_ Git - rust-lightning/blob - lightning/src/util/enforcing_trait_impls.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 use ln::chan_utils::{HTLCOutputInCommitment, ChannelPublicKeys, HolderCommitmentTransaction, CommitmentTransaction, ChannelTransactionParameters, TrustedCommitmentTransaction};
  11 use ln::{chan_utils, msgs};
  12 use chain::keysinterface::{Sign, InMemorySigner, BaseSign};
  13
  14 use io;
  15 use prelude::*;
  16 use core::cmp;
  17 use sync::{Mutex, Arc};
  18
  19 use bitcoin::blockdata::transaction::{Transaction, SigHashType};
  20 use bitcoin::util::bip143;
  21
  22 use bitcoin::secp256k1;
  23 use bitcoin::secp256k1::key::{SecretKey, PublicKey};
  24 use bitcoin::secp256k1::{Secp256k1, Signature};
  25 use util::ser::{Writeable, Writer, Readable};
  26 use io::Error;
  27 use ln::msgs::DecodeError;
  28
  29 /// Initial value for revoked commitment downward counter
  30 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
  31
  32 /// An implementation of Sign that enforces some policy checks.  The current checks
  33 /// are an incomplete set.  They include:
  34 ///
  35 /// - When signing, the holder transaction has not been revoked
  36 /// - When revoking, the holder transaction has not been signed
  37 /// - The holder commitment number is monotonic and without gaps
  38 /// - The counterparty commitment number is monotonic and without gaps
  39 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
  40 ///
  41 /// Eventually we will probably want to expose a variant of this which would essentially
  42 /// be what you'd want to run on a hardware wallet.
  43 ///
  44 /// Note that before we do so we should ensure its serialization format has backwards- and
  45 /// forwards-compatibility prefix/suffixes!
  46 #[derive(Clone)]
  47 pub struct EnforcingSigner {
  48         pub inner: InMemorySigner,
  49         /// Channel state used for policy enforcement
  50         pub state: Arc<Mutex<EnforcementState>>,
  51         pub disable_revocation_policy_check: bool,
  52 }
  53
  54 impl EnforcingSigner {
  55         /// Construct an EnforcingSigner
  56         pub fn new(inner: InMemorySigner) -> Self {
  57                 let state = Arc::new(Mutex::new(EnforcementState::new()));
  58                 Self {
  59                         inner,
  60                         state,
  61                         disable_revocation_policy_check: false
  62                 }
  63         }
  64
  65         /// Construct an EnforcingSigner with externally managed storage
  66         ///
  67         /// Since there are multiple copies of this struct for each channel, some coordination is needed
  68         /// so that all copies are aware of enforcement state.  A pointer to this state is provided
  69         /// here, usually by an implementation of KeysInterface.
  70         pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
  71                 Self {
  72                         inner,
  73                         state,
  74                         disable_revocation_policy_check
  75                 }
  76         }
  77 }
  78
  79 impl BaseSign for EnforcingSigner {
  80         fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
  81                 self.inner.get_per_commitment_point(idx, secp_ctx)
  82         }
  83
  84         fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
  85                 {
  86                         let mut state = self.state.lock().unwrap();
  87                         assert!(idx == state.revoked_commitment || idx == state.revoked_commitment - 1, "can only revoke the current or next unrevoked commitment - trying {}, revoked {}", idx, state.revoked_commitment);
  88                         state.revoked_commitment = idx;
  89                 }
  90                 self.inner.release_commitment_secret(idx)
  91         }
  92
  93         fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
  94         fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
  95
  96         fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
  97                 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
  98
  99                 {
 100                         let mut state = self.state.lock().unwrap();
 101                         let actual_commitment_number = commitment_tx.commitment_number();
 102                         let last_commitment_number = state.last_counterparty_commitment;
 103                         // These commitment numbers are backwards counting.  We expect either the same as the previously encountered,
 104                         // or the next one.
