messages.py

# Authors:
#   Trevor Perrin
#   Google - handling CertificateRequest.certificate_types
#   Google (adapted by Sam Rushing and Marcelo Fernandez) - NPN support
#   Dimitris Moraitis - Anon ciphersuites
#   Yngve Pettersen (ported by Paul Sokolovsky) - TLS 1.2
#   Hubert Kario - 'extensions' cleanup
#
# See the LICENSE file for legal information regarding use of this file.

"""Classes representing TLS messages."""

from .utils.compat import *
from .utils.cryptomath import *
from .errors import *
from .utils.codec import *
from .constants import *
from .x509 import X509
from .x509certchain import X509CertChain
from .utils.tackwrapper import *
from .utils.deprecations import deprecated_attrs, deprecated_params
from .extensions import *
from .utils.format_output import none_as_unknown


class RecordHeader(object):
    """Generic interface to SSLv2 and SSLv3 (and later) record headers."""

    def __init__(self, ssl2):
        """Define instance variables."""
        self.type = 0
        self.version = (0, 0)
        self.length = 0
        self.ssl2 = ssl2


class RecordHeader3(RecordHeader):
    """SSLv3 (and later) TLS record header."""

    def __init__(self):
        """Define a SSLv3 style class."""
        super(RecordHeader3, self).__init__(ssl2=False)

    def create(self, version, type, length):
        """Set object values for writing (serialisation)."""
        self.type = type
        self.version = version
        self.length = length
        return self

    def write(self):
        """Serialise object to bytearray."""
        writer = Writer()
        writer.add(self.type, 1)
        writer.add(self.version[0], 1)
        writer.add(self.version[1], 1)
        writer.add(self.length, 2)
        return writer.bytes

    def parse(self, parser):
        """Deserialise object from Parser."""
        self.type = parser.get(1)
        self.version = (parser.get(1), parser.get(1))
        self.length = parser.get(2)
        self.ssl2 = False
        return self

    @property
    def typeName(self):
        matching = [x[0] for x in ContentType.__dict__.items()
                    if x[1] == self.type]
        if len(matching) == 0:
            return "unknown(" + str(self.type) + ")"
        else:
            return str(matching[0])

    def __str__(self):
        return "SSLv3 record,version({0[0]}.{0[1]}),"\
                "content type({1}),length({2})".format(self.version,
                                                       self.typeName,
                                                       self.length)

    def __repr__(self):
        return "RecordHeader3(type={0}, version=({1[0]}.{1[1]}), length={2})".\
                format(self.type, self.version, self.length)


class RecordHeader2(RecordHeader):
    """
    SSLv2 record header.

    :vartype padding: int
    :ivar padding: number of bytes added at end of message to make it multiple
        of block cipher size
    :vartype securityEscape: boolean
    :ivar securityEscape: whether the record contains a security escape message
    """

    def __init__(self):
        """Define a SSLv2 style class."""
        super(RecordHeader2, self).__init__(ssl2=True)
        self.padding = 0
        self.securityEscape = False

    def parse(self, parser):
        """Deserialise object from Parser."""
        firstByte = parser.get(1)
        secondByte = parser.get(1)
        if firstByte & 0x80:
            self.length = ((firstByte & 0x7f) << 8) | secondByte
        else:
            self.length = ((firstByte & 0x3f) << 8) | secondByte
            self.securityEscape = firstByte & 0x40 != 0
            self.padding = parser.get(1)

        self.type = ContentType.handshake
        self.version = (2, 0)
        return self

    def create(self, length, padding=0, securityEscape=False):
        """Set object's values."""
        self.length = length
        self.padding = padding
        self.securityEscape = securityEscape
        return self

    def write(self):
        """Serialise object to bytearray."""
        writer = Writer()

        shortHeader = not (self.padding or self.securityEscape)

        if ((shortHeader and self.length >= 0x8000) or
                (not shortHeader and self.length >= 0x4000)):
            raise ValueError("length too large")

        firstByte = 0
        if shortHeader:
            firstByte |= 0x80
        if self.securityEscape:
            firstByte |= 0x40
        firstByte |= self.length >> 8
        secondByte = self.length & 0xff

        writer.add(firstByte, 1)
        writer.add(secondByte, 1)
        if not shortHeader:
            writer.add(self.padding, 1)

        return writer.bytes


class Message(object):
    """Generic TLS message."""

    def __init__(self, contentType, data):
        """
        Initialize object with specified contentType and data.

        :type contentType: int
        :param contentType: TLS record layer content type of associated data
        :type data: bytearray
        :param data: data
        """
        self.contentType = contentType
        self.data = data

    def write(self):
        """Return serialised object data."""
        return self.data


class Alert(object):
    def __init__(self):
        self.contentType = ContentType.alert
        self.level = 0
        self.description = 0

    def create(self, description, level=AlertLevel.fatal):
        self.level = level
        self.description = description
        return self

    def parse(self, p):
        p.setLengthCheck(2)
        self.level = p.get(1)
        self.description = p.get(1)
        p.stopLengthCheck()
        return self

    def write(self):
        w = Writer()
        w.add(self.level, 1)
        w.add(self.description, 1)
        return w.bytes

    @property
    def levelName(self):
        return none_as_unknown(AlertLevel.toRepr(self.level),
                             self.level)

    @property
    def descriptionName(self):
        return none_as_unknown(AlertDescription.toRepr(self.description),
                             self.description)

    def __str__(self):
        return "Alert, level:{0}, description:{1}".format(self.levelName,
                                                          self.descriptionName)

    def __repr__(self):
        return "Alert(level={0}, description={1})".format(self.level,
                                                          self.description)


class HandshakeMsg(object):
    def __init__(self, handshakeType):
        self.contentType = ContentType.handshake
        self.handshakeType = handshakeType

    def __eq__(self, other):
        """Check if other object represents the same data as this object."""
        if hasattr(self, "write") and hasattr(other, "write"):
            return self.write() == other.write()
        else:
            return False

    def __ne__(self, other):
        """Check if other object represents different data as this object."""
        return not self.__eq__(other)

    def postWrite(self, w):
        headerWriter = Writer()
        headerWriter.add(self.handshakeType, 1)
        headerWriter.add(len(w.bytes), 3)
        return headerWriter.bytes + w.bytes


class HelloMessage(HandshakeMsg):
    """
    Class for sharing code between :py:class:`ClientHello` and
    :py:class:`ServerHello`.
    """

    def __init__(self, *args, **kwargs):
        """Initialize object."""
        super(HelloMessage, self).__init__(*args, **kwargs)
        self.extensions = None

    def getExtension(self, extType):
        """
        Return extension of given type if present, None otherwise.

        :rtype: ~tlslite.extensions.TLSExtension
        :raises TLSInternalError: when there are multiple extensions of the
            same type
        """
        if self.extensions is None:
            return None

        exts = [ext for ext in self.extensions if ext.extType == extType]
        if len(exts) > 1:
            raise TLSInternalError(
                "Multiple extensions of the same type present")
        elif len(exts) == 1:
            return exts[0]
        else:
            return None

    def addExtension(self, ext):
        """
        Add extension to internal list of extensions.

        :type ext: TLSExtension
        :param ext: extension object to add to list
        """
        if self.extensions is None:
            self.extensions = []

        self.extensions.append(ext)

    def _addExt(self, extType):
        """Add en empty extension of given type, if not already present"""
        ext = self.getExtension(extType)
        if ext is None:
            ext = TLSExtension(extType=extType).create(bytearray(0))
            self.addExtension(ext)

    def _removeExt(self, extType):
        """Remove extension of given type"""
        if self.extensions is not None:
            self.extensions[:] = (i for i in self.extensions
                                  if i.extType != extType)


    def _addOrRemoveExt(self, extType, add):
        """
        Remove or add an empty extension of given type.

        :type extType: int
        :param extType: numeric id of extension to add or remove
        :type add: boolean
        :param add: whether to add (True) or remove (False) the extension
        """
        if add:
            self._addExt(extType)
        else:
            self._removeExt(extType)


class ClientHello(HelloMessage):
    """
    Class for handling the ClientHello SSLv2/SSLv3/TLS message.

    :vartype certificate_types: list
    :ivar certificate_types: list of supported certificate types
        (deprecated)
    :vartype srp_username: bytearray
    :ivar srp_username: name of the user in SRP extension (deprecated)

    :vartype ~.supports_npn: boolean
    :ivar ~.supports_npn: NPN extension presence (deprecated)

    :vartype ~.tack: boolean
    :ivar ~.tack: TACK extension presence (deprecated)

    :vartype ~.server_name: bytearray
    :ivar ~.server_name: first host_name (type 0) present in SNI extension
        (deprecated)

    :vartype extensions: list of :py:class:`TLSExtension`
    :ivar extensions: list of TLS extensions parsed from wire or to send, see
        :py:class:`TLSExtension` and child classes for exact examples
    """

    def __init__(self, ssl2=False):
        super(ClientHello, self).__init__(HandshakeType.client_hello)
        self.ssl2 = ssl2
        self.client_version = (0, 0)
        self.random = bytearray(32)
        self.session_id = bytearray(0)
        self.cipher_suites = []         # a list of 16-bit values
        self.compression_methods = []   # a list of 8-bit values

    def __str__(self):
        """
        Return human readable representation of Client Hello.

