Move cryptographic algorithms and utilities to a new crypto mod

As we'd generally like the `lightning` crate to, over time, have
more modules rather than being very monolithic, we should move the
cryptographic things into their own module, which we do here.

We also take this opportunity to move stream adapters into their
own module and make clear that the ChaChaPoly `decrypt` method is
variable time.

lightning/src/blinded_path/message.rs

@@ -8,7 +8,7 @@ use crate::ln::onion_utils;
 use crate::onion_message::packet::ControlTlvs;
 use crate::prelude::*;
 use crate::sign::{NodeSigner, Recipient};
-use crate::util::chacha20poly1305rfc::ChaChaPolyReadAdapter;
+use crate::crypto::streams::ChaChaPolyReadAdapter;
 use crate::util::ser::{FixedLengthReader, LengthReadableArgs, Writeable, Writer};
 
 use core::mem;

lightning/src/blinded_path/utils.rs

@@ -19,7 +19,7 @@ use super::{BlindedHop, BlindedPath};
 use crate::ln::msgs::DecodeError;
 use crate::ln::onion_utils;
 use crate::onion_message::messenger::Destination;
-use crate::util::chacha20poly1305rfc::ChaChaPolyWriteAdapter;
+use crate::crypto::streams::ChaChaPolyWriteAdapter;
 use crate::util::ser::{Readable, Writeable};
 
 use crate::io;

lightning/src/chain/channelmonitor.rs

@@ -4808,7 +4808,7 @@ mod tests {
 				preimages_slice_to_htlcs!($preimages_slice).into_iter().map(|(htlc, _)| (htlc, None)).collect()
 			}
 		}
-		let dummy_sig = crate::util::crypto::sign(&secp_ctx,
+		let dummy_sig = crate::crypto::utils::sign(&secp_ctx,
 			&bitcoin::secp256k1::Message::from_slice(&[42; 32]).unwrap(),
 			&SecretKey::from_slice(&[42; 32]).unwrap());
 

lightning/src/util/chacha20.rs → lightning/src/crypto/chacha20.rs

@@ -9,8 +9,6 @@
 // You may not use this file except in accordance with one or both of these
 // licenses.
 
-use crate::io;
-
 #[cfg(not(fuzzing))]
 mod real_chacha {
 	use core::cmp;
@@ -335,27 +333,14 @@ mod fuzzy_chacha {
 #[cfg(fuzzing)]
 pub use self::fuzzy_chacha::ChaCha20;
 
-pub(crate) struct ChaChaReader<'a, R: io::Read> {
-	pub chacha: &'a mut ChaCha20,
-	pub read: R,
-}
-impl<'a, R: io::Read> io::Read for ChaChaReader<'a, R> {
-	fn read(&mut self, dest: &mut [u8]) -> Result<usize, io::Error> {
-		let res = self.read.read(dest)?;
-		if res > 0 {
-			self.chacha.process_in_place(&mut dest[0..res]);
-		}
-		Ok(res)
-	}
-}
-
 #[cfg(test)]
 mod test {
-	use crate::prelude::*;
+	use alloc::vec;
+	use alloc::vec::{Vec};
+	use core::convert::TryInto;
 	use core::iter::repeat;
 
 	use super::ChaCha20;
-	use std::convert::TryInto;
 
