package btcwallet import ( "fmt" "github.com/lightningnetwork/lnd/lnwallet" "github.com/roasbeef/btcd/btcec" "github.com/roasbeef/btcd/txscript" "github.com/roasbeef/btcd/wire" "github.com/roasbeef/btcutil" "github.com/roasbeef/btcwallet/waddrmgr" ) // 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() // Otherwse, we manually look up the output within the tx store. txDetail, err := b.wallet.TxStore.TxDetails(&prevOut.Hash) if err != nil { return nil, err } else if txDetail == nil { return nil, lnwallet.ErrNotMine } output = txDetail.TxRecord.MsgTx.TxOut[prevOut.Index] b.cacheMtx.Lock() b.utxoCache[*prevOut] = output b.cacheMtx.Unlock() return output, nil } // fetchOutputKey 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 { wAddr, err := b.wallet.Manager.Address(addr) if err == nil { return wAddr, nil } } // TODO(roasbeef): use the errors.wrap package return nil, fmt.Errorf("address not found") } // fetchPrivKey attempts to retrieve the raw private key corresponding to the // passed public key. // TODO(roasbeef): alternatively can extract all the data pushes within the // script, then attempt to match keys one by one func (b *BtcWallet) fetchPrivKey(pub *btcec.PublicKey) (*btcec.PrivateKey, error) { hash160 := btcutil.Hash160(pub.SerializeCompressed()) addr, err := btcutil.NewAddressWitnessPubKeyHash(hash160, b.netParams) if err != nil { return nil, err } walletddr, err := b.wallet.Manager.Address(addr) if err != nil { return nil, err } return walletddr.(waddrmgr.ManagedPubKeyAddress).PrivKey() } // 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.PubKey) if err != nil { return nil, err } // If a tweak is specified, then we'll need to use this tweak to derive // the final private key to be used for signing this output. if signDesc.PrivateTweak != nil { privKey = lnwallet.DeriveRevocationPrivKey(privKey, signDesc.PrivateTweak) } amt := signDesc.Output.Value sig, err := txscript.RawTxInWitnessSignature(tx, signDesc.SigHashes, signDesc.InputIndex, amt, witnessScript, txscript.SigHashAll, 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 InputIndex 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, nil } pka := walletAddr.(waddrmgr.ManagedPubKeyAddress) privKey, err := pka.PrivKey() if err != nil { return nil, err } var witnessProgram []byte inputScript := &lnwallet.InputScript{} // If we're spending p2wkh output nested within a p2sh output, then // we'll need to attach a sigScript in addition to witness data. switch { case pka.IsNestedWitness(): pubKey := privKey.PubKey() pubKeyHash := btcutil.Hash160(pubKey.SerializeCompressed()) // Next, we'll generate a valid sigScript that'll 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 } // Generate a valid witness stack for the input. // TODO(roasbeef): adhere to passed HashType witnessScript, err := txscript.WitnessScript(tx, signDesc.SigHashes, signDesc.InputIndex, signDesc.Output.Value, witnessProgram, txscript.SigHashAll, 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)