        :rtype: str
        """
        if self.session_id.count(bytearray(b'\x00')) == len(self.session_id)\
                and len(self.session_id) != 0:
            session = "bytearray(b'\\x00'*{0})".format(len(self.session_id))
        else:
            session = repr(self.session_id)
        ret = "client_hello,version({0[0]}.{0[1]}),random(...),"\
              "session ID({1!s}),cipher suites({2!r}),"\
              "compression methods({3!r})".format(
                  self.client_version, session,
                  self.cipher_suites, self.compression_methods)

        if self.extensions is not None:
            ret += ",extensions({0!r})".format(self.extensions)

        return ret

    def __repr__(self):
        """
        Return machine readable representation of Client Hello.

        :rtype: str
        """
        return "ClientHello(ssl2={0}, client_version=({1[0]}.{1[1]}), "\
               "random={2!r}, session_id={3!r}, cipher_suites={4!r}, "\
               "compression_methods={5}, extensions={6})".format(
                   self.ssl2, self.client_version, self.random,
                   self.session_id, self.cipher_suites,
                   self.compression_methods, self.extensions)

    @property
    def certificate_types(self):
        """
        Return the list of certificate types supported.

        .. deprecated:: 0.5
            use extensions field to get the extension for inspection
        """
        cert_type = self.getExtension(ExtensionType.cert_type)
        if cert_type is None:
            # XXX backwards compatibility: TLSConnection
            # depends on a default value of this property
            return [CertificateType.x509]
        else:
            return cert_type.certTypes

    @certificate_types.setter
    def certificate_types(self, val):
        """
        Set list of supported certificate types.

        Sets the list of supported types to list given in :py:obj:`val` if the
        cert_type extension is present. Creates the extension and places it
        last in the list otherwise.

        :type val: list
        :param val: list of supported certificate types by client encoded as
            single byte integers
        """
        cert_type = self.getExtension(ExtensionType.cert_type)

        if cert_type is None:
            ext = ClientCertTypeExtension().create(val)
            self.addExtension(ext)
        else:
            cert_type.certTypes = val

    @property
    def srp_username(self):
        """
        Return username for the SRP.

        .. deprecated:: 0.5
            use extensions field to get the extension for inspection
        """
        srp_ext = self.getExtension(ExtensionType.srp)

        if srp_ext is None:
            return None
        else:
            return srp_ext.identity

    @srp_username.setter
    def srp_username(self, name):
        """
        Set the username for SRP.

        :type name: bytearray
        :param name: UTF-8 encoded username
        """
        srp_ext = self.getExtension(ExtensionType.srp)

        if srp_ext is None:
            ext = SRPExtension().create(name)
            self.addExtension(ext)
        else:
            srp_ext.identity = name

    @property
    def tack(self):
        """
        Return whether the client supports TACK.

        .. deprecated:: 0.5
            use extensions field to get the extension for inspection

        :rtype: boolean
        """
        return self.getExtension(ExtensionType.tack) is not None

    @tack.setter
    def tack(self, present):
        """
        Create or delete the TACK extension.

        :type present: boolean
        :param present: True will create extension while False will remove
            extension from client hello
        """
        self._addOrRemoveExt(ExtensionType.tack, present)

    @property
    def supports_npn(self):
        """
        Return whether client supports NPN extension.

        .. deprecated:: 0.5
            use extensions field to get the extension for inspection

        :rtype: boolean
        """
        return self.getExtension(ExtensionType.supports_npn) is not None

    @supports_npn.setter
    def supports_npn(self, present):
        """
        Create or delete the NPN extension.

        :type present: boolean
        :param present: selects whatever to create or remove the extension
            from list of supported ones
        """
        self._addOrRemoveExt(ExtensionType.supports_npn, present)

    @property
    def server_name(self):
        """
        Return first host_name present in SNI extension.

        .. deprecated:: 0.5
            use extensions field to get the extension for inspection

        :rtype: bytearray
        """
        sni_ext = self.getExtension(ExtensionType.server_name)
        if sni_ext is None:
            return bytearray(0)
        else:
            if len(sni_ext.hostNames) > 0:
                return sni_ext.hostNames[0]
            else:
                return bytearray(0)

    @server_name.setter
    def server_name(self, hostname):
        """
        Set the first host_name present in SNI extension.

        :type hostname: bytearray
        :param hostname: name of the host_name to set
        """
        sni_ext = self.getExtension(ExtensionType.server_name)
        if sni_ext is None:
            sni_ext = SNIExtension().create(hostname)
            self.addExtension(sni_ext)
        else:
            names = list(sni_ext.hostNames)
            names[0] = hostname
            sni_ext.hostNames = names

    def create(self, version, random, session_id, cipher_suites,
               certificate_types=None, srpUsername=None,
               tack=False, supports_npn=None, serverName=None,
               extensions=None):
        """
        Create a ClientHello message for sending.

        :type version: tuple
        :param version: the highest supported TLS version encoded as two int
            tuple

        :type random: bytearray
        :param random: client provided random value, in old versions of TLS
            (before 1.2) the first 32 bits should include system time, also
            used as the "challenge" field in SSLv2

        :type session_id: bytearray
        :param session_id: ID of session, set when doing session resumption

        :type cipher_suites: list
        :param cipher_suites: list of ciphersuites advertised as supported

        :type certificate_types: list
        :param certificate_types: list of supported certificate types, uses
            TLS extension for signalling, as such requires TLS1.0 to work

        :type srpUsername: bytearray
        :param srpUsername: utf-8 encoded username for SRP, TLS extension

        :type tack: boolean
        :param tack: whatever to advertise support for TACK, TLS extension

        :type supports_npn: boolean
        :param supports_npn: whatever to advertise support for NPN, TLS
            extension

        :type serverName: bytearray
        :param serverName: the hostname to request in server name indication
            extension, TLS extension. Note that SNI allows to set multiple
            hostnames and values that are not hostnames, use
            :py:class:`~.extensions.SNIExtension`
            together with :py:obj:`extensions` to use it.

        :type extensions: list of :py:class:`~.extensions.TLSExtension`
        :param extensions: list of extensions to advertise
        """
        self.client_version = version
        self.random = random
        self.session_id = session_id
        self.cipher_suites = cipher_suites
        self.compression_methods = [0]
        if extensions is not None:
            self.extensions = extensions
        if certificate_types is not None:
            self.certificate_types = certificate_types
        if srpUsername is not None:
            if not isinstance(srpUsername, bytearray):
                raise TypeError("srpUsername must be a bytearray object")
            self.srp_username = srpUsername
        self.tack = tack
        if supports_npn is not None:
            self.supports_npn = supports_npn
        if serverName is not None:
            self.server_name = bytearray(serverName, "utf-8")
        return self

    def parse(self, p):
        """Deserialise object from on the wire data."""
        if self.ssl2:
            self.client_version = (p.get(1), p.get(1))
            cipherSpecsLength = p.get(2)
            sessionIDLength = p.get(2)
            randomLength = p.get(2)
            p.setLengthCheck(cipherSpecsLength +
                             sessionIDLength +
                             randomLength)
            self.cipher_suites = p.getFixList(3, cipherSpecsLength//3)
            self.session_id = p.getFixBytes(sessionIDLength)
            self.random = p.getFixBytes(randomLength)
            if len(self.random) < 32:
                zeroBytes = 32-len(self.random)
                self.random = bytearray(zeroBytes) + self.random
            self.compression_methods = [0]  # Fake this value
            p.stopLengthCheck()
        else:
            p.startLengthCheck(3)
            self.client_version = (p.get(1), p.get(1))
            self.random = p.getFixBytes(32)
            self.session_id = p.getVarBytes(1)
            self.cipher_suites = p.getVarList(2, 2)
            self.compression_methods = p.getVarList(1, 1)
            if not p.atLengthCheck():
                self.extensions = []
                totalExtLength = p.get(2)
                p2 = Parser(p.getFixBytes(totalExtLength))
                while p2.getRemainingLength() > 0:
                    ext = TLSExtension().parse(p2)
                    self.extensions += [ext]
            p.stopLengthCheck()
        return self

    def _writeSSL2(self):
        """Serialise SSLv2 object to on the wire data."""
        writer = Writer()
        writer.add(self.handshakeType, 1)
        writer.add(self.client_version[0], 1)
        writer.add(self.client_version[1], 1)

        ciphersWriter = Writer()
        ciphersWriter.addFixSeq(self.cipher_suites, 3)

        writer.add(len(ciphersWriter.bytes), 2)
        writer.add(len(self.session_id), 2)
        writer.add(len(self.random), 2)

        writer.bytes += ciphersWriter.bytes
        writer.bytes += self.session_id
        writer.bytes += self.random

        # postWrite() is necessary only for SSLv3/TLS
        return writer.bytes

    def _write(self):
        """Serialise SSLv3 or TLS object to on the wire data."""
        w = Writer()
        w.add(self.client_version[0], 1)
        w.add(self.client_version[1], 1)
        w.bytes += self.random
        w.addVarSeq(self.session_id, 1, 1)
        w.addVarSeq(self.cipher_suites, 2, 2)
        w.addVarSeq(self.compression_methods, 1, 1)

        if self.extensions is not None:
            w2 = Writer()
            for ext in self.extensions:
                w2.bytes += ext.write()

            w.add(len(w2.bytes), 2)
            w.bytes += w2.bytes
        return self.postWrite(w)

    def psk_truncate(self):
        """Return a truncated encoding of message without binders.

