Merge pull request #1039 from lightning-signer/2021-08-more-enforcement
authorMatt Corallo <649246+TheBlueMatt@users.noreply.github.com>
Mon, 30 Aug 2021 02:43:01 +0000 (02:43 +0000)
committerGitHub <noreply@github.com>
Mon, 30 Aug 2021 02:43:01 +0000 (02:43 +0000)
Introduce EnforcementState, validate release of revocation secret

fuzz/src/chanmon_consistency.rs
fuzz/src/full_stack.rs
lightning/src/chain/keysinterface.rs
lightning/src/ln/channel.rs
lightning/src/ln/functional_tests.rs
lightning/src/ln/msgs.rs
lightning/src/util/enforcing_trait_impls.rs
lightning/src/util/test_utils.rs

index 7eacf25365b0a45157f578ad210be31540dee052..88826d65570fb94c7cfda47de7cfa58c53e5027e 100644 (file)
@@ -41,7 +41,7 @@ use lightning::ln::channel::FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE;
 use lightning::ln::features::{ChannelFeatures, InitFeatures, NodeFeatures};
 use lightning::ln::msgs::{CommitmentUpdate, ChannelMessageHandler, DecodeError, UpdateAddHTLC, Init};
 use lightning::ln::script::ShutdownScript;
-use lightning::util::enforcing_trait_impls::{EnforcingSigner, INITIAL_REVOKED_COMMITMENT_NUMBER};
+use lightning::util::enforcing_trait_impls::{EnforcingSigner, EnforcementState};
 use lightning::util::errors::APIError;
 use lightning::util::events;
 use lightning::util::logger::Logger;
@@ -161,7 +161,7 @@ impl chain::Watch<EnforcingSigner> for TestChainMonitor {
 struct KeyProvider {
        node_id: u8,
        rand_bytes_id: atomic::AtomicU32,
-       revoked_commitments: Mutex<HashMap<[u8;32], Arc<Mutex<u64>>>>,
+       enforcement_states: Mutex<HashMap<[u8;32], Arc<Mutex<EnforcementState>>>>,
 }
 impl KeysInterface for KeyProvider {
        type Signer = EnforcingSigner;
@@ -198,7 +198,7 @@ impl KeysInterface for KeyProvider {
                        channel_value_satoshis,
                        [0; 32],
                );
-               let revoked_commitment = self.make_revoked_commitment_cell(keys.commitment_seed);
+               let revoked_commitment = self.make_enforcement_state_cell(keys.commitment_seed);
                EnforcingSigner::new_with_revoked(keys, revoked_commitment, false)
        }
 
@@ -213,14 +213,11 @@ impl KeysInterface for KeyProvider {
                let mut reader = std::io::Cursor::new(buffer);
 
                let inner: InMemorySigner = Readable::read(&mut reader)?;
-               let revoked_commitment = self.make_revoked_commitment_cell(inner.commitment_seed);
-
-               let last_commitment_number = Readable::read(&mut reader)?;
+               let state = self.make_enforcement_state_cell(inner.commitment_seed);
 
                Ok(EnforcingSigner {
                        inner,
-                       last_commitment_number: Arc::new(Mutex::new(last_commitment_number)),
-                       revoked_commitment,
+                       state,
                        disable_revocation_policy_check: false,
                })
        }
@@ -231,10 +228,10 @@ impl KeysInterface for KeyProvider {
 }
 
