lnd.xprv/lnrpc/walletrpc/walletkit_server.go

// +build walletrpc

package walletrpc

import (
	"bytes"
	fmt "fmt"
	"io/ioutil"
	"os"
	"path/filepath"

	"github.com/btcsuite/btcd/wire"
	"github.com/lightningnetwork/lnd/keychain"
	"github.com/lightningnetwork/lnd/lnrpc"
	signrpc "github.com/lightningnetwork/lnd/lnrpc/signrpc"
	"github.com/lightningnetwork/lnd/lnwallet"
	context "golang.org/x/net/context"
	grpc "google.golang.org/grpc"
	"gopkg.in/macaroon-bakery.v2/bakery"
)

const (
	// subServerName is the name of the sub rpc server. We'll use this name
	// to register ourselves, and we also require that the main
	// SubServerConfigDispatcher instance recognize as the name of our
	subServerName = "WalletKitRPC"
)

var (
	// macaroonOps are the set of capabilities that our minted macaroon (if
	// it doesn't already exist) will have.
	macaroonOps = []bakery.Op{
		{
			Entity: "address",
			Action: "write",
		},
		{
			Entity: "address",
			Action: "read",
		},
		{
			Entity: "onchain",
			Action: "write",
		},
		{
			Entity: "onchain",
			Action: "read",
		},
	}

	// macPermissions maps RPC calls to the permissions they require.
	macPermissions = map[string][]bakery.Op{
		"/walletrpc.WalletKit/DeriveNextKey": {{
			Entity: "address",
			Action: "read",
		}},
		"/walletrpc.WalletKit/DeriveKey": {{
			Entity: "address",
			Action: "read",
		}},
		"/walletrpc.WalletKit/NextAddr": {{
			Entity: "address",
			Action: "read",
		}},
		"/walletrpc.WalletKit/PublishTransaction": {{
			Entity: "onchain",
			Action: "write",
		}},
		"/walletrpc.WalletKit/SendOutputs": {{
			Entity: "onchain",
			Action: "write",
		}},
		"/walletrpc.WalletKit/EstimateFee": {{
			Entity: "onchain",
			Action: "read",
		}},
	}

	// DefaultWalletKitMacFilename is the default name of the wallet kit
	// macaroon that we expect to find via a file handle within the main
	// configuration file in this package.
	DefaultWalletKitMacFilename = "walletkit.macaroon"
)

// WalletKit is a sub-RPC server that exposes a tool kit which allows clients
// to execute common wallet operations. This includes requesting new addresses,
// keys (for contracts!), and publishing transactions.
type WalletKit struct {
	cfg *Config
}

// A compile time check to ensure that WalletKit fully implements the
// WalletKitServer gRPC service.
var _ WalletKitServer = (*WalletKit)(nil)

// fileExists reports whether the named file or directory exists.
func fileExists(name string) bool {
	if _, err := os.Stat(name); err != nil {
		if os.IsNotExist(err) {
			return false
		}
	}
	return true
}

// New creates a new instance of the WalletKit sub-RPC server.
func New(cfg *Config) (*WalletKit, lnrpc.MacaroonPerms, error) {
	// If the path of the wallet kit macaroon wasn't specified, then we'll
	// assume that it's found at the default network directory.
	if cfg.WalletKitMacPath == "" {
		cfg.WalletKitMacPath = filepath.Join(
			cfg.NetworkDir, DefaultWalletKitMacFilename,
		)
	}

	// Now that we know the full path of the wallet kit macaroon, we can
	// check to see if we need to create it or not.
	macFilePath := cfg.WalletKitMacPath
	if !fileExists(macFilePath) && cfg.MacService != nil {
		log.Infof("Baking macaroons for WaleltKit RPC Server at: %v",
			macFilePath)

		// At this point, we know that the wallet kit macaroon doesn't
		// yet, exist, so we need to create it with the help of the
		// main macaroon service.
		walletKitMac, err := cfg.MacService.Oven.NewMacaroon(
			context.Background(), bakery.LatestVersion, nil,
			macaroonOps...,
		)
		if err != nil {
			return nil, nil, err
		}
		walletKitMacBytes, err := walletKitMac.M().MarshalBinary()
		if err != nil {
			return nil, nil, err
		}
		err = ioutil.WriteFile(macFilePath, walletKitMacBytes, 0644)
		if err != nil {
			os.Remove(macFilePath)
			return nil, nil, err
		}
	}

	walletKit := &WalletKit{
		cfg: cfg,
	}

	return walletKit, macPermissions, nil
}

// Start launches any helper goroutines required for the sub-server to function.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (w *WalletKit) Start() error {
	return nil
}

// Stop signals any active goroutines for a graceful closure.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (w *WalletKit) Stop() error {
	return nil
}

// Name returns a unique string representation of the sub-server. This can be
// used to identify the sub-server and also de-duplicate them.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (w *WalletKit) Name() string {
	return subServerName
}

