aboutsummaryrefslogblamecommitdiff
path: root/accounts/scwallet/wallet.go
blob: 2f08c1718458493d865c509596bc0ddf6dbf4d37 (plain) (tree)
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775



































                                                                                  


                                                  






























































































































                                                                                                                                 
                                                                                                                                                                 


















































































                                                                                            
                                                          

























































                                                                                                                                    
                                                            



                                                                                                                        
                                                               
                
                                    







































                                                                                                             
                                                                                                       
























































































































































































































































































































































































































                                                                                                                                                                        
                                                                                                                     


                                                         
                                                                             
































                                                                                            
                                                                             


































                                                                                                        
                                                                                                                                


























                                                                                                          
                                                              
















































































































                                                                                                            
                                                              




                                                                    
                                                              















































































                                                                                                                           
// 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/>.

package scwallet

import (
	"bytes"
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"crypto/sha512"
	"encoding/asn1"
	"encoding/binary"
	"errors"
	"fmt"
	"math/big"
	"regexp"
	"sort"
	"strings"
	"sync"
	"time"

	"github.com/ava-labs/coreth/accounts"
	"github.com/ava-labs/coreth/core/types"
	ethereum "github.com/ethereum/go-ethereum"
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/log"
	pcsc "github.com/gballet/go-libpcsclite"
	"github.com/status-im/keycard-go/derivationpath"
)

// ErrPairingPasswordNeeded is returned if opening the smart card requires pairing with a pairing
// password. In this case, the calling application should request user input to enter
// the pairing password and send it back.
var ErrPairingPasswordNeeded = errors.New("smartcard: pairing password needed")

// ErrPINNeeded is returned if opening the smart card requires a PIN code. In
// this case, the calling application should request user input to enter the PIN
// and send it back.
var ErrPINNeeded = errors.New("smartcard: pin needed")

// ErrPINUnblockNeeded is returned if opening the smart card requires a PIN code,
// but all PIN attempts have already been exhausted. In this case the calling
// application should request user input for the PUK and a new PIN code to set
// fo the card.
var ErrPINUnblockNeeded = errors.New("smartcard: pin unblock needed")

// ErrAlreadyOpen is returned if the smart card is attempted to be opened, but
// there is already a paired and unlocked session.
var ErrAlreadyOpen = errors.New("smartcard: already open")

// ErrPubkeyMismatch is returned if the public key recovered from a signature
// does not match the one expected by the user.
var ErrPubkeyMismatch = errors.New("smartcard: recovered public key mismatch")

var (
	appletAID = []byte{0xA0, 0x00, 0x00, 0x08, 0x04, 0x00, 0x01, 0x01, 0x01}
	// DerivationSignatureHash is used to derive the public key from the signature of this hash
	DerivationSignatureHash = sha256.Sum256(common.Hash{}.Bytes())
)

// List of APDU command-related constants
const (
	claISO7816  = 0
	claSCWallet = 0x80

	insSelect      = 0xA4
	insGetResponse = 0xC0
	sw1GetResponse = 0x61
	sw1Ok          = 0x90

	insVerifyPin  = 0x20
	insUnblockPin = 0x22
	insExportKey  = 0xC2
	insSign       = 0xC0
	insLoadKey    = 0xD0
	insDeriveKey  = 0xD1
	insStatus     = 0xF2
)

// List of ADPU command parameters
const (
	P1DeriveKeyFromMaster  = uint8(0x00)
	P1DeriveKeyFromParent  = uint8(0x01)
	P1DeriveKeyFromCurrent = uint8(0x10)
	statusP1WalletStatus   = uint8(0x00)
	statusP1Path           = uint8(0x01)
	signP1PrecomputedHash  = uint8(0x01)
	signP2OnlyBlock        = uint8(0x81)
	exportP1Any            = uint8(0x00)
	exportP2Pubkey         = uint8(0x01)
)

// Minimum time to wait between self derivation attempts, even it the user is
// requesting accounts like crazy.
const selfDeriveThrottling = time.Second

// Wallet represents a smartcard wallet instance.
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    *pcsc.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

	deriveNextPaths []accounts.DerivationPath // Next derivation paths for account auto-discovery (multiple bases supported)
	deriveNextAddrs []common.Address          // Next derived account addresses for auto-discovery (multiple bases supported)
	deriveChain     ethereum.ChainStateReader // Blockchain state reader to discover used account with
	deriveReq       chan chan struct{}        // Channel to request a self-derivation on
	deriveQuit      chan chan error           // Channel to terminate the self-deriver with
}

