1 /* SPDX-License-Identifier: LGPL-2.1+ */
3 This file is part of systemd.
5 Copyright 2014 Lennart Poettering
7 systemd is free software; you can redistribute it and/or modify it
8 under the terms of the GNU Lesser General Public License as published by
9 the Free Software Foundation; either version 2.1 of the License, or
10 (at your option) any later version.
12 systemd is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public License
18 along with systemd; If not, see <http://www.gnu.org/licenses/>.
21 #include "sd-messages.h"
24 #include "alloc-util.h"
25 #include "dns-domain.h"
26 #include "errno-list.h"
28 #include "random-util.h"
29 #include "resolved-dns-cache.h"
30 #include "resolved-dns-transaction.h"
31 #include "resolved-llmnr.h"
32 #include "string-table.h"
34 #define TRANSACTIONS_MAX 4096
35 #define TRANSACTION_TCP_TIMEOUT_USEC (10U*USEC_PER_SEC)
37 static void dns_transaction_reset_answer(DnsTransaction
*t
) {
40 t
->received
= dns_packet_unref(t
->received
);
41 t
->answer
= dns_answer_unref(t
->answer
);
43 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
44 t
->answer_source
= _DNS_TRANSACTION_SOURCE_INVALID
;
45 t
->answer_authenticated
= false;
46 t
->answer_nsec_ttl
= (uint32_t) -1;
50 static void dns_transaction_flush_dnssec_transactions(DnsTransaction
*t
) {
55 while ((z
= set_steal_first(t
->dnssec_transactions
))) {
56 set_remove(z
->notify_transactions
, t
);
57 set_remove(z
->notify_transactions_done
, t
);
58 dns_transaction_gc(z
);
62 static void dns_transaction_close_connection(DnsTransaction
*t
) {
66 /* Let's detach the stream from our transaction, in case something else keeps a reference to it. */
67 t
->stream
->complete
= NULL
;
68 t
->stream
->on_packet
= NULL
;
69 t
->stream
->transaction
= NULL
;
70 t
->stream
= dns_stream_unref(t
->stream
);
73 t
->dns_udp_event_source
= sd_event_source_unref(t
->dns_udp_event_source
);
74 t
->dns_udp_fd
= safe_close(t
->dns_udp_fd
);
77 static void dns_transaction_stop_timeout(DnsTransaction
*t
) {
80 t
->timeout_event_source
= sd_event_source_unref(t
->timeout_event_source
);
83 DnsTransaction
* dns_transaction_free(DnsTransaction
*t
) {
91 log_debug("Freeing transaction %" PRIu16
".", t
->id
);
93 dns_transaction_close_connection(t
);
94 dns_transaction_stop_timeout(t
);
96 dns_packet_unref(t
->sent
);
97 dns_transaction_reset_answer(t
);
99 dns_server_unref(t
->server
);
102 hashmap_remove_value(t
->scope
->transactions_by_key
, t
->key
, t
);
103 LIST_REMOVE(transactions_by_scope
, t
->scope
->transactions
, t
);
106 hashmap_remove(t
->scope
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
));
109 while ((c
= set_steal_first(t
->notify_query_candidates
)))
110 set_remove(c
->transactions
, t
);
111 set_free(t
->notify_query_candidates
);
113 while ((c
= set_steal_first(t
->notify_query_candidates_done
)))
114 set_remove(c
->transactions
, t
);
115 set_free(t
->notify_query_candidates_done
);
117 while ((i
= set_steal_first(t
->notify_zone_items
)))
118 i
->probe_transaction
= NULL
;
119 set_free(t
->notify_zone_items
);
121 while ((i
= set_steal_first(t
->notify_zone_items_done
)))
122 i
->probe_transaction
= NULL
;
123 set_free(t
->notify_zone_items_done
);
125 while ((z
= set_steal_first(t
->notify_transactions
)))
126 set_remove(z
->dnssec_transactions
, t
);
127 set_free(t
->notify_transactions
);
129 while ((z
= set_steal_first(t
->notify_transactions_done
)))
130 set_remove(z
->dnssec_transactions
, t
);
131 set_free(t
->notify_transactions_done
);
133 dns_transaction_flush_dnssec_transactions(t
);
134 set_free(t
->dnssec_transactions
);
136 dns_answer_unref(t
->validated_keys
);
137 dns_resource_key_unref(t
->key
);
142 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsTransaction
*, dns_transaction_free
);
144 bool dns_transaction_gc(DnsTransaction
*t
) {
150 if (set_isempty(t
->notify_query_candidates
) &&
151 set_isempty(t
->notify_query_candidates_done
) &&
152 set_isempty(t
->notify_zone_items
) &&
153 set_isempty(t
->notify_zone_items_done
) &&
154 set_isempty(t
->notify_transactions
) &&
155 set_isempty(t
->notify_transactions_done
)) {
156 dns_transaction_free(t
);
163 static uint16_t pick_new_id(Manager
*m
) {
166 /* Find a fresh, unused transaction id. Note that this loop is bounded because there's a limit on the number of
167 * transactions, and it's much lower than the space of IDs. */
169 assert_cc(TRANSACTIONS_MAX
< 0xFFFF);
172 random_bytes(&new_id
, sizeof(new_id
));
173 while (new_id
== 0 ||
174 hashmap_get(m
->dns_transactions
, UINT_TO_PTR(new_id
)));
179 int dns_transaction_new(DnsTransaction
**ret
, DnsScope
*s
, DnsResourceKey
*key
) {
180 _cleanup_(dns_transaction_freep
) DnsTransaction
*t
= NULL
;
187 /* Don't allow looking up invalid or pseudo RRs */
188 if (!dns_type_is_valid_query(key
->type
))
190 if (dns_type_is_obsolete(key
->type
))
193 /* We only support the IN class */
194 if (!IN_SET(key
->class, DNS_CLASS_IN
, DNS_CLASS_ANY
))
197 if (hashmap_size(s
->manager
->dns_transactions
) >= TRANSACTIONS_MAX
)
200 r
= hashmap_ensure_allocated(&s
->manager
->dns_transactions
, NULL
);
204 r
= hashmap_ensure_allocated(&s
->transactions_by_key
, &dns_resource_key_hash_ops
);
208 t
= new0(DnsTransaction
, 1);
213 t
->answer_source
= _DNS_TRANSACTION_SOURCE_INVALID
;
214 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
215 t
->answer_nsec_ttl
= (uint32_t) -1;
216 t
->key
= dns_resource_key_ref(key
);
217 t
->current_feature_level
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
218 t
->clamp_feature_level
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
220 t
->id
= pick_new_id(s
->manager
);
222 r
= hashmap_put(s
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
), t
);
228 r
= hashmap_replace(s
->transactions_by_key
, t
->key
, t
);
230 hashmap_remove(s
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
));
234 LIST_PREPEND(transactions_by_scope
, s
->transactions
, t
);
237 s
->manager
->n_transactions_total
++;
247 static void dns_transaction_shuffle_id(DnsTransaction
*t
) {
251 /* Pick a new ID for this transaction. */
253 new_id
= pick_new_id(t
->scope
->manager
);
254 assert_se(hashmap_remove_and_put(t
->scope
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
), UINT_TO_PTR(new_id
), t
) >= 0);
256 log_debug("Transaction %" PRIu16
" is now %" PRIu16
".", t
->id
, new_id
);
259 /* Make sure we generate a new packet with the new ID */
260 t
->sent
= dns_packet_unref(t
->sent
);
263 static void dns_transaction_tentative(DnsTransaction
*t
, DnsPacket
*p
) {
264 _cleanup_free_
char *pretty
= NULL
;
265 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
271 if (manager_our_packet(t
->scope
->manager
, p
) != 0)
274 (void) in_addr_to_string(p
->family
, &p
->sender
, &pretty
);
276 log_debug("Transaction %" PRIu16
" for <%s> on scope %s on %s/%s got tentative packet from %s.",
278 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
),
279 dns_protocol_to_string(t
->scope
->protocol
),
280 t
->scope
->link
? t
->scope
->link
->name
: "*",
281 af_to_name_short(t
->scope
->family
),
284 /* RFC 4795, Section 4.1 says that the peer with the
285 * lexicographically smaller IP address loses */
286 if (memcmp(&p
->sender
, &p
->destination
, FAMILY_ADDRESS_SIZE(p
->family
)) >= 0) {
287 log_debug("Peer has lexicographically larger IP address and thus lost in the conflict.");
291 log_debug("We have the lexicographically larger IP address and thus lost in the conflict.");
295 while ((z
= set_first(t
->notify_zone_items
))) {
296 /* First, make sure the zone item drops the reference
298 dns_zone_item_probe_stop(z
);
300 /* Secondly, report this as conflict, so that we might
301 * look for a different hostname */
302 dns_zone_item_conflict(z
);
306 dns_transaction_gc(t
);
309 void dns_transaction_complete(DnsTransaction
*t
, DnsTransactionState state
) {
310 DnsQueryCandidate
*c
;
314 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
317 assert(!DNS_TRANSACTION_IS_LIVE(state
));
319 if (state
== DNS_TRANSACTION_DNSSEC_FAILED
) {
320 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
);
322 log_struct(LOG_NOTICE
,
323 "MESSAGE_ID=" SD_MESSAGE_DNSSEC_FAILURE_STR
,
324 LOG_MESSAGE("DNSSEC validation failed for question %s: %s", key_str
, dnssec_result_to_string(t
->answer_dnssec_result
)),
325 "DNS_TRANSACTION=%" PRIu16
, t
->id
,
326 "DNS_QUESTION=%s", key_str
,
327 "DNSSEC_RESULT=%s", dnssec_result_to_string(t
->answer_dnssec_result
),
328 "DNS_SERVER=%s", dns_server_string(t
->server
),
329 "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(t
->server
->possible_feature_level
),
333 /* Note that this call might invalidate the query. Callers
334 * should hence not attempt to access the query or transaction
335 * after calling this function. */
337 if (state
== DNS_TRANSACTION_ERRNO
)
338 st
= errno_to_name(t
->answer_errno
);
340 st
= dns_transaction_state_to_string(state
);
342 log_debug("Transaction %" PRIu16
" for <%s> on scope %s on %s/%s now complete with <%s> from %s (%s).",
344 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
),
345 dns_protocol_to_string(t
->scope
->protocol
),
346 t
->scope
->link
? t
->scope
->link
->name
: "*",
347 af_to_name_short(t
->scope
->family
),
349 t
->answer_source
< 0 ? "none" : dns_transaction_source_to_string(t
->answer_source
),
350 t
->answer_authenticated
? "authenticated" : "unsigned");
354 dns_transaction_close_connection(t
);
355 dns_transaction_stop_timeout(t
);
357 /* Notify all queries that are interested, but make sure the
358 * transaction isn't freed while we are still looking at it */
361 SET_FOREACH_MOVE(c
, t
->notify_query_candidates_done
, t
->notify_query_candidates
)
362 dns_query_candidate_notify(c
);
363 SWAP_TWO(t
->notify_query_candidates
, t
->notify_query_candidates_done
);
365 SET_FOREACH_MOVE(z
, t
->notify_zone_items_done
, t
->notify_zone_items
)
366 dns_zone_item_notify(z
);
367 SWAP_TWO(t
->notify_zone_items
, t
->notify_zone_items_done
);
369 (void) dns_scope_announce(t
->scope
, false);
371 SET_FOREACH_MOVE(d
, t
->notify_transactions_done
, t
->notify_transactions
)
372 dns_transaction_notify(d
, t
);
373 SWAP_TWO(t
->notify_transactions
, t
->notify_transactions_done
);
376 dns_transaction_gc(t
);
379 static int dns_transaction_pick_server(DnsTransaction
*t
) {
383 assert(t
->scope
->protocol
== DNS_PROTOCOL_DNS
);
385 /* Pick a DNS server and a feature level for it. */
387 server
= dns_scope_get_dns_server(t
->scope
);
391 /* If we changed the server invalidate the feature level clamping, as the new server might have completely
392 * different properties. */
393 if (server
!= t
->server
)
394 t
->clamp_feature_level
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
396 t
->current_feature_level
= dns_server_possible_feature_level(server
);
