--[[ Copyright (c) 2017, Vsevolod Stakhov 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. ]] -- local rspamd_logger = require "rspamd_logger" local lua_util = require "lua_util" local dkim_sign_tools = require "lua_dkim_tools" local rspamd_util = require "rspamd_util" local rspamd_rsa_privkey = require "rspamd_rsa_privkey" local rspamd_rsa = require "rspamd_rsa" local fun = require "fun" local auth_results = require "lua_auth_results" local hash = require "rspamd_cryptobox_hash" if confighelp then return end local N = 'arc' if not rspamd_plugins.dkim then rspamd_logger.errx(rspamd_config, "cannot enable arc plugin: dkim is disabled") return end local dkim_verify = rspamd_plugins.dkim.verify local dkim_sign = rspamd_plugins.dkim.sign local dkim_canonicalize = rspamd_plugins.dkim.canon_header_relaxed local redis_params if not dkim_verify or not dkim_sign or not dkim_canonicalize then rspamd_logger.errx(rspamd_config, "cannot enable arc plugin: dkim is disabled") return end local arc_symbols = { allow = 'ARC_ALLOW', invalid = 'ARC_INVALID', dnsfail = 'ARC_DNSFAIL', na = 'ARC_NA', reject = 'ARC_REJECT', } local symbols = { spf_allow_symbol = 'R_SPF_ALLOW', spf_deny_symbol = 'R_SPF_FAIL', spf_softfail_symbol = 'R_SPF_SOFTFAIL', spf_neutral_symbol = 'R_SPF_NEUTRAL', spf_tempfail_symbol = 'R_SPF_DNSFAIL', spf_permfail_symbol = 'R_SPF_PERMFAIL', spf_na_symbol = 'R_SPF_NA', dkim_allow_symbol = 'R_DKIM_ALLOW', dkim_deny_symbol = 'R_DKIM_REJECT', dkim_tempfail_symbol = 'R_DKIM_TEMPFAIL', dkim_na_symbol = 'R_DKIM_NA', dkim_permfail_symbol = 'R_DKIM_PERMFAIL', } local settings = { allow_envfrom_empty = true, allow_hdrfrom_mismatch = false, allow_hdrfrom_mismatch_local = false, allow_hdrfrom_mismatch_sign_networks = false, allow_hdrfrom_multiple = false, allow_username_mismatch = false, auth_only = true, domain = {}, path = string.format('%s/%s/%s', rspamd_paths['DBDIR'], 'arc', '$domain.$selector.key'), sign_local = true, selector = 'arc', sign_symbol = 'ARC_SIGNED', try_fallback = true, use_domain = 'header', use_esld = true, use_redis = false, key_prefix = 'arc_keys', -- default hash name reuse_auth_results = false, -- Reuse the existing authentication results } local function parse_arc_header(hdr, target) local arr = fun.totable(fun.map( function(val) return fun.totable(fun.map(lua_util.rspamd_str_trim, fun.filter(function(v) return v and #v > 0 end, lua_util.rspamd_str_split(val.decoded, ';')))) end, hdr )) -- Now we have two tables in format: -- [sigs] -> [{sig1_elts}, {sig2_elts}...] for i,elts in ipairs(arr) do fun.each(function(v) if not target[i] then target[i] = {} end if v[1] and v[2] then target[i][v[1]] = v[2] end end, fun.map(function(elt) return lua_util.rspamd_str_split(elt, '=') end, elts)) target[i].header = hdr[i].decoded target[i].raw_header = hdr[i].value end end local function arc_validate_seals(task, seals, sigs, seal_headers, sig_headers) for i = 1,#seals do if (sigs[i].i or 0) ~= i then rspamd_logger.infox(task, 'bad i value for signature: %s, expected %s', sigs[i].i, i) task:insert_result(arc_symbols['invalid'], 1.0, 'invalid count of seals and signatures') return false end if (seals[i].i or 0) ~= i then rspamd_logger.infox(task, 'bad i value for seal: %s, expected %s', seals[i].i, i) task:insert_result(arc_symbols['invalid'], 1.0, 'invalid count of seals and signatures') return false end if not seals[i].cv then task:insert_result(arc_symbols['invalid'], 1.0, 'no cv on i=' .. tostring(i)) return false end if i == 1 then -- We need to ensure that cv of seal is equal to 'none' if seals[i].cv ~= 'none' then task:insert_result(arc_symbols['invalid'], 1.0, 'cv is not "none" for i=1') return false end else if seals[i].cv ~= 'pass' then task:insert_result(arc_symbols['reject'], 1.0, string.format('cv is %s on i=%d', seals[i].cv, i)) return false end end end return true end local function arc_callback(task) local arc_sig_headers = task:get_header_full('ARC-Message-Signature') local arc_seal_headers = task:get_header_full('ARC-Seal') if not arc_sig_headers or not arc_seal_headers then task:insert_result(arc_symbols['na'], 1.0) return end if #arc_sig_headers ~= #arc_seal_headers then -- We mandate that count of seals is equal to count of signatures rspamd_logger.infox(task, 'number of seals (%s) is not equal to number of signatures (%s)', #arc_seal_headers, #arc_sig_headers) task:insert_result(arc_symbols['invalid'], 'invalid count of seals and signatures') return end local cbdata = { seals = {}, sigs = {}, checked = 0, res = 'success', errors = {} } parse_arc_header(arc_seal_headers, cbdata.seals) parse_arc_header(arc_sig_headers, cbdata.sigs) -- Fix i type fun.each(function(hdr) hdr.i = tonumber(hdr.i) or 0 end, cbdata.seals) fun.each(function(hdr) hdr.i = tonumber(hdr.i) or 0 end, cbdata.sigs) -- Now we need to sort elements according to their [i] value table.sort(cbdata.seals, function(e1, e2) return (e1.i or 0) < (e2.i or 0) end) table.sort(cbdata.sigs, function(e1, e2) return (e1.i or 0) < (e2.i or 0) end) lua_util.debugm(N, task, 'got %s arc sections', #cbdata.seals) -- Now check sanity of what we have if not arc_validate_seals(task, cbdata.seals, cbdata.sigs, arc_seal_headers, arc_sig_headers) then return end task:cache_set('arc-sigs', cbdata.sigs) task:cache_set('arc-seals', cbdata.seals) local function arc_seal_cb(_, res, err, domain) cbdata.checked = cbdata.checked + 1 lua_util.debugm(N, task, 'checked arc seal: %s(%s), %s processed', res, err, cbdata.checked) if not res then cbdata.res = 'fail' if err and domain then table.insert(cbdata.errors, string.format('sig:%s:%s', domain, err)) end end if cbdata.checked == #arc_sig_headers then if cbdata.res == 'success' then task:insert_result(arc_symbols['allow'], 1.0, 'i=' .. tostring(cbdata.checked)) else task:insert_result(arc_symbols['reject'], 1.0, rspamd_logger.slog('seal check failed: %s, %s', cbdata.res, cbdata.errors)) end end end local function arc_signature_cb(_, res, err, domain) lua_util.debugm(N, task, 'checked arc signature %s: %s(%s), %s processed', domain, res, err, cbdata.checked) if not res then cbdata.res = 'fail' if err and domain then table.insert(cbdata.errors, string.format('sig:%s:%s', domain, err)) end end if cbdata.res == 'success' then -- Verify seals cbdata.checked = 0 fun.each( function(sig) local ret, lerr = dkim_verify(task, sig.header, arc_seal_cb, 'arc-seal') if not ret then cbdata.res = 'fail' table.insert(cbdata.errors, string.format('sig:%s:%s', sig.d or '', lerr)) cbdata.checked = cbdata.checked + 1 lua_util.debugm(N, task, 'checked arc seal %s: %s(%s), %s processed', sig.d, ret, lerr, cbdata.checked) end end, cbdata.seals) else task:insert_result(arc_symbols['reject'], 1.0, rspamd_logger.slog('signature check failed: %s, %s', cbdata.res, cbdata.errors)) end end --[[ 1. Collect all ARC Sets currently attached to the message. If there are none, the Chain Validation Status is "none" and the algorithm stops here. The maximum number of ARC Sets that can be attached to a message is 50. If more than the maximum number exist the Chain Validation Status is "fail" and the algorithm stops here. In the following algorithm, the maximum ARC instance value is referred to as "N". 2. If the Chain Validation Status of the highest instance value ARC Set is "fail", then the Chain Validation status is "fail" and the algorithm stops here. 3. Validate the structure of the Authenticated Received Chain. A valid ARC has the following conditions: 1. Each ARC Set MUST contain exactly one each of the three ARC header fields (AAR, AMS, and AS). 2. The instance values of the ARC Sets MUST form a continuous sequence from 1..N with no gaps or repetition. 3. The "cv" value for all ARC-Seal header fields must be non- failing. For instance values > 1, the value must be "pass". For instance value = 1, the value must be "none". * If any of these conditions are not met, the Chain Validation Status is "fail" and the algorithm stops here. 4. Validate the AMS with the greatest instance value (most recent). If validation fails, then the Chain Validation Status is "fail" and the algorithm stops here. 5 - 7. Optional, not implemented 8. Validate each AS beginning with the greatest instance value and proceeding in decreasing order to the AS with the instance value of 1. If any AS fails to validate, the Chain Validation Status is "fail" and the algorithm stops here. 9. If the algorithm reaches this step, then the Chain Validation Status is "pass", and the algorithm is complete. ]]-- local processed = 0 local sig = cbdata.sigs[#cbdata.sigs] -- last AMS local ret,err = dkim_verify(task, sig.header, arc_signature_cb, 