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 "glyph-util.h"
12 #include "random-util.h"
13 #include "resolved-dns-cache.h"
14 #include "resolved-dns-transaction.h"
15 #include "resolved-dnstls.h"
16 #include "resolved-llmnr.h"
17 #include "string-table.h"
19 #define TRANSACTIONS_MAX 4096
20 #define TRANSACTION_TCP_TIMEOUT_USEC (10U*USEC_PER_SEC)
22 /* After how much time to repeat classic DNS requests */
23 #define DNS_TIMEOUT_USEC (SD_RESOLVED_QUERY_TIMEOUT_USEC / DNS_TRANSACTION_ATTEMPTS_MAX)
25 static void dns_transaction_reset_answer(DnsTransaction
*t
) {
28 t
->received
= dns_packet_unref(t
->received
);
29 t
->answer
= dns_answer_unref(t
->answer
);
31 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
32 t
->answer_source
= _DNS_TRANSACTION_SOURCE_INVALID
;
33 t
->answer_query_flags
= 0;
34 t
->answer_nsec_ttl
= UINT32_MAX
;
38 static void dns_transaction_flush_dnssec_transactions(DnsTransaction
*t
) {
43 while ((z
= set_steal_first(t
->dnssec_transactions
))) {
44 set_remove(z
->notify_transactions
, t
);
45 set_remove(z
->notify_transactions_done
, t
);
46 dns_transaction_gc(z
);
50 static void dns_transaction_close_connection(
52 bool use_graveyard
) { /* Set use_graveyard = false when you know the connection is already
53 * dead, for example because you got a connection error back from the
54 * kernel. In that case there's no point in keeping the fd around,
61 /* Let's detach the stream from our transaction, in case something else keeps a reference to it. */
62 LIST_REMOVE(transactions_by_stream
, t
->stream
->transactions
, t
);
64 /* Remove packet in case it's still in the queue */
65 dns_packet_unref(ordered_set_remove(t
->stream
->write_queue
, t
->sent
));
67 t
->stream
= dns_stream_unref(t
->stream
);
70 t
->dns_udp_event_source
= sd_event_source_disable_unref(t
->dns_udp_event_source
);
72 /* If we have an UDP socket where we sent a packet, but never received one, then add it to the socket
73 * graveyard, instead of closing it right away. That way it will stick around for a moment longer,
74 * and the reply we might still get from the server will be eaten up instead of resulting in an ICMP
75 * port unreachable error message. */
77 if (use_graveyard
&& t
->dns_udp_fd
>= 0 && t
->sent
&& !t
->received
) {
78 r
= manager_add_socket_to_graveyard(t
->scope
->manager
, t
->dns_udp_fd
);
80 log_debug_errno(r
, "Failed to add UDP socket to graveyard, closing immediately: %m");
82 TAKE_FD(t
->dns_udp_fd
);
85 t
->dns_udp_fd
= safe_close(t
->dns_udp_fd
);
88 static void dns_transaction_stop_timeout(DnsTransaction
*t
) {
91 t
->timeout_event_source
= sd_event_source_disable_unref(t
->timeout_event_source
);
94 DnsTransaction
* dns_transaction_free(DnsTransaction
*t
) {
102 log_debug("Freeing transaction %" PRIu16
".", t
->id
);
104 dns_transaction_close_connection(t
, true);
105 dns_transaction_stop_timeout(t
);
107 dns_packet_unref(t
->sent
);
108 dns_transaction_reset_answer(t
);
110 dns_server_unref(t
->server
);
114 DnsTransaction
*first
;
116 first
= hashmap_get(t
->scope
->transactions_by_key
, t
->key
);
117 LIST_REMOVE(transactions_by_key
, first
, t
);
119 hashmap_replace(t
->scope
->transactions_by_key
, first
->key
, first
);
121 hashmap_remove(t
->scope
->transactions_by_key
, t
->key
);
124 LIST_REMOVE(transactions_by_scope
, t
->scope
->transactions
, t
);
127 hashmap_remove(t
->scope
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
));
130 while ((c
= set_steal_first(t
->notify_query_candidates
)))
131 set_remove(c
->transactions
, t
);
132 set_free(t
->notify_query_candidates
);
134 while ((c
= set_steal_first(t
->notify_query_candidates_done
)))
135 set_remove(c
->transactions
, t
);
136 set_free(t
->notify_query_candidates_done
);
138 while ((i
= set_steal_first(t
->notify_zone_items
)))
139 i
->probe_transaction
= NULL
;
140 set_free(t
->notify_zone_items
);
142 while ((i
= set_steal_first(t
->notify_zone_items_done
)))
143 i
->probe_transaction
= NULL
;
144 set_free(t
->notify_zone_items_done
);
146 while ((z
= set_steal_first(t
->notify_transactions
)))
147 set_remove(z
->dnssec_transactions
, t
);
148 set_free(t
->notify_transactions
);
150 while ((z
= set_steal_first(t
->notify_transactions_done
)))
151 set_remove(z
->dnssec_transactions
, t
);
152 set_free(t
->notify_transactions_done
);
154 dns_transaction_flush_dnssec_transactions(t
);
155 set_free(t
->dnssec_transactions
);
157 dns_answer_unref(t
->validated_keys
);
158 dns_resource_key_unref(t
->key
);
159 dns_packet_unref(t
->bypass
);
164 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsTransaction
*, dns_transaction_free
);
166 DnsTransaction
* dns_transaction_gc(DnsTransaction
*t
) {
169 /* Returns !NULL if we can't gc yet. */
174 if (set_isempty(t
->notify_query_candidates
) &&
175 set_isempty(t
->notify_query_candidates_done
) &&
176 set_isempty(t
->notify_zone_items
) &&
177 set_isempty(t
->notify_zone_items_done
) &&
178 set_isempty(t
->notify_transactions
) &&
179 set_isempty(t
->notify_transactions_done
))
180 return dns_transaction_free(t
);
185 static uint16_t pick_new_id(Manager
*m
) {
188 /* Find a fresh, unused transaction id. Note that this loop is bounded because there's a limit on the
189 * number of transactions, and it's much lower than the space of IDs. */
191 assert_cc(TRANSACTIONS_MAX
< 0xFFFF);
194 random_bytes(&new_id
, sizeof(new_id
));
195 while (new_id
== 0 ||
196 hashmap_get(m
->dns_transactions
, UINT_TO_PTR(new_id
)));
203 DnsResourceKey
*key
) {
205 /* Don't allow looking up invalid or pseudo RRs */
206 if (!dns_type_is_valid_query(key
->type
))
208 if (dns_type_is_obsolete(key
->type
))
211 /* We only support the IN class */
212 if (!IN_SET(key
->class, DNS_CLASS_IN
, DNS_CLASS_ANY
))
215 /* Don't allows DNSSEC RRs to be looked up via LLMNR/mDNS. They don't really make sense
216 * there, and it speeds up our queries if we refuse this early */
217 if (scope
->protocol
!= DNS_PROTOCOL_DNS
&&
218 dns_type_is_dnssec(key
->type
))
224 int dns_transaction_new(
225 DnsTransaction
**ret
,
229 uint64_t query_flags
) {
231 _cleanup_(dns_transaction_freep
) DnsTransaction
*t
= NULL
;
247 r
= dns_packet_validate_query(bypass
);
251 DNS_QUESTION_FOREACH(qk
, bypass
->question
) {
258 if (hashmap_size(s
->manager
->dns_transactions
) >= TRANSACTIONS_MAX
)
261 r
= hashmap_ensure_allocated(&s
->manager
->dns_transactions
, NULL
);
266 r
= hashmap_ensure_allocated(&s
->transactions_by_key
, &dns_resource_key_hash_ops
);
271 t
= new(DnsTransaction
, 1);
275 *t
= (DnsTransaction
) {
276 .dns_udp_fd
= -EBADF
,
277 .answer_source
= _DNS_TRANSACTION_SOURCE_INVALID
,
278 .answer_dnssec_result
= _DNSSEC_RESULT_INVALID
,
279 .answer_nsec_ttl
= UINT32_MAX
,
280 .key
= dns_resource_key_ref(key
),
281 .query_flags
= query_flags
,
282 .bypass
= dns_packet_ref(bypass
),
283 .current_feature_level
= _DNS_SERVER_FEATURE_LEVEL_INVALID
,
284 .clamp_feature_level_servfail
= _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 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
341 assert(t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
);
343 if (manager_packet_from_local_address(t
->scope
->manager
, p
) != 0)
346 log_debug("Transaction %" PRIu16
" for <%s> on scope %s on %s/%s got tentative packet from %s.",
348 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
),
349 dns_protocol_to_string(t
->scope
->protocol
),
350 t
->scope
->link
? t
->scope
->link
->ifname
: "*",
351 af_to_name_short(t
->scope
->family
),
352 IN_ADDR_TO_STRING(p
->family
, &p
->sender
));
354 /* RFC 4795, Section 4.1 says that the peer with the
355 * lexicographically smaller IP address loses */
356 if (memcmp(&p
->sender
, &p
->destination
, FAMILY_ADDRESS_SIZE(p
->family
)) >= 0) {
357 log_debug("Peer has lexicographically larger IP address and thus lost in the conflict.");
361 log_debug("We have the lexicographically larger IP address and thus lost in the conflict.");
365 while ((z
= set_first(t
->notify_zone_items
))) {
366 /* First, make sure the zone item drops the reference
368 dns_zone_item_probe_stop(z
);
370 /* Secondly, report this as conflict, so that we might
371 * look for a different hostname */
372 dns_zone_item_conflict(z
);
376 dns_transaction_gc(t
);
379 void dns_transaction_complete(DnsTransaction
*t
, DnsTransactionState state
) {
380 DnsQueryCandidate
*c
;
384 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
387 assert(!DNS_TRANSACTION_IS_LIVE(state
));
389 if (state
== DNS_TRANSACTION_DNSSEC_FAILED
) {
390 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
);
392 log_struct(LOG_NOTICE
,
393 "MESSAGE_ID=" SD_MESSAGE_DNSSEC_FAILURE_STR
,
394 LOG_MESSAGE("DNSSEC validation failed for question %s: %s",
395 key_str
, dnssec_result_to_string(t
->answer_dnssec_result
)),
396 "DNS_TRANSACTION=%" PRIu16
, t
->id
,
397 "DNS_QUESTION=%s", key_str
,
398 "DNSSEC_RESULT=%s", dnssec_result_to_string(t
->answer_dnssec_result
),
399 "DNS_SERVER=%s", strna(dns_server_string_full(t
->server
)),
400 "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(t
->server
->possible_feature_level
));
403 /* Note that this call might invalidate the query. Callers
404 * should hence not attempt to access the query or transaction
405 * after calling this function. */
407 if (state
== DNS_TRANSACTION_ERRNO
)
408 st
= errno_to_name(t
->answer_errno
);
410 st
= dns_transaction_state_to_string(state
);
412 log_debug("%s transaction %" PRIu16
" for <%s> on scope %s on %s/%s now complete with <%s> from %s (%s; %s).",
413 t
->bypass
? "Bypass" : "Regular",
415 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
),
416 dns_protocol_to_string(t
->scope
->protocol
),
417 t
->scope
->link
? t
->scope
->link
->ifname
: "*",
418 af_to_name_short(t
->scope
->family
),
420 t
->answer_source
< 0 ? "none" : dns_transaction_source_to_string(t
->answer_source
),
421 FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) ? "not validated" :
422 (FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
) ? "authenticated" : "unsigned"),
423 FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
) ? "confidential" : "non-confidential");
427 dns_transaction_close_connection(t
, true);
428 dns_transaction_stop_timeout(t
);
430 /* Notify all queries that are interested, but make sure the
431 * transaction isn't freed while we are still looking at it */
434 SET_FOREACH_MOVE(c
, t
->notify_query_candidates_done
, t
->notify_query_candidates
)
435 dns_query_candidate_notify(c
);
436 SWAP_TWO(t
->notify_query_candidates
, t
->notify_query_candidates_done
);
438 SET_FOREACH_MOVE(z
, t
->notify_zone_items_done
, t
->notify_zone_items
)
439 dns_zone_item_notify(z
);
440 SWAP_TWO(t
->notify_zone_items
, t
->notify_zone_items_done
);
441 if (t
->probing
&& t
->state
== DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
)
442 (void) dns_scope_announce(t
->scope
, false);
444 SET_FOREACH_MOVE(d
, t
->notify_transactions_done
, t
->notify_transactions
)
445 dns_transaction_notify(d
, t
);
446 SWAP_TWO(t
->notify_transactions
, t
->notify_transactions_done
);
449 dns_transaction_gc(t
);
452 static void dns_transaction_complete_errno(DnsTransaction
*t
, int error
) {
456 t
->answer_errno
= abs(error
);
457 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
460 static int dns_transaction_pick_server(DnsTransaction
*t
) {
464 assert(t
->scope
->protocol
== DNS_PROTOCOL_DNS
);
466 /* Pick a DNS server and a feature level for it. */
468 server
= dns_scope_get_dns_server(t
->scope
);
472 /* If we changed the server invalidate the feature level clamping, as the new server might have completely
