Fix bug in onion message payload decode

Previously, we were decoding payload lengths as a VarInt. Per the spec, this is
wrong -- it should be decoded as a BigSize.  This bug also exists in our
payment payload decoding, to be fixed separately.

Upcoming reply path tests caught this bug because we hadn't encoded a payload
greater than 253 before, so we hadn't hit the problem that VarInts are encoded
as little-endian whereas BigSizes are encoded as big-endian.

diff --git a/lightning/src/onion_message/packet.rs b/lightning/src/onion_message/packet.rs
index d4ba28c843b9dde23be1e41111bda0797e44128a..5afe578121ba1440c1a66f40a0c2995b4fadb7de 100644 (file)
--- a/lightning/src/onion_message/packet.rs
+++ b/lightning/src/onion_message/packet.rs
@@ -16,7 +16,7 @@ use ln::msgs::DecodeError;
 use ln::onion_utils;
 use super::blinded_route::{ForwardTlvs, ReceiveTlvs};
 use util::chacha20poly1305rfc::{ChaChaPolyReadAdapter, ChaChaPolyWriteAdapter};
-use util::ser::{FixedLengthReader, LengthRead, LengthReadable, LengthReadableArgs, Readable, ReadableArgs, Writeable, Writer};
+use util::ser::{BigSize, FixedLengthReader, LengthRead, LengthReadable, LengthReadableArgs, Readable, ReadableArgs, Writeable, Writer};
 
 use core::cmp;
 use io::{self, Read};
@@ -161,13 +161,7 @@ impl Writeable for (Payload, [u8; 32]) {
 // Uses the provided secret to simultaneously decode and decrypt the control TLVs.
 impl ReadableArgs<SharedSecret> for Payload {
        fn read<R: Read>(mut r: &mut R, encrypted_tlvs_ss: SharedSecret) -> Result<Self, DecodeError> {
-               use bitcoin::consensus::encode::{Decodable, Error, VarInt};
-               let v: VarInt = Decodable::consensus_decode(&mut r)
-                       .map_err(|e| match e {
-                               Error::Io(ioe) => DecodeError::from(ioe),
-                               _ => DecodeError::InvalidValue
-                       })?;
-
+               let v: BigSize = Readable::read(r)?;
                let mut rd = FixedLengthReader::new(r, v.0);
                // TODO: support reply paths
                let mut _reply_path_bytes: Option<Vec<u8>> = Some(Vec::new());