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