Add a method to get session secret for onion packet to KeysInterface
[rust-lightning] / src / chain / keysinterface.rs
index 84ebde34252c95a530c4c0bb6c5f6ef63d9f64ac..4e35e6764d246ced9b431ad473bfe84bf13ecb7f 100644 (file)
@@ -14,11 +14,16 @@ use secp256k1::Secp256k1;
 use secp256k1;
 
 use crypto::hkdf::{hkdf_extract,hkdf_expand};
+use crypto::digest::Digest;
 
 use util::sha2::Sha256;
 use util::logger::Logger;
+use util::rng;
+use util::byte_utils;
 
+use std::time::{SystemTime, UNIX_EPOCH};
 use std::sync::Arc;
+use std::sync::atomic::{AtomicUsize, Ordering};
 
 /// When on-chain outputs are created by rust-lightning an event is generated which informs the
 /// user thereof. This enum describes the format of the output and provides the OutPoint.
@@ -32,19 +37,34 @@ pub enum SpendableOutputDescriptor {
                /// The output which is referenced by the given outpoint
                output: TxOut,
        },
-       /// Outpoint commits to a P2WSH, should be spend by the following witness :
+       /// Outpoint commits to a P2WSH
+       /// P2WSH should be spend by the following witness :
        /// <local_delayedsig> 0 <witnessScript>
        /// With input nSequence set to_self_delay.
-       /// Outputs from a HTLC-Success/Timeout tx
-       DynamicOutput {
+       /// Outputs from a HTLC-Success/Timeout tx/commitment tx
+       DynamicOutputP2WSH {
                /// Outpoint spendable by user wallet
                outpoint: OutPoint,
-               /// local_delayedkey = delayed_payment_basepoint_secret + SHA256(per_commitment_point || delayed_payment_basepoint
-               local_delayedkey: SecretKey,
-               /// witness redeemScript encumbering output
+               /// local_delayedkey = delayed_payment_basepoint_secret + SHA256(per_commitment_point || delayed_payment_basepoint) OR
+               key: SecretKey,
+               /// witness redeemScript encumbering output.
                witness_script: Script,
                /// nSequence input must commit to self_delay to satisfy script's OP_CSV
                to_self_delay: u16,
+               /// The output which is referenced by the given outpoint
+               output: TxOut,
+       },
+       /// Outpoint commits to a P2WPKH
+       /// P2WPKH should be spend by the following witness :
+       /// <local_sig> <local_pubkey>
+       /// Outputs to_remote from a commitment tx
+       DynamicOutputP2WPKH {
+               /// Outpoint spendable by user wallet
+               outpoint: OutPoint,
+               /// localkey = payment_basepoint_secret + SHA256(per_commitment_point || payment_basepoint
+               key: SecretKey,
+               /// The output which is reference by the given outpoint
+               output: TxOut,
        }
 }
 
@@ -59,6 +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
@@ -74,12 +96,19 @@ pub struct ChannelKeys {
        pub delayed_payment_base_key: SecretKey,
        /// Local htlc secret key used in commitment tx htlc outputs
        pub htlc_base_key: SecretKey,
-       /// Local secret key used in justice tx, claim tx and preimage tx outputs
-       pub channel_monitor_claim_key: SecretKey,
        /// Commitment seed
        pub commitment_seed: [u8; 32],
 }
 
+impl_writeable!(ChannelKeys, 0, {
+       funding_key,
+       revocation_base_key,
+       payment_base_key,
+       delayed_payment_base_key,
+       htlc_base_key,
+       commitment_seed
+});
+
 impl ChannelKeys {
        /// Generate a set of lightning keys needed to operate a channel by HKDF-expanding a given
        /// random 32-byte seed
@@ -104,9 +133,6 @@ impl ChannelKeys {
                hkdf_expand(Sha256::new(), &prk, b"rust-lightning htlc base key info", &mut okm);
                let htlc_base_key = SecretKey::from_slice(&secp_ctx, &okm).expect("Sha256 is broken");
 
-               hkdf_expand(Sha256::new(), &prk, b"rust-lightning channel monitor claim key info", &mut okm);
-               let channel_monitor_claim_key = SecretKey::from_slice(&secp_ctx, &okm).expect("Sha256 is broken");
-
                hkdf_expand(Sha256::new(), &prk, b"rust-lightning local commitment seed info", &mut okm);
 
                ChannelKeys {
@@ -115,7 +141,6 @@ impl ChannelKeys {
                        payment_base_key: payment_base_key,
                        delayed_payment_base_key: delayed_payment_base_key,
                        htlc_base_key: htlc_base_key,
-                       channel_monitor_claim_key: channel_monitor_claim_key,
                        commitment_seed: okm
                }
        }
@@ -134,6 +159,9 @@ pub struct KeysManager {
        destination_script: Script,
        shutdown_pubkey: PublicKey,
        channel_master_key: ExtendedPrivKey,
+       channel_child_index: AtomicUsize,
+       session_master_key: ExtendedPrivKey,
+       session_child_index: AtomicUsize,
 
        logger: Arc<Logger>,
 }
@@ -160,12 +188,16 @@ 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,
                                        destination_script,
                                        shutdown_pubkey,
                                        channel_master_key,
+                                       channel_child_index: AtomicUsize::new(0),
+                                       session_master_key,
+                                       session_child_index: AtomicUsize::new(0),
 
                                        logger,
                                }
@@ -189,11 +221,40 @@ impl KeysInterface for KeysManager {
        }
 
        fn get_channel_keys(&self, _inbound: bool) -> ChannelKeys {
-               let channel_pubkey = ExtendedPubKey::from_private(&self.secp_ctx, &self. channel_master_key);
-               let mut seed = [0; 32];
-               for (arr, slice) in seed.iter_mut().zip((&channel_pubkey.public_key.serialize()[0..32]).iter()) {
-                       *arr = *slice;
-               }
+               // We only seriously intend to rely on the channel_master_key for true secure
+               // entropy, everything else just ensures uniqueness. We generally don't expect
+               // all clients to have non-broken RNGs here, so we also include the current
+               // time as a fallback to get uniqueness.
+               let mut sha = Sha256::new();
+
+               let mut seed = [0u8; 32];
+               rng::fill_bytes(&mut seed[..]);
+               sha.input(&seed);
+
+               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.channel_child_index.fetch_add(1, Ordering::AcqRel);
+               let child_privkey = self.channel_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 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")
+       }
 }