473 * different properties. */
474 if (server
!= t
->server
)
475 t
->clamp_feature_level_servfail
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
477 t
->current_feature_level
= dns_server_possible_feature_level(server
);
479 /* Clamp the feature level if that is requested. */
480 if (t
->clamp_feature_level_servfail
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
&&
481 t
->current_feature_level
> t
->clamp_feature_level_servfail
)
482 t
->current_feature_level
= t
->clamp_feature_level_servfail
;
484 log_debug("Using feature level %s for transaction %u.", dns_server_feature_level_to_string(t
->current_feature_level
), t
->id
);
486 if (server
== t
->server
)
489 dns_server_unref(t
->server
);
490 t
->server
= dns_server_ref(server
);
492 t
->n_picked_servers
++;
494 log_debug("Using DNS server %s for transaction %u.", strna(dns_server_string_full(t
->server
)), t
->id
);
499 static void dns_transaction_retry(DnsTransaction
*t
, bool next_server
) {
504 /* Retries the transaction as it is, possibly on a different server */
506 if (next_server
&& t
->scope
->protocol
== DNS_PROTOCOL_DNS
)
507 log_debug("Retrying transaction %" PRIu16
", after switching servers.", t
->id
);
509 log_debug("Retrying transaction %" PRIu16
".", t
->id
);
511 /* Before we try again, switch to a new server. */
513 dns_scope_next_dns_server(t
->scope
, t
->server
);
515 r
= dns_transaction_go(t
);
517 dns_transaction_complete_errno(t
, r
);
520 static bool dns_transaction_limited_retry(DnsTransaction
*t
) {
523 /* If we haven't tried all different servers yet, let's try again with a different server */
525 if (t
->n_picked_servers
>= dns_scope_get_n_dns_servers(t
->scope
))
528 dns_transaction_retry(t
, /* next_server= */ true);
532 static int dns_transaction_maybe_restart(DnsTransaction
*t
) {
537 /* Restarts the transaction, under a new ID if the feature level of the server changed since we first
538 * tried, without changing DNS server. Returns > 0 if the transaction was restarted, 0 if not. */
543 if (t
->current_feature_level
<= dns_server_possible_feature_level(t
->server
))
546 /* The server's current feature level is lower than when we sent the original query. We learnt something from
547 the response or possibly an auxiliary DNSSEC response that we didn't know before. We take that as reason to
548 restart the whole transaction. This is a good idea to deal with servers that respond rubbish if we include
549 OPT RR or DO bit. One of these cases is documented here, for example:
550 https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */
552 log_debug("Server feature level is now lower than when we began our transaction. Restarting with new ID.");
553 dns_transaction_shuffle_id(t
);
555 r
= dns_transaction_go(t
);
562 static void on_transaction_stream_error(DnsTransaction
*t
, int error
) {
565 dns_transaction_close_connection(t
, true);
567 if (ERRNO_IS_DISCONNECT(error
)) {
568 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
) {
569 /* If the LLMNR/TCP connection failed, the host doesn't support LLMNR, and we cannot answer the
570 * question on this scope. */
571 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
575 dns_transaction_retry(t
, true);
579 dns_transaction_complete_errno(t
, error
);
582 static int dns_transaction_on_stream_packet(DnsTransaction
*t
, DnsStream
*s
, DnsPacket
*p
) {
589 encrypted
= s
->encrypted
;
591 dns_transaction_close_connection(t
, true);
593 if (dns_packet_validate_reply(p
) <= 0) {
594 log_debug("Invalid TCP reply packet.");
595 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
599 dns_scope_check_conflicts(t
->scope
, p
);
602 dns_transaction_process_reply(t
, p
, encrypted
);
605 /* If the response wasn't useful, then complete the transition
606 * now. After all, we are the worst feature set now with TCP
607 * sockets, and there's really no point in retrying. */
608 if (t
->state
== DNS_TRANSACTION_PENDING
)
609 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
611 dns_transaction_gc(t
);
616 static int on_stream_complete(DnsStream
*s
, int error
) {
619 if (ERRNO_IS_DISCONNECT(error
) && s
->protocol
!= DNS_PROTOCOL_LLMNR
) {
620 log_debug_errno(error
, "Connection failure for DNS TCP stream: %m");
622 if (s
->transactions
) {
626 dns_server_packet_lost(t
->server
, IPPROTO_TCP
, t
->current_feature_level
);
631 LIST_FOREACH(transactions_by_stream
, t
, s
->transactions
)
632 on_transaction_stream_error(t
, error
);
637 static int on_stream_packet(DnsStream
*s
, DnsPacket
*p
) {
644 t
= hashmap_get(s
->manager
->dns_transactions
, UINT_TO_PTR(DNS_PACKET_ID(p
)));
645 if (t
&& t
->stream
== s
) /* Validate that the stream we got this on actually is the stream the
646 * transaction was using. */
647 return dns_transaction_on_stream_packet(t
, s
, p
);
649 /* Ignore incorrect transaction id as an old transaction can have been canceled. */
650 log_debug("Received unexpected TCP reply packet with id %" PRIu16
", ignoring.", DNS_PACKET_ID(p
));
654 static uint16_t dns_transaction_port(DnsTransaction
*t
) {
657 if (t
->server
->port
> 0)
658 return t
->server
->port
;
660 return DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
) ? 853 : 53;
663 static int dns_transaction_emit_tcp(DnsTransaction
*t
) {
664 usec_t stream_timeout_usec
= DNS_STREAM_DEFAULT_TIMEOUT_USEC
;
665 _cleanup_(dns_stream_unrefp
) DnsStream
*s
= NULL
;
666 _cleanup_close_
int fd
= -EBADF
;
667 union sockaddr_union sa
;
674 dns_transaction_close_connection(t
, true);
676 switch (t
->scope
->protocol
) {
678 case DNS_PROTOCOL_DNS
:
679 r
= dns_transaction_pick_server(t
);
683 if (manager_server_is_stub(t
->scope
->manager
, t
->server
))
687 if (!dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(dns_transaction_key(t
)->type
))
690 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
695 if (t
->server
->stream
&& (DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
) == t
->server
->stream
->encrypted
))
696 s
= dns_stream_ref(t
->server
->stream
);
698 fd
= dns_scope_socket_tcp(t
->scope
, AF_UNSPEC
, NULL
, t
->server
, dns_transaction_port(t
), &sa
);
700 /* Lower timeout in DNS-over-TLS opportunistic mode. In environments where DoT is blocked
701 * without ICMP response overly long delays when contacting DoT servers are nasty, in
702 * particular if multiple DNS servers are defined which we try in turn and all are
703 * blocked. Hence, substantially lower the timeout in that case. */
704 if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
) &&
705 dns_server_get_dns_over_tls_mode(t
->server
) == DNS_OVER_TLS_OPPORTUNISTIC
)
706 stream_timeout_usec
= DNS_STREAM_OPPORTUNISTIC_TLS_TIMEOUT_USEC
;
708 type
= DNS_STREAM_LOOKUP
;
711 case DNS_PROTOCOL_LLMNR
:
712 /* When we already received a reply to this (but it was truncated), send to its sender address */
714 fd
= dns_scope_socket_tcp(t
->scope
, t
->received
->family
, &t
->received
->sender
, NULL
, t
->received
->sender_port
, &sa
);
716 union in_addr_union address
;
717 int family
= AF_UNSPEC
;
719 /* Otherwise, try to talk to the owner of a
720 * the IP address, in case this is a reverse
723 r
= dns_name_address(dns_resource_key_name(dns_transaction_key(t
)), &family
, &address
);
728 if (family
!= t
->scope
->family
)
731 fd
= dns_scope_socket_tcp(t
->scope
, family
, &address
, NULL
, LLMNR_PORT
, &sa
);
734 type
= DNS_STREAM_LLMNR_SEND
;
738 return -EAFNOSUPPORT
;
745 r
= dns_stream_new(t
->scope
->manager
, &s
, type
, t
->scope
->protocol
, fd
, &sa
,
746 on_stream_packet
, on_stream_complete
, stream_timeout_usec
);
752 #if ENABLE_DNS_OVER_TLS
753 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
754 DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
)) {
757 r
= dnstls_stream_connect_tls(s
, t
->server
);
764 dns_server_unref_stream(t
->server
);
765 s
->server
= dns_server_ref(t
->server
);
766 t
->server
->stream
= dns_stream_ref(s
);
769 /* The interface index is difficult to determine if we are
770 * connecting to the local host, hence fill this in right away
771 * instead of determining it from the socket */
772 s
->ifindex
= dns_scope_ifindex(t
->scope
);
775 t
->stream
= TAKE_PTR(s
);
776 LIST_PREPEND(transactions_by_stream
, t
->stream
->transactions
, t
);
778 r
= dns_stream_write_packet(t
->stream
, t
->sent
);
780 dns_transaction_close_connection(t
, /* use_graveyard= */ false);
784 dns_transaction_reset_answer(t
);
786 t
->tried_stream
= true;
791 static void dns_transaction_cache_answer(DnsTransaction
*t
) {
794 /* For mDNS we cache whenever we get the packet, rather than
795 * in each transaction. */
796 if (!IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_DNS
, DNS_PROTOCOL_LLMNR
))
799 /* Caching disabled? */
800 if (t
->scope
->manager
->enable_cache
== DNS_CACHE_MODE_NO
)
803 /* If validation is turned off for this transaction, but DNSSEC is on, then let's not cache this */
804 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) && t
->scope
->dnssec_mode
!= DNSSEC_NO
)
807 /* Packet from localhost? */
808 if (!t
->scope
->manager
->cache_from_localhost
&&
809 in_addr_is_localhost(t
->received
->family
, &t
->received
->sender
) != 0)
812 dns_cache_put(&t
->scope
->cache
,
813 t
->scope
->manager
->enable_cache
,
815 dns_transaction_key(t
),
818 DNS_PACKET_CD(t
->received
) ? t
->received
: NULL
, /* only cache full packets with CD on,
819 * since our usecase for caching them
820 * is "bypass" mode which is only
821 * enabled for CD packets. */
822 t
->answer_query_flags
,
823 t
->answer_dnssec_result
,
826 &t
->received
->sender
);
829 static bool dns_transaction_dnssec_is_live(DnsTransaction
*t
) {
834 SET_FOREACH(dt
, t
->dnssec_transactions
)
835 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
841 static int dns_transaction_dnssec_ready(DnsTransaction
*t
) {
847 /* Checks whether the auxiliary DNSSEC transactions of our transaction have completed, or are still
848 * ongoing. Returns 0, if we aren't ready for the DNSSEC validation, positive if we are. */
850 SET_FOREACH(dt
, t
->dnssec_transactions
) {
854 case DNS_TRANSACTION_NULL
:
855 case DNS_TRANSACTION_PENDING
:
856 case DNS_TRANSACTION_VALIDATING
:
860 case DNS_TRANSACTION_RCODE_FAILURE
:
861 if (!IN_SET(dt
->answer_rcode
, DNS_RCODE_NXDOMAIN
, DNS_RCODE_SERVFAIL
)) {
862 log_debug("Auxiliary DNSSEC RR query failed with rcode=%s.", FORMAT_DNS_RCODE(dt
->answer_rcode
));
866 /* Fall-through: NXDOMAIN/SERVFAIL is good enough for us. This is because some DNS servers
867 * erroneously return NXDOMAIN/SERVFAIL for empty non-terminals (Akamai...) or missing DS
868 * records (Facebook), and we need to handle that nicely, when asking for parent SOA or similar
869 * RRs to make unsigned proofs. */
871 case DNS_TRANSACTION_SUCCESS
:
875 case DNS_TRANSACTION_DNSSEC_FAILED
:
876 /* We handle DNSSEC failures different from other errors, as we care about the DNSSEC
877 * validation result */
879 log_debug("Auxiliary DNSSEC RR query failed validation: %s", dnssec_result_to_string(dt
->answer_dnssec_result
));
880 t
->answer_dnssec_result
= dt
->answer_dnssec_result
; /* Copy error code over */
881 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
885 log_debug("Auxiliary DNSSEC RR query failed with %s", dns_transaction_state_to_string(dt
->state
));
890 /* All is ready, we can go and validate */
894 /* Some auxiliary DNSSEC transaction failed for some reason. Maybe we learned something about the
895 * server due to this failure, and the feature level is now different? Let's see and restart the
896 * transaction if so. If not, let's propagate the auxiliary failure.