398 /* Clamp the feature level if that is requested. */
399 if (t
->clamp_feature_level
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
&&
400 t
->current_feature_level
> t
->clamp_feature_level
)
401 t
->current_feature_level
= t
->clamp_feature_level
;
403 log_debug("Using feature level %s for transaction %u.", dns_server_feature_level_to_string(t
->current_feature_level
), t
->id
);
405 if (server
== t
->server
)
408 dns_server_unref(t
->server
);
409 t
->server
= dns_server_ref(server
);
411 log_debug("Using DNS server %s for transaction %u.", dns_server_string(t
->server
), t
->id
);
416 static void dns_transaction_retry(DnsTransaction
*t
, bool next_server
) {
421 log_debug("Retrying transaction %" PRIu16
".", t
->id
);
423 /* Before we try again, switch to a new server. */
425 dns_scope_next_dns_server(t
->scope
);
427 r
= dns_transaction_go(t
);
429 t
->answer_errno
= -r
;
430 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
434 static int dns_transaction_maybe_restart(DnsTransaction
*t
) {
439 /* Returns > 0 if the transaction was restarted, 0 if not */
444 if (t
->current_feature_level
<= dns_server_possible_feature_level(t
->server
))
447 /* The server's current feature level is lower than when we sent the original query. We learnt something from
448 the response or possibly an auxiliary DNSSEC response that we didn't know before. We take that as reason to
449 restart the whole transaction. This is a good idea to deal with servers that respond rubbish if we include
450 OPT RR or DO bit. One of these cases is documented here, for example:
451 https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */
453 log_debug("Server feature level is now lower than when we began our transaction. Restarting with new ID.");
454 dns_transaction_shuffle_id(t
);
456 r
= dns_transaction_go(t
);
463 static int on_stream_complete(DnsStream
*s
, int error
) {
464 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
468 assert(s
->transaction
);
470 /* Copy the data we care about out of the stream before we
473 p
= dns_packet_ref(s
->read_packet
);
475 dns_transaction_close_connection(t
);
477 if (ERRNO_IS_DISCONNECT(error
)) {
480 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
) {
481 /* If the LLMNR/TCP connection failed, the host doesn't support LLMNR, and we cannot answer the
482 * question on this scope. */
483 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
487 log_debug_errno(error
, "Connection failure for DNS TCP stream: %m");
488 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &usec
) >= 0);
489 dns_server_packet_lost(t
->server
, IPPROTO_TCP
, t
->current_feature_level
, usec
- t
->start_usec
);
491 dns_transaction_retry(t
, true);
495 t
->answer_errno
= error
;
496 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
500 if (dns_packet_validate_reply(p
) <= 0) {
501 log_debug("Invalid TCP reply packet.");
502 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
506 dns_scope_check_conflicts(t
->scope
, p
);
509 dns_transaction_process_reply(t
, p
);
512 /* If the response wasn't useful, then complete the transition
513 * now. After all, we are the worst feature set now with TCP
514 * sockets, and there's really no point in retrying. */
515 if (t
->state
== DNS_TRANSACTION_PENDING
)
516 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
518 dns_transaction_gc(t
);
523 static int dns_transaction_open_tcp(DnsTransaction
*t
) {
524 _cleanup_close_
int fd
= -1;
529 dns_transaction_close_connection(t
);
531 switch (t
->scope
->protocol
) {
533 case DNS_PROTOCOL_DNS
:
534 r
= dns_transaction_pick_server(t
);
538 if (!dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(t
->key
->type
))
541 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
545 fd
= dns_scope_socket_tcp(t
->scope
, AF_UNSPEC
, NULL
, t
->server
, 53);
548 case DNS_PROTOCOL_LLMNR
:
549 /* When we already received a reply to this (but it was truncated), send to its sender address */
551 fd
= dns_scope_socket_tcp(t
->scope
, t
->received
->family
, &t
->received
->sender
, NULL
, t
->received
->sender_port
);
553 union in_addr_union address
;
554 int family
= AF_UNSPEC
;
556 /* Otherwise, try to talk to the owner of a
557 * the IP address, in case this is a reverse
560 r
= dns_name_address(dns_resource_key_name(t
->key
), &family
, &address
);
565 if (family
!= t
->scope
->family
)
568 fd
= dns_scope_socket_tcp(t
->scope
, family
, &address
, NULL
, LLMNR_PORT
);
574 return -EAFNOSUPPORT
;
580 r
= dns_stream_new(t
->scope
->manager
, &t
->stream
, t
->scope
->protocol
, fd
);
585 r
= dns_stream_write_packet(t
->stream
, t
->sent
);
587 t
->stream
= dns_stream_unref(t
->stream
);
591 t
->stream
->complete
= on_stream_complete
;
592 t
->stream
->transaction
= t
;
594 /* The interface index is difficult to determine if we are
595 * connecting to the local host, hence fill this in right away
596 * instead of determining it from the socket */
597 t
->stream
->ifindex
= dns_scope_ifindex(t
->scope
);
599 dns_transaction_reset_answer(t
);
601 t
->tried_stream
= true;
606 static void dns_transaction_cache_answer(DnsTransaction
*t
) {
609 /* For mDNS we cache whenever we get the packet, rather than
610 * in each transaction. */
611 if (!IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_DNS
, DNS_PROTOCOL_LLMNR
))
614 /* Caching disabled? */
615 if (!t
->scope
->manager
->enable_cache
)
618 /* We never cache if this packet is from the local host, under
619 * the assumption that a locally running DNS server would
620 * cache this anyway, and probably knows better when to flush
621 * the cache then we could. */
622 if (!DNS_PACKET_SHALL_CACHE(t
->received
))
625 dns_cache_put(&t
->scope
->cache
,
629 t
->answer_authenticated
,
633 &t
->received
->sender
);
636 static bool dns_transaction_dnssec_is_live(DnsTransaction
*t
) {
642 SET_FOREACH(dt
, t
->dnssec_transactions
, i
)
643 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
649 static int dns_transaction_dnssec_ready(DnsTransaction
*t
) {
655 /* Checks whether the auxiliary DNSSEC transactions of our transaction have completed, or are still
656 * ongoing. Returns 0, if we aren't ready for the DNSSEC validation, positive if we are. */
658 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
662 case DNS_TRANSACTION_NULL
:
663 case DNS_TRANSACTION_PENDING
:
664 case DNS_TRANSACTION_VALIDATING
:
668 case DNS_TRANSACTION_RCODE_FAILURE
:
669 if (!IN_SET(dt
->answer_rcode
, DNS_RCODE_NXDOMAIN
, DNS_RCODE_SERVFAIL
)) {
670 log_debug("Auxiliary DNSSEC RR query failed with rcode=%s.", dns_rcode_to_string(dt
->answer_rcode
));
674 /* Fall-through: NXDOMAIN/SERVFAIL is good enough for us. This is because some DNS servers
675 * erronously return NXDOMAIN/SERVFAIL for empty non-terminals (Akamai...) or missing DS
676 * records (Facebook), and we need to handle that nicely, when asking for parent SOA or similar
677 * RRs to make unsigned proofs. */
679 case DNS_TRANSACTION_SUCCESS
:
683 case DNS_TRANSACTION_DNSSEC_FAILED
:
684 /* We handle DNSSEC failures different from other errors, as we care about the DNSSEC
685 * validationr result */
687 log_debug("Auxiliary DNSSEC RR query failed validation: %s", dnssec_result_to_string(dt
->answer_dnssec_result
));
688 t
->answer_dnssec_result
= dt
->answer_dnssec_result
; /* Copy error code over */
689 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
694 log_debug("Auxiliary DNSSEC RR query failed with %s", dns_transaction_state_to_string(dt
->state
));
699 /* All is ready, we can go and validate */
703 t
->answer_dnssec_result
= DNSSEC_FAILED_AUXILIARY
;
704 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
708 static void dns_transaction_process_dnssec(DnsTransaction
*t
) {
713 /* Are there ongoing DNSSEC transactions? If so, let's wait for them. */
714 r
= dns_transaction_dnssec_ready(t
);
717 if (r
== 0) /* We aren't ready yet (or one of our auxiliary transactions failed, and we shouldn't validate now */
720 /* See if we learnt things from the additional DNSSEC transactions, that we didn't know before, and better
721 * restart the lookup immediately. */
722 r
= dns_transaction_maybe_restart(t
);
725 if (r
> 0) /* Transaction got restarted... */
728 /* All our auxiliary DNSSEC transactions are complete now. Try
729 * to validate our RRset now. */
730 r
= dns_transaction_validate_dnssec(t
);
732 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
738 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
&&
739 t
->scope
->dnssec_mode
== DNSSEC_YES
) {
740 /* We are not in automatic downgrade mode, and the
741 * server is bad, refuse operation. */
742 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
746 if (!IN_SET(t
->answer_dnssec_result
,
747 _DNSSEC_RESULT_INVALID
, /* No DNSSEC validation enabled */
748 DNSSEC_VALIDATED
, /* Answer is signed and validated successfully */
749 DNSSEC_UNSIGNED
, /* Answer is right-fully unsigned */
750 DNSSEC_INCOMPATIBLE_SERVER
)) { /* Server does not do DNSSEC (Yay, we are downgrade attack vulnerable!) */
751 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
755 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
)
756 dns_server_warn_downgrade(t
->server
);
758 dns_transaction_cache_answer(t
);
760 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
761 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
763 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
768 t
->answer_errno
= -r
;
769 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
772 static int dns_transaction_has_positive_answer(DnsTransaction
*t
, DnsAnswerFlags
*flags
) {
777 /* Checks whether the answer is positive, i.e. either a direct
778 * answer to the question, or a CNAME/DNAME for it */
780 r
= dns_answer_match_key(t
->answer
, t
->key
, flags
);
784 r
= dns_answer_find_cname_or_dname(t
->answer
, t
->key
, NULL
, flags
);
791 static int dns_transaction_fix_rcode(DnsTransaction
*t
) {
796 /* Fix up the RCODE to SUCCESS if we get at least one matching RR in a response. Note that this contradicts the
797 * DNS RFCs a bit. Specifically, RFC 6604 Section 3 clarifies that the RCODE shall say something about a
798 * CNAME/DNAME chain element coming after the last chain element contained in the message, and not the first
799 * one included. However, it also indicates that not all DNS servers implement this correctly. Moreover, when
800 * using DNSSEC we usually only can prove the first element of a CNAME/DNAME chain anyway, hence let's settle
801 * on always processing the RCODE as referring to the immediate look-up we do, i.e. the first element of a
802 * CNAME/DNAME chain. This way, we uniformly handle CNAME/DNAME chains, regardless if the DNS server
803 * incorrectly implements RCODE, whether DNSSEC is in use, or whether the DNS server only supplied us with an
804 * incomplete CNAME/DNAME chain.
