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|
// 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"
"sort"
"strings"
"sync"
"time"
"github.com/ebfe/scard"
ethereum "github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/accounts"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/crypto/secp256k1"
"github.com/ethereum/go-ethereum/log"
)
// ErrPUKNeeded is returned if opening the smart card requires pairing with a PUK
// code. In this case, the calling application should request user input to enter
// the PUK and send it back.
var ErrPUKNeeded = errors.New("smartcard: puk 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{0x53, 0x74, 0x61, 0x74, 0x75, 0x73, 0x57, 0x61, 0x6C, 0x6C, 0x65, 0x74, 0x41, 0x70, 0x70}
DerivationSignatureHash = sha256.Sum256([]byte("STATUS KEY DERIVATION"))
)
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
deriveP1Assisted = uint8(0x01)
deriveP1Append = uint8(0x80)
deriveP2KeyPath = uint8(0x00)
deriveP2PublicKey = uint8(0x01)
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.
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 *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
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 *scard.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 *scard.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 PUK", 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:
return fmt.Sprintf("Blocked, waiting for PUK and new PIN"), nil
case !w.session.verified:
return fmt.Sprintf("Locked, waiting for PIN (%d attempts left)", status.PinRetryCount), nil
case !status.Initialized:
return fmt.Sprintf("Empty, waiting for initialization"), nil
case status.SupportsPKDerivation:
return fmt.Sprintf("Online, can derive public keys"), nil
default:
return fmt.Sprintf("Online, cannot derive public keys"), 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 ErrPUKNeeded
}
// 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 becase 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 err := w.session.verifyPin([]byte(passphrase)); err != nil {
return err
}
default:
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
nextAddr = w.deriveNextAddr
nextPath = w.deriveNextPath
context = context.Background()
)
for empty := false; !empty; {
// Retrieve the next derived Ethereum account
if nextAddr == (common.Address{}) {
if nextAcc, err = w.session.derive(nextPath); err != nil {
w.log.Warn("Smartcard wallet account derivation failed", "err", err)
break
}
nextAddr = nextAcc.Address
}
// Check the account's status against the current chain state
var (
balance *big.Int
nonce uint64
)
balance, err = w.deriveChain.BalanceAt(context, nextAddr, nil)
if err != nil {
w.log.Warn("Smartcard wallet balance retrieval failed", "err", err)
break
}
nonce, err = w.deriveChain.NonceAt(context, nextAddr, 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 it nonetheless
if balance.Sign() == 0 && nonce == 0 {
empty = true
}
// We've just self-derived a new account, start tracking it locally
path := make(accounts.DerivationPath, len(nextPath))
copy(path[:], nextPath[:])
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", nextAddr, "path", path, "balance", balance, "nonce", nonce)
}
pairing.Accounts[nextAddr] = path
// Fetch the next potential account
if !empty {
nextAddr = common.Address{}
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
// 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 {
w.lock.Lock()
defer w.lock.Unlock()
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.
//
// You can disable automatic account discovery by calling SelfDerive with a nil
// chain state reader.
func (w *Wallet) SelfDerive(base accounts.DerivationPath, chain ethereum.ChainStateReader) {
w.lock.Lock()
defer w.lock.Unlock()
w.deriveNextPath = make(accounts.DerivationPath, len(base))
copy(w.deriveNextPath[:], base[:])
w.deriveNextAddr = common.Address{}
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(scard.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
SupportsPKDerivation bool // Whether the card supports doing public key derivation itself
}
// 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.
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 {
// 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) {
// If the current path is a prefix of the desired path, we don't have to
// start again.
remainingPath := path
pubkey, err := s.publicKey()
if err != nil {
return accounts.Account{}, err
}
currentPath, err := s.derivationPath()
if err != nil {
return accounts.Account{}, err
}
reset := false
if len(currentPath) <= len(path) {
for i := 0; i < len(currentPath); i++ {
if path[i] != currentPath[i] {
reset = true
break
}
}
if !reset {
remainingPath = path[len(currentPath):]
}
} else {
reset = true
}
for _, pathComponent := range remainingPath {
pubkey, err = s.deriveKeyAssisted(reset, pathComponent)
reset = false
if err != nil {
return accounts.Account{}, err
}
}
pub, err := crypto.UnmarshalPubkey(pubkey)
if err != nil {
return accounts.Account{}, err
}
return s.Wallet.makeAccount(crypto.PubkeyToAddress(*pub), path), nil
}
// keyDerivationInfo contains information on the current key derivation step.
type keyDerivationInfo struct {
PublicKeyX []byte `asn1:"tag:3"` // The X coordinate of the current public key
Signature struct {
R *big.Int
S *big.Int
}
}
// deriveKeyAssisted does one step of assisted key generation, asking the card to generate
// a specific path, and performing the necessary computations to finish the public key
// generation step.
func (s *Session) deriveKeyAssisted(reset bool, pathComponent uint32) ([]byte, error) {
p1 := deriveP1Assisted
if !reset {
p1 |= deriveP1Append
}
buf := new(bytes.Buffer)
if err := binary.Write(buf, binary.BigEndian, pathComponent); err != nil {
return nil, err
}
response, err := s.Channel.TransmitEncrypted(claSCWallet, insDeriveKey, p1, deriveP2KeyPath, buf.Bytes())
if err != nil {
return nil, err
}
keyinfo := new(keyDerivationInfo)
if _, err := asn1.UnmarshalWithParams(response.Data, keyinfo, "tag:2"); err != nil {
return nil, err
}
rbytes, sbytes := keyinfo.Signature.R.Bytes(), keyinfo.Signature.S.Bytes()
sig := make([]byte, 65)
copy(sig[32-len(rbytes):32], rbytes)
copy(sig[64-len(sbytes):64], sbytes)
pubkey, err := determinePublicKey(sig, keyinfo.PublicKeyX)
if err != nil {
return nil, err
}
_, err = s.Channel.TransmitEncrypted(claSCWallet, insDeriveKey, deriveP1Assisted|deriveP1Append, deriveP2PublicKey, pubkey)
if err != nil {
return nil, err
}
return pubkey, nil
}
// keyExport contains information on an exported keypair.
type keyExport struct {
PublicKey []byte `asn1:"tag:0"`
PrivateKey []byte `asn1:"tag:1,optional"`
}
// publicKey returns the public key for the current derivation path.
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
}
// determinePublicKey uses a signature and the X component of a public key to
// recover the entire public key.
func determinePublicKey(sig, pubkeyX []byte) ([]byte, error) {
for v := 0; v < 2; v++ {
sig[64] = byte(v)
pubkey, err := crypto.Ecrecover(DerivationSignatureHash[:], sig)
if err == nil {
if bytes.Equal(pubkey[1:33], pubkeyX) {
return pubkey, nil
}
} else if v == 1 || err != secp256k1.ErrRecoverFailed {
return nil, err
}
}
return nil, ErrPubkeyMismatch
}
// 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) {
for v := 0; v < 2; v++ {
sig[64] = byte(v)
pubkey, err := crypto.Ecrecover(hash, sig)
if err == nil {
if bytes.Equal(pubkey, expectedPubkey) {
return sig, nil
}
} else if v == 1 || err != secp256k1.ErrRecoverFailed {
return nil, err
}
}
return nil, ErrPubkeyMismatch
}
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