > 2*expected ) after a PaymentReceived event
-	AmountMismatch,
-}
-
 /// We hold back HTLCs we intend to relay for a random interval in the range (this, 5*this). This
 /// provides some limited amount of privacy. Ideally this would range from somewhere like 1 second
 /// to 30 seconds, but people expect lightning to be, you know, kinda fast, sadly. We could
@@ -1532,16 +1522,21 @@ impl ChannelManager {
 		events.append(&mut new_events);
 	}
 
-	/// Indicates that the preimage for payment_hash is unknown or the received amount is incorrect after a PaymentReceived event.
-	pub fn fail_htlc_backwards(&self, payment_hash: &PaymentHash, reason: PaymentFailReason) -> bool {
+	/// Indicates that the preimage for payment_hash is unknown or the received amount is incorrect
+	/// after a PaymentReceived event.
+	/// expected_value is the value you expected the payment to be for (not the amount it actually
+	/// was for from the PaymentReceived event).
+	pub fn fail_htlc_backwards(&self, payment_hash: &PaymentHash, expected_value: u64) -> bool {
 		let _ = self.total_consistency_lock.read().unwrap();
 
 		let mut channel_state = Some(self.channel_state.lock().unwrap());
 		let removed_source = channel_state.as_mut().unwrap().claimable_htlcs.remove(payment_hash);
 		if let Some(mut sources) = removed_source {
 			for htlc_with_hash in sources.drain(..) {
 				if channel_state.is_none() { channel_state = Some(self.channel_state.lock().unwrap()); }
-				self.fail_htlc_backwards_internal(channel_state.take().unwrap(), HTLCSource::PreviousHopData(htlc_with_hash), payment_hash, HTLCFailReason::Reason { failure_code: if reason == PaymentFailReason::PreimageUnknown {0x4000 | 15} else {0x4000 | 16}, data: Vec::new() });
+				self.fail_htlc_backwards_internal(channel_state.take().unwrap(),
+						HTLCSource::PreviousHopData(htlc_with_hash), payment_hash,
+						HTLCFailReason::Reason { failure_code: 0x4000 | 15, data: byte_utils::be64_to_array(expected_value).to_vec() });
 			}
 			true
 		} else { false }
@@ -3366,7 +3361,7 @@ mod tests {
 	use chain::keysinterface::{KeysInterface, SpendableOutputDescriptor};
 	use chain::keysinterface;
 	use ln::channel::{COMMITMENT_TX_BASE_WEIGHT, COMMITMENT_TX_WEIGHT_PER_HTLC};
-	use ln::channelmanager::{ChannelManager,ChannelManagerReadArgs,OnionKeys,PaymentFailReason,RAACommitmentOrder, PaymentPreimage, PaymentHash};
+	use ln::channelmanager::{ChannelManager,ChannelManagerReadArgs,OnionKeys,RAACommitmentOrder, PaymentPreimage, PaymentHash};
 	use ln::channelmonitor::{ChannelMonitor, ChannelMonitorUpdateErr, CLTV_CLAIM_BUFFER, HTLC_FAIL_TIMEOUT_BLOCKS, ManyChannelMonitor};
 	use ln::channel::{ACCEPTED_HTLC_SCRIPT_WEIGHT, OFFERED_HTLC_SCRIPT_WEIGHT};
 	use ln::router::{Route, RouteHop, Router};
@@ -4224,7 +4219,7 @@ mod tests {
 	}
 
 	fn fail_payment_along_route(origin_node: &Node, expected_route: &[&Node], skip_last: bool, our_payment_hash: PaymentHash) {
-		assert!(expected_route.last().unwrap().node.fail_htlc_backwards(&our_payment_hash, PaymentFailReason::PreimageUnknown));
+		assert!(expected_route.last().unwrap().node.fail_htlc_backwards(&our_payment_hash, 0));
 		check_added_monitors!(expected_route.last().unwrap(), 1);
 
 		let mut next_msgs: Option<(msgs::UpdateFailHTLC, msgs::CommitmentSigned)> = None;
@@ -6351,7 +6346,7 @@ mod tests {
 		// Brodacast legit commitment tx from C on B's chain
 		let commitment_tx = nodes[2].node.channel_state.lock().unwrap().by_id.get(&chan_2.2).unwrap().last_local_commitment_txn.clone();
 		check_spends!(commitment_tx[0], chan_2.3.clone());
-		nodes[2].node.fail_htlc_backwards(&payment_hash, PaymentFailReason::PreimageUnknown);
+		nodes[2].node.fail_htlc_backwards(&payment_hash, 0);
 		{
 			let mut added_monitors = nodes[2].chan_monitor.added_monitors.lock().unwrap();
 			assert_eq!(added_monitors.len(), 1);
@@ -6536,7 +6531,7 @@ mod tests {
 		let (_, second_payment_hash) = route_payment(&nodes[0], &[&nodes[1], &nodes[2]], 3000000);
 		let (_, third_payment_hash) = route_payment(&nodes[0], &[&nodes[1], &nodes[2]], 3000000);
 
