git.bitcoin.ninja Git - rust-lightning/blob - lightning/src/blinded_path/payment.rs

   1 //! Data structures and methods for constructing [`BlindedPath`]s to send a payment over.
   2 //!
   3 //! [`BlindedPath`]: crate::blinded_path::BlindedPath
   4
   5 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
   6
   7 use crate::blinded_path::BlindedHop;
   8 use crate::blinded_path::utils;
   9 use crate::io;
  10 use crate::ln::PaymentSecret;
  11 use crate::ln::features::BlindedHopFeatures;
  12 use crate::ln::msgs::DecodeError;
  13 use crate::offers::invoice::BlindedPayInfo;
  14 use crate::prelude::*;
  15 use crate::util::ser::{Readable, Writeable, Writer};
  16
  17 use core::convert::TryFrom;
  18
  19 /// Data to construct a [`BlindedHop`] for forwarding a payment.
  20 pub struct ForwardTlvs {
  21         /// The short channel id this payment should be forwarded out over.
  22         short_channel_id: u64,
  23         /// Payment parameters for relaying over [`Self::short_channel_id`].
  24         payment_relay: PaymentRelay,
  25         /// Payment constraints for relaying over [`Self::short_channel_id`].
  26         payment_constraints: PaymentConstraints,
  27         /// Supported and required features when relaying a payment onion containing this object's
  28         /// corresponding [`BlindedHop::encrypted_payload`].
  29         ///
  30         /// [`BlindedHop::encrypted_payload`]: crate::blinded_path::BlindedHop::encrypted_payload
  31         features: BlindedHopFeatures,
  32 }
  33
  34 /// Data to construct a [`BlindedHop`] for receiving a payment. This payload is custom to LDK and
  35 /// may not be valid if received by another lightning implementation.
  36 pub struct ReceiveTlvs {
  37         /// Used to authenticate the sender of a payment to the receiver and tie MPP HTLCs together.
  38         payment_secret: PaymentSecret,
  39         /// Constraints for the receiver of this payment.
  40         payment_constraints: PaymentConstraints,
  41 }
  42
  43 /// Data to construct a [`BlindedHop`] for sending a payment over.
  44 ///
  45 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  46 pub(crate) enum BlindedPaymentTlvs {
  47         /// This blinded payment data is for a forwarding node.
  48         Forward(ForwardTlvs),
  49         /// This blinded payment data is for the receiving node.
  50         Receive(ReceiveTlvs),
  51 }
  52
  53 // Used to include forward and receive TLVs in the same iterator for encoding.
  54 enum BlindedPaymentTlvsRef<'a> {
  55         Forward(&'a ForwardTlvs),
  56         Receive(&'a ReceiveTlvs),
  57 }
  58
  59 /// Parameters for relaying over a given [`BlindedHop`].
  60 ///
  61 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  62 pub struct PaymentRelay {
  63         /// Number of blocks subtracted from an incoming HTLC's `cltv_expiry` for this [`BlindedHop`].
  64         ///
  65         ///[`BlindedHop`]: crate::blinded_path::BlindedHop
  66         pub cltv_expiry_delta: u16,
  67         /// Liquidity fee charged (in millionths of the amount transferred) for relaying a payment over
  68         /// this [`BlindedHop`], (i.e., 10,000 is 1%).
  69         ///
  70         ///[`BlindedHop`]: crate::blinded_path::BlindedHop
  71         pub fee_proportional_millionths: u32,
  72         /// Base fee charged (in millisatoshi) for relaying a payment over this [`BlindedHop`].
  73         ///
  74         ///[`BlindedHop`]: crate::blinded_path::BlindedHop
  75         pub fee_base_msat: u32,
  76 }
  77
  78 /// Constraints for relaying over a given [`BlindedHop`].
  79 ///
  80 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
  81 pub struct PaymentConstraints {
  82         /// The maximum total CLTV delta that is acceptable when relaying a payment over this
  83         /// [`BlindedHop`].
  84         ///
  85         ///[`BlindedHop`]: crate::blinded_path::BlindedHop
  86         pub max_cltv_expiry: u32,
  87         /// The minimum value, in msat, that may be relayed over this [`BlindedHop`].
