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// 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/>.
// This file contains the implementation for interacting with the Ledger hardware
// wallets. The wire protocol spec can be found in the Ledger Blue GitHub repo:
// https://raw.githubusercontent.com/LedgerHQ/blue-app-eth/master/doc/ethapp.asc
package usbwallet
import (
"errors"
"runtime"
"sync"
"time"
"github.com/ethereum/go-ethereum/accounts"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/log"
"github.com/karalabe/hid"
)
// LedgerScheme is the protocol scheme prefixing account and wallet URLs.
var LedgerScheme = "ledger"
// ledgerDeviceIDs are the known device IDs that Ledger wallets use.
var ledgerDeviceIDs = []deviceID{
{Vendor: 0x2c97, Product: 0x0000}, // Ledger Blue
{Vendor: 0x2c97, Product: 0x0001}, // Ledger Nano S
}
// Maximum time between wallet refreshes (if USB hotplug notifications don't work).
const ledgerRefreshCycle = time.Second
// Minimum time between wallet refreshes to avoid USB trashing.
const ledgerRefreshThrottling = 500 * time.Millisecond
// LedgerHub is a accounts.Backend that can find and handle Ledger hardware wallets.
type LedgerHub struct {
refreshed time.Time // Time instance when the list of wallets was last refreshed
wallets []accounts.Wallet // List of Ledger devices currently tracking
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
// TODO(karalabe): remove if hotplug lands on Windows
commsPend int // Number of operations blocking enumeration
commsLock sync.Mutex // Lock protecting the pending counter and enumeration
}
// NewLedgerHub creates a new hardware wallet manager for Ledger devices.
func NewLedgerHub() (*LedgerHub, error) {
if !hid.Supported() {
return nil, errors.New("unsupported platform")
}
hub := &LedgerHub{
quit: make(chan chan error),
}
hub.refreshWallets()
return hub, nil
}
// Wallets implements accounts.Backend, returning all the currently tracked USB
// devices that appear to be Ledger hardware wallets.
func (hub *LedgerHub) 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, len(hub.wallets))
copy(cpy, hub.wallets)
return cpy
}
// refreshWallets scans the USB devices attached to the machine and updates the
// list of wallets based on the found devices.
func (hub *LedgerHub) 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 < ledgerRefreshThrottling {
return
}
// Retrieve the current list of Ledger devices
var ledgers []hid.DeviceInfo
if runtime.GOOS == "linux" {
// hidapi on Linux opens the device during enumeration to retrieve some infos,
// breaking the Ledger protocol if that is waiting for user confirmation. This
// is a bug acknowledged at Ledger, but it won't be fixed on old devices so we
// need to prevent concurrent comms ourselves. The more elegant solution would
// be to ditch enumeration in favor of hutplug events, but that don't work yet
// on Windows so if we need to hack it anyway, this is more elegant for now.
hub.commsLock.Lock()
if hub.commsPend > 0 { // A confirmation is pending, don't refresh
hub.commsLock.Unlock()
return
}
}
for _, info := range hid.Enumerate(0, 0) { // Can't enumerate directly, one valid ID is the 0 wildcard
for _, id := range ledgerDeviceIDs {
if info.VendorID == id.Vendor && info.ProductID == id.Product {
ledgers = append(ledgers, info)
break
}
}
}
if runtime.GOOS == "linux" {
// See rationale before the enumeration why this is needed and only on Linux.
hub.commsLock.Unlock()
}
// Transform the current list of wallets into the new one
hub.stateLock.Lock()
wallets := make([]accounts.Wallet, 0, len(ledgers))
events := []accounts.WalletEvent{}
for _, ledger := range ledgers {
url := accounts.URL{Scheme: LedgerScheme, Path: ledger.Path}
// Drop wallets in front of the next device or those that failed for some reason
for len(hub.wallets) > 0 && (hub.wallets[0].URL().Cmp(url) < 0 || hub.wallets[0].(*ledgerWallet).failed()) {
events = append(events, accounts.WalletEvent{Wallet: hub.wallets[0], Arrive: false})
hub.wallets = hub.wallets[1:]
}
// If there are no more wallets or the device is before the next, wrap new wallet
if len(hub.wallets) == 0 || hub.wallets[0].URL().Cmp(url) > 0 {
wallet := &ledgerWallet{hub: hub, url: &url, info: ledger, log: log.New("url", url)}
events = append(events, accounts.WalletEvent{Wallet: wallet, Arrive: true})
wallets = append(wallets, wallet)
continue
}
// If the device is the same as the first wallet, keep it
if hub.wallets[0].URL().Cmp(url) == 0 {
wallets = append(wallets, hub.wallets[0])
hub.wallets = hub.wallets[1:]
continue
}
}
// Drop any leftover wallets and set the new batch
for _, wallet := range hub.wallets {
events = append(events, accounts.WalletEvent{Wallet: wallet, Arrive: false})
}
hub.refreshed = time.Now()
hub.wallets = wallets
hub.stateLock.Unlock()
// Fire all wallet events and return
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 Ledger wallets.
func (hub *LedgerHub) 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 stored in
// the keystore, and for firing wallet addition/removal events. It listens for
// account change events from the underlying account cache, and also periodically
// forces a manual refresh (only triggers for systems where the filesystem notifier
// is not running).
func (hub *LedgerHub) updater() {
for {
// TODO: Wait for a USB hotplug event (not supported yet) or a refresh timeout
// <-hub.changes
time.Sleep(ledgerRefreshCycle)
// 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()
}
}
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