Merge pull request #111 from mailgun/sergey/tagscount

restrict html processing to a certain number of tags

setup.py

@@ -29,7 +29,7 @@ class InstallCommand(install):
 
 
 setup(name='talon',
-      version='1.2.16',
+      version='1.3.2',
       description=("Mailgun library "
                    "to extract message quotations and signatures."),
       long_description=open("README.rst").read(),
@@ -53,6 +53,7 @@ setup(name='talon',
           'cchardet>=0.3.5',
           'cssselect',
           'six>=1.10.0',
+          'html5lib'
           ],
       tests_require=[
           "mock",

talon/html_quotations.py

@@ -6,6 +6,7 @@ messages (without quoted messages) from html
 from __future__ import absolute_import
 import regex as re
 
+from talon.utils import cssselect 
 
 CHECKPOINT_PREFIX = '#!%!'
 CHECKPOINT_SUFFIX = '!%!#'
@@ -78,7 +79,7 @@ def delete_quotation_tags(html_note, counter, quotation_checkpoints):
 
 def cut_gmail_quote(html_message):
     ''' Cuts the outermost block element with class gmail_quote. '''
-    gmail_quote = html_message.cssselect('div.gmail_quote')
+    gmail_quote = cssselect('div.gmail_quote', html_message)
     if gmail_quote and (gmail_quote[0].text is None or not RE_FWD.match(gmail_quote[0].text)):
         gmail_quote[0].getparent().remove(gmail_quote[0])
         return True
@@ -135,7 +136,7 @@ def cut_microsoft_quote(html_message):
 def cut_by_id(html_message):
     found = False
     for quote_id in QUOTE_IDS:
-        quote = html_message.cssselect('#{}'.format(quote_id))
+        quote = cssselect('#{}'.format(quote_id), html_message)
         if quote:
             found = True
             quote[0].getparent().remove(quote[0])

talon/quotations.py

@@ -12,7 +12,8 @@ from copy import deepcopy
 
 from lxml import html, etree
 
-from talon.utils import get_delimiter, html_tree_to_text
+from talon.utils import (get_delimiter, html_tree_to_text,
+                         html_document_fromstring)
 from talon import html_quotations
 from six.moves import range
 import six
@@ -385,17 +386,15 @@ def _extract_from_html(msg_body):
     then checking deleted checkpoints,
     then deleting necessary tags.
     """
-    if len(msg_body) > MAX_HTML_LEN:
-        return msg_body
-
     if msg_body.strip() == b'':
         return msg_body
 
     msg_body = msg_body.replace(b'\r\n', b'\n')
-    html_tree = html.document_fromstring(
+    html_tree = html_document_fromstring(msg_body)
-        msg_body,
+
-        parser=html.HTMLParser(encoding="utf-8")
+    if html_tree is None:
-    )
+        return msg_body
+
     cut_quotations = (html_quotations.cut_gmail_quote(html_tree) or
                       html_quotations.cut_zimbra_quote(html_tree) or
                       html_quotations.cut_blockquote(html_tree) or
@@ -468,7 +467,7 @@ def is_splitter(line):
 
 def text_content(context):
     '''XPath Extension function to return a node text content.'''
-    return context.context_node.text_content().strip()
+    return context.context_node.xpath("string()").strip()
 
 
 def tail(context):

talon/utils.py

@@ -7,9 +7,11 @@ import chardet
 import cchardet
 import regex as re
 
-from lxml import html
+from lxml.html import html5parser
 from lxml.cssselect import CSSSelector
 
+import html5lib
+
 from talon.constants import RE_DELIMITER
 import six
 
@@ -112,6 +114,7 @@ def get_delimiter(msg_body):
 
     return delimiter
 
+
 def html_tree_to_text(tree):
     for style in CSSSelector('style')(tree):
         style.getparent().remove(style)
@@ -120,7 +123,7 @@ def html_tree_to_text(tree):
         parent = c.getparent()
 
         # comment with no parent does not impact produced text
-        if not parent:
+        if parent is None:
             continue
 
         parent.remove(c)
@@ -156,17 +159,53 @@ def html_to_text(string):
     NOTES:
         1. the string is expected to contain UTF-8 encoded HTML!
         2. returns utf-8 encoded str (not unicode)
+        3. if html can't be parsed returns None
     """
     if isinstance(string, six.text_type):
         string = string.encode('utf8')
 
     s = _prepend_utf8_declaration(string)
     s = s.replace(b"\n", b"")
+    tree = html_fromstring(s)
+
+    if tree is None:
+        return None
 
-    tree = html.fromstring(s)
     return html_tree_to_text(tree)
 