        In TLS 1.3, with PSK exchange, the ClientHello message is signed
        by the binders in it. Return the part that is symmetrically signed
        by those binders.

        See "PSK Binder" in draft-ietf-tls-tls13-23.

        :rtype: bytearray
        """
        ext = self.extensions[-1]
        if not isinstance(ext, PreSharedKeyExtension):
            raise ValueError("Last extension must be the pre_shared_key "
                             "extension")
        bts = self.write()
        # every binder has 1 byte long header and the list of them
        # has a 2 byte header
        length = sum(len(i) + 1 for i in ext.binders) + 2

        return bts[:-length]


    def write(self):
        """Serialise object to on the wire data."""
        if self.ssl2:
            return self._writeSSL2()
        else:
            return self._write()


class HelloRequest(HandshakeMsg):
    """
    Handling of Hello Request messages.
    """

    def __init__(self):
        super(HelloRequest, self).__init__(HandshakeType.hello_request)

    def create(self):
        return self

    def write(self):
        return self.postWrite(Writer())

    def parse(self, parser):
        # verify that the message is empty (the buffer will just contain
        # the length from header)
        parser.startLengthCheck(3)
        parser.stopLengthCheck()
        return self


class ServerHello(HelloMessage):
    """
    Handling of Server Hello messages.

    :vartype server_version: tuple
    :ivar server_version: protocol version encoded as two int tuple

    :vartype random: bytearray
    :ivar random: server random value

    :vartype session_id: bytearray
    :ivar session_id: session identifier for resumption

    :vartype cipher_suite: int
    :ivar cipher_suite: server selected cipher_suite

    :vartype compression_method: int
    :ivar compression_method: server selected compression method

    :vartype next_protos: list of bytearray
    :ivar next_protos: list of advertised protocols in NPN extension

    :vartype next_protos_advertised: list of bytearray
    :ivar next_protos_advertised: list of protocols advertised in NPN extension

    :vartype certificate_type: int
    :ivar certificate_type: certificate type selected by server

    :vartype extensions: list
    :ivar extensions: list of TLS extensions present in server_hello message,
        see :py:class:`~.extensions.TLSExtension` and child classes for exact
        examples
    """

    def __init__(self):
        """Initialise ServerHello object."""
        super(ServerHello, self).__init__(HandshakeType.server_hello)
        self.server_version = (0, 0)
        self.random = bytearray(32)
        self.session_id = bytearray(0)
        self.cipher_suite = 0
        self.compression_method = 0
        self._tack_ext = None

    def __str__(self):
        base = "server_hello,length({0}),version({1[0]}.{1[1]}),random(...),"\
                "session ID({2!r}),cipher({3:#x}),compression method({4})"\
                .format(len(self.write())-4, self.server_version,
                        self.session_id, self.cipher_suite,
                        self.compression_method)

        if self.extensions is None:
            return base

        ret = ",extensions["
        ret += ",".join(repr(x) for x in self.extensions)
        ret += "]"
        return base + ret

    def __repr__(self):
        return "ServerHello(server_version=({0[0]}, {0[1]}), random={1!r}, "\
                "session_id={2!r}, cipher_suite={3}, compression_method={4}, "\
                "_tack_ext={5}, extensions={6!r})".format(
                    self.server_version, self.random, self.session_id,
                    self.cipher_suite, self.compression_method, self._tack_ext,
                    self.extensions)

    @property
    def tackExt(self):
        """Return the TACK extension."""
        if self._tack_ext is None:
            ext = self.getExtension(ExtensionType.tack)
            if ext is None or not tackpyLoaded:
                return None
            else:
                self._tack_ext = TackExtension(ext.extData)
        return self._tack_ext

    @tackExt.setter
    def tackExt(self, val):
        """Set the TACK extension."""
        self._tack_ext = val
        # makes sure that extensions are included in the on the wire encoding
        if val is not None:
            if self.extensions is None:
                self.extensions = []

    @property
    def certificate_type(self):
        """
        Return the certificate type selected by server.

        :rtype: int
        """
        cert_type = self.getExtension(ExtensionType.cert_type)
        if cert_type is None:
            # XXX backwards compatibility, TLSConnection expects the default
            # value to be that
            return CertificateType.x509
        return cert_type.cert_type

    @certificate_type.setter
    def certificate_type(self, val):
        """
        Set the certificate type supported.

        :type val: int
        :param val: type of certificate
        """
        if val == CertificateType.x509 or val is None:
            # XXX backwards compatibility, x509 value should not be sent
            self._removeExt(ExtensionType.cert_type)
            return

        cert_type = self.getExtension(ExtensionType.cert_type)
        if cert_type is None:
            ext = ServerCertTypeExtension().create(val)
            self.addExtension(ext)
        else:
            cert_type.cert_type = val

    @property
    def next_protos(self):
        """
        Return the advertised protocols in NPN extension.

        :rtype: list of bytearrays
        """
        npn_ext = self.getExtension(ExtensionType.supports_npn)

        if npn_ext is None:
            return None
        else:
            return npn_ext.protocols

    @next_protos.setter
    def next_protos(self, val):
        """
        Set the advertised protocols in NPN extension.

        :type val: list
        :param val: list of protocols to advertise as UTF-8 encoded names
        """
        if val is None:
            # XXX: do not send empty extension
            self._removeExt(ExtensionType.supports_npn)
            return
        else:
            # convinience function, make sure the values are properly encoded
            val = [bytearray(x) for x in val]

        npn_ext = self.getExtension(ExtensionType.supports_npn)

        if npn_ext is None:
            ext = NPNExtension().create(val)
            self.addExtension(ext)
        else:
            npn_ext.protocols = val

    @property
    def next_protos_advertised(self):
        """
        Return the advertised protocols in NPN extension.

        :rtype: list of bytearrays
        """
        return self.next_protos

    @next_protos_advertised.setter
    def next_protos_advertised(self, val):
        """
        Set the advertised protocols in NPN extension.

        :type val: list
        :param val: list of protocols to advertise as UTF-8 encoded names
        """
        self.next_protos = val

    def create(self, version, random, session_id, cipher_suite,
               certificate_type=None, tackExt=None,
               next_protos_advertised=None,
               extensions=None):
        """Initialize the object for deserialisation."""
        self.extensions = extensions
        self.server_version = version
        self.random = random
        self.session_id = session_id
        self.cipher_suite = cipher_suite
        self.certificate_type = certificate_type
        self.compression_method = 0
        if tackExt is not None:
            self.tackExt = tackExt
        self.next_protos_advertised = next_protos_advertised
        return self

    def parse(self, p):
        p.startLengthCheck(3)
        self.server_version = (p.get(1), p.get(1))
        self.random = p.getFixBytes(32)
        self.session_id = p.getVarBytes(1)
        self.cipher_suite = p.get(2)
        self.compression_method = p.get(1)
        if not p.atLengthCheck():
            self.extensions = []
            totalExtLength = p.get(2)
            p2 = Parser(p.getFixBytes(totalExtLength))
            while p2.getRemainingLength() > 0:
                if self.random == TLS_1_3_HRR:
                    ext = TLSExtension(hrr=True).parse(p2)
                else:
                    ext = TLSExtension(server=True).parse(p2)
                self.extensions += [ext]
        p.stopLengthCheck()
        return self

    def write(self):
        w = Writer()
        w.add(self.server_version[0], 1)
        w.add(self.server_version[1], 1)
        w.bytes += self.random
        w.addVarSeq(self.session_id, 1, 1)
        w.add(self.cipher_suite, 2)
        w.add(self.compression_method, 1)

        if self.extensions is not None:
            w2 = Writer()
            for ext in self.extensions:
                w2.bytes += ext.write()

            if self.tackExt:
                b = self.tackExt.serialize()
                w2.add(ExtensionType.tack, 2)
                w2.add(len(b), 2)
                w2.bytes += b

            w.add(len(w2.bytes), 2)
            w.bytes += w2.bytes
        return self.postWrite(w)


class ServerHello2(HandshakeMsg):
    """
    SERVER-HELLO message from SSLv2.

