2 This file is part of systemd.
4 Copyright 2014 Lennart Poettering
6 systemd is free software; you can redistribute it and/or modify it
7 under the terms of the GNU Lesser General Public License as published by
8 the Free Software Foundation; either version 2.1 of the License, or
9 (at your option) any later version.
11 systemd is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public License
17 along with systemd; If not, see <http://www.gnu.org/licenses/>.
20 #include "sd-messages.h"
23 #include "alloc-util.h"
24 #include "dns-domain.h"
25 #include "errno-list.h"
27 #include "random-util.h"
28 #include "resolved-dns-cache.h"
29 #include "resolved-dns-transaction.h"
30 #include "resolved-llmnr.h"
31 #include "string-table.h"
33 #define TRANSACTIONS_MAX 4096
34 #define TRANSACTION_TCP_TIMEOUT_USEC (10U*USEC_PER_SEC)
36 static void dns_transaction_reset_answer(DnsTransaction
*t
) {
39 t
->received
= dns_packet_unref(t
->received
);
40 t
->answer
= dns_answer_unref(t
->answer
);
42 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
43 t
->answer_source
= _DNS_TRANSACTION_SOURCE_INVALID
;
44 t
->answer_authenticated
= false;
45 t
->answer_nsec_ttl
= (uint32_t) -1;
49 static void dns_transaction_flush_dnssec_transactions(DnsTransaction
*t
) {
54 while ((z
= set_steal_first(t
->dnssec_transactions
))) {
55 set_remove(z
->notify_transactions
, t
);
56 set_remove(z
->notify_transactions_done
, t
);
57 dns_transaction_gc(z
);
61 static void dns_transaction_close_connection(DnsTransaction
*t
) {
65 /* Let's detach the stream from our transaction, in case something else keeps a reference to it. */
66 t
->stream
->complete
= NULL
;
67 t
->stream
->on_packet
= NULL
;
68 t
->stream
->transaction
= NULL
;
69 t
->stream
= dns_stream_unref(t
->stream
);
72 t
->dns_udp_event_source
= sd_event_source_unref(t
->dns_udp_event_source
);
73 t
->dns_udp_fd
= safe_close(t
->dns_udp_fd
);
76 static void dns_transaction_stop_timeout(DnsTransaction
*t
) {
79 t
->timeout_event_source
= sd_event_source_unref(t
->timeout_event_source
);
82 DnsTransaction
* dns_transaction_free(DnsTransaction
*t
) {
90 log_debug("Freeing transaction %" PRIu16
".", t
->id
);
92 dns_transaction_close_connection(t
);
93 dns_transaction_stop_timeout(t
);
95 dns_packet_unref(t
->sent
);
96 dns_transaction_reset_answer(t
);
98 dns_server_unref(t
->server
);
101 hashmap_remove_value(t
->scope
->transactions_by_key
, t
->key
, t
);
102 LIST_REMOVE(transactions_by_scope
, t
->scope
->transactions
, t
);
105 hashmap_remove(t
->scope
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
));
108 while ((c
= set_steal_first(t
->notify_query_candidates
)))
109 set_remove(c
->transactions
, t
);
110 set_free(t
->notify_query_candidates
);
112 while ((c
= set_steal_first(t
->notify_query_candidates_done
)))
113 set_remove(c
->transactions
, t
);
114 set_free(t
->notify_query_candidates_done
);
116 while ((i
= set_steal_first(t
->notify_zone_items
)))
117 i
->probe_transaction
= NULL
;
118 set_free(t
->notify_zone_items
);
120 while ((i
= set_steal_first(t
->notify_zone_items_done
)))
121 i
->probe_transaction
= NULL
;
122 set_free(t
->notify_zone_items_done
);
124 while ((z
= set_steal_first(t
->notify_transactions
)))
125 set_remove(z
->dnssec_transactions
, t
);
126 set_free(t
->notify_transactions
);
128 while ((z
= set_steal_first(t
->notify_transactions_done
)))
129 set_remove(z
->dnssec_transactions
, t
);
130 set_free(t
->notify_transactions_done
);
132 dns_transaction_flush_dnssec_transactions(t
);
133 set_free(t
->dnssec_transactions
);
135 dns_answer_unref(t
->validated_keys
);
136 dns_resource_key_unref(t
->key
);
141 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsTransaction
*, dns_transaction_free
);
143 bool dns_transaction_gc(DnsTransaction
*t
) {
149 if (set_isempty(t
->notify_query_candidates
) &&
150 set_isempty(t
->notify_query_candidates_done
) &&
151 set_isempty(t
->notify_zone_items
) &&
152 set_isempty(t
->notify_zone_items_done
) &&
153 set_isempty(t
->notify_transactions
) &&
154 set_isempty(t
->notify_transactions_done
)) {
155 dns_transaction_free(t
);
162 static uint16_t pick_new_id(Manager
*m
) {
165 /* Find a fresh, unused transaction id. Note that this loop is bounded because there's a limit on the number of
166 * transactions, and it's much lower than the space of IDs. */
168 assert_cc(TRANSACTIONS_MAX
< 0xFFFF);
171 random_bytes(&new_id
, sizeof(new_id
));
172 while (new_id
== 0 ||
173 hashmap_get(m
->dns_transactions
, UINT_TO_PTR(new_id
)));
178 int dns_transaction_new(DnsTransaction
**ret
, DnsScope
*s
, DnsResourceKey
*key
) {
179 _cleanup_(dns_transaction_freep
) DnsTransaction
*t
= NULL
;
186 /* Don't allow looking up invalid or pseudo RRs */
187 if (!dns_type_is_valid_query(key
->type
))
189 if (dns_type_is_obsolete(key
->type
))
192 /* We only support the IN class */
193 if (key
->class != DNS_CLASS_IN
&& key
->class != DNS_CLASS_ANY
)
196 if (hashmap_size(s
->manager
->dns_transactions
) >= TRANSACTIONS_MAX
)
199 r
= hashmap_ensure_allocated(&s
->manager
->dns_transactions
, NULL
);
203 r
= hashmap_ensure_allocated(&s
->transactions_by_key
, &dns_resource_key_hash_ops
);
207 t
= new0(DnsTransaction
, 1);
212 t
->answer_source
= _DNS_TRANSACTION_SOURCE_INVALID
;
213 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
214 t
->answer_nsec_ttl
= (uint32_t) -1;
215 t
->key
= dns_resource_key_ref(key
);
216 t
->current_feature_level
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
217 t
->clamp_feature_level
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
219 t
->id
= pick_new_id(s
->manager
);
221 r
= hashmap_put(s
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
), t
);
227 r
= hashmap_replace(s
->transactions_by_key
, t
->key
, t
);
229 hashmap_remove(s
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
));
233 LIST_PREPEND(transactions_by_scope
, s
->transactions
, t
);
236 s
->manager
->n_transactions_total
++;
246 static void dns_transaction_shuffle_id(DnsTransaction
*t
) {
250 /* Pick a new ID for this transaction. */
252 new_id
= pick_new_id(t
->scope
->manager
);
253 assert_se(hashmap_remove_and_put(t
->scope
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
), UINT_TO_PTR(new_id
), t
) >= 0);
255 log_debug("Transaction %" PRIu16
" is now %" PRIu16
".", t
->id
, new_id
);
258 /* Make sure we generate a new packet with the new ID */
259 t
->sent
= dns_packet_unref(t
->sent
);
262 static void dns_transaction_tentative(DnsTransaction
*t
, DnsPacket
*p
) {
263 _cleanup_free_
char *pretty
= NULL
;
264 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
270 if (manager_our_packet(t
->scope
->manager
, p
) != 0)
273 (void) in_addr_to_string(p
->family
, &p
->sender
, &pretty
);
275 log_debug("Transaction %" PRIu16
" for <%s> on scope %s on %s/%s got tentative packet from %s.",
277 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
),
278 dns_protocol_to_string(t
->scope
->protocol
),
279 t
->scope
->link
? t
->scope
->link
->name
: "*",
280 af_to_name_short(t
->scope
->family
),
283 /* RFC 4795, Section 4.1 says that the peer with the
284 * lexicographically smaller IP address loses */
285 if (memcmp(&p
->sender
, &p
->destination
, FAMILY_ADDRESS_SIZE(p
->family
)) >= 0) {
286 log_debug("Peer has lexicographically larger IP address and thus lost in the conflict.");
290 log_debug("We have the lexicographically larger IP address and thus lost in the conflict.");
294 while ((z
= set_first(t
->notify_zone_items
))) {
295 /* First, make sure the zone item drops the reference
297 dns_zone_item_probe_stop(z
);
299 /* Secondly, report this as conflict, so that we might
300 * look for a different hostname */
301 dns_zone_item_conflict(z
);
305 dns_transaction_gc(t
);
308 void dns_transaction_complete(DnsTransaction
*t
, DnsTransactionState state
) {
309 DnsQueryCandidate
*c
;
313 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
316 assert(!DNS_TRANSACTION_IS_LIVE(state
));
318 if (state
== DNS_TRANSACTION_DNSSEC_FAILED
) {
319 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
);
321 log_struct(LOG_NOTICE
,
322 "MESSAGE_ID=" SD_MESSAGE_DNSSEC_FAILURE_STR
,
323 LOG_MESSAGE("DNSSEC validation failed for question %s: %s", key_str
, dnssec_result_to_string(t
->answer_dnssec_result
)),
324 "DNS_TRANSACTION=%" PRIu16
, t
->id
,
325 "DNS_QUESTION=%s", key_str
,
326 "DNSSEC_RESULT=%s", dnssec_result_to_string(t
->answer_dnssec_result
),
327 "DNS_SERVER=%s", dns_server_string(t
->server
),
328 "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(t
->server
->possible_feature_level
),
332 /* Note that this call might invalidate the query. Callers
333 * should hence not attempt to access the query or transaction
334 * after calling this function. */
336 if (state
== DNS_TRANSACTION_ERRNO
)
337 st
= errno_to_name(t
->answer_errno
);
339 st
= dns_transaction_state_to_string(state
);
341 log_debug("Transaction %" PRIu16
" for <%s> on scope %s on %s/%s now complete with <%s> from %s (%s).",
343 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
),
344 dns_protocol_to_string(t
->scope
->protocol
),
345 t
->scope
->link
? t
->scope
->link
->name
: "*",
346 af_to_name_short(t
->scope
->family
),
348 t
->answer_source
< 0 ? "none" : dns_transaction_source_to_string(t
->answer_source
),
349 t
->answer_authenticated
? "authenticated" : "unsigned");
353 dns_transaction_close_connection(t
);
354 dns_transaction_stop_timeout(t
);
356 /* Notify all queries that are interested, but make sure the
357 * transaction isn't freed while we are still looking at it */
360 SET_FOREACH_MOVE(c
, t
->notify_query_candidates_done
, t
->notify_query_candidates
)
361 dns_query_candidate_notify(c
);
362 SWAP_TWO(t
->notify_query_candidates
, t
->notify_query_candidates_done
);
364 SET_FOREACH_MOVE(z
, t
->notify_zone_items_done
, t
->notify_zone_items
)
365 dns_zone_item_notify(z
);
366 SWAP_TWO(t
->notify_zone_items
, t
->notify_zone_items_done
);
368 (void) dns_scope_announce(t
->scope
, false);
370 SET_FOREACH_MOVE(d
, t
->notify_transactions_done
, t
->notify_transactions
)
371 dns_transaction_notify(d
, t
);
372 SWAP_TWO(t
->notify_transactions
, t
->notify_transactions_done
);
375 dns_transaction_gc(t
);
378 static int dns_transaction_pick_server(DnsTransaction
*t
) {
382 assert(t
->scope
->protocol
== DNS_PROTOCOL_DNS
);
384 /* Pick a DNS server and a feature level for it. */
386 server
= dns_scope_get_dns_server(t
->scope
);
390 /* If we changed the server invalidate the feature level clamping, as the new server might have completely
391 * different properties. */
392 if (server
!= t
->server
)
393 t
->clamp_feature_level
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
395 t
->current_feature_level
= dns_server_possible_feature_level(server
);
397 /* Clamp the feature level if that is requested. */
