254 lines
7.1 KiB
Python
254 lines
7.1 KiB
Python
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# This file is part of Scapy.
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# See http://www.secdev.org/projects/scapy for more information.
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#
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# Scapy is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 2 of the License, or
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# (at your option) any later version.
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#
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# Scapy is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with Scapy. If not, see <http://www.gnu.org/licenses/>.
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#
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# Copyright (C) 2016 Anmol Sarma <me@anmolsarma.in>
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# scapy.contrib.description = Constrained Application Protocol (CoAP)
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# scapy.contrib.status = loads
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"""
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RFC 7252 - Constrained Application Protocol (CoAP) layer for Scapy
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"""
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import struct
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from scapy.fields import BitEnumField, BitField, BitFieldLenField, \
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ByteEnumField, ShortField, StrField, StrLenField
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from scapy.layers.inet import UDP
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from scapy.packet import Packet, bind_layers
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from scapy.error import warning
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from scapy.compat import raw
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coap_codes = {
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0: "Empty",
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# Request codes
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1: "GET",
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2: "POST",
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3: "PUT",
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4: "DELETE",
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# Response codes
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65: "2.01 Created",
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66: "2.02 Deleted",
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67: "2.03 Valid",
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68: "2.04 Changed",
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69: "2.05 Content",
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128: "4.00 Bad Request",
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129: "4.01 Unauthorized",
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130: "4.02 Bad Option",
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131: "4.03 Forbidden",
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132: "4.04 Not Found",
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133: "4.05 Method Not Allowed",
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134: "4.06 Not Acceptable",
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140: "4.12 Precondition Failed",
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141: "4.13 Request Entity Too Large",
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143: "4.15 Unsupported Content-Format",
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160: "5.00 Internal Server Error",
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161: "5.01 Not Implemented",
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162: "5.02 Bad Gateway",
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163: "5.03 Service Unavailable",
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164: "5.04 Gateway Timeout",
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165: "Proxying Not Supported"}
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coap_options = ({
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1: "If-Match",
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3: "Uri-Host",
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4: "ETag",
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5: "If-None-Match",
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7: "Uri-Port",
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8: "Location-Path",
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11: "Uri-Path",
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12: "Content-Format",
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14: "Max-Age",
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15: "Uri-Query",
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17: "Accept",
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20: "Location-Query",
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35: "Proxy-Uri",
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39: "Proxy-Scheme",
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60: "Size1"
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},
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{
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"If-Match": 1,
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"Uri-Host": 3,
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"ETag": 4,
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"If-None-Match": 5,
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"Uri-Port": 7,
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"Location-Path": 8,
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"Uri-Path": 11,
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"Content-Format": 12,
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"Max-Age": 14,
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"Uri-Query": 15,
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"Accept": 17,
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"Location-Query": 20,
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"Proxy-Uri": 35,
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"Proxy-Scheme": 39,
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"Size1": 60
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})
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def _get_ext_field_size(val):
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if val >= 15:
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warning("Invalid Option Delta or Length")
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if val == 14:
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return 2
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if val == 13:
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return 1
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return 0
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def _get_delta_ext_size(pkt):
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return _get_ext_field_size(pkt.delta)
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def _get_len_ext_size(pkt):
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return _get_ext_field_size(pkt.len)
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def _get_abs_val(val, ext_val):
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if val >= 15:
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warning("Invalid Option Length or Delta %d" % val)
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if val == 14:
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return 269 + struct.unpack('H', ext_val)[0]
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if val == 13:
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return 13 + struct.unpack('B', ext_val)[0]
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return val
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def _get_opt_val_size(pkt):
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return _get_abs_val(pkt.len, pkt.len_ext)
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class _CoAPOpt(Packet):
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fields_desc = [BitField("delta", 0, 4),
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BitField("len", 0, 4),
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StrLenField("delta_ext", None, length_from=_get_delta_ext_size), # noqa: E501
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StrLenField("len_ext", None, length_from=_get_len_ext_size),
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StrLenField("opt_val", None, length_from=_get_opt_val_size)]
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@staticmethod
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def _populate_extended(val):
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if val >= 269:
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return struct.pack('H', val - 269), 14
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if val >= 13:
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return struct.pack('B', val - 13), 13
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return None, val
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def do_build(self):
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self.delta_ext, self.delta = self._populate_extended(self.delta)
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self.len_ext, self.len = self._populate_extended(len(self.opt_val))
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return Packet.do_build(self)
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def guess_payload_class(self, payload):
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if payload[:1] != b"\xff":
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return _CoAPOpt
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else:
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return Packet.guess_payload_class(self, payload)
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class _CoAPOptsField(StrField):
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islist = 1
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def i2h(self, pkt, x):
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return [(coap_options[0][o[0]], o[1]) if o[0] in coap_options[0] else o for o in x] # noqa: E501
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# consume only the coap layer from the wire string
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def getfield(self, pkt, s):
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opts = self.m2i(pkt, s)
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used = 0
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for o in opts:
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used += o[0]
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return s[used:], [(o[1], o[2]) for o in opts]
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def m2i(self, pkt, x):
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opts = []
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o = _CoAPOpt(x)
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cur_delta = 0
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while isinstance(o, _CoAPOpt):
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cur_delta += _get_abs_val(o.delta, o.delta_ext)
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# size of this option in bytes
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u = 1 + len(o.opt_val) + len(o.delta_ext) + len(o.len_ext)
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opts.append((u, cur_delta, o.opt_val))
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o = o.payload
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return opts
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def i2m(self, pkt, x):
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if not x:
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return b""
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opt_lst = []
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for o in x:
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if isinstance(o[0], str):
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opt_lst.append((coap_options[1][o[0]], o[1]))
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else:
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opt_lst.append(o)
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opt_lst.sort(key=lambda o: o[0])
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opts = _CoAPOpt(delta=opt_lst[0][0], opt_val=opt_lst[0][1])
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high_opt = opt_lst[0][0]
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for o in opt_lst[1:]:
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opts = opts / _CoAPOpt(delta=o[0] - high_opt, opt_val=o[1])
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high_opt = o[0]
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return raw(opts)
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class _CoAPPaymark(StrField):
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def i2h(self, pkt, x):
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return x
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def getfield(self, pkt, s):
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(u, m) = self.m2i(pkt, s)
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return s[u:], m
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def m2i(self, pkt, x):
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if len(x) > 0 and x[:1] == b"\xff":
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return 1, b'\xff'
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return 0, b''
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def i2m(self, pkt, x):
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return x
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class CoAP(Packet):
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__slots__ = ["content_format"]
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name = "CoAP"
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fields_desc = [BitField("ver", 1, 2),
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BitEnumField("type", 0, 2, {0: "CON", 1: "NON", 2: "ACK", 3: "RST"}), # noqa: E501
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BitFieldLenField("tkl", None, 4, length_of='token'),
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ByteEnumField("code", 0, coap_codes),
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ShortField("msg_id", 0),
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StrLenField("token", "", length_from=lambda pkt: pkt.tkl),
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_CoAPOptsField("options", []),
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_CoAPPaymark("paymark", b"")
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]
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def getfieldval(self, attr):
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v = getattr(self, attr)
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if v:
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return v
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return Packet.getfieldval(self, attr)
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def post_dissect(self, pay):
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for k in self.options:
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if k[0] == "Content-Format":
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self.content_format = k[1]
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return pay
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bind_layers(UDP, CoAP, sport=5683)
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bind_layers(UDP, CoAP, dport=5683)
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