github.com/theQRL/go-zond@v0.2.1/accounts/usbwallet/ledger.go (about)

     1  // Copyright 2017 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  // This file contains the implementation for interacting with the Ledger hardware
    18  // wallets. The wire protocol spec can be found in the Ledger Blue GitHub repo:
    19  // https://raw.githubusercontent.com/LedgerHQ/blue-app-eth/master/doc/ethapp.asc
    20  
    21  package usbwallet
    22  
    23  /*
    24  import (
    25  	"encoding/binary"
    26  	"encoding/hex"
    27  	"errors"
    28  	"fmt"
    29  	"io"
    30  	"math/big"
    31  
    32  	"github.com/theQRL/go-zond/accounts"
    33  	"github.com/theQRL/go-zond/common"
    34  	"github.com/theQRL/go-zond/common/hexutil"
    35  	"github.com/theQRL/go-zond/core/types"
    36  	"github.com/theQRL/go-zond/crypto"
    37  	"github.com/theQRL/go-zond/log"
    38  	"github.com/theQRL/go-zond/rlp"
    39  )
    40  
    41  // ledgerOpcode is an enumeration encoding the supported Ledger opcodes.
    42  type ledgerOpcode byte
    43  
    44  // ledgerParam1 is an enumeration encoding the supported Ledger parameters for
    45  // specific opcodes. The same parameter values may be reused between opcodes.
    46  type ledgerParam1 byte
    47  
    48  // ledgerParam2 is an enumeration encoding the supported Ledger parameters for
    49  // specific opcodes. The same parameter values may be reused between opcodes.
    50  type ledgerParam2 byte
    51  
    52  const (
    53  	ledgerOpRetrieveAddress  ledgerOpcode = 0x02 // Returns the public key and Ethereum address for a given BIP 32 path
    54  	ledgerOpSignTransaction  ledgerOpcode = 0x04 // Signs an Ethereum transaction after having the user validate the parameters
    55  	ledgerOpGetConfiguration ledgerOpcode = 0x06 // Returns specific wallet application configuration
    56  	ledgerOpSignTypedMessage ledgerOpcode = 0x0c // Signs an Ethereum message following the EIP 712 specification
    57  
    58  	ledgerP1DirectlyFetchAddress    ledgerParam1 = 0x00 // Return address directly from the wallet
    59  	ledgerP1InitTypedMessageData    ledgerParam1 = 0x00 // First chunk of Typed Message data
    60  	ledgerP1InitTransactionData     ledgerParam1 = 0x00 // First transaction data block for signing
    61  	ledgerP1ContTransactionData     ledgerParam1 = 0x80 // Subsequent transaction data block for signing
    62  	ledgerP2DiscardAddressChainCode ledgerParam2 = 0x00 // Do not return the chain code along with the address
    63  
    64  	ledgerEip155Size int = 3 // Size of the EIP-155 chain_id,r,s in unsigned transactions
    65  )
    66  
    67  // errLedgerReplyInvalidHeader is the error message returned by a Ledger data exchange
    68  // if the device replies with a mismatching header. This usually means the device
    69  // is in browser mode.
    70  var errLedgerReplyInvalidHeader = errors.New("ledger: invalid reply header")
    71  
    72  // errLedgerInvalidVersionReply is the error message returned by a Ledger version retrieval
    73  // when a response does arrive, but it does not contain the expected data.
    74  var errLedgerInvalidVersionReply = errors.New("ledger: invalid version reply")
    75  
    76  // ledgerDriver implements the communication with a Ledger hardware wallet.
    77  type ledgerDriver struct {
    78  	device  io.ReadWriter // USB device connection to communicate through
    79  	version [3]byte       // Current version of the Ledger firmware (zero if app is offline)
    80  	browser bool          // Flag whether the Ledger is in browser mode (reply channel mismatch)
    81  	failure error         // Any failure that would make the device unusable
    82  	log     log.Logger    // Contextual logger to tag the ledger with its id
    83  }
    84  
    85  // newLedgerDriver creates a new instance of a Ledger USB protocol driver.
    86  func newLedgerDriver(logger log.Logger) driver {
    87  	return &ledgerDriver{
    88  		log: logger,
    89  	}
    90  }
    91  
    92  // Status implements usbwallet.driver, returning various states the Ledger can
    93  // currently be in.
