package btcwallet import ( "github.com/btcsuite/btcd/btcec" "github.com/btcsuite/btcd/chaincfg/chainhash" "github.com/btcsuite/btcd/txscript" "github.com/btcsuite/btcd/wire" "github.com/btcsuite/btcutil" "github.com/btcsuite/btcwallet/waddrmgr" base "github.com/btcsuite/btcwallet/wallet" "github.com/btcsuite/btcwallet/walletdb" "github.com/go-errors/errors" "github.com/lightningnetwork/lnd/keychain" "github.com/lightningnetwork/lnd/lnwallet" ) // FetchInputInfo queries for the WalletController's knowledge of the passed // outpoint. If the base wallet determines this output is under its control, // then the original txout should be returned. Otherwise, a non-nil error value // of ErrNotMine should be returned instead. // // This is a part of the WalletController interface. func (b *BtcWallet) FetchInputInfo(prevOut *wire.OutPoint) (*wire.TxOut, error) { var ( err error output *wire.TxOut ) // First check to see if the output is already within the utxo cache. // If so we can return directly saving a disk access. b.cacheMtx.RLock() if output, ok := b.utxoCache[*prevOut]; ok { b.cacheMtx.RUnlock() return output, nil } b.cacheMtx.RUnlock() // Otherwise, we manually look up the output within the tx store. txid := &prevOut.Hash txDetail, err := base.UnstableAPI(b.wallet).TxDetails(txid) if err != nil { return nil, err } else if txDetail == nil { return nil, lnwallet.ErrNotMine } // With the output retrieved, we'll make an additional check to ensure // we actually have control of this output. We do this because the check // above only guarantees that the transaction is somehow relevant to us, // like in the event of us being the sender of the transaction. output = txDetail.TxRecord.MsgTx.TxOut[prevOut.Index] if _, err := b.fetchOutputAddr(output.PkScript); err != nil { return nil, err } b.cacheMtx.Lock() b.utxoCache[*prevOut] = output b.cacheMtx.Unlock() return output, nil } // fetchOutputAddr attempts to fetch the managed address corresponding to the // passed output script. This function is used to look up the proper key which // should be used to sign a specified input. func (b *BtcWallet) fetchOutputAddr(script []byte) (waddrmgr.ManagedAddress, error) { _, addrs, _, err := txscript.ExtractPkScriptAddrs(script, b.netParams) if err != nil { return nil, err } // If the case of a multi-sig output, several address may be extracted. // Therefore, we simply select the key for the first address we know // of. for _, addr := range addrs { addr, err := b.wallet.AddressInfo(addr) if err == nil { return addr, nil } } return nil, lnwallet.ErrNotMine } // fetchPrivKey attempts to retrieve the raw private key corresponding to the // passed public key if populated, or the key descriptor path (if non-empty). func (b *BtcWallet) fetchPrivKey(keyDesc *keychain.KeyDescriptor) (*btcec.PrivateKey, error) { // If the key locator within the descriptor *isn't* empty, then we can // directly derive the keys raw. if !keyDesc.KeyLocator.IsEmpty() { // We'll assume the special lightning key scope in this case. scopedMgr, err := b.wallet.Manager.FetchScopedKeyManager( b.chainKeyScope, ) if err != nil { return nil, err } var key *btcec.PrivateKey err = walletdb.View(b.db, func(tx walletdb.ReadTx) error { addrmgrNs := tx.ReadBucket(waddrmgrNamespaceKey) path := waddrmgr.DerivationPath{ Account: uint32(keyDesc.Family), Branch: 0, Index: uint32(keyDesc.Index), } addr, err := scopedMgr.DeriveFromKeyPath(addrmgrNs, path) if err != nil { return err } key, err = addr.(waddrmgr.ManagedPubKeyAddress).PrivKey() return err }) if err != nil { return nil, err } return key, nil } hash160 := btcutil.Hash160(keyDesc.PubKey.SerializeCompressed()) addr, err := btcutil.NewAddressWitnessPubKeyHash(hash160, b.netParams) if err != nil { return nil, err } return b.wallet.PrivKeyForAddress(addr) } // maybeTweakPrivKey examines the single and double tweak parameters on the // passed sign descriptor and may perform a mapping on the passed private key // in order to utilize the tweaks, if populated. func maybeTweakPrivKey(signDesc *lnwallet.SignDescriptor, privKey *btcec.PrivateKey) (*btcec.PrivateKey, error) { var retPriv *btcec.PrivateKey switch { case signDesc.SingleTweak != nil: retPriv = lnwallet.TweakPrivKey(privKey, signDesc.SingleTweak) case signDesc.DoubleTweak != nil: retPriv = lnwallet.DeriveRevocationPrivKey(privKey, signDesc.DoubleTweak) default: retPriv = privKey } return retPriv, nil } // SignOutputRaw generates a signature for the passed transaction according to // the data within the passed SignDescriptor. // // This is a part of the WalletController