File: //proc/1/task/1/root/usr/share/rspamd/plugins/arc.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.
]] --
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 fun = require "fun"
local lua_auth_results = require "lua_auth_results"
local lua_mime = require "lua_mime"
local hash = require "rspamd_cryptobox_hash"
if confighelp then
return
end
local N = 'arc'
local AR_TRUSTED_CACHE_KEY = 'arc_trusted_aar'
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_load_sign_key = rspamd_plugins.dkim.load_sign_key
local dkim_sign_key_get_alg = rspamd_plugins.dkim.sign_key_get_alg
local dkim_sign_digest = rspamd_plugins.dkim.sign_digest
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 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,
sign_authenticated = 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
trusted_authserv_id = nil, -- AuthservID to match when reusing auth results
whitelisted_signers_map = nil, -- Trusted signers domains
whitelist = nil, -- Domains with broken ARC implementations to trust despite validation failures
adjust_dmarc = true, -- Adjust DMARC rejected policy for trusted forwarders
allowed_ids = nil, -- Allowed settings id
forbidden_ids = nil, -- Banned settings id
}
-- To match normal AR
local ar_settings = lua_auth_results.default_settings
-- Get Authentication-Results header, optionally filtering by trusted authserv-id
local function get_trusted_ar_header(task)
if settings.trusted_authserv_id then
local ar_headers = task:get_header_full('Authentication-Results')
if ar_headers then
for _, hdr in ipairs(ar_headers) do
local authserv_id = string.match(hdr.decoded, '^%s*([^;%s]+)')
if authserv_id and authserv_id == settings.trusted_authserv_id then
lua_util.debugm(N, task, 'found trusted AR header with authserv-id: %s', authserv_id)
return hdr.decoded
end
end
lua_util.debugm(N, task, 'no AR header matched trusted authserv-id: %s',
settings.trusted_authserv_id)
end
return nil
else
return task:get_header('Authentication-Results')
end
end
local function parse_arc_header(hdr, target, is_aar)
-- v[1] is the key and v[2] is the value
local function fill_arc_header_table(v, t)
if v[1] and v[2] then
local key = lua_util.rspamd_str_trim(v[1])
local value = lua_util.rspamd_str_trim(v[2])
t[key] = value
end
end
for i, val in ipairs(hdr) do
if not target[i] then
target[i] = {}
end
if not is_aar then
-- For ARC-Seal / ARC-Message-Signature: split by ';' then by '='
local elts = 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, ';')
)
))
fun.each(function(v)
fill_arc_header_table(v, target[i])
end,
fun.map(function(elt)
return lua_util.rspamd_str_split(elt, '=')
end, elts)
)
else
-- For AAR: use LPeg-based parser that respects comments and quoted
-- strings when splitting on ';' (fixes #5963)
local parsed = lua_auth_results.parse_aar_header(val.decoded)
if parsed then
if parsed.i then
target[i].i = parsed.i
end
if parsed.ar then
target[i].ar = parsed.ar
end
end
end
target[i].header = val.decoded
target[i].raw_header = val.value
end
-- sort by i= attribute
table.sort(target, function(a, b)
return (tonumber(a.i) or 0) < (tonumber(b.i) or 0)
end)
end
local function arc_validate_seals(task, seals, sigs, seal_headers, sig_headers)
local fail_reason
for i = 1, #seals do
if (sigs[i].i or 0) ~= i then
fail_reason = string.format('bad i for signature: %d, expected %d; d=%s',
sigs[i].i, i, sigs[i].d)
rspamd_logger.infox(task, fail_reason)
task:insert_result(arc_symbols['invalid'], 1.0, fail_reason)
return false, fail_reason
end
if (seals[i].i or 0) ~= i then
fail_reason = string.format('bad i for seal: %d, expected %d; d=%s',
