Merge pull request #1812 from valentinewallace/2022-10-chanman-router-param

[rust-lightning] / lightning / src / chain / keysinterface.rs

diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs
index 58abe7e9ddcb2dcf71ce26ec9ddd9d1824bb2f47..16075cdac4b2375b989abd28c7eec105af610c79 100644 (file)
--- a/lightning/src/chain/keysinterface.rs
+++ b/lightning/src/chain/keysinterface.rs
@@ -1072,7 +1072,9 @@ impl KeysManager {
                // We only seriously intend to rely on the channel_master_key for true secure
                // entropy, everything else just ensures uniqueness. We rely on the unique_start (ie
                // starting_time provided in the constructor) to be unique.
-               let child_privkey = self.channel_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(chan_id as u32).expect("key space exhausted")).expect("Your RNG is busted");
+               let child_privkey = self.channel_master_key.ckd_priv(&self.secp_ctx,
+                               ChildNumber::from_hardened_idx((chan_id as u32) % (1 << 31)).expect("key space exhausted")
+                       ).expect("Your RNG is busted");
                unique_start.input(&child_privkey.private_key[..]);
 
                let seed = Sha256::from_engine(unique_start).into_inner();
@@ -1298,7 +1300,12 @@ impl SignerProvider for KeysManager {
 
        fn generate_channel_keys_id(&self, _inbound: bool, _channel_value_satoshis: u64, user_channel_id: u128) -> [u8; 32] {
                let child_idx = self.channel_child_index.fetch_add(1, Ordering::AcqRel);
-               assert!(child_idx <= core::u32::MAX as usize);
+               // `child_idx` is the only thing guaranteed to make each channel unique without a restart
+               // (though `user_channel_id` should help, depending on user behavior). If it manages to
+               // roll over, we may generate duplicate keys for two different channels, which could result
+               // in loss of funds. Because we only support 32-bit+ systems, assert that our `AtomicUsize`
+               // doesn't reach `u32::MAX`.
+               assert!(child_idx < core::u32::MAX as usize, "2^32 channels opened without restart");
                let mut id = [0; 32];
                id[0..4].copy_from_slice(&(child_idx as u32).to_be_bytes());
                id[4..8].copy_from_slice(&self.starting_time_nanos.to_be_bytes());