898 * This is particularly relevant if an auxiliary request figured out that DNSSEC doesn't work, and we
899 * are in permissive DNSSEC mode, and thus should restart things without DNSSEC magic. */
900 r
= dns_transaction_maybe_restart(t
);
904 return 0; /* don't validate just yet, we restarted things */
906 t
->answer_dnssec_result
= DNSSEC_FAILED_AUXILIARY
;
907 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
911 static void dns_transaction_process_dnssec(DnsTransaction
*t
) {
916 /* Are there ongoing DNSSEC transactions? If so, let's wait for them. */
917 r
= dns_transaction_dnssec_ready(t
);
920 if (r
== 0) /* We aren't ready yet (or one of our auxiliary transactions failed, and we shouldn't validate now */
923 /* See if we learnt things from the additional DNSSEC transactions, that we didn't know before, and better
924 * restart the lookup immediately. */
925 r
= dns_transaction_maybe_restart(t
);
928 if (r
> 0) /* Transaction got restarted... */
931 /* All our auxiliary DNSSEC transactions are complete now. Try
932 * to validate our RRset now. */
933 r
= dns_transaction_validate_dnssec(t
);
935 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
941 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
&&
942 t
->scope
->dnssec_mode
== DNSSEC_YES
) {
944 /* We are not in automatic downgrade mode, and the server is bad. Let's try a different server, maybe
947 if (dns_transaction_limited_retry(t
))
950 /* OK, let's give up, apparently all servers we tried didn't work. */
951 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
955 if (!IN_SET(t
->answer_dnssec_result
,
956 _DNSSEC_RESULT_INVALID
, /* No DNSSEC validation enabled */
957 DNSSEC_VALIDATED
, /* Answer is signed and validated successfully */
958 DNSSEC_UNSIGNED
, /* Answer is right-fully unsigned */
959 DNSSEC_INCOMPATIBLE_SERVER
)) { /* Server does not do DNSSEC (Yay, we are downgrade attack vulnerable!) */
960 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
964 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
)
965 dns_server_warn_downgrade(t
->server
);
967 dns_transaction_cache_answer(t
);
969 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
970 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
972 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
977 dns_transaction_complete_errno(t
, r
);
980 static int dns_transaction_has_positive_answer(DnsTransaction
*t
, DnsAnswerFlags
*flags
) {
985 /* Checks whether the answer is positive, i.e. either a direct
986 * answer to the question, or a CNAME/DNAME for it */
988 r
= dns_answer_match_key(t
->answer
, dns_transaction_key(t
), flags
);
992 r
= dns_answer_find_cname_or_dname(t
->answer
, dns_transaction_key(t
), NULL
, flags
);
999 static int dns_transaction_fix_rcode(DnsTransaction
*t
) {
1004 /* Fix up the RCODE to SUCCESS if we get at least one matching RR in a response. Note that this contradicts the
1005 * DNS RFCs a bit. Specifically, RFC 6604 Section 3 clarifies that the RCODE shall say something about a
1006 * CNAME/DNAME chain element coming after the last chain element contained in the message, and not the first
1007 * one included. However, it also indicates that not all DNS servers implement this correctly. Moreover, when
1008 * using DNSSEC we usually only can prove the first element of a CNAME/DNAME chain anyway, hence let's settle
1009 * on always processing the RCODE as referring to the immediate look-up we do, i.e. the first element of a
1010 * CNAME/DNAME chain. This way, we uniformly handle CNAME/DNAME chains, regardless if the DNS server
1011 * incorrectly implements RCODE, whether DNSSEC is in use, or whether the DNS server only supplied us with an
1012 * incomplete CNAME/DNAME chain.
1014 * Or in other words: if we get at least one positive reply in a message we patch NXDOMAIN to become SUCCESS,
1015 * and then rely on the CNAME chasing logic to figure out that there's actually a CNAME error with a new
1018 if (t
->answer_rcode
!= DNS_RCODE_NXDOMAIN
)
1021 r
= dns_transaction_has_positive_answer(t
, NULL
);
1025 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1029 void dns_transaction_process_reply(DnsTransaction
*t
, DnsPacket
*p
, bool encrypted
) {
1030 bool retry_with_tcp
= false;
1036 assert(t
->scope
->manager
);
1038 if (t
->state
!= DNS_TRANSACTION_PENDING
)
1041 /* Note that this call might invalidate the query. Callers
1042 * should hence not attempt to access the query or transaction
1043 * after calling this function. */
1045 log_debug("Processing incoming packet of size %zu on transaction %" PRIu16
" (rcode=%s).",
1047 t
->id
, FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)));
1049 switch (t
->scope
->protocol
) {
1051 case DNS_PROTOCOL_LLMNR
:
1052 /* For LLMNR we will not accept any packets from other interfaces */
1054 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
1057 if (p
->family
!= t
->scope
->family
)
1060 /* Tentative packets are not full responses but still
1061 * useful for identifying uniqueness conflicts during
1063 if (DNS_PACKET_LLMNR_T(p
)) {
1064 dns_transaction_tentative(t
, p
);
1070 case DNS_PROTOCOL_MDNS
:
1071 /* For mDNS we will not accept any packets from other interfaces */
1073 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
1076 if (p
->family
!= t
->scope
->family
)
1081 case DNS_PROTOCOL_DNS
:
1082 /* Note that we do not need to verify the
1083 * addresses/port numbers of incoming traffic, as we
1084 * invoked connect() on our UDP socket in which case
1085 * the kernel already does the needed verification for
1090 assert_not_reached();
1093 if (t
->received
!= p
)
1094 DNS_PACKET_REPLACE(t
->received
, dns_packet_ref(p
));
1096 t
->answer_source
= DNS_TRANSACTION_NETWORK
;
1098 if (p
->ipproto
== IPPROTO_TCP
) {
1099 if (DNS_PACKET_TC(p
)) {
1100 /* Truncated via TCP? Somebody must be fucking with us */
1101 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1105 if (DNS_PACKET_ID(p
) != t
->id
) {
1106 /* Not the reply to our query? Somebody must be fucking with us */
1107 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1112 switch (t
->scope
->protocol
) {
1114 case DNS_PROTOCOL_DNS
:
1118 IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_FORMERR
, DNS_RCODE_SERVFAIL
, DNS_RCODE_NOTIMP
)) {
1120 /* Request failed, immediately try again with reduced features */
1122 if (t
->current_feature_level
<= DNS_SERVER_FEATURE_LEVEL_UDP
) {
1124 /* This was already at UDP feature level? If so, it doesn't make sense to downgrade
1125 * this transaction anymore, but let's see if it might make sense to send the request
1126 * to a different DNS server instead. If not let's process the response, and accept the
1127 * rcode. Note that we don't retry on TCP, since that's a suitable way to mitigate
1128 * packet loss, but is not going to give us better rcodes should we actually have
1129 * managed to get them already at UDP level. */
1131 if (dns_transaction_limited_retry(t
))
1134 /* Give up, accept the rcode */
1135 log_debug("Server returned error: %s", FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)));
1139 /* SERVFAIL can happen for many reasons and may be transient.
1140 * To avoid unnecessary downgrades retry once with the initial level.
1141 * Check for clamp_feature_level_servfail having an invalid value as a sign that this is the
1142 * first attempt to downgrade. If so, clamp to the current value so that the transaction
1143 * is retried without actually downgrading. If the next try also fails we will downgrade by
1144 * hitting the else branch below. */
1145 if (DNS_PACKET_RCODE(p
) == DNS_RCODE_SERVFAIL
&&
1146 t
->clamp_feature_level_servfail
< 0) {
1147 t
->clamp_feature_level_servfail
= t
->current_feature_level
;
1148 log_debug("Server returned error %s, retrying transaction.",
1149 FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)));
1151 /* Reduce this feature level by one and try again. */
1152 switch (t
->current_feature_level
) {
1153 case DNS_SERVER_FEATURE_LEVEL_TLS_DO
:
1154 t
->clamp_feature_level_servfail
= DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
;
1156 case DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
+ 1:
1157 /* Skip plain TLS when TLS is not supported */
1158 t
->clamp_feature_level_servfail
= DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
- 1;
1161 t
->clamp_feature_level_servfail
= t
->current_feature_level
- 1;
1164 log_debug("Server returned error %s, retrying transaction with reduced feature level %s.",
1165 FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)),
1166 dns_server_feature_level_to_string(t
->clamp_feature_level_servfail
));
1169 dns_transaction_retry(t
, false /* use the same server */);
1173 if (DNS_PACKET_RCODE(p
) == DNS_RCODE_REFUSED
) {
1174 /* This server refused our request? If so, try again, use a different server */
1175 log_debug("Server returned REFUSED, switching servers, and retrying.");
1177 if (dns_transaction_limited_retry(t
))
1183 if (DNS_PACKET_TC(p
))
1184 dns_server_packet_truncated(t
->server
, t
->current_feature_level
);
1188 case DNS_PROTOCOL_LLMNR
:
1189 case DNS_PROTOCOL_MDNS
:
1190 dns_scope_packet_received(t
->scope
, p
->timestamp
- t
->start_usec
);
1194 assert_not_reached();
1197 if (DNS_PACKET_TC(p
)) {
1199 /* Truncated packets for mDNS are not allowed. Give up immediately. */
1200 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
) {
1201 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1205 /* Response was truncated, let's try again with good old TCP */
1206 log_debug("Reply truncated, retrying via TCP.");
1207 retry_with_tcp
= true;
1209 } else if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1210 DNS_PACKET_IS_FRAGMENTED(p
)) {
1212 /* Report the fragment size, so that we downgrade from LARGE to regular EDNS0 if needed */
1214 dns_server_packet_udp_fragmented(t
->server
, dns_packet_size_unfragmented(p
));
1216 if (t
->current_feature_level
> DNS_SERVER_FEATURE_LEVEL_UDP
) {
1217 /* Packet was fragmented. Let's retry with TCP to avoid fragmentation attack
1218 * issues. (We don't do that on the lowest feature level however, since crappy DNS
1219 * servers often do not implement TCP, hence falling back to TCP on fragmentation is
1220 * counter-productive there.) */
1222 log_debug("Reply fragmented, retrying via TCP. (Largest fragment size: %zu; Datagram size: %zu)",
1223 p
->fragsize
, p
->size
);
1224 retry_with_tcp
= true;
1228 if (retry_with_tcp
) {
1229 r
= dns_transaction_emit_tcp(t
);
1231 /* No servers found? Damn! */
1232 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
1235 if (r
== -EOPNOTSUPP
) {
1236 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
1237 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
1241 /* On LLMNR, if we cannot connect to the host,
1242 * we immediately give up */
1243 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1246 /* On DNS, couldn't send? Try immediately again, with a new server */
1247 if (dns_transaction_limited_retry(t
))
1250 /* No new server to try, give up */
1251 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1257 /* After the superficial checks, actually parse the message. */
1258 r
= dns_packet_extract(p
);
1261 dns_server_packet_invalid(t
->server
, t
->current_feature_level
);
1263 r
= dns_transaction_maybe_restart(t
);
1266 if (r
> 0) /* Transaction got restarted... */
1270 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1275 /* Report that we successfully received a valid packet with a good rcode after we initially got a bad
1276 * rcode and subsequently downgraded the protocol */
1278 if (IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_SUCCESS
, DNS_RCODE_NXDOMAIN
) &&
1279 t
->clamp_feature_level_servfail
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
)
1280 dns_server_packet_rcode_downgrade(t
->server
, t
->clamp_feature_level_servfail
);
1282 /* Report that the OPT RR was missing */
1284 dns_server_packet_bad_opt(t
->server
, t
->current_feature_level
);
1286 /* Report that the server didn't copy our query DO bit from request to response */
1287 if (DNS_PACKET_DO(t
->sent
) && !DNS_PACKET_DO(t
->received
))
1288 dns_server_packet_do_off(t
->server
, t
->current_feature_level
);
1290 /* Report that we successfully received a packet. We keep track of the largest packet
