X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=src%2Fln%2Fchannel.rs;h=5446dd914353c23bd034f61e54e59e084461a939;hb=e79e61f595d7f3cf54390354148d5fd9edf7296d;hp=2b8b085a8e4f84979697d9df26fc7515fce2e112;hpb=e9b1af277f36d1840370e9f5bdb062a0197c34d9;p=rust-lightning

diff --git a/src/ln/channel.rs b/src/ln/channel.rs
index 2b8b085a..5446dd91 100644
--- a/src/ln/channel.rs
+++ b/src/ln/channel.rs
@@ -13,7 +13,6 @@ use secp256k1;
 
 use crypto::digest::Digest;
 use crypto::hkdf::{hkdf_extract,hkdf_expand};
-use crypto::sha2::Sha256;
 
 use ln::msgs;
 use ln::msgs::{HandleError, MsgEncodable};
@@ -22,9 +21,8 @@ use ln::channelmanager::PendingForwardHTLCInfo;
 use ln::chan_utils::{TxCreationKeys,HTLCOutputInCommitment};
 use ln::chan_utils;
 use chain::chaininterface::{FeeEstimator,ConfirmationTarget};
-use util::transaction_utils;
-
-use rand::{thread_rng,Rng};
+use util::{transaction_utils,rng};
+use util::sha2::Sha256;
 
 use std::default::Default;
 use std::cmp;
@@ -151,7 +149,20 @@ enum ChannelState {
 	/// later.
 	/// Flag is set on ChannelFunded.
 	AwaitingRemoteRevoke = (1 << 7),
+	/// Flag which is set on ChannelFunded or FundingSent after receiving a shutdown message from
+	/// the remote end. If set, they may not add any new HTLCs to the channel, and we are expected
+	/// to respond with our own shutdown message when possible.
+	RemoteShutdownSent = (1 << 8),
+	/// Flag which is set on ChannelFunded or FundingSent after sending a shutdown message. At this
+	/// point, we may not add any new HTLCs to the channel.
+	/// TODO: Investigate some kind of timeout mechanism by which point the remote end must provide
+	/// us their shutdown.
+	LocalShutdownSent = (1 << 9),
+	/// We've successfully negotiated a closing_signed dance. At this point ChannelManager is about
+	/// to drop us, but we store this anyway.
+	ShutdownComplete = (1 << 10),
 }
+const BOTH_SIDES_SHUTDOWN_MASK: u32 = (ChannelState::LocalShutdownSent as u32 | ChannelState::RemoteShutdownSent as u32);
 
 // TODO: We should refactor this to be an Inbound/OutboundChannel until initial setup handshaking
 // has been completed, and then turn into a Channel to get compiler-time enforcement of things like
@@ -179,6 +190,8 @@ pub struct Channel {
 	channel_update_count: u32,
 	feerate_per_kw: u64,
 
+	last_sent_closing_fee: Option<(u64, u64)>, // (feerate, fee)
+
 	/// The hash of the block in which the funding transaction reached our CONF_TARGET. We use this
 	/// to detect unconfirmation after a serialize-unserialize roudtrip where we may not see a full
 	/// series of block_connected/block_disconnected calls. Obviously this is not a guarantee as we
@@ -210,10 +223,12 @@ pub struct Channel {
 	their_cur_commitment_point: PublicKey,
 	their_node_id: PublicKey,
 
+	their_shutdown_scriptpubkey: Option<Script>,
+
 	channel_monitor: ChannelMonitor,
 }
 
-const OUR_MAX_HTLCS: u16 = 1; //TODO
+const OUR_MAX_HTLCS: u16 = 5; //TODO
 const CONF_TARGET: u32 = 12; //TODO: Should be much higher
 /// Confirmation count threshold at which we close a channel. Ideally we'd keep the channel around
 /// on ice until the funding transaction gets more confirmations, but the LN protocol doesn't
@@ -232,21 +247,20 @@ const SPENDING_INPUT_FOR_A_OUTPUT_WEIGHT: u64 = 79; // prevout: 36, nSequence: 4
 const B_OUTPUT_PLUS_SPENDING_INPUT_WEIGHT: u64 = 104; // prevout: 40, nSequence: 4, script len: 1, witness lengths: 3/4, sig: 73/4, pubkey: 33/4, output: 31 (TODO: Wrong? Useless?)
 
 macro_rules! secp_call {
-	( $res : expr ) => {
+	( $res: expr, $err: expr ) => {
 		match $res {
 			Ok(key) => key,
 			//TODO: make the error a parameter
-			Err(_) => return Err(HandleError{err: "Secp call failed - probably bad signature or evil data generated a bad pubkey/privkey", msg: None})
+			Err(_) => return Err(HandleError{err: $err, msg: Some(msgs::ErrorAction::DisconnectPeer{})})
 		}
 	};
 }
 
-macro_rules! get_key {
-	( $ctx : expr, $slice : expr ) => {
-		secp_call! (SecretKey::from_slice($ctx, $slice))
-	};
+macro_rules! secp_derived_key {
+	( $res: expr ) => {
+		secp_call!($res, "Derived invalid key, peer is maliciously selecting parameters")
+	}
 }
-
 impl Channel {
 	// Convert constants + channel value to limits:
 	fn get_our_max_htlc_value_in_flight_msat(channel_value_satoshis: u64) -> u64 {
@@ -274,12 +288,11 @@ impl Channel {
 			panic!("funding value > 2^24");
 		}
 
-		let mut rng = thread_rng();
 		let feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Normal);
 		let background_feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Background);
 
 		let mut key_seed = [0u8; 32];
-		rng.fill_bytes(&mut key_seed);
+		rng::fill_bytes(&mut key_seed);
 		let chan_keys = match ChannelKeys::new_from_seed(&key_seed) {
 			Ok(key) => key,
 			Err(_) => panic!("RNG is busted!")
@@ -296,7 +309,7 @@ impl Channel {
 		Channel {
 			user_id: user_id,
 
-			channel_id: Uint256([rng.gen(), rng.gen(), rng.gen(), rng.gen()]),
+			channel_id: rng::rand_uint256(),
 			channel_state: ChannelState::OurInitSent as u32,
 			channel_outbound: true,
 			secp_ctx: secp_ctx,
@@ -313,6 +326,8 @@ impl Channel {
 			next_remote_htlc_id: 0,
 			channel_update_count: 0,
 
+			last_sent_closing_fee: None,
+
 			funding_tx_confirmed_in: Default::default(),
 			short_channel_id: None,
 			last_block_connected: Default::default(),
@@ -336,54 +351,58 @@ impl Channel {
 			their_cur_commitment_point: PublicKey::new(),
 			their_node_id: their_node_id,
 
+			their_shutdown_scriptpubkey: None,
+
 			channel_monitor: channel_monitor,
 		}
 	}
 
 	fn check_remote_fee(fee_estimator: &FeeEstimator, feerate_per_kw: u32) -> Result<(), HandleError> {
 		if (feerate_per_kw as u64) < fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Background) * 250 {
-			return Err(HandleError{err: "Peer's feerate much too low", msg: None});
+			return Err(HandleError{err: "Peer's feerate much too low", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 		if (feerate_per_kw as u64) > fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::HighPriority) * 375 { // 375 = 250 * 1.5x
-			return Err(HandleError{err: "Peer's feerate much too high", msg: None});
+			return Err(HandleError{err: "Peer's feerate much too high", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 		Ok(())
 	}
 
