From 6c472d3a1d334d4eeb4a25eba7bf3b01611bf667 Mon Sep 17 00:00:00 2001

From: "Miss Islington (bot)"

 <31488909+miss-islington@users.noreply.github.com>

Date: Thu, 6 May 2021 09:56:01 -0700

Subject: [PATCH] [3.6] bpo-43882 - urllib.parse should sanitize urls

 containing ASCII newline and tabs (GH-25924)

Co-authored-by: Gregory P. Smith <greg@krypto.org>

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

(cherry picked from commit 76cd81d60310d65d01f9d7b48a8985d8ab89c8b4)

Co-authored-by: Senthil Kumaran <senthil@uthcode.com>

(cherry picked from commit 515a7bc4e13645d0945b46a8e1d9102b918cd407)

Co-authored-by: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>

---

 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 3c2e37ef2093a..b717d7cc05b2e 100644

--- a/Doc/library/urllib.parse.rst

+++ b/Doc/library/urllib.parse.rst

@@ -288,6 +288,9 @@ 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`.

@@ -296,6 +299,10 @@ or on combining URL components into a URL string.

       Characters that affect netloc parsing under NFKC normalization will

       now raise :exc:`ValueError`.

+   .. versionchanged:: 3.6.14

+      ASCII newline and tab characters are stripped from the URL.

+

+.. _WHATWG spec: https://url.spec.whatwg.org/#concept-basic-url-parser

 .. function:: urlunsplit(parts)

@@ -633,6 +640,10 @@ 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

@@ -656,3 +667,5 @@ 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 e3088b2f39bd7..3509278a01694 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 66056bf589bf6..ac6e7a9cee0b9 100644

--- a/Lib/urllib/parse.py

+++ b/Lib/urllib/parse.py

@@ -76,6 +76,9 @@

                 '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 = {}

@@ -409,6 +412,11 @@ 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:

     <scheme>://<netloc>/<path>?<query>#<fragment>

@@ -416,6 +424,8 @@ 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 0000000000000..a326d079dff4a

--- /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.