mirror of
https://gitlab.com/pulsechaincom/go-pulse.git
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347 lines
9.2 KiB
Go
347 lines
9.2 KiB
Go
// Copyright 2018 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package scwallet
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"crypto/sha256"
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"crypto/sha512"
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"fmt"
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"github.com/ethereum/go-ethereum/crypto"
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pcsc "github.com/gballet/go-libpcsclite"
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"github.com/wsddn/go-ecdh"
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"golang.org/x/crypto/pbkdf2"
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"golang.org/x/text/unicode/norm"
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)
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const (
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maxPayloadSize = 223
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pairP1FirstStep = 0
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pairP1LastStep = 1
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scSecretLength = 32
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scBlockSize = 16
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insOpenSecureChannel = 0x10
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insMutuallyAuthenticate = 0x11
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insPair = 0x12
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insUnpair = 0x13
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pairingSalt = "Keycard Pairing Password Salt"
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)
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// SecureChannelSession enables secure communication with a hardware wallet.
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type SecureChannelSession struct {
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card *pcsc.Card // A handle to the smartcard for communication
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secret []byte // A shared secret generated from our ECDSA keys
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publicKey []byte // Our own ephemeral public key
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PairingKey []byte // A permanent shared secret for a pairing, if present
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sessionEncKey []byte // The current session encryption key
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sessionMacKey []byte // The current session MAC key
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iv []byte // The current IV
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PairingIndex uint8 // The pairing index
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}
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// NewSecureChannelSession creates a new secure channel for the given card and public key.
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func NewSecureChannelSession(card *pcsc.Card, keyData []byte) (*SecureChannelSession, error) {
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// Generate an ECDSA keypair for ourselves
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gen := ecdh.NewEllipticECDH(crypto.S256())
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private, public, err := gen.GenerateKey(rand.Reader)
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if err != nil {
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return nil, err
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}
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cardPublic, ok := gen.Unmarshal(keyData)
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if !ok {
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return nil, fmt.Errorf("Could not unmarshal public key from card")
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}
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secret, err := gen.GenerateSharedSecret(private, cardPublic)
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if err != nil {
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return nil, err
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}
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return &SecureChannelSession{
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card: card,
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secret: secret,
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publicKey: gen.Marshal(public),
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}, nil
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}
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// Pair establishes a new pairing with the smartcard.
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func (s *SecureChannelSession) Pair(pairingPassword []byte) error {
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secretHash := pbkdf2.Key(norm.NFKD.Bytes(pairingPassword), norm.NFKD.Bytes([]byte(pairingSalt)), 50000, 32, sha256.New)
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challenge := make([]byte, 32)
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if _, err := rand.Read(challenge); err != nil {
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return err
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}
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response, err := s.pair(pairP1FirstStep, challenge)
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if err != nil {
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return err
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}
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md := sha256.New()
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md.Write(secretHash[:])
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md.Write(challenge)
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expectedCryptogram := md.Sum(nil)
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cardCryptogram := response.Data[:32]
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cardChallenge := response.Data[32:64]
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if !bytes.Equal(expectedCryptogram, cardCryptogram) {
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return fmt.Errorf("Invalid card cryptogram %v != %v", expectedCryptogram, cardCryptogram)
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}
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md.Reset()
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md.Write(secretHash[:])
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md.Write(cardChallenge)
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response, err = s.pair(pairP1LastStep, md.Sum(nil))
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if err != nil {
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return err
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}
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md.Reset()
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md.Write(secretHash[:])
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md.Write(response.Data[1:])
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s.PairingKey = md.Sum(nil)
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s.PairingIndex = response.Data[0]
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return nil
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}
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// Unpair disestablishes an existing pairing.
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func (s *SecureChannelSession) Unpair() error {
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if s.PairingKey == nil {
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return fmt.Errorf("Cannot unpair: not paired")
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}
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_, err := s.transmitEncrypted(claSCWallet, insUnpair, s.PairingIndex, 0, []byte{})
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if err != nil {
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return err
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}
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s.PairingKey = nil
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// Close channel
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s.iv = nil
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return nil
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}
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// Open initializes the secure channel.
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func (s *SecureChannelSession) Open() error {
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if s.iv != nil {
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return fmt.Errorf("Session already opened")
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}
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response, err := s.open()
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if err != nil {
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return err
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}
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// Generate the encryption/mac key by hashing our shared secret,
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// pairing key, and the first bytes returned from the Open APDU.
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md := sha512.New()
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md.Write(s.secret)
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md.Write(s.PairingKey)
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md.Write(response.Data[:scSecretLength])
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keyData := md.Sum(nil)
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s.sessionEncKey = keyData[:scSecretLength]
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s.sessionMacKey = keyData[scSecretLength : scSecretLength*2]
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// The IV is the last bytes returned from the Open APDU.
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s.iv = response.Data[scSecretLength:]
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return s.mutuallyAuthenticate()
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}
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// mutuallyAuthenticate is an internal method to authenticate both ends of the
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// connection.
