[Feature] Antivirus: Add preliminary virustotal support

Issue: #3109

2 files changed, 192 insertions, 0 deletions

diff --git a/lualib/lua_scanners/init.lua b/lualib/lua_scanners/init.lua
index b92ba45d9..4c369bb8b 100644
--- a/lualib/lua_scanners/init.lua
+++ b/lualib/lua_scanners/init.lua
@@ -37,6 +37,7 @@ require_scanner('kaspersky_av')
 require_scanner('kaspersky_se')
 require_scanner('savapi')
 require_scanner('sophos')
+require_scanner('virustotal')
 
 -- Other scanners
 require_scanner('dcc')
diff --git a/lualib/lua_scanners/virustotal.lua b/lualib/lua_scanners/virustotal.lua
new file mode 100644
index 000000000..9d06f9108
--- /dev/null
+++ b/lualib/lua_scanners/virustotal.lua
@@ -0,0 +1,191 @@
+--[[
+Copyright (c) 2019, 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.
+]]--
+
+--[[[
+-- @module virustotal
+-- This module contains Virustotal integaration support
+-- https://www.virustotal.com/
+--]]
+
+local lua_util = require "lua_util"
+local http = require "rspamd_http"
+local rspamd_cryptobox_hash = require "rspamd_cryptobox_hash"
+local rspamd_logger = require "rspamd_logger"
+local common = require "lua_scanners/common"
+
+local N = 'virustotal'
+
+local function virustotal_config(opts)
+
+  local default_conf = {
+    name = N,
+    url = 'https://www.virustotal.com/vtapi/v2/file',
+    timeout = 5.0,
+    log_clean = false,
+    retransmits = 1,
+    cache_expire = 7200, -- expire redis in 2h
+    message = '${SCANNER}: spam message found: "${VIRUS}"',
+    detection_category = "virus",
+    default_score = 1,
+    action = false,
+    scan_mime_parts = true,
+    scan_text_mime = false,
+    scan_image_mime = false,
+    apikey = nil, -- Required to set by user
+    -- Specific for virustotal
+    minimum_engines = 3, -- Minimum required to get scored
+    full_score_engines = 7, -- After this number we set max score
+  }
+
+  default_conf = lua_util.override_defaults(default_conf, opts)
+
+  if not default_conf.prefix then
+    default_conf.prefix = 'rs_' .. default_conf.name .. '_'
+  end
+
+  if not default_conf.log_prefix then
+    if default_conf.name:lower() == default_conf.type:lower() then
+      default_conf.log_prefix = default_conf.name
+    else
+      default_conf.log_prefix = default_conf.name .. ' (' .. default_conf.type .. ')'
+    end
+  end
+
+  if not default_conf.apikey then
+    rspamd_logger.errx(rspamd_config, 'no apikey defined for virustotal, disable checks')
+
+    return nil
+  end
+
+  lua_util.add_debug_alias('external_services', default_conf.name)
+  return default_conf
+end
+
+local function virustotal_check(task, content, digest, rule)
+  local function virustotal_check_uncached()
+    local function make_url(hash)
+      return string.format('%s/report?apikey=%s&resource=%s',
+          rule.url, rule.apikey, hash)
+    end
+
+    local hash = rspamd_cryptobox_hash.create_specific('md5')
+    hash:update(content)
+    hash = hash:hex()
+
+    local url = make_url(hash)
+    lua_util.debugm(N, task, "send request %s", url)
+    local request_data = {
+      task = task,
+      url = url,
+      timeout = rule.timeout,
+    }
+
+    local function vt_http_callback(http_err, code, body, headers)
+      if http_err then
+        rspamd_logger.errx(task, 'HTTP error: %s, body: %s, headers: %s', http_err, body, headers)
+      else
+        local cached
+        -- Parse the response
+        if code ~= 200 then
+          if code == 404 then
+            cached = 'OK'
+            if rule['log_clean'] then
+              rspamd_logger.infox(task, '%s: hash %s clean (not found)',
+                  rule.log_prefix, hash)
+            else
+              lua_util.debugm(rule.name, task, '%s: hash %s clean (not found)',
+                  rule.log_prefix)
+            end
+          else
+            rspamd_logger.errx(task, 'invalid HTTP code: %s, body: %s, headers: %s', code, body, headers)
+            task:insert_result(rule.symbol_fail, 1.0, 'Bad HTTP code: ' .. code)
+            return
+          end
+        else
+          local ucl = require "ucl"
+          local parser = ucl.parser()
+          local res,json_err = parser:parse_string(body)
+
+          lua_util.debugm(rule.name, task, '%s: got reply data: "%s"',
+              rule.log_prefix, body)
+
+          if res then
+            local obj = parser:get_object()
+            if not obj.positives then
+              rspamd_logger.errx(task, 'invalid JSON reply: %s, body: %s, headers: %s',
+                  'no positives element', body, headers)
+              task:insert_result(rule.symbol_fail, 1.0, 'Bad JSON reply: no `positives` element')
+              return
+            end
+            if obj.positives < rule.minimum_engines then
+              lua_util.debugm(rule.name, task, '%s: hash %s has not enough hits: %s where %s is min',
+                  rule.log_prefix, obj.positives, rule.minimum_engines)
+              -- TODO: add proper hashing!
+              cached = 'OK'
+            else
+              local dyn_score
+              if obj.positives > rule.full_score_engines then
+                dyn_score = 1.0
+              else
+                local norm_pos = obj.positives - rule.minimum_engines
+                dyn_score = norm_pos / (rule.full_score_engines - rule.minimum_engines)
+              end
+
+              if dyn_score < 0 or dyn_score > 1 then
+                dyn_score = 1.0
+              end
+              common.yield_result(task, rule, {
+                hash,
+                string.format("%s/%s", obj.positives, obj.total)
+              }, dyn_score)
+              cached = hash
+            end
+          else
+            rspamd_logger.errx(task, 'invalid JSON reply: %s, body: %s, headers: %s',
+                json_err, body, headers)
+            task:insert_result(rule.symbol_fail, 1.0, 'Bad JSON reply: ' .. json_err)
+            return
+          end
+
+        end
+
+        if cached then
+          common.save_cache(task, digest, rule, cached)
+        end
+      end
+    end
+
+    request_data.callback = vt_http_callback
+    http.request(request_data)
+  end
+
+  if common.condition_check_and_continue(task, content, rule, digest,
+      virustotal_check_uncached) then
+    return
+  else
+
+    virustotal_check_uncached()
+  end
+
+end
+
+return {
+  type = 'antivirus',
+  description = 'Virustotal integration',
+  configure = virustotal_config,
+  check = virustotal_check,
+  name = N
+}