 	/// Creates a new channel from a remote sides' request for one.
 	/// Assumes chain_hash has already been checked and corresponds with what we expect!
+	/// Generally prefers to take the DisconnectPeer action on failure, as a notice to the sender
+	/// that we're rejecting the new channel.
 	pub fn new_from_req(fee_estimator: &FeeEstimator, their_node_id: PublicKey, msg: &msgs::OpenChannel, user_id: u64, announce_publicly: bool) -> Result<Channel, HandleError> {
 		// Check sanity of message fields:
 		if msg.funding_satoshis >= (1 << 24) {
-			return Err(HandleError{err: "funding value > 2^24", msg: None});
+			return Err(HandleError{err: "funding value > 2^24", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 		if msg.funding_satoshis > 21000000 * 100000000 {
-			return Err(HandleError{err: "More funding_satoshis than there are satoshis!", msg: None});
+			return Err(HandleError{err: "More funding_satoshis than there are satoshis!", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 		if msg.channel_reserve_satoshis > msg.funding_satoshis {
-			return Err(HandleError{err: "Bogus channel_reserve_satoshis", msg: None});
+			return Err(HandleError{err: "Bogus channel_reserve_satoshis", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 		if msg.push_msat > (msg.funding_satoshis - msg.channel_reserve_satoshis) * 1000 {
-			return Err(HandleError{err: "push_msat more than highest possible value", msg: None});
+			return Err(HandleError{err: "push_msat more than highest possible value", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
-		if msg.dust_limit_satoshis > 21000000 * 100000000 {
-			return Err(HandleError{err: "Peer never wants payout outputs?", msg: None});
+		if msg.dust_limit_satoshis > msg.funding_satoshis {
+			return Err(HandleError{err: "Peer never wants payout outputs?", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 		if msg.max_htlc_value_in_flight_msat > msg.funding_satoshis * 1000 {
-			return Err(HandleError{err: "Bogus max_htlc_value_in_flight_satoshis", msg: None});
+			return Err(HandleError{err: "Bogus max_htlc_value_in_flight_satoshis", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 		if msg.htlc_minimum_msat >= (msg.funding_satoshis - msg.channel_reserve_satoshis) * 1000 {
-			return Err(HandleError{err: "Minimum htlc value is full channel value", msg: None});
+			return Err(HandleError{err: "Minimum htlc value is full channel value", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 		Channel::check_remote_fee(fee_estimator, msg.feerate_per_kw)?;
 		if msg.to_self_delay > MAX_LOCAL_BREAKDOWN_TIMEOUT {
-			return Err(HandleError{err: "They wanted our payments to be delayed by a needlessly long period", msg: None});
+			return Err(HandleError{err: "They wanted our payments to be delayed by a needlessly long period", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 		if msg.max_accepted_htlcs < 1 {
-			return Err(HandleError{err: "0 max_accpted_htlcs makes for a useless channel", msg: None});
+			return Err(HandleError{err: "0 max_accpted_htlcs makes for a useless channel", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 		if (msg.channel_flags & 254) != 0 {
-			return Err(HandleError{err: "unknown channel_flags", msg: None});
+			return Err(HandleError{err: "unknown channel_flags", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
 
 		// Convert things into internal flags and prep our state:
@@ -392,9 +411,8 @@ impl Channel {
 
 		let background_feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Background);
 
-		let mut rng = thread_rng();
 		let mut key_seed = [0u8; 32];
-		rng.fill_bytes(&mut key_seed);
+		rng::fill_bytes(&mut key_seed);
 		let chan_keys = match ChannelKeys::new_from_seed(&key_seed) {
 			Ok(key) => key,
 			Err(_) => panic!("RNG is busted!")
@@ -428,6 +446,8 @@ impl Channel {
 			next_remote_htlc_id: 0,
 			channel_update_count: 0,
 
+			last_sent_closing_fee: None,
+
 			funding_tx_confirmed_in: Default::default(),
 			short_channel_id: None,
 			last_block_connected: Default::default(),
@@ -452,6 +472,8 @@ impl Channel {
 			their_cur_commitment_point: msg.first_per_commitment_point,
 			their_node_id: their_node_id,
 
+			their_shutdown_scriptpubkey: None,
+
 			channel_monitor: channel_monitor,
 		};
 
@@ -463,9 +485,9 @@ impl Channel {
 
 	// Utilities to derive keys:
 
-	fn build_local_commitment_secret(&self, idx: u64) -> Result<SecretKey, HandleError> {
+	fn build_local_commitment_secret(&self, idx: u64) -> SecretKey {
 		let res = chan_utils::build_commitment_secret(self.local_keys.commitment_seed, idx);
-		Ok(get_key!(&self.secp_ctx, &res))
+		SecretKey::from_slice(&self.secp_ctx, &res).unwrap()
 	}
 
 	// Utilities to build transactions:
@@ -506,7 +528,7 @@ impl Channel {
 	/// generated by the peer which proposed adding the HTLCs, and thus we need to understand both
 	/// which peer generated this transaction and "to whom" this transaction flows.
 	#[inline]
-	fn build_commitment_transaction(&self, commitment_number: u64, keys: &TxCreationKeys, local: bool, generated_by_local: bool) -> Result<(Transaction, Vec<HTLCOutputInCommitment>), HandleError> {
+	fn build_commitment_transaction(&self, commitment_number: u64, keys: &TxCreationKeys, local: bool, generated_by_local: bool) -> (Transaction, Vec<HTLCOutputInCommitment>) {
 		let obscured_commitment_transaction_number = self.get_commitment_transaction_number_obscure_factor() ^ commitment_number;
 
 		let txins = {
@@ -515,12 +537,11 @@ impl Channel {
 				prev_hash: self.channel_monitor.get_funding_txo().unwrap().0,
 				prev_index: self.channel_monitor.get_funding_txo().unwrap().1 as u32,
 				script_sig: Script::new(),
-				sequence: ((0x80 as u32) << 8*3) | ((obscured_commitment_transaction_number >> 3*8) as u32)
+				sequence: ((0x80 as u32) << 8*3) | ((obscured_commitment_transaction_number >> 3*8) as u32),
+				witness: Vec::new(),
 			});
 			ins
 		};
-		let mut witness: Vec<Vec<Vec<u8>>> = Vec::new();
-		witness.push(Vec::new());
 
 		let mut txouts: Vec<(TxOut, Option<HTLCOutputInCommitment>)> = Vec::new();
 
@@ -595,13 +616,81 @@ impl Channel {
 			}
 		}
 
-		Ok((Transaction {
+		(Transaction {
 			version: 2,
 			lock_time: ((0x20 as u32) << 8*3) | ((obscured_commitment_transaction_number & 0xffffffu64) as u32),
 			input: txins,
 			output: outputs,
-			witness: witness
-		}, htlcs_used))
+		}, htlcs_used)
+	}
+
+	#[inline]
+	fn get_closing_scriptpubkey(&self) -> Script {
+		let our_channel_close_key_hash = Hash160::from_data(&PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.channel_close_key).unwrap().serialize());
+		Builder::new().push_opcode(opcodes::All::OP_PUSHBYTES_0).push_slice(&our_channel_close_key_hash[..]).into_script()
+	}
+
+	#[inline]
+	fn get_closing_transaction_weight(a_scriptpubkey: &Script, b_scriptpubkey: &Script) -> u64 {
+		(4 + 1 + 36 + 4 + 1 + 1 + 2*(8+1) + 4 + a_scriptpubkey.len() as u64 + b_scriptpubkey.len() as u64)*4 + 2 + 1 + 1 + 2*(1 + 72)
+	}
+
+	#[inline]
+	fn build_closing_transaction(&self, proposed_total_fee_satoshis: u64, skip_remote_output: bool) -> (Transaction, u64) {
+		let txins = {
+			let mut ins: Vec<TxIn> = Vec::new();
+			ins.push(TxIn {
+				prev_hash: self.channel_monitor.get_funding_txo().unwrap().0,
+				prev_index: self.channel_monitor.get_funding_txo().unwrap().1 as u32,
+				script_sig: Script::new(),
+				sequence: 0xffffffff,
+				witness: Vec::new(),
+			});
+			ins
+		};
+
+		assert!(self.pending_htlcs.is_empty());
+		let mut txouts: Vec<(TxOut, ())> = Vec::new();
+
+		let mut total_fee_satoshis = proposed_total_fee_satoshis;
+		let value_to_self: i64 = (self.value_to_self_msat as i64) / 1000 - if self.channel_outbound { total_fee_satoshis as i64 } else { 0 };
+		let value_to_remote: i64 = ((self.channel_value_satoshis * 1000 - self.value_to_self_msat) as i64 / 1000) - if self.channel_outbound { 0 } else { total_fee_satoshis as i64 };
+
+		if value_to_self < 0 {
+			assert!(self.channel_outbound);
+			total_fee_satoshis += (-value_to_self) as u64;
+		} else if value_to_remote < 0 {
+			assert!(!self.channel_outbound);
+			total_fee_satoshis += (-value_to_remote) as u64;
+		}
+
+		if !skip_remote_output && value_to_remote as u64 > self.our_dust_limit_satoshis {
+			txouts.push((TxOut {
+				script_pubkey: self.their_shutdown_scriptpubkey.clone().unwrap(),
+				value: value_to_remote as u64
+			}, ()));
+		}
+
+		if value_to_self as u64 > self.our_dust_limit_satoshis {
+			txouts.push((TxOut {
+				script_pubkey: self.get_closing_scriptpubkey(),
+				value: value_to_self as u64
+			}, ()));
+		}
+
+		transaction_utils::sort_outputs(&mut txouts);
+
+		let mut outputs: Vec<TxOut> = Vec::new();
+		for out in txouts.drain(..) {
+			outputs.push(out.0);
+		}
+
+		(Transaction {
+			version: 2,
+			lock_time: 0,
+			input: txins,
+			output: outputs,
+		}, total_fee_satoshis)
 	}
 