-		assert!(nodes[2].node.fail_htlc_backwards(&first_payment_hash, PaymentFailReason::PreimageUnknown));
+		assert!(nodes[2].node.fail_htlc_backwards(&first_payment_hash, 0));
 		check_added_monitors!(nodes[2], 1);
 		let updates = get_htlc_update_msgs!(nodes[2], nodes[1].node.get_our_node_id());
 		assert!(updates.update_add_htlcs.is_empty());
@@ -6548,7 +6543,7 @@ mod tests {
 		let bs_raa = commitment_signed_dance!(nodes[1], nodes[2], updates.commitment_signed, false, true, false, true);
 		// Drop the last RAA from 3 -> 2
 
-		assert!(nodes[2].node.fail_htlc_backwards(&second_payment_hash, PaymentFailReason::PreimageUnknown));
+		assert!(nodes[2].node.fail_htlc_backwards(&second_payment_hash, 0));
 		check_added_monitors!(nodes[2], 1);
 		let updates = get_htlc_update_msgs!(nodes[2], nodes[1].node.get_our_node_id());
 		assert!(updates.update_add_htlcs.is_empty());
@@ -6564,7 +6559,7 @@ mod tests {
 		nodes[2].node.handle_revoke_and_ack(&nodes[1].node.get_our_node_id(), &as_raa).unwrap();
 		check_added_monitors!(nodes[2], 1);
 
-		assert!(nodes[2].node.fail_htlc_backwards(&third_payment_hash, PaymentFailReason::PreimageUnknown));
+		assert!(nodes[2].node.fail_htlc_backwards(&third_payment_hash, 0));
 		check_added_monitors!(nodes[2], 1);
 		let updates = get_htlc_update_msgs!(nodes[2], nodes[1].node.get_our_node_id());
 		assert!(updates.update_add_htlcs.is_empty());
@@ -8159,7 +8154,7 @@ mod tests {
 		let (_, payment_hash_1) = route_payment(&nodes[0], &[&nodes[1], &nodes[2]], 1000000);
 
 		// Fail the payment backwards, failing the monitor update on nodes[1]'s receipt of the RAA
-		assert!(nodes[2].node.fail_htlc_backwards(&payment_hash_1, PaymentFailReason::PreimageUnknown));
+		assert!(nodes[2].node.fail_htlc_backwards(&payment_hash_1, 0));
 		check_added_monitors!(nodes[2], 1);
 
 		let updates = get_htlc_update_msgs!(nodes[2], nodes[1].node.get_our_node_id());
@@ -9724,7 +9719,7 @@ mod tests {
 			let onion_keys = ChannelManager::construct_onion_keys(&Secp256k1::new(), &route, &session_priv).unwrap();
 			msg.reason = ChannelManager::build_first_hop_failure_packet(&onion_keys[1].shared_secret[..], NODE|2, &[0;0]);
 		}, ||{
-			nodes[2].node.fail_htlc_backwards(&payment_hash, PaymentFailReason::PreimageUnknown);
+			nodes[2].node.fail_htlc_backwards(&payment_hash, 0);
 		}, true, Some(NODE|2), Some(msgs::HTLCFailChannelUpdate::NodeFailure{node_id: route.hops[1].pubkey, is_permanent: false}));
 
 		// intermediate node failure
@@ -9742,7 +9737,7 @@ mod tests {
 			let onion_keys = ChannelManager::construct_onion_keys(&Secp256k1::new(), &route, &session_priv).unwrap();
 			msg.reason = ChannelManager::build_first_hop_failure_packet(&onion_keys[1].shared_secret[..], PERM|NODE|2, &[0;0]);
 		}, ||{
-			nodes[2].node.fail_htlc_backwards(&payment_hash, PaymentFailReason::PreimageUnknown);
+			nodes[2].node.fail_htlc_backwards(&payment_hash, 0);
 		}, false, Some(PERM|NODE|2), Some(msgs::HTLCFailChannelUpdate::NodeFailure{node_id: route.hops[1].pubkey, is_permanent: true}));
 
 		// intermediate node failure
@@ -9753,7 +9748,7 @@ mod tests {
 			let onion_keys = ChannelManager::construct_onion_keys(&Secp256k1::new(), &route, &session_priv).unwrap();
 			msg.reason = ChannelManager::build_first_hop_failure_packet(&onion_keys[0].shared_secret[..], PERM|NODE|3, &[0;0]);
 		}, ||{
-			nodes[2].node.fail_htlc_backwards(&payment_hash, PaymentFailReason::PreimageUnknown);
+			nodes[2].node.fail_htlc_backwards(&payment_hash, 0);
 		}, true, Some(PERM|NODE|3), Some(msgs::HTLCFailChannelUpdate::NodeFailure{node_id: route.hops[0].pubkey, is_permanent: true}));
 
