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PyBitmessage/src/helper_msgcoding.py

153 lines
5.0 KiB

#!/usr/bin/python2.7
try:
import msgpack
except ImportError:
try:
import umsgpack as msgpack
except ImportError:
import fallback.umsgpack.umsgpack as msgpack
import string
import zlib
from bmconfigparser import BMConfigParser
from debug import logger
import messagetypes
from tr import _translate
BITMESSAGE_ENCODING_IGNORE = 0
BITMESSAGE_ENCODING_TRIVIAL = 1
BITMESSAGE_ENCODING_SIMPLE = 2
BITMESSAGE_ENCODING_EXTENDED = 3
class DecompressionSizeException(Exception):
def __init__(self, size):
self.size = size
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)
else:
raise ValueError("Unknown encoding %i" % (encoding))
def encodeExtended(self, message):
try:
msgObj = messagetypes.message.Message()
self.data = zlib.compress(msgpack.dumps(msgObj.encode(message)), 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)
else:
self.body = _translate("MsgDecode", "The message has an unknown encoding.\nPerhaps you should upgrade Bitmessage.")
self.subject = _translate("MsgDecode", "Unknown encoding")
def decodeExtended(self, data):
dc = zlib.decompressobj()
tmp = ""
while len(tmp) <= BMConfigParser().safeGetInt("zlib", "maxsize"):
try:
got = dc.decompress(data, BMConfigParser().safeGetInt("zlib", "maxsize") + 1 - len(tmp))
# EOF
if got == "":
break
tmp += got
data = dc.unconsumed_tail
except zlib.error:
logger.error("Error decompressing message")
raise
else:
raise DecompressionSizeException(len(tmp))
try:
tmp = msgpack.loads(tmp)
except (msgpack.exceptions.UnpackException,
msgpack.exceptions.ExtraData):
logger.error("Error msgunpacking message")
raise
try:
msgType = tmp[""]
except KeyError:
logger.error("Message type missing")
raise
msgObj = messagetypes.constructObject(tmp)
if msgObj is None:
raise ValueError("Malformed message")
try:
msgObj.process()
except:
raise ValueError("Malformed message")
if msgType == "message":
self.subject = msgObj.subject
self.body = msgObj.body
def decodeSimple(self, data):
bodyPositionIndex = string.find(data, '\nBody:')
if bodyPositionIndex > 1:
subject = data[8:bodyPositionIndex]
# Only save and show the first 500 characters of the subject.
# Any more is probably an attack.
subject = subject[:500]
body = data[bodyPositionIndex + 6:]
else:
subject = ''
body = data
# Throw away any extra lines (headers) after the subject.
if subject:
subject = subject.splitlines()[0]
self.subject = subject
self.body = body
if __name__ == '__main__':
import random
messageData = {
"subject": ''.join(random.choice(string.ascii_lowercase + string.digits) for _ in range(40)),
"body": ''.join(random.choice(string.ascii_lowercase + string.digits) for _ in range(10000))
}
obj1 = MsgEncode(messageData, 1)
obj2 = MsgEncode(messageData, 2)
obj3 = MsgEncode(messageData, 3)
print "1:%i 2:%i 3:%i" %(len(obj1.data), len(obj2.data), len(obj3.data))
obj1e = MsgDecode(1, obj1.data)
# no subject in trivial encoding
assert messageData["body"] == obj1e.body
obj2e = MsgDecode(2, obj2.data)
assert messageData["subject"] == obj2e.subject
assert messageData["body"] == obj2e.body
obj3e = MsgDecode(3, obj3.data)
assert messageData["subject"] == obj3e.subject
assert messageData["body"] == obj3e.body