    :vartype session_id_hit: int
    :ivar session_id_hit: non zero if the client provided session ID was
        matched in server's session cache

    :vartype certificate_type: int
    :ivar certificate_type: type of certificate sent

    :vartype server_version: tuple of ints
    :ivar server_version: protocol version selected by server

    :vartype certificate: bytearray
    :ivar certificate: certificate sent by server

    :vartype ciphers: array of int
    :ivar ciphers: list of ciphers supported by server

    :vartype session_id: bytearray
    :ivar session_id: idendifier of negotiated session
    """

    def __init__(self):
        super(ServerHello2, self).__init__(SSL2HandshakeType.server_hello)
        self.session_id_hit = 0
        self.certificate_type = 0
        self.server_version = (0, 0)
        self.certificate = bytearray(0)
        self.ciphers = []
        self.session_id = bytearray(0)

    def create(self, session_id_hit, certificate_type, server_version,
               certificate, ciphers, session_id):
        """Initialize fields of the SERVER-HELLO message."""
        self.session_id_hit = session_id_hit
        self.certificate_type = certificate_type
        self.server_version = server_version
        self.certificate = certificate
        self.ciphers = ciphers
        self.session_id = session_id
        return self

    def write(self):
        """Serialise object to on the wire data."""
        writer = Writer()
        writer.add(self.handshakeType, 1)
        writer.add(self.session_id_hit, 1)
        writer.add(self.certificate_type, 1)
        if len(self.server_version) != 2:
            raise ValueError("server version must be a 2-element tuple")
        writer.addFixSeq(self.server_version, 1)
        writer.add(len(self.certificate), 2)

        ciphersWriter = Writer()
        ciphersWriter.addFixSeq(self.ciphers, 3)

        writer.add(len(ciphersWriter.bytes), 2)
        writer.add(len(self.session_id), 2)

        writer.bytes += self.certificate
        writer.bytes += ciphersWriter.bytes
        writer.bytes += self.session_id

        # postWrite() is necessary only for SSLv3/TLS
        return writer.bytes

    def parse(self, parser):
        """Deserialise object from on the wire data."""
        self.session_id_hit = parser.get(1)
        self.certificate_type = parser.get(1)
        self.server_version = (parser.get(1), parser.get(1))
        certificateLength = parser.get(2)
        ciphersLength = parser.get(2)
        sessionIDLength = parser.get(2)
        parser.setLengthCheck(certificateLength +
                              ciphersLength +
                              sessionIDLength)
        self.certificate = parser.getFixBytes(certificateLength)
        self.ciphers = parser.getFixList(3, ciphersLength // 3)
        self.session_id = parser.getFixBytes(sessionIDLength)
        parser.stopLengthCheck()
        return self


class CertificateEntry(object):
    """
    Object storing a single certificate from TLS 1.3.

    Stores a certificate (or possibly a raw public key) together with
    associated extensions
    """

    def __init__(self, certificateType):
        """Initialise the object for given certificate type."""
        self.certificateType = certificateType
        self.certificate = None
        self.extensions = None

    def create(self, certificate, extensions):
        """Set all values of the certificate entry."""
        self.certificate = certificate
        self.extensions = extensions
        return self

    def write(self):
        """Serialise the object."""
        writer = Writer()
        if self.certificateType == CertificateType.x509:
            writer.addVarSeq(self.certificate.writeBytes(), 1, 3)
        else:
            raise ValueError("Set certificate type ({0}) unsupported"
                             .format(self.certificateType))

        if self.extensions is not None:
            writer2 = Writer()
            for ext in self.extensions:
                writer2.bytes += ext.write()
            writer.addVarSeq(writer2.bytes, 1, 2)

        return writer.bytes

    def parse(self, parser):
        """Deserialise the object from on the wire data."""
        if self.certificateType == CertificateType.x509:
            certBytes = parser.getVarBytes(3)
            x509 = X509()
            x509.parseBinary(certBytes)
            self.certificate = x509
        else:
            raise ValueError("Set certificate type ({0}) unsupported"
                             .format(self.certificateType))

        self.extensions = []
        parser.startLengthCheck(2)
        while not parser.atLengthCheck():
            ext = TLSExtension(cert=True).parse(parser)
            self.extensions.append(ext)
        parser.stopLengthCheck()
        return self

    def __repr__(self):
        return "CertificateEntry(certificate={0!r}, extensions={1!r})".format(
                self.certificate, self.extensions)


@deprecated_attrs({"cert_chain": "certChain"})
class Certificate(HandshakeMsg):
    def __init__(self, certificateType, version=(3, 2)):
        HandshakeMsg.__init__(self, HandshakeType.certificate)
        self.certificateType = certificateType
        self._cert_chain = None
        self.version = version
        self.certificate_list = []
        self.certificate_request_context = None

    @property
    def cert_chain(self):
        """Getter for the cert_chain property."""
        if self._cert_chain:
            return self._cert_chain
        elif self.certificate_list:
            return X509CertChain([i.certificate
                                  for i in self.certificate_list])
        else:
            return None

    @cert_chain.setter
    def cert_chain(self, cert_chain):
        """Setter for the cert_chain property."""
        if isinstance(cert_chain, X509CertChain):
            self._cert_chain = cert_chain
            self.certificate_list = [CertificateEntry(self.certificateType)
                                     .create(i, []) for i
                                     in cert_chain.x509List]
        elif cert_chain is None:
            self.certificate_list = []
        else:
            self.certificate_list = cert_chain

    @deprecated_params({"cert_chain": "certChain"})
    def create(self, cert_chain, context=b''):
        """Initialise fields of the class."""
        self.cert_chain = cert_chain
        self.certificate_request_context = context
        return self

    def _parse_certificate_list(self, parser):
        self.certificate_list = []
        while parser.getRemainingLength():
            entry = CertificateEntry(self.certificateType)
            self.certificate_list.append(entry.parse(parser))

    def _parse_tls13(self, parser):
        parser.startLengthCheck(3)
        self.certificate_request_context = parser.getVarBytes(1)
        self._parse_certificate_list(Parser(parser.getVarBytes(3)))
        parser.stopLengthCheck()
        return self

    def _parse_tls12(self, p):
        p.startLengthCheck(3)
        if self.certificateType == CertificateType.x509:
            chainLength = p.get(3)
            index = 0
            certificate_list = []
            while index != chainLength:
                certBytes = p.getVarBytes(3)
                if not certBytes:
                    raise DecodeError("Client certificate is empty")
                x509 = X509()
                try:
                    x509.parseBinary(certBytes)
                except SyntaxError:
                    raise BadCertificateError("Certificate could not be parsed")
                certificate_list.append(x509)
                index += len(certBytes)+3
            if certificate_list:
                self._cert_chain = X509CertChain(certificate_list)
        else:
            raise AssertionError()

        p.stopLengthCheck()
        return self

    def parse(self, p):
        if self.version <= (3, 3):
            return self._parse_tls12(p)
        else:
            return self._parse_tls13(p)

    def _write_tls13(self):
        w = Writer()
        w.addVarSeq(self.certificate_request_context, 1, 1)
        w2 = Writer()
        for entry in self.certificate_list:
            w2.bytes += entry.write()
        w.addVarSeq(w2.bytes, 1, 3)
        return w

    def _write_tls12(self):
        w = Writer()
        if self.certificateType == CertificateType.x509:
            chainLength = 0
            if self._cert_chain:
                certificate_list = self._cert_chain.x509List
            else:
                certificate_list = []
            # determine length
            for cert in certificate_list:
                bytes = cert.writeBytes()
                chainLength += len(bytes)+3
            # add bytes
            w.add(chainLength, 3)
            for cert in certificate_list:
                bytes = cert.writeBytes()
                w.addVarSeq(bytes, 1, 3)
        else:
            raise AssertionError()
        return w

    def write(self):
        if self.version <= (3, 3):
            writer = self._write_tls12()
        else:
            writer = self._write_tls13()
        return self.postWrite(writer)

    def __repr__(self):
        if self.version <= (3, 3):
            return "Certificate(cert_chain={0!r})"\
                   .format(self.cert_chain.x509List)
        return "Certificate(request_context={0!r}, "\
               "certificate_list={1!r})"\
               .format(self.certificate_request_context,
                       self.certificate_list)


class CertificateRequest(HelloMessage):
    def __init__(self, version):
        super(CertificateRequest, self).__init__(
                HandshakeType.certificate_request)
        self.certificate_types = []
        self.certificate_authorities = []
        self.version = version
        self.certificate_request_context = b''
        self.extensions = None

    @property
    def supported_signature_algs(self):
        """
        Returns the list of supported algorithms.

