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removed accounts/scwallet

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Signed-off-by: Leo Chen <leo@harmony.one>
pull/832/head
Leo Chen 6 years ago
parent d794c7bcc1
commit 57b599d208
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  1. 102
      accounts/scwallet/README.md
  2. 87
      accounts/scwallet/apdu.go
  3. 302
      accounts/scwallet/hub.go
  4. 346
      accounts/scwallet/securechannel.go
  5. 1082
      accounts/scwallet/wallet.go

102
accounts/scwallet/README.md
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# Using the smartcard wallet
## Requirements
* A USB smartcard reader
* A keycard that supports the status app
* PCSCD version 4.3 running on your system **Only version 4.3 is currently supported**
## Preparing the smartcard
**WARNING: FOILLOWING THESE INSTRUCTIONS WILL DESTROY THE MASTER KEY ON YOUR CARD. ONLY PROCEED IF NO FUNDS ARE ASSOCIATED WITH THESE ACCOUNTS**
You can use status' [keycard-cli](https://github.com/status-im/keycard-cli) and you should get _at least_ version 2.1.1 of their [smartcard application](https://github.com/status-im/status-keycard/releases/download/2.2.1/keycard_v2.2.1.cap)
You also need to make sure that the PCSC daemon is running on your system.
Then, you can install the application to the card by typing:
```
keycard install -a keycard_v2.2.1.cap && keycard init
```
At the end of this process, you will be provided with a PIN, a PUK and a pairing password. Write them down, you'll need them shortly.
Start `geth` with the `console` command. You will notice the following warning:
```
WARN [04-09|16:58:38.898] Failed to open wallet url=pcsc://044def09 err="smartcard: pairing password needed"
```
Write down the URL (`pcsc://044def09` in this example). Then ask `geth` to open the wallet:
```
> personal.openWallet("pcsc://044def09")
Please enter the pairing password:
```
Enter the pairing password that you have received during card initialization. Same with the PIN that you will subsequently be
asked for.
If everything goes well, you should see your new account when typing `personal` on the console:
```
> personal
WARN [04-09|17:02:07.330] Smartcard wallet account derivation failed url=pcsc://044def09 err="Unexpected response status Cla=0x80, Ins=0xd1, Sw=0x6985"
{
listAccounts: [],
listWallets: [{
status: "Empty, waiting for initialization",
url: "pcsc://044def09"
}],
...
}
```
So the communication with the card is working, but there is no key associated with this wallet. Let's create it:
```
> personal.initializeWallet("pcsc://044def09")
"tilt ... impact"
```
You should get a list of words, this is your seed so write them down. Your wallet should now be initialized:
```
> personal.listWallets
[{
accounts: [{
address: "0x678b7cd55c61917defb23546a41803c5bfefbc7a",
url: "pcsc://044d/m/44'/60'/0'/0/0"
}],
status: "Online",
url: "pcsc://044def09"
}]
```
You're all set!
## Usage
1. Start `geth` with the `console` command
2. Check the card's URL by checking `personal.listWallets`:
```
listWallets: [{
status: "Online, can derive public keys",
url: "pcsc://a4d73015"
}]
```
3. Open the wallet, you will be prompted for your pairing password, then PIN:
```
personal.openWallet("pcsc://a4d73015")
```
4. Check that creation was successful by typing e.g. `personal`. Then use it like a regular wallet.
## Known issues
* Starting geth with a valid card seems to make firefox crash.
* PCSC version 4.4 should work, but is currently untested

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accounts/scwallet/apdu.go
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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"
"encoding/binary"
"fmt"
)
// commandAPDU represents an application data unit sent to a smartcard.
type commandAPDU struct {
Cla, Ins, P1, P2 uint8 // Class, Instruction, Parameter 1, Parameter 2
Data []byte // Command data
Le uint8 // Command data length
}
// serialize serializes a command APDU.
