accounts/scwallet: ordered wallets, tighter events, derivation logs

accounts/scwallet/hub.go

@@ -36,14 +36,12 @@ import (
 	"encoding/json"
 	"io/ioutil"
 	"os"
-	"reflect"
 	"sync"
 	"time"
 
 	"github.com/ebfe/scard"
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/log"
 )
@@ -71,9 +69,10 @@ type smartcardPairing struct {
 type Hub struct {
 	scheme string // Protocol scheme prefixing account and wallet URLs.
 
-	context     *scard.Context
-	datadir     string
-	pairings    map[string]smartcardPairing
+	context  *scard.Context
+	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
@@ -82,11 +81,9 @@ type Hub struct {
 
 	quit chan chan error
 
-	stateLock sync.Mutex // Protects the internals of the hub from racey access
+	stateLock sync.RWMutex // Protects the internals of the hub from racey access
 }
 
-var HubType = reflect.TypeOf(&Hub{})
-
 func (hub *Hub) readPairings() error {
 	hub.pairings = make(map[string]smartcardPairing)
 	pairingFile, err := os.Open(hub.datadir + "/smartcards.json")
@@ -158,7 +155,6 @@ func NewHub(scheme string, datadir string) (*Hub, error) {
 	if err != nil {
 		return nil, err
 	}
-
 	hub := &Hub{
 		scheme:  scheme,
 		context: context,
@@ -166,28 +162,31 @@ func NewHub(scheme string, datadir string) (*Hub, error) {
 		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
-// devices that appear to be hardware wallets.
+// 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.stateLock.Lock()
-	defer hub.stateLock.Unlock()
-
 	hub.refreshWallets()
 
+	hub.stateLock.RLock()
+	defer hub.stateLock.RUnlock()
+
 	cpy := make([]accounts.Wallet, 0, len(hub.wallets))
 	for _, wallet := range hub.wallets {
-		if wallet != nil {
-			cpy = append(cpy, wallet)
+		cpy = append(cpy, wallet)
+	}
+	for i := 0; i < len(cpy); i++ {
+		for j := i + 1; j < len(cpy); j++ {
+			if cpy[i].URL().Cmp(cpy[j].URL()) > 0 {
+				cpy[i], cpy[j] = cpy[j], cpy[i]
+			}
 		}
 	}
 	return cpy
@@ -196,67 +195,77 @@ func (hub *Hub) Wallets() []accounts.Wallet {
 // 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 {
-		log.Error("Error listing readers", "err", err)
+		// 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 {
-			// We already know about this card; check it's still present
-			if err := wallet.ping(); err != nil {
-				log.Debug("Got error pinging wallet", "reader", reader, "err", err)
-			} else {
-				seen[reader] = struct{}{}
+			if err := wallet.ping(); err == nil {
+				continue
 			}
-			continue
+			wallet.Close()
+			events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletDropped})
+			delete(hub.wallets, reader)
 		}
-		seen[reader] = struct{}{}
-
+		// New card detected, try to connect to it
 		card, err := hub.context.Connect(reader, scard.ShareShared, scard.ProtocolAny)
 		if err != nil {
-			log.Debug("Error opening card", "reader", reader, "err", err)
+			log.Debug("Failed to open smart card", "reader", reader, "err", err)
 			continue
 		}
-
 		wallet := NewWallet(hub, card)
-		err = wallet.connect()
-		if err != nil {
-			log.Debug("Error connecting to wallet", "reader", reader, "err", err)
+		if err = wallet.connect(); err != nil {
+			log.Debug("Failed to connect to smart card", "reader", reader, "err", err)
 			card.Disconnect(scard.LeaveCard)
 			continue
 		}
-
+		// Card connected, start tracking in amongs the wallets
 		hub.wallets[reader] = wallet
 		events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletArrived})
-		log.Info("Found new smartcard wallet", "reader", reader, "publicKey", hexutil.Encode(wallet.PublicKey[:4]))
 	}
-
-	// Remove any wallets we no longer see
-	for k, wallet := range hub.wallets {
-		if _, ok := seen[k]; !ok {
-			log.Info("Wallet disconnected", "pubkey", hexutil.Encode(wallet.PublicKey[:4]), "reader", k)
+	// 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, k)
+			delete(hub.wallets, reader)
 		}
 	}
+	hub.refreshed = time.Now()
+	hub.stateLock.Unlock()
 
 	for _, event := range events {
 		hub.updateFeed.Send(event)
 	}
-	hub.refreshed = time.Now()
 }
 
 // Subscribe implements accounts.Backend, creating an async subscription to
-// receive notifications on the addition or removal of wallets.
+// 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()
@@ -274,16 +283,18 @@ func (hub *Hub) Subscribe(sink chan<- accounts.WalletEvent) event.Subscription {
 }
 
 // updater is responsible for maintaining an up-to-date list of wallets managed
-// by the hub, and for firing wallet addition/removal events.
+// 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.stateLock.Lock()
 		hub.refreshWallets()
 
 		// If all our subscribers left, stop the updater
+		hub.stateLock.Lock()
 		if hub.updateScope.Count() == 0 {
 			hub.updating = false
 			hub.stateLock.Unlock()

accounts/scwallet/wallet.go

@@ -93,10 +93,11 @@ type Wallet struct {
 	Hub       *Hub   // A handle to the Hub that instantiated this wallet.
 	PublicKey []byte // The wallet's public key (used for communication and identification, not signing!)
 
