--- /dev/null
+From 979daae300916adb399ab5b51410b6ebd0888f13 Mon Sep 17 00:00:00 2001
+From: Xtreak <tir.karthi@gmail.com>
+Date: Sat, 15 Jun 2019 20:59:43 +0530
+Subject: [PATCH] [2.7] bpo-35121: prefix dot in domain for proper subdomain
+ validation (GH-10258) (GH-13426)
+
+This is a manual backport of ca7fe5063593958e5efdf90f068582837f07bd14 since 2.7 has `http.cookiejar` in `cookielib`
+
+
+https://bugs.python.org/issue35121
+---
+ Lib/cookielib.py | 13 ++++++--
+ Lib/test/test_cookielib.py | 30 +++++++++++++++++++
+ .../2019-05-20-00-35-12.bpo-35121.RRi-HU.rst | 4 +++
+ 3 files changed, 45 insertions(+), 2 deletions(-)
+ create mode 100644 Misc/NEWS.d/next/Security/2019-05-20-00-35-12.bpo-35121.RRi-HU.rst
+
+diff --git a/Lib/cookielib.py b/Lib/cookielib.py
+index 2dd7c48728..0b471a42f2 100644
+--- a/Lib/cookielib.py
++++ b/Lib/cookielib.py
+@@ -1139,6 +1139,11 @@ class DefaultCookiePolicy(CookiePolicy):
+ req_host, erhn = eff_request_host(request)
+ domain = cookie.domain
+
++ if domain and not domain.startswith("."):
++ dotdomain = "." + domain
++ else:
++ dotdomain = domain
++
+ # strict check of non-domain cookies: Mozilla does this, MSIE5 doesn't
+ if (cookie.version == 0 and
+ (self.strict_ns_domain & self.DomainStrictNonDomain) and
+@@ -1151,7 +1156,7 @@ class DefaultCookiePolicy(CookiePolicy):
+ _debug(" effective request-host name %s does not domain-match "
+ "RFC 2965 cookie domain %s", erhn, domain)
+ return False
+- if cookie.version == 0 and not ("."+erhn).endswith(domain):
++ if cookie.version == 0 and not ("."+erhn).endswith(dotdomain):
+ _debug(" request-host %s does not match Netscape cookie domain "
+ "%s", req_host, domain)
+ return False
+@@ -1165,7 +1170,11 @@ class DefaultCookiePolicy(CookiePolicy):
+ req_host = "."+req_host
+ if not erhn.startswith("."):
+ erhn = "."+erhn
+- if not (req_host.endswith(domain) or erhn.endswith(domain)):
++ if domain and not domain.startswith("."):
++ dotdomain = "." + domain
++ else:
++ dotdomain = domain
++ if not (req_host.endswith(dotdomain) or erhn.endswith(dotdomain)):
+ #_debug(" request domain %s does not match cookie domain %s",
+ # req_host, domain)
+ return False
+diff --git a/Lib/test/test_cookielib.py b/Lib/test/test_cookielib.py
+index f2dd9727d1..7f7ff614d6 100644
+--- a/Lib/test/test_cookielib.py
++++ b/Lib/test/test_cookielib.py
+@@ -368,6 +368,7 @@ class CookieTests(TestCase):
+ ("http://foo.bar.com/", ".foo.bar.com", True),
+ ("http://foo.bar.com/", "foo.bar.com", True),
+ ("http://foo.bar.com/", ".bar.com", True),
++ ("http://foo.bar.com/", "bar.com", True),
+ ("http://foo.bar.com/", "com", True),
+ ("http://foo.com/", "rhubarb.foo.com", False),
+ ("http://foo.com/", ".foo.com", True),
+@@ -378,6 +379,8 @@ class CookieTests(TestCase):
+ ("http://foo/", "foo", True),
+ ("http://foo/", "foo.local", True),
+ ("http://foo/", ".local", True),
++ ("http://barfoo.com", ".foo.com", False),
++ ("http://barfoo.com", "foo.com", False),
+ ]:
+ request = urllib2.Request(url)
+ r = pol.domain_return_ok(domain, request)
+@@ -938,6 +941,33 @@ class CookieTests(TestCase):
+ c.add_cookie_header(req)
+ self.assertFalse(req.has_header("Cookie"))
+
++ c.clear()
++
++ pol.set_blocked_domains([])
++ req = Request("http://acme.com/")
++ res = FakeResponse(headers, "http://acme.com/")
++ cookies = c.make_cookies(res, req)
++ c.extract_cookies(res, req)
++ self.assertEqual(len(c), 1)
++
++ req = Request("http://acme.com/")
++ c.add_cookie_header(req)
++ self.assertTrue(req.has_header("Cookie"))
++
++ req = Request("http://badacme.com/")
++ c.add_cookie_header(req)
++ self.assertFalse(pol.return_ok(cookies[0], req))
++ self.assertFalse(req.has_header("Cookie"))
++
++ p = pol.set_blocked_domains(["acme.com"])
++ req = Request("http://acme.com/")
++ c.add_cookie_header(req)
++ self.assertFalse(req.has_header("Cookie"))
++
++ req = Request("http://badacme.com/")
++ c.add_cookie_header(req)
++ self.assertFalse(req.has_header("Cookie"))
++
+ def test_secure(self):
+ from cookielib import CookieJar, DefaultCookiePolicy
+
+diff --git a/Misc/NEWS.d/next/Security/2019-05-20-00-35-12.bpo-35121.RRi-HU.rst b/Misc/NEWS.d/next/Security/2019-05-20-00-35-12.bpo-35121.RRi-HU.rst
+new file mode 100644
+index 0000000000..7725180616
+--- /dev/null
++++ b/Misc/NEWS.d/next/Security/2019-05-20-00-35-12.bpo-35121.RRi-HU.rst
+@@ -0,0 +1,4 @@
++Don't send cookies of domain A without Domain attribute to domain B when
++domain A is a suffix match of domain B while using a cookiejar with
++:class:`cookielib.DefaultCookiePolicy` policy. Patch by Karthikeyan
++Singaravelan.
+--
+2.20.1
+