806 * Or in other words: if we get at least one positive reply in a message we patch NXDOMAIN to become SUCCESS,
807 * and then rely on the CNAME chasing logic to figure out that there's actually a CNAME error with a new
810 if (t
->answer_rcode
!= DNS_RCODE_NXDOMAIN
)
813 r
= dns_transaction_has_positive_answer(t
, NULL
);
817 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
821 void dns_transaction_process_reply(DnsTransaction
*t
, DnsPacket
*p
) {
828 assert(t
->scope
->manager
);
830 if (t
->state
!= DNS_TRANSACTION_PENDING
)
833 /* Note that this call might invalidate the query. Callers
834 * should hence not attempt to access the query or transaction
835 * after calling this function. */
837 log_debug("Processing incoming packet on transaction %" PRIu16
". (rcode=%s)", t
->id
, dns_rcode_to_string(DNS_PACKET_RCODE(p
)));
839 switch (t
->scope
->protocol
) {
841 case DNS_PROTOCOL_LLMNR
:
842 /* For LLMNR we will not accept any packets from other interfaces */
844 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
847 if (p
->family
!= t
->scope
->family
)
850 /* Tentative packets are not full responses but still
851 * useful for identifying uniqueness conflicts during
853 if (DNS_PACKET_LLMNR_T(p
)) {
854 dns_transaction_tentative(t
, p
);
860 case DNS_PROTOCOL_MDNS
:
861 /* For mDNS we will not accept any packets from other interfaces */
863 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
866 if (p
->family
!= t
->scope
->family
)
871 case DNS_PROTOCOL_DNS
:
872 /* Note that we do not need to verify the
873 * addresses/port numbers of incoming traffic, as we
874 * invoked connect() on our UDP socket in which case
875 * the kernel already does the needed verification for
880 assert_not_reached("Invalid DNS protocol.");
883 if (t
->received
!= p
) {
884 dns_packet_unref(t
->received
);
885 t
->received
= dns_packet_ref(p
);
888 t
->answer_source
= DNS_TRANSACTION_NETWORK
;
890 if (p
->ipproto
== IPPROTO_TCP
) {
891 if (DNS_PACKET_TC(p
)) {
892 /* Truncated via TCP? Somebody must be fucking with us */
893 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
897 if (DNS_PACKET_ID(p
) != t
->id
) {
898 /* Not the reply to our query? Somebody must be fucking with us */
899 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
904 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &ts
) >= 0);
906 switch (t
->scope
->protocol
) {
908 case DNS_PROTOCOL_DNS
:
911 if (IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_FORMERR
, DNS_RCODE_SERVFAIL
, DNS_RCODE_NOTIMP
)) {
913 /* Request failed, immediately try again with reduced features */
915 if (t
->current_feature_level
<= DNS_SERVER_FEATURE_LEVEL_UDP
) {
916 /* This was already at UDP feature level? If so, it doesn't make sense to downgrade
917 * this transaction anymore, hence let's process the response, and accept the
918 * rcode. Note that we don't retry on TCP, since that's a suitable way to mitigate
919 * packet loss, but is not going to give us better rcodes should we actually have
920 * managed to get them already at UDP level. */
922 log_debug("Server returned error: %s", dns_rcode_to_string(DNS_PACKET_RCODE(p
)));
926 /* Reduce this feature level by one and try again. */
927 t
->clamp_feature_level
= t
->current_feature_level
- 1;
929 log_debug("Server returned error %s, retrying transaction with reduced feature level %s.",
930 dns_rcode_to_string(DNS_PACKET_RCODE(p
)),
931 dns_server_feature_level_to_string(t
->clamp_feature_level
));
933 dns_transaction_retry(t
, false /* use the same server */);
937 if (DNS_PACKET_RCODE(p
) == DNS_RCODE_REFUSED
) {
938 /* This server refused our request? If so, try again, use a different server */
939 log_debug("Server returned REFUSED, switching servers, and retrying.");
940 dns_transaction_retry(t
, true /* pick a new server */);
944 if (DNS_PACKET_TC(p
))
945 dns_server_packet_truncated(t
->server
, t
->current_feature_level
);
949 case DNS_PROTOCOL_LLMNR
:
950 case DNS_PROTOCOL_MDNS
:
951 dns_scope_packet_received(t
->scope
, ts
- t
->start_usec
);
955 assert_not_reached("Invalid DNS protocol.");
958 if (DNS_PACKET_TC(p
)) {
960 /* Truncated packets for mDNS are not allowed. Give up immediately. */
961 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
) {
962 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
966 log_debug("Reply truncated, retrying via TCP.");
968 /* Response was truncated, let's try again with good old TCP */
969 r
= dns_transaction_open_tcp(t
);
971 /* No servers found? Damn! */
972 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
975 if (r
== -EOPNOTSUPP
) {
976 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
977 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
981 /* On LLMNR, if we cannot connect to the host,
982 * we immediately give up */
983 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
986 /* On DNS, couldn't send? Try immediately again, with a new server */
987 dns_transaction_retry(t
, true);
993 /* After the superficial checks, actually parse the message. */
994 r
= dns_packet_extract(p
);
996 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1001 /* Report that we successfully received a valid packet with a good rcode after we initially got a bad
1002 * rcode and subsequently downgraded the protocol */
1004 if (IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_SUCCESS
, DNS_RCODE_NXDOMAIN
) &&
1005 t
->clamp_feature_level
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
)
1006 dns_server_packet_rcode_downgrade(t
->server
, t
->clamp_feature_level
);
1008 /* Report that the OPT RR was missing */
1010 dns_server_packet_bad_opt(t
->server
, t
->current_feature_level
);
1012 /* Report that we successfully received a packet */
1013 dns_server_packet_received(t
->server
, p
->ipproto
, t
->current_feature_level
, ts
- t
->start_usec
, p
->size
);
1016 /* See if we know things we didn't know before that indicate we better restart the lookup immediately. */
1017 r
= dns_transaction_maybe_restart(t
);
1020 if (r
> 0) /* Transaction got restarted... */
1023 if (IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_DNS
, DNS_PROTOCOL_LLMNR
, DNS_PROTOCOL_MDNS
)) {
1025 /* When dealing with protocols other than mDNS only consider responses with
1026 * equivalent query section to the request. For mDNS this check doesn't make
1027 * sense, because the section 6 of RFC6762 states that "Multicast DNS responses MUST NOT
1028 * contain any questions in the Question Section". */
1029 if (t
->scope
->protocol
!= DNS_PROTOCOL_MDNS
) {
1030 r
= dns_packet_is_reply_for(p
, t
->key
);
1034 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1039 /* Install the answer as answer to the transaction */
1040 dns_answer_unref(t
->answer
);
1041 t
->answer
= dns_answer_ref(p
->answer
);
1042 t
->answer_rcode
= DNS_PACKET_RCODE(p
);
1043 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
1044 t
->answer_authenticated
= false;
1046 r
= dns_transaction_fix_rcode(t
);
1050 /* Block GC while starting requests for additional DNSSEC RRs */
1052 r
= dns_transaction_request_dnssec_keys(t
);
1055 /* Maybe the transaction is ready for GC'ing now? If so, free it and return. */
1056 if (!dns_transaction_gc(t
))
1059 /* Requesting additional keys might have resulted in
1060 * this transaction to fail, since the auxiliary
1061 * request failed for some reason. If so, we are not
1062 * in pending state anymore, and we should exit
1064 if (t
->state
!= DNS_TRANSACTION_PENDING
)
1069 /* There are DNSSEC transactions pending now. Update the state accordingly. */
1070 t
->state
= DNS_TRANSACTION_VALIDATING
;
1071 dns_transaction_close_connection(t
);
1072 dns_transaction_stop_timeout(t
);
1077 dns_transaction_process_dnssec(t
);
1081 t
->answer_errno
= -r
;
1082 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
1085 static int on_dns_packet(sd_event_source
*s
, int fd
, uint32_t revents
, void *userdata
) {
1086 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1087 DnsTransaction
*t
= userdata
;
1093 r
= manager_recv(t
->scope
->manager
, fd
, DNS_PROTOCOL_DNS
, &p
);
1094 if (ERRNO_IS_DISCONNECT(-r
)) {
1097 /* UDP connection failure get reported via ICMP and then are possible delivered to us on the next
1098 * recvmsg(). Treat this like a lost packet. */
1100 log_debug_errno(r