398 if (t
->clamp_feature_level
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
&&
399 t
->current_feature_level
> t
->clamp_feature_level
)
400 t
->current_feature_level
= t
->clamp_feature_level
;
402 log_debug("Using feature level %s for transaction %u.", dns_server_feature_level_to_string(t
->current_feature_level
), t
->id
);
404 if (server
== t
->server
)
407 dns_server_unref(t
->server
);
408 t
->server
= dns_server_ref(server
);
410 log_debug("Using DNS server %s for transaction %u.", dns_server_string(t
->server
), t
->id
);
415 static void dns_transaction_retry(DnsTransaction
*t
, bool next_server
) {
420 log_debug("Retrying transaction %" PRIu16
".", t
->id
);
422 /* Before we try again, switch to a new server. */
424 dns_scope_next_dns_server(t
->scope
);
426 r
= dns_transaction_go(t
);
428 t
->answer_errno
= -r
;
429 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
433 static int dns_transaction_maybe_restart(DnsTransaction
*t
) {
438 /* Returns > 0 if the transaction was restarted, 0 if not */
443 if (t
->current_feature_level
<= dns_server_possible_feature_level(t
->server
))
446 /* The server's current feature level is lower than when we sent the original query. We learnt something from
447 the response or possibly an auxiliary DNSSEC response that we didn't know before. We take that as reason to
448 restart the whole transaction. This is a good idea to deal with servers that respond rubbish if we include
449 OPT RR or DO bit. One of these cases is documented here, for example:
450 https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */
452 log_debug("Server feature level is now lower than when we began our transaction. Restarting with new ID.");
453 dns_transaction_shuffle_id(t
);
455 r
= dns_transaction_go(t
);
462 static int on_stream_complete(DnsStream
*s
, int error
) {
463 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
467 assert(s
->transaction
);
469 /* Copy the data we care about out of the stream before we
472 p
= dns_packet_ref(s
->read_packet
);
474 dns_transaction_close_connection(t
);
476 if (ERRNO_IS_DISCONNECT(error
)) {
479 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
) {
480 /* If the LLMNR/TCP connection failed, the host doesn't support LLMNR, and we cannot answer the
481 * question on this scope. */
482 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
486 log_debug_errno(error
, "Connection failure for DNS TCP stream: %m");
487 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &usec
) >= 0);
488 dns_server_packet_lost(t
->server
, IPPROTO_TCP
, t
->current_feature_level
, usec
- t
->start_usec
);
490 dns_transaction_retry(t
, true);
494 t
->answer_errno
= error
;
495 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
499 if (dns_packet_validate_reply(p
) <= 0) {
500 log_debug("Invalid TCP reply packet.");
501 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
505 dns_scope_check_conflicts(t
->scope
, p
);
508 dns_transaction_process_reply(t
, p
);
511 /* If the response wasn't useful, then complete the transition
512 * now. After all, we are the worst feature set now with TCP
513 * sockets, and there's really no point in retrying. */
514 if (t
->state
== DNS_TRANSACTION_PENDING
)
515 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
517 dns_transaction_gc(t
);
522 static int dns_transaction_open_tcp(DnsTransaction
*t
) {
523 _cleanup_close_
int fd
= -1;
528 dns_transaction_close_connection(t
);
530 switch (t
->scope
->protocol
) {
532 case DNS_PROTOCOL_DNS
:
533 r
= dns_transaction_pick_server(t
);
537 if (!dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(t
->key
->type
))
540 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
544 fd
= dns_scope_socket_tcp(t
->scope
, AF_UNSPEC
, NULL
, t
->server
, 53);
547 case DNS_PROTOCOL_LLMNR
:
548 /* When we already received a reply to this (but it was truncated), send to its sender address */
550 fd
= dns_scope_socket_tcp(t
->scope
, t
->received
->family
, &t
->received
->sender
, NULL
, t
->received
->sender_port
);
552 union in_addr_union address
;
553 int family
= AF_UNSPEC
;
555 /* Otherwise, try to talk to the owner of a
556 * the IP address, in case this is a reverse
559 r
= dns_name_address(dns_resource_key_name(t
->key
), &family
, &address
);
564 if (family
!= t
->scope
->family
)
567 fd
= dns_scope_socket_tcp(t
->scope
, family
, &address
, NULL
, LLMNR_PORT
);
573 return -EAFNOSUPPORT
;
579 r
= dns_stream_new(t
->scope
->manager
, &t
->stream
, t
->scope
->protocol
, fd
);
584 r
= dns_stream_write_packet(t
->stream
, t
->sent
);
586 t
->stream
= dns_stream_unref(t
->stream
);
590 t
->stream
->complete
= on_stream_complete
;
591 t
->stream
->transaction
= t
;
593 /* The interface index is difficult to determine if we are
594 * connecting to the local host, hence fill this in right away
595 * instead of determining it from the socket */
596 t
->stream
->ifindex
= dns_scope_ifindex(t
->scope
);
598 dns_transaction_reset_answer(t
);
600 t
->tried_stream
= true;
605 static void dns_transaction_cache_answer(DnsTransaction
*t
) {
608 /* For mDNS we cache whenever we get the packet, rather than
609 * in each transaction. */
610 if (!IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_DNS
, DNS_PROTOCOL_LLMNR
))
613 /* Caching disabled? */
614 if (!t
->scope
->manager
->enable_cache
)
617 /* We never cache if this packet is from the local host, under
618 * the assumption that a locally running DNS server would
619 * cache this anyway, and probably knows better when to flush
620 * the cache then we could. */
621 if (!DNS_PACKET_SHALL_CACHE(t
->received
))
624 dns_cache_put(&t
->scope
->cache
,
628 t
->answer_authenticated
,
632 &t
->received
->sender
);
635 static bool dns_transaction_dnssec_is_live(DnsTransaction
*t
) {
641 SET_FOREACH(dt
, t
->dnssec_transactions
, i
)
642 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
648 static int dns_transaction_dnssec_ready(DnsTransaction
*t
) {
654 /* Checks whether the auxiliary DNSSEC transactions of our transaction have completed, or are still
655 * ongoing. Returns 0, if we aren't ready for the DNSSEC validation, positive if we are. */
657 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
661 case DNS_TRANSACTION_NULL
:
662 case DNS_TRANSACTION_PENDING
:
663 case DNS_TRANSACTION_VALIDATING
:
667 case DNS_TRANSACTION_RCODE_FAILURE
:
668 if (!IN_SET(dt
->answer_rcode
, DNS_RCODE_NXDOMAIN
, DNS_RCODE_SERVFAIL
)) {
669 log_debug("Auxiliary DNSSEC RR query failed with rcode=%s.", dns_rcode_to_string(dt
->answer_rcode
));
673 /* Fall-through: NXDOMAIN/SERVFAIL is good enough for us. This is because some DNS servers
674 * erronously return NXDOMAIN/SERVFAIL for empty non-terminals (Akamai...) or missing DS
675 * records (Facebook), and we need to handle that nicely, when asking for parent SOA or similar
676 * RRs to make unsigned proofs. */
678 case DNS_TRANSACTION_SUCCESS
:
682 case DNS_TRANSACTION_DNSSEC_FAILED
:
683 /* We handle DNSSEC failures different from other errors, as we care about the DNSSEC
684 * validationr result */
686 log_debug("Auxiliary DNSSEC RR query failed validation: %s", dnssec_result_to_string(dt
->answer_dnssec_result
));
687 t
->answer_dnssec_result
= dt
->answer_dnssec_result
; /* Copy error code over */
688 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
693 log_debug("Auxiliary DNSSEC RR query failed with %s", dns_transaction_state_to_string(dt
->state
));
698 /* All is ready, we can go and validate */
702 t
->answer_dnssec_result
= DNSSEC_FAILED_AUXILIARY
;
703 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
707 static void dns_transaction_process_dnssec(DnsTransaction
*t
) {
712 /* Are there ongoing DNSSEC transactions? If so, let's wait for them. */
713 r
= dns_transaction_dnssec_ready(t
);
716 if (r
== 0) /* We aren't ready yet (or one of our auxiliary transactions failed, and we shouldn't validate now */
719 /* See if we learnt things from the additional DNSSEC transactions, that we didn't know before, and better
720 * restart the lookup immediately. */
721 r
= dns_transaction_maybe_restart(t
);
724 if (r
> 0) /* Transaction got restarted... */
727 /* All our auxiliary DNSSEC transactions are complete now. Try
728 * to validate our RRset now. */
729 r
= dns_transaction_validate_dnssec(t
);
731 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
737 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
&&
738 t
->scope
->dnssec_mode
== DNSSEC_YES
) {
739 /* We are not in automatic downgrade mode, and the
740 * server is bad, refuse operation. */
741 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
745 if (!IN_SET(t
->answer_dnssec_result
,
746 _DNSSEC_RESULT_INVALID
, /* No DNSSEC validation enabled */
747 DNSSEC_VALIDATED
, /* Answer is signed and validated successfully */
748 DNSSEC_UNSIGNED
, /* Answer is right-fully unsigned */
749 DNSSEC_INCOMPATIBLE_SERVER
)) { /* Server does not do DNSSEC (Yay, we are downgrade attack vulnerable!) */
750 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
754 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
)
755 dns_server_warn_downgrade(t
->server
);
757 dns_transaction_cache_answer(t
);
759 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
760 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
762 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
767 t
->answer_errno
= -r
;
768 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
771 static int dns_transaction_has_positive_answer(DnsTransaction
*t
, DnsAnswerFlags
*flags
) {
776 /* Checks whether the answer is positive, i.e. either a direct
777 * answer to the question, or a CNAME/DNAME for it */
779 r
= dns_answer_match_key(t
->answer
, t
->key
, flags
);
783 r
= dns_answer_find_cname_or_dname(t
->answer
, t
->key
, NULL
, flags
);
790 static int dns_transaction_fix_rcode(DnsTransaction
*t
) {
795 /* Fix up the RCODE to SUCCESS if we get at least one matching RR in a response. Note that this contradicts the
796 * DNS RFCs a bit. Specifically, RFC 6604 Section 3 clarifies that the RCODE shall say something about a
797 * CNAME/DNAME chain element coming after the last chain element contained in the message, and not the first
798 * one included. However, it also indicates that not all DNS servers implement this correctly. Moreover, when
799 * using DNSSEC we usually only can prove the first element of a CNAME/DNAME chain anyway, hence let's settle
800 * on always processing the RCODE as referring to the immediate look-up we do, i.e. the first element of a
801 * CNAME/DNAME chain. This way, we uniformly handle CNAME/DNAME chains, regardless if the DNS server
802 * incorrectly implements RCODE, whether DNSSEC is in use, or whether the DNS server only supplied us with an
803 * incomplete CNAME/DNAME chain.
