// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
// Package usbwallet implements support for USB hardware wallets.
package usbwallet
import (
"context"
"fmt"
"io"
"math/big"
"sync"
"time"
ethereum "github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/accounts"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/log"
"github.com/karalabe/hid"
)
// Maximum time between wallet health checks to detect USB unplugs.
const heartbeatCycle = time.Second
// Minimum time to wait between self derivation attempts, even it the user is
// requesting accounts like crazy.
const selfDeriveThrottling = time.Second
// driver defines the vendor specific functionality hardware wallets instances
// must implement to allow using them with the wallet lifecycle management.
type driver interface {
// Status returns a textual status to aid the user in the current state of the
// wallet. It also returns an error indicating any failure the wallet might have
// encountered.
Status() (string, error)
// Open initializes access to a wallet instance. The passphrase parameter may
// or may not be used by the implementation of a particular wallet instance.
Open(device io.ReadWriter, passphrase string) error
// Close releases any resources held by an open wallet instance.
Close() error
// Heartbeat performs a sanity check against the hardware wallet to see if it
// is still online and healthy.
Heartbeat() error
// Derive sends a derivation request to the USB device and returns the Ethereum
// address located on that path.
Derive(path accounts.DerivationPath) (common.Address, error)
// SignTx sends the transaction to the USB device and waits for the user to confirm
// or deny the transaction.
SignTx(path accounts.DerivationPath, tx *types.Transaction, chainID *big.Int) (common.Address, *types.Transaction, error)
}
// wallet represents the common functionality shared by all USB hardware
// wallets to prevent reimplementing the same complex maintenance mechanisms
// for different vendors.
type wallet struct {
hub *Hub // USB hub scanning
driver driver // Hardware implementation of the low level device operations
url *accounts.URL // Textual URL uniquely identifying this wallet
info hid.DeviceInfo // Known USB device infos about the wallet
device hid.Device // USB device advertising itself as a hardware wallet
accounts []accounts.Account // List of derive accounts pinned on the hardware wallet
paths map[common.Address]accounts.DerivationPath // Known derivation paths for signing operations
deriveNextPaths []accounts.DerivationPath // Next derivation paths for account auto-discovery (multiple bases supported)
deriveNextAddrs []common.Address // Next derived account addresses for auto-discovery (multiple bases supported)
deriveChain ethereum.ChainStateReader // Blockchain state reader to discover used account with
deriveReq chan chan struct{} // Channel to request a self-derivation on
deriveQuit chan chan error // Channel to terminate the self-deriver with
healthQuit chan chan error
// Locking a hardware wallet is a bit special. Since hardware devices are lower
// performing, any communication with them might take a non negligible amount of
// time. Worse still, waiting for user confirmation can take arbitrarily long,
// but exclusive communication must be upheld during. Locking the entire wallet
// in the mean time however would stall any parts of the system that don't want
// to communicate, just read some state (e.g. list the accounts).
//
// As such, a hardware wallet needs two locks to function correctly. A state
// lock can be used to protect the wallet's software-side internal state, which
// must not be held exclusively during hardware communication. A communication
// lock can be used to achieve exclusive access to the device itself, this one
// however should allow "skipping" waiting for operations that might want to
// use the device, but can live without too (e.g. account self-derivation).
//
// Since we have two locks, it's important to know how to properly use them:
// - Communication requires the `device` to not change, so obtaining the
// commsLock should be done after having a stateLock.
// - Communication must not disable read access to the wallet state, so it
// must only ever hold a *read* lock to stateLock.
commsLock chan struct{} // Mutex (buf=1) for the USB comms without keeping the state locked
stateLock sync.RWMutex // Protects read and write access to the wallet struct fields
log log.Logger // Contextual logger to tag the base with its id
}
// URL implements accounts.Wallet, returning the URL of the USB hardware device.
func (w *wallet) URL() accounts.URL {
return *w.url // Immutable, no need for a lock
}
// Status implements accounts.Wallet, returning a custom status message from the
// underlying vendor-specific hardware wallet implementation.
func (w *wallet) Status() (string, error) {
w.stateLock.RLock() // No device communication, state lock is enough
defer w.stateLock.RUnlock()
status, failure := w.driver.Status()
if w.device == nil {
return "Closed", failure
}
return status, failure
}
// Open implements accounts.Wallet, attempting to open a USB connection to the
// hardware wallet.