, "Connection failure for DNS UDP packet: %m");
1101 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &usec
) >= 0);
1102 dns_server_packet_lost(t
->server
, IPPROTO_UDP
, t
->current_feature_level
, usec
- t
->start_usec
);
1104 dns_transaction_retry(t
, true);
1108 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
1109 t
->answer_errno
= -r
;
1113 r
= dns_packet_validate_reply(p
);
1115 log_debug_errno(r
, "Received invalid DNS packet as response, ignoring: %m");
1119 log_debug("Received inappropriate DNS packet as response, ignoring.");
1123 if (DNS_PACKET_ID(p
) != t
->id
) {
1124 log_debug("Received packet with incorrect transaction ID, ignoring.");
1128 dns_transaction_process_reply(t
, p
);
1132 static int dns_transaction_emit_udp(DnsTransaction
*t
) {
1137 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
) {
1139 r
= dns_transaction_pick_server(t
);
1143 if (t
->current_feature_level
< DNS_SERVER_FEATURE_LEVEL_UDP
)
1144 return -EAGAIN
; /* Sorry, can't do UDP, try TCP! */
1146 if (!dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(t
->key
->type
))
1149 if (r
> 0 || t
->dns_udp_fd
< 0) { /* Server changed, or no connection yet. */
1152 dns_transaction_close_connection(t
);
1154 fd
= dns_scope_socket_udp(t
->scope
, t
->server
, 53);
1158 r
= sd_event_add_io(t
->scope
->manager
->event
, &t
->dns_udp_event_source
, fd
, EPOLLIN
, on_dns_packet
, t
);
1164 (void) sd_event_source_set_description(t
->dns_udp_event_source
, "dns-transaction-udp");
1168 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
1172 dns_transaction_close_connection(t
);
1174 r
= dns_scope_emit_udp(t
->scope
, t
->dns_udp_fd
, t
->sent
);
1178 dns_transaction_reset_answer(t
);
1183 static int on_transaction_timeout(sd_event_source
*s
, usec_t usec
, void *userdata
) {
1184 DnsTransaction
*t
= userdata
;
1189 if (!t
->initial_jitter_scheduled
|| t
->initial_jitter_elapsed
) {
1190 /* Timeout reached? Increase the timeout for the server used */
1191 switch (t
->scope
->protocol
) {
1193 case DNS_PROTOCOL_DNS
:
1195 dns_server_packet_lost(t
->server
, t
->stream
? IPPROTO_TCP
: IPPROTO_UDP
, t
->current_feature_level
, usec
- t
->start_usec
);
1198 case DNS_PROTOCOL_LLMNR
:
1199 case DNS_PROTOCOL_MDNS
:
1200 dns_scope_packet_lost(t
->scope
, usec
- t
->start_usec
);
1204 assert_not_reached("Invalid DNS protocol.");
1207 if (t
->initial_jitter_scheduled
)
1208 t
->initial_jitter_elapsed
= true;
1211 log_debug("Timeout reached on transaction %" PRIu16
".", t
->id
);
1213 dns_transaction_retry(t
, true);
1217 static usec_t
transaction_get_resend_timeout(DnsTransaction
*t
) {
1222 switch (t
->scope
->protocol
) {
1224 case DNS_PROTOCOL_DNS
:
1226 /* When we do TCP, grant a much longer timeout, as in this case there's no need for us to quickly
1227 * resend, as the kernel does that anyway for us, and we really don't want to interrupt it in that
1230 return TRANSACTION_TCP_TIMEOUT_USEC
;
1233 return t
->server
->resend_timeout
;
1235 case DNS_PROTOCOL_MDNS
:
1236 assert(t
->n_attempts
> 0);
1238 return MDNS_PROBING_INTERVAL_USEC
;
1240 return (1 << (t
->n_attempts
- 1)) * USEC_PER_SEC
;
1242 case DNS_PROTOCOL_LLMNR
:
1243 return t
->scope
->resend_timeout
;
1246 assert_not_reached("Invalid DNS protocol.");
1250 static int dns_transaction_prepare(DnsTransaction
*t
, usec_t ts
) {
1255 dns_transaction_stop_timeout(t
);
1257 r
= dns_scope_network_good(t
->scope
);
1261 dns_transaction_complete(t
, DNS_TRANSACTION_NETWORK_DOWN
);
1265 if (t
->n_attempts
>= TRANSACTION_ATTEMPTS_MAX(t
->scope
->protocol
)) {
1266 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1270 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& t
->tried_stream
) {
1271 /* If we already tried via a stream, then we don't
1272 * retry on LLMNR. See RFC 4795, Section 2.7. */
1273 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1280 dns_transaction_reset_answer(t
);
1281 dns_transaction_flush_dnssec_transactions(t
);
1283 /* Check the trust anchor. Do so only on classic DNS, since DNSSEC does not apply otherwise. */
1284 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
) {
1285 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, t
->key
, &t
->answer
);
1289 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1290 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1291 t
->answer_authenticated
= true;
1292 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1296 if (dns_name_is_root(dns_resource_key_name(t
->key
)) &&
1297 t
->key
->type
== DNS_TYPE_DS
) {
1299 /* Hmm, this is a request for the root DS? A
1300 * DS RR doesn't exist in the root zone, and
1301 * if our trust anchor didn't know it either,
1302 * this means we cannot do any DNSSEC logic
1305 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
1306 /* We are in downgrade mode. In this
1307 * case, synthesize an unsigned empty
1308 * response, so that the any lookup
1309 * depending on this one can continue
1310 * assuming there was no DS, and hence
1311 * the root zone was unsigned. */
1313 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1314 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1315 t
->answer_authenticated
= false;
1316 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1318 /* If we are not in downgrade mode,
1319 * then fail the lookup, because we
1320 * cannot reasonably answer it. There
1321 * might be DS RRs, but we don't know
1322 * them, and the DNS server won't tell
1323 * them to us (and even if it would,
1324 * we couldn't validate and trust them. */
1325 dns_transaction_complete(t
, DNS_TRANSACTION_NO_TRUST_ANCHOR
);
1331 /* Check the zone, but only if this transaction is not used
1332 * for probing or verifying a zone item. */
1333 if (set_isempty(t
->notify_zone_items
)) {
1335 r
= dns_zone_lookup(&t
->scope
->zone
, t
->key
, dns_scope_ifindex(t
->scope
), &t
->answer
, NULL
, NULL
);
1339 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1340 t
->answer_source
= DNS_TRANSACTION_ZONE
;
1341 t
->answer_authenticated
= true;
1342 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1347 /* Check the cache, but only if this transaction is not used
1348 * for probing or verifying a zone item. */
1349 if (set_isempty(t
->notify_zone_items
)) {
1351 /* Before trying the cache, let's make sure we figured out a
1352 * server to use. Should this cause a change of server this
1353 * might flush the cache. */
1354 dns_scope_get_dns_server(t
->scope
);
1356 /* Let's then prune all outdated entries */
1357 dns_cache_prune(&t
->scope
->cache
);
1359 r
= dns_cache_lookup(&t
->scope
->cache
, t
->key
, t
->clamp_ttl
, &t
->answer_rcode
, &t
->answer
, &t
->answer_authenticated
);
1363 t
->answer_source
= DNS_TRANSACTION_CACHE
;
1364 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
1365 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1367 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
1375 static int dns_transaction_make_packet_mdns(DnsTransaction
*t
) {
1377 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1378 bool add_known_answers
= false;
1379 DnsTransaction
*other
;
1385 assert(t
->scope
->protocol
== DNS_PROTOCOL_MDNS
);
1387 /* Discard any previously prepared packet, so we can start over and coalesce again */
1388 t
->sent
= dns_packet_unref(t
->sent
);
1390 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, false);
1394 r
= dns_packet_append_key(p
, t
->key
, 0, NULL
);
1400 if (dns_key_is_shared(t
->key
))
1401 add_known_answers
= true;
1404 * For mDNS, we want to coalesce as many open queries in pending transactions into one single
1405 * query packet on the wire as possible. To achieve that, we iterate through all pending transactions
1406 * in our current scope, and see whether their timing contraints allow them to be sent.
1409 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &ts
) >= 0);
1411 LIST_FOREACH(transactions_by_scope
, other
, t
->scope
->transactions
) {
1413 /* Skip ourselves */
1417 if (other
->state
!= DNS_TRANSACTION_PENDING
)
1420 if (other
->next_attempt_after
> ts
)
1423 if (qdcount
>= UINT16_MAX
)
1426 r
= dns_packet_append_key(p
, other
->key
, 0, NULL
);
1429 * If we can't stuff more questions into the packet, just give up.
1430 * One of the 'other' transactions will fire later and take care of the rest.
