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
) {
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 .clamp_feature_level_nxdomain
= _DNS_SERVER_FEATURE_LEVEL_INVALID
,
286 .id
= pick_new_id(s
->manager
),
289 r
= hashmap_put(s
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
), t
);
296 DnsTransaction
*first
;
298 first
= hashmap_get(s
->transactions_by_key
, t
->key
);
299 LIST_PREPEND(transactions_by_key
, first
, t
);
301 r
= hashmap_replace(s
->transactions_by_key
, first
->key
, first
);
303 LIST_REMOVE(transactions_by_key
, first
, t
);
308 LIST_PREPEND(transactions_by_scope
, s
->transactions
, t
);
311 s
->manager
->n_transactions_total
++;
320 static void dns_transaction_shuffle_id(DnsTransaction
*t
) {
324 /* Pick a new ID for this transaction. */
326 new_id
= pick_new_id(t
->scope
->manager
);
327 assert_se(hashmap_remove_and_put(t
->scope
->manager
->dns_transactions
, UINT_TO_PTR(t
->id
), UINT_TO_PTR(new_id
), t
) >= 0);
329 log_debug("Transaction %" PRIu16
" is now %" PRIu16
".", t
->id
, new_id
);
332 /* Make sure we generate a new packet with the new ID */
333 t
->sent
= dns_packet_unref(t
->sent
);
336 static void dns_transaction_tentative(DnsTransaction
*t
, DnsPacket
*p
) {
337 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
342 assert(t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
);
344 if (manager_packet_from_local_address(t
->scope
->manager
, p
) != 0)
347 log_debug("Transaction %" PRIu16
" for <%s> on scope %s on %s/%s got tentative packet from %s.",
349 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
),
350 dns_protocol_to_string(t
->scope
->protocol
),
351 t
->scope
->link
? t
->scope
->link
->ifname
: "*",
352 af_to_name_short(t
->scope
->family
),
353 IN_ADDR_TO_STRING(p
->family
, &p
->sender
));
355 /* RFC 4795, Section 4.1 says that the peer with the
356 * lexicographically smaller IP address loses */
357 if (memcmp(&p
->sender
, &p
->destination
, FAMILY_ADDRESS_SIZE(p
->family
)) >= 0) {
358 log_debug("Peer has lexicographically larger IP address and thus lost in the conflict.");
362 log_debug("We have the lexicographically larger IP address and thus lost in the conflict.");
366 while ((z
= set_first(t
->notify_zone_items
))) {
367 /* First, make sure the zone item drops the reference
369 dns_zone_item_probe_stop(z
);
371 /* Secondly, report this as conflict, so that we might
372 * look for a different hostname */
373 dns_zone_item_conflict(z
);
377 dns_transaction_gc(t
);
380 void dns_transaction_complete(DnsTransaction
*t
, DnsTransactionState state
) {
381 DnsQueryCandidate
*c
;
385 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
388 assert(!DNS_TRANSACTION_IS_LIVE(state
));
390 if (state
== DNS_TRANSACTION_DNSSEC_FAILED
) {
391 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
);
393 log_struct(LOG_NOTICE
,
394 "MESSAGE_ID=" SD_MESSAGE_DNSSEC_FAILURE_STR
,
395 LOG_MESSAGE("DNSSEC validation failed for question %s: %s",
396 key_str
, dnssec_result_to_string(t
->answer_dnssec_result
)),
397 "DNS_TRANSACTION=%" PRIu16
, t
->id
,
398 "DNS_QUESTION=%s", key_str
,
399 "DNSSEC_RESULT=%s", dnssec_result_to_string(t
->answer_dnssec_result
),
400 "DNS_SERVER=%s", strna(dns_server_string_full(t
->server
)),
401 "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(t
->server
->possible_feature_level
));
404 /* Note that this call might invalidate the query. Callers
405 * should hence not attempt to access the query or transaction
406 * after calling this function. */
408 if (state
== DNS_TRANSACTION_ERRNO
)
409 st
= errno_to_name(t
->answer_errno
);
411 st
= dns_transaction_state_to_string(state
);
413 log_debug("%s transaction %" PRIu16
" for <%s> on scope %s on %s/%s now complete with <%s> from %s (%s; %s).",
414 t
->bypass
? "Bypass" : "Regular",
416 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
),
417 dns_protocol_to_string(t
->scope
->protocol
),
418 t
->scope
->link
? t
->scope
->link
->ifname
: "*",
419 af_to_name_short(t
->scope
->family
),
421 t
->answer_source
< 0 ? "none" : dns_transaction_source_to_string(t
->answer_source
),
422 FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) ? "not validated" :
423 (FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
) ? "authenticated" : "unsigned"),
424 FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
) ? "confidential" : "non-confidential");
428 dns_transaction_close_connection(t
, true);
