mirror of https://github.com/guggero/chantools
Oliver Gugger
4 years ago
parent
a95f475c6a
commit
4a633da99e
@ -0,0 +1,168 @@
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package main
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import (
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"bytes"
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"fmt"
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"github.com/btcsuite/btcd/btcec"
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"github.com/btcsuite/btcutil/psbt"
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"github.com/lightningnetwork/lnd/keychain"
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"github.com/btcsuite/btcutil/hdkeychain"
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"github.com/guggero/chantools/lnd"
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)
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type signRescueFundingCommand struct {
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RootKey string `long:"rootkey" description:"BIP32 HD root (m/) key to derive the key for our part of the signature from."`
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Psbt string `long:"psbt" description:"The Partially Signed Bitcoin Transaction that was provided by the initiator of the channel to rescue."`
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}
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func (c *signRescueFundingCommand) Execute(_ []string) error {
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setupChainParams(cfg)
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var (
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extendedKey *hdkeychain.ExtendedKey
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err error
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)
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// Check that root key is valid or fall back to console input.
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switch {
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case c.RootKey != "":
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extendedKey, err = hdkeychain.NewKeyFromString(c.RootKey)
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default:
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extendedKey, _, err = lnd.ReadAezeedFromTerminal(chainParams)
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}
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if err != nil {
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return fmt.Errorf("error reading root key: %v", err)
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}
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signer := &lnd.Signer{
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ExtendedKey: extendedKey,
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ChainParams: chainParams,
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}
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// Decode the PSBT.
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packet, err := psbt.NewFromRawBytes(
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bytes.NewReader([]byte(c.Psbt)), true,
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)
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if err != nil {
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return fmt.Errorf("error decoding PSBT: %v", err)
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}
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return signRescueFunding(extendedKey, packet, signer)
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}
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func signRescueFunding(rootKey *hdkeychain.ExtendedKey,
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packet *psbt.Packet, signer *lnd.Signer) error {
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// First, we need to derive the correct branch from the local root key.
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localMultisig, err := lnd.DeriveChildren(rootKey, []uint32{
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lnd.HardenedKeyStart + uint32(keychain.BIP0043Purpose),
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lnd.HardenedKeyStart + chainParams.HDCoinType,
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lnd.HardenedKeyStart + uint32(keychain.KeyFamilyMultiSig),
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0,
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})
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if err != nil {
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return fmt.Errorf("could not derive local multisig key: %v",
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err)
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}
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// Now let's check that the packet has the expected proprietary key with
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// our pubkey that we need to sign with.
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if len(packet.Inputs) != 1 {
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return fmt.Errorf("invalid PSBT, expected 1 input, got %d",
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len(packet.Inputs))
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}
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if len(packet.Inputs[0].Unknowns) != 1 {
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return fmt.Errorf("invalid PSBT, expected 1 unknown in input, "+
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"got %d", len(packet.Inputs[0].Unknowns))
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}
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unknown := packet.Inputs[0].Unknowns[0]
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if !bytes.Equal(unknown.Key, PsbtKeyTypeOutputMissingSigPubkey) {
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return fmt.Errorf("invalid PSBT, unknown has invalid key %x, "+
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"expected %x", unknown.Key,
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PsbtKeyTypeOutputMissingSigPubkey)
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}
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targetKey, err := btcec.ParsePubKey(unknown.Value, btcec.S256())
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if err != nil {
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return fmt.Errorf("invalid PSBT, proprietary key has invalid "+
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"pubkey: %v", err)
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}
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// Now we can look up the local key and check the PSBT further, then
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// add our signature.
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localKeyDesc, err := findLocalMultisigKey(localMultisig, targetKey)
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if err != nil {
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return fmt.Errorf("could not find local multisig key: %v", err)
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}
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if len(packet.Inputs[0].WitnessScript) == 0 {
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return fmt.Errorf("invalid PSBT, missing witness script")
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}
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witnessScript := packet.Inputs[0].WitnessScript
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if packet.Inputs[0].WitnessUtxo == nil {
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return fmt.Errorf("invalid PSBT, witness UTXO missing")
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}
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utxo := packet.Inputs[0].WitnessUtxo
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err = signer.AddPartialSignature(
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packet, *localKeyDesc, utxo, witnessScript, 0,
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)
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if err != nil {
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return fmt.Errorf("error adding partial signature: %v", err)
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}
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// We're almost done. Now we just need to make sure we can finalize and
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// extract the final TX.
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err = psbt.MaybeFinalizeAll(packet)
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if err != nil {
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return fmt.Errorf("error finalizing PSBT: %v", err)
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}
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finalTx, err := psbt.Extract(packet)
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if err != nil {
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return fmt.Errorf("unable to extract final TX: %v", err)
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}
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var buf bytes.Buffer
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err = finalTx.Serialize(&buf)
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if err != nil {
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return fmt.Errorf("unable to serialize final TX: %v", err)
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}
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fmt.Printf("Success, we counter signed the PSBT and extracted the "+
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"final\ntransaction. Please publish this using any bitcoin "+
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"node:\n\n%x\n\n", buf.Bytes())
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return nil
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}
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func findLocalMultisigKey(multisigBranch *hdkeychain.ExtendedKey,
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targetPubkey *btcec.PublicKey) (*keychain.KeyDescriptor, error) {
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// Loop through the local multisig keys to find the target key.
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for index := uint32(0); index < MaxChannelLookup; index++ {
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currentKey, err := multisigBranch.Child(index)
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if err != nil {
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return nil, fmt.Errorf("error deriving child key: %v",
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err)
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}
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currentPubkey, err := currentKey.ECPubKey()
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if err != nil {
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return nil, fmt.Errorf("error deriving public key: %v",
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err)
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}
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if !targetPubkey.IsEqual(currentPubkey) {
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continue
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}
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return &keychain.KeyDescriptor{
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PubKey: currentPubkey,
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KeyLocator: keychain.KeyLocator{
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Family: keychain.KeyFamilyMultiSig,
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Index: index,
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},
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}, nil
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}
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return nil, fmt.Errorf("no matching pubkeys found")
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}
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