public static peel_onion method on OnionMessenger
authorEvan Feenstra <evanfeenstra@gmail.com>
Tue, 26 Sep 2023 18:29:16 +0000 (11:29 -0700)
committerEvan Feenstra <evanfeenstra@gmail.com>
Tue, 17 Oct 2023 21:48:09 +0000 (14:48 -0700)
lightning/src/onion_message/messenger.rs
lightning/src/onion_message/mod.rs

index 03dc6a5b002f01be6e706396190f1eddeb84f839..1a0145441e2e45f2f8bfb17c0a8c9f54bf1b4f4c 100644 (file)
@@ -246,6 +246,14 @@ pub trait CustomOnionMessageHandler {
        fn read_custom_message<R: io::Read>(&self, message_type: u64, buffer: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
 }
 
+/// A processed incoming onion message, containing either a Forward (another onion message)
+/// or a Receive payload with decrypted contents.
+pub enum PeeledOnion<CM: CustomOnionMessageContents> {
+       /// Forwarded onion, with the next node id and a new onion
+       Forward(PublicKey, msgs::OnionMessage),
+       /// Received onion message, with decrypted contents, path_id, and reply path
+       Receive(OnionMessageContents<CM>, Option<[u8; 32]>, Option<BlindedPath>)
+}
 
 /// Create an onion message with contents `message` to the destination of `path`.
 /// Returns (introduction_node_id, onion_msg)
@@ -304,6 +312,101 @@ where
        }))
 }
 
