lnd/cmd/lncli/cmd_walletunlocker.go

package main

import (
	"bufio"
	"bytes"
	"encoding/hex"
	"fmt"
	"io/ioutil"
	"os"
	"strconv"
	"strings"

	"github.com/lightningnetwork/lnd/lncfg"
	"github.com/lightningnetwork/lnd/lnrpc"
	"github.com/lightningnetwork/lnd/lnrpc/walletrpc"
	"github.com/lightningnetwork/lnd/walletunlocker"
	"github.com/urfave/cli"
)

var (
	statelessInitFlag = cli.BoolFlag{
		Name: "stateless_init",
		Usage: "do not create any macaroon files in the file " +
			"system of the daemon",
	}
	saveToFlag = cli.StringFlag{
		Name:  "save_to",
		Usage: "save returned admin macaroon to this file",
	}
)

var createCommand = cli.Command{
	Name:     "create",
	Category: "Startup",
	Usage:    "Initialize a wallet when starting lnd for the first time.",
	Description: `
	The create command is used to initialize an lnd wallet from scratch for
	the very first time. This is interactive command with one required
	argument (the password), and one optional argument (the mnemonic
	passphrase).

	The first argument (the password) is required and MUST be greater than
	8 characters. This will be used to encrypt the wallet within lnd. This
	MUST be remembered as it will be required to fully start up the daemon.

	The second argument is an optional 24-word mnemonic derived from BIP
	39. If provided, then the internal wallet will use the seed derived
	from this mnemonic to generate all keys.

	This command returns a 24-word seed in the scenario that NO mnemonic
	was provided by the user. This should be written down as it can be used
	to potentially recover all on-chain funds, and most off-chain funds as
	well.

	If the --stateless_init flag is set, no macaroon files are created by
	the daemon. Instead, the binary serialized admin macaroon is returned
	in the answer. This answer MUST be stored somewhere, otherwise all
	access to the RPC server will be lost and the wallet must be recreated
	to re-gain access.
	If the --save_to parameter is set, the macaroon is saved to this file,
	otherwise it is printed to standard out.

	Finally, it's also possible to use this command and a set of static
	channel backups to trigger a recover attempt for the provided Static
	Channel Backups. Only one of the three parameters will be accepted. See
	the restorechanbackup command for further details w.r.t the format
	accepted.
	`,
	Flags: []cli.Flag{
		cli.StringFlag{
			Name: "single_backup",
			Usage: "a hex encoded single channel backup obtained " +
				"from exportchanbackup",
		},
		cli.StringFlag{
			Name: "multi_backup",
			Usage: "a hex encoded multi-channel backup obtained " +
				"from exportchanbackup",
		},
		cli.StringFlag{
			Name:  "multi_file",
			Usage: "the path to a multi-channel back up file",
		},
		statelessInitFlag,
		saveToFlag,
	},
	Action: actionDecorator(create),
}

// monowidthColumns takes a set of words, and the number of desired columns,
// and returns a new set of words that have had white space appended to the
// word in order to create a mono-width column.
func monowidthColumns(words []string, ncols int) []string {
	// Determine max size of words in each column.
	colWidths := make([]int, ncols)
	for i, word := range words {
		col := i % ncols
		curWidth := colWidths[col]
		if len(word) > curWidth {
			colWidths[col] = len(word)
		}
	}

	// Append whitespace to each word to make columns mono-width.
	finalWords := make([]string, len(words))
	for i, word := range words {
		col := i % ncols
		width := colWidths[col]

		diff := width - len(word)
		finalWords[i] = word + strings.Repeat(" ", diff)
	}

	return finalWords
}

func create(ctx *cli.Context) error {
	ctxc := getContext()
	client, cleanUp := getWalletUnlockerClient(ctx)
	defer cleanUp()

	var (
		chanBackups *lnrpc.ChanBackupSnapshot

		// We use var restoreSCB to track if we will be including an SCB
		// recovery in the init wallet request.
		restoreSCB = false
	)

	backups, err := parseChanBackups(ctx)