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func (s *SecureChannelSession) mutuallyAuthenticate() error {
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data := make([]byte, scSecretLength)
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if _, err := rand.Read(data); err != nil {
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return err
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}
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response, err := s.transmitEncrypted(claSCWallet, insMutuallyAuthenticate, 0, 0, data)
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if err != nil {
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return err
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}
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if response.Sw1 != 0x90 || response.Sw2 != 0x00 {
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return fmt.Errorf("Got unexpected response from MUTUALLY_AUTHENTICATE: 0x%x%x", response.Sw1, response.Sw2)
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}
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if len(response.Data) != scSecretLength {
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return fmt.Errorf("Response from MUTUALLY_AUTHENTICATE was %d bytes, expected %d", len(response.Data), scSecretLength)
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}
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return nil
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}
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// open is an internal method that sends an open APDU.
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func (s *SecureChannelSession) open() (*responseAPDU, error) {
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return transmit(s.card, &commandAPDU{
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Cla: claSCWallet,
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Ins: insOpenSecureChannel,
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P1: s.PairingIndex,
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P2: 0,
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Data: s.publicKey,
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Le: 0,
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})
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}
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// pair is an internal method that sends a pair APDU.
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func (s *SecureChannelSession) pair(p1 uint8, data []byte) (*responseAPDU, error) {
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return transmit(s.card, &commandAPDU{
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Cla: claSCWallet,
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Ins: insPair,
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P1: p1,
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P2: 0,
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Data: data,
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Le: 0,
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})
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}
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// transmitEncrypted sends an encrypted message, and decrypts and returns the response.
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func (s *SecureChannelSession) transmitEncrypted(cla, ins, p1, p2 byte, data []byte) (*responseAPDU, error) {
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if s.iv == nil {
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return nil, fmt.Errorf("Channel not open")
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}
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data, err := s.encryptAPDU(data)
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if err != nil {
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return nil, err
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}
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meta := [16]byte{cla, ins, p1, p2, byte(len(data) + scBlockSize)}
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if err = s.updateIV(meta[:], data); err != nil {
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return nil, err
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}
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fulldata := make([]byte, len(s.iv)+len(data))
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copy(fulldata, s.iv)
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copy(fulldata[len(s.iv):], data)
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response, err := transmit(s.card, &commandAPDU{
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Cla: cla,
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Ins: ins,
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P1: p1,
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P2: p2,
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Data: fulldata,
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})
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if err != nil {
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return nil, err
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}
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rmeta := [16]byte{byte(len(response.Data))}
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rmac := response.Data[:len(s.iv)]
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rdata := response.Data[len(s.iv):]
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plainData, err := s.decryptAPDU(rdata)
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if err != nil {
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return nil, err
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}
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if err = s.updateIV(rmeta[:], rdata); err != nil {
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return nil, err
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}
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if !bytes.Equal(s.iv, rmac) {
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return nil, fmt.Errorf("Invalid MAC in response")
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}
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rapdu := &responseAPDU{}
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rapdu.deserialize(plainData)
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if rapdu.Sw1 != sw1Ok {
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return nil, fmt.Errorf("Unexpected response status Cla=0x%x, Ins=0x%x, Sw=0x%x%x", cla, ins, rapdu.Sw1, rapdu.Sw2)
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}
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return rapdu, nil
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}
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// encryptAPDU is an internal method that serializes and encrypts an APDU.
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func (s *SecureChannelSession) encryptAPDU(data []byte) ([]byte, error) {
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if len(data) > maxPayloadSize {
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return nil, fmt.Errorf("Payload of %d bytes exceeds maximum of %d", len(data), maxPayloadSize)
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}
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data = pad(data, 0x80)
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ret := make([]byte, len(data))
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a, err := aes.NewCipher(s.sessionEncKey)
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if err != nil {
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return nil, err
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}
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crypter := cipher.NewCBCEncrypter(a, s.iv)
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crypter.CryptBlocks(ret, data)
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return ret, nil
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}
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// pad applies message padding to a 16 byte boundary.
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func pad(data []byte, terminator byte) []byte {
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padded := make([]byte, (len(data)/16+1)*16)
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copy(padded, data)
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padded[len(data)] = terminator
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return padded
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}
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// decryptAPDU is an internal method that decrypts and deserializes an APDU.
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func (s *SecureChannelSession) decryptAPDU(data []byte) ([]byte, error) {
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a, err := aes.NewCipher(s.sessionEncKey)
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if err != nil {
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return nil, err
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}
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ret := make([]byte, len(data))
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crypter := cipher.NewCBCDecrypter(a, s.iv)
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crypter.CryptBlocks(ret, data)
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return unpad(ret, 0x80)
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}
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// unpad strips padding from a message.
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func unpad(data []byte, terminator byte) ([]byte, error) {
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for i := 1; i <= 16; i++ {
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switch data[len(data)-i] {
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case 0:
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continue
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case terminator:
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return data[:len(data)-i], nil
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default:
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return nil, fmt.Errorf("Expected end of padding, got %d", data[len(data)-i])
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}
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}
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return nil, fmt.Errorf("Expected end of padding, got 0")
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}
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// updateIV is an internal method that updates the initialization vector after
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// each message exchanged.
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func (s *SecureChannelSession) updateIV(meta, data []byte) error {
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data = pad(data, 0)
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a, err := aes.NewCipher(s.sessionMacKey)
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if err != nil {
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return err
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}
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crypter := cipher.NewCBCEncrypter(a, make([]byte, 16))
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crypter.CryptBlocks(meta, meta)
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crypter.CryptBlocks(data, data)
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// The first 16 bytes of the last block is the MAC
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s.iv = data[len(data)-32 : len(data)-16]
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return nil
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}
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