// NewWallet constructs and returns a new Wallet instance.
func NewWallet(hub *Hub, card *pcsc.Card) *Wallet {
	wallet := &Wallet{
		Hub:  hub,
		card: card,
	}
	return wallet
}

// transmit sends an APDU to the smartcard and receives and decodes the response.
// It automatically handles requests by the card to fetch the return data separately,
// and returns an error if the response status code is not success.
func transmit(card *pcsc.Card, command *commandAPDU) (*responseAPDU, error) {
	data, err := command.serialize()
	if err != nil {
		return nil, err
	}

	responseData, _, err := card.Transmit(data)
	if err != nil {
		return nil, err
	}

	response := new(responseAPDU)
	if err = response.deserialize(responseData); err != nil {
		return nil, err
	}

	// Are we being asked to fetch the response separately?
	if response.Sw1 == sw1GetResponse && (command.Cla != claISO7816 || command.Ins != insGetResponse) {
		return transmit(card, &commandAPDU{
			Cla:  claISO7816,
			Ins:  insGetResponse,
			P1:   0,
			P2:   0,
			Data: nil,
			Le:   response.Sw2,
		})
	}

	if response.Sw1 != sw1Ok {
		return nil, fmt.Errorf("unexpected insecure response status Cla=0x%x, Ins=0x%x, Sw=0x%x%x", command.Cla, command.Ins, response.Sw1, response.Sw2)
	}

	return response, nil
}

// applicationInfo encodes information about the smartcard application - its
// instance UID and public key.
type applicationInfo struct {
	InstanceUID []byte `asn1:"tag:15"`
	PublicKey   []byte `asn1:"tag:0"`
}

// connect connects to the wallet application and establishes a secure channel with it.
// must be called before any other interaction with the wallet.
func (w *Wallet) connect() error {
	w.lock.Lock()
	defer w.lock.Unlock()

	appinfo, err := w.doselect()
	if err != nil {
		return err
	}

	channel, err := NewSecureChannelSession(w.card, appinfo.PublicKey)
	if err != nil {
		return err
	}

	w.PublicKey = appinfo.PublicKey
	w.log = log.New("url", w.URL())
	w.session = &Session{
		Wallet:  w,
		Channel: channel,
	}
	return nil
}

// doselect is an internal (unlocked) function to send a SELECT APDU to the card.
func (w *Wallet) doselect() (*applicationInfo, error) {
	response, err := transmit(w.card, &commandAPDU{
		Cla:  claISO7816,
		Ins:  insSelect,
		P1:   4,
		P2:   0,
		Data: appletAID,
	})
	if err != nil {
		return nil, err
	}

	appinfo := new(applicationInfo)
	if _, err := asn1.UnmarshalWithParams(response.Data, appinfo, "tag:4"); err != nil {
		return nil, err
	}
	return appinfo, nil
}

// ping checks the card's status and returns an error if unsuccessful.
func (w *Wallet) ping() error {
	w.lock.Lock()
	defer w.lock.Unlock()

	// We can't ping if not paired
	if !w.session.paired() {
		return nil
	}
	if _, err := w.session.walletStatus(); err != nil {
		return err
	}
	return nil
}

// release releases any resources held by an open wallet instance.
func (w *Wallet) release() error {
	if w.session != nil {
		return w.session.release()
	}
	return nil
}

// pair is an internal (unlocked) function for establishing a new pairing
// with the wallet.
func (w *Wallet) pair(puk []byte) error {
	if w.session.paired() {
		return fmt.Errorf("wallet already paired")
	}
	pairing, err := w.session.pair(puk)
	if err != nil {
		return err
	}
	if err = w.Hub.setPairing(w, &pairing); err != nil {
		return err
	}
	return w.session.authenticate(pairing)
}

// Unpair deletes an existing wallet pairing.
func (w *Wallet) Unpair(pin []byte) error {
	w.lock.Lock()
	defer w.lock.Unlock()

	if !w.session.paired() {
		return fmt.Errorf("wallet %x not paired", w.PublicKey)
	}
	if err := w.session.verifyPin(pin); err != nil {
		return fmt.Errorf("failed to verify pin: %s", err)
	}
	if err := w.session.unpair(); err != nil {
		return fmt.Errorf("failed to unpair: %s", err)
	}
	if err := w.Hub.setPairing(w, nil); err != nil {
		return err
	}
	return nil
}

// URL retrieves the canonical path under which this wallet is reachable. It is
// user by upper layers to define a sorting order over all wallets from multiple
// backends.
func (w *Wallet) URL() accounts.URL {
	return accounts.URL{
		Scheme: w.Hub.scheme,
		Path:   fmt.Sprintf("%x", w.PublicKey[1:5]), // Byte #0 isn't unique; 1:5 covers << 64K cards, bump to 1:9 for << 4M
	}
}