 impl KeyProvider {
-       fn make_revoked_commitment_cell(&self, commitment_seed: [u8; 32]) -> Arc<Mutex<u64>> {
-               let mut revoked_commitments = self.revoked_commitments.lock().unwrap();
+       fn make_enforcement_state_cell(&self, commitment_seed: [u8; 32]) -> Arc<Mutex<EnforcementState>> {
+               let mut revoked_commitments = self.enforcement_states.lock().unwrap();
                if !revoked_commitments.contains_key(&commitment_seed) {
-                       revoked_commitments.insert(commitment_seed, Arc::new(Mutex::new(INITIAL_REVOKED_COMMITMENT_NUMBER)));
+                       revoked_commitments.insert(commitment_seed, Arc::new(Mutex::new(EnforcementState::new())));
                }
                let cell = revoked_commitments.get(&commitment_seed).unwrap();
                Arc::clone(cell)
@@ -351,7 +348,7 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
        macro_rules! make_node {
                ($node_id: expr, $fee_estimator: expr) => { {
                        let logger: Arc<dyn Logger> = Arc::new(test_logger::TestLogger::new($node_id.to_string(), out.clone()));
-                       let keys_manager = Arc::new(KeyProvider { node_id: $node_id, rand_bytes_id: atomic::AtomicU32::new(0), revoked_commitments: Mutex::new(HashMap::new()) });
+                       let keys_manager = Arc::new(KeyProvider { node_id: $node_id, rand_bytes_id: atomic::AtomicU32::new(0), enforcement_states: Mutex::new(HashMap::new()) });
                        let monitor = Arc::new(TestChainMonitor::new(broadcast.clone(), logger.clone(), $fee_estimator.clone(), Arc::new(TestPersister{}), Arc::clone(&keys_manager)));
 
                        let mut config = UserConfig::default();
index 510966f0d4a63dd1c33815073a1f07b42548f56f..28592ffda512fe6677a6431ebf35303526b2a648 100644 (file)
@@ -42,7 +42,7 @@ use lightning::routing::network_graph::NetGraphMsgHandler;
 use lightning::util::config::UserConfig;
 use lightning::util::errors::APIError;
 use lightning::util::events::Event;
-use lightning::util::enforcing_trait_impls::EnforcingSigner;
+use lightning::util::enforcing_trait_impls::{EnforcingSigner, EnforcementState};
 use lightning::util::logger::Logger;
 use lightning::util::ser::Readable;
 
@@ -315,8 +315,15 @@ impl KeysInterface for KeyProvider {
                (ctr >> 8*7) as u8, (ctr >> 8*6) as u8, (ctr >> 8*5) as u8, (ctr >> 8*4) as u8, (ctr >> 8*3) as u8, (ctr >> 8*2) as u8, (ctr >> 8*1) as u8, 14, (ctr >> 8*0) as u8]
        }
 
-       fn read_chan_signer(&self, data: &[u8]) -> Result<EnforcingSigner, DecodeError> {
-               EnforcingSigner::read(&mut std::io::Cursor::new(data))
+       fn read_chan_signer(&self, mut data: &[u8]) -> Result<EnforcingSigner, DecodeError> {
+               let inner: InMemorySigner = Readable::read(&mut data)?;
+               let state = Arc::new(Mutex::new(EnforcementState::new()));
+
+               Ok(EnforcingSigner::new_with_revoked(
+                       inner,
+                       state,
+                       false
+               ))
        }
 
        fn sign_invoice(&self, _invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()> {
index c2e78a79394ea84cdbc69e88e269b863a614b948..44a03d09f8e717019c19c070159a7b7556b24723 100644 (file)
@@ -212,6 +212,13 @@ pub trait BaseSign {
        /// Note that the commitment number starts at (1 << 48) - 1 and counts backwards.
        // TODO: return a Result so we can signal a validation error
        fn release_commitment_secret(&self, idx: u64) -> [u8; 32];
+       /// Validate the counterparty's signatures on the holder commitment transaction and HTLCs.
+       ///
+       /// This is required in order for the signer to make sure that releasing a commitment
+       /// secret won't leave us without a broadcastable holder transaction.
+       /// Policy checks should be implemented in this function, including checking the amount
+       /// sent to us and checking the HTLCs.
+       fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction) -> Result<(), ()>;
        /// Gets the holder's channel public keys and basepoints
        fn pubkeys(&self) -> &ChannelPublicKeys;
        /// Gets an arbitrary identifier describing the set of keys which are provided back to you in
@@ -222,9 +229,17 @@ pub trait BaseSign {
        /// Create a signature for a counterparty's commitment transaction and associated HTLC transactions.
        ///
        /// Note that if signing fails or is rejected, the channel will be force-closed.
+       ///
+       /// Policy checks should be implemented in this function, including checking the amount
+       /// sent to us and checking the HTLCs.
        //
        // TODO: Document the things someone using this interface should enforce before signing.
        fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()>;
+       /// Validate the counterparty's revocation.
+       ///
+       /// This is required in order for the signer to make sure that the state has moved
+       /// forward and it is safe to sign the next counterparty commitment.
+       fn validate_counterparty_revocation(&self, idx: u64, secret: &SecretKey) -> Result<(), ()>;
 