 	#[inline]
@@ -611,11 +700,11 @@ impl Channel {
 	/// The result is a transaction which we can revoke ownership of (ie a "local" transaction)
 	/// TODO Some magic rust shit to compile-time check this?
 	fn build_local_transaction_keys(&self, commitment_number: u64) -> Result<TxCreationKeys, HandleError> {
-		let per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &self.build_local_commitment_secret(commitment_number)?).unwrap();
+		let per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &self.build_local_commitment_secret(commitment_number)).unwrap();
 		let delayed_payment_base = PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.delayed_payment_base_key).unwrap();
 		let htlc_basepoint = PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.htlc_base_key).unwrap();
 
-		Ok(secp_call!(TxCreationKeys::new(&self.secp_ctx, &per_commitment_point, &delayed_payment_base, &htlc_basepoint, &self.their_revocation_basepoint, &self.their_payment_basepoint, &self.their_htlc_basepoint)))
+		Ok(secp_derived_key!(TxCreationKeys::new(&self.secp_ctx, &per_commitment_point, &delayed_payment_base, &htlc_basepoint, &self.their_revocation_basepoint, &self.their_payment_basepoint, &self.their_htlc_basepoint)))
 	}
 
 	#[inline]
@@ -628,7 +717,7 @@ impl Channel {
 		let revocation_basepoint = PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.revocation_base_key).unwrap();
 		let htlc_basepoint = PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.htlc_base_key).unwrap();
 
-		Ok(secp_call!(TxCreationKeys::new(&self.secp_ctx, &self.their_cur_commitment_point, &self.their_delayed_payment_basepoint, &self.their_htlc_basepoint, &revocation_basepoint, &payment_basepoint, &htlc_basepoint)))
+		Ok(secp_derived_key!(TxCreationKeys::new(&self.secp_ctx, &self.their_cur_commitment_point, &self.their_delayed_payment_basepoint, &self.their_htlc_basepoint, &revocation_basepoint, &payment_basepoint, &htlc_basepoint)))
 	}
 
 	/// Gets the redeemscript for the funding transaction output (ie the funding transaction output
@@ -646,36 +735,36 @@ impl Channel {
 		}.push_opcode(opcodes::All::OP_PUSHNUM_2).push_opcode(opcodes::All::OP_CHECKMULTISIG).into_script()
 	}
 
-	fn sign_commitment_transaction(&self, tx: &mut Transaction, their_sig: &Signature) -> Result<(), HandleError> {
+	fn sign_commitment_transaction(&self, tx: &mut Transaction, their_sig: &Signature) -> Signature {
 		if tx.input.len() != 1 {
 			panic!("Tried to sign commitment transaction that had input count != 1!");
 		}
-		if tx.witness.len() != 1 || tx.witness[0].len() != 0 {
+		if tx.input[0].witness.len() != 0 {
 			panic!("Tried to re-sign commitment transaction");
 		}
 
 		let funding_redeemscript = self.get_funding_redeemscript();
 
-		let sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&tx).sighash_all(&tx, 0, &funding_redeemscript, self.channel_value_satoshis)[..]));
-		let our_sig = secp_call!(self.secp_ctx.sign(&sighash, &self.local_keys.funding_key));
+		let sighash = Message::from_slice(&bip143::SighashComponents::new(&tx).sighash_all(&tx.input[0], &funding_redeemscript, self.channel_value_satoshis)[..]).unwrap();
+		let our_sig = self.secp_ctx.sign(&sighash, &self.local_keys.funding_key).unwrap();
 
-		tx.witness[0].push(Vec::new()); // First is the multisig dummy
+		tx.input[0].witness.push(Vec::new()); // First is the multisig dummy
 
 		let our_funding_key = PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.funding_key).unwrap().serialize();
 		let their_funding_key = self.their_funding_pubkey.serialize();
 		if our_funding_key[..] < their_funding_key[..] {
-			tx.witness[0].push(our_sig.serialize_der(&self.secp_ctx).to_vec());
-			tx.witness[0].push(their_sig.serialize_der(&self.secp_ctx).to_vec());
+			tx.input[0].witness.push(our_sig.serialize_der(&self.secp_ctx).to_vec());
+			tx.input[0].witness.push(their_sig.serialize_der(&self.secp_ctx).to_vec());
 		} else {
-			tx.witness[0].push(their_sig.serialize_der(&self.secp_ctx).to_vec());
-			tx.witness[0].push(our_sig.serialize_der(&self.secp_ctx).to_vec());
+			tx.input[0].witness.push(their_sig.serialize_der(&self.secp_ctx).to_vec());
+			tx.input[0].witness.push(our_sig.serialize_der(&self.secp_ctx).to_vec());
 		}
-		tx.witness[0][1].push(SigHashType::All as u8);
-		tx.witness[0][2].push(SigHashType::All as u8);
+		tx.input[0].witness[1].push(SigHashType::All as u8);
+		tx.input[0].witness[2].push(SigHashType::All as u8);
 
-		tx.witness[0].push(funding_redeemscript.into_vec());
+		tx.input[0].witness.push(funding_redeemscript.into_vec());
 
-		Ok(())
+		our_sig
 	}
 
 	/// Builds the htlc-success or htlc-timeout transaction which spends a given HTLC output
@@ -687,12 +776,10 @@ impl Channel {
 			prev_hash: prev_hash.clone(),
 			prev_index: htlc.transaction_output_index,
 			script_sig: Script::new(),
-			sequence: 0
+			sequence: 0,
+			witness: Vec::new(),
 		});
 
-		let mut witnesses: Vec<Vec<Vec<u8>>> = Vec::new();
-		witnesses.push(Vec::new());
-
 		let total_fee = if htlc.offered {
 				self.feerate_per_kw * HTLC_TIMEOUT_TX_WEIGHT / 1000
 			} else {
@@ -712,7 +799,6 @@ impl Channel {
 			lock_time: if htlc.offered { htlc.cltv_expiry } else { 0 },
 			input: txins,
 			output: txouts,
-			witness: witnesses
 		})
 	}
 
@@ -722,45 +808,50 @@ impl Channel {
 		if tx.input.len() != 1 {
 			panic!("Tried to sign HTLC transaction that had input count != 1!");
 		}
-		if tx.witness.len() != 1 || tx.witness[0].len() != 0 {
+		if tx.input[0].witness.len() != 0 {
 			panic!("Tried to re-sign HTLC transaction");
 		}
 
 		let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &keys, htlc.offered);
 
-		let our_htlc_key = secp_call!(chan_utils::derive_private_key(&self.secp_ctx, &keys.per_commitment_point, &self.local_keys.htlc_base_key));
-		let sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&tx).sighash_all(&tx, 0, &htlc_redeemscript, htlc.amount_msat / 1000)[..]));
-		let our_sig = secp_call!(self.secp_ctx.sign(&sighash, &our_htlc_key));
+		let our_htlc_key = secp_derived_key!(chan_utils::derive_private_key(&self.secp_ctx, &keys.per_commitment_point, &self.local_keys.htlc_base_key));
+		let sighash = Message::from_slice(&bip143::SighashComponents::new(&tx).sighash_all(&tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]).unwrap();
+		let our_sig = self.secp_ctx.sign(&sighash, &our_htlc_key).unwrap();
 
 		let local_tx = PublicKey::from_secret_key(&self.secp_ctx, &our_htlc_key).unwrap() == keys.a_htlc_key;
 