    94  func (w *ledgerDriver) Status() (string, error) {
    95  	if w.failure != nil {
    96  		return fmt.Sprintf("Failed: %v", w.failure), w.failure
    97  	}
    98  	if w.browser {
    99  		return "Ethereum app in browser mode", w.failure
   100  	}
   101  	if w.offline() {
   102  		return "Ethereum app offline", w.failure
   103  	}
   104  	return fmt.Sprintf("Ethereum app v%d.%d.%d online", w.version[0], w.version[1], w.version[2]), w.failure
   105  }
   106  
   107  // offline returns whether the wallet and the Ethereum app is offline or not.
   108  //
   109  // The method assumes that the state lock is held!
   110  func (w *ledgerDriver) offline() bool {
   111  	return w.version == [3]byte{0, 0, 0}
   112  }
   113  
   114  // Open implements usbwallet.driver, attempting to initialize the connection to the
   115  // Ledger hardware wallet. The Ledger does not require a user passphrase, so that
   116  // parameter is silently discarded.
   117  func (w *ledgerDriver) Open(device io.ReadWriter, passphrase string) error {
   118  	w.device, w.failure = device, nil
   119  
   120  	_, err := w.ledgerDerive(accounts.DefaultBaseDerivationPath)
   121  	if err != nil {
   122  		// Ethereum app is not running or in browser mode, nothing more to do, return
   123  		if err == errLedgerReplyInvalidHeader {
   124  			w.browser = true
   125  		}
   126  		return nil
   127  	}
   128  	// Try to resolve the Ethereum app's version, will fail prior to v1.0.2
   129  	if w.version, err = w.ledgerVersion(); err != nil {
   130  		w.version = [3]byte{1, 0, 0} // Assume worst case, can't verify if v1.0.0 or v1.0.1
   131  	}
   132  	return nil
   133  }
   134  
   135  // Close implements usbwallet.driver, cleaning up and metadata maintained within
   136  // the Ledger driver.
   137  func (w *ledgerDriver) Close() error {
   138  	w.browser, w.version = false, [3]byte{}
   139  	return nil
   140  }
   141  
   142  // Heartbeat implements usbwallet.driver, performing a sanity check against the
   143  // Ledger to see if it's still online.
   144  func (w *ledgerDriver) Heartbeat() error {
   145  	if _, err := w.ledgerVersion(); err != nil && err != errLedgerInvalidVersionReply {
   146  		w.failure = err
   147  		return err
   148  	}
   149  	return nil
   150  }
   151  
   152  // Derive implements usbwallet.driver, sending a derivation request to the Ledger
   153  // and returning the Ethereum address located on that derivation path.
   154  func (w *ledgerDriver) Derive(path accounts.DerivationPath) (common.Address, error) {
   155  	return w.ledgerDerive(path)
   156  }
   157  
   158  // SignTx implements usbwallet.driver, sending the transaction to the Ledger and
   159  // waiting for the user to confirm or deny the transaction.
   160  //
   161  // Note, if the version of the Ethereum application running on the Ledger wallet is
   162  // too old to sign EIP-155 transactions, but such is requested nonetheless, an error
   163  // will be returned opposed to silently signing in Homestead mode.
   164  func (w *ledgerDriver) SignTx(path accounts.DerivationPath, tx *types.Transaction, chainID *big.Int) (common.Address, *types.Transaction, error) {
   165  	// If the Ethereum app doesn't run, abort
   166  	if w.offline() {
   167  		return common.Address{}, nil, accounts.ErrWalletClosed
   168  	}
   169  	// Ensure the wallet is capable of signing the given transaction
   170  	if chainID != nil && w.version[0] <= 1 && w.version[1] <= 0 && w.version[2] <= 2 {
   171  		//lint:ignore ST1005 brand name displayed on the console
   172  		return common.Address{}, nil, fmt.Errorf("Ledger v%d.%d.%d doesn't support signing this transaction, please update to v1.0.3 at least", w.version[0], w.version[1], w.version[2])
   173  	}
   174  	// All infos gathered and metadata checks out, request signing
   175  	return w.ledgerSign(path, tx, chainID)
   176  }
   177  
   178  // SignTypedMessage implements usbwallet.driver, sending the message to the Ledger and
   179  // waiting for the user to sign or deny the transaction.
