From 19ca21e044a9485c85b08aab297a5cbb8680b8d1 Mon Sep 17 00:00:00 2001 From: Seth Michael Larson Date: Tue, 20 Jan 2026 15:23:42 -0600 Subject: [PATCH] gh-143919: Reject control characters in http cookies (cherry picked from commit 95746b3a13a985787ef53b977129041971ed7f70) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Co-authored-by: Seth Michael Larson Co-authored-by: Bartosz Sławecki Co-authored-by: sobolevn --- Doc/library/http.cookies.rst | 4 Lib/http/cookies.py | 25 ++++ Lib/test/support/__init__.py | 8 + Lib/test/test_http_cookies.py | 52 +++++++++- Misc/NEWS.d/next/Security/2026-01-16-11-13-15.gh-issue-143919.kchwZV.rst | 1 5 files changed, 81 insertions(+), 9 deletions(-) create mode 100644 Misc/NEWS.d/next/Security/2026-01-16-11-13-15.gh-issue-143919.kchwZV.rst Index: Python-3.13.11/Doc/library/http.cookies.rst =================================================================== --- Python-3.13.11.orig/Doc/library/http.cookies.rst 2025-12-05 17:06:33.000000000 +0100 +++ Python-3.13.11/Doc/library/http.cookies.rst 2026-02-03 01:14:38.406889249 +0100 @@ -275,9 +275,9 @@ Set-Cookie: chips=ahoy Set-Cookie: vienna=finger >>> C = cookies.SimpleCookie() - >>> C.load('keebler="E=everybody; L=\\"Loves\\"; fudge=\\012;";') + >>> C.load('keebler="E=everybody; L=\\"Loves\\"; fudge=;";') >>> print(C) - Set-Cookie: keebler="E=everybody; L=\"Loves\"; fudge=\012;" + Set-Cookie: keebler="E=everybody; L=\"Loves\"; fudge=;" >>> C = cookies.SimpleCookie() >>> C["oreo"] = "doublestuff" >>> C["oreo"]["path"] = "/" Index: Python-3.13.11/Lib/http/cookies.py =================================================================== --- Python-3.13.11.orig/Lib/http/cookies.py 2025-12-05 17:06:33.000000000 +0100 +++ Python-3.13.11/Lib/http/cookies.py 2026-02-03 01:14:38.407180728 +0100 @@ -87,9 +87,9 @@ such trickeries do not confuse it. >>> C = cookies.SimpleCookie() - >>> C.load('keebler="E=everybody; L=\\"Loves\\"; fudge=\\012;";') + >>> C.load('keebler="E=everybody; L=\\"Loves\\"; fudge=;";') >>> print(C) - Set-Cookie: keebler="E=everybody; L=\"Loves\"; fudge=\012;" + Set-Cookie: keebler="E=everybody; L=\"Loves\"; fudge=;" Each element of the Cookie also supports all of the RFC 2109 Cookie attributes. Here's an example which sets the Path @@ -170,6 +170,15 @@ }) _is_legal_key = re.compile('[%s]+' % re.escape(_LegalChars)).fullmatch +_control_character_re = re.compile(r'[\x00-\x1F\x7F]') + + +def _has_control_character(*val): + """Detects control characters within a value. + Supports any type, as header values can be any type. + """ + return any(_control_character_re.search(str(v)) for v in val) + def _quote(str): r"""Quote a string for use in a cookie header. @@ -292,12 +301,16 @@ K = K.lower() if not K in self._reserved: raise CookieError("Invalid attribute %r" % (K,)) + if _has_control_character(K, V): + raise CookieError(f"Control characters are not allowed in cookies {K!r} {V!r}") dict.__setitem__(self, K, V) def setdefault(self, key, val=None): key = key.lower() if key not in self._reserved: raise CookieError("Invalid attribute %r" % (key,)) + if _has_control_character(key, val): + raise CookieError("Control characters are not allowed in cookies %r %r" % (key, val,)) return dict.setdefault(self, key, val) def __eq__(self, morsel): @@ -333,6 +346,9 @@ raise CookieError('Attempt to set a reserved key %r' % (key,)) if not _is_legal_key(key): raise CookieError('Illegal key %r' % (key,)) + if _has_control_character(key, val, coded_val): + raise CookieError( + "Control characters are not allowed in cookies %r %r %r" % (key, val, coded_val,)) # It's a good key, so save it. self._key = key @@ -486,7 +502,10 @@ result = [] items = sorted(self.items()) for key, value in items: - result.append(value.output(attrs, header)) + value_output = value.output(attrs, header) + if _has_control_character(value_output): + raise CookieError("Control characters are not allowed in cookies") + result.append(value_output) return sep.join(result) __str__ = output Index: Python-3.13.11/Lib/test/support/__init__.py =================================================================== --- Python-3.13.11.orig/Lib/test/support/__init__.py 2025-12-05 17:06:33.000000000 +0100 +++ Python-3.13.11/Lib/test/support/__init__.py 2026-02-03 01:16:59.080295540 +0100 @@ -64,6 +64,7 @@ "force_not_colorized_test_class", "make_clean_env", "BrokenIter", + "control_characters_c0", ] @@ -2845,3 +2846,10 @@ except (OSError, subprocess.CalledProcessError): return False return ('musl' in stdout) + + +def control_characters_c0() -> list[str]: + """Returns a list of C0 control characters as strings. + C0 control characters defined as the byte range 0x00-0x1F, and 0x7F. + """ + return [chr(c) for c in range(0x00, 0x20)] + ["\x7F"] Index: Python-3.13.11/Lib/test/test_http_cookies.py =================================================================== --- Python-3.13.11.orig/Lib/test/test_http_cookies.py 2025-12-05 17:06:33.000000000 +0100 +++ Python-3.13.11/Lib/test/test_http_cookies.py 2026-02-03 01:14:38.407381716 +0100 @@ -18,10 +18,10 @@ 'repr': "", 'output': 'Set-Cookie: chips=ahoy\nSet-Cookie: vienna=finger'}, - {'data': 'keebler="E=mc2; L=\\"Loves\\"; fudge=\\012;"', - 'dict': {'keebler' : 'E=mc2; L="Loves"; fudge=\012;'}, - 'repr': '''''', - 'output': 'Set-Cookie: keebler="E=mc2; L=\\"Loves\\"; fudge=\\012;"'}, + {'data': 'keebler="E=mc2; L=\\"Loves\\"; fudge=;"', + 'dict': {'keebler' : 'E=mc2; L="Loves"; fudge=;'}, + 'repr': '''''', + 'output': 'Set-Cookie: keebler="E=mc2; L=\\"Loves\\"; fudge=;"'}, # Check illegal cookies that have an '=' char in an unquoted value {'data': 'keebler=E=mc2', @@ -564,6 +564,50 @@ r'Set-Cookie: key=coded_val; ' r'expires=\w+, \d+ \w+ \d+ \d+:\d+:\d+ \w+') + def test_control_characters(self): + for c0 in support.control_characters_c0(): + morsel = cookies.Morsel() + + # .__setitem__() + with self.assertRaises(cookies.CookieError): + morsel[c0] = "val" + with self.assertRaises(cookies.CookieError): + morsel["path"] = c0 + + # .setdefault() + with self.assertRaises(cookies.CookieError): + morsel.setdefault("path", c0) + with self.assertRaises(cookies.CookieError): + morsel.setdefault(c0, "val") + + # .set() + with self.assertRaises(cookies.CookieError): + morsel.set(c0, "val", "coded-value") + with self.assertRaises(cookies.CookieError): + morsel.set("path", c0, "coded-value") + with self.assertRaises(cookies.CookieError): + morsel.set("path", "val", c0) + + def test_control_characters_output(self): + # Tests that even if the internals of Morsel are modified + # that a call to .output() has control character safeguards. + for c0 in support.control_characters_c0(): + morsel = cookies.Morsel() + morsel.set("key", "value", "coded-value") + morsel._key = c0 # Override private variable. + cookie = cookies.SimpleCookie() + cookie["cookie"] = morsel + with self.assertRaises(cookies.CookieError): + cookie.output() + + morsel = cookies.Morsel() + morsel.set("key", "value", "coded-value") + morsel._coded_value = c0 # Override private variable. + cookie = cookies.SimpleCookie() + cookie["cookie"] = morsel + with self.assertRaises(cookies.CookieError): + cookie.output() + def load_tests(loader, tests, pattern): tests.addTest(doctest.DocTestSuite(cookies)) Index: Python-3.13.11/Misc/NEWS.d/next/Security/2026-01-16-11-13-15.gh-issue-143919.kchwZV.rst =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ Python-3.13.11/Misc/NEWS.d/next/Security/2026-01-16-11-13-15.gh-issue-143919.kchwZV.rst 2026-02-03 01:14:38.407545685 +0100 @@ -0,0 +1 @@ +Reject control characters in :class:`http.cookies.Morsel` fields and values.