429 dns_transaction_stop_timeout(t
);
431 /* Notify all queries that are interested, but make sure the
432 * transaction isn't freed while we are still looking at it */
435 SET_FOREACH_MOVE(c
, t
->notify_query_candidates_done
, t
->notify_query_candidates
)
436 dns_query_candidate_notify(c
);
437 SWAP_TWO(t
->notify_query_candidates
, t
->notify_query_candidates_done
);
439 SET_FOREACH_MOVE(z
, t
->notify_zone_items_done
, t
->notify_zone_items
)
440 dns_zone_item_notify(z
);
441 SWAP_TWO(t
->notify_zone_items
, t
->notify_zone_items_done
);
442 if (t
->probing
&& t
->state
== DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
)
443 (void) dns_scope_announce(t
->scope
, false);
445 SET_FOREACH_MOVE(d
, t
->notify_transactions_done
, t
->notify_transactions
)
446 dns_transaction_notify(d
, t
);
447 SWAP_TWO(t
->notify_transactions
, t
->notify_transactions_done
);
450 dns_transaction_gc(t
);
453 static void dns_transaction_complete_errno(DnsTransaction
*t
, int error
) {
457 t
->answer_errno
= abs(error
);
458 dns_transaction_complete(t
, DNS_TRANSACTION_ERRNO
);
461 static int dns_transaction_pick_server(DnsTransaction
*t
) {
465 assert(t
->scope
->protocol
== DNS_PROTOCOL_DNS
);
467 /* Pick a DNS server and a feature level for it. */
469 server
= dns_scope_get_dns_server(t
->scope
);
473 /* If we changed the server invalidate the feature level clamping, as the new server might have completely
474 * different properties. */
475 if (server
!= t
->server
) {
476 t
->clamp_feature_level_servfail
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
477 t
->clamp_feature_level_nxdomain
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
480 t
->current_feature_level
= dns_server_possible_feature_level(server
);
482 /* Clamp the feature level if that is requested. */
483 if (t
->clamp_feature_level_servfail
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
&&
484 t
->current_feature_level
> t
->clamp_feature_level_servfail
)
485 t
->current_feature_level
= t
->clamp_feature_level_servfail
;
486 if (t
->clamp_feature_level_nxdomain
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
&&
487 t
->current_feature_level
> t
->clamp_feature_level_nxdomain
)
488 t
->current_feature_level
= t
->clamp_feature_level_nxdomain
;
490 log_debug("Using feature level %s for transaction %u.", dns_server_feature_level_to_string(t
->current_feature_level
), t
->id
);
492 if (server
== t
->server
)
495 dns_server_unref(t
->server
);
496 t
->server
= dns_server_ref(server
);
498 t
->n_picked_servers
++;
500 log_debug("Using DNS server %s for transaction %u.", strna(dns_server_string_full(t
->server
)), t
->id
);
505 static void dns_transaction_retry(DnsTransaction
*t
, bool next_server
) {
510 /* Retries the transaction as it is, possibly on a different server */
512 if (next_server
&& t
->scope
->protocol
== DNS_PROTOCOL_DNS
)
513 log_debug("Retrying transaction %" PRIu16
", after switching servers.", t
->id
);
515 log_debug("Retrying transaction %" PRIu16
".", t
->id
);
517 /* Before we try again, switch to a new server. */
519 dns_scope_next_dns_server(t
->scope
, t
->server
);
521 r
= dns_transaction_go(t
);
523 dns_transaction_complete_errno(t
, r
);
526 static bool dns_transaction_limited_retry(DnsTransaction
*t
) {
529 /* If we haven't tried all different servers yet, let's try again with a different server */
531 if (t
->n_picked_servers
>= dns_scope_get_n_dns_servers(t
->scope
))
534 dns_transaction_retry(t
, /* next_server= */ true);
538 static int dns_transaction_maybe_restart(DnsTransaction
*t
) {
543 /* Restarts the transaction, under a new ID if the feature level of the server changed since we first
544 * tried, without changing DNS server. Returns > 0 if the transaction was restarted, 0 if not. */
549 if (t
->current_feature_level
<= dns_server_possible_feature_level(t
->server
))
552 /* The server's current feature level is lower than when we sent the original query. We learnt something from
553 the response or possibly an auxiliary DNSSEC response that we didn't know before. We take that as reason to
554 restart the whole transaction. This is a good idea to deal with servers that respond rubbish if we include
555 OPT RR or DO bit. One of these cases is documented here, for example:
556 https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */
558 log_debug("Server feature level is now lower than when we began our transaction. Restarting with new ID.");
