1 //! Defines ECDSA-specific signer types.
3 use bitcoin::blockdata::transaction::Transaction;
5 use bitcoin::secp256k1;
6 use bitcoin::secp256k1::ecdsa::Signature;
7 use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
9 use crate::ln::chan_utils::{
10 ClosingTransaction, CommitmentTransaction, HTLCOutputInCommitment, HolderCommitmentTransaction,
12 use crate::ln::msgs::UnsignedChannelAnnouncement;
13 use crate::ln::PaymentPreimage;
14 use crate::util::ser::Writeable;
16 #[allow(unused_imports)]
17 use crate::prelude::*;
19 use crate::sign::{ChannelSigner, HTLCDescriptor};
21 /// A trait to sign Lightning channel transactions as described in
22 /// [BOLT 3](https://github.com/lightning/bolts/blob/master/03-transactions.md).
24 /// Signing services could be implemented on a hardware wallet and should implement signing
25 /// policies in order to be secure. Please refer to the [VLS Policy
26 /// Controls](https://gitlab.com/lightning-signer/validating-lightning-signer/-/blob/main/docs/policy-controls.md)
27 /// for an example of such policies.
28 pub trait EcdsaChannelSigner: ChannelSigner {
29 /// Create a signature for a counterparty's commitment transaction and associated HTLC transactions.
31 /// Note that if signing fails or is rejected, the channel will be force-closed.
33 /// Policy checks should be implemented in this function, including checking the amount
34 /// sent to us and checking the HTLCs.
36 /// The preimages of outbound and inbound HTLCs that were fulfilled since the last commitment
37 /// are provided. A validating signer should ensure that an outbound HTLC output is removed
38 /// only when the matching preimage is provided and after the corresponding inbound HTLC has
39 /// been removed for forwarded payments.
41 /// Note that all the relevant preimages will be provided, but there may also be additional
42 /// irrelevant or duplicate preimages.
44 // TODO: Document the things someone using this interface should enforce before signing.
45 fn sign_counterparty_commitment(
46 &self, commitment_tx: &CommitmentTransaction, inbound_htlc_preimages: Vec<PaymentPreimage>,
47 outbound_htlc_preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<secp256k1::All>,
48 ) -> Result<(Signature, Vec<Signature>), ()>;
49 /// Creates a signature for a holder's commitment transaction.
51 /// This will be called
52 /// - with a non-revoked `commitment_tx`.
53 /// - with the latest `commitment_tx` when we initiate a force-close.
55 /// This may be called multiple times for the same transaction.
57 /// An external signer implementation should check that the commitment has not been revoked.
59 /// An `Err` can be returned to signal that the signer is unavailable/cannot produce a valid
60 /// signature and should be retried later. Once the signer is ready to provide a signature after
61 /// previously returning an `Err`, [`ChannelMonitor::signer_unblocked`] must be called on its
64 /// [`ChannelMonitor::signer_unblocked`]: crate::chain::channelmonitor::ChannelMonitor::signer_unblocked
66 // TODO: Document the things someone using this interface should enforce before signing.
67 fn sign_holder_commitment(
68 &self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>,
69 ) -> Result<Signature, ()>;
70 /// Same as [`sign_holder_commitment`], but exists only for tests to get access to holder
71 /// commitment transactions which will be broadcasted later, after the channel has moved on to a
72 /// newer state. Thus, needs its own method as [`sign_holder_commitment`] may enforce that we
73 /// only ever get called once.
74 #[cfg(any(test, feature = "unsafe_revoked_tx_signing"))]
75 fn unsafe_sign_holder_commitment(
76 &self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>,
77 ) -> Result<Signature, ()>;
78 /// Create a signature for the given input in a transaction spending an HTLC transaction output
79 /// or a commitment transaction `to_local` output when our counterparty broadcasts an old state.
81 /// A justice transaction may claim multiple outputs at the same time if timelocks are
82 /// similar, but only a signature for the input at index `input` should be signed for here.
83 /// It may be called multiple times for same output(s) if a fee-bump is needed with regards
84 /// to an upcoming timelock expiration.
86 /// Amount is value of the output spent by this input, committed to in the BIP 143 signature.
88 /// `per_commitment_key` is revocation secret which was provided by our counterparty when they
89 /// revoked the state which they eventually broadcast. It's not a _holder_ secret key and does
90 /// not allow the spending of any funds by itself (you need our holder `revocation_secret` to do
93 /// An `Err` can be returned to signal that the signer is unavailable/cannot produce a valid
94 /// signature and should be retried later. Once the signer is ready to provide a signature after
95 /// previously returning an `Err`, [`ChannelMonitor::signer_unblocked`] must be called on its
98 /// [`ChannelMonitor::signer_unblocked`]: crate::chain::channelmonitor::ChannelMonitor::signer_unblocked
99 fn sign_justice_revoked_output(
100 &self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey,
101 secp_ctx: &Secp256k1<secp256k1::All>,
102 ) -> Result<Signature, ()>;
103 /// Create a signature for the given input in a transaction spending a commitment transaction
104 /// HTLC output when our counterparty broadcasts an old state.
106 /// A justice transaction may claim multiple outputs at the same time if timelocks are
107 /// similar, but only a signature for the input at index `input` should be signed for here.
108 /// It may be called multiple times for same output(s) if a fee-bump is needed with regards
109 /// to an upcoming timelock expiration.
