Add a method to get session secret for onion packet to KeysInterface

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

diff --git a/src/chain/keysinterface.rs b/src/chain/keysinterface.rs
index 8e71625df73c29338d71a7457180c8f59d4d962e..4e35e6764d246ced9b431ad473bfe84bf13ecb7f 100644 (file)
--- a/src/chain/keysinterface.rs
+++ b/src/chain/keysinterface.rs
@@ -79,6 +79,8 @@ pub trait KeysInterface: Send + Sync {
        /// Get a new set of ChannelKeys for per-channel secrets. These MUST be unique even if you
        /// restarted with some stale data!
        fn get_channel_keys(&self, inbound: bool) -> ChannelKeys;
+       /// Get a secret for construting an onion packet
+       fn get_session_key(&self) -> SecretKey;
 }
 
 /// Set of lightning keys needed to operate a channel as described in BOLT 3
@@ -158,6 +160,8 @@ pub struct KeysManager {
        shutdown_pubkey: PublicKey,
        channel_master_key: ExtendedPrivKey,
        channel_child_index: AtomicUsize,
+       session_master_key: ExtendedPrivKey,
+       session_child_index: AtomicUsize,
 
        logger: Arc<Logger>,
 }
@@ -184,6 +188,7 @@ impl KeysManager {
                                        Err(_) => panic!("Your RNG is busted"),
                                };
                                let channel_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(3)).expect("Your RNG is busted");
+                               let session_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(4)).expect("Your RNG is busted");
                                KeysManager {
                                        secp_ctx,
                                        node_secret,
@@ -191,6 +196,8 @@ impl KeysManager {
                                        shutdown_pubkey,
                                        channel_master_key,
                                        channel_child_index: AtomicUsize::new(0),
+                                       session_master_key,
+                                       session_child_index: AtomicUsize::new(0),
 
                                        logger,
                                }
@@ -235,4 +242,19 @@ impl KeysInterface for KeysManager {
                sha.result(&mut seed);
                ChannelKeys::new_from_seed(&seed)
        }
+
+       fn get_session_key(&self) -> SecretKey {
+               let mut sha = Sha256::new();
+               let mut res = [0u8; 32];
+
+               let now = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time went backwards");
+               sha.input(&byte_utils::be32_to_array(now.subsec_nanos()));
+               sha.input(&byte_utils::be64_to_array(now.as_secs()));
+
+               let child_ix = self.session_child_index.fetch_add(1, Ordering::AcqRel);
+               let child_privkey = self.session_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(child_ix as u32)).expect("Your RNG is busted");
+               sha.input(&child_privkey.secret_key[..]);
+               sha.result(&mut res);
+               SecretKey::from_slice(&self.secp_ctx, &res).expect("Your RNG is busted")
+       }
 }