Framework for extended message encoding

- helper classes for encoding/decoding messages
- includes both old as well as new extended one (msgpack+zlib)
- the classes are unused yet and are supposed to be for experimenting
This commit is contained in:
Peter Šurda 2016-06-24 22:45:56 +02:00
parent 6add48e036
commit e649adbe37
Signed by: PeterSurda
GPG Key ID: 0C5F50C0B5F37D87
3 changed files with 86 additions and 144 deletions

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class BTFailure(Exception):
pass

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# coding: utf-8
# The contents of this file are subject to the BitTorrent Open Source License
# Version 1.1 (the License). You may not copy or use this file, in either
# source code or executable form, except in compliance with the License. You
# may obtain a copy of the License at http://www.bittorrent.com/license/.
#
# Software distributed under the License is distributed on an AS IS basis,
# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
# for the specific language governing rights and limitations under the
# License.
# Written by Petru Paler
# Modifed by Peter Šurda
from BTL import BTFailure
def decode_int(x, f):
f += 1
newf = x.index('e', f)
n = int(x[f:newf])
if x[f] == '-':
if x[f + 1] == '0':
raise ValueError
elif x[f] == '0' and newf != f+1:
raise ValueError
return (n, newf+1)
def decode_string(x, f):
colon = x.index(':', f)
n = int(x[f:colon])
if x[f] == '0' and colon != f+1:
raise ValueError
colon += 1
return (x[colon:colon+n], colon+n)
def decode_list(x, f):
r, f = [], f+1
while x[f] != 'e':
v, f = decode_func[x[f]](x, f)
r.append(v)
return (r, f + 1)
def decode_dict(x, f):
r, f = {}, f+1
while x[f] != 'e':
k, f = decode_string(x, f)
r[k], f = decode_func[x[f]](x, f)
return (r, f + 1)
decode_func = {}
decode_func['l'] = decode_list
decode_func['d'] = decode_dict
decode_func['i'] = decode_int
decode_func['0'] = decode_string
decode_func['1'] = decode_string
decode_func['2'] = decode_string
decode_func['3'] = decode_string
decode_func['4'] = decode_string
decode_func['5'] = decode_string
decode_func['6'] = decode_string
decode_func['7'] = decode_string
decode_func['8'] = decode_string
decode_func['9'] = decode_string
def bdecode(x):
try:
r, l = decode_func[x[0]](x, 0)
except (IndexError, KeyError, ValueError):
raise BTFailure("not a valid bencoded string")
if l != len(x):
raise BTFailure("invalid bencoded value (data after valid prefix)")
return r
from types import StringType, IntType, LongType, DictType, ListType, TupleType, UnicodeType, NoneType
class Bencached(object):
__slots__ = ['bencoded']
def __init__(self, s):
self.bencoded = s
def encode_bencached(x,r):
r.append(x.bencoded)
def encode_int(x, r):
r.extend(('i', str(x), 'e'))
def encode_bool(x, r):
if x:
encode_int(1, r)
else:
encode_int(0, r)
def encode_string(x, r):
r.extend((str(len(x)), ':', x))
def encode_unicode(x, r):
raw = x.encode('utf8')
r.extend((str(len(raw)), ':', raw))
def encode_none(x, r):
r.extend('0:')
def encode_list(x, r):
r.append('l')
for i in x:
encode_func[type(i)](i, r)
r.append('e')
def encode_dict(x,r):
r.append('d')
ilist = x.items()
ilist.sort()
for k, v in ilist:
r.extend((str(len(k)), ':', k))
encode_func[type(v)](v, r)
r.append('e')
encode_func = {}
encode_func[Bencached] = encode_bencached
encode_func[IntType] = encode_int
encode_func[LongType] = encode_int
encode_func[StringType] = encode_string
encode_func[ListType] = encode_list
encode_func[TupleType] = encode_list
encode_func[DictType] = encode_dict
encode_func[UnicodeType] = encode_unicode
encode_func[NoneType] = encode_none
try:
from types import BooleanType
encode_func[BooleanType] = encode_bool
except ImportError:
pass
def bencode(x):
r = []
encode_func[type(x)](x, r)
return ''.join(r)

86
src/helper_msgcoding.py Normal file
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#!/usr/bin/python2.7
import msgpack
import zlib
from debug import logger
BITMESSAGE_ENCODING_IGNORE = 0
BITMESSAGE_ENCODING_TRIVIAL = 1
BITMESSAGE_ENCODING_SIMPLE = 2
BITMESSAGE.ENCODING_EXTENDED = 3
class MsgEncode(object):
def __init__(self, message, encoding = BITMESSAGE_ENCODING_SIMPLE):
self.data = None
self.encoding = encoding
self.length = 0
if self.encoding == BITMESSAGE_ENCODING_EXTENDED:
self.encodeExtended(message)
elif self.encoding == BITMESSAGE_ENCODING_SIMPLE:
self.encodeSimple(message)
elif self.encoding == BITMESSAGE_ENCODING_TRIVIAL:
self.encodeTrivial(message)
def encodeExtended(self, message):
try:
self.data = zlib.compress(msgpack.dumps({"": "message", "subject": message['subject'], "message": ['body']}), 9)
except zlib.error:
logger.error ("Error compressing message")
raise
except msgpack.exceptions.PackException:
logger.error ("Error msgpacking message")
raise
self.length = len(self.data)
def encodeSimple(self, message):
self.data = 'Subject:' + message['subject'] + '\n' + 'Body:' + message['body']
self.length = len(self.data)
def encodeTrivial(self, message):
self.data = message['body']
self.length = len(self.data)
class MsgDecode(object):
def __init__(self, encoding, data):
self.encoding = encoding
if self.encoding == BITMESSAGE_ENCODING_EXTENDED:
self.decodeExtended(data)
elif self.encoding in [BITMESSAGE_ENCODING_SIMPLE, BITMESSAGE_ENCODING_TRIVIAL]:
self.decodeSimple(data)
return
def decodeExtended(self, data):
try:
tmp = msgpack.loads(zlib.decompress(data))
except zlib.error:
logger.error ("Error decompressing message")
raise
except (msgpack.exceptions.UnpackException,
msgpack.exceptions.ExtraData):
logger.error ("Error msgunpacking message")
raise
try:
if tmp[""] == "message":
self.body = tmp["body"]
self.subject = tmp["subject"]
except:
logger.error ("Malformed message")
raise
def decodeSimple(self, data):
bodyPositionIndex = string.find(data, '\nBody:')
if bodyPositionIndex > 1:
subject = message[8:bodyPositionIndex]
# Only save and show the first 500 characters of the subject.
# Any more is probably an attack.
subject = subject[:500]
body = message[bodyPositionIndex + 6:]
else:
subject = ''
body = message
# Throw away any extra lines (headers) after the subject.
if subject:
subject = subject.splitlines()[0]
self.subject = subject
self.message = body