Use sha256 instead of ChaCha20 for randomness.

Author: tnull

lightning-invoice/src/utils.rs

@@ -4,7 +4,7 @@ use {CreationError, Currency, DEFAULT_EXPIRY_TIME, Invoice, InvoiceBuilder, Sign
 use payment::{Payer, Router};
 
 use bech32::ToBase32;
-use bitcoin_hashes::Hash;
+use bitcoin_hashes::{Hash, sha256};
 use crate::prelude::*;
 use lightning::chain;
 use lightning::chain::chaininterface::{BroadcasterInterface, FeeEstimator};
@@ -16,7 +16,6 @@ use lightning::routing::scoring::Score;
 use lightning::routing::network_graph::{NetworkGraph, RoutingFees};
 use lightning::routing::router::{Route, RouteHint, RouteHintHop, RouteParameters, find_route};
 use lightning::util::logger::Logger;
-use lightning::util::chacha20::ChaCha20;
 use secp256k1::key::PublicKey;
 use core::convert::TryInto;
 use core::ops::Deref;
@@ -224,14 +223,14 @@ where
 pub struct DefaultRouter<G: Deref<Target = NetworkGraph>, L: Deref> where L::Target: Logger {
 	network_graph: G,
 	logger: L,
-    prng: Mutex<ChaCha20>,
+	random_seed_bytes: Mutex<[u8; 32]>,
 }
 
 impl<G: Deref<Target = NetworkGraph>, L: Deref> DefaultRouter<G, L> where L::Target: Logger {
 	/// Creates a new router using the given [`NetworkGraph`], a [`Logger`], and a randomness source `random_seed_bytes`.
 	pub fn new(network_graph: G, logger: L, random_seed_bytes: [u8; 32]) -> Self {
-        let prng = Mutex::new(ChaCha20::new(&random_seed_bytes, &[0; 8]));
-		Self { network_graph, logger, prng }
+		let random_seed_bytes = Mutex::new(random_seed_bytes);
+		Self { network_graph, logger, random_seed_bytes }
 	}
 }
 
@@ -240,10 +239,10 @@ where L::Target: Logger {
 	fn find_route(
 		&self, payer: &PublicKey, params: &RouteParameters, _payment_hash: &PaymentHash,
 		first_hops: Option<&[&ChannelDetails]>, scorer: &S
-	) -> Result<Route, LightningError> {
-        let mut random_seed_bytes = [0u8; 32];
-        self.prng.lock().unwrap().process_in_place(&mut random_seed_bytes);
-		find_route(payer, params, &*self.network_graph, first_hops, &*self.logger, scorer, &random_seed_bytes)
+		) -> Result<Route, LightningError> {
+		let mut locked_random_seed_bytes = self.random_seed_bytes.lock().unwrap();
+		*locked_random_seed_bytes = sha256::Hash::hash(&*locked_random_seed_bytes).into_inner();
+		find_route(payer, params, &*self.network_graph, first_hops, &*self.logger, scorer, &locked_random_seed_bytes.clone())
 	}
 }