1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
3 #include "sd-messages.h"
6 #include "alloc-util.h"
7 #include "dns-domain.h"
8 #include "errno-list.h"
9 #include "errno-util.h"
11 #include "random-util.h"
12 #include "resolved-dns-cache.h"
13 #include "resolved-dns-transaction.h"
14 #include "resolved-dnstls.h"
15 #include "resolved-llmnr.h"
16 #include "string-table.h"
18 #define TRANSACTIONS_MAX 4096
19 #define TRANSACTION_TCP_TIMEOUT_USEC (10U*USEC_PER_SEC)
21 /* After how much time to repeat classic DNS requests */
22 #define DNS_TIMEOUT_USEC (SD_RESOLVED_QUERY_TIMEOUT_USEC / DNS_TRANSACTION_ATTEMPTS_MAX)
24 static void dns_transaction_reset_answer(DnsTransaction
*t
) {
27 t
->received
= dns_packet_unref(t
->received
);
28 t
->answer
= dns_answer_unref(t
->answer
);
30 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
31 t
->answer_source
= _DNS_TRANSACTION_SOURCE_INVALID
;
32 t
->answer_query_flags
= 0;
33 t
->answer_nsec_ttl
= UINT32_MAX
;
37 static void dns_transaction_flush_dnssec_transactions(DnsTransaction
*t
) {
42 while ((z
= set_steal_first(t
->dnssec_transactions
))) {
43 set_remove(z
->notify_transactions
, t
);
44 set_remove(z
->notify_transactions_done
, t
);
45 dns_transaction_gc(z
);
49 static void dns_transaction_close_connection(
51 bool use_graveyard
) { /* Set use_graveyard = false when you know the connection is already
52 * dead, for example because you got a connection error back from the
53 * kernel. In that case there's no point in keeping the fd around,
60 /* Let's detach the stream from our transaction, in case something else keeps a reference to it. */
61 LIST_REMOVE(transactions_by_stream
, t
->stream
->transactions
, t
);
63 /* Remove packet in case it's still in the queue */
64 dns_packet_unref(ordered_set_remove(t
->stream
->write_queue
, t
->sent
));
66 t
->stream
= dns_stream_unref(t
->stream
);
69 t
->dns_udp_event_source
= sd_event_source_disable_unref(t
->dns_udp_event_source
);
71 /* If we have an UDP socket where we sent a packet, but never received one, then add it to the socket
72 * graveyard, instead of closing it right away. That way it will stick around for a moment longer,
73 * and the reply we might still get from the server will be eaten up instead of resulting in an ICMP
74 * port unreachable error message. */
76 if (use_graveyard
&& t
->dns_udp_fd
>= 0 && t
->sent
&& !t
->received
) {
77 r
= manager_add_socket_to_graveyard(t
->scope
->manager
, t
->dns_udp_fd
);
79 log_debug_errno(r
, "Failed to add UDP socket to graveyard, closing immediately: %m");
81 TAKE_FD(t
->dns_udp_fd
);
84 t
->dns_udp_fd
= safe_close(t
->dns_udp_fd
);
87 static void dns_transaction_stop_timeout(DnsTransaction
*t
) {
90 t
->timeout_event_source
= sd_event_source_disable_unref(t
->timeout_event_source
);
93 DnsTransaction
* dns_transaction_free(DnsTransaction
*t
) {
101 log_debug("Freeing transaction %" PRIu16
".", t
->id
);
103 dns_transaction_close_connection(t
, true);
104 dns_transaction_stop_timeout(t
);
106 dns_packet_unref(t
->sent
);
107 dns_transaction_reset_answer(t
);
109 dns_server_unref(t
->server
);
113 DnsTransaction
*first
;
115 first
= hashmap_get(t
->scope
->transactions_by_key
, t
->key
);
116 LIST_REMOVE(transactions_by_key
, first
, t
);
118 hashmap_replace(t
->scope
->transactions_by_key
, first
->key
, first
);
120 hashmap_remove(t
->scope
->transactions_by_key
, t
->key
);
123 LIST_REMOVE(transactions_by_scope
, t
->scope
->transactions
, t
);
126 hashmap_remove(t
->scope
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
));
129 while ((c
= set_steal_first(t
->notify_query_candidates
)))
130 set_remove(c
->transactions
, t
);
131 set_free(t
->notify_query_candidates
);
133 while ((c
= set_steal_first(t
->notify_query_candidates_done
)))
134 set_remove(c
->transactions
, t
);
135 set_free(t
->notify_query_candidates_done
);
137 while ((i
= set_steal_first(t
->notify_zone_items
)))
138 i
->probe_transaction
= NULL
;
139 set_free(t
->notify_zone_items
);
141 while ((i
= set_steal_first(t
->notify_zone_items_done
)))
142 i
->probe_transaction
= NULL
;
143 set_free(t
->notify_zone_items_done
);
145 while ((z
= set_steal_first(t
->notify_transactions
)))
146 set_remove(z
->dnssec_transactions
, t
);
147 set_free(t
->notify_transactions
);
149 while ((z
= set_steal_first(t
->notify_transactions_done
)))
150 set_remove(z
->dnssec_transactions
, t
);
151 set_free(t
->notify_transactions_done
);
153 dns_transaction_flush_dnssec_transactions(t
);
154 set_free(t
->dnssec_transactions
);
156 dns_answer_unref(t
->validated_keys
);
157 dns_resource_key_unref(t
->key
);
158 dns_packet_unref(t
->bypass
);
163 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsTransaction
*, dns_transaction_free
);
165 DnsTransaction
* dns_transaction_gc(DnsTransaction
*t
) {
168 /* Returns !NULL if we can't gc yet. */
173 if (set_isempty(t
->notify_query_candidates
) &&
174 set_isempty(t
->notify_query_candidates_done
) &&
175 set_isempty(t
->notify_zone_items
) &&
176 set_isempty(t
->notify_zone_items_done
) &&
177 set_isempty(t
->notify_transactions
) &&
178 set_isempty(t
->notify_transactions_done
))
179 return dns_transaction_free(t
);
184 static uint16_t pick_new_id(Manager
*m
) {
187 /* Find a fresh, unused transaction id. Note that this loop is bounded because there's a limit on the
188 * number of transactions, and it's much lower than the space of IDs. */
190 assert_cc(TRANSACTIONS_MAX
< 0xFFFF);
193 random_bytes(&new_id
, sizeof(new_id
));
194 while (new_id
== 0 ||
195 hashmap_get(m
->dns_transactions
, UINT_TO_PTR(new_id
)));
202 DnsResourceKey
*key
) {
204 /* Don't allow looking up invalid or pseudo RRs */
205 if (!dns_type_is_valid_query(key
->type
))
207 if (dns_type_is_obsolete(key
->type
))
210 /* We only support the IN class */
211 if (!IN_SET(key
->class, DNS_CLASS_IN
, DNS_CLASS_ANY
))
214 /* Don't allows DNSSEC RRs to be looked up via LLMNR/mDNS. They don't really make sense
215 * there, and it speeds up our queries if we refuse this early */
216 if (scope
->protocol
!= DNS_PROTOCOL_DNS
&&
217 dns_type_is_dnssec(key
->type
))
223 int dns_transaction_new(
224 DnsTransaction
**ret
,
228 uint64_t query_flags
) {
230 _cleanup_(dns_transaction_freep
) DnsTransaction
*t
= NULL
;
246 r
= dns_packet_validate_query(bypass
);
250 DNS_QUESTION_FOREACH(qk
, bypass
->question
) {
257 if (hashmap_size(s
->manager
->dns_transactions
) >= TRANSACTIONS_MAX
)
260 r
= hashmap_ensure_allocated(&s
->manager
->dns_transactions
, NULL
);
265 r
= hashmap_ensure_allocated(&s
->transactions_by_key
, &dns_resource_key_hash_ops
);
270 t
= new(DnsTransaction
, 1);
274 *t
= (DnsTransaction
) {
276 .answer_source
= _DNS_TRANSACTION_SOURCE_INVALID
,
277 .answer_dnssec_result
= _DNSSEC_RESULT_INVALID
,
278 .answer_nsec_ttl
= UINT32_MAX
,
279 .key
= dns_resource_key_ref(key
),
280 .query_flags
= query_flags
,
281 .bypass
= dns_packet_ref(bypass
),
282 .current_feature_level
= _DNS_SERVER_FEATURE_LEVEL_INVALID
,
283 .clamp_feature_level_servfail
= _DNS_SERVER_FEATURE_LEVEL_INVALID
,
284 .clamp_feature_level_nxdomain
= _DNS_SERVER_FEATURE_LEVEL_INVALID
,
285 .id
= pick_new_id(s
->manager
),
288 r
= hashmap_put(s
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
), t
);
295 DnsTransaction
*first
;
297 first
= hashmap_get(s
->transactions_by_key
, t
->key
);
298 LIST_PREPEND(transactions_by_key
, first
, t
);
300 r
= hashmap_replace(s
->transactions_by_key
, first
->key
, first
);
302 LIST_REMOVE(transactions_by_key
, first
, t
);
307 LIST_PREPEND(transactions_by_scope
, s
->transactions
, t
);
310 s
->manager
->n_transactions_total
++;
319 static void dns_transaction_shuffle_id(DnsTransaction
*t
) {
323 /* Pick a new ID for this transaction. */
325 new_id
= pick_new_id(t
->scope
->manager
);
326 assert_se(hashmap_remove_and_put(t
->scope
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
), UINT_TO_PTR(new_id
), t
) >= 0);
328 log_debug("Transaction %" PRIu16
" is now %" PRIu16
".", t
->id
, new_id
);
331 /* Make sure we generate a new packet with the new ID */
332 t
->sent
= dns_packet_unref(t
->sent
);
335 static void dns_transaction_tentative(DnsTransaction
*t
, DnsPacket
*p
) {
336 _cleanup_free_
char *pretty
= NULL
;
337 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
342 assert(t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
);
344 if (manager_packet_from_local_address(t
->scope
->manager
, p
) != 0)
347 (void) in_addr_to_string(p
->family
, &p
->sender
, &pretty
);
349 log_debug("Transaction %" PRIu16
" for <%s> on scope %s on %s/%s got tentative packet from %s.",
351 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
),
352 dns_protocol_to_string(t
->scope
->protocol
),
353 t
->scope
->link
? t
->scope
->link
->ifname
: "*",
354 af_to_name_short(t
->scope
->family
),
357 /* RFC 4795, Section 4.1 says that the peer with the
358 * lexicographically smaller IP address loses */
359 if (memcmp(&p
->sender
, &p
->destination
, FAMILY_ADDRESS_SIZE(p
->family
)) >= 0) {
360 log_debug("Peer has lexicographically larger IP address and thus lost in the conflict.");
364 log_debug("We have the lexicographically larger IP address and thus lost in the conflict.");
368 while ((z
= set_first(t
->notify_zone_items
))) {
369 /* First, make sure the zone item drops the reference
371 dns_zone_item_probe_stop(z
);
373 /* Secondly, report this as conflict, so that we might
374 * look for a different hostname */
375 dns_zone_item_conflict(z
);
379 dns_transaction_gc(t
);
382 void dns_transaction_complete(DnsTransaction
*t
, DnsTransactionState state
) {
383 DnsQueryCandidate
*c
;
387 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
390 assert(!DNS_TRANSACTION_IS_LIVE(state
));
392 if (state
== DNS_TRANSACTION_DNSSEC_FAILED
) {
393 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
);
395 log_struct(LOG_NOTICE
,
396 "MESSAGE_ID=" SD_MESSAGE_DNSSEC_FAILURE_STR
,
397 LOG_MESSAGE("DNSSEC validation failed for question %s: %s", key_str
, dnssec_result_to_string(t
->answer_dnssec_result
)),
398 "DNS_TRANSACTION=%" PRIu16
, t
->id
,
399 "DNS_QUESTION=%s", key_str
,
400 "DNSSEC_RESULT=%s", dnssec_result_to_string(t
->answer_dnssec_result
),
401 "DNS_SERVER=%s", strna(dns_server_string_full(t
->server
)),
402 "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(t
->server
->possible_feature_level
));
405 /* Note that this call might invalidate the query. Callers
406 * should hence not attempt to access the query or transaction
407 * after calling this function. */
409 if (state
== DNS_TRANSACTION_ERRNO
)
410 st
= errno_to_name(t
->answer_errno
);
412 st
= dns_transaction_state_to_string(state
);
414 log_debug("%s transaction %" PRIu16
" for <%s> on scope %s on %s/%s now complete with <%s> from %s (%s; %s).",
415 t
->bypass
? "Bypass" : "Regular",
417 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
),
418 dns_protocol_to_string(t
->scope
->protocol
),
419 t
->scope
->link
? t
->scope
->link
->ifname
: "*",
420 af_to_name_short(t
->scope
->family
),
422 t
->answer_source
< 0 ? "none" : dns_transaction_source_to_string(t
->answer_source
),
423 FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) ? "not validated" :
424 (FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
) ? "authenticated" : "unsigned"),
425 FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
) ? "confidential" : "non-confidential");
429 dns_transaction_close_connection(t
, true);
430 dns_transaction_stop_timeout(t
);
432 /* Notify all queries that are interested, but make sure the
433 * transaction isn't freed while we are still looking at it */
436 SET_FOREACH_MOVE(c
, t
->notify_query_candidates_done
, t
->notify_query_candidates
)
437 dns_query_candidate_notify(c
);
438 SWAP_TWO(t
->notify_query_candidates
, t
->notify_query_candidates_done
);
440 SET_FOREACH_MOVE(z
, t
->notify_zone_items_done
, t
->notify_zone_items
)
441 dns_zone_item_notify(z
);
442 SWAP_TWO(t
->notify_zone_items
, t
->notify_zone_items_done
);
443 if (t
->probing
&& t
->state
== DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
)
444 (void) dns_scope_announce(t
->scope
, false);
446 SET_FOREACH_MOVE(d
, t