	// We'll check to see if the user provided any static channel backups (SCB),
	// if so, we will warn the user that SCB recovery closes all open channels
	// and ask them to confirm their intention.
	// If the user agrees, we'll add the SCB recovery onto the final init wallet
	// request.
	switch {
	// parseChanBackups returns an errMissingBackup error (which we ignore) if
	// the user did not request a SCB recovery.
	case err == errMissingChanBackup:

	// Passed an invalid channel backup file.
	case err != nil:
		return fmt.Errorf("unable to parse chan backups: %v", err)

	// We have an SCB recovery option with a valid backup file.
	default:

	warningLoop:
		for {
			fmt.Println()
			fmt.Printf("WARNING: You are attempting to restore from a " +
				"static channel backup (SCB) file.\nThis action will CLOSE " +
				"all currently open channels, and you will pay on-chain fees." +
				"\n\nAre you sure you want to recover funds from a" +
				" static channel backup? (Enter y/n): ")

			reader := bufio.NewReader(os.Stdin)
			answer, err := reader.ReadString('\n')
			if err != nil {
				return err
			}

			answer = strings.TrimSpace(answer)
			answer = strings.ToLower(answer)

			switch answer {
			case "y":
				restoreSCB = true
				break warningLoop
			case "n":
				fmt.Println("Aborting SCB recovery")
				return nil
			}
		}
	}

	// Proceed with SCB recovery.
	if restoreSCB {
		fmt.Println("Static Channel Backup (SCB) recovery selected!")
		if backups != nil {
			switch {
			case backups.GetChanBackups() != nil:
				singleBackup := backups.GetChanBackups()
				chanBackups = &lnrpc.ChanBackupSnapshot{
					SingleChanBackups: singleBackup,
				}

			case backups.GetMultiChanBackup() != nil:
				multiBackup := backups.GetMultiChanBackup()
				chanBackups = &lnrpc.ChanBackupSnapshot{
					MultiChanBackup: &lnrpc.MultiChanBackup{
						MultiChanBackup: multiBackup,
					},
				}
			}
		}
	}

	// Should the daemon be initialized stateless? Then we expect an answer
	// with the admin macaroon later. Because the --save_to is related to
	// stateless init, it doesn't make sense to be set on its own.
	statelessInit := ctx.Bool(statelessInitFlag.Name)
	if !statelessInit && ctx.IsSet(saveToFlag.Name) {
		return fmt.Errorf("cannot set save_to parameter without " +
			"stateless_init")
	}

	walletPassword, err := capturePassword(
		"Input wallet password: ", false, walletunlocker.ValidatePassword,
	)
	if err != nil {
		return err
	}

	// Next, we'll see if the user has 24-word mnemonic they want to use to
	// derive a seed within the wallet or if they want to specify an
	// extended master root key (xprv) directly.
	var (
		hasMnemonic bool
		hasXprv     bool
	)

mnemonicCheck:
	for {
		fmt.Println()
		fmt.Printf("Do you have an existing cipher seed " +
			"mnemonic or extended master root key you want to " +
			"use?\nEnter 'y' to use an existing cipher seed " +
			"mnemonic, 'x' to use an extended master root key " +
			"\nor 'n' to create a new seed (Enter y/x/n): ")

		reader := bufio.NewReader(os.Stdin)
		answer, err := reader.ReadString('\n')
		if err != nil {
			return err
		}

		fmt.Println()

		answer = strings.TrimSpace(answer)
		answer = strings.ToLower(answer)

		switch answer {
		case "y":
			hasMnemonic = true
			break mnemonicCheck

		case "x":
			hasXprv = true
			break mnemonicCheck

		case "n":
			break mnemonicCheck
		}
	}

	// If the user *does* have an existing seed or root key they want to
	// use, then we'll read that in directly from the terminal.
	var (
		cipherSeedMnemonic      []string
		aezeedPass              []byte
		extendedRootKey         string
		extendedRootKeyBirthday uint64
		recoveryWindow          int32
	)
	switch {
	// Use an existing cipher seed mnemonic in the aezeed format.
	case hasMnemonic:
		// We'll now prompt the user to enter in their 24-word
		// mnemonic.
		fmt.Printf("Input your 24-word mnemonic separated by spaces: ")
		reader := bufio.NewReader(os.Stdin)
		mnemonic, err := reader.ReadString('\n')
		if err != nil {
			return err
		}

