_ 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 core::cmp;
  15 use std::sync::{Mutex, Arc};
  16
  17 use bitcoin::blockdata::transaction::{Transaction, SigHashType};
  18 use bitcoin::util::bip143;
  19
  20 use bitcoin::secp256k1;
  21 use bitcoin::secp256k1::key::{SecretKey, PublicKey};
  22 use bitcoin::secp256k1::{Secp256k1, Signature};
  23 use util::ser::{Writeable, Writer, Readable};
  24 use std::io::Error;
  25 use ln::msgs::DecodeError;
  26
  27 /// Initial value for revoked commitment downward counter
  28 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
  29
  30 /// An implementation of Sign that enforces some policy checks.  The current checks
  31 /// are an incomplete set.  They include:
  32 ///
  33 /// - When signing, the holder transaction has not been revoked
  34 /// - When revoking, the holder transaction has not been signed
  35 /// - The holder commitment number is monotonic and without gaps
  36 /// - The counterparty commitment number is monotonic and without gaps
  37 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
  38 ///
  39 /// Eventually we will probably want to expose a variant of this which would essentially
  40 /// be what you'd want to run on a hardware wallet.
  41 ///
  42 /// Note that before we do so we should ensure its serialization format has backwards- and
  43 /// forwards-compatibility prefix/suffixes!
  44 #[derive(Clone)]
  45 pub struct EnforcingSigner {
  46         pub inner: InMemorySigner,
  47         /// The last counterparty commitment number we signed, backwards counting
  48         pub last_commitment_number: Arc<Mutex<Option<u64>>>,
  49         /// The last holder commitment number we revoked, backwards counting
  50         pub revoked_commitment: Arc<Mutex<u64>>,
  51         pub disable_revocation_policy_check: bool,
  52 }
  53
  54 impl EnforcingSigner {
  55         /// Construct an EnforcingSigner
  56         pub fn new(inner: InMemorySigner) -> Self {
  57                 Self {
  58                         inner,
  59                         last_commitment_number: Arc::new(Mutex::new(None)),
  60                         revoked_commitment: Arc::new(Mutex::new(INITIAL_REVOKED_COMMITMENT_NUMBER)),
  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 revocations.  A pointer to this state is provided here, usually
  69         /// by an implementation of KeysInterface.
  70         pub fn new_with_revoked(inner: InMemorySigner, revoked_commitment: Arc<Mutex<u64>>, disable_revocation_policy_check: bool) -> Self {
  71                 Self {
  72                         inner,
  73                         last_commitment_number: Arc::new(Mutex::new(None)),
  74                         revoked_commitment,
  75                         disable_revocation_policy_check
  76                 }
  77         }
  78 }
  79
  80 impl BaseSign for EnforcingSigner {
  81         fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
  82                 self.inner.get_per_commitment_point(idx, secp_ctx)
  83         }
  84
  85         fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
  86                 {
  87                         let mut revoked = self.revoked_commitment.lock().unwrap();
  88                         assert!(idx == *revoked || idx == *revoked - 1, "can only revoke the current or next unrevoked commitment - trying {}, revoked {}", idx, *revoked);
  89                         *revoked = idx;
  90                 }
  91                 self.inner.release_commitment_secret(idx)
  92         }
  93
  94         fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
  95         fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
  96
  97         fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
  98                 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
  99
 100                 {
 101                         let mut last_commitment_number_guard = self.last_commitment_number.lock().unwrap();
 102                         let actual_commitment_number = commitment_tx.commitment_number();
 103                         let last_commitment_number = last_commitment_number_guard.unwrap_or(actual_commitment_number);
 104                         // These commitment numbers are backwards counting.  We expect either the same as the previously encountered,
 105                         // or the next one.
 106                         assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
 107                         *last_commitment_number_guard = Some(cmp::min(last_commitment_number, actual_commitment_number))
 108                 }
 109
 110                 Ok(self.inner.sign_counterparty_commitment(commitment_tx, secp_ctx).unwrap())
 111         }
 112
 113         fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 114                 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
 115                 let commitment_txid = trusted_tx.txid();
 116                 let holder_csv = self.inner.counterparty_selected_contest_delay();
 117
 118                 let revoked = self.revoked_commitment.lock().unwrap();
 119                 let commitment_number = trusted_tx.commitment_number();
 120                 if *revoked - 1 != commitment_number && *revoked - 2 != commitment_number {
 121                         if !self.disable_revocation_policy_check {
 122                                 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
 123                                        *revoked, commitment_number, self.inner.commitment_seed[0])
 124                         }
 125                 }
 126
 127                 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
 128                         assert!(this_htlc.transaction_output_index.is_some());
 129                         let keys = trusted_tx.keys();
 130                         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);
 131
 132                         let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, &keys);
 133
 134                         let sighash = hash_to_message!(&bip143::SigHashCache::new(&htlc_tx).signature_hash(0, &htlc_redeemscript, this_htlc.amount_msat / 1000, SigHashType::All)[..]);
 135                         secp_ctx.verify(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
 136                 }
 137
 138                 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 139         }
 140
 141         #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
 142         fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 143                 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 144         }
 145
 146         fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 147                 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
 148         }
 149
 150         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, ()> {
 151                 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
 152         }
 153
 154         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, ()> {
 155                 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
 156         }
 157
 158         fn sign_closing_transaction(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 159                 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
 160         }
 161
 162         fn sign_channel_announcement(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 163                 self.inner.sign_channel_announcement(msg, secp_ctx)
 164         }
 165
 166         fn ready_channel(&mut self, channel_parameters: &ChannelTransactionParameters) {
 167                 self.inner.ready_channel(channel_parameters)
 168         }
 169 }
 170
 171 impl Sign for EnforcingSigner {}
 172
 173 impl Writeable for EnforcingSigner {
 174         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
 175                 self.inner.write(writer)?;
 176                 let last = *self.last_commitment_number.lock().unwrap();
 177                 last.write(writer)?;
 178                 Ok(())
 179         }
 180 }
 181
 182 impl Readable for EnforcingSigner {
 183         fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
 184                 let inner = Readable::read(reader)?;
 185                 let last_commitment_number = Readable::read(reader)?;
 186                 Ok(EnforcingSigner {
 187                         inner,
 188                         last_commitment_number: Arc::new(Mutex::new(last_commitment_number)),
 189                         revoked_commitment: Arc::new(Mutex::new(INITIAL_REVOKED_COMMITMENT_NUMBER)),
 190                         disable_revocation_policy_check: false,
 191                 })
 192         }
 193 }
 194
 195 impl EnforcingSigner {
 196         fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
 197                 commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
 198                                      self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
 199                         .expect("derived different per-tx keys or built transaction")
 200         }
 201
 202         fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
 203                 commitment_tx.verify(&self.inner.get_channel_parameters().as_holder_broadcastable(),
 204                                      self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
 205                         .expect("derived different per-tx keys or built transaction")
 206         }
 207 }