805 * Or in other words: if we get at least one positive reply in a message we patch NXDOMAIN to become SUCCESS,
806 * and then rely on the CNAME chasing logic to figure out that there's actually a CNAME error with a new
809 if (t
->answer_rcode
!= DNS_RCODE_NXDOMAIN
)
812 r
= dns_transaction_has_positive_answer(t
, NULL
);
816 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
820 void dns_transaction_process_reply(DnsTransaction
*t
, DnsPacket
*p
) {
827 assert(t
->scope
->manager
);
829 if (t
->state
!= DNS_TRANSACTION_PENDING
)
832 /* Note that this call might invalidate the query. Callers
833 * should hence not attempt to access the query or transaction
834 * after calling this function. */
836 log_debug("Processing incoming packet on transaction %" PRIu16
". (rcode=%s)", t
->id
, dns_rcode_to_string(DNS_PACKET_RCODE(p
)));
838 switch (t
->scope
->protocol
) {
840 case DNS_PROTOCOL_LLMNR
:
841 /* For LLMNR we will not accept any packets from other interfaces */
843 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
846 if (p
->family
!= t
->scope
->family
)
849 /* Tentative packets are not full responses but still
850 * useful for identifying uniqueness conflicts during
852 if (DNS_PACKET_LLMNR_T(p
)) {
853 dns_transaction_tentative(t
, p
);
859 case DNS_PROTOCOL_MDNS
:
860 /* For mDNS we will not accept any packets from other interfaces */
862 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
865 if (p
->family
!= t
->scope
->family
)
870 case DNS_PROTOCOL_DNS
:
871 /* Note that we do not need to verify the
872 * addresses/port numbers of incoming traffic, as we
873 * invoked connect() on our UDP socket in which case
874 * the kernel already does the needed verification for
879 assert_not_reached("Invalid DNS protocol.");
882 if (t
->received
!= p
) {
883 dns_packet_unref(t
->received
);
884 t
->received
= dns_packet_ref(p
);
887 t
->answer_source
= DNS_TRANSACTION_NETWORK
;
889 if (p
->ipproto
== IPPROTO_TCP
) {
890 if (DNS_PACKET_TC(p
)) {
891 /* Truncated via TCP? Somebody must be fucking with us */
892 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
896 if (DNS_PACKET_ID(p
) != t
->id
) {
897 /* Not the reply to our query? Somebody must be fucking with us */
898 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
903 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &ts
) >= 0);
905 switch (t
->scope
->protocol
) {
907 case DNS_PROTOCOL_DNS
:
910 if (IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_FORMERR
, DNS_RCODE_SERVFAIL
, DNS_RCODE_NOTIMP
)) {
912 /* Request failed, immediately try again with reduced features */
914 if (t
->current_feature_level
<= DNS_SERVER_FEATURE_LEVEL_UDP
) {
915 /* This was already at UDP feature level? If so, it doesn't make sense to downgrade
916 * this transaction anymore, hence let's process the response, and accept the
917 * rcode. Note that we don't retry on TCP, since that's a suitable way to mitigate
918 * packet loss, but is not going to give us better rcodes should we actually have
919 * managed to get them already at UDP level. */
921 log_debug("Server returned error: %s", dns_rcode_to_string(DNS_PACKET_RCODE(p
)));
925 /* Reduce this feature level by one and try again. */
926 t
->clamp_feature_level
= t
->current_feature_level
- 1;
928 log_debug("Server returned error %s, retrying transaction with reduced feature level %s.",
929 dns_rcode_to_string(DNS_PACKET_RCODE(p
)),
930 dns_server_feature_level_to_string(t
->clamp_feature_level
));
932 dns_transaction_retry(t
, false /* use the same server */);
936 if (DNS_PACKET_RCODE(p
) == DNS_RCODE_REFUSED
) {
937 /* This server refused our request? If so, try again, use a different server */
938 log_debug("Server returned REFUSED, switching servers, and retrying.");
939 dns_transaction_retry(t
, true /* pick a new server */);
943 if (DNS_PACKET_TC(p
))
944 dns_server_packet_truncated(t
->server
, t
->current_feature_level
);
948 case DNS_PROTOCOL_LLMNR
:
949 case DNS_PROTOCOL_MDNS
:
950 dns_scope_packet_received(t
->scope
, ts
- t
->start_usec
);
954 assert_not_reached("Invalid DNS protocol.");
957 if (DNS_PACKET_TC(p
)) {
959 /* Truncated packets for mDNS are not allowed. Give up immediately. */
960 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
) {
961 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
965 log_debug("Reply truncated, retrying via TCP.");
967 /* Response was truncated, let's try again with good old TCP */
968 r
= dns_transaction_open_tcp(t
);
970 /* No servers found? Damn! */
971 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
974 if (r
== -EOPNOTSUPP
) {
975 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
976 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
980 /* On LLMNR, if we cannot connect to the host,
981 * we immediately give up */
982 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
985 /* On DNS, couldn't send? Try immediately again, with a new server */
986 dns_transaction_retry(t
, true);
992 /* After the superficial checks, actually parse the message. */
993 r
= dns_packet_extract(p
);
995 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1000 /* Report that we successfully received a valid packet with a good rcode after we initially got a bad
1001 * rcode and subsequently downgraded the protocol */
1003 if (IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_SUCCESS
, DNS_RCODE_NXDOMAIN
) &&
1004 t
->clamp_feature_level
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
)
1005 dns_server_packet_rcode_downgrade(t
->server
, t
->clamp_feature_level
);
1007 /* Report that the OPT RR was missing */
1009 dns_server_packet_bad_opt(t
->server
, t
->current_feature_level
);
1011 /* Report that we successfully received a packet */
1012 dns_server_packet_received(t
->server
, p
->ipproto
, t
->current_feature_level
, ts
- t
->start_usec
, p
->size
);
1015 /* See if we know things we didn't know before that indicate we better restart the lookup immediately. */
1016 r
= dns_transaction_maybe_restart(t
);
1019 if (r
> 0) /* Transaction got restarted... */
1022 if (IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_DNS
, DNS_PROTOCOL_LLMNR
, DNS_PROTOCOL_MDNS
)) {
1024 /* When dealing with protocols other than mDNS only consider responses with
1025 * equivalent query section to the request. For mDNS this check doesn't make
1026 * sense, because the section 6 of RFC6762 states that "Multicast DNS responses MUST NOT
1027 * contain any questions in the Question Section". */
1028 if (t
->scope
->protocol
!= DNS_PROTOCOL_MDNS
) {
1029 r
= dns_packet_is_reply_for(p
, t
->key
);
1033 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1038 /* Install the answer as answer to the transaction */
1039 dns_answer_unref(t
->answer
);
1040 t
->answer
= dns_answer_ref(p
->answer
);
1041 t
->answer_rcode
= DNS_PACKET_RCODE(p
);
1042 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
1043 t
->answer_authenticated
= false;
1045 r
= dns_transaction_fix_rcode(t
);
1049 /* Block GC while starting requests for additional DNSSEC RRs */
1051 r
= dns_transaction_request_dnssec_keys(t
);
1054 /* Maybe the transaction is ready for GC'ing now? If so, free it and return. */
1055 if (!dns_transaction_gc(t
))
1058 /* Requesting additional keys might have resulted in
1059 * this transaction to fail, since the auxiliary
1060 * request failed for some reason. If so, we are not
1061 * in pending state anymore, and we should exit
1063 if (t
->state
!= DNS_TRANSACTION_PENDING
)
1068 /* There are DNSSEC transactions pending now. Update the state accordingly. */
1069 t
->state
= DNS_TRANSACTION_VALIDATING
;
1070 dns_transaction_close_connection(t
);
1071 dns_transaction_stop_timeout(t
);
1076 dns_transaction_process_dnssec(t
);
1080 t
->answer_errno
= -r
;
1081 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
1084 static int on_dns_packet(sd_event_source
*s
, int fd
, uint32_t revents
, void *userdata
) {
1085 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1086 DnsTransaction
*t
= userdata
;
1092 r
= manager_recv(t
->scope
->manager
, fd
, DNS_PROTOCOL_DNS
, &p
);
1093 if (ERRNO_IS_DISCONNECT(-r
)) {
1096 /* UDP connection failure get reported via ICMP and then are possible delivered to us on the next
1097 * recvmsg(). Treat this like a lost packet. */
1099 log_debug_errno(r
