+++ /dev/null
-From 3ab6f812653e79d008d5eba31dc25d34f3ca7170 Mon Sep 17 00:00:00 2001
-From: Senthil Kumaran <senthil@uthcode.com>
-Date: Mon, 15 Feb 2021 10:15:02 -0800
-Subject: [PATCH] bpo-42967: only use '&' as a query string separator
-MIME-Version: 1.0
-Content-Type: text/plain; charset=UTF-8
-Content-Transfer-Encoding: 8bit
-
- (GH-24297) (#24529)
-MIME-Version: 1.0
-Content-Type: text/plain; charset=UTF-8
-Content-Transfer-Encoding: 8bit
-
-* bpo-42967: only use '&' as a query string separator (#24297)
-
-bpo-42967: [security] Address a web cache-poisoning issue reported in
-urllib.parse.parse_qsl().
-
-urllib.parse will only us "&" as query string separator by default
-instead of both ";" and "&" as allowed in earlier versions. An optional
-argument seperator with default value "&" is added to specify the
-separator.
-
-Co-authored-by: Éric Araujo <merwok@netwok.org>
-Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
-Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
-Co-authored-by: Éric Araujo <merwok@netwok.org>
-(cherry picked from commit fcbe0cb04d35189401c0c880ebfb4311e952d776)
-
-* [3.8] bpo-42967: only use '&' as a query string separator (GH-24297)
-
-bpo-42967: [security] Address a web cache-poisoning issue reported in urllib.parse.parse_qsl().
-
-urllib.parse will only us "&" as query string separator by default instead of both ";" and "&" as allowed in earlier versions. An optional argument seperator with default value "&" is added to specify the separator.
-
-Co-authored-by: Éric Araujo <merwok@netwok.org>
-Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
-Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
-Co-authored-by: Éric Araujo <merwok@netwok.org>.
-(cherry picked from commit fcbe0cb04d35189401c0c880ebfb4311e952d776)
-
-Co-authored-by: Adam Goldschmidt <adamgold7@gmail.com>
-
-* Update correct version information.
-
-* fix docs and make logic clearer
-
-Co-authored-by: Adam Goldschmidt <adamgold7@gmail.com>
-Co-authored-by: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
-
-Upstream-Status: Backport [https://github.com/python/cpython/commit/e3110c3cfbb7daa690d54d0eff6c264c870a71bf]
-CVE: CVE-2020-23336
-Signed-off-by: Chee Yang Lee <chee.yang.lee@intel.com>
-
----
- Doc/library/cgi.rst | 11 ++-
- Doc/library/urllib.parse.rst | 22 +++++-
- Doc/whatsnew/3.6.rst | 13 ++++
- Doc/whatsnew/3.7.rst | 13 ++++
- Lib/cgi.py | 23 ++++---
- Lib/test/test_cgi.py | 29 ++++++--
- Lib/test/test_urlparse.py | 68 +++++++++++++------
- Lib/urllib/parse.py | 19 ++++--
- .../2021-02-14-15-59-16.bpo-42967.YApqDS.rst | 1 +
- 9 files changed, 153 insertions(+), 46 deletions(-)
- create mode 100644 Misc/NEWS.d/next/Security/2021-02-14-15-59-16.bpo-42967.YApqDS.rst
-
-diff --git a/Doc/library/cgi.rst b/Doc/library/cgi.rst
-index 4048592..880074b 100644
---- a/Doc/library/cgi.rst
-+++ b/Doc/library/cgi.rst
-@@ -277,14 +277,16 @@ These are useful if you want more control, or if you want to employ some of the
- algorithms implemented in this module in other circumstances.
