Package tlslite :: Module messages |
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# Source Code for Module tlslite.messages

      1  # Authors:
      2  #   Trevor Perrin
      3  #   Google - handling CertificateRequest.certificate_types
      4  #   Google (adapted by Sam Rushing and Marcelo Fernandez) - NPN support
      5  #   Dimitris Moraitis - Anon ciphersuites
      6  #
      7  # See the LICENSE file for legal information regarding use of this file.
      8
      9  """Classes representing TLS messages."""
     10
     11  from .utils.compat import *
     12  from .utils.cryptomath import *
     13  from .errors import *
     14  from .utils.codec import *
     15  from .constants import *
     16  from .x509 import X509
     17  from .x509certchain import X509CertChain
     18  from .utils.tackwrapper import *
     19
     20 -class RecordHeader3(object):
     21 -    def __init__(self):
     22          self.type = 0
     23          self.version = (0,0)
     24          self.length = 0
     25          self.ssl2 = False
     26
     27 -    def create(self, version, type, length):
     28          self.type = type
     29          self.version = version
     30          self.length = length
     31          return self
     32
     33 -    def write(self):
     34          w = Writer()
     35          w.add(self.type, 1)
     36          w.add(self.version[0], 1)
     37          w.add(self.version[1], 1)
     38          w.add(self.length, 2)
     39          return w.bytes
     40
     41 -    def parse(self, p):
     42          self.type = p.get(1)
     43          self.version = (p.get(1), p.get(1))
     44          self.length = p.get(2)
     45          self.ssl2 = False
     46          return self
     47
     48 -class RecordHeader2(object):
     49 -    def __init__(self):
     50          self.type = 0
     51          self.version = (0,0)
     52          self.length = 0
     53          self.ssl2 = True
     54
     55 -    def parse(self, p):
     56          if p.get(1)!=128:
     57              raise SyntaxError()
     58          self.type = ContentType.handshake
     59          self.version = (2,0)
     60          #We don't support 2-byte-length-headers; could be a problem
     61          self.length = p.get(1)
     62          return self
     63
     64
     65 -class Alert(object):
     66 -    def __init__(self):
     67          self.contentType = ContentType.alert
     68          self.level = 0
     69          self.description = 0
     70
     71 -    def create(self, description, level=AlertLevel.fatal):
     72          self.level = level
     73          self.description = description
     74          return self
     75
     76 -    def parse(self, p):
     77          p.setLengthCheck(2)
     78          self.level = p.get(1)
     79          self.description = p.get(1)
     80          p.stopLengthCheck()
     81          return self
     82
     83 -    def write(self):
     84          w = Writer()
     85          w.add(self.level, 1)
     86          w.add(self.description, 1)
     87          return w.bytes
     88
     89
     90 -class HandshakeMsg(object):
     91 -    def __init__(self, handshakeType):
     92          self.contentType = ContentType.handshake
     93          self.handshakeType = handshakeType
     94
     95 -    def postWrite(self, w):
     96          headerWriter = Writer()
     97          headerWriter.add(self.handshakeType, 1)
     98          headerWriter.add(len(w.bytes), 3)
     99          return headerWriter.bytes + w.bytes
    100
    101 -class ClientHello(HandshakeMsg):
    102 -    def __init__(self, ssl2=False):
    103          HandshakeMsg.__init__(self, HandshakeType.client_hello)
    104          self.ssl2 = ssl2
    105          self.client_version = (0,0)
    106          self.random = bytearray(32)
    107          self.session_id = bytearray(0)
    108          self.cipher_suites = []         # a list of 16-bit values
    109          self.certificate_types = [CertificateType.x509]
    110          self.compression_methods = []   # a list of 8-bit values
    111          self.srp_username = None        # a string
    112          self.tack = False
    113          self.supports_npn = False
    114          self.server_name = bytearray(0)
    115
    116 -    def create(self, version, random, session_id, cipher_suites,
    117                 certificate_types=None, srpUsername=None,
    118                 tack=False, supports_npn=False, serverName=None):
    119          self.client_version = version
    120          self.random = random
    121          self.session_id = session_id
    122          self.cipher_suites = cipher_suites
    123          self.certificate_types = certificate_types
    124          self.compression_methods = [0]
    125          if srpUsername:
    126              self.srp_username = bytearray(srpUsername, "utf-8")
    127          self.tack = tack
    128          self.supports_npn = supports_npn
    129          if serverName:
    130              self.server_name = bytearray(serverName, "utf-8")
    131          return self
    132
    133 -    def parse(self, p):
    134          if self.ssl2:
    135              self.client_version = (p.get(1), p.get(1))
    136              cipherSpecsLength = p.get(2)
    137              sessionIDLength = p.get(2)
    138              randomLength = p.get(2)
    139              self.cipher_suites = p.getFixList(3, cipherSpecsLength//3)
    140              self.session_id = p.getFixBytes(sessionIDLength)
    141              self.random = p.getFixBytes(randomLength)
    142              if len(self.random) < 32:
    143                  zeroBytes = 32-len(self.random)
    144                  self.random = bytearray(zeroBytes) + self.random
    145              self.compression_methods = [0]#Fake this value
    146
    147              #We're not doing a stopLengthCheck() for SSLv2, oh well..
