kallithea Changeset - 2ac4499b25eb

Changeset - 2ac4499b25eb

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Thomas De Schampheleire - 7 years ago 2019-01-26 20:27:50
thomas.de_schampheleire@nokia.com

lib: sanitize HTML for all types of README rendering, not only markdown

The repository summary page will display a rendered version of the
repository 'readme' based on its file extension. In commit 5746cc3b3fa5,
the rendered output was already sanitized when the input was markdown.
However, also readmes written in other formats, like ReStructuredText (RST)
or plain text could have content that we want sanitized.

Therefore, move the sanitizing one level up so it covers all renderers, for
now and the future.

This fixes an XSS issue when a repository readme contains javascript code,
which would be executed when the repository summary page is visited by a
user.

Reported by Bob Hogg <wombat@rwhogg.site> (thanks!).

1 file changed with 17 insertions and 17 deletions:

kallithea/lib/markup_renderer.py

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kallithea/lib/markup_renderer.py

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@@ @@ -115,25 +115,37 @@ class MarkupRenderer(object): @@
     def render(self, source, filename=None):
         """
         Renders a given filename using detected renderer
         it detects renderers based on file extension or mimetype.
         At last it will just do a simple html replacing new lines with <br/>
         :param file_name:
         :param source:
         """
         renderer = self._detect_renderer(source, filename)
         readme_data = renderer(source)
         return readme_data
         # Allow most HTML, while preventing XSS issues:
         # no <script> tags, no onclick attributes, no javascript
         # "protocol", and also limit styling to prevent defacing.
         return bleach.clean(readme_data,
             tags=['a', 'abbr', 'b', 'blockquote', 'br', 'code', 'dd',
                   'div', 'dl', 'dt', 'em', 'h1', 'h2', 'h3', 'h4', 'h5',
                   'h6', 'hr', 'i', 'img', 'li', 'ol', 'p', 'pre', 'span',
                   'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'th',
                   'thead', 'tr', 'ul'],
             attributes=['class', 'id', 'style', 'label', 'title', 'alt', 'href', 'src'],
             styles=['color'],
             protocols=['http', 'https', 'mailto'],
+            )
     @classmethod
     def plain(cls, source, universal_newline=True):
         source = safe_unicode(source)
         if universal_newline:
             newline = '\n'
             source = newline.join(source.splitlines())
         def url_func(match_obj):
             url_full = match_obj.group(0)
             return '<a href="%(url)s">%(url)s</a>' % ({'url': url_full})
         source = url_re.sub(url_func, source)
@@ @@ -153,40 +165,28 @@ class MarkupRenderer(object): @@
         u'<p><a href="foo">foo</a></p>'
         >>> MarkupRenderer.markdown('''<script>alert(1)</script>''')
         u'&lt;script&gt;alert(1)&lt;/script&gt;'
         >>> MarkupRenderer.markdown('''<div onclick="alert(2)">yo</div>''')
         u'<div>yo</div>'
         >>> MarkupRenderer.markdown('''<a href="javascript:alert(3)">yo</a>''')
         u'<p><a>yo</a></p>'
         """
         source = safe_unicode(source)
         try:
             if flavored:
                 source = cls._flavored_markdown(source)
             markdown_html = markdown_mod.markdown(source,
                                        extensions=['codehilite', 'extra'],
                                        extension_configs={'codehilite': {'css_class': 'code-highlight'}})
             # Allow most HTML, while preventing XSS issues:
             # no <script> tags, no onclick attributes, no javascript
             # "protocol", and also limit styling to prevent defacing.
             return bleach.clean(markdown_html,
                 tags=['a', 'abbr', 'b', 'blockquote', 'br', 'code', 'dd',
                       'div', 'dl', 'dt', 'em', 'h1', 'h2', 'h3', 'h4', 'h5',
                       'h6', 'hr', 'i', 'img', 'li', 'ol', 'p', 'pre', 'span',
                       'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'th',
                       'thead', 'tr', 'ul'],
                 attributes=['class', 'id', 'style', 'label', 'title', 'alt', 'href', 'src'],
                 styles=['color'],
                 protocols=['http', 'https', 'mailto'],
+                )
             return markdown_mod.markdown(
                 source,
                 extensions=['codehilite', 'extra'],
                 extension_configs={'codehilite': {'css_class': 'code-highlight'}})
         except Exception:
             log.error(traceback.format_exc())
             if safe:
                 log.debug('Falling back to render in plain mode')
                 return cls.plain(source)
             else:
                 raise
     @classmethod
     def rst(cls, source, safe=True):
         source = safe_unicode(source)
         try:

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