->notify_transactions_done
, t
->notify_transactions
)
447 dns_transaction_notify(d
, t
);
448 SWAP_TWO(t
->notify_transactions
, t
->notify_transactions_done
);
451 dns_transaction_gc(t
);
454 static void dns_transaction_complete_errno(DnsTransaction
*t
, int error
) {
458 t
->answer_errno
= abs(error
);
459 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
462 static int dns_transaction_pick_server(DnsTransaction
*t
) {
466 assert(t
->scope
->protocol
== DNS_PROTOCOL_DNS
);
468 /* Pick a DNS server and a feature level for it. */
470 server
= dns_scope_get_dns_server(t
->scope
);
474 /* If we changed the server invalidate the feature level clamping, as the new server might have completely
475 * different properties. */
476 if (server
!= t
->server
) {
477 t
->clamp_feature_level_servfail
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
478 t
->clamp_feature_level_nxdomain
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
481 t
->current_feature_level
= dns_server_possible_feature_level(server
);
483 /* Clamp the feature level if that is requested. */
484 if (t
->clamp_feature_level_servfail
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
&&
485 t
->current_feature_level
> t
->clamp_feature_level_servfail
)
486 t
->current_feature_level
= t
->clamp_feature_level_servfail
;
487 if (t
->clamp_feature_level_nxdomain
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
&&
488 t
->current_feature_level
> t
->clamp_feature_level_nxdomain
)
489 t
->current_feature_level
= t
->clamp_feature_level_nxdomain
;
491 log_debug("Using feature level %s for transaction %u.", dns_server_feature_level_to_string(t
->current_feature_level
), t
->id
);
493 if (server
== t
->server
)
496 dns_server_unref(t
->server
);
497 t
->server
= dns_server_ref(server
);
499 t
->n_picked_servers
++;
501 log_debug("Using DNS server %s for transaction %u.", strna(dns_server_string_full(t
->server
)), t
->id
);
506 static void dns_transaction_retry(DnsTransaction
*t
, bool next_server
) {
511 /* Retries the transaction as it is, possibly on a different server */
514 log_debug("Retrying transaction %" PRIu16
", after switching servers.", t
->id
);
516 log_debug("Retrying transaction %" PRIu16
".", t
->id
);
518 /* Before we try again, switch to a new server. */
520 dns_scope_next_dns_server(t
->scope
, t
->server
);
522 r
= dns_transaction_go(t
);
524 dns_transaction_complete_errno(t
, r
);
527 static bool dns_transaction_limited_retry(DnsTransaction
*t
) {
530 /* If we haven't tried all different servers yet, let's try again with a different server */
532 if (t
->n_picked_servers
>= dns_scope_get_n_dns_servers(t
->scope
))
535 dns_transaction_retry(t
, /* next_server= */ true);
539 static int dns_transaction_maybe_restart(DnsTransaction
*t
) {
544 /* Restarts the transaction, under a new ID if the feature level of the server changed since we first
545 * tried, without changing DNS server. Returns > 0 if the transaction was restarted, 0 if not. */
550 if (t
->current_feature_level
<= dns_server_possible_feature_level(t
->server
))
553 /* The server's current feature level is lower than when we sent the original query. We learnt something from
554 the response or possibly an auxiliary DNSSEC response that we didn't know before. We take that as reason to
555 restart the whole transaction. This is a good idea to deal with servers that respond rubbish if we include
556 OPT RR or DO bit. One of these cases is documented here, for example:
557 https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */
559 log_debug("Server feature level is now lower than when we began our transaction. Restarting with new ID.");
560 dns_transaction_shuffle_id(t
);
562 r
= dns_transaction_go(t
);
569 static void on_transaction_stream_error(DnsTransaction
*t
, int error
) {
572 dns_transaction_close_connection(t
, true);
574 if (ERRNO_IS_DISCONNECT(error
)) {
575 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
) {
576 /* If the LLMNR/TCP connection failed, the host doesn't support LLMNR, and we cannot answer the
577 * question on this scope. */
578 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
582 dns_transaction_retry(t
, true);
586 dns_transaction_complete_errno(t
, error
);
589 static int dns_transaction_on_stream_packet(DnsTransaction
*t
, DnsStream
*s
, DnsPacket
*p
) {
596 encrypted
= s
->encrypted
;
598 dns_transaction_close_connection(t
, true);
600 if (dns_packet_validate_reply(p
) <= 0) {
601 log_debug("Invalid TCP reply packet.");
602 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
606 dns_scope_check_conflicts(t
->scope
, p
);
609 dns_transaction_process_reply(t
, p
, encrypted
);
612 /* If the response wasn't useful, then complete the transition
613 * now. After all, we are the worst feature set now with TCP
614 * sockets, and there's really no point in retrying. */
615 if (t
->state
== DNS_TRANSACTION_PENDING
)
616 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
618 dns_transaction_gc(t
);
623 static int on_stream_complete(DnsStream
*s
, int error
) {
626 if (ERRNO_IS_DISCONNECT(error
) && s
->protocol
!= DNS_PROTOCOL_LLMNR
) {
627 log_debug_errno(error
, "Connection failure for DNS TCP stream: %m");
629 if (s
->transactions
) {
633 dns_server_packet_lost(t
->server
, IPPROTO_TCP
, t
->current_feature_level
);
638 DnsTransaction
*t
, *n
;
640 LIST_FOREACH_SAFE(transactions_by_stream
, t
, n
, s
->transactions
)
641 on_transaction_stream_error(t
, error
);
647 static int on_stream_packet(DnsStream
*s
) {
648 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
653 /* Take ownership of packet to be able to receive new packets */
654 assert_se(p
= dns_stream_take_read_packet(s
));
656 t
= hashmap_get(s
->manager
->dns_transactions
, UINT_TO_PTR(DNS_PACKET_ID(p
)));
657 if (t
&& t
->stream
== s
) /* Validate that the stream we got this on actually is the stream the
658 * transaction was using. */
659 return dns_transaction_on_stream_packet(t
, s
, p
);
661 /* Ignore incorrect transaction id as an old transaction can have been canceled. */
662 log_debug("Received unexpected TCP reply packet with id %" PRIu16
", ignoring.", DNS_PACKET_ID(p
));
666 static uint16_t dns_transaction_port(DnsTransaction
*t
) {
669 if (t
->server
->port
> 0)
670 return t
->server
->port
;
672 return DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
) ? 853 : 53;
675 static int dns_transaction_emit_tcp(DnsTransaction
*t
) {
676 _cleanup_(dns_stream_unrefp
) DnsStream
*s
= NULL
;
677 _cleanup_close_
int fd
= -1;
678 union sockaddr_union sa
;
685 dns_transaction_close_connection(t
, true);
687 switch (t
->scope
->protocol
) {
689 case DNS_PROTOCOL_DNS
:
690 r
= dns_transaction_pick_server(t
);
694 if (manager_server_is_stub(t
->scope
->manager
, t
->server
))
698 if (!dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(dns_transaction_key(t
)->type
))
701 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
706 if (t
->server
->stream
&& (DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
) == t
->server
->stream
->encrypted
))
707 s
= dns_stream_ref(t
->server
->stream
);
709 fd
= dns_scope_socket_tcp(t
->scope
, AF_UNSPEC
, NULL
, t
->server
, dns_transaction_port(t
), &sa
);
711 type
= DNS_STREAM_LOOKUP
;
714 case DNS_PROTOCOL_LLMNR
:
715 /* When we already received a reply to this (but it was truncated), send to its sender address */
717 fd
= dns_scope_socket_tcp(t
->scope
, t
->received
->family
, &t
->received
->sender
, NULL
, t
->received
->sender_port
, &sa
);
719 union in_addr_union address
;
720 int family
= AF_UNSPEC
;
722 /* Otherwise, try to talk to the owner of a
723 * the IP address, in case this is a reverse
726 r
= dns_name_address(dns_resource_key_name(dns_transaction_key(t
)), &family
, &address
);
731 if (family
!= t
->scope
->family
)
734 fd
= dns_scope_socket_tcp(t
->scope
, family
, &address
, NULL
, LLMNR_PORT
, &sa
);
737 type
= DNS_STREAM_LLMNR_SEND
;
741 return -EAFNOSUPPORT
;
748 r
= dns_stream_new(t
->scope
->manager
, &s
, type
, t
->scope
->protocol
, fd
, &sa
);
754 #if ENABLE_DNS_OVER_TLS
755 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
756 DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
)) {
759 r
= dnstls_stream_connect_tls(s
, t
->server
);
766 dns_server_unref_stream(t
->server
);
767 s
->server
= dns_server_ref(t
->server
);
768 t
->server
->stream
= dns_stream_ref(s
);
771 s
->complete
= on_stream_complete
;
772 s
->on_packet
= on_stream_packet
;
774 /* The interface index is difficult to determine if we are
775 * connecting to the local host, hence fill this in right away
776 * instead of determining it from the socket */
777 s
->ifindex
= dns_scope_ifindex(t
->scope
);
780 t
->stream
= TAKE_PTR(s
);
781 LIST_PREPEND(transactions_by_stream
, t
->stream
->transactions
, t
);
783 r
= dns_stream_write_packet(t
->stream
, t
->sent
);
785 dns_transaction_close_connection(t
, /* use_graveyard= */ false);
789 dns_transaction_reset_answer(t
);
791 t
->tried_stream
= true;
796 static void dns_transaction_cache_answer(DnsTransaction
*t
) {
799 /* For mDNS we cache whenever we get the packet, rather than
800 * in each transaction. */
801 if (!IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_DNS
, DNS_PROTOCOL_LLMNR
))
804 /* Caching disabled? */
805 if (t
->scope
->manager
->enable_cache
== DNS_CACHE_MODE_NO
)
808 /* If validation is turned off for this transaction, but DNSSEC is on, then let's not cache this */
809 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) && t
->scope
->dnssec_mode
!= DNSSEC_NO
)
812 /* Packet from localhost? */
813 if (!t
->scope
->manager
->cache_from_localhost
&&
814 in_addr_is_localhost(t
->received
->family
, &t
->received
->sender
) != 0)
817 dns_cache_put(&t
->scope
->cache
,
818 t
->scope
->manager
->enable_cache
,
819 dns_transaction_key(t
),
822 DNS_PACKET_CD(t
->received
) ? t
->received
: NULL
, /* only cache full packets with CD on,
823 * since our usecase for caching them
824 * is "bypass" mode which is only
825 * enabled for CD packets. */
826 t
->answer_query_flags
,
827 t
->answer_dnssec_result
,
830 &t
->received
->sender
);
833 static bool dns_transaction_dnssec_is_live(DnsTransaction
*t
) {
838 SET_FOREACH(dt
, t
->dnssec_transactions
)
839 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
845 static int dns_transaction_dnssec_ready(DnsTransaction
*t
) {
851 /* Checks whether the auxiliary DNSSEC transactions of our transaction have completed, or are still
852 * ongoing. Returns 0, if we aren't ready for the DNSSEC validation, positive if we are. */
854 SET_FOREACH(dt
, t
->dnssec_transactions
) {
858 case DNS_TRANSACTION_NULL
:
859 case DNS_TRANSACTION_PENDING
:
860 case DNS_TRANSACTION_VALIDATING
:
864 case DNS_TRANSACTION_RCODE_FAILURE
:
865 if (!IN_SET(dt
->answer_rcode
, DNS_RCODE_NXDOMAIN
, DNS_RCODE_SERVFAIL
)) {
866 log_debug("Auxiliary DNSSEC RR query failed with rcode=%s.", dns_rcode_to_string(dt
->answer_rcode
));
870 /* Fall-through: NXDOMAIN/SERVFAIL is good enough for us. This is because some DNS servers
871 * erroneously return NXDOMAIN/SERVFAIL for empty non-terminals (Akamai...) or missing DS
872 * records (Facebook), and we need to handle that nicely, when asking for parent SOA or similar
873 * RRs to make unsigned proofs. */
875 case DNS_TRANSACTION_SUCCESS
:
879 case DNS_TRANSACTION_DNSSEC_FAILED
:
880 /* We handle DNSSEC failures different from other errors, as we care about the DNSSEC
881 * validation result */
883 log_debug("Auxiliary DNSSEC RR query failed validation: %s", dnssec_result_to_string(dt
->answer_dnssec_result
));
884 t
->answer_dnssec_result
= dt
->answer_dnssec_result
; /* Copy error code over */
885 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
889 log_debug("Auxiliary DNSSEC RR query failed with %s", dns_transaction_state_to_string(dt
->state
));
894 /* All is ready, we can go and validate */
898 /* Some auxiliary DNSSEC transaction failed for some reason. Maybe we learned something about the
899 * server due to this failure, and the feature level is now different? Let's see and restart the
900 * transaction if so. If not, let's propagate the auxiliary failure.