    148          else:
    149              p.startLengthCheck(3)
    150              self.client_version = (p.get(1), p.get(1))
    151              self.random = p.getFixBytes(32)
    152              self.session_id = p.getVarBytes(1)
    153              self.cipher_suites = p.getVarList(2, 2)
    154              self.compression_methods = p.getVarList(1, 1)
    155              if not p.atLengthCheck():
    156                  totalExtLength = p.get(2)
    157                  soFar = 0
    158                  while soFar != totalExtLength:
    159                      extType = p.get(2)
    160                      extLength = p.get(2)
    161                      index1 = p.index
    162                      if extType == ExtensionType.srp:
    163                          self.srp_username = p.getVarBytes(1)
    164                      elif extType == ExtensionType.cert_type:
    165                          self.certificate_types = p.getVarList(1, 1)
    166                      elif extType == ExtensionType.tack:
    167                          self.tack = True
    168                      elif extType == ExtensionType.supports_npn:
    169                          self.supports_npn = True
    170                      elif extType == ExtensionType.server_name:
    171                          serverNameListBytes = p.getFixBytes(extLength)
    172                          p2 = Parser(serverNameListBytes)
    173                          p2.startLengthCheck(2)
    174                          while 1:
    175                              if p2.atLengthCheck():
    176                                  break # no host_name, oh well
    177                              name_type = p2.get(1)
    178                              hostNameBytes = p2.getVarBytes(2)
    179                              if name_type == NameType.host_name:
    180                                  self.server_name = hostNameBytes
    181                                  break
    182                      else:
    183                          _ = p.getFixBytes(extLength)
    184                      index2 = p.index
    185                      if index2 - index1 != extLength:
    186                          raise SyntaxError("Bad length for extension_data")
    187                      soFar += 4 + extLength
    188              p.stopLengthCheck()
    189          return self
    190
    191 -    def write(self):
    192          w = Writer()
    193          w.add(self.client_version[0], 1)
    194          w.add(self.client_version[1], 1)
    195          w.addFixSeq(self.random, 1)
    196          w.addVarSeq(self.session_id, 1, 1)
    197          w.addVarSeq(self.cipher_suites, 2, 2)
    198          w.addVarSeq(self.compression_methods, 1, 1)
    199
    200          w2 = Writer() # For Extensions
    201          if self.certificate_types and self.certificate_types != \
    202                  [CertificateType.x509]:
    203              w2.add(ExtensionType.cert_type, 2)
    204              w2.add(len(self.certificate_types)+1, 2)
    205              w2.addVarSeq(self.certificate_types, 1, 1)
    206          if self.srp_username:
    207              w2.add(ExtensionType.srp, 2)
    208              w2.add(len(self.srp_username)+1, 2)
    209              w2.addVarSeq(self.srp_username, 1, 1)
    210          if self.supports_npn:
    211              w2.add(ExtensionType.supports_npn, 2)
    212              w2.add(0, 2)
    213          if self.server_name:
    214              w2.add(ExtensionType.server_name, 2)
    215              w2.add(len(self.server_name)+5, 2)
    216              w2.add(len(self.server_name)+3, 2)
    217              w2.add(NameType.host_name, 1)
    218              w2.addVarSeq(self.server_name, 1, 2)
    219          if self.tack:
    220              w2.add(ExtensionType.tack, 2)
    221              w2.add(0, 2)
    222          if len(w2.bytes):
    223              w.add(len(w2.bytes), 2)
    224              w.bytes += w2.bytes
    225          return self.postWrite(w)
    226
    227 -class BadNextProtos(Exception):
    228 -    def __init__(self, l):
    229          self.length = l
    230
    231 -    def __str__(self):
    232          return 'Cannot encode a list of next protocols because it contains an element with invalid length %d. Element lengths must be 0 < x < 256' % self.length
    233
    234 -class ServerHello(HandshakeMsg):
    235 -    def __init__(self):
    236          HandshakeMsg.__init__(self, HandshakeType.server_hello)