func (w *wallet) Open(passphrase string) error {
w.stateLock.Lock() // State lock is enough since there's no connection yet at this point
defer w.stateLock.Unlock()
// If the device was already opened once, refuse to try again
if w.paths != nil {
return accounts.ErrWalletAlreadyOpen
}
// Make sure the actual device connection is done only once
if w.device == nil {
device, err := w.info.Open()
if err != nil {
return err
}
w.device = device
w.commsLock = make(chan struct{}, 1)
w.commsLock <- struct{}{} // Enable lock
}
// Delegate device initialization to the underlying driver
if err := w.driver.Open(w.device, passphrase); err != nil {
return err
}
// Connection successful, start life-cycle management
w.paths = make(map[common.Address]accounts.DerivationPath)
w.deriveReq = make(chan chan struct{})
w.deriveQuit = make(chan chan error)
w.healthQuit = make(chan chan error)
go w.heartbeat()
go w.selfDerive()
// Notify anyone listening for wallet events that a new device is accessible
go w.hub.updateFeed.Send(accounts.WalletEvent{Wallet: w, Kind: accounts.WalletOpened})
return nil
}
// heartbeat is a health check loop for the USB wallets to periodically verify
// whether they are still present or if they malfunctioned.
func (w *wallet) heartbeat() {
w.log.Debug("USB wallet health-check started")
defer w.log.Debug("USB wallet health-check stopped")
// Execute heartbeat checks until termination or error
var (
errc chan error
err error
)
for errc == nil && err == nil {
// Wait until termination is requested or the heartbeat cycle arrives
select {
case errc = <-w.healthQuit:
// Termination requested
continue
case <-time.After(heartbeatCycle):
// Heartbeat time
}
// Execute a tiny data exchange to see responsiveness
w.stateLock.RLock()
if w.device == nil {
// Terminated while waiting for the lock
w.stateLock.RUnlock()
continue
}
<-w.commsLock // Don't lock state while resolving version
err = w.driver.Heartbeat()
w.commsLock <- struct{}{}
w.stateLock.RUnlock()
if err != nil {
w.stateLock.Lock() // Lock state to tear the wallet down
w.close()
w.stateLock.Unlock()
}
// Ignore non hardware related errors
err = nil
}
// In case of error, wait for termination
if err != nil {
w.log.Debug("USB wallet health-check failed", "err", err)
errc = <-w.healthQuit
}
errc <- err
}
// Close implements accounts.Wallet, closing the USB connection to the device.
func (w *wallet) Close() error {
// Ensure the wallet was opened
w.stateLock.RLock()
hQuit, dQuit := w.healthQuit, w.deriveQuit
w.stateLock.RUnlock()
// Terminate the health checks
var herr error
if hQuit != nil {
errc := make(chan error)
hQuit <- errc
herr = <-errc // Save for later, we *must* close the USB
}
// Terminate the self-derivations
var derr error
if dQuit != nil {
errc := make(chan error)
dQuit <- errc
derr = <-errc // Save for later, we *must* close the USB
}
// Terminate the device connection
w.stateLock.Lock()
defer w.stateLock.Unlock()
w.healthQuit = nil
w.deriveQuit = nil
w.deriveReq = nil
if err := w.close(); err != nil {
return err
}
if herr != nil {
return herr
}
return derr
}
// close is the internal wallet closer that terminates the USB connection and
// resets all the fields to their defaults.
//
// Note, close assumes the state lock is held!
func (w *wallet) close() error {
// Allow duplicate closes, especially for health-check failures
if w.device == nil {
return nil
}
// Close the device, clear everything, then return
w.device.Close()
w.device = nil
w.accounts, w.paths = nil, nil
return w.driver.Close()
}
// Accounts implements accounts.Wallet, returning the list of accounts pinned to
// the USB hardware wallet. If self-derivation was enabled, the account list is
// periodically expanded based on current chain state.
func (w *wallet) Accounts() []accounts.Account {
// Attempt self-derivation if it's running
reqc := make(chan struct{}, 1)
select {
case w.deriveReq <- reqc:
// Self-derivation request accepted, wait for it
<-reqc
default:
// Self-derivation offline, throttled or busy, skip
}
// Return whatever account list we ended up with
w.stateLock.RLock()
defer w.stateLock.RUnlock()
cpy := make([]accounts.Account, len(w.accounts))
copy(cpy, w.accounts)
return cpy
}
// selfDerive is an account derivation loop that upon request attempts to find
// new non-zero accounts.
func (w *wallet) selfDerive() {
w.log.Debug("USB wallet self-derivation started")
defer w.log.Debug("USB wallet self-derivation stopped")
// Execute self-derivations until termination or error
var (
reqc chan struct{}
errc chan error
err error
)
for errc == nil && err == nil {
// Wait until either derivation or termination is requested
select {
case errc = <-w.deriveQuit:
// Termination requested
continue
case reqc = <-w.deriveReq:
// Account discovery requested
}
// Derivation needs a chain and device access, skip if either unavailable
w.stateLock.RLock()
if w.device == nil || w.deriveChain == nil {
w.stateLock.RUnlock()
reqc <- struct{}{}
continue
}
select {
case <-w.commsLock:
default:
w.stateLock.RUnlock()
reqc <- struct{}{}
continue
}
// Device lock obtained, derive the next batch of accounts
var (
accs []accounts.Account
paths []accounts.DerivationPath
nextPaths = append([]accounts.DerivationPath{}, w.deriveNextPaths...)