// RegisterWithRootServer will be called by the root gRPC server to direct a
// sub RPC server to register itself with the main gRPC root server. Until this
// is called, each sub-server won't be able to have requests routed towards it.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (w *WalletKit) RegisterWithRootServer(grpcServer *grpc.Server) error {
	// We make sure that we register it with the main gRPC server to ensure
	// all our methods are routed properly.
	RegisterWalletKitServer(grpcServer, w)

	log.Debugf("WalletKit RPC server successfully registered with " +
		"root gRPC server")

	return nil
}

// DeriveNextKey attempts to derive the *next* key within the key family
// (account in BIP43) specified. This method should return the next external
// child within this branch.
func (w *WalletKit) DeriveNextKey(ctx context.Context,
	req *KeyReq) (*signrpc.KeyDescriptor, error) {

	nextKeyDesc, err := w.cfg.KeyRing.DeriveNextKey(
		keychain.KeyFamily(req.KeyFamily),
	)
	if err != nil {
		return nil, err
	}

	return &signrpc.KeyDescriptor{
		KeyLoc: &signrpc.KeyLocator{
			KeyFamily: int32(nextKeyDesc.Family),
			KeyIndex:  int32(nextKeyDesc.Index),
		},
		RawKeyBytes: nextKeyDesc.PubKey.SerializeCompressed(),
	}, nil
}

// DeriveKey attempts to derive an arbitrary key specified by the passed
// KeyLocator.
func (w *WalletKit) DeriveKey(ctx context.Context,
	req *signrpc.KeyLocator) (*signrpc.KeyDescriptor, error) {

	keyDesc, err := w.cfg.KeyRing.DeriveKey(keychain.KeyLocator{
		Family: keychain.KeyFamily(req.KeyFamily),
		Index:  uint32(req.KeyIndex),
	})
	if err != nil {
		return nil, err
	}

	return &signrpc.KeyDescriptor{
		KeyLoc: &signrpc.KeyLocator{
			KeyFamily: int32(keyDesc.Family),
			KeyIndex:  int32(keyDesc.Index),
		},
		RawKeyBytes: keyDesc.PubKey.SerializeCompressed(),
	}, nil
}

// NextAddr returns the next unused address within the wallet.
func (w *WalletKit) NextAddr(ctx context.Context,
	req *AddrRequest) (*AddrResponse, error) {

	addr, err := w.cfg.Wallet.NewAddress(lnwallet.WitnessPubKey, false)
	if err != nil {
		return nil, err
	}

	return &AddrResponse{
		Addr: addr.String(),
	}, nil
}

// Attempts to publish the passed transaction to the network. Once this returns
// without an error, the wallet will continually attempt to re-broadcast the
// transaction on start up, until it enters the chain.
func (w *WalletKit) PublishTransaction(ctx context.Context,
	req *Transaction) (*PublishResponse, error) {

	switch {
	// If the client doesn't specify a transaction, then there's nothing to
	// publish.
	case len(req.TxHex) == 0:
		return nil, fmt.Errorf("must provide a transaction to " +
			"publish")
	}

	tx := &wire.MsgTx{}
	txReader := bytes.NewReader(req.TxHex)
	if err := tx.Deserialize(txReader); err != nil {
		return nil, err
	}

	err := w.cfg.Wallet.PublishTransaction(tx)
	if err != nil {
		return nil, err
	}

	return &PublishResponse{}, nil
}

// SendOutputs is similar to the existing sendmany call in Bitcoind, and allows
// the caller to create a transaction that sends to several outputs at once.
// This is ideal when wanting to batch create a set of transactions.
func (w *WalletKit) SendOutputs(ctx context.Context,
	req *SendOutputsRequest) (*SendOutputsResponse, error) {

	switch {
	// If the client didn't specify any outputs to create, then  we can't
	// proceed .
	case len(req.Outputs) == 0:
		return nil, fmt.Errorf("must specify at least one output " +
			"to create")
	}

	// Before we can request this transaction to be created, we'll need to
	// amp the protos back into the format that the internal wallet will
	// recognize.
	outputsToCreate := make([]*wire.TxOut, 0, len(req.Outputs))
	for _, output := range req.Outputs {
		outputsToCreate = append(outputsToCreate, &wire.TxOut{
			Value:    output.Value,
			PkScript: output.PkScript,
		})
	}

	// Now that we have the outputs mapped, we can request that the wallet
	// attempt to create this transaction.
	tx, err := w.cfg.Wallet.SendOutputs(
		outputsToCreate, lnwallet.SatPerKWeight(req.SatPerKw),
	)
	if err != nil {
		return nil, err
	}

	var b bytes.Buffer
	if err := tx.Serialize(&b); err != nil {
		return nil, err
	}

	return &SendOutputsResponse{
		RawTx: b.Bytes(),
	}, nil
}

// EstimateFee attempts to query the internal fee estimator of the wallet to
// determine the fee (in sat/kw) to attach to a transaction in order to achieve
// the confirmation target.
func (w *WalletKit) EstimateFee(ctx context.Context,
	req *EstimateFeeRequest) (*EstimateFeeResponse, error) {

	switch {
	// A confirmation target of zero doesn't make any sense. Similarly, we
	// reject confirmation targets of 1 as they're unreasonable.
	case req.ConfTarget == 0 || req.ConfTarget == 1:
		return nil, fmt.Errorf("confirmation target must be greater " +
			"than 1")
	}

	satPerKw, err := w.cfg.FeeEstimator.EstimateFeePerKW(
		uint32(req.ConfTarget),
	)
	if err != nil {
		return nil, err
	}

	return &EstimateFeeResponse{
		SatPerKw: int64(satPerKw),
	}, nil
}