    237          self.server_version = (0,0)
    238          self.random = bytearray(32)
    239          self.session_id = bytearray(0)
    240          self.cipher_suite = 0
    241          self.certificate_type = CertificateType.x509
    242          self.compression_method = 0
    243          self.tackExt = None
    244          self.next_protos_advertised = None
    245          self.next_protos = None
    246
    247 -    def create(self, version, random, session_id, cipher_suite,
    248                 certificate_type, tackExt, next_protos_advertised):
    249          self.server_version = version
    250          self.random = random
    251          self.session_id = session_id
    252          self.cipher_suite = cipher_suite
    253          self.certificate_type = certificate_type
    254          self.compression_method = 0
    255          self.tackExt = tackExt
    256          self.next_protos_advertised = next_protos_advertised
    257          return self
    258
    259 -    def parse(self, p):
    260          p.startLengthCheck(3)
    261          self.server_version = (p.get(1), p.get(1))
    262          self.random = p.getFixBytes(32)
    263          self.session_id = p.getVarBytes(1)
    264          self.cipher_suite = p.get(2)
    265          self.compression_method = p.get(1)
    266          if not p.atLengthCheck():
    267              totalExtLength = p.get(2)
    268              soFar = 0
    269              while soFar != totalExtLength:
    270                  extType = p.get(2)
    271                  extLength = p.get(2)
    272                  if extType == ExtensionType.cert_type:
    273                      if extLength != 1:
    274                          raise SyntaxError()
    275                      self.certificate_type = p.get(1)
    276                  elif extType == ExtensionType.tack and tackpyLoaded:
    277                      self.tackExt = TackExtension(p.getFixBytes(extLength))
    278                  elif extType == ExtensionType.supports_npn:
    279                      self.next_protos = self.__parse_next_protos(p.getFixBytes(extLength))
    280                  else:
    281                      p.getFixBytes(extLength)
    282                  soFar += 4 + extLength
    283          p.stopLengthCheck()
    284          return self
    285
    286 -    def __parse_next_protos(self, b):
    287          protos = []
    288          while True:
    289              if len(b) == 0:
    290                  break
    291              l = b[0]
    292              b = b[1:]
    293              if len(b) < l:
    294                  raise BadNextProtos(len(b))
    295              protos.append(b[:l])
    296              b = b[l:]
    297          return protos
    298
    299 -    def __next_protos_encoded(self):
    300          b = bytearray()
    301          for e in self.next_protos_advertised:
    302              if len(e) > 255 or len(e) == 0:
    303                  raise BadNextProtos(len(e))
    304              b += bytearray( [len(e)] ) + bytearray(e)
    305          return b
    306
    307 -    def write(self):
    308          w = Writer()
    309          w.add(self.server_version[0], 1)
    310          w.add(self.server_version[1], 1)
    311          w.addFixSeq(self.random, 1)
    312          w.addVarSeq(self.session_id, 1, 1)
    313          w.add(self.cipher_suite, 2)
    314          w.add(self.compression_method, 1)
    315
    316          w2 = Writer() # For Extensions
    317          if self.certificate_type and self.certificate_type != \
    318                  CertificateType.x509:
    319              w2.add(ExtensionType.cert_type, 2)
    320              w2.add(1, 2)
    321              w2.add(self.certificate_type, 1)
    322          if self.tackExt:
    323              b = self.tackExt.serialize()
    324              w2.add(ExtensionType.tack, 2)
    325              w2.add(len(b), 2)
    326              w2.bytes += b
    327          if self.next_protos_advertised is not None:
    328              encoded_next_protos_advertised = self.__next_protos_encoded()
    329              w2.add(ExtensionType.supports_npn, 2)
    330              w2.add(len(encoded_next_protos_advertised), 2)
    331              w2.addFixSeq(encoded_next_protos_advertised, 1)
    332          if len(w2.bytes):
    333              w.add(len(w2.bytes), 2)
    334              w.bytes += w2.bytes
    335          return self.postWrite(w)
    336
    337
    338 -class Certificate(HandshakeMsg):
    339 -    def __init__(self, certificateType):