, "Connection failure for DNS UDP packet: %m");
1100 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &usec
) >= 0);
1101 dns_server_packet_lost(t
->server
, IPPROTO_UDP
, t
->current_feature_level
, usec
- t
->start_usec
);
1103 dns_transaction_retry(t
, true);
1107 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
1108 t
->answer_errno
= -r
;
1112 r
= dns_packet_validate_reply(p
);
1114 log_debug_errno(r
, "Received invalid DNS packet as response, ignoring: %m");
1118 log_debug("Received inappropriate DNS packet as response, ignoring.");
1122 if (DNS_PACKET_ID(p
) != t
->id
) {
1123 log_debug("Received packet with incorrect transaction ID, ignoring.");
1127 dns_transaction_process_reply(t
, p
);
1131 static int dns_transaction_emit_udp(DnsTransaction
*t
) {
1136 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
) {
1138 r
= dns_transaction_pick_server(t
);
1142 if (t
->current_feature_level
< DNS_SERVER_FEATURE_LEVEL_UDP
)
1143 return -EAGAIN
; /* Sorry, can't do UDP, try TCP! */
1145 if (!dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(t
->key
->type
))
1148 if (r
> 0 || t
->dns_udp_fd
< 0) { /* Server changed, or no connection yet. */
1151 dns_transaction_close_connection(t
);
1153 fd
= dns_scope_socket_udp(t
->scope
, t
->server
, 53);
1157 r
= sd_event_add_io(t
->scope
->manager
->event
, &t
->dns_udp_event_source
, fd
, EPOLLIN
, on_dns_packet
, t
);
1163 (void) sd_event_source_set_description(t
->dns_udp_event_source
, "dns-transaction-udp");
1167 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
1171 dns_transaction_close_connection(t
);
1173 r
= dns_scope_emit_udp(t
->scope
, t
->dns_udp_fd
, t
->sent
);
1177 dns_transaction_reset_answer(t
);
1182 static int on_transaction_timeout(sd_event_source
*s
, usec_t usec
, void *userdata
) {
1183 DnsTransaction
*t
= userdata
;
1188 if (!t
->initial_jitter_scheduled
|| t
->initial_jitter_elapsed
) {
1189 /* Timeout reached? Increase the timeout for the server used */
1190 switch (t
->scope
->protocol
) {
1192 case DNS_PROTOCOL_DNS
:
1194 dns_server_packet_lost(t
->server
, t
->stream
? IPPROTO_TCP
: IPPROTO_UDP
, t
->current_feature_level
, usec
- t
->start_usec
);
1197 case DNS_PROTOCOL_LLMNR
:
1198 case DNS_PROTOCOL_MDNS
:
1199 dns_scope_packet_lost(t
->scope
, usec
- t
->start_usec
);
1203 assert_not_reached("Invalid DNS protocol.");
1206 if (t
->initial_jitter_scheduled
)
1207 t
->initial_jitter_elapsed
= true;
1210 log_debug("Timeout reached on transaction %" PRIu16
".", t
->id
);
1212 dns_transaction_retry(t
, true);
1216 static usec_t
transaction_get_resend_timeout(DnsTransaction
*t
) {
1221 switch (t
->scope
->protocol
) {
1223 case DNS_PROTOCOL_DNS
:
1225 /* When we do TCP, grant a much longer timeout, as in this case there's no need for us to quickly
1226 * resend, as the kernel does that anyway for us, and we really don't want to interrupt it in that
1229 return TRANSACTION_TCP_TIMEOUT_USEC
;
1232 return t
->server
->resend_timeout
;
1234 case DNS_PROTOCOL_MDNS
:
1235 assert(t
->n_attempts
> 0);
1237 return MDNS_PROBING_INTERVAL_USEC
;
1239 return (1 << (t
->n_attempts
- 1)) * USEC_PER_SEC
;
1241 case DNS_PROTOCOL_LLMNR
:
1242 return t
->scope
->resend_timeout
;
1245 assert_not_reached("Invalid DNS protocol.");
1249 static int dns_transaction_prepare(DnsTransaction
*t
, usec_t ts
) {
1254 dns_transaction_stop_timeout(t
);
1256 r
= dns_scope_network_good(t
->scope
);
1260 dns_transaction_complete(t
, DNS_TRANSACTION_NETWORK_DOWN
);
1264 if (t
->n_attempts
>= TRANSACTION_ATTEMPTS_MAX(t
->scope
->protocol
)) {
1265 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1269 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& t
->tried_stream
) {
1270 /* If we already tried via a stream, then we don't
1271 * retry on LLMNR. See RFC 4795, Section 2.7. */
1272 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1279 dns_transaction_reset_answer(t
);
1280 dns_transaction_flush_dnssec_transactions(t
);
1282 /* Check the trust anchor. Do so only on classic DNS, since DNSSEC does not apply otherwise. */
1283 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
) {
1284 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, t
->key
, &t
->answer
);
1288 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1289 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1290 t
->answer_authenticated
= true;
1291 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1295 if (dns_name_is_root(dns_resource_key_name(t
->key
)) &&
1296 t
->key
->type
== DNS_TYPE_DS
) {
1298 /* Hmm, this is a request for the root DS? A
1299 * DS RR doesn't exist in the root zone, and
1300 * if our trust anchor didn't know it either,
1301 * this means we cannot do any DNSSEC logic
1304 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
1305 /* We are in downgrade mode. In this
1306 * case, synthesize an unsigned empty
1307 * response, so that the any lookup
1308 * depending on this one can continue
1309 * assuming there was no DS, and hence
1310 * the root zone was unsigned. */
1312 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1313 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1314 t
->answer_authenticated
= false;
1315 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1317 /* If we are not in downgrade mode,
1318 * then fail the lookup, because we
1319 * cannot reasonably answer it. There
1320 * might be DS RRs, but we don't know
1321 * them, and the DNS server won't tell
1322 * them to us (and even if it would,
1323 * we couldn't validate and trust them. */
1324 dns_transaction_complete(t
, DNS_TRANSACTION_NO_TRUST_ANCHOR
);
1330 /* Check the zone, but only if this transaction is not used
1331 * for probing or verifying a zone item. */
1332 if (set_isempty(t
->notify_zone_items
)) {
1334 r
= dns_zone_lookup(&t
->scope
->zone
, t
->key
, dns_scope_ifindex(t
->scope
), &t
->answer
, NULL
, NULL
);
1338 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1339 t
->answer_source
= DNS_TRANSACTION_ZONE
;
1340 t
->answer_authenticated
= true;
1341 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1346 /* Check the cache, but only if this transaction is not used
1347 * for probing or verifying a zone item. */
1348 if (set_isempty(t
->notify_zone_items
)) {
1350 /* Before trying the cache, let's make sure we figured out a
1351 * server to use. Should this cause a change of server this
1352 * might flush the cache. */
1353 dns_scope_get_dns_server(t
->scope
);
1355 /* Let's then prune all outdated entries */
1356 dns_cache_prune(&t
->scope
->cache
);
1358 r
= dns_cache_lookup(&t
->scope
->cache
, t
->key
, t
->clamp_ttl
, &t
->answer_rcode
, &t
->answer
, &t
->answer_authenticated
);
1362 t
->answer_source
= DNS_TRANSACTION_CACHE
;
1363 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
1364 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1366 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
1374 static int dns_transaction_make_packet_mdns(DnsTransaction
*t
) {
1376 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1377 bool add_known_answers
= false;
1378 DnsTransaction
*other
;
1384 assert(t
->scope
->protocol
== DNS_PROTOCOL_MDNS
);
1386 /* Discard any previously prepared packet, so we can start over and coalesce again */
1387 t
->sent
= dns_packet_unref(t
->sent
);
1389 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, false);
1393 r
= dns_packet_append_key(p
, t
->key
, 0, NULL
);
1399 if (dns_key_is_shared(t
->key
))
1400 add_known_answers
= true;
1403 * For mDNS, we want to coalesce as many open queries in pending transactions into one single
1404 * query packet on the wire as possible. To achieve that, we iterate through all pending transactions
1405 * in our current scope, and see whether their timing contraints allow them to be sent.
1408 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &ts
) >= 0);
1410 LIST_FOREACH(transactions_by_scope
, other
, t
->scope
->transactions
) {
1412 /* Skip ourselves */
1416 if (other
->state
!= DNS_TRANSACTION_PENDING
)
1419 if (other
->next_attempt_after
> ts
)
1422 if (qdcount
>= UINT16_MAX
)
1425 r
= dns_packet_append_key(p
, other
->key
, 0, NULL
);
1428 * If we can't stuff more questions into the packet, just give up.
1429 * One of the 'other' transactions will fire later and take care of the rest.