        /// Create a signatures for a holder's commitment transaction and its claiming HTLC transactions.
        /// This will only ever be called with a non-revoked commitment_tx.  This will be called with the
@@ -558,6 +573,10 @@ impl BaseSign for InMemorySigner {
                chan_utils::build_commitment_secret(&self.commitment_seed, idx)
        }
 
+       fn validate_holder_commitment(&self, _holder_tx: &HolderCommitmentTransaction) -> Result<(), ()> {
+               Ok(())
+       }
+
        fn pubkeys(&self) -> &ChannelPublicKeys { &self.holder_channel_pubkeys }
        fn channel_keys_id(&self) -> [u8; 32] { self.channel_keys_id }
 
@@ -584,6 +603,10 @@ impl BaseSign for InMemorySigner {
                Ok((commitment_sig, htlc_sigs))
        }
 
+       fn validate_counterparty_revocation(&self, _idx: u64, _secret: &SecretKey) -> Result<(), ()> {
+               Ok(())
+       }
+
        fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
                let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
                let funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &self.counterparty_pubkeys().funding_pubkey);
index 03968118a16a59aa481cd148a81309f30cfdcc95..e2a19618be52c4eaace19472cbdbf1a72d6800ef 100644 (file)
@@ -1791,6 +1791,9 @@ impl<Signer: Sign> Channel<Signer> {
                        self.counterparty_funding_pubkey()
                );
 
+               self.holder_signer.validate_holder_commitment(&holder_commitment_tx)
+                       .map_err(|_| ChannelError::Close("Failed to validate our commitment".to_owned()))?;
+
                // Now that we're past error-generating stuff, update our local state:
 
                let funding_redeemscript = self.get_funding_redeemscript();
@@ -1865,6 +1868,9 @@ impl<Signer: Sign> Channel<Signer> {
                        self.counterparty_funding_pubkey()
                );
 
+               self.holder_signer.validate_holder_commitment(&holder_commitment_tx)
+                       .map_err(|_| ChannelError::Close("Failed to validate our commitment".to_owned()))?;
+
 
                let funding_redeemscript = self.get_funding_redeemscript();
                let funding_txo = self.get_funding_txo().unwrap();
@@ -2502,6 +2508,8 @@ impl<Signer: Sign> Channel<Signer> {
                );
 
                let next_per_commitment_point = self.holder_signer.get_per_commitment_point(self.cur_holder_commitment_transaction_number - 1, &self.secp_ctx);
+               self.holder_signer.validate_holder_commitment(&holder_commitment_tx)
+                       .map_err(|_| (None, ChannelError::Close("Failed to validate our commitment".to_owned())))?;
                let per_commitment_secret = self.holder_signer.release_commitment_secret(self.cur_holder_commitment_transaction_number + 1);
 
                // Update state now that we've passed all the can-fail calls...
@@ -2738,8 +2746,10 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(ChannelError::Close("Peer sent revoke_and_ack after we'd started exchanging closing_signeds".to_owned()));
                }
 
+               let secret = secp_check!(SecretKey::from_slice(&msg.per_commitment_secret), "Peer provided an invalid per_commitment_secret".to_owned());
+
                if let Some(counterparty_prev_commitment_point) = self.counterparty_prev_commitment_point {
-                       if PublicKey::from_secret_key(&self.secp_ctx, &secp_check!(SecretKey::from_slice(&msg.per_commitment_secret), "Peer provided an invalid per_commitment_secret".to_owned())) != counterparty_prev_commitment_point {
+                       if PublicKey::from_secret_key(&self.secp_ctx, &secret) != counterparty_prev_commitment_point {
                                return Err(ChannelError::Close("Got a revoke commitment secret which didn't correspond to their current pubkey".to_owned()));
                        }
                }
@@ -2761,6 +2771,11 @@ impl<Signer: Sign> Channel<Signer> {
                        *self.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = None;
                }
 