902 * This is particularly relevant if an auxiliary request figured out that DNSSEC doesn't work, and we
903 * are in permissive DNSSEC mode, and thus should restart things without DNSSEC magic. */
904 r
= dns_transaction_maybe_restart(t
);
908 return 0; /* don't validate just yet, we restarted things */
910 t
->answer_dnssec_result
= DNSSEC_FAILED_AUXILIARY
;
911 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
915 static void dns_transaction_process_dnssec(DnsTransaction
*t
) {
920 /* Are there ongoing DNSSEC transactions? If so, let's wait for them. */
921 r
= dns_transaction_dnssec_ready(t
);
924 if (r
== 0) /* We aren't ready yet (or one of our auxiliary transactions failed, and we shouldn't validate now */
927 /* See if we learnt things from the additional DNSSEC transactions, that we didn't know before, and better
928 * restart the lookup immediately. */
929 r
= dns_transaction_maybe_restart(t
);
932 if (r
> 0) /* Transaction got restarted... */
935 /* All our auxiliary DNSSEC transactions are complete now. Try
936 * to validate our RRset now. */
937 r
= dns_transaction_validate_dnssec(t
);
939 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
945 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
&&
946 t
->scope
->dnssec_mode
== DNSSEC_YES
) {
948 /* We are not in automatic downgrade mode, and the server is bad. Let's try a different server, maybe
951 if (dns_transaction_limited_retry(t
))
954 /* OK, let's give up, apparently all servers we tried didn't work. */
955 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
959 if (!IN_SET(t
->answer_dnssec_result
,
960 _DNSSEC_RESULT_INVALID
, /* No DNSSEC validation enabled */
961 DNSSEC_VALIDATED
, /* Answer is signed and validated successfully */
962 DNSSEC_UNSIGNED
, /* Answer is right-fully unsigned */
963 DNSSEC_INCOMPATIBLE_SERVER
)) { /* Server does not do DNSSEC (Yay, we are downgrade attack vulnerable!) */
964 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
968 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
)
969 dns_server_warn_downgrade(t
->server
);
971 dns_transaction_cache_answer(t
);
973 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
974 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
976 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
981 dns_transaction_complete_errno(t
, r
);
984 static int dns_transaction_has_positive_answer(DnsTransaction
*t
, DnsAnswerFlags
*flags
) {
989 /* Checks whether the answer is positive, i.e. either a direct
990 * answer to the question, or a CNAME/DNAME for it */
992 r
= dns_answer_match_key(t
->answer
, dns_transaction_key(t
), flags
);
996 r
= dns_answer_find_cname_or_dname(t
->answer
, dns_transaction_key(t
), NULL
, flags
);
1003 static int dns_transaction_fix_rcode(DnsTransaction
*t
) {
1008 /* Fix up the RCODE to SUCCESS if we get at least one matching RR in a response. Note that this contradicts the
1009 * DNS RFCs a bit. Specifically, RFC 6604 Section 3 clarifies that the RCODE shall say something about a
1010 * CNAME/DNAME chain element coming after the last chain element contained in the message, and not the first
1011 * one included. However, it also indicates that not all DNS servers implement this correctly. Moreover, when
1012 * using DNSSEC we usually only can prove the first element of a CNAME/DNAME chain anyway, hence let's settle
1013 * on always processing the RCODE as referring to the immediate look-up we do, i.e. the first element of a
1014 * CNAME/DNAME chain. This way, we uniformly handle CNAME/DNAME chains, regardless if the DNS server
1015 * incorrectly implements RCODE, whether DNSSEC is in use, or whether the DNS server only supplied us with an
1016 * incomplete CNAME/DNAME chain.
1018 * Or in other words: if we get at least one positive reply in a message we patch NXDOMAIN to become SUCCESS,
1019 * and then rely on the CNAME chasing logic to figure out that there's actually a CNAME error with a new
1022 if (t
->answer_rcode
!= DNS_RCODE_NXDOMAIN
)
1025 r
= dns_transaction_has_positive_answer(t
, NULL
);
1029 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1033 void dns_transaction_process_reply(DnsTransaction
*t
, DnsPacket
*p
, bool encrypted
) {
1034 bool retry_with_tcp
= false;
1040 assert(t
->scope
->manager
);
1042 if (t
->state
!= DNS_TRANSACTION_PENDING
)
1045 /* Note that this call might invalidate the query. Callers
1046 * should hence not attempt to access the query or transaction
1047 * after calling this function. */
1049 log_debug("Processing incoming packet of size %zu on transaction %" PRIu16
" (rcode=%s).",
1051 t
->id
, dns_rcode_to_string(DNS_PACKET_RCODE(p
)));
1053 switch (t
->scope
->protocol
) {
1055 case DNS_PROTOCOL_LLMNR
:
1056 /* For LLMNR we will not accept any packets from other interfaces */
1058 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
1061 if (p
->family
!= t
->scope
->family
)
1064 /* Tentative packets are not full responses but still
1065 * useful for identifying uniqueness conflicts during
1067 if (DNS_PACKET_LLMNR_T(p
)) {
1068 dns_transaction_tentative(t
, p
);
1074 case DNS_PROTOCOL_MDNS
:
1075 /* For mDNS we will not accept any packets from other interfaces */
1077 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
1080 if (p
->family
!= t
->scope
->family
)
1085 case DNS_PROTOCOL_DNS
:
1086 /* Note that we do not need to verify the
1087 * addresses/port numbers of incoming traffic, as we
1088 * invoked connect() on our UDP socket in which case
1089 * the kernel already does the needed verification for
1094 assert_not_reached("Invalid DNS protocol.");
1097 if (t
->received
!= p
) {
1098 dns_packet_unref(t
->received
);
1099 t
->received
= dns_packet_ref(p
);
1102 t
->answer_source
= DNS_TRANSACTION_NETWORK
;
1104 if (p
->ipproto
== IPPROTO_TCP
) {
1105 if (DNS_PACKET_TC(p
)) {
1106 /* Truncated via TCP? Somebody must be fucking with us */
1107 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1111 if (DNS_PACKET_ID(p
) != t
->id
) {
1112 /* Not the reply to our query? Somebody must be fucking with us */
1113 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1118 switch (t
->scope
->protocol
) {
1120 case DNS_PROTOCOL_DNS
:
1124 IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_FORMERR
, DNS_RCODE_SERVFAIL
, DNS_RCODE_NOTIMP
)) {
1126 /* Request failed, immediately try again with reduced features */
1128 if (t
->current_feature_level
<= DNS_SERVER_FEATURE_LEVEL_UDP
) {
1130 /* This was already at UDP feature level? If so, it doesn't make sense to downgrade
1131 * this transaction anymore, but let's see if it might make sense to send the request
1132 * to a different DNS server instead. If not let's process the response, and accept the
1133 * rcode. Note that we don't retry on TCP, since that's a suitable way to mitigate
1134 * packet loss, but is not going to give us better rcodes should we actually have
1135 * managed to get them already at UDP level. */
1137 if (dns_transaction_limited_retry(t
))
1140 /* Give up, accept the rcode */
1141 log_debug("Server returned error: %s", dns_rcode_to_string(DNS_PACKET_RCODE(p
)));
1145 /* Reduce this feature level by one and try again. */
1146 switch (t
->current_feature_level
) {
1147 case DNS_SERVER_FEATURE_LEVEL_TLS_DO
:
1148 t
->clamp_feature_level_servfail
= DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
;
1150 case DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
+ 1:
1151 /* Skip plain TLS when TLS is not supported */
1152 t
->clamp_feature_level_servfail
= DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
- 1;
1155 t
->clamp_feature_level_servfail
= t
->current_feature_level
- 1;
1158 log_debug("Server returned error %s, retrying transaction with reduced feature level %s.",
1159 dns_rcode_to_string(DNS_PACKET_RCODE(p
)),
1160 dns_server_feature_level_to_string(t
->clamp_feature_level_servfail
));
1162 dns_transaction_retry(t
, false /* use the same server */);
1166 if (DNS_PACKET_RCODE(p
) == DNS_RCODE_REFUSED
) {
1167 /* This server refused our request? If so, try again, use a different server */
1168 log_debug("Server returned REFUSED, switching servers, and retrying.");
1170 if (dns_transaction_limited_retry(t
))
1176 if (DNS_PACKET_TC(p
))
1177 dns_server_packet_truncated(t
->server
, t
->current_feature_level
);
1181 case DNS_PROTOCOL_LLMNR
:
1182 case DNS_PROTOCOL_MDNS
:
1183 dns_scope_packet_received(t
->scope
, p
->timestamp
- t
->start_usec
);
1187 assert_not_reached("Invalid DNS protocol.");
1190 if (DNS_PACKET_TC(p
)) {
1192 /* Truncated packets for mDNS are not allowed. Give up immediately. */
1193 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
) {
1194 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1198 /* Response was truncated, let's try again with good old TCP */
1199 log_debug("Reply truncated, retrying via TCP.");
1200 retry_with_tcp
= true;
1202 } else if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1203 DNS_PACKET_IS_FRAGMENTED(p
)) {
1205 /* Report the fragment size, so that we downgrade from LARGE to regular EDNS0 if needed */
1207 dns_server_packet_udp_fragmented(t
->server
, dns_packet_size_unfragmented(p
));
1209 if (t
->current_feature_level
> DNS_SERVER_FEATURE_LEVEL_UDP
) {
1210 /* Packet was fragmented. Let's retry with TCP to avoid fragmentation attack
1211 * issues. (We don't do that on the lowest feature level however, since crappy DNS
1212 * servers often do not implement TCP, hence falling back to TCP on fragmentation is
1213 * counter-productive there.) */
1215 log_debug("Reply fragmented, retrying via TCP. (Largest fragment size: %zu; Datagram size: %zu)",
1216 p
->fragsize
, p
->size
);
1217 retry_with_tcp
= true;
1221 if (retry_with_tcp
) {
1222 r
= dns_transaction_emit_tcp(t
);
1224 /* No servers found? Damn! */
1225 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
1228 if (r
== -EOPNOTSUPP
) {
1229 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
1230 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
1234 /* On LLMNR, if we cannot connect to the host,
1235 * we immediately give up */
1236 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1239 /* On DNS, couldn't send? Try immediately again, with a new server */
1240 if (dns_transaction_limited_retry(t
))
1243 /* No new server to try, give up */
1244 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1250 /* After the superficial checks, actually parse the message. */
1251 r
= dns_packet_extract(p
);
1254 dns_server_packet_invalid(t
->server
, t
->current_feature_level
);
1256 r
= dns_transaction_maybe_restart(t
);
1259 if (r
> 0) /* Transaction got restarted... */
1263 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1267 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1269 DNS_PACKET_RCODE(p
) == DNS_RCODE_NXDOMAIN
&&
1270 p
->opt
&& !DNS_PACKET_DO(p
) &&
1271 DNS_SERVER_FEATURE_LEVEL_IS_EDNS0(t
->current_feature_level
) &&
1272 DNS_SERVER_FEATURE_LEVEL_IS_UDP(t
->current_feature_level
) &&
1273 t
->scope
->dnssec_mode
!= DNSSEC_YES
) {
1275 /* Some captive portals are special in that the Aruba/Datavalet hardware will miss
1276 * replacing the packets with the local server IP to point to the authenticated side
1277 * of the network if EDNS0 is enabled. Instead they return NXDOMAIN, with DO bit set
1278 * to zero... nothing to see here, yet respond with the captive portal IP, when using
1279 * the more simple UDP level.