559 dns_transaction_shuffle_id(t
);
561 r
= dns_transaction_go(t
);
568 static void on_transaction_stream_error(DnsTransaction
*t
, int error
) {
571 dns_transaction_close_connection(t
, true);
573 if (ERRNO_IS_DISCONNECT(error
)) {
574 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
) {
575 /* If the LLMNR/TCP connection failed, the host doesn't support LLMNR, and we cannot answer the
576 * question on this scope. */
577 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
581 dns_transaction_retry(t
, true);
585 dns_transaction_complete_errno(t
, error
);
588 static int dns_transaction_on_stream_packet(DnsTransaction
*t
, DnsStream
*s
, DnsPacket
*p
) {
595 encrypted
= s
->encrypted
;
597 dns_transaction_close_connection(t
, true);
599 if (dns_packet_validate_reply(p
) <= 0) {
600 log_debug("Invalid TCP reply packet.");
601 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
605 dns_scope_check_conflicts(t
->scope
, p
);
608 dns_transaction_process_reply(t
, p
, encrypted
);
611 /* If the response wasn't useful, then complete the transition
612 * now. After all, we are the worst feature set now with TCP
613 * sockets, and there's really no point in retrying. */
614 if (t
->state
== DNS_TRANSACTION_PENDING
)
615 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
617 dns_transaction_gc(t
);
622 static int on_stream_complete(DnsStream
*s
, int error
) {
625 if (ERRNO_IS_DISCONNECT(error
) && s
->protocol
!= DNS_PROTOCOL_LLMNR
) {
626 log_debug_errno(error
, "Connection failure for DNS TCP stream: %m");
628 if (s
->transactions
) {
632 dns_server_packet_lost(t
->server
, IPPROTO_TCP
, t
->current_feature_level
);
637 LIST_FOREACH(transactions_by_stream
, t
, s
->transactions
)
638 on_transaction_stream_error(t
, error
);
643 static int on_stream_packet(DnsStream
*s
, DnsPacket
*p
) {
650 t
= hashmap_get(s
->manager
->dns_transactions
, UINT_TO_PTR(DNS_PACKET_ID(p
)));
651 if (t
&& t
->stream
== s
) /* Validate that the stream we got this on actually is the stream the
652 * transaction was using. */
653 return dns_transaction_on_stream_packet(t
, s
, p
);
655 /* Ignore incorrect transaction id as an old transaction can have been canceled. */
656 log_debug("Received unexpected TCP reply packet with id %" PRIu16
", ignoring.", DNS_PACKET_ID(p
));
660 static uint16_t dns_transaction_port(DnsTransaction
*t
) {
663 if (t
->server
->port
> 0)
664 return t
->server
->port
;
666 return DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
) ? 853 : 53;
669 static int dns_transaction_emit_tcp(DnsTransaction
*t
) {
670 usec_t stream_timeout_usec
= DNS_STREAM_DEFAULT_TIMEOUT_USEC
;
671 _cleanup_(dns_stream_unrefp
) DnsStream
*s
= NULL
;
672 _cleanup_close_
int fd
= -1;
673 union sockaddr_union sa
;
680 dns_transaction_close_connection(t
, true);
682 switch (t
->scope
->protocol
) {
684 case DNS_PROTOCOL_DNS
:
685 r
= dns_transaction_pick_server(t
);
689 if (manager_server_is_stub(t
->scope
->manager
, t
->server
))
693 if (!dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(dns_transaction_key(t
)->type
))
696 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
701 if (t
->server
->stream
&& (DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
) == t
->server
->stream
->encrypted
))
702 s
= dns_stream_ref(t
->server
->stream
);
704 fd
= dns_scope_socket_tcp(t
->scope
, AF_UNSPEC
, NULL
, t
->server
, dns_transaction_port(t
), &sa
);
706 /* Lower timeout in DNS-over-TLS opportunistic mode. In environments where DoT is blocked
707 * without ICMP response overly long delays when contacting DoT servers are nasty, in
708 * particular if multiple DNS servers are defined which we try in turn and all are
709 * blocked. Hence, substantially lower the timeout in that case. */
710 if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
) &&
711 dns_server_get_dns_over_tls_mode(t
->server
) == DNS_OVER_TLS_OPPORTUNISTIC
)
712 stream_timeout_usec
= DNS_STREAM_OPPORTUNISTIC_TLS_TIMEOUT_USEC
;
714 type
= DNS_STREAM_LOOKUP
;
717 case DNS_PROTOCOL_LLMNR
:
718 /* When we already received a reply to this (but it was truncated), send to its sender address */
720 fd
= dns_scope_socket_tcp(t
->scope
, t
->received
->family
, &t
->received
->sender
, NULL
, t
->received
->sender_port
, &sa
);
722 union in_addr_union address
;
723 int family
= AF_UNSPEC
;
725 /* Otherwise, try to talk to the owner of a
726 * the IP address, in case this is a reverse
729 r