func (ca commandAPDU) serialize() ([]byte, error) {
buf := new(bytes.Buffer)
if err := binary.Write(buf, binary.BigEndian, ca.Cla); err != nil {
return nil, err
}
if err := binary.Write(buf, binary.BigEndian, ca.Ins); err != nil {
return nil, err
}
if err := binary.Write(buf, binary.BigEndian, ca.P1); err != nil {
return nil, err
}
if err := binary.Write(buf, binary.BigEndian, ca.P2); err != nil {
return nil, err
}
if len(ca.Data) > 0 {
if err := binary.Write(buf, binary.BigEndian, uint8(len(ca.Data))); err != nil {
return nil, err
}
if err := binary.Write(buf, binary.BigEndian, ca.Data); err != nil {
return nil, err
}
}
if err := binary.Write(buf, binary.BigEndian, ca.Le); err != nil {
return nil, err
}
return buf.Bytes(), nil
}
// responseAPDU represents an application data unit received from a smart card.
type responseAPDU struct {
Data []byte // response data
Sw1, Sw2 uint8 // status words 1 and 2
}
// deserialize deserializes a response APDU.
func (ra *responseAPDU) deserialize(data []byte) error {
if len(data) < 2 {
return fmt.Errorf("can not deserialize data: payload too short (%d < 2)", len(data))
}
ra.Data = make([]byte, len(data)-2)
buf := bytes.NewReader(data)
if err := binary.Read(buf, binary.BigEndian, &ra.Data); err != nil {
return err
}
if err := binary.Read(buf, binary.BigEndian, &ra.Sw1); err != nil {
return err
}
if err := binary.Read(buf, binary.BigEndian, &ra.Sw2); err != nil {
return err
}
return nil
}

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accounts/scwallet/hub.go
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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/>.
// This package implements support for smartcard-based hardware wallets such as
// the one written by Status: https://github.com/status-im/hardware-wallet
//
// This implementation of smartcard wallets have a different interaction process
// to other types of hardware wallet. The process works like this:
//
// 1. (First use with a given client) Establish a pairing between hardware
// wallet and client. This requires a secret value called a 'pairing password'.
// You can pair with an unpaired wallet with `personal.openWallet(URI, pairing password)`.
// 2. (First use only) Initialize the wallet, which generates a keypair, stores
// it on the wallet, and returns it so the user can back it up. You can
// initialize a wallet with `personal.initializeWallet(URI)`.
// 3. Connect to the wallet using the pairing information established in step 1.
// You can connect to a paired wallet with `personal.openWallet(URI, PIN)`.
// 4. Interact with the wallet as normal.
package scwallet
import (
"encoding/json"
"io/ioutil"
"os"
"path/filepath"
"sort"
"sync"
"time"
"github.com/ethereum/go-ethereum/accounts"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/log"
pcsc "github.com/gballet/go-libpcsclite"
)
// Scheme is the URI prefix for smartcard wallets.
const Scheme = "pcsc"
// refreshCycle is the maximum time between wallet refreshes (if USB hotplug
// notifications don't work).
const refreshCycle = time.Second
// refreshThrottling is the minimum time between wallet refreshes to avoid thrashing.
const refreshThrottling = 500 * time.Millisecond
// smartcardPairing contains information about a smart card we have paired with
// or might pair with the hub.
type smartcardPairing struct {
PublicKey []byte `json:"publicKey"`
PairingIndex uint8 `json:"pairingIndex"`
PairingKey []byte `json:"pairingKey"`
Accounts map[common.Address]accounts.DerivationPath `json:"accounts"`
}
// Hub is a accounts.Backend that can find and handle generic PC/SC hardware wallets.
type Hub struct {
scheme string // Protocol scheme prefixing account and wallet URLs.