1281 * Common portal names that fail like so are:
1282 * secure.datavalet.io
1283 * securelogin.arubanetworks.com
1284 * securelogin.networks.mycompany.com
1286 * Thus retry NXDOMAIN RCODES with a lower feature level.
1288 * Do not lower the server's tracked feature level, as the captive portal should not
1289 * be lying for the wider internet (e.g. _other_ queries were observed fine with
1290 * EDNS0 on these networks, post auth), i.e. let's just lower the level transaction's
1293 * This is reported as https://github.com/dns-violations/dns-violations/blob/master/2018/DVE-2018-0001.md
1296 t
->clamp_feature_level_nxdomain
= DNS_SERVER_FEATURE_LEVEL_UDP
;
1298 log_debug("Server returned error %s in EDNS0 mode, retrying transaction with reduced feature level %s (DVE-2018-0001 mitigation)",
1299 dns_rcode_to_string(DNS_PACKET_RCODE(p
)),
1300 dns_server_feature_level_to_string(t
->clamp_feature_level_nxdomain
));
1302 dns_transaction_retry(t
, false /* use the same server */);
1307 /* Report that we successfully received a valid packet with a good rcode after we initially got a bad
1308 * rcode and subsequently downgraded the protocol */
1310 if (IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_SUCCESS
, DNS_RCODE_NXDOMAIN
) &&
1311 t
->clamp_feature_level_servfail
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
)
1312 dns_server_packet_rcode_downgrade(t
->server
, t
->clamp_feature_level_servfail
);
1314 /* Report that the OPT RR was missing */
1316 dns_server_packet_bad_opt(t
->server
, t
->current_feature_level
);
1318 /* Report that the server didn't copy our query DO bit from request to response */
1319 if (DNS_PACKET_DO(t
->sent
) && !DNS_PACKET_DO(t
->received
))
1320 dns_server_packet_do_off(t
->server
, t
->current_feature_level
);
1322 /* Report that we successfully received a packet. We keep track of the largest packet
1323 * size/fragment size we got. Which is useful for announcing the EDNS(0) packet size we can
1324 * receive to our server. */
1325 dns_server_packet_received(t
->server
, p
->ipproto
, t
->current_feature_level
, dns_packet_size_unfragmented(p
));
1328 /* See if we know things we didn't know before that indicate we better restart the lookup immediately. */
1329 r
= dns_transaction_maybe_restart(t
);
1332 if (r
> 0) /* Transaction got restarted... */
1335 /* When dealing with protocols other than mDNS only consider responses with equivalent query section
1336 * to the request. For mDNS this check doesn't make sense, because the section 6 of RFC6762 states
1337 * that "Multicast DNS responses MUST NOT contain any questions in the Question Section". */
1338 if (t
->scope
->protocol
!= DNS_PROTOCOL_MDNS
) {
1339 r
= dns_packet_is_reply_for(p
, dns_transaction_key(t
));
1343 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1348 /* Install the answer as answer to the transaction. We ref the answer twice here: the main `answer`
1349 * field is later replaced by the DNSSEC validated subset. The 'answer_auxiliary' field carries the
1350 * original complete record set, including RRSIG and friends. We use this when passing data to
1351 * clients that ask for DNSSEC metadata. */
1352 dns_answer_unref(t
->answer
);
1353 t
->answer
= dns_answer_ref(p
->answer
);
1354 t
->answer_rcode
= DNS_PACKET_RCODE(p
);
1355 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
1356 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
1357 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
, encrypted
);
1359 r
= dns_transaction_fix_rcode(t
);
1363 /* Block GC while starting requests for additional DNSSEC RRs */
1365 r
= dns_transaction_request_dnssec_keys(t
);
1368 /* Maybe the transaction is ready for GC'ing now? If so, free it and return. */
1369 if (!dns_transaction_gc(t
))
1372 /* Requesting additional keys might have resulted in this transaction to fail, since the auxiliary
1373 * request failed for some reason. If so, we are not in pending state anymore, and we should exit
1375 if (t
->state
!= DNS_TRANSACTION_PENDING
)
1380 /* There are DNSSEC transactions pending now. Update the state accordingly. */
1381 t
->state
= DNS_TRANSACTION_VALIDATING
;
1382 dns_transaction_close_connection(t
, true);
1383 dns_transaction_stop_timeout(t
);
1387 dns_transaction_process_dnssec(t
);
1391 dns_transaction_complete_errno(t
, r
);
1394 static int on_dns_packet(sd_event_source
*s
, int fd
, uint32_t revents
, void *userdata
) {
1395 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1396 DnsTransaction
*t
= userdata
;
1402 r
= manager_recv(t
->scope
->manager
, fd
, DNS_PROTOCOL_DNS
, &p
);
1403 if (ERRNO_IS_DISCONNECT(r
)) {
1406 /* UDP connection failures get reported via ICMP and then are possibly delivered to us on the
1407 * next recvmsg(). Treat this like a lost packet. */
1409 log_debug_errno(r
, "Connection failure for DNS UDP packet: %m");
1410 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &usec
) >= 0);
1411 dns_server_packet_lost(t
->server
, IPPROTO_UDP
, t
->current_feature_level
);
1413 dns_transaction_close_connection(t
, /* use_graveyard = */ false);
1415 if (dns_transaction_limited_retry(t
)) /* Try a different server */
1418 dns_transaction_complete_errno(t
, r
);
1422 dns_transaction_complete_errno(t
, r
);
1426 /* Spurious wakeup without any data */
1429 r
= dns_packet_validate_reply(p
);
1431 log_debug_errno(r
, "Received invalid DNS packet as response, ignoring: %m");
1435 log_debug("Received inappropriate DNS packet as response, ignoring.");
1439 if (DNS_PACKET_ID(p
) != t
->id
) {
1440 log_debug("Received packet with incorrect transaction ID, ignoring.");
1444 dns_transaction_process_reply(t
, p
, false);
1448 static int dns_transaction_emit_udp(DnsTransaction
*t
) {
1453 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
) {
1455 r
= dns_transaction_pick_server(t
);
1459 if (manager_server_is_stub(t
->scope
->manager
, t
->server
))
1462 if (t
->current_feature_level
< DNS_SERVER_FEATURE_LEVEL_UDP
|| DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
))
1463 return -EAGAIN
; /* Sorry, can't do UDP, try TCP! */
1465 if (!t
->bypass
&& !dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(dns_transaction_key(t
)->type
))
1468 if (r
> 0 || t
->dns_udp_fd
< 0) { /* Server changed, or no connection yet. */
1471 dns_transaction_close_connection(t
, true);
1473 /* Before we allocate a new UDP socket, let's process the graveyard a bit to free some fds */
1474 manager_socket_graveyard_process(t
->scope
->manager
);
1476 fd
= dns_scope_socket_udp(t
->scope
, t
->server
);
1480 r
= sd_event_add_io(t
->scope
->manager
->event
, &t
->dns_udp_event_source
, fd
, EPOLLIN
, on_dns_packet
, t
);
1486 (void) sd_event_source_set_description(t
->dns_udp_event_source
, "dns-transaction-udp");
1491 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
1496 dns_transaction_close_connection(t
, true);
1498 r
= dns_scope_emit_udp(t
->scope
, t
->dns_udp_fd
, t
->server
? t
->server
->family
: AF_UNSPEC
, t
->sent
);
1502 dns_transaction_reset_answer(t
);
1507 static int on_transaction_timeout(sd_event_source
*s
, usec_t usec
, void *userdata
) {
1508 DnsTransaction
*t
= userdata
;
1513 if (!t
->initial_jitter_scheduled
|| t
->initial_jitter_elapsed
) {
1514 /* Timeout reached? Increase the timeout for the server used */
1515 switch (t
->scope
->protocol
) {
1517 case DNS_PROTOCOL_DNS
:
1519 dns_server_packet_lost(t
->server
, t
->stream
? IPPROTO_TCP
: IPPROTO_UDP
, t
->current_feature_level
);
1522 case DNS_PROTOCOL_LLMNR
:
1523 case DNS_PROTOCOL_MDNS
:
1524 dns_scope_packet_lost(t
->scope
, usec
- t
->start_usec
);
1528 assert_not_reached("Invalid DNS protocol.");
1531 if (t
->initial_jitter_scheduled
)
1532 t
->initial_jitter_elapsed
= true;
1535 log_debug("Timeout reached on transaction %" PRIu16
".", t
->id
);
1537 dns_transaction_retry(t
, true); /* try a different server, but given this means packet loss, let's do
1538 * so even if we already tried a bunch */
1542 static usec_t
transaction_get_resend_timeout(DnsTransaction
*t
) {
1546 switch (t
->scope
->protocol
) {
1548 case DNS_PROTOCOL_DNS
:
1550 /* When we do TCP, grant a much longer timeout, as in this case there's no need for us to quickly
1551 * resend, as the kernel does that anyway for us, and we really don't want to interrupt it in that
1554 return TRANSACTION_TCP_TIMEOUT_USEC
;
1556 return DNS_TIMEOUT_USEC
;
1558 case DNS_PROTOCOL_MDNS
:
1559 assert(t
->n_attempts
> 0);
1561 return MDNS_PROBING_INTERVAL_USEC
;
1563 return (1 << (t
->n_attempts
- 1)) * USEC_PER_SEC
;
1565 case DNS_PROTOCOL_LLMNR
:
1566 return t
->scope
->resend_timeout
;
1569 assert_not_reached("Invalid DNS protocol.");
1573 static void dns_transaction_randomize_answer(DnsTransaction
*t
) {
1578 /* Randomizes the order of the answer array. This is done for all cached responses, so that we return
1579 * a different order each time. We do this only for DNS traffic, in order to do some minimal, crappy
1580 * load balancing. We don't do this for LLMNR or mDNS, since the order (preferring link-local
1581 * addresses, and such like) might have meaning there, and load balancing is pointless. */
1583 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1586 /* No point in randomizing, if there's just one RR */
1587 if (dns_answer_size(t
->answer
) <= 1)
1590 r
= dns_answer_reserve_or_clone(&t
->answer
, 0);
1591 if (r
< 0) /* If this fails, just don't randomize, this is non-essential stuff after all */
1592 return (void) log_debug_errno(r
, "Failed to clone answer record, not randomizing RR order of answer: %m");
1594 dns_answer_randomize(t
->answer
);
1597 static int dns_transaction_prepare(DnsTransaction
*t
, usec_t ts
) {
1602 /* Returns 0 if dns_transaction_complete() has been called. In that case the transaction and query
1603 * candidate objects may have been invalidated and must not be accessed. Returns 1 if the transaction
1604 * has been prepared. */
1606 dns_transaction_stop_timeout(t
);
1608 if (!dns_scope_network_good(t
->scope
)) {
1609 dns_transaction_complete(t
, DNS_TRANSACTION_NETWORK_DOWN
);
1613 if (t
->n_attempts
>= TRANSACTION_ATTEMPTS_MAX(t
->scope
->protocol
)) {
1614 DnsTransactionState result
;
1616 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
)
1617 /* If we didn't find anything on LLMNR, it's not an error, but a failure to resolve
1619 result
= DNS_TRANSACTION_NOT_FOUND
;
1621 result
= DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
;
1623 dns_transaction_complete(t
, result
);
1627 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& t
->tried_stream
) {
1628 /* If we already tried via a stream, then we don't
1629 * retry on LLMNR. See RFC 4795, Section 2.7. */
1630 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1637 dns_transaction_reset_answer(t
);
1638 dns_transaction_flush_dnssec_transactions(t
);
1640 /* Check the trust anchor. Do so only on classic DNS, since DNSSEC does not apply otherwise. */
1641 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1642 !FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_TRUST_ANCHOR
)) {
1643 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, dns_transaction_key(t
), &t
->answer
);
1647 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1648 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1649 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
|SD_RESOLVED_CONFIDENTIAL
, true);
1650 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1654 if (dns_name_is_root(dns_resource_key_name(dns_transaction_key(t
))) &&
1655 dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
1657 /* Hmm, this is a request for the root DS? A DS RR doesn't exist in the root zone,
1658 * and if our trust anchor didn't know it either, this means we cannot do any DNSSEC
1661 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
1662 /* We are in downgrade mode. In this case, synthesize an unsigned empty
1663 * response, so that the any lookup depending on this one can continue
1664 * assuming there was no DS, and hence the root zone was unsigned. */
1666 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1667 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1668 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
1669 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
, true);
1670 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1672 /* If we are not in downgrade mode, then fail the lookup, because we cannot
1673 * reasonably answer it. There might be DS RRs, but we don't know them, and
1674 * the DNS server won't tell them to us (and even if it would, we couldn't
1675 * validate and trust them. */
1676 dns_transaction_complete(t
, DNS_TRANSACTION_NO_TRUST_ANCHOR
);
1682 /* Check the zone. */
1683 if (!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_ZONE
)) {
1684 r
= dns_zone_lookup(&t
->scope
->zone