-		tx.witness[0].push(Vec::new()); // First is the multisig dummy
+		tx.input[0].witness.push(Vec::new()); // First is the multisig dummy
 
 		if local_tx { // b, then a
-			tx.witness[0].push(their_sig.serialize_der(&self.secp_ctx).to_vec());
-			tx.witness[0].push(our_sig.serialize_der(&self.secp_ctx).to_vec());
+			tx.input[0].witness.push(their_sig.serialize_der(&self.secp_ctx).to_vec());
+			tx.input[0].witness.push(our_sig.serialize_der(&self.secp_ctx).to_vec());
 		} else {
-			tx.witness[0].push(our_sig.serialize_der(&self.secp_ctx).to_vec());
-			tx.witness[0].push(their_sig.serialize_der(&self.secp_ctx).to_vec());
+			tx.input[0].witness.push(our_sig.serialize_der(&self.secp_ctx).to_vec());
+			tx.input[0].witness.push(their_sig.serialize_der(&self.secp_ctx).to_vec());
 		}
-		tx.witness[0][1].push(SigHashType::All as u8);
-		tx.witness[0][2].push(SigHashType::All as u8);
+		tx.input[0].witness[1].push(SigHashType::All as u8);
+		tx.input[0].witness[2].push(SigHashType::All as u8);
 
 		if htlc.offered {
-			tx.witness[0].push(Vec::new());
+			tx.input[0].witness.push(Vec::new());
 		} else {
-			tx.witness[0].push(preimage.unwrap().to_vec());
+			tx.input[0].witness.push(preimage.unwrap().to_vec());
 		}
 
-		tx.witness[0].push(htlc_redeemscript.into_vec());
+		tx.input[0].witness.push(htlc_redeemscript.into_vec());
 
 		Ok(())
 	}
 
 	pub fn get_update_fulfill_htlc(&mut self, payment_preimage: [u8; 32]) -> Result<msgs::UpdateFulfillHTLC, HandleError> {
+		// Either ChannelFunded got set (which means it wont bet unset) or there is no way any
+		// caller thought we could have something claimed (cause we wouldn't have accepted in an
+		// incoming HTLC anyway). If we got to ShutdownComplete, callers aren't allowed to call us,
+		// either.
 		if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
-			return Err(HandleError{err: "Was asked to fulfill an HTLC when channel was not in an operational state", msg: None});
+			panic!("Was asked to fulfill an HTLC when channel was not in an operational state");
 		}
+		assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
 
 		let mut sha = Sha256::new();
 		sha.input(&payment_preimage);
@@ -769,6 +860,7 @@ impl Channel {
 
 		let mut htlc_id = 0;
 		let mut htlc_amount_msat = 0;
+		//TODO: swap_remove since we dont need to maintain ordering here
 		self.pending_htlcs.retain(|ref htlc| {
 			if !htlc.outbound && htlc.payment_hash == payment_hash {
 				if htlc_id != 0 {
@@ -797,9 +889,11 @@ impl Channel {
 		if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
 			return Err(HandleError{err: "Was asked to fail an HTLC when channel was not in an operational state", msg: None});
 		}
+		assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
 
 		let mut htlc_id = 0;
 		let mut htlc_amount_msat = 0;
+		//TODO: swap_remove since we dont need to maintain ordering here
 		self.pending_htlcs.retain(|ref htlc| {
 			if !htlc.outbound && htlc.payment_hash == *payment_hash {
 				if htlc_id != 0 {
@@ -881,18 +975,18 @@ impl Channel {
 		let funding_script = self.get_funding_redeemscript();
 
 		let remote_keys = self.build_remote_transaction_keys()?;
-		let remote_initial_commitment_tx = self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, false)?.0;
-		let remote_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&remote_initial_commitment_tx).sighash_all(&remote_initial_commitment_tx, 0, &funding_script, self.channel_value_satoshis)[..]));
+		let remote_initial_commitment_tx = self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, false).0;
+		let remote_sighash = Message::from_slice(&bip143::SighashComponents::new(&remote_initial_commitment_tx).sighash_all(&remote_initial_commitment_tx.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
 
 		let local_keys = self.build_local_transaction_keys(self.cur_local_commitment_transaction_number)?;
-		let local_initial_commitment_tx = self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false)?.0;
-		let local_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&local_initial_commitment_tx).sighash_all(&local_initial_commitment_tx, 0, &funding_script, self.channel_value_satoshis)[..]));
+		let local_initial_commitment_tx = self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false).0;
+		let local_sighash = Message::from_slice(&bip143::SighashComponents::new(&local_initial_commitment_tx).sighash_all(&local_initial_commitment_tx.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
 
 		// They sign the "local" commitment transaction, allowing us to broadcast the tx if we wish.
-		secp_call!(self.secp_ctx.verify(&local_sighash, &sig, &self.their_funding_pubkey));
+		secp_call!(self.secp_ctx.verify(&local_sighash, &sig, &self.their_funding_pubkey), "Invalid funding_created signature from peer");
 
 		// We sign the "remote" commitment transaction, allowing them to broadcast the tx if they wish.
-		Ok((remote_initial_commitment_tx, secp_call!(self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key))))
+		Ok((remote_initial_commitment_tx, self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key).unwrap()))
 	}
 
 	pub fn funding_created(&mut self, msg: &msgs::FundingCreated) -> Result<msgs::FundingSigned, HandleError> {
@@ -947,11 +1041,11 @@ impl Channel {
 		let funding_script = self.get_funding_redeemscript();
 
 		let local_keys = self.build_local_transaction_keys(self.cur_local_commitment_transaction_number)?;
-		let local_initial_commitment_tx = self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false)?.0;
-		let local_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&local_initial_commitment_tx).sighash_all(&local_initial_commitment_tx, 0, &funding_script, self.channel_value_satoshis)[..]));
+		let local_initial_commitment_tx = self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false).0;
+		let local_sighash = Message::from_slice(&bip143::SighashComponents::new(&local_initial_commitment_tx).sighash_all(&local_initial_commitment_tx.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
 
 		// They sign the "local" commitment transaction, allowing us to broadcast the tx if we wish.
-		secp_call!(self.secp_ctx.verify(&local_sighash, &msg.signature, &self.their_funding_pubkey));
+		secp_call!(self.secp_ctx.verify(&local_sighash, &msg.signature, &self.their_funding_pubkey), "Invalid funding_signed signature from peer");
 
 		self.channel_state = ChannelState::FundingSent as u32;
 
@@ -959,12 +1053,13 @@ impl Channel {
 	}
 
 	pub fn funding_locked(&mut self, msg: &msgs::FundingLocked) -> Result<(), HandleError> {
-		if self.channel_state == ChannelState::FundingSent as u32 {
+		let non_shutdown_state = self.channel_state & (!BOTH_SIDES_SHUTDOWN_MASK);
+		if non_shutdown_state == ChannelState::FundingSent as u32 {
 			self.channel_state |= ChannelState::TheirFundingLocked as u32;
-		} else if self.channel_state == (ChannelState::FundingSent as u32 | ChannelState::OurFundingLocked as u32) {
-			self.channel_state = ChannelState::ChannelFunded as u32;
-		} else if self.channel_state < ChannelState::FundingSent as u32 {
-			return Err(HandleError{err: "Peer sent a funding_locked before we'd even been told the funding txid", msg: None});
+		} else if non_shutdown_state == (ChannelState::FundingSent as u32 | ChannelState::OurFundingLocked as u32) {
+			self.channel_state = ChannelState::ChannelFunded as u32 | (self.channel_state & BOTH_SIDES_SHUTDOWN_MASK);
+		} else {
+			return Err(HandleError{err: "Peer sent a funding_locked at a strange time", msg: None});
 		}
 
 		//TODO: Note that this must be a duplicate of the previous commitment point they sent us,
@@ -997,7 +1092,7 @@ impl Channel {
 	}
 
 	pub fn update_add_htlc(&mut self, msg: &msgs::UpdateAddHTLC, pending_forward_state: PendingForwardHTLCInfo) -> Result<(), HandleError> {
-		if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
+		if (self.channel_state & (ChannelState::ChannelFunded as u32 | ChannelState::RemoteShutdownSent as u32)) != (ChannelState::ChannelFunded as u32) {
 			return Err(HandleError{err: "Got add HTLC message when channel was not in an operational state", msg: None});
 		}
 		if msg.amount_msat > self.channel_value_satoshis * 1000 {
@@ -1107,23 +1202,7 @@ impl Channel {
 		}
 	}
 
