From daad2c482c91de32d8305abbccc76a5de8b3a8be Mon Sep 17 00:00:00 2001 From: Steve Dower Date: Thu, 7 Mar 2019 09:08:18 -0800 Subject: [PATCH] bpo-36216: Add check for characters in netloc that normalize to separators (GH-12201) Upstream-Status: Backport CVE: CVE-2019-9636 Signed-off-by: Anuj Mittal --- Doc/library/urllib.parse.rst | 18 +++++++++++++++ Lib/test/test_urlparse.py | 23 +++++++++++++++++++ Lib/urllib/parse.py | 17 ++++++++++++++ .../2019-03-06-09-38-40.bpo-36216.6q1m4a.rst | 3 +++ 4 files changed, 61 insertions(+) create mode 100644 Misc/NEWS.d/next/Security/2019-03-06-09-38-40.bpo-36216.6q1m4a.rst diff --git a/Doc/library/urllib.parse.rst b/Doc/library/urllib.parse.rst index 0c8f0f607314..b565e1edd321 100644 --- a/Doc/library/urllib.parse.rst +++ b/Doc/library/urllib.parse.rst @@ -124,6 +124,11 @@ or on combining URL components into a URL string. Unmatched square brackets in the :attr:`netloc` attribute will raise a :exc:`ValueError`. + Characters in the :attr:`netloc` attribute that decompose under NFKC + normalization (as used by the IDNA encoding) into any of ``/``, ``?``, + ``#``, ``@``, or ``:`` will raise a :exc:`ValueError`. If the URL is + decomposed before parsing, no error will be raised. + .. versionchanged:: 3.2 Added IPv6 URL parsing capabilities. @@ -136,6 +141,10 @@ or on combining URL components into a URL string. Out-of-range port numbers now raise :exc:`ValueError`, instead of returning :const:`None`. + .. versionchanged:: 3.7.3 + Characters that affect netloc parsing under NFKC normalization will + now raise :exc:`ValueError`. + .. function:: parse_qs(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None) @@ -257,10 +266,19 @@ or on combining URL components into a URL string. Unmatched square brackets in the :attr:`netloc` attribute will raise a :exc:`ValueError`. + Characters in the :attr:`netloc` attribute that decompose under NFKC + normalization (as used by the IDNA encoding) into any of ``/``, ``?``, + ``#``, ``@``, or ``:`` will raise a :exc:`ValueError`. If the URL is + decomposed before parsing, no error will be raised. + .. versionchanged:: 3.6 Out-of-range port numbers now raise :exc:`ValueError`, instead of returning :const:`None`. + .. versionchanged:: 3.7.3 + Characters that affect netloc parsing under NFKC normalization will + now raise :exc:`ValueError`. + .. function:: urlunsplit(parts) diff --git a/Lib/test/test_urlparse.py b/Lib/test/test_urlparse.py index be50b47603aa..e6638aee2244 100644 --- a/Lib/test/test_urlparse.py +++ b/Lib/test/test_urlparse.py @@ -1,3 +1,5 @@ +import sys +import unicodedata import unittest import urllib.parse @@ -984,6 +986,27 @@ def test_all(self): expected.append(name) self.assertCountEqual(urllib.parse.__all__, expected) + def test_urlsplit_normalization(self): + # Certain characters should never occur in the netloc, + # including under normalization. + # Ensure that ALL of them are detected and cause an error + illegal_chars = '/:#?@' + hex_chars = {'{:04X}'.format(ord(c)) for c in illegal_chars} + denorm_chars = [ + c for c in map(chr, range(128, sys.maxunicode)) + if (hex_chars & set(unicodedata.decomposition(c).split())) + and c not in illegal_chars + ] + # Sanity check that we found at least one such character + self.assertIn('\u2100', denorm_chars) + self.assertIn('\uFF03', denorm_chars) + + for scheme in ["http", "https", "ftp"]: + for c in denorm_chars: + url = "{}://netloc{}false.netloc/path".format(scheme, c) + with self.subTest(url=url, char='{:04X}'.format(ord(c))): + with self.assertRaises(ValueError): + urllib.parse.urlsplit(url) class Utility_Tests(unittest.TestCase): """Testcase to test the various utility functions in the urllib.""" diff --git a/Lib/urllib/parse.py b/Lib/urllib/parse.py index f691ab74f87f..39c5d6a80824 100644 --- a/Lib/urllib/parse.py +++ b/Lib/urllib/parse.py @@ -391,6 +391,21 @@ def _splitnetloc(url, start=0): delim = min(delim, wdelim) # use earliest delim position return url[start:delim], url[delim:] # return (domain, rest) +def _checknetloc(netloc): + if not netloc or netloc.isascii(): + return + # looking for characters like \u2100 that expand to 'a/c' + # IDNA uses NFKC equivalence, so normalize for this check + import unicodedata + netloc2 = unicodedata.normalize('NFKC', netloc) + if netloc == netloc2: + return + _, _, netloc = netloc.rpartition('@') # anything to the left of '@' is okay + for c in '/?#@:': + if c in netloc2: + raise ValueError("netloc '" + netloc2 + "' contains invalid " + + "characters under NFKC normalization") + def urlsplit(url, scheme='', allow_fragments=True): """Parse a URL into 5 components: :///?# @@ -419,6 +434,7 @@ def urlsplit(url, scheme='', allow_fragments=True): url, fragment = url.split('#', 1) if '?' in url: url, query = url.split('?', 1) + _checknetloc(netloc) v = SplitResult('http', netloc, url, query, fragment) _parse_cache[key] = v return _coerce_result(v) @@ -442,6 +458,7 @@ def urlsplit(url, scheme='', allow_fragments=True): url, fragment = url.split('#', 1) if '?' in url: url, query = url.split('?', 1) + _checknetloc(netloc) v = SplitResult(scheme, netloc, url, query, fragment) _parse_cache[key] = v return _coerce_result(v) diff --git a/Misc/NEWS.d/next/Security/2019-03-06-09-38-40.bpo-36216.6q1m4a.rst b/Misc/NEWS.d/next/Security/2019-03-06-09-38-40.bpo-36216.6q1m4a.rst new file mode 100644 index 000000000000..5546394157f9 --- /dev/null +++ b/Misc/NEWS.d/next/Security/2019-03-06-09-38-40.bpo-36216.6q1m4a.rst @@ -0,0 +1,3 @@ +Changes urlsplit() to raise ValueError when the URL contains characters that +decompose under IDNA encoding (NFKC-normalization) into characters that +affect how the URL is parsed.