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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright 2017, Martin Kacer <kacer.martin[AT]gmail.com>
#
# Wireshark - Network traffic analyzer
# By Gerald Combs <gerald@wireshark.org>
# Copyright 1998 Gerald Combs
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
import sys
import json
import operator
import copy
import os
import binascii
import array
import argparse
import subprocess
from collections import OrderedDict
def make_unique(key, dct):
counter = 0
unique_key = key
while unique_key in dct:
counter += 1
unique_key = '{}_{}'.format(key, counter)
return unique_key
def parse_object_pairs(pairs):
dct = OrderedDict()
for key, value in pairs:
if key in dct:
key = make_unique(key, dct)
dct[key] = value
return dct
#
# ********* PY TEMPLATES *********
#
def read_py_function(name):
s = ''
record = False
indent = 0
file = open(__file__)
for line in file:
ind = len(line) - len(line.lstrip())
if (line.find("def " + name) != -1):
record = True
indent = ind
elif (record == True and indent == ind and len(line) > 1):
record = False
if (record == True):
s = s + line
file.close()
return s
py_header = """#!/usr/bin/env python
# -*- coding: utf-8 -*-
# File generated by json2pcap.py
# json2pcap.py created by Martin Kacer, 2017
import os
import binascii
import array
import sys
import subprocess
from collections import OrderedDict
# *****************************************************
# * PACKET PAYLOAD GENERATED FROM INPUT PCAP *
# * Modify this function to edit the packet *
# *****************************************************
def main():
d = OrderedDict()
"""
py_footer = """ generate_pcap(d)
# *****************************************************
# * FUNCTIONS from TEMPLATE *
# * Do not edit these functions if not required *
# *****************************************************
"""
py_footer = py_footer + read_py_function("to_pcap_file")
py_footer = py_footer + read_py_function("hex_to_txt")
py_footer = py_footer + read_py_function("to_bytes")
py_footer = py_footer + read_py_function("lsb")
py_footer = py_footer + read_py_function("rewrite_frame")
py_footer = py_footer + read_py_function("assemble_frame")
py_footer = py_footer + read_py_function("generate_pcap")
py_footer = py_footer + """
if __name__ == '__main__':
main()
"""
#
# ***** End of PY TEMPLATES ******
#
#
# ********** FUNCTIONS ***********
#
def to_pcap_file(filename, output_pcap_file):
subprocess.call(["text2pcap", filename, output_pcap_file])
def hex_to_txt(hexstring, output_file):
h = hexstring.lower()
file = open(output_file, 'a')
for i in range(0, len(h), 2):
if(i % 32 == 0):
file.write(format(i / 2, '06x') + ' ')
file.write(h[i:i + 2] + ' ')
if(i % 32 == 30):
file.write('\n')
file.write('\n')
file.close()
def raw_flat_collector(dict):
if hasattr(dict, 'items'):
for k, v in dict.items():
if k.endswith("_raw"):
yield k, v
else:
for val in raw_flat_collector(v):
yield val
# d - input dictionary, parsed from json
# r - result dictionary
# frame_name - parent protocol name
# frame_position - parent protocol position
def py_generator(d, r, frame_name='frame_raw', frame_position=0):
if (d is None or d is None):
return
if hasattr(d, 'items'):
for k, v in d.items():
# no recursion
if ( k.endswith("_raw") or ("_raw_" in k) ):
if (isinstance(v[1], (list, tuple)) or isinstance(v[2], (list, tuple)) ):
#i = 1;
for _v in v:
h = _v[0]
p = _v[1]
l = _v[2] * 2
b = _v[3]
t = _v[4]
if (len(h) != l):
l = len(h)
p = p - frame_position
# Add into result dictionary
key = str(k).replace('.', '_')
key = make_unique(key, r)
fn = frame_name.replace('.', '_')
if (fn == key):
fn = None
value = [fn , h, p, l, b, t]
r[key] = value
else:
h = v[0]
p = v[1]
l = v[2] * 2
b = v[3]
t = v[4]
if (len(h) != l):
l = len(h)
p = p - frame_position
# Add into result dictionary
key = str(k).replace('.', '_')
key = make_unique(key, r)
fn = frame_name.replace('.', '_')
if (fn == key):
fn = None
value = [fn , h, p, l, b, t]
