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Diffstat (limited to 'accounts/scwallet/hub.go')
| -rw-r--r-- | accounts/scwallet/hub.go | 302 |
1 files changed, 302 insertions, 0 deletions
diff --git a/accounts/scwallet/hub.go b/accounts/scwallet/hub.go new file mode 100644 index 0000000..ceb422c --- /dev/null +++ b/accounts/scwallet/hub.go @@ -0,0 +1,302 @@ +// 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() + } +} |