X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Futil%2Fenforcing_trait_impls.rs;h=88c1754f13599162b185350612b2b2f03abcd87a;hb=75d71cead386cac3c42a6c4d4f204869ec8dacc5;hp=8229f6048600f79172be41c7451580524831764e;hpb=25c9a37e18b6e3e30a9ad0c8645fb8da34413199;p=rust-lightning

diff --git a/lightning/src/util/enforcing_trait_impls.rs b/lightning/src/util/enforcing_trait_impls.rs
index 8229f604..88c1754f 100644
--- a/lightning/src/util/enforcing_trait_impls.rs
+++ b/lightning/src/util/enforcing_trait_impls.rs
@@ -24,21 +24,52 @@ use util::ser::{Writeable, Writer, Readable};
 use std::io::Error;
 use ln::msgs::DecodeError;
 
-/// An implementation of ChannelKeys that enforces some policy checks.
+/// Initial value for revoked commitment downward counter
+pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
+
+/// An implementation of ChannelKeys that enforces some policy checks.  The current checks
+/// are an incomplete set.  They include:
+///
+/// - When signing, the holder transaction has not been revoked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 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.
 #[derive(Clone)]
 pub struct EnforcingChannelKeys {
 	pub inner: InMemoryChannelKeys,
-	last_commitment_number: Arc<Mutex<Option<u64>>>,
+	/// 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>>,
+	pub disable_revocation_policy_check: bool,
 }
 
 impl EnforcingChannelKeys {
+	/// Construct an EnforcingChannelKeys
 	pub fn new(inner: InMemoryChannelKeys) -> Self {
 		Self {
 			inner,
 			last_commitment_number: Arc::new(Mutex::new(None)),
+			revoked_commitment: Arc::new(Mutex::new(INITIAL_REVOKED_COMMITMENT_NUMBER)),
+			disable_revocation_policy_check: false
+		}
+	}
+
+	/// Construct an EnforcingChannelKeys 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: InMemoryChannelKeys, revoked_commitment: Arc<Mutex<u64>>, disable_revocation_policy_check: bool) -> Self {
+		Self {
+			inner,
+			last_commitment_number: Arc::new(Mutex::new(None)),
+			revoked_commitment,
+			disable_revocation_policy_check
 		}
 	}
 }
@@ -49,7 +80,11 @@ impl ChannelKeys for EnforcingChannelKeys {
 	}
 
 	fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
-		// TODO: enforce the ChannelKeys contract - error here if we already signed this commitment
+		{
+			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;
+		}
 		self.inner.release_commitment_secret(idx)
 	}
 
@@ -77,6 +112,15 @@ impl ChannelKeys for EnforcingChannelKeys {
 		let commitment_txid = trusted_tx.txid();
 		let holder_csv = self.inner.counterparty_selected_contest_delay();
 
+		let revoked = self.revoked_commitment.lock().unwrap();
+		let commitment_number = trusted_tx.commitment_number();
+		if *revoked - 1 != commitment_number && *revoked - 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])
+			}
+		}
+
 		for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
 			assert!(this_htlc.transaction_output_index.is_some());
 			let keys = trusted_tx.keys();
@@ -88,14 +132,12 @@ impl ChannelKeys for EnforcingChannelKeys {
 			secp_ctx.verify(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
 		}
 
-		// TODO: enforce the ChannelKeys contract - error if this commitment was already revoked
-		// TODO: need the commitment number
 		Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 	}
 
 	#[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
-	fn unsafe_sign_holder_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
-		Ok(self.inner.unsafe_sign_holder_commitment(commitment_tx, secp_ctx).unwrap())
+	fn unsafe_sign_holder_commitment_and_htlcs<T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<T>) -> Result<(Signature, Vec<Signature>), ()> {
+		Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 	}
 
 	fn sign_justice_transaction<T: secp256k1::Signing + secp256k1::Verification>(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &Option<HTLCOutputInCommitment>, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
@@ -135,7 +177,9 @@ impl Readable for EnforcingChannelKeys {
 		let last_commitment_number = Readable::read(reader)?;
 		Ok(EnforcingChannelKeys {
 			inner,
-			last_commitment_number: Arc::new(Mutex::new(last_commitment_number))
+			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,
 		})
 	}
 }