context *pcsc.Client
datadir string
pairings map[string]smartcardPairing
refreshed time.Time // Time instance when the list of wallets was last refreshed
wallets map[string]*Wallet // Mapping from reader names to wallet instances
updateFeed event.Feed // Event feed to notify wallet additions/removals
updateScope event.SubscriptionScope // Subscription scope tracking current live listeners
updating bool // Whether the event notification loop is running
quit chan chan error
stateLock sync.RWMutex // Protects the internals of the hub from racey access
}
func (hub *Hub) readPairings() error {
hub.pairings = make(map[string]smartcardPairing)
pairingFile, err := os.Open(filepath.Join(hub.datadir, "smartcards.json"))
if err != nil {
if os.IsNotExist(err) {
return nil
}
return err
}
pairingData, err := ioutil.ReadAll(pairingFile)
if err != nil {
return err
}
var pairings []smartcardPairing
if err := json.Unmarshal(pairingData, &pairings); err != nil {
return err
}
for _, pairing := range pairings {
hub.pairings[string(pairing.PublicKey)] = pairing
}
return nil
}
func (hub *Hub) writePairings() error {
pairingFile, err := os.OpenFile(filepath.Join(hub.datadir, "smartcards.json"), os.O_RDWR|os.O_CREATE, 0755)
if err != nil {
return err
}
defer pairingFile.Close()
pairings := make([]smartcardPairing, 0, len(hub.pairings))
for _, pairing := range hub.pairings {
pairings = append(pairings, pairing)
}
pairingData, err := json.Marshal(pairings)
if err != nil {
return err
}
if _, err := pairingFile.Write(pairingData); err != nil {
return err
}
return nil
}
func (hub *Hub) pairing(wallet *Wallet) *smartcardPairing {
if pairing, ok := hub.pairings[string(wallet.PublicKey)]; ok {
return &pairing
}
return nil
}
func (hub *Hub) setPairing(wallet *Wallet, pairing *smartcardPairing) error {
if pairing == nil {
delete(hub.pairings, string(wallet.PublicKey))
} else {
hub.pairings[string(wallet.PublicKey)] = *pairing
}
return hub.writePairings()
}
// NewHub creates a new hardware wallet manager for smartcards.
func NewHub(scheme string, datadir string) (*Hub, error) {
context, err := pcsc.EstablishContext(pcsc.ScopeSystem)
if err != nil {
return nil, err
}
hub := &Hub{
scheme: scheme,
context: context,
datadir: datadir,
wallets: make(map[string]*Wallet),
quit: make(chan chan error),
}
if err := hub.readPairings(); err != nil {
return nil, err
}
hub.refreshWallets()
return hub, nil
}
// Wallets implements accounts.Backend, returning all the currently tracked smart
// cards that appear to be hardware wallets.
func (hub *Hub) Wallets() []accounts.Wallet {
// Make sure the list of wallets is up to date
hub.refreshWallets()
hub.stateLock.RLock()
defer hub.stateLock.RUnlock()
cpy := make([]accounts.Wallet, 0, len(hub.wallets))
for _, wallet := range hub.wallets {
cpy = append(cpy, wallet)
}
sort.Sort(accounts.WalletsByURL(cpy))
return cpy
}
// refreshWallets scans the devices attached to the machine and updates the
// list of wallets based on the found devices.
func (hub *Hub) refreshWallets() {
// Don't scan the USB like crazy it the user fetches wallets in a loop
hub.stateLock.RLock()
elapsed := time.Since(hub.refreshed)
hub.stateLock.RUnlock()
if elapsed < refreshThrottling {
return
}
// Retrieve all the smart card reader to check for cards
readers, err := hub.context.ListReaders()
if err != nil {
// This is a perverted hack, the scard library returns an error if no card
// readers are present instead of simply returning an empty list. We don't
// want to fill the user's log with errors, so filter those out.
