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|
--[[
Copyright (c) 2022, Vsevolod Stakhov <vsevolod@rspamd.com>
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 lua_scanners_common
-- This module contains common external scanners functions
--]]
local rspamd_logger = require "rspamd_logger"
local rspamd_regexp = require "rspamd_regexp"
local lua_util = require "lua_util"
local lua_redis = require "lua_redis"
local lua_magic_types = require "lua_magic/types"
local fun = require "fun"
local exports = {}
local function log_clean(task, rule, msg)
msg = msg or 'message or mime_part is clean'
if rule.log_clean then
rspamd_logger.infox(task, '%s: %s', rule.log_prefix, msg)
else
lua_util.debugm(rule.name, task, '%s: %s', rule.log_prefix, msg)
end
end
local function match_patterns(default_sym, found, patterns, dyn_weight)
if type(patterns) ~= 'table' then return default_sym, dyn_weight end
if not patterns[1] then
for sym, pat in pairs(patterns) do
if pat:match(found) then
return sym, '1'
end
end
return default_sym, dyn_weight
else
for _, p in ipairs(patterns) do
for sym, pat in pairs(p) do
if pat:match(found) then
return sym, '1'
end
end
end
return default_sym, dyn_weight
end
end
local function yield_result(task, rule, vname, dyn_weight, is_fail, maybe_part)
local all_whitelisted = true
local patterns
local symbol
local threat_table
local threat_info
local flags
if type(vname) == 'string' then
threat_table = {vname}
elseif type(vname) == 'table' then
threat_table = vname
end
-- This should be more generic
if not is_fail then
patterns = rule.patterns
symbol = rule.symbol
threat_info = rule.detection_category .. 'found'
if not dyn_weight then dyn_weight = 1.0 end
elseif is_fail == 'fail' then
patterns = rule.patterns_fail
symbol = rule.symbol_fail
threat_info = "FAILED with error"
dyn_weight = 0.0
elseif is_fail == 'encrypted' then
patterns = rule.patterns
symbol = rule.symbol_encrypted
threat_info = "Scan has returned that input was encrypted"
dyn_weight = 1.0
elseif is_fail == 'macro' then
patterns = rule.patterns
symbol = rule.symbol_macro
threat_info = "Scan has returned that input contains macros"
dyn_weight = 1.0
end
for _, tm in ipairs(threat_table) do
local symname, symscore = match_patterns(symbol, tm, patterns, dyn_weight)
if rule.whitelist and rule.whitelist:get_key(tm) then
rspamd_logger.infox(task, '%s: "%s" is in whitelist', rule.log_prefix, tm)
else
all_whitelisted = false
rspamd_logger.infox(task, '%s: result - %s: "%s - score: %s"',
rule.log_prefix, threat_info, tm, symscore)
if maybe_part and rule.show_attachments and maybe_part:get_filename() then
local fname = maybe_part:get_filename()
task:insert_result(symname, symscore, string.format("%s|%s",
tm, fname))
else
task:insert_result(symname, symscore, tm)
end
end
end
if rule.action and is_fail ~= 'fail' and not all_whitelisted then
threat_table = table.concat(threat_table, '; ')
if rule.action ~= 'reject' then
flags = 'least'
end
task:set_pre_result(rule.action,
lua_util.template(rule.message or 'Rejected', {
SCANNER = rule.name,
VIRUS = threat_table,
}), rule.name, nil, nil, flags)
end
end
local function message_not_too_large(task, content, rule)
local max_size = tonumber(rule.max_size)
if not max_size then return true end
if #content > max_size then
rspamd_logger.infox(task, "skip %s check as it is too large: %s (%s is allowed)",
rule.log_prefix, #content, max_size)
return false
end
return true
end
local function message_not_too_small(task, content, rule)
local min_size = tonumber(rule.min_size)
if not min_size then return true end
if #content < min_size then
rspamd_logger.infox(task, "skip %s check as it is too small: %s (%s is allowed)",
rule.log_prefix, #content, min_size)
return false
end
return true
end
local function message_min_words(task, rule)
if rule.text_part_min_words and tonumber(rule.text_part_min_words) > 0 then
local text_part_above_limit = false
local text_parts = task:get_text_parts()
local filter_func = function(p)
return p:get_words_count() >= tonumber(rule.text_part_min_words)
end
fun.each(function(p)
text_part_above_limit = true
end, fun.filter(filter_func, text_parts))
if not text_part_above_limit then
rspamd_logger.infox(task, '%s: #words in all text parts is below text_part_min_words limit: %s',
rule.log_prefix, rule.text_part_min_words)
end
return text_part_above_limit
else
return true
end
end
local function dynamic_scan(task, rule)
if rule.dynamic_scan then
if rule.action ~= 'reject' then
local metric_result = task:get_metric_score('default')
local metric_action = task:get_metric_action('default')
local has_pre_result = task:has_pre_result()
-- ToDo: needed?