-
-
--.. function:: parse(fp=None, environ=os.environ, keep_blank_values=False, strict_parsing=False)
-+.. function:: parse(fp=None, environ=os.environ, keep_blank_values=False, strict_parsing=False, separator="&")
-
- Parse a query in the environment or from a file (the file defaults to
-- ``sys.stdin``). The *keep_blank_values* and *strict_parsing* parameters are
-+ ``sys.stdin``). The *keep_blank_values*, *strict_parsing* and *separator* parameters are
- passed to :func:`urllib.parse.parse_qs` unchanged.
-
-+ .. versionchanged:: 3.8.8
-+ Added the *separator* parameter.
-
--.. function:: parse_multipart(fp, pdict, encoding="utf-8", errors="replace")
-+.. function:: parse_multipart(fp, pdict, encoding="utf-8", errors="replace", separator="&")
-
- Parse input of type :mimetype:`multipart/form-data` (for file uploads).
- Arguments are *fp* for the input file, *pdict* for a dictionary containing
-@@ -303,6 +305,9 @@ algorithms implemented in this module in other circumstances.
- Added the *encoding* and *errors* parameters. For non-file fields, the
- value is now a list of strings, not bytes.
-
-+ .. versionchanged:: 3.8.8
-+ Added the *separator* parameter.
-+
-
- .. function:: parse_header(string)
-
-diff --git a/Doc/library/urllib.parse.rst b/Doc/library/urllib.parse.rst
-index 52f98ef..45ca03a 100644
---- a/Doc/library/urllib.parse.rst
-+++ b/Doc/library/urllib.parse.rst
-@@ -165,7 +165,7 @@ or on combining URL components into a URL string.
- now raise :exc:`ValueError`.
-
-
--.. function:: parse_qs(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None)
-+.. function:: parse_qs(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None, separator='&')
-
- Parse a query string given as a string argument (data of type
- :mimetype:`application/x-www-form-urlencoded`). Data are returned as a
-@@ -190,6 +190,9 @@ or on combining URL components into a URL string.
- read. If set, then throws a :exc:`ValueError` if there are more than
- *max_num_fields* fields read.
-
-+ The optional argument *separator* is the symbol to use for separating the
-+ query arguments. It defaults to ``&``.
-+
- Use the :func:`urllib.parse.urlencode` function (with the ``doseq``
- parameter set to ``True``) to convert such dictionaries into query
- strings.
-@@ -201,8 +204,14 @@ or on combining URL components into a URL string.
- .. versionchanged:: 3.8
- Added *max_num_fields* parameter.
-
-+ .. versionchanged:: 3.8.8
-+ Added *separator* parameter with the default value of ``&``. Python
-+ versions earlier than Python 3.8.8 allowed using both ``;`` and ``&`` as
-+ query parameter separator. This has been changed to allow only a single
-+ separator key, with ``&`` as the default separator.
-+
-
--.. function:: parse_qsl(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None)
-+.. function:: parse_qsl(qs, keep_blank_values=False, strict_parsing=False, encoding='utf-8', errors='replace', max_num_fields=None, separator='&')
-
- Parse a query string given as a string argument (data of type
- :mimetype:`application/x-www-form-urlencoded`). Data are returned as a list of
-@@ -226,6 +235,9 @@ or on combining URL components into a URL string.
- read. If set, then throws a :exc:`ValueError` if there are more than
- *max_num_fields* fields read.
-
-+ The optional argument *separator* is the symbol to use for separating the
-+ query arguments. It defaults to ``&``.
-+
- Use the :func:`urllib.parse.urlencode` function to convert such lists of pairs into
- query strings.
-
-@@ -235,6 +247,12 @@ or on combining URL components into a URL string.
- .. versionchanged:: 3.8
- Added *max_num_fields* parameter.
-
-+ .. versionchanged:: 3.8.8
-+ Added *separator* parameter with the default value of ``&``. Python
-+ versions earlier than Python 3.8.8 allowed using both ``;`` and ``&`` as
-+ query parameter separator. This has been changed to allow only a single
-+ separator key, with ``&`` as the default separator.