seals[i].i, i, seals[i].d)
rspamd_logger.infox(task, fail_reason)
task:insert_result(arc_symbols['invalid'], 1.0, fail_reason)
return false, fail_reason
end
if not seals[i].cv then
fail_reason = string.format('no cv on i=%d', i)
task:insert_result(arc_symbols['invalid'], 1.0, fail_reason)
return false, fail_reason
end
if i == 1 then
-- We need to ensure that cv of seal is equal to 'none'
if seals[i].cv ~= 'none' then
fail_reason = 'cv is not "none" for i=1'
task:insert_result(arc_symbols['invalid'], 1.0, fail_reason)
return false, fail_reason
end
else
if seals[i].cv ~= 'pass' then
fail_reason = string.format('cv is %s on i=%d', seals[i].cv, i)
task:insert_result(arc_symbols['reject'], 1.0, fail_reason)
return true, fail_reason
end
end
end
return true, nil
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')
local arc_ar_headers = task:get_header_full('ARC-Authentication-Results')
lua_util.debugm(N, task, 'ARC verification: found %s ARC-MS, %s ARC-Seal, %s ARC-AR headers',
arc_sig_headers and #arc_sig_headers or 0,
arc_seal_headers and #arc_seal_headers or 0,
arc_ar_headers and #arc_ar_headers or 0)
if arc_sig_headers then
for i, hdr in ipairs(arc_sig_headers) do
lua_util.debugm(N, task, 'ARC-Message-Signature[%s]: %s', i, hdr.decoded)
end
end
if arc_seal_headers then
for i, hdr in ipairs(arc_seal_headers) do
lua_util.debugm(N, task, 'ARC-Seal[%s]: %s', i, hdr.decoded)
end
end
if arc_ar_headers then
for i, hdr in ipairs(arc_ar_headers) do
lua_util.debugm(N, task, 'ARC-Authentication-Results[%s]: %s', i, hdr.decoded)
end
end
if not arc_sig_headers or not arc_seal_headers then
lua_util.debugm(N, task, 'ARC verification failed: missing required headers')
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'], 1.0, 'invalid count of seals and signatures')
return
end
local cbdata = {
seals = {},
sigs = {},
ars = {},
res = 'success',
errors = {},
allowed_by_trusted = false
}
parse_arc_header(arc_seal_headers, cbdata.seals, false)
parse_arc_header(arc_sig_headers, cbdata.sigs, false)
if arc_ar_headers then
parse_arc_header(arc_ar_headers, cbdata.ars, true)
end
-- 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
local valid, validation_error = arc_validate_seals(task, cbdata.seals, cbdata.sigs,
arc_seal_headers, arc_sig_headers)
if not valid then
task:cache_set('arc-failure', validation_error)
return
end
task:cache_set('arc-sigs', cbdata.sigs)
task:cache_set('arc-seals', cbdata.seals)
task:cache_set('arc-authres', cbdata.ars)
if validation_error then
-- ARC rejection but no strong failure for signing
return
end
local function gen_arc_seal_cb(index, sig)
return function(_, res, err, domain)
lua_util.debugm(N, task, 'checked arc seal: %s(%s), %s processed',
res, err, index)
if not res then
-- Check if this domain is whitelisted for broken ARC implementations
if settings.whitelist and domain and settings.whitelist:get_key(domain) then
rspamd_logger.infox(task, 'ARC seal validation failed for whitelisted domain %s, treating as valid: %s',
domain, err)
lua_util.debugm(N, task, 'whitelisted domain %s ARC seal failure ignored', domain)
res = true -- Treat as valid to continue the chain
else
cbdata.res = 'fail'
if err and domain then
table.insert(cbdata.errors, string.format('sig:%s:%s', domain, err))
end
end
end
if settings.whitelisted_signers_map and cbdata.res == 'success' then
if settings.whitelisted_signers_map:get_key(sig.d) then
-- Whitelisted signer has been found in a valid chain
local mult = 1.0
local cur_aar = cbdata.ars[index]
if not cur_aar then
rspamd_logger.warnx(task, "cannot find Arc-Authentication-Results for trusted " ..
