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"""
mitmproxy protocol architecture
In mitmproxy, protocols are implemented as a set of layers, which are composed on top each other.
For example, the following scenarios depict possible scenarios (lowest layer first):
Transparent HTTP proxy, no SSL:
TransparentModeLayer
HttpLayer
Regular proxy, CONNECT request with WebSockets over SSL:
RegularModeLayer
HttpLayer
SslLayer
WebsocketLayer (or TcpLayer)
Automated protocol detection by peeking into the buffer:
TransparentModeLayer
AutoLayer
SslLayer
AutoLayer
Http2Layer
Communication between layers is done as follows:
- lower layers provide context information to higher layers
- higher layers can "yield" commands to lower layers,
which are propagated until they reach a suitable layer.
Further goals:
- Connections should always be peekable to make automatic protocol detection work.
- Upstream connections should be established as late as possible;
inline scripts shall have a chance to handle everything locally.
"""
from __future__ import (absolute_import, print_function, division)
import Queue
import threading
from netlib import tcp
from ..proxy import ProxyError2, Log
from ..proxy.connection import ServerConnection
from .messages import Connect, Reconnect, ChangeServer
class RootContext(object):
"""
The outmost context provided to the root layer.
As a consequence, every layer has .client_conn, .channel and .config.
"""
def __init__(self, client_conn, config, channel):
self.client_conn = client_conn # Client Connection
self.channel = channel # provides .ask() method to communicate with FlowMaster
self.config = config # Proxy Configuration
class _LayerCodeCompletion(object):
"""
Dummy class that provides type hinting in PyCharm, which simplifies development a lot.
"""
def __init__(self):
if True:
return
self.config = None
"""@type: libmproxy.proxy.config.ProxyConfig"""
self.client_conn = None
"""@type: libmproxy.proxy.connection.ClientConnection"""
self.channel = None
"""@type: libmproxy.controller.Channel"""
class Layer(_LayerCodeCompletion):
def __init__(self, ctx):
"""
Args:
ctx: The (read-only) higher layer.
"""
super(Layer, self).__init__()
self.ctx = ctx
def __call__(self):
"""
Logic of the layer.
Raises:
ProxyError2 in case of protocol exceptions.
"""
raise NotImplementedError
def __getattr__(self, name):
"""
Attributes not present on the current layer may exist on a higher layer.
"""
return getattr(self.ctx, name)
def log(self, msg, level, subs=()):
full_msg = [
"%s:%s: %s" %
(self.client_conn.address.host,
self.client_conn.address.port,
msg)]
for i in subs:
full_msg.append(" -> " + i)
full_msg = "\n".join(full_msg)
self.channel.tell("log", Log(full_msg, level))
class ServerConnectionMixin(object):
"""
Mixin that provides a layer with the capabilities to manage a server connection.
"""
def __init__(self):
self._server_address = None
self.server_conn = None
def _handle_server_message(self, message):
if message == Reconnect:
self._disconnect()
self._connect()
return True
elif message == Connect:
self._connect()
return True
elif message == ChangeServer:
raise NotImplementedError
return False
@property
def server_address(self):
return self._server_address
@server_address.setter
def server_address(self, address):
self._server_address = tcp.Address.wrap(address)
self.log("Set new server address: " + repr(self.server_address), "debug")
def _disconnect(self):
"""
Deletes (and closes) an existing server connection.
"""
self.log("serverdisconnect", "debug", [repr(self.server_address)])
self.server_conn.finish()
self.server_conn.close()
# self.channel.tell("serverdisconnect", self)
self.server_conn = None
def _connect(self):
self.log("serverconnect", "debug", [repr(self.server_address)])
self.server_conn = ServerConnection(self.server_address)
try:
self.server_conn.connect()
except tcp.NetLibError as e:
raise ProxyError2("Server connection to '%s' failed: %s" % (self.server_address, e), e)
def yield_from_callback(fun):
"""
Decorator which makes it possible to yield from callbacks in the original thread.
As a use case, take the pyOpenSSL handle_sni callback: If we receive a new SNI from the client,
we need to reconnect to the server with the new SNI. Reconnecting would normally be done using "yield Reconnect()",
but we're in a pyOpenSSL callback here, outside of the main program flow. With this decorator, it looks as follows:
def handle_sni(self):
# ...
self.yield_from_callback(Reconnect())
@yield_from_callback
def establish_ssl_with_client():
self.client_conn.convert_to_ssl(...)
for message in self.establish_ssl_with_client(): # will yield Reconnect at some point
yield message
Limitations:
- You cannot yield True.
"""
yield_queue = Queue.Queue()
def do_yield(self, msg):
yield_queue.put(msg)
yield_queue.get()
def wrapper(self, *args, **kwargs):
self.yield_from_callback = do_yield
def run():
try:
fun(self, *args, **kwargs)
yield_queue.put(True)
except Exception as e:
yield_queue.put(e)
threading.Thread(target=run, name="YieldFromCallbackThread").start()
while True:
e = yield_queue.get()
if e is True:
break
elif isinstance(e, Exception):
# TODO: Include func name?
raise ProxyError2("Error from callback: " + repr(e), e)
else:
yield e
yield_queue.put(None)
self.yield_from_callback = None
return wrapper
|