nextAddrs = append([]common.Address{}, w.deriveNextAddrs...)
context = context.Background()
)
for i := 0; i < len(nextAddrs); i++ {
for empty := false; !empty; {
// Retrieve the next derived Ethereum account
if nextAddrs[i] == (common.Address{}) {
if nextAddrs[i], err = w.driver.Derive(nextPaths[i]); err != nil {
w.log.Warn("USB wallet account derivation failed", "err", err)
break
}
}
// Check the account's status against the current chain state
var (
balance *big.Int
nonce uint64
)
balance, err = w.deriveChain.BalanceAt(context, nextAddrs[i], nil)
if err != nil {
w.log.Warn("USB wallet balance retrieval failed", "err", err)
break
}
nonce, err = w.deriveChain.NonceAt(context, nextAddrs[i], nil)
if err != nil {
w.log.Warn("USB wallet nonce retrieval failed", "err", err)
break
}
// If the next account is empty, stop self-derivation, but add for the last base path
if balance.Sign() == 0 && nonce == 0 {
empty = true
if i < len(nextAddrs)-1 {
break
}
}
// We've just self-derived a new account, start tracking it locally
path := make(accounts.DerivationPath, len(nextPaths[i]))
copy(path[:], nextPaths[i][:])
paths = append(paths, path)
account := accounts.Account{
Address: nextAddrs[i],
URL: accounts.URL{Scheme: w.url.Scheme, Path: fmt.Sprintf("%s/%s", w.url.Path, path)},
}
accs = append(accs, account)
// Display a log message to the user for new (or previously empty accounts)
if _, known := w.paths[nextAddrs[i]]; !known || (!empty && nextAddrs[i] == w.deriveNextAddrs[i]) {
w.log.Info("USB wallet discovered new account", "address", nextAddrs[i], "path", path, "balance", balance, "nonce", nonce)
}
// Fetch the next potential account
if !empty {
nextAddrs[i] = common.Address{}
nextPaths[i][len(nextPaths[i])-1]++
}
}
}
// Self derivation complete, release device lock
w.commsLock <- struct{}{}
w.stateLock.RUnlock()
// Insert any accounts successfully derived
w.stateLock.Lock()
for i := 0; i < len(accs); i++ {
if _, ok := w.paths[accs[i].Address]; !ok {
w.accounts = append(w.accounts, accs[i])
w.paths[accs[i].Address] = paths[i]
}
}
// Shift the self-derivation forward
// TODO(karalabe): don't overwrite changes from wallet.SelfDerive
w.deriveNextAddrs = nextAddrs
w.deriveNextPaths = nextPaths
w.stateLock.Unlock()
// Notify the user of termination and loop after a bit of time (to avoid trashing)
reqc <- struct{}{}
if err == nil {
select {
case errc = <-w.deriveQuit:
// Termination requested, abort
case <-time.After(selfDeriveThrottling):
// Waited enough, willing to self-derive again
}
}
}
// In case of error, wait for termination
if err != nil {
w.log.Debug("USB wallet self-derivation failed", "err", err)
errc = <-w.deriveQuit
}
errc <- err
}
// Contains implements accounts.Wallet, returning whether a particular account is
// or is not pinned into this wallet instance. Although we could attempt to resolve
// unpinned accounts, that would be an non-negligible hardware operation.
func (w *wallet) Contains(account accounts.Account) bool {
w.stateLock.RLock()
defer w.stateLock.RUnlock()
_, exists := w.paths[account.Address]
return exists
}
// Derive implements accounts.Wallet, deriving a new account at the specific
// derivation path. If pin is set to true, the account will be added to the list
// of tracked accounts.
func (w *wallet) Derive(path accounts.DerivationPath, pin bool) (accounts.Account, error) {
// Try to derive the actual account and update its URL if successful
w.stateLock.RLock() // Avoid device disappearing during derivation
if w.device == nil {
w.stateLock.RUnlock()
return accounts.Account{}, accounts.ErrWalletClosed
}
<-w.commsLock // Avoid concurrent hardware access
address, err := w.driver.Derive(path)
w.commsLock <- struct{}{}
w.stateLock.RUnlock()
// If an error occurred or no pinning was requested, return
if err != nil {
return accounts.Account{}, err
}
account := accounts.Account{
Address: address,
URL: accounts.URL{Scheme: w.url.Scheme, Path: fmt.Sprintf("%s/%s", w.url.Path, path)},
}
if !pin {
return account, nil
}
// Pinning needs to modify the state
w.stateLock.Lock()
defer w.stateLock.Unlock()
if _, ok := w.paths[address]; !ok {
w.accounts = append(w.accounts, account)
w.paths[address] = path
}
return account, nil
}
// SelfDerive sets a base account derivation path from which the wallet attempts
// to discover non zero accounts and automatically add them to list of tracked
// accounts.