  88         pub htlc_minimum_msat: u64,
  89 }
  90
  91 impl_writeable_tlv_based!(ForwardTlvs, {
  92         (2, short_channel_id, required),
  93         (10, payment_relay, required),
  94         (12, payment_constraints, required),
  95         (14, features, required),
  96 });
  97
  98 impl_writeable_tlv_based!(ReceiveTlvs, {
  99         (12, payment_constraints, required),
 100         (65536, payment_secret, required),
 101 });
 102
 103 impl<'a> Writeable for BlindedPaymentTlvsRef<'a> {
 104         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 105                 // TODO: write padding
 106                 match self {
 107                         Self::Forward(tlvs) => tlvs.write(w)?,
 108                         Self::Receive(tlvs) => tlvs.write(w)?,
 109                 }
 110                 Ok(())
 111         }
 112 }
 113
 114 impl Readable for BlindedPaymentTlvs {
 115         fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
 116                 _init_and_read_tlv_stream!(r, {
 117                         (1, _padding, option),
 118                         (2, scid, option),
 119                         (10, payment_relay, option),
 120                         (12, payment_constraints, required),
 121                         (14, features, option),
 122                         (65536, payment_secret, option),
 123                 });
 124                 let _padding: Option<utils::Padding> = _padding;
 125
 126                 if let Some(short_channel_id) = scid {
 127                         if payment_secret.is_some() { return Err(DecodeError::InvalidValue) }
 128                         Ok(BlindedPaymentTlvs::Forward(ForwardTlvs {
 129                                 short_channel_id,
 130                                 payment_relay: payment_relay.ok_or(DecodeError::InvalidValue)?,
 131                                 payment_constraints: payment_constraints.0.unwrap(),
 132                                 features: features.ok_or(DecodeError::InvalidValue)?,
 133                         }))
 134                 } else {
 135                         if payment_relay.is_some() || features.is_some() { return Err(DecodeError::InvalidValue) }
 136                         Ok(BlindedPaymentTlvs::Receive(ReceiveTlvs {
 137                                 payment_secret: payment_secret.ok_or(DecodeError::InvalidValue)?,
 138                                 payment_constraints: payment_constraints.0.unwrap(),
 139                         }))
 140                 }
 141         }
 142 }
 143
 144 /// Construct blinded payment hops for the given `intermediate_nodes` and payee info.
 145 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 146         secp_ctx: &Secp256k1<T>, intermediate_nodes: &[(PublicKey, ForwardTlvs)],
 147         payee_node_id: PublicKey, payee_tlvs: ReceiveTlvs, session_priv: &SecretKey
 148 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
 149         let pks = intermediate_nodes.iter().map(|(pk, _)| pk)
 150                 .chain(core::iter::once(&payee_node_id));
 151         let tlvs = intermediate_nodes.iter().map(|(_, tlvs)| BlindedPaymentTlvsRef::Forward(tlvs))
 152                 .chain(core::iter::once(BlindedPaymentTlvsRef::Receive(&payee_tlvs)));
 153         utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
 154 }
 155
 156 pub(super) fn compute_payinfo(
 157         intermediate_nodes: &[(PublicKey, ForwardTlvs)], payee_tlvs: &ReceiveTlvs
 158 ) -> Result<BlindedPayInfo, ()> {
 159         let mut curr_base_fee: u64 = 0;
 160         let mut curr_prop_mil: u64 = 0;
 161         let mut cltv_expiry_delta: u16 = 0;
 162         for (_, tlvs) in intermediate_nodes.iter().rev() {
 163                 // In the future, we'll want to take the intersection of all supported features for the
 164                 // `BlindedPayInfo`, but there are no features in that context right now.
