Ensure `derive_channel_keys` doesn't panic if per-run seed is high

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

diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs
index 1426ff5ce887f4d0ef440874ab9df00849de978a..0a464193d0d6ba1765bc584514b1661b9164c4f3 100644 (file)
--- a/lightning/src/chain/keysinterface.rs
+++ b/lightning/src/chain/keysinterface.rs
@@ -1051,7 +1051,9 @@ 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();