+               self.holder_signer.validate_counterparty_revocation(
+                       self.cur_counterparty_commitment_transaction_number + 1,
+                       &secret
+               ).map_err(|_| ChannelError::Close("Failed to validate revocation from peer".to_owned()))?;
+
                self.commitment_secrets.provide_secret(self.cur_counterparty_commitment_transaction_number + 1, msg.per_commitment_secret)
                        .map_err(|_| ChannelError::Close("Previous secrets did not match new one".to_owned()))?;
                self.latest_monitor_update_id += 1;
index 1328939570eb9204b31153597841fbda151f2ef3..7391523485d533ba306f06c0a14176e661b2351f 100644 (file)
@@ -1301,6 +1301,9 @@ fn test_fee_spike_violation_fails_htlc() {
                let chan_lock = nodes[0].node.channel_state.lock().unwrap();
                let local_chan = chan_lock.by_id.get(&chan.2).unwrap();
                let chan_signer = local_chan.get_signer();
+               // Make the signer believe we validated another commitment, so we can release the secret
+               chan_signer.get_enforcement_state().last_holder_commitment -= 1;
+
                let pubkeys = chan_signer.pubkeys();
                (pubkeys.revocation_basepoint, pubkeys.htlc_basepoint,
                 chan_signer.release_commitment_secret(INITIAL_COMMITMENT_NUMBER),
@@ -7981,7 +7984,7 @@ fn test_counterparty_raa_skip_no_crash() {
        // commitment transaction, we would have happily carried on and provided them the next
        // commitment transaction based on one RAA forward. This would probably eventually have led to
        // channel closure, but it would not have resulted in funds loss. Still, our
-       // EnforcingSigner would have paniced as it doesn't like jumps into the future. Here, we
+       // EnforcingSigner would have panicked as it doesn't like jumps into the future. Here, we
        // check simply that the channel is closed in response to such an RAA, but don't check whether
        // we decide to punish our counterparty for revoking their funds (as we don't currently
        // implement that).
@@ -7992,11 +7995,19 @@ fn test_counterparty_raa_skip_no_crash() {
        let channel_id = create_announced_chan_between_nodes(&nodes, 0, 1, InitFeatures::known(), InitFeatures::known()).2;
 
        let mut guard = nodes[0].node.channel_state.lock().unwrap();
-       let keys = &guard.by_id.get_mut(&channel_id).unwrap().get_signer();
+       let keys = guard.by_id.get_mut(&channel_id).unwrap().get_signer();
+
        const INITIAL_COMMITMENT_NUMBER: u64 = (1 << 48) - 1;
+
+       // Make signer believe we got a counterparty signature, so that it allows the revocation
+       keys.get_enforcement_state().last_holder_commitment -= 1;
        let per_commitment_secret = keys.release_commitment_secret(INITIAL_COMMITMENT_NUMBER);
+
        // Must revoke without gaps
+       keys.get_enforcement_state().last_holder_commitment -= 1;
        keys.release_commitment_secret(INITIAL_COMMITMENT_NUMBER - 1);
+
+       keys.get_enforcement_state().last_holder_commitment -= 1;
        let next_per_commitment_point = PublicKey::from_secret_key(&Secp256k1::new(),
                &SecretKey::from_slice(&keys.release_commitment_secret(INITIAL_COMMITMENT_NUMBER - 2)).unwrap());
 
index f94909a9ae5499c35a5c6f5719c1705ede98ed91..5b49f43b1188013c5f44822e59622409590aefb3 100644 (file)
@@ -194,7 +194,7 @@ pub struct FundingCreated {
        pub funding_txid: Txid,
        /// The specific output index funding this channel
        pub funding_output_index: u16,
-       /// The signature of the channel initiator (funder) on the funding transaction
+       /// The signature of the channel initiator (funder) on the initial commitment transaction
        pub signature: Signature,
 }
 