 
+def html_fromstring(s):
+    """Parse html tree from string. Return None if the string can't be parsed.
+    """
+    try:
+        if html_too_big(s):
+            return None
+
+        return html5parser.fromstring(s, parser=_html5lib_parser())
+    except Exception:
+        pass
+
+
+def html_document_fromstring(s):
+    """Parse html tree from string. Return None if the string can't be parsed.
+    """
+    try:
+        if html_too_big(s):
+            return None
+
+        return html5parser.document_fromstring(s, parser=_html5lib_parser())
+    except Exception:
+        pass
+
+
+def cssselect(expr, tree):
+    return CSSSelector(expr)(tree)
+
+
+def html_too_big(s):
+    return s.count('<') > _MAX_TAGS_COUNT
+
+
 def _contains_charset_spec(s):
     """Return True if the first 4KB contain charset spec
     """
@@ -191,6 +230,21 @@ def _encode_utf8(s):
     return s.encode('utf-8') if isinstance(s, six.text_type) else s
 
 
+def _html5lib_parser():
+    """
+    html5lib is a pure-python library that conforms to the WHATWG HTML spec
+    and is not vulnarable to certain attacks common for XML libraries
+    """
+    return html5lib.HTMLParser(
+        # build lxml tree
+        html5lib.treebuilders.getTreeBuilder("lxml"),
+        # remove namespace value from inside lxml.html.html5paser element tag
+        # otherwise it yields something like "{http://www.w3.org/1999/xhtml}div"
+        # instead of "div", throwing the algo off
+        namespaceHTMLElements=False
+    )
+
+
 _UTF8_DECLARATION = (b'<meta http-equiv="Content-Type" content="text/html;'
                      b'charset=utf-8">')
 
@@ -198,5 +252,8 @@ _UTF8_DECLARATION = (b'<meta http-equiv="Content-Type" content="text/html;'
 _BLOCKTAGS  = ['div', 'p', 'ul', 'li', 'h1', 'h2', 'h3']
 _HARDBREAKS = ['br', 'hr', 'tr']
 
-
 _RE_EXCESSIVE_NEWLINES = re.compile("\n{2,10}")
+
+# an extensive research shows that exceeding this limit
+# might lead to excessive processing time
+_MAX_TAGS_COUNT = 419

tests/html_quotations_test.py

@@ -27,7 +27,7 @@ def test_quotation_splitter_inside_blockquote():
 
 </blockquote>"""
 
-    eq_("<html><body><p>Reply</p></body></html>",
+    eq_("<html><head></head><body>Reply</body></html>",
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
 
 
@@ -44,7 +44,7 @@ def test_quotation_splitter_outside_blockquote():
   </div>
 </blockquote>
 """
-    eq_("<html><body><p>Reply</p></body></html>",
+    eq_("<html><head></head><body>Reply</body></html>",
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
 
 
@@ -62,7 +62,7 @@ def test_regular_blockquote():
   </div>
 </blockquote>
 """
-    eq_("<html><body><p>Reply</p><blockquote>Regular</blockquote></body></html>",
+    eq_("<html><head></head><body>Reply<blockquote>Regular</blockquote></body></html>",
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
 
 
@@ -85,6 +85,7 @@ Reply
 
     reply = """
 <html>
+<head></head>
 <body>
 Reply
 
@@ -128,7 +129,7 @@ def test_gmail_quote():
     </div>
   </div>
 </div>"""
-    eq_("<html><body><p>Reply</p></body></html>",
+    eq_("<html><head></head><body>Reply</body></html>",
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
 
 
@@ -139,7 +140,7 @@ def test_gmail_quote_compact():
                '<div>Test</div>' \
                '</div>' \
                '</div>'
-    eq_("<html><body><p>Reply</p></body></html>",
+    eq_("<html><head></head><body>Reply</body></html>",
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
 
 
@@ -166,7 +167,7 @@ def test_unicode_in_reply():
   Quote
 </blockquote>""".encode("utf-8")
 
-    eq_("<html><body><p>Reply&#160;&#160;Text<br></p><div><br></div>"
+    eq_("<html><head></head><body>Reply&#160;&#160;Text<br><div><br></div>"
         "</body></html>",
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
 
@@ -192,6 +193,7 @@ def test_blockquote_disclaimer():
 
     stripped_html = """
 <html>
+  <head></head>
   <body>
   <div>
     <div>
@@ -223,7 +225,7 @@ def test_date_block():
   </div>
 </div>
 """
-    eq_('<html><body><div>message<br></div></body></html>',
+    eq_('<html><head></head><body><div>message<br></div></body></html>',
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
 
 
@@ -240,7 +242,7 @@ Subject: You Have New Mail From Mary!<br><br>
 text
 </div></div>
 """
-    eq_('<html><body><div>message<br></div></body></html>',
+    eq_('<html><head></head><body><div>message<br></div></body></html>',
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
 