1291 * size/fragment size we got. Which is useful for announcing the EDNS(0) packet size we can
1292 * receive to our server. */
1293 dns_server_packet_received(t
->server
, p
->ipproto
, t
->current_feature_level
, dns_packet_size_unfragmented(p
));
1296 /* See if we know things we didn't know before that indicate we better restart the lookup immediately. */
1297 r
= dns_transaction_maybe_restart(t
);
1300 if (r
> 0) /* Transaction got restarted... */
1303 /* When dealing with protocols other than mDNS only consider responses with equivalent query section
1304 * to the request. For mDNS this check doesn't make sense, because the section 6 of RFC6762 states
1305 * that "Multicast DNS responses MUST NOT contain any questions in the Question Section". */
1306 if (t
->scope
->protocol
!= DNS_PROTOCOL_MDNS
) {
1307 r
= dns_packet_is_reply_for(p
, dns_transaction_key(t
));
1311 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1316 /* Install the answer as answer to the transaction. We ref the answer twice here: the main `answer`
1317 * field is later replaced by the DNSSEC validated subset. The 'answer_auxiliary' field carries the
1318 * original complete record set, including RRSIG and friends. We use this when passing data to
1319 * clients that ask for DNSSEC metadata. */
1320 DNS_ANSWER_REPLACE(t
->answer
, dns_answer_ref(p
->answer
));
1321 t
->answer_rcode
= DNS_PACKET_RCODE(p
);
1322 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
1323 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
1324 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
, encrypted
);
1326 r
= dns_transaction_fix_rcode(t
);
1330 /* Block GC while starting requests for additional DNSSEC RRs */
1332 r
= dns_transaction_request_dnssec_keys(t
);
1335 /* Maybe the transaction is ready for GC'ing now? If so, free it and return. */
1336 if (!dns_transaction_gc(t
))
1339 /* Requesting additional keys might have resulted in this transaction to fail, since the auxiliary
1340 * request failed for some reason. If so, we are not in pending state anymore, and we should exit
1342 if (t
->state
!= DNS_TRANSACTION_PENDING
)
1347 /* There are DNSSEC transactions pending now. Update the state accordingly. */
1348 t
->state
= DNS_TRANSACTION_VALIDATING
;
1349 dns_transaction_close_connection(t
, true);
1350 dns_transaction_stop_timeout(t
);
1354 dns_transaction_process_dnssec(t
);
1358 dns_transaction_complete_errno(t
, r
);
1361 static int on_dns_packet(sd_event_source
*s
, int fd
, uint32_t revents
, void *userdata
) {
1362 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1363 DnsTransaction
*t
= ASSERT_PTR(userdata
);
1368 r
= manager_recv(t
->scope
->manager
, fd
, DNS_PROTOCOL_DNS
, &p
);
1369 if (ERRNO_IS_DISCONNECT(r
)) {
1372 /* UDP connection failures get reported via ICMP and then are possibly delivered to us on the
1373 * next recvmsg(). Treat this like a lost packet. */
1375 log_debug_errno(r
, "Connection failure for DNS UDP packet: %m");
1376 assert_se(sd_event_now(t
->scope
->manager
->event
, CLOCK_BOOTTIME
, &usec
) >= 0);
1377 dns_server_packet_lost(t
->server
, IPPROTO_UDP
, t
->current_feature_level
);
1379 dns_transaction_close_connection(t
, /* use_graveyard = */ false);
1381 if (dns_transaction_limited_retry(t
)) /* Try a different server */
1384 dns_transaction_complete_errno(t
, r
);
1388 dns_transaction_complete_errno(t
, r
);
1392 /* Spurious wakeup without any data */
1395 r
= dns_packet_validate_reply(p
);
1397 log_debug_errno(r
, "Received invalid DNS packet as response, ignoring: %m");
1401 log_debug("Received inappropriate DNS packet as response, ignoring.");
1405 if (DNS_PACKET_ID(p
) != t
->id
) {
1406 log_debug("Received packet with incorrect transaction ID, ignoring.");
1410 dns_transaction_process_reply(t
, p
, false);
1414 static int dns_transaction_emit_udp(DnsTransaction
*t
) {
1419 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
) {
1421 r
= dns_transaction_pick_server(t
);
1425 if (manager_server_is_stub(t
->scope
->manager
, t
->server
))
1428 if (t
->current_feature_level
< DNS_SERVER_FEATURE_LEVEL_UDP
|| DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
))
1429 return -EAGAIN
; /* Sorry, can't do UDP, try TCP! */
1431 if (!t
->bypass
&& !dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(dns_transaction_key(t
)->type
))
1434 if (r
> 0 || t
->dns_udp_fd
< 0) { /* Server changed, or no connection yet. */
1437 dns_transaction_close_connection(t
, true);
1439 /* Before we allocate a new UDP socket, let's process the graveyard a bit to free some fds */
1440 manager_socket_graveyard_process(t
->scope
->manager
);
1442 fd
= dns_scope_socket_udp(t
->scope
, t
->server
);
1446 r
= sd_event_add_io(t
->scope
->manager
->event
, &t
->dns_udp_event_source
, fd
, EPOLLIN
, on_dns_packet
, t
);
1452 (void) sd_event_source_set_description(t
->dns_udp_event_source
, "dns-transaction-udp");
1457 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
1462 dns_transaction_close_connection(t
, true);
1464 r
= dns_scope_emit_udp(t
->scope
, t
->dns_udp_fd
, t
->server
? t
->server
->family
: AF_UNSPEC
, t
->sent
);
1468 dns_transaction_reset_answer(t
);
1473 static int on_transaction_timeout(sd_event_source
*s
, usec_t usec
, void *userdata
) {
1474 DnsTransaction
*t
= ASSERT_PTR(userdata
);
1478 if (t
->initial_jitter_scheduled
&& !t
->initial_jitter_elapsed
) {
1479 log_debug("Initial jitter phase for transaction %" PRIu16
" elapsed.", t
->id
);
1480 t
->initial_jitter_elapsed
= true;
1482 /* Timeout reached? Increase the timeout for the server used */
1483 switch (t
->scope
->protocol
) {
1485 case DNS_PROTOCOL_DNS
:
1487 dns_server_packet_lost(t
->server
, t
->stream
? IPPROTO_TCP
: IPPROTO_UDP
, t
->current_feature_level
);
1490 case DNS_PROTOCOL_LLMNR
:
1491 case DNS_PROTOCOL_MDNS
:
1492 dns_scope_packet_lost(t
->scope
, usec
- t
->start_usec
);
1496 assert_not_reached();
1499 log_debug("Timeout reached on transaction %" PRIu16
".", t
->id
);
1502 dns_transaction_retry(t
, /* next_server= */ true); /* try a different server, but given this means
1503 * packet loss, let's do so even if we already
1508 static int dns_transaction_setup_timeout(
1510 usec_t timeout_usec
/* relative */,
1511 usec_t next_usec
/* CLOCK_BOOTTIME */) {
1517 dns_transaction_stop_timeout(t
);
1519 r
= sd_event_add_time_relative(
1520 t
->scope
->manager
->event
,
1521 &t
->timeout_event_source
,
1524 on_transaction_timeout
, t
);
1528 (void) sd_event_source_set_description(t
->timeout_event_source
, "dns-transaction-timeout");
1530 t
->next_attempt_after
= next_usec
;
1531 t
->state
= DNS_TRANSACTION_PENDING
;
1535 static usec_t
transaction_get_resend_timeout(DnsTransaction
*t
) {
1539 switch (t
->scope
->protocol
) {
1541 case DNS_PROTOCOL_DNS
:
1543 /* When we do TCP, grant a much longer timeout, as in this case there's no need for us to quickly
1544 * resend, as the kernel does that anyway for us, and we really don't want to interrupt it in that
1547 return TRANSACTION_TCP_TIMEOUT_USEC
;
1549 return DNS_TIMEOUT_USEC
;
1551 case DNS_PROTOCOL_MDNS
:
1553 return MDNS_PROBING_INTERVAL_USEC
;
1555 /* See RFC 6762 Section 5.1 suggests that timeout should be a few seconds. */
1556 assert(t
->n_attempts
> 0);
1557 return (1 << (t
->n_attempts
- 1)) * USEC_PER_SEC
;
1559 case DNS_PROTOCOL_LLMNR
:
1560 return t
->scope
->resend_timeout
;
1563 assert_not_reached();
1567 static void dns_transaction_randomize_answer(DnsTransaction
*t
) {
1572 /* Randomizes the order of the answer array. This is done for all cached responses, so that we return
1573 * a different order each time. We do this only for DNS traffic, in order to do some minimal, crappy
1574 * load balancing. We don't do this for LLMNR or mDNS, since the order (preferring link-local
1575 * addresses, and such like) might have meaning there, and load balancing is pointless. */
1577 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1580 /* No point in randomizing, if there's just one RR */
1581 if (dns_answer_size(t
->answer
) <= 1)
1584 r
= dns_answer_reserve_or_clone(&t
->answer
, 0);
1585 if (r
< 0) /* If this fails, just don't randomize, this is non-essential stuff after all */
1586 return (void) log_debug_errno(r
, "Failed to clone answer record, not randomizing RR order of answer: %m");
1588 dns_answer_randomize(t
->answer
);
1591 static int dns_transaction_prepare(DnsTransaction
*t
, usec_t ts
) {
1596 /* Returns 0 if dns_transaction_complete() has been called. In that case the transaction and query
1597 * candidate objects may have been invalidated and must not be accessed. Returns 1 if the transaction
1598 * has been prepared. */
1600 dns_transaction_stop_timeout(t
);
1602 if (!dns_scope_network_good(t
->scope
)) {
1603 dns_transaction_complete(t
, DNS_TRANSACTION_NETWORK_DOWN
);
1607 if (t
->n_attempts
>= TRANSACTION_ATTEMPTS_MAX(t
->scope
->protocol
)) {
1608 DnsTransactionState result
;
1610 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
)
1611 /* If we didn't find anything on LLMNR, it's not an error, but a failure to resolve
1613 result
= DNS_TRANSACTION_NOT_FOUND
;
1615 result
= DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
;
1617 dns_transaction_complete(t
, result
);
1621 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& t
->tried_stream
) {
1622 /* If we already tried via a stream, then we don't
1623 * retry on LLMNR. See RFC 4795, Section 2.7. */
1624 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1631 dns_transaction_reset_answer(t
);
1632 dns_transaction_flush_dnssec_transactions(t
);
1634 /* Check the trust anchor. Do so only on classic DNS, since DNSSEC does not apply otherwise. */
1635 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1636 !FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_TRUST_ANCHOR
)) {
1637 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, dns_transaction_key(t
), &t
->answer
);
1641 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1642 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1643 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
|SD_RESOLVED_CONFIDENTIAL
, true);
1644 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1648 if (dns_name_is_root(dns_resource_key_name(dns_transaction_key(t
))) &&
1649 dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
1651 /* Hmm, this is a request for the root DS? A DS RR doesn't exist in the root zone,
1652 * and if our trust anchor didn't know it either, this means we cannot do any DNSSEC
1655 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
1656 /* We are in downgrade mode. In this case, synthesize an unsigned empty
1657 * response, so that the any lookup depending on this one can continue
1658 * assuming there was no DS, and hence the root zone was unsigned. */
1660 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1661 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1662 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
1663 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
, true);
1664 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1666 /* If we are not in downgrade mode, then fail the lookup, because we cannot
1667 * reasonably answer it. There might be DS RRs, but we don't know them, and
1668 * the DNS server won't tell them to us (and even if it would, we couldn't
1669 * validate and trust them. */
1670 dns_transaction_complete(t
, DNS_TRANSACTION_NO_TRUST_ANCHOR
);
1676 /* Check the zone. */
1677 if (!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_ZONE
)) {
1678 r
= dns_zone_lookup(&t
->scope
->zone
, dns_transaction_key(t
), dns_scope_ifindex(t
->scope
), &t
->answer
, NULL
, NULL
);
1682 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1683 t
->answer_source
= DNS_TRANSACTION_ZONE
;
1684 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
|SD_RESOLVED_CONFIDENTIAL
, true);
1685 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1690 /* Check the cache. */
1691 if (!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_CACHE
)) {
1693 /* Before trying the cache, let's make sure we figured out a server to use. Should this cause
1694 * a change of server this might flush the cache. */
1695 (void) dns_scope_get_dns_server(t
->scope
);
1697 /* Let's then prune all outdated entries */
1698 dns_cache_prune(&t
->scope
->cache
);
1700 r
= dns_cache_lookup(
1702 dns_transaction_key(t