if err.Error() != "scard: Cannot find a smart card reader." {
log.Error("Failed to enumerate smart card readers", "err", err)
return
}
}
// Transform the current list of wallets into the new one
hub.stateLock.Lock()
events := []accounts.WalletEvent{}
seen := make(map[string]struct{})
for _, reader := range readers {
// Mark the reader as present
seen[reader] = struct{}{}
// If we alreay know about this card, skip to the next reader, otherwise clean up
if wallet, ok := hub.wallets[reader]; ok {
if err := wallet.ping(); err == nil {
continue
}
wallet.Close()
events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletDropped})
delete(hub.wallets, reader)
}
// New card detected, try to connect to it
card, err := hub.context.Connect(reader, pcsc.ShareShared, pcsc.ProtocolAny)
if err != nil {
log.Debug("Failed to open smart card", "reader", reader, "err", err)
continue
}
wallet := NewWallet(hub, card)
if err = wallet.connect(); err != nil {
log.Debug("Failed to connect to smart card", "reader", reader, "err", err)
card.Disconnect(pcsc.LeaveCard)
continue
}
// Card connected, start tracking in amongs the wallets
hub.wallets[reader] = wallet
events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletArrived})
}
// Remove any wallets no longer present
for reader, wallet := range hub.wallets {
if _, ok := seen[reader]; !ok {
wallet.Close()
events = append(events, accounts.WalletEvent{Wallet: wallet, Kind: accounts.WalletDropped})
delete(hub.wallets, reader)
}
}
hub.refreshed = time.Now()
hub.stateLock.Unlock()
for _, event := range events {
hub.updateFeed.Send(event)
}
}
// Subscribe implements accounts.Backend, creating an async subscription to
// receive notifications on the addition or removal of smart card wallets.
func (hub *Hub) Subscribe(sink chan<- accounts.WalletEvent) event.Subscription {
// We need the mutex to reliably start/stop the update loop
hub.stateLock.Lock()
defer hub.stateLock.Unlock()
// Subscribe the caller and track the subscriber count
sub := hub.updateScope.Track(hub.updateFeed.Subscribe(sink))
// Subscribers require an active notification loop, start it
if !hub.updating {
hub.updating = true
go hub.updater()
}
return sub
}
// updater is responsible for maintaining an up-to-date list of wallets managed
// by the smart card hub, and for firing wallet addition/removal events.
func (hub *Hub) updater() {
for {
// TODO: Wait for a USB hotplug event (not supported yet) or a refresh timeout
// <-hub.changes
time.Sleep(refreshCycle)
// Run the wallet refresher
hub.refreshWallets()
// If all our subscribers left, stop the updater
hub.stateLock.Lock()
if hub.updateScope.Count() == 0 {
hub.updating = false
hub.stateLock.Unlock()
return
}
hub.stateLock.Unlock()
}
}

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accounts/scwallet/securechannel.go
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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"
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"crypto/sha256"
"crypto/sha512"
"fmt"
"github.com/ethereum/go-ethereum/crypto"
pcsc "github.com/gballet/go-libpcsclite"
"github.com/wsddn/go-ecdh"
"golang.org/x/crypto/pbkdf2"
"golang.org/x/text/unicode/norm"
)
const (
maxPayloadSize = 223
pairP1FirstStep = 0
pairP1LastStep = 1
scSecretLength = 32
scBlockSize = 16
insOpenSecureChannel = 0x10
insMutuallyAuthenticate = 0x11
insPair = 0x12
insUnpair = 0x13
pairingSalt = "Keycard Pairing Password Salt"
)
// SecureChannelSession enables secure communication with a hardware wallet.
type SecureChannelSession struct {
card *pcsc.Card // A handle to the smartcard for communication
secret []byte // A shared secret generated from our ECDSA keys
publicKey []byte // Our own ephemeral public key
PairingKey []byte // A permanent shared secret for a pairing, if present
sessionEncKey []byte // The current session encryption key
sessionMacKey []byte // The current session MAC key
iv []byte // The current IV
PairingIndex uint8 // The pairing index
}
// NewSecureChannelSession creates a new secure channel for the given card and public key.
func NewSecureChannelSession(card *pcsc.Card, keyData []byte) (*SecureChannelSession, error) {
// Generate an ECDSA keypair for ourselves
gen := ecdh.NewEllipticECDH(crypto.S256())
private, public, err := gen.GenerateKey(rand.Reader)
if err != nil {
return nil, err
}
cardPublic, ok := gen.Unmarshal(keyData)
if !ok {
return nil, fmt.Errorf("Could not unmarshal public key from card")
}
secret, err := gen.GenerateSharedSecret(private, cardPublic)
if err != nil {
return nil, err
}
return &SecureChannelSession{
card: card,
secret: secret,
publicKey: gen.Marshal(public),
}, nil
}
// Pair establishes a new pairing with the smartcard.
