Merge pull request lightningdevkit#1518 from valentinewallace/2022-06-OMs-prefactor

Onion messages v1 pre-refactor

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -24,7 +24,7 @@ use bitcoin::blockdata::transaction::Transaction;
 use bitcoin::blockdata::constants::genesis_block;
 use bitcoin::network::constants::Network;
 
-use bitcoin::hashes::{Hash, HashEngine};
+use bitcoin::hashes::Hash;
 use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::hashes::sha256d::Hash as Sha256dHash;
 use bitcoin::hash_types::{BlockHash, Txid};
@@ -2175,22 +2175,10 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 				}
 			},
 			onion_utils::Hop::Forward { next_hop_data, next_hop_hmac, new_packet_bytes } => {
-				let mut new_pubkey = msg.onion_routing_packet.public_key.unwrap();
-
-				let blinding_factor = {
-					let mut sha = Sha256::engine();
-					sha.input(&new_pubkey.serialize()[..]);
-					sha.input(&shared_secret);
-					Sha256::from_engine(sha).into_inner()
-				};
-
-				let public_key = if let Err(e) = new_pubkey.mul_assign(&self.secp_ctx, &blinding_factor[..]) {
-					Err(e)
-				} else { Ok(new_pubkey) };
-
+				let new_pubkey = msg.onion_routing_packet.public_key.unwrap();
 				let outgoing_packet = msgs::OnionPacket {
 					version: 0,
-					public_key,
+					public_key: onion_utils::next_hop_packet_pubkey(&self.secp_ctx, new_pubkey, &shared_secret),
 					hop_data: new_packet_bytes,
 					hmac: next_hop_hmac.clone(),
 				};

lightning/src/ln/onion_utils.rs

@@ -74,6 +74,17 @@ pub(super) fn gen_ammag_from_shared_secret(shared_secret: &[u8]) -> [u8; 32] {
 	Hmac::from_engine(hmac).into_inner()
 }
 
+pub(super) fn next_hop_packet_pubkey<T: secp256k1::Signing + secp256k1::Verification>(secp_ctx: &Secp256k1<T>, mut packet_pubkey: PublicKey, packet_shared_secret: &[u8; 32]) -> Result<PublicKey, secp256k1::Error> {
+	let blinding_factor = {
+		let mut sha = Sha256::engine();
+		sha.input(&packet_pubkey.serialize()[..]);
+		sha.input(packet_shared_secret);
+		Sha256::from_engine(sha).into_inner()
+	};
+
+	packet_pubkey.mul_assign(secp_ctx, &blinding_factor[..]).map(|_| packet_pubkey)
+}
+
 // can only fail if an intermediary hop has an invalid public key or session_priv is invalid
 #[inline]
 pub(super) fn construct_onion_keys_callback<T: secp256k1::Signing, FType: FnMut(SharedSecret, [u8; 32], PublicKey, &RouteHop, usize)> (secp_ctx: &Secp256k1<T>, path: &Vec<RouteHop>, session_priv: &SecretKey, mut callback: FType) -> Result<(), secp256k1::Error> {

lightning/src/util/chacha20poly1305rfc.rs

@@ -10,6 +10,10 @@
 // This is a port of Andrew Moons poly1305-donna
 // https://github.com/floodyberry/poly1305-donna
 
+use ln::msgs::DecodeError;
+use util::ser::{FixedLengthReader, LengthRead, LengthReadableArgs, Readable, Writeable, Writer};
+use io::{self, Read, Write};
+
 #[cfg(not(fuzzing))]
 mod real_chachapoly {
 	use util::chacha20::ChaCha20;
@@ -70,6 +74,26 @@ mod real_chachapoly {
 			self.mac.raw_result(out_tag);
 		}
 