 
@@ -258,7 +260,7 @@ def test_reply_shares_div_with_from_block():
 
   </div>
 </body>'''
-    eq_('<html><body><div>Blah<br><br></div></body></html>',
+    eq_('<html><head></head><body><div>Blah<br><br></div></body></html>',
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
 
 
@@ -269,13 +271,13 @@ def test_reply_quotations_share_block():
 
 
 def test_OLK_SRC_BODY_SECTION_stripped():
-    eq_('<html><body><div>Reply</div></body></html>',
+    eq_('<html><head></head><body><div>Reply</div></body></html>',
         RE_WHITESPACE.sub(
             '', quotations.extract_from_html(OLK_SRC_BODY_SECTION)))
 
 
 def test_reply_separated_by_hr():
-    eq_('<html><body><div>Hi<div>there</div></div></body></html>',
+    eq_('<html><head></head><body><div>Hi<div>there</div></div></body></html>',
         RE_WHITESPACE.sub(
             '', quotations.extract_from_html(REPLY_SEPARATED_BY_HR)))
 
@@ -296,7 +298,7 @@ Reply
   </div>
 </div>
 '''
-    eq_('<html><body><p>Reply</p><div><hr></div></body></html>',
+    eq_('<html><head></head><body>Reply<div><hr></div></body></html>',
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
 
 
@@ -373,7 +375,7 @@ reply
     extracted = quotations.extract_from_html(msg_body)
     assert_false(symbol in extracted)    
     # Keep new lines otherwise "My reply" becomes one word - "Myreply" 
-    eq_("<html><body><p>My\nreply\n</p></body></html>", extracted)
+    eq_("<html><head></head><body>My\nreply\n</body></html>", extracted)
 
 
 def test_gmail_forwarded_msg():
@@ -383,7 +385,7 @@ def test_gmail_forwarded_msg():
     eq_(RE_WHITESPACE.sub('', msg_body), RE_WHITESPACE.sub('', extracted))
 
 
-@patch.object(quotations, 'MAX_HTML_LEN', 1)
+@patch.object(u, '_MAX_TAGS_COUNT', 4)
 def test_too_large_html():
     msg_body = 'Reply' \
                '<div class="gmail_quote">' \
@@ -411,3 +413,9 @@ def test_readable_html_empty():
 
     eq_(RE_WHITESPACE.sub('', msg_body),
         RE_WHITESPACE.sub('', quotations.extract_from_html(msg_body)))
+
+
+@patch.object(quotations, 'html_document_fromstring', Mock(return_value=None))
+def test_bad_html():
+    bad_html = "<html></html>"
+    eq_(bad_html, quotations.extract_from_html(bad_html))

tests/utils_test.py

@@ -112,5 +112,47 @@ font: 13px 'Lucida Grande', Arial, sans-serif;
 
 def test_comment_no_parent():
     s = "<!-- COMMENT 1 --> no comment"
-    d = html.document_fromstring(s)
+    d = u.html_document_fromstring(s)
     eq_("no comment", u.html_tree_to_text(d))
+
+
+@patch.object(u.html5parser, 'fromstring', Mock(side_effect=Exception()))
+def test_html_fromstring_exception():
+    eq_(None, u.html_fromstring("<html></html>"))
+
+@patch.object(u, 'html_too_big', Mock())
+@patch.object(u.html5parser, 'fromstring')
+def test_html_fromstring_too_big(fromstring):
+    eq_(None, u.html_fromstring("<html></html>"))
+    assert_false(fromstring.called)
+
+
+@patch.object(u.html5parser, 'document_fromstring')
+def test_html_document_fromstring_exception(document_fromstring):
+    document_fromstring.side_effect = Exception()
+    eq_(None, u.html_document_fromstring("<html></html>"))
+
+
+@patch.object(u, 'html_too_big', Mock())
+@patch.object(u.html5parser, 'document_fromstring')
+def test_html_document_fromstring_too_big(document_fromstring):
+    eq_(None, u.html_document_fromstring("<html></html>"))
+    assert_false(document_fromstring.called)
+
+
+@patch.object(u, 'html_fromstring', Mock(return_value=None))
+def test_bad_html_to_text():
+    bad_html = "one<br>two<br>three"
+    eq_(None, u.html_to_text(bad_html))
+
+
+@patch.object(u, '_MAX_TAGS_COUNT', 3)
+def test_html_too_big():
+    eq_(False, u.html_too_big("<div></div>"))
+    eq_(True, u.html_too_big("<div><span>Hi</span></div>"))
+
+
+@patch.object(u, '_MAX_TAGS_COUNT', 3)
+def test_html_to_text():
+    eq_("Hello", u.html_to_text("<div>Hello</div>"))
+    eq_(None, u.html_to_text("<div><span>Hi</span></div>"))