Make the PaymentSecret in `PaymentReceived` events non-Optional
[rust-lightning] / lightning / src / ln / channelmanager.rs
index 80edbacf573a7a545107a7908698fb0bf371cb13..b1890853ec10630f4953f61cae03f99c4310a56d 100644 (file)
@@ -96,7 +96,7 @@ enum PendingHTLCRouting {
                short_channel_id: u64, // This should be NonZero<u64> eventually when we bump MSRV
        },
        Receive {
-               payment_data: Option<msgs::FinalOnionHopData>,
+               payment_data: msgs::FinalOnionHopData,
                incoming_cltv_expiry: u32, // Used to track when we should expire pending HTLCs that go unclaimed
        },
 }
@@ -156,11 +156,10 @@ pub(crate) struct HTLCPreviousHopData {
 struct ClaimableHTLC {
        prev_hop: HTLCPreviousHopData,
        value: u64,
-       /// Filled in when the HTLC was received with a payment_secret packet, which contains a
-       /// total_msat (which may differ from value if this is a Multi-Path Payment) and a
+       /// Contains a total_msat (which may differ from value if this is a Multi-Path Payment) and a
        /// payment_secret which prevents path-probing attacks and can associate different HTLCs which
        /// are part of the same payment.
-       payment_data: Option<msgs::FinalOnionHopData>,
+       payment_data: msgs::FinalOnionHopData,
        cltv_expiry: u32,
 }
 
@@ -327,12 +326,11 @@ pub(super) struct ChannelHolder<Signer: Sign> {
        /// guarantees are made about the existence of a channel with the short id here, nor the short
        /// ids in the PendingHTLCInfo!
        pub(super) forward_htlcs: HashMap<u64, Vec<HTLCForwardInfo>>,
-       /// (payment_hash, payment_secret) -> Vec<HTLCs> for tracking HTLCs that
-       /// were to us and can be failed/claimed by the user
+       /// Map from payment hash to any HTLCs which are to us and can be failed/claimed by the user.
        /// Note that while this is held in the same mutex as the channels themselves, no consistency
        /// guarantees are made about the channels given here actually existing anymore by the time you
        /// go to read them!
-       claimable_htlcs: HashMap<(PaymentHash, Option<PaymentSecret>), Vec<ClaimableHTLC>>,
+       claimable_htlcs: HashMap<PaymentHash, Vec<ClaimableHTLC>>,
        /// Messages to send to peers - pushed to in the same lock that they are generated in (except
        /// for broadcast messages, where ordering isn't as strict).
        pub(super) pending_msg_events: Vec<MessageSendEvent>,
@@ -353,6 +351,24 @@ struct PeerState {
        latest_features: InitFeatures,
 }
 
+/// Stores a PaymentSecret and any other data we may need to validate an inbound payment is
+/// actually ours and not some duplicate HTLC sent to us by a node along the route.
+///
+/// For users who don't want to bother doing their own payment preimage storage, we also store that
+/// here.
+struct PendingInboundPayment {
+       /// The payment secret that the sender must use for us to accept this payment
+       payment_secret: PaymentSecret,
+       /// Time at which this HTLC expires - blocks with a header time above this value will result in
+       /// this payment being removed.
+       expiry_time: u64,
+       /// Arbitrary identifier the user specifies (or not)
+       user_payment_id: u64,
+       // Other required attributes of the payment, optionally enforced:
+       payment_preimage: Option<PaymentPreimage>,
+       min_value_msat: Option<u64>,
+}
+
 /// SimpleArcChannelManager is useful when you need a ChannelManager with a static lifetime, e.g.
 /// when you're using lightning-net-tokio (since tokio::spawn requires parameters with static
 /// lifetimes). Other times you can afford a reference, which is more efficient, in which case
@@ -431,6 +447,14 @@ pub struct ChannelManager<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref,
        pub(super) channel_state: Mutex<ChannelHolder<Signer>>,
        #[cfg(not(any(test, feature = "_test_utils")))]
        channel_state: Mutex<ChannelHolder<Signer>>,
+
+       /// Storage for PaymentSecrets and any requirements on future inbound payments before we will
+       /// expose them to users via a PaymentReceived event. HTLCs which do not meet the requirements
+       /// here are failed when we process them as pending-forwardable-HTLCs, and entries are removed
+       /// after we generate a PaymentReceived upon receipt of all MPP parts.
+       /// Locked *after* channel_state.
+       pending_inbound_payments: Mutex<HashMap<PaymentHash, PendingInboundPayment>>,
+
        our_network_key: SecretKey,
        our_network_pubkey: PublicKey,
 
