[1.3.X] 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.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.3.X@17734 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
@@ -65,10 +67,21 @@ def markdown(value, arg=''):
 
             # 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):
                 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("Versions of markdown prior to 2.1 do not "
+                            "support disabling of attributes, no "
+                            "attributes have been removed and the result "
+                            "is insecure.")
+                    return mark_safe(markdown.markdown(force_unicode(value), extensions, safe_mode=safe_mode))
         else:
             return mark_safe(force_unicode(markdown.markdown(smart_str(value))))
 markdown.is_safe = True

django/contrib/markup/tests.py

@@ -60,6 +60,20 @@ 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("{{ markdown_content|markdown }}")

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.