//
// Note, self derivaton will increment the last component of the specified path
// opposed to decending into a child path to allow discovering accounts starting
// from non zero components.
//
// Some hardware wallets switched derivation paths through their evolution, so
// this method supports providing multiple bases to discover old user accounts
// too. Only the last base will be used to derive the next empty account.
//
// You can disable automatic account discovery by calling SelfDerive with a nil
// chain state reader.
func (w *wallet) SelfDerive(bases []accounts.DerivationPath, chain ethereum.ChainStateReader) {
w.stateLock.Lock()
defer w.stateLock.Unlock()
w.deriveNextPaths = make([]accounts.DerivationPath, len(bases))
for i, base := range bases {
w.deriveNextPaths[i] = make(accounts.DerivationPath, len(base))
copy(w.deriveNextPaths[i][:], base[:])
}
w.deriveNextAddrs = make([]common.Address, len(bases))
w.deriveChain = chain
}
// signHash implements accounts.Wallet, however signing arbitrary data is not
// supported for hardware wallets, so this method will always return an error.
func (w *wallet) signHash(account accounts.Account, hash []byte) ([]byte, error) {
return nil, accounts.ErrNotSupported
}
// SignData signs keccak256(data). The mimetype parameter describes the type of data being signed
func (w *wallet) SignData(account accounts.Account, mimeType string, data []byte) ([]byte, error) {
return w.signHash(account, crypto.Keccak256(data))
}
// SignDataWithPassphrase implements accounts.Wallet, attempting to sign the given
// data with the given account using passphrase as extra authentication.
// Since USB wallets don't rely on passphrases, these are silently ignored.
func (w *wallet) SignDataWithPassphrase(account accounts.Account, passphrase, mimeType string, data []byte) ([]byte, error) {
return w.SignData(account, mimeType, data)
}
func (w *wallet) SignText(account accounts.Account, text []byte) ([]byte, error) {
return w.signHash(account, accounts.TextHash(text))
}
// SignTx implements accounts.Wallet. It sends the transaction over to the Ledger
// wallet to request a confirmation from the user. It returns either the signed
// transaction or a failure if the user denied the transaction.
//
// Note, if the version of the Ethereum application running on the Ledger wallet is
// too old to sign EIP-155 transactions, but such is requested nonetheless, an error
// will be returned opposed to silently signing in Homestead mode.
func (w *wallet) SignTx(account accounts.Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
w.stateLock.RLock() // Comms have own mutex, this is for the state fields
defer w.stateLock.RUnlock()
// If the wallet is closed, abort
if w.device == nil {
return nil, accounts.ErrWalletClosed
}
// Make sure the requested account is contained within
path, ok := w.paths[account.Address]
if !ok {
return nil, accounts.ErrUnknownAccount
}
// All infos gathered and metadata checks out, request signing
<-w.commsLock
defer func() { w.commsLock <- struct{}{} }()
// Ensure the device isn't screwed with while user confirmation is pending
// TODO(karalabe): remove if hotplug lands on Windows
w.hub.commsLock.Lock()
w.hub.commsPend++
w.hub.commsLock.Unlock()
defer func() {
w.hub.commsLock.Lock()
w.hub.commsPend--
w.hub.commsLock.Unlock()
}()
// Sign the transaction and verify the sender to avoid hardware fault surprises
sender, signed, err := w.driver.SignTx(path, tx, chainID)
if err != nil {
return nil, err
}
if sender != account.Address {
return nil, fmt.Errorf("signer mismatch: expected %s, got %s", account.Address.Hex(), sender.Hex())
}
return signed, nil
}
// SignHashWithPassphrase implements accounts.Wallet, however signing arbitrary
// data is not supported for Ledger wallets, so this method will always return
// an error.
func (w *wallet) SignTextWithPassphrase(account accounts.Account, passphrase string, text []byte) ([]byte, error) {
return w.SignText(account, accounts.TextHash(text))
}
// SignTxWithPassphrase implements accounts.Wallet, attempting to sign the given
// transaction with the given account using passphrase as extra authentication.
// Since USB wallets don't rely on passphrases, these are silently ignored.
func (w *wallet) SignTxWithPassphrase(account accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
return w.SignTx(account, tx, chainID)
}