        We store the list in an extension even for TLS < 1.3
        Extensions are used/valid only for TLS 1.3 but they are a good
        unified storage mechanism for all versions.
        """
        ext = self.getExtension(ExtensionType.signature_algorithms)
        if ext:
            return ext.sigalgs
        return None

    @supported_signature_algs.setter
    def supported_signature_algs(self, val):
        self._removeExt(ExtensionType.signature_algorithms)
        if val is not None:
            ext = SignatureAlgorithmsExtension().create(val)
            self.addExtension(ext)

    def create(self, certificate_types=None, certificate_authorities=None,
               sig_algs=None, context=b'', extensions=None):
        """
            Creates a Certificate Request message.
            For TLS 1.3 only the context and extensions parameters should be
            provided, the others are ignored.
            For TLS versions below 1.3 instead only the first three parameters
            are considered.
        """
        self.certificate_types = certificate_types
        self.certificate_authorities = certificate_authorities
        self.certificate_request_context = context
        self.extensions = extensions
        # do this after setting extensions, or it will be overwritten
        if sig_algs is not None:
            self.supported_signature_algs = sig_algs
        return self

    def _parse_tls13(self, parser):
        parser.startLengthCheck(3)
        self.certificate_request_context = parser.getVarBytes(1)
        if not parser.getRemainingLength():
            raise SyntaxError("No list of extensions")
        else:
            self.extensions = []
            sub_parser = Parser(parser.getVarBytes(2))
            while sub_parser.getRemainingLength():
                # We care only for universal extensions so far
                ext = TLSExtension().parse(sub_parser)
                self.extensions.append(ext)

        parser.stopLengthCheck()
        return self

    def _parse_tls12(self, p):
        p.startLengthCheck(3)
        self.certificate_types = p.getVarList(1, 1)
        if self.version == (3, 3):
            self.supported_signature_algs = p.getVarTupleList(1, 2, 2)
        ca_list_length = p.get(2)
        index = 0
        self.certificate_authorities = []
        while index != ca_list_length:
            ca_bytes = p.getVarBytes(2)
            self.certificate_authorities.append(ca_bytes)
            index += len(ca_bytes)+2
        p.stopLengthCheck()
        return self

    def parse(self, parser):
        if self.version <= (3, 3):
            return self._parse_tls12(parser)
        return self._parse_tls13(parser)

    def _write_tls13(self):
        writer = Writer()
        writer.addVarSeq(self.certificate_request_context, 1, 1)
        sub_writer = Writer()
        for ext in self.extensions or []:
            sub_writer.bytes += ext.write()
        writer.addVarSeq(sub_writer.bytes, 1, 2)
        return writer

    def _write_tls12(self):
        w = Writer()
        w.addVarSeq(self.certificate_types, 1, 1)
        if self.version >= (3, 3):
            w.addVarTupleSeq(self.supported_signature_algs, 1, 2)
        caLength = 0
        # determine length
        for ca_dn in self.certificate_authorities:
            caLength += len(ca_dn)+2
        w.add(caLength, 2)
        # add bytes
        for ca_dn in self.certificate_authorities:
            w.addVarSeq(ca_dn, 1, 2)
        return w

    def write(self):
        if self.version <= (3, 3):
            writer = self._write_tls12()
        else:
            writer = self._write_tls13()
        return self.postWrite(writer)


class ServerKeyExchange(HandshakeMsg):
    """
    Handling TLS Handshake protocol Server Key Exchange messages.

    :vartype cipherSuite: int
    :cvar cipherSuite: id of ciphersuite selected in Server Hello message
    :vartype srp_N: int
    :cvar srp_N: SRP protocol prime
    :vartype srp_N_len: int
    :cvar srp_N_len: length of srp_N in bytes
    :vartype srp_g: int
    :cvar srp_g: SRP protocol generator
    :vartype srp_g_len: int
    :cvar srp_g_len: length of srp_g in bytes
    :vartype srp_s: bytearray
    :cvar srp_s: SRP protocol salt value
    :vartype srp_B: int
    :cvar srp_B: SRP protocol server public value
    :vartype srp_B_len: int
    :cvar srp_B_len: length of srp_B in bytes
    :vartype dh_p: int
    :cvar dh_p: FFDHE protocol prime
    :vartype dh_p_len: int
    :cvar dh_p_len: length of dh_p in bytes
    :vartype dh_g: int
    :cvar dh_g: FFDHE protocol generator
    :vartype dh_g_len: int
    :cvar dh_g_len: length of dh_g in bytes
    :vartype dh_Ys: int
    :cvar dh_Ys: FFDH protocol server key share
    :vartype dh_Ys_len: int
    :cvar dh_Ys_len: length of dh_Ys in bytes
    :vartype curve_type: int
    :cvar curve_type: Type of curve used (explicit, named, etc.)
    :vartype named_curve: int
    :cvar named_curve: TLS ID of named curve
    :vartype ecdh_Ys: bytearray
    :cvar ecdh_Ys: ECDH protocol encoded point key share
    :vartype signature: bytearray
    :cvar signature: signature performed over the parameters by server
    :vartype hashAlg: int
    :cvar hashAlg: id of hash algorithm used for signature
    :vartype signAlg: int
    :cvar signAlg: id of signature algorithm used for signature
    """

    def __init__(self, cipherSuite, version):
        """
        Initialise Server Key Exchange for reading or writing.

        :type cipherSuite: int
        :param cipherSuite: id of ciphersuite selected by server
        """
        HandshakeMsg.__init__(self, HandshakeType.server_key_exchange)
        self.cipherSuite = cipherSuite
        self.version = version
        self.srp_N = 0
        self.srp_N_len = None
        self.srp_g = 0
        self.srp_g_len = None
        self.srp_s = bytearray(0)
        self.srp_B = 0
        self.srp_B_len = None
        # Anon DH params:
        self.dh_p = 0
        self.dh_p_len = None
        self.dh_g = 0
        self.dh_g_len = None
        self.dh_Ys = 0
        self.dh_Ys_len = None
        # EC settings
        self.curve_type = None
        self.named_curve = None
        self.ecdh_Ys = bytearray(0)
        # signature for certificate authenticated ciphersuites
        self.signature = bytearray(0)
        # signature hash algorithm and signing algorithm for TLSv1.2
        self.hashAlg = 0
        self.signAlg = 0

    def __repr__(self):
        ret = "ServerKeyExchange(cipherSuite=CipherSuite.{0}, version={1}"\
              "".format(CipherSuite.ietfNames[self.cipherSuite], self.version)

        if self.srp_N != 0:
            ret += ", srp_N={0}, srp_g={1}, srp_s={2!r}, srp_B={3}".format(
                self.srp_N, self.srp_g, self.srp_s, self.srp_B)
        if self.dh_p != 0:
            ret += ", dh_p={0}, dh_g={1}, dh_Ys={2}".format(
                self.dh_p, self.dh_g, self.dh_Ys)
        if self.signAlg != 0:
            ret += ", hashAlg={0}, signAlg={1}".format(
                self.hashAlg, self.signAlg)
        if self.signature != bytearray(0):
            ret += ", signature={0!r}".format(self.signature)
        ret += ")"

        return ret

    def createSRP(self, srp_N, srp_g, srp_s, srp_B):
        """Set SRP protocol parameters."""
        self.srp_N = srp_N
        self.srp_N_len = None
        self.srp_g = srp_g
        self.srp_g_len = None
        self.srp_s = srp_s
        self.srp_B = srp_B
        self.srp_B_len = None
        return self

    def createDH(self, dh_p, dh_g, dh_Ys):
        """Set FFDH protocol parameters."""
        self.dh_p = dh_p
        self.dh_p_len = None
        self.dh_g = dh_g
        self.dh_g_len = None
        self.dh_Ys = dh_Ys
        self.dh_Ys_len = None
        return self

    def createECDH(self, curve_type, named_curve=None, point=None):
        """Set ECDH protocol parameters."""
        self.curve_type = curve_type
        self.named_curve = named_curve
        self.ecdh_Ys = point
        return self

    def parse(self, parser):
        """
        Deserialise message from :py:class:`Parser`.

