accounts/usbwallet: initial support for Ledger wallets

4 files changed, 762 insertions, 2 deletions

diff --git a/accounts/usbwallet/ledger.go b/accounts/usbwallet/ledger.go
new file mode 100644
index 000000000..55b313df9
--- /dev/null
+++ b/accounts/usbwallet/ledger.go
@@ -0,0 +1,648 @@
+// Copyright 2017 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 file contains the implementation for interacting with the Ledger hardware
+// wallets. The wire protocol spec can be found in the Ledger Blue GitHub repo:
+// https://raw.githubusercontent.com/LedgerHQ/blue-app-eth/master/doc/ethapp.asc
+
+package usbwallet
+
+import (
+	"encoding/binary"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"math/big"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/accounts"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/karalabe/gousb/usb"
+)
+
+// ledgerDeviceIDs are the known device IDs that Ledger wallets use.
+var ledgerDeviceIDs = []deviceID{
+	{Vendor: 0x2c97, Product: 0x0000}, // Ledger Blue
+	{Vendor: 0x2c97, Product: 0x0001}, // Ledger Nano S
+}
+
+// ledgerDerivationPath is the key derivation parameters used by the wallet.
+var ledgerDerivationPath = [4]uint32{0x80000000 + 44, 0x80000000 + 60, 0x80000000 + 0, 0}
+
+// ledgerOpcode is an enumeration encoding the supported Ledger opcodes.
+type ledgerOpcode byte
+
+// ledgerParam1 is an enumeration encoding the supported Ledger parameters for
+// specific opcodes. The same parameter values may be reused between opcodes.
+type ledgerParam1 byte
+
+// ledgerParam2 is an enumeration encoding the supported Ledger parameters for
+// specific opcodes. The same parameter values may be reused between opcodes.
+type ledgerParam2 byte
+
+const (
+	ledgerOpRetrieveAddress  ledgerOpcode = 0x02 // Returns the public key and Ethereum address for a given BIP 32 path
+	ledgerOpSignTransaction  ledgerOpcode = 0x04 // Signs an Ethereum transaction after having the user validate the parameters
+	ledgerOpGetConfiguration ledgerOpcode = 0x06 // Returns specific wallet application configuration
+
+	ledgerP1DirectlyFetchAddress    ledgerParam1 = 0x00 // Return address directly from the wallet
+	ledgerP1ConfirmFetchAddress     ledgerParam1 = 0x01 // Require a user confirmation before returning the address
+	ledgerP1InitTransactionData     ledgerParam1 = 0x00 // First transaction data block for signing
+	ledgerP1ContTransactionData     ledgerParam1 = 0x80 // Subsequent transaction data block for signing
+	ledgerP2DiscardAddressChainCode ledgerParam2 = 0x00 // Do not return the chain code along with the address
+	ledgerP2ReturnAddressChainCode  ledgerParam2 = 0x01 // Require a user confirmation before returning the address
+)
+
+// ledgerWallet represents a live USB Ledger hardware wallet.
+type ledgerWallet struct {
+	device *usb.Device  // USB device advertising itself as a Ledger wallet
+	input  usb.Endpoint // Input endpoint to send data to this device
+	output usb.Endpoint // Output endpoint to receive data from this device
+
+	address common.Address // Current address of the wallet (may be zero if Ethereum app offline)
+	url     string         // Textual URL uniquely identifying this wallet
+	version [3]byte        // Current version of the Ledger Ethereum app (zero if app is offline)
+}
+
+// LedgerHub is a USB hardware wallet interface that can find and handle Ledger
+// wallets.
+type LedgerHub struct {
+	ctx *usb.Context // Context interfacing with a libusb instance
+
+	wallets  map[uint16]*ledgerWallet  // Apparent Ledger wallets (some may be inactive)
+	accounts []accounts.Account        // List of active Ledger accounts
+	index    map[common.Address]uint16 // Set of addresses with active wallets
+
+	quit chan chan error
+	lock sync.RWMutex
+}
+
+// NewLedgerHub creates a new hardware wallet manager for Ledger devices.