= dns_name_address(dns_resource_key_name(dns_transaction_key(t
)), &family
, &address
);
734 if (family
!= t
->scope
->family
)
737 fd
= dns_scope_socket_tcp(t
->scope
, family
, &address
, NULL
, LLMNR_PORT
, &sa
);
740 type
= DNS_STREAM_LLMNR_SEND
;
744 return -EAFNOSUPPORT
;
751 r
= dns_stream_new(t
->scope
->manager
, &s
, type
, t
->scope
->protocol
, fd
, &sa
,
752 on_stream_packet
, on_stream_complete
, stream_timeout_usec
);
758 #if ENABLE_DNS_OVER_TLS
759 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
760 DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
)) {
763 r
= dnstls_stream_connect_tls(s
, t
->server
);
770 dns_server_unref_stream(t
->server
);
771 s
->server
= dns_server_ref(t
->server
);
772 t
->server
->stream
= dns_stream_ref(s
);
775 /* The interface index is difficult to determine if we are
776 * connecting to the local host, hence fill this in right away
777 * instead of determining it from the socket */
778 s
->ifindex
= dns_scope_ifindex(t
->scope
);
781 t
->stream
= TAKE_PTR(s
);
782 LIST_PREPEND(transactions_by_stream
, t
->stream
->transactions
, t
);
784 r
= dns_stream_write_packet(t
->stream
, t
->sent
);
786 dns_transaction_close_connection(t
, /* use_graveyard= */ false);
790 dns_transaction_reset_answer(t
);
792 t
->tried_stream
= true;
797 static void dns_transaction_cache_answer(DnsTransaction
*t
) {
800 /* For mDNS we cache whenever we get the packet, rather than
801 * in each transaction. */
802 if (!IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_DNS
, DNS_PROTOCOL_LLMNR
))
805 /* Caching disabled? */
806 if (t
->scope
->manager
->enable_cache
== DNS_CACHE_MODE_NO
)
809 /* If validation is turned off for this transaction, but DNSSEC is on, then let's not cache this */
810 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) && t
->scope
->dnssec_mode
!= DNSSEC_NO
)
813 /* Packet from localhost? */
814 if (!t
->scope
->manager
->cache_from_localhost
&&
815 in_addr_is_localhost(t
->received
->family
, &t
->received
->sender
) != 0)
818 dns_cache_put(&t
->scope
->cache
,
819 t
->scope
->manager
->enable_cache
,
821 dns_transaction_key(t
),
824 DNS_PACKET_CD(t
->received
) ? t
->received
: NULL
, /* only cache full packets with CD on,
825 * since our usecase for caching them
826 * is "bypass" mode which is only
827 * enabled for CD packets. */
828 t
->answer_query_flags
,
829 t
->answer_dnssec_result
,
832 &t
->received
->sender
);
835 static bool dns_transaction_dnssec_is_live(DnsTransaction
*t
) {
840 SET_FOREACH(dt
, t
->dnssec_transactions
)
841 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
847 static int dns_transaction_dnssec_ready(DnsTransaction
*t
) {
853 /* Checks whether the auxiliary DNSSEC transactions of our transaction have completed, or are still
854 * ongoing. Returns 0, if we aren't ready for the DNSSEC validation, positive if we are. */
856 SET_FOREACH(dt
, t
->dnssec_transactions
) {
860 case DNS_TRANSACTION_NULL
:
861 case DNS_TRANSACTION_PENDING
:
862 case DNS_TRANSACTION_VALIDATING
:
866 case DNS_TRANSACTION_RCODE_FAILURE
:
867 if (!IN_SET(dt
->answer_rcode
, DNS_RCODE_NXDOMAIN
, DNS_RCODE_SERVFAIL
)) {
868 log_debug("Auxiliary DNSSEC RR query failed with rcode=%s.", FORMAT_DNS_RCODE(dt
->answer_rcode
));
872 /* Fall-through: NXDOMAIN/SERVFAIL is good enough for us. This is because some DNS servers
873 * erroneously return NXDOMAIN/SERVFAIL for empty non-terminals (Akamai...) or missing DS
874 * records (Facebook), and we need to handle that nicely, when asking for parent SOA or similar
875 * RRs to make unsigned proofs. */
877 case DNS_TRANSACTION_SUCCESS
:
881 case DNS_TRANSACTION_DNSSEC_FAILED
:
882 /* We handle DNSSEC failures different from other errors, as we care about the DNSSEC
883 * validation result */
885 log_debug("Auxiliary DNSSEC RR query failed validation: %s", dnssec_result_to_string(dt
->answer_dnssec_result
));
886 t
->answer_dnssec_result
= dt
->answer_dnssec_result
; /* Copy error code over */
887 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
891 log_debug("Auxiliary DNSSEC RR query failed with %s", dns_transaction_state_to_string(dt
->state
));
896 /* All is ready, we can go and validate */
900 /* Some auxiliary DNSSEC transaction failed for some reason. Maybe we learned something about the
901 * server due to this failure, and the feature level is now different? Let's see and restart the
902 * transaction if so. If not, let's propagate the auxiliary failure.