// Status returns a textual status to aid the user in the current state of the
// wallet. It also returns an error indicating any failure the wallet might have
// encountered.
func (w *Wallet) Status() (string, error) {
	w.lock.Lock()
	defer w.lock.Unlock()

	// If the card is not paired, we can only wait
	if !w.session.paired() {
		return "Unpaired, waiting for pairing password", nil
	}
	// Yay, we have an encrypted session, retrieve the actual status
	status, err := w.session.walletStatus()
	if err != nil {
		return fmt.Sprintf("Failed: %v", err), err
	}
	switch {
	case !w.session.verified && status.PinRetryCount == 0 && status.PukRetryCount == 0:
		return "Bricked, waiting for full wipe", nil
	case !w.session.verified && status.PinRetryCount == 0:
		return fmt.Sprintf("Blocked, waiting for PUK (%d attempts left) and new PIN", status.PukRetryCount), nil
	case !w.session.verified:
		return fmt.Sprintf("Locked, waiting for PIN (%d attempts left)", status.PinRetryCount), nil
	case !status.Initialized:
		return "Empty, waiting for initialization", nil
	default:
		return "Online", nil
	}
}

// Open initializes access to a wallet instance. It is not meant to unlock or
// decrypt account keys, rather simply to establish a connection to hardware
// wallets and/or to access derivation seeds.
//
// The passphrase parameter may or may not be used by the implementation of a
// particular wallet instance. The reason there is no passwordless open method
// is to strive towards a uniform wallet handling, oblivious to the different
// backend providers.
//
// Please note, if you open a wallet, you must close it to release any allocated
// resources (especially important when working with hardware wallets).
func (w *Wallet) Open(passphrase string) error {
	w.lock.Lock()
	defer w.lock.Unlock()

	// If the session is already open, bail out
	if w.session.verified {
		return ErrAlreadyOpen
	}
	// If the smart card is not yet paired, attempt to do so either from a previous
	// pairing key or form the supplied PUK code.
	if !w.session.paired() {
		// If a previous pairing exists, only ever try to use that
		if pairing := w.Hub.pairing(w); pairing != nil {
			if err := w.session.authenticate(*pairing); err != nil {
				return fmt.Errorf("failed to authenticate card %x: %s", w.PublicKey[:4], err)
			}
			// Pairing still ok, fall through to PIN checks
		} else {
			// If no passphrase was supplied, request the PUK from the user
			if passphrase == "" {
				return ErrPairingPasswordNeeded
			}
			// Attempt to pair the smart card with the user supplied PUK
			if err := w.pair([]byte(passphrase)); err != nil {
				return err
			}
			// Pairing succeeded, fall through to PIN checks. This will of course fail,
			// but we can't return ErrPINNeeded directly here because we don't know whether
			// a PIN check or a PIN reset is needed.
			passphrase = ""
		}
	}
	// The smart card was successfully paired, retrieve its status to check whether
	// PIN verification or unblocking is needed.
	status, err := w.session.walletStatus()
	if err != nil {
		return err
	}
	// Request the appropriate next authentication data, or use the one supplied
	switch {
	case passphrase == "" && status.PinRetryCount > 0:
		return ErrPINNeeded
	case passphrase == "":
		return ErrPINUnblockNeeded
	case status.PinRetryCount > 0:
		if !regexp.MustCompile(`^[0-9]{6,}$`).MatchString(passphrase) {
			w.log.Error("PIN needs to be at least 6 digits")
			return ErrPINNeeded
		}
		if err := w.session.verifyPin([]byte(passphrase)); err != nil {
			return err
		}
	default:
		if !regexp.MustCompile(`^[0-9]{12,}$`).MatchString(passphrase) {
			w.log.Error("PUK needs to be at least 12 digits")
			return ErrPINUnblockNeeded
		}
		if err := w.session.unblockPin([]byte(passphrase)); err != nil {
			return err
		}
	}
	// Smart card paired and unlocked, initialize and register
	w.deriveReq = make(chan chan struct{})
	w.deriveQuit = make(chan chan error)

	go w.selfDerive()

	// Notify anyone listening for wallet events that a new device is accessible
	go w.Hub.updateFeed.Send(accounts.WalletEvent{Wallet: w, Kind: accounts.WalletOpened})

	return nil
}

// Close stops and closes the wallet, freeing any resources.
func (w *Wallet) Close() error {
	// Ensure the wallet was opened
	w.lock.Lock()
	dQuit := w.deriveQuit
	w.lock.Unlock()