 105                         assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
 106                         state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
 107                 }
 108
 109                 Ok(self.inner.sign_counterparty_commitment(commitment_tx, secp_ctx).unwrap())
 110         }
 111
 112         fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 113                 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
 114                 let commitment_txid = trusted_tx.txid();
 115                 let holder_csv = self.inner.counterparty_selected_contest_delay();
 116
 117                 let state = self.state.lock().unwrap();
 118                 let commitment_number = trusted_tx.commitment_number();
 119                 if state.revoked_commitment - 1 != commitment_number && state.revoked_commitment - 2 != commitment_number {
 120                         if !self.disable_revocation_policy_check {
 121                                 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
 122                                        state.revoked_commitment, commitment_number, self.inner.commitment_seed[0])
 123                         }
 124                 }
 125
 126                 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
 127                         assert!(this_htlc.transaction_output_index.is_some());
 128                         let keys = trusted_tx.keys();
 129                         let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, trusted_tx.feerate_per_kw(), holder_csv, &this_htlc, &keys.broadcaster_delayed_payment_key, &keys.revocation_key);
 130
 131                         let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, &keys);
 132
 133                         let sighash = hash_to_message!(&bip143::SigHashCache::new(&htlc_tx).signature_hash(0, &htlc_redeemscript, this_htlc.amount_msat / 1000, SigHashType::All)[..]);
 134                         secp_ctx.verify(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
 135                 }
 136
 137                 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 138         }
 139
 140         #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
 141         fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 142                 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 143         }
 144
 145         fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 146                 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
 147         }
 148
 149         fn sign_justice_revoked_htlc(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 150                 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
 151         }
 152
 153         fn sign_counterparty_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 154                 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
 155         }
 156
 157         fn sign_closing_transaction(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 158                 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
 159         }
 160
 161         fn sign_channel_announcement(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 162                 self.inner.sign_channel_announcement(msg, secp_ctx)
 163         }
 164
 165         fn ready_channel(&mut self, channel_parameters: &ChannelTransactionParameters) {
 166                 self.inner.ready_channel(channel_parameters)
 167         }
 168 }
 169
 170 impl Sign for EnforcingSigner {}
 171
 172 impl Writeable for EnforcingSigner {
 173         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
 174                 self.inner.write(writer)?;
 175                 // NOTE - the commitment state is maintained by KeysInterface, so we don't persist it
 176                 Ok(())
 177         }
 178 }
 179
 180 impl Readable for EnforcingSigner {
 181         fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
 182                 let inner = Readable::read(reader)?;
 183                 let state = Arc::new(Mutex::new(EnforcementState::new()));
 184                 Ok(EnforcingSigner {
 185                         inner,
 186                         state,
 187                         disable_revocation_policy_check: false,
 188                 })
 189         }
 190 }
 191
 192 impl EnforcingSigner {
 193         fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
 194                 commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
 195                                      self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
 196                         .expect("derived different per-tx keys or built transaction")
 197         }
 198
 199         fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
 200                 commitment_tx.verify(&self.inner.get_channel_parameters().as_holder_broadcastable(),
 201                                      self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
 202                         .expect("derived different per-tx keys or built transaction")
 203         }
 204 }
 205
 206 /// The state used by [`EnforcingSigner`] in order to enforce policy checks
 207 ///
 208 /// This structure is maintained by KeysInterface since we may have multiple copies of
 209 /// the signer and they must coordinate their state.
 210 #[derive(Clone)]
 211 pub struct EnforcementState {
 212         /// The last counterparty commitment number we signed, backwards counting
 213         pub last_counterparty_commitment: u64,
 214         /// The last holder commitment number we revoked, backwards counting
 215         pub revoked_commitment: u64,
 216
 217 }
 218
 219 impl EnforcementState {
 220         /// Enforcement state for a new channel
 221         pub fn new() -> Self {
 222                 EnforcementState {
 223                         last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 224                         revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 225                 }
 226         }
 227 }