		// We'll trim off extra spaces, and ensure the mnemonic is all
		// lower case, then populate our request.
		mnemonic = strings.TrimSpace(mnemonic)
		mnemonic = strings.ToLower(mnemonic)

		cipherSeedMnemonic = strings.Split(mnemonic, " ")

		fmt.Println()

		if len(cipherSeedMnemonic) != 24 {
			return fmt.Errorf("wrong cipher seed mnemonic "+
				"length: got %v words, expecting %v words",
				len(cipherSeedMnemonic), 24)
		}

		// Additionally, the user may have a passphrase, that will also
		// need to be provided so the daemon can properly decipher the
		// cipher seed.
		aezeedPass, err = readPassword("Input your cipher seed " +
			"passphrase (press enter if your seed doesn't have a " +
			"passphrase): ")
		if err != nil {
			return err
		}

		recoveryWindow, err = askRecoveryWindow()
		if err != nil {
			return err
		}

	// Use an existing extended master root key to create the wallet.
	case hasXprv:
		// We'll now prompt the user to enter in their extended master
		// root key.
		fmt.Printf("Input your extended master root key (usually " +
			"starting with xprv... on mainnet): ")
		reader := bufio.NewReader(os.Stdin)
		extendedRootKey, err = reader.ReadString('\n')
		if err != nil {
			return err
		}
		extendedRootKey = strings.TrimSpace(extendedRootKey)

		extendedRootKeyBirthday, err = askBirthdayTimestamp()
		if err != nil {
			return err
		}

		recoveryWindow, err = askRecoveryWindow()
		if err != nil {
			return err
		}

	// Neither a seed nor a master root key was specified, the user wants
	// to create a new seed.
	default:
		// Otherwise, if the user doesn't have a mnemonic that they
		// want to use, we'll generate a fresh one with the GenSeed
		// command.
		fmt.Println("Your cipher seed can optionally be encrypted.")

		instruction := "Input your passphrase if you wish to encrypt it " +
			"(or press enter to proceed without a cipher seed " +
			"passphrase): "
		aezeedPass, err = capturePassword(
			instruction, true, func(_ []byte) error { return nil },
		)
		if err != nil {
			return err
		}

		fmt.Println()
		fmt.Println("Generating fresh cipher seed...")
		fmt.Println()

		genSeedReq := &lnrpc.GenSeedRequest{
			AezeedPassphrase: aezeedPass,
		}
		seedResp, err := client.GenSeed(ctxc, genSeedReq)
		if err != nil {
			return fmt.Errorf("unable to generate seed: %v", err)
		}

		cipherSeedMnemonic = seedResp.CipherSeedMnemonic
	}

	// Before we initialize the wallet, we'll display the cipher seed to
	// the user so they can write it down.
	if len(cipherSeedMnemonic) > 0 {
		printCipherSeedWords(cipherSeedMnemonic)
	}

	// With either the user's prior cipher seed, or a newly generated one,
	// we'll go ahead and initialize the wallet.
	req := &lnrpc.InitWalletRequest{
		WalletPassword:                     walletPassword,
		CipherSeedMnemonic:                 cipherSeedMnemonic,
		AezeedPassphrase:                   aezeedPass,
		ExtendedMasterKey:                  extendedRootKey,
		ExtendedMasterKeyBirthdayTimestamp: extendedRootKeyBirthday,
		RecoveryWindow:                     recoveryWindow,
		ChannelBackups:                     chanBackups,
		StatelessInit:                      statelessInit,
	}
	response, err := client.InitWallet(ctxc, req)
	if err != nil {
		return err
	}

	fmt.Println("\nlnd successfully initialized!")