	// Terminate the self-derivations
	var derr error
	if dQuit != nil {
		errc := make(chan error)
		dQuit <- errc
		derr = <-errc // Save for later, we *must* close the USB
	}
	// Terminate the device connection
	w.lock.Lock()
	defer w.lock.Unlock()

	w.deriveQuit = nil
	w.deriveReq = nil

	if err := w.release(); err != nil {
		return err
	}
	return derr
}

// selfDerive is an account derivation loop that upon request attempts to find
// new non-zero accounts.
func (w *Wallet) selfDerive() {
	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 (
		reqc chan struct{}
		errc chan error
		err  error
	)
	for errc == nil && err == nil {
		// Wait until either derivation or termination is requested
		select {
		case errc = <-w.deriveQuit:
			// Termination requested
			continue
		case reqc = <-w.deriveReq:
			// Account discovery requested
		}
		// Derivation needs a chain and device access, skip if either unavailable
		w.lock.Lock()
		if w.session == nil || w.deriveChain == nil {
			w.lock.Unlock()
			reqc <- struct{}{}
			continue
		}
		pairing := w.Hub.pairing(w)

		// Device lock obtained, derive the next batch of accounts
		var (
			paths   []accounts.DerivationPath
			nextAcc accounts.Account

			nextPaths = append([]accounts.DerivationPath{}, w.deriveNextPaths...)
			nextAddrs = append([]common.Address{}, w.deriveNextAddrs...)

			context = context.Background()
		)
		for i := 0; i < len(nextAddrs); i++ {
			for empty := false; !empty; {
				// Retrieve the next derived Ethereum account
				if nextAddrs[i] == (common.Address{}) {
					if nextAcc, err = w.session.derive(nextPaths[i]); err != nil {
						w.log.Warn("Smartcard wallet account derivation failed", "err", err)
						break
					}
					nextAddrs[i] = nextAcc.Address
				}
				// Check the account's status against the current chain state
				var (
					balance *big.Int
					nonce   uint64
				)
				balance, err = w.deriveChain.BalanceAt(context, nextAddrs[i], nil)
				if err != nil {
					w.log.Warn("Smartcard wallet balance retrieval failed", "err", err)
					break
				}
				nonce, err = w.deriveChain.NonceAt(context, nextAddrs[i], nil)
				if err != nil {
					w.log.Warn("Smartcard wallet nonce retrieval failed", "err", err)
					break
				}
				// If the next account is empty, stop self-derivation, but add for the last base path
				if balance.Sign() == 0 && nonce == 0 {
					empty = true
					if i < len(nextAddrs)-1 {
						break
					}
				}
				// We've just self-derived a new account, start tracking it locally
				path := make(accounts.DerivationPath, len(nextPaths[i]))
				copy(path[:], nextPaths[i][:])
				paths = append(paths, path)

				// Display a log message to the user for new (or previously empty accounts)
				if _, known := pairing.Accounts[nextAddrs[i]]; !known || !empty || nextAddrs[i] != w.deriveNextAddrs[i] {
					w.log.Info("Smartcard wallet discovered new account", "address", nextAddrs[i], "path", path, "balance", balance, "nonce", nonce)
				}
				pairing.Accounts[nextAddrs[i]] = path

				// Fetch the next potential account
				if !empty {
					nextAddrs[i] = common.Address{}
					nextPaths[i][len(nextPaths[i])-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.deriveNextAddrs = nextAddrs
		w.deriveNextPaths = nextPaths

		// Self derivation complete, release device lock
		w.lock.Unlock()

		// Notify the user of termination and loop after a bit of time (to avoid trashing)
		reqc <- struct{}{}
		if err == nil {
			select {
			case errc = <-w.deriveQuit:
				// Termination requested, abort
			case <-time.After(selfDeriveThrottling):
				// Waited enough, willing to self-derive again
			}
		}
	}
	// In case of error, wait for termination
	if err != nil {
		w.log.Debug("Smartcard wallet self-derivation failed", "err", err)
		errc = <-w.deriveQuit
	}
	errc <- err
}