"forwarder %s on i=%s", domain, cbdata.index)
else
task:cache_set(AR_TRUSTED_CACHE_KEY, cur_aar)
local seen_dmarc
for _, ar in ipairs(cur_aar.ar or {}) do
if ar.dmarc then
local dmarc_fwd = ar.dmarc
seen_dmarc = true
if dmarc_fwd == 'reject' or dmarc_fwd == 'fail' or dmarc_fwd == 'quarantine' then
lua_util.debugm(N, "found rejected dmarc on forwarding")
mult = 0.0
elseif dmarc_fwd == 'pass' then
mult = 1.0
end
elseif ar.spf then
local spf_fwd = ar.spf
if spf_fwd == 'reject' or spf_fwd == 'fail' or spf_fwd == 'quarantine' then
lua_util.debugm(N, "found rejected spf on forwarding")
if not seen_dmarc then
mult = mult * 0.5
end
end
end
end
end
task:insert_result(arc_symbols.trusted_allow, mult,
string.format('%s:s=%s:i=%d', domain, sig.s, index))
end
end
if index == #arc_sig_headers then
if cbdata.res == 'success' then
local arc_allow_result = string.format('%s:s=%s:i=%d',
domain, sig.s, index)
task:insert_result(arc_symbols.allow, 1.0, arc_allow_result)
task:cache_set('arc-allow', arc_allow_result)
else
task:insert_result(arc_symbols.reject, 1.0,
rspamd_logger.slog('seal check failed: %s, %s', cbdata.res,
cbdata.errors))
end
end
end
end
local function arc_signature_cb(_, res, err, domain)
lua_util.debugm(N, task, 'checked arc signature %s: %s(%s)',
domain, res, err)
if not res then
-- Check if this domain is whitelisted for broken ARC implementations
if settings.whitelist and domain and settings.whitelist:get_key(domain) then
rspamd_logger.infox(task, 'ARC signature validation failed for whitelisted domain %s, treating as valid: %s',
domain, err)
lua_util.debugm(N, task, 'whitelisted domain %s ARC signature failure ignored', domain)
res = true -- Treat as valid to continue the chain
else
cbdata.res = 'fail'
if err and domain then
table.insert(cbdata.errors, string.format('sig:%s:%s', domain, err))
end
end
end
if cbdata.res == 'success' then
-- Verify seals
for i, sig in ipairs(cbdata.seals) do
local ret, lerr = dkim_verify(task, sig.header, gen_arc_seal_cb(i, sig), 'arc-seal')
if not ret then
-- Check if this domain is whitelisted for broken ARC implementations
if settings.whitelist and sig.d and settings.whitelist:get_key(sig.d) then
rspamd_logger.infox(task, 'ARC seal dkim_verify failed for whitelisted domain %s, treating as valid: %s',
sig.d, lerr)
lua_util.debugm(N, task, 'whitelisted domain %s ARC seal dkim_verify failure ignored', sig.d)
else
cbdata.res = 'fail'
table.insert(cbdata.errors, string.format('seal:%s:s=%s:i=%s:%s',
sig.d or '', sig.s or '', sig.i or '', lerr))
lua_util.debugm(N, task, 'checked arc seal %s: %s(%s), %s processed',
sig.d, ret, lerr, i)
end
end
end
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
-- Check if this domain is whitelisted for broken ARC implementations
if settings.whitelist and sig.d and settings.whitelist:get_key(sig.d) then
rspamd_logger.infox(task, 'ARC signature dkim_verify failed for whitelisted domain %s, treating as valid: %s',
sig.d, err)
lua_util.debugm(N, task, 'whitelisted domain %s ARC signature dkim_verify failure ignored', sig.d)
processed = processed + 1
else
cbdata.res = 'fail'
table.insert(cbdata.errors, string.format('sig:%s:%s', sig.d or '', err))
end
else
processed = processed + 1
lua_util.debugm(N, task, 'processed arc signature %s[%s]: %s(%s), %s total',
sig.d, sig.i, ret, err, #cbdata.seals)
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_CHECK',
type = 'callback',
group = 'policies',
groups = { 'arc' },
callback = arc_callback,
augmentations = { lua_util.dns_timeout_augmentation(rspamd_config) },
})
rspamd_config:register_symbol({
name = 'ARC_CALLBACK', -- compatibility symbol
type = 'virtual,skip',
parent = id,
})
rspamd_config:register_symbol({
name = arc_symbols['allow'],
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' },
})
-- Weak deps: ARC verification works without SPF/DKIM, just less info in AAR header
rspamd_config:register_dependency('ARC_CHECK', 'SPF_CHECK')
rspamd_config:register_dependency('ARC_CHECK', 'DKIM_CHECK')
