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--[[
Copyright (c) 2018, 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 lua_fuzzy
-- This module contains helper functions for supporting fuzzy check module
--]]
local N = "lua_fuzzy"
local lua_util = require "lua_util"
local rspamd_regexp = require "rspamd_regexp"
local fun = require "fun"
local rspamd_logger = require "rspamd_logger"
local ts = require("tableshape").types
-- Filled by C code, indexed by number in this table
local rules = {}
-- Pre-defined rules options
local policies = {
recommended = {
min_bytes = 1024,
min_height = 500,
min_width = 500,
min_length = 64,
text_multiplier = 4.0, -- divide min_bytes by 4 for texts
mime_types = {"application/*"},
scan_archives = true,
short_text_direct_hash = true,
text_shingles = true,
skip_images = false,
}
}
local default_policy = policies.recommended
local policy_schema = ts.shape{
min_bytes = ts.number + ts.string / tonumber,
min_height = ts.number + ts.string / tonumber,
min_width = ts.number + ts.string / tonumber,
min_length = ts.number + ts.string / tonumber,
text_multiplier = ts.number,
mime_types = ts.array_of(ts.string),
scan_archives = ts.boolean,
short_text_direct_hash = ts.boolean,
text_shingles = ts.boolean,
skip_images = ts.boolean,
}
local exports = {}
--[[[
-- @function lua_fuzzy.register_policy(name, policy)
-- Adds a new policy with name `name`. Must be valid, checked using policy_schema
--]]
exports.register_policy = function(name, policy)
if policies[name] then
rspamd_logger.warnx(rspamd_config, "overriding policy %s", name)
end
local parsed_policy,err = policy_schema:transform(policy)
if not parsed_policy then
rspamd_logger.errx(rspamd_config, 'invalid fuzzy rule policy %s: %s',
name, err)
return
else
policies.name = parsed_policy
end
end
--[[[
-- @function lua_fuzzy.process_rule(rule)
-- Processes fuzzy rule (applying policies or defaults if needed). Returns policy id
--]]
exports.process_rule = function(rule)
local processed_rule = lua_util.shallowcopy(rule)
local policy = default_policy
if processed_rule.policy then
policy = policies[processed_rule.policy]
end
if policy then
processed_rule = lua_util.override_defaults(policy, processed_rule)
else
rspamd_logger.warnx(rspamd_config, "unknown policy %s", processed_rule.policy)
end
if processed_rule.mime_types then
processed_rule.mime_types = fun.totable(fun.map(function(gl)
return rspamd_regexp.import_glob(gl, 'i')
end, processed_rule.mime_types))
end
table.insert(rules, processed_rule)
return #rules
end
local function check_length(task, part, rule)
local bytes = part:get_length()
local length_ok = bytes > 0
local id = part:get_id()
lua_util.debugm(N, task, 'check size of part %s', id)
if length_ok and rule.min_bytes > 0 then
local adjusted_bytes = bytes
if part:is_text() then
bytes = part:get_text():get_length()
if rule.text_multiplier then
adjusted_bytes = bytes * rule.text_multiplier
end
end
if rule.min_bytes > adjusted_bytes then
lua_util.debugm(N, task, 'skip part of length %s (%s adjusted) ' ..