, dns_transaction_key(t
), dns_scope_ifindex(t
->scope
), &t
->answer
, NULL
, NULL
);
1688 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1689 t
->answer_source
= DNS_TRANSACTION_ZONE
;
1690 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
|SD_RESOLVED_CONFIDENTIAL
, true);
1691 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1696 /* Check the cache. */
1697 if (!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_CACHE
)) {
1699 /* Before trying the cache, let's make sure we figured out a server to use. Should this cause
1700 * a change of server this might flush the cache. */
1701 (void) dns_scope_get_dns_server(t
->scope
);
1703 /* Let's then prune all outdated entries */
1704 dns_cache_prune(&t
->scope
->cache
);
1706 r
= dns_cache_lookup(
1708 dns_transaction_key(t
),
1713 &t
->answer_query_flags
,
1714 &t
->answer_dnssec_result
);
1718 dns_transaction_randomize_answer(t
);
1720 if (t
->bypass
&& t
->scope
->protocol
== DNS_PROTOCOL_DNS
&& !t
->received
)
1721 /* When bypass mode is on, do not use cached data unless it came with a full
1723 dns_transaction_reset_answer(t
);
1725 t
->answer_source
= DNS_TRANSACTION_CACHE
;
1726 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
1727 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1729 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
1735 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_NETWORK
)) {
1736 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SOURCE
);
1743 static int dns_transaction_make_packet_mdns(DnsTransaction
*t
) {
1744 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1745 bool add_known_answers
= false;
1746 DnsTransaction
*other
;
1747 DnsResourceKey
*tkey
;
1748 _cleanup_set_free_ Set
*keys
= NULL
;
1750 unsigned nscount
= 0;
1755 assert(t
->scope
->protocol
== DNS_PROTOCOL_MDNS
);
1757 /* Discard any previously prepared packet, so we can start over and coalesce again */
1758 t
->sent
= dns_packet_unref(t
->sent
);
1760 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, false);
1764 r
= dns_packet_append_key(p
, dns_transaction_key(t
), 0, NULL
);
1770 if (dns_key_is_shared(dns_transaction_key(t
)))
1771 add_known_answers
= true;
1773 if (dns_transaction_key(t
)->type
== DNS_TYPE_ANY
) {
1774 r
= set_ensure_put(&keys
, &dns_resource_key_hash_ops
, dns_transaction_key(t
));
1780 * For mDNS, we want to coalesce as many open queries in pending transactions into one single
1781 * query packet on the wire as possible. To achieve that, we iterate through all pending transactions
1782 * in our current scope, and see whether their timing constraints allow them to be sent.
1785 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &ts
) >= 0);
1787 LIST_FOREACH(transactions_by_scope
, other
, t
->scope
->transactions
) {
1789 /* Skip ourselves */
1793 if (other
->state
!= DNS_TRANSACTION_PENDING
)
1796 if (other
->next_attempt_after
> ts
)
1799 if (qdcount
>= UINT16_MAX
)
1802 r
= dns_packet_append_key(p
, dns_transaction_key(other
), 0, NULL
);
1805 * If we can't stuff more questions into the packet, just give up.
1806 * One of the 'other' transactions will fire later and take care of the rest.
1814 r
= dns_transaction_prepare(other
, ts
);
1818 ts
+= transaction_get_resend_timeout(other
);
1820 r
= sd_event_add_time(
1821 other
->scope
->manager
->event
,
1822 &other
->timeout_event_source
,
1823 clock_boottime_or_monotonic(),
1825 on_transaction_timeout
, other
);
1829 (void) sd_event_source_set_description(other
->timeout_event_source
, "dns-transaction-timeout");
1831 other
->state
= DNS_TRANSACTION_PENDING
;
1832 other
->next_attempt_after
= ts
;
1836 if (dns_key_is_shared(dns_transaction_key(other
)))
1837 add_known_answers
= true;
1839 if (dns_transaction_key(other
)->type
== DNS_TYPE_ANY
) {
1840 r
= set_ensure_put(&keys
, &dns_resource_key_hash_ops
, dns_transaction_key(other
));
1846 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(qdcount
);
1848 /* Append known answer section if we're asking for any shared record */
1849 if (add_known_answers
) {
1850 r
= dns_cache_export_shared_to_packet(&t
->scope
->cache
, p
);
1855 SET_FOREACH(tkey
, keys
) {
1856 _cleanup_(dns_answer_unrefp
) DnsAnswer
*answer
= NULL
;
1859 r
= dns_zone_lookup(&t
->scope
->zone
, tkey
, t
->scope
->link
->ifindex
, &answer
, NULL
, &tentative
);
1863 r
= dns_packet_append_answer(p
, answer
, &nscount
);
1867 DNS_PACKET_HEADER(p
)->nscount
= htobe16(nscount
);
1869 t
->sent
= TAKE_PTR(p
);
1874 static int dns_transaction_make_packet(DnsTransaction
*t
) {
1875 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1880 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
)
1881 return dns_transaction_make_packet_mdns(t
);
1886 if (t
->bypass
&& t
->bypass
->protocol
== t
->scope
->protocol
) {
1887 /* If bypass logic is enabled and the protocol if the original packet and our scope match,
1888 * take the original packet, copy it, and patch in our new ID */
1889 r
= dns_packet_dup(&p
, t
->bypass
);
1893 r
= dns_packet_new_query(
1894 &p
, t
->scope
->protocol
,
1895 /* min_alloc_dsize = */ 0,
1896 /* dnssec_cd = */ !FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) &&
1897 t
->scope
->dnssec_mode
!= DNSSEC_NO
);
1901 r
= dns_packet_append_key(p
, dns_transaction_key(t
), 0, NULL
);
1905 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(1);
1908 DNS_PACKET_HEADER(p
)->id
= t
->id
;
1910 t
->sent
= TAKE_PTR(p
);
1914 int dns_transaction_go(DnsTransaction
*t
) {
1917 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
1921 /* Returns > 0 if the transaction is now pending, returns 0 if could be processed immediately and has
1922 * finished now. In the latter case, the transaction and query candidate objects must not be accessed.
1925 assert_se(sd_event_now(t
->scope
->manager
->event
, clock_boottime_or_monotonic(), &ts
) >= 0);
1927 r
= dns_transaction_prepare(t
, ts
);
1931 log_debug("%s transaction %" PRIu16
" for <%s> scope %s on %s/%s (validate=%s).",
1932 t
->bypass
? "Bypass" : "Regular",
1934 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
),
1935 dns_protocol_to_string(t
->scope
->protocol
),
1936 t
->scope
->link
? t
->scope
->link
->ifname
: "*",
1937 af_to_name_short(t
->scope
->family
),
1938 yes_no(!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
)));
1940 if (!t
->initial_jitter_scheduled
&&
1941 IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_LLMNR
, DNS_PROTOCOL_MDNS
)) {
1942 usec_t jitter
, accuracy
;
1944 /* RFC 4795 Section 2.7 suggests all queries should be
1945 * delayed by a random time from 0 to JITTER_INTERVAL. */
1947 t
->initial_jitter_scheduled
= true;
1949 random_bytes(&jitter
, sizeof(jitter
));
1951 switch (t
->scope
->protocol
) {
1953 case DNS_PROTOCOL_LLMNR
:
1954 jitter
%= LLMNR_JITTER_INTERVAL_USEC
;
1955 accuracy
= LLMNR_JITTER_INTERVAL_USEC
;
1958 case DNS_PROTOCOL_MDNS
:
1959 jitter
%= MDNS_JITTER_RANGE_USEC
;
1960 jitter
+= MDNS_JITTER_MIN_USEC
;
1961 accuracy
= MDNS_JITTER_RANGE_USEC
;
1964 assert_not_reached("bad protocol");
1967 r
= sd_event_add_time(
1968 t
->scope
->manager
->event
,
1969 &t
->timeout_event_source
,
1970 clock_boottime_or_monotonic(),
1971 ts
+ jitter
, accuracy
,
1972 on_transaction_timeout
, t
);
1976 (void) sd_event_source_set_description(t
->timeout_event_source
, "dns-transaction-timeout");
1979 t
->next_attempt_after
= ts
;
1980 t
->state
= DNS_TRANSACTION_PENDING
;
1982 log_debug("Delaying %s transaction for " USEC_FMT
"us.", dns_protocol_to_string(t
->scope
->protocol
), jitter
);
1986 /* Otherwise, we need to ask the network */
1987 r
= dns_transaction_make_packet(t
);
1991 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&&
1992 (dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), "in-addr.arpa") > 0 ||
1993 dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), "ip6.arpa") > 0)) {
1995 /* RFC 4795, Section 2.4. says reverse lookups shall
1996 * always be made via TCP on LLMNR */
1997 r
= dns_transaction_emit_tcp(t
);
1999 /* Try via UDP, and if that fails due to large size or lack of
2000 * support try via TCP */
2001 r
= dns_transaction_emit_udp(t
);
2003 log_debug("Sending query via TCP since it is too large.");
2004 else if (r
== -EAGAIN
)
2005 log_debug("Sending query via TCP since UDP isn't supported or DNS-over-TLS is selected.");
2006 if (IN_SET(r
, -EMSGSIZE
, -EAGAIN
))
2007 r
= dns_transaction_emit_tcp(t
);
2010 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2013 /* One of our own stub listeners */
2014 log_debug_errno(r
, "Detected that specified DNS server is our own extra listener, switching DNS servers.");
2016 dns_scope_next_dns_server(t
->scope
, t
->server
);
2018 if (dns_scope_get_dns_server(t
->scope
) == t
->server
) {
2019 log_debug_errno(r
, "Still pointing to extra listener after switching DNS servers, refusing operation.");
2020 dns_transaction_complete(t
, DNS_TRANSACTION_STUB_LOOP
);
2024 return dns_transaction_go(t
);
2027 /* No servers to send this to? */
2028 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
2031 if (r
== -EOPNOTSUPP
) {
2032 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
2033 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
2036 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& ERRNO_IS_DISCONNECT(r
)) {
2037 /* On LLMNR, if we cannot connect to a host via TCP when doing reverse lookups. This means we cannot
2038 * answer this request with this protocol. */
2039 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
2043 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2046 /* Couldn't send? Try immediately again, with a new server */
2047 dns_scope_next_dns_server(t
->scope
, t
->server
);
2049 return dns_transaction_go(t
);
2052 ts
+= transaction_get_resend_timeout(t
);
2054 r
= sd_event_add_time(
2055 t
->scope
->manager
->event
,
2056 &t
->timeout_event_source
,
2057 clock_boottime_or_monotonic(),
2059 on_transaction_timeout
, t
);
2063 (void) sd_event_source_set_description(t
->timeout_event_source
, "dns-transaction-timeout");
2065 t
->state
= DNS_TRANSACTION_PENDING
;
2066 t
->next_attempt_after
= ts
;
2071 static int dns_transaction_find_cyclic(DnsTransaction
*t
, DnsTransaction
*aux
) {
2078 /* Try to find cyclic dependencies between transaction objects */
2083 SET_FOREACH(n
, aux
->dnssec_transactions
) {
2084 r
= dns_transaction_find_cyclic(t
, n
);
2092 static int dns_transaction_add_dnssec_transaction(DnsTransaction
*t
, DnsResourceKey
*key
, DnsTransaction
**ret
) {
2093 _cleanup_(dns_transaction_gcp
) DnsTransaction
*aux
= NULL
;
2100 aux
= dns_scope_find_transaction(t
->scope
, key
, t
->query_flags
);
2102 r
= dns_transaction_new(&aux
, t
->scope
, key
, NULL
, t
->query_flags
);
2106 if (set_contains(t
->dnssec_transactions
, aux
)) {
2111 r
= dns_transaction_find_cyclic(t
, aux
);
2115 char s
[DNS_RESOURCE_KEY_STRING_MAX
], saux
[DNS_RESOURCE_KEY_STRING_MAX
];
2117 return log_debug_errno(SYNTHETIC_ERRNO(ELOOP
),
2118 "Potential cyclic dependency, refusing to add transaction %" PRIu16
" (%s) as dependency for %" PRIu16
" (%s).",
2120 dns_resource_key_to_string(dns_transaction_key(t
), s
, sizeof s
),
2122 dns_resource_key_to_string(dns_transaction_key(aux
), saux
, sizeof saux
));
2126 r
= set_ensure_allocated(&aux
->notify_transactions_done
, NULL
);
2130 r
= set_ensure_put(&t
->dnssec_transactions
, NULL
, aux
);
2134 r
= set_ensure_put(&aux
->notify_transactions
, NULL
, t
);
2136 (void) set_remove(t
->dnssec_transactions
, aux
);
2140 *ret
= TAKE_PTR(aux
);
2144 static int dns_transaction_request_dnssec_rr(DnsTransaction
*t
, DnsResourceKey
*key
) {
2145 _cleanup_(dns_answer_unrefp
) DnsAnswer
*a
= NULL
;
2146 DnsTransaction
*aux
;
2152 /* Try to get the data from the trust anchor */
2153 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, key
, &a
);
2157 r
= dns_answer_extend(&t
->validated_keys
, a
);
2164 /* This didn't work, ask for it via the network/cache then. */
2165 r
= dns_transaction_add_dnssec_transaction(t
, key
, &aux
);
2166 if (r
== -ELOOP
) /* This would result in a cyclic dependency */
2171 if (aux
->state
== DNS_TRANSACTION_NULL
) {
2172 r
= dns_transaction_go(aux
);
2180 static int dns_transaction_negative_trust_anchor_lookup(DnsTransaction
*t
, const char *name
) {
2185 /* Check whether the specified name is in the NTA
2186 * database, either in the global one, or the link-local
2189 r
= dns_trust_anchor_lookup_negative(&t
->scope
->manager
->trust_anchor
, name
);
2193 if (!t
->scope
->link
)
2196 return link_negative_trust_anchor_lookup(t
->scope
->link
, name
);
2199 static int dns_transaction_has_unsigned_negative_answer(DnsTransaction
*t
) {
2204 /* Checks whether the answer is negative, and lacks NSEC/NSEC3
2205 * RRs to prove it */
2207 r
= dns_transaction_has_positive_answer(t
, NULL
);
2213 /* Is this key explicitly listed as a negative trust anchor?
