// 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" "path/filepath" "sort" "sync" "time" "github.com/ava-labs/coreth/accounts" "github.com/ava-labs/go-ethereum/common" "github.com/ava-labs/go-ethereum/event" "github.com/ava-labs/go-ethereum/log" pcsc "github.com/gballet/go-libpcsclite" ) // Scheme is the URI prefix for smartcard wallets. const Scheme = "keycard" // 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(filepath.Join(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(filepath.Join(hub.datadir, "smartcards.json"), os.O_RDWR|os.O_CREATE, 0755) if err != nil { return err } defer pairingFile.Close() 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 nil } func (hub *Hub) pairing(wallet *Wallet) *smartcardPairing { if pairing, ok := hub.pairings[string(wallet.PublicKey)]; 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(daemonPath string, scheme string, datadir string) (*Hub, error) { context, err := pcsc.EstablishContext(daemonPath, 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) return } } // 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() } }