func (s *SecureChannelSession) Pair(pairingPassword []byte) error {
secretHash := pbkdf2.Key(norm.NFKD.Bytes(pairingPassword), norm.NFKD.Bytes([]byte(pairingSalt)), 50000, 32, sha256.New)
challenge := make([]byte, 32)
if _, err := rand.Read(challenge); err != nil {
return err
}
response, err := s.pair(pairP1FirstStep, challenge)
if err != nil {
return err
}
md := sha256.New()
md.Write(secretHash[:])
md.Write(challenge)
expectedCryptogram := md.Sum(nil)
cardCryptogram := response.Data[:32]
cardChallenge := response.Data[32:64]
if !bytes.Equal(expectedCryptogram, cardCryptogram) {
return fmt.Errorf("Invalid card cryptogram %v != %v", expectedCryptogram, cardCryptogram)
}
md.Reset()
md.Write(secretHash[:])
md.Write(cardChallenge)
response, err = s.pair(pairP1LastStep, md.Sum(nil))
if err != nil {
return err
}
md.Reset()
md.Write(secretHash[:])
md.Write(response.Data[1:])
s.PairingKey = md.Sum(nil)
s.PairingIndex = response.Data[0]
return nil
}
// Unpair disestablishes an existing pairing.
func (s *SecureChannelSession) Unpair() error {
if s.PairingKey == nil {
return fmt.Errorf("Cannot unpair: not paired")
}
_, err := s.transmitEncrypted(claSCWallet, insUnpair, s.PairingIndex, 0, []byte{})
if err != nil {
return err
}
s.PairingKey = nil
// Close channel
s.iv = nil
return nil
}
// Open initializes the secure channel.
func (s *SecureChannelSession) Open() error {
if s.iv != nil {
return fmt.Errorf("Session already opened")
}
response, err := s.open()
if err != nil {
return err
}
// Generate the encryption/mac key by hashing our shared secret,
// pairing key, and the first bytes returned from the Open APDU.
md := sha512.New()
md.Write(s.secret)
md.Write(s.PairingKey)
md.Write(response.Data[:scSecretLength])
keyData := md.Sum(nil)
s.sessionEncKey = keyData[:scSecretLength]
s.sessionMacKey = keyData[scSecretLength : scSecretLength*2]
// The IV is the last bytes returned from the Open APDU.
s.iv = response.Data[scSecretLength:]
return s.mutuallyAuthenticate()
}
// mutuallyAuthenticate is an internal method to authenticate both ends of the
// connection.
func (s *SecureChannelSession) mutuallyAuthenticate() error {
data := make([]byte, scSecretLength)
if _, err := rand.Read(data); err != nil {
return err
}
response, err := s.transmitEncrypted(claSCWallet, insMutuallyAuthenticate, 0, 0, data)
if err != nil {
return err
}
if response.Sw1 != 0x90 || response.Sw2 != 0x00 {
return fmt.Errorf("Got unexpected response from MUTUALLY_AUTHENTICATE: 0x%x%x", response.Sw1, response.Sw2)
}
if len(response.Data) != scSecretLength {
return fmt.Errorf("Response from MUTUALLY_AUTHENTICATE was %d bytes, expected %d", len(response.Data), scSecretLength)
}
return nil
}
// open is an internal method that sends an open APDU.
func (s *SecureChannelSession) open() (*responseAPDU, error) {
return transmit(s.card, &commandAPDU{
Cla: claSCWallet,
Ins: insOpenSecureChannel,
P1: s.PairingIndex,
P2: 0,
Data: s.publicKey,
Le: 0,
})
}
// pair is an internal method that sends a pair APDU.
func (s *SecureChannelSession) pair(p1 uint8, data []byte) (*responseAPDU, error) {
return transmit(s.card, &commandAPDU{
Cla: claSCWallet,
Ins: insPair,
P1: p1,
P2: 0,
Data: data,
Le: 0,
})
}
// transmitEncrypted sends an encrypted message, and decrypts and returns the response.