// Accounts retrieves the list of signing accounts the wallet is currently aware
// of. For hierarchical deterministic wallets, the list will not be exhaustive,
// rather only contain the accounts explicitly pinned during account derivation.
func (w *Wallet) Accounts() []accounts.Account {
	// Attempt self-derivation if it's running
	reqc := make(chan struct{}, 1)
	select {
	case w.deriveReq <- reqc:
		// Self-derivation request accepted, wait for it
		<-reqc
	default:
		// Self-derivation offline, throttled or busy, skip
	}

	w.lock.Lock()
	defer w.lock.Unlock()

	if pairing := w.Hub.pairing(w); pairing != nil {
		ret := make([]accounts.Account, 0, len(pairing.Accounts))
		for address, path := range pairing.Accounts {
			ret = append(ret, w.makeAccount(address, path))
		}
		sort.Sort(accounts.AccountsByURL(ret))
		return ret
	}
	return nil
}

func (w *Wallet) makeAccount(address common.Address, path accounts.DerivationPath) accounts.Account {
	return accounts.Account{
		Address: address,
		URL: accounts.URL{
			Scheme: w.Hub.scheme,
			Path:   fmt.Sprintf("%x/%s", w.PublicKey[1:3], path.String()),
		},
	}
}

// Contains returns whether an account is part of this particular wallet or not.
func (w *Wallet) Contains(account accounts.Account) bool {
	if pairing := w.Hub.pairing(w); pairing != nil {
		_, ok := pairing.Accounts[account.Address]
		return ok
	}
	return false
}

// Initialize installs a keypair generated from the provided key into the wallet.
func (w *Wallet) Initialize(seed []byte) error {
	go w.selfDerive()
	// DO NOT lock at this stage, as the initialize
	// function relies on Status()
	return w.session.initialize(seed)
}

// Derive attempts to explicitly derive a hierarchical deterministic account at
// the specified derivation path. If requested, the derived account will be added
// to the wallet's tracked account list.
func (w *Wallet) Derive(path accounts.DerivationPath, pin bool) (accounts.Account, error) {
	w.lock.Lock()
	defer w.lock.Unlock()

	account, err := w.session.derive(path)
	if err != nil {
		return accounts.Account{}, err
	}

	if pin {
		pairing := w.Hub.pairing(w)
		pairing.Accounts[account.Address] = path
		if err := w.Hub.setPairing(w, pairing); err != nil {
			return accounts.Account{}, err
		}
	}

	return account, nil
}

// SelfDerive sets a base account derivation path from which the wallet attempts
// to discover non zero accounts and automatically add them to list of tracked
// accounts.
//
// Note, self derivaton will increment the last component of the specified path
// opposed to decending into a child path to allow discovering accounts starting
// from non zero components.
//
// Some hardware wallets switched derivation paths through their evolution, so
// this method supports providing multiple bases to discover old user accounts
// too. Only the last base will be used to derive the next empty account.
//
// You can disable automatic account discovery by calling SelfDerive with a nil
// chain state reader.
func (w *Wallet) SelfDerive(bases []accounts.DerivationPath, chain ethereum.ChainStateReader) {
	w.lock.Lock()
	defer w.lock.Unlock()

	w.deriveNextPaths = make([]accounts.DerivationPath, len(bases))
	for i, base := range bases {
		w.deriveNextPaths[i] = make(accounts.DerivationPath, len(base))
		copy(w.deriveNextPaths[i][:], base[:])
	}
	w.deriveNextAddrs = make([]common.Address, len(bases))
	w.deriveChain = chain
}

// SignData requests the wallet to sign the hash of the given data.
//
// It looks up the account specified either solely via its address contained within,
// or optionally with the aid of any location metadata from the embedded URL field.
//
// If the wallet requires additional authentication to sign the request (e.g.
// a password to decrypt the account, or a PIN code o verify the transaction),
// an AuthNeededError instance will be returned, containing infos for the user
// about which fields or actions are needed. The user may retry by providing
// the needed details via SignDataWithPassphrase, or by other means (e.g. unlock
// the account in a keystore).
func (w *Wallet) SignData(account accounts.Account, mimeType string, data []byte) ([]byte, error) {
	return w.signHash(account, crypto.Keccak256(data))
}

func (w *Wallet) signHash(account accounts.Account, hash []byte) ([]byte, error) {
	w.lock.Lock()
	defer w.lock.Unlock()

	path, err := w.findAccountPath(account)
	if err != nil {
		return nil, err
	}

	return w.session.sign(path, hash)
}

// SignTx requests the wallet to sign the given transaction.
//
// It looks up the account specified either solely via its address contained within,
// or optionally with the aid of any location metadata from the embedded URL field.
//
// If the wallet requires additional authentication to sign the request (e.g.
// a password to decrypt the account, or a PIN code o verify the transaction),
// an AuthNeededError instance will be returned, containing infos for the user
// about which fields or actions are needed. The user may retry by providing
// the needed details via SignTxWithPassphrase, or by other means (e.g. unlock
// the account in a keystore).
func (w *Wallet) SignTx(account accounts.Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
	signer := types.NewEIP155Signer(chainID)
	hash := signer.Hash(tx)
	sig, err := w.signHash(account, hash[:])
	if err != nil {
		return nil, err
	}
	return tx.WithSignature(signer, sig)
}