'as it has less than %s bytes',
bytes, adjusted_bytes, rule.min_bytes)
length_ok = false
else
lua_util.debugm(N, task, 'allow part of length %s (%s adjusted)',
bytes, adjusted_bytes, rule.min_bytes)
end
else
lua_util.debugm(N, task, 'allow part %s, no length limits', id)
end
return length_ok
end
local function check_text_part(task, part, rule, text)
local allow_direct,allow_shingles = false,false
local id = part:get_id()
lua_util.debugm(N, task, 'check text part %s', id)
local wcnt = text:get_words_count()
if rule.text_shingles then
-- Check number of words
local min_words = rule.min_length or 0
if min_words < 32 then
min_words = 32 -- Minimum for shingles
end
if wcnt < min_words then
lua_util.debugm(N, task, 'text has less than %s words: %s; disable shingles',
rule.min_length, wcnt)
allow_shingles = false
else
lua_util.debugm(N, task, 'allow shingles in text %s, %s words',
id, wcnt)
allow_shingles = true
end
if not rule.short_text_direct_hash and not allow_shingles then
allow_direct = false
else
if not allow_shingles then
lua_util.debugm(N, task,
'allow direct hash for short text %s, %s words',
id, wcnt)
allow_direct = check_length(task, part, rule)
else
allow_direct = wcnt > 0
end
end
else
lua_util.debugm(N, task,
'disable shingles in text %s', id)
allow_direct = check_length(task, part, rule)
end
return allow_direct,allow_shingles
end
--local function has_sane_text_parts(task)
-- local text_parts = task:get_text_parts() or {}
-- return fun.any(function(tp) return tp:get_words_count() > 32 end, text_parts)
--end
local function check_image_part(task, part, rule, image)
if rule.skip_images then
lua_util.debugm(N, task, 'skip image part as images are disabled')
return false,false
end
local id = part:get_id()
lua_util.debugm(N, task, 'check image part %s', id)
if rule.min_width > 0 or rule.min_height > 0 then
-- Check dimensions
local min_width = rule.min_width or rule.min_height
local min_height = rule.min_height or rule.min_width
local height = image:get_height()
local width = image:get_width()
if height and width then
if height < min_height or width < min_width then
lua_util.debugm(N, task, 'skip image part %s as it does not meet minimum sizes: %sx%s < %sx%s',
id, width, height, min_width, min_height)
return false, false
else
lua_util.debugm(N, task, 'allow image part %s: %sx%s',
id, width, height)
end
end
end
return check_length(task, part, rule),false
end
local function mime_types_check(task, part, rule)
local t,st = part:get_type()
if not t then return false, false end
local ct = string.format('%s/%s', t, st)
local detected_ct
t,st = part:get_detected_type()
if t then
detected_ct = string.format('%s/%s', t, st)
else
detected_ct = ct
end
local id = part:get_id()
lua_util.debugm(N, task, 'check binary part %s: %s', id, ct)
-- For bad mime parts we implicitly enable fuzzy check
local mime_trace = (task:get_symbol('MIME_TRACE') or {})[1]
local opts = {}
if mime_trace then
opts = mime_trace.options or opts
end
opts = fun.tomap(fun.map(function(opt)
local elts = lua_util.str_split(opt, ':')
return elts[1],elts[2]
end, opts))
if opts[id] and opts[id] == '-' then
lua_util.debugm(N, task, 'explicitly check binary part %s: bad mime type %s', id, ct)
return check_length(task, part, rule),false
end
if rule.mime_types then
if fun.any(function(gl_re)
if gl_re:match(ct) or (detected_ct and gl_re:match(detected_ct)) then
return true
else
return false
end
end, rule.mime_types) then
lua_util.debugm(N, task, 'found mime type match for part %s: %s (%s detected)',
id, ct, detected_ct)
return check_length(task, part, rule),false
end
return false, false
end
return false,false
end
exports.check_mime_part = function(task, part, rule_id)
local rule = rules[rule_id]
if not rule then
rspamd_logger.errx(task, 'cannot find rule with id %s', rule_id)
return false,false
end
if part:is_text() then
return check_text_part(task, part, rule, part:get_text())
end
if part:is_image() then
return check_image_part(task, part, rule, part:get_image())
end
if part:is_archive() and rule.scan_archives then
-- Always send archives
lua_util.debugm(N, task, 'check archive part %s', part:get_id())
return true,false
end
if part:is_specific() then
local sp = part:get_specific()
if type(sp) == 'table' and sp.fuzzy_hashes then
lua_util.debugm(N, task, 'check specific part %s', part:get_id())
return true,false
end
end
if part:is_attachment() then
return mime_types_check(task, part, rule)
end
return false,false
end
exports.cleanup_rules = function()
rules = {}
end
return exports
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