@@ -438,6 +462,11 @@ pub struct ChannelManager<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref,
        /// value increases strictly since we don't assume access to a time source.
        last_node_announcement_serial: AtomicUsize,
 
+       /// The highest block timestamp we've seen, which is usually a good guess at the current time.
+       /// Assuming most miners are generating blocks with reasonable timestamps, this shouldn't be
+       /// very far in the past, and can only ever be up to two hours in the future.
+       highest_seen_timestamp: AtomicUsize,
+
        /// The bulk of our storage will eventually be here (channels and message queues and the like).
        /// If we are connected to a peer we always at least have an entry here, even if no channels
        /// are currently open with that peer.
@@ -853,11 +882,14 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                claimable_htlcs: HashMap::new(),
                                pending_msg_events: Vec::new(),
                        }),
+                       pending_inbound_payments: Mutex::new(HashMap::new()),
+
                        our_network_key: keys_manager.get_node_secret(),
                        our_network_pubkey: PublicKey::from_secret_key(&secp_ctx, &keys_manager.get_node_secret()),
                        secp_ctx,
 
                        last_node_announcement_serial: AtomicUsize::new(0),
+                       highest_seen_timestamp: AtomicUsize::new(0),
 
                        per_peer_state: RwLock::new(HashMap::new()),
 
@@ -1215,6 +1247,10 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        msgs::OnionHopDataFormat::FinalNode { payment_data } => payment_data,
                                };
 