-	/// Checks if there are any LocalAnnounced HTLCs remaining and sets
-	/// ChannelState::AwaitingRemoteRevoke accordingly, possibly calling free_holding_cell_htlcs.
-	fn check_and_free_holding_cell_htlcs(&mut self) -> Result<Option<(Vec<msgs::UpdateAddHTLC>, msgs::CommitmentSigned)>, HandleError> {
-		if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) == (ChannelState::AwaitingRemoteRevoke as u32) {
-			for htlc in self.pending_htlcs.iter() {
-				if htlc.state == HTLCState::LocalAnnounced {
-					return Ok(None);
-				}
-			}
-			self.channel_state &= !(ChannelState::AwaitingRemoteRevoke as u32);
-			self.free_holding_cell_htlcs()
-		} else {
-			Ok(None)
-		}
-	}
-
-	pub fn update_fulfill_htlc(&mut self, msg: &msgs::UpdateFulfillHTLC) -> Result<Option<(Vec<msgs::UpdateAddHTLC>, msgs::CommitmentSigned)>, HandleError> {
+	pub fn update_fulfill_htlc(&mut self, msg: &msgs::UpdateFulfillHTLC) -> Result<(), HandleError> {
 		if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
 			return Err(HandleError{err: "Got add HTLC message when channel was not in an operational state", msg: None});
 		}
@@ -1141,11 +1220,10 @@ impl Channel {
 				self.value_to_self_msat -= htlc.amount_msat;
 			}
 		}
-
-		self.check_and_free_holding_cell_htlcs()
+		Ok(())
 	}
 
-	pub fn update_fail_htlc(&mut self, msg: &msgs::UpdateFailHTLC) -> Result<([u8; 32], Option<(Vec<msgs::UpdateAddHTLC>, msgs::CommitmentSigned)>), HandleError> {
+	pub fn update_fail_htlc(&mut self, msg: &msgs::UpdateFailHTLC) -> Result<[u8; 32], HandleError> {
 		if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
 			return Err(HandleError{err: "Got add HTLC message when channel was not in an operational state", msg: None});
 		}
@@ -1158,12 +1236,10 @@ impl Channel {
 				htlc.payment_hash
 			}
 		};
-
-		let holding_cell_freedom = self.check_and_free_holding_cell_htlcs()?;
-		Ok((payment_hash, holding_cell_freedom))
+		Ok(payment_hash)
 	}
 
-	pub fn update_fail_malformed_htlc(&mut self, msg: &msgs::UpdateFailMalformedHTLC) -> Result<([u8; 32], Option<(Vec<msgs::UpdateAddHTLC>, msgs::CommitmentSigned)>), HandleError> {
+	pub fn update_fail_malformed_htlc(&mut self, msg: &msgs::UpdateFailMalformedHTLC) -> Result<[u8; 32], HandleError> {
 		if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
 			return Err(HandleError{err: "Got add HTLC message when channel was not in an operational state", msg: None});
 		}
@@ -1176,9 +1252,7 @@ impl Channel {
 				htlc.payment_hash
 			}
 		};
-
-		let holding_cell_freedom = self.check_and_free_holding_cell_htlcs()?;
-		Ok((payment_hash, holding_cell_freedom))
+		Ok(payment_hash)
 	}
 
 	pub fn commitment_signed(&mut self, msg: &msgs::CommitmentSigned) -> Result<(msgs::RevokeAndACK, Vec<PendingForwardHTLCInfo>), HandleError> {
@@ -1189,22 +1263,23 @@ impl Channel {
 		let funding_script = self.get_funding_redeemscript();
 
 		let local_keys = self.build_local_transaction_keys(self.cur_local_commitment_transaction_number)?;
-		let local_commitment_tx = self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false)?;
-		let local_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&local_commitment_tx.0).sighash_all(&local_commitment_tx.0, 0, &funding_script, self.channel_value_satoshis)[..]));
-		secp_call!(self.secp_ctx.verify(&local_sighash, &msg.signature, &self.their_funding_pubkey));
+		let local_commitment_tx = self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false);
+		let local_commitment_txid = local_commitment_tx.0.txid();
+		let local_sighash = Message::from_slice(&bip143::SighashComponents::new(&local_commitment_tx.0).sighash_all(&local_commitment_tx.0.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
+		secp_call!(self.secp_ctx.verify(&local_sighash, &msg.signature, &self.their_funding_pubkey), "Invalid commitment tx signature from peer");
 
 		if msg.htlc_signatures.len() != local_commitment_tx.1.len() {
 			return Err(HandleError{err: "Got wrong number of HTLC signatures from remote", msg: None});
 		}
 
 		for (idx, ref htlc) in local_commitment_tx.1.iter().enumerate() {
-			let htlc_tx = self.build_htlc_transaction(&local_commitment_tx.0.txid(), htlc, true, &local_keys)?;
+			let htlc_tx = self.build_htlc_transaction(&local_commitment_txid, htlc, true, &local_keys)?;
 			let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &local_keys, htlc.offered);
-			let htlc_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx, 0, &htlc_redeemscript, htlc.amount_msat / 1000)[..]));
-			secp_call!(self.secp_ctx.verify(&htlc_sighash, &msg.htlc_signatures[idx], &local_keys.b_htlc_key));
+			let htlc_sighash = Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]).unwrap();
+			secp_call!(self.secp_ctx.verify(&htlc_sighash, &msg.htlc_signatures[idx], &local_keys.b_htlc_key), "Invalid HTLC tx siganture from peer");
 		}
 
-		let next_per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &self.build_local_commitment_secret(self.cur_local_commitment_transaction_number - 1)?).unwrap();
+		let next_per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &self.build_local_commitment_secret(self.cur_local_commitment_transaction_number - 1)).unwrap();
 		let per_commitment_secret = chan_utils::build_commitment_secret(self.local_keys.commitment_seed, self.cur_local_commitment_transaction_number);
 
 		//TODO: Store htlc keys in our channel_watcher
@@ -1237,7 +1312,7 @@ impl Channel {
 		if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
 			return Err(HandleError{err: "Got revoke/ACK message when channel was not in an operational state", msg: None});
 		}
-		if PublicKey::from_secret_key(&self.secp_ctx, &get_key!(&self.secp_ctx, &msg.per_commitment_secret)).unwrap() != self.their_cur_commitment_point {
+		if PublicKey::from_secret_key(&self.secp_ctx, &secp_call!(SecretKey::from_slice(&self.secp_ctx, &msg.per_commitment_secret), "Peer provided an invalid per_commitment_secret")).unwrap() != self.their_cur_commitment_point {
 			return Err(HandleError{err: "Got a revoke commitment secret which didn't correspond to their current pubkey", msg: None});
 		}
 		self.channel_monitor.provide_secret(self.cur_remote_commitment_transaction_number, msg.per_commitment_secret)?;
@@ -1262,11 +1337,184 @@ impl Channel {
         if self.channel_outbound {
 			return Err(HandleError{err: "Non-funding remote tried to update channel fee", msg: None});
         }
-		Channel::check_remote_fee(fee_estimator, msg.feerate_per_kw).unwrap();
+		Channel::check_remote_fee(fee_estimator, msg.feerate_per_kw)?;
 		self.feerate_per_kw = msg.feerate_per_kw as u64;
 		Ok(())
 	}
 