@@ -203,7 +203,7 @@ pub struct FundingCreated {
 pub struct FundingSigned {
        /// The channel ID
        pub channel_id: [u8; 32],
-       /// The signature of the channel acceptor (fundee) on the funding transaction
+       /// The signature of the channel acceptor (fundee) on the initial commitment transaction
        pub signature: Signature,
 }
 
index baa9e7cd16d98b05be00abcf5d7ebc46a75cbbf8..b7dfe767057836cdd59dd61c5bae32d88c362c6a 100644 (file)
@@ -11,10 +11,10 @@ use ln::chan_utils::{HTLCOutputInCommitment, ChannelPublicKeys, HolderCommitment
 use ln::{chan_utils, msgs};
 use chain::keysinterface::{Sign, InMemorySigner, BaseSign};
 
-use io;
 use prelude::*;
 use core::cmp;
 use sync::{Mutex, Arc};
+#[cfg(test)] use sync::MutexGuard;
 
 use bitcoin::blockdata::transaction::{Transaction, SigHashType};
 use bitcoin::util::bip143;
@@ -22,9 +22,8 @@ use bitcoin::util::bip143;
 use bitcoin::secp256k1;
 use bitcoin::secp256k1::key::{SecretKey, PublicKey};
 use bitcoin::secp256k1::{Secp256k1, Signature};
-use util::ser::{Writeable, Writer, Readable};
+use util::ser::{Writeable, Writer};
 use io::Error;
-use ln::msgs::DecodeError;
 
 /// Initial value for revoked commitment downward counter
 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
@@ -35,31 +34,34 @@ pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
 /// - When signing, the holder transaction has not been revoked
 /// - When revoking, the holder transaction has not been signed
 /// - The holder commitment number is monotonic and without gaps
+/// - The revoked holder commitment number is monotonic and without gaps
+/// - There is at least one unrevoked holder transaction at all times
 /// - The counterparty commitment number is monotonic and without gaps
 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
 ///
 /// Eventually we will probably want to expose a variant of this which would essentially
 /// be what you'd want to run on a hardware wallet.
 ///
+/// Note that counterparty signatures on the holder transaction are not checked, but it should
+/// be in a complete implementation.
+///
 /// Note that before we do so we should ensure its serialization format has backwards- and
 /// forwards-compatibility prefix/suffixes!
 #[derive(Clone)]
 pub struct EnforcingSigner {
        pub inner: InMemorySigner,
-       /// The last counterparty commitment number we signed, backwards counting
-       pub last_commitment_number: Arc<Mutex<Option<u64>>>,
-       /// The last holder commitment number we revoked, backwards counting
-       pub revoked_commitment: Arc<Mutex<u64>>,
+       /// Channel state used for policy enforcement
+       pub state: Arc<Mutex<EnforcementState>>,
        pub disable_revocation_policy_check: bool,
 }
 
 impl EnforcingSigner {
        /// Construct an EnforcingSigner
        pub fn new(inner: InMemorySigner) -> Self {
+               let state = Arc::new(Mutex::new(EnforcementState::new()));
                Self {
                        inner,
-                       last_commitment_number: Arc::new(Mutex::new(None)),
-                       revoked_commitment: Arc::new(Mutex::new(INITIAL_REVOKED_COMMITMENT_NUMBER)),
+                       state,
                        disable_revocation_policy_check: false
                }
        }
@@ -67,16 +69,20 @@ impl EnforcingSigner {
        /// Construct an EnforcingSigner with externally managed storage
        ///
        /// Since there are multiple copies of this struct for each channel, some coordination is needed
-       /// so that all copies are aware of revocations.  A pointer to this state is provided here, usually
-       /// by an implementation of KeysInterface.
-       pub fn new_with_revoked(inner: InMemorySigner, revoked_commitment: Arc<Mutex<u64>>, disable_revocation_policy_check: bool) -> Self {
+       /// so that all copies are aware of enforcement state.  A pointer to this state is provided
+       /// here, usually by an implementation of KeysInterface.
+       pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
                Self {
                        inner,
-                       last_commitment_number: Arc::new(Mutex::new(None)),
-                       revoked_commitment,
+                       state,
                        disable_revocation_policy_check
                }
        }
+
+       #[cfg(test)]
+       pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
+               self.state.lock().unwrap()
+       }
 }
 