-+
-
- .. function:: urlunparse(parts)
-
-diff --git a/Doc/whatsnew/3.6.rst b/Doc/whatsnew/3.6.rst
-index 04c1f7e..4409a3a 100644
---- a/Doc/whatsnew/3.6.rst
-+++ b/Doc/whatsnew/3.6.rst
-@@ -2443,3 +2443,16 @@ because of the behavior of the socket option ``SO_REUSEADDR`` in UDP. For more
- details, see the documentation for ``loop.create_datagram_endpoint()``.
- (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in
- :issue:`37228`.)
-+
-+Notable changes in Python 3.6.13
-+================================
-+
-+Earlier Python versions allowed using both ``;`` and ``&`` as
-+query parameter separators in :func:`urllib.parse.parse_qs` and
-+:func:`urllib.parse.parse_qsl`. Due to security concerns, and to conform with
-+newer W3C recommendations, this has been changed to allow only a single
-+separator key, with ``&`` as the default. This change also affects
-+:func:`cgi.parse` and :func:`cgi.parse_multipart` as they use the affected
-+functions internally. For more details, please see their respective
-+documentation.
-+(Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in :issue:`42967`.)
-diff --git a/Doc/whatsnew/3.7.rst b/Doc/whatsnew/3.7.rst
-index b9b5021..8f47a9f 100644
---- a/Doc/whatsnew/3.7.rst
-+++ b/Doc/whatsnew/3.7.rst
-@@ -2556,3 +2556,16 @@ because of the behavior of the socket option ``SO_REUSEADDR`` in UDP. For more
- details, see the documentation for ``loop.create_datagram_endpoint()``.
- (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in
- :issue:`37228`.)
-+
-+Notable changes in Python 3.7.10
-+================================
-+
-+Earlier Python versions allowed using both ``;`` and ``&`` as
-+query parameter separators in :func:`urllib.parse.parse_qs` and
-+:func:`urllib.parse.parse_qsl`. Due to security concerns, and to conform with
-+newer W3C recommendations, this has been changed to allow only a single
-+separator key, with ``&`` as the default. This change also affects
-+:func:`cgi.parse` and :func:`cgi.parse_multipart` as they use the affected
-+functions internally. For more details, please see their respective
-+documentation.
-+(Contributed by Adam Goldschmidt, Senthil Kumaran and Ken Jin in :issue:`42967`.)
-diff --git a/Lib/cgi.py b/Lib/cgi.py
-index 5ace46a..13255a9 100755
---- a/Lib/cgi.py
-+++ b/Lib/cgi.py
-@@ -106,7 +106,8 @@ log = initlog # The current logging function
- # 0 ==> unlimited input
- maxlen = 0
-
--def parse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0):
-+def parse(fp=None, environ=os.environ, keep_blank_values=0,
-+ strict_parsing=0, separator='&'):
- """Parse a query in the environment or from a file (default stdin)
-
- Arguments, all optional:
-@@ -125,6 +126,9 @@ def parse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0):
- strict_parsing: flag indicating what to do with parsing errors.
- If false (the default), errors are silently ignored.
- If true, errors raise a ValueError exception.
-+
-+ separator: str. The symbol to use for separating the query arguments.
-+ Defaults to &.
- """
- if fp is None:
- fp = sys.stdin
-@@ -145,7 +149,7 @@ def parse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0):
- if environ['REQUEST_METHOD'] == 'POST':
- ctype, pdict = parse_header(environ['CONTENT_TYPE'])
- if ctype == 'multipart/form-data':
-- return parse_multipart(fp, pdict)
-+ return parse_multipart(fp, pdict, separator=separator)
- elif ctype == 'application/x-www-form-urlencoded':
- clength = int(environ['CONTENT_LENGTH'])
- if maxlen and clength > maxlen:
-@@ -169,10 +173,10 @@ def parse(fp=None, environ=os.environ, keep_blank_values=0, strict_parsing=0):
- qs = ""
- environ['QUERY_STRING'] = qs # XXX Shouldn't, really
- return urllib.parse.parse_qs(qs, keep_blank_values, strict_parsing,
-- encoding=encoding)
-+ encoding=encoding, separator=separator)
-
-
--def parse_multipart(fp, pdict, encoding="utf-8", errors="replace"):
-+def parse_multipart(fp, pdict, encoding="utf-8", errors="replace", separator='&'):
- """Parse multipart input.
