accounts, internal: Changes in response to review

accounts/hd.go

@@ -139,12 +139,12 @@ func (path DerivationPath) MarshalJSON() ([]byte, error) {
 	return []byte(fmt.Sprintf("\"%s\"", path.String())), nil
 }
 
-func (dp *DerivationPath) UnmarshalJSON(b []byte) error {
-	var path string
+func (path *DerivationPath) UnmarshalJSON(b []byte) error {
+	var dp string
 	var err error
-	if err = json.Unmarshal(b, &path); err != nil {
+	if err = json.Unmarshal(b, &dp); err != nil {
 		return err
 	}
-	*dp, err = ParseDerivationPath(path)
+	*path, err = ParseDerivationPath(dp)
 	return err
 }

accounts/scwallet/apdu.go

@@ -22,20 +22,20 @@ import (
 )
 
 const (
-	CLA_ISO7816 = 0
+	claISO7816 = 0
 
-	INS_SELECT                = 0xA4
-	INS_GET_RESPONSE          = 0xC0
-	INS_PAIR                  = 0x12
-	INS_UNPAIR                = 0x13
-	INS_OPEN_SECURE_CHANNEL   = 0x10
-	INS_MUTUALLY_AUTHENTICATE = 0x11
+	insSelect               = 0xA4
+	insGetResponse          = 0xC0
+	insPair                 = 0x12
+	insUnpair               = 0x13
+	insOpenSecureChannel    = 0x10
+	insMutuallyAuthenticate = 0x11
 
-	SW1_GET_RESPONSE = 0x61
-	SW1_OK           = 0x90
+	sw1GetResponse = 0x61
+	sw1Ok          = 0x90
 )
 
-// CommandAPDU represents an application data unit sent to a smartcard
+// 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
@@ -72,13 +72,13 @@ func (ca CommandAPDU) serialize() ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
-// ResponseAPDU represents an application data unit received from a smart card
+// 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
+// deserialize deserializes a response APDU.
 func (ra *ResponseAPDU) deserialize(data []byte) error {
 	ra.Data = make([]byte, len(data)-2)
 

accounts/scwallet/hub.go

@@ -14,6 +14,22 @@
 // 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 'PUK'. You can
+//    pair with an unpaired wallet with `personal.openWallet(URI, PUK)`.
+// 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 (
@@ -32,6 +48,7 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 )
 
+// Scheme is the URI prefix for smartcard wallets.
 const Scheme = "pcsc"
 
 // refreshCycle is the maximum time between wallet refreshes (if USB hotplug
@@ -41,9 +58,9 @@ const refreshCycle = 5 * 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 withub.
-type SmartcardPairing struct {
+// 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"`
@@ -56,7 +73,7 @@ type Hub struct {
 
 	context     *scard.Context
 	datadir     string
-	pairings    map[string]SmartcardPairing
+	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
@@ -71,7 +88,7 @@ type Hub struct {
 var HubType = reflect.TypeOf(&Hub{})
 
 func (hub *Hub) readPairings() error {
-	hub.pairings = make(map[string]SmartcardPairing)
+	hub.pairings = make(map[string]smartcardPairing)
 	pairingFile, err := os.Open(hub.datadir + "/smartcards.json")
 	if err != nil {
 		if os.IsNotExist(err) {
@@ -84,7 +101,7 @@ func (hub *Hub) readPairings() error {
 	if err != nil {
 		return err
 	}
-	var pairings []SmartcardPairing
+	var pairings []smartcardPairing
 	if err := json.Unmarshal(pairingData, &pairings); err != nil {
 		return err
 	}
@@ -101,7 +118,7 @@ func (hub *Hub) writePairings() error {
 		return err
 	}
 
-	pairings := make([]SmartcardPairing, 0, len(hub.pairings))
+	pairings := make([]smartcardPairing, 0, len(hub.pairings))
 	for _, pairing := range hub.pairings {
 		pairings = append(pairings, pairing)
 	}
@@ -118,7 +135,7 @@ func (hub *Hub) writePairings() error {
 	return pairingFile.Close()
 }
 
-func (hub *Hub) getPairing(wallet *Wallet) *SmartcardPairing {
+func (hub *Hub) getPairing(wallet *Wallet) *smartcardPairing {
 	pairing, ok := hub.pairings[string(wallet.PublicKey)]
 	if ok {
 		return &pairing
@@ -126,7 +143,7 @@ func (hub *Hub) getPairing(wallet *Wallet) *SmartcardPairing {
 	return nil
 }
 
-func (hub *Hub) setPairing(wallet *Wallet, pairing *SmartcardPairing) error {
+func (hub *Hub) setPairing(wallet *Wallet, pairing *smartcardPairing) error {
 	if pairing == nil {
 		delete(hub.pairings, string(wallet.PublicKey))
 	} else {
@@ -158,7 +175,7 @@ func NewHub(scheme string, datadir string) (*Hub, error) {
 	return hub, nil
 }
 