    340          HandshakeMsg.__init__(self, HandshakeType.certificate)
    341          self.certificateType = certificateType
    342          self.certChain = None
    343
    344 -    def create(self, certChain):
    345          self.certChain = certChain
    346          return self
    347
    348 -    def parse(self, p):
    349          p.startLengthCheck(3)
    350          if self.certificateType == CertificateType.x509:
    351              chainLength = p.get(3)
    352              index = 0
    353              certificate_list = []
    354              while index != chainLength:
    355                  certBytes = p.getVarBytes(3)
    356                  x509 = X509()
    357                  x509.parseBinary(certBytes)
    358                  certificate_list.append(x509)
    359                  index += len(certBytes)+3
    360              if certificate_list:
    361                  self.certChain = X509CertChain(certificate_list)
    362          else:
    363              raise AssertionError()
    364
    365          p.stopLengthCheck()
    366          return self
    367
    368 -    def write(self):
    369          w = Writer()
    370          if self.certificateType == CertificateType.x509:
    371              chainLength = 0
    372              if self.certChain:
    373                  certificate_list = self.certChain.x509List
    374              else:
    375                  certificate_list = []
    376              #determine length
    377              for cert in certificate_list:
    378                  bytes = cert.writeBytes()
    379                  chainLength += len(bytes)+3
    380              #add bytes
    381              w.add(chainLength, 3)
    382              for cert in certificate_list:
    383                  bytes = cert.writeBytes()
    384                  w.addVarSeq(bytes, 1, 3)
    385          else:
    386              raise AssertionError()
    387          return self.postWrite(w)
    388
    389 -class CertificateRequest(HandshakeMsg):
    390 -    def __init__(self):
    391          HandshakeMsg.__init__(self, HandshakeType.certificate_request)
    392          #Apple's Secure Transport library rejects empty certificate_types, so
    393          #default to rsa_sign.
    394          self.certificate_types = [ClientCertificateType.rsa_sign]
    395          self.certificate_authorities = []
    396
    397 -    def create(self, certificate_types, certificate_authorities):
    398          self.certificate_types = certificate_types
    399          self.certificate_authorities = certificate_authorities
    400          return self
    401
    402 -    def parse(self, p):
    403          p.startLengthCheck(3)
    404          self.certificate_types = p.getVarList(1, 1)
    405          ca_list_length = p.get(2)
    406          index = 0
    407          self.certificate_authorities = []
    408          while index != ca_list_length:
    409            ca_bytes = p.getVarBytes(2)
    410            self.certificate_authorities.append(ca_bytes)
    411            index += len(ca_bytes)+2
    412          p.stopLengthCheck()
    413          return self
    414
    415 -    def write(self):
    416          w = Writer()
    417          w.addVarSeq(self.certificate_types, 1, 1)
    418          caLength = 0
    419          #determine length
    420          for ca_dn in self.certificate_authorities:
    421              caLength += len(ca_dn)+2
    422          w.add(caLength, 2)
    423          #add bytes
    424          for ca_dn in self.certificate_authorities:
    425              w.addVarSeq(ca_dn, 1, 2)
    426          return self.postWrite(w)
    427
    428 -class ServerKeyExchange(HandshakeMsg):
    429 -    def __init__(self, cipherSuite):
    430          HandshakeMsg.__init__(self, HandshakeType.server_key_exchange)
    431          self.cipherSuite = cipherSuite
    432          self.srp_N = 0
    433          self.srp_g = 0
    434          self.srp_s = bytearray(0)
    435          self.srp_B = 0
    436          # Anon DH params:
    437          self.dh_p = 0
    438          self.dh_g = 0
    439          self.dh_Ys = 0
    440          self.signature = bytearray(0)
    441
    442 -    def createSRP(self, srp_N, srp_g, srp_s, srp_B):
    443          self.srp_N = srp_N
    444          self.srp_g = srp_g
    445          self.srp_s = srp_s
    446          self.srp_B = srp_B
    447          return self
    448
    449 -    def createDH(self, dh_p, dh_g, dh_Ys):
