# Copyright (c) 2015, Hubert Kario
#
# See the LICENSE file for legal information regarding use of this file.
"""Helper package for handling fragmentation of messages."""
from __future__ import generators
from .utils.codec import Parser
from .utils.deprecations import deprecated_attrs, deprecated_params
[docs]
@deprecated_attrs({"add_static_size": "addStaticSize",
"add_dynamic_size": "addDynamicSize",
"add_data": "addData",
"get_message": "getMessage",
"clear_buffers": "clearBuffers"})
class Defragmenter(object):
"""
Class for demultiplexing TLS messages.
Since the messages can be interleaved and fragmented between each other
we need to cache not complete ones and return in order of urgency.
Supports messages with given size (like Alerts) or with a length header
in specific place (like Handshake messages).
:ivar priorities: order in which messages from given types should be
returned.
:ivar buffers: data buffers for message types
:ivar decoders: functions which check buffers if a message of given type
is complete
"""
[docs]
def __init__(self):
"""Set up empty defregmenter"""
self.priorities = []
self.buffers = {}
self.decoders = {}
[docs]
@deprecated_params({"msg_type": "msgType"})
def add_static_size(self, msg_type, size):
"""Add a message type which all messages are of same length"""
if msg_type in self.priorities:
raise ValueError("Message type already defined")
if size < 1:
raise ValueError("Message size must be positive integer")
self.priorities += [msg_type]
self.buffers[msg_type] = bytearray(0)
def size_handler(data):
"""
Size of message in parameter
If complete message is present in parameter returns its size,
None otherwise.
"""
if len(data) < size:
return None
else:
return size
self.decoders[msg_type] = size_handler
[docs]
@deprecated_params({"msg_type": "msgType",
"size_offset": "sizeOffset",
"size_of_size": "sizeOfSize"})
def add_dynamic_size(self, msg_type, size_offset, size_of_size):
"""Add a message type which has a dynamic size set in a header"""
if msg_type in self.priorities:
raise ValueError("Message type already defined")
if size_of_size < 1:
raise ValueError("Size of size must be positive integer")
if size_offset < 0:
raise ValueError("Offset can't be negative")
self.priorities += [msg_type]
self.buffers[msg_type] = bytearray(0)
def size_handler(data):
"""
Size of message in parameter
If complete message is present in parameter returns its size,
None otherwise.
"""
if len(data) < size_offset+size_of_size:
return None
else:
parser = Parser(data)
# skip the header
parser.skip_bytes(size_offset)
payload_length = parser.get(size_of_size)
if parser.getRemainingLength() < payload_length:
# not enough bytes in buffer
return None
return size_offset + size_of_size + payload_length
self.decoders[msg_type] = size_handler
[docs]
@deprecated_params({"msg_type": "msgType"})
def add_data(self, msg_type, data):
"""Adds data to buffers"""
if msg_type not in self.priorities:
raise ValueError("Message type not defined")
self.buffers[msg_type] += data
[docs]
def get_message(self):
"""Extract the highest priority complete message from buffer"""
for msg_type in self.priorities:
buf = self.buffers[msg_type]
length = self.decoders[msg_type](buf)
if length is None:
continue
# extract message
data = buf[:length]
# remove it from buffer
del buf[:length]
return (msg_type, data)
return None
[docs]
def clear_buffers(self):
"""Remove all data from buffers"""
for key in self.buffers.keys():
self.buffers[key] = bytearray(0)
[docs]
def is_empty(self):
"""Return True if all buffers are empty."""
return all(not i for i in self.buffers.values())