Use chacha20 - Iterating nonce approach

lightning/src/chain/keysinterface.rs

@@ -46,9 +46,9 @@ use crate::ln::script::ShutdownScript;
 use crate::prelude::*;
 use core::convert::TryInto;
 use core::sync::atomic::{AtomicUsize, Ordering};
-use crate::sync::Mutex;
 use crate::io::{self, Error};
 use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
+use crate::util::atomic_counter::AtomicCounter;
 use crate::util::chacha20::ChaCha20;
 use crate::util::invoice::construct_invoice_preimage;
 
@@ -980,7 +980,8 @@ pub struct KeysManager {
 	channel_master_key: ExtendedPrivKey,
 	channel_child_index: AtomicUsize,
 
-	chacha: Mutex<ChaCha20>,
+	rand_bytes_unique_start: [u8; 32],
+	rand_bytes_index: AtomicCounter,
 
 	seed: [u8; 32],
 	starting_time_secs: u64,
@@ -1030,10 +1031,11 @@ impl KeysManager {
 				let mut inbound_pmt_key_bytes = [0; 32];
 				inbound_pmt_key_bytes.copy_from_slice(&inbound_payment_key[..]);
 
-				let mut nonce = [0u8; 12];
-				nonce[..8].copy_from_slice(&starting_time_secs.to_be_bytes());
-				nonce[8..12].copy_from_slice(&starting_time_nanos.to_be_bytes());
-				let chacha = Mutex::new(ChaCha20::new(seed, &nonce));
+				let mut rand_bytes_unique_start = Sha256::engine();
+				rand_bytes_unique_start.input(&starting_time_secs.to_be_bytes());
+				rand_bytes_unique_start.input(&starting_time_nanos.to_be_bytes());
+				rand_bytes_unique_start.input(seed);
+				let rand_bytes_unique_start = Sha256::from_engine(rand_bytes_unique_start).into_inner();
 
 				let mut res = KeysManager {
 					secp_ctx,
@@ -1047,7 +1049,8 @@ impl KeysManager {
 					channel_master_key,
 					channel_child_index: AtomicUsize::new(0),
 
-					chacha,
+					rand_bytes_unique_start,
+					rand_bytes_index: AtomicCounter::new(),
 
 					seed: *seed,
 					starting_time_secs,
@@ -1244,11 +1247,10 @@ impl KeysManager {
 
 impl EntropySource for KeysManager {
 	fn get_secure_random_bytes(&self) -> [u8; 32] {
-		let mut chacha = self.chacha.lock().unwrap();
-
-		let mut random_bytes = [0u8; 32];
-		chacha.process_in_place(&mut random_bytes);
-		random_bytes
+		let index = self.rand_bytes_index.get_increment();
+		let mut nonce = [0u8; 16];
+		nonce[..8].copy_from_slice(&index.to_be_bytes());
+		ChaCha20::get_single_block(&self.rand_bytes_unique_start, &nonce)
 	}
 }