   180  //
   181  // Note: this was introduced in the ledger 1.5.0 firmware
   182  func (w *ledgerDriver) SignTypedMessage(path accounts.DerivationPath, domainHash []byte, messageHash []byte) ([]byte, error) {
   183  	// If the Ethereum app doesn't run, abort
   184  	if w.offline() {
   185  		return nil, accounts.ErrWalletClosed
   186  	}
   187  	// Ensure the wallet is capable of signing the given transaction
   188  	if w.version[0] < 1 && w.version[1] < 5 {
   189  		//lint:ignore ST1005 brand name displayed on the console
   190  		return nil, fmt.Errorf("Ledger version >= 1.5.0 required for EIP-712 signing (found version v%d.%d.%d)", w.version[0], w.version[1], w.version[2])
   191  	}
   192  	// All infos gathered and metadata checks out, request signing
   193  	return w.ledgerSignTypedMessage(path, domainHash, messageHash)
   194  }
   195  
   196  // ledgerVersion retrieves the current version of the Ethereum wallet app running
   197  // on the Ledger wallet.
   198  //
   199  // The version retrieval protocol is defined as follows:
   200  //
   201  //	CLA | INS | P1 | P2 | Lc | Le
   202  //	----+-----+----+----+----+---
   203  //	 E0 | 06  | 00 | 00 | 00 | 04
   204  //
   205  // With no input data, and the output data being:
   206  //
   207  //	Description                                        | Length
   208  //	---------------------------------------------------+--------
   209  //	Flags 01: arbitrary data signature enabled by user | 1 byte
   210  //	Application major version                          | 1 byte
   211  //	Application minor version                          | 1 byte
   212  //	Application patch version                          | 1 byte
   213  func (w *ledgerDriver) ledgerVersion() ([3]byte, error) {
   214  	// Send the request and wait for the response
   215  	reply, err := w.ledgerExchange(ledgerOpGetConfiguration, 0, 0, nil)
   216  	if err != nil {
   217  		return [3]byte{}, err
   218  	}
   219  	if len(reply) != 4 {
   220  		return [3]byte{}, errLedgerInvalidVersionReply
   221  	}
   222  	// Cache the version for future reference
   223  	var version [3]byte
   224  	copy(version[:], reply[1:])
   225  	return version, nil
   226  }
   227  
   228  // ledgerDerive retrieves the currently active Ethereum address from a Ledger
   229  // wallet at the specified derivation path.
   230  //
   231  // The address derivation protocol is defined as follows:
   232  //
   233  //	CLA | INS | P1 | P2 | Lc  | Le
   234  //	----+-----+----+----+-----+---
   235  //	 E0 | 02  | 00 return address
   236  //	            01 display address and confirm before returning
   237  //	               | 00: do not return the chain code
   238  //	               | 01: return the chain code
   239  //	                    | var | 00
   240  //
   241  // Where the input data is:
   242  //
   243  //	Description                                      | Length
   244  //	-------------------------------------------------+--------
   245  //	Number of BIP 32 derivations to perform (max 10) | 1 byte
   246  //	First derivation index (big endian)              | 4 bytes
   247  //	...                                              | 4 bytes
   248  //	Last derivation index (big endian)               | 4 bytes
   249  //
   250  // And the output data is:
   251  //
   252  //	Description             | Length
   253  //	------------------------+-------------------
   254  //	Public Key length       | 1 byte
   255  //	Uncompressed Public Key | arbitrary
   256  //	Ethereum address length | 1 byte
   257  //	Ethereum address        | 40 bytes hex ascii
   258  //	Chain code if requested | 32 bytes
   259  func (w *ledgerDriver) ledgerDerive(derivationPath []uint32) (common.Address, error) {
   260  	// Flatten the derivation path into the Ledger request
   261  	path := make([]byte, 1+4*len(derivationPath))
   262  	path[0] = byte(len(derivationPath))
   263  	for i, component := range derivationPath {
   264  		binary.BigEndian.PutUint32(path[1+4*i:], component)
   265  	}
   266  	// Send the request and wait for the response
   267  	reply, err := w.ledgerExchange(ledgerOpRetrieveAddress, ledgerP1DirectlyFetchAddress, ledgerP2DiscardAddressChainCode, path)
   268  	if err != nil {
   269  		return common.Address{}, err
   270  	}
   271  	// Discard the public key, we don't need that for now
   272  	if len(reply) < 1 || len(reply) < 1+int(reply[0]) {
   273  		return common.Address{}, errors.New("reply lacks public key entry")
   274  	}
   275  	reply = reply[1+int(reply[0]):]
   276  
   277  	// Extract the Ethereum hex address string
   278  	if len(reply) < 1 || len(reply) < 1+int(reply[0]) {
   279  		return common.Address{}, errors.New("reply lacks address entry")
   280  	}
   281  	hexstr := reply[1 : 1+int(reply[0])]
   282  
   283  	// Decode the hex sting into an Ethereum address and return
   284  	var address common.Address
   285  	if _, err = hex.Decode(address[:], hexstr); err != nil {
   286  		return common.Address{}, err
   287  	}
   288  	return address, nil
   289  }
   290  
   291  // ledgerSign sends the transaction to the Ledger wallet, and waits for the user
   292  // to confirm or deny the transaction.