interface. func (b *BtcWallet) SignOutputRaw(tx *wire.MsgTx, signDesc *lnwallet.SignDescriptor) ([]byte, error) { witnessScript := signDesc.WitnessScript // First attempt to fetch the private key which corresponds to the // specified public key. privKey, err := b.fetchPrivKey(&signDesc.KeyDesc) if err != nil { return nil, err } // If a tweak (single or double) is specified, then we'll need to use // this tweak to derive the final private key to be used for signing // this output. privKey, err = maybeTweakPrivKey(signDesc, privKey) if err != nil { return nil, err } // TODO(roasbeef): generate sighash midstate if not present? amt := signDesc.Output.Value sig, err := txscript.RawTxInWitnessSignature(tx, signDesc.SigHashes, signDesc.InputIndex, amt, witnessScript, signDesc.HashType, privKey) if err != nil { return nil, err } // Chop off the sighash flag at the end of the signature. return sig[:len(sig)-1], nil } // ComputeInputScript generates a complete InputScript for the passed // transaction with the signature as defined within the passed SignDescriptor. // This method is capable of generating the proper input script for both // regular p2wkh output and p2wkh outputs nested within a regular p2sh output. // // This is a part of the WalletController interface. func (b *BtcWallet) ComputeInputScript(tx *wire.MsgTx, signDesc *lnwallet.SignDescriptor) (*lnwallet.InputScript, error) { outputScript := signDesc.Output.PkScript walletAddr, err := b.fetchOutputAddr(outputScript) if err != nil { return nil, err } pka := walletAddr.(waddrmgr.ManagedPubKeyAddress) privKey, err := pka.PrivKey() if err != nil { return nil, err } var witnessProgram []byte inputScript := &lnwallet.InputScript{} switch { // If we're spending p2wkh output nested within a p2sh output, then // we'll need to attach a sigScript in addition to witness data. case pka.AddrType() == waddrmgr.NestedWitnessPubKey: pubKey := privKey.PubKey() pubKeyHash := btcutil.Hash160(pubKey.SerializeCompressed()) // Next, we'll generate a valid sigScript that will allow us to // spend the p2sh output. The sigScript will contain only a // single push of the p2wkh witness program corresponding to // the matching public key of this address. p2wkhAddr, err := btcutil.NewAddressWitnessPubKeyHash(pubKeyHash, b.netParams) if err != nil { return nil, err } witnessProgram, err = txscript.PayToAddrScript(p2wkhAddr) if err != nil { return nil, err } bldr := txscript.NewScriptBuilder() bldr.AddData(witnessProgram) sigScript, err := bldr.Script() if err != nil { return nil, err } inputScript.ScriptSig = sigScript // Otherwise, this is a regular p2wkh output, so we include the // witness program itself as the subscript to generate the proper // sighash digest. As part of the new sighash digest algorithm, the // p2wkh witness program will be expanded into a regular p2kh // script. default: witnessProgram = outputScript } // If a tweak (single or double) is specified, then we'll need to use // this tweak to derive the final private key to be used for signing // this output. privKey, err = maybeTweakPrivKey(signDesc, privKey) if err != nil { return nil, err } // Generate a valid witness stack for the input. // TODO(roasbeef): adhere to passed HashType witnessScript, err := txscript.WitnessSignature(tx, signDesc.SigHashes, signDesc.InputIndex, signDesc.Output.Value, witnessProgram, signDesc.HashType, privKey, true) if err != nil { return nil, err } inputScript.Witness = witnessScript return inputScript, nil } // A compile time check to ensure that BtcWallet implements the Signer // interface. var _ lnwallet.Signer = (*BtcWallet)(nil) // SignMessage attempts to sign a target message with the private key that // corresponds to the passed public key. If the target private key is unable to // be found, then an error will be returned. The actual digest signed is the // double SHA-256 of the passed message. // // NOTE: This is a part of the MessageSigner interface. func (b *BtcWallet) SignMessage(pubKey *btcec.PublicKey, msg []byte) (*btcec.Signature, error) { // First attempt to fetch the private key which corresponds to the // specified public key. privKey, err := b.fetchPrivKey(&keychain.KeyDescriptor{ PubKey: pubKey, }) if err != nil { return nil, err } // Double hash and sign the data. msgDigest := chainhash.DoubleHashB(msg) sign, err := privKey.Sign(msgDigest) if err != nil { return nil, errors.Errorf("unable sign the message: %v", err) } return sign, nil } // A compile time check to ensure that BtcWallet implements the MessageSigner // interface. var _ lnwallet.MessageSigner = (*BtcWallet)(nil)