+func NewLedgerHub() (*LedgerHub, error) {
+	// Initialize the USB library to access Ledgers through
+	ctx, err := usb.NewContext()
+	if err != nil {
+		return nil, err
+	}
+	// Create the USB hub, start and return it
+	hub := &LedgerHub{
+		ctx:     ctx,
+		wallets: make(map[uint16]*ledgerWallet),
+		index:   make(map[common.Address]uint16),
+		quit:    make(chan chan error),
+	}
+	go hub.watch()
+	return hub, nil
+}
+
+// Accounts retrieves the live of accounts currently known by the Ledger hub.
+func (hub *LedgerHub) Accounts() []accounts.Account {
+	hub.lock.RLock()
+	defer hub.lock.RUnlock()
+
+	cpy := make([]accounts.Account, len(hub.accounts))
+	copy(cpy, hub.accounts)
+	return cpy
+}
+
+// HasAddress reports whether an account with the given address is present.
+func (hub *LedgerHub) HasAddress(addr common.Address) bool {
+	hub.lock.RLock()
+	defer hub.lock.RUnlock()
+
+	_, known := hub.index[addr]
+	return known
+}
+
+// SignHash is not supported for Ledger wallets, so this method will always
+// return an error.
+func (hub *LedgerHub) SignHash(acc accounts.Account, hash []byte) ([]byte, error) {
+	return nil, accounts.ErrNotSupported
+}
+
+// SignTx sends the transaction over to the Ledger wallet to request a confirmation
+// from the user. It returns either the signed transaction or a failure if the user
+// denied the transaction.
+//
+// Note, if the version of the Ethereum application running on the Ledger wallet is
+// too old to sign EIP-155 transactions, but such is requested nonetheless, an error
+// will be returned opposed to silently signing in Homestead mode.
+func (hub *LedgerHub) SignTx(acc accounts.Account, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	hub.lock.RLock()
+	defer hub.lock.RUnlock()
+
+	// If the account contains the device URL, flatten it to make sure
+	var id uint16
+	if acc.URL != "" {
+		if parts := strings.Split(acc.URL, "."); len(parts) == 2 {
+			bus, busErr := strconv.Atoi(parts[0])
+			addr, addrErr := strconv.Atoi(parts[1])
+
+			if busErr == nil && addrErr == nil {
+				id = uint16(bus)<<8 + uint16(addr)
+			}
+		}
+	}
+	// If the id is still zero, URL is either missing or bad, resolve
+	if id == 0 {
+		var ok bool
+		if id, ok = hub.index[acc.Address]; !ok {
+			return nil, accounts.ErrUnknownAccount
+		}
+	}
+	// Retrieve the wallet associated with the URL
+	wallet, ok := hub.wallets[id]
+	if !ok {
+		return nil, accounts.ErrUnknownAccount
+	}
+	// Ensure the wallet is capable of signing the given transaction
+	if chainID != nil && wallet.version[0] <= 1 && wallet.version[1] <= 0 && wallet.version[2] <= 2 {
+		return nil, fmt.Errorf("Ledger v%d.%d.%d doesn't support signing this transaction, please update to v1.0.3 at least",
+			wallet.version[0], wallet.version[1], wallet.version[2])
+	}
+	return wallet.sign(tx, chainID)
+}
+
+// SignHashWithPassphrase is not supported for Ledger wallets, so this method
+// will always return an error.
+func (hub *LedgerHub) SignHashWithPassphrase(acc accounts.Account, passphrase string, hash []byte) ([]byte, error) {
+	return nil, accounts.ErrNotSupported
+}
+
+// SignTxWithPassphrase requests the backend to sign the given transaction, with the
+// given passphrase as extra authentication information. Since the Ledger does not
+// support this feature, it will just silently ignore the passphrase.
+func (hub *LedgerHub) SignTxWithPassphrase(acc accounts.Account, passphrase string, tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	return hub.SignTx(acc, tx, chainID)
+}
+
+// Close terminates the usb watching for Ledger wallets and returns when it
+// successfully terminated.
+func (hub *LedgerHub) Close() error {
+	// Terminate the USB scanner
+	errc := make(chan error)
+	hub.quit <- errc
+	err := <-errc
+
+	// Release the USB interface and return
+	hub.ctx.Close()
+	return err
+}
+
+// watch starts watching the local machine's USB ports for the connection or
+// disconnection of Ledger devices.
+func (hub *LedgerHub) watch() {
+	for {
+		// Rescan the USB ports for devices newly added or removed
+		hub.rescan()
+
+		// Sleep for a certain amount of time or until terminated
+		select {
+		case errc := <-hub.quit:
+			errc <- nil
+			return
+		case <-time.After(time.Second):
+		}
+	}
+}
+
+// rescan searches the USB ports for attached Ledger hardware wallets.