    450          self.dh_p = dh_p
    451          self.dh_g = dh_g
    452          self.dh_Ys = dh_Ys
    453          return self
    454
    455 -    def parse(self, p):
    456          p.startLengthCheck(3)
    457          if self.cipherSuite in CipherSuite.srpAllSuites:
    458              self.srp_N = bytesToNumber(p.getVarBytes(2))
    459              self.srp_g = bytesToNumber(p.getVarBytes(2))
    460              self.srp_s = p.getVarBytes(1)
    461              self.srp_B = bytesToNumber(p.getVarBytes(2))
    462              if self.cipherSuite in CipherSuite.srpCertSuites:
    463                  self.signature = p.getVarBytes(2)
    464          elif self.cipherSuite in CipherSuite.anonSuites:
    465              self.dh_p = bytesToNumber(p.getVarBytes(2))
    466              self.dh_g = bytesToNumber(p.getVarBytes(2))
    467              self.dh_Ys = bytesToNumber(p.getVarBytes(2))
    468          p.stopLengthCheck()
    469          return self
    470
    471 -    def write(self):
    472          w = Writer()
    473          if self.cipherSuite in CipherSuite.srpAllSuites:
    474              w.addVarSeq(numberToByteArray(self.srp_N), 1, 2)
    475              w.addVarSeq(numberToByteArray(self.srp_g), 1, 2)
    476              w.addVarSeq(self.srp_s, 1, 1)
    477              w.addVarSeq(numberToByteArray(self.srp_B), 1, 2)
    478              if self.cipherSuite in CipherSuite.srpCertSuites:
    479                  w.addVarSeq(self.signature, 1, 2)
    480          elif self.cipherSuite in CipherSuite.anonSuites:
    481              w.addVarSeq(numberToByteArray(self.dh_p), 1, 2)
    482              w.addVarSeq(numberToByteArray(self.dh_g), 1, 2)
    483              w.addVarSeq(numberToByteArray(self.dh_Ys), 1, 2)
    484              if self.cipherSuite in []: # TODO support for signed_params
    485                  w.addVarSeq(self.signature, 1, 2)
    486          return self.postWrite(w)
    487
    488 -    def hash(self, clientRandom, serverRandom):
    489          oldCipherSuite = self.cipherSuite
    490          self.cipherSuite = None
    491          try:
    492              bytes = clientRandom + serverRandom + self.write()[4:]
    493              return MD5(bytes) + SHA1(bytes)
    494          finally:
    495              self.cipherSuite = oldCipherSuite
    496
    497 -class ServerHelloDone(HandshakeMsg):
    498 -    def __init__(self):
    499          HandshakeMsg.__init__(self, HandshakeType.server_hello_done)
    500
    501 -    def create(self):
    502          return self
    503
    504 -    def parse(self, p):
    505          p.startLengthCheck(3)
    506          p.stopLengthCheck()
    507          return self
    508
    509 -    def write(self):
    510          w = Writer()
    511          return self.postWrite(w)
    512
    513 -class ClientKeyExchange(HandshakeMsg):
    514 -    def __init__(self, cipherSuite, version=None):
    515          HandshakeMsg.__init__(self, HandshakeType.client_key_exchange)
    516          self.cipherSuite = cipherSuite
    517          self.version = version
    518          self.srp_A = 0
    519          self.encryptedPreMasterSecret = bytearray(0)
    520
    521 -    def createSRP(self, srp_A):
    522          self.srp_A = srp_A
    523          return self
    524
    525 -    def createRSA(self, encryptedPreMasterSecret):
    526          self.encryptedPreMasterSecret = encryptedPreMasterSecret
    527          return self
    528
    529 -    def createDH(self, dh_Yc):
    530          self.dh_Yc = dh_Yc
    531          return self
    532
    533 -    def parse(self, p):
    534          p.startLengthCheck(3)
    535          if self.cipherSuite in CipherSuite.srpAllSuites:
    536              self.srp_A = bytesToNumber(p.getVarBytes(2))
    537          elif self.cipherSuite in CipherSuite.certSuites:
    538              if self.version in ((3,1), (3,2)):
    539                  self.encryptedPreMasterSecret = p.getVarBytes(2)
    540              elif self.version == (3,0):
    541                  self.encryptedPreMasterSecret = \
    542                      p.getFixBytes(len(p.bytes)-p.index)
    543              else:
    544                  raise AssertionError()
    545          elif self.cipherSuite in CipherSuite.anonSuites:
    546              self.dh_Yc = bytesToNumber(p.getVarBytes(2))
    547          else:
    548              raise AssertionError()
    549          p.stopLengthCheck()
    550          return self
    551
    552 -    def write(self):
    553          w = Writer()
