[Feature] lua_scanners - spamassassin spam scanner

diff --git a/lualib/lua_scanners/spamassassin.lua b/lualib/lua_scanners/spamassassin.lua
new file mode 100644 (file)
index 0000000..eae9346
--- /dev/null
+++ b/lualib/lua_scanners/spamassassin.lua
@@ -0,0 +1,217 @@
+--[[
+Copyright (c) 2019, Vsevolod Stakhov <vsevolod@highsecure.ru>
+Copyright (c) 2019, Carsten Rosenberg <c.rosenberg@heinlein-support.de>
+
+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.
+]]--
+
+--[[[
+-- @module spamassassin
+-- This module contains spamd access functions.
+--]]
+
+local lua_util = require "lua_util"
+local tcp = require "rspamd_tcp"
+local upstream_list = require "rspamd_upstream_list"
+local rspamd_logger = require "rspamd_logger"
+local common = require "lua_scanners/common"
+
+local N = 'spamassassin'
+
+local function spamassassin_check(task, content, digest, rule)
+  local function spamassassin_check_uncached ()
+    local upstream = rule.upstreams:get_upstream_round_robin()
+    local addr = upstream:get_addr()
+    local retransmits = rule.retransmits
+
+    -- Build the spamd query
+    -- https://svn.apache.org/repos/asf/spamassassin/trunk/spamd/PROTOCOL
+    local request_data = {
+      "HEADERS SPAMC/1.5\r\n",
+      "User: root\r\n",
+      "Content-length: ".. #content .. "\r\n",
+      "\r\n",
+      content,
+    }
+
+    local function spamassassin_callback(err, data, conn)
+
+      local function spamassassin_requery(error)
+        -- set current upstream to fail because an error occurred
+        upstream:fail()
+
+        -- retry with another upstream until retransmits exceeds
+        if retransmits > 0 then
+
+          retransmits = retransmits - 1
+
+          lua_util.debugm(rule.N, task, '%s: Request Error: %s - retries left: %s',
+            rule.log_prefix, error, retransmits)
+
+          -- Select a different upstream!
+          upstream = rule.upstreams:get_upstream_round_robin()
+          addr = upstream:get_addr()
+
+          lua_util.debugm(rule.N, task, '%s: retry IP: %s:%s',
+            rule.log_prefix, addr, addr:get_port())
+
+          tcp.request({
+            task = task,
+            host = addr:to_string(),
+            port = addr:get_port(),
+            timeout = rule['timeout'],
+            data = request_data,
+            callback = spamassassin_callback,
+          })
+        else
+          rspamd_logger.errx(task, '%s: failed to scan, maximum retransmits '..
+            'exceed - err: %s', rule.log_prefix, error)
+          common.yield_result(task, rule, 'failed to scan and retransmits exceed: ' .. error, 0.0, 'fail')
+        end
+      end
+
+      if err then
+
+        spamassassin_requery(err)
+
+      else
+        -- Parse the response
+        if upstream then upstream:ok() end
+
+        --lua_util.debugm(rule.N, task, '%s: returned result: %s', rule.log_prefix, data)
+
+        --[[
+        patterns tested against Spamassassin 3.4.2
+
+        Spam: False ; 1.1 / 5.0
+
+        X-Spam-Status: No, score=1.1 required=5.0 tests=HTML_MESSAGE,MIME_HTML_ONLY,
+          TVD_RCVD_SPACE_BRACKET,UNPARSEABLE_RELAY autolearn=no
+          autolearn_force=no version=3.4.2
+        ]] --
+        local header = string.gsub(tostring(data), "[\r\n]+[\t ]", " ")
+        --lua_util.debugm(rule.N, task, '%s: returned header: %s', rule.log_prefix, header)
+
+        local symbols
+        local spam_score
+        for s in header:gmatch("[^\r\n]+") do
+            if string.find(s, 'Spam: .* / 5.0') then