+                               if payment_data.is_none() {
+                                       return_err!("We require payment_secrets", 0x4000|0x2000|3, &[0;0]);
+                               }
+
                                // Note that we could obviously respond immediately with an update_fulfill_htlc
                                // message, however that would leak that we are the recipient of this payment, so
                                // instead we stay symmetric with the forwarding case, only responding (after a
@@ -1222,7 +1258,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
                                PendingHTLCStatus::Forward(PendingHTLCInfo {
                                        routing: PendingHTLCRouting::Receive {
-                                               payment_data,
+                                               payment_data: payment_data.unwrap(),
                                                incoming_cltv_expiry: msg.cltv_expiry,
                                        },
                                        payment_hash: msg.payment_hash.clone(),
@@ -1916,61 +1952,94 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                        routing: PendingHTLCRouting::Receive { payment_data, incoming_cltv_expiry },
                                                                        incoming_shared_secret, payment_hash, amt_to_forward, .. },
                                                                        prev_funding_outpoint } => {
-                                                               let prev_hop = HTLCPreviousHopData {
-                                                                       short_channel_id: prev_short_channel_id,
-                                                                       outpoint: prev_funding_outpoint,
-                                                                       htlc_id: prev_htlc_id,
-                                                                       incoming_packet_shared_secret: incoming_shared_secret,
-                                                               };
-
-                                                               let mut total_value = 0;
-                                                               let payment_secret_opt =
-                                                                       if let &Some(ref data) = &payment_data { Some(data.payment_secret.clone()) } else { None };
-                                                               let htlcs = channel_state.claimable_htlcs.entry((payment_hash, payment_secret_opt))
-                                                                       .or_insert(Vec::new());
-                                                               htlcs.push(ClaimableHTLC {
-                                                                       prev_hop,
+                                                               let claimable_htlc = ClaimableHTLC {
+                                                                       prev_hop: HTLCPreviousHopData {
+                                                                               short_channel_id: prev_short_channel_id,
+                                                                               outpoint: prev_funding_outpoint,
+                                                                               htlc_id: prev_htlc_id,
+                                                                               incoming_packet_shared_secret: incoming_shared_secret,
+                                                                       },
                                                                        value: amt_to_forward,
                                                                        payment_data: payment_data.clone(),
                                                                        cltv_expiry: incoming_cltv_expiry,
-                                                               });
-                                                               if let &Some(ref data) = &payment_data {
-                                                                       for htlc in htlcs.iter() {
-                                                                               total_value += htlc.value;
-                                                                               if htlc.payment_data.as_ref().unwrap().total_msat != data.total_msat {
-                                                                                       total_value = msgs::MAX_VALUE_MSAT;
-                                                                               }
-                                                                               if total_value >= msgs::MAX_VALUE_MSAT { break; }
-                                                                       }
-                                                                       if total_value >= msgs::MAX_VALUE_MSAT || total_value > data.total_msat  {
-                                                                               for htlc in htlcs.iter() {
-                                                                                       let mut htlc_msat_height_data = byte_utils::be64_to_array(htlc.value).to_vec();
-                                                                                       htlc_msat_height_data.extend_from_slice(
-                                                                                               &byte_utils::be32_to_array(self.best_block.read().unwrap().height()),
-                                                                                       );
-                                                                                       failed_forwards.push((HTLCSource::PreviousHopData(HTLCPreviousHopData {
-                                                                                                       short_channel_id: htlc.prev_hop.short_channel_id,
-                                                                                                       outpoint: prev_funding_outpoint,
-                                                                                                       htlc_id: htlc.prev_hop.htlc_id,
-                                                                                                       incoming_packet_shared_secret: htlc.prev_hop.incoming_packet_shared_secret,
-                                                                                               }), payment_hash,
-                                                                                               HTLCFailReason::Reason { failure_code: 0x4000 | 15, data: htlc_msat_height_data }
-                                                                                       ));
-                                                                               }
-                                                                       } else if total_value == data.total_msat {
-                                                                               new_events.push(events::Event::PaymentReceived {
-                                                                                       payment_hash,
-                                                                                       payment_secret: Some(data.payment_secret),
-                                                                                       amt: total_value,
-                                                                               });
+                                                               };
+
+                                                               macro_rules! fail_htlc {
+                                                                       ($htlc: expr) => {
+                                                                               let mut htlc_msat_height_data = byte_utils::be64_to_array($htlc.value).to_vec();
+                                                                               htlc_msat_height_data.extend_from_slice(
+                                                                                       &byte_utils::be32_to_array(self.best_block.read().unwrap().height()),
+                                                                               );
+                                                                               failed_forwards.push((HTLCSource::PreviousHopData(HTLCPreviousHopData {
+                                                                                               short_channel_id: $htlc.prev_hop.short_channel_id,
+                                                                                               outpoint: prev_funding_outpoint,
+                                                                                               htlc_id: $htlc.prev_hop.htlc_id,
+                                                                                               incoming_packet_shared_secret: $htlc.prev_hop.incoming_packet_shared_secret,
+                                                                                       }), payment_hash,
+                                                                                       HTLCFailReason::Reason { failure_code: 0x4000 | 15, data: htlc_msat_height_data }
+                                                                               ));
                                                                        }
-                                                               } else {
-                                                                       new_events.push(events::Event::PaymentReceived {
-                                                                               payment_hash,
-                                                                               payment_secret: None,
-                                                                               amt: amt_to_forward,
-                                                                       });
                                                                }
+
+                                                               // Check that the payment hash and secret are known. Note that we
+                                                               // MUST take care to handle the "unknown payment hash" and
+                                                               // "incorrect payment secret" cases here identically or we'd expose
+                                                               // that we are the ultimate recipient of the given payment hash.
+                                                               // Further, we must not expose whether we have any other HTLCs
