/usr/lib/python2.7/dist-packages/impacket/helper.py is in python-impacket 0.9.12-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#
# This software is provided under under a slightly modified version
# of the Apache Software License. See the accompanying LICENSE file
# for more information.
#
# $Id$
#
# Description:
# Helper used to build ProtocolPackets
#
# Author:
# Aureliano Calvo
import impacket.ImpactPacket as ip
import struct
import functools
def rebind(f):
functools.wraps(f)
def rebinder(*args, **kwargs):
return f(*args, **kwargs)
return rebinder
class Field(object):
def __init__(self, index):
self.index = index
def __call__(self, k, d):
getter = rebind(self.getter)
getter_name = "get_" + k
getter.__name__ = getter_name
getter.__doc__ = "Get the %s field" % k
d[getter_name] = getter
setter = rebind(self.setter)
setter_name = "set_" + k
setter.__name__ = setter_name
setter.__doc__ = "Set the %s field" % k
d["set_" + k] = setter
d[k] = property(getter, setter, doc="%s property" % k)
class Bit(Field):
def __init__(self, index, bit_number):
Field.__init__(self, index)
self.mask = 2 ** bit_number
self.off_mask = (~self.mask) & 0xff
def getter(self, o):
return (o.header.get_byte(self.index) & self.mask) != 0
def setter(self, o, value=True):
b = o.header.get_byte(self.index)
if value:
b |= self.mask
else:
b &= self.off_mask
o.header.set_byte(self.index, b)
class Byte(Field):
def __init__(self, index):
Field.__init__(self, index)
def getter(self, o):
return o.header.get_byte(self.index)
def setter(self, o, value):
o.header.set_byte(self.index, value)
class Word(Field):
def __init__(self, index, order="!"):
Field.__init__(self, index)
self.order = order
def getter(self, o):
return o.header.get_word(self.index, self.order)
def setter(self, o, value):
o.header.set_word(self.index, value, self.order)
class Long(Field):
def __init__(self, index, order="!"):
Field.__init__(self, index)
self.order = order
def getter(self, o):
return o.header.get_long(self.index, self.order)
def setter(self, o, value):
o.header.set_long(self.index, value, self.order)
class ThreeBytesBigEndian(Field):
def __init__(self, index):
Field.__init__(self, index)
def getter(self, o):
b=o.header.get_bytes()[self.index:self.index+3].tostring()
#unpack requires a string argument of length 4 and b is 3 bytes long
(value,)=struct.unpack('!L', '\x00'+b)
return value
def setter(self, o, value):
# clear the bits
mask = ((~0xFFFFFF00) & 0xFF)
masked = o.header.get_long(self.index, ">") & mask
# set the bits
nb = masked | ((value & 0x00FFFFFF) << 8)
o.header.set_long(self.index, nb, ">")
class ProtocolPacketMetaklass(type):
def __new__(cls, name, bases, d):
d["_fields"] = []
items = d.items()
if not object in bases:
bases += (object,)
for k,v in items:
if isinstance(v, Field):
d["_fields"].append(k)
v(k, d)
d["_fields"].sort()
def _fields_repr(self):
return " ".join( "%s:%s" % (f, repr(getattr(self, f))) for f in self._fields )
def __repr__(self):
return "<%(name)s %(fields)s \nchild:%(r_child)s>" % {
"name": name,
"fields": self._fields_repr(),
"r_child": repr(self.child()),
}
d["_fields_repr"] = _fields_repr
d["__repr__"] = __repr__
return type.__new__(cls, name, bases, d)
class ProtocolPacket(ip.ProtocolPacket):
__metaclass__ = ProtocolPacketMetaklass
def __init__(self, buff = None):
ip.ProtocolPacket.__init__(self, self.header_size, self.tail_size)
if buff:
self.load_packet(buff)
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