From 515a7bc4e13645d0945b46a8e1d9102b918cd407 Mon Sep 17 00:00:00 2001 From: "Miss Islington (bot)" <31488909+miss-islington@users.noreply.github.com> Date: Wed, 5 May 2021 10:25:29 -0700 Subject: [PATCH] [3.8] bpo-43882 - urllib.parse should sanitize urls containing ASCII newline and tabs. (GH-25595) (#25726) Co-authored-by: Gregory P. Smith Co-authored-by: Serhiy Storchaka (cherry picked from commit 76cd81d60310d65d01f9d7b48a8985d8ab89c8b4) Co-authored-by: Senthil Kumaran Co-authored-by: Senthil Kumaran --- Doc/library/urllib.parse.rst | 13 +++++ Lib/test/test_urlparse.py | 48 +++++++++++++++++++ Lib/urllib/parse.py | 10 ++++ .../2021-04-25-07-46-37.bpo-43882.Jpwx85.rst | 6 +++ 4 files changed, 77 insertions(+) create mode 100644 Misc/NEWS.d/next/Security/2021-04-25-07-46-37.bpo-43882.Jpwx85.rst diff --git a/Doc/library/urllib.parse.rst b/Doc/library/urllib.parse.rst index fcad7076e6c77b..a6cfc5d3dc13a1 100644 --- a/Doc/library/urllib.parse.rst +++ b/Doc/library/urllib.parse.rst @@ -312,6 +312,9 @@ or on combining URL components into a URL string. ``#``, ``@``, or ``:`` will raise a :exc:`ValueError`. If the URL is decomposed before parsing, no error will be raised. + Following the `WHATWG spec`_ that updates RFC 3986, ASCII newline + ``\n``, ``\r`` and tab ``\t`` characters are stripped from the URL. + .. versionchanged:: 3.6 Out-of-range port numbers now raise :exc:`ValueError`, instead of returning :const:`None`. @@ -320,6 +323,10 @@ or on combining URL components into a URL string. Characters that affect netloc parsing under NFKC normalization will now raise :exc:`ValueError`. + .. versionchanged:: 3.8.10 + ASCII newline and tab characters are stripped from the URL. + +.. _WHATWG spec: https://url.spec.whatwg.org/#concept-basic-url-parser .. function:: urlunsplit(parts) @@ -668,6 +675,10 @@ task isn't already covered by the URL parsing functions above. .. seealso:: + `WHATWG`_ - URL Living standard + Working Group for the URL Standard that defines URLs, domains, IP addresses, the + application/x-www-form-urlencoded format, and their API. + :rfc:`3986` - Uniform Resource Identifiers This is the current standard (STD66). Any changes to urllib.parse module should conform to this. Certain deviations could be observed, which are @@ -691,3 +702,5 @@ task isn't already covered by the URL parsing functions above. :rfc:`1738` - Uniform Resource Locators (URL) This specifies the formal syntax and semantics of absolute URLs. + +.. _WHATWG: https://url.spec.whatwg.org/ diff --git a/Lib/test/test_urlparse.py b/Lib/test/test_urlparse.py index d2ec0dadbcb071..0f99130f5da8ac 100644 --- a/Lib/test/test_urlparse.py +++ b/Lib/test/test_urlparse.py @@ -612,6 +612,54 @@ def test_urlsplit_attributes(self): with self.assertRaisesRegex(ValueError, "out of range"): p.port + def test_urlsplit_remove_unsafe_bytes(self): + # Remove ASCII tabs and newlines from input, for http common case scenario. + url = "h\nttp://www.python\n.org\t/java\nscript:\talert('msg\r\n')/?query\n=\tsomething#frag\nment" + p = urllib.parse.urlsplit(url) + self.assertEqual(p.scheme, "http") + self.assertEqual(p.netloc, "www.python.org") + self.assertEqual(p.path, "/javascript:alert('msg')/") + self.assertEqual(p.query, "query=something") + self.assertEqual(p.fragment, "fragment") + self.assertEqual(p.username, None) + self.assertEqual(p.password, None) + self.assertEqual(p.hostname, "www.python.org") + self.assertEqual(p.port, None) + self.assertEqual(p.geturl(), "http://www.python.org/javascript:alert('msg')/?query=something#fragment") + + # Remove ASCII tabs and newlines from input as bytes, for http common case