-// Wallets implements accounts.Backend, returning all the currently tracked USB
+// Wallets implements accounts.Backend, returning all the currently tracked
 // devices that appear to be hardware wallets.
 func (hub *Hub) Wallets() []accounts.Wallet {
 	// Make sure the list of wallets is up to date
@@ -176,7 +193,7 @@ func (hub *Hub) Wallets() []accounts.Wallet {
 	return cpy
 }
 
-// refreshWallets scans the USB devices attached to the machine and updates the
+// refreshWallets scans the devices attached to the machine and updates the
 // list of wallets based on the found devices.
 func (hub *Hub) refreshWallets() {
 	elapsed := time.Since(hub.refreshed)

accounts/scwallet/securechannel.go

@@ -32,15 +32,15 @@ import (
 )
 
 const (
-	MAX_PAYLOAD_SIZE   = 223
-	PAIR_P1_FIRST_STEP = 0
-	PAIR_P1_LAST_STEP  = 1
+	maxPayloadSize  = 223
+	pairP1FirstStep = 0
+	pairP1LastStep  = 1
 
-	SC_SECRET_LENGTH = 32
-	SC_BLOCK_SIZE    = 16
+	scSecretLength = 32
+	scBlockSize    = 16
 )
 
-// SecureChannelSession enables secure communication with a hardware wallet
+// SecureChannelSession enables secure communication with a hardware wallet.
 type SecureChannelSession struct {
 	card          *scard.Card // A handle to the smartcard for communication
 	secret        []byte      // A shared secret generated from our ECDSA keys
@@ -52,7 +52,7 @@ type SecureChannelSession struct {
 	PairingIndex  uint8       // The pairing index
 }
 
-// NewSecureChannelSession creates a new secure channel for the given card and public key
+// NewSecureChannelSession creates a new secure channel for the given card and public key.
 func NewSecureChannelSession(card *scard.Card, keyData []byte) (*SecureChannelSession, error) {
 	// Generate an ECDSA keypair for ourselves
 	gen := ecdh.NewEllipticECDH(crypto.S256())
@@ -78,7 +78,7 @@ func NewSecureChannelSession(card *scard.Card, keyData []byte) (*SecureChannelSe
 	}, nil
 }
 
-// Pair establishes a new pairing with the smartcard
+// Pair establishes a new pairing with the smartcard.
 func (s *SecureChannelSession) Pair(sharedSecret []byte) error {
 	secretHash := sha256.Sum256(sharedSecret)
 
@@ -87,7 +87,7 @@ func (s *SecureChannelSession) Pair(sharedSecret []byte) error {
 		return err
 	}
 
-	response, err := s.pair(PAIR_P1_FIRST_STEP, challenge)
+	response, err := s.pair(pairP1FirstStep, challenge)
 	if err != nil {
 		return err
 	}
@@ -107,7 +107,7 @@ func (s *SecureChannelSession) Pair(sharedSecret []byte) error {
 	md.Reset()
 	md.Write(secretHash[:])
 	md.Write(cardChallenge)
-	response, err = s.pair(PAIR_P1_LAST_STEP, md.Sum(nil))
+	response, err = s.pair(pairP1LastStep, md.Sum(nil))
 	if err != nil {
 		return err
 	}
@@ -121,13 +121,13 @@ func (s *SecureChannelSession) Pair(sharedSecret []byte) error {
 	return nil
 }
 
-// Unpair disestablishes an existing pairing
+// Unpair disestablishes an existing pairing.
 func (s *SecureChannelSession) Unpair() error {
 	if s.PairingKey == nil {
 		return fmt.Errorf("Cannot unpair: not paired")
 	}
 
-	_, err := s.TransmitEncrypted(CLA_SCWALLET, INS_UNPAIR, s.PairingIndex, 0, []byte{})
+	_, err := s.TransmitEncrypted(claSCWallet, insUnpair, s.PairingIndex, 0, []byte{})
 	if err != nil {
 		return err
 	}
@@ -137,7 +137,7 @@ func (s *SecureChannelSession) Unpair() error {
 	return nil
 }
 
-// Open initializes the secure channel
+// Open initializes the secure channel.
 func (s *SecureChannelSession) Open() error {
 	if s.iv != nil {
 		return fmt.Errorf("Session already opened")
@@ -153,13 +153,13 @@ func (s *SecureChannelSession) Open() error {
 	md := sha512.New()
 	md.Write(s.secret)
 	md.Write(s.PairingKey)
-	md.Write(response.Data[:SC_SECRET_LENGTH])
+	md.Write(response.Data[:scSecretLength])
 	keyData := md.Sum(nil)
-	s.sessionEncKey = keyData[:SC_SECRET_LENGTH]
-	s.sessionMacKey = keyData[SC_SECRET_LENGTH : SC_SECRET_LENGTH*2]
+	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[SC_SECRET_LENGTH:]
+	s.iv = response.Data[scSecretLength:]
 
 	if err := s.mutuallyAuthenticate(); err != nil {
 		return err
@@ -171,12 +171,12 @@ func (s *SecureChannelSession) Open() error {
 // mutuallyAuthenticate is an internal method to authenticate both ends of the
 // connection.
 func (s *SecureChannelSession) mutuallyAuthenticate() error {
-	data := make([]byte, SC_SECRET_LENGTH)
+	data := make([]byte, scSecretLength)
 	if _, err := rand.Read(data); err != nil {
 		return err
 	}
 