-
- Arguments:
-@@ -193,7 +197,7 @@ def parse_multipart(fp, pdict, encoding="utf-8", errors="replace"):
- headers.set_type(ctype)
- headers['Content-Length'] = pdict['CONTENT-LENGTH']
- fs = FieldStorage(fp, headers=headers, encoding=encoding, errors=errors,
-- environ={'REQUEST_METHOD': 'POST'})
-+ environ={'REQUEST_METHOD': 'POST'}, separator=separator)
- return {k: fs.getlist(k) for k in fs}
-
- def _parseparam(s):
-@@ -303,7 +307,7 @@ class FieldStorage:
- def __init__(self, fp=None, headers=None, outerboundary=b'',
- environ=os.environ, keep_blank_values=0, strict_parsing=0,
- limit=None, encoding='utf-8', errors='replace',
-- max_num_fields=None):
-+ max_num_fields=None, separator='&'):
- """Constructor. Read multipart/* until last part.
-
- Arguments, all optional:
-@@ -351,6 +355,7 @@ class FieldStorage:
- self.keep_blank_values = keep_blank_values
- self.strict_parsing = strict_parsing
- self.max_num_fields = max_num_fields
-+ self.separator = separator
- if 'REQUEST_METHOD' in environ:
- method = environ['REQUEST_METHOD'].upper()
- self.qs_on_post = None
-@@ -577,7 +582,7 @@ class FieldStorage:
- query = urllib.parse.parse_qsl(
- qs, self.keep_blank_values, self.strict_parsing,
- encoding=self.encoding, errors=self.errors,
-- max_num_fields=self.max_num_fields)
-+ max_num_fields=self.max_num_fields, separator=self.separator)
- self.list = [MiniFieldStorage(key, value) for key, value in query]
- self.skip_lines()
-
-@@ -593,7 +598,7 @@ class FieldStorage:
- query = urllib.parse.parse_qsl(
- self.qs_on_post, self.keep_blank_values, self.strict_parsing,
- encoding=self.encoding, errors=self.errors,
-- max_num_fields=self.max_num_fields)
-+ max_num_fields=self.max_num_fields, separator=self.separator)
- self.list.extend(MiniFieldStorage(key, value) for key, value in query)
-
- klass = self.FieldStorageClass or self.__class__
-@@ -637,7 +642,7 @@ class FieldStorage:
- else self.limit - self.bytes_read
- part = klass(self.fp, headers, ib, environ, keep_blank_values,
- strict_parsing, limit,
-- self.encoding, self.errors, max_num_fields)
-+ self.encoding, self.errors, max_num_fields, self.separator)
-
- if max_num_fields is not None:
- max_num_fields -= 1
-diff --git a/Lib/test/test_cgi.py b/Lib/test/test_cgi.py
-index ab86771..bda03ee 100644
---- a/Lib/test/test_cgi.py
-+++ b/Lib/test/test_cgi.py
-@@ -53,12 +53,9 @@ parse_strict_test_cases = [
- ("", ValueError("bad query field: ''")),
- ("&", ValueError("bad query field: ''")),
- ("&&", ValueError("bad query field: ''")),
-- (";", ValueError("bad query field: ''")),
-- (";&;", ValueError("bad query field: ''")),
- # Should the next few really be valid?
