email forwarder: encode stream names so they are safe in email addresses.

(imported from commit 6699d656e3cae58fad062a1403fb9923429fde89)

zerver/lib/actions.py

@@ -1042,6 +1042,24 @@ def do_update_message(user_profile, message_id, subject, content):
     notice = dict(event=event, users=recipients)
     tornado_callbacks.send_notification(notice)
 
+def encode_email_address(stream):
+    # Given the fact that we have almost no restrictions on stream names and
+    # that what characters are allowed in e-mail addresses is complicated and
+    # dependent on context in the address, we opt for a very simple scheme:
+    #
+    # Only encode the stream name (leave the + and token alone). Encode
+    # everything that isn't alphanumeric plus _ as the percent-prefixed integer
+    # ordinal of that character, padded with zeroes to the maximum number of
+    # bytes of a UTF-8 encoded Unicode character.
+    encoded_name = re.sub("\W", lambda x: "%" + str(ord(x.group(0))).zfill(4),
+                          stream.name)
+    return "%s+%s@streams.zulip.com" % (encoded_name, stream.email_token)
+
+def decode_email_address(email):
+    # Perform the reverse of encode_email_address. Only the stream name will be
+    # transformed.
+    return re.sub("%\d{4}", lambda x: unichr(int(x.group(0)[1:])), email)
+
 def gather_subscriptions(user_profile):
     # For now, don't display subscriptions for private messages.
     subs = Subscription.objects.select_related().filter(

zerver/management/commands/email-mirror.py

@@ -24,6 +24,7 @@ import sys
 from django.conf import settings
 from django.core.management.base import BaseCommand
 
+from zerver.lib.actions import decode_email_address
 from zerver.models import Stream, get_user_profile_by_email
 
 from twisted.internet import protocol, reactor, ssl
@@ -104,7 +105,7 @@ def extract_and_validate(email):
     # Recipient is of the form
     # <stream name>+<regenerable stream token>@streams.zulip.com
     try:
-        stream_name_and_token = email.rsplit("@", 1)[0]
+        stream_name_and_token = decode_email_address(email).rsplit("@", 1)[0]
         stream_name, token = stream_name_and_token.rsplit("+", 1)
     except ValueError:
         log_and_raise("Malformed email recipient " + email)