+                                                               // associated with the same payment_hash pending or not.
+                                                               let mut payment_secrets = self.pending_inbound_payments.lock().unwrap();
+                                                               match payment_secrets.entry(payment_hash) {
+                                                                       hash_map::Entry::Vacant(_) => {
+                                                                               log_trace!(self.logger, "Failing new HTLC with payment_hash {} as we didn't have a corresponding inbound payment.", log_bytes!(payment_hash.0));
+                                                                               fail_htlc!(claimable_htlc);
+                                                                       },
+                                                                       hash_map::Entry::Occupied(inbound_payment) => {
+                                                                               if inbound_payment.get().payment_secret != payment_data.payment_secret {
+                                                                                       log_trace!(self.logger, "Failing new HTLC with payment_hash {} as it didn't match our expected payment secret.", log_bytes!(payment_hash.0));
+                                                                                       fail_htlc!(claimable_htlc);
+                                                                               } else if inbound_payment.get().min_value_msat.is_some() && payment_data.total_msat < inbound_payment.get().min_value_msat.unwrap() {
+                                                                                       log_trace!(self.logger, "Failing new HTLC with payment_hash {} as it didn't match our minimum value (had {}, needed {}).",
+                                                                                               log_bytes!(payment_hash.0), payment_data.total_msat, inbound_payment.get().min_value_msat.unwrap());
+                                                                                       fail_htlc!(claimable_htlc);
+                                                                               } else {
+                                                                                       let mut total_value = 0;
+                                                                                       let htlcs = channel_state.claimable_htlcs.entry(payment_hash)
+                                                                                               .or_insert(Vec::new());
+                                                                                       htlcs.push(claimable_htlc);
+                                                                                       for htlc in htlcs.iter() {
+                                                                                               total_value += htlc.value;
+                                                                                               if htlc.payment_data.total_msat != payment_data.total_msat {
+                                                                                                       log_trace!(self.logger, "Failing HTLCs with payment_hash {} as the HTLCs had inconsistent total values (eg {} and {})",
+                                                                                                               log_bytes!(payment_hash.0), payment_data.total_msat, htlc.payment_data.total_msat);
+                                                                                                       total_value = msgs::MAX_VALUE_MSAT;
+                                                                                               }
+                                                                                               if total_value >= msgs::MAX_VALUE_MSAT { break; }
+                                                                                       }
+                                                                                       if total_value >= msgs::MAX_VALUE_MSAT || total_value > payment_data.total_msat {
+                                                                                               log_trace!(self.logger, "Failing HTLCs with payment_hash {} as the total value {} ran over expected value {} (or HTLCs were inconsistent)",
+                                                                                                       log_bytes!(payment_hash.0), total_value, payment_data.total_msat);
+                                                                                               for htlc in htlcs.iter() {
+                                                                                                       fail_htlc!(htlc);
+                                                                                               }
+                                                                                       } else if total_value == payment_data.total_msat {
+                                                                                               new_events.push(events::Event::PaymentReceived {
+                                                                                                       payment_hash,
+                                                                                                       payment_secret: payment_data.payment_secret,
+                                                                                                       amt: total_value,
+                                                                                                       user_payment_id: inbound_payment.get().user_payment_id,
+                                                                                               });
+                                                                                               // Only ever generate at most one PaymentReceived
+                                                                                               // per registered payment_hash, even if it isn't
+                                                                                               // claimed.
+                                                                                               inbound_payment.remove_entry();
+                                                                                       } else {
+                                                                                               // Nothing to do - we haven't reached the total
+                                                                                               // payment value yet, wait until we receive more
+                                                                                               // MPP parts.
+                                                                                       }
+                                                                               }
+                                                                       },
+                                                               };
                                                        },
                                                        HTLCForwardInfo::AddHTLC { .. } => {
                                                                panic!("short_channel_id == 0 should imply any pending_forward entries are of type Receive");
@@ -2056,11 +2125,11 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
        /// along the path (including in our own channel on which we received it).
        /// Returns false if no payment was found to fail backwards, true if the process of failing the
        /// HTLC backwards has been started.
-       pub fn fail_htlc_backwards(&self, payment_hash: &PaymentHash, payment_secret: &Option<PaymentSecret>) -> bool {
+       pub fn fail_htlc_backwards(&self, payment_hash: &PaymentHash) -> bool {
                let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                let mut channel_state = Some(self.channel_state.lock().unwrap());
-               let removed_source = channel_state.as_mut().unwrap().claimable_htlcs.remove(&(*payment_hash, *payment_secret));
+               let removed_source = channel_state.as_mut().unwrap().claimable_htlcs.remove(payment_hash);
                if let Some(mut sources) = removed_source {
                        for htlc in sources.drain(..) {
                                if channel_state.is_none() { channel_state = Some(self.channel_state.lock().unwrap()); }
@@ -2225,24 +2294,22 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
        /// generating message events for the net layer to claim the payment, if possible. Thus, you
        /// should probably kick the net layer to go send messages if this returns true!
        ///
-       /// You must specify the expected amounts for this HTLC, and we will only claim HTLCs
-       /// available within a few percent of the expected amount. This is critical for several
-       /// reasons : a) it avoids providing senders with `proof-of-payment` (in the form of the
-       /// payment_preimage without having provided the full value and b) it avoids certain
-       /// privacy-breaking recipient-probing attacks which may reveal payment activity to
-       /// motivated attackers.
-       ///
-       /// Note that the privacy concerns in (b) are not relevant in payments with a payment_secret
-       /// set. Thus, for such payments we will claim any payments which do not under-pay.
+       /// Note that if you did not set an `amount_msat` when calling [`create_inbound_payment`] or
+       /// [`create_inbound_payment_for_hash`] you must check that the amount in the `PaymentReceived`
+       /// event matches your expectation. If you fail to do so and call this method, you may provide
+       /// the sender "proof-of-payment" when they did not fulfill the full expected payment.
        ///
        /// May panic if called except in response to a PaymentReceived event.
-       pub fn claim_funds(&self, payment_preimage: PaymentPreimage, payment_secret: &Option<PaymentSecret>, expected_amount: u64) -> bool {
+       ///
+       /// [`create_inbound_payment`]: Self::create_inbound_payment
+       /// [`create_inbound_payment_for_hash`]: Self::create_inbound_payment_for_hash
+       pub fn claim_funds(&self, payment_preimage: PaymentPreimage) -> bool {
                let payment_hash = PaymentHash(Sha256::hash(&payment_preimage.0).into_inner());
 