// SignDataWithPassphrase requests the wallet to sign the given hash with the
// given passphrase as extra authentication information.
//
// It looks up the account specified either solely via its address contained within,
// or optionally with the aid of any location metadata from the embedded URL field.
func (w *Wallet) SignDataWithPassphrase(account accounts.Account, passphrase, mimeType string, data []byte) ([]byte, error) {
	return w.signHashWithPassphrase(account, passphrase, crypto.Keccak256(data))
}

func (w *Wallet) signHashWithPassphrase(account accounts.Account, passphrase string, hash []byte) ([]byte, error) {
	if !w.session.verified {
		if err := w.Open(passphrase); err != nil {
			return nil, err
		}
	}

	return w.signHash(account, hash)
}

// SignText requests the wallet to sign the hash of a given piece of data, prefixed
// by the Ethereum prefix scheme
// It looks up the account specified either solely via its address contained within,
// or optionally with the aid of any location metadata from the embedded URL field.
//
// If the wallet requires additional authentication to sign the request (e.g.
// a password to decrypt the account, or a PIN code o verify the transaction),
// an AuthNeededError instance will be returned, containing infos for the user
// about which fields or actions are needed. The user may retry by providing
// the needed details via SignHashWithPassphrase, or by other means (e.g. unlock
// the account in a keystore).
func (w *Wallet) SignText(account accounts.Account, text []byte) ([]byte, error) {
	return w.signHash(account, accounts.TextHash(text))
}

// SignTextWithPassphrase implements accounts.Wallet, attempting to sign the
// given hash with the given account using passphrase as extra authentication
func (w *Wallet) SignTextWithPassphrase(account accounts.Account, passphrase string, text []byte) ([]byte, error) {
	return w.signHashWithPassphrase(account, passphrase, crypto.Keccak256(accounts.TextHash(text)))
}

// SignTxWithPassphrase requests the wallet to sign the given transaction, with the
// given passphrase as extra authentication information.
//
// It looks up the account specified either solely via its address contained within,
// or optionally with the aid of any location metadata from the embedded URL field.
func (w *Wallet) SignTxWithPassphrase(account accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
	if !w.session.verified {
		if err := w.Open(passphrase); err != nil {
			return nil, err
		}
	}
	return w.SignTx(account, tx, chainID)
}

// findAccountPath returns the derivation path for the provided account.
// It first checks for the address in the list of pinned accounts, and if it is
// not found, attempts to parse the derivation path from the account's URL.
func (w *Wallet) findAccountPath(account accounts.Account) (accounts.DerivationPath, error) {
	pairing := w.Hub.pairing(w)
	if path, ok := pairing.Accounts[account.Address]; ok {
		return path, nil
	}

	// Look for the path in the URL
	if account.URL.Scheme != w.Hub.scheme {
		return nil, fmt.Errorf("scheme %s does not match wallet scheme %s", account.URL.Scheme, w.Hub.scheme)
	}

	parts := strings.SplitN(account.URL.Path, "/", 2)
	if len(parts) != 2 {
		return nil, fmt.Errorf("invalid URL format: %s", account.URL)
	}

	if parts[0] != fmt.Sprintf("%x", w.PublicKey[1:3]) {
		return nil, fmt.Errorf("URL %s is not for this wallet", account.URL)
	}

	return accounts.ParseDerivationPath(parts[1])
}

// Session represents a secured communication session with the wallet.
type Session struct {
	Wallet   *Wallet               // A handle to the wallet that opened the session
	Channel  *SecureChannelSession // A secure channel for encrypted messages
	verified bool                  // Whether the pin has been verified in this session.
}

// pair establishes a new pairing over this channel, using the provided secret.
func (s *Session) pair(secret []byte) (smartcardPairing, error) {
	err := s.Channel.Pair(secret)
	if err != nil {
		return smartcardPairing{}, err
	}

	return smartcardPairing{
		PublicKey:    s.Wallet.PublicKey,
		PairingIndex: s.Channel.PairingIndex,
		PairingKey:   s.Channel.PairingKey,
		Accounts:     make(map[common.Address]accounts.DerivationPath),
	}, nil
}

// unpair deletes an existing pairing.
func (s *Session) unpair() error {
	if !s.verified {
		return fmt.Errorf("unpair requires that the PIN be verified")
	}
	return s.Channel.Unpair()
}

// verifyPin unlocks a wallet with the provided pin.
func (s *Session) verifyPin(pin []byte) error {
	if _, err := s.Channel.transmitEncrypted(claSCWallet, insVerifyPin, 0, 0, pin); err != nil {
		return err
	}
	s.verified = true
	return nil
}

