// Copyright 2018 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/>.
// This package implements support for smartcard-based hardware wallets such as
// the one written by Status: https://github.com/status-im/hardware-wallet
//
// This implementation of smartcard wallets have a different interaction process
// to other types of hardware wallet. The process works like this:
//
// 1. (First use with a given client) Establish a pairing between hardware
// wallet and client. This requires a secret value called a 'pairing password'.
// You can pair with an unpaired wallet with `personal.openWallet(URI, pairing password)`.
// 2. (First use only) Initialize the wallet, which generates a keypair, stores
// it on the wallet, and returns it so the user can back it up. You can
// initialize a wallet with `personal.initializeWallet(URI)`.
// 3. Connect to the wallet using the pairing information established in step 1.
// You can connect to a paired wallet with `personal.openWallet(URI, PIN)`.
// 4. Interact with the wallet as normal.
package scwallet
import (
"encoding/json"
"io/ioutil"
"os"
"sort"
"sync"
"time"
"github.com/ethereum/go-ethereum/accounts"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/log"
pcsc "github.com/gballet/go-libpcsclite"
)
// Scheme is the URI prefix for smartcard wallets.
const Scheme = "pcsc"
// refreshCycle is the maximum time between wallet refreshes (if USB hotplug
// notifications don't work).
const refreshCycle = time.Second
// refreshThrottling is the minimum time between wallet refreshes to avoid thrashing.
const refreshThrottling = 500 * time.Millisecond
// smartcardPairing contains information about a smart card we have paired with
// or might pair with the hub.
type smartcardPairing struct {
PublicKey []byte `json:"publicKey"`
PairingIndex uint8 `json:"pairingIndex"`
PairingKey []byte `json:"pairingKey"`
Accounts map[common.Address]accounts.DerivationPath `json:"accounts"`
}
// Hub is a accounts.Backend that can find and handle generic PC/SC hardware wallets.
type Hub struct {
scheme string // Protocol scheme prefixing account and wallet URLs.
context *pcsc.Client
datadir string
pairings map[string]smartcardPairing
refreshed time.Time // Time instance when the list of wallets was last refreshed
wallets map[string]*Wallet // Mapping from reader names to wallet instances
updateFeed event.Feed // Event feed to notify wallet additions/removals
updateScope event.SubscriptionScope // Subscription scope tracking current live listeners
updating bool // Whether the event notification loop is running
quit chan chan error
stateLock sync.RWMutex // Protects the internals of the hub from racey access
}
func (hub *Hub) readPairings() error {
hub.pairings = make(map[string]smartcardPairing)
pairingFile, err := os.Open(hub.datadir + "/smartcards.json")
if err != nil {
if os.IsNotExist(err) {
return nil
}
return err
}
pairingData, err := ioutil.ReadAll(pairingFile)
if err != nil {
return err
}
var pairings []smartcardPairing
if err := json.Unmarshal(pairingData, &pairings); err != nil {
return err
}
for _, pairing := range pairings {
hub.pairings[string(pairing.PublicKey)] = pairing
}
return nil
}
func (hub *Hub) writePairings() error {
pairingFile, err := os.OpenFile(hub.datadir+"/smartcards.json", os.O_RDWR|os.O_CREATE, 0755)
if err != nil {
return err
}
pairings := make([]smartcardPairing, 0, len(hub.pairings))
for _, pairing := range hub.pairings {
pairings = append(pairings, pairing)
}
pairingData, err := json.Marshal(pairings)
if err != nil {
return err
}
if _, err := pairingFile.Write(pairingData); err != nil {
return err
}
return pairingFile.Close()
}
func (hub *Hub) pairing(wallet *Wallet) *smartcardPairing {
pairing, ok := hub.pairings[string(wallet.PublicKey)]
if ok {
return &pairing
}
return nil
}
func (hub *Hub) setPairing(wallet *Wallet, pairing *smartcardPairing) error {
if pairing == nil {
delete(hub.pairings, string(wallet.PublicKey))
} else {
hub.pairings[string(wallet.PublicKey)] = *pairing
}
return hub.writePairings()
}
// NewHub creates a new hardware wallet manager for smartcards.