- ("=", {}),
- ("=&=", {}),
-- ("=;=", {}),
- # This rest seem to make sense
- ("=a", {'': ['a']}),
- ("&=a", ValueError("bad query field: ''")),
-@@ -73,8 +70,6 @@ parse_strict_test_cases = [
- ("a=a+b&b=b+c", {'a': ['a b'], 'b': ['b c']}),
- ("a=a+b&a=b+a", {'a': ['a b', 'b a']}),
- ("x=1&y=2.0&z=2-3.%2b0", {'x': ['1'], 'y': ['2.0'], 'z': ['2-3.+0']}),
-- ("x=1;y=2.0&z=2-3.%2b0", {'x': ['1'], 'y': ['2.0'], 'z': ['2-3.+0']}),
-- ("x=1;y=2.0;z=2-3.%2b0", {'x': ['1'], 'y': ['2.0'], 'z': ['2-3.+0']}),
- ("Hbc5161168c542333633315dee1182227:key_store_seqid=400006&cuyer=r&view=bustomer&order_id=0bb2e248638833d48cb7fed300000f1b&expire=964546263&lobale=en-US&kid=130003.300038&ss=env",
- {'Hbc5161168c542333633315dee1182227:key_store_seqid': ['400006'],
- 'cuyer': ['r'],
-@@ -187,6 +182,30 @@ Content-Length: 3
- else:
- self.assertEqual(fs.getvalue(key), expect_val[0])
-
-+ def test_separator(self):
-+ parse_semicolon = [
-+ ("x=1;y=2.0", {'x': ['1'], 'y': ['2.0']}),
-+ ("x=1;y=2.0;z=2-3.%2b0", {'x': ['1'], 'y': ['2.0'], 'z': ['2-3.+0']}),
-+ (";", ValueError("bad query field: ''")),
-+ (";;", ValueError("bad query field: ''")),
-+ ("=;a", ValueError("bad query field: 'a'")),
-+ (";b=a", ValueError("bad query field: ''")),
-+ ("b;=a", ValueError("bad query field: 'b'")),
-+ ("a=a+b;b=b+c", {'a': ['a b'], 'b': ['b c']}),
-+ ("a=a+b;a=b+a", {'a': ['a b', 'b a']}),
-+ ]
-+ for orig, expect in parse_semicolon:
-+ env = {'QUERY_STRING': orig}
-+ fs = cgi.FieldStorage(separator=';', environ=env)
-+ if isinstance(expect, dict):
-+ for key in expect.keys():
-+ expect_val = expect[key]
-+ self.assertIn(key, fs)
-+ if len(expect_val) > 1:
-+ self.assertEqual(fs.getvalue(key), expect_val)
-+ else:
-+ self.assertEqual(fs.getvalue(key), expect_val[0])
-+
- def test_log(self):
- cgi.log("Testing")
-
-diff --git a/Lib/test/test_urlparse.py b/Lib/test/test_urlparse.py
-index 4ae6ed3..90c8d69 100644
---- a/Lib/test/test_urlparse.py
-+++ b/Lib/test/test_urlparse.py
-@@ -32,16 +32,10 @@ parse_qsl_test_cases = [
- (b"&a=b", [(b'a', b'b')]),
- (b"a=a+b&b=b+c", [(b'a', b'a b'), (b'b', b'b c')]),
- (b"a=1&a=2", [(b'a', b'1'), (b'a', b'2')]),
-- (";", []),
-- (";;", []),
-- (";a=b", [('a', 'b')]),
-- ("a=a+b;b=b+c", [('a', 'a b'), ('b', 'b c')]),
-- ("a=1;a=2", [('a', '1'), ('a', '2')]),
-- (b";", []),
-- (b";;", []),
-- (b";a=b", [(b'a', b'b')]),
-- (b"a=a+b;b=b+c", [(b'a', b'a b'), (b'b', b'b c')]),
-- (b"a=1;a=2", [(b'a', b'1'), (b'a', b'2')]),
-+ (";a=b", [(';a', 'b')]),
-+ ("a=a+b;b=b+c", [('a', 'a b;b=b c')]),
-+ (b";a=b", [(b';a', b'b')]),