// unblockPin unblocks a wallet with the provided puk and resets the pin to the
// new one specified.
func (s *Session) unblockPin(pukpin []byte) error {
	if _, err := s.Channel.transmitEncrypted(claSCWallet, insUnblockPin, 0, 0, pukpin); err != nil {
		return err
	}
	s.verified = true
	return nil
}

// release releases resources associated with the channel.
func (s *Session) release() error {
	return s.Wallet.card.Disconnect(pcsc.LeaveCard)
}

// paired returns true if a valid pairing exists.
func (s *Session) paired() bool {
	return s.Channel.PairingKey != nil
}

// authenticate uses an existing pairing to establish a secure channel.
func (s *Session) authenticate(pairing smartcardPairing) error {
	if !bytes.Equal(s.Wallet.PublicKey, pairing.PublicKey) {
		return fmt.Errorf("cannot pair using another wallet's pairing; %x != %x", s.Wallet.PublicKey, pairing.PublicKey)
	}
	s.Channel.PairingKey = pairing.PairingKey
	s.Channel.PairingIndex = pairing.PairingIndex
	return s.Channel.Open()
}

// walletStatus describes a smartcard wallet's status information.
type walletStatus struct {
	PinRetryCount int  // Number of remaining PIN retries
	PukRetryCount int  // Number of remaining PUK retries
	Initialized   bool // Whether the card has been initialized with a private key
}

// walletStatus fetches the wallet's status from the card.
func (s *Session) walletStatus() (*walletStatus, error) {
	response, err := s.Channel.transmitEncrypted(claSCWallet, insStatus, statusP1WalletStatus, 0, nil)
	if err != nil {
		return nil, err
	}

	status := new(walletStatus)
	if _, err := asn1.UnmarshalWithParams(response.Data, status, "tag:3"); err != nil {
		return nil, err
	}
	return status, nil
}

// derivationPath fetches the wallet's current derivation path from the card.
//lint:ignore U1000 needs to be added to the console interface
func (s *Session) derivationPath() (accounts.DerivationPath, error) {
	response, err := s.Channel.transmitEncrypted(claSCWallet, insStatus, statusP1Path, 0, nil)
	if err != nil {
		return nil, err
	}
	buf := bytes.NewReader(response.Data)
	path := make(accounts.DerivationPath, len(response.Data)/4)
	return path, binary.Read(buf, binary.BigEndian, &path)
}

// initializeData contains data needed to initialize the smartcard wallet.
type initializeData struct {
	PublicKey  []byte `asn1:"tag:0"`
	PrivateKey []byte `asn1:"tag:1"`
	ChainCode  []byte `asn1:"tag:2"`
}

// initialize initializes the card with new key data.
func (s *Session) initialize(seed []byte) error {
	// Check that the wallet isn't currently initialized,
	// otherwise the key would be overwritten.
	status, err := s.Wallet.Status()
	if err != nil {
		return err
	}
	if status == "Online" {
		return fmt.Errorf("card is already initialized, cowardly refusing to proceed")
	}

	s.Wallet.lock.Lock()
	defer s.Wallet.lock.Unlock()

	// HMAC the seed to produce the private key and chain code
	mac := hmac.New(sha512.New, []byte("Bitcoin seed"))
	mac.Write(seed)
	seed = mac.Sum(nil)

	key, err := crypto.ToECDSA(seed[:32])
	if err != nil {
		return err
	}

	id := initializeData{}
	id.PublicKey = crypto.FromECDSAPub(&key.PublicKey)
	id.PrivateKey = seed[:32]
	id.ChainCode = seed[32:]
	data, err := asn1.Marshal(id)
	if err != nil {
		return err
	}

	// Nasty hack to force the top-level struct tag to be context-specific
	data[0] = 0xA1

	_, err = s.Channel.transmitEncrypted(claSCWallet, insLoadKey, 0x02, 0, data)
	return err
}

// derive derives a new HD key path on the card.
func (s *Session) derive(path accounts.DerivationPath) (accounts.Account, error) {
	startingPoint, path, err := derivationpath.Decode(path.String())
	if err != nil {
		return accounts.Account{}, err
	}

	var p1 uint8
	switch startingPoint {
	case derivationpath.StartingPointMaster:
		p1 = P1DeriveKeyFromMaster
	case derivationpath.StartingPointParent:
		p1 = P1DeriveKeyFromParent
	case derivationpath.StartingPointCurrent:
		p1 = P1DeriveKeyFromCurrent
	default:
		return accounts.Account{}, fmt.Errorf("invalid startingPoint %d", startingPoint)
	}

	data := new(bytes.Buffer)
	for _, segment := range path {
		if err := binary.Write(data, binary.BigEndian, segment); err != nil {
			return accounts.Account{}, err
		}
	}