2214 * If so, it's nothing we need to care about */
2215 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(dns_transaction_key(t
)));
2221 /* The answer does not contain any RRs that match to the
2222 * question. If so, let's see if there are any NSEC/NSEC3 RRs
2223 * included. If not, the answer is unsigned. */
2225 r
= dns_answer_contains_nsec_or_nsec3(t
->answer
);
2234 static int dns_transaction_is_primary_response(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2240 /* Check if the specified RR is the "primary" response,
2241 * i.e. either matches the question precisely or is a
2242 * CNAME/DNAME for it. */
2244 r
= dns_resource_key_match_rr(dns_transaction_key(t
), rr
, NULL
);
2248 return dns_resource_key_match_cname_or_dname(dns_transaction_key(t
), rr
->key
, NULL
);
2251 static bool dns_transaction_dnssec_supported(DnsTransaction
*t
) {
2254 /* Checks whether our transaction's DNS server is assumed to be compatible with DNSSEC. Returns false as soon
2255 * as we changed our mind about a server, and now believe it is incompatible with DNSSEC. */
2257 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2260 /* If we have picked no server, then we are working from the cache or some other source, and DNSSEC might well
2261 * be supported, hence return true. */
2265 /* Note that we do not check the feature level actually used for the transaction but instead the feature level
2266 * the server is known to support currently, as the transaction feature level might be lower than what the
2267 * server actually supports, since we might have downgraded this transaction's feature level because we got a
2268 * SERVFAIL earlier and wanted to check whether downgrading fixes it. */
2270 return dns_server_dnssec_supported(t
->server
);
2273 static bool dns_transaction_dnssec_supported_full(DnsTransaction
*t
) {
2278 /* Checks whether our transaction our any of the auxiliary transactions couldn't do DNSSEC. */
2280 if (!dns_transaction_dnssec_supported(t
))
2283 SET_FOREACH(dt
, t
->dnssec_transactions
)
2284 if (!dns_transaction_dnssec_supported(dt
))
2290 int dns_transaction_request_dnssec_keys(DnsTransaction
*t
) {
2291 DnsResourceRecord
*rr
;
2298 * Retrieve all auxiliary RRs for the answer we got, so that
2299 * we can verify signatures or prove that RRs are rightfully
2300 * unsigned. Specifically:
2302 * - For RRSIG we get the matching DNSKEY
2303 * - For DNSKEY we get the matching DS
2304 * - For unsigned SOA/NS we get the matching DS
2305 * - For unsigned CNAME/DNAME/DS we get the parent SOA RR
2306 * - For other unsigned RRs we get the matching SOA RR
2307 * - For SOA/NS queries with no matching response RR, and no NSEC/NSEC3, the DS RR
2308 * - For DS queries with no matching response RRs, and no NSEC/NSEC3, the parent's SOA RR
2309 * - For other queries with no matching response RRs, and no NSEC/NSEC3, the SOA RR
2312 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) || t
->scope
->dnssec_mode
== DNSSEC_NO
)
2314 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
2315 return 0; /* We only need to validate stuff from the network */
2316 if (!dns_transaction_dnssec_supported(t
))
2317 return 0; /* If we can't do DNSSEC anyway there's no point in getting the auxiliary RRs */
2319 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
2321 if (dns_type_is_pseudo(rr
->key
->type
))
2324 /* If this RR is in the negative trust anchor, we don't need to validate it. */
2325 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2331 switch (rr
->key
->type
) {
2333 case DNS_TYPE_RRSIG
: {
2334 /* For each RRSIG we request the matching DNSKEY */
2335 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*dnskey
= NULL
;
2337 /* If this RRSIG is about a DNSKEY RR and the
2338 * signer is the same as the owner, then we
2339 * already have the DNSKEY, and we don't have
2340 * to look for more. */
2341 if (rr
->rrsig
.type_covered
== DNS_TYPE_DNSKEY
) {
2342 r
= dns_name_equal(rr
->rrsig
.signer
, dns_resource_key_name(rr
->key
));
2349 /* If the signer is not a parent of our
2350 * original query, then this is about an
2351 * auxiliary RRset, but not anything we asked
2352 * for. In this case we aren't interested,
2353 * because we don't want to request additional
2354 * RRs for stuff we didn't really ask for, and
2355 * also to avoid request loops, where
2356 * additional RRs from one transaction result
2357 * in another transaction whose additional RRs
2358 * point back to the original transaction, and
2360 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), rr
->rrsig
.signer
);
2366 dnskey
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DNSKEY
, rr
->rrsig
.signer
);
2370 log_debug("Requesting DNSKEY to validate transaction %" PRIu16
" (%s, RRSIG with key tag: %" PRIu16
").",
2371 t
->id
, dns_resource_key_name(rr
->key
), rr
->rrsig
.key_tag
);
2372 r
= dns_transaction_request_dnssec_rr(t
, dnskey
);
2378 case DNS_TYPE_DNSKEY
: {
2379 /* For each DNSKEY we request the matching DS */
2380 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
2382 /* If the DNSKEY we are looking at is not for
2383 * zone we are interested in, nor any of its
2384 * parents, we aren't interested, and don't
2385 * request it. After all, we don't want to end
2386 * up in request loops, and want to keep
2387 * additional traffic down. */
2389 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), dns_resource_key_name(rr
->key
));
2395 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
2399 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, DNSKEY with key tag: %" PRIu16
").",
2400 t
->id
, dns_resource_key_name(rr
->key
), dnssec_keytag(rr
, false));
2401 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2410 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
2412 /* For an unsigned SOA or NS, try to acquire
2413 * the matching DS RR, as we are at a zone cut
2414 * then, and whether a DS exists tells us
2415 * whether the zone is signed. Do so only if
2416 * this RR matches our original question,
2419 r
= dns_resource_key_match_rr(dns_transaction_key(t
), rr
, NULL
);
2423 /* Hmm, so this SOA RR doesn't match our original question. In this case, maybe this is
2424 * a negative reply, and we need the SOA RR's TTL in order to cache a negative entry?