	if statelessInit {
		return storeOrPrintAdminMac(ctx, response.AdminMacaroon)
	}

	return nil
}

// capturePassword returns a password value that has been entered twice by the
// user, to ensure that the user knows what password they have entered. The user
// will be prompted to retry until the passwords match. If the optional param is
// true, the function may return an empty byte array if the user opts against
// using a password.
func capturePassword(instruction string, optional bool,
	validate func([]byte) error) ([]byte, error) {

	for {
		password, err := readPassword(instruction)
		if err != nil {
			return nil, err
		}

		// Do not require users to repeat password if
		// it is optional and they are not using one.
		if len(password) == 0 && optional {
			return nil, nil
		}

		// If the password provided is not valid, restart
		// password capture process from the beginning.
		if err := validate(password); err != nil {
			fmt.Println(err.Error())
			fmt.Println()
			continue
		}

		passwordConfirmed, err := readPassword("Confirm password: ")
		if err != nil {
			return nil, err
		}

		if bytes.Equal(password, passwordConfirmed) {
			return password, nil
		}

		fmt.Println("Passwords don't match, please try again")
		fmt.Println()
	}
}

var unlockCommand = cli.Command{
	Name:     "unlock",
	Category: "Startup",
	Usage:    "Unlock an encrypted wallet at startup.",
	Description: `
	The unlock command is used to decrypt lnd's wallet state in order to
	start up. This command MUST be run after booting up lnd before it's
	able to carry out its duties. An exception is if a user is running with
	--noseedbackup, then a default passphrase will be used.

	If the --stateless_init flag is set, no macaroon files are created by
	the daemon. This should be set for every unlock if the daemon was
	initially initialized stateless. Otherwise the daemon will create
	unencrypted macaroon files which could leak information to the system
	that the daemon runs on.
	`,
	Flags: []cli.Flag{
		cli.IntFlag{
			Name: "recovery_window",
			Usage: "address lookahead to resume recovery rescan, " +
				"value should be non-zero --  To recover all " +
				"funds, this should be greater than the " +
				"maximum number of consecutive, unused " +
				"addresses ever generated by the wallet.",
		},
		cli.BoolFlag{
			Name: "stdin",
			Usage: "read password from standard input instead of " +
				"prompting for it. THIS IS CONSIDERED TO " +
				"BE DANGEROUS if the password is located in " +
				"a file that can be read by another user. " +
				"This flag should only be used in " +
				"combination with some sort of password " +
				"manager or secrets vault.",
		},
		statelessInitFlag,
	},
	Action: actionDecorator(unlock),
}

func unlock(ctx *cli.Context) error {
	ctxc := getContext()
	client, cleanUp := getWalletUnlockerClient(ctx)
	defer cleanUp()

	var (
		pw  []byte
		err error
	)
	switch {
	// Read the password from standard in as if it were a file. This should
	// only be used if the password is piped into lncli from some sort of
	// password manager. If the user types the password instead, it will be
	// echoed in the console.
	case ctx.IsSet("stdin"):
		reader := bufio.NewReader(os.Stdin)
		pw, err = reader.ReadBytes('\n')

		// Remove carriage return and newline characters.
		pw = bytes.Trim(pw, "\r\n")

	// Read the password from a terminal by default. This requires the
	// terminal to be a real tty and will fail if a string is piped into
	// lncli.
	default:
		pw, err = readPassword("Input wallet password: ")
	}
	if err != nil {
		return err
	}

	args := ctx.Args()

	// Parse the optional recovery window if it is specified. By default,
	// the recovery window will be 0, indicating no lookahead should be
	// used.
	var recoveryWindow int32
	switch {
	case ctx.IsSet("recovery_window"):
		recoveryWindow = int32(ctx.Int64("recovery_window"))
	case args.Present():
		window, err := strconv.ParseInt(args.First(), 10, 64)
		if err != nil {
			return err
		}
		recoveryWindow = int32(window)
	}

	req := &lnrpc.UnlockWalletRequest{
		WalletPassword: pw,
		RecoveryWindow: recoveryWindow,
		StatelessInit:  ctx.Bool(statelessInitFlag.Name),
	}
	_, err = client.UnlockWallet(ctxc, req)
	if err != nil {
		return err
	}

	fmt.Println("\nlnd successfully unlocked!")

