Explicit Message Padding for OnionRealm0HopData

Author: varunsrin

lightning/src/ln/msgs.rs

@@ -27,6 +27,7 @@ use std::error::Error;
 use std::{cmp, fmt};
 use std::io::Read;
 use std::result::Result;
+use std::marker::PhantomData;
 
 use util::events;
 use util::ser::{Readable, Writeable, Writer};
@@ -610,7 +611,7 @@ pub(crate) struct OnionRealm0HopData {
 	pub(crate) short_channel_id: u64,
 	pub(crate) amt_to_forward: u64,
 	pub(crate) outgoing_cltv_value: u32,
-	// 12 bytes of 0-padding
+	pub(crate) padding: PhantomData<[u8; 12]>,
 }
 
 mod fuzzy_internal_msgs {
@@ -964,7 +965,7 @@ impl Writeable for OnionRealm0HopData {
 		self.short_channel_id.write(w)?;
 		self.amt_to_forward.write(w)?;
 		self.outgoing_cltv_value.write(w)?;
-		w.write_all(&[0;12])?;
+		self.padding.write(w)?;
 		Ok(())
 	}
 }
@@ -974,11 +975,8 @@ impl<R: Read> Readable<R> for OnionRealm0HopData {
 		Ok(OnionRealm0HopData {
 			short_channel_id: Readable::read(r)?,
 			amt_to_forward: Readable::read(r)?,
-			outgoing_cltv_value: {
-				let v: u32 = Readable::read(r)?;
-				r.read_exact(&mut [0; 12])?;
-				v
-			}
+			outgoing_cltv_value: Readable::read(r)?,
+			padding: Readable::read(r)?,
 		})
 	}
 }

lightning/src/ln/onion_utils.rs

@@ -16,6 +16,7 @@ use secp256k1::key::{SecretKey,PublicKey};
 use secp256k1::Secp256k1;
 use secp256k1::ecdh::SharedSecret;
 use secp256k1;
+use std::marker::PhantomData;
 
 use std::io::Cursor;
 use std::sync::Arc;
@@ -126,6 +127,7 @@ pub(super) fn build_onion_payloads(route: &Route, starting_htlc_offset: u32) ->
 				short_channel_id: last_short_channel_id,
 				amt_to_forward: value_msat,
 				outgoing_cltv_value: cltv,
+				padding: PhantomData,
 			},
 			hmac: [0; 32],
 		});
@@ -429,6 +431,8 @@ mod tests {
 	use ln::router::{Route, RouteHop};
 	use ln::msgs;
 	use util::ser::Writeable;
+	
+	use std::marker::PhantomData;
 
 	use hex;
 
@@ -521,6 +525,7 @@ mod tests {
 					short_channel_id: 0,
 					amt_to_forward: 0,
 					outgoing_cltv_value: 0,
+					padding: PhantomData,
 				},
 				hmac: [0; 32],
 			},
@@ -530,6 +535,7 @@ mod tests {
 					short_channel_id: 0x0101010101010101,
 					amt_to_forward: 0x0100000001,
 					outgoing_cltv_value: 0,
+					padding: PhantomData,
 				},
 				hmac: [0; 32],
 			},
@@ -539,6 +545,7 @@ mod tests {
 					short_channel_id: 0x0202020202020202,
 					amt_to_forward: 0x0200000002,
 					outgoing_cltv_value: 0,
+					padding: PhantomData,
 				},
 				hmac: [0; 32],
 			},
@@ -548,6 +555,7 @@ mod tests {
 					short_channel_id: 0x0303030303030303,
 					amt_to_forward: 0x0300000003,
 					outgoing_cltv_value: 0,
+					padding: PhantomData,
 				},
 				hmac: [0; 32],
 			},
@@ -557,6 +565,7 @@ mod tests {
 					short_channel_id: 0x0404040404040404,
 					amt_to_forward: 0x0400000004,
 					outgoing_cltv_value: 0,
+					padding: PhantomData,
 				},
 				hmac: [0; 32],
 			},

lightning/src/util/ser.rs

@@ -6,6 +6,7 @@ use std::io::{Read, Write};
 use std::collections::HashMap;
 use std::hash::Hash;
 use std::sync::Mutex;
+use std::marker::PhantomData;
 
 use secp256k1::Signature;
 use secp256k1::key::{PublicKey, SecretKey};
@@ -208,6 +209,7 @@ macro_rules! impl_array {
 impl_array!(3); // for rgb
 impl_array!(4); // for IPv4
 impl_array!(10); // for OnionV2
+impl_array!(12); // for OnionRealm0HopData
 impl_array!(16); // for IPv6
 impl_array!(32); // for channel id & hmac
 impl_array!(33); // for PublicKey
@@ -392,6 +394,20 @@ impl Writeable for PaymentHash {
 	}
 }
 
+impl<R: Read> Readable<R> for PhantomData<[u8; 12]> {
+	fn read(r: &mut R) -> Result<Self, DecodeError> {
+		let _buf: [u8; 12] = Readable::read(r)?; 
+		Ok(PhantomData)
+	}
+}
+
+impl Writeable for PhantomData<[u8; 12]> {
+	fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
+		w.write_all(&[0;12])?;
+		Ok(())
+	}
+}
+
 impl<R: Read> Readable<R> for PaymentHash {
 	fn read(r: &mut R) -> Result<Self, DecodeError> {
 		let buf: [u8; 32] = Readable::read(r)?;