mitmproxy/docs/features/passthrough.rst
2015-09-07 10:52:18 +02:00

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.. _passthrough:
Ignore Domains
==============
There are two main reasons why you may want to exempt some traffic from mitmproxy's interception
mechanism:
- **Certificate pinning:** Some traffic is is protected using `Certificate Pinning`_ and
mitmproxy's interception leads to errors. For example, the Twitter app, Windows Update or
the Apple App Store fail to work if mitmproxy is active.
- **Convenience:** You really don't care about some parts of the traffic and just want them to go
away.
If you want to peek into (SSL-protected) non-HTTP connections, check out the :ref:`tcpproxy`
feature.
If you want to ignore traffic from mitmproxy's processing because of large response bodies,
take a look at the :ref:`responsestreaming` feature.
How it works
------------
================== =============================
command-line :option:`--ignore regex`
mitmproxy shortcut :kbd:`o` then :kbd:`I`
================== =============================
mitmproxy allows you to specify a regex which is matched against a ``host:port`` string
(e.g. "example.com:443") to determine hosts that should be excluded.
There are two important quirks to consider:
- **In transparent mode, the ignore pattern is matched against the IP.** While we usually infer the
hostname from the Host header if the :option:`--host` argument is passed to mitmproxy, we do not
have access to this information before the SSL handshake.
- In regular mode, explicit HTTP requests are never ignored. [#explicithttp]_ The ignore pattern is
applied on CONNECT requests, which initiate HTTPS or clear-text WebSocket connections.
Tutorial
--------
If you just want to ignore one specific domain, there's usually a bulletproof method to do so:
1. Run mitmproxy or mitmdump in verbose mode (:option:`-v`) and observe the ``host:port``
information in the serverconnect messages. mitmproxy will filter on these.
2. Take the ``host:port`` string, surround it with ^ and $, escape all dots (. becomes \\.)
and use this as your ignore pattern:
.. code-block:: none
:emphasize-lines: 6,7,9
>>> mitmdump -v
127.0.0.1:50588: clientconnect
127.0.0.1:50588: request
-> CONNECT example.com:443 HTTP/1.1
127.0.0.1:50588: Set new server address: example.com:443
127.0.0.1:50588: serverconnect
-> example.com:443
^C
>>> mitmproxy --ignore ^example\.com:443$
Here are some other examples for ignore patterns:
.. code-block:: none
# Exempt traffic from the iOS App Store (the regex is lax, but usually just works):
--ignore apple.com:443
# "Correct" version without false-positives:
--ignore '^(.+\.)?apple\.com:443$'
# Ignore example.com, but not its subdomains:
--ignore '^example.com:'
# Ignore everything but example.com and mitmproxy.org:
--ignore '^(?!example\.com)(?!mitmproxy\.org)'
# Transparent mode:
--ignore 17\.178\.96\.59:443
# IP address range:
--ignore 17\.178\.\d+\.\d+:443
.. seealso::
- :ref:`tcpproxy`
- :ref:`responsestreaming`
.. rubric:: Footnotes
.. [#explicithttp] This stems from an limitation of explicit HTTP proxying:
A single connection can be re-used for multiple target domains - a
``GET http://example.com/`` request may be followed by a ``GET http://evil.com/`` request on the
same connection. If we start to ignore the connection after the first request,
we would miss the relevant second one.
.. _Certificate Pinning: https://security.stackexchange.com/questions/29988/what-is-certificate-pinning