 	#[test]
 	fn test_chacha20_256_tls_vectors() {

lightning/src/crypto/chacha20poly1305rfc.rs

@@ -0,0 +1,237 @@
+// ring has a garbage API so its use is avoided, but rust-crypto doesn't have RFC-variant poly1305
+// Instead, we steal rust-crypto's implementation and tweak it to match the RFC.
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+//
+// This is a port of Andrew Moons poly1305-donna
+// https://github.com/floodyberry/poly1305-donna
+
+#[cfg(not(fuzzing))]
+mod real_chachapoly {
+	use super::super::chacha20::ChaCha20;
+	use super::super::poly1305::Poly1305;
+	use super::super::fixed_time_eq;
+
+	#[derive(Clone, Copy)]
+	pub struct ChaCha20Poly1305RFC {
+		cipher: ChaCha20,
+		mac: Poly1305,
+		finished: bool,
+		data_len: usize,
+		aad_len: u64,
+	}
+
+	impl ChaCha20Poly1305RFC {
+		#[inline]
+		fn pad_mac_16(mac: &mut Poly1305, len: usize) {
+			if len % 16 != 0 {
+				mac.input(&[0; 16][0..16 - (len % 16)]);
+			}
+		}
+		pub fn new(key: &[u8], nonce: &[u8], aad: &[u8]) -> ChaCha20Poly1305RFC {
+			assert!(key.len() == 16 || key.len() == 32);
+			assert!(nonce.len() == 12);
+
+			// Ehh, I'm too lazy to *also* tweak ChaCha20 to make it RFC-compliant
+			assert!(nonce[0] == 0 && nonce[1] == 0 && nonce[2] == 0 && nonce[3] == 0);
+
+			let mut cipher = ChaCha20::new(key, &nonce[4..]);
+			let mut mac_key = [0u8; 64];
+			let zero_key = [0u8; 64];
+			cipher.process(&zero_key, &mut mac_key);
+
+			let mut mac = Poly1305::new(&mac_key[..32]);
+			mac.input(aad);
+			ChaCha20Poly1305RFC::pad_mac_16(&mut mac, aad.len());
+
+			ChaCha20Poly1305RFC {
+				cipher,
+				mac,
+				finished: false,
+				data_len: 0,
+				aad_len: aad.len() as u64,
+			}
+		}
+
+		pub fn encrypt(&mut self, input: &[u8], output: &mut [u8], out_tag: &mut [u8]) {
+			assert!(input.len() == output.len());
+			assert!(self.finished == false);
+			self.cipher.process(input, output);
+			self.data_len += input.len();
+			self.mac.input(output);
+			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 encrypt_full_message_in_place(&mut self, input_output: &mut [u8], out_tag: &mut [u8]) {
+			self.encrypt_in_place(input_output);
+			self.finish_and_get_tag(out_tag);
+		}
+
+		// Encrypt `input_output` in-place. To finish and calculate the tag, use `finish_and_get_tag`
+		// below.
+		pub(in super::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(in super::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);
+		}
+
+		/// Decrypt the `input`, checking the given `tag` prior to writing the decrypted contents
+		/// into `output`. Note that, because `output` is not touched until the `tag` is checked,
+		/// this decryption is *variable time*.
+		pub fn variable_time_decrypt(&mut self, input: &[u8], output: &mut [u8], tag: &[u8]) -> Result<(), ()> {
+			assert!(input.len() == output.len());
+			assert!(self.finished == false);
+
+			self.finished = true;
+
+			self.mac.input(input);
+
+			self.data_len += input.len();
+			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) {
+				self.cipher.process(input, output);
+				Ok(())
+			} else {
+				Err(())
+			}
+		}
+
+		pub fn check_decrypt_in_place(&mut self, input_output: &mut [u8], tag: &[u8]) -> Result<(), ()> {
+			self.decrypt_in_place(input_output);
+			if self.finish_and_check_tag(tag) { Ok(()) } else { Err(()) }
+		}
+
+		/// 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(in super::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 `just_decrypt_in_place`, this method must be used
+		/// to check the tag. Returns whether or not the tag is valid.
+		pub(in super::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;
+
+#[cfg(fuzzing)]
+mod fuzzy_chachapoly {
+	#[derive(Clone, Copy)]
+	pub struct ChaCha20Poly1305RFC {
+		tag: [u8; 16],
+		finished: bool,
+	}
+	impl ChaCha20Poly1305RFC {
+		pub fn new(key: &[u8], nonce: &[u8], _aad: &[u8]) -> ChaCha20Poly1305RFC {
+			assert!(key.len() == 16 || key.len() == 32);
+			assert!(nonce.len() == 12);
+
+			// Ehh, I'm too lazy to *also* tweak ChaCha20 to make it RFC-compliant
+			assert!(nonce[0] == 0 && nonce[1] == 0 && nonce[2] == 0 && nonce[3] == 0);
+
+			let mut tag = [0; 16];
+			tag.copy_from_slice(&key[0..16]);
+
+			ChaCha20Poly1305RFC {
+				tag,
+				finished: false,
+			}
+		}
+
+		pub fn encrypt(&mut self, input: &[u8], output: &mut [u8], out_tag: &mut [u8]) {
+			assert!(input.len() == output.len());
+			assert!(self.finished == false);
+
+			output.copy_from_slice(&input);
+			out_tag.copy_from_slice(&self.tag);
+			self.finished = true;
+		}
+
+		pub fn encrypt_full_message_in_place(&mut self, input_output: &mut [u8], out_tag: &mut [u8]) {
+			self.encrypt_in_place(input_output);
+			self.finish_and_get_tag(out_tag);
+		}
+
+		pub(in super::super) fn encrypt_in_place(&mut self, _input_output: &mut [u8]) {
+			assert!(self.finished == false);
+		}
+
+		pub(in super::super) fn finish_and_get_tag(&mut self, out_tag: &mut [u8]) {
+			assert!(self.finished == false);
+			out_tag.copy_from_slice(&self.tag);
+			self.finished = true;
+		}
+
+		pub fn variable_time_decrypt(&mut self, input: &[u8], output: &mut [u8], tag: &[u8]) -> Result<(), ()> {
+			assert!(input.len() == output.len());
+			assert!(self.finished == false);
+
+			if tag[..] != self.tag[..] { return Err(()); }
+			output.copy_from_slice(input);
+			self.finished = true;
+			Ok(())
+		}
+
+		pub fn check_decrypt_in_place(&mut self, input_output: &mut [u8], tag: &[u8]) -> Result<(), ()> {
+			self.decrypt_in_place(input_output);
+			if self.finish_and_check_tag(tag) { Ok(()) } else { Err(()) }
+		}
+
+		pub(in super::super) fn decrypt_in_place(&mut self, _input: &mut [u8]) {
+			assert!(self.finished == false);
+		}
+
+		pub(in super::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;

lightning/src/crypto/mod.rs

@@ -0,0 +1,8 @@
+use bitcoin::hashes::cmp::fixed_time_eq;
+
+pub(crate) mod chacha20;
+#[cfg(not(fuzzing))]
+pub(crate) mod poly1305;
+pub(crate) mod chacha20poly1305rfc;
+pub(crate) mod streams;
+pub(crate) mod utils;

lightning/src/util/poly1305.rs → lightning/src/crypto/poly1305.rs

@@ -205,10 +205,10 @@ impl Poly1305 {
 
 #[cfg(test)]
 mod test {
-	use crate::prelude::*;
 	use core::iter::repeat;
+	use alloc::vec::Vec;
 
-	use crate::util::poly1305::Poly1305;
+	use super::Poly1305;
 
 	fn poly1305(key: &[u8], msg: &[u8], mac: &mut [u8]) {
 		let mut poly = Poly1305::new(key);