1438 r
= dns_transaction_prepare(other
, ts
);
1442 ts
+= transaction_get_resend_timeout(other
);
1444 r
= sd_event_add_time(
1445 other
->scope
->manager
->event
,
1446 &other
->timeout_event_source
,
1447 clock_boottime_or_monotonic(),
1449 on_transaction_timeout
, other
);
1453 (void) sd_event_source_set_description(other
->timeout_event_source
, "dns-transaction-timeout");
1455 other
->state
= DNS_TRANSACTION_PENDING
;
1456 other
->next_attempt_after
= ts
;
1460 if (dns_key_is_shared(other
->key
))
1461 add_known_answers
= true;
1464 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(qdcount
);
1466 /* Append known answer section if we're asking for any shared record */
1467 if (add_known_answers
) {
1468 r
= dns_cache_export_shared_to_packet(&t
->scope
->cache
, p
);
1479 static int dns_transaction_make_packet(DnsTransaction
*t
) {
1480 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1485 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
)
1486 return dns_transaction_make_packet_mdns(t
);
1491 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, t
->scope
->dnssec_mode
!= DNSSEC_NO
);
1495 r
= dns_packet_append_key(p
, t
->key
, 0, NULL
);
1499 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(1);
1500 DNS_PACKET_HEADER(p
)->id
= t
->id
;
1508 int dns_transaction_go(DnsTransaction
*t
) {
1511 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
1515 /* Returns > 0 if the transaction is now pending, returns 0 if could be processed immediately and has finished
1518 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &ts
) >= 0);
1520 r
= dns_transaction_prepare(t
, ts
);
1524 log_debug("Transaction %" PRIu16
" for <%s> scope %s on %s/%s.",
1526 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
),
1527 dns_protocol_to_string(t
->scope
->protocol
),
1528 t
->scope
->link
? t
->scope
->link
->name
: "*",
1529 af_to_name_short(t
->scope
->family
));
1531 if (!t
->initial_jitter_scheduled
&&
1532 IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_LLMNR
, DNS_PROTOCOL_MDNS
)) {
1533 usec_t jitter
, accuracy
;
1535 /* RFC 4795 Section 2.7 suggests all queries should be
1536 * delayed by a random time from 0 to JITTER_INTERVAL. */
1538 t
->initial_jitter_scheduled
= true;
1540 random_bytes(&jitter
, sizeof(jitter
));
1542 switch (t
->scope
->protocol
) {
1544 case DNS_PROTOCOL_LLMNR
:
1545 jitter
%= LLMNR_JITTER_INTERVAL_USEC
;
1546 accuracy
= LLMNR_JITTER_INTERVAL_USEC
;
1549 case DNS_PROTOCOL_MDNS
:
1550 jitter
%= MDNS_JITTER_RANGE_USEC
;
1551 jitter
+= MDNS_JITTER_MIN_USEC
;
1552 accuracy
= MDNS_JITTER_RANGE_USEC
;
1555 assert_not_reached("bad protocol");
1558 r
= sd_event_add_time(
1559 t
->scope
->manager
->event
,
1560 &t
->timeout_event_source
,
1561 clock_boottime_or_monotonic(),
1562 ts
+ jitter
, accuracy
,
1563 on_transaction_timeout
, t
);
1567 (void) sd_event_source_set_description(t
->timeout_event_source
, "dns-transaction-timeout");
1570 t
->next_attempt_after
= ts
;
1571 t
->state
= DNS_TRANSACTION_PENDING
;
1573 log_debug("Delaying %s transaction for " USEC_FMT
"us.", dns_protocol_to_string(t
->scope
->protocol
), jitter
);
1577 /* Otherwise, we need to ask the network */
1578 r
= dns_transaction_make_packet(t
);
1582 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&&
1583 (dns_name_endswith(dns_resource_key_name(t
->key
), "in-addr.arpa") > 0 ||
1584 dns_name_endswith(dns_resource_key_name(t
->key
), "ip6.arpa") > 0)) {
1586 /* RFC 4795, Section 2.4. says reverse lookups shall
1587 * always be made via TCP on LLMNR */
1588 r
= dns_transaction_open_tcp(t
);
1590 /* Try via UDP, and if that fails due to large size or lack of
1591 * support try via TCP */
1592 r
= dns_transaction_emit_udp(t
);
1594 log_debug("Sending query via TCP since it is too large.");
1595 else if (r
== -EAGAIN
)
1596 log_debug("Sending query via TCP since server doesn't support UDP.");
1597 if (IN_SET(r
, -EMSGSIZE
, -EAGAIN
))
1598 r
= dns_transaction_open_tcp(t
);
1602 /* No servers to send this to? */
1603 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
1606 if (r
== -EOPNOTSUPP
) {
1607 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
1608 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
1611 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& ERRNO_IS_DISCONNECT(-r
)) {
1612 /* On LLMNR, if we cannot connect to a host via TCP when doing reverse lookups. This means we cannot
1613 * answer this request with this protocol. */
1614 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
1618 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1621 /* Couldn't send? Try immediately again, with a new server */
1622 dns_scope_next_dns_server(t
->scope
);
1624 return dns_transaction_go(t
);
1627 ts
+= transaction_get_resend_timeout(t
);
1629 r
= sd_event_add_time(
1630 t
->scope
->manager
->event
,
1631 &t
->timeout_event_source
,
1632 clock_boottime_or_monotonic(),
1634 on_transaction_timeout
, t
);
1638 (void) sd_event_source_set_description(t
->timeout_event_source
, "dns-transaction-timeout");
1640 t
->state
= DNS_TRANSACTION_PENDING
;
1641 t
->next_attempt_after
= ts
;
1646 static int dns_transaction_find_cyclic(DnsTransaction
*t
, DnsTransaction
*aux
) {
1654 /* Try to find cyclic dependencies between transaction objects */
1659 SET_FOREACH(n
, aux
->dnssec_transactions
, i
) {
1660 r
= dns_transaction_find_cyclic(t
, n
);
1668 static int dns_transaction_add_dnssec_transaction(DnsTransaction
*t
, DnsResourceKey
*key
, DnsTransaction
**ret
) {
1669 DnsTransaction
*aux
;
1676 aux
= dns_scope_find_transaction(t
->scope
, key
, true);
1678 r
= dns_transaction_new(&aux
, t
->scope
, key
);
1682 if (set_contains(t
->dnssec_transactions
, aux
)) {
1687 r
= dns_transaction_find_cyclic(t
, aux
);
1691 char s
[DNS_RESOURCE_KEY_STRING_MAX
], saux
[DNS_RESOURCE_KEY_STRING_MAX
];
1693 log_debug("Potential cyclic dependency, refusing to add transaction %" PRIu16
" (%s) as dependency for %" PRIu16
" (%s).",
1695 dns_resource_key_to_string(t
->key
, s
, sizeof s
),
1697 dns_resource_key_to_string(aux
->key
, saux
, sizeof saux
));
1703 r
= set_ensure_allocated(&t
->dnssec_transactions
, NULL
);
1707 r
= set_ensure_allocated(&aux
->notify_transactions
, NULL
);
1711 r
= set_ensure_allocated(&aux
->notify_transactions_done
, NULL
);
1715 r
= set_put(t
->dnssec_transactions
, aux
);
1719 r
= set_put(aux
->notify_transactions
, t
);
1721 (void) set_remove(t
->dnssec_transactions
, aux
);
1729 dns_transaction_gc(aux
);
1733 static int dns_transaction_request_dnssec_rr(DnsTransaction
*t
, DnsResourceKey
*key
) {
1734 _cleanup_(dns_answer_unrefp
) DnsAnswer
*a
= NULL
;
1735 DnsTransaction
*aux
;
1741 /* Try to get the data from the trust anchor */
1742 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, key
, &a
);
1746 r
= dns_answer_extend(&t
->validated_keys
, a
);
1753 /* This didn't work, ask for it via the network/cache then. */
1754 r
= dns_transaction_add_dnssec_transaction(t
, key
, &aux
);
1755 if (r
== -ELOOP
) /* This would result in a cyclic dependency */
1760 if (aux
->state
== DNS_TRANSACTION_NULL
) {
1761 r
= dns_transaction_go(aux
);
1769 static int dns_transaction_negative_trust_anchor_lookup(DnsTransaction
*t
, const char *name
) {
1774 /* Check whether the specified name is in the NTA
1775 * database, either in the global one, or the link-local
1778 r
= dns_trust_anchor_lookup_negative(&t
->scope
->manager
->trust_anchor
, name
);
1782 if (!t
->scope
->link
)
1785 return set_contains(t
->scope
->link
->dnssec_negative_trust_anchors
, name
);
1788 static int dns_transaction_has_unsigned_negative_answer(DnsTransaction
*t
) {
1793 /* Checks whether the answer is negative, and lacks NSEC/NSEC3
1794 * RRs to prove it */
1796 r
= dns_transaction_has_positive_answer(t
, NULL
);
1802 /* Is this key explicitly listed as a negative trust anchor?
1803 * If so, it's nothing we need to care about */
1804 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(t
->key
));
1810 /* The answer does not contain any RRs that match to the
1811 * question. If so, let's see if there are any NSEC/NSEC3 RRs
1812 * included. If not, the answer is unsigned. */
1814 r
= dns_answer_contains_nsec_or_nsec3(t
->answer
);
1823 static int dns_transaction_is_primary_response(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
1829 /* Check if the specified RR is the "primary" response,
1830 * i.e. either matches the question precisely or is a
1831 * CNAME/DNAME for it. */
1833 r
= dns_resource_key_match_rr(t
->key
, rr
, NULL
);
1837 return dns_resource_key_match_cname_or_dname(t
->key
, rr
->key
, NULL
);
1840 static bool dns_transaction_dnssec_supported(DnsTransaction
*t
) {
1843 /* Checks whether our transaction's DNS server is assumed to be compatible with DNSSEC. Returns false as soon
1844 * as we changed our mind about a server, and now believe it is incompatible with DNSSEC. */
1846 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1849 /* If we have picked no server, then we are working from the cache or some other source, and DNSSEC might well
1850 * be supported, hence return true. */
1854 /* Note that we do not check the feature level actually used for the transaction but instead the feature level
1855 * the server is known to support currently, as the transaction feature level might be lower than what the
1856 * server actually supports, since we might have downgraded this transaction's feature level because we got a
1857 * SERVFAIL earlier and wanted to check whether downgrading fixes it. */
1859 return dns_server_dnssec_supported(t
->server
);
1862 static bool dns_transaction_dnssec_supported_full(DnsTransaction
*t
) {
1868 /* Checks whether our transaction our any of the auxiliary transactions couldn't do DNSSEC. */
1870 if (!dns_transaction_dnssec_supported(t
))
1873 SET_FOREACH(dt
, t
->dnssec_transactions
, i
)
1874 if (!dns_transaction_dnssec_supported(dt
))
1880 int dns_transaction_request_dnssec_keys(DnsTransaction
*t
) {
1881 DnsResourceRecord
*rr
;
1888 * Retrieve all auxiliary RRs for the answer we got, so that
1889 * we can verify signatures or prove that RRs are rightfully
1890 * unsigned. Specifically:
1892 * - For RRSIG we get the matching DNSKEY
1893 * - For DNSKEY we get the matching DS
1894 * - For unsigned SOA/NS we get the matching DS
1895 * - For unsigned CNAME/DNAME/DS we get the parent SOA RR
1896 * - For other unsigned RRs we get the matching SOA RR
1897 * - For SOA/NS queries with no matching response RR, and no NSEC/NSEC3, the DS RR
1898 * - For DS queries with no matching response RRs, and no NSEC/NSEC3, the parent's SOA RR
1899 * - For other queries with no matching response RRs, and no NSEC/NSEC3, the SOA RR
1902 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
1904 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
1905 return 0; /* We only need to validate stuff from the network */
1906 if (!dns_transaction_dnssec_supported(t
))
1907 return 0; /* If we can't do DNSSEC anyway there's no point in geting the auxiliary RRs */
1909 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
1911 if (dns_type_is_pseudo(rr
->key
->type
))
1914 /* If this RR is in the negative trust anchor, we don't need to validate it. */
1915 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
1921 switch (rr
->key
->type
) {
1923 case DNS_TYPE_RRSIG
: {
1924 /* For each RRSIG we request the matching DNSKEY */
1925 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*dnskey
= NULL
;
1927 /* If this RRSIG is about a DNSKEY RR and the
1928 * signer is the same as the owner, then we
1929 * already have the DNSKEY, and we don't have
1930 * to look for more. */
1931 if (rr
->rrsig
.type_covered
== DNS_TYPE_DNSKEY
) {
1932 r
= dns_name_equal(rr
->rrsig
.signer
, dns_resource_key_name(rr
->key
));
1939 /* If the signer is not a parent of our
1940 * original query, then this is about an
1941 * auxiliary RRset, but not anything we asked
1942 * for. In this case we aren't interested,
1943 * because we don't want to request additional
1944 * RRs for stuff we didn't really ask for, and
1945 * also to avoid request loops, where
1946 * additional RRs from one transaction result
1947 * in another transaction whose additonal RRs
1948 * point back to the original transaction, and
1950 r
= dns_name_endswith(dns_resource_key_name(t
->key
), rr
->rrsig
.signer
);
1956 dnskey
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DNSKEY
, rr
->rrsig
.signer
);
1960 log_debug("Requesting DNSKEY to validate transaction %" PRIu16
" (%s, RRSIG with key tag: %" PRIu16
").",
1961 t
->id
, dns_resource_key_name(rr
->key
), rr
->rrsig
.key_tag
);
1962 r
= dns_transaction_request_dnssec_rr(t
, dnskey
);
1968 case DNS_TYPE_DNSKEY
: {
1969 /* For each DNSKEY we request the matching DS */
1970 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
1972 /* If the DNSKEY we are looking at is not for
1973 * zone we are interested in, nor any of its
1974 * parents, we aren't interested, and don't
1975 * request it. After all, we don't want to end
1976 * up in request loops, and want to keep
1977 * additional traffic down. */
1979 r
= dns_name_endswith(dns_resource_key_name(t
->key
), dns_resource_key_name(rr
->key
));
1985 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
1989 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, DNSKEY with key tag: %" PRIu16
").",
1990 t
->id
, dns_resource_key_name(rr
->key
), dnssec_keytag(rr
, false));
1991 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2000 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
2002 /* For an unsigned SOA or NS, try to acquire
2003 * the matching DS RR, as we are at a zone cut
2004 * then, and whether a DS exists tells us
2005 * whether the zone is signed. Do so only if
2006 * this RR matches our original question,
2009 r
= dns_resource_key_match_rr(t
->key
, rr
, NULL
);
2013 /* Hmm, so this SOA RR doesn't match our original question. In this case, maybe this is
2014 * a negative reply, and we need the a SOA RR's TTL in order to cache a negative entry?