),
1707 &t
->answer_query_flags
,
1708 &t
->answer_dnssec_result
);
1712 dns_transaction_randomize_answer(t
);
1714 if (t
->bypass
&& t
->scope
->protocol
== DNS_PROTOCOL_DNS
&& !t
->received
)
1715 /* When bypass mode is on, do not use cached data unless it came with a full
1717 dns_transaction_reset_answer(t
);
1719 t
->answer_source
= DNS_TRANSACTION_CACHE
;
1720 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
1721 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1723 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
1729 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_NETWORK
)) {
1730 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SOURCE
);
1737 static int dns_packet_append_zone(DnsPacket
*p
, DnsTransaction
*t
, DnsResourceKey
*k
, unsigned *nscount
) {
1738 _cleanup_(dns_answer_unrefp
) DnsAnswer
*answer
= NULL
;
1746 if (k
->type
!= DNS_TYPE_ANY
)
1749 r
= dns_zone_lookup(&t
->scope
->zone
, k
, t
->scope
->link
->ifindex
, &answer
, NULL
, &tentative
);
1753 return dns_packet_append_answer(p
, answer
, nscount
);
1756 static int dns_transaction_make_packet_mdns(DnsTransaction
*t
) {
1757 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1758 _cleanup_set_free_ Set
*keys
= NULL
;
1759 unsigned qdcount
, ancount
= 0 /* avoid false maybe-uninitialized warning */, nscount
;
1760 bool add_known_answers
= false;
1765 assert(t
->scope
->protocol
== DNS_PROTOCOL_MDNS
);
1767 /* Discard any previously prepared packet, so we can start over and coalesce again */
1768 t
->sent
= dns_packet_unref(t
->sent
);
1770 /* First, create a dummy packet to calculate packet size. */
1771 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, false);
1775 r
= dns_packet_append_key(p
, dns_transaction_key(t
), 0, NULL
);
1781 if (dns_key_is_shared(dns_transaction_key(t
)))
1782 add_known_answers
= true;
1784 r
= dns_packet_append_zone(p
, t
, dns_transaction_key(t
), NULL
);
1788 /* Save appended keys */
1789 r
= set_ensure_put(&keys
, &dns_resource_key_hash_ops
, dns_transaction_key(t
));
1794 * For mDNS, we want to coalesce as many open queries in pending transactions into one single
1795 * query packet on the wire as possible. To achieve that, we iterate through all pending transactions
1796 * in our current scope, and see whether their timing constraints allow them to be sent.
1799 assert_se(sd_event_now(t
->scope
->manager
->event
, CLOCK_BOOTTIME
, &ts
) >= 0);
1801 for (bool restart
= true; restart
;) {
1803 LIST_FOREACH(transactions_by_scope
, other
, t
->scope
->transactions
) {
1804 size_t saved_packet_size
;
1805 bool append
= false;
1807 /* Skip ourselves */
1811 if (other
->state
!= DNS_TRANSACTION_PENDING
)
1814 if (other
->next_attempt_after
> ts
)
1817 if (!set_contains(keys
, dns_transaction_key(other
))) {
1818 r
= dns_packet_append_key(p
, dns_transaction_key(other
), 0, &saved_packet_size
);
1819 /* If we can't stuff more questions into the packet, just give up.
1820 * One of the 'other' transactions will fire later and take care of the rest. */
1826 r
= dns_packet_append_zone(p
, t
, dns_transaction_key(other
), NULL
);
1835 r
= dns_transaction_prepare(other
, ts
);
1840 dns_packet_truncate(p
, saved_packet_size
);
1842 /* In this case, not only this transaction, but multiple transactions may be
1843 * freed. Hence, we need to restart the loop. */
1848 usec_t timeout
= transaction_get_resend_timeout(other
);
1849 r
= dns_transaction_setup_timeout(other
, timeout
, usec_add(ts
, timeout
));
1853 if (dns_key_is_shared(dns_transaction_key(other
)))
1854 add_known_answers
= true;
1857 r
= set_ensure_put(&keys
, &dns_resource_key_hash_ops
, dns_transaction_key(other
));
1863 if (qdcount
>= UINT16_MAX
)
1868 /* Append known answer section if we're asking for any shared record */
1869 if (add_known_answers
) {
1870 r
= dns_cache_export_shared_to_packet(&t
->scope
->cache
, p
, ts
, 0);
1874 ancount
= be16toh(DNS_PACKET_HEADER(p
)->ancount
);
1877 /* Then, create actual packet. */
1878 p
= dns_packet_unref(p
);
1879 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, false);
1885 SET_FOREACH(k
, keys
) {
1886 r
= dns_packet_append_key(p
, k
, 0, NULL
);
1890 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(qdcount
);
1893 if (add_known_answers
) {
1894 r
= dns_cache_export_shared_to_packet(&t
->scope
->cache
, p
, ts
, ancount
);
1901 SET_FOREACH(k
, keys
) {
1902 r
= dns_packet_append_zone(p
, t
, k
, &nscount
);
1906 DNS_PACKET_HEADER(p
)->nscount
= htobe16(nscount
);
1908 t
->sent
= TAKE_PTR(p
);
1912 static int dns_transaction_make_packet(DnsTransaction
*t
) {
1913 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1918 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
)
1919 return dns_transaction_make_packet_mdns(t
);
1924 if (t
->bypass
&& t
->bypass
->protocol
== t
->scope
->protocol
) {
1925 /* If bypass logic is enabled and the protocol if the original packet and our scope match,
1926 * take the original packet, copy it, and patch in our new ID */
1927 r
= dns_packet_dup(&p
, t
->bypass
);
1931 r
= dns_packet_new_query(
1932 &p
, t
->scope
->protocol
,
1933 /* min_alloc_dsize = */ 0,
1934 /* dnssec_cd = */ !FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) &&
1935 t
->scope
->dnssec_mode
!= DNSSEC_NO
);
1939 r
= dns_packet_append_key(p
, dns_transaction_key(t
), 0, NULL
);
1943 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(1);
1946 DNS_PACKET_HEADER(p
)->id
= t
->id
;
1948 t
->sent
= TAKE_PTR(p
);
1952 int dns_transaction_go(DnsTransaction
*t
) {
1955 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
1959 /* Returns > 0 if the transaction is now pending, returns 0 if could be processed immediately and has
1960 * finished now. In the latter case, the transaction and query candidate objects must not be accessed.
1963 assert_se(sd_event_now(t
->scope
->manager
->event
, CLOCK_BOOTTIME
, &ts
) >= 0);
1965 r
= dns_transaction_prepare(t
, ts
);
1969 log_debug("Firing %s transaction %" PRIu16
" for <%s> scope %s on %s/%s (validate=%s).",
1970 t
->bypass
? "bypass" : "regular",
1972 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
),
1973 dns_protocol_to_string(t
->scope
->protocol
),
1974 t
->scope
->link
? t
->scope
->link
->ifname
: "*",
1975 af_to_name_short(t
->scope
->family
),
1976 yes_no(!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
)));
1978 if (!t
->initial_jitter_scheduled
&&
1979 IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_LLMNR
, DNS_PROTOCOL_MDNS
)) {
1982 /* RFC 4795 Section 2.7 suggests all LLMNR queries should be delayed by a random time from 0 to
1984 * RFC 6762 Section 8.1 suggests initial probe queries should be delayed by a random time from
1987 t
->initial_jitter_scheduled
= true;
1990 switch (t
->scope
->protocol
) {
1992 case DNS_PROTOCOL_LLMNR
:
1993 jitter
= random_u64_range(LLMNR_JITTER_INTERVAL_USEC
);
1996 case DNS_PROTOCOL_MDNS
:
1998 jitter
= random_u64_range(MDNS_PROBING_INTERVAL_USEC
);
2003 assert_not_reached();
2006 r
= dns_transaction_setup_timeout(t
, jitter
, ts
);
2010 log_debug("Delaying %s transaction %" PRIu16
" for " USEC_FMT
"us.",
2011 dns_protocol_to_string(t
->scope
->protocol
),
2017 /* Otherwise, we need to ask the network */
2018 r
= dns_transaction_make_packet(t
);
2022 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&&
2023 (dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), "in-addr.arpa") > 0 ||
2024 dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), "ip6.arpa") > 0)) {
2026 /* RFC 4795, Section 2.4. says reverse lookups shall
2027 * always be made via TCP on LLMNR */
2028 r
= dns_transaction_emit_tcp(t
);
2030 /* Try via UDP, and if that fails due to large size or lack of
2031 * support try via TCP */
2032 r
= dns_transaction_emit_udp(t
);
2034 log_debug("Sending query via TCP since it is too large.");
2035 else if (r
== -EAGAIN
)
2036 log_debug("Sending query via TCP since UDP isn't supported or DNS-over-TLS is selected.");
2037 else if (r
== -EPERM
)
2038 log_debug("Sending query via TCP since UDP is blocked.");
2039 if (IN_SET(r
, -EMSGSIZE
, -EAGAIN
, -EPERM
))
2040 r
= dns_transaction_emit_tcp(t
);
2043 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2046 /* One of our own stub listeners */
2047 log_debug_errno(r
, "Detected that specified DNS server is our own extra listener, switching DNS servers.");
2049 dns_scope_next_dns_server(t
->scope
, t
->server
);
2051 if (dns_scope_get_dns_server(t
->scope
) == t
->server
) {
2052 log_debug_errno(r
, "Still pointing to extra listener after switching DNS servers, refusing operation.");
2053 dns_transaction_complete(t
, DNS_TRANSACTION_STUB_LOOP
);
2057 return dns_transaction_go(t
);
2060 /* No servers to send this to? */
2061 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
2064 if (r
== -EOPNOTSUPP
) {
2065 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
2066 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
2069 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& ERRNO_IS_DISCONNECT(r
)) {
2070 /* On LLMNR, if we cannot connect to a host via TCP when doing reverse lookups. This means we cannot
2071 * answer this request with this protocol. */
2072 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
2076 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2079 /* Couldn't send? Try immediately again, with a new server */
2080 dns_scope_next_dns_server(t
->scope
, t
->server
);
2082 return dns_transaction_go(t
);
2085 usec_t timeout
= transaction_get_resend_timeout(t
);
2086 r
= dns_transaction_setup_timeout(t
, timeout
, usec_add(ts
, timeout
));
2093 static int dns_transaction_find_cyclic(DnsTransaction
*t
, DnsTransaction
*aux
) {
2100 /* Try to find cyclic dependencies between transaction objects */
2105 SET_FOREACH(n
, aux
->dnssec_transactions
) {
2106 r
= dns_transaction_find_cyclic(t
, n
);
2114 static int dns_transaction_add_dnssec_transaction(DnsTransaction
*t
, DnsResourceKey
*key
, DnsTransaction
**ret
) {
2115 _cleanup_(dns_transaction_gcp
) DnsTransaction
*aux
= NULL
;
2122 aux
= dns_scope_find_transaction(t
->scope
, key
, t
->query_flags
);
2124 r
= dns_transaction_new(&aux
, t
->scope
, key
, NULL
, t
->query_flags
);
2128 if (set_contains(t
->dnssec_transactions
, aux
)) {
2133 r
= dns_transaction_find_cyclic(t
, aux
);
2137 char s
[DNS_RESOURCE_KEY_STRING_MAX
], saux
[DNS_RESOURCE_KEY_STRING_MAX
];
2139 return log_debug_errno(SYNTHETIC_ERRNO(ELOOP
),
2140 "Potential cyclic dependency, refusing to add transaction %" PRIu16
" (%s) as dependency for %" PRIu16
" (%s).",
2142 dns_resource_key_to_string(dns_transaction_key(t
), s
, sizeof s
),
2144 dns_resource_key_to_string(dns_transaction_key(aux
), saux
, sizeof saux
));
2148 r
= set_ensure_allocated(&aux
->notify_transactions_done
, NULL
);
2152 r
= set_ensure_put(&t
->dnssec_transactions
, NULL
, aux
);
2156 r
= set_ensure_put(&aux
->notify_transactions
, NULL
, t
);
2158 (void) set_remove(t
->dnssec_transactions
, aux
);
2162 *ret
= TAKE_PTR(aux
);
2166 static int dns_transaction_request_dnssec_rr(DnsTransaction
*t
, DnsResourceKey
*key
) {
2167 _cleanup_(dns_answer_unrefp
) DnsAnswer
*a
= NULL
;
2168 DnsTransaction
*aux
;
2174 /* Try to get the data from the trust anchor */
2175 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, key
, &a
);
2179 r
= dns_answer_extend(&t
->validated_keys
, a
);
2186 /* This didn't work, ask for it via the network/cache then. */
2187 r
= dns_transaction_add_dnssec_transaction(t
, key
, &aux
);
2188 if (r
== -ELOOP
) /* This would result in a cyclic dependency */
2193 if (aux
->state
== DNS_TRANSACTION_NULL
) {
2194 r
= dns_transaction_go(aux
);
2202 static int dns_transaction_negative_trust_anchor_lookup(DnsTransaction
*t
, const char *name
) {
2207 /* Check whether the specified name is in the NTA
2208 * database, either in the global one, or the link-local
2211 r
= dns_trust_anchor_lookup_negative(&t
->scope
->manager
->trust_anchor
, name
);
2215 if (!t
->scope
->link
)
2218 return link_negative_trust_anchor_lookup(t
->scope
->link
, name
);
2221 static int dns_transaction_has_negative_answer(DnsTransaction
*t
) {
2226 /* Checks whether the answer is negative, and lacks NSEC/NSEC3
2227 * RRs to prove it */
2229 r
= dns_transaction_has_positive_answer(t
, NULL
);
2235 /* Is this key explicitly listed as a negative trust anchor?