+func (hub *LedgerHub) rescan() {
+	hub.lock.Lock()
+	defer hub.lock.Unlock()
+
+	// Iterate over all attached devices and fetch those seemingly Ledger
+	present := make(map[uint16]bool)
+	devices, _ := hub.ctx.ListDevices(func(desc *usb.Descriptor) bool {
+		// Discard all devices not advertizing as Ledger
+		ledger := false
+		for _, id := range ledgerDeviceIDs {
+			if desc.Vendor == id.Vendor && desc.Product == id.Product {
+				ledger = true
+			}
+		}
+		if !ledger {
+			return false
+		}
+		// If we have a Ledger, mark as still present, or open as new
+		id := uint16(desc.Bus)<<8 + uint16(desc.Address)
+		if _, known := hub.wallets[id]; known {
+			// Track it's presence, but don't open again
+			present[id] = true
+			return false
+		}
+		// New Ledger device, open it for communication
+		return true
+	})
+	// Drop any tracker wallet which disconnected
+	for id, wallet := range hub.wallets {
+		if !present[id] {
+			if wallet.address == (common.Address{}) {
+				glog.V(logger.Info).Infof("ledger wallet [%03d.%03d] disconnected", wallet.device.Bus, wallet.device.Address)
+			} else {
+				// A live account disconnected, remove it from the tracked accounts
+				for i, account := range hub.accounts {
+					if account.Address == wallet.address && account.URL == wallet.url {
+						hub.accounts = append(hub.accounts[:i], hub.accounts[i+1:]...)
+						break
+					}
+				}
+				delete(hub.index, wallet.address)
+
+				glog.V(logger.Info).Infof("ledger wallet [%03d.%03d] v%d.%d.%d disconnected: %s", wallet.device.Bus, wallet.device.Address,
+					wallet.version[0], wallet.version[1], wallet.version[2], wallet.address.Hex())
+			}
+			delete(hub.wallets, id)
+			wallet.device.Close()
+		}
+	}
+	// Start tracking all wallets which newly appeared
+	var err error
+	for _, device := range devices {
+		// Make sure the alleged device has the correct IO endpoints
+		wallet := &ledgerWallet{
+			device: device,
+			url:    fmt.Sprintf("%03d.%03d", device.Bus, device.Address),
+		}
+		var invalid string
+		switch {
+		case len(device.Descriptor.Configs) == 0:
+			invalid = "no endpoint config available"
+		case len(device.Descriptor.Configs[0].Interfaces) == 0:
+			invalid = "no endpoint interface available"
+		case len(device.Descriptor.Configs[0].Interfaces[0].Setups) == 0:
+			invalid = "no endpoint setup available"
+		case len(device.Descriptor.Configs[0].Interfaces[0].Setups[0].Endpoints) < 2:
+			invalid = "not enough IO endpoints available"
+		}
+		if invalid != "" {
+			glog.V(logger.Debug).Infof("ledger wallet [%s] deemed invalid: %s", wallet.url, invalid)
+			device.Close()
+			continue
+		}
+		// Open the input and output endpoints to the device
+		wallet.input, err = device.OpenEndpoint(
+			device.Descriptor.Configs[0].Config,
+			device.Descriptor.Configs[0].Interfaces[0].Number,
+			device.Descriptor.Configs[0].Interfaces[0].Setups[0].Number,
+			device.Descriptor.Configs[0].Interfaces[0].Setups[0].Endpoints[1].Address,
+		)
+		if err != nil {
+			glog.V(logger.Debug).Infof("ledger wallet [%s] input open failed: %v", wallet.url, err)
+			device.Close()
+			continue
+		}
+		wallet.output, err = device.OpenEndpoint(
+			device.Descriptor.Configs[0].Config,
+			device.Descriptor.Configs[0].Interfaces[0].Number,
+			device.Descriptor.Configs[0].Interfaces[0].Setups[0].Number,
+			device.Descriptor.Configs[0].Interfaces[0].Setups[0].Endpoints[0].Address,
+		)
+		if err != nil {
+			glog.V(logger.Debug).Infof("ledger wallet [%s] output open failed: %v", wallet.url, err)
+			device.Close()
+			continue
+		}
+		// Start tracking the device as a probably Ledger wallet
+		id := uint16(device.Bus)<<8 + uint16(device.Address)
+		hub.wallets[id] = wallet
+
+		if wallet.resolveVersion() != nil || wallet.resolveAddress() != nil {
+			glog.V(logger.Info).Infof("ledger wallet [%s] connected, Ethereum app not started", wallet.url)
+		} else {
+			hub.accounts = append(hub.accounts, accounts.Account{
+				Address: wallet.address,
+				URL:     wallet.url,
+			})
+			hub.index[wallet.address] = id
+
+			glog.V(logger.Info).Infof("ledger wallet [%s] v%d.%d.%d connected: %s", wallet.url,
+				wallet.version[0], wallet.version[1], wallet.version[2], wallet.address.Hex())
+		}
+	}
+}
+
+// resolveVersion retrieves the current version of the Ethereum wallet app running
+// on the Ledger wallet and caches it for future reference.
