mitmproxy/docs/features/passthrough.rst

.. _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