 impl BaseSign for EnforcingSigner {
@@ -86,13 +92,22 @@ impl BaseSign for EnforcingSigner {
 
        fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
                {
-                       let mut revoked = self.revoked_commitment.lock().unwrap();
-                       assert!(idx == *revoked || idx == *revoked - 1, "can only revoke the current or next unrevoked commitment - trying {}, revoked {}", idx, *revoked);
-                       *revoked = idx;
+                       let mut state = self.state.lock().unwrap();
+                       assert!(idx == state.last_holder_revoked_commitment || idx == state.last_holder_revoked_commitment - 1, "can only revoke the current or next unrevoked commitment - trying {}, last revoked {}", idx, state.last_holder_revoked_commitment);
+                       assert!(idx > state.last_holder_commitment, "cannot revoke the last holder commitment - attempted to revoke {} last commitment {}", idx, state.last_holder_commitment);
+                       state.last_holder_revoked_commitment = idx;
                }
                self.inner.release_commitment_secret(idx)
        }
 
+       fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction) -> Result<(), ()> {
+               let mut state = self.state.lock().unwrap();
+               let idx = holder_tx.commitment_number();
+               assert!(idx == state.last_holder_commitment || idx == state.last_holder_commitment - 1, "expecting to validate the current or next holder commitment - trying {}, current {}", idx, state.last_holder_commitment);
+               state.last_holder_commitment = idx;
+               Ok(())
+       }
+
        fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
        fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
 
@@ -100,29 +115,39 @@ impl BaseSign for EnforcingSigner {
                self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
 
                {
-                       let mut last_commitment_number_guard = self.last_commitment_number.lock().unwrap();
+                       let mut state = self.state.lock().unwrap();
                        let actual_commitment_number = commitment_tx.commitment_number();
-                       let last_commitment_number = last_commitment_number_guard.unwrap_or(actual_commitment_number);
+                       let last_commitment_number = state.last_counterparty_commitment;
                        // These commitment numbers are backwards counting.  We expect either the same as the previously encountered,
                        // or the next one.
                        assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
-                       *last_commitment_number_guard = Some(cmp::min(last_commitment_number, actual_commitment_number))
+                       // Ensure that the counterparty doesn't get more than two broadcastable commitments -
+                       // the last and the one we are trying to sign
+                       assert!(actual_commitment_number >= state.last_counterparty_revoked_commitment - 2, "cannot sign a commitment if second to last wasn't revoked - signing {} revoked {}", actual_commitment_number, state.last_counterparty_revoked_commitment);
+                       state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
                }
 
                Ok(self.inner.sign_counterparty_commitment(commitment_tx, secp_ctx).unwrap())
        }
 
+       fn validate_counterparty_revocation(&self, idx: u64, _secret: &SecretKey) -> Result<(), ()> {
+               let mut state = self.state.lock().unwrap();
+               assert!(idx == state.last_counterparty_revoked_commitment || idx == state.last_counterparty_revoked_commitment - 1, "expecting to validate the current or next counterparty revocation - trying {}, current {}", idx, state.last_counterparty_revoked_commitment);
+               state.last_counterparty_revoked_commitment = idx;
+               Ok(())
+       }
+
        fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
                let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
                let commitment_txid = trusted_tx.txid();
                let holder_csv = self.inner.counterparty_selected_contest_delay();
 
-               let revoked = self.revoked_commitment.lock().unwrap();
+               let state = self.state.lock().unwrap();
                let commitment_number = trusted_tx.commitment_number();
-               if *revoked - 1 != commitment_number && *revoked - 2 != commitment_number {
+               if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
                        if !self.disable_revocation_policy_check {
                                panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
-                                      *revoked, commitment_number, self.inner.commitment_seed[0])
+                                      state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
                        }
                }
 