2015 * If so, we need to validate it, too. */
2017 r
= dns_answer_match_key(t
->answer
, t
->key
, NULL
);
2020 if (r
> 0) /* positive reply, we won't need the SOA and hence don't need to validate
2025 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2031 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
2035 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, unsigned SOA/NS RRset).",
2036 t
->id
, dns_resource_key_name(rr
->key
));
2037 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2045 case DNS_TYPE_CNAME
:
2046 case DNS_TYPE_DNAME
: {
2047 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2050 /* CNAMEs and DNAMEs cannot be located at a
2051 * zone apex, hence ask for the parent SOA for
2052 * unsigned CNAME/DNAME RRs, maybe that's the
2053 * apex. But do all that only if this is
2054 * actually a response to our original
2057 * Similar for DS RRs, which are signed when
2058 * the parent SOA is signed. */
2060 r
= dns_transaction_is_primary_response(t
, rr
);
2066 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2072 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
2078 name
= dns_resource_key_name(rr
->key
);
2079 r
= dns_name_parent(&name
);
2085 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, name
);
2089 log_debug("Requesting parent SOA to validate transaction %" PRIu16
" (%s, unsigned CNAME/DNAME/DS RRset).",
2090 t
->id
, dns_resource_key_name(rr
->key
));
2091 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2099 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2101 /* For other unsigned RRsets (including
2102 * NSEC/NSEC3!), look for proof the zone is
2103 * unsigned, by requesting the SOA RR of the
2104 * zone. However, do so only if they are
2105 * directly relevant to our original
2108 r
= dns_transaction_is_primary_response(t
, rr
);
2114 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2120 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, dns_resource_key_name(rr
->key
));
2124 log_debug("Requesting SOA to validate transaction %" PRIu16
" (%s, unsigned non-SOA/NS RRset <%s>).",
2125 t
->id
, dns_resource_key_name(rr
->key
), dns_resource_record_to_string(rr
));
2126 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2133 /* Above, we requested everything necessary to validate what
2134 * we got. Now, let's request what we need to validate what we
2137 r
= dns_transaction_has_unsigned_negative_answer(t
);
2144 name
= dns_resource_key_name(t
->key
);
2146 /* If this was a SOA or NS request, then check if there's a DS RR for the same domain. Note that this
2147 * could also be used as indication that we are not at a zone apex, but in real world setups there are
2148 * too many broken DNS servers (Hello, incapdns.net!) where non-terminal zones return NXDOMAIN even
2149 * though they have further children. If this was a DS request, then it's signed when the parent zone
2150 * is signed, hence ask the parent SOA in that case. If this was any other RR then ask for the SOA RR,
2151 * to see if that is signed. */
2153 if (t
->key
->type
== DNS_TYPE_DS
) {
2154 r
= dns_name_parent(&name
);
2156 type
= DNS_TYPE_SOA
;
2157 log_debug("Requesting parent SOA to validate transaction %" PRIu16
" (%s, unsigned empty DS response).",
2158 t
->id
, dns_resource_key_name(t
->key
));
2162 } else if (IN_SET(t
->key
->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
)) {
2165 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, unsigned empty SOA/NS response).",
2166 t
->id
, dns_resource_key_name(t
->key
));
2169 type
= DNS_TYPE_SOA
;
2170 log_debug("Requesting SOA to validate transaction %" PRIu16
" (%s, unsigned empty non-SOA/NS/DS response).",
2171 t
->id
, dns_resource_key_name(t
->key
));
2175 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2177 soa
= dns_resource_key_new(t
->key
->class, type
, name
);
2181 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2187 return dns_transaction_dnssec_is_live(t
);
2190 void dns_transaction_notify(DnsTransaction
*t
, DnsTransaction
*source
) {
2194 /* Invoked whenever any of our auxiliary DNSSEC transactions completed its work. If the state is still PENDING,
2195 we are still in the loop that adds further DNSSEC transactions, hence don't check if we are ready yet. If
2196 the state is VALIDATING however, we should check if we are complete now. */
2198 if (t
->state
== DNS_TRANSACTION_VALIDATING
)
2199 dns_transaction_process_dnssec(t
);
2202 static int dns_transaction_validate_dnskey_by_ds(DnsTransaction
*t
) {
2203 DnsResourceRecord
*rr
;
2208 /* Add all DNSKEY RRs from the answer that are validated by DS
2209 * RRs from the list of validated keys to the list of
2210 * validated keys. */
2212 DNS_ANSWER_FOREACH_IFINDEX(rr
, ifindex
, t
->answer
) {
2214 r
= dnssec_verify_dnskey_by_ds_search(rr
, t
->validated_keys
);
2220 /* If so, the DNSKEY is validated too. */
2221 r
= dns_answer_add_extend(&t
->validated_keys
, rr
, ifindex
, DNS_ANSWER_AUTHENTICATED
);
2229 static int dns_transaction_requires_rrsig(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2235 /* Checks if the RR we are looking for must be signed with an
2236 * RRSIG. This is used for positive responses. */
2238 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2241 if (dns_type_is_pseudo(rr
->key
->type
))
2244 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2250 switch (rr
->key
->type
) {
2252 case DNS_TYPE_RRSIG
:
2253 /* RRSIGs are the signatures themselves, they need no signing. */
2261 /* For SOA or NS RRs we look for a matching DS transaction */
2263 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2265 if (dt
->key
->class != rr
->key
->class)
2267 if (dt
->key
->type
!= DNS_TYPE_DS
)
2270 r
= dns_name_equal(dns_resource_key_name(dt
->key
), dns_resource_key_name(rr
->key
));
2276 /* We found a DS transactions for the SOA/NS
2277 * RRs we are looking at. If it discovered signed DS
2278 * RRs, then we need to be signed, too. */
2280 if (!dt
->answer_authenticated
)
2283 return dns_answer_match_key(dt
->answer
, dt
->key
, NULL
);
2286 /* We found nothing that proves this is safe to leave
2287 * this unauthenticated, hence ask inist on
2288 * authentication. */
2293 case DNS_TYPE_CNAME
:
2294 case DNS_TYPE_DNAME
: {
2295 const char *parent
= NULL
;
2300 * CNAME/DNAME RRs cannot be located at a zone apex, hence look directly for the parent SOA.
2302 * DS RRs are signed if the parent is signed, hence also look at the parent SOA
2305 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2307 if (dt
->key
->class != rr
->key
->class)
2309 if (dt
->key
->type
!= DNS_TYPE_SOA
)
2313 parent
= dns_resource_key_name(rr
->key
);
2314 r
= dns_name_parent(&parent
);
2318 if (rr
->key
->type
== DNS_TYPE_DS
)
2321 /* A CNAME/DNAME without a parent? That's sooo weird. */
2322 log_debug("Transaction %" PRIu16
" claims CNAME/DNAME at root. Refusing.", t
->id
);
2327 r
= dns_name_equal(dns_resource_key_name(dt
->key
), parent
);
2333 return t
->answer_authenticated
;
2343 /* Any other kind of RR (including DNSKEY/NSEC/NSEC3). Let's see if our SOA lookup was authenticated */
2345 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2347 if (dt
->key
->class != rr
->key
->class)
2349 if (dt
->key
->type
!= DNS_TYPE_SOA
)
2352 r
= dns_name_equal(dns_resource_key_name(dt
->key
), dns_resource_key_name(rr
->key
));
2358 /* We found the transaction that was supposed to find
2359 * the SOA RR for us. It was successful, but found no
2360 * RR for us. This means we are not at a zone cut. In
2361 * this case, we require authentication if the SOA
2362 * lookup was authenticated too. */
2363 return t
->answer_authenticated
;
2370 static int dns_transaction_in_private_tld(DnsTransaction
*t
, const DnsResourceKey
*key
) {
2376 /* If DNSSEC downgrade mode is on, checks whether the
2377 * specified RR is one level below a TLD we have proven not to
2378 * exist. In such a case we assume that this is a private
2379 * domain, and permit it.