   293  //
   294  // The transaction signing protocol is defined as follows:
   295  //
   296  //	CLA | INS | P1 | P2 | Lc  | Le
   297  //	----+-----+----+----+-----+---
   298  //	 E0 | 04  | 00: first transaction data block
   299  //	            80: subsequent transaction data block
   300  //	               | 00 | variable | variable
   301  //
   302  // Where the input for the first transaction block (first 255 bytes) is:
   303  //
   304  //	Description                                      | Length
   305  //	-------------------------------------------------+----------
   306  //	Number of BIP 32 derivations to perform (max 10) | 1 byte
   307  //	First derivation index (big endian)              | 4 bytes
   308  //	...                                              | 4 bytes
   309  //	Last derivation index (big endian)               | 4 bytes
   310  //	RLP transaction chunk                            | arbitrary
   311  //
   312  // And the input for subsequent transaction blocks (first 255 bytes) are:
   313  //
   314  //	Description           | Length
   315  //	----------------------+----------
   316  //	RLP transaction chunk | arbitrary
   317  //
   318  // And the output data is:
   319  //
   320  //	Description | Length
   321  //	------------+---------
   322  //	signature V | 1 byte
   323  //	signature R | 32 bytes
   324  //	signature S | 32 bytes
   325  func (w *ledgerDriver) ledgerSign(derivationPath []uint32, tx *types.Transaction, chainID *big.Int) (common.Address, *types.Transaction, error) {
   326  	// Flatten the derivation path into the Ledger request
   327  	path := make([]byte, 1+4*len(derivationPath))
   328  	path[0] = byte(len(derivationPath))
   329  	for i, component := range derivationPath {
   330  		binary.BigEndian.PutUint32(path[1+4*i:], component)
   331  	}
   332  	// Create the transaction RLP based on whether legacy or EIP155 signing was requested
   333  	var (
   334  		txrlp []byte
   335  		err   error
   336  	)
   337  	if chainID == nil {
   338  		if txrlp, err = rlp.EncodeToBytes([]interface{}{tx.Nonce(), tx.GasPrice(), tx.Gas(), tx.To(), tx.Value(), tx.Data()}); err != nil {
   339  			return common.Address{}, nil, err
   340  		}
   341  	} else {
   342  		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 {
   343  			return common.Address{}, nil, err
   344  		}
   345  	}
   346  	payload := append(path, txrlp...)
   347  
   348  	// Send the request and wait for the response
   349  	var (
   350  		op    = ledgerP1InitTransactionData
   351  		reply []byte
   352  	)
   353  
   354  	// Chunk size selection to mitigate an underlying RLP deserialization issue on the ledger app.