@@ -174,26 +199,15 @@ impl Sign for EnforcingSigner {}
 
 impl Writeable for EnforcingSigner {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
+               // EnforcingSigner has two fields - `inner` ([`InMemorySigner`]) and `state`
+               // ([`EnforcementState`]). `inner` is serialized here and deserialized by
+               // [`KeysInterface::read_chan_signer`]. `state` is managed by [`KeysInterface`]
+               // and will be serialized as needed by the implementation of that trait.
                self.inner.write(writer)?;
-               let last = *self.last_commitment_number.lock().unwrap();
-               last.write(writer)?;
                Ok(())
        }
 }
 
-impl Readable for EnforcingSigner {
-       fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
-               let inner = Readable::read(reader)?;
-               let last_commitment_number = Readable::read(reader)?;
-               Ok(EnforcingSigner {
-                       inner,
-                       last_commitment_number: Arc::new(Mutex::new(last_commitment_number)),
-                       revoked_commitment: Arc::new(Mutex::new(INITIAL_REVOKED_COMMITMENT_NUMBER)),
-                       disable_revocation_policy_check: false,
-               })
-       }
-}
-
 impl EnforcingSigner {
        fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
                commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
@@ -207,3 +221,31 @@ impl EnforcingSigner {
                        .expect("derived different per-tx keys or built transaction")
        }
 }
+
+/// The state used by [`EnforcingSigner`] in order to enforce policy checks
+///
+/// This structure is maintained by KeysInterface since we may have multiple copies of
+/// the signer and they must coordinate their state.
+#[derive(Clone)]
+pub struct EnforcementState {
+       /// The last counterparty commitment number we signed, backwards counting
+       pub last_counterparty_commitment: u64,
+       /// The last counterparty commitment they revoked, backwards counting
+       pub last_counterparty_revoked_commitment: u64,
+       /// The last holder commitment number we revoked, backwards counting
+       pub last_holder_revoked_commitment: u64,
+       /// The last validated holder commitment number, backwards counting
+       pub last_holder_commitment: u64,
+}
+
+impl EnforcementState {
+       /// Enforcement state for a new channel
+       pub fn new() -> Self {
+               EnforcementState {
+                       last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
+                       last_counterparty_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
+                       last_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
+                       last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
+               }
+       }
+}
index 15157e50e556554a38988d67e2a38043d23a938f..64b88acb0081487495f997ac2706f9783dd62d9c 100644 (file)
@@ -20,7 +20,7 @@ use ln::features::{ChannelFeatures, InitFeatures};
 use ln::msgs;
 use ln::msgs::OptionalField;
 use ln::script::ShutdownScript;
-use util::enforcing_trait_impls::{EnforcingSigner, INITIAL_REVOKED_COMMITMENT_NUMBER};
+use util::enforcing_trait_impls::{EnforcingSigner, EnforcementState};
 use util::events;
 use util::logger::{Logger, Level, Record};
 use util::ser::{Readable, ReadableArgs, Writer, Writeable};
@@ -76,8 +76,15 @@ impl keysinterface::KeysInterface for OnlyReadsKeysInterface {
        fn get_channel_signer(&self, _inbound: bool, _channel_value_satoshis: u64) -> EnforcingSigner { unreachable!(); }
        fn get_secure_random_bytes(&self) -> [u8; 32] { [0; 32] }
 
-       fn read_chan_signer(&self, reader: &[u8]) -> Result<Self::Signer, msgs::DecodeError> {
-               EnforcingSigner::read(&mut io::Cursor::new(reader))
+       fn read_chan_signer(&self, mut reader: &[u8]) -> Result<Self::Signer, msgs::DecodeError> {
+               let inner: InMemorySigner = Readable::read(&mut reader)?;
+               let state = Arc::new(Mutex::new(EnforcementState::new()));
+
+               Ok(EnforcingSigner::new_with_revoked(
+                       inner,
+                       state,
+                       false
+               ))
        }
        fn sign_invoice(&self, _invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()> { unreachable!(); }
 }
@@ -452,7 +459,7 @@ pub struct TestKeysInterface {
        pub override_session_priv: Mutex<Option<[u8; 32]>>,
        pub override_channel_id_priv: Mutex<Option<[u8; 32]>>,
        pub disable_revocation_policy_check: bool,
-       revoked_commitments: Mutex<HashMap<[u8;32], Arc<Mutex<u64>>>>,
+       enforcement_states: Mutex<HashMap<[u8;32], Arc<Mutex<EnforcementState>>>>,
        expectations: Mutex<Option<VecDeque<OnGetShutdownScriptpubkey>>>,
 }
 