-+ (b"a=a+b;b=b+c", [(b'a', b'a b;b=b c')]),
- ]
-
- # Each parse_qs testcase is a two-tuple that contains
-@@ -68,16 +62,10 @@ parse_qs_test_cases = [
- (b"&a=b", {b'a': [b'b']}),
- (b"a=a+b&b=b+c", {b'a': [b'a b'], b'b': [b'b c']}),
- (b"a=1&a=2", {b'a': [b'1', b'2']}),
-- (";", {}),
-- (";;", {}),
-- (";a=b", {'a': ['b']}),
-- ("a=a+b;b=b+c", {'a': ['a b'], 'b': ['b c']}),
-- ("a=1;a=2", {'a': ['1', '2']}),
-- (b";", {}),
-- (b";;", {}),
-- (b";a=b", {b'a': [b'b']}),
-- (b"a=a+b;b=b+c", {b'a': [b'a b'], b'b': [b'b c']}),
-- (b"a=1;a=2", {b'a': [b'1', b'2']}),
-+ (";a=b", {';a': ['b']}),
-+ ("a=a+b;b=b+c", {'a': ['a b;b=b c']}),
-+ (b";a=b", {b';a': [b'b']}),
-+ (b"a=a+b;b=b+c", {b'a':[ b'a b;b=b c']}),
- ]
-
- class UrlParseTestCase(unittest.TestCase):
-@@ -884,10 +872,46 @@ class UrlParseTestCase(unittest.TestCase):
- def test_parse_qsl_max_num_fields(self):
- with self.assertRaises(ValueError):
- urllib.parse.parse_qs('&'.join(['a=a']*11), max_num_fields=10)
-- with self.assertRaises(ValueError):
-- urllib.parse.parse_qs(';'.join(['a=a']*11), max_num_fields=10)
- urllib.parse.parse_qs('&'.join(['a=a']*10), max_num_fields=10)
-
-+ def test_parse_qs_separator(self):
-+ parse_qs_semicolon_cases = [
-+ (";", {}),
-+ (";;", {}),
-+ (";a=b", {'a': ['b']}),
-+ ("a=a+b;b=b+c", {'a': ['a b'], 'b': ['b c']}),
-+ ("a=1;a=2", {'a': ['1', '2']}),
-+ (b";", {}),
-+ (b";;", {}),
-+ (b";a=b", {b'a': [b'b']}),
-+ (b"a=a+b;b=b+c", {b'a': [b'a b'], b'b': [b'b c']}),
-+ (b"a=1;a=2", {b'a': [b'1', b'2']}),
-+ ]
-+ for orig, expect in parse_qs_semicolon_cases:
-+ with self.subTest(f"Original: {orig!r}, Expected: {expect!r}"):
-+ result = urllib.parse.parse_qs(orig, separator=';')
-+ self.assertEqual(result, expect, "Error parsing %r" % orig)
-+
-+
-+ def test_parse_qsl_separator(self):
-+ parse_qsl_semicolon_cases = [
-+ (";", []),
-+ (";;", []),
-+ (";a=b", [('a', 'b')]),
-+ ("a=a+b;b=b+c", [('a', 'a b'), ('b', 'b c')]),
-+ ("a=1;a=2", [('a', '1'), ('a', '2')]),
-+ (b";", []),
-+ (b";;", []),
-+ (b";a=b", [(b'a', b'b')]),
-+ (b"a=a+b;b=b+c", [(b'a', b'a b'), (b'b', b'b c')]),
-+ (b"a=1;a=2", [(b'a', b'1'), (b'a', b'2')]),
-+ ]
-+ for orig, expect in parse_qsl_semicolon_cases:
-+ with self.subTest(f"Original: {orig!r}, Expected: {expect!r}"):
-+ result = urllib.parse.parse_qsl(orig, separator=';')
-+ self.assertEqual(result, expect, "Error parsing %r" % orig)
-+
-+
- def test_urlencode_sequences(self):
- # Other tests incidentally urlencode things; test non-covered cases:
- # Sequence and object values.