+/// Decode one layer of an incoming onion message
+/// Returns either a Forward (another onion message), or Receive (decrypted content)
+pub fn peel_onion<NS: Deref, L: Deref, CMH: Deref>(
+       node_signer: NS, secp_ctx: &Secp256k1<secp256k1::All>, logger: L, custom_handler: CMH,
+       msg: &msgs::OnionMessage,
+) -> Result<PeeledOnion<<<CMH>::Target as CustomOnionMessageHandler>::CustomMessage>, ()>
+where
+       NS::Target: NodeSigner,
+       L::Target: Logger,
+       CMH::Target: CustomOnionMessageHandler,
+{
+       let control_tlvs_ss = match node_signer.ecdh(Recipient::Node, &msg.blinding_point, None) {
+               Ok(ss) => ss,
+               Err(e) =>  {
+                       log_error!(logger, "Failed to retrieve node secret: {:?}", e);
+                       return Err(());
+               }
+       };
+       let onion_decode_ss = {
+               let blinding_factor = {
+                       let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
+                       hmac.input(control_tlvs_ss.as_ref());
+                       Hmac::from_engine(hmac).into_inner()
+               };
+               match node_signer.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
+                       Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
+               {
+                       Ok(ss) => ss.secret_bytes(),
+                       Err(()) => {
+                               log_trace!(logger, "Failed to compute onion packet shared secret");
+                               return Err(());
+                       }
+               }
+       };
+       match onion_utils::decode_next_untagged_hop(
+               onion_decode_ss, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
+               (control_tlvs_ss, custom_handler.deref(), logger.deref())
+       ) {
+               Ok((Payload::Receive::<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage> {
+                       message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
+               }, None)) => {
+                       Ok(PeeledOnion::Receive(message, path_id, reply_path))
+               },
+               Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
+                       next_node_id, next_blinding_override
+               })), Some((next_hop_hmac, new_packet_bytes)))) => {
+                       // TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
+                       // blinded hop and this onion message is destined for us. In this situation, we should keep
+                       // unwrapping the onion layers to get to the final payload. Since we don't have the option
+                       // of creating blinded paths with dummy hops currently, we should be ok to not handle this
+                       // for now.
+                       let new_pubkey = match onion_utils::next_hop_pubkey(&secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
+                               Ok(pk) => pk,
+                               Err(e) => {
+                                       log_trace!(logger, "Failed to compute next hop packet pubkey: {}", e);
+                                       return Err(())
+                               }
+                       };
+                       let outgoing_packet = Packet {
+                               version: 0,
+                               public_key: new_pubkey,
+                               hop_data: new_packet_bytes,
+                               hmac: next_hop_hmac,
+                       };
+                       let onion_message = msgs::OnionMessage {
+                               blinding_point: match next_blinding_override {
+                                       Some(blinding_point) => blinding_point,
+                                       None => {
+                                               match onion_utils::next_hop_pubkey(
+                                                       &secp_ctx, msg.blinding_point, control_tlvs_ss.as_ref()
+                                               ) {
+                                                       Ok(bp) => bp,
+                                                       Err(e) => {
+                                                               log_trace!(logger, "Failed to compute next blinding point: {}", e);
+                                                               return Err(())
+                                                       }
+                                               }
+                                       }
+                               },
+                               onion_routing_packet: outgoing_packet,
+                       };
+
+                       Ok(PeeledOnion::Forward(next_node_id, onion_message))
+               },
+               Err(e) => {
+                       log_trace!(logger, "Errored decoding onion message packet: {:?}", e);
+                       Err(())
+               },
+               _ => {
+                       log_trace!(logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
+                       Err(())
+               },
+       }
+}
+
 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref>
 OnionMessenger<ES, NS, L, MR, OMH, CMH>
 where
@@ -457,40 +560,13 @@ where
        /// soon we'll delegate the onion message to a handler that can generate invoices or send
        /// payments.
        fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &msgs::OnionMessage) {
-               let control_tlvs_ss = match self.node_signer.ecdh(Recipient::Node, &msg.blinding_point, None) {
-                       Ok(ss) => ss,
-                       Err(e) =>  {
-                               log_error!(self.logger, "Failed to retrieve node secret: {:?}", e);
-                               return
-                       }
-               };
-               let onion_decode_ss = {
-                       let blinding_factor = {
-                               let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
-                               hmac.input(control_tlvs_ss.as_ref());
-                               Hmac::from_engine(hmac).into_inner()
-                       };
-                       match self.node_signer.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
-                               Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
-                       {
-                               Ok(ss) => ss.secret_bytes(),
-                               Err(()) => {
-                                       log_trace!(self.logger, "Failed to compute onion packet shared secret");
-                                       return
-                               }
-                       }
-               };
-               match onion_utils::decode_next_untagged_hop(
-                       onion_decode_ss, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
-                       (control_tlvs_ss, &*self.custom_handler, &*self.logger)
+               match peel_onion(
+                       &*self.node_signer, &self.secp_ctx, &*self.logger, &*self.custom_handler, msg
                ) {
-                       Ok((Payload::Receive::<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage> {
-                               message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
-                       }, None)) => {
+                       Ok(PeeledOnion::Receive(message, path_id, reply_path)) => {
                                log_trace!(self.logger,
                                        "Received an onion message with path_id {:02x?} and {} reply_path",
                                                path_id, if reply_path.is_some() { "a" } else { "no" });
-
                                let response = match message {
                                        OnionMessageContents::Offers(msg) => {
                                                self.offers_handler.handle_message(msg)
@@ -501,50 +577,11 @@ where
                                                        .map(|msg| OnionMessageContents::Custom(msg))
                                        },
                                };
-
                                if let Some(response) = response {
                                        self.respond_with_onion_message(response, path_id, reply_path);
                                }
                        },
-                       Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
-                               next_node_id, next_blinding_override
-                       })), Some((next_hop_hmac, new_packet_bytes)))) => {
-                               // TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
-                               // blinded hop and this onion message is destined for us. In this situation, we should keep
-                               // unwrapping the onion layers to get to the final payload. Since we don't have the option
-                               // of creating blinded paths with dummy hops currently, we should be ok to not handle this
-                               // for now.
-                               let new_pubkey = match onion_utils::next_hop_pubkey(&self.secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
-                                       Ok(pk) => pk,
-                                       Err(e) => {
-                                               log_trace!(self.logger, "Failed to compute next hop packet pubkey: {}", e);
-                                               return
-                                       }
-                               };
-                               let outgoing_packet = Packet {
-                                       version: 0,
-                                       public_key: new_pubkey,
-                                       hop_data: new_packet_bytes,
-                                       hmac: next_hop_hmac,
-                               };
-                               let onion_message = msgs::OnionMessage {
-                                       blinding_point: match next_blinding_override {
-                                               Some(blinding_point) => blinding_point,
-                                               None => {
-                                                       match onion_utils::next_hop_pubkey(
-                                                               &self.secp_ctx, msg.blinding_point, control_tlvs_ss.as_ref()
-                                                       ) {
-                                                               Ok(bp) => bp,
-                                                               Err(e) => {
-                                                                       log_trace!(self.logger, "Failed to compute next blinding point: {}", e);
-                                                                       return
-                                                               }
-                                                       }
-                                               }
-                                       },
-                                       onion_routing_packet: outgoing_packet,
-                               };
-
+                       Ok(PeeledOnion::Forward(next_node_id, onion_message)) => {
                                let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
                                if outbound_buffer_full(&next_node_id, &pending_per_peer_msgs) {
                                        log_trace!(self.logger, "Dropping forwarded onion message to peer {:?}: outbound buffer full", next_node_id);
@@ -563,15 +600,12 @@ where
                                                e.get_mut().push_back(onion_message);
                                                log_trace!(self.logger, "Forwarding an onion message to peer {}", next_node_id);
                                        }
-                               };
+                               }
                        },
                        Err(e) => {
-                               log_trace!(self.logger, "Errored decoding onion message packet: {:?}", e);
-                       },
-                       _ => {
-                               log_trace!(self.logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
-                       },
-               };
+                               log_error!(self.logger, "Failed to process onion message {:?}", e);
+                       }
+               }
        }
 
        fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init, _inbound: bool) -> Result<(), ()> {
index ae8bae1fb14fe9e7781c7343b4812892758f85b4..fb2943425dd9b448124459b5329cc7444b3245e1 100644 (file)
@@ -27,7 +27,7 @@ mod packet;
 mod functional_tests;
 
 // Re-export structs so they can be imported with just the `onion_message::` module prefix.
-pub use self::messenger::{CustomOnionMessageContents, CustomOnionMessageHandler, DefaultMessageRouter, Destination, MessageRouter, OnionMessageContents, OnionMessagePath, OnionMessenger, SendError, SimpleArcOnionMessenger, SimpleRefOnionMessenger};
+pub use self::messenger::{CustomOnionMessageContents, CustomOnionMessageHandler, DefaultMessageRouter, Destination, MessageRouter, OnionMessageContents, OnionMessagePath, OnionMessenger, PeeledOnion, SendError, SimpleArcOnionMessenger, SimpleRefOnionMessenger};
 pub use self::offers::{OffersMessage, OffersMessageHandler};
 pub use self::packet::Packet;
 pub(crate) use self::packet::ControlTlvs;