2425 * If so, we need to validate it, too. */
2427 r
= dns_answer_match_key(t
->answer
, dns_transaction_key(t
), NULL
);
2430 if (r
> 0) /* positive reply, we won't need the SOA and hence don't need to validate
2434 /* Only bother with this if the SOA/NS RR we are looking at is actually a parent of
2435 * what we are looking for, otherwise there's no value in it for us. */
2436 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), dns_resource_key_name(rr
->key
));
2443 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2449 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
2453 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, unsigned SOA/NS RRset).",
2454 t
->id
, dns_resource_key_name(rr
->key
));
2455 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2463 case DNS_TYPE_CNAME
:
2464 case DNS_TYPE_DNAME
: {
2465 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2468 /* CNAMEs and DNAMEs cannot be located at a
2469 * zone apex, hence ask for the parent SOA for
2470 * unsigned CNAME/DNAME RRs, maybe that's the
2471 * apex. But do all that only if this is
2472 * actually a response to our original
2475 * Similar for DS RRs, which are signed when
2476 * the parent SOA is signed. */
2478 r
= dns_transaction_is_primary_response(t
, rr
);
2484 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2490 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
2496 name
= dns_resource_key_name(rr
->key
);
2497 r
= dns_name_parent(&name
);
2503 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, name
);
2507 log_debug("Requesting parent SOA to validate transaction %" PRIu16
" (%s, unsigned CNAME/DNAME/DS RRset).",
2508 t
->id
, dns_resource_key_name(rr
->key
));
2509 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2517 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2519 /* For other unsigned RRsets (including
2520 * NSEC/NSEC3!), look for proof the zone is
2521 * unsigned, by requesting the SOA RR of the
2522 * zone. However, do so only if they are
2523 * directly relevant to our original
2526 r
= dns_transaction_is_primary_response(t
, rr
);
2532 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2538 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, dns_resource_key_name(rr
->key
));
2542 log_debug("Requesting SOA to validate transaction %" PRIu16
" (%s, unsigned non-SOA/NS RRset <%s>).",
2543 t
->id
, dns_resource_key_name(rr
->key
), dns_resource_record_to_string(rr
));
2544 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2551 /* Above, we requested everything necessary to validate what
2552 * we got. Now, let's request what we need to validate what we
2555 r
= dns_transaction_has_unsigned_negative_answer(t
);
2562 name
= dns_resource_key_name(dns_transaction_key(t
));
2564 /* If this was a SOA or NS request, then check if there's a DS RR for the same domain. Note that this
2565 * could also be used as indication that we are not at a zone apex, but in real world setups there are
2566 * too many broken DNS servers (Hello, incapdns.net!) where non-terminal zones return NXDOMAIN even
2567 * though they have further children. If this was a DS request, then it's signed when the parent zone
2568 * is signed, hence ask the parent SOA in that case. If this was any other RR then ask for the SOA RR,
2569 * to see if that is signed. */
2571 if (dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
2572 r
= dns_name_parent(&name
);
2574 type
= DNS_TYPE_SOA
;
2575 log_debug("Requesting parent SOA (→ %s) to validate transaction %" PRIu16
" (%s, unsigned empty DS response).",
2576 name
, t
->id
, dns_resource_key_name(dns_transaction_key(t
)));
2580 } else if (IN_SET(dns_transaction_key(t
)->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
)) {
2583 log_debug("Requesting DS (→ %s) to validate transaction %" PRIu16
" (%s, unsigned empty SOA/NS response).",
2587 type
= DNS_TYPE_SOA
;
2588 log_debug("Requesting SOA (→ %s) to validate transaction %" PRIu16
" (%s, unsigned empty non-SOA/NS/DS response).",
2593 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2595 soa
= dns_resource_key_new(dns_transaction_key(t
)->class, type
, name
);
2599 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2605 return dns_transaction_dnssec_is_live(t
);
2608 void dns_transaction_notify(DnsTransaction
*t
, DnsTransaction
*source
) {
2612 /* Invoked whenever any of our auxiliary DNSSEC transactions completed its work. If the state is still PENDING,
2613 we are still in the loop that adds further DNSSEC transactions, hence don't check if we are ready yet. If
2614 the state is VALIDATING however, we should check if we are complete now. */
2616 if (t
->state
== DNS_TRANSACTION_VALIDATING
)
2617 dns_transaction_process_dnssec(t
);
2620 static int dns_transaction_validate_dnskey_by_ds(DnsTransaction
*t
) {
2621 DnsAnswerItem
*item
;
2626 /* Add all DNSKEY RRs from the answer that are validated by DS
2627 * RRs from the list of validated keys to the list of
2628 * validated keys. */
2630 DNS_ANSWER_FOREACH_ITEM(item
, t
->answer
) {
2632 r
= dnssec_verify_dnskey_by_ds_search(item
->rr
, t
->validated_keys
);
2638 /* If so, the DNSKEY is validated too. */
2639 r
= dns_answer_add_extend(&t
->validated_keys
, item
->rr
, item
->ifindex
, item
->flags
|DNS_ANSWER_AUTHENTICATED
, item
->rrsig
);
2647 static int dns_transaction_requires_rrsig(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2653 /* Checks if the RR we are looking for must be signed with an
2654 * RRSIG. This is used for positive responses. */
2656 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2659 if (dns_type_is_pseudo(rr
->key
->type
))
2662 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2668 switch (rr
->key
->type
) {
2670 case DNS_TYPE_RRSIG
:
2671 /* RRSIGs are the signatures themselves, they need no signing. */
2678 /* For SOA or NS RRs we look for a matching DS transaction */
2680 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2682 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2684 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_DS
)
2687 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), dns_resource_key_name(rr
->key
));
2693 /* We found a DS transactions for the SOA/NS
2694 * RRs we are looking at. If it discovered signed DS
2695 * RRs, then we need to be signed, too. */
2697 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
2700 return dns_answer_match_key(dt
->answer
, dns_transaction_key(dt
), NULL
);
2703 /* We found nothing that proves this is safe to leave
2704 * this unauthenticated, hence ask inist on
2705 * authentication. */
2710 case DNS_TYPE_CNAME
:
2711 case DNS_TYPE_DNAME
: {
2712 const char *parent
= NULL
;
2716 * CNAME/DNAME RRs cannot be located at a zone apex, hence look directly for the parent SOA.
2718 * DS RRs are signed if the parent is signed, hence also look at the parent SOA
2721 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2723 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2725 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_SOA
)
2729 parent
= dns_resource_key_name(rr
->key
);
2730 r
= dns_name_parent(&parent
);
2734 if (rr
->key
->type
== DNS_TYPE_DS
)
2737 /* A CNAME/DNAME without a parent? That's sooo weird. */
2738 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG
),
2739 "Transaction %" PRIu16
" claims CNAME/DNAME at root. Refusing.", t
->id
);
2743 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), parent
);
2749 return FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2758 /* Any other kind of RR (including DNSKEY/NSEC/NSEC3). Let's see if our SOA lookup was authenticated */
2760 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2762 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2764 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_SOA
)
2767 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), dns_resource_key_name(rr
->key
));
2773 /* We found the transaction that was supposed to find the SOA RR for us. It was
2774 * successful, but found no RR for us. This means we are not at a zone cut. In this
2775 * case, we require authentication if the SOA lookup was authenticated too. */
2776 return FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2783 static int dns_transaction_in_private_tld(DnsTransaction
*t
, const DnsResourceKey
*key
) {
2788 /* If DNSSEC downgrade mode is on, checks whether the
2789 * specified RR is one level below a TLD we have proven not to
2790 * exist. In such a case we assume that this is a private
2791 * domain, and permit it.
2793 * This detects cases like the Fritz!Box router networks. Each
2794 * Fritz!Box router serves a private "fritz.box" zone, in the
2795 * non-existing TLD "box". Requests for the "fritz.box" domain
2796 * are served by the router itself, while requests for the
2797 * "box" domain will result in NXDOMAIN.
2799 * Note that this logic is unable to detect cases where a
2800 * router serves a private DNS zone directly under
2801 * non-existing TLD. In such a case we cannot detect whether
2802 * the TLD is supposed to exist or not, as all requests we
2803 * make for it will be answered by the router's zone, and not
2804 * by the root zone. */
2808 if (t
->scope
->dnssec_mode
!= DNSSEC_ALLOW_DOWNGRADE
)
2809 return false; /* In strict DNSSEC mode what doesn't exist, doesn't exist */
2811 tld
= dns_resource_key_name(key
);
2812 r
= dns_name_parent(&tld
);
2816 return false; /* Already the root domain */
2818 if (!dns_name_is_single_label(tld
))
2821 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2823 if (dns_transaction_key(dt
)->class != key
->class)
2826 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), tld
);
2832 /* We found an auxiliary lookup we did for the TLD. If
2833 * that returned with NXDOMAIN, we know the TLD didn't
2834 * exist, and hence this might be a private zone. */
2836 return dt
->answer_rcode
== DNS_RCODE_NXDOMAIN
;
2842 static int dns_transaction_requires_nsec(DnsTransaction
*t
) {
2843 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
2851 /* Checks if we need to insist on NSEC/NSEC3 RRs for proving
2852 * this negative reply */
2854 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2857 if (dns_type_is_pseudo(dns_transaction_key(t
)->type
))
2860 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(dns_transaction_key(t
)));
2866 r
= dns_transaction_in_private_tld(t
, dns_transaction_key(t
));
2870 /* The lookup is from a TLD that is proven not to
2871 * exist, and we are in downgrade mode, hence ignore
2872 * that fact that we didn't get any NSEC RRs. */
2874 log_info("Detected a negative query %s in a private DNS zone, permitting unsigned response.",
2875 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
));
2879 name
= dns_resource_key_name(dns_transaction_key(t
));
2881 if (dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
2883 /* We got a negative reply for this DS lookup? DS RRs are signed when their parent zone is signed,
2884 * hence check the parent SOA in this case. */
2886 r
= dns_name_parent(&name
);
2892 type
= DNS_TYPE_SOA
;
2894 } else if (IN_SET(dns_transaction_key(t
)->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
))
2895 /* We got a negative reply for this SOA/NS lookup? If so, check if there's a DS RR for this */
2898 /* For all other negative replies, check for the SOA lookup */
2899 type
= DNS_TYPE_SOA
;
2901 /* For all other RRs we check the SOA on the same level to see
2902 * if it's signed. */
2904 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2906 if (dns_transaction_key(dt
)->class != dns_transaction_key(t
)->class)
2908 if (dns_transaction_key(dt
)->type
!= type
)
2911 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), name
);
2917 return FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2920 /* If in doubt, require NSEC/NSEC3 */
2924 static int dns_transaction_dnskey_authenticated(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2925 DnsResourceRecord
*rrsig
;
2929 /* Checks whether any of the DNSKEYs used for the RRSIGs for
2930 * the specified RRset is authenticated (i.e. has a matching
2933 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2939 DNS_ANSWER_FOREACH(rrsig
, t
->answer
) {
2942 r
= dnssec_key_match_rrsig(rr
->key
, rrsig
);
2948 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2950 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2953 if (dns_transaction_key(dt
)->type
== DNS_TYPE_DNSKEY
) {
2955 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), rrsig
->rrsig
.signer
);
2961 /* OK, we found an auxiliary DNSKEY lookup. If that lookup is authenticated,
2964 if (FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
2969 } else if (dns_transaction_key(dt
)->type
== DNS_TYPE_DS
) {
2971 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), rrsig
->rrsig
.signer
);
2977 /* OK, we found an auxiliary DS lookup. If that lookup is authenticated and
2978 * non-zero, we won! */
2980 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
2983 return dns_answer_match_key(dt
->answer
, dns_transaction_key(dt
), NULL
);
2988 return found
? false : -ENXIO
;
2991 static int dns_transaction_known_signed(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2995 /* We know that the root domain is signed, hence if it appears
2996 * not to be signed, there's a problem with the DNS server */
2998 return rr
->key
->class == DNS_CLASS_IN
&&
2999 dns_name_is_root(dns_resource_key_name(rr
->key
));
3002 static int dns_transaction_check_revoked_trust_anchors(DnsTransaction
*t
) {
3003 DnsResourceRecord
*rr
;
3008 /* Maybe warn the user that we encountered a revoked DNSKEY
3009 * for a key from our trust anchor. Note that we don't care
3010 * whether the DNSKEY can be authenticated or not. It's
3011 * sufficient if it is self-signed. */
3013 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
3014 r
= dns_trust_anchor_check_revoked(&t
->scope
->manager
->trust_anchor
, rr
, t
->answer
);
3022 static int dns_transaction_invalidate_revoked_keys(DnsTransaction
*t
) {
3028 /* Removes all DNSKEY/DS objects from t->validated_keys that
3029 * our trust anchors database considers revoked. */
3032 DnsResourceRecord
*rr
;
3036 DNS_ANSWER_FOREACH(rr
, t
->validated_keys
) {
3037 r
= dns_trust_anchor_is_revoked(&t
->scope
->manager