2236 * If so, it's nothing we need to care about */
2237 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(dns_transaction_key(t
)));
2243 static int dns_transaction_is_primary_response(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2249 /* Check if the specified RR is the "primary" response,
2250 * i.e. either matches the question precisely or is a
2251 * CNAME/DNAME for it. */
2253 r
= dns_resource_key_match_rr(dns_transaction_key(t
), rr
, NULL
);
2257 return dns_resource_key_match_cname_or_dname(dns_transaction_key(t
), rr
->key
, NULL
);
2260 static bool dns_transaction_dnssec_supported(DnsTransaction
*t
) {
2263 /* Checks whether our transaction's DNS server is assumed to be compatible with DNSSEC. Returns false as soon
2264 * as we changed our mind about a server, and now believe it is incompatible with DNSSEC. */
2266 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2269 /* If we have picked no server, then we are working from the cache or some other source, and DNSSEC might well
2270 * be supported, hence return true. */
2274 /* Note that we do not check the feature level actually used for the transaction but instead the feature level
2275 * the server is known to support currently, as the transaction feature level might be lower than what the
2276 * server actually supports, since we might have downgraded this transaction's feature level because we got a
2277 * SERVFAIL earlier and wanted to check whether downgrading fixes it. */
2279 return dns_server_dnssec_supported(t
->server
);
2282 static bool dns_transaction_dnssec_supported_full(DnsTransaction
*t
) {
2287 /* Checks whether our transaction our any of the auxiliary transactions couldn't do DNSSEC. */
2289 if (!dns_transaction_dnssec_supported(t
))
2292 SET_FOREACH(dt
, t
->dnssec_transactions
)
2293 if (!dns_transaction_dnssec_supported(dt
))
2299 int dns_transaction_request_dnssec_keys(DnsTransaction
*t
) {
2300 DnsResourceRecord
*rr
;
2307 * Retrieve all auxiliary RRs for the answer we got, so that
2308 * we can verify signatures or prove that RRs are rightfully
2309 * unsigned. Specifically:
2311 * - For RRSIG we get the matching DNSKEY
2312 * - For DNSKEY we get the matching DS
2313 * - For unsigned SOA/NS we get the matching DS
2314 * - For unsigned CNAME/DNAME/DS we get the parent SOA RR
2315 * - For other unsigned RRs we get the matching SOA RR
2316 * - For SOA/NS queries with no matching response RR, and no NSEC/NSEC3, the DS RR
2317 * - For DS queries with no matching response RRs, and no NSEC/NSEC3, the parent's SOA RR
2318 * - For other queries with no matching response RRs, and no NSEC/NSEC3, the SOA RR
2321 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) || t
->scope
->dnssec_mode
== DNSSEC_NO
)
2323 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
2324 return 0; /* We only need to validate stuff from the network */
2325 if (!dns_transaction_dnssec_supported(t
))
2326 return 0; /* If we can't do DNSSEC anyway there's no point in getting the auxiliary RRs */
2328 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
2330 if (dns_type_is_pseudo(rr
->key
->type
))
2333 /* If this RR is in the negative trust anchor, we don't need to validate it. */
2334 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2340 switch (rr
->key
->type
) {
2342 case DNS_TYPE_RRSIG
: {
2343 /* For each RRSIG we request the matching DNSKEY */
2344 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*dnskey
= NULL
;
2346 /* If this RRSIG is about a DNSKEY RR and the
2347 * signer is the same as the owner, then we
2348 * already have the DNSKEY, and we don't have
2349 * to look for more. */
2350 if (rr
->rrsig
.type_covered
== DNS_TYPE_DNSKEY
) {
2351 r
= dns_name_equal(rr
->rrsig
.signer
, dns_resource_key_name(rr
->key
));
2358 /* If the signer is not a parent of our
2359 * original query, then this is about an
2360 * auxiliary RRset, but not anything we asked
2361 * for. In this case we aren't interested,
2362 * because we don't want to request additional
2363 * RRs for stuff we didn't really ask for, and
2364 * also to avoid request loops, where
2365 * additional RRs from one transaction result
2366 * in another transaction whose additional RRs
2367 * point back to the original transaction, and
2369 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), rr
->rrsig
.signer
);
2375 dnskey
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DNSKEY
, rr
->rrsig
.signer
);
2379 log_debug("Requesting DNSKEY to validate transaction %" PRIu16
" (%s, RRSIG with key tag: %" PRIu16
").",
2380 t
->id
, dns_resource_key_name(rr
->key
), rr
->rrsig
.key_tag
);
2381 r
= dns_transaction_request_dnssec_rr(t
, dnskey
);
2387 case DNS_TYPE_DNSKEY
: {
2388 /* For each DNSKEY we request the matching DS */
2389 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
2391 /* If the DNSKEY we are looking at is not for
2392 * zone we are interested in, nor any of its
2393 * parents, we aren't interested, and don't
2394 * request it. After all, we don't want to end
2395 * up in request loops, and want to keep
2396 * additional traffic down. */
2398 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), dns_resource_key_name(rr
->key
));
2404 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
2408 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, DNSKEY with key tag: %" PRIu16
").",
2409 t
->id
, dns_resource_key_name(rr
->key
), dnssec_keytag(rr
, false));
2410 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2419 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
2421 /* For an unsigned SOA or NS, try to acquire
2422 * the matching DS RR, as we are at a zone cut
2423 * then, and whether a DS exists tells us
2424 * whether the zone is signed. Do so only if
2425 * this RR matches our original question,
2428 r
= dns_resource_key_match_rr(dns_transaction_key(t
), rr
, NULL
);
2432 /* Hmm, so this SOA RR doesn't match our original question. In this case, maybe this is
2433 * a negative reply, and we need the SOA RR's TTL in order to cache a negative entry?
2434 * If so, we need to validate it, too. */
2436 r
= dns_answer_match_key(t
->answer
, dns_transaction_key(t
), NULL
);
2439 if (r
> 0) /* positive reply, we won't need the SOA and hence don't need to validate
2443 /* Only bother with this if the SOA/NS RR we are looking at is actually a parent of
2444 * what we are looking for, otherwise there's no value in it for us. */
2445 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), dns_resource_key_name(rr
->key
));
2452 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2458 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
2462 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, unsigned SOA/NS RRset).",
2463 t
->id
, dns_resource_key_name(rr
->key
));
2464 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2472 case DNS_TYPE_CNAME
:
2473 case DNS_TYPE_DNAME
: {
2474 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2477 /* CNAMEs and DNAMEs cannot be located at a
2478 * zone apex, hence ask for the parent SOA for
2479 * unsigned CNAME/DNAME RRs, maybe that's the
2480 * apex. But do all that only if this is
2481 * actually a response to our original
2484 * Similar for DS RRs, which are signed when
2485 * the parent SOA is signed. */
2487 r
= dns_transaction_is_primary_response(t
, rr
);
2493 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2499 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
2505 name
= dns_resource_key_name(rr
->key
);
2506 r
= dns_name_parent(&name
);
2512 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, name
);
2516 log_debug("Requesting parent SOA to validate transaction %" PRIu16
" (%s, unsigned CNAME/DNAME/DS RRset).",
2517 t
->id
, dns_resource_key_name(rr
->key
));
2518 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2526 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2528 /* For other unsigned RRsets (including
2529 * NSEC/NSEC3!), look for proof the zone is
2530 * unsigned, by requesting the SOA RR of the
2531 * zone. However, do so only if they are
2532 * directly relevant to our original
2535 r
= dns_transaction_is_primary_response(t
, rr
);
2541 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2547 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, dns_resource_key_name(rr
->key
));
2551 log_debug("Requesting SOA to validate transaction %" PRIu16
" (%s, unsigned non-SOA/NS RRset <%s>).",
2552 t
->id
, dns_resource_key_name(rr
->key
), dns_resource_record_to_string(rr
));
2553 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2560 /* Above, we requested everything necessary to validate what
2561 * we got. Now, let's request what we need to validate what we
2564 r
= dns_transaction_has_negative_answer(t
);
2568 const char *name
, *signed_status
;
2571 name
= dns_resource_key_name(dns_transaction_key(t
));
2572 signed_status
= dns_answer_contains_nsec_or_nsec3(t
->answer
) ? "signed" : "unsigned";
2574 /* If this was a SOA or NS request, then check if there's a DS RR for the same domain. Note that this
2575 * could also be used as indication that we are not at a zone apex, but in real world setups there are
2576 * too many broken DNS servers (Hello, incapdns.net!) where non-terminal zones return NXDOMAIN even
2577 * though they have further children. If this was a DS request, then it's signed when the parent zone
2578 * is signed, hence ask the parent SOA in that case. If this was any other RR then ask for the SOA RR,
2579 * to see if that is signed. */
2581 if (dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
2582 r
= dns_name_parent(&name
);
2584 type
= DNS_TYPE_SOA
;
2585 log_debug("Requesting parent SOA (%s %s) to validate transaction %" PRIu16
" (%s, %s empty DS response).",
2586 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT
), name
, t
->id
,
2587 dns_resource_key_name(dns_transaction_key(t
)), signed_status
);
2591 } else if (IN_SET(dns_transaction_key(t
)->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
)) {
2594 log_debug("Requesting DS (%s %s) to validate transaction %" PRIu16
" (%s, %s empty SOA/NS response).",
2595 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT
), name
, t
->id
, name
, signed_status
);
2598 type
= DNS_TYPE_SOA
;
2599 log_debug("Requesting SOA (%s %s) to validate transaction %" PRIu16
" (%s, %s empty non-SOA/NS/DS response).",
2600 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT
), name
, t
->id
, name
, signed_status
);
2604 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2606 soa
= dns_resource_key_new(dns_transaction_key(t
)->class, type
, name
);
2610 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2616 return dns_transaction_dnssec_is_live(t
);
2619 void dns_transaction_notify(DnsTransaction
*t
, DnsTransaction
*source
) {
2623 /* Invoked whenever any of our auxiliary DNSSEC transactions completed its work. If the state is still PENDING,
2624 we are still in the loop that adds further DNSSEC transactions, hence don't check if we are ready yet. If
2625 the state is VALIDATING however, we should check if we are complete now. */
2627 if (t
->state
== DNS_TRANSACTION_VALIDATING
)
2628 dns_transaction_process_dnssec(t
);
2631 static int dns_transaction_validate_dnskey_by_ds(DnsTransaction
*t
) {
2632 DnsAnswerItem
*item
;
2637 /* Add all DNSKEY RRs from the answer that are validated by DS
2638 * RRs from the list of validated keys to the list of
2639 * validated keys. */
2641 DNS_ANSWER_FOREACH_ITEM(item
, t
->answer
) {
2643 r
= dnssec_verify_dnskey_by_ds_search(item
->rr
, t
->validated_keys
);
2649 /* If so, the DNSKEY is validated too. */
2650 r
= dns_answer_add_extend(&t
->validated_keys
, item
->rr
, item
->ifindex
, item
->flags
|DNS_ANSWER_AUTHENTICATED
, item
->rrsig
);
2658 static int dns_transaction_requires_rrsig(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2664 /* Checks if the RR we are looking for must be signed with an
2665 * RRSIG. This is used for positive responses. */
2667 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2670 if (dns_type_is_pseudo(rr
->key
->type
))
2673 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2679 switch (rr
->key
->type
) {
2681 case DNS_TYPE_RRSIG
:
2682 /* RRSIGs are the signatures themselves, they need no signing. */
2689 /* For SOA or NS RRs we look for a matching DS transaction */
2691 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2693 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2695 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_DS
)
2698 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), dns_resource_key_name(rr
->key
));
2704 /* We found a DS transactions for the SOA/NS
2705 * RRs we are looking at. If it discovered signed DS
2706 * RRs, then we need to be signed, too. */
2708 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
2711 return dns_answer_match_key(dt
->answer
, dns_transaction_key(dt
), NULL
);
2714 /* We found nothing that proves this is safe to leave
2715 * this unauthenticated, hence ask inist on
2716 * authentication. */
2721 case DNS_TYPE_CNAME
:
2722 case DNS_TYPE_DNAME
: {
2723 const char *parent
= NULL
;
2727 * CNAME/DNAME RRs cannot be located at a zone apex, hence look directly for the parent SOA.
