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nodesigner.go
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/
nodesigner.go
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package main
import (
"fmt"
"github.com/lightningnetwork/lnd/lnwallet"
"github.com/btcsuite/btcd/btcec"
"github.com/btcsuite/btcd/chaincfg/chainhash"
)
// nodeSigner is an implementation of the MessageSigner interface backed by the
// identity private key of running lnd node.
type nodeSigner struct {
privKey *btcec.PrivateKey
}
// newNodeSigner creates a new instance of the nodeSigner backed by the target
// private key.
func newNodeSigner(key *btcec.PrivateKey) *nodeSigner {
priv := &btcec.PrivateKey{}
priv.Curve = btcec.S256()
priv.PublicKey.X = key.X
priv.PublicKey.Y = key.Y
priv.D = key.D
return &nodeSigner{
privKey: priv,
}
}
// SignMessage signs a double-sha256 digest of the passed msg under the
// resident node's private key. If the target public key is _not_ the node's
// private key, then an error will be returned.
func (n *nodeSigner) SignMessage(pubKey *btcec.PublicKey,
msg []byte) (*btcec.Signature, error) {
// If this isn't our identity public key, then we'll exit early with an
// error as we can't sign with this key.
if !pubKey.IsEqual(n.privKey.PubKey()) {
return nil, fmt.Errorf("unknown public key")
}
// Otherwise, we'll sign the dsha256 of the target message.
digest := chainhash.DoubleHashB(msg)
sign, err := n.privKey.Sign(digest)
if err != nil {
return nil, fmt.Errorf("can't sign the message: %v", err)
}
return sign, nil
}
// SignCompact signs a double-sha256 digest of the msg parameter under the
// resident node's private key. The returned signature is a pubkey-recoverable
// signature.
func (n *nodeSigner) SignCompact(msg []byte) ([]byte, error) {
// We'll sign the dsha256 of the target message.
digest := chainhash.DoubleHashB(msg)
return n.SignDigestCompact(digest)
}
// SignDigestCompact signs the provided message digest under the resident
// node's private key. The returned signature is a pubkey-recoverable signature.
func (n *nodeSigner) SignDigestCompact(hash []byte) ([]byte, error) {
// Should the signature reference a compressed public key or not.
isCompressedKey := true
// btcec.SignCompact returns a pubkey-recoverable signature
sig, err := btcec.SignCompact(
btcec.S256(), n.privKey, hash, isCompressedKey,
)
if err != nil {
return nil, fmt.Errorf("can't sign the hash: %v", err)
}
return sig, nil
}
// A compile time check to ensure that nodeSigner implements the MessageSigner
// interface.
var _ lnwallet.MessageSigner = (*nodeSigner)(nil)