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Editing: virustotal.lua
--[[ Copyright (c) 2022, Vsevolod Stakhov <vsevolod@rspamd.com> 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 integration 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 -- Threshold-based categorization low_category = 5, -- Low threat: minimum_engines to low_category-1 medium_category = 10, -- Medium threat: low_category to medium_category-1 -- High threat: medium_category and above -- Symbol categories symbols = { clean = { symbol = 'VIRUSTOTAL_CLEAN', score = -0.5, description = 'VirusTotal decided attachment to be clean' }, low = { symbol = 'VIRUSTOTAL_LOW', score = 2.0, description = 'VirusTotal found low number of threats' }, medium = { symbol = 'VIRUSTOTAL_MEDIUM', score = 5.0, description = 'VirusTotal found medium number of threats' }, high = { symbol = 'VIRUSTOTAL_HIGH', score = 8.0, description = 'VirusTotal found high number of threats' }, }, } 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, maybe_part) 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, hash) end elseif code == 204 then -- Request rate limit exceeded rspamd_logger.infox(task, 'virustotal request rate limit exceeded') task:insert_result(rule.symbol_fail, 1.0, 'rate limit exceeded') return 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 or type(obj.positives) ~= 'number' then if obj.response_code then if obj.response_code == 0 then 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, hash) end -- Insert CLEAN symbol if rule.symbols and rule.symbols.clean then local clean_sym = rule.symbols.clean.symbol or 'VIRUSTOTAL_CLEAN' local sopt = string.format("%s:0", hash) task:insert_result(clean_sym, 1.0, sopt) -- Save with symbol name for proper cache retrieval cached = string.format("%s\v%s", clean_sym, sopt) else cached = 'OK' end else rspamd_logger.errx(task, 'invalid JSON reply: %s, body: %s, headers: %s', 'bad response code: ' .. tostring(obj.response_code), body, headers) task:insert_result(rule.symbol_fail, 1.0, 'Bad JSON reply: no `positives` element') return end else rspamd_logger.errx(task, 'invalid JSON reply: %s, body: %s, headers: %s', 'no response_code', body, headers) task:insert_result(rule.symbol_fail, 1.0, 'Bad JSON reply: no `positives` element') return end else if obj.positives == 0 then if rule['log_clean'] then rspamd_logger.infox(task, '%s: hash %s clean', rule.log_prefix, hash) else lua_util.debugm(rule.name, task, '%s: hash %s clean', rule.log_prefix, hash) end -- Insert CLEAN symbol if rule.symbols and rule.symbols.clean then local clean_sym = rule.symbols.clean.symbol or 'VIRUSTOTAL_CLEAN' local sopt = string.format("%s:0/%s", hash, obj.total or 0) task:insert_result(clean_sym, 1.0, sopt) -- Save with symbol name for proper cache retrieval cached = string.format("%s\v%s", clean_sym, sopt) else cached = 'OK' end elseif 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, hash, obj.positives, rule.minimum_engines) cached = 'OK' else -- Determine category based on detection count local category local category_sym local sopt = string.format("%s:%s/%s", hash, obj.positives, obj.total) if obj.positives >= rule.medium_category then category = 'high' category_sym = rule.symbols.high.symbol or 'VIRUSTOTAL_HIGH' elseif obj.positives >= rule.low_category then category = 'medium' category_sym = rule.symbols.medium.symbol or 'VIRUSTOTAL_MEDIUM' else category = 'low' category_sym = rule.symbols.low.symbol or 'VIRUSTOTAL_LOW' end rspamd_logger.infox(task, '%s: result - %s: "%s" - category: %s', rule.log_prefix, rule.detection_category .. 'found', sopt, category) task:insert_result(category_sym, 1.0, sopt) -- Save with symbol name for proper cache retrieval cached = string.format("%s\v%s", category_sym, sopt) end end else -- not res 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, 1.0, maybe_part) 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 }
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