Commit fa350e2f authored by Erik Romijn's avatar Erik Romijn Committed by Tim Graham
Browse files

Fixed #24464 -- Made built-in HTML template filter functions escape their input by default. 

This may cause some backwards compatibility issues, but may also
resolve security issues in third party projects that fail to heed warnings
in our documentation.

Thanks Markus Holtermann for help with tests and docs.
parent fb146193

django/template/defaultfilters.py

+7 −7
Original line number Diff line number Diff line
@@ -191,7 +191,7 @@ def iriencode(value): 


@register.filter(is_safe=True, needs_autoescape=True)

@stringfilter

def linenumbers(value, autoescape=None):

def linenumbers(value, autoescape=True):

    """Displays text with line numbers."""

    lines = value.split('\n')

    # Find the maximum width of the line count, for use with zero padding
@@ -353,14 +353,14 @@ def urlencode(value, safe=None): 


@register.filter(is_safe=True, needs_autoescape=True)

@stringfilter

def urlize(value, autoescape=None):

def urlize(value, autoescape=True):

    """Converts URLs in plain text into clickable links."""

    return mark_safe(_urlize(value, nofollow=True, autoescape=autoescape))





@register.filter(is_safe=True, needs_autoescape=True)

@stringfilter

def urlizetrunc(value, limit, autoescape=None):

def urlizetrunc(value, limit, autoescape=True):

    """

    Converts URLs into clickable links, truncating URLs to the given character

    limit, and adding 'rel=nofollow' attribute to discourage spamming.
@@ -457,7 +457,7 @@ def force_escape(value): 


@register.filter("linebreaks", is_safe=True, needs_autoescape=True)

@stringfilter

def linebreaks_filter(value, autoescape=None):

def linebreaks_filter(value, autoescape=True):

    """

    Replaces line breaks in plain text with appropriate HTML; a single

    newline becomes an HTML line break (``<br />``) and a new line
@@ -469,7 +469,7 @@ def linebreaks_filter(value, autoescape=None): 


@register.filter(is_safe=True, needs_autoescape=True)

@stringfilter

def linebreaksbr(value, autoescape=None):

def linebreaksbr(value, autoescape=True):

    """

    Converts all newlines in a piece of plain text to HTML line breaks

    (``<br />``).
@@ -552,7 +552,7 @@ def first(value): 




@register.filter(is_safe=True, needs_autoescape=True)

def join(value, arg, autoescape=None):

def join(value, arg, autoescape=True):

    """

    Joins a list with a string, like Python's ``str.join(list)``.

    """
@@ -622,7 +622,7 @@ def slice_filter(value, arg): 




@register.filter(is_safe=True, needs_autoescape=True)

def unordered_list(value, autoescape=None):

def unordered_list(value, autoescape=True):

    """

    Recursively takes a self-nested list and returns an HTML unordered list --

    WITHOUT opening and closing <ul> tags.

docs/howto/custom-template-tags.txt

+19 −8
Original line number Diff line number Diff line
@@ -281,7 +281,9 @@ Template filter code falls into one of two situations: 
   (If you don't specify this flag, it defaults to ``False``). This flag tells

   Django that your filter function wants to be passed an extra keyword

   argument, called ``autoescape``, that is ``True`` if auto-escaping is in

   effect and ``False`` otherwise.

   effect and ``False`` otherwise. It is recommended to set the default of the

   ``autoescape`` parameter to ``True``, so that if you call the function

   from Python code it will have escaping enabled by default.



   For example, let's write a filter that emphasizes the first character of

   a string::
@@ -293,7 +295,7 @@ Template filter code falls into one of two situations: 
      register = template.Library()



      @register.filter(needs_autoescape=True)

      def initial_letter_filter(text, autoescape=None):

      def initial_letter_filter(text, autoescape=True):

          first, other = text[0], text[1:]

          if autoescape:

              esc = conditional_escape
@@ -323,9 +325,15 @@ Template filter code falls into one of two situations: 


.. warning:: Avoiding XSS vulnerabilities when reusing built-in filters



    Be careful when reusing Django's built-in filters. You'll need to pass

    ``autoescape=True`` to the filter in order to get the proper autoescaping

    behavior and avoid a cross-site script vulnerability.

    .. versionchanged:: 1.8



    Django's built-in filters have ``autoescape=True`` by default in order to

    get the proper autoescaping behavior and avoid a cross-site script

    vulnerability.



    In older versions of Django, be careful when reusing Django's built-in

    filters as ``autoescape`` defaults to ``None``. You'll need to pass

    ``autoescape=True`` to get autoescaping.



    For example, if you wanted to write a custom filter called

    ``urlize_and_linebreaks`` that combined the :tfilter:`urlize` and
@@ -333,9 +341,12 @@ Template filter code falls into one of two situations: 


        from django.template.defaultfilters import linebreaksbr, urlize



        @register.filter

        def urlize_and_linebreaks(text):

            return linebreaksbr(urlize(text, autoescape=True), autoescape=True)

        @register.filter(needs_autoescape=True)

        def urlize_and_linebreaks(text, autoescape=True):

            return linebreaksbr(

                urlize(text, autoescape=autoescape),

                autoescape=autoescape

            )



    Then:

docs/releases/1.8.txt

+20 −0
Original line number Diff line number Diff line
@@ -1012,6 +1012,26 @@ those writing third-party backends in updating their code: 
  now takes a second argument named ``obj_id`` which is the serialized

  identifier used to retrieve the object before deletion.



Default autoescaping of functions in ``django.template.defaultfilters``

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



In order to make built-in template filters that output HTML "safe by default"

when calling them in Python code, the following functions in

``django.template.defaultfilters`` have been changed to automatically escape

their input value:



* ``join``

* ``linebreaksbr``

* ``linebreaks_filter``

* ``linenumbers``

* ``unordered_list``

* ``urlize``

* ``urlizetrunc``



You can revert to the old behavior by specifying ``autoescape=False`` if you

are passing trusted content. This change doesn't have any effect when using

the corresponding filters in templates.



Miscellaneous

~~~~~~~~~~~~~

tests/template_tests/filter_tests/test_join.py

+12 −0
Original line number Diff line number Diff line
@@ -54,3 +54,15 @@ class FunctionTests(SimpleTestCase): 


    def test_list(self):

        self.assertEqual(join([0, 1, 2], 'glue'), '0glue1glue2')



    def test_autoescape(self):

        self.assertEqual(

            join(['<a>', '<img>', '</a>'], '<br>'),

            '&lt;a&gt;&lt;br&gt;&lt;img&gt;&lt;br&gt;&lt;/a&gt;',

        )



    def test_autoescape_off(self):

        self.assertEqual(

            join(['<a>', '<img>', '</a>'], '<br>', autoescape=False),

            '<a>&lt;br&gt;<img>&lt;br&gt;</a>',

        )

tests/template_tests/filter_tests/test_linebreaks.py

+12 −0
Original line number Diff line number Diff line
@@ -39,3 +39,15 @@ class FunctionTests(SimpleTestCase): 


    def test_non_string_input(self):

        self.assertEqual(linebreaks_filter(123), '<p>123</p>')



    def test_autoescape(self):

        self.assertEqual(

            linebreaks_filter('foo\n<a>bar</a>\nbuz'),

            '<p>foo<br />&lt;a&gt;bar&lt;/a&gt;<br />buz</p>',

        )



    def test_autoescape_off(self):

        self.assertEqual(

            linebreaks_filter('foo\n<a>bar</a>\nbuz', autoescape=False),

            '<p>foo<br /><a>bar</a><br />buz</p>',

        )