core: set SameSite=Lax on authentication cookie

https://tools.ietf.org/html/draft-ietf-httpbis-rfc6265bis-02

SameSite=None breaks the compatibility with some browser versions.
https://www.chromium.org/updates/same-site/incompatible-clients

We choose Lax and not Strict so that we can open links to ERP5 from
external applications and so that OAuth Logins work. Implementing the
"two cookies, one for read one for write" approach suggested in
https://tools.ietf.org/html/draft-ietf-httpbis-rfc6265bis-02#section-8.8.2
would be too big change at this point.

Allow instances to surcharge the SameSite value for some specific domains if needed,
by surcharging the ERP5Site_getAuthCookieSameSite script.

bt5/erp5_oauth_facebook_login/TestTemplateItem/portal_components/test.erp5.testFacebookLogin.py

@@ -168,6 +168,7 @@ class TestFacebookLogin(ERP5TypeTestCase):
     ac_cookie, = [v for (k, v) in response.listHeaders() if k.lower() == 'set-cookie' and '__ac_facebook_hash=' in v]
     self.assertIn('; Secure', ac_cookie)
     self.assertIn('; HTTPOnly', ac_cookie)
+    self.assertIn('; SameSite=Lax', ac_cookie)
 
   def test_create_user_in_ERP5Site_createFacebookUserToOAuth(self):
     """

bt5/erp5_oauth_google_login/TestTemplateItem/portal_components/test.erp5.testGoogleLogin.py

@@ -210,6 +210,7 @@ class TestGoogleLogin(ERP5TypeTestCase):
     ac_cookie, = [v for (k, v) in response.listHeaders() if k.lower() == 'set-cookie' and '__ac_google_hash=' in v]
     self.assertIn('; Secure', ac_cookie)
     self.assertIn('; HTTPOnly', ac_cookie)
+    self.assertIn('; SameSite=Lax', ac_cookie)
 
   def test_create_user_in_ERP5Site_createGoogleUserToOAuth(self):
     """

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_auto_logout/ERP5Site_getAuthCookieSameSite.py

+return 'Lax'

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_auto_logout/ERP5Site_getAuthCookieSameSite.xml

+<?xml version="1.0"?>
+<ZopeData>
+  <record id="1" aka="AAAAAAAAAAE=">
+    <pickle>
+      <global name="PythonScript" module="Products.PythonScripts.PythonScript"/>
+    </pickle>
+    <pickle>
+      <dictionary>
+        <item>
+            <key> <string>Script_magic</string> </key>
+            <value> <int>3</int> </value>
+        </item>
+        <item>
+            <key> <string>_bind_names</string> </key>
+            <value>
+              <object>
+                <klass>
+                  <global name="NameAssignments" module="Shared.DC.Scripts.Bindings"/>
+                </klass>
+                <tuple/>
+                <state>
+                  <dictionary>
+                    <item>
+                        <key> <string>_asgns</string> </key>
+                        <value>
+                          <dictionary>
+                            <item>
+                                <key> <string>name_container</string> </key>
+                                <value> <string>container</string> </value>
+                            </item>
+                            <item>
+                                <key> <string>name_context</string> </key>
+                                <value> <string>context</string> </value>
+                            </item>
+                            <item>
+                                <key> <string>name_m_self</string> </key>
+                                <value> <string>script</string> </value>
+                            </item>
+                            <item>
+                                <key> <string>name_subpath</string> </key>
+                                <value> <string>traverse_subpath</string> </value>
+                            </item>
+                          </dictionary>
+                        </value>
+                    </item>
+                  </dictionary>
+                </state>
+              </object>
+            </value>
+        </item>
+        <item>
+            <key> <string>_params</string> </key>
+            <value> <string>scheme, hostname, port, path, user_agent</string> </value>
+        </item>
+        <item>
+            <key> <string>id</string> </key>
+            <value> <string>ERP5Site_getAuthCookieSameSite</string> </value>
+        </item>
+      </dictionary>
+    </pickle>
+  </record>
+</ZopeData>

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_auto_logout/setAuthCookie.py

+from urlparse import urlparse
+
 portal = context.getPortalObject()
 kw = {}
 expire_interval = portal.portal_preferences.getPreferredMaxUserInactivityDuration()
@@ -15,12 +17,24 @@ portal.portal_sessions[
     )
   )
 ]['ac_renew'] = ac_renew
+
+REQUEST = portal.REQUEST
+parse_dict = urlparse(REQUEST.other.get('ACTUAL_URL'))
+same_site = portal.ERP5Site_getAuthCookieSameSite(scheme=parse_dict.scheme,
+                                                  hostname=parse_dict.hostname,
+                                                  port=parse_dict.port,
+                                                  path=parse_dict.path,
+                                                  user_agent=REQUEST.environ.get('HTTP_USER_AGENT'))
+if same_site not in ('None', 'Lax', 'Strict'):
+  # Do not use the SameSite attribute
+  same_site = None
+
 resp.setCookie(
   name=cookie_name,
   value=cookie_value,
   path='/',
-  secure=getattr(portal, 'REQUEST', {}).get('SERVER_URL', '').startswith('https:'),
+  secure=REQUEST.get('SERVER_URL', '').startswith('https:'),
   http_only=True,
-  same_site='None',
+  same_site=same_site,
   **kw
 )

product/ERP5Security/tests/testERP5Security.py

@@ -1302,6 +1302,11 @@ class TestAuthenticationCookie(UserManagementTestCase):
     # HTTPOnly flag so that javascript cannot access cookie
     self.assertIn('; HTTPOnly', ac_cookie)
 
+    # SameSite=Lax flag so that cookie is not sent on cross origin requests.
+    # We set Lax (and not strict) so that opening a link to ERP5 from an
+    # external site does not prompt for login.
+    self.assertIn('; SameSite=Lax', ac_cookie)
+
 
 class TestReindexObjectSecurity(UserManagementTestCase):
   def afterSetUp(self):