1 //! Defines ECDSA-specific signer types.
3 use bitcoin::blockdata::transaction::Transaction;
5 use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
6 use bitcoin::secp256k1::ecdsa::Signature;
7 use bitcoin::secp256k1;
9 use crate::util::ser::Writeable;
10 use crate::ln::PaymentPreimage;
11 use crate::ln::chan_utils::{HTLCOutputInCommitment, HolderCommitmentTransaction, CommitmentTransaction, ClosingTransaction};
12 use crate::ln::msgs::UnsignedChannelAnnouncement;
14 use crate::prelude::*;
15 use crate::sign::{ChannelSigner, HTLCDescriptor};
17 /// A trait to sign Lightning channel transactions as described in
18 /// [BOLT 3](https://github.com/lightning/bolts/blob/master/03-transactions.md).
20 /// Signing services could be implemented on a hardware wallet and should implement signing
21 /// policies in order to be secure. Please refer to the [VLS Policy
22 /// Controls](https://gitlab.com/lightning-signer/validating-lightning-signer/-/blob/main/docs/policy-controls.md)
23 /// for an example of such policies.
24 pub trait EcdsaChannelSigner: ChannelSigner {
25 /// Create a signature for a counterparty's commitment transaction and associated HTLC transactions.
27 /// Note that if signing fails or is rejected, the channel will be force-closed.
29 /// Policy checks should be implemented in this function, including checking the amount
30 /// sent to us and checking the HTLCs.
32 /// The preimages of outbound and inbound HTLCs that were fulfilled since the last commitment
33 /// are provided. A validating signer should ensure that an outbound HTLC output is removed
34 /// only when the matching preimage is provided and after the corresponding inbound HTLC has
35 /// been removed for forwarded payments.
37 /// Note that all the relevant preimages will be provided, but there may also be additional
38 /// irrelevant or duplicate preimages.
40 // TODO: Document the things someone using this interface should enforce before signing.
41 fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction,
42 inbound_htlc_preimages: Vec<PaymentPreimage>,
43 outbound_htlc_preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<secp256k1::All>,
44 ) -> Result<(Signature, Vec<Signature>), ()>;
45 /// Validate the counterparty's revocation.
47 /// This is required in order for the signer to make sure that the state has moved
48 /// forward and it is safe to sign the next counterparty commitment.
49 fn validate_counterparty_revocation(&self, idx: u64, secret: &SecretKey) -> Result<(), ()>;
50 /// Creates a signature for a holder's commitment transaction.
52 /// This will be called
53 /// - with a non-revoked `commitment_tx`.
54 /// - with the latest `commitment_tx` when we initiate a force-close.
56 /// This may be called multiple times for the same transaction.
58 /// An external signer implementation should check that the commitment has not been revoked.
60 // TODO: Document the things someone using this interface should enforce before signing.
61 fn sign_holder_commitment(&self, commitment_tx: &HolderCommitmentTransaction,
62 secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()>;
63 /// Same as [`sign_holder_commitment`], but exists only for tests to get access to holder
64 /// commitment transactions which will be broadcasted later, after the channel has moved on to a
65 /// newer state. Thus, needs its own method as [`sign_holder_commitment`] may enforce that we
66 /// only ever get called once.
67 #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
68 fn unsafe_sign_holder_commitment(&self, commitment_tx: &HolderCommitmentTransaction,
69 secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()>;
70 /// Create a signature for the given input in a transaction spending an HTLC transaction output
71 /// or a commitment transaction `to_local` output when our counterparty broadcasts an old state.
73 /// A justice transaction may claim multiple outputs at the same time if timelocks are
74 /// similar, but only a signature for the input at index `input` should be signed for here.
75 /// It may be called multiple times for same output(s) if a fee-bump is needed with regards
76 /// to an upcoming timelock expiration.
78 /// Amount is value of the output spent by this input, committed to in the BIP 143 signature.
80 /// `per_commitment_key` is revocation secret which was provided by our counterparty when they
81 /// revoked the state which they eventually broadcast. It's not a _holder_ secret key and does
82 /// not allow the spending of any funds by itself (you need our holder `revocation_secret` to do
84 fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64,
85 per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>
86 ) -> Result<Signature, ()>;
87 /// Create a signature for the given input in a transaction spending a commitment transaction
88 /// HTLC output when our counterparty broadcasts an old state.
90 /// A justice transaction may claim multiple outputs at the same time if timelocks are
91 /// similar, but only a signature for the input at index `input` should be signed for here.