	_, err = s.Channel.transmitEncrypted(claSCWallet, insDeriveKey, p1, 0, data.Bytes())
	if err != nil {
		return accounts.Account{}, err
	}

	response, err := s.Channel.transmitEncrypted(claSCWallet, insSign, 0, 0, DerivationSignatureHash[:])
	if err != nil {
		return accounts.Account{}, err
	}

	sigdata := new(signatureData)
	if _, err := asn1.UnmarshalWithParams(response.Data, sigdata, "tag:0"); err != nil {
		return accounts.Account{}, err
	}
	rbytes, sbytes := sigdata.Signature.R.Bytes(), sigdata.Signature.S.Bytes()
	sig := make([]byte, 65)
	copy(sig[32-len(rbytes):32], rbytes)
	copy(sig[64-len(sbytes):64], sbytes)

	if err := confirmPublicKey(sig, sigdata.PublicKey); err != nil {
		return accounts.Account{}, err
	}
	pub, err := crypto.UnmarshalPubkey(sigdata.PublicKey)
	if err != nil {
		return accounts.Account{}, err
	}
	return s.Wallet.makeAccount(crypto.PubkeyToAddress(*pub), path), nil
}

// keyExport contains information on an exported keypair.
//lint:ignore U1000 needs to be added to the console interface
type keyExport struct {
	PublicKey  []byte `asn1:"tag:0"`
	PrivateKey []byte `asn1:"tag:1,optional"`
}

// publicKey returns the public key for the current derivation path.
//lint:ignore U1000 needs to be added to the console interface
func (s *Session) publicKey() ([]byte, error) {
	response, err := s.Channel.transmitEncrypted(claSCWallet, insExportKey, exportP1Any, exportP2Pubkey, nil)
	if err != nil {
		return nil, err
	}
	keys := new(keyExport)
	if _, err := asn1.UnmarshalWithParams(response.Data, keys, "tag:1"); err != nil {
		return nil, err
	}
	return keys.PublicKey, nil
}

// signatureData contains information on a signature - the signature itself and
// the corresponding public key.
type signatureData struct {
	PublicKey []byte `asn1:"tag:0"`
	Signature struct {
		R *big.Int
		S *big.Int
	}
}

// sign asks the card to sign a message, and returns a valid signature after
// recovering the v value.
func (s *Session) sign(path accounts.DerivationPath, hash []byte) ([]byte, error) {
	startTime := time.Now()
	_, err := s.derive(path)
	if err != nil {
		return nil, err
	}
	deriveTime := time.Now()

	response, err := s.Channel.transmitEncrypted(claSCWallet, insSign, signP1PrecomputedHash, signP2OnlyBlock, hash)
	if err != nil {
		return nil, err
	}
	sigdata := new(signatureData)
	if _, err := asn1.UnmarshalWithParams(response.Data, sigdata, "tag:0"); err != nil {
		return nil, err
	}
	// Serialize the signature
	rbytes, sbytes := sigdata.Signature.R.Bytes(), sigdata.Signature.S.Bytes()
	sig := make([]byte, 65)
	copy(sig[32-len(rbytes):32], rbytes)
	copy(sig[64-len(sbytes):64], sbytes)

	// Recover the V value.
	sig, err = makeRecoverableSignature(hash, sig, sigdata.PublicKey)
	if err != nil {
		return nil, err
	}
	log.Debug("Signed using smartcard", "deriveTime", deriveTime.Sub(startTime), "signingTime", time.Since(deriveTime))

	return sig, nil
}

// confirmPublicKey confirms that the given signature belongs to the specified key.
func confirmPublicKey(sig, pubkey []byte) error {
	_, err := makeRecoverableSignature(DerivationSignatureHash[:], sig, pubkey)
	return err
}

// makeRecoverableSignature uses a signature and an expected public key to
// recover the v value and produce a recoverable signature.
func makeRecoverableSignature(hash, sig, expectedPubkey []byte) ([]byte, error) {
	var libraryError error
	for v := 0; v < 2; v++ {
		sig[64] = byte(v)
		if pubkey, err := crypto.Ecrecover(hash, sig); err == nil {
			if bytes.Equal(pubkey, expectedPubkey) {
				return sig, nil
			}
		} else {
			libraryError = err
		}
	}
	if libraryError != nil {
		return nil, libraryError
	}
	return nil, ErrPubkeyMismatch
}