scenario. + url = b"h\nttp://www.python\n.org\t/java\nscript:\talert('msg\r\n')/?query\n=\tsomething#frag\nment" + p = urllib.parse.urlsplit(url) + self.assertEqual(p.scheme, b"http") + self.assertEqual(p.netloc, b"www.python.org") + self.assertEqual(p.path, b"/javascript:alert('msg')/") + self.assertEqual(p.query, b"query=something") + self.assertEqual(p.fragment, b"fragment") + self.assertEqual(p.username, None) + self.assertEqual(p.password, None) + self.assertEqual(p.hostname, b"www.python.org") + self.assertEqual(p.port, None) + self.assertEqual(p.geturl(), b"http://www.python.org/javascript:alert('msg')/?query=something#fragment") + + # any scheme + url = "x-new-scheme\t://www.python\n.org\t/java\nscript:\talert('msg\r\n')/?query\n=\tsomething#frag\nment" + p = urllib.parse.urlsplit(url) + self.assertEqual(p.geturl(), "x-new-scheme://www.python.org/javascript:alert('msg')/?query=something#fragment") + + # Remove ASCII tabs and newlines from input as bytes, any scheme. + url = b"x-new-scheme\t://www.python\n.org\t/java\nscript:\talert('msg\r\n')/?query\n=\tsomething#frag\nment" + p = urllib.parse.urlsplit(url) + self.assertEqual(p.geturl(), b"x-new-scheme://www.python.org/javascript:alert('msg')/?query=something#fragment") + + # Unsafe bytes is not returned from urlparse cache. + # scheme is stored after parsing, sending an scheme with unsafe bytes *will not* return an unsafe scheme + url = "https://www.python\n.org\t/java\nscript:\talert('msg\r\n')/?query\n=\tsomething#frag\nment" + scheme = "htt\nps" + for _ in range(2): + p = urllib.parse.urlsplit(url, scheme=scheme) + self.assertEqual(p.scheme, "https") + self.assertEqual(p.geturl(), "https://www.python.org/javascript:alert('msg')/?query=something#fragment") + def test_attributes_bad_port(self): """Check handling of invalid ports.""" for bytes in (False, True): diff --git a/Lib/urllib/parse.py b/Lib/urllib/parse.py index 36fd8fe2803e22..f0d9d4d803c4e3 100644 --- a/Lib/urllib/parse.py +++ b/Lib/urllib/parse.py @@ -77,6 +77,9 @@ '0123456789' '+-.') +# Unsafe bytes to be removed per WHATWG spec +_UNSAFE_URL_BYTES_TO_REMOVE = ['\t', '\r', '\n'] + # XXX: Consider replacing with functools.lru_cache MAX_CACHE_SIZE = 20 _parse_cache = {} @@ -414,6 +417,11 @@ def _checknetloc(netloc): raise ValueError("netloc '" + netloc + "' contains invalid " + "characters under NFKC normalization") +def _remove_unsafe_bytes_from_url(url): + for b in _UNSAFE_URL_BYTES_TO_REMOVE: + url = url.replace(b, "") + return url + def urlsplit(url, scheme='', allow_fragments=True): """Parse a URL into 5 components: :///?# @@ -421,6 +429,8 @@ def urlsplit(url, scheme='', allow_fragments=True): Note that we don't break the components up in smaller bits (e.g. netloc is a single string) and we don't expand % escapes.""" url, scheme, _coerce_result = _coerce_args(url, scheme) + url = _remove_unsafe_bytes_from_url(url) + scheme = _remove_unsafe_bytes_from_url(scheme) allow_fragments = bool(allow_fragments) key = url, scheme, allow_fragments, type(url), type(scheme) cached = _parse_cache.get(key, None) diff --git a/Misc/NEWS.d/next/Security/2021-04-25-07-46-37.bpo-43882.Jpwx85.rst b/Misc/NEWS.d/next/Security/2021-04-25-07-46-37.bpo-43882.Jpwx85.rst new file mode 100644 index 00000000000000..a326d079dff4a4 --- /dev/null +++ b/Misc/NEWS.d/next/Security/2021-04-25-07-46-37.bpo-43882.Jpwx85.rst @@ -0,0 +1,6 @@ +The presence of newline or tab characters in parts of a URL could allow +some forms of attacks. + +Following the controlling specification for URLs defined by WHATWG +:func:`urllib.parse` now removes ASCII newlines and tabs from URLs, +preventing such attacks.