Require length limited reader for custom LN messages

When reading a raw LSP message specifically, it will consume the provided
reader until it is out of bytes. Readable is not an appropriate trait for this
situation, and over the past few commits we've been transitioning any struct
that always reads-to-end to require a length limited reader. This is less
error-prone because there is no risk of a bug being introduced because a custom
message read more data than it was supposed to from the provided reader.

Author: valentinewallace

lightning-custom-message/src/lib.rs

@@ -24,7 +24,7 @@
 //! use lightning::ln::peer_handler::CustomMessageHandler;
 //! use lightning::ln::wire::{CustomMessageReader, self};
 //! # use lightning::types::features::{InitFeatures, NodeFeatures};
-//! use lightning::util::ser::Writeable;
+//! use lightning::util::ser::{LengthLimitedRead, Writeable};
 //! # use lightning::util::ser::Writer;
 //!
 //! // Assume that `FooHandler` and `BarHandler` are defined in one crate and `BazHandler` is
@@ -52,7 +52,7 @@
 //! impl CustomMessageReader for FooHandler {
 //!     // ...
 //! #     type CustomMessage = Foo;
-//! #     fn read<R: io::Read>(
+//! #     fn read<R: LengthLimitedRead>(
 //! #         &self, _message_type: u16, _buffer: &mut R
 //! #     ) -> Result<Option<Self::CustomMessage>, DecodeError> {
 //! #         unimplemented!()
@@ -104,7 +104,7 @@
 //! impl CustomMessageReader for BarHandler {
 //!     // ...
 //! #     type CustomMessage = Bar;
-//! #     fn read<R: io::Read>(
+//! #     fn read<R: LengthLimitedRead>(
 //! #         &self, _message_type: u16, _buffer: &mut R
 //! #     ) -> Result<Option<Self::CustomMessage>, DecodeError> {
 //! #         unimplemented!()
@@ -156,7 +156,7 @@
 //! impl CustomMessageReader for BazHandler {
 //!     // ...
 //! #     type CustomMessage = Baz;
-//! #     fn read<R: io::Read>(
+//! #     fn read<R: LengthLimitedRead>(
 //! #         &self, _message_type: u16, _buffer: &mut R
 //! #     ) -> Result<Option<Self::CustomMessage>, DecodeError> {
 //! #         unimplemented!()
@@ -340,7 +340,7 @@ macro_rules! composite_custom_message_handler {
 
 		impl $crate::lightning::ln::wire::CustomMessageReader for $handler {
 			type CustomMessage = $message;
-			fn read<R: $crate::lightning::io::Read>(
+			fn read<R: $crate::lightning::util::ser::LengthLimitedRead>(
 				&self, message_type: u16, buffer: &mut R
 			) -> Result<Option<Self::CustomMessage>, $crate::lightning::ln::msgs::DecodeError> {
 				match message_type {

lightning-liquidity/src/lsps0/ser.rs

@@ -18,9 +18,9 @@ use crate::lsps2::msgs::{
 };
 use crate::prelude::{HashMap, String};
 
-use lightning::ln::msgs::LightningError;
+use lightning::ln::msgs::{DecodeError, LightningError};
 use lightning::ln::wire;
-use lightning::util::ser::WithoutLength;
+use lightning::util::ser::{LengthLimitedRead, LengthReadable, WithoutLength};
 
 use bitcoin::secp256k1::PublicKey;
 
@@ -168,9 +168,10 @@ impl lightning::util::ser::Writeable for RawLSPSMessage {
 	}
 }
 
-impl lightning::util::ser::Readable for RawLSPSMessage {
-	fn read<R: lightning::io::Read>(r: &mut R) -> Result<Self, lightning::ln::msgs::DecodeError> {
-		let payload_without_length = WithoutLength::read(r)?;
+impl LengthReadable for RawLSPSMessage {
+	fn read_from_fixed_length_buffer<R: LengthLimitedRead>(r: &mut R) -> Result<Self, DecodeError> {
+		let payload_without_length: WithoutLength<String> =
+			LengthReadable::read_from_fixed_length_buffer(r)?;
 		Ok(Self { payload: payload_without_length.0 })
 	}
 }

lightning-liquidity/src/manager.rs

@@ -27,7 +27,7 @@ use lightning::ln::peer_handler::CustomMessageHandler;
 use lightning::ln::wire::CustomMessageReader;
 use lightning::sign::EntropySource;
 use lightning::util::logger::Level;
-use lightning::util::ser::Readable;
+use lightning::util::ser::{LengthLimitedRead, LengthReadable};
 
 use lightning_types::features::{InitFeatures, NodeFeatures};
 
@@ -449,11 +449,13 @@ where
 {
 	type CustomMessage = RawLSPSMessage;
 
-	fn read<RD: lightning::io::Read>(
+	fn read<RD: LengthLimitedRead>(
 		&self, message_type: u16, buffer: &mut RD,
 	) -> Result<Option<Self::CustomMessage>, lightning::ln::msgs::DecodeError> {
 		match message_type {
-			LSPS_MESSAGE_TYPE_ID => Ok(Some(RawLSPSMessage::read(buffer)?)),
+			LSPS_MESSAGE_TYPE_ID => {
+				Ok(Some(RawLSPSMessage::read_from_fixed_length_buffer(buffer)?))
+			},
 			_ => Ok(None),
 		}
 	}

lightning/src/ln/wire.rs

@@ -25,7 +25,7 @@ pub trait CustomMessageReader {
 	/// implementation and the message could be decoded, must return `Ok(Some(message))`. If the
 	/// message type is unknown to the implementation, must return `Ok(None)`. If a decoding error
 	/// occur, must return `Err(DecodeError::X)` where `X` details the encountered error.
-	fn read<R: io::Read>(
+	fn read<R: LengthLimitedRead>(
 		&self, message_type: u16, buffer: &mut R,
 	) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
 }