+		// Encrypt `input_output` in-place. To finish and calculate the tag, use `finish_and_get_tag`
+		// below.
+		pub(super) fn encrypt_in_place(&mut self, input_output: &mut [u8]) {
+			debug_assert!(self.finished == false);
+			self.cipher.process_in_place(input_output);
+			self.data_len += input_output.len();
+			self.mac.input(input_output);
+		}
+
+		// If we were previously encrypting with `encrypt_in_place`, this method can be used to finish
+		// encrypting and calculate the tag.
+		pub(super) fn finish_and_get_tag(&mut self, out_tag: &mut [u8]) {
+			debug_assert!(self.finished == false);
+			ChaCha20Poly1305RFC::pad_mac_16(&mut self.mac, self.data_len);
+			self.finished = true;
+			self.mac.input(&self.aad_len.to_le_bytes());
+			self.mac.input(&(self.data_len as u64).to_le_bytes());
+			self.mac.raw_result(out_tag);
+		}
+
 		pub fn decrypt(&mut self, input: &[u8], output: &mut [u8], tag: &[u8]) -> bool {
 			assert!(input.len() == output.len());
 			assert!(self.finished == false);
@@ -92,11 +116,141 @@ mod real_chachapoly {
 				false
 			}
 		}
+
+		// Decrypt in place, without checking the tag. Use `finish_and_check_tag` to check it
+		// later when decryption finishes.
+		//
+		// Should never be `pub` because the public API should always enforce tag checking.
+		pub(super) fn decrypt_in_place(&mut self, input_output: &mut [u8]) {
+			debug_assert!(self.finished == false);
+			self.mac.input(input_output);
+			self.data_len += input_output.len();
+			self.cipher.process_in_place(input_output);
+		}
+
+		// If we were previously decrypting with `decrypt_in_place`, this method must be used to finish
+		// decrypting and check the tag. Returns whether or not the tag is valid.
+		pub(super) fn finish_and_check_tag(&mut self, tag: &[u8]) -> bool {
+			debug_assert!(self.finished == false);
+			self.finished = true;
+			ChaCha20Poly1305RFC::pad_mac_16(&mut self.mac, self.data_len);
+			self.mac.input(&self.aad_len.to_le_bytes());
+			self.mac.input(&(self.data_len as u64).to_le_bytes());
+
+			let mut calc_tag =  [0u8; 16];
+			self.mac.raw_result(&mut calc_tag);
+			if fixed_time_eq(&calc_tag, tag) {
+				true
+			} else {
+				false
+			}
+		}
 	}
 }
 #[cfg(not(fuzzing))]
 pub use self::real_chachapoly::ChaCha20Poly1305RFC;
 