	// TODO(roasbeef): add ability to accept hex single and multi backups

	return nil
}

var changePasswordCommand = cli.Command{
	Name:     "changepassword",
	Category: "Startup",
	Usage:    "Change an encrypted wallet's password at startup.",
	Description: `
	The changepassword command is used to Change lnd's encrypted wallet's
	password. It will automatically unlock the daemon if the password change
	is successful.

	If one did not specify a password for their wallet (running lnd with
	--noseedbackup), one must restart their daemon without
	--noseedbackup and use this command. The "current password" field
	should be left empty.

	If the daemon was originally initialized stateless, then the
	--stateless_init flag needs to be set for the change password request
	as well! Otherwise the daemon will generate unencrypted macaroon files
	in its file system again and possibly leak sensitive information.
	Changing the password will by default not change the macaroon root key
	(just re-encrypt the macaroon database with the new password). So all
	macaroons will still be valid.
	If one wants to make sure that all previously created macaroons are
	invalidated, a new macaroon root key can be generated by using the
	--new_mac_root_key flag.

	After a successful password change with the --stateless_init flag set,
	the current or new admin macaroon is returned binary serialized in the
	answer. This answer MUST then be stored somewhere, otherwise
	all access to the RPC server will be lost and the wallet must be re-
	created to re-gain access. If the --save_to parameter is set, the
	macaroon is saved to this file, otherwise it is printed to standard out.
	`,
	Flags: []cli.Flag{
		statelessInitFlag,
		saveToFlag,
		cli.BoolFlag{
			Name: "new_mac_root_key",
			Usage: "rotate the macaroon root key resulting in " +
				"all previously created macaroons to be " +
				"invalidated",
		},
	},
	Action: actionDecorator(changePassword),
}

func changePassword(ctx *cli.Context) error {
	ctxc := getContext()
	client, cleanUp := getWalletUnlockerClient(ctx)
	defer cleanUp()

	currentPw, err := readPassword("Input current wallet password: ")
	if err != nil {
		return err
	}

	newPw, err := readPassword("Input new wallet password: ")
	if err != nil {
		return err
	}

	confirmPw, err := readPassword("Confirm new wallet password: ")
	if err != nil {
		return err
	}

	if !bytes.Equal(newPw, confirmPw) {
		return fmt.Errorf("passwords don't match")
	}

	// Should the daemon be initialized stateless? Then we expect an answer
	// with the admin macaroon later. Because the --save_to is related to
	// stateless init, it doesn't make sense to be set on its own.
	statelessInit := ctx.Bool(statelessInitFlag.Name)
	if !statelessInit && ctx.IsSet(saveToFlag.Name) {
		return fmt.Errorf("cannot set save_to parameter without " +
			"stateless_init")
	}

	req := &lnrpc.ChangePasswordRequest{
		CurrentPassword:    currentPw,
		NewPassword:        newPw,
		StatelessInit:      statelessInit,
		NewMacaroonRootKey: ctx.Bool("new_mac_root_key"),
	}

	response, err := client.ChangePassword(ctxc, req)
	if err != nil {
		return err
	}

	if statelessInit {
		return storeOrPrintAdminMac(ctx, response.AdminMacaroon)
	}

	return nil
}

var createWatchOnlyCommand = cli.Command{
	Name:      "createwatchonly",
	Category:  "Startup",
	ArgsUsage: "accounts-json-file",
	Usage: "Initialize a watch-only wallet after starting lnd for the " +
		"first time.",
	Description: `
	The create command is used to initialize an lnd wallet from scratch for
	the very first time, in watch-only mode. Watch-only means, there will be
	no private keys in lnd's wallet. This is only useful in combination with
	a remote signer or when lnd should be used as an on-chain wallet with
	PSBT interaction only.