+//
+// The version retrieval protocol is defined as follows:
+//
+//   CLA | INS | P1 | P2 | Lc | Le
+//   ----+-----+----+----+----+---
+//    E0 | 06  | 00 | 00 | 00 | 04
+//
+// With no input data, and the output data being:
+//
+//   Description                                        | Length
+//   ---------------------------------------------------+--------
+//   Flags 01: arbitrary data signature enabled by user | 1 byte
+//   Application major version                          | 1 byte
+//   Application minor version                          | 1 byte
+//   Application patch version                          | 1 byte
+func (wallet *ledgerWallet) resolveVersion() error {
+	// Send the request and wait for the response
+	reply, err := wallet.exchange(ledgerOpGetConfiguration, 0, 0, nil)
+	if err != nil {
+		return err
+	}
+	if len(reply) != 4 {
+		return errors.New("reply not of correct size")
+	}
+	// Cache the version for future reference
+	copy(wallet.version[:], reply[1:])
+	return nil
+}
+
+// resolveAddress retrieves the currently active Ethereum address from a Ledger
+// wallet and caches it for future reference.
+//
+// The address derivation protocol is defined as follows:
+//
+//   CLA | INS | P1 | P2 | Lc  | Le
+//   ----+-----+----+----+-----+---
+//    E0 | 02  | 00 return address
+//               01 display address and confirm before returning
+//                  | 00: do not return the chain code
+//                  | 01: return the chain code
+//                       | var | 00
+//
+// Where the input data is:
+//
+//   Description                                      | Length
+//   -------------------------------------------------+--------
+//   Number of BIP 32 derivations to perform (max 10) | 1 byte
+//   First derivation index (big endian)              | 4 bytes
+//   ...                                              | 4 bytes
+//   Last derivation index (big endian)               | 4 bytes
+//
+// And the output data is:
+//
+//   Description             | Length
+//   ------------------------+-------------------
+//   Public Key length       | 1 byte
+//   Uncompressed Public Key | arbitrary
+//   Ethereum address length | 1 byte
+//   Ethereum address        | 40 bytes hex ascii
+//   Chain code if requested | 32 bytes
+func (wallet *ledgerWallet) resolveAddress() error {
+	// Flatten the derivation path into the Ledger request
+	path := make([]byte, 1+4*len(ledgerDerivationPath))
+	path[0] = byte(len(ledgerDerivationPath))
+	for i, component := range ledgerDerivationPath {
+		binary.BigEndian.PutUint32(path[1+4*i:], component)
+	}
+	// Send the request and wait for the response
+	reply, err := wallet.exchange(ledgerOpRetrieveAddress, ledgerP1DirectlyFetchAddress, ledgerP2DiscardAddressChainCode, path)
+	if err != nil {
+		return err
+	}
+	// Discard the public key, we don't need that for now
+	if len(reply) < 1 || len(reply) < 1+int(reply[0]) {
+		return errors.New("reply lacks public key entry")
+	}
+	reply = reply[1+int(reply[0]):]
+
+	// Extract the Ethereum hex address string
+	if len(reply) < 1 || len(reply) < 1+int(reply[0]) {
+		return errors.New("reply lacks address entry")
+	}
+	hexstr := reply[1 : 1+int(reply[0])]
+
+	// Decode the hex sting into an Ethereum address and return
+	hex.Decode(wallet.address[:], hexstr)
+	return nil
+}
+
+// sign sends the transaction to the Ledger wallet, and waits for the user to
+// confirm or deny the transaction.