-	response, err := s.TransmitEncrypted(CLA_SCWALLET, INS_MUTUALLY_AUTHENTICATE, 0, 0, data)
+	response, err := s.TransmitEncrypted(claSCWallet, insMutuallyAuthenticate, 0, 0, data)
 	if err != nil {
 		return err
 	}
@@ -184,18 +184,18 @@ func (s *SecureChannelSession) mutuallyAuthenticate() error {
 		return fmt.Errorf("Got unexpected response from MUTUALLY_AUTHENTICATE: 0x%x%x", response.Sw1, response.Sw2)
 	}
 
-	if len(response.Data) != SC_SECRET_LENGTH {
-		return fmt.Errorf("Response from MUTUALLY_AUTHENTICATE was %d bytes, expected %d", len(response.Data), SC_SECRET_LENGTH)
+	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
+// open is an internal method that sends an open APDU.
 func (s *SecureChannelSession) open() (*ResponseAPDU, error) {
 	return transmit(s.card, &CommandAPDU{
-		Cla:  CLA_SCWALLET,
-		Ins:  INS_OPEN_SECURE_CHANNEL,
+		Cla:  claSCWallet,
+		Ins:  insOpenSecureChannel,
 		P1:   s.PairingIndex,
 		P2:   0,
 		Data: s.publicKey,
@@ -203,11 +203,11 @@ func (s *SecureChannelSession) open() (*ResponseAPDU, error) {
 	})
 }
 
-// pair is an internal method that sends a pair APDU
+// 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:  CLA_SCWALLET,
-		Ins:  INS_PAIR,
+		Cla:  claSCWallet,
+		Ins:  insPair,
 		P1:   p1,
 		P2:   0,
 		Data: data,
@@ -215,7 +215,7 @@ func (s *SecureChannelSession) pair(p1 uint8, data []byte) (*ResponseAPDU, error
 	})
 }
 
-// TransmitEncrypted sends an encrypted message, and decrypts and returns the response
+// 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")
@@ -225,7 +225,7 @@ func (s *SecureChannelSession) TransmitEncrypted(cla, ins, p1, p2 byte, data []b
 	if err != nil {
 		return nil, err
 	}
-	meta := []byte{cla, ins, p1, p2, byte(len(data) + SC_BLOCK_SIZE), 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+	meta := []byte{cla, ins, p1, p2, byte(len(data) + scBlockSize), 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
 	if err = s.updateIV(meta, data); err != nil {
 		return nil, err
 	}
@@ -263,17 +263,17 @@ func (s *SecureChannelSession) TransmitEncrypted(cla, ins, p1, p2 byte, data []b
 	rapdu := &ResponseAPDU{}
 	rapdu.deserialize(plainData)
 
-	if rapdu.Sw1 != SW1_OK {
+	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
+// encryptAPDU is an internal method that serializes and encrypts an APDU.
 func (s *SecureChannelSession) encryptAPDU(data []byte) ([]byte, error) {
-	if len(data) > MAX_PAYLOAD_SIZE {
-		return nil, fmt.Errorf("Payload of %d bytes exceeds maximum of %d", len(data), MAX_PAYLOAD_SIZE)
+	if len(data) > maxPayloadSize {
+		return nil, fmt.Errorf("Payload of %d bytes exceeds maximum of %d", len(data), maxPayloadSize)
 	}
 	data = pad(data, 0x80)
 
@@ -288,7 +288,7 @@ func (s *SecureChannelSession) encryptAPDU(data []byte) ([]byte, error) {
 	return ret, nil
 }
 
-// pad applies message padding to a 16 byte boundary
+// 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)
@@ -296,7 +296,7 @@ func pad(data []byte, terminator byte) []byte {
 	return padded
 }
 
-// decryptAPDU is an internal method that decrypts and deserializes an APDU
+// 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 {
@@ -310,7 +310,7 @@ func (s *SecureChannelSession) decryptAPDU(data []byte) ([]byte, error) {
 	return unpad(ret, 0x80)
 }
 
-// unpad strips padding from a message
+// 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] {

internal/ethapi/api.go

@@ -473,6 +473,7 @@ func (s *PrivateAccountAPI) SignAndSendTransaction(ctx context.Context, args Sen
 	return s.SendTransaction(ctx, args, passwd)
 }
 
+// InitializeWallet initializes a new wallet at the provided URL, by generating and returning a new private key.
 func (s *PrivateAccountAPI) InitializeWallet(ctx context.Context, url string) (string, error) {
 	wallet, err := s.am.Wallet(url)
 	if err != nil {
@@ -499,6 +500,7 @@ func (s *PrivateAccountAPI) InitializeWallet(ctx context.Context, url string) (s
 	}
 }
 
+// Unpair deletes a pairing between wallet and geth.
 func (s *PrivateAccountAPI) Unpair(ctx context.Context, url string, pin string) error {
 	wallet, err := s.am.Wallet(url)
 	if err != nil {