From 4c8d560bbff5a11d6ac7c5f9b497f678b6aaccab Mon Sep 17 00:00:00 2001
From: Andrew Lewis <nerf@judo.za.org>
Date: Tue, 20 Dec 2016 12:08:09 +0200
Subject: [PATCH] [Feature] Add preliminary version of DKIM signing module

---
 src/plugins/lua/dkim_signing.lua | 131 +++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 src/plugins/lua/dkim_signing.lua

diff --git a/src/plugins/lua/dkim_signing.lua b/src/plugins/lua/dkim_signing.lua
new file mode 100644
index 000000000..3f1e1885d
--- /dev/null
+++ b/src/plugins/lua/dkim_signing.lua
@@ -0,0 +1,131 @@
+--[[
+Copyright (c) 2016, Andrew Lewis <nerf@judo.za.org>
+Copyright (c) 2016, Vsevolod Stakhov <vsevolod@highsecure.ru>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+]]--
+
+local rspamd_logger = require "rspamd_logger"
+local rspamd_util = require "rspamd_util"
+
+local settings = {
+  allow_envfrom_empty = true,
+  allow_hdrfrom_mismatch = false,
+  allow_hdrfrom_multiple = false,
+  allow_username_mismatch = false,
+  auth_only = true,
+  domain = {},
+  path = string.format('%s/%s/%s', rspamd_paths['DBDIR'], 'dkim', '$domain.$selector.key'),
+  selector = 'dkim',
+  symbol = 'DKIM_SIGNED',
+  try_fallback = true,
+  use_domain = 'header',
+  use_esld = true,
+}
+
+local E = {}
+local N = 'dkim_signing'
+
+local function dkim_signing_cb(task)
+  local auser = task:get_user()
+  if settings.auth_only and not auser then
+    if not (settings.sign_networks and settings.sign_networks:get_key(task:get_from_ip())) then
+      rspamd_logger.debugm(N, task, 'ignoring unauthenticated user')
+      return
+    else
+      rspamd_logger.debugm(N, task, 'mail is from address in sign_networks')
+    end
+  end
+  local efrom = task:get_from('smtp')
+  if not settings.allow_envfrom_empty and
+      #(((efrom or E)[1] or E).addr or '') == 0 then
+    rspamd_logger.debugm(N, task, 'empty envelope from not allowed')
+    return false
+  end
+  local hfrom = task:get_from('mime')
+  if not settings.allow_hdrfrom_multiple and hfrom[2] then
+    rspamd_logger.debugm(N, task, 'multiple header from not allowed')
+    return false
+  end
+  local dkim_domain
+  local hdom = ((hfrom or E)[1] or E).domain
+  local edom = ((efrom or E)[1] or E).domain
+  if settings.use_domain == 'header' then
+    dkim_domain = hdom
+  else
+    dkim_domain = edom
+  end
+  if not dkim_domain then
+    rspamd_logger.debugm(N, task, 'could not extract dkim domain')
+    return false
+  end
+  if settings.use_esld then
+    dkim_domain = rspamd_util.get_tld(dkim_domain)
+  end
+  if not settings.allow_hdrfrom_mismatch and hdom ~= edom then
+    rspamd_logger.debugm(N, task, 'domain mismatch not allowed: %1 != %2', hdom, edom)
+    return false
+  end
+  if not settings.allow_username_mismatch then
+    local udom = string.match(auser, '.*@(.*)')
+    if not udom then
+      rspamd_logger.debugm(N, task, 'couldnt find domain in username')
+      return false
+    end
+    if settings.use_esld then
+      udom = rspamd_util.get_tld(udom)
+    end
+    if udom ~= dkim_domain then
+      rspamd_logger.debugm(N, task, 'user domain mismatch')
+      return false
+    end
+  end
+  local p = {}
+  if settings.domain[dkim_domain] then
+    p.selector = (settings.domain[dkim_domain] or E).selector
+    p.key = (settings.domain[dkim_domain] or E).key
+  end
+  if not (p.key and p.selector) and not settings.try_fallback then
+    rspamd_logger.debugm(N, task, 'dkim unconfigured and fallback disabled')
+    return false
+  end
+  if not p.key then
+    p.key = settings.path
+  end
+  if not p.selector then
+    p.selector = settings.selector
+  end
+  p.key = string.gsub(p.key, '$selector', p.selector)
+  p.key = string.gsub(p.key, '$domain', dkim_domain)
+  p.domain = dkim_domain
+  return rspamd_plugins.dkim.sign(task, p)
+end
+
+local opts =  rspamd_config:get_all_opt('dkim_signing')
+if not opts then return end
+for k,v in pairs(opts) do
+  if k == 'sign_networks' then
+    settings[k] = rspamd_map_add(N, k, 'radix', 'DKIM signing networks')
+  else
+    settings[k] = v
+  end
+end
+if settings.use_domain ~= 'header' and settings.use_domain ~= 'envelope' then
+  rspamd_logger.errx(rspamd_config, "Value for 'use_domain' is invalid")
+  settings.use_domain = 'header'
+end
+
+rspamd_config:register_symbol({
+  name = settings['symbol'],
+  callback = dkim_signing_cb
+})
-- 
2.39.5