Class TLS13ClientHello

scapy/layers/tls/handshake.py:352–479

TLS 1.3 ClientHello, with abilities to handle extensions. The Random structure is 32 random bytes without any GMT time

class TLS13ClientHello(_TLSHandshake):
    """
    TLS 1.3 ClientHello, with abilities to handle extensions.

    The Random structure is 32 random bytes without any GMT time
    """
    name = "TLS 1.3 Handshake - Client Hello"
    fields_desc = [ByteEnumField("msgtype", 1, _tls_handshake_type),
                   ThreeBytesField("msglen", None),
                   _TLSClientVersionField("version", None, _tls_version),

                   _TLSRandomBytesField("random_bytes", None, 32),

                   FieldLenField("sidlen", None, fmt="B", length_of="sid"),
                   _SessionIDField("sid", "",
                                   length_from=lambda pkt: pkt.sidlen),

                   FieldLenField("cipherslen", None, fmt="!H",
                                 length_of="ciphers"),
                   _CipherSuitesField("ciphers", None,
                                      _tls_cipher_suites, itemfmt="!H",
                                      length_from=lambda pkt: pkt.cipherslen),

                   FieldLenField("complen", None, fmt="B", length_of="comp"),
                   _CompressionMethodsField("comp", [0],
                                            _tls_compression_algs,
                                            itemfmt="B",
                                            length_from=lambda pkt: pkt.complen),  # noqa: E501

                   _ExtensionsLenField("extlen", None, length_of="ext"),
                   _ExtensionsField("ext", None,
                                    length_from=lambda pkt: (pkt.msglen -
                                                             (pkt.sidlen or 0) -  # noqa: E501
                                                             (pkt.cipherslen or 0) -  # noqa: E501
                                                             (pkt.complen or 0) -  # noqa: E501
                                                             40))]

    def post_build(self, p, pay):
        if self.random_bytes is None:
            p = p[:6] + randstring(32) + p[6 + 32:]
        # We don't call the post_build function from class _TLSHandshake
        # to compute the message length because we need that value now
        # for the HMAC in binder
        tmp_len = len(p)
        if self.msglen is None:
            sz = tmp_len - 4
            p = struct.pack("!I", (orb(p[0]) << 24) | sz) + p[4:]
        s = self.tls_session
        if self.ext:
            for e in self.ext:
                if isinstance(e, TLS_Ext_PreSharedKey_CH):
                    if s.client_session_ticket:
                        # For a resumed PSK, the hash function use
                        # to compute the binder must be the same
                        # as the one used to establish the original
                        # connection. For that, we assume that
                        # the ciphersuite associate with the ticket
                        # is given as argument to tlsSession