2729 * DS RRs are signed if the parent is signed, hence also look at the parent SOA
2732 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2734 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2736 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_SOA
)
2740 parent
= dns_resource_key_name(rr
->key
);
2741 r
= dns_name_parent(&parent
);
2745 if (rr
->key
->type
== DNS_TYPE_DS
)
2748 /* A CNAME/DNAME without a parent? That's sooo weird. */
2749 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG
),
2750 "Transaction %" PRIu16
" claims CNAME/DNAME at root. Refusing.", t
->id
);
2754 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), parent
);
2760 return FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2769 /* Any other kind of RR (including DNSKEY/NSEC/NSEC3). Let's see if our SOA lookup was authenticated */
2771 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2773 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2775 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_SOA
)
2778 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), dns_resource_key_name(rr
->key
));
2784 /* We found the transaction that was supposed to find the SOA RR for us. It was
2785 * successful, but found no RR for us. This means we are not at a zone cut. In this
2786 * case, we require authentication if the SOA lookup was authenticated too. */
2787 return FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2794 static int dns_transaction_in_private_tld(DnsTransaction
*t
, const DnsResourceKey
*key
) {
2799 /* If DNSSEC downgrade mode is on, checks whether the
2800 * specified RR is one level below a TLD we have proven not to
2801 * exist. In such a case we assume that this is a private
2802 * domain, and permit it.
2804 * This detects cases like the Fritz!Box router networks. Each
2805 * Fritz!Box router serves a private "fritz.box" zone, in the
2806 * non-existing TLD "box". Requests for the "fritz.box" domain
2807 * are served by the router itself, while requests for the
2808 * "box" domain will result in NXDOMAIN.
2810 * Note that this logic is unable to detect cases where a
2811 * router serves a private DNS zone directly under
2812 * non-existing TLD. In such a case we cannot detect whether
2813 * the TLD is supposed to exist or not, as all requests we
2814 * make for it will be answered by the router's zone, and not
2815 * by the root zone. */
2819 if (t
->scope
->dnssec_mode
!= DNSSEC_ALLOW_DOWNGRADE
)
2820 return false; /* In strict DNSSEC mode what doesn't exist, doesn't exist */
2822 tld
= dns_resource_key_name(key
);
2823 r
= dns_name_parent(&tld
);
2827 return false; /* Already the root domain */
2829 if (!dns_name_is_single_label(tld
))
2832 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2834 if (dns_transaction_key(dt
)->class != key
->class)
2837 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), tld
);
2843 /* We found an auxiliary lookup we did for the TLD. If
2844 * that returned with NXDOMAIN, we know the TLD didn't
2845 * exist, and hence this might be a private zone. */
2847 return dt
->answer_rcode
== DNS_RCODE_NXDOMAIN
;
2853 static int dns_transaction_requires_nsec(DnsTransaction
*t
) {
2854 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
2862 /* Checks if we need to insist on NSEC/NSEC3 RRs for proving
2863 * this negative reply */
2865 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2868 if (dns_type_is_pseudo(dns_transaction_key(t
)->type
))
2871 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(dns_transaction_key(t
)));
2877 r
= dns_transaction_in_private_tld(t
, dns_transaction_key(t
));
2881 /* The lookup is from a TLD that is proven not to
2882 * exist, and we are in downgrade mode, hence ignore
2883 * that fact that we didn't get any NSEC RRs. */
2885 log_info("Detected a negative query %s in a private DNS zone, permitting unsigned response.",
2886 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
));
2890 name
= dns_resource_key_name(dns_transaction_key(t
));
2892 if (dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
2894 /* We got a negative reply for this DS lookup? DS RRs are signed when their parent zone is signed,
2895 * hence check the parent SOA in this case. */
2897 r
= dns_name_parent(&name
);
2903 type
= DNS_TYPE_SOA
;
2905 } else if (IN_SET(dns_transaction_key(t
)->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
))
2906 /* We got a negative reply for this SOA/NS lookup? If so, check if there's a DS RR for this */
2909 /* For all other negative replies, check for the SOA lookup */
2910 type
= DNS_TYPE_SOA
;
2912 /* For all other RRs we check the SOA on the same level to see
2913 * if it's signed. */
2915 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2917 if (dns_transaction_key(dt
)->class != dns_transaction_key(t
)->class)
2919 if (dns_transaction_key(dt
)->type
!= type
)
2922 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), name
);
2928 return FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2931 /* If in doubt, require NSEC/NSEC3 */
2935 static int dns_transaction_dnskey_authenticated(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2936 DnsResourceRecord
*rrsig
;
2940 /* Checks whether any of the DNSKEYs used for the RRSIGs for
2941 * the specified RRset is authenticated (i.e. has a matching
2944 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2950 DNS_ANSWER_FOREACH(rrsig
, t
->answer
) {
2953 r
= dnssec_key_match_rrsig(rr
->key
, rrsig
);
2959 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2961 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2964 if (dns_transaction_key(dt
)->type
== DNS_TYPE_DNSKEY
) {
2966 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), rrsig
->rrsig
.signer
);
2972 /* OK, we found an auxiliary DNSKEY lookup. If that lookup is authenticated,
2975 if (FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
2980 } else if (dns_transaction_key(dt
)->type
== DNS_TYPE_DS
) {
2982 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), rrsig
->rrsig
.signer
);
2988 /* OK, we found an auxiliary DS lookup. If that lookup is authenticated and
2989 * non-zero, we won! */
2991 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
2994 return dns_answer_match_key(dt
->answer
, dns_transaction_key(dt
), NULL
);
2999 return found
? false : -ENXIO
;
3002 static int dns_transaction_known_signed(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
3006 /* We know that the root domain is signed, hence if it appears
3007 * not to be signed, there's a problem with the DNS server */
3009 return rr
->key
->class == DNS_CLASS_IN
&&
3010 dns_name_is_root(dns_resource_key_name(rr
->key
));
3013 static int dns_transaction_check_revoked_trust_anchors(DnsTransaction
*t
) {
3014 DnsResourceRecord
*rr
;
3019 /* Maybe warn the user that we encountered a revoked DNSKEY
3020 * for a key from our trust anchor. Note that we don't care
3021 * whether the DNSKEY can be authenticated or not. It's
3022 * sufficient if it is self-signed. */
3024 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
3025 r
= dns_trust_anchor_check_revoked(&t
->scope
->manager
->trust_anchor
, rr
, t
->answer
);
3033 static int dns_transaction_invalidate_revoked_keys(DnsTransaction
*t
) {
3039 /* Removes all DNSKEY/DS objects from t->validated_keys that
3040 * our trust anchors database considers revoked. */
3043 DnsResourceRecord
*rr
;
3047 DNS_ANSWER_FOREACH(rr
, t
->validated_keys
) {
3048 r
= dns_trust_anchor_is_revoked(&t
->scope
->manager
->trust_anchor
, rr
);
3052 r
= dns_answer_remove_by_rr(&t
->validated_keys
, rr
);
3066 static int dns_transaction_copy_validated(DnsTransaction
*t
) {
3072 /* Copy all validated RRs from the auxiliary DNSSEC transactions into our set of validated RRs */
3074 SET_FOREACH(dt
, t
->dnssec_transactions
) {
3076 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
3079 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
3082 r
= dns_answer_extend(&t
->validated_keys
, dt
->answer
);
3091 DNSSEC_PHASE_DNSKEY
, /* Phase #1, only validate DNSKEYs */
3092 DNSSEC_PHASE_NSEC
, /* Phase #2, only validate NSEC+NSEC3 */
3093 DNSSEC_PHASE_ALL
, /* Phase #3, validate everything else */
3096 static int dnssec_validate_records(
3100 DnsAnswer
**validated
) {
3102 DnsResourceRecord
*rr
;
3105 /* Returns negative on error, 0 if validation failed, 1 to restart validation, 2 when finished. */
3107 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
3108 _unused_
_cleanup_(dns_resource_record_unrefp
) DnsResourceRecord
*rr_ref
= dns_resource_record_ref(rr
);
3109 DnsResourceRecord
*rrsig
= NULL
;
3110 DnssecResult result
;
3112 switch (rr
->key
->type
) {
3113 case DNS_TYPE_RRSIG
:
3116 case DNS_TYPE_DNSKEY
:
3117 /* We validate DNSKEYs only in the DNSKEY and ALL phases */
3118 if (phase
== DNSSEC_PHASE_NSEC
)
3123 case DNS_TYPE_NSEC3
:
3126 /* We validate NSEC/NSEC3 only in the NSEC and ALL phases */
3127 if (phase
== DNSSEC_PHASE_DNSKEY
)
3132 /* We validate all other RRs only in the ALL phases */
3133 if (phase
!= DNSSEC_PHASE_ALL
)
3137 r
= dnssec_verify_rrset_search(
3147 log_debug("Looking at %s: %s", strna(dns_resource_record_to_string(rr
)), dnssec_result_to_string(result
));
3149 if (result
== DNSSEC_VALIDATED
) {
3152 if (rr
->key
->type
== DNS_TYPE_DNSKEY
) {
3153 /* If we just validated a DNSKEY RRset, then let's add these keys to
3154 * the set of validated keys for this transaction. */
3156 r
= dns_answer_copy_by_key(&t
->validated_keys
, t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
, rrsig
);
3160 /* Some of the DNSKEYs we just added might already have been revoked,
3161 * remove them again in that case. */
3162 r
= dns_transaction_invalidate_revoked_keys(t
);
3167 /* Add the validated RRset to the new list of validated RRsets, and remove it from
3168 * the unvalidated RRsets. We mark the RRset as authenticated and cacheable. */
3169 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
, rrsig
);
3173 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_SECURE
, rr
->key
);
3175 /* Exit the loop, we dropped something from the answer, start from the beginning */
3179 /* If we haven't read all DNSKEYs yet a negative result of the validation is irrelevant, as
3180 * there might be more DNSKEYs coming. Similar, if we haven't read all NSEC/NSEC3 RRs yet,
3181 * we cannot do positive wildcard proofs yet, as those require the NSEC/NSEC3 RRs. */
3182 if (phase
!= DNSSEC_PHASE_ALL
)
3185 if (result
== DNSSEC_VALIDATED_WILDCARD
) {
3186 bool authenticated
= false;
3191 /* This RRset validated, but as a wildcard. This means we need
3192 * to prove via NSEC/NSEC3 that no matching non-wildcard RR exists. */
3194 /* First step, determine the source of synthesis */
3195 r
= dns_resource_record_source(rrsig
, &source
);
3199 r
= dnssec_test_positive_wildcard(*validated
,
3200 dns_resource_key_name(rr
->key
),
3202 rrsig
->rrsig
.signer
,
3205 /* Unless the NSEC proof showed that the key really doesn't exist something is off. */
3207 result
= DNSSEC_INVALID
