// 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"
"github.com/ava-labs/coreth/accounts"
"github.com/ava-labs/coreth/core/types"
ethereum "github.com/ava-labs/go-ethereum"
"github.com/ava-labs/go-ethereum/common"
"github.com/ava-labs/go-ethereum/crypto"
"github.com/ava-labs/go-ethereum/log"
"github.com/karalabe/usb"
)
// 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 usb.DeviceInfo // Known USB device infos about the wallet
device usb.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.