->trust_anchor
, rr
);
3041 r
= dns_answer_remove_by_rr(&t
->validated_keys
, rr
);
3055 static int dns_transaction_copy_validated(DnsTransaction
*t
) {
3061 /* Copy all validated RRs from the auxiliary DNSSEC transactions into our set of validated RRs */
3063 SET_FOREACH(dt
, t
->dnssec_transactions
) {
3065 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
3068 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
3071 r
= dns_answer_extend(&t
->validated_keys
, dt
->answer
);
3080 DNSSEC_PHASE_DNSKEY
, /* Phase #1, only validate DNSKEYs */
3081 DNSSEC_PHASE_NSEC
, /* Phase #2, only validate NSEC+NSEC3 */
3082 DNSSEC_PHASE_ALL
, /* Phase #3, validate everything else */
3085 static int dnssec_validate_records(
3089 DnsAnswer
**validated
) {
3091 DnsResourceRecord
*rr
;
3094 /* Returns negative on error, 0 if validation failed, 1 to restart validation, 2 when finished. */
3096 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
3097 DnsResourceRecord
*rrsig
= NULL
;
3098 DnssecResult result
;
3100 switch (rr
->key
->type
) {
3101 case DNS_TYPE_RRSIG
:
3104 case DNS_TYPE_DNSKEY
:
3105 /* We validate DNSKEYs only in the DNSKEY and ALL phases */
3106 if (phase
== DNSSEC_PHASE_NSEC
)
3111 case DNS_TYPE_NSEC3
:
3114 /* We validate NSEC/NSEC3 only in the NSEC and ALL phases */
3115 if (phase
== DNSSEC_PHASE_DNSKEY
)
3120 /* We validate all other RRs only in the ALL phases */
3121 if (phase
!= DNSSEC_PHASE_ALL
)
3125 r
= dnssec_verify_rrset_search(
3135 log_debug("Looking at %s: %s", strna(dns_resource_record_to_string(rr
)), dnssec_result_to_string(result
));
3137 if (result
== DNSSEC_VALIDATED
) {
3140 if (rr
->key
->type
== DNS_TYPE_DNSKEY
) {
3141 /* If we just validated a DNSKEY RRset, then let's add these keys to
3142 * the set of validated keys for this transaction. */
3144 r
= dns_answer_copy_by_key(&t
->validated_keys
, t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
, rrsig
);
3148 /* Some of the DNSKEYs we just added might already have been revoked,
3149 * remove them again in that case. */
3150 r
= dns_transaction_invalidate_revoked_keys(t
);
3155 /* Add the validated RRset to the new list of validated RRsets, and remove it from
3156 * the unvalidated RRsets. We mark the RRset as authenticated and cacheable. */
3157 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
, rrsig
);
3161 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_SECURE
, rr
->key
);
3163 /* Exit the loop, we dropped something from the answer, start from the beginning */
3167 /* If we haven't read all DNSKEYs yet a negative result of the validation is irrelevant, as
3168 * there might be more DNSKEYs coming. Similar, if we haven't read all NSEC/NSEC3 RRs yet,
3169 * we cannot do positive wildcard proofs yet, as those require the NSEC/NSEC3 RRs. */
3170 if (phase
!= DNSSEC_PHASE_ALL
)
3173 if (result
== DNSSEC_VALIDATED_WILDCARD
) {
3174 bool authenticated
= false;
3179 /* This RRset validated, but as a wildcard. This means we need
3180 * to prove via NSEC/NSEC3 that no matching non-wildcard RR exists. */
3182 /* First step, determine the source of synthesis */
3183 r
= dns_resource_record_source(rrsig
, &source
);
3187 r
= dnssec_test_positive_wildcard(*validated
,
3188 dns_resource_key_name(rr
->key
),
3190 rrsig
->rrsig
.signer
,
3193 /* Unless the NSEC proof showed that the key really doesn't exist something is off. */
3195 result
= DNSSEC_INVALID
;
3197 r
= dns_answer_move_by_key(
3201 authenticated
? (DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
) : 0,
3206 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, rr
->key
);
3208 /* Exit the loop, we dropped something from the answer, start from the beginning */
3213 if (result
== DNSSEC_NO_SIGNATURE
) {
3214 r
= dns_transaction_requires_rrsig(t
, rr
);
3218 /* Data does not require signing. In that case, just copy it over,
3219 * but remember that this is by no means authenticated. */
3220 r
= dns_answer_move_by_key(
3229 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3233 r
= dns_transaction_known_signed(t
, rr
);
3237 /* This is an RR we know has to be signed. If it isn't this means
3238 * the server is not attaching RRSIGs, hence complain. */
3240 dns_server_packet_rrsig_missing(t
->server
, t
->current_feature_level
);
3242 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
3244 /* Downgrading is OK? If so, just consider the information unsigned */
3246 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3250 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3254 /* Otherwise, fail */
3255 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
3259 r
= dns_transaction_in_private_tld(t
, rr
->key
);
3263 char s
[DNS_RESOURCE_KEY_STRING_MAX
];
3265 /* The data is from a TLD that is proven not to exist, and we are in downgrade
3266 * mode, hence ignore the fact that this was not signed. */
3268 log_info("Detected RRset %s is in a private DNS zone, permitting unsigned RRs.",
3269 dns_resource_key_to_string(rr
->key
, s
, sizeof s
));
3271 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3275 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3282 DNSSEC_SIGNATURE_EXPIRED
,
3283 DNSSEC_UNSUPPORTED_ALGORITHM
)) {
3285 r
= dns_transaction_dnskey_authenticated(t
, rr
);
3286 if (r
< 0 && r
!= -ENXIO
)
3289 /* The DNSKEY transaction was not authenticated, this means there's
3290 * no DS for this, which means it's OK if no keys are found for this signature. */
3292 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3296 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3301 r
= dns_transaction_is_primary_response(t
, rr
);
3305 /* Look for a matching DNAME for this CNAME */
3306 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
3310 /* Also look among the stuff we already validated */
3311 r
= dns_answer_has_dname_for_cname(*validated
, rr
);
3319 DNSSEC_SIGNATURE_EXPIRED
,
3320 DNSSEC_NO_SIGNATURE
))
3321 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, rr
->key
);
3322 else /* DNSSEC_MISSING_KEY or DNSSEC_UNSUPPORTED_ALGORITHM */
3323 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, rr
->key
);
3325 /* This is a primary response to our question, and it failed validation.
3327 t
->answer_dnssec_result
= result
;
3331 /* This is a primary response, but we do have a DNAME RR
3332 * in the RR that can replay this CNAME, hence rely on
3333 * that, and we can remove the CNAME in favour of it. */
3336 /* This is just some auxiliary data. Just remove the RRset and continue. */
3337 r
= dns_answer_remove_by_key(&t
->answer
, rr
->key
);
3341 /* We dropped something from the answer, start from the beginning. */
3345 return 2; /* Finito. */
3348 int dns_transaction_validate_dnssec(DnsTransaction
*t
) {
3349 _cleanup_(dns_answer_unrefp
) DnsAnswer
*validated
= NULL
;
3351 DnsAnswerFlags flags
;
3353 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
3357 /* We have now collected all DS and DNSKEY RRs in t->validated_keys, let's see which RRs we can now
3358 * authenticate with that. */
3360 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) || t
->scope
->dnssec_mode
== DNSSEC_NO
)
3363 /* Already validated */
3364 if (t
->answer_dnssec_result
!= _DNSSEC_RESULT_INVALID
)
3367 /* Our own stuff needs no validation */
3368 if (IN_SET(t
->answer_source
, DNS_TRANSACTION_ZONE
, DNS_TRANSACTION_TRUST_ANCHOR
)) {
3369 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3370 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, true);
3374 /* Cached stuff is not affected by validation. */
3375 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
3378 if (!dns_transaction_dnssec_supported_full(t
)) {
3379 /* The server does not support DNSSEC, or doesn't augment responses with RRSIGs. */
3380 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
3381 log_debug("Not validating response for %" PRIu16
", used server feature level does not support DNSSEC.", t
->id
);
3385 log_debug("Validating response from transaction %" PRIu16
" (%s).",
3387 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
));
3389 /* First, see if this response contains any revoked trust
3390 * anchors we care about */
3391 r
= dns_transaction_check_revoked_trust_anchors(t
);
3395 /* Third, copy all RRs we acquired successfully from auxiliary RRs over. */
3396 r
= dns_transaction_copy_validated(t
);
3400 /* Second, see if there are DNSKEYs we already know a
3401 * validated DS for. */
3402 r
= dns_transaction_validate_dnskey_by_ds(t
);
3406 /* Fourth, remove all DNSKEY and DS RRs again that our trust
3407 * anchor says are revoked. After all we might have marked
3408 * some keys revoked above, but they might still be lingering
3409 * in our validated_keys list. */
3410 r
= dns_transaction_invalidate_revoked_keys(t
);
3414 phase
= DNSSEC_PHASE_DNSKEY
;
3416 bool have_nsec
= false;
3418 r
= dnssec_validate_records(t
, phase
, &have_nsec
, &validated
);
3422 /* Try again as long as we managed to achieve something */
3426 if (phase
== DNSSEC_PHASE_DNSKEY
&& have_nsec
) {
3427 /* OK, we processed all DNSKEYs, and there are NSEC/NSEC3 RRs, look at those now. */
3428 phase
= DNSSEC_PHASE_NSEC
;
3432 if (phase
!= DNSSEC_PHASE_ALL
) {
3433 /* OK, we processed all DNSKEYs and NSEC/NSEC3 RRs, look at all the rest now.
3434 * Note that in this third phase we start to remove RRs we couldn't validate. */
3435 phase
= DNSSEC_PHASE_ALL
;
3443 dns_answer_unref(t
->answer
);
3444 t
->answer
= TAKE_PTR(validated
);
3446 /* At this point the answer only contains validated
3447 * RRsets. Now, let's see if it actually answers the question
3448 * we asked. If so, great! If it doesn't, then see if
3449 * NSEC/NSEC3 can prove this. */
3450 r
= dns_transaction_has_positive_answer(t
, &flags
);
3452 /* Yes, it answers the question! */
3454 if (flags
& DNS_ANSWER_AUTHENTICATED
) {
3455 /* The answer is fully authenticated, yay. */
3456 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3457 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3458 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, true);
3460 /* The answer is not fully authenticated. */
3461 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3462 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3465 } else if (r
== 0) {
3466 DnssecNsecResult nr
;
3467 bool authenticated
= false;
3469 /* Bummer! Let's check NSEC/NSEC3 */
3470 r
= dnssec_nsec_test(t
->answer
, dns_transaction_key(t
), &nr
, &authenticated
, &t
->answer_nsec_ttl
);
3476 case DNSSEC_NSEC_NXDOMAIN
:
3477 /* NSEC proves the domain doesn't exist. Very good. */
3478 log_debug("Proved NXDOMAIN via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3479 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3480 t
->answer_rcode
= DNS_RCODE_NXDOMAIN
;
3481 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, authenticated
);
3483 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, dns_transaction_key(t
));
3486 case DNSSEC_NSEC_NODATA
:
3487 /* NSEC proves that there's no data here, very good. */
3488 log_debug("Proved NODATA via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3489 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3490 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3491 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, authenticated
);
3493 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, dns_transaction_key(t
));
3496 case DNSSEC_NSEC_OPTOUT
:
3497 /* NSEC3 says the data might not be signed */
3498 log_debug("Data is NSEC3 opt-out via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3499 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3500 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3502 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, dns_transaction_key(t
));
3505 case DNSSEC_NSEC_NO_RR
:
3506 /* No NSEC data? Bummer! */
3508 r
= dns_transaction_requires_nsec(t
);
3512 t
->answer_dnssec_result
= DNSSEC_NO_SIGNATURE
;
3513 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, dns_transaction_key(t
));
3515 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3516 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3517 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, dns_transaction_key(t
));
3522 case DNSSEC_NSEC_UNSUPPORTED_ALGORITHM
:
3523 /* We don't know the NSEC3 algorithm used? */
3524 t
->answer_dnssec_result
= DNSSEC_UNSUPPORTED_ALGORITHM
;
3525 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, dns_transaction_key(t
));
3528 case DNSSEC_NSEC_FOUND
:
3529 case DNSSEC_NSEC_CNAME
:
3530 /* NSEC says it needs to be there, but we couldn't find it? Bummer! */
3531 t
->answer_dnssec_result
= DNSSEC_NSEC_MISMATCH
;
3532 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, dns_transaction_key(t
));
3536 assert_not_reached("Unexpected NSEC result.");
3543 static const char* const dns_transaction_state_table
[_DNS_TRANSACTION_STATE_MAX
] = {
3544 [DNS_TRANSACTION_NULL
] = "null",
3545 [DNS_TRANSACTION_PENDING
] = "pending",
3546 [DNS_TRANSACTION_VALIDATING
] = "validating",
3547 [DNS_TRANSACTION_RCODE_FAILURE
] = "rcode-failure",
3548 [DNS_TRANSACTION_SUCCESS
] = "success",
3549 [DNS_TRANSACTION_NO_SERVERS
] = "no-servers",
3550 [DNS_TRANSACTION_TIMEOUT
] = "timeout",
3551 [DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
] = "attempts-max-reached",
3552 [DNS_TRANSACTION_INVALID_REPLY
] = "invalid-reply",
3553 [DNS_TRANSACTION_ERRNO
] = "errno",
3554 [DNS_TRANSACTION_ABORTED
] = "aborted",
3555 [DNS_TRANSACTION_DNSSEC_FAILED
] = "dnssec-failed",
3556 [DNS_TRANSACTION_NO_TRUST_ANCHOR
] = "no-trust-anchor",
3557 [DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
] = "rr-type-unsupported",
3558 [DNS_TRANSACTION_NETWORK_DOWN
] = "network-down",
3559 [DNS_TRANSACTION_NOT_FOUND
] = "not-found",
3560 [DNS_TRANSACTION_NO_SOURCE
] = "no-source",
3561 [DNS_TRANSACTION_STUB_LOOP
] = "stub-loop",
3563 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state
, DnsTransactionState
);
3565 static const char* const dns_transaction_source_table
[_DNS_TRANSACTION_SOURCE_MAX
] = {
3566 [DNS_TRANSACTION_NETWORK
] = "network",
3567 [DNS_TRANSACTION_CACHE
] = "cache",
3568 [DNS_TRANSACTION_ZONE
] = "zone",
3569 [DNS_TRANSACTION_TRUST_ANCHOR
] = "trust-anchor",
3571 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source
, DnsTransactionSource
);