+//
+// The transaction signing protocol is defined as follows:
+//
+//   CLA | INS | P1 | P2 | Lc  | Le
+//   ----+-----+----+----+-----+---
+//    E0 | 04  | 00: first transaction data block
+//               80: subsequent transaction data block
+//                  | 00 | variable | variable
+//
+// Where the input for the first transaction block (first 255 bytes) is:
+//
+//   Description                                      | Length
+//   -------------------------------------------------+----------
+//   Number of BIP 32 derivations to perform (max 10) | 1 byte
+//   First derivation index (big endian)              | 4 bytes
+//   ...                                              | 4 bytes
+//   Last derivation index (big endian)               | 4 bytes
+//   RLP transaction chunk                            | arbitrary
+//
+// And the input for subsequent transaction blocks (first 255 bytes) are:
+//
+//   Description           | Length
+//   ----------------------+----------
+//   RLP transaction chunk | arbitrary
+//
+// And the output data is:
+//
+//   Description | Length
+//   ------------+---------
+//   signature V | 1 byte
+//   signature R | 32 bytes
+//   signature S | 32 bytes
+func (wallet *ledgerWallet) sign(tx *types.Transaction, chainID *big.Int) (*types.Transaction, error) {
+	// We need to modify the timeouts to account for user feedback
+	defer func(old time.Duration) { wallet.device.ReadTimeout = old }(wallet.device.ReadTimeout)
+	wallet.device.ReadTimeout = time.Minute
+
+	// Flatten the derivation path into the Ledger request
+	path := make([]byte, 1+4*len(ledgerDerivationPath))
+	path[0] = byte(len(ledgerDerivationPath))
+	for i, component := range ledgerDerivationPath {
+		binary.BigEndian.PutUint32(path[1+4*i:], component)
+	}
+	// Create the transaction RLP based on whether legacy or EIP155 signing was requeste
+	var (
+		txrlp []byte
+		err   error
+	)
+	if chainID == nil {
+		if txrlp, err = rlp.EncodeToBytes([]interface{}{tx.Nonce(), tx.GasPrice(), tx.Gas(), tx.To(), tx.Value(), tx.Data()}); err != nil {
+			return nil, err
+		}
+	} else {
+		if txrlp, err = rlp.EncodeToBytes([]interface{}{tx.Nonce(), tx.GasPrice(), tx.Gas(), tx.To(), tx.Value(), tx.Data(), chainID, big.NewInt(0), big.NewInt(0)}); err != nil {
+			return nil, err
+		}
+	}
+	payload := append(path, txrlp...)
+
+	// Send the request and wait for the response
+	var (
+		op    = ledgerP1InitTransactionData
+		reply []byte
+	)
+	for len(payload) > 0 {
+		// Calculate the size of the next data chunk
+		chunk := 255
+		if chunk > len(payload) {
+			chunk = len(payload)
+		}
+		// Send the chunk over, ensuring it's processed correctly
+		reply, err = wallet.exchange(ledgerOpSignTransaction, op, 0, payload[:chunk])
+		if err != nil {
+			return nil, err
+		}
+		// Shift the payload and ensure subsequent chunks are marked as such
+		payload = payload[chunk:]
+		op = ledgerP1ContTransactionData
+	}
+	// Extract the Ethereum signature and do a sanity validation
+	if len(reply) != 65 {
+		return nil, errors.New("reply lacks signature")
+	}
+	signature := append(reply[1:], reply[0])
+
+	// Create the correct signer and signature transform based on the chain ID
+	var signer types.Signer
+	if chainID == nil {
+		signer = new(types.HomesteadSigner)
+	} else {
+		signer = types.NewEIP155Signer(chainID)
+		signature[64] = (signature[64]-34)/2 - byte(chainID.Uint64())
+	}
+	// Inject the final signature into the transaction and sanity check the sender
+	signed, err := tx.WithSignature(signer, signature)
+	if err != nil {
+		return nil, err
+	}
+	sender, err := types.Sender(signer, signed)
+	if err != nil {
+		return nil, err
+	}
+	if sender != wallet.address {
+		glog.V(logger.Error).Infof("Ledger signer mismatch: expected %s, got %s", wallet.address.Hex(), sender.Hex())
+		return nil, fmt.Errorf("signer mismatch: expected %s, got %s", wallet.address.Hex(), sender.Hex())
+	}
+	return signed, nil
+}
+
+// exchange performs a data exchange with the Ledger wallet, sending it a message
+// and retrieving the response.
