--- /dev/null
+From 3e3669c9c41a27e1466e2c28b3906e3dd0ce3e7e Mon Sep 17 00:00:00 2001
+From: Steve Dower <steve.dower@python.org>
+Date: Thu, 7 Mar 2019 08:25:22 -0800
+Subject: [PATCH] bpo-36216: Add check for characters in netloc that normalize
+ to separators (GH-12201)
+
+---
+ Doc/library/urlparse.rst | 20 ++++++++++++++++
+ Lib/test/test_urlparse.py | 24 +++++++++++++++++++
+ Lib/urlparse.py | 17 +++++++++++++
+ .../2019-03-06-09-38-40.bpo-36216.6q1m4a.rst | 3 +++
+ 4 files changed, 64 insertions(+)
+ create mode 100644 Misc/NEWS.d/next/Security/2019-03-06-09-38-40.bpo-36216.6q1m4a.rst
+
+diff --git a/Doc/library/urlparse.rst b/Doc/library/urlparse.rst
+index 22249da54fbb..0989c88c3022 100644
+--- a/Doc/library/urlparse.rst
++++ b/Doc/library/urlparse.rst
+@@ -119,12 +119,22 @@ The :mod:`urlparse` module defines the following functions:
+ See section :ref:`urlparse-result-object` for more information on the result
+ object.
+
++ 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, or is not a Unicode string, no error will be
++ raised.
++
+ .. versionchanged:: 2.5
+ Added attributes to return value.
+
+ .. versionchanged:: 2.7
+ Added IPv6 URL parsing capabilities.
+
++ .. versionchanged:: 2.7.17
++ Characters that affect netloc parsing under NFKC normalization will
++ now raise :exc:`ValueError`.
++
+
+ .. function:: parse_qs(qs[, keep_blank_values[, strict_parsing[, max_num_fields]]])
+
+@@ -232,11 +242,21 @@ The :mod:`urlparse` module defines the following functions:
+ See section :ref:`urlparse-result-object` for more information on the result
+ object.
+
++ 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, or is not a Unicode string, no error will be
++ raised.
++
+ .. versionadded:: 2.2
+
+ .. versionchanged:: 2.5
+ Added attributes to return value.
+
++ .. versionchanged:: 2.7.17
++ 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 4e1ded73c266..73b0228ea8e3 100644
+--- a/Lib/test/test_urlparse.py
++++ b/Lib/test/test_urlparse.py
+@@ -1,4 +1,6 @@
+ from test import test_support
++import sys
++import unicodedata
+ import unittest
+ import urlparse
+
+@@ -624,6 +626,28 @@ def test_portseparator(self):
+ self.assertEqual(urlparse.urlparse("http://www.python.org:80"),
+ ('http','www.python.org:80','','','',''))
+
++ 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 = u'/:#?@'
++ hex_chars = {'{:04X}'.format(ord(c)) for c in illegal_chars}
++ denorm_chars = [
++ c for c in map(unichr, 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(u'\u2100', denorm_chars)
++ self.assertIn(u'\uFF03', denorm_chars)
++
++ for scheme in [u"http", u"https", u"ftp"]:
++ for c in denorm_chars:
++ url = u"{}://netloc{}false.netloc/path".format(scheme, c)
++ print "Checking %r" % url
++ with self.assertRaises(ValueError):
++ urlparse.urlsplit(url)
++
+ def test_main():
+ test_support.run_unittest(UrlParseTestCase)
+
+diff --git a/Lib/urlparse.py b/Lib/urlparse.py
+index f7c2b032b097..54eda08651ab 100644
+--- a/Lib/urlparse.py
++++ b/Lib/urlparse.py
+@@ -165,6 +165,21 @@ 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 not isinstance(netloc, unicode):
++ 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:
+ <scheme>://<netloc>/<path>?<query>#<fragment>
+@@ -193,6 +208,7 @@ 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 v
+@@ -216,6 +232,7 @@ 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 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..1e1ad92c6feb
+--- /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.
+\ No newline at end of file
--- /dev/null
+From 8f5285ac12bd185202fdaac56fd19dfb858ec947 Mon Sep 17 00:00:00 2001
+From: Steve Dower <steve.dower@python.org>
+Date: Thu, 7 Mar 2019 08:09:56 -0800
+Subject: [PATCH 1/2] bpo-36216: Add check for characters in netloc that
+ normalize to separators (GH-12201)
+
+---
+ 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 d991254d5ca1..647af613a315 100644
+--- a/Doc/library/urllib.parse.rst
++++ b/Doc/library/urllib.parse.rst
+@@ -121,6 +121,11 @@ 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.
+
+@@ -133,6 +138,10 @@ or on combining URL components into a URL string.
+ Out-of-range port numbers now raise :exc:`ValueError`, instead of
+ returning :const:`None`.
+
++ .. versionchanged:: 3.6.9
++ 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)
+
+@@ -256,10 +265,19 @@ 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:: 3.6.9
++ 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 85e68c8b42c7..24a628915e53 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:
+ <scheme>://<netloc>/<path>?<query>#<fragment>
+@@ -420,6 +435,7 @@ 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)
+@@ -443,6 +459,7 @@ 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.
+
+From 379c71551a3f005bbedccc3758568918612c1765 Mon Sep 17 00:00:00 2001
+From: Steve Dower <steve.dower@python.org>
+Date: Thu, 7 Mar 2019 08:28:39 -0800
+Subject: [PATCH 2/2] Replace isascii call with any() call
+
+---
+ Lib/urllib/parse.py | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/Lib/urllib/parse.py b/Lib/urllib/parse.py
+index 24a628915e53..7b06f4d71d67 100644
+--- a/Lib/urllib/parse.py
++++ b/Lib/urllib/parse.py
+@@ -392,7 +392,7 @@ def _splitnetloc(url, start=0):
+ return url[start:delim], url[delim:] # return (domain, rest)
+
+ def _checknetloc(netloc):
+- if not netloc or netloc.isascii():
++ if not netloc or not any(ord(c) > 127 for c in netloc):
+ return
+ # looking for characters like \u2100 that expand to 'a/c'
+ # IDNA uses NFKC equivalence, so normalize for this check