+              local pattern_symbols = "(Spam:.*; )(%-?%d?%d%.%d)( / 5%.0)"
+              spam_score = string.gsub(s, pattern_symbols, "%2")
+              lua_util.debugm(rule.N, task, '%s: spamd Spam line: %s', rule.log_prefix, spam_score)
+            end
+            if string.find(s, 'X%-Spam%-Status') then
+              local pattern_symbols = "(.*X%-Spam%-Status.*tests%=)(.*)(autolearn%=.*version%=%d%.%d%.%d.*)"
+              symbols = string.gsub(s, pattern_symbols, "%2")
+              symbols = string.gsub(symbols, "%s", "")
+            end
+        end
+
+        if tonumber(spam_score) > 0 and #symbols > 0 and symbols ~= "none" then
+
+          if rule.extended == false then
+            common.yield_result(task, rule, symbols, spam_score)
+            common.save_av_cache(task, digest, rule, symbols, spam_score)
+          else
+            local symbols_table = {}
+            symbols_table = rspamd_str_split(symbols, ",")
+            lua_util.debugm(rule.N, task, '%s: returned symbols as table: %s', rule.log_prefix, symbols_table)
+
+            common.yield_result(task, rule, symbols_table, spam_score)
+            common.save_av_cache(task, digest, rule, symbols_table, spam_score)
+          end
+        else
+          common.log_clean(task, rule, 'no spam detected - spam score: ' .. spam_score .. ', symbols: ' .. symbols)
+        end
+      end
+    end
+
+    tcp.request({
+      task = task,
+      host = addr:to_string(),
+      port = addr:get_port(),
+      timeout = rule['timeout'],
+      data = request_data,
+      callback = spamassassin_callback,
+    })
+  end
+  if common.need_av_check(task, content, rule) then
+    if common.check_av_cache(task, digest, rule, spamassassin_check_uncached) then
+      return
+    else
+      spamassassin_check_uncached()
+    end
+  end
+end
+
+local function spamassassin_config(opts)
+
+  local spamassassin_conf = {
+    N = N,
+    scan_mime_parts = false,
+    scan_text_mime = false,
+    scan_image_mime = false,
+    default_port = 783,
+    timeout = 15.0,
+    log_clean = false,
+    retransmits = 2,
+    cache_expire = 3600, -- expire redis in one hour
+    symbol = "SPAMD",
+    message = '${SCANNER}: Spamassassin bulk message found: "${VIRUS}"',
+    detection_category = "spam",
+    default_score = 1,
+    action = false,
+    extended = false,
+  }
+
+  spamassassin_conf = lua_util.override_defaults(spamassassin_conf, opts)
+
+  if not spamassassin_conf.prefix then
+    spamassassin_conf.prefix = 'rs_' .. spamassassin_conf.name .. '_'
+  end
+
+  if not spamassassin_conf.log_prefix then
+    if spamassassin_conf.name:lower() == spamassassin_conf.type:lower() then
+      spamassassin_conf.log_prefix = spamassassin_conf.name
+    else
+      spamassassin_conf.log_prefix = spamassassin_conf.name .. ' (' .. spamassassin_conf.type .. ')'
+    end
+  end
+
+  if not spamassassin_conf.servers then
+    rspamd_logger.errx(rspamd_config, 'no servers defined')
+
+    return nil
+  end
+
+  spamassassin_conf.upstreams = upstream_list.create(rspamd_config,
+    spamassassin_conf.servers,
+    spamassassin_conf.default_port)
+
+  if spamassassin_conf.upstreams then
+    lua_util.add_debug_alias('external_services', spamassassin_conf.N)
+    return spamassassin_conf
+  end
+
+  rspamd_logger.errx(rspamd_config, 'cannot parse servers %s',
+    spamassassin_conf.servers)
+  return nil
+end
+
+return {
+  type = {N,'spam', 'scanner'},
+  description = 'spamassassin spam scanner',
+  configure = spamassassin_config,
+  check = spamassassin_check,
+  name = N
+}