   355  	// https://github.com/LedgerHQ/app-ethereum/issues/409
   356  	chunk := 255
   357  	for ; len(payload)%chunk <= ledgerEip155Size; chunk-- {
   358  	}
   359  
   360  	for len(payload) > 0 {
   361  		// Calculate the size of the next data chunk
   362  		if chunk > len(payload) {
   363  			chunk = len(payload)
   364  		}
   365  		// Send the chunk over, ensuring it's processed correctly
   366  		reply, err = w.ledgerExchange(ledgerOpSignTransaction, op, 0, payload[:chunk])
   367  		if err != nil {
   368  			return common.Address{}, nil, err
   369  		}
   370  		// Shift the payload and ensure subsequent chunks are marked as such
   371  		payload = payload[chunk:]
   372  		op = ledgerP1ContTransactionData
   373  	}
   374  	// Extract the Ethereum signature and do a sanity validation
   375  	if len(reply) != crypto.SignatureLength {
   376  		return common.Address{}, nil, errors.New("reply lacks signature")
   377  	}
   378  	signature := append(reply[1:], reply[0])
   379  
   380  	// Create the correct signer and signature transform based on the chain ID
   381  	var signer types.Signer
   382  	if chainID == nil {
   383  		signer = new(types.HomesteadSigner)
   384  	} else {
   385  		signer = types.NewEIP155Signer(chainID)
   386  		signature[64] -= byte(chainID.Uint64()*2 + 35)
   387  	}
   388  	// TODO (cyyber): intentionally added pk as nil, fix this issue later
   389  	signed, err := tx.WithSignatureAndPublicKey(signer, signature, nil)
   390  	if err != nil {
   391  		return common.Address{}, nil, err
   392  	}
   393  	sender, err := types.Sender(signer, signed)
   394  	if err != nil {
   395  		return common.Address{}, nil, err
   396  	}
   397  	return sender, signed, nil
   398  }
   399  
   400  // ledgerSignTypedMessage sends the transaction to the Ledger wallet, and waits for the user
   401  // to confirm or deny the transaction.
   402  //
   403  // The signing protocol is defined as follows:
   404  //
   405  //	CLA | INS | P1 | P2                          | Lc  | Le
   406  //	----+-----+----+-----------------------------+-----+---
   407  //	 E0 | 0C  | 00 | implementation version : 00 | variable | variable
   408  //
   409  // Where the input is:
   410  //
   411  //	Description                                      | Length
   412  //	-------------------------------------------------+----------
   413  //	Number of BIP 32 derivations to perform (max 10) | 1 byte
   414  //	First derivation index (big endian)              | 4 bytes
   415  //	...                                              | 4 bytes
   416  //	Last derivation index (big endian)               | 4 bytes
   417  //	domain hash                                      | 32 bytes
   418  //	message hash                                     | 32 bytes
   419  //
   420  // And the output data is:
   421  //
   422  //	Description | Length
   423  //	------------+---------
   424  //	signature V | 1 byte
   425  //	signature R | 32 bytes
   426  //	signature S | 32 bytes
   427  func (w *ledgerDriver) ledgerSignTypedMessage(derivationPath []uint32, domainHash []byte, messageHash []byte) ([]byte, error) {
   428  	// Flatten the derivation path into the Ledger request
   429  	path := make([]byte, 1+4*len(derivationPath))
   430  	path[0] = byte(len(derivationPath))
   431  	for i, component := range derivationPath {
   432  		binary.BigEndian.PutUint32(path[1+4*i:], component)
   433  	}
   434  	// Create the 712 message
   435  	payload := append(path, domainHash...)
   436  	payload = append(payload, messageHash...)
   437  
   438  	// Send the request and wait for the response
   439  	var (
   440  		op    = ledgerP1InitTypedMessageData
   441  		reply []byte
   442  		err   error
   443  	)
   444  
   445  	// Send the message over, ensuring it's processed correctly
   446  	reply, err = w.ledgerExchange(ledgerOpSignTypedMessage, op, 0, payload)
   447  
   448  	if err != nil {
   449  		return nil, err
   450  	}
   451  
   452  	// Extract the Ethereum signature and do a sanity validation
   453  	if len(reply) != crypto.SignatureLength {
   454  		return nil, errors.New("reply lacks signature")
   455  	}
   456  	signature := append(reply[1:], reply[0])
   457  	return signature, nil
   458  }
   459  
   460  // ledgerExchange performs a data exchange with the Ledger wallet, sending it a
   461  // message and retrieving the response.
