Add the groupsio webhook

This is the backend that receives webhook events from groups.io and
feeds them into the local postfix queue for indexing with public-inbox.

Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>

1 files changed, 119 insertions, 0 deletions

diff --git a/groupsio-webhook.py b/groupsio-webhook.py
new file mode 100644
index 0000000..5cbc5f9
--- /dev/null
+++ b/groupsio-webhook.py
@@ -0,0 +1,119 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+#
+# This webhook receives events from groups_io and injects them into the
+# local mail queue to be processed as if it came in via the SMTP gateway.
+#
+__author__ = 'Konstantin Ryabitsev <konstantin@linuxfoundation.org>'
+
+import falcon
+import json
+import socket
+import email
+import email.utils
+import email.header
+import hmac
+import smtplib
+import os
+
+
+# noinspection PyBroadException, PyMethodMayBeStatic
+class GroupsioListener(object):
+
+    def on_get(self, req, resp): # noqa
+        resp.status = falcon.HTTP_200
+        resp.body = "We don't serve GETs here\n"
+
+    def _inject_message(self, doc, req):
+        success = True
+        try:
+            msg = email.message_from_string(doc['message'])
+            try:
+                theirname = socket.gethostbyaddr(req.remote_addr)[0]
+                them = f'{theirname} [{req.remote_addr}]'
+            except:
+                them = f'[{req.remote_addr}]'
+            try:
+                us = socket.gethostname()
+            except:
+                us = 'localhost'
+
+            groupaddr = doc['group']['email_address']
+            groupurl = doc['group']['group_url']
+            listid = groupaddr.replace('@', '.')
+            scheme = req.scheme.upper()
+            rdate = email.utils.formatdate()
+            rline = f'from {them} by {us} with {scheme} for <{groupaddr}>; {rdate}'
+            rhdr = email.header.make_header([(rline.encode(), 'us-ascii')], maxlinelen=78)
+            if msg.get('list-id'):
+                msg.replace_header('List-Id', f'<{listid}>')
+            else:
+                msg.add_header('List-Id', f'<{listid}>')
+            msg.add_header('X-Webhook-Received', rhdr.encode())
+            msgnum = doc['msg_num']
+            msg.add_header('X-Groupsio-URL', f'{groupurl}/message/{msgnum}')
+
+            try:
+                mailfrom = doc['member_info']['email']
+            except:
+                mailfrom = 'webhook@localhost'
+
+            mailhost = os.getenv('MAILHOST', 'localhost')
+            mailto = os.getenv('MAILTO', 'webhook@archiver.kernel.org')
+
+            smtp = smtplib.SMTP(mailhost)
+            smtp.sendmail(mailfrom, [mailto], msg.as_bytes())
+            smtp.close()
+
+        except:
+            return False
+
+        return success
+
+    def _verify_psk(self, psk, raw, vdigest):
+        hm = hmac.new(psk.encode(), digestmod='sha256')
+        hm.update(raw)
+        return hmac.compare_digest(vdigest, hm.hexdigest())
+
+    def on_post(self, req, resp):
+        if not req.content_length:
+            resp.status = falcon.HTTP_500
+            resp.body = 'Payload required\n'
+            return
+
+        raw = req.stream.read()
+        psk = os.getenv('GROUPSIO_PSK')
+        if psk:
+            vdigest = req.get_header('X-Groupsio-Signature')
+            if not vdigest:
+                resp.status = falcon.HTTP_401
+                resp.body = 'HMAC signature header required\n'
+                return
+            if not self._verify_psk(psk, raw, vdigest):
+                resp.status = falcon.HTTP_401
+                resp.body = 'HMAC signature verification failed\n'
+                return
+
+        try:
+            doc = json.loads(raw)
+        except:
+            resp.status = falcon.HTTP_500
+            resp.body = 'Failed to parse payload as json\n'
+            return
+
+        success = True
+        if doc.get('action', '') == 'sent_message_accepted' and 'message' in doc:
+            success = self._inject_message(doc, req)
+
+        if success:
+            resp.status = falcon.HTTP_200
+            resp.body = 'OK thanks\n'
+        else:
+            resp.status = falcon.HTTP_500
+            resp.body = 'Something went wrong, sorry.\n'
+
+
+app = falcon.API()
+gl = GroupsioListener()
+mp = os.getenv('MOUNTPOINT', '/groupsio_webhook')
+app.add_route(mp, gl)