path: root/accounts/usbwallet/wallet.go

// 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.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 t