                let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
                let mut channel_state = Some(self.channel_state.lock().unwrap());
-               let removed_source = channel_state.as_mut().unwrap().claimable_htlcs.remove(&(payment_hash, *payment_secret));
+               let removed_source = channel_state.as_mut().unwrap().claimable_htlcs.remove(&payment_hash);
                if let Some(mut sources) = removed_source {
                        assert!(!sources.is_empty());
 
@@ -2257,27 +2324,19 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                        // we got all the HTLCs and then a channel closed while we were waiting for the user to
                        // provide the preimage, so worrying too much about the optimal handling isn't worth
                        // it.
-
-                       let (is_mpp, mut valid_mpp) = if let &Some(ref data) = &sources[0].payment_data {
-                               assert!(payment_secret.is_some());
-                               (true, data.total_msat >= expected_amount)
-                       } else {
-                               assert!(payment_secret.is_none());
-                               (false, false)
-                       };
-
+                       let mut valid_mpp = true;
                        for htlc in sources.iter() {
-                               if !is_mpp || !valid_mpp { break; }
                                if let None = channel_state.as_ref().unwrap().short_to_id.get(&htlc.prev_hop.short_channel_id) {
                                        valid_mpp = false;
+                                       break;
                                }
                        }
 
                        let mut errs = Vec::new();
                        let mut claimed_any_htlcs = false;
                        for htlc in sources.drain(..) {
-                               if channel_state.is_none() { channel_state = Some(self.channel_state.lock().unwrap()); }
-                               if (is_mpp && !valid_mpp) || (!is_mpp && (htlc.value < expected_amount || htlc.value > expected_amount * 2)) {
+                               if !valid_mpp {
+                                       if channel_state.is_none() { channel_state = Some(self.channel_state.lock().unwrap()); }
                                        let mut htlc_msat_height_data = byte_utils::be64_to_array(htlc.value).to_vec();
                                        htlc_msat_height_data.extend_from_slice(&byte_utils::be32_to_array(
                                                        self.best_block.read().unwrap().height()));
@@ -2294,10 +2353,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                claimed_any_htlcs = true;
                                                        } else { errs.push(e); }
                                                },
-                                               Err(None) if is_mpp => unreachable!("We already checked for channel existence, we can't fail here!"),
-                                               Err(None) => {
-                                                       log_warn!(self.logger, "Channel we expected to claim an HTLC from was closed.");
-                                               },
+                                               Err(None) => unreachable!("We already checked for channel existence, we can't fail here!"),
                                                Ok(()) => claimed_any_htlcs = true,
                                        }
                                }
@@ -3321,6 +3377,92 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                        self.finish_force_close_channel(failure);
                }
        }
+
+       fn set_payment_hash_secret_map(&self, payment_hash: PaymentHash, payment_preimage: Option<PaymentPreimage>, min_value_msat: Option<u64>, invoice_expiry_delta_secs: u32, user_payment_id: u64) -> Result<PaymentSecret, APIError> {
+               assert!(invoice_expiry_delta_secs <= 60*60*24*365); // Sadly bitcoin timestamps are u32s, so panic before 2106
+
+               let payment_secret = PaymentSecret(self.keys_manager.get_secure_random_bytes());
+
+               let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
+               let mut payment_secrets = self.pending_inbound_payments.lock().unwrap();
+               match payment_secrets.entry(payment_hash) {
+                       hash_map::Entry::Vacant(e) => {
+                               e.insert(PendingInboundPayment {
+                                       payment_secret, min_value_msat, user_payment_id, payment_preimage,
+                                       // We assume that highest_seen_timestamp is pretty close to the current time -
+                                       // its updated when we receive a new block with the maximum time we've seen in
+                                       // a header. It should never be more than two hours in the future.
+                                       // Thus, we add two hours here as a buffer to ensure we absolutely
+                                       // never fail a payment too early.
+                                       // Note that we assume that received blocks have reasonably up-to-date
+                                       // timestamps.
+                                       expiry_time: self.highest_seen_timestamp.load(Ordering::Acquire) as u64 + invoice_expiry_delta_secs as u64 + 7200,
+                               });
+                       },
+                       hash_map::Entry::Occupied(_) => return Err(APIError::APIMisuseError { err: "Duplicate payment hash".to_owned() }),
+               }
+               Ok(payment_secret)
+       }
+
+       /// Gets a payment secret and payment hash for use in an invoice given to a third party wishing
+       /// to pay us.
+       ///
+       /// This differs from [`create_inbound_payment_for_hash`] only in that it generates the
+       /// [`PaymentHash`] and [`PaymentPreimage`] for you, returning the first and storing the second.
+       ///
+       /// See [`create_inbound_payment_for_hash`] for detailed documentation on behavior and requirements.
+       ///
+       /// [`create_inbound_payment_for_hash`]: Self::create_inbound_payment_for_hash
+       pub fn create_inbound_payment(&self, min_value_msat: Option<u64>, invoice_expiry_delta_secs: u32, user_payment_id: u64) -> (PaymentHash, PaymentSecret) {
+               let payment_preimage = PaymentPreimage(self.keys_manager.get_secure_random_bytes());
+               let payment_hash = PaymentHash(Sha256::hash(&payment_preimage.0).into_inner());
+
+               (payment_hash,
+                       self.set_payment_hash_secret_map(payment_hash, Some(payment_preimage), min_value_msat, invoice_expiry_delta_secs, user_payment_id)
+                               .expect("RNG Generated Duplicate PaymentHash"))
+       }
+
+       /// Gets a [`PaymentSecret`] for a given [`PaymentHash`], for which the payment preimage is
+       /// stored external to LDK.
+       ///
+       /// A [`PaymentReceived`] event will only be generated if the [`PaymentSecret`] matches a
+       /// payment secret fetched via this method or [`create_inbound_payment`], and which is at least
+       /// the `min_value_msat` provided here, if one is provided.
+       ///
+       /// The [`PaymentHash`] (and corresponding [`PaymentPreimage`]) must be globally unique. This
+       /// method may return an Err if another payment with the same payment_hash is still pending.
+       ///
+       /// `user_payment_id` will be provided back in [`PaymentReceived::user_payment_id`] events to
+       /// allow tracking of which events correspond with which calls to this and
+       /// [`create_inbound_payment`]. `user_payment_id` has no meaning inside of LDK, it is simply
+       /// copied to events and otherwise ignored. It may be used to correlate PaymentReceived events
+       /// with invoice metadata stored elsewhere.
+       ///
+       /// `min_value_msat` should be set if the invoice being generated contains a value. Any payment
+       /// received for the returned [`PaymentHash`] will be required to be at least `min_value_msat`
+       /// before a [`PaymentReceived`] event will be generated, ensuring that we do not provide the
+       /// sender "proof-of-payment" unless they have paid the required amount.
+       ///
+       /// `invoice_expiry_delta_secs` describes the number of seconds that the invoice is valid for
+       /// in excess of the current time. This should roughly match the expiry time set in the invoice.
+       /// After this many seconds, we will remove the inbound payment, resulting in any attempts to
+       /// pay the invoice failing. The BOLT spec suggests 7,200 secs as a default validity time for
+       /// invoices when no timeout is set.
+       ///
+       /// Note that we use block header time to time-out pending inbound payments (with some margin
+       /// to compensate for the inaccuracy of block header timestamps). Thus, in practice we will
+       /// accept a payment and generate a [`PaymentReceived`] event for some time after the expiry.
+       /// If you need exact expiry semantics, you should enforce them upon receipt of
+       /// [`PaymentReceived`].
+       ///
+       /// May panic if `invoice_expiry_delta_secs` is greater than one year.
+       ///
+       /// [`create_inbound_payment`]: Self::create_inbound_payment
+       /// [`PaymentReceived`]: events::Event::PaymentReceived
+       /// [`PaymentReceived::user_payment_id`]: events::Event::PaymentReceived::user_payment_id
+       pub fn create_inbound_payment_for_hash(&self, payment_hash: PaymentHash, min_value_msat: Option<u64>, invoice_expiry_delta_secs: u32, user_payment_id: u64) -> Result<PaymentSecret, APIError> {
+               self.set_payment_hash_secret_map(payment_hash, None, min_value_msat, invoice_expiry_delta_secs, user_payment_id)
+       }
 }
 
 impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> MessageSendEventsProvider for ChannelManager<Signer, M, T, K, F, L>
@@ -3433,18 +3575,24 @@ where
 
                self.do_chain_event(Some(height), |channel| channel.best_block_updated(height, header.time));
 
-               loop {
-                       // Update last_node_announcement_serial to be the max of its current value and the
-                       // block timestamp. This should keep us close to the current time without relying on
-                       // having an explicit local time source.
-                       // Just in case we end up in a race, we loop until we either successfully update
-                       // last_node_announcement_serial or decide we don't need to.
-                       let old_serial = self.last_node_announcement_serial.load(Ordering::Acquire);
-                       if old_serial >= header.time as usize { break; }
-                       if self.last_node_announcement_serial.compare_exchange(old_serial, header.time as usize, Ordering::AcqRel, Ordering::Relaxed).is_ok() {
-                               break;
+               macro_rules! max_time {
+                       ($timestamp: expr) => {
+                               loop {
+                                       // Update $timestamp to be the max of its current value and the block
+                                       // timestamp. This should keep us close to the current time without relying on
+                                       // having an explicit local time source.
+                                       // Just in case we end up in a race, we loop until we either successfully
+                                       // update $timestamp or decide we don't need to.
+                                       let old_serial = $timestamp.load(Ordering::Acquire);
+                                       if old_serial >= header.time as usize { break; }
+                                       if $timestamp.compare_exchange(old_serial, header.time as usize, Ordering::AcqRel, Ordering::Relaxed).is_ok() {
+                                               break;
+                                       }
+                               }
                        }
                }
+               max_time!(self.last_node_announcement_serial);
+               max_time!(self.highest_seen_timestamp);
        }
 
        fn get_relevant_txids(&self) -> Vec<Txid> {
@@ -3542,7 +3690,7 @@ where
                        });
 