+/// Enables simultaneously reading and decrypting a ChaCha20Poly1305RFC stream from a std::io::Read.
+struct ChaChaPolyReader<'a, R: Read> {
+	pub chacha: &'a mut ChaCha20Poly1305RFC,
+	pub read: R,
+}
+
+impl<'a, R: Read> Read for ChaChaPolyReader<'a, R> {
+	// Decrypt bytes from Self::read into `dest`.
+	// `ChaCha20Poly1305RFC::finish_and_check_tag` must be called to check the tag after all reads
+	// complete.
+	fn read(&mut self, dest: &mut [u8]) -> Result<usize, io::Error> {
+		let res = self.read.read(dest)?;
+		if res > 0 {
+			self.chacha.decrypt_in_place(&mut dest[0..res]);
+		}
+		Ok(res)
+	}
+}
+
+/// Enables simultaneously writing and encrypting a byte stream into a Writer.
+struct ChaChaPolyWriter<'a, W: Writer> {
+	pub chacha: &'a mut ChaCha20Poly1305RFC,
+	pub write: &'a mut W,
+}
+
+impl<'a, W: Writer> Writer for ChaChaPolyWriter<'a, W> {
+	// Encrypt then write bytes from `src` into Self::write.
+	// `ChaCha20Poly1305RFC::finish_and_get_tag` can be called to retrieve the tag after all writes
+	// complete.
+	fn write_all(&mut self, src: &[u8]) -> Result<(), io::Error> {
+		let mut src_idx = 0;
+		while src_idx < src.len() {
+			let mut write_buffer = [0; 8192];
+			let bytes_written = (&mut write_buffer[..]).write(&src[src_idx..]).expect("In-memory writes can't fail");
+			self.chacha.encrypt_in_place(&mut write_buffer[..bytes_written]);
+			self.write.write_all(&write_buffer[..bytes_written])?;
+			src_idx += bytes_written;
+		}
+		Ok(())
+	}
+}
+
+/// Enables the use of the serialization macros for objects that need to be simultaneously encrypted and
+/// serialized. This allows us to avoid an intermediate Vec allocation.
+pub(crate) struct ChaChaPolyWriteAdapter<'a, W: Writeable> {
+	pub rho: [u8; 32],
+	pub writeable: &'a W,
+}
+
+impl<'a, W: Writeable> ChaChaPolyWriteAdapter<'a, W> {
+	#[allow(unused)] // This will be used for onion messages soon
+	pub fn new(rho: [u8; 32], writeable: &'a W) -> ChaChaPolyWriteAdapter<'a, W> {
+		Self { rho, writeable }
+	}
+}
+
+impl<'a, T: Writeable> Writeable for ChaChaPolyWriteAdapter<'a, T> {
+	// Simultaneously write and encrypt Self::writeable.
+	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+		let mut chacha = ChaCha20Poly1305RFC::new(&self.rho, &[0; 12], &[]);
+		let mut chacha_stream = ChaChaPolyWriter { chacha: &mut chacha, write: w };
+		self.writeable.write(&mut chacha_stream)?;
+		let mut tag = [0 as u8; 16];
+		chacha.finish_and_get_tag(&mut tag);
+		tag.write(w)?;
+
+		Ok(())
+	}
+}
+
+/// Enables the use of the serialization macros for objects that need to be simultaneously decrypted and
+/// deserialized. This allows us to avoid an intermediate Vec allocation.
+pub(crate) struct ChaChaPolyReadAdapter<R: Readable> {
+	#[allow(unused)] // This will be used soon for onion messages
+	pub readable: R,
+}
+
+impl<T: Readable> LengthReadableArgs<[u8; 32]> for ChaChaPolyReadAdapter<T> {
+	// Simultaneously read and decrypt an object from a LengthRead, storing it in Self::readable.
+	// LengthRead must be used instead of std::io::Read because we need the total length to separate
+	// out the tag at the end.
+	fn read<R: LengthRead>(mut r: &mut R, secret: [u8; 32]) -> Result<Self, DecodeError> {
+		if r.total_bytes() < 16 { return Err(DecodeError::InvalidValue) }
+
+		let mut chacha = ChaCha20Poly1305RFC::new(&secret, &[0; 12], &[]);
+		let decrypted_len = r.total_bytes() - 16;
+		let s = FixedLengthReader::new(&mut r, decrypted_len);
+		let mut chacha_stream = ChaChaPolyReader { chacha: &mut chacha, read: s };
+		let readable: T = Readable::read(&mut chacha_stream)?;
+		chacha_stream.read.eat_remaining()?;
+
+		let mut tag = [0 as u8; 16];
+		r.read_exact(&mut tag)?;
+		if !chacha.finish_and_check_tag(&tag) {
+			return Err(DecodeError::InvalidValue)
+		}
+
+		Ok(Self { readable })
+	}
+}
+
 #[cfg(fuzzing)]
 mod fuzzy_chachapoly {
 	#[derive(Clone, Copy)]
@@ -130,6 +284,16 @@ mod fuzzy_chachapoly {
 			self.finished = true;
 		}
 
