Fixed #17837. Improved markdown safety.

Markdown enable_attributes is now False when safe_mode is enabled. Documented
the markdown "safe" argument. Added warnings when the safe argument is
passed to versions of markdown which cannot be made safe. Deprecated
versions of markdown < 2.1. Many thanks to ptone for the patch.



git-svn-id: http://code.djangoproject.com/svn/django/trunk@17735 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/markup/templatetags/markup.py

@@ -11,6 +11,8 @@ markup syntaxes to HTML; currently there is support for:
     * reStructuredText, which requires docutils from http://docutils.sf.net/
 """
 
+import warnings
+
 from django import template
 from django.conf import settings
 from django.utils.encoding import smart_str, force_unicode
@@ -63,14 +65,25 @@ def markdown(value, arg=''):
                 safe_mode = True
             else:
                 safe_mode = False
-
+            python_markdown_deprecation = "The use of Python-Markdown "
+            "< 2.1 in Django is deprecated; please update to the current version"
             # Unicode support only in markdown v1.7 or above. Version_info
             # exist only in markdown v1.6.2rc-2 or above.
-            if getattr(markdown, "version_info", None) < (1,7):
+            markdown_vers = getattr(markdown, "version_info", None)
+            if markdown_vers < (1,7):
+                warnings.warn(python_markdown_deprecation, DeprecationWarning)
                 return mark_safe(force_unicode(markdown.markdown(smart_str(value), extensions, safe_mode=safe_mode)))
             else:
-                return mark_safe(markdown.markdown(force_unicode(value), extensions, safe_mode=safe_mode))
+                if markdown_vers >= (2,1):
+                    if safe_mode:
+                        return mark_safe(markdown.markdown(force_unicode(value), extensions, safe_mode=safe_mode, enable_attributes=False))
+                    else:
+                        return mark_safe(markdown.markdown(force_unicode(value), extensions, safe_mode=safe_mode))
+                else:
+                    warnings.warn(python_markdown_deprecation, DeprecationWarning)
+                    return mark_safe(markdown.markdown(force_unicode(value), extensions, safe_mode=safe_mode))
         else:
+            warnings.warn(python_markdown_deprecation, DeprecationWarning)
             return mark_safe(force_unicode(markdown.markdown(smart_str(value))))
 
 @register.filter(is_safe=True)

django/contrib/markup/tests.py

@@ -58,6 +58,20 @@ Paragraph 2 with a link_
         pattern = re.compile("""<p>Paragraph 1\s*</p>\s*<h2>\s*An h2</h2>""")
         self.assertTrue(pattern.match(rendered))
 
+    @unittest.skipUnless(markdown, 'markdown no installed')
+    def test_markdown_attribute_disable(self):
+        t = Template("{% load markup %}{{ markdown_content|markdown:'safe' }}")
+        markdown_content = "{@onclick=alert('hi')}some paragraph"
+        rendered = t.render(Context({'markdown_content':markdown_content})).strip()
+        self.assertTrue('@' in rendered)
+
+    @unittest.skipUnless(markdown, 'markdown no installed')
+    def test_markdown_attribute_enable(self):
+        t = Template("{% load markup %}{{ markdown_content|markdown }}")
+        markdown_content = "{@onclick=alert('hi')}some paragraph"
+        rendered = t.render(Context({'markdown_content':markdown_content})).strip()
+        self.assertFalse('@' in rendered)
+
     @unittest.skipIf(markdown, 'markdown is installed')
     def test_no_markdown(self):
         t = Template("{% load markup %}{{ markdown_content|markdown }}")

docs/internals/deprecation.txt

@@ -196,6 +196,11 @@ these changes.
   filesystem path to a ``locale`` directory containing non-app-specific
   translations in its value.
 
+* The Markup contrib app will no longer support versions of Python-Markdown
+  library earlier than 2.1. An accelerated timeline was used as this was
+  a security related deprecation.
+
+
 1.6
 ---
 

docs/ref/contrib/markup.txt

@@ -47,3 +47,19 @@ override the default writer settings. See the `restructuredtext writer
 settings`_ for details on what these settings are.
 
 .. _restructuredtext writer settings: http://docutils.sourceforge.net/docs/user/config.html#html4css1-writer
+
+Markdown
+--------
+
+The Python Markdown library supports options named "safe_mode" and
+"enable_attributes". Both relate to the security of the output. To enable both
+options in tandem, the markdown filter supports the "safe" argument.
+
+    {{ markdown_content_var|markdown:"safe" }}
+
+.. warning::
+
+    Versions of the Python-Markdown library prior to 2.1 do not support the
+    optional disabling of attributes and by default they will be included in
+    any output from the markdown filter - a warning is issued if this is the
+    case.

docs/releases/1.4.txt

@@ -1096,6 +1096,16 @@ field. This was something that should not have worked, and in 1.4 loading such
 incomplete fixtures will fail. Because fixtures are a raw import, they should
 explicitly specify all field values, regardless of field options on the model.
 
+Attributes disabled in markdown when safe mode set
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Prior to Django 1.4, attributes were included in any markdown output regardless
+of safe mode setting of the filter. With version > 2.1 of the Python-Markdown
+library, an enable_attributes option was added. When the safe argument is
+passed to the markdown filter, both the ``safe_mode=True`` and
+``enable_attributes=False`` options are set. If using a version of the
+Python-Markdown library less than 2.1, a warning is issued that the output is
+insecure.
 
 Features deprecated in 1.4
 ==========================
@@ -1262,3 +1272,12 @@ each request to a site map now creates a new Paginator object and calls the
 ``items()`` method is doing, this may have a negative performance impact.
 To mitigate the performance impact, consider using the :doc:`caching
 framework </topics/cache>` within your ``Sitemap`` subclass.
+
+Versions of Python-Markdown earlier than 2.1
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Versions of Python-Markdown earlier than 2.1 do not support the option to
+disable attributes. As a security issue, earlier versions of this library will
+not be supported by the markup contrib app in 1.5 under an accelerated
+deprecation timeline.
+