 165                 if tlvs.features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
 166
 167                 let next_base_fee = tlvs.payment_relay.fee_base_msat as u64;
 168                 let next_prop_mil = tlvs.payment_relay.fee_proportional_millionths as u64;
 169                 // Use integer arithmetic to compute `ceil(a/b)` as `(a+b-1)/b`
 170                 // ((curr_base_fee * (1_000_000 + next_prop_mil)) / 1_000_000) + next_base_fee
 171                 curr_base_fee = curr_base_fee.checked_mul(1_000_000 + next_prop_mil)
 172                         .and_then(|f| f.checked_add(1_000_000 - 1))
 173                         .map(|f| f / 1_000_000)
 174                         .and_then(|f| f.checked_add(next_base_fee))
 175                         .ok_or(())?;
 176                 // ceil(((curr_prop_mil + 1_000_000) * (next_prop_mil + 1_000_000)) / 1_000_000) - 1_000_000
 177                 curr_prop_mil = curr_prop_mil.checked_add(1_000_000)
 178                         .and_then(|f1| next_prop_mil.checked_add(1_000_000).and_then(|f2| f2.checked_mul(f1)))
 179                         .and_then(|f| f.checked_add(1_000_000 - 1))
 180                         .map(|f| f / 1_000_000)
 181                         .and_then(|f| f.checked_sub(1_000_000))
 182                         .ok_or(())?;
 183
 184                 cltv_expiry_delta = cltv_expiry_delta.checked_add(tlvs.payment_relay.cltv_expiry_delta).ok_or(())?;
 185         }
 186         Ok(BlindedPayInfo {
 187                 fee_base_msat: u32::try_from(curr_base_fee).map_err(|_| ())?,
 188                 fee_proportional_millionths: u32::try_from(curr_prop_mil).map_err(|_| ())?,
 189                 cltv_expiry_delta,
 190                 htlc_minimum_msat: 1, // TODO
 191                 htlc_maximum_msat: 21_000_000 * 100_000_000 * 1_000, // TODO
 192                 features: BlindedHopFeatures::empty(),
 193         })
 194 }
 195
 196 impl_writeable_msg!(PaymentRelay, {
 197         cltv_expiry_delta,
 198         fee_proportional_millionths,
 199         fee_base_msat
 200 }, {});
 201
 202 impl_writeable_msg!(PaymentConstraints, {
 203         max_cltv_expiry,
 204         htlc_minimum_msat
 205 }, {});
 206
 207 #[cfg(test)]
 208 mod tests {
 209         use bitcoin::secp256k1::PublicKey;
 210         use crate::blinded_path::payment::{ForwardTlvs, ReceiveTlvs, PaymentConstraints, PaymentRelay};
 211         use crate::ln::PaymentSecret;
 212         use crate::ln::features::BlindedHopFeatures;
 213
 214         #[test]
 215         fn compute_payinfo() {
 216                 // Taken from the spec example for aggregating blinded payment info. See
 217                 // https://github.com/lightning/bolts/blob/master/proposals/route-blinding.md#blinded-payments
 218                 let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
 219                 let intermediate_nodes = vec![(dummy_pk, ForwardTlvs {
 220                         short_channel_id: 0,
 221                         payment_relay: PaymentRelay {
 222                                 cltv_expiry_delta: 144,
 223                                 fee_proportional_millionths: 500,
 224                                 fee_base_msat: 100,
 225                         },
 226                         payment_constraints: PaymentConstraints {
 227                                 max_cltv_expiry: 0,
 228                                 htlc_minimum_msat: 100,
 229                         },
 230                         features: BlindedHopFeatures::empty(),
 231                 }), (dummy_pk, ForwardTlvs {
 232                         short_channel_id: 0,
 233                         payment_relay: PaymentRelay {
 234                                 cltv_expiry_delta: 144,
 235                                 fee_proportional_millionths: 500,
 236                                 fee_base_msat: 100,
 237                         },
 238                         payment_constraints: PaymentConstraints {
 239                                 max_cltv_expiry: 0,
 240                                 htlc_minimum_msat: 1_000,
 241                         },
 242                         features: BlindedHopFeatures::empty(),
 243                 })];
 244                 let recv_tlvs = ReceiveTlvs {
 245                         payment_secret: PaymentSecret([0; 32]),
 246                         payment_constraints: PaymentConstraints {
 247                                 max_cltv_expiry: 0,
 248                                 htlc_minimum_msat: 1,
 249                         },
 250                 };
 251                 let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs).unwrap();
 252                 assert_eq!(blinded_payinfo.fee_base_msat, 201);
 253                 assert_eq!(blinded_payinfo.fee_proportional_millionths, 1001);
 254                 assert_eq!(blinded_payinfo.cltv_expiry_delta, 288);
 255         }
 256
 257         #[test]
 258         fn compute_payinfo_1_hop() {
 259                 let recv_tlvs = ReceiveTlvs {
 260                         payment_secret: PaymentSecret([0; 32]),
 261                         payment_constraints: PaymentConstraints {
 262                                 max_cltv_expiry: 0,
 263                                 htlc_minimum_msat: 1,
 264                         },
 265                 };
 266                 let blinded_payinfo = super::compute_payinfo(&[], &recv_tlvs).unwrap();
 267                 assert_eq!(blinded_payinfo.fee_base_msat, 0);
 268                 assert_eq!(blinded_payinfo.fee_proportional_millionths, 0);
 269                 assert_eq!(blinded_payinfo.cltv_expiry_delta, 0);
 270         }
 271 }