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diff --git a/docs/features/replacements.rst b/docs/features/replacements.rst new file mode 100644 index 00000000..8f760866 --- /dev/null +++ b/docs/features/replacements.rst @@ -0,0 +1,72 @@ +.. _replacements: + +Replacements +============ + +Mitmproxy lets you specify an arbitrary number of patterns that define text +replacements within flows. Each pattern has 3 components: a filter that defines +which flows a replacement applies to, a regular expression that defines what +gets replaced, and a target value that defines what is substituted in. + +Replace hooks fire when either a client request or a server response is +received. Only the matching flow component is affected: so, for example, if a +replace hook is triggered on server response, the replacement is only run on +the Response object leaving the Request intact. You control whether the hook +triggers on the request, response or both using the filter pattern. If you need +finer-grained control than this, it's simple to create a script using the +replacement API on Flow components. + +Replacement hooks are extremely handy in interactive testing of applications. +For instance you can use a replace hook to replace the text "XSS" with a +complicated XSS exploit, and then "inject" the exploit simply by interacting +with the application through the browser. When used with tools like Firebug and +mitmproxy's own interception abilities, replacement hooks can be an amazingly +flexible and powerful feature. + + +On the command-line +------------------- + +The replacement hook command-line options use a compact syntax to make it easy +to specify all three components at once. The general form is as follows: + +.. code-block:: none + + /patt/regex/replacement + +Here, **patt** is a mitmproxy filter expression, **regex** is a valid Python +regular expression, and **replacement** is a string literal. The first +character in the expression (``/`` in this case) defines what the separation +character is. Here's an example of a valid expression that replaces "foo" with +"bar" in all requests: + +.. code-block:: none + + :~q:foo:bar + +In practice, it's pretty common for the replacement literal to be long and +complex. For instance, it might be an XSS exploit that weighs in at hundreds or +thousands of characters. To cope with this, there's a variation of the +replacement hook specifier that lets you load the replacement text from a file. +So, you might start **mitmdump** as follows: + +>>> mitmdump --replace-from-file :~q:foo:~/xss-exploit + +This will load the replacement text from the file ``~/xss-exploit``. + +Both the :option:`--replace` and :option:`--replace-from-file` flags can be passed multiple +times. + + +Interactively +------------- + +The :kbd:`R` shortcut key in the mitmproxy options menu (:kbd:`o`) lets you add and edit +replacement hooks using a built-in editor. The context-sensitive help (:kbd:`?`) has +complete usage information. + +================== ============================= +command-line :option:`--replace`, + :option:`--replace-from-file` +mitmproxy shortcut :kbd:`o` then :kbd:`R` +================== ============================= |