904 * This is particularly relevant if an auxiliary request figured out that DNSSEC doesn't work, and we
905 * are in permissive DNSSEC mode, and thus should restart things without DNSSEC magic. */
906 r
= dns_transaction_maybe_restart(t
);
910 return 0; /* don't validate just yet, we restarted things */
912 t
->answer_dnssec_result
= DNSSEC_FAILED_AUXILIARY
;
913 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
917 static void dns_transaction_process_dnssec(DnsTransaction
*t
) {
922 /* Are there ongoing DNSSEC transactions? If so, let's wait for them. */
923 r
= dns_transaction_dnssec_ready(t
);
926 if (r
== 0) /* We aren't ready yet (or one of our auxiliary transactions failed, and we shouldn't validate now */
929 /* See if we learnt things from the additional DNSSEC transactions, that we didn't know before, and better
930 * restart the lookup immediately. */
931 r
= dns_transaction_maybe_restart(t
);
934 if (r
> 0) /* Transaction got restarted... */
937 /* All our auxiliary DNSSEC transactions are complete now. Try
938 * to validate our RRset now. */
939 r
= dns_transaction_validate_dnssec(t
);
941 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
947 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
&&
948 t
->scope
->dnssec_mode
== DNSSEC_YES
) {
950 /* We are not in automatic downgrade mode, and the server is bad. Let's try a different server, maybe
953 if (dns_transaction_limited_retry(t
))
956 /* OK, let's give up, apparently all servers we tried didn't work. */
957 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
961 if (!IN_SET(t
->answer_dnssec_result
,
962 _DNSSEC_RESULT_INVALID
, /* No DNSSEC validation enabled */
963 DNSSEC_VALIDATED
, /* Answer is signed and validated successfully */
964 DNSSEC_UNSIGNED
, /* Answer is right-fully unsigned */
965 DNSSEC_INCOMPATIBLE_SERVER
)) { /* Server does not do DNSSEC (Yay, we are downgrade attack vulnerable!) */
966 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
970 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
)
971 dns_server_warn_downgrade(t
->server
);
973 dns_transaction_cache_answer(t
);
975 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
976 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
978 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
983 dns_transaction_complete_errno(t
, r
);
986 static int dns_transaction_has_positive_answer(DnsTransaction
*t
, DnsAnswerFlags
*flags
) {
991 /* Checks whether the answer is positive, i.e. either a direct
992 * answer to the question, or a CNAME/DNAME for it */
994 r
= dns_answer_match_key(t
->answer
, dns_transaction_key(t
), flags
);
998 r
= dns_answer_find_cname_or_dname(t
->answer
, dns_transaction_key(t
), NULL
, flags
);
1005 static int dns_transaction_fix_rcode(DnsTransaction
*t
) {
1010 /* Fix up the RCODE to SUCCESS if we get at least one matching RR in a response. Note that this contradicts the
1011 * DNS RFCs a bit. Specifically, RFC 6604 Section 3 clarifies that the RCODE shall say something about a
1012 * CNAME/DNAME chain element coming after the last chain element contained in the message, and not the first
1013 * one included. However, it also indicates that not all DNS servers implement this correctly. Moreover, when
1014 * using DNSSEC we usually only can prove the first element of a CNAME/DNAME chain anyway, hence let's settle
1015 * on always processing the