r[key] = value
# recursion
else:
if isinstance(v, dict):
fn = frame_name
fp = frame_position
# if there is also preceding raw protocol frame use it
# remove tree suffix
key = k
if (key.endswith("_tree") or ("_tree_" in key)):
key = key.replace('_tree', '')
raw_key = key + "_raw"
if (raw_key in d):
# f = d[raw_key][0]
fn = raw_key
fp = d[raw_key][1]
py_generator(v, r, fn, fp)
elif isinstance(v, (list, tuple)):
fn = frame_name
fp = frame_position
# if there is also preceding raw protocol frame use it
# remove tree suffix
key = k
if (key.endswith("_tree") or ("_tree_" in key)):
key = key.replace('_tree', '')
raw_key = key + "_raw"
if (raw_key in d):
fn = raw_key
fp = d[raw_key][1]
for _v in v:
py_generator(_v, r, frame_name, frame_position)
# To emulate Python 3.2
def to_bytes(n, length, endianess='big'):
h = '%x' % n
s = ('0' * (len(h) % 2) + h).zfill(length * 2).decode('hex')
return s if endianess == 'big' else s[::-1]
# Returns the index, counting from 0, of the least significant set bit in x
def lsb(x):
return (x & -x).bit_length() - 1
# Rewrite frame
# h - hex bytes
# p - position
# l - length
# b - bitmask
# t - type
def rewrite_frame(frame_raw, h, p, l, b, t):
# no bitmask
if(b == 0):
if (len(h) != l):
l = len(h)
return frame_raw[:p] + h + frame_raw[p + l:]
# bitmask
else:
# get hex string from frame which will be replaced
_h = frame_raw[p:p + l]
# add 0 padding to have correct length
if (len(_h) % 2 == 1):
_h = '0' + _h
if (len(h) % 2 == 1):
h = '0' + h
# Only replace bits defined by mask
# new_hex = (old_hex & !mask) | (new_hex & mask)
_H = _h.decode("hex")
_H = array.array('B', _H)
M = to_bytes(b, len(_H))
M = array.array('B', M)
# shift mask aligned to position
for i in range(len(M)):
if (i + p / 2) < len(M):
M[i] = M[i + p / 2]
else:
M[i] = 0x00
H = h.decode("hex")
H = array.array('B', H)
# for i in range(len(_H)):
# print "{0:08b}".format(_H[i]),
# print
# for i in range(len(M)):
# print "{0:08b}".format(M[i]),
# print
j = 0;
for i in range(len(_H)):
if (M[i] != 0):
v = H[j] << lsb(M[i])
# print "Debug: {0:08b}".format(v),
_H[i] = (_H[i] & ~M[i]) | (v & M[i])
# print "Debug: " + str(_H[i]),
j = j + 1;
# for i in range(len(_H)):
# print "{0:08b}".format(_H[i]),
# print
masked_h = binascii.hexlify(_H)
return frame_raw[:p] + masked_h + frame_raw[p + l:]
def assemble_frame(d):
input = d['frame_raw'][1]
isFlat = False
linux_cooked_header = False;
while(isFlat == False):
isFlat = True
for key, val in d.items():
h = str(val[1]) # hex
p = val[2] * 2 # position
l = val[3] * 2 # length
b = val[4] # bitmask
t = val[5] # type
if (key == "sll_raw"):
linux_cooked_header = True;
# only if the node is not parent
isParent = False
for k, v in d.items():
if (v[0] == key):
isParent = True
isFlat = False
break
if (isParent == False and val[0] is not None):
d[val[0]][1] = rewrite_frame(d[val[0]][1], h, p, l, b, t)
del d[key]
output = d['frame_raw'][1]
# for Linux cooked header replace dest MAC and remove two bytes to reconstruct normal frame using text2pcap
if (linux_cooked_header):
output = "000000000000" + output[6*2:] # replce dest MAC
output = output[:12*2] + "" + output[14*2:] # remove two bytes before Protocol
return output
def generate_pcap(d):
# 1. Assemble frame
input = d['frame_raw'][1]
output = assemble_frame(d)
print(input)
print(output)
# 2. Testing: compare input and output for not modified json
if (input != output):
print("Modified frames: ")
s1 = input
s2 = output
print(s1)
print(s2)
if (len(s1) == len(s2)):
d = [i for i in xrange(len(s1)) if s1[i] != s2[i]]
print(d)
# 3. Open TMP file used by text2pcap
file = sys.argv[0] + '.tmp'
f = open(file,'w')
hex_to_txt(output, file)
f.close()
# 4. Generate pcap
to_pcap_file(sys.argv[0] + '.tmp', sys.argv[0] + '.pcap')
print("Generated " + sys.argv[0] + ".tmp")
print("Generated " + sys.argv[0] + ".pcap")
#
# ************ MAIN **************
#
parser = argparse.ArgumentParser(description="""
Utility to generate pcap from json format.