-	lock           sync.Mutex                // Lock that gates access to struct fields and communication with the card
-	card           *scard.Card               // A handle to the smartcard interface for the wallet.
-	session        *Session                  // The secure communication session with the card
-	log            log.Logger                // Contextual logger to tag the base with its id
+	lock    sync.Mutex  // Lock that gates access to struct fields and communication with the card
+	card    *scard.Card // A handle to the smartcard interface for the wallet.
+	session *Session    // The secure communication session with the card
+	log     log.Logger  // Contextual logger to tag the base with its id
+
 	deriveNextPath accounts.DerivationPath   // Next derivation path for account auto-discovery
 	deriveNextAddr common.Address            // Next derived account address for auto-discovery
 	deriveChain    ethereum.ChainStateReader // Blockchain state reader to discover used account with
@@ -273,7 +274,7 @@ func (w *Wallet) Unpair(pin []byte) error {
 func (w *Wallet) URL() accounts.URL {
 	return accounts.URL{
 		Scheme: w.Hub.scheme,
-		Path:   fmt.Sprintf("%x", w.PublicKey[1:3]),
+		Path:   fmt.Sprintf("%x", w.PublicKey[1:5]), // Byte #0 isn't unique; 1:5 covers << 64K cards, bump to 1:9 for << 4M
 	}
 }
 
@@ -327,7 +328,7 @@ func (w *Wallet) Open(passphrase string) error {
 			if err := w.session.authenticate(*pairing); err != nil {
 				return fmt.Errorf("failed to authenticate card %x: %s", w.PublicKey[:4], err)
 			}
-			return nil
+			return ErrPINNeeded
 		}
 		// If no passphrase was supplied, request the PUK from the user
 		if passphrase == "" {
@@ -389,8 +390,8 @@ func (w *Wallet) Close() error {
 // selfDerive is an account derivation loop that upon request attempts to find
 // new non-zero accounts.
 func (w *Wallet) selfDerive() {
-	w.log.Debug("Smartcard wallet self-derivation started")
-	defer w.log.Debug("Smartcard wallet self-derivation stopped")
+	w.log.Debug("Smart card wallet self-derivation started")
+	defer w.log.Debug("Smart card wallet self-derivation stopped")
 
 	// Execute self-derivations until termination or error
 	var (
@@ -418,21 +419,22 @@ func (w *Wallet) selfDerive() {
 
 		// Device lock obtained, derive the next batch of accounts
 		var (
-			paths       []accounts.DerivationPath
-			nextAccount accounts.Account
-			nextAddr    = w.deriveNextAddr
-			nextPath    = w.deriveNextPath
+			paths   []accounts.DerivationPath
+			nextAcc accounts.Account
+
+			nextAddr = w.deriveNextAddr
+			nextPath = w.deriveNextPath
 
 			context = context.Background()
 		)
 		for empty := false; !empty; {
 			// Retrieve the next derived Ethereum account
 			if nextAddr == (common.Address{}) {
-				if nextAccount, err = w.session.derive(nextPath); err != nil {
+				if nextAcc, err = w.session.derive(nextPath); err != nil {
 					w.log.Warn("Smartcard wallet account derivation failed", "err", err)
 					break
 				}
-				nextAddr = nextAccount.Address
+				nextAddr = nextAcc.Address
 			}
 			// Check the account's status against the current chain state
 			var (
@@ -459,8 +461,8 @@ func (w *Wallet) selfDerive() {
 			paths = append(paths, path)
 
 			// Display a log message to the user for new (or previously empty accounts)
-			if _, known := pairing.Accounts[nextAddr]; !known || (!empty && nextAddr == w.deriveNextAddr) {
-				w.log.Info("Smartcard wallet discovered new account", "address", nextAccount.Address, "path", path, "balance", balance, "nonce", nonce)
+			if _, known := pairing.Accounts[nextAddr]; !known || !empty || nextAddr != w.deriveNextAddr {
+				w.log.Info("Smartcard wallet discovered new account", "address", nextAddr, "path", path, "balance", balance, "nonce", nonce)
 			}
 			pairing.Accounts[nextAddr] = path
 
@@ -470,12 +472,10 @@ func (w *Wallet) selfDerive() {
 				nextPath[len(nextPath)-1]++
 			}
 		}
-
 		// If there are new accounts, write them out
 		if len(paths) > 0 {
 			err = w.Hub.setPairing(w, pairing)
 		}
-
 		// Shift the self-derivation forward
 		w.deriveNextAddr = nextAddr
 		w.deriveNextPath = nextPath
@@ -524,6 +524,13 @@ func (w *Wallet) Accounts() []accounts.Account {
 		for address, path := range pairing.Accounts {
 			ret = append(ret, w.makeAccount(address, path))
 		}
+		for i := 0; i < len(ret); i++ {
+			for j := i + 1; j < len(ret); j++ {
+				if ret[i].URL.Cmp(ret[j].URL) > 0 {
+					ret[i], ret[j] = ret[j], ret[i]
+				}
+			}
+		}
 		return ret
 	}
 	return nil