1437 r
= dns_transaction_prepare(other
, ts
);
1441 ts
+= transaction_get_resend_timeout(other
);
1443 r
= sd_event_add_time(
1444 other
->scope
->manager
->event
,
1445 &other
->timeout_event_source
,
1446 clock_boottime_or_monotonic(),
1448 on_transaction_timeout
, other
);
1452 (void) sd_event_source_set_description(other
->timeout_event_source
, "dns-transaction-timeout");
1454 other
->state
= DNS_TRANSACTION_PENDING
;
1455 other
->next_attempt_after
= ts
;
1459 if (dns_key_is_shared(other
->key
))
1460 add_known_answers
= true;
1463 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(qdcount
);
1465 /* Append known answer section if we're asking for any shared record */
1466 if (add_known_answers
) {
1467 r
= dns_cache_export_shared_to_packet(&t
->scope
->cache
, p
);
1478 static int dns_transaction_make_packet(DnsTransaction
*t
) {
1479 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1484 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
)
1485 return dns_transaction_make_packet_mdns(t
);
1490 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, t
->scope
->dnssec_mode
!= DNSSEC_NO
);
1494 r
= dns_packet_append_key(p
, t
->key
, 0, NULL
);
1498 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(1);
1499 DNS_PACKET_HEADER(p
)->id
= t
->id
;
1507 int dns_transaction_go(DnsTransaction
*t
) {
1510 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
1514 /* Returns > 0 if the transaction is now pending, returns 0 if could be processed immediately and has finished
1517 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &ts
) >= 0);
1519 r
= dns_transaction_prepare(t
, ts
);
1523 log_debug("Transaction %" PRIu16
" for <%s> scope %s on %s/%s.",
1525 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
),
1526 dns_protocol_to_string(t
->scope
->protocol
),
1527 t
->scope
->link
? t
->scope
->link
->name
: "*",
1528 af_to_name_short(t
->scope
->family
));
1530 if (!t
->initial_jitter_scheduled
&&
1531 IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_LLMNR
, DNS_PROTOCOL_MDNS
)) {
1532 usec_t jitter
, accuracy
;
1534 /* RFC 4795 Section 2.7 suggests all queries should be
1535 * delayed by a random time from 0 to JITTER_INTERVAL. */
1537 t
->initial_jitter_scheduled
= true;
1539 random_bytes(&jitter
, sizeof(jitter
));
1541 switch (t
->scope
->protocol
) {
1543 case DNS_PROTOCOL_LLMNR
:
1544 jitter
%= LLMNR_JITTER_INTERVAL_USEC
;
1545 accuracy
= LLMNR_JITTER_INTERVAL_USEC
;
1548 case DNS_PROTOCOL_MDNS
:
1549 jitter
%= MDNS_JITTER_RANGE_USEC
;
1550 jitter
+= MDNS_JITTER_MIN_USEC
;
1551 accuracy
= MDNS_JITTER_RANGE_USEC
;
1554 assert_not_reached("bad protocol");
1557 r
= sd_event_add_time(
1558 t
->scope
->manager
->event
,
1559 &t
->timeout_event_source
,
1560 clock_boottime_or_monotonic(),
1561 ts
+ jitter
, accuracy
,
1562 on_transaction_timeout
, t
);
1566 (void) sd_event_source_set_description(t
->timeout_event_source
, "dns-transaction-timeout");
1569 t
->next_attempt_after
= ts
;
1570 t
->state
= DNS_TRANSACTION_PENDING
;
1572 log_debug("Delaying %s transaction for " USEC_FMT
"us.", dns_protocol_to_string(t
->scope
->protocol
), jitter
);
1576 /* Otherwise, we need to ask the network */
1577 r
= dns_transaction_make_packet(t
);
1581 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&&
1582 (dns_name_endswith(dns_resource_key_name(t
->key
), "in-addr.arpa") > 0 ||
1583 dns_name_endswith(dns_resource_key_name(t
->key
), "ip6.arpa") > 0)) {
1585 /* RFC 4795, Section 2.4. says reverse lookups shall
1586 * always be made via TCP on LLMNR */
1587 r
= dns_transaction_open_tcp(t
);
1589 /* Try via UDP, and if that fails due to large size or lack of
1590 * support try via TCP */
1591 r
= dns_transaction_emit_udp(t
);
1593 log_debug("Sending query via TCP since it is too large.");
1594 else if (r
== -EAGAIN
)
1595 log_debug("Sending query via TCP since server doesn't support UDP.");
1596 if (r
== -EMSGSIZE
|| r
== -EAGAIN
)
1597 r
= dns_transaction_open_tcp(t
);
1601 /* No servers to send this to? */
1602 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
1605 if (r
== -EOPNOTSUPP
) {
1606 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
1607 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
1610 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& ERRNO_IS_DISCONNECT(-r
)) {
1611 /* On LLMNR, if we cannot connect to a host via TCP when doing reverse lookups. This means we cannot
1612 * answer this request with this protocol. */
1613 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
1617 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1620 /* Couldn't send? Try immediately again, with a new server */
1621 dns_scope_next_dns_server(t
->scope
);
1623 return dns_transaction_go(t
);
1626 ts
+= transaction_get_resend_timeout(t
);
1628 r
= sd_event_add_time(
1629 t
->scope
->manager
->event
,
1630 &t
->timeout_event_source
,
1631 clock_boottime_or_monotonic(),
1633 on_transaction_timeout
, t
);
1637 (void) sd_event_source_set_description(t
->timeout_event_source
, "dns-transaction-timeout");
1639 t
->state
= DNS_TRANSACTION_PENDING
;
1640 t
->next_attempt_after
= ts
;
1645 static int dns_transaction_find_cyclic(DnsTransaction
*t
, DnsTransaction
*aux
) {
1653 /* Try to find cyclic dependencies between transaction objects */
1658 SET_FOREACH(n
, aux
->dnssec_transactions
, i
) {
1659 r
= dns_transaction_find_cyclic(t
, n
);
1667 static int dns_transaction_add_dnssec_transaction(DnsTransaction
*t
, DnsResourceKey
*key
, DnsTransaction
**ret
) {
1668 DnsTransaction
*aux
;
1675 aux
= dns_scope_find_transaction(t
->scope
, key
, true);
1677 r
= dns_transaction_new(&aux
, t
->scope
, key
);
1681 if (set_contains(t
->dnssec_transactions
, aux
)) {
1686 r
= dns_transaction_find_cyclic(t
, aux
);
1690 char s
[DNS_RESOURCE_KEY_STRING_MAX
], saux
[DNS_RESOURCE_KEY_STRING_MAX
];
1692 log_debug("Potential cyclic dependency, refusing to add transaction %" PRIu16
" (%s) as dependency for %" PRIu16
" (%s).",
1694 dns_resource_key_to_string(t
->key
, s
, sizeof s
),
1696 dns_resource_key_to_string(aux
->key
, saux
, sizeof saux
));
1702 r
= set_ensure_allocated(&t
->dnssec_transactions
, NULL
);
1706 r
= set_ensure_allocated(&aux
->notify_transactions
, NULL
);
1710 r
= set_ensure_allocated(&aux
->notify_transactions_done
, NULL
);
1714 r
= set_put(t
->dnssec_transactions
, aux
);
1718 r
= set_put(aux
->notify_transactions
, t
);
1720 (void) set_remove(t
->dnssec_transactions
, aux
);
1728 dns_transaction_gc(aux
);
1732 static int dns_transaction_request_dnssec_rr(DnsTransaction
*t
, DnsResourceKey
*key
) {
1733 _cleanup_(dns_answer_unrefp
) DnsAnswer
*a
= NULL
;
1734 DnsTransaction
*aux
;
1740 /* Try to get the data from the trust anchor */
1741 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, key
, &a
);
1745 r
= dns_answer_extend(&t
->validated_keys
, a
);
1752 /* This didn't work, ask for it via the network/cache then. */
1753 r
= dns_transaction_add_dnssec_transaction(t
, key
, &aux
);
1754 if (r
== -ELOOP
) /* This would result in a cyclic dependency */
1759 if (aux
->state
== DNS_TRANSACTION_NULL
) {
1760 r
= dns_transaction_go(aux
);
1768 static int dns_transaction_negative_trust_anchor_lookup(DnsTransaction
*t
, const char *name
) {
1773 /* Check whether the specified name is in the NTA
1774 * database, either in the global one, or the link-local
1777 r
= dns_trust_anchor_lookup_negative(&t
->scope
->manager
->trust_anchor
, name
);
1781 if (!t
->scope
->link
)
1784 return set_contains(t
->scope
->link
->dnssec_negative_trust_anchors
, name
);
1787 static int dns_transaction_has_unsigned_negative_answer(DnsTransaction
*t
) {
1792 /* Checks whether the answer is negative, and lacks NSEC/NSEC3
1793 * RRs to prove it */
1795 r
= dns_transaction_has_positive_answer(t
, NULL
);
1801 /* Is this key explicitly listed as a negative trust anchor?
1802 * If so, it's nothing we need to care about */
1803 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(t
->key
));
1809 /* The answer does not contain any RRs that match to the
1810 * question. If so, let's see if there are any NSEC/NSEC3 RRs
1811 * included. If not, the answer is unsigned. */
1813 r
= dns_answer_contains_nsec_or_nsec3(t
->answer
);
1822 static int dns_transaction_is_primary_response(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
1828 /* Check if the specified RR is the "primary" response,
1829 * i.e. either matches the question precisely or is a
1830 * CNAME/DNAME for it. */
1832 r
= dns_resource_key_match_rr(t
->key
, rr
, NULL
);
1836 return dns_resource_key_match_cname_or_dname(t
->key
, rr
->key
, NULL
);
1839 static bool dns_transaction_dnssec_supported(DnsTransaction
*t
) {
1842 /* Checks whether our transaction's DNS server is assumed to be compatible with DNSSEC. Returns false as soon
1843 * as we changed our mind about a server, and now believe it is incompatible with DNSSEC. */
1845 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1848 /* If we have picked no server, then we are working from the cache or some other source, and DNSSEC might well
1849 * be supported, hence return true. */
1853 /* Note that we do not check the feature level actually used for the transaction but instead the feature level
1854 * the server is known to support currently, as the transaction feature level might be lower than what the
1855 * server actually supports, since we might have downgraded this transaction's feature level because we got a
1856 * SERVFAIL earlier and wanted to check whether downgrading fixes it. */
1858 return dns_server_dnssec_supported(t
->server
);
1861 static bool dns_transaction_dnssec_supported_full(DnsTransaction
*t
) {
1867 /* Checks whether our transaction our any of the auxiliary transactions couldn't do DNSSEC. */
1869 if (!dns_transaction_dnssec_supported(t
))
1872 SET_FOREACH(dt
, t
->dnssec_transactions
, i
)
1873 if (!dns_transaction_dnssec_supported(dt
))
1879 int dns_transaction_request_dnssec_keys(DnsTransaction
*t
) {
1880 DnsResourceRecord
*rr
;
1887 * Retrieve all auxiliary RRs for the answer we got, so that
1888 * we can verify signatures or prove that RRs are rightfully
1889 * unsigned. Specifically:
1891 * - For RRSIG we get the matching DNSKEY
1892 * - For DNSKEY we get the matching DS
1893 * - For unsigned SOA/NS we get the matching DS
1894 * - For unsigned CNAME/DNAME/DS we get the parent SOA RR
1895 * - For other unsigned RRs we get the matching SOA RR
1896 * - For SOA/NS queries with no matching response RR, and no NSEC/NSEC3, the DS RR
1897 * - For DS queries with no matching response RRs, and no NSEC/NSEC3, the parent's SOA RR
1898 * - For other queries with no matching response RRs, and no NSEC/NSEC3, the SOA RR
1901 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
1903 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
1904 return 0; /* We only need to validate stuff from the network */
1905 if (!dns_transaction_dnssec_supported(t
))
1906 return 0; /* If we can't do DNSSEC anyway there's no point in geting the auxiliary RRs */
1908 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
1910 if (dns_type_is_pseudo(rr
->key
->type
))
1913 /* If this RR is in the negative trust anchor, we don't need to validate it. */
1914 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
1920 switch (rr
->key
->type
) {
1922 case DNS_TYPE_RRSIG
: {
1923 /* For each RRSIG we request the matching DNSKEY */
1924 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*dnskey
= NULL
;
1926 /* If this RRSIG is about a DNSKEY RR and the
1927 * signer is the same as the owner, then we
1928 * already have the DNSKEY, and we don't have
1929 * to look for more. */
1930 if (rr
->rrsig
.type_covered
== DNS_TYPE_DNSKEY
) {
1931 r
= dns_name_equal(rr
->rrsig
.signer
, dns_resource_key_name(rr
->key
));
1938 /* If the signer is not a parent of our
1939 * original query, then this is about an
1940 * auxiliary RRset, but not anything we asked
1941 * for. In this case we aren't interested,
1942 * because we don't want to request additional
1943 * RRs for stuff we didn't really ask for, and
1944 * also to avoid request loops, where
1945 * additional RRs from one transaction result
1946 * in another transaction whose additonal RRs
1947 * point back to the original transaction, and
1949 r
= dns_name_endswith(dns_resource_key_name(t
->key
), rr
->rrsig
.signer
);
1955 dnskey
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DNSKEY
, rr
->rrsig
.signer
);
1959 log_debug("Requesting DNSKEY to validate transaction %" PRIu16
" (%s, RRSIG with key tag: %" PRIu16
").",
1960 t
->id
, dns_resource_key_name(rr
->key
), rr
->rrsig
.key_tag
);
1961 r
= dns_transaction_request_dnssec_rr(t
, dnskey
);
1967 case DNS_TYPE_DNSKEY
: {
1968 /* For each DNSKEY we request the matching DS */
1969 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
1971 /* If the DNSKEY we are looking at is not for
1972 * zone we are interested in, nor any of its
1973 * parents, we aren't interested, and don't
1974 * request it. After all, we don't want to end
1975 * up in request loops, and want to keep
1976 * additional traffic down. */
1978 r
= dns_name_endswith(dns_resource_key_name(t
->key
), dns_resource_key_name(rr
->key
));
1984 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
1988 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, DNSKEY with key tag: %" PRIu16
").",
1989 t
->id
, dns_resource_key_name(rr
->key
), dnssec_keytag(rr
, false));
1990 r
= dns_transaction_request_dnssec_rr(t
, ds
);
1999 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
2001 /* For an unsigned SOA or NS, try to acquire
2002 * the matching DS RR, as we are at a zone cut
2003 * then, and whether a DS exists tells us
2004 * whether the zone is signed. Do so only if
2005 * this RR matches our original question,
2008 r
= dns_resource_key_match_rr(t
->key
, rr
, NULL
);
2012 /* Hmm, so this SOA RR doesn't match our original question. In this case, maybe this is
2013 * a negative reply, and we need the a SOA RR's TTL in order to cache a negative entry?