-diff --git a/Lib/urllib/parse.py b/Lib/urllib/parse.py
-index e2b6f13..5a3e847 100644
---- a/Lib/urllib/parse.py
-+++ b/Lib/urllib/parse.py
-@@ -648,7 +648,7 @@ def unquote(string, encoding='utf-8', errors='replace'):
-
-
- def parse_qs(qs, keep_blank_values=False, strict_parsing=False,
-- encoding='utf-8', errors='replace', max_num_fields=None):
-+ encoding='utf-8', errors='replace', max_num_fields=None, separator='&'):
- """Parse a query given as a string argument.
-
- Arguments:
-@@ -672,12 +672,15 @@ def parse_qs(qs, keep_blank_values=False, strict_parsing=False,
- max_num_fields: int. If set, then throws a ValueError if there
- are more than n fields read by parse_qsl().
-
-+ separator: str. The symbol to use for separating the query arguments.
-+ Defaults to &.
-+
- Returns a dictionary.
- """
- parsed_result = {}
- pairs = parse_qsl(qs, keep_blank_values, strict_parsing,
- encoding=encoding, errors=errors,
-- max_num_fields=max_num_fields)
-+ max_num_fields=max_num_fields, separator=separator)
- for name, value in pairs:
- if name in parsed_result:
- parsed_result[name].append(value)
-@@ -687,7 +690,7 @@ def parse_qs(qs, keep_blank_values=False, strict_parsing=False,
-
-
- def parse_qsl(qs, keep_blank_values=False, strict_parsing=False,
-- encoding='utf-8', errors='replace', max_num_fields=None):
-+ encoding='utf-8', errors='replace', max_num_fields=None, separator='&'):
- """Parse a query given as a string argument.
-
- Arguments:
-@@ -710,19 +713,25 @@ def parse_qsl(qs, keep_blank_values=False, strict_parsing=False,
- max_num_fields: int. If set, then throws a ValueError
- if there are more than n fields read by parse_qsl().
-
-+ separator: str. The symbol to use for separating the query arguments.
-+ Defaults to &.
-+
- Returns a list, as G-d intended.
- """
- qs, _coerce_result = _coerce_args(qs)
-
-+ if not separator or (not isinstance(separator, (str, bytes))):
-+ raise ValueError("Separator must be of type string or bytes.")
-+
- # If max_num_fields is defined then check that the number of fields
- # is less than max_num_fields. This prevents a memory exhaustion DOS
- # attack via post bodies with many fields.
- if max_num_fields is not None:
-- num_fields = 1 + qs.count('&') + qs.count(';')
-+ num_fields = 1 + qs.count(separator)
- if max_num_fields < num_fields:
- raise ValueError('Max number of fields exceeded')
-
-- pairs = [s2 for s1 in qs.split('&') for s2 in s1.split(';')]
-+ pairs = [s1 for s1 in qs.split(separator)]
- r = []
- for name_value in pairs:
- if not name_value and not strict_parsing:
-diff --git a/Misc/NEWS.d/next/Security/2021-02-14-15-59-16.bpo-42967.YApqDS.rst b/Misc/NEWS.d/next/Security/2021-02-14-15-59-16.bpo-42967.YApqDS.rst
-new file mode 100644
-index 0000000..f08489b
---- /dev/null
-+++ b/Misc/NEWS.d/next/Security/2021-02-14-15-59-16.bpo-42967.YApqDS.rst
-@@ -0,0 +1 @@
-+Fix web cache poisoning vulnerability by defaulting the query args separator to ``&``, and allowing the user to choose a custom separator.
