+ type CustomMessage: OnionMessageContents;
+
+ /// Called with the custom message that was received, returning a response to send, if any.
+ ///
+ /// The returned [`Self::CustomMessage`], if any, is enqueued to be sent by [`OnionMessenger`].
+ fn handle_custom_message(&self, msg: Self::CustomMessage) -> Option<Self::CustomMessage>;
+
+ /// Read a custom message of type `message_type` from `buffer`, returning `Ok(None)` if the
+ /// message type is unknown.
+ fn read_custom_message<R: io::Read>(&self, message_type: u64, buffer: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
+
+ /// Releases any [`Self::CustomMessage`]s that need to be sent.
+ ///
+ /// Typically, this is used for messages initiating a message flow rather than in response to
+ /// another message. The latter should use the return value of [`Self::handle_custom_message`].
+ fn release_pending_custom_messages(&self) -> Vec<PendingOnionMessage<Self::CustomMessage>>;
+}
+
+/// A processed incoming onion message, containing either a Forward (another onion message)
+/// or a Receive payload with decrypted contents.
+pub enum PeeledOnion<T: OnionMessageContents> {
+ /// Forwarded onion, with the next node id and a new onion
+ Forward(PublicKey, OnionMessage),
+ /// Received onion message, with decrypted contents, path_id, and reply path
+ Receive(ParsedOnionMessageContents<T>, Option<[u8; 32]>, Option<BlindedPath>)
+}
+
+/// Creates an [`OnionMessage`] with the given `contents` for sending to the destination of
+/// `path`.
+///
+/// Returns both the node id of the peer to send the message to and the message itself.
+pub fn create_onion_message<ES: Deref, NS: Deref, T: OnionMessageContents>(
+ entropy_source: &ES, node_signer: &NS, secp_ctx: &Secp256k1<secp256k1::All>,
+ path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
+) -> Result<(PublicKey, OnionMessage), SendError>
+where
+ ES::Target: EntropySource,
+ NS::Target: NodeSigner,
+{
+ let OnionMessagePath { intermediate_nodes, mut destination } = path;
+ if let Destination::BlindedPath(BlindedPath { ref blinded_hops, .. }) = destination {
+ if blinded_hops.is_empty() {
+ return Err(SendError::TooFewBlindedHops);
+ }
+ }
+
+ if contents.tlv_type() < 64 { return Err(SendError::InvalidMessage) }
+
+ // If we are sending straight to a blinded path and we are the introduction node, we need to
+ // advance the blinded path by 1 hop so the second hop is the new introduction node.
+ if intermediate_nodes.len() == 0 {
+ if let Destination::BlindedPath(ref mut blinded_path) = destination {
+ let our_node_id = node_signer.get_node_id(Recipient::Node)
+ .map_err(|()| SendError::GetNodeIdFailed)?;
+ if blinded_path.introduction_node_id == our_node_id {
+ advance_path_by_one(blinded_path, node_signer, &secp_ctx)
+ .map_err(|()| SendError::BlindedPathAdvanceFailed)?;
+ }
+ }
+ }
+
+ let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
+ let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
+ let (first_node_id, blinding_point) = if let Some(first_node_id) = intermediate_nodes.first() {
+ (*first_node_id, PublicKey::from_secret_key(&secp_ctx, &blinding_secret))
+ } else {
+ match destination {
+ Destination::Node(pk) => (pk, PublicKey::from_secret_key(&secp_ctx, &blinding_secret)),
+ Destination::BlindedPath(BlindedPath { introduction_node_id, blinding_point, .. }) =>
+ (introduction_node_id, blinding_point),
+ }
+ };
+ let (packet_payloads, packet_keys) = packet_payloads_and_keys(
+ &secp_ctx, &intermediate_nodes, destination, contents, reply_path, &blinding_secret)
+ .map_err(|e| SendError::Secp256k1(e))?;
+
+ let prng_seed = entropy_source.get_secure_random_bytes();
+ let onion_routing_packet = construct_onion_message_packet(
+ packet_payloads, packet_keys, prng_seed).map_err(|()| SendError::TooBigPacket)?;
+
+ Ok((first_node_id, OnionMessage {
+ blinding_point,
+ onion_routing_packet
+ }))
+}
+
+/// Decode one layer of an incoming [`OnionMessage`].
+///
+/// Returns either the next layer of the onion for forwarding or the decrypted content for the
+/// receiver.
+pub fn peel_onion_message<NS: Deref, L: Deref, CMH: Deref>(
+ msg: &OnionMessage, secp_ctx: &Secp256k1<secp256k1::All>, node_signer: NS, logger: L,
+ custom_handler: CMH,
+) -> 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::<ParsedOnionMessageContents<<<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 = 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(())
+ },
+ }