2014 * If so, we need to validate it, too. */
2016 r
= dns_answer_match_key(t
->answer
, t
->key
, NULL
);
2019 if (r
> 0) /* positive reply, we won't need the SOA and hence don't need to validate
2024 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2030 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
2034 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, unsigned SOA/NS RRset).",
2035 t
->id
, dns_resource_key_name(rr
->key
));
2036 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2044 case DNS_TYPE_CNAME
:
2045 case DNS_TYPE_DNAME
: {
2046 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2049 /* CNAMEs and DNAMEs cannot be located at a
2050 * zone apex, hence ask for the parent SOA for
2051 * unsigned CNAME/DNAME RRs, maybe that's the
2052 * apex. But do all that only if this is
2053 * actually a response to our original
2056 * Similar for DS RRs, which are signed when
2057 * the parent SOA is signed. */
2059 r
= dns_transaction_is_primary_response(t
, rr
);
2065 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2071 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
2077 name
= dns_resource_key_name(rr
->key
);
2078 r
= dns_name_parent(&name
);
2084 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, name
);
2088 log_debug("Requesting parent SOA to validate transaction %" PRIu16
" (%s, unsigned CNAME/DNAME/DS RRset).",
2089 t
->id
, dns_resource_key_name(rr
->key
));
2090 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2098 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2100 /* For other unsigned RRsets (including
2101 * NSEC/NSEC3!), look for proof the zone is
2102 * unsigned, by requesting the SOA RR of the
2103 * zone. However, do so only if they are
2104 * directly relevant to our original
2107 r
= dns_transaction_is_primary_response(t
, rr
);
2113 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2119 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, dns_resource_key_name(rr
->key
));
2123 log_debug("Requesting SOA to validate transaction %" PRIu16
" (%s, unsigned non-SOA/NS RRset <%s>).",
2124 t
->id
, dns_resource_key_name(rr
->key
), dns_resource_record_to_string(rr
));
2125 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2132 /* Above, we requested everything necessary to validate what
2133 * we got. Now, let's request what we need to validate what we
2136 r
= dns_transaction_has_unsigned_negative_answer(t
);
2143 name
= dns_resource_key_name(t
->key
);
2145 /* If this was a SOA or NS request, then check if there's a DS RR for the same domain. Note that this
2146 * could also be used as indication that we are not at a zone apex, but in real world setups there are
2147 * too many broken DNS servers (Hello, incapdns.net!) where non-terminal zones return NXDOMAIN even
2148 * though they have further children. If this was a DS request, then it's signed when the parent zone
2149 * is signed, hence ask the parent SOA in that case. If this was any other RR then ask for the SOA RR,
2150 * to see if that is signed. */
2152 if (t
->key
->type
== DNS_TYPE_DS
) {
2153 r
= dns_name_parent(&name
);
2155 type
= DNS_TYPE_SOA
;
2156 log_debug("Requesting parent SOA to validate transaction %" PRIu16
" (%s, unsigned empty DS response).",
2157 t
->id
, dns_resource_key_name(t
->key
));
2161 } else if (IN_SET(t
->key
->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
)) {
2164 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, unsigned empty SOA/NS response).",
2165 t
->id
, dns_resource_key_name(t
->key
));
2168 type
= DNS_TYPE_SOA
;
2169 log_debug("Requesting SOA to validate transaction %" PRIu16
" (%s, unsigned empty non-SOA/NS/DS response).",
2170 t
->id
, dns_resource_key_name(t
->key
));
2174 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2176 soa
= dns_resource_key_new(t
->key
->class, type
, name
);
2180 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2186 return dns_transaction_dnssec_is_live(t
);
2189 void dns_transaction_notify(DnsTransaction
*t
, DnsTransaction
*source
) {
2193 /* Invoked whenever any of our auxiliary DNSSEC transactions completed its work. If the state is still PENDING,
2194 we are still in the loop that adds further DNSSEC transactions, hence don't check if we are ready yet. If
2195 the state is VALIDATING however, we should check if we are complete now. */
2197 if (t
->state
== DNS_TRANSACTION_VALIDATING
)
2198 dns_transaction_process_dnssec(t
);
2201 static int dns_transaction_validate_dnskey_by_ds(DnsTransaction
*t
) {
2202 DnsResourceRecord
*rr
;
2207 /* Add all DNSKEY RRs from the answer that are validated by DS
2208 * RRs from the list of validated keys to the list of
2209 * validated keys. */
2211 DNS_ANSWER_FOREACH_IFINDEX(rr
, ifindex
, t
->answer
) {
2213 r
= dnssec_verify_dnskey_by_ds_search(rr
, t
->validated_keys
);
2219 /* If so, the DNSKEY is validated too. */
2220 r
= dns_answer_add_extend(&t
->validated_keys
, rr
, ifindex
, DNS_ANSWER_AUTHENTICATED
);
2228 static int dns_transaction_requires_rrsig(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2234 /* Checks if the RR we are looking for must be signed with an
2235 * RRSIG. This is used for positive responses. */
2237 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2240 if (dns_type_is_pseudo(rr
->key
->type
))
2243 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2249 switch (rr
->key
->type
) {
2251 case DNS_TYPE_RRSIG
:
2252 /* RRSIGs are the signatures themselves, they need no signing. */
2260 /* For SOA or NS RRs we look for a matching DS transaction */
2262 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2264 if (dt
->key
->class != rr
->key
->class)
2266 if (dt
->key
->type
!= DNS_TYPE_DS
)
2269 r
= dns_name_equal(dns_resource_key_name(dt
->key
), dns_resource_key_name(rr
->key
));
2275 /* We found a DS transactions for the SOA/NS
2276 * RRs we are looking at. If it discovered signed DS
2277 * RRs, then we need to be signed, too. */
2279 if (!dt
->answer_authenticated
)
2282 return dns_answer_match_key(dt
->answer
, dt
->key
, NULL
);
2285 /* We found nothing that proves this is safe to leave
2286 * this unauthenticated, hence ask inist on
2287 * authentication. */
2292 case DNS_TYPE_CNAME
:
2293 case DNS_TYPE_DNAME
: {
2294 const char *parent
= NULL
;
2299 * CNAME/DNAME RRs cannot be located at a zone apex, hence look directly for the parent SOA.
2301 * DS RRs are signed if the parent is signed, hence also look at the parent SOA
2304 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2306 if (dt
->key
->class != rr
->key
->class)
2308 if (dt
->key
->type
!= DNS_TYPE_SOA
)
2312 parent
= dns_resource_key_name(rr
->key
);
2313 r
= dns_name_parent(&parent
);
2317 if (rr
->key
->type
== DNS_TYPE_DS
)
2320 /* A CNAME/DNAME without a parent? That's sooo weird. */
2321 log_debug("Transaction %" PRIu16
" claims CNAME/DNAME at root. Refusing.", t
->id
);
2326 r
= dns_name_equal(dns_resource_key_name(dt
->key
), parent
);
2332 return t
->answer_authenticated
;
2342 /* Any other kind of RR (including DNSKEY/NSEC/NSEC3). Let's see if our SOA lookup was authenticated */
2344 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2346 if (dt
->key
->class != rr
->key
->class)
2348 if (dt
->key
->type
!= DNS_TYPE_SOA
)
2351 r
= dns_name_equal(dns_resource_key_name(dt
->key
), dns_resource_key_name(rr
->key
));
2357 /* We found the transaction that was supposed to find
2358 * the SOA RR for us. It was successful, but found no
2359 * RR for us. This means we are not at a zone cut. In
2360 * this case, we require authentication if the SOA
2361 * lookup was authenticated too. */
2362 return t
->answer_authenticated
;
2369 static int dns_transaction_in_private_tld(DnsTransaction
*t
, const DnsResourceKey
*key
) {
2375 /* If DNSSEC downgrade mode is on, checks whether the
2376 * specified RR is one level below a TLD we have proven not to
2377 * exist. In such a case we assume that this is a private
2378 * domain, and permit it.