                        if let Some(height) = height_opt {
-                               channel_state.claimable_htlcs.retain(|&(ref payment_hash, _), htlcs| {
+                               channel_state.claimable_htlcs.retain(|payment_hash, htlcs| {
                                        htlcs.retain(|htlc| {
                                                // If height is approaching the number of blocks we think it takes us to get
                                                // our commitment transaction confirmed before the HTLC expires, plus the
@@ -3916,7 +4064,8 @@ impl Writeable for PendingHTLCInfo {
                        },
                        &PendingHTLCRouting::Receive { ref payment_data, ref incoming_cltv_expiry } => {
                                1u8.write(writer)?;
-                               payment_data.write(writer)?;
+                               payment_data.payment_secret.write(writer)?;
+                               payment_data.total_msat.write(writer)?;
                                incoming_cltv_expiry.write(writer)?;
                        },
                }
@@ -3937,7 +4086,10 @@ impl Readable for PendingHTLCInfo {
                                        short_channel_id: Readable::read(reader)?,
                                },
                                1u8 => PendingHTLCRouting::Receive {
-                                       payment_data: Readable::read(reader)?,
+                                       payment_data: msgs::FinalOnionHopData {
+                                               payment_secret: Readable::read(reader)?,
+                                               total_msat: Readable::read(reader)?,
+                                       },
                                        incoming_cltv_expiry: Readable::read(reader)?,
                                },
                                _ => return Err(DecodeError::InvalidValue),
@@ -4009,12 +4161,29 @@ impl_writeable!(HTLCPreviousHopData, 0, {
        incoming_packet_shared_secret
 });
 
-impl_writeable!(ClaimableHTLC, 0, {
-       prev_hop,
-       value,
-       payment_data,
-       cltv_expiry
-});
+impl Writeable for ClaimableHTLC {
+       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+               self.prev_hop.write(writer)?;
+               self.value.write(writer)?;
+               self.payment_data.payment_secret.write(writer)?;
+               self.payment_data.total_msat.write(writer)?;
+               self.cltv_expiry.write(writer)
+       }
+}
+
+impl Readable for ClaimableHTLC {
+       fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+               Ok(ClaimableHTLC {
+                       prev_hop: Readable::read(reader)?,
+                       value: Readable::read(reader)?,
+                       payment_data: msgs::FinalOnionHopData {
+                               payment_secret: Readable::read(reader)?,
+                               total_msat: Readable::read(reader)?,
+                       },
+                       cltv_expiry: Readable::read(reader)?,
+               })
+       }
+}
 
 impl Writeable for HTLCSource {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
@@ -4116,6 +4285,14 @@ impl Readable for HTLCForwardInfo {
        }
 }
 
+impl_writeable!(PendingInboundPayment, 0, {
+       payment_secret,
+       expiry_time,
+       user_payment_id,
+       payment_preimage,
+       min_value_msat
+});
+
 impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> Writeable for ChannelManager<Signer, M, T, K, F, L>
        where M::Target: chain::Watch<Signer>,
         T::Target: BroadcasterInterface,
@@ -4195,6 +4372,14 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> Writeable f
                }
 
                (self.last_node_announcement_serial.load(Ordering::Acquire) as u32).write(writer)?;
+               (self.highest_seen_timestamp.load(Ordering::Acquire) as u32).write(writer)?;
+
+               let pending_inbound_payments = self.pending_inbound_payments.lock().unwrap();
+               (pending_inbound_payments.len() as u64).write(writer)?;
+               for (hash, pending_payment) in pending_inbound_payments.iter() {
+                       hash.write(writer)?;
+                       pending_payment.write(writer)?;
+               }
 