2381 * This detects cases like the Fritz!Box router networks. Each
2382 * Fritz!Box router serves a private "fritz.box" zone, in the
2383 * non-existing TLD "box". Requests for the "fritz.box" domain
2384 * are served by the router itself, while requests for the
2385 * "box" domain will result in NXDOMAIN.
2387 * Note that this logic is unable to detect cases where a
2388 * router serves a private DNS zone directly under
2389 * non-existing TLD. In such a case we cannot detect whether
2390 * the TLD is supposed to exist or not, as all requests we
2391 * make for it will be answered by the router's zone, and not
2392 * by the root zone. */
2396 if (t
->scope
->dnssec_mode
!= DNSSEC_ALLOW_DOWNGRADE
)
2397 return false; /* In strict DNSSEC mode what doesn't exist, doesn't exist */
2399 tld
= dns_resource_key_name(key
);
2400 r
= dns_name_parent(&tld
);
2404 return false; /* Already the root domain */
2406 if (!dns_name_is_single_label(tld
))
2409 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2411 if (dt
->key
->class != key
->class)
2414 r
= dns_name_equal(dns_resource_key_name(dt
->key
), tld
);
2420 /* We found an auxiliary lookup we did for the TLD. If
2421 * that returned with NXDOMAIN, we know the TLD didn't
2422 * exist, and hence this might be a private zone. */
2424 return dt
->answer_rcode
== DNS_RCODE_NXDOMAIN
;
2430 static int dns_transaction_requires_nsec(DnsTransaction
*t
) {
2431 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
2440 /* Checks if we need to insist on NSEC/NSEC3 RRs for proving
2441 * this negative reply */
2443 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2446 if (dns_type_is_pseudo(t
->key
->type
))
2449 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(t
->key
));
2455 r
= dns_transaction_in_private_tld(t
, t
->key
);
2459 /* The lookup is from a TLD that is proven not to
2460 * exist, and we are in downgrade mode, hence ignore
2461 * that fact that we didn't get any NSEC RRs. */
2463 log_info("Detected a negative query %s in a private DNS zone, permitting unsigned response.",
2464 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
));
2468 name
= dns_resource_key_name(t
->key
);
2470 if (t
->key
->type
== DNS_TYPE_DS
) {
2472 /* We got a negative reply for this DS lookup? DS RRs are signed when their parent zone is signed,
2473 * hence check the parent SOA in this case. */
2475 r
= dns_name_parent(&name
);
2481 type
= DNS_TYPE_SOA
;
2483 } else if (IN_SET(t
->key
->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
))
2484 /* We got a negative reply for this SOA/NS lookup? If so, check if there's a DS RR for this */
2487 /* For all other negative replies, check for the SOA lookup */
2488 type
= DNS_TYPE_SOA
;
2490 /* For all other RRs we check the SOA on the same level to see
2491 * if it's signed. */
2493 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2495 if (dt
->key
->class != t
->key
->class)
2497 if (dt
->key
->type
!= type
)
2500 r
= dns_name_equal(dns_resource_key_name(dt
->key
), name
);
2506 return dt
->answer_authenticated
;
2509 /* If in doubt, require NSEC/NSEC3 */
2513 static int dns_transaction_dnskey_authenticated(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2514 DnsResourceRecord
*rrsig
;
2518 /* Checks whether any of the DNSKEYs used for the RRSIGs for
2519 * the specified RRset is authenticated (i.e. has a matching
2522 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2528 DNS_ANSWER_FOREACH(rrsig
, t
->answer
) {
2532 r
= dnssec_key_match_rrsig(rr
->key
, rrsig
);
2538 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2540 if (dt
->key
->class != rr
->key
->class)
2543 if (dt
->key
->type
== DNS_TYPE_DNSKEY
) {
2545 r
= dns_name_equal(dns_resource_key_name(dt
->key
), rrsig
->rrsig
.signer
);
2551 /* OK, we found an auxiliary DNSKEY
2552 * lookup. If that lookup is
2553 * authenticated, report this. */
2555 if (dt
->answer_authenticated
)
2560 } else if (dt
->key
->type
== DNS_TYPE_DS
) {
2562 r
= dns_name_equal(dns_resource_key_name(dt
->key
), rrsig
->rrsig
.signer
);
2568 /* OK, we found an auxiliary DS
2569 * lookup. If that lookup is
2570 * authenticated and non-zero, we
2573 if (!dt
->answer_authenticated
)
2576 return dns_answer_match_key(dt
->answer
, dt
->key
, NULL
);
2581 return found
? false : -ENXIO
;
2584 static int dns_transaction_known_signed(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2588 /* We know that the root domain is signed, hence if it appears
2589 * not to be signed, there's a problem with the DNS server */
2591 return rr
->key
->class == DNS_CLASS_IN
&&
2592 dns_name_is_root(dns_resource_key_name(rr
->key
));
2595 static int dns_transaction_check_revoked_trust_anchors(DnsTransaction
*t
) {
2596 DnsResourceRecord
*rr
;
2601 /* Maybe warn the user that we encountered a revoked DNSKEY
2602 * for a key from our trust anchor. Note that we don't care
2603 * whether the DNSKEY can be authenticated or not. It's
2604 * sufficient if it is self-signed. */
2606 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
2607 r
= dns_trust_anchor_check_revoked(&t
->scope
->manager
->trust_anchor
, rr
, t
->answer
);
2615 static int dns_transaction_invalidate_revoked_keys(DnsTransaction
*t
) {
2621 /* Removes all DNSKEY/DS objects from t->validated_keys that
2622 * our trust anchors database considers revoked. */
2625 DnsResourceRecord
*rr
;
2629 DNS_ANSWER_FOREACH(rr
, t
->validated_keys
) {
2630 r
= dns_trust_anchor_is_revoked(&t
->scope
->manager
->trust_anchor
, rr
);
2634 r
= dns_answer_remove_by_rr(&t
->validated_keys
, rr
);
2648 static int dns_transaction_copy_validated(DnsTransaction
*t
) {
2655 /* Copy all validated RRs from the auxiliary DNSSEC transactions into our set of validated RRs */
2657 SET_FOREACH(dt
, t
->dnssec_transactions
, i
) {
2659 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
2662 if (!dt
->answer_authenticated
)
2665 r
= dns_answer_extend(&t
->validated_keys
, dt
->answer
);
2674 DNSSEC_PHASE_DNSKEY
, /* Phase #1, only validate DNSKEYs */
2675 DNSSEC_PHASE_NSEC
, /* Phase #2, only validate NSEC+NSEC3 */
2676 DNSSEC_PHASE_ALL
, /* Phase #3, validate everything else */
2679 static int dnssec_validate_records(
2683 DnsAnswer
**validated
) {
2685 DnsResourceRecord
*rr
;
2688 /* Returns negative on error, 0 if validation failed, 1 to restart validation, 2 when finished. */
2690 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
2691 DnsResourceRecord
*rrsig
= NULL
;
2692 DnssecResult result
;
2694 switch (rr
->key
->type
) {
2695 case DNS_TYPE_RRSIG
:
2698 case DNS_TYPE_DNSKEY
:
2699 /* We validate DNSKEYs only in the DNSKEY and ALL phases */
2700 if (phase
== DNSSEC_PHASE_NSEC
)
2705 case DNS_TYPE_NSEC3
:
2708 /* We validate NSEC/NSEC3 only in the NSEC and ALL phases */
2709 if (phase
== DNSSEC_PHASE_DNSKEY
)
2714 /* We validate all other RRs only in the ALL phases */
2715 if (phase
!= DNSSEC_PHASE_ALL
)
2719 r
= dnssec_verify_rrset_search(t
->answer
, rr
->key
, t
->validated_keys
, USEC_INFINITY
, &result
, &rrsig
);
2723 log_debug("Looking at %s: %s", strna(dns_resource_record_to_string(rr
)), dnssec_result_to_string(result
));
2725 if (result
== DNSSEC_VALIDATED
) {
2727 if (rr
->key
->type
== DNS_TYPE_DNSKEY
) {
2728 /* If we just validated a DNSKEY RRset, then let's add these keys to
2729 * the set of validated keys for this transaction. */
2731 r
= dns_answer_copy_by_key(&t
->validated_keys
, t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
);
2735 /* Some of the DNSKEYs we just added might already have been revoked,
2736 * remove them again in that case. */
2737 r
= dns_transaction_invalidate_revoked_keys(t
);
2742 /* Add the validated RRset to the new list of validated
2743 * RRsets, and remove it from the unvalidated RRsets.
