Add the List-Unsubscribe header for notification emails. (#16274)

Adds both the List-Unsubscribe (RFC2369) and List-Unsubscribe-Post (RFC8058)
headers to push notification emails, which together should:

* Show an "Unsubscribe" link in the MUA UI when viewing Synapse notification emails.
* Enable "one-click" unsubscribe (the user never leaves their MUA, which automatically
  makes a POST request to the specified endpoint).

1 files changed, 55 insertions, 0 deletions

diff --git a/tests/push/test_email.py b/tests/push/test_email.py
index 4b5c96aeae..73a430ddc6 100644
--- a/tests/push/test_email.py
+++ b/tests/push/test_email.py
@@ -13,10 +13,12 @@
 # limitations under the License.
 import email.message
 import os
+from http import HTTPStatus
 from typing import Any, Dict, List, Sequence, Tuple
 
 import attr
 import pkg_resources
+from parameterized import parameterized
 
 from twisted.internet.defer import Deferred
 from twisted.test.proto_helpers import MemoryReactor
@@ -25,9 +27,11 @@ import synapse.rest.admin
 from synapse.api.errors import Codes, SynapseError
 from synapse.push.emailpusher import EmailPusher
 from synapse.rest.client import login, room
+from synapse.rest.synapse.client.unsubscribe import UnsubscribeResource
 from synapse.server import HomeServer
 from synapse.util import Clock
 
+from tests.server import FakeSite, make_request
 from tests.unittest import HomeserverTestCase
 
 
@@ -175,6 +179,57 @@ class EmailPusherTests(HomeserverTestCase):
 
         self._check_for_mail()
 
+    @parameterized.expand([(False,), (True,)])
+    def test_unsubscribe(self, use_post: bool) -> None:
+        # Create a simple room with two users
+        room = self.helper.create_room_as(self.user_id, tok=self.access_token)
+        self.helper.invite(
+            room=room, src=self.user_id, tok=self.access_token, targ=self.others[0].id
+        )
+        self.helper.join(room=room, user=self.others[0].id, tok=self.others[0].token)
+
+        # The other user sends a single message.
+        self.helper.send(room, body="Hi!", tok=self.others[0].token)
+
+        # We should get emailed about that message
+        args, kwargs = self._check_for_mail()
+
+        # That email should contain an unsubscribe link in the body and header.
+        msg: bytes = args[5]
+
+        # Multipart: plain text, base 64 encoded; html, base 64 encoded
+        multipart_msg = email.message_from_bytes(msg)
+        txt = multipart_msg.get_payload()[0].get_payload(decode=True).decode()
+        html = multipart_msg.get_payload()[1].get_payload(decode=True).decode()
+        self.assertIn("/_synapse/client/unsubscribe", txt)
+        self.assertIn("/_synapse/client/unsubscribe", html)
+
+        # The unsubscribe headers should exist.
+        assert multipart_msg.get("List-Unsubscribe") is not None
+        self.assertIsNotNone(multipart_msg.get("List-Unsubscribe-Post"))
+
+        # Open the unsubscribe link.
+        unsubscribe_link = multipart_msg["List-Unsubscribe"].strip("<>")
+        unsubscribe_resource = UnsubscribeResource(self.hs)
+        channel = make_request(
+            self.reactor,
+            FakeSite(unsubscribe_resource, self.reactor),
+            "POST" if use_post else "GET",
+            unsubscribe_link,
+            shorthand=False,
+        )
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+
+        # Ensure the pusher was removed.
+        pushers = list(
+            self.get_success(
+                self.hs.get_datastores().main.get_pushers_by(
+                    {"user_name": self.user_id}
+                )
+            )
+        )
+        self.assertEqual(pushers, [])
+
     def test_invite_sends_email(self) -> None:
         # Create a room and invite the user to it
         room = self.helper.create_room_as(self.others[0].id, tok=self.others[0].token)