func NewHub(scheme string, datadir string) (*Hub, error) {
context, err := pcsc.EstablishContext(pcsc.ScopeSystem)
if err != nil {
return nil, err
}
hub := &Hub{
scheme: scheme,
context: context,
datadir: datadir,
wallets: make(map[string]*Wallet),
quit: make(chan chan error),
}
if err := hub.readPairings(); err != nil {
return nil, err
}
hub.refreshWallets()
return hub, nil
}
// Wallets implements accounts.Backend, returning all the currently tracked smart
// cards that appear to be hardware wallets.
func (hub *Hub) Wallets() []accounts.Wallet {
// Make sure the list of wallets is up to date
hub.refreshWallets()
hub.stateLock.RLock()
defer hub.stateLock.RUnlock()
cpy := make([]accounts.Wallet, 0, len(hub.wallets))
for _, wallet := range hub.wallets {
cpy = append(cpy, wallet)
}
sort.Sort(accounts.WalletsByURL(cpy))
return cpy
}
// refreshWallets scans the devices attached to the machine and updates the
// list of wallets based on the found devices.
func (hub *Hub) refreshWallets() {
// Don't scan the USB like crazy it the user fetches wallets in a loop
hub.stateLock.RLock()
elapsed := time.Since(hub.refreshed)
hub.stateLock.RUnlock()
if elapsed < refreshThrottling {
return
}
// Retrieve all the smart card reader to check for cards
readers, err := hub.context.ListReaders()
if err != nil {
// This is a perverted hack, the scard library returns an error if no card
// readers are present instead of simply returning an empty list. We don't
// want to fill the user's log with errors, so filter those out.
if err.Error() != "scard: Cannot find a smart card reader." {
log.Error("Failed to enumerate smart card readers", "err", err)
}
}
// Transform the current list of wallets into the new one
hub.stateLock.Lock()
events := []accounts.WalletEvent{}
seen := make(map[string]struct{})
for _, reader := range readers {
// Mark the reader as present
seen[reader] = struct{}{}
// If we alreay know about this card, skip to the next reader, otherwise clean up
if wallet, ok := hub.wallets[reader]; ok {
if err := wallet.ping(); err == nil {
continue
}
wallet.Close()
events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletDropped})
delete(hub.wallets, reader)
}
// New card detected, try to connect to it
card, err := hub.context.Connect(reader, pcsc.ShareShared, pcsc.ProtocolAny)
if err != nil {
log.Debug("Failed to open smart card", "reader", reader, "err", err)
continue
}
wallet := NewWallet(hub, card)
if err = wallet.connect(); err != nil {
log.Debug("Failed to connect to smart card", "reader", reader, "err", err)
card.Disconnect(pcsc.LeaveCard)
continue
}
// Card connected, start tracking in amongs the wallets
hub.wallets[reader] = wallet
events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletArrived})
}
// Remove any wallets no longer present
for reader, wallet := range hub.wallets {
if _, ok := seen[reader]; !ok {
wallet.Close()
events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletDropped})
delete(hub.wallets, reader)
}
}
hub.refreshed = time.Now()
hub.stateLock.Unlock()
for _, event := range events {
hub.updateFeed.Send(event)
}
}
// Subscribe implements accounts.Backend, creating an async subscription to
// receive notifications on the addition or removal of smart card wallets.
func (hub *Hub) Subscribe(sink chan<- accounts.WalletEvent) event.Subscription {
// We need the mutex to reliably start/stop the update loop
hub.stateLock.Lock()
defer hub.stateLock.Unlock()
// Subscribe the caller and track the subscriber count
sub := hub.updateScope.Track(hub.updateFeed.Subscribe(sink))
// Subscribers require an active notification loop, start it
if !hub.updating {
hub.updating = true
go hub.updater()
}
return sub
}
// updater is responsible for maintaining an up-to-date list of wallets managed
// by the smart card hub, and for firing wallet addition/removal events.
func (hub *Hub) updater() {
for {
// TODO: Wait for a USB hotplug event (not supported yet) or a refresh timeout
// <-hub.changes
time.Sleep(refreshCycle)
// Run the wallet refresher
hub.refreshWallets()
// If all our subscribers left, stop the updater
hub.stateLock.Lock()
if hub.updateScope.Count() == 0 {
hub.updating = false
hub.stateLock.Unlock()
return
}
hub.stateLock.Unlock()
}
}