        :type parser: Parser
        :param parser: parser to read data from
        """
        parser.startLengthCheck(3)
        if self.cipherSuite in CipherSuite.srpAllSuites:
            self.srp_N_len = parser.get(2)
            self.srp_N = bytesToNumber(parser.getFixBytes(self.srp_N_len))
            self.srp_g_len = parser.get(2)
            self.srp_g = bytesToNumber(parser.getFixBytes(self.srp_g_len))
            self.srp_s = parser.getVarBytes(1)
            self.srp_B_len = parser.get(2)
            self.srp_B = bytesToNumber(parser.getFixBytes(self.srp_B_len))
        elif self.cipherSuite in CipherSuite.dhAllSuites:
            self.dh_p_len = parser.get(2)
            self.dh_p = bytesToNumber(parser.getFixBytes(self.dh_p_len))
            self.dh_g_len = parser.get(2)
            self.dh_g = bytesToNumber(parser.getFixBytes(self.dh_g_len))
            self.dh_Ys_len = parser.get(2)
            self.dh_Ys = bytesToNumber(parser.getFixBytes(self.dh_Ys_len))
        elif self.cipherSuite in CipherSuite.ecdhAllSuites:
            self.curve_type = parser.get(1)
            # only named curves supported
            assert self.curve_type == 3
            self.named_curve = parser.get(2)
            self.ecdh_Ys = parser.getVarBytes(1)
        else:
            raise AssertionError()

        if self.cipherSuite in CipherSuite.certAllSuites or\
                self.cipherSuite in CipherSuite.ecdheEcdsaSuites or\
                self.cipherSuite in CipherSuite.dheDsaSuites:
            if self.version == (3, 3):
                self.hashAlg = parser.get(1)
                self.signAlg = parser.get(1)
            self.signature = parser.getVarBytes(2)

        parser.stopLengthCheck()
        return self

    def writeParams(self):
        """
        Serialise the key exchange parameters.

        :rtype: bytearray
        """
        writer = Writer()
        if self.cipherSuite in CipherSuite.srpAllSuites:
            writer.addVarSeq(numberToByteArray(self.srp_N, self.srp_N_len),
                             1, 2)
            writer.addVarSeq(numberToByteArray(self.srp_g, self.srp_g_len),
                             1, 2)
            writer.addVarSeq(self.srp_s, 1, 1)
            writer.addVarSeq(numberToByteArray(self.srp_B, self.srp_B_len),
                             1, 2)
        elif self.cipherSuite in CipherSuite.dhAllSuites:
            writer.addVarSeq(numberToByteArray(self.dh_p, self.dh_p_len),
                             1, 2)
            writer.addVarSeq(numberToByteArray(self.dh_g, self.dh_g_len),
                             1, 2)
            writer.addVarSeq(numberToByteArray(self.dh_Ys, self.dh_Ys_len),
                             1, 2)
        elif self.cipherSuite in CipherSuite.ecdhAllSuites:
            writer.add(self.curve_type, 1)
            assert self.curve_type == 3
            writer.add(self.named_curve, 2)
            writer.addVarSeq(self.ecdh_Ys, 1, 1)
        else:
            assert(False)
        return writer.bytes

    def write(self):
        """
        Serialise complete message.

        :rtype: bytearray
        """
        writer = Writer()
        writer.bytes += self.writeParams()
        if self.cipherSuite in CipherSuite.certAllSuites or \
                self.cipherSuite in CipherSuite.ecdheEcdsaSuites or \
                self.cipherSuite in CipherSuite.dheDsaSuites:
            if self.version >= (3, 3):
                assert self.hashAlg != 0 and self.signAlg != 0
                writer.add(self.hashAlg, 1)
                writer.add(self.signAlg, 1)
            writer.addVarSeq(self.signature, 1, 2)
        return self.postWrite(writer)

    def hash(self, clientRandom, serverRandom):
        """
        Calculate hash of parameters to sign.

        :rtype: bytearray
        """
        bytesToHash = clientRandom + serverRandom + self.writeParams()
        if self.version >= (3, 3):
            sigScheme = SignatureScheme.toRepr((self.hashAlg, self.signAlg))
            if sigScheme is None:
                hashAlg = HashAlgorithm.toRepr(self.hashAlg)
                if hashAlg is None:
                    raise AssertionError("Unknown hash algorithm: {0}".
                                         format(self.hashAlg))
            else:
                hashAlg = SignatureScheme.getHash(sigScheme)
            return secureHash(bytesToHash, hashAlg)
        # DSA and ECDSA ciphers in TLS 1.1 and earlier sign the messages using
        # SHA-1 only
        if self.cipherSuite in CipherSuite.ecdheEcdsaSuites or\
                self.cipherSuite in CipherSuite.dheDsaSuites:
            return SHA1(bytesToHash)
        return MD5(bytesToHash) + SHA1(bytesToHash)


class ServerHelloDone(HandshakeMsg):
    def __init__(self):
        HandshakeMsg.__init__(self, HandshakeType.server_hello_done)

    def create(self):
        return self

    def parse(self, p):
        p.startLengthCheck(3)
        p.stopLengthCheck()
        return self

    def write(self):
        w = Writer()
        return self.postWrite(w)

    def __repr__(self):
        """Human readable representation of object."""
        return "ServerHelloDone()"


class ClientKeyExchange(HandshakeMsg):
    """
    Handling of TLS Handshake protocol ClientKeyExchange message.

    :vartype cipherSuite: int
    :ivar cipherSuite: the cipher suite id used for the connection
    :vartype ~.version: tuple(int, int)
    :ivar ~.version: TLS protocol version used for the connection
    :vartype srp_A: int
    :ivar srp_A: SRP protocol client answer value
    :vartype dh_Yc: int
    :ivar dh_Yc: client Finite Field Diffie-Hellman protocol key share
    :vartype ecdh_Yc: bytearray
    :ivar ecdh_Yc: encoded curve coordinates
    :vartype encryptedPreMasterSecret: bytearray
    :ivar encryptedPreMasterSecret: client selected PremMaster secret encrypted
        with server public key (from certificate)
    """

    def __init__(self, cipherSuite, version=None):
        """
        Initialise ClientKeyExchange for reading or writing.

        :type cipherSuite: int
        :param cipherSuite: id of the ciphersuite selected by server
        :type version: tuple(int, int)
        :param version: protocol version selected by server
        """
        HandshakeMsg.__init__(self, HandshakeType.client_key_exchange)
        self.cipherSuite = cipherSuite
        self.version = version
        self.srp_A = 0
        self.dh_Yc = 0
        self.ecdh_Yc = bytearray(0)
        self.encryptedPreMasterSecret = bytearray(0)

    def createSRP(self, srp_A):
        """
        Set the SRP client answer.

        returns self

        :type srp_A: int
        :param srp_A: client SRP answer
        :rtype: ClientKeyExchange
        """
        self.srp_A = srp_A
        return self

    def createRSA(self, encryptedPreMasterSecret):
        """
        Set the encrypted PreMaster Secret.

        returns self

        :type encryptedPreMasterSecret: bytearray
        :rtype: ClientKeyExchange
        """
        self.encryptedPreMasterSecret = encryptedPreMasterSecret
        return self

    def createDH(self, dh_Yc):
        """
        Set the client FFDH key share.

        returns self

        :type dh_Yc: int
        :rtype: ClientKeyExchange
        """
        self.dh_Yc = dh_Yc
        return self

    def createECDH(self, ecdh_Yc):
        """
        Set the client ECDH key share.

        returns self

        :type ecdh_Yc: bytearray
        :rtype: ClientKeyExchange
        """
        self.ecdh_Yc = ecdh_Yc
        return self

    def parse(self, parser):
        """
        Deserialise the message from :py:class:`Parser`,

        returns self

        :type parser: Parser
        :rtype: ClientKeyExchange
        """
        parser.startLengthCheck(3)
        if self.cipherSuite in CipherSuite.srpAllSuites:
            self.srp_A = bytesToNumber(parser.getVarBytes(2))
        elif self.cipherSuite in CipherSuite.certSuites:
            if self.version in ((3, 1), (3, 2), (3, 3)):
                self.encryptedPreMasterSecret = parser.getVarBytes(2)
            elif self.version == (3, 0):
                self.encryptedPreMasterSecret = \
                    parser.getFixBytes(parser.getRemainingLength())
            else:
                raise AssertionError()
        elif self.cipherSuite in CipherSuite.dhAllSuites:
            self.dh_Yc = bytesToNumber(parser.getVarBytes(2))
        elif self.cipherSuite in CipherSuite.ecdhAllSuites:
            self.ecdh_Yc = parser.getVarBytes(1)
        else:
            raise AssertionError()
        parser.stopLengthCheck()
        return self

    def write(self):
        """
        Serialise the object.

        :rtype: bytearray
        """
        w = Writer()
        if self.cipherSuite in CipherSuite.srpAllSuites:
            w.addVarSeq(numberToByteArray(self.srp_A), 1, 2)
        elif self.cipherSuite in CipherSuite.certSuites:
            if self.version in ((3, 1), (3, 2), (3, 3)):
                w.addVarSeq(self.encryptedPreMasterSecret, 1, 2)
            elif self.version == (3, 0):
                w.bytes += self.encryptedPreMasterSecret
            else:
                raise AssertionError()
        elif self.cipherSuite in CipherSuite.dhAllSuites:
            w.addVarSeq(numberToByteArray(self.dh_Yc), 1, 2)
        elif self.cipherSuite in CipherSuite.ecdhAllSuites:
            w.addVarSeq(self.ecdh_Yc, 1, 1)
        else:
            raise AssertionError()
        return self.postWrite(w)


class ClientMasterKey(HandshakeMsg):
    """
    Handling of SSLv2 CLIENT-MASTER-KEY message.