local function arc_sign_seal(task, params, header)
local arc_seals = task:cache_get('arc-seals')
local cur_auth_results
if settings.reuse_auth_results then
local ar_header = get_trusted_ar_header(task)
if ar_header then
lua_util.debugm(N, task, 'reuse authentication results header for ARC')
cur_auth_results = ar_header
else
lua_util.debugm(N, task, 'cannot reuse authentication results, header is missing')
cur_auth_results = lua_auth_results.gen_auth_results(task, ar_settings) or ''
end
else
cur_auth_results = lua_auth_results.gen_auth_results(task, ar_settings) or ''
end
local cur_idx = 1
if arc_seals then
cur_idx = #arc_seals + 1
end
header = lua_util.fold_header_with_encoding(task,
'ARC-Message-Signature',
header,
{ structured = true, encode = false })
cur_auth_results = string.format('i=%d; %s', cur_idx, cur_auth_results)
cur_auth_results = lua_util.fold_header_with_encoding(task,
'ARC-Authentication-Results',
cur_auth_results,
{ stop_chars = ';', structured = true, encode = false })
-- Create ARC-Seal signature manually using SHA256 hash
-- We must canonicalize all ARC headers in order and sign them
local sha_ctx = hash.create_specific('sha256')
-- Canonicalize previous ARC sets if they exist (arc_seals already retrieved above)
local arc_sigs = task:cache_get('arc-sigs')
local arc_auth_results = task:cache_get('arc-authres')
if arc_seals then
for i = 1, #arc_seals do
if arc_auth_results[i] then
local s = dkim_canonicalize('ARC-Authentication-Results', arc_auth_results[i].raw_header)
sha_ctx:update(s)
lua_util.debugm(N, task, 'canonicalized previous AAR[%d]: %s', i, 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, 'canonicalized previous AMS[%d]: %s', i, 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, 'canonicalized previous AS[%d]: %s', i, s)
end
end
end
-- Canonicalize the new ARC-Authentication-Results header
local s = dkim_canonicalize('ARC-Authentication-Results', cur_auth_results)
sha_ctx:update(s)
lua_util.debugm(N, task, 'canonicalized new AAR: %s', s)
-- Canonicalize the new ARC-Message-Signature header
s = dkim_canonicalize('ARC-Message-Signature', header)
sha_ctx:update(s)
lua_util.debugm(N, task, 'canonicalized new AMS: %s', s)
-- Load the signing key
local sign_key = dkim_load_sign_key(task, {
key = params.key,
rawkey = params.rawkey,
})
if not sign_key then
rspamd_logger.errx(task, 'cannot load signing key')
return
end
-- Get the algorithm from the key
local algorithm = dkim_sign_key_get_alg(sign_key)
if not algorithm or algorithm == 'unknown' then
rspamd_logger.errx(task, 'cannot determine key algorithm')
return
end
-- Construct partial ARC-Seal header (without signature) using detected algorithm
local cur_arc_seal = string.format('i=%d; a=%s; d=%s; s=%s; cv=%s; t=%d; b=',
cur_idx, algorithm, params.domain, params.selector, params.arc_cv,
math.floor(rspamd_util.get_time()))
-- Canonicalize the partial ARC-Seal and add to hash
local seal_canon = string.format('%s:%s', 'arc-seal', cur_arc_seal)
sha_ctx:update(seal_canon)
lua_util.debugm(N, task, 'canonicalized partial seal: %s', seal_canon)
-- Now sign the complete digest
local dret, sig_b64 = dkim_sign_digest(task, {
sign_key = sign_key,
digest = sha_ctx:bin(),
})
if not dret or not sig_b64 then
rspamd_logger.errx(task, 'cannot create ARC seal signature')
return
end
-- Get appropriate line ending
local nl_type
if task:has_flag("milter") then
nl_type = "lf"
else
nl_type = task:get_newlines_type()
end
-- Fold the signature to 70 chars per line
local folded_sig = rspamd_util.encode_base64(rspamd_util.decode_base64(sig_b64), 70, nl_type)
cur_arc_seal = cur_arc_seal .. folded_sig
-- Add all ARC headers with a deterministic order. Each header is prepended
-- (order = 1), and the `order` list controls the emission sequence, so the
-- resulting message has ARC-Seal, ARC-Message-Signature, ARC-Authentication-Results
-- top to bottom. Some validators (e.g. O365) reject sets in any other layout.
