Class ASN1F_SEQUENCE

scapy/asn1fields.py:426–508

class ASN1F_SEQUENCE(ASN1F_field[List[Any], List[Any]]):
    # Here is how you could decode a SEQUENCE
    # with an unknown, private high-tag prefix :
    # class PrivSeq(ASN1_Packet):
    #     ASN1_codec = ASN1_Codecs.BER
    #     ASN1_root = ASN1F_SEQUENCE(
    #                       <asn1 field #0>,
    #                       ...
    #                       <asn1 field #N>,
    #                       explicit_tag=0,
    #                       flexible_tag=True)
    # Because we use flexible_tag, the value of the explicit_tag does not matter.  # noqa: E501
    ASN1_tag = ASN1_Class_UNIVERSAL.SEQUENCE
    holds_packets = 1

    def __init__(self, *seq, **kwargs):
        # type: (*Any, **Any) -> None
        name = "dummy_seq_name"
        default = [field.default for field in seq]
        super(ASN1F_SEQUENCE, self).__init__(
            name, default, **kwargs
        )
        self.seq = seq
        self.islist = len(seq) > 1

    def __repr__(self):
        # type: () -> str
        return "<%s%r>" % (self.__class__.__name__, self.seq)

    def is_empty(self, pkt):
        # type: (ASN1_Packet) -> bool
        return all(f.is_empty(pkt) for f in self.seq)

    def get_fields_list(self):
        # type: () -> List[ASN1F_field[Any, Any]]
        return reduce(lambda x, y: x + y.get_fields_list(),
                      self.seq, [])

    def m2i(self, pkt, s):
        # type: (Any, bytes) -> Tuple[Any, bytes]
        """
        ASN1F_SEQUENCE behaves transparently, with nested ASN1_objects being
        dissected one by one. Because we use obj.dissect (see loop below)
        instead of obj.m2i (as we trust dissect to do the appropriate set_vals)
        we do not directly retrieve the list of nested objects.
        Thus m2i returns an empty list (along with the proper remainder).
        It is discarded by dissect() and should not be missed elsewhere.
        """
        diff_tag, s = BER_tagging_dec(s, hidden_tag=self.ASN1_tag,
                                      implicit_tag=self.implicit_tag,
                                      explicit_tag=self.explicit_tag,
                                      safe=self.flexible_tag,
                                      _fname=pkt.name)
        if diff_tag is not None:
            if self.implicit_tag is not None:
                self.implicit_tag = diff_tag
            elif self.explicit_tag is not None:
                self.explicit_tag = diff_tag