    :vartype cipher: int
    :ivar cipher: negotiated cipher

    :vartype clear_key: bytearray
    :ivar clear_key: the part of master secret key that is sent in clear for
        export cipher suites

    :vartype encrypted_key: bytearray
    :ivar encrypted_key: (part of) master secret encrypted using server key

    :vartype key_argument: bytearray
    :ivar key_argument: additional key argument for block ciphers
    """

    def __init__(self):
        super(ClientMasterKey,
              self).__init__(SSL2HandshakeType.client_master_key)
        self.cipher = 0
        self.clear_key = bytearray(0)
        self.encrypted_key = bytearray(0)
        self.key_argument = bytearray(0)

    def create(self, cipher, clear_key, encrypted_key, key_argument):
        """Set values of the CLIENT-MASTER-KEY object."""
        self.cipher = cipher
        self.clear_key = clear_key
        self.encrypted_key = encrypted_key
        self.key_argument = key_argument
        return self

    def write(self):
        """Serialise the object to on the wire data."""
        writer = Writer()
        writer.add(self.handshakeType, 1)
        writer.add(self.cipher, 3)
        writer.add(len(self.clear_key), 2)
        writer.add(len(self.encrypted_key), 2)
        writer.add(len(self.key_argument), 2)
        writer.bytes += self.clear_key
        writer.bytes += self.encrypted_key
        writer.bytes += self.key_argument
        return writer.bytes

    def parse(self, parser):
        """Deserialise object from on the wire data."""
        self.cipher = parser.get(3)
        clear_key_length = parser.get(2)
        encrypted_key_length = parser.get(2)
        key_argument_length = parser.get(2)
        parser.setLengthCheck(clear_key_length +
                              encrypted_key_length +
                              key_argument_length)
        self.clear_key = parser.getFixBytes(clear_key_length)
        self.encrypted_key = parser.getFixBytes(encrypted_key_length)
        self.key_argument = parser.getFixBytes(key_argument_length)
        parser.stopLengthCheck()
        return self


class CertificateVerify(HandshakeMsg):
    """Serializer for TLS handshake protocol Certificate Verify message."""

    def __init__(self, version):
        """
        Create message.

        :param version: TLS protocol version in use
        """
        HandshakeMsg.__init__(self, HandshakeType.certificate_verify)
        self.version = version
        self.signatureAlgorithm = None
        self.signature = bytearray(0)

    def create(self, signature, signatureAlgorithm=None):
        """
        Provide data for serialisation of message.

        :param signature: signature carried in the message
        :param signatureAlgorithm: signature algorithm used to make the
            signature (TLSv1.2 only)
        """
        self.signatureAlgorithm = signatureAlgorithm
        self.signature = signature
        return self

    def parse(self, parser):
        """
        Deserialize message from parser.

        :param parser: parser with data to read
        """
        parser.startLengthCheck(3)
        if self.version >= (3, 3):
            self.signatureAlgorithm = (parser.get(1), parser.get(1))
        self.signature = parser.getVarBytes(2)
        parser.stopLengthCheck()
        return self

    def write(self):
        """
        Serialize the data to bytearray.

        :rtype: bytearray
        """
        writer = Writer()
        if self.version >= (3, 3):
            writer.add(self.signatureAlgorithm[0], 1)
            writer.add(self.signatureAlgorithm[1], 1)
        writer.addVarSeq(self.signature, 1, 2)
        return self.postWrite(writer)


class ChangeCipherSpec(object):
    def __init__(self):
        self.contentType = ContentType.change_cipher_spec
        self.type = 1

    def create(self):
        self.type = 1
        return self

    def parse(self, p):
        p.setLengthCheck(1)
        self.type = p.get(1)
        p.stopLengthCheck()
        return self

    def write(self):
        w = Writer()
        w.add(self.type, 1)
        return w.bytes


class NextProtocol(HandshakeMsg):
    def __init__(self):
        HandshakeMsg.__init__(self, HandshakeType.next_protocol)
        self.next_proto = None

    def create(self, next_proto):
        self.next_proto = next_proto
        return self

    def parse(self, p):
        p.startLengthCheck(3)
        self.next_proto = p.getVarBytes(1)
        _ = p.getVarBytes(1)
        p.stopLengthCheck()
        return self

    def write(self, trial=False):
        w = Writer()
        w.addVarSeq(self.next_proto, 1, 1)
        paddingLen = 32 - ((len(self.next_proto) + 2) % 32)
        w.addVarSeq(bytearray(paddingLen), 1, 1)
        return self.postWrite(w)


class Finished(HandshakeMsg):
    def __init__(self, version, hash_length=None):
        HandshakeMsg.__init__(self, HandshakeType.finished)
        self.version = version
        self.verify_data = bytearray(0)
        self.hash_length = hash_length

    def create(self, verify_data):
        self.verify_data = verify_data
        return self

    def parse(self, p):
        p.startLengthCheck(3)
        if self.version == (3, 0):
            self.verify_data = p.getFixBytes(36)
        elif self.version in ((3, 1), (3, 2), (3, 3)):
            self.verify_data = p.getFixBytes(12)
        elif self.version > (3, 3):
            self.verify_data = p.getFixBytes(self.hash_length)
        else:
            raise AssertionError()
        p.stopLengthCheck()
        return self

    def write(self):
        w = Writer()
        w.bytes += self.verify_data
        return self.postWrite(w)


class EncryptedExtensions(HelloMessage):
    """Handling of the TLS1.3 Encrypted Extensions message."""

    def __init__(self):
        super(EncryptedExtensions, self).__init__(
                HandshakeType.encrypted_extensions)

    def create(self, extensions):
        """Set the extensions in the message."""
        self.extensions = extensions
        return self

    def parse(self, parser):
        """Parse the extensions from on the wire data."""
        parser.startLengthCheck(3)

        if not parser.getRemainingLength():
            raise SyntaxError("No list of extensions")
        else:
            self.extensions = []
            p2 = Parser(parser.getVarBytes(2))
            while p2.getRemainingLength():
                self.extensions.append(TLSExtension(encExt=True).parse(p2))

        parser.stopLengthCheck()
        return self

    def write(self):
        """
        Serialise the message to on the wire data.

        :rtype: bytearray
        """
        w = Writer()
        w2 = Writer()
        for ext in self.extensions:
            w2.bytes += ext.write()

        w.add(len(w2.bytes), 2)
        w.bytes += w2.bytes

        return self.postWrite(w)


class NewSessionTicket(HelloMessage):
    """Handling of the TLS1.3 New Session Ticket message."""

    def __init__(self):
        """Create New Session Ticket object."""
        super(NewSessionTicket, self).__init__(HandshakeType
                                               .new_session_ticket)
        self.ticket_lifetime = 0
        self.ticket_age_add = 0
        self.ticket_nonce = bytearray(0)
        self.ticket = bytearray(0)
        self.extensions = []
        # time at which the ticket was received, not sent on the wire
        # in seconds in Unix Epoch
        self.time = None

    def create(self, ticket_lifetime, ticket_age_add, ticket_nonce, ticket,
               extensions):
        """Initialise a New Session Ticket."""
        self.ticket_lifetime = ticket_lifetime
        self.ticket_age_add = ticket_age_add
        self.ticket_nonce = ticket_nonce
        self.ticket = ticket
        self.extensions = extensions
        return self

    def write(self):
        """
        Serialise the message to on the wire data.

        :rtype: bytearray
        """
        w = Writer()
        w.add(self.ticket_lifetime, 4)
        w.add(self.ticket_age_add, 4)
        w.addVarSeq(self.ticket_nonce, 1, 1)
        w.addVarSeq(self.ticket, 1, 2)
        w2 = Writer()
        for ext in self.extensions:
            w2.bytes += ext.write()
        w.add(len(w2.bytes), 2)
        w.bytes += w2.bytes

        return self.postWrite(w)

    def parse(self, parser):
        """Parse the object from on the wire data."""
        parser.startLengthCheck(3)

        self.ticket_lifetime = parser.get(4)
        self.ticket_age_add = parser.get(4)
        self.ticket_nonce = parser.getVarBytes(1)
        self.ticket = parser.getVarBytes(2)
        self.extensions = []
        ext_parser = Parser(parser.getVarBytes(2))
        while ext_parser.getRemainingLength():
            self.extensions.append(TLSExtension().parse(ext_parser))

        parser.stopLengthCheck()
        return self


class SessionTicketPayload(object):
    """Serialisation and deserialisation of server state for resumption.