2744 * We mark the RRset as authenticated and cacheable. */
2745 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
);
2749 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_SECURE
, rr
->key
);
2751 /* Exit the loop, we dropped something from the answer, start from the beginning */
2755 /* If we haven't read all DNSKEYs yet a negative result of the validation is irrelevant, as
2756 * there might be more DNSKEYs coming. Similar, if we haven't read all NSEC/NSEC3 RRs yet,
2757 * we cannot do positive wildcard proofs yet, as those require the NSEC/NSEC3 RRs. */
2758 if (phase
!= DNSSEC_PHASE_ALL
)
2761 if (result
== DNSSEC_VALIDATED_WILDCARD
) {
2762 bool authenticated
= false;
2765 /* This RRset validated, but as a wildcard. This means we need
2766 * to prove via NSEC/NSEC3 that no matching non-wildcard RR exists. */
2768 /* First step, determine the source of synthesis */
2769 r
= dns_resource_record_source(rrsig
, &source
);
2773 r
= dnssec_test_positive_wildcard(*validated
,
2774 dns_resource_key_name(rr
->key
),
2776 rrsig
->rrsig
.signer
,
2779 /* Unless the NSEC proof showed that the key really doesn't exist something is off. */
2781 result
= DNSSEC_INVALID
;
2783 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
,
2784 authenticated
? (DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
) : 0);
2788 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, rr
->key
);
2790 /* Exit the loop, we dropped something from the answer, start from the beginning */
2795 if (result
== DNSSEC_NO_SIGNATURE
) {
2796 r
= dns_transaction_requires_rrsig(t
, rr
);
2800 /* Data does not require signing. In that case, just copy it over,
2801 * but remember that this is by no means authenticated. */
2802 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0);
2806 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
2810 r
= dns_transaction_known_signed(t
, rr
);
2814 /* This is an RR we know has to be signed. If it isn't this means
2815 * the server is not attaching RRSIGs, hence complain. */
2817 dns_server_packet_rrsig_missing(t
->server
, t
->current_feature_level
);
2819 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
2821 /* Downgrading is OK? If so, just consider the information unsigned */
2823 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0);
2827 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
2831 /* Otherwise, fail */
2832 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
2836 r
= dns_transaction_in_private_tld(t
, rr
->key
);
2840 char s
[DNS_RESOURCE_KEY_STRING_MAX
];
2842 /* The data is from a TLD that is proven not to exist, and we are in downgrade
2843 * mode, hence ignore the fact that this was not signed. */
2845 log_info("Detected RRset %s is in a private DNS zone, permitting unsigned RRs.",
2846 dns_resource_key_to_string(rr
->key
, s
, sizeof s
));
2848 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0);
2852 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
2859 DNSSEC_SIGNATURE_EXPIRED
,
2860 DNSSEC_UNSUPPORTED_ALGORITHM
)) {
2862 r
= dns_transaction_dnskey_authenticated(t
, rr
);
2863 if (r
< 0 && r
!= -ENXIO
)
2866 /* The DNSKEY transaction was not authenticated, this means there's
2867 * no DS for this, which means it's OK if no keys are found for this signature. */
2869 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0);
2873 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
2878 r
= dns_transaction_is_primary_response(t
, rr
);
2882 /* Look for a matching DNAME for this CNAME */
2883 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
2887 /* Also look among the stuff we already validated */
2888 r
= dns_answer_has_dname_for_cname(*validated
, rr
);
2896 DNSSEC_SIGNATURE_EXPIRED
,
2897 DNSSEC_NO_SIGNATURE
))
2898 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, rr
->key
);
2899 else /* DNSSEC_MISSING_KEY or DNSSEC_UNSUPPORTED_ALGORITHM */
2900 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, rr
->key
);
2902 /* This is a primary response to our question, and it failed validation.
2904 t
->answer_dnssec_result
= result
;
2908 /* This is a primary response, but we do have a DNAME RR
2909 * in the RR that can replay this CNAME, hence rely on
2910 * that, and we can remove the CNAME in favour of it. */
2913 /* This is just some auxiliary data. Just remove the RRset and continue. */
2914 r
= dns_answer_remove_by_key(&t
->answer
, rr
->key
);
2918 /* We dropped something from the answer, start from the beginning. */
2922 return 2; /* Finito. */
2925 int dns_transaction_validate_dnssec(DnsTransaction
*t
) {
2926 _cleanup_(dns_answer_unrefp
) DnsAnswer
*validated
= NULL
;
2928 DnsAnswerFlags flags
;
2930 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
2934 /* We have now collected all DS and DNSKEY RRs in
2935 * t->validated_keys, let's see which RRs we can now
2936 * authenticate with that. */
2938 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2941 /* Already validated */
2942 if (t
->answer_dnssec_result
!= _DNSSEC_RESULT_INVALID
)
2945 /* Our own stuff needs no validation */
2946 if (IN_SET(t
->answer_source
, DNS_TRANSACTION_ZONE
, DNS_TRANSACTION_TRUST_ANCHOR
)) {
2947 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
2948 t
->answer_authenticated
= true;
2952 /* Cached stuff is not affected by validation. */
2953 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
2956 if (!dns_transaction_dnssec_supported_full(t
)) {
2957 /* The server does not support DNSSEC, or doesn't augment responses with RRSIGs. */
2958 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
2959 log_debug("Not validating response for %" PRIu16
", used server feature level does not support DNSSEC.", t
->id
);
2963 log_debug("Validating response from transaction %" PRIu16
" (%s).",
2965 dns_resource_key_to_string(t
->key
, key_str
, sizeof key_str
));
2967 /* First, see if this response contains any revoked trust
2968 * anchors we care about */
2969 r
= dns_transaction_check_revoked_trust_anchors(t
);
2973 /* Third, copy all RRs we acquired successfully from auxiliary RRs over. */
2974 r
= dns_transaction_copy_validated(t
);
2978 /* Second, see if there are DNSKEYs we already know a
2979 * validated DS for. */
2980 r
= dns_transaction_validate_dnskey_by_ds(t
);
2984 /* Fourth, remove all DNSKEY and DS RRs again that our trust
2985 * anchor says are revoked. After all we might have marked
2986 * some keys revoked above, but they might still be lingering
2987 * in our validated_keys list. */
2988 r
= dns_transaction_invalidate_revoked_keys(t
);
2992 phase
= DNSSEC_PHASE_DNSKEY
;
2994 bool have_nsec
= false;
2996 r
= dnssec_validate_records(t
, phase
, &have_nsec
, &validated
);
3000 /* Try again as long as we managed to achieve something */
3004 if (phase
== DNSSEC_PHASE_DNSKEY
&& have_nsec
) {
3005 /* OK, we processed all DNSKEYs, and there are NSEC/NSEC3 RRs, look at those now. */
3006 phase
= DNSSEC_PHASE_NSEC
;
3010 if (phase
!= DNSSEC_PHASE_ALL
) {
3011 /* OK, we processed all DNSKEYs and NSEC/NSEC3 RRs, look at all the rest now.
3012 * Note that in this third phase we start to remove RRs we couldn't validate. */
3013 phase
= DNSSEC_PHASE_ALL
;
3021 dns_answer_unref(t
->answer
);
3022 t
->answer
= validated
;
3025 /* At this point the answer only contains validated
3026 * RRsets. Now, let's see if it actually answers the question
3027 * we asked. If so, great! If it doesn't, then see if
3028 * NSEC/NSEC3 can prove this. */
3029 r
= dns_transaction_has_positive_answer(t
, &flags
);
3031 /* Yes, it answers the question! */
3033 if (flags
& DNS_ANSWER_AUTHENTICATED
) {
3034 /* The answer is fully authenticated, yay. */
3035 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3036 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3037 t
->answer_authenticated
= true;
3039 /* The answer is not fully authenticated. */
3040 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3041 t
->answer_authenticated
= false;
3044 } else if (r
== 0) {
3045 DnssecNsecResult nr
;
3046 bool authenticated
= false;
3048 /* Bummer! Let's check NSEC/NSEC3 */
3049 r
= dnssec_nsec_test(t
->answer
, t
->key
, &nr
, &authenticated
, &t
->answer_nsec_ttl
);
3055 case DNSSEC_NSEC_NXDOMAIN
:
3056 /* NSEC proves the domain doesn't exist. Very good. */
3057 log_debug("Proved NXDOMAIN via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3058 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3059 t
->answer_rcode
= DNS_RCODE_NXDOMAIN
;
3060 t
->answer_authenticated
= authenticated
;
3062 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, t
->key
);
3065 case DNSSEC_NSEC_NODATA
:
3066 /* NSEC proves that there's no data here, very good. */
3067 log_debug("Proved NODATA via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3068 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3069 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3070 t
->answer_authenticated
= authenticated
;
3072 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, t
->key
);
3075 case DNSSEC_NSEC_OPTOUT
:
3076 /* NSEC3 says the data might not be signed */
3077 log_debug("Data is NSEC3 opt-out via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3078 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3079 t
->answer_authenticated
= false;
3081 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, t
->key
);
3084 case DNSSEC_NSEC_NO_RR
:
3085 /* No NSEC data? Bummer! */
3087 r
= dns_transaction_requires_nsec(t
);
3091 t
->answer_dnssec_result
= DNSSEC_NO_SIGNATURE
;
3092 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, t
->key
);
3094 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3095 t
->answer_authenticated
= false;
3096 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, t
->key
);
3101 case DNSSEC_NSEC_UNSUPPORTED_ALGORITHM
:
3102 /* We don't know the NSEC3 algorithm used? */
3103 t
->answer_dnssec_result
= DNSSEC_UNSUPPORTED_ALGORITHM
;
3104 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, t
->key
);
3107 case DNSSEC_NSEC_FOUND
:
3108 case DNSSEC_NSEC_CNAME
:
3109 /* NSEC says it needs to be there, but we couldn't find it? Bummer! */
3110 t
->answer_dnssec_result
= DNSSEC_NSEC_MISMATCH
;
3111 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, t
->key
);
3115 assert_not_reached("Unexpected NSEC result.");
3122 static const char* const dns_transaction_state_table
[_DNS_TRANSACTION_STATE_MAX
] = {
3123 [DNS_TRANSACTION_NULL
] = "null",
3124 [DNS_TRANSACTION_PENDING
] = "pending",
3125 [DNS_TRANSACTION_VALIDATING
] = "validating",
3126 [DNS_TRANSACTION_RCODE_FAILURE
] = "rcode-failure",
3127 [DNS_TRANSACTION_SUCCESS
] = "success",
3128 [DNS_TRANSACTION_NO_SERVERS
] = "no-servers",
3129 [DNS_TRANSACTION_TIMEOUT
] = "timeout",
3130 [DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
] = "attempts-max-reached",
3131 [DNS_TRANSACTION_INVALID_REPLY
] = "invalid-reply",
3132 [DNS_TRANSACTION_ERRNO
] = "errno",
3133 [DNS_TRANSACTION_ABORTED
] = "aborted",
3134 [DNS_TRANSACTION_DNSSEC_FAILED
] = "dnssec-failed",
3135 [DNS_TRANSACTION_NO_TRUST_ANCHOR
] = "no-trust-anchor",
3136 [DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
] = "rr-type-unsupported",
3137 [DNS_TRANSACTION_NETWORK_DOWN
] = "network-down",
3138 [DNS_TRANSACTION_NOT_FOUND
] = "not-found",
3140 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state
, DnsTransactionState
);
3142 static const char* const dns_transaction_source_table
[_DNS_TRANSACTION_SOURCE_MAX
] = {
3143 [DNS_TRANSACTION_NETWORK
] = "network",
3144 [DNS_TRANSACTION_CACHE
] = "cache",
3145 [DNS_TRANSACTION_ZONE
] = "zone",
3146 [DNS_TRANSACTION_TRUST_ANCHOR
] = "trust-anchor",
3148 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source
, DnsTransactionSource
);