 		// final node failure
@@ -9762,7 +9757,7 @@ mod tests {
 			let onion_keys = ChannelManager::construct_onion_keys(&Secp256k1::new(), &route, &session_priv).unwrap();
 			msg.reason = ChannelManager::build_first_hop_failure_packet(&onion_keys[1].shared_secret[..], PERM|NODE|3, &[0;0]);
 		}, ||{
-			nodes[2].node.fail_htlc_backwards(&payment_hash, PaymentFailReason::PreimageUnknown);
+			nodes[2].node.fail_htlc_backwards(&payment_hash, 0);
 		}, false, Some(PERM|NODE|3), Some(msgs::HTLCFailChannelUpdate::NodeFailure{node_id: route.hops[1].pubkey, is_permanent: true}));
 
 		run_onion_failure_test("invalid_onion_version", 0, &nodes, &route, &payment_hash, |msg| { msg.onion_routing_packet.version = 1; }, ||{}, true,
@@ -9829,13 +9824,9 @@ mod tests {
 		}, ||{}, true, Some(UPDATE|14), Some(msgs::HTLCFailChannelUpdate::ChannelUpdateMessage{msg: ChannelUpdate::dummy()}));
 
 		run_onion_failure_test("unknown_payment_hash", 2, &nodes, &route, &payment_hash, |_| {}, || {
-			nodes[2].node.fail_htlc_backwards(&payment_hash, PaymentFailReason::PreimageUnknown);
+			nodes[2].node.fail_htlc_backwards(&payment_hash, 0);
 		}, false, Some(PERM|15), None);
 
-		run_onion_failure_test("incorrect_payment_amount", 2, &nodes, &route, &payment_hash, |_| {}, || {
-			nodes[2].node.fail_htlc_backwards(&payment_hash, PaymentFailReason::AmountMismatch);
-		}, false, Some(PERM|16), None);
-
 		run_onion_failure_test("final_expiry_too_soon", 1, &nodes, &route, &payment_hash, |msg| {
 			let height = msg.cltv_expiry - CLTV_CLAIM_BUFFER - HTLC_FAIL_TIMEOUT_BLOCKS + 1;
 			let header = BlockHeader { version: 0x20000000, prev_blockhash: Default::default(), merkle_root: Default::default(), time: 42, bits: 42, nonce: 42 };

src/util/errors.rs

@@ -84,7 +84,7 @@ pub(crate) fn get_onion_error_description(error_code: u16) -> (&'static str, &'s
 		_c if _c == UPDATE|12 => ("Node indicated the fee amount does not meet the required level", "fee_insufficient"),
 		_c if _c == UPDATE|13 => ("Node indicated the cltv_expiry does not comply with the cltv_expiry_delta required by the outgoing channel", "incorrect_cltv_expiry"),
 		_c if _c == UPDATE|14 => ("Node indicated the CLTV expiry too close to the current block height for safe handling", "expiry_too_soon"),
-		_c if _c == PERM|15 => ("The final node indicated the payment hash is unknown", "unknown_payment_hash"),
+		_c if _c == PERM|15 => ("The final node indicated the payment hash is unknown or amount is incorrect", "incorrect_or_unknown_payment_details"),
 		_c if _c == PERM|16 => ("The final node indicated the payment amount is incorrect", "incorrect_payment_amount"),
 		_c if _c == 17 => ("The final node indicated the CLTV expiry is too close to the current block height for safe handling", "final_expiry_too_soon"),
 		_c if _c == 18 => ("The final node indicated the CLTV expiry in the HTLC does not match the value in the onion", "final_incorrect_cltv_expiry"),

src/util/events.rs

@@ -54,14 +54,15 @@ pub enum Event {
 	/// Indicates we've received money! Just gotta dig out that payment preimage and feed it to
 	/// ChannelManager::claim_funds to get it....
 	/// Note that if the preimage is not known or the amount paid is incorrect, you must call
-	/// ChannelManager::fail_htlc_backwards with PaymentFailReason::PreimageUnknown or
-	/// PaymentFailReason::AmountMismatch, respectively, to free up resources for this HTLC.
+	/// ChannelManager::fail_htlc_backwards to free up resources for this HTLC.
 	/// The amount paid should be considered 'incorrect' when it is less than or more than twice
 	/// the amount expected.
 	PaymentReceived {
 		/// The hash for which the preimage should be handed to the ChannelManager.
 		payment_hash: PaymentHash,
-		/// The value, in thousandths of a satoshi, that this payment is for.
+		/// The value, in thousandths of a satoshi, that this payment is for. Note that you must
+		/// compare this to the expected value before accepting the payment (as otherwise you are
+		/// providing proof-of-payment for less than the value you expected!).
 		amt: u64,
 	},
 	/// Indicates an outbound payment we made succeeded (ie it made it all the way to its target