2380 * This detects cases like the Fritz!Box router networks. Each
2381 * Fritz!Box router serves a private "fritz.box" zone, in the
2382 * non-existing TLD "box". Requests for the "fritz.box" domain
2383 * are served by the router itself, while requests for the
2384 * "box" domain will result in NXDOMAIN.
2386 * Note that this logic is unable to detect cases where a
2387 * router serves a private DNS zone directly under
2388 * non-existing TLD. In such a case we cannot detect whether
2389 * the TLD is supposed to exist or not, as all requests we
2390 * make for it will be answered by the router's zone, and not
2391 * by the root zone. */
2395 if (t
->scope
->dnssec_mode
!= DNSSEC_ALLOW_DOWNGRADE
)
2396 return false; /* In strict DNSSEC mode what doesn't exist, doesn't exist */
2398 tld
= dns_resource_key_name(key
);
2399 r
= dns_name_parent(&tld
);
2403 return false; /* Already the root domain */
2405 if (!dns_name_is_single_label(tld
))
2408 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2410 if (dt
->key
->class != key
->class)
2413 r
= dns_name_equal(dns_resource_key_name(dt
->key
), tld
);
2419 /* We found an auxiliary lookup we did for the TLD. If
2420 * that returned with NXDOMAIN, we know the TLD didn't
2421 * exist, and hence this might be a private zone. */
2423 return dt
->answer_rcode
== DNS_RCODE_NXDOMAIN
;
2429 static int dns_transaction_requires_nsec(DnsTransaction
*t
) {
2430 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
2439 /* Checks if we need to insist on NSEC/NSEC3 RRs for proving
2440 * this negative reply */
2442 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2445 if (dns_type_is_pseudo(t
->key
->type
))
2448 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(t
->key
));
2454 r
= dns_transaction_in_private_tld(t
, t
->key
);
2458 /* The lookup is from a TLD that is proven not to
2459 * exist, and we are in downgrade mode, hence ignore
2460 * that fact that we didn't get any NSEC RRs. */
2462 log_info("Detected a negative query %s in a private DNS zone, permitting unsigned response.",
2463 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
));
2467 name
= dns_resource_key_name(t
->key
);
2469 if (t
->key
->type
== DNS_TYPE_DS
) {
2471 /* We got a negative reply for this DS lookup? DS RRs are signed when their parent zone is signed,
2472 * hence check the parent SOA in this case. */
2474 r
= dns_name_parent(&name
);
2480 type
= DNS_TYPE_SOA
;
2482 } else if (IN_SET(t
->key
->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
))
2483 /* We got a negative reply for this SOA/NS lookup? If so, check if there's a DS RR for this */
2486 /* For all other negative replies, check for the SOA lookup */
2487 type
= DNS_TYPE_SOA
;
2489 /* For all other RRs we check the SOA on the same level to see
2490 * if it's signed. */
2492 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2494 if (dt
->key
->class != t
->key
->class)
2496 if (dt
->key
->type
!= type
)
2499 r
= dns_name_equal(dns_resource_key_name(dt
->key
), name
);
2505 return dt
->answer_authenticated
;
2508 /* If in doubt, require NSEC/NSEC3 */
2512 static int dns_transaction_dnskey_authenticated(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2513 DnsResourceRecord
*rrsig
;
2517 /* Checks whether any of the DNSKEYs used for the RRSIGs for
2518 * the specified RRset is authenticated (i.e. has a matching
2521 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2527 DNS_ANSWER_FOREACH(rrsig
, t
->answer
) {
2531 r
= dnssec_key_match_rrsig(rr
->key
, rrsig
);
2537 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2539 if (dt
->key
->class != rr
->key
->class)
2542 if (dt
->key
->type
== DNS_TYPE_DNSKEY
) {
2544 r
= dns_name_equal(dns_resource_key_name(dt
->key
), rrsig
->rrsig
.signer
);
2550 /* OK, we found an auxiliary DNSKEY
2551 * lookup. If that lookup is
2552 * authenticated, report this. */
2554 if (dt
->answer_authenticated
)
2559 } else if (dt
->key
->type
== DNS_TYPE_DS
) {
2561 r
= dns_name_equal(dns_resource_key_name(dt
->key
), rrsig
->rrsig
.signer
);
2567 /* OK, we found an auxiliary DS
2568 * lookup. If that lookup is
2569 * authenticated and non-zero, we
2572 if (!dt
->answer_authenticated
)
2575 return dns_answer_match_key(dt
->answer
, dt
->key
, NULL
);
2580 return found
? false : -ENXIO
;
2583 static int dns_transaction_known_signed(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2587 /* We know that the root domain is signed, hence if it appears
2588 * not to be signed, there's a problem with the DNS server */
2590 return rr
->key
->class == DNS_CLASS_IN
&&
2591 dns_name_is_root(dns_resource_key_name(rr
->key
));
2594 static int dns_transaction_check_revoked_trust_anchors(DnsTransaction
*t
) {
2595 DnsResourceRecord
*rr
;
2600 /* Maybe warn the user that we encountered a revoked DNSKEY
2601 * for a key from our trust anchor. Note that we don't care
2602 * whether the DNSKEY can be authenticated or not. It's
2603 * sufficient if it is self-signed. */
2605 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
2606 r
= dns_trust_anchor_check_revoked(&t
->scope
->manager
->trust_anchor
, rr
, t
->answer
);
2614 static int dns_transaction_invalidate_revoked_keys(DnsTransaction
*t
) {
2620 /* Removes all DNSKEY/DS objects from t->validated_keys that
2621 * our trust anchors database considers revoked. */
2624 DnsResourceRecord
*rr
;
2628 DNS_ANSWER_FOREACH(rr
, t
->validated_keys
) {
2629 r
= dns_trust_anchor_is_revoked(&t
->scope
->manager
->trust_anchor
, rr
);
2633 r
= dns_answer_remove_by_rr(&t
->validated_keys
, rr
);
2647 static int dns_transaction_copy_validated(DnsTransaction
*t
) {
2654 /* Copy all validated RRs from the auxiliary DNSSEC transactions into our set of validated RRs */
2656 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2658 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
2661 if (!dt
->answer_authenticated
)
2664 r
= dns_answer_extend(&t
->validated_keys
, dt
->answer
);
2673 DNSSEC_PHASE_DNSKEY
, /* Phase #1, only validate DNSKEYs */
2674 DNSSEC_PHASE_NSEC
, /* Phase #2, only validate NSEC+NSEC3 */
2675 DNSSEC_PHASE_ALL
, /* Phase #3, validate everything else */
2678 static int dnssec_validate_records(
2682 DnsAnswer
**validated
) {
2684 DnsResourceRecord
*rr
;
2687 /* Returns negative on error, 0 if validation failed, 1 to restart validation, 2 when finished. */
2689 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
2690 DnsResourceRecord
*rrsig
= NULL
;
2691 DnssecResult result
;
2693 switch (rr
->key
->type
) {
2694 case DNS_TYPE_RRSIG
:
2697 case DNS_TYPE_DNSKEY
:
2698 /* We validate DNSKEYs only in the DNSKEY and ALL phases */
2699 if (phase
== DNSSEC_PHASE_NSEC
)
2704 case DNS_TYPE_NSEC3
:
2707 /* We validate NSEC/NSEC3 only in the NSEC and ALL phases */
2708 if (phase
== DNSSEC_PHASE_DNSKEY
)
2713 /* We validate all other RRs only in the ALL phases */
2714 if (phase
!= DNSSEC_PHASE_ALL
)
2718 r
= dnssec_verify_rrset_search(t
->answer
, rr
->key
, t
->validated_keys
, USEC_INFINITY
, &result
, &rrsig
);
2722 log_debug("Looking at %s: %s", strna(dns_resource_record_to_string(rr
)), dnssec_result_to_string(result
));
2724 if (result
== DNSSEC_VALIDATED
) {
2726 if (rr
->key
->type
== DNS_TYPE_DNSKEY
) {
2727 /* If we just validated a DNSKEY RRset, then let's add these keys to
2728 * the set of validated keys for this transaction. */
2730 r
= dns_answer_copy_by_key(&t
->validated_keys
, t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
);
2734 /* Some of the DNSKEYs we just added might already have been revoked,
2735 * remove them again in that case. */
2736 r
= dns_transaction_invalidate_revoked_keys(t
);
2741 /* Add the validated RRset to the new list of validated
2742 * RRsets, and remove it from the unvalidated RRsets.