	This is an interactive command that takes a JSON file as its first and
	only argument. The JSON is in the same format as the output of the
	'lncli wallet accounts list' command. This makes it easy to initialize
	the remote signer with the seed, then export the extended public account
	keys (xpubs) to import the watch-only wallet.

	Example JSON (non-mandatory or ignored fields are omitted):
	{
	    "accounts": [
		{
		    "extended_public_key": "upub5Eep7....",
		    "derivation_path": "m/49'/0'/0'"
		},
		{
		    "extended_public_key": "vpub5ZU1PH...",
		    "derivation_path": "m/84'/0'/0'"
		},
		{
		    "extended_public_key": "tpubDDXFH...",
		    "derivation_path": "m/1017'/1'/0'"
		},
	        ...
		{
		    "extended_public_key": "tpubDDXFH...",
		    "derivation_path": "m/1017'/1'/9'"
		}
	   ]
	}

	There must be an account for each of the existing key families that lnd
	uses internally (currently 0-9, see keychain/derivation.go).

	Read the documentation under docs/remote-signing.md for more information
	on how to set up a remote signing node over RPC.
	`,
	Flags: []cli.Flag{
		statelessInitFlag,
		saveToFlag,
	},
	Action: actionDecorator(createWatchOnly),
}

func createWatchOnly(ctx *cli.Context) error {
	ctxc := getContext()
	client, cleanUp := getWalletUnlockerClient(ctx)
	defer cleanUp()

	if ctx.NArg() != 1 {
		return cli.ShowCommandHelp(ctx, "createwatchonly")
	}

	// Should the daemon be initialized stateless? Then we expect an answer
	// with the admin macaroon later. Because the --save_to is related to
	// stateless init, it doesn't make sense to be set on its own.
	statelessInit := ctx.Bool(statelessInitFlag.Name)
	if !statelessInit && ctx.IsSet(saveToFlag.Name) {
		return fmt.Errorf("cannot set save_to parameter without " +
			"stateless_init")
	}

	jsonFile := lncfg.CleanAndExpandPath(ctx.Args().First())
	jsonBytes, err := ioutil.ReadFile(jsonFile)
	if err != nil {
		return fmt.Errorf("error reading JSON from file %v: %v",
			jsonFile, err)
	}

	jsonAccts := &walletrpc.ListAccountsResponse{}
	err = lnrpc.ProtoJSONUnmarshalOpts.Unmarshal(jsonBytes, jsonAccts)
	if err != nil {
		return fmt.Errorf("error parsing JSON: %v", err)
	}
	if len(jsonAccts.Accounts) == 0 {
		return fmt.Errorf("cannot import empty account list")
	}

	walletPassword, err := capturePassword(
		"Input wallet password: ", false,
		walletunlocker.ValidatePassword,
	)
	if err != nil {
		return err
	}

	extendedRootKeyBirthday, err := askBirthdayTimestamp()
	if err != nil {
		return err
	}

	recoveryWindow, err := askRecoveryWindow()
	if err != nil {
		return err
	}

	rpcAccounts, err := walletrpc.AccountsToWatchOnly(jsonAccts.Accounts)
	if err != nil {
		return err
	}

	rpcResp := &lnrpc.WatchOnly{
		MasterKeyBirthdayTimestamp: extendedRootKeyBirthday,
		Accounts:                   rpcAccounts,
	}

