mitmproxy/docs/scripting/inlinescripts.rst
2016-07-07 23:50:55 -07:00

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.. _inlinescripts:
Inline Scripts
==============
**mitmproxy** has a powerful scripting API that allows you to modify flows
on-the-fly or rewrite previously saved flows locally.
The mitmproxy scripting API is event driven - a script is simply a Python
module that exposes a set of event methods. Here's a complete mitmproxy script
that adds a new header to every HTTP response before it is returned to the
client:
.. literalinclude:: ../../examples/add_header.py
:caption: examples/add_header.py
:language: python
All events that deal with an HTTP request get an instance of :py:class:`~mitmproxy.models.HTTPFlow`,
which we can use to manipulate the response itself.
We can now run this script using mitmdump or mitmproxy as follows:
>>> mitmdump -s add_header.py
The new header will be added to all responses passing through the proxy.
Examples
--------
mitmproxy comes with a variety of example inline scripts, which demonstrate many basic tasks.
We encourage you to either browse them locally or on `GitHub`_.
Events
------
Script Lifecycle Events
^^^^^^^^^^^^^^^^^^^^^^^
.. py:function:: start(context)
Called once on startup, before any other events.
:param List[str] argv: The inline scripts' arguments.
For example, ``mitmproxy -s 'example.py --foo 42'`` sets argv to ``["--foo", "42"]``.
.. py:function:: done(context)
Called once on script shutdown, after any other events.
Connection Events
^^^^^^^^^^^^^^^^^
.. py:function:: clientconnect(context, root_layer)
Called when a client initiates a connection to the proxy. Note that
a connection can correspond to multiple HTTP requests.
.. versionchanged:: 0.14
:param Layer root_layer: The root layer (see :ref:`protocols` for an explanation what the root
layer is), which provides transparent access to all attributes of the
:py:class:`~mitmproxy.proxy.RootContext`. For example, ``root_layer.client_conn.address``
gives the remote address of the connecting client.
.. py:function:: clientdisconnect(context, root_layer)
Called when a client disconnects from the proxy.
.. versionchanged:: 0.14
:param Layer root_layer: see :py:func:`clientconnect`
.. py:function:: serverconnect(context, server_conn)
Called before the proxy initiates a connection to the target server. Note that
a connection can correspond to multiple HTTP requests.
:param ServerConnection server_conn: The server connection object. It is guaranteed to have a
non-None ``address`` attribute.
.. py:function:: serverdisconnect(context, server_conn)
Called when the proxy has closed the server connection.
.. versionadded:: 0.14
:param ServerConnection server_conn: see :py:func:`serverconnect`
HTTP Events
^^^^^^^^^^^
.. py:function:: request(context, flow)
Called when a client request has been received. The ``flow`` object is
guaranteed to have a non-None ``request`` attribute.
:param HTTPFlow flow: The flow containing the request which has been received.
The object is guaranteed to have a non-None ``request`` attribute.
.. py:function:: responseheaders(context, flow)
Called when the headers of a server response have been received.
This will always be called before the response hook.
:param HTTPFlow flow: The flow containing the request and response.
The object is guaranteed to have non-None ``request`` and
``response`` attributes. ``response.content`` will be ``None``,
as the response body has not been read yet.
.. py:function:: response(context, flow)
Called when a server response has been received.
:param HTTPFlow flow: The flow containing the request and response.
The object is guaranteed to have non-None ``request`` and
``response`` attributes. ``response.body`` will contain the raw response body,
unless response streaming has been enabled.
.. py:function:: error(context, flow)
Called when a flow error has occurred, e.g. invalid server responses, or
interrupted connections. This is distinct from a valid server HTTP error
response, which is simply a response with an HTTP error code.
:param HTTPFlow flow: The flow containing the error.
It is guaranteed to have non-None ``error`` attribute.
TCP Events
^^^^^^^^^^
.. py:function:: tcp_message(context, tcp_msg)
.. warning:: API is subject to change
If the proxy is in :ref:`TCP mode <tcpproxy>`, this event is called when it
receives a TCP payload from the client or server.
The sender and receiver are identifiable. The message is user-modifiable.
:param TcpMessage tcp_msg: see *examples/tcp_message.py*
API
---
The canonical API documentation is the code, which you can browse here, locally or on `GitHub`_.
*Use the Source, Luke!*
The main classes you will deal with in writing mitmproxy scripts are:
:py:class:`mitmproxy.flow.FlowMaster`
- The "heart" of mitmproxy, usually subclassed as :py:class:`mitmproxy.dump.DumpMaster` or
:py:class:`mitmproxy.console.ConsoleMaster`.
:py:class:`~mitmproxy.models.ClientConnection`
- Describes a client connection.
:py:class:`~mitmproxy.models.ServerConnection`
- Describes a server connection.
:py:class:`~mitmproxy.models.HTTPFlow`
- A collection of objects representing a single HTTP transaction.
:py:class:`~mitmproxy.models.HTTPRequest`
- An HTTP request.
:py:class:`~mitmproxy.models.HTTPResponse`
- An HTTP response.
:py:class:`~mitmproxy.models.Error`
- A communications error.
:py:class:`netlib.http.Headers`
- A dictionary-like object for managing HTTP headers.
:py:class:`netlib.certutils.SSLCert`
- Exposes information SSL certificates.
Running scripts in parallel
---------------------------
We have a single flow primitive, so when a script is blocking, other requests are not processed.
While that's usually a very desirable behaviour, blocking scripts can be run threaded by using the
:py:obj:`mitmproxy.script.concurrent` decorator.
**If your script does not block, you should avoid the overhead of the decorator.**
.. literalinclude:: ../../examples/nonblocking.py
:caption: examples/nonblocking.py
:language: python
Make scripts configurable with arguments
----------------------------------------
Sometimes, you want to pass runtime arguments to the inline script. This can be simply done by
surrounding the script call with quotes, e.g. ```mitmdump -s 'script.py --foo 42'``.
The arguments are then exposed in the start event:
.. literalinclude:: ../../examples/modify_response_body.py
:caption: examples/modify_response_body.py
:language: python
Running scripts on saved flows
------------------------------
Sometimes, we want to run a script on :py:class:`~mitmproxy.models.Flow` objects that are already
complete. This happens when you start a script, and then load a saved set of flows from a file
(see the "scripted data transformation" example :ref:`here <mitmdump>`).
It also happens when you run a one-shot script on a single flow through the ``|`` (pipe) shortcut
in mitmproxy.
In this case, there are no client connections, and the events are run in the following order:
**start**, **request**, **responseheaders**, **response**, **error**, **done**.
If the flow doesn't have a **response** or **error** associated with it, the matching events will
be skipped.
Spaces in the script path
-------------------------
By default, spaces are interpreted as a separator between the inline script and its arguments
(e.g. ``-s 'foo.py 42'``). Consequently, the script path needs to be wrapped in a separate pair of
quotes if it contains spaces: ``-s '\'./foo bar/baz.py\' 42'``.
.. _GitHub: https://github.com/mitmproxy/mitmproxy