func (s *SecureChannelSession) transmitEncrypted(cla, ins, p1, p2 byte, data []byte) (*responseAPDU, error) {
if s.iv == nil {
return nil, fmt.Errorf("Channel not open")
}
data, err := s.encryptAPDU(data)
if err != nil {
return nil, err
}
meta := [16]byte{cla, ins, p1, p2, byte(len(data) + scBlockSize)}
if err = s.updateIV(meta[:], data); err != nil {
return nil, err
}
fulldata := make([]byte, len(s.iv)+len(data))
copy(fulldata, s.iv)
copy(fulldata[len(s.iv):], data)
response, err := transmit(s.card, &commandAPDU{
Cla: cla,
Ins: ins,
P1: p1,
P2: p2,
Data: fulldata,
})
if err != nil {
return nil, err
}
rmeta := [16]byte{byte(len(response.Data))}
rmac := response.Data[:len(s.iv)]
rdata := response.Data[len(s.iv):]
plainData, err := s.decryptAPDU(rdata)
if err != nil {
return nil, err
}
if err = s.updateIV(rmeta[:], rdata); err != nil {
return nil, err
}
if !bytes.Equal(s.iv, rmac) {
return nil, fmt.Errorf("Invalid MAC in response")
}
rapdu := &responseAPDU{}
rapdu.deserialize(plainData)
if rapdu.Sw1 != sw1Ok {
return nil, fmt.Errorf("Unexpected response status Cla=0x%x, Ins=0x%x, Sw=0x%x%x", cla, ins, rapdu.Sw1, rapdu.Sw2)
}
return rapdu, nil
}
// encryptAPDU is an internal method that serializes and encrypts an APDU.
func (s *SecureChannelSession) encryptAPDU(data []byte) ([]byte, error) {
if len(data) > maxPayloadSize {
return nil, fmt.Errorf("Payload of %d bytes exceeds maximum of %d", len(data), maxPayloadSize)
}
data = pad(data, 0x80)
ret := make([]byte, len(data))
a, err := aes.NewCipher(s.sessionEncKey)
if err != nil {
return nil, err
}
crypter := cipher.NewCBCEncrypter(a, s.iv)
crypter.CryptBlocks(ret, data)
return ret, nil
}
// pad applies message padding to a 16 byte boundary.
func pad(data []byte, terminator byte) []byte {
padded := make([]byte, (len(data)/16+1)*16)
copy(padded, data)
padded[len(data)] = terminator
return padded
}
// decryptAPDU is an internal method that decrypts and deserializes an APDU.
func (s *SecureChannelSession) decryptAPDU(data []byte) ([]byte, error) {
a, err := aes.NewCipher(s.sessionEncKey)
if err != nil {
return nil, err
}
ret := make([]byte, len(data))
crypter := cipher.NewCBCDecrypter(a, s.iv)
crypter.CryptBlocks(ret, data)
return unpad(ret, 0x80)
}
// unpad strips padding from a message.
func unpad(data []byte, terminator byte) ([]byte, error) {
for i := 1; i <= 16; i++ {
switch data[len(data)-i] {
case 0:
continue
case terminator:
return data[:len(data)-i], nil
default:
return nil, fmt.Errorf("Expected end of padding, got %d", data[len(data)-i])
}
}
return nil, fmt.Errorf("Expected end of padding, got 0")
}
// updateIV is an internal method that updates the initialization vector after
// each message exchanged.
func (s *SecureChannelSession) updateIV(meta, data []byte) error {
data = pad(data, 0)
a, err := aes.NewCipher(s.sessionMacKey)
if err != nil {
return err
}
crypter := cipher.NewCBCEncrypter(a, make([]byte, 16))
crypter.CryptBlocks(meta, meta)
crypter.CryptBlocks(data, data)
// The first 16 bytes of the last block is the MAC
s.iv = data[len(data)-32 : len(data)-16]
return nil
}

1082
accounts/scwallet/wallet.go
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