+	pub fn shutdown(&mut self, fee_estimator: &FeeEstimator, msg: &msgs::Shutdown) -> Result<(Option<msgs::Shutdown>, Option<msgs::ClosingSigned>, Vec<[u8; 32]>), HandleError> {
+		if self.channel_state < ChannelState::FundingSent as u32 {
+			self.channel_state = ChannelState::ShutdownComplete as u32;
+			return Ok((None, None, Vec::new()));
+		}
+		for htlc in self.pending_htlcs.iter() {
+			if htlc.state == HTLCState::RemoteAnnounced {
+				return Err(HandleError{err: "Got shutdown with remote pending HTLCs", msg: None});
+			}
+		}
+		if (self.channel_state & ChannelState::RemoteShutdownSent as u32) == ChannelState::RemoteShutdownSent as u32 {
+			return Err(HandleError{err: "Remote peer sent duplicate shutdown message", msg: None});
+		}
+		assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
+
+		// BOLT 2 says we must only send a scriptpubkey of certain standard forms, which are up to
+		// 34 bytes in length, so dont let the remote peer feed us some super fee-heavy script.
+		if self.channel_outbound && msg.scriptpubkey.len() > 34 {
+			return Err(HandleError{err: "Got shutdown_scriptpubkey of absurd length from remote peer", msg: None});
+		}
+		//TODO: Check shutdown_scriptpubkey form as BOLT says we must? WHYYY
+
+		if self.their_shutdown_scriptpubkey.is_some() {
+			if Some(&msg.scriptpubkey) != self.their_shutdown_scriptpubkey.as_ref() {
+				return Err(HandleError{err: "Got shutdown request with a scriptpubkey which did not match their previous scriptpubkey", msg: None});
+			}
+		} else {
+			self.their_shutdown_scriptpubkey = Some(msg.scriptpubkey.clone());
+		}
+
+		let our_closing_script = self.get_closing_scriptpubkey();
+
+		let (proposed_feerate, proposed_fee, our_sig) = if self.channel_outbound && self.pending_htlcs.is_empty() {
+			let mut proposed_feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Background);
+			if self.feerate_per_kw > proposed_feerate * 250 {
+				proposed_feerate = self.feerate_per_kw / 250;
+			}
+			let tx_weight = Self::get_closing_transaction_weight(&our_closing_script, &msg.scriptpubkey);
+			let proposed_total_fee_satoshis = proposed_feerate * tx_weight / 4;
+
+			let (closing_tx, total_fee_satoshis) = self.build_closing_transaction(proposed_total_fee_satoshis, false);
+			let funding_redeemscript = self.get_funding_redeemscript();
+			let sighash = Message::from_slice(&bip143::SighashComponents::new(&closing_tx).sighash_all(&closing_tx.input[0], &funding_redeemscript, self.channel_value_satoshis)[..]).unwrap();
+
+			(Some(proposed_feerate), Some(total_fee_satoshis), Some(self.secp_ctx.sign(&sighash, &self.local_keys.funding_key).unwrap()))
+		} else { (None, None, None) };
+
+		// From here on out, we may not fail!
+
+		self.channel_state |= ChannelState::RemoteShutdownSent as u32;
+
+		// We can't send our shutdown until we've committed all of our pending HTLCs, but the
+		// remote side is unlikely to accept any new HTLCs, so we go ahead and "free" any holding
+		// cell HTLCs and return them to fail the payment.
+		let mut dropped_outbound_htlcs = Vec::with_capacity(self.holding_cell_htlcs.len());
+		for htlc in self.holding_cell_htlcs.drain(..) {
+			dropped_outbound_htlcs.push(htlc.payment_hash);
+		}
+		for htlc in self.pending_htlcs.iter() {
+			if htlc.state == HTLCState::LocalAnnounced {
+				return Ok((None, None, dropped_outbound_htlcs));
+			}
+		}
+
+		let our_shutdown = if (self.channel_state & ChannelState::LocalShutdownSent as u32) == ChannelState::LocalShutdownSent as u32 {
+			None
+		} else {
+			Some(msgs::Shutdown {
+				channel_id: self.channel_id,
+				scriptpubkey: our_closing_script,
+			})
+		};
+
+		self.channel_state |= ChannelState::LocalShutdownSent as u32;
+		if self.pending_htlcs.is_empty() && self.channel_outbound {
+			// There are no more HTLCs and we're the funder, this means we start the closing_signed
+			// dance with an initial fee proposal!
+			self.last_sent_closing_fee = Some((proposed_feerate.unwrap(), proposed_fee.unwrap()));
+			Ok((our_shutdown, Some(msgs::ClosingSigned {
+				channel_id: self.channel_id,
+				fee_satoshis: proposed_fee.unwrap(),
+				signature: our_sig.unwrap(),
+			}), dropped_outbound_htlcs))
+		} else {
+			Ok((our_shutdown, None, dropped_outbound_htlcs))
+		}
+	}
+
+	pub fn closing_signed(&mut self, fee_estimator: &FeeEstimator, msg: &msgs::ClosingSigned) -> Result<(Option<msgs::ClosingSigned>, Option<Transaction>), HandleError> {
+		if self.channel_state & BOTH_SIDES_SHUTDOWN_MASK != BOTH_SIDES_SHUTDOWN_MASK {
+			return Err(HandleError{err: "Remote end sent us a closing_signed before both sides provided a shutdown", msg: None});
+		}
+		if !self.pending_htlcs.is_empty() {
+			return Err(HandleError{err: "Remote end sent us a closing_signed while there were still pending HTLCs", msg: None});
+		}
+		if msg.fee_satoshis > 21000000 * 10000000 {
+			return Err(HandleError{err: "Remote tried to send us a closing tx with > 21 million BTC fee", msg: None});
+		}
+
+		let funding_redeemscript = self.get_funding_redeemscript();
+		let (mut closing_tx, used_total_fee) = self.build_closing_transaction(msg.fee_satoshis, false);
+		if used_total_fee != msg.fee_satoshis {
+			return Err(HandleError{err: "Remote sent us a closing_signed with a fee greater than the value they can claim", msg: None});
+		}
+		let mut sighash = Message::from_slice(&bip143::SighashComponents::new(&closing_tx).sighash_all(&closing_tx.input[0], &funding_redeemscript, self.channel_value_satoshis)[..]).unwrap();
+
+		match self.secp_ctx.verify(&sighash, &msg.signature, &self.their_funding_pubkey) {
+			Ok(_) => {},
+			Err(_) => {
+				// The remote end may have decided to revoke their output due to inconsistent dust
+				// limits, so check for that case by re-checking the signature here.
+				closing_tx = self.build_closing_transaction(msg.fee_satoshis, true).0;
+				sighash = Message::from_slice(&bip143::SighashComponents::new(&closing_tx).sighash_all(&closing_tx.input[0], &funding_redeemscript, self.channel_value_satoshis)[..]).unwrap();
+				secp_call!(self.secp_ctx.verify(&sighash, &msg.signature, &self.their_funding_pubkey), "Invalid closing tx signature from peer");
+			},
+		};
+
+		if let Some((_, last_fee)) = self.last_sent_closing_fee {
+			if last_fee == msg.fee_satoshis {
+				self.sign_commitment_transaction(&mut closing_tx, &msg.signature);
+				self.channel_state = ChannelState::ShutdownComplete as u32;
+				return Ok((None, Some(closing_tx)));
+			}
+		}
+
+		macro_rules! propose_new_feerate {
+			($new_feerate: expr) => {
+				let closing_tx_max_weight = Self::get_closing_transaction_weight(&self.get_closing_scriptpubkey(), self.their_shutdown_scriptpubkey.as_ref().unwrap());
+				let (closing_tx, used_total_fee) = self.build_closing_transaction($new_feerate * closing_tx_max_weight / 4, false);
+				sighash = Message::from_slice(&bip143::SighashComponents::new(&closing_tx).sighash_all(&closing_tx.input[0], &funding_redeemscript, self.channel_value_satoshis)[..]).unwrap();
+				let our_sig = self.secp_ctx.sign(&sighash, &self.local_keys.funding_key).unwrap();
+				self.last_sent_closing_fee = Some(($new_feerate, used_total_fee));
+				return Ok((Some(msgs::ClosingSigned {
+					channel_id: self.channel_id,
+					fee_satoshis: used_total_fee,
+					signature: our_sig,
+				}), None))
+			}
+		}
+
+		let proposed_sat_per_vbyte = msg.fee_satoshis * 4 / closing_tx.get_weight();
+		if self.channel_outbound {
+			let our_max_feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Normal);
+			if proposed_sat_per_vbyte > our_max_feerate {
+				if let Some((last_feerate, _)) = self.last_sent_closing_fee {
+					if our_max_feerate <= last_feerate {
+						return Err(HandleError{err: "Unable to come to consensus about closing feerate, remote wanted something higher than our Normal feerate", msg: None});
+					}
+				}
+				propose_new_feerate!(our_max_feerate);
+			}
+		} else {
+			let our_min_feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Background);
+			if proposed_sat_per_vbyte < our_min_feerate {
+				if let Some((last_feerate, _)) = self.last_sent_closing_fee {
+					if our_min_feerate >= last_feerate {
+						return Err(HandleError{err: "Unable to come to consensus about closing feerate, remote wanted something lower than our Background feerate", msg: None});
+					}
+				}
+				propose_new_feerate!(our_min_feerate);
+			}
+		}
+
+		let our_sig = self.sign_commitment_transaction(&mut closing_tx, &msg.signature);
+		self.channel_state = ChannelState::ShutdownComplete as u32;
+
+		Ok((Some(msgs::ClosingSigned {
+			channel_id: self.channel_id,
+			fee_satoshis: msg.fee_satoshis,
+			signature: our_sig,
+		}), Some(closing_tx)))
+	}
+
 	// Public utilities:
 
 	pub fn channel_id(&self) -> Uint256 {
@@ -1336,7 +1584,8 @@ impl Channel {
 
 	/// Returns true if this channel is fully established and not known to be closing.
 	pub fn is_usable(&self) -> bool {
-		(self.channel_state & (ChannelState::ChannelFunded as u32)) == (ChannelState::ChannelFunded as u32)
+		let mask = ChannelState::ChannelFunded as u32 | BOTH_SIDES_SHUTDOWN_MASK;
+		(self.channel_state & mask) == (ChannelState::ChannelFunded as u32)
 	}
 