-- Sometimes leads to FPs
--if rule.symbol_type == 'postfilter' and metric_action == 'reject' then
-- rspamd_logger.infox(task, '%s: aborting: %s', rule.log_prefix, "result is already reject")
-- return false
--elseif metric_result[1] > metric_result[2]*2 then
if metric_result[1] > metric_result[2]*2 then
rspamd_logger.infox(task, '%s: aborting: %s', rule.log_prefix, 'score > 2 * reject_level: ' .. metric_result[1])
return false
elseif has_pre_result and metric_action == 'reject' then
rspamd_logger.infox(task, '%s: aborting: %s', rule.log_prefix, 'pre_result reject is set')
return false
else
return true, 'undecided'
end
else
return true, 'dynamic_scan is not possible with config `action=reject;`'
end
else
return true
end
end
local function need_check(task, content, rule, digest, fn, maybe_part)
local uncached = true
local key = digest
local function redis_av_cb(err, data)
if data and type(data) == 'string' then
-- Cached
data = lua_util.str_split(data, '\t')
local threat_string = lua_util.str_split(data[1], '\v')
local score = data[2] or rule.default_score
if threat_string[1] ~= 'OK' then
if threat_string[1] == 'MACRO' then
yield_result(task, rule, 'File contains macros',
0.0, 'macro', maybe_part)
elseif threat_string[1] == 'ENCRYPTED' then
yield_result(task, rule, 'File is encrypted',
0.0, 'encrypted', maybe_part)
else
lua_util.debugm(rule.name, task, '%s: got cached threat result for %s: %s - score: %s',
rule.log_prefix, key, threat_string[1], score)
yield_result(task, rule, threat_string, score, false, maybe_part)
end
else
lua_util.debugm(rule.name, task, '%s: got cached negative result for %s: %s',
rule.log_prefix, key, threat_string[1])
end
uncached = false
else
if err then
rspamd_logger.errx(task, 'got error checking cache: %s', err)
end
end
local f_message_not_too_large = message_not_too_large(task, content, rule)
local f_message_not_too_small = message_not_too_small(task, content, rule)
local f_message_min_words = message_min_words(task, rule)
local f_dynamic_scan = dynamic_scan(task, rule)
if uncached and
f_message_not_too_large and
f_message_not_too_small and
f_message_min_words and
f_dynamic_scan then
fn()
end
end
if rule.redis_params and not rule.no_cache then
key = rule.prefix .. key
if lua_redis.redis_make_request(task,
rule.redis_params, -- connect params
key, -- hash key
false, -- is write
redis_av_cb, --callback
'GET', -- command
{key} -- arguments)
) then
return true
end
end
return false
end
local function save_cache(task, digest, rule, to_save, dyn_weight, maybe_part)
local key = digest
if not dyn_weight then dyn_weight = 1.0 end
local function redis_set_cb(err)
-- Do nothing
if err then
rspamd_logger.errx(task, 'failed to save %s cache for %s -> "%s": %s',
rule.detection_category, to_save, key, err)
else
lua_util.debugm(rule.name, task, '%s: saved cached result for %s: %s - score %s - ttl %s',
rule.log_prefix, key, to_save, dyn_weight, rule.cache_expire)
end
end
if type(to_save) == 'table' then
to_save = table.concat(to_save, '\v')
end
local value_tbl = {to_save, dyn_weight}
if maybe_part and rule.show_attachments and maybe_part:get_filename() then
local fname = maybe_part:get_filename()
table.insert(value_tbl, fname)
end
local value = table.concat(value_tbl, '\t')
if rule.redis_params and rule.prefix then
key = rule.prefix .. key
lua_redis.redis_make_request(task,
rule.redis_params, -- connect params
key, -- hash key
true, -- is write
redis_set_cb, --callback
'SETEX', -- command
{ key, rule.cache_expire or 0, value }
)
end
return false
end
local function create_regex_table(patterns)
local regex_table = {}
if patterns[1] then
for i, p in ipairs(patterns) do
if type(p) == 'table' then
local new_set = {}
for k, v in pairs(p) do
new_set[k] = rspamd_regexp.create_cached(v)
end
regex_table[i] = new_set
else
regex_table[i] = {}
end
end
else
for k, v in pairs(patterns) do
regex_table[k] = rspamd_regexp.create_cached(v)
end
end
return regex_table
end
local function match_filter(task, rule, found, patterns, pat_type)
if type(patterns) ~= 'table' or not found then
return false
end
if not patterns[1] then
for _, pat in pairs(patterns) do
if pat_type == 'ext' and tostring(pat) == tostring(found) then
return true
elseif pat_type == 'regex' and pat:match(found) then
return true
end
end
return false
else
for _, p in ipairs(patterns) do
for _, pat in ipairs(p) do
if pat_type == 'ext' and tostring(pat) == tostring(found) then
return true
elseif pat_type == 'regex' and pat:match(found) then
return true
end
end
end
return false
end
end
-- borrowed from mime_types.lua
-- ext is the last extension, LOWERCASED
-- ext2 is the one before last extension LOWERCASED
local function gen_extension(fname)
local filename_parts = lua_util.str_split(fname, '.')