+//
+// The common transport header is defined as follows:
+//
+//  Description                           | Length
+//  --------------------------------------+----------
+//  Communication channel ID (big endian) | 2 bytes
+//  Command tag                           | 1 byte
+//  Packet sequence index (big endian)    | 2 bytes
+//  Payload                               | arbitrary
+//
+// The Communication channel ID allows commands multiplexing over the same
+// physical link. It is not used for the time being, and should be set to 0101
+// to avoid compatibility issues with implementations ignoring a leading 00 byte.
+//
+// The Command tag describes the message content. Use TAG_APDU (0x05) for standard
+// APDU payloads, or TAG_PING (0x02) for a simple link test.
+//
+// The Packet sequence index describes the current sequence for fragmented payloads.
+// The first fragment index is 0x00.
+//
+// APDU Command payloads are encoded as follows:
+//
+//  Description              | Length
+//  -----------------------------------
+//  APDU length (big endian) | 2 bytes
+//  APDU CLA                 | 1 byte
+//  APDU INS                 | 1 byte
+//  APDU P1                  | 1 byte
+//  APDU P2                  | 1 byte
+//  APDU length              | 1 byte
+//  Optional APDU data       | arbitrary
+func (wallet *ledgerWallet) exchange(opcode ledgerOpcode, p1 ledgerParam1, p2 ledgerParam2, data []byte) ([]byte, error) {
+	// Construct the message payload, possibly split into multiple chunks
+	var chunks [][]byte
+	for left := data; len(left) > 0 || len(chunks) == 0; {
+		// Create the chunk header
+		var chunk []byte
+
+		if len(chunks) == 0 {
+			// The first chunk encodes the length and all the opcodes
+			chunk = []byte{0x00, 0x00, 0xe0, byte(opcode), byte(p1), byte(p2), byte(len(data))}
+			binary.BigEndian.PutUint16(chunk, uint16(5+len(data)))
+		}
+		// Append the data blob to the end of the chunk
+		space := 64 - len(chunk) - 5 // 5 == header size
+		if len(left) > space {
+			chunks, left = append(chunks, append(chunk, left[:space]...)), left[space:]
+			continue
+		}
+		chunks, left = append(chunks, append(chunk, left...)), nil
+	}
+	// Stream all the chunks to the device
+	for i, chunk := range chunks {
+		// Construct the new message to stream
+		header := []byte{0x01, 0x01, 0x05, 0x00, 0x00} // Channel ID and command tag appended
+		binary.BigEndian.PutUint16(header[3:], uint16(i))
+
+		msg := append(header, chunk...)
+
+		// Send over to the device
+		if glog.V(logger.Core) {
+			glog.Infof("-> %03d.%03d: %x", wallet.device.Bus, wallet.device.Address, msg)
+		}
+		if _, err := wallet.input.Write(msg); err != nil {
+			return nil, err
+		}
+	}
+	// Stream the reply back from the wallet in 64 byte chunks
+	var reply []byte
+	for {
+		// Read the next chunk from the Ledger wallet
+		chunk := make([]byte, 64)
+		if _, err := io.ReadFull(wallet.output, chunk); err != nil {
+			return nil, err
+		}
+		if glog.V(logger.Core) {
+			glog.Infof("<- %03d.%03d: %x", wallet.device.Bus, wallet.device.Address, chunk)
+		}
+		// Make sure the transport header matches
+		if chunk[0] != 0x01 || chunk[1] != 0x01 || chunk[2] != 0x05 {
+			return nil, fmt.Errorf("invalid reply header: %x", chunk[:3])
+		}
+		// If it's the first chunk, retrieve the total message length
+		if chunk[3] == 0x00 && chunk[4] == 0x00 {
+			reply = make([]byte, 0, int(binary.BigEndian.Uint16(chunk[5:7])))
+			chunk = chunk[7:]
+		} else {
+			chunk = chunk[5:]
+		}
+		// Append to the reply and stop when filled up
+		if left := cap(reply) - len(reply); left > len(chunk) {
+			reply = append(reply, chunk...)
+		} else {
+			reply = append(reply, chunk[:left]...)
