[feature] SMTP delivery bounces

We catch any error on SMTP delivery and format it as a bounce message
delivered to the user Inbox.

this doesn't comply with the bounce format, but it's a nice first start.
leaving proper structuring of the delivery failure report for future
iterations.

- Resolves: #7263

1 files changed, 89 insertions, 0 deletions

diff --git a/src/leap/mail/smtp/bounces.py b/src/leap/mail/smtp/bounces.py
new file mode 100644
index 0000000..64f2dd7
--- /dev/null
+++ b/src/leap/mail/smtp/bounces.py
@@ -0,0 +1,89 @@
+# -*- coding: utf-8 -*-
+# bounces.py
+# Copyright (C) 2016 LEAP
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+"""
+Deliver bounces to the user Inbox.
+"""
+import time
+from email.message import Message
+from email.utils import formatdate
+
+from leap.mail.constants import INBOX_NAME
+from leap.mail.mail import Account
+
+
+# TODO implement localization for this template.
+
+BOUNCE_TEMPLATE = """This is your local Bitmask Mail Agent running at localhost.
+
+I'm sorry to have to inform you that your message could not be delivered to one
+or more recipients.
+
+The reasons I got for the error are:
+
+{raw_error}
+
+If the problem persists and it's not a network connectivity issue, you might
+want to contact your provider ({provider}) with this information (remove any
+sensitive data before).
+
+--- Original message (*before* it was encrypted by bitmask) below ----:
+
+{orig}"""
+
+
+class Bouncer(object):
+    """
+    Implements a mechanism to deliver bounces to user inbox.
+    """
+    # TODO this should follow RFC 6522, and compose a correct multipart
+    # attaching the report and the original message. Leaving this for a future
+    # iteration.
+
+    def __init__(self, inbox_collection):
+        self._inbox_collection = inbox_collection
+
+    def bounce_message(self, error_data, to, date=None, orig=''):
+        if not date:
+            date = formatdate(time.time())
+
+        raw_data = self._format_msg(error_data, to, date, orig)
+        d = self._inbox_collection.add_msg(
+            raw_data, ('\\Recent',), date=date)
+        return d
+
+    def _format_msg(self, error_data, to, date, orig):
+        provider = to.split('@')[1]
+
+        msg = Message()
+        msg.add_header(
+            'From', 'bitmask-bouncer@localhost (Bitmask Local Agent)')
+        msg.add_header('To', to)
+        msg.add_header('Subject', 'Undelivered Message')
+        msg.add_header('Date', date)
+        msg.set_payload(BOUNCE_TEMPLATE.format(
+            raw_error=error_data,
+            provider=provider,
+            orig=orig))
+
+        return msg.as_string()
+
+
+def bouncerFactory(soledad):
+    acc = Account(soledad)
+    d = acc.callWhenReady(lambda _: acc.get_collection_by_mailbox(INBOX_NAME))
+    d.addCallback(lambda inbox: Bouncer(inbox))
+    return d