Packet modification:
In input json it is possible to modify the raw values of decoded fields.
The output pcap will include the modified values. The algorithm of
generating the output pcap is to get all raw hex fields from input json and
then assembling them by layering from longest (less decoded fields) to
shortest (more decoded fields). It means if the modified raw field is
shorter field (more decoded field) it takes precedence against modification
in longer field (less decoded field). If the json includes duplicated raw
fields with same position and length, the behavior is not deterministic.
For manual packet editing it is always possible to remove any not required
raw fields from json, only frame_raw is field mandatory for reconstruction.
Packet modification with -p switch:
The python script is generated instead of pcap. This python script when
executed will generate the pcap of 1st packet from input json. The
generated code includes the decoded fields and the function to assembly the
packet. This enables to modify the script and programmatically edit or
encode the packet variables. The assembling algorithm is different, because
the decoded packet fields are relative and points to parent node with their
position (compared to input json which has absolute positions).
""", formatter_class=argparse.RawTextHelpFormatter)
parser.add_argument('infile', nargs='+', help='json generated by tshark -T jsonraw or by tshark -T json -x')
parser.add_argument('-p', '--python', help='generate python payload instead of pcap (only 1st packet)', default=False, action='store_true')
args = parser.parse_args()
# read JSON
infile = args.infile[0]
with open(infile) as data_file:
#json = json.load(data_file, object_pairs_hook=OrderedDict)
json = json.load(data_file, object_pairs_hook=parse_object_pairs)
input_frame_raw = ''
frame_raw = ''
# Generate pcap
if args.python == False:
# open TMP file used by text2pcap
file = infile + '.tmp'
f = open(file, 'w')
# Iterate over packets in JSON
for packet in json:
_list = []
linux_cooked_header = False;
# get flat raw fields into _list
for raw in raw_flat_collector(packet['_source']['layers']):
if (raw[0] == "frame_raw"):
frame_raw = raw[1][0]
input_frame_raw = copy.copy(frame_raw)
else:
_list.append(raw[1])
if (raw[0] == "sll_raw"):
linux_cooked_header = True
# sort _list
sorted_list = sorted(_list, key=operator.itemgetter(1), reverse=False)
sorted_list = sorted(sorted_list, key=operator.itemgetter(2), reverse=True)
# print("Debug: " + str(sorted_list))
# rewrite frame
for raw in sorted_list:
h = str(raw[0]) # hex
p = raw[1] * 2 # position
l = raw[2] * 2 # length
b = raw[3] # bitmask
t = raw[4] # type
if (isinstance(p, (list, tuple)) or isinstance(l, (list, tuple))):
for r in raw:
_h = str(r[0]) # hex
_p = r[1] * 2 # position
_l = r[2] * 2 # length
_b = r[3] # bitmask
_t = r[4] # type
# print("Debug: " + str(raw))
frame_raw = rewrite_frame(frame_raw, _h, _p, _l, _b, _t)
else:
# print("Debug: " + str(raw))
frame_raw = rewrite_frame(frame_raw, h, p, l, b, t)
# for Linux cooked header replace dest MAC and remove two bytes to reconstruct normal frame using text2pcap
if (linux_cooked_header):
frame_raw = "000000000000" + frame_raw[6 * 2:] # replce dest MAC
frame_raw = frame_raw[:12 * 2] + "" + frame_raw[14 * 2:] # remove two bytes before Protocol
# Testing: remove comment to compare input and output for not modified json
if (input_frame_raw != frame_raw):
print("Modified frames: ")
s1 = input_frame_raw
s2 = frame_raw
print(s1)
print(s2)
if (len(s1) == len(s2)):
d = [i for i in xrange(len(s1)) if s1[i] != s2[i]]
print(d)
hex_to_txt(frame_raw, file)
f.close()
to_pcap_file(infile + '.tmp', sys.argv[1] + '.pcap')
os.remove(infile + '.tmp')
# Generate python payload only for first packet
else:
file = infile + '.py'
f = open(file, 'w')
for packet in json:
f.write(py_header)
r = OrderedDict({})
#print "packet = " + str(packet['_source']['layers'])
py_generator(packet['_source']['layers'], r)
for key, value in r.iteritems() :
f.write(" d['" + key + "'] =",)
f.write(" " + str(value) + "\n")
f.write(py_footer)
# Currently only first packet is used from pcap
f.close
print("Generated " + infile + '.py')
break
|