+			break
+		}
+	}
+	return reply[:len(reply)-2], nil
+}
diff --git a/accounts/usbwallet/ledger_test.go b/accounts/usbwallet/ledger_test.go
new file mode 100644
index 000000000..aeab2f0f0
--- /dev/null
+++ b/accounts/usbwallet/ledger_test.go
@@ -0,0 +1,75 @@
+// Copyright 2017 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 usbwallet
+
+/*
+func TestLedgerHub(t *testing.T) {
+	glog.SetV(6)
+	glog.SetToStderr(true)
+
+	// Create a USB hub watching for Ledger devices
+	hub, err := NewLedgerHub()
+	if err != nil {
+		t.Fatalf("Failed to create Ledger hub: %v", err)
+	}
+	defer hub.Close()
+
+	// Wait for events :P
+	time.Sleep(time.Minute)
+}
+*/
+/*
+func TestLedger(t *testing.T) {
+	// Create a USB context to access devices through
+	ctx, err := usb.NewContext()
+	defer ctx.Close()
+	ctx.Debug(6)
+
+	// List all of the Ledger wallets
+	wallets, err := findLedgerWallets(ctx)
+	if err != nil {
+		t.Fatalf("Failed to list Ledger wallets: %v", err)
+	}
+	// Retrieve the address from every one of them
+	for _, wallet := range wallets {
+		// Retrieve the version of the wallet app
+		ver, err := wallet.Version()
+		if err != nil {
+			t.Fatalf("Failed to retrieve wallet version: %v", err)
+		}
+		fmt.Printf("Ledger version: %s\n", ver)
+
+		// Retrieve the address of the wallet
+		addr, err := wallet.Address()
+		if err != nil {
+			t.Fatalf("Failed to retrieve wallet address: %v", err)
+		}
+		fmt.Printf("Ledger address: %x\n", addr)
+
+		// Try to sign a transaction with the wallet
+		unsigned := types.NewTransaction(1, common.HexToAddress("0xbabababababababababababababababababababa"), common.Ether, big.NewInt(20000), common.Shannon, nil)
+		signed, err := wallet.Sign(unsigned)
+		if err != nil {
+			t.Fatalf("Failed to sign transactions: %v", err)
+		}
+		signer, err := types.Sender(types.NewEIP155Signer(big.NewInt(1)), signed)
+		if err != nil {
+			t.Fatalf("Failed to recover signer: %v", err)
+		}
+		fmt.Printf("Ledger signature by: %x\n", signer)
+	}
+}*/
diff --git a/accounts/usbwallet/usb.go b/accounts/usbwallet/usb.go
new file mode 100644
index 000000000..550f05ba6
--- /dev/null
+++ b/accounts/usbwallet/usb.go
@@ -0,0 +1,27 @@
+// Copyright 2017 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 usbwallet implements support for USB hardware wallets.
+package usbwallet
+
+import "github.com/karalabe/gousb/usb"
+
+// deviceID is a combined vendor/product identifier to uniquely identify a USB
+// hardware device.
+type deviceID struct {
+	Vendor  usb.ID // The Vendor identifer
+	Product usb.ID // The Product identifier
+}
diff --git a/node/config.go b/node/config.go
index f3b4dcc73..9ae9406a9 100644
--- a/node/config.go
+++ b/node/config.go
@@ -28,6 +28,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/accounts/keystore"
+	"github.com/ethereum/go-ethereum/accounts/usbwallet"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/logger"
@@ -432,6 +433,15 @@ func makeAccountManager(conf *Config) (am *accounts.Manager, ephemeralKeystore s
 	if err := os.MkdirAll(keydir, 0700); err != nil {
 		return nil, "", err
 	}
-	ks := keystore.NewKeyStore(keydir, scryptN, scryptP)
-	return accounts.NewManager(ks), ephemeralKeystore, nil
+
+	// Assemble the account manager and supported backends
+	backends := []accounts.Backend{
+		keystore.NewKeyStore(keydir, scryptN, scryptP),
+	}
+	if ledgerhub, err := usbwallet.NewLedgerHub(); err != nil {
+		glog.V(logger.Warn).Infof("Failed to start Ledger hub, disabling: %v", err)
+	} else {
+		backends = append(backends, ledgerhub)
+	}
+	return accounts.NewManager(backends...), ephemeralKeystore, nil
 }