 	/// Returns true if this channel is currently available for use. This is a superset of
@@ -1345,19 +1594,30 @@ impl Channel {
 		self.is_usable()
 	}
 
+	/// Returns true if this channel is fully shut down. True here implies that no further actions
+	/// may/will be taken on this channel, and thus this object should be freed. Any future changes
+	/// will be handled appropriately by the chain monitor.
+	pub fn is_shutdown(&self) -> bool {
+		if (self.channel_state & ChannelState::ShutdownComplete as u32) == ChannelState::ShutdownComplete as u32  {
+			assert!(self.channel_state == ChannelState::ShutdownComplete as u32);
+			true
+		} else { false }
+	}
+
 	/// Called by channelmanager based on chain blocks being connected.
 	/// Note that we only need to use this to detect funding_signed, anything else is handled by
 	/// the channel_monitor.
 	pub fn block_connected(&mut self, header: &BlockHeader, height: u32, txn_matched: &[&Transaction], indexes_of_txn_matched: &[u32]) -> Option<msgs::FundingLocked> {
+		let non_shutdown_state = self.channel_state & (!BOTH_SIDES_SHUTDOWN_MASK);
 		if self.funding_tx_confirmations > 0 {
 			if header.bitcoin_hash() != self.last_block_connected {
 				self.last_block_connected = header.bitcoin_hash();
 				self.funding_tx_confirmations += 1;
 				if self.funding_tx_confirmations == CONF_TARGET as u64 {
-					if self.channel_state == ChannelState::FundingSent as u32 {
+					if non_shutdown_state == ChannelState::FundingSent as u32 {
 						self.channel_state |= ChannelState::OurFundingLocked as u32;
-					} else if self.channel_state == (ChannelState::FundingSent as u32 | ChannelState::TheirFundingLocked as u32) {
-						self.channel_state = ChannelState::ChannelFunded as u32;
+					} else if non_shutdown_state == (ChannelState::FundingSent as u32 | ChannelState::TheirFundingLocked as u32) {
+						self.channel_state = ChannelState::ChannelFunded as u32 | (self.channel_state & BOTH_SIDES_SHUTDOWN_MASK);
 						//TODO: Something about a state where we "lost confirmation"
 					} else if self.channel_state < ChannelState::ChannelFunded as u32 {
 						panic!("Started confirming a channel in a state pre-FundingSent?");
@@ -1368,11 +1628,7 @@ impl Channel {
 					//as otherwise we will have a commitment transaction that they can't revoke (well, kinda,
 					//they can by sending two revoke_and_acks back-to-back, but not really). This appears to be
 					//a protocol oversight, but I assume I'm just missing something.
-					let next_per_commitment_secret = match self.build_local_commitment_secret(self.cur_local_commitment_transaction_number) {
-						Ok(secret) => secret,
-						Err(_) => return None
-					};
-
+					let next_per_commitment_secret = self.build_local_commitment_secret(self.cur_local_commitment_transaction_number);
 					let next_per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &next_per_commitment_secret).unwrap();
 					return Some(msgs::FundingLocked {
 						channel_id: self.channel_id,
@@ -1381,13 +1637,19 @@ impl Channel {
 				}
 			}
 		}
-		if self.channel_state & !(ChannelState::TheirFundingLocked as u32) == ChannelState::FundingSent as u32 {
+		if non_shutdown_state & !(ChannelState::TheirFundingLocked as u32) == ChannelState::FundingSent as u32 {
 			for (ref tx, index_in_block) in txn_matched.iter().zip(indexes_of_txn_matched) {
 				if tx.txid() == self.channel_monitor.get_funding_txo().unwrap().0 {
-					self.funding_tx_confirmations = 1;
-					self.short_channel_id = Some(((height as u64)          << (5*8)) |
-					                             ((*index_in_block as u64) << (2*8)) |
-					                             ((self.channel_monitor.get_funding_txo().unwrap().1 as u64) << (2*8)));
+					let txo_idx = self.channel_monitor.get_funding_txo().unwrap().1 as usize;
+					if txo_idx >= tx.output.len() || tx.output[txo_idx].script_pubkey != self.get_funding_redeemscript().to_v0_p2wsh() ||
+						tx.output[txo_idx].value != self.channel_value_satoshis {
+						self.channel_state = ChannelState::ShutdownComplete as u32;
+					} else {
+						self.funding_tx_confirmations = 1;
+						self.short_channel_id = Some(((height as u64)          << (5*8)) |
+						                             ((*index_in_block as u64) << (2*8)) |
+						                             ((self.channel_monitor.get_funding_txo().unwrap().1 as u64) << (2*8)));
+					}
 				}
 			}
 		}
@@ -1425,7 +1687,7 @@ impl Channel {
 			panic!("Tried to send an open_channel for a channel that has already advanced");
 		}
 
-		let local_commitment_secret = self.build_local_commitment_secret(self.cur_local_commitment_transaction_number)?;
+		let local_commitment_secret = self.build_local_commitment_secret(self.cur_local_commitment_transaction_number);
 
 		Ok(msgs::OpenChannel {
 			chain_hash: chain_hash,
@@ -1461,7 +1723,7 @@ impl Channel {
 			panic!("Tried to send an accept_channel for a channel that has already advanced");
 		}
 
-		let local_commitment_secret = self.build_local_commitment_secret(self.cur_local_commitment_transaction_number)?;
+		let local_commitment_secret = self.build_local_commitment_secret(self.cur_local_commitment_transaction_number);
 
 		Ok(msgs::AcceptChannel {
 			temporary_channel_id: self.channel_id,
@@ -1486,11 +1748,11 @@ impl Channel {
 		let funding_script = self.get_funding_redeemscript();
 
 		let remote_keys = self.build_remote_transaction_keys()?;
-		let remote_initial_commitment_tx = self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, false)?.0;
-		let remote_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&remote_initial_commitment_tx).sighash_all(&remote_initial_commitment_tx, 0, &funding_script, self.channel_value_satoshis)[..]));
+		let remote_initial_commitment_tx = self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, false).0;
+		let remote_sighash = Message::from_slice(&bip143::SighashComponents::new(&remote_initial_commitment_tx).sighash_all(&remote_initial_commitment_tx.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
 
 		// We sign the "remote" commitment transaction, allowing them to broadcast the tx if they wish.
-		Ok(secp_call!(self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key)))
+		Ok(self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key).unwrap())
 	}
 
 	/// Updates channel state with knowledge of the funding transaction's txid/index, and generates
@@ -1540,11 +1802,14 @@ impl Channel {
 	/// bitcoin_key, if available, for this channel. The channel must be publicly announceable and
 	/// available for use (have exchanged FundingLocked messages in both directions. Should be used
 	/// for both loose and in response to an AnnouncementSignatures message from the remote peer.
+	/// Note that you can get an announcement for a channel which is closing, though you should
+	/// likely not announce such a thing. In case its already been announced, a channel_update
+	/// message can mark the channel disabled.
 	pub fn get_channel_announcement(&self, our_node_id: PublicKey, chain_hash: Sha256dHash) -> Result<(msgs::UnsignedChannelAnnouncement, Signature), HandleError> {
 		if !self.announce_publicly {
 			return Err(HandleError{err: "Channel is not available for public announcements", msg: None});
 		}
-		if self.channel_state < ChannelState::ChannelFunded as u32 {
+		if self.channel_state & (ChannelState::ChannelFunded as u32) != (ChannelState::ChannelFunded as u32) {
 			return Err(HandleError{err: "Cannot get a ChannelAnnouncement until the channel funding has been locked", msg: None});
 		}
 