2743 * We mark the RRset as authenticated and cacheable. */
2744 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
);
2748 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_SECURE
, rr
->key
);
2750 /* Exit the loop, we dropped something from the answer, start from the beginning */
2754 /* If we haven't read all DNSKEYs yet a negative result of the validation is irrelevant, as
2755 * there might be more DNSKEYs coming. Similar, if we haven't read all NSEC/NSEC3 RRs yet,
2756 * we cannot do positive wildcard proofs yet, as those require the NSEC/NSEC3 RRs. */
2757 if (phase
!= DNSSEC_PHASE_ALL
)
2760 if (result
== DNSSEC_VALIDATED_WILDCARD
) {
2761 bool authenticated
= false;
2764 /* This RRset validated, but as a wildcard. This means we need
2765 * to prove via NSEC/NSEC3 that no matching non-wildcard RR exists. */
2767 /* First step, determine the source of synthesis */
2768 r
= dns_resource_record_source(rrsig
, &source
);
2772 r
= dnssec_test_positive_wildcard(*validated
,
2773 dns_resource_key_name(rr
->key
),
2775 rrsig
->rrsig
.signer
,
2778 /* Unless the NSEC proof showed that the key really doesn't exist something is off. */
2780 result
= DNSSEC_INVALID
;
2782 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
,
2783 authenticated
? (DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
) : 0);
2787 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, rr
->key
);
2789 /* Exit the loop, we dropped something from the answer, start from the beginning */
2794 if (result
== DNSSEC_NO_SIGNATURE
) {
2795 r
= dns_transaction_requires_rrsig(t
, rr
);
2799 /* Data does not require signing. In that case, just copy it over,
2800 * but remember that this is by no means authenticated. */
2801 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0);
2805 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
2809 r
= dns_transaction_known_signed(t
, rr
);
2813 /* This is an RR we know has to be signed. If it isn't this means
2814 * the server is not attaching RRSIGs, hence complain. */
2816 dns_server_packet_rrsig_missing(t
->server
, t
->current_feature_level
);
2818 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
2820 /* Downgrading is OK? If so, just consider the information unsigned */
2822 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0);
2826 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
2830 /* Otherwise, fail */
2831 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
2835 r
= dns_transaction_in_private_tld(t
, rr
->key
);
2839 char s
[DNS_RESOURCE_KEY_STRING_MAX
];
2841 /* The data is from a TLD that is proven not to exist, and we are in downgrade
2842 * mode, hence ignore the fact that this was not signed. */
2844 log_info("Detected RRset %s is in a private DNS zone, permitting unsigned RRs.",
2845 dns_resource_key_to_string(rr
->key
, s
, sizeof s
));
2847 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0);
2851 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
2858 DNSSEC_SIGNATURE_EXPIRED
,
2859 DNSSEC_UNSUPPORTED_ALGORITHM
)) {
2861 r
= dns_transaction_dnskey_authenticated(t
, rr
);
2862 if (r
< 0 && r
!= -ENXIO
)
2865 /* The DNSKEY transaction was not authenticated, this means there's
2866 * no DS for this, which means it's OK if no keys are found for this signature. */
2868 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0);
2872 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
2877 r
= dns_transaction_is_primary_response(t
, rr
);
2881 /* Look for a matching DNAME for this CNAME */
2882 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
2886 /* Also look among the stuff we already validated */
2887 r
= dns_answer_has_dname_for_cname(*validated
, rr
);
2895 DNSSEC_SIGNATURE_EXPIRED
,
2896 DNSSEC_NO_SIGNATURE
))
2897 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, rr
->key
);
2898 else /* DNSSEC_MISSING_KEY or DNSSEC_UNSUPPORTED_ALGORITHM */
2899 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, rr
->key
);
2901 /* This is a primary response to our question, and it failed validation.
2903 t
->answer_dnssec_result
= result
;
2907 /* This is a primary response, but we do have a DNAME RR
2908 * in the RR that can replay this CNAME, hence rely on
2909 * that, and we can remove the CNAME in favour of it. */
2912 /* This is just some auxiliary data. Just remove the RRset and continue. */
2913 r
= dns_answer_remove_by_key(&t
->answer
, rr
->key
);
2917 /* We dropped something from the answer, start from the beginning. */
2921 return 2; /* Finito. */
2924 int dns_transaction_validate_dnssec(DnsTransaction
*t
) {
2925 _cleanup_(dns_answer_unrefp
) DnsAnswer
*validated
= NULL
;
2927 DnsAnswerFlags flags
;
2929 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
2933 /* We have now collected all DS and DNSKEY RRs in
2934 * t->validated_keys, let's see which RRs we can now
2935 * authenticate with that. */
2937 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2940 /* Already validated */
2941 if (t
->answer_dnssec_result
!= _DNSSEC_RESULT_INVALID
)
2944 /* Our own stuff needs no validation */
2945 if (IN_SET(t
->answer_source
, DNS_TRANSACTION_ZONE
, DNS_TRANSACTION_TRUST_ANCHOR
)) {
2946 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
2947 t
->answer_authenticated
= true;
2951 /* Cached stuff is not affected by validation. */
2952 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
2955 if (!dns_transaction_dnssec_supported_full(t
)) {
2956 /* The server does not support DNSSEC, or doesn't augment responses with RRSIGs. */
2957 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
2958 log_debug("Not validating response for %" PRIu16
", used server feature level does not support DNSSEC.", t
->id
);
2962 log_debug("Validating response from transaction %" PRIu16
" (%s).",
2964 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
));
2966 /* First, see if this response contains any revoked trust
2967 * anchors we care about */
2968 r
= dns_transaction_check_revoked_trust_anchors(t
);
2972 /* Third, copy all RRs we acquired successfully from auxiliary RRs over. */
2973 r
= dns_transaction_copy_validated(t
);
2977 /* Second, see if there are DNSKEYs we already know a
2978 * validated DS for. */
2979 r
= dns_transaction_validate_dnskey_by_ds(t
);
2983 /* Fourth, remove all DNSKEY and DS RRs again that our trust
2984 * anchor says are revoked. After all we might have marked
2985 * some keys revoked above, but they might still be lingering
2986 * in our validated_keys list. */
2987 r
= dns_transaction_invalidate_revoked_keys(t
);
2991 phase
= DNSSEC_PHASE_DNSKEY
;
2993 bool have_nsec
= false;
2995 r
= dnssec_validate_records(t
, phase
, &have_nsec
, &validated
);
2999 /* Try again as long as we managed to achieve something */
3003 if (phase
== DNSSEC_PHASE_DNSKEY
&& have_nsec
) {
3004 /* OK, we processed all DNSKEYs, and there are NSEC/NSEC3 RRs, look at those now. */
3005 phase
= DNSSEC_PHASE_NSEC
;
3009 if (phase
!= DNSSEC_PHASE_ALL
) {
3010 /* OK, we processed all DNSKEYs and NSEC/NSEC3 RRs, look at all the rest now.
3011 * Note that in this third phase we start to remove RRs we couldn't validate. */
3012 phase
= DNSSEC_PHASE_ALL
;
3020 dns_answer_unref(t
->answer
);
3021 t
->answer
= validated
;
3024 /* At this point the answer only contains validated
3025 * RRsets. Now, let's see if it actually answers the question
3026 * we asked. If so, great! If it doesn't, then see if
3027 * NSEC/NSEC3 can prove this. */
3028 r
= dns_transaction_has_positive_answer(t
, &flags
);
3030 /* Yes, it answers the question! */
3032 if (flags
& DNS_ANSWER_AUTHENTICATED
) {
3033 /* The answer is fully authenticated, yay. */
3034 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3035 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3036 t
->answer_authenticated
= true;
3038 /* The answer is not fully authenticated. */
3039 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3040 t
->answer_authenticated
= false;
3043 } else if (r
== 0) {
3044 DnssecNsecResult nr
;
3045 bool authenticated
= false;
3047 /* Bummer! Let's check NSEC/NSEC3 */
3048 r
= dnssec_nsec_test(t
->answer
, t
->key
, &nr
, &authenticated
, &t
->answer_nsec_ttl
);
3054 case DNSSEC_NSEC_NXDOMAIN
:
3055 /* NSEC proves the domain doesn't exist. Very good. */
3056 log_debug("Proved NXDOMAIN via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3057 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3058 t
->answer_rcode
= DNS_RCODE_NXDOMAIN
;
3059 t
->answer_authenticated
= authenticated
;
3061 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, t
->key
);
3064 case DNSSEC_NSEC_NODATA
:
3065 /* NSEC proves that there's no data here, very good. */
3066 log_debug("Proved NODATA via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3067 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3068 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3069 t
->answer_authenticated
= authenticated
;
3071 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, t
->key
);
3074 case DNSSEC_NSEC_OPTOUT
:
3075 /* NSEC3 says the data might not be signed */
3076 log_debug("Data is NSEC3 opt-out via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3077 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3078 t
->answer_authenticated
= false;
3080 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, t
->key
);
3083 case DNSSEC_NSEC_NO_RR
:
3084 /* No NSEC data? Bummer! */
3086 r
= dns_transaction_requires_nsec(t
);
3090 t
->answer_dnssec_result
= DNSSEC_NO_SIGNATURE
;
3091 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, t
->key
);
3093 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3094 t
->answer_authenticated
= false;
3095 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, t
->key
);
3100 case DNSSEC_NSEC_UNSUPPORTED_ALGORITHM
:
3101 /* We don't know the NSEC3 algorithm used? */
3102 t
->answer_dnssec_result
= DNSSEC_UNSUPPORTED_ALGORITHM
;
3103 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, t
->key
);
3106 case DNSSEC_NSEC_FOUND
:
3107 case DNSSEC_NSEC_CNAME
:
3108 /* NSEC says it needs to be there, but we couldn't find it? Bummer! */
3109 t
->answer_dnssec_result
= DNSSEC_NSEC_MISMATCH
;
3110 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, t
->key
);
3114 assert_not_reached("Unexpected NSEC result.");
3121 static const char* const dns_transaction_state_table
[_DNS_TRANSACTION_STATE_MAX
] = {
3122 [DNS_TRANSACTION_NULL
] = "null",
3123 [DNS_TRANSACTION_PENDING
] = "pending",
3124 [DNS_TRANSACTION_VALIDATING
] = "validating",
3125 [DNS_TRANSACTION_RCODE_FAILURE
] = "rcode-failure",
3126 [DNS_TRANSACTION_SUCCESS
] = "success",
3127 [DNS_TRANSACTION_NO_SERVERS
] = "no-servers",
3128 [DNS_TRANSACTION_TIMEOUT
] = "timeout",
3129 [DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
] = "attempts-max-reached",
3130 [DNS_TRANSACTION_INVALID_REPLY
] = "invalid-reply",
3131 [DNS_TRANSACTION_ERRNO
] = "errno",
3132 [DNS_TRANSACTION_ABORTED
] = "aborted",
3133 [DNS_TRANSACTION_DNSSEC_FAILED
] = "dnssec-failed",
3134 [DNS_TRANSACTION_NO_TRUST_ANCHOR
] = "no-trust-anchor",
3135 [DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
] = "rr-type-unsupported",
3136 [DNS_TRANSACTION_NETWORK_DOWN
] = "network-down",
3137 [DNS_TRANSACTION_NOT_FOUND
] = "not-found",
3139 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state
, DnsTransactionState
);
3141 static const char* const dns_transaction_source_table
[_DNS_TRANSACTION_SOURCE_MAX
] = {
3142 [DNS_TRANSACTION_NETWORK
] = "network",
3143 [DNS_TRANSACTION_CACHE
] = "cache",
3144 [DNS_TRANSACTION_ZONE
] = "zone",
3145 [DNS_TRANSACTION_TRUST_ANCHOR
] = "trust-anchor",
3147 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source
, DnsTransactionSource
);