    This is the internal (meant to be encrypted) representation of server
    state that is set to client in the NewSessionTicket message.

    :ivar int ~.version: implementation detail for forward compatibility
    :ivar bytearray master_secret: master secret for TLS 1.2-, resumption
        master secret for TLS 1.3

    :ivar tuple protocol_version: version of protocol that was previously
        negotiated in this session

    :ivar int cipher_suite: numerical ID of ciphersuite that was negotiated
        previously

    :ivar bytearray nonce: nonce for TLS 1.3 KDF

    :ivar int creation_time: Unix time in seconds when was the ticket created
    :ivar X509CertChain client_cert_chain: Client X509 Certificate Chain
    """

    def __init__(self):
        """Create instance of the object."""
        self.version = 0
        self.master_secret = bytearray()
        self.protocol_version = bytearray()
        self.cipher_suite = 0
        self.creation_time = 0
        self.nonce = bytearray()
        self._cert_chain = None

    @property
    def client_cert_chain(self):
        """Getter for the client_cert_chain property."""
        if self._cert_chain:
            return X509CertChain([i.certificate
                                  for i in self._cert_chain])
        return None

    @client_cert_chain.setter
    def client_cert_chain(self, client_cert_chain):
        """Setter for the cert_chain property."""
        self._cert_chain = [CertificateEntry(CertificateType.x509)
                            .create(i, []) for i in client_cert_chain.x509List]

    def create(self, master_secret, protocol_version, cipher_suite,
               creation_time, nonce=bytearray(), client_cert_chain=None):
        """Initialise the object with cryptographic data."""
        self.master_secret = master_secret
        self.protocol_version = protocol_version
        self.cipher_suite = cipher_suite
        self.creation_time = creation_time
        self.nonce = nonce
        if client_cert_chain:
            self.version = 1
            self.client_cert_chain = client_cert_chain
        return self

    def _parse_cert_chain(self, parser):
        self._cert_chain = []
        while parser.getRemainingLength():
            entry = CertificateEntry(CertificateType.x509)
            self._cert_chain.append(entry.parse(parser))

    def parse(self, parser):
        self.version = parser.get(2)
        if self.version > 1:
            raise ValueError("Unrecognised version number")
        self.master_secret = parser.getVarBytes(2)
        self.protocol_version = (parser.get(1), parser.get(1))
        self.cipher_suite = parser.get(2)
        self.nonce = parser.getVarBytes(1)
        self.creation_time = parser.get(8)
        if self.version == 1:
            self._parse_cert_chain(Parser(parser.getVarBytes(3)))
        if parser.getRemainingLength():
            raise ValueError("Malformed ticket")
        return self

    def write(self):
        writer = Writer()
        writer.addTwo(self.version)
        writer.addTwo(len(self.master_secret))
        writer.bytes += self.master_secret
        writer.addOne(self.protocol_version[0])
        writer.addOne(self.protocol_version[1])
        writer.addTwo(self.cipher_suite)
        writer.addOne(len(self.nonce))
        writer.bytes += self.nonce
        writer.add(self.creation_time, 8)
        if self.version == 1:
            wcert = Writer()
            for entry in self._cert_chain:
                wcert.bytes += entry.write()
            writer.addVarSeq(wcert.bytes, 1, 3)
        return writer.bytes


class SSL2Finished(HandshakeMsg):
    """Handling of the SSL2 FINISHED messages."""

    def __init__(self, msg_type):
        super(SSL2Finished, self).__init__(msg_type)
        self.verify_data = bytearray(0)

    def create(self, verify_data):
        """Set the message payload."""
        self.verify_data = verify_data
        return self

    def parse(self, parser):
        """Deserialise the message from on the wire data."""
        self.verify_data = parser.getFixBytes(parser.getRemainingLength())
        return self

    def write(self):
        """Serialise the message to on the wire data."""
        writer = Writer()
        writer.add(self.handshakeType, 1)
        writer.bytes += self.verify_data
        # does not use postWrite() as it's a SSLv2 message
        return writer.bytes


class ClientFinished(SSL2Finished):
    """
    Handling of SSLv2 CLIENT-FINISHED message.

    :vartype verify_data: bytearray
    :ivar verify_data: payload of the message, should be the CONNECTION-ID
    """

    def __init__(self):
        super(ClientFinished, self).__init__(SSL2HandshakeType.client_finished)


class ServerFinished(SSL2Finished):
    """
    Handling of SSLv2 SERVER-FINISHED message.

    :vartype verify_data: bytearray
    :ivar verify_data: payload of the message, should be SESSION-ID
    """

    def __init__(self):
        super(ServerFinished, self).__init__(SSL2HandshakeType.server_finished)


class CertificateStatus(HandshakeMsg):
    """
    Handling of the CertificateStatus message from RFC 6066.

    Handling of the handshake protocol message that includes the OCSP staple.

    :vartype status_type: int
    :ivar status_type: type of response returned

    :vartype ocsp: bytearray
    :ivar ocsp: OCSPResponse from RFC 2560
    """

    def __init__(self):
        """Create the objet, set its type."""
        super(CertificateStatus, self).__init__(
                HandshakeType.certificate_status)
        self.status_type = None
        self.ocsp = bytearray()

    def create(self, status_type, ocsp):
        """Set up message payload."""
        self.status_type = status_type
        self.ocsp = ocsp
        return self

    def parse(self, parser):
        """Deserialise the message from one the wire data."""
        parser.startLengthCheck(3)
        self.status_type = parser.get(1)
        self.ocsp = parser.getVarBytes(3)
        parser.stopLengthCheck()
        return self

    def write(self):
        """Serialise the message."""
        writer = Writer()
        writer.add(self.status_type, 1)
        writer.add(len(self.ocsp), 3)
        writer.bytes += self.ocsp
        return self.postWrite(writer)


class ApplicationData(object):
    def __init__(self):
        self.contentType = ContentType.application_data
        self.bytes = bytearray(0)

    def create(self, bytes):
        self.bytes = bytes
        return self

    def splitFirstByte(self):
        newMsg = ApplicationData().create(self.bytes[:1])
        self.bytes = self.bytes[1:]
        return newMsg

    def parse(self, p):
        self.bytes = p.bytes
        return self

    def write(self):
        return self.bytes


class Heartbeat(object):
    """
    Handling Heartbeat messages from RFC 6520

    :type message_type: int
    :ivar message_type: type of message (response or request)

    :type payload: bytearray
    :ivar payload: payload

    :type padding: bytearray
    :ivar padding: random padding of selected length
    """

    def __init__(self):
        self.contentType = ContentType.heartbeat
        self.message_type = 0
        self.payload = bytearray(0)
        self.padding = bytearray(0)

    def create(self, message_type, payload, padding_length):
        """Create heartbeat request or response with selected parameters"""
        self.message_type = message_type
        self.payload = payload
        self.padding = getRandomBytes(padding_length)
        return self

    def create_response(self):
        """Creates heartbeat response based on request."""
        heartbeat_response = Heartbeat().create(
            HeartbeatMessageType.heartbeat_response,
            self.payload,
            16)
        return heartbeat_response

    def parse(self, p):
        """
        Deserialize heartbeat message from parser.

        We are reading only message type and payload, ignoring
        leftover bytes (padding).
        """
        self.message_type = p.get(1)
        self.payload = p.getVarBytes(2)
        self.padding = p.getFixBytes(p.getRemainingLength())
        return self

    def write(self):
        """Serialise heartbeat message."""
        w = Writer()
        w.add(self.message_type, 1)
        w.add(len(self.payload), 2)
        w.bytes += self.payload
        w.bytes += self.padding
        return w.bytes

    @property
    def _message_type(self):
        """Format heartbeat message to human readable representation."""
        return none_as_unknown(HeartbeatMessageType.toRepr(self.message_type),
                               self.message_type)

    def __str__(self):
        """Return human readable representation of heartbeat message."""
        return "heartbeat {0}".format(self._message_type)


class KeyUpdate(HandshakeMsg):
    """
    Handling KeyUpdate message from RFC 8446

    :vartype message_type: int
    :ivar message_type: type of message (update_not_requested or
                                         update_requested)
    """

    def __init__(self):
        super(KeyUpdate, self).__init__(HandshakeType.key_update)
        self.message_type = 0

    def create(self, message_type):
        """Create KeyUpdate message with selected parameter."""
        self.message_type = message_type
        return self

    def parse(self, p):
        """Deserialize keyupdate message from parser."""
        p.startLengthCheck(3)
        self.message_type = p.get(1)
        p.stopLengthCheck()
        return self

    def write(self):
        """Serialise keyupdate message."""
        writer = Writer()
        writer.add(self.message_type, 1)
        return self.postWrite(writer)