@@ -1562,7 +1827,7 @@ impl Channel {
 		};
 
 		let msghash = Message::from_slice(&Sha256dHash::from_data(&msg.encode()[..])[..]).unwrap();
-		let sig = secp_call!(self.secp_ctx.sign(&msghash, &self.local_keys.funding_key));
+		let sig = self.secp_ctx.sign(&msghash, &self.local_keys.funding_key).unwrap();
 
 		Ok((msg, sig))
 	}
@@ -1576,8 +1841,8 @@ impl Channel {
 	/// waiting on the remote peer to send us a revoke_and_ack during which time we cannot add new
 	/// HTLCs on the wire or we wouldn't be able to determine what they actually ACK'ed.
 	pub fn send_htlc(&mut self, amount_msat: u64, payment_hash: [u8; 32], cltv_expiry: u32, onion_routing_packet: msgs::OnionPacket) -> Result<Option<msgs::UpdateAddHTLC>, HandleError> {
-		if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
-			return Err(HandleError{err: "Cannot send HTLC until channel is fully established", msg: None});
+		if (self.channel_state & (ChannelState::ChannelFunded as u32 | BOTH_SIDES_SHUTDOWN_MASK)) != (ChannelState::ChannelFunded as u32) {
+			return Err(HandleError{err: "Cannot send HTLC until channel is fully established and we haven't started shutting down", msg: None});
 		}
 
 		if amount_msat > self.channel_value_satoshis * 1000 {
@@ -1644,22 +1909,36 @@ impl Channel {
 		if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
 			return Err(HandleError{err: "Cannot create commitment tx until channel is fully established", msg: None});
 		}
+		if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) == (ChannelState::AwaitingRemoteRevoke as u32) {
+			return Err(HandleError{err: "Cannot create commitment tx until remote revokes their previous commitment", msg: None});
+		}
+		let mut have_updates = false; // TODO initialize with "have we sent a fee update?"
+		for htlc in self.pending_htlcs.iter() {
+			if htlc.state == HTLCState::LocalAnnounced {
+				have_updates = true;
+			}
+			if have_updates { break; }
+		}
+		if !have_updates {
+			return Err(HandleError{err: "Cannot create commitment tx until we have some updates to send", msg: None});
+		}
 
 		let funding_script = self.get_funding_redeemscript();
 
 		let remote_keys = self.build_remote_transaction_keys()?;
-		let remote_commitment_tx = self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, true)?;
-		let remote_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&remote_commitment_tx.0).sighash_all(&remote_commitment_tx.0, 0, &funding_script, self.channel_value_satoshis)[..]));
-		let our_sig = secp_call!(self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key));
+		let remote_commitment_tx = self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, true);
+		let remote_commitment_txid = remote_commitment_tx.0.txid();
+		let remote_sighash = Message::from_slice(&bip143::SighashComponents::new(&remote_commitment_tx.0).sighash_all(&remote_commitment_tx.0.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
+		let our_sig = self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key).unwrap();
 
 		let mut htlc_sigs = Vec::new();
 
 		for ref htlc in remote_commitment_tx.1.iter() {
-			let htlc_tx = self.build_htlc_transaction(&remote_commitment_tx.0.txid(), htlc, false, &remote_keys)?;
+			let htlc_tx = self.build_htlc_transaction(&remote_commitment_txid, htlc, false, &remote_keys)?;
 			let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &remote_keys, htlc.offered);
-			let htlc_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx, 0, &htlc_redeemscript, htlc.amount_msat / 1000)[..]));
-			let our_htlc_key = secp_call!(chan_utils::derive_private_key(&self.secp_ctx, &remote_keys.per_commitment_point, &self.local_keys.htlc_base_key));
-			htlc_sigs.push(secp_call!(self.secp_ctx.sign(&htlc_sighash, &our_htlc_key)));
+			let htlc_sighash = Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]).unwrap();
+			let our_htlc_key = secp_derived_key!(chan_utils::derive_private_key(&self.secp_ctx, &remote_keys.per_commitment_point, &self.local_keys.htlc_base_key));
+			htlc_sigs.push(self.secp_ctx.sign(&htlc_sighash, &our_htlc_key).unwrap());
 		}
 
 		// Update state now that we've passed all the can-fail calls...
@@ -1683,6 +1962,42 @@ impl Channel {
 			None => Ok(None)
 		}
 	}
+
+	/// Begins the shutdown process, getting a message for the remote peer and returning all
+	/// holding cell HTLCs for payment failure.
+	pub fn get_shutdown(&mut self) -> Result<(msgs::Shutdown, Vec<[u8; 32]>), HandleError> {
+		for htlc in self.pending_htlcs.iter() {
+			if htlc.state == HTLCState::LocalAnnounced {
+				return Err(HandleError{err: "Cannot begin shutdown with pending HTLCs, call send_commitment first", msg: None});
+			}
+		}
+		if self.channel_state & BOTH_SIDES_SHUTDOWN_MASK != 0 {
+			return Err(HandleError{err: "Shutdown already in progress", msg: None});
+		}
+		assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
+
+		let our_closing_script = self.get_closing_scriptpubkey();
+
+		// From here on out, we may not fail!
+		if self.channel_state < ChannelState::FundingSent as u32 {
+			self.channel_state = ChannelState::ShutdownComplete as u32;
+		} else {
+			self.channel_state |= ChannelState::LocalShutdownSent as u32;
+		}
+
+		// We can't send our shutdown until we've committed all of our pending HTLCs, but the
+		// remote side is unlikely to accept any new HTLCs, so we go ahead and "free" any holding
+		// cell HTLCs and return them to fail the payment.
+		let mut dropped_outbound_htlcs = Vec::with_capacity(self.holding_cell_htlcs.len());
+		for htlc in self.holding_cell_htlcs.drain(..) {
+			dropped_outbound_htlcs.push(htlc.payment_hash);
+		}
+
+		Ok((msgs::Shutdown {
+			channel_id: self.channel_id,
+			scriptpubkey: our_closing_script,
+		}, dropped_outbound_htlcs))
+	}
 }
 
 #[cfg(test)]
@@ -1757,12 +2072,12 @@ mod tests {
 
 		macro_rules! test_commitment {
 			( $their_sig_hex: expr, $our_sig_hex: expr, $tx_hex: expr) => {
-				unsigned_tx = chan.build_commitment_transaction(42, &keys, true, false).unwrap();
+				unsigned_tx = chan.build_commitment_transaction(42, &keys, true, false);
 				let their_signature = Signature::from_der(&secp_ctx, &hex_bytes($their_sig_hex).unwrap()[..]).unwrap();
-				let sighash = Message::from_slice(&bip143::SighashComponents::new(&unsigned_tx.0).sighash_all(&unsigned_tx.0, 0, &chan.get_funding_redeemscript(), chan.channel_value_satoshis)[..]).unwrap();
+				let sighash = Message::from_slice(&bip143::SighashComponents::new(&unsigned_tx.0).sighash_all(&unsigned_tx.0.input[0], &chan.get_funding_redeemscript(), chan.channel_value_satoshis)[..]).unwrap();
 				secp_ctx.verify(&sighash, &their_signature, &chan.their_funding_pubkey).unwrap();
 
-				chan.sign_commitment_transaction(&mut unsigned_tx.0, &their_signature).unwrap();
+				chan.sign_commitment_transaction(&mut unsigned_tx.0, &their_signature);
 
 				assert_eq!(serialize(&unsigned_tx.0).unwrap()[..],
 						hex_bytes($tx_hex).unwrap()[..]);
@@ -1776,7 +2091,7 @@ mod tests {
 				let ref htlc = unsigned_tx.1[$htlc_idx];
 				let mut htlc_tx = chan.build_htlc_transaction(&unsigned_tx.0.txid(), &htlc, true, &keys).unwrap();
 				let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &keys, htlc.offered);
-				let htlc_sighash = Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx, 0, &htlc_redeemscript, htlc.amount_msat / 1000)[..]).unwrap();
+				let htlc_sighash = Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]).unwrap();
 				secp_ctx.verify(&htlc_sighash, &remote_signature, &keys.b_htlc_key).unwrap();
 
 				let mut preimage: Option<[u8; 32]> = None;