                Ok(())
        }
@@ -4425,6 +4610,15 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                }
 
                let last_node_announcement_serial: u32 = Readable::read(reader)?;
+               let highest_seen_timestamp: u32 = Readable::read(reader)?;
+
+               let pending_inbound_payment_count: u64 = Readable::read(reader)?;
+               let mut pending_inbound_payments: HashMap<PaymentHash, PendingInboundPayment> = HashMap::with_capacity(cmp::min(pending_inbound_payment_count as usize, MAX_ALLOC_SIZE/(3*32)));
+               for _ in 0..pending_inbound_payment_count {
+                       if pending_inbound_payments.insert(Readable::read(reader)?, Readable::read(reader)?).is_some() {
+                               return Err(DecodeError::InvalidValue);
+                       }
+               }
 
                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&args.keys_manager.get_secure_random_bytes());
@@ -4444,11 +4638,14 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
                                claimable_htlcs,
                                pending_msg_events: Vec::new(),
                        }),
+                       pending_inbound_payments: Mutex::new(pending_inbound_payments),
+
                        our_network_key: args.keys_manager.get_node_secret(),
                        our_network_pubkey: PublicKey::from_secret_key(&secp_ctx, &args.keys_manager.get_node_secret()),
                        secp_ctx,
 
                        last_node_announcement_serial: AtomicUsize::new(last_node_announcement_serial as usize),
+                       highest_seen_timestamp: AtomicUsize::new(highest_seen_timestamp as usize),
 
                        per_peer_state: RwLock::new(per_peer_state),
 
@@ -4531,7 +4728,7 @@ pub mod bench {
        use chain::channelmonitor::Persist;
        use chain::keysinterface::{KeysManager, InMemorySigner};
        use ln::channelmanager::{BestBlock, ChainParameters, ChannelManager, PaymentHash, PaymentPreimage};
-       use ln::features::InitFeatures;
+       use ln::features::{InitFeatures, InvoiceFeatures};
        use ln::functional_test_utils::*;
        use ln::msgs::ChannelMessageHandler;
        use routing::network_graph::NetworkGraph;
@@ -4625,15 +4822,20 @@ pub mod bench {
 
                let dummy_graph = NetworkGraph::new(genesis_hash);
 
+               let mut payment_count: u64 = 0;
                macro_rules! send_payment {
                        ($node_a: expr, $node_b: expr) => {
                                let usable_channels = $node_a.list_usable_channels();
-                               let route = get_route(&$node_a.get_our_node_id(), &dummy_graph, &$node_b.get_our_node_id(), None, Some(&usable_channels.iter().map(|r| r).collect::<Vec<_>>()), &[], 10_000, TEST_FINAL_CLTV, &logger_a).unwrap();
+                               let route = get_route(&$node_a.get_our_node_id(), &dummy_graph, &$node_b.get_our_node_id(), Some(InvoiceFeatures::known()),
+                                       Some(&usable_channels.iter().map(|r| r).collect::<Vec<_>>()), &[], 10_000, TEST_FINAL_CLTV, &logger_a).unwrap();
 
-                               let payment_preimage = PaymentPreimage([0; 32]);
+                               let mut payment_preimage = PaymentPreimage([0; 32]);
+                               payment_preimage.0[0..8].copy_from_slice(&payment_count.to_le_bytes());
+                               payment_count += 1;
                                let payment_hash = PaymentHash(Sha256::hash(&payment_preimage.0[..]).into_inner());
+                               let payment_secret = $node_b.create_inbound_payment_for_hash(payment_hash, None, 7200, 0).unwrap();
 
-                               $node_a.send_payment(&route, payment_hash, &None).unwrap();
+                               $node_a.send_payment(&route, payment_hash, &Some(payment_secret)).unwrap();
                                let payment_event = SendEvent::from_event($node_a.get_and_clear_pending_msg_events().pop().unwrap());
                                $node_b.handle_update_add_htlc(&$node_a.get_our_node_id(), &payment_event.msgs[0]);
                                $node_b.handle_commitment_signed(&$node_a.get_our_node_id(), &payment_event.commitment_msg);
@@ -4643,8 +4845,8 @@ pub mod bench {
                                $node_b.handle_revoke_and_ack(&$node_a.get_our_node_id(), &get_event_msg!(NodeHolder { node: &$node_a }, MessageSendEvent::SendRevokeAndACK, $node_b.get_our_node_id()));
 
                                expect_pending_htlcs_forwardable!(NodeHolder { node: &$node_b });
-                               expect_payment_received!(NodeHolder { node: &$node_b }, payment_hash, 10_000);
-                               assert!($node_b.claim_funds(payment_preimage, &None, 10_000));
+                               expect_payment_received!(NodeHolder { node: &$node_b }, payment_hash, payment_secret, 10_000);
+                               assert!($node_b.claim_funds(payment_preimage));
 
                                match $node_b.get_and_clear_pending_msg_events().pop().unwrap() {
                                        MessageSendEvent::UpdateHTLCs { node_id, updates } => {