111 /// `amount` is the value of the output spent by this input, committed to in the BIP 143
114 /// `per_commitment_key` is revocation secret which was provided by our counterparty when they
115 /// revoked the state which they eventually broadcast. It's not a _holder_ secret key and does
116 /// not allow the spending of any funds by itself (you need our holder revocation_secret to do
119 /// `htlc` holds HTLC elements (hash, timelock), thus changing the format of the witness script
120 /// (which is committed to in the BIP 143 signatures).
122 /// An `Err` can be returned to signal that the signer is unavailable/cannot produce a valid
123 /// signature and should be retried later. Once the signer is ready to provide a signature after
124 /// previously returning an `Err`, [`ChannelMonitor::signer_unblocked`] must be called on its
127 /// [`ChannelMonitor::signer_unblocked`]: crate::chain::channelmonitor::ChannelMonitor::signer_unblocked
128 fn sign_justice_revoked_htlc(
129 &self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey,
130 htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1<secp256k1::All>,
131 ) -> Result<Signature, ()>;
132 /// Computes the signature for a commitment transaction's HTLC output used as an input within
133 /// `htlc_tx`, which spends the commitment transaction at index `input`. The signature returned
134 /// must be be computed using [`EcdsaSighashType::All`].
136 /// Note that this may be called for HTLCs in the penultimate commitment transaction if a
137 /// [`ChannelMonitor`] [replica](https://github.com/lightningdevkit/rust-lightning/blob/main/GLOSSARY.md#monitor-replicas)
138 /// broadcasts it before receiving the update for the latest commitment transaction.
140 /// An `Err` can be returned to signal that the signer is unavailable/cannot produce a valid
141 /// signature and should be retried later. Once the signer is ready to provide a signature after
142 /// previously returning an `Err`, [`ChannelMonitor::signer_unblocked`] must be called on its
145 /// [`EcdsaSighashType::All`]: bitcoin::sighash::EcdsaSighashType::All
146 /// [`ChannelMonitor`]: crate::chain::channelmonitor::ChannelMonitor
147 /// [`ChannelMonitor::signer_unblocked`]: crate::chain::channelmonitor::ChannelMonitor::signer_unblocked
148 fn sign_holder_htlc_transaction(
149 &self, htlc_tx: &Transaction, input: usize, htlc_descriptor: &HTLCDescriptor,
150 secp_ctx: &Secp256k1<secp256k1::All>,
151 ) -> Result<Signature, ()>;
152 /// Create a signature for a claiming transaction for a HTLC output on a counterparty's commitment
153 /// transaction, either offered or received.
155 /// Such a transaction may claim multiples offered outputs at same time if we know the
156 /// preimage for each when we create it, but only the input at index `input` should be
157 /// signed for here. It may be called multiple times for same output(s) if a fee-bump is
158 /// needed with regards to an upcoming timelock expiration.
160 /// `witness_script` is either an offered or received script as defined in BOLT3 for HTLC
163 /// `amount` is value of the output spent by this input, committed to in the BIP 143 signature.
165 /// `per_commitment_point` is the dynamic point corresponding to the channel state
166 /// detected onchain. It has been generated by our counterparty and is used to derive
167 /// channel state keys, which are then included in the witness script and committed to in the
168 /// BIP 143 signature.
170 /// An `Err` can be returned to signal that the signer is unavailable/cannot produce a valid
171 /// signature and should be retried later. Once the signer is ready to provide a signature after
172 /// previously returning an `Err`, [`ChannelMonitor::signer_unblocked`] must be called on its
175 /// [`ChannelMonitor::signer_unblocked`]: crate::chain::channelmonitor::ChannelMonitor::signer_unblocked
176 fn sign_counterparty_htlc_transaction(
177 &self, htlc_tx: &Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey,
178 htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1<secp256k1::All>,
179 ) -> Result<Signature, ()>;
180 /// Create a signature for a (proposed) closing transaction.
182 /// Note that, due to rounding, there may be one "missing" satoshi, and either party may have
183 /// chosen to forgo their output as dust.
184 fn sign_closing_transaction(
185 &self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1<secp256k1::All>,
186 ) -> Result<Signature, ()>;
187 /// Computes the signature for a commitment transaction's anchor output used as an
188 /// input within `anchor_tx`, which spends the commitment transaction, at index `input`.
190 /// An `Err` can be returned to signal that the signer is unavailable/cannot produce a valid
191 /// signature and should be retried later. Once the signer is ready to provide a signature after
192 /// previously returning an `Err`, [`ChannelMonitor::signer_unblocked`] must be called on its
195 /// [`ChannelMonitor::signer_unblocked`]: crate::chain::channelmonitor::ChannelMonitor::signer_unblocked
196 fn sign_holder_anchor_input(
197 &self, anchor_tx: &Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
198 ) -> Result<Signature, ()>;
199 /// Signs a channel announcement message with our funding key proving it comes from one of the
200 /// channel participants.
202 /// Channel announcements also require a signature from each node's network key. Our node
203 /// signature is computed through [`NodeSigner::sign_gossip_message`].
205 /// Note that if this fails or is rejected, the channel will not be publicly announced and
206 /// our counterparty may (though likely will not) close the channel on us for violating the
209 /// [`NodeSigner::sign_gossip_message`]: crate::sign::NodeSigner::sign_gossip_message
210 fn sign_channel_announcement_with_funding_key(
211 &self, msg: &UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>,
212 ) -> Result<Signature, ()>;
215 /// A writeable signer.
217 /// There will always be two instances of a signer per channel, one occupied by the
218 /// [`ChannelManager`] and another by the channel's [`ChannelMonitor`].
220 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
221 /// [`ChannelMonitor`]: crate::chain::channelmonitor::ChannelMonitor
222 pub trait WriteableEcdsaChannelSigner: EcdsaChannelSigner + Writeable {}