From 31c16d62fc762ab87e66e7f47e36dbfcfc8b5224 Mon Sep 17 00:00:00 2001
From: Xtreak <tir.karthi@gmail.com>
Date: Sun, 17 Mar 2019 05:33:39 +0530
Subject: [PATCH] [3.5] bpo-35121: prefix dot in domain for proper subdomain
 validation (GH-10258) (#12281)

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 `http.cookiejar.DefaultCookiePolicy` policy.  Patch by Karthikeyan Singaravelan.
(cherry picked from commit ca7fe5063593958e5efdf90f068582837f07bd14)

Co-authored-by: Xtreak <tir.karthi@gmail.com>

CVE: CVE-2018-20852
Upstream-Status: Backport
[https://github.com/python/cpython/commit/4749f1b69000259e23b4cc6f63c542a9bdc62f1b]

Signed-off-by: Dan Tran <dantran@microsoft.com>
---
 Lib/http/cookiejar.py                         | 13 ++++++--
 Lib/test/test_http_cookiejar.py               | 30 +++++++++++++++++++
 .../2018-10-31-15-39-17.bpo-35121.EgHv9k.rst  |  4 +++
 3 files changed, 45 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Security/2018-10-31-15-39-17.bpo-35121.EgHv9k.rst

diff --git a/Lib/http/cookiejar.py b/Lib/http/cookiejar.py
index 6d4572af03..1cc9378ae4 100644
--- a/Lib/http/cookiejar.py
+++ b/Lib/http/cookiejar.py
@@ -1148,6 +1148,11 @@ 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
@@ -1160,7 +1165,7 @@ 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
@@ -1174,7 +1179,11 @@ 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_http_cookiejar.py b/Lib/test/test_http_cookiejar.py
index 49c01ae489..e67e6ae780 100644
--- a/Lib/test/test_http_cookiejar.py
+++ b/Lib/test/test_http_cookiejar.py
@@ -417,6 +417,7 @@ class CookieTests(unittest.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),
@@ -427,6 +428,8 @@ class CookieTests(unittest.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 = urllib.request.Request(url)
             r = pol.domain_return_ok(domain, request)
@@ -961,6 +964,33 @@ class CookieTests(unittest.TestCase):
         c.add_cookie_header(req)
         self.assertFalse(req.has_header("Cookie"))
 
+        c.clear()
+
+        pol.set_blocked_domains([])
+        req = urllib.request.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 = urllib.request.Request("http://acme.com/")
+        c.add_cookie_header(req)
+        self.assertTrue(req.has_header("Cookie"))
+
+        req = urllib.request.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 = urllib.request.Request("http://acme.com/")
+        c.add_cookie_header(req)
+        self.assertFalse(req.has_header("Cookie"))
+
+        req = urllib.request.Request("http://badacme.com/")
+        c.add_cookie_header(req)
+        self.assertFalse(req.has_header("Cookie"))
+
     def test_secure(self):
         for ns in True, False:
             for whitespace in " ", "":
diff --git a/Misc/NEWS.d/next/Security/2018-10-31-15-39-17.bpo-35121.EgHv9k.rst b/Misc/NEWS.d/next/Security/2018-10-31-15-39-17.bpo-35121.EgHv9k.rst
new file mode 100644
index 0000000000..d2eb8f1f35
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2018-10-31-15-39-17.bpo-35121.EgHv9k.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:`http.cookiejar.DefaultCookiePolicy` policy. Patch by
+Karthikeyan Singaravelan.
-- 
2.22.0.vfs.1.1.57.gbaf16c8