+		pub(super) fn encrypt_in_place(&mut self, _input_output: &mut [u8]) {
+			assert!(self.finished == false);
+			self.finished = true;
+		}
+
+		pub(super) fn finish_and_get_tag(&mut self, out_tag: &mut [u8]) {
+			out_tag.copy_from_slice(&self.tag);
+			self.finished = true;
+		}
+
 		pub fn decrypt(&mut self, input: &[u8], output: &mut [u8], tag: &[u8]) -> bool {
 			assert!(input.len() == output.len());
 			assert!(self.finished == false);
@@ -139,7 +303,106 @@ mod fuzzy_chachapoly {
 			self.finished = true;
 			true
 		}
+
+		pub(super) fn decrypt_in_place(&mut self, _input: &mut [u8]) {
+			assert!(self.finished == false);
+		}
+
+		pub(super) fn finish_and_check_tag(&mut self, tag: &[u8]) -> bool {
+			if tag[..] != self.tag[..] { return false; }
+			self.finished = true;
+			true
+		}
 	}
 }
 #[cfg(fuzzing)]
 pub use self::fuzzy_chachapoly::ChaCha20Poly1305RFC;
+
+#[cfg(test)]
+mod tests {
+	use ln::msgs::DecodeError;
+	use super::{ChaChaPolyReadAdapter, ChaChaPolyWriteAdapter};
+	use util::ser::{self, FixedLengthReader, LengthReadableArgs, Writeable};
+
+	// Used for for testing various lengths of serialization.
+	#[derive(Debug, PartialEq)]
+	struct TestWriteable {
+		field1: Vec<u8>,
+		field2: Vec<u8>,
+		field3: Vec<u8>,
+	}
+	impl_writeable_tlv_based!(TestWriteable, {
+		(1, field1, vec_type),
+		(2, field2, vec_type),
+		(3, field3, vec_type),
+	});
+
+	#[test]
+	fn test_chacha_stream_adapters() {
+		// Check that ChaChaPolyReadAdapter and ChaChaPolyWriteAdapter correctly encode and decode an
+		// encrypted object.
+		macro_rules! check_object_read_write {
+			($obj: expr) => {
+				// First, serialize the object, encrypted with ChaCha20Poly1305.
+				let rho = [42; 32];
+				let writeable_len = $obj.serialized_length() as u64 + 16;
+				let write_adapter = ChaChaPolyWriteAdapter::new(rho, &$obj);
+				let encrypted_writeable_bytes = write_adapter.encode();
+				let encrypted_writeable = &encrypted_writeable_bytes[..];
+
+				// Now deserialize the object back and make sure it matches the original.
+				let mut rd = FixedLengthReader::new(encrypted_writeable, writeable_len);
+				let read_adapter = <ChaChaPolyReadAdapter<TestWriteable>>::read(&mut rd, rho).unwrap();
+				assert_eq!($obj, read_adapter.readable);
+			};
+		}
+
+		// Try a big object that will require multiple write buffers.
+		let big_writeable = TestWriteable {
+			field1: vec![43],
+			field2: vec![44; 4192],
+			field3: vec![45; 4192 + 1],
+		};
+		check_object_read_write!(big_writeable);
+
+		// Try a small object that fits into one write buffer.
+		let small_writeable = TestWriteable {
+			field1: vec![43],
+			field2: vec![44],
+			field3: vec![45],
+		};
+		check_object_read_write!(small_writeable);
+	}
+
+	fn do_chacha_stream_adapters_ser_macros() -> Result<(), DecodeError> {
+		let writeable = TestWriteable {
+			field1: vec![43],
+			field2: vec![44; 4192],
+			field3: vec![45; 4192 + 1],
+		};
+
+		// First, serialize the object into a TLV stream, encrypted with ChaCha20Poly1305.
+		let rho = [42; 32];
+		let write_adapter = ChaChaPolyWriteAdapter::new(rho, &writeable);
+		let mut writer = ser::VecWriter(Vec::new());
+		encode_tlv_stream!(&mut writer, {
+			(1, write_adapter, required),
+		});
+
+		// Now deserialize the object back and make sure it matches the original.
+		let mut read_adapter: Option<ChaChaPolyReadAdapter<TestWriteable>> = None;
+		decode_tlv_stream!(&writer.0[..], {
+			(1, read_adapter, (option: LengthReadableArgs, rho)),
+		});
+		assert_eq!(writeable, read_adapter.unwrap().readable);
+
+		Ok(())
+	}
+
+	#[test]
+	fn chacha_stream_adapters_ser_macros() {
+		// Test that our stream adapters work as expected with the TLV macros.
+		// This also serves to test the `option: $trait` variant of the `decode_tlv` ser macro.
+		do_chacha_stream_adapters_ser_macros().unwrap()
+	}
+}

lightning/src/util/ser.rs

@@ -134,6 +134,13 @@ impl<R: Read> Read for FixedLengthReader<R> {
 	}
 }
 
+impl<R: Read> LengthRead for FixedLengthReader<R> {
+	#[inline]
+	fn total_bytes(&self) -> u64 {
+		self.total_bytes
+	}
+}
+
 /// A Read which tracks whether any bytes have been read at all. This allows us to distinguish
 /// between "EOF reached before we started" and "EOF reached mid-read".
 pub(crate) struct ReadTrackingReader<R: Read> {
@@ -220,6 +227,21 @@ pub trait ReadableArgs<P>
 	fn read<R: Read>(reader: &mut R, params: P) -> Result<Self, DecodeError>;
 }
 
+/// A std::io::Read that also provides the total bytes available to read.
+pub(crate) trait LengthRead: Read {
+	/// The total number of bytes available to read.
+	fn total_bytes(&self) -> u64;
+}
+
+/// A trait that various higher-level rust-lightning types implement allowing them to be read in
+/// from a Read given some additional set of arguments which is required to deserialize, requiring
+/// the implementer to provide the total length of the read.
+pub(crate) trait LengthReadableArgs<P> where Self: Sized
+{
+	/// Reads a Self in from the given LengthRead
+	fn read<R: LengthRead>(reader: &mut R, params: P) -> Result<Self, DecodeError>;
+}
+
 /// A trait that various rust-lightning types implement allowing them to (maybe) be read in from a Read
 ///
 /// (C-not exported) as we only export serialization to/from byte arrays instead