   462  //
   463  // The common transport header is defined as follows:
   464  //
   465  //	Description                           | Length
   466  //	--------------------------------------+----------
   467  //	Communication channel ID (big endian) | 2 bytes
   468  //	Command tag                           | 1 byte
   469  //	Packet sequence index (big endian)    | 2 bytes
   470  //	Payload                               | arbitrary
   471  //
   472  // The Communication channel ID allows commands multiplexing over the same
   473  // physical link. It is not used for the time being, and should be set to 0101
   474  // to avoid compatibility issues with implementations ignoring a leading 00 byte.
   475  //
   476  // The Command tag describes the message content. Use TAG_APDU (0x05) for standard
   477  // APDU payloads, or TAG_PING (0x02) for a simple link test.
   478  //
   479  // The Packet sequence index describes the current sequence for fragmented payloads.
   480  // The first fragment index is 0x00.
   481  //
   482  // APDU Command payloads are encoded as follows:
   483  //
   484  //	Description              | Length
   485  //	-----------------------------------
   486  //	APDU length (big endian) | 2 bytes
   487  //	APDU CLA                 | 1 byte
   488  //	APDU INS                 | 1 byte
   489  //	APDU P1                  | 1 byte
   490  //	APDU P2                  | 1 byte
   491  //	APDU length              | 1 byte
   492  //	Optional APDU data       | arbitrary
   493  func (w *ledgerDriver) ledgerExchange(opcode ledgerOpcode, p1 ledgerParam1, p2 ledgerParam2, data []byte) ([]byte, error) {
   494  	// Construct the message payload, possibly split into multiple chunks
   495  	apdu := make([]byte, 2, 7+len(data))
   496  
   497  	binary.BigEndian.PutUint16(apdu, uint16(5+len(data)))
   498  	apdu = append(apdu, []byte{0xe0, byte(opcode), byte(p1), byte(p2), byte(len(data))}...)
   499  	apdu = append(apdu, data...)
   500  
   501  	// Stream all the chunks to the device
   502  	header := []byte{0x01, 0x01, 0x05, 0x00, 0x00} // Channel ID and command tag appended
   503  	chunk := make([]byte, 64)
   504  	space := len(chunk) - len(header)
   505  
   506  	for i := 0; len(apdu) > 0; i++ {
   507  		// Construct the new message to stream
   508  		chunk = append(chunk[:0], header...)
   509  		binary.BigEndian.PutUint16(chunk[3:], uint16(i))
   510  
   511  		if len(apdu) > space {
   512  			chunk = append(chunk, apdu[:space]...)
   513  			apdu = apdu[space:]
   514  		} else {
   515  			chunk = append(chunk, apdu...)
   516  			apdu = nil
   517  		}
   518  		// Send over to the device
   519  		w.log.Trace("Data chunk sent to the Ledger", "chunk", hexutil.Bytes(chunk))
   520  		if _, err := w.device.Write(chunk); err != nil {
   521  			return nil, err
   522  		}
   523  	}
   524  	// Stream the reply back from the wallet in 64 byte chunks
   525  	var reply []byte
   526  	chunk = chunk[:64] // Yeah, we surely have enough space
   527  	for {
   528  		// Read the next chunk from the Ledger wallet
   529  		if _, err := io.ReadFull(w.device, chunk); err != nil {
   530  			return nil, err
   531  		}
   532  		w.log.Trace("Data chunk received from the Ledger", "chunk", hexutil.Bytes(chunk))
   533  
   534  		// Make sure the transport header matches
   535  		if chunk[0] != 0x01 || chunk[1] != 0x01 || chunk[2] != 0x05 {
   536  			return nil, errLedgerReplyInvalidHeader
   537  		}
   538  		// If it's the first chunk, retrieve the total message length
   539  		var payload []byte
   540  
   541  		if chunk[3] == 0x00 && chunk[4] == 0x00 {
   542  			reply = make([]byte, 0, int(binary.BigEndian.Uint16(chunk[5:7])))
   543  			payload = chunk[7:]
   544  		} else {
   545  			payload = chunk[5:]
   546  		}
   547  		// Append to the reply and stop when filled up
   548  		if left := cap(reply) - len(reply); left > len(payload) {
   549  			reply = append(reply, payload...)
   550  		} else {
   551  			reply = append(reply, payload[:left]...)
   552  			break
   553  		}
   554  	}
   555  	return reply[:len(reply)-2], nil
   556  }
   557  */