	// We assume that all accounts were exported from the same master root
	// key. So if one is set, we just forward that. If other accounts should
	// be watched later on, they should be imported into the watch-only
	// node, that then also forwards the import request to the remote
	// signer.
	for _, acct := range jsonAccts.Accounts {
		if len(acct.MasterKeyFingerprint) > 0 {
			rpcResp.MasterKeyFingerprint = acct.MasterKeyFingerprint
		}
	}

	initResp, err := client.InitWallet(ctxc, &lnrpc.InitWalletRequest{
		WalletPassword: walletPassword,
		WatchOnly:      rpcResp,
		RecoveryWindow: recoveryWindow,
		StatelessInit:  statelessInit,
	})
	if err != nil {
		return err
	}

	if statelessInit {
		return storeOrPrintAdminMac(ctx, initResp.AdminMacaroon)
	}

	return nil
}

// storeOrPrintAdminMac either stores the admin macaroon to a file specified or
// prints it to standard out, depending on the user flags set.
func storeOrPrintAdminMac(ctx *cli.Context, adminMac []byte) error {
	// The user specified the optional --save_to parameter. We'll save the
	// macaroon to that file.
	if ctx.IsSet(saveToFlag.Name) {
		macSavePath := lncfg.CleanAndExpandPath(ctx.String(
			saveToFlag.Name,
		))
		err := os.WriteFile(macSavePath, adminMac, 0644)
		if err != nil {
			_ = os.Remove(macSavePath)
			return err
		}
		fmt.Printf("Admin macaroon saved to %s\n", macSavePath)
		return nil
	}

	// Otherwise we just print it. The user MUST store this macaroon
	// somewhere so we either save it to a provided file path or just print
	// it to standard output.
	fmt.Printf("Admin macaroon: %s\n", hex.EncodeToString(adminMac))
	return nil
}

func askRecoveryWindow() (int32, error) {
	for {
		fmt.Println()
		fmt.Printf("Input an optional address look-ahead used to scan "+
			"for used keys (default %d): ", defaultRecoveryWindow)

		reader := bufio.NewReader(os.Stdin)
		answer, err := reader.ReadString('\n')
		if err != nil {
			return 0, err
		}

		fmt.Println()

		answer = strings.TrimSpace(answer)

		if len(answer) == 0 {
			return defaultRecoveryWindow, nil
		}

		lookAhead, err := strconv.ParseInt(answer, 10, 32)
		if err != nil {
			fmt.Printf("Unable to parse recovery window: %v\n", err)
			continue
		}

		return int32(lookAhead), nil
	}
}

func askBirthdayTimestamp() (uint64, error) {
	for {
		fmt.Println()
		fmt.Printf("Input an optional wallet birthday unix timestamp " +
			"of first block to start scanning from (default 0): ")

		reader := bufio.NewReader(os.Stdin)
		answer, err := reader.ReadString('\n')
		if err != nil {
			return 0, err
		}

		fmt.Println()

		answer = strings.TrimSpace(answer)

		if len(answer) == 0 {
			return 0, nil
		}

		birthdayTimestamp, err := strconv.ParseUint(answer, 10, 64)
		if err != nil {
			fmt.Printf("Unable to parse birthday timestamp: %v\n",
				err)

			continue
		}

		return birthdayTimestamp, nil
	}
}

func printCipherSeedWords(mnemonicWords []string) {
	fmt.Println("!!!YOU MUST WRITE DOWN THIS SEED TO BE ABLE TO " +
		"RESTORE THE WALLET!!!")
	fmt.Println()

	fmt.Println("---------------BEGIN LND CIPHER SEED---------------")

	numCols := 4
	colWords := monowidthColumns(mnemonicWords, numCols)
	for i := 0; i < len(colWords); i += numCols {
		fmt.Printf("%2d. %3s  %2d. %3s  %2d. %3s  %2d. %3s\n",
			i+1, colWords[i], i+2, colWords[i+1], i+3,
			colWords[i+2], i+4, colWords[i+3])
	}

	fmt.Println("---------------END LND CIPHER SEED-----------------")

	fmt.Println("\n!!!YOU MUST WRITE DOWN THIS SEED TO BE ABLE TO " +
		"RESTORE THE WALLET!!!")
}