'arc-sign') if not ret then cbdata.res = 'fail' table.insert(cbdata.errors, string.format('sig:%s:%s', sig.d or '', err)) else processed = processed + 1 lua_util.debugm(N, task, 'processed arc signature %s[%s]: %s(%s), %s processed', sig.d, sig.i, ret, err, cbdata.checked) end if processed == 0 then task:insert_result(arc_symbols['reject'], 1.0, rspamd_logger.slog('cannot verify %s of %s signatures: %s', #arc_sig_headers - processed, #arc_sig_headers, cbdata.errors)) end end local opts = rspamd_config:get_all_opt('arc') if not opts or type(opts) ~= 'table' then return end if opts['symbols'] then for k,_ in pairs(arc_symbols) do if opts['symbols'][k] then arc_symbols[k] = opts['symbols'][k] end end end local id = rspamd_config:register_symbol({ name = 'ARC_CALLBACK', type = 'callback', group = 'policies', groups = {'arc'}, callback = arc_callback }) rspamd_config:register_symbol({ name = arc_symbols['allow'], flags = 'nice', parent = id, type = 'virtual', score = -1.0, group = 'policies', groups = {'arc'}, }) rspamd_config:register_symbol({ name = arc_symbols['reject'], parent = id, type = 'virtual', score = 2.0, group = 'policies', groups = {'arc'}, }) rspamd_config:register_symbol({ name = arc_symbols['invalid'], parent = id, type = 'virtual', score = 1.0, group = 'policies', groups = {'arc'}, }) rspamd_config:register_symbol({ name = arc_symbols['dnsfail'], parent = id, type = 'virtual', score = 0.0, group = 'policies', groups = {'arc'}, }) rspamd_config:register_symbol({ name = arc_symbols['na'], parent = id, type = 'virtual', score = 0.0, group = 'policies', groups = {'arc'}, }) rspamd_config:register_dependency('ARC_CALLBACK', symbols['spf_allow_symbol']) rspamd_config:register_dependency('ARC_CALLBACK', symbols['dkim_allow_symbol']) local function arc_sign_seal(task, params, header) local arc_sigs = task:cache_get('arc-sigs') local arc_seals = task:cache_get('arc-seals') local arc_auth_results = task:get_header_full('ARC-Authentication-Results') or {} local cur_auth_results local privkey if params.rawkey then -- Distinguish between pem and base64 if string.match(params.rawkey, '^-----BEGIN') then privkey = rspamd_rsa_privkey.load_pem(params.rawkey) else privkey = rspamd_rsa_privkey.load_base64(params.rawkey) end elseif params.key then privkey = rspamd_rsa_privkey.load_file(params.key) end if not privkey then rspamd_logger.errx(task, 'cannot load private key for signing') return end if settings.reuse_auth_results then local ar_header = task:get_header('Authentication-Results') if ar_header then rspamd_logger.debugm(N, task, 'reuse authentication results header for ARC') cur_auth_results = ar_header else rspamd_logger.debugm(N, task, 'cannot reuse authentication results, header is missing') cur_auth_results = auth_results.gen_auth_results(task) or '' end else cur_auth_results = auth_results.gen_auth_results(task) or '' end local sha_ctx = hash.create_specific('sha256') -- Update using previous seals + sigs + AAR local cur_idx = 1 if arc_seals then cur_idx = #arc_seals + 1 for i = (cur_idx - 1), 1, (-1) do if arc_auth_results[i] then local s = dkim_canonicalize('ARC-Authentication-Results', arc_auth_results[i].value) sha_ctx:update(s) lua_util.debugm(N, task, 'update signature with header: %s', s) end if arc_sigs[i] then local s = dkim_canonicalize('ARC-Message-Signature', arc_sigs[i].raw_header) sha_ctx:update(s) lua_util.debugm(N, task, 'update signature with header: %s', s) end if arc_seals[i] then local s = dkim_canonicalize('ARC-Seal', arc_seals[i].raw_header) sha_ctx:update(s) lua_util.debugm(N, task, 'update signature with header: %s', s) end end end header = lua_util.fold_header(task, 'ARC-Message-Signature', header) cur_auth_results = string.format('i=%d; %s', cur_idx, cur_auth_results) cur_auth_results = lua_util.fold_header(task, 'ARC-Authentication-Results', cur_auth_results, ';') local s = dkim_canonicalize('ARC-Authentication-Results', cur_auth_results) sha_ctx:update(s) lua_util.debugm(N, task, 'update signature with header: %s', s) s = dkim_canonicalize('ARC-Message-Signature', header) sha_ctx:update(s) lua_util.debugm(N, task, 'update signature with header: %s', s) local cur_arc_seal = string.format('i=%d; s=%s; d=%s; t=%d; a=rsa-sha256; cv=%s; b=', cur_idx, params.selector, params.domain, math.floor(rspamd_util.get_time()), params.arc_cv) s = string.format('%s:%s', 'arc-seal', cur_arc_seal) sha_ctx:update(s) lua_util.debugm(N, task, 'initial update signature with header: %s', s) local sig = rspamd_rsa.sign_memory(privkey, sha_ctx:bin()) cur_arc_seal = string.format('%s%s', cur_arc_seal, sig:base64()) task:set_milter_reply({ add_headers = { ['ARC-Authentication-Results'] = {order = 1, value = cur_auth_results}, ['ARC-Message-Signature'] = {order = 1, value = header}, ['ARC-Seal'] = {order = 1, value = lua_util.fold_header(task, 'ARC-Seal', cur_arc_seal) } } }) task:insert_result(settings.sign_symbol, 1.0, string.format('i=%d', cur_idx)) end local function arc_signing_cb(task) local arc_seals = task:cache_get('arc-seals') local ret,p = dkim_sign_tools.prepare_dkim_signing(N, task, settings) if not ret then return end p.arc_cv = 'none' p.arc_idx = 1 p.no_cache = true p.sign_type = 'arc-sign' if arc_seals then p.arc_idx = #arc_seals + 1 if task:has_symbol(arc_symbols.allow) then p.arc_cv = 'pass' else p.arc_cv = 'fail' end end if settings.use_redis then local function try_redis_key(selector) p.key = nil p.selector = selector local rk = string.format('%s.%s', p.selector, p.domain) local function redis_key_cb(err, data) if err or type(data) ~= 'string' then rspamd_logger.infox(rspamd_config, "cannot make request to load DKIM key for %s: %s", rk, err) else p.rawkey = data local dret, hdr = dkim_sign(task, p) if dret then return arc_sign_seal(task, p, hdr) end end end local rret = rspamd_redis_make_request(task, redis_params, -- connect params rk, -- hash key false, -- is write redis_key_cb, --callback 'HGET', -- command {settings.key_prefix, rk} -- arguments ) if not rret then rspamd_logger.infox(rspamd_config, "cannot make request to load DKIM key for %s", rk) end end if settings.selector_prefix then rspamd_logger.infox(rspamd_config, "Using selector prefix %s for domain %s", settings.selector_prefix, p.domain); local function redis_selector_cb(err, data) if err or type(data) ~= 'string' then rspamd_logger.infox(rspamd_config, "cannot make request to load DKIM selector for domain %s: %s", p.domain, err) else try_redis_key(data) end end local rret = rspamd_redis_make_request(task, redis_params, -- connect params p.domain, -- hash key false, -- is write redis_selector_cb, --callback 'HGET', -- command {settings.selector_prefix, p.domain} -- arguments ) if not rret then rspamd_logger.infox(rspamd_config, "cannot make request to load DKIM selector for %s", p.domain) end else if not p.selector then rspamd_logger.errx(task, 'No selector specified') return false end try_redis_key(p.selector) end else if ((p.key or p.rawkey) and p.selector) then if p.key then p.key = lua_util.template(p.key, { domain = p.domain, selector = p.selector }) local exists,err = rspamd_util.file_exists(p.key) if not exists then if err and err == 'No such file or directory' then lua_util.debugm(N, task, 'cannot read key from %s: %s', p.key, err) else rspamd_logger.warnx(N, task, 'cannot read key from %s: %s', p.key, err) end return false end end local dret, hdr = dkim_sign(task, p) if dret then return arc_sign_seal(task, p, hdr) end else rspamd_logger.infox(task, 'key path or dkim selector unconfigured; no signing') return false end end end for k,v in pairs(opts) do if k == 'sign_networks' then settings[k] = rspamd_map_add(N, k, 'radix', 'DKIM signing networks') elseif k == 'path_map' then settings[k] = rspamd_map_add(N, k, 'map', 'Paths to DKIM signing keys') elseif k == 'selector_map' then settings[k] = rspamd_map_add(N, k, 'map', 'DKIM selectors') else settings[k] = v end end if not (settings.use_redis or settings.path or settings.domain or settings.path_map or settings.selector_map or settings.use_http_headers) then rspamd_logger.infox(rspamd_config, 'mandatory parameters missing, disable arc signing') return end if settings.use_redis then redis_params = rspamd_parse_redis_server('arc') if not redis_params then rspamd_logger.errx(rspamd_config, 'no servers are specified, but module is configured to load keys from redis, disable arc signing') return end end rspamd_config:register_symbol({ name = settings['sign_symbol'], callback = arc_signing_cb, groups = {"policies", "arc"}, score = 0.0, }) -- Do not sign unless valid rspamd_config:register_dependency(settings['sign_symbol'], 'ARC_CALLBACK')