;
3209 r
= dns_answer_move_by_key(
3213 authenticated
? (DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
) : 0,
3218 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, rr
->key
);
3220 /* Exit the loop, we dropped something from the answer, start from the beginning */
3225 if (result
== DNSSEC_NO_SIGNATURE
) {
3226 r
= dns_transaction_requires_rrsig(t
, rr
);
3230 /* Data does not require signing. In that case, just copy it over,
3231 * but remember that this is by no means authenticated. */
3232 r
= dns_answer_move_by_key(
3241 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3245 r
= dns_transaction_known_signed(t
, rr
);
3249 /* This is an RR we know has to be signed. If it isn't this means
3250 * the server is not attaching RRSIGs, hence complain. */
3252 dns_server_packet_rrsig_missing(t
->server
, t
->current_feature_level
);
3254 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
3256 /* Downgrading is OK? If so, just consider the information unsigned */
3258 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3262 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3266 /* Otherwise, fail */
3267 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
3271 r
= dns_transaction_in_private_tld(t
, rr
->key
);
3275 char s
[DNS_RESOURCE_KEY_STRING_MAX
];
3277 /* The data is from a TLD that is proven not to exist, and we are in downgrade
3278 * mode, hence ignore the fact that this was not signed. */
3280 log_info("Detected RRset %s is in a private DNS zone, permitting unsigned RRs.",
3281 dns_resource_key_to_string(rr
->key
, s
, sizeof s
));
3283 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3287 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3292 /* https://datatracker.ietf.org/doc/html/rfc6840#section-5.2 */
3293 if (result
== DNSSEC_UNSUPPORTED_ALGORITHM
) {
3294 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3298 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3304 DNSSEC_SIGNATURE_EXPIRED
)) {
3306 r
= dns_transaction_dnskey_authenticated(t
, rr
);
3307 if (r
< 0 && r
!= -ENXIO
)
3310 /* The DNSKEY transaction was not authenticated, this means there's
3311 * no DS for this, which means it's OK if no keys are found for this signature. */
3313 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3317 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3322 r
= dns_transaction_is_primary_response(t
, rr
);
3326 /* Look for a matching DNAME for this CNAME */
3327 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
3331 /* Also look among the stuff we already validated */
3332 r
= dns_answer_has_dname_for_cname(*validated
, rr
);
3340 DNSSEC_SIGNATURE_EXPIRED
,
3341 DNSSEC_NO_SIGNATURE
))
3342 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, rr
->key
);
3343 else /* DNSSEC_MISSING_KEY or DNSSEC_UNSUPPORTED_ALGORITHM */
3344 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, rr
->key
);
3346 /* This is a primary response to our question, and it failed validation.
3348 t
->answer_dnssec_result
= result
;
3352 /* This is a primary response, but we do have a DNAME RR
3353 * in the RR that can replay this CNAME, hence rely on
3354 * that, and we can remove the CNAME in favour of it. */
3357 /* This is just some auxiliary data. Just remove the RRset and continue. */
3358 r
= dns_answer_remove_by_key(&t
->answer
, rr
->key
);
3362 /* We dropped something from the answer, start from the beginning. */
3366 return 2; /* Finito. */
3369 int dns_transaction_validate_dnssec(DnsTransaction
*t
) {
3370 _cleanup_(dns_answer_unrefp
) DnsAnswer
*validated
= NULL
;
3372 DnsAnswerFlags flags
;
3374 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
3378 /* We have now collected all DS and DNSKEY RRs in t->validated_keys, let's see which RRs we can now
3379 * authenticate with that. */
3381 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) || t
->scope
->dnssec_mode
== DNSSEC_NO
)
3384 /* Already validated */
3385 if (t
->answer_dnssec_result
!= _DNSSEC_RESULT_INVALID
)
3388 /* Our own stuff needs no validation */
3389 if (IN_SET(t
->answer_source
, DNS_TRANSACTION_ZONE
, DNS_TRANSACTION_TRUST_ANCHOR
)) {
3390 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3391 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, true);
3395 /* Cached stuff is not affected by validation. */
3396 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
3399 if (!dns_transaction_dnssec_supported_full(t
)) {
3400 /* The server does not support DNSSEC, or doesn't augment responses with RRSIGs. */
3401 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
3402 log_debug("Not validating response for %" PRIu16
", used server feature level does not support DNSSEC.", t
->id
);
3406 log_debug("Validating response from transaction %" PRIu16
" (%s).",
3408 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
));
3410 /* First, see if this response contains any revoked trust
3411 * anchors we care about */
3412 r
= dns_transaction_check_revoked_trust_anchors(t
);
3416 /* Third, copy all RRs we acquired successfully from auxiliary RRs over. */
3417 r
= dns_transaction_copy_validated(t
);
3421 /* Second, see if there are DNSKEYs we already know a
3422 * validated DS for. */
3423 r
= dns_transaction_validate_dnskey_by_ds(t
);
3427 /* Fourth, remove all DNSKEY and DS RRs again that our trust
3428 * anchor says are revoked. After all we might have marked
3429 * some keys revoked above, but they might still be lingering
3430 * in our validated_keys list. */
3431 r
= dns_transaction_invalidate_revoked_keys(t
);
3435 phase
= DNSSEC_PHASE_DNSKEY
;
3437 bool have_nsec
= false;
3439 r
= dnssec_validate_records(t
, phase
, &have_nsec
, &validated
);
3443 /* Try again as long as we managed to achieve something */
3447 if (phase
== DNSSEC_PHASE_DNSKEY
&& have_nsec
) {
3448 /* OK, we processed all DNSKEYs, and there are NSEC/NSEC3 RRs, look at those now. */
3449 phase
= DNSSEC_PHASE_NSEC
;
3453 if (phase
!= DNSSEC_PHASE_ALL
) {
3454 /* OK, we processed all DNSKEYs and NSEC/NSEC3 RRs, look at all the rest now.
3455 * Note that in this third phase we start to remove RRs we couldn't validate. */
3456 phase
= DNSSEC_PHASE_ALL
;
3464 DNS_ANSWER_REPLACE(t
->answer
, TAKE_PTR(validated
));
3466 /* At this point the answer only contains validated
3467 * RRsets. Now, let's see if it actually answers the question
3468 * we asked. If so, great! If it doesn't, then see if
3469 * NSEC/NSEC3 can prove this. */
3470 r
= dns_transaction_has_positive_answer(t
, &flags
);
3472 /* Yes, it answers the question! */
3474 if (flags
& DNS_ANSWER_AUTHENTICATED
) {
3475 /* The answer is fully authenticated, yay. */
3476 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3477 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3478 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, true);
3480 /* The answer is not fully authenticated. */
3481 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3482 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3485 } else if (r
== 0) {
3486 DnssecNsecResult nr
;
3487 bool authenticated
= false;
3489 /* Bummer! Let's check NSEC/NSEC3 */
3490 r
= dnssec_nsec_test(t
->answer
, dns_transaction_key(t
), &nr
, &authenticated
, &t
->answer_nsec_ttl
);
3496 case DNSSEC_NSEC_NXDOMAIN
:
3497 /* NSEC proves the domain doesn't exist. Very good. */
3498 log_debug("Proved NXDOMAIN via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3499 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3500 t
->answer_rcode
= DNS_RCODE_NXDOMAIN
;
3501 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, authenticated
);
3503 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, dns_transaction_key(t
));
3506 case DNSSEC_NSEC_NODATA
:
3507 /* NSEC proves that there's no data here, very good. */
3508 log_debug("Proved NODATA via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3509 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3510 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3511 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, authenticated
);
3513 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, dns_transaction_key(t
));
3516 case DNSSEC_NSEC_OPTOUT
:
3517 /* NSEC3 says the data might not be signed */
3518 log_debug("Data is NSEC3 opt-out via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3519 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3520 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3522 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, dns_transaction_key(t
));
3525 case DNSSEC_NSEC_NO_RR
:
3526 /* No NSEC data? Bummer! */
3528 r
= dns_transaction_requires_nsec(t
);
3532 t
->answer_dnssec_result
= DNSSEC_NO_SIGNATURE
;
3533 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, dns_transaction_key(t
));
3535 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3536 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3537 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, dns_transaction_key(t
));
3542 case DNSSEC_NSEC_UNSUPPORTED_ALGORITHM
:
3543 /* We don't know the NSEC3 algorithm used? */
3544 t
->answer_dnssec_result
= DNSSEC_UNSUPPORTED_ALGORITHM
;
3545 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, dns_transaction_key(t
));
3548 case DNSSEC_NSEC_FOUND
:
3549 case DNSSEC_NSEC_CNAME
:
3550 /* NSEC says it needs to be there, but we couldn't find it? Bummer! */
3551 t
->answer_dnssec_result
= DNSSEC_NSEC_MISMATCH
;
3552 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, dns_transaction_key(t
));
3556 assert_not_reached();
3563 static const char* const dns_transaction_state_table
[_DNS_TRANSACTION_STATE_MAX
] = {
3564 [DNS_TRANSACTION_NULL
] = "null",
3565 [DNS_TRANSACTION_PENDING
] = "pending",
3566 [DNS_TRANSACTION_VALIDATING
] = "validating",
3567 [DNS_TRANSACTION_RCODE_FAILURE
] = "rcode-failure",
3568 [DNS_TRANSACTION_SUCCESS
] = "success",
3569 [DNS_TRANSACTION_NO_SERVERS
] = "no-servers",
3570 [DNS_TRANSACTION_TIMEOUT
] = "timeout",
3571 [DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
] = "attempts-max-reached",
3572 [DNS_TRANSACTION_INVALID_REPLY
] = "invalid-reply",
3573 [DNS_TRANSACTION_ERRNO
] = "errno",
3574 [DNS_TRANSACTION_ABORTED
] = "aborted",
3575 [DNS_TRANSACTION_DNSSEC_FAILED
] = "dnssec-failed",
3576 [DNS_TRANSACTION_NO_TRUST_ANCHOR
] = "no-trust-anchor",
3577 [DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
] = "rr-type-unsupported",
3578 [DNS_TRANSACTION_NETWORK_DOWN
] = "network-down",
3579 [DNS_TRANSACTION_NOT_FOUND
] = "not-found",
3580 [DNS_TRANSACTION_NO_SOURCE
] = "no-source",
3581 [DNS_TRANSACTION_STUB_LOOP
] = "stub-loop",
3583 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state
, DnsTransactionState
);
3585 static const char* const dns_transaction_source_table
[_DNS_TRANSACTION_SOURCE_MAX
] = {
3586 [DNS_TRANSACTION_NETWORK
] = "network",
3587 [DNS_TRANSACTION_CACHE
] = "cache",
3588 [DNS_TRANSACTION_ZONE
] = "zone",
3589 [DNS_TRANSACTION_TRUST_ANCHOR
] = "trust-anchor",
3591 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source
, DnsTransactionSource
);