local ext = {}
for n = 1, 2 do
ext[n] = #filename_parts > n and string.lower(filename_parts[#filename_parts + 1 - n]) or nil
end
return ext[1],ext[2],filename_parts
end
local function check_parts_match(task, rule)
local filter_func = function(p)
local mtype,msubtype = p:get_type()
local detected_ext = p:get_detected_ext()
local fname = p:get_filename()
local ext, ext2
if rule.scan_all_mime_parts == false then
-- check file extension and filename regex matching
--lua_util.debugm(rule.name, task, '%s: filename: |%s|%s|', rule.log_prefix, fname)
if fname ~= nil then
ext,ext2 = gen_extension(fname)
--lua_util.debugm(rule.name, task, '%s: extension, fname: |%s|%s|%s|', rule.log_prefix, ext, ext2, fname)
if match_filter(task, rule, ext, rule.mime_parts_filter_ext, 'ext')
or match_filter(task, rule, ext2, rule.mime_parts_filter_ext, 'ext') then
lua_util.debugm(rule.name, task, '%s: extension matched: |%s|%s|', rule.log_prefix, ext, ext2)
return true
elseif match_filter(task, rule, fname, rule.mime_parts_filter_regex, 'regex') then
lua_util.debugm(rule.name, task, '%s: filename regex matched', rule.log_prefix)
return true
end
end
-- check content type string regex matching
if mtype ~= nil and msubtype ~= nil then
local ct = string.format('%s/%s', mtype, msubtype):lower()
if match_filter(task, rule, ct, rule.mime_parts_filter_regex, 'regex') then
lua_util.debugm(rule.name, task, '%s: regex content-type: %s', rule.log_prefix, ct)
return true
end
end
-- check detected content type (libmagic) regex matching
if detected_ext then
local magic = lua_magic_types[detected_ext] or {}
if match_filter(task, rule, detected_ext, rule.mime_parts_filter_ext, 'ext') then
lua_util.debugm(rule.name, task, '%s: detected extension matched: |%s|', rule.log_prefix, detected_ext)
return true
elseif magic.ct and match_filter(task, rule, magic.ct, rule.mime_parts_filter_regex, 'regex') then
lua_util.debugm(rule.name, task, '%s: regex detected libmagic content-type: %s',
rule.log_prefix, magic.ct)
return true
end
end
-- check filenames in archives
if p:is_archive() then
local arch = p:get_archive()
local filelist = arch:get_files_full(1000)
for _,f in ipairs(filelist) do
ext,ext2 = gen_extension(f.name)
if match_filter(task, rule, ext, rule.mime_parts_filter_ext, 'ext')
or match_filter(task, rule, ext2, rule.mime_parts_filter_ext, 'ext') then
lua_util.debugm(rule.name, task, '%s: extension matched in archive: |%s|%s|', rule.log_prefix, ext, ext2)
--lua_util.debugm(rule.name, task, '%s: extension matched in archive: %s', rule.log_prefix, ext)
return true
elseif match_filter(task, rule, f.name, rule.mime_parts_filter_regex, 'regex') then
lua_util.debugm(rule.name, task, '%s: filename regex matched in archive', rule.log_prefix)
return true
end
end
end
end
-- check text_part has more words than text_part_min_words_check
if rule.scan_text_mime and rule.text_part_min_words and p:is_text() and
p:get_words_count() >= tonumber(rule.text_part_min_words) then
return true
end
if rule.scan_image_mime and p:is_image() then
return true
end
if rule.scan_all_mime_parts ~= false then
local is_part_checkable = (p:is_attachment() and (not p:is_image() or rule.scan_image_mime))
if detected_ext then
-- We know what to scan!
local magic = lua_magic_types[detected_ext] or {}
if magic.av_check ~= false or is_part_checkable then
return true
end
elseif is_part_checkable then
-- Just rely on attachment property
return true
end
end
return false
end
return fun.filter(filter_func, task:get_parts())
end
local function check_metric_results(task, rule)
if rule.action ~= 'reject' then
local metric_result = task:get_metric_score('default')
local metric_action = task:get_metric_action('default')
local has_pre_result = task:has_pre_result()
if rule.symbol_type == 'postfilter' and metric_action == 'reject' then
return true, 'result is already reject'
elseif metric_result[1] > metric_result[2]*2 then
return true, 'score > 2 * reject_level: ' .. metric_result[1]
elseif has_pre_result and metric_action == 'reject' then
return true, 'pre_result reject is set'
else
return false, 'undecided'
end
else
return false, 'dynamic_scan is not possible with config `action=reject;`'
end
end
exports.log_clean = log_clean
exports.yield_result = yield_result
exports.match_patterns = match_patterns
exports.condition_check_and_continue = need_check
exports.save_cache = save_cache
exports.create_regex_table = create_regex_table
exports.check_parts_match = check_parts_match
exports.check_metric_results = check_metric_results
setmetatable(exports, {
__call = function(t, override)
for k, v in pairs(t) do
if _G[k] ~= nil then
local msg = 'function ' .. k .. ' already exists in global scope.'
if override then
_G[k] = v
print('WARNING: ' .. msg .. ' Overwritten.')
else
print('NOTICE: ' .. msg .. ' Skipped.')
end
else
_G[k] = v
end
end
end,
})
return exports
|