@@ -474,8 +481,8 @@ impl keysinterface::KeysInterface for TestKeysInterface {
 
        fn get_channel_signer(&self, inbound: bool, channel_value_satoshis: u64) -> EnforcingSigner {
                let keys = self.backing.get_channel_signer(inbound, channel_value_satoshis);
-               let revoked_commitment = self.make_revoked_commitment_cell(keys.commitment_seed);
-               EnforcingSigner::new_with_revoked(keys, revoked_commitment, self.disable_revocation_policy_check)
+               let state = self.make_enforcement_state_cell(keys.commitment_seed);
+               EnforcingSigner::new_with_revoked(keys, state, self.disable_revocation_policy_check)
        }
 
        fn get_secure_random_bytes(&self) -> [u8; 32] {
@@ -497,16 +504,13 @@ impl keysinterface::KeysInterface for TestKeysInterface {
                let mut reader = io::Cursor::new(buffer);
 
                let inner: InMemorySigner = Readable::read(&mut reader)?;
-               let revoked_commitment = self.make_revoked_commitment_cell(inner.commitment_seed);
-
-               let last_commitment_number = Readable::read(&mut reader)?;
+               let state = self.make_enforcement_state_cell(inner.commitment_seed);
 
-               Ok(EnforcingSigner {
+               Ok(EnforcingSigner::new_with_revoked(
                        inner,
-                       last_commitment_number: Arc::new(Mutex::new(last_commitment_number)),
-                       revoked_commitment,
-                       disable_revocation_policy_check: self.disable_revocation_policy_check,
-               })
+                       state,
+                       self.disable_revocation_policy_check
+               ))
        }
 
        fn sign_invoice(&self, invoice_preimage: Vec<u8>) -> Result<RecoverableSignature, ()> {
@@ -522,7 +526,7 @@ impl TestKeysInterface {
                        override_session_priv: Mutex::new(None),
                        override_channel_id_priv: Mutex::new(None),
                        disable_revocation_policy_check: false,
-                       revoked_commitments: Mutex::new(HashMap::new()),
+                       enforcement_states: Mutex::new(HashMap::new()),
                        expectations: Mutex::new(None),
                }
        }
@@ -538,16 +542,17 @@ impl TestKeysInterface {
 
        pub fn derive_channel_keys(&self, channel_value_satoshis: u64, id: &[u8; 32]) -> EnforcingSigner {
                let keys = self.backing.derive_channel_keys(channel_value_satoshis, id);
-               let revoked_commitment = self.make_revoked_commitment_cell(keys.commitment_seed);
-               EnforcingSigner::new_with_revoked(keys, revoked_commitment, self.disable_revocation_policy_check)
+               let state = self.make_enforcement_state_cell(keys.commitment_seed);
+               EnforcingSigner::new_with_revoked(keys, state, self.disable_revocation_policy_check)
        }
 
-       fn make_revoked_commitment_cell(&self, commitment_seed: [u8; 32]) -> Arc<Mutex<u64>> {
-               let mut revoked_commitments = self.revoked_commitments.lock().unwrap();
-               if !revoked_commitments.contains_key(&commitment_seed) {
-                       revoked_commitments.insert(commitment_seed, Arc::new(Mutex::new(INITIAL_REVOKED_COMMITMENT_NUMBER)));
+       fn make_enforcement_state_cell(&self, commitment_seed: [u8; 32]) -> Arc<Mutex<EnforcementState>> {
+               let mut states = self.enforcement_states.lock().unwrap();
+               if !states.contains_key(&commitment_seed) {
+                       let state = EnforcementState::new();
+                       states.insert(commitment_seed, Arc::new(Mutex::new(state)));
                }
-               let cell = revoked_commitments.get(&commitment_seed).unwrap();
+               let cell = states.get(&commitment_seed).unwrap();
                Arc::clone(cell)
        }
 }