    554          if self.cipherSuite in CipherSuite.srpAllSuites:
    555              w.addVarSeq(numberToByteArray(self.srp_A), 1, 2)
    556          elif self.cipherSuite in CipherSuite.certSuites:
    557              if self.version in ((3,1), (3,2)):
    558                  w.addVarSeq(self.encryptedPreMasterSecret, 1, 2)
    559              elif self.version == (3,0):
    560                  w.addFixSeq(self.encryptedPreMasterSecret, 1)
    561              else:
    562                  raise AssertionError()
    563          elif self.cipherSuite in CipherSuite.anonSuites:
    564              w.addVarSeq(numberToByteArray(self.dh_Yc), 1, 2)
    565          else:
    566              raise AssertionError()
    567          return self.postWrite(w)
    568
    569 -class CertificateVerify(HandshakeMsg):
    570 -    def __init__(self):
    571          HandshakeMsg.__init__(self, HandshakeType.certificate_verify)
    572          self.signature = bytearray(0)
    573
    574 -    def create(self, signature):
    575          self.signature = signature
    576          return self
    577
    578 -    def parse(self, p):
    579          p.startLengthCheck(3)
    580          self.signature = p.getVarBytes(2)
    581          p.stopLengthCheck()
    582          return self
    583
    584 -    def write(self):
    585          w = Writer()
    586          w.addVarSeq(self.signature, 1, 2)
    587          return self.postWrite(w)
    588
    589 -class ChangeCipherSpec(object):
    590 -    def __init__(self):
    591          self.contentType = ContentType.change_cipher_spec
    592          self.type = 1
    593
    594 -    def create(self):
    595          self.type = 1
    596          return self
    597
    598 -    def parse(self, p):
    599          p.setLengthCheck(1)
    600          self.type = p.get(1)
    601          p.stopLengthCheck()
    602          return self
    603
    604 -    def write(self):
    605          w = Writer()
    606          w.add(self.type,1)
    607          return w.bytes
    608
    609
    610 -class NextProtocol(HandshakeMsg):
    611 -    def __init__(self):
    612          HandshakeMsg.__init__(self, HandshakeType.next_protocol)
    613          self.next_proto = None
    614
    615 -    def create(self, next_proto):
    616          self.next_proto = next_proto
    617          return self
    618
    619 -    def parse(self, p):
    620          p.startLengthCheck(3)
    621          self.next_proto = p.getVarBytes(1)
    622          _ = p.getVarBytes(1)
    623          p.stopLengthCheck()
    624          return self
    625
    626 -    def write(self, trial=False):
    627          w = Writer()
    628          w.addVarSeq(self.next_proto, 1, 1)
    629          paddingLen = 32 - ((len(self.next_proto) + 2) % 32)
    630          w.addVarSeq(bytearray(paddingLen), 1, 1)
    631          return self.postWrite(w)
    632
    633 -class Finished(HandshakeMsg):
    634 -    def __init__(self, version):
    635          HandshakeMsg.__init__(self, HandshakeType.finished)
    636          self.version = version
    637          self.verify_data = bytearray(0)
    638
    639 -    def create(self, verify_data):
    640          self.verify_data = verify_data
    641          return self
    642
    643 -    def parse(self, p):
    644          p.startLengthCheck(3)
    645          if self.version == (3,0):
    646              self.verify_data = p.getFixBytes(36)
    647          elif self.version in ((3,1), (3,2)):
    648              self.verify_data = p.getFixBytes(12)
    649          else:
    650              raise AssertionError()
    651          p.stopLengthCheck()
    652          return self
    653
    654 -    def write(self):
    655          w = Writer()
    656          w.addFixSeq(self.verify_data, 1)
    657          return self.postWrite(w)
    658
    659 -class ApplicationData(object):
    660 -    def __init__(self):
    661          self.contentType = ContentType.application_data
    662          self.bytes = bytearray(0)
    663
    664 -    def create(self, bytes):
    665          self.bytes = bytes
    666          return self
    667
    668 -    def splitFirstByte(self):
    669          newMsg = ApplicationData().create(self.bytes[:1])
    670          self.bytes = self.bytes[1:]
    671          return newMsg
    672
    673 -    def parse(self, p):
    674          self.bytes = p.bytes
    675          return self
    676
    677 -    def write(self):
    678          return self.bytes
    679