--[[
Copyright (c) 2011-2015, 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.
]]--

-- Plugin for comparing smtp dialog recipients and sender with recipients and sender
-- in mime headers

local logger = require "rspamd_logger"
local symbol_rcpt = 'FORGED_RECIPIENTS'
local symbol_sender = 'FORGED_SENDER'

local function check_forged_headers(task)
  local smtp_rcpt = task:get_recipients(1)
  local res = false
  local score = 1.0

  if smtp_rcpt then
    local mime_rcpt = task:get_recipients(2)
    local count = 0
    if mime_rcpt then
      count = table.maxn(mime_rcpt)
    end
    if count > 0 and count < table.maxn(smtp_rcpt) then
      task:insert_result(symbol_rcpt, 1)
    elseif count > 0 then
      -- Find pair for each smtp recipient recipient in To or Cc headers
      for _,sr in ipairs(smtp_rcpt) do
        if mime_rcpt then
          for _,mr in ipairs(mime_rcpt) do
            if mr['addr'] and sr['addr'] and
              string.lower(mr['addr']) == string.lower(sr['addr']) then
              res = true
              break
            elseif mr['user'] and sr['user'] and
              string.lower(mr['user']) == string.lower(sr['user']) then
              -- If we have the same username but for another domain, then
              -- lower the overall score
              score = score / 2
            end
          end
        end
        if not res then
          task:insert_result(symbol_rcpt, score)
          break
        end
      end
    end
  end
  -- Check sender
  local smtp_from = task:get_from(1)
  if smtp_from and smtp_from[1] and smtp_from[1]['addr'] ~= '' then
    local mime_from = task:get_from(2)
    if not mime_from or not mime_from[1] or
      not (string.lower(mime_from[1]['addr']) == string.lower(smtp_from[1]['addr'])) then
      task:insert_result(symbol_sender, 1)
    end
  end
end

-- Configuration
local opts =  rspamd_config:get_all_opt('forged_recipients')
if opts then
  if opts['symbol_rcpt'] or opts['symbol_sender'] then
    local id = rspamd_config:register_symbol({
      callback = check_forged_headers,
      type = 'callback',
    })
    if opts['symbol_rcpt'] then
      symbol_rcpt = opts['symbol_rcpt']
      rspamd_config:register_symbol({
        name = symbol_rcpt,
        type = 'virtual',
        parent = id,
      })
    end
    if opts['symbol_sender'] then
      symbol_sender = opts['symbol_sender']
       rspamd_config:register_symbol({
        name = symbol_sender,
        type = 'virtual',
        parent = id,
      })
    end
  end
end