92 /// It may be called multiple times for same output(s) if a fee-bump is needed with regards
93 /// to an upcoming timelock expiration.
95 /// `amount` is the value of the output spent by this input, committed to in the BIP 143
98 /// `per_commitment_key` is revocation secret which was provided by our counterparty when they
99 /// revoked the state which they eventually broadcast. It's not a _holder_ secret key and does
100 /// not allow the spending of any funds by itself (you need our holder revocation_secret to do
103 /// `htlc` holds HTLC elements (hash, timelock), thus changing the format of the witness script
104 /// (which is committed to in the BIP 143 signatures).
105 fn sign_justice_revoked_htlc(&self, justice_tx: &Transaction, input: usize, amount: u64,
106 per_commitment_key: &SecretKey, htlc: &HTLCOutputInCommitment,
107 secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()>;
108 /// Computes the signature for a commitment transaction's HTLC output used as an input within
109 /// `htlc_tx`, which spends the commitment transaction at index `input`. The signature returned
110 /// must be be computed using [`EcdsaSighashType::All`].
112 /// Note that this may be called for HTLCs in the penultimate commitment transaction if a
113 /// [`ChannelMonitor`] [replica](https://github.com/lightningdevkit/rust-lightning/blob/main/GLOSSARY.md#monitor-replicas)
114 /// broadcasts it before receiving the update for the latest commitment transaction.
116 /// [`EcdsaSighashType::All`]: bitcoin::sighash::EcdsaSighashType::All
117 /// [`ChannelMonitor`]: crate::chain::channelmonitor::ChannelMonitor
118 fn sign_holder_htlc_transaction(&self, htlc_tx: &Transaction, input: usize,
119 htlc_descriptor: &HTLCDescriptor, secp_ctx: &Secp256k1<secp256k1::All>
120 ) -> Result<Signature, ()>;
121 /// Create a signature for a claiming transaction for a HTLC output on a counterparty's commitment
122 /// transaction, either offered or received.
124 /// Such a transaction may claim multiples offered outputs at same time if we know the
125 /// preimage for each when we create it, but only the input at index `input` should be
126 /// signed for here. It may be called multiple times for same output(s) if a fee-bump is
127 /// needed with regards to an upcoming timelock expiration.
129 /// `witness_script` is either an offered or received script as defined in BOLT3 for HTLC
132 /// `amount` is value of the output spent by this input, committed to in the BIP 143 signature.
134 /// `per_commitment_point` is the dynamic point corresponding to the channel state
135 /// detected onchain. It has been generated by our counterparty and is used to derive
136 /// channel state keys, which are then included in the witness script and committed to in the
137 /// BIP 143 signature.
138 fn sign_counterparty_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, amount: u64,
139 per_commitment_point: &PublicKey, htlc: &HTLCOutputInCommitment,
140 secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()>;
141 /// Create a signature for a (proposed) closing transaction.
143 /// Note that, due to rounding, there may be one "missing" satoshi, and either party may have
144 /// chosen to forgo their output as dust.
145 fn sign_closing_transaction(&self, closing_tx: &ClosingTransaction,
146 secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()>;
147 /// Computes the signature for a commitment transaction's anchor output used as an
148 /// input within `anchor_tx`, which spends the commitment transaction, at index `input`.
149 fn sign_holder_anchor_input(
150 &self, anchor_tx: &Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
151 ) -> Result<Signature, ()>;
152 /// Signs a channel announcement message with our funding key proving it comes from one of the
153 /// channel participants.
155 /// Channel announcements also require a signature from each node's network key. Our node
156 /// signature is computed through [`NodeSigner::sign_gossip_message`].
158 /// Note that if this fails or is rejected, the channel will not be publicly announced and
159 /// our counterparty may (though likely will not) close the channel on us for violating the
162 /// [`NodeSigner::sign_gossip_message`]: crate::sign::NodeSigner::sign_gossip_message
163 fn sign_channel_announcement_with_funding_key(
164 &self, msg: &UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>
165 ) -> Result<Signature, ()>;
168 /// A writeable signer.
170 /// There will always be two instances of a signer per channel, one occupied by the
171 /// [`ChannelManager`] and another by the channel's [`ChannelMonitor`].
173 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
174 /// [`ChannelMonitor`]: crate::chain::channelmonitor::ChannelMonitor
175 pub trait WriteableEcdsaChannelSigner: EcdsaChannelSigner + Writeable {}