lua_util.debugm(N, task, 'adding ARC-Authentication-Results: %s', cur_auth_results)
lua_util.debugm(N, task, 'adding ARC-Message-Signature: %s', header)
lua_util.debugm(N, task, 'adding ARC-Seal: %s', cur_arc_seal)
lua_mime.modify_headers(task, {
add = {
['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_with_encoding(task,
'ARC-Seal', cur_arc_seal,
{ structured = true, encode = false })
}
},
-- Emission order: each header is prepended, so listing AAR, AMS, AS here
-- yields AS, AMS, AAR in the final message (newest seal on top)
order = { 'ARC-Authentication-Results', 'ARC-Message-Signature', 'ARC-Seal' },
})
task:insert_result(settings.sign_symbol, 1.0,
string.format('%s:s=%s:i=%d', params.domain, params.selector, cur_idx))
end
local function prepare_arc_selector(task, sel)
local arc_seals = task:cache_get('arc-seals')
if not arc_seals then
-- Check if our arc is broken
local failure_reason = task:cache_get('arc-failure')
if failure_reason then
rspamd_logger.infox(task, 'skip ARC as the existing chain is broken: %s', failure_reason)
return false
end
end
sel.arc_cv = 'none'
sel.arc_idx = 1
sel.no_cache = true
sel.sign_type = 'arc-sign'
if arc_seals then
sel.arc_idx = #arc_seals + 1
local function default_arc_cv()
if task:cache_get('arc-allow') then
sel.arc_cv = 'pass'
else
sel.arc_cv = 'fail'
end
end
local function arc_result_from_ar(ar_header)
ar_header = ar_header or ""
for k, v in string.gmatch(ar_header, "(%w+)=(%w+)") do
if k == 'arc' then
return v
end
end
return nil
end
if settings.reuse_auth_results then
local ar_header = get_trusted_ar_header(task)
if ar_header then
local arc_match = arc_result_from_ar(ar_header)
if arc_match then
if arc_match == 'none' or arc_match == 'pass' then
-- none should be converted to `pass`
sel.arc_cv = 'pass'
else
sel.arc_cv = 'fail'
end
else
default_arc_cv()
end
else
-- Cannot reuse, use normal path
default_arc_cv()
end
else
default_arc_cv()
end
end
return true
end
local function do_sign(task, sign_params)
if not prepare_arc_selector(task, sign_params) then
-- Broken arc
return
end
if settings.check_pubkey then
local resolve_name = sign_params.selector .. "._domainkey." .. sign_params.domain
task:get_resolver():resolve_txt({
task = task,
name = resolve_name,
callback = function(_, _, results, err)
if not err and results and results[1] then
sign_params.pubkey = results[1]
sign_params.strict_pubkey_check = not settings.allow_pubkey_mismatch
elseif not settings.allow_pubkey_mismatch then
rspamd_logger.errx(task, 'public key for domain %s/%s is not found: %s, skip signing',
sign_params.domain, sign_params.selector, err)
return
else
rspamd_logger.infox(task, 'public key for domain %s/%s is not found: %s',
sign_params.domain, sign_params.selector, err)
end
local dret, hdr = dkim_sign(task, sign_params)
if dret then
arc_sign_seal(task, sign_params, hdr)
end
end,
forced = true
})
else
local dret, hdr = dkim_sign(task, sign_params)
if dret then
arc_sign_seal(task, sign_params, hdr)
end
end
end
local function sign_error(task, msg)
rspamd_logger.errx(task, 'signing failure: %s', msg)
end
local function arc_signing_cb(task)
local ret, selectors = dkim_sign_tools.prepare_dkim_signing(N, task, settings)
if not ret then
return
end
if settings.use_redis then
dkim_sign_tools.sign_using_redis(N, task, settings, selectors, do_sign, sign_error)
else
if selectors.vault then
dkim_sign_tools.sign_using_vault(N, task, settings, selectors, do_sign, sign_error)
else
-- TODO: no support for multiple sigs
local cur_selector = selectors[1]
prepare_arc_selector(task, cur_selector)
if ((cur_selector.key or cur_selector.rawkey) and cur_selector.selector) then
if cur_selector.key then
cur_selector.key = lua_util.template(cur_selector.key, {
domain = cur_selector.domain,
selector = cur_selector.selector
})
local exists, err = rspamd_util.file_exists(cur_selector.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', cur_selector.key, err)
