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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 settings (lowest layer first):
Transparent HTTP proxy, no SSL:
TransparentProxy
Http1Layer
HttpLayer
Regular proxy, CONNECT request with WebSockets over SSL:
HttpProxy
Http1Layer
HttpLayer
SslLayer
WebsocketLayer (or TcpLayer)
Automated protocol detection by peeking into the buffer:
TransparentProxy
TLSLayer
Http2Layer
HttpLayer
Communication between layers is done as follows:
- lower layers provide context information to higher layers
- higher layers can call functions provided by 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)
from netlib import tcp
from ..models import ServerConnection
from ..exceptions import ProtocolException
class _LayerCodeCompletion(object):
"""
Dummy class that provides type hinting in PyCharm, which simplifies development a lot.
"""
def __init__(self, *args, **kwargs): # pragma: nocover
super(_LayerCodeCompletion, self).__init__(*args, **kwargs)
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, **kwargs):
"""
Args:
ctx: The (read-only) higher layer.
"""
super(Layer, self).__init__(*args, **kwargs)
self.ctx = ctx
def __call__(self):
"""
Logic of the layer.
Raises:
ProtocolException 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 = [
"{}: {}".format(repr(self.client_conn.address), msg)
]
for i in subs:
full_msg.append(" -> " + i)
full_msg = "\n".join(full_msg)
self.channel.tell("log", Log(full_msg, level))
@property
def layers(self):
return [self] + self.ctx.layers
def __repr__(self):
return type(self).__name__
class ServerConnectionMixin(object):
"""
Mixin that provides a layer with the capabilities to manage a server connection.
"""
def __init__(self, server_address=None):
super(ServerConnectionMixin, self).__init__()
self.server_conn = ServerConnection(server_address)
self._check_self_connect()
def reconnect(self):
address = self.server_conn.address
self._disconnect()
self.server_conn.address = address
self.connect()
def _check_self_connect(self):
"""
We try to protect the proxy from _accidentally_ connecting to itself,
e.g. because of a failed transparent lookup or an invalid configuration.
"""
address = self.server_conn.address
if address:
self_connect = (
address.port == self.config.port and
address.host in ("localhost", "127.0.0.1", "::1")
)
if self_connect:
raise ProtocolException(
"Invalid server address: {}\r\n"
"The proxy shall not connect to itself.".format(repr(address))
)
def set_server(self, address, server_tls=None, sni=None, depth=1):
if depth == 1:
if self.server_conn:
self._disconnect()
self.log("Set new server address: " + repr(address), "debug")
self.server_conn.address = address
self._check_self_connect()
if server_tls:
raise ProtocolException(
"Cannot upgrade to TLS, no TLS layer on the protocol stack."
)
else:
self.ctx.set_server(address, server_tls, sni, depth - 1)
def _disconnect(self):
"""
Deletes (and closes) an existing server connection.
"""
self.log("serverdisconnect", "debug", [repr(self.server_conn.address)])
self.server_conn.finish()
self.server_conn.close()
# self.channel.tell("serverdisconnect", self)
self.server_conn = ServerConnection(None)
def connect(self):
if not self.server_conn.address:
raise ProtocolException("Cannot connect to server, no server address given.")
self.log("serverconnect", "debug", [repr(self.server_conn.address)])
try:
self.server_conn.connect()
except tcp.NetLibError as e:
raise ProtocolException(
"Server connection to %s failed: %s" % (repr(self.server_conn.address), e), e)
class Log(object):
def __init__(self, msg, level="info"):
self.msg = msg
self.level = level
class Kill(Exception):
"""
Kill a connection.
"""
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