Cherry picked 2f630e1, with some minor fixups by hand

Doc/library/urllib.parse.rst

@@ -338,6 +338,9 @@ or on combining URL components into a URL string.
    .. versionchanged:: 3.7.17
       Leading WHATWG C0 control and space characters are stripped from the URL.
 
+   .. versionchanged:: 3.7.17.1
+      Leading WHATWG C0 control and space characters are stripped from the URL.
+
 .. _WHATWG spec: https://url.spec.whatwg.org/#concept-basic-url-parser
 
 .. function:: urlunsplit(parts)
@@ -428,6 +431,35 @@ code before trusting a returned component part.  Does that ``scheme`` make
 sense?  Is that a sensible ``path``?  Is there anything strange about that
 ``hostname``?  etc.
 
+.. _url-parsing-security:
+
+URL parsing security
+--------------------
+
+The :func:`urlsplit` and :func:`urlparse` APIs do not perform **validation** of
+inputs.  They may not raise errors on inputs that other applications consider
+invalid.  They may also succeed on some inputs that might not be considered
+URLs elsewhere.  Their purpose is for practical functionality rather than
+purity.
+
+Instead of raising an exception on unusual input, they may instead return some
+component parts as empty strings. Or components may contain more than perhaps
+they should.
+
+We recommend that users of these APIs where the values may be used anywhere
+with security implications code defensively. Do some verification within your
+code before trusting a returned component part.  Does that ``scheme`` make
+sense?  Is that a sensible ``path``?  Is there anything strange about that
+``hostname``?  etc.
+
+What constitutes a URL is not universally well defined.  Different applications
+have different needs and desired constraints.  For instance the living `WHATWG
+spec`_ describes what user facing web clients such as a web browser require.
+While :rfc:`3986` is more general.  These functions incorporate some aspects of
+both, but cannot be claimed compliant with either.  The APIs and existing user
+code with expectations on specific behaviors predate both standards leading us
+to be very cautious about making API behavior changes.
+
 .. _parsing-ascii-encoded-bytes:
 
 Parsing ASCII Encoded Bytes

Lib/test/test_urlparse.py

@@ -719,6 +719,65 @@ def test_urlsplit_strip_url(self):
             self.assertEqual(p.scheme, "https")
             self.assertEqual(p.geturl(), "https://www.python.org/")
 
+    def test_urlsplit_strip_url(self):
+        noise = bytes(range(0, 0x20 + 1))
+        base_url = "http://User:[email protected]:080/doc/?query=yes#frag"
+
+        url = noise.decode("utf-8") + base_url
+        p = urllib.parse.urlsplit(url)
+        self.assertEqual(p.scheme, "http")
+        self.assertEqual(p.netloc, "User:[email protected]:080")
+        self.assertEqual(p.path, "/doc/")
+        self.assertEqual(p.query, "query=yes")
+        self.assertEqual(p.fragment, "frag")
+        self.assertEqual(p.username, "User")
+        self.assertEqual(p.password, "Pass")
+        self.assertEqual(p.hostname, "www.python.org")
+        self.assertEqual(p.port, 80)
+        self.assertEqual(p.geturl(), base_url)
+
+        url = noise + base_url.encode("utf-8")
+        p = urllib.parse.urlsplit(url)
+        self.assertEqual(p.scheme, b"http")
+        self.assertEqual(p.netloc, b"User:[email protected]:080")
+        self.assertEqual(p.path, b"/doc/")
+        self.assertEqual(p.query, b"query=yes")
+        self.assertEqual(p.fragment, b"frag")
+        self.assertEqual(p.username, b"User")
+        self.assertEqual(p.password, b"Pass")
+        self.assertEqual(p.hostname, b"www.python.org")
+        self.assertEqual(p.port, 80)
+        self.assertEqual(p.geturl(), base_url.encode("utf-8"))
+
+        # Test that trailing space is preserved as some applications rely on
+        # this within query strings.
+        query_spaces_url = "https://www.python.org:88/doc/?query=    "
+        p = urllib.parse.urlsplit(noise.decode("utf-8") + query_spaces_url)
+        self.assertEqual(p.scheme, "https")
+        self.assertEqual(p.netloc, "www.python.org:88")
+        self.assertEqual(p.path, "/doc/")
+        self.assertEqual(p.query, "query=    ")
+        self.assertEqual(p.port, 88)
+        self.assertEqual(p.geturl(), query_spaces_url)
+
+        p = urllib.parse.urlsplit("www.pypi.org ")
+        # That "hostname" gets considered a "path" due to the
+        # trailing space and our existing logic...  YUCK...
+        # and re-assembles via geturl aka unurlsplit into the original.
+        # django.core.validators.URLValidator (at least through v3.2) relies on
+        # this, for better or worse, to catch it in a ValidationError via its
+        # regular expressions.
+        # Here we test the basic round trip concept of such a trailing space.
+        self.assertEqual(urllib.parse.urlunsplit(p), "www.pypi.org ")
+
+        # with scheme as cache-key
+        url = "//www.python.org/"
+        scheme = noise.decode("utf-8") + "https" + noise.decode("utf-8")
+        for _ in range(2):
+            p = urllib.parse.urlsplit(url, scheme=scheme)
+            self.assertEqual(p.scheme, "https")
+            self.assertEqual(p.geturl(), "https://www.python.org/")
+
     def test_attributes_bad_port(self):
         """Check handling of invalid ports."""
         for bytes in (False, True):

Lib/urllib/parse.py

@@ -432,12 +432,15 @@ 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)
     # Only lstrip url as some applications rely on preserving trailing space.
     # (https://url.spec.whatwg.org/#concept-basic-url-parser would strip both)
     url = url.lstrip(_WHATWG_C0_CONTROL_OR_SPACE)
     scheme = scheme.strip(_WHATWG_C0_CONTROL_OR_SPACE)
+
+    for b in _UNSAFE_URL_BYTES_TO_REMOVE:
+        url = url.replace(b, "")
+        scheme = scheme.replace(b, "")
+
     allow_fragments = bool(allow_fragments)
     key = url, scheme, allow_fragments, type(url), type(scheme)
     cached = _parse_cache.get(key, None)

Misc/NEWS.d/next/Security/2023-03-07-20-59-17.gh-issue-102153.14CLSZ.rst

@@ -0,0 +1,3 @@
+:func:`urllib.parse.urlsplit` now strips leading C0 control and space
+characters following the specification for URLs defined by WHATWG in
+response to CVE-2023-24329. Patch by Illia Volochii.