else
rspamd_logger.warnx(task, 'cannot read key from %s: %s', cur_selector.key, err)
end
return false
end
end
do_sign(task, cur_selector)
else
rspamd_logger.infox(task, 'key path or dkim selector unconfigured; no signing')
return false
end
end
end
end
dkim_sign_tools.process_signing_settings(N, settings, opts)
-- Process ARC-specific maps that aren't handled by dkim_sign_tools
local lua_maps = require "lua_maps"
if opts.whitelisted_signers_map then
settings.whitelisted_signers_map = lua_maps.map_add_from_ucl(opts.whitelisted_signers_map, 'set',
'ARC trusted signers domains')
if not settings.whitelisted_signers_map then
rspamd_logger.errx(rspamd_config, 'cannot load whitelisted_signers_map')
settings.whitelisted_signers_map = nil
else
rspamd_logger.infox(rspamd_config, 'loaded ARC whitelisted signers map')
end
end
if opts.whitelist then
settings.whitelist = lua_maps.map_add_from_ucl(opts.whitelist, 'set',
'ARC domains with broken implementations')
if not settings.whitelist then
rspamd_logger.errx(rspamd_config, 'cannot load ARC whitelist map')
settings.whitelist = nil
else
rspamd_logger.infox(rspamd_config, 'loaded ARC whitelist map')
end
end
if not dkim_sign_tools.validate_signing_settings(settings) then
rspamd_logger.infox(rspamd_config, 'mandatory parameters missing, disable arc signing')
return
end
local ar_opts = rspamd_config:get_all_opt('milter_headers')
if ar_opts and ar_opts.routines then
local routines = ar_opts.routines
if routines['authentication-results'] then
ar_settings = lua_util.override_defaults(ar_settings,
routines['authentication-results'])
end
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
settings.redis_params = redis_params
end
local sym_reg_tbl = {
name = settings['sign_symbol'],
callback = arc_signing_cb,
groups = { "policies", "arc" },
flags = 'ignore_passthrough',
score = 0.0,
}
if type(settings.allowed_ids) == 'table' then
sym_reg_tbl.allowed_ids = settings.allowed_ids
end
if type(settings.forbidden_ids) == 'table' then
sym_reg_tbl.forbidden_ids = settings.forbidden_ids
end
if settings.whitelisted_signers_map then
arc_symbols.trusted_allow = arc_symbols.trusted_allow or 'ARC_ALLOW_TRUSTED'
rspamd_config:register_symbol({
name = arc_symbols.trusted_allow,
parent = id,
type = 'virtual',
score = -2.0,
group = 'policies',
groups = { 'arc' },
})
end
rspamd_config:register_symbol(sym_reg_tbl)
-- Hard: ARC signing needs arc-seals cache from ARC_CHECK
rspamd_config:register_dependency(settings['sign_symbol'], 'ARC_CHECK', true)
-- Hard: ARC signing needs DMARC result for valid AAR header (#3613)
rspamd_config:register_dependency(settings['sign_symbol'], 'DMARC_CHECK', true)
if settings.adjust_dmarc and settings.whitelisted_signers_map then
local function arc_dmarc_adjust_cb(task)
local trusted_arc_ar = task:cache_get(AR_TRUSTED_CACHE_KEY)
local sym_to_adjust
if task:has_symbol(ar_settings.dmarc_symbols.reject) then
sym_to_adjust = ar_settings.dmarc_symbols.reject
elseif task:has_symbol(ar_settings.dmarc_symbols.quarantine) then
sym_to_adjust = ar_settings.dmarc_symbols.quarantine
end
if sym_to_adjust and trusted_arc_ar and trusted_arc_ar.ar then
for _, ar in ipairs(trusted_arc_ar.ar) do
if ar.dmarc then
local dmarc_fwd = ar.dmarc
if dmarc_fwd == 'pass' then
rspamd_logger.infox(task, "adjust dmarc reject score as trusted forwarder "
.. "proved DMARC validity for %s", ar['header.from'])
task:adjust_result(sym_to_adjust, 0.1,
'ARC trusted')
end
end
end
end
end
rspamd_config:register_symbol({
name = 'ARC_DMARC_ADJUSTMENT',
callback = arc_dmarc_adjust_cb,
type = 'callback',
})
-- Hard: reads both DMARC policy symbols and ARC trusted cache
rspamd_config:register_dependency('ARC_DMARC_ADJUSTMENT', 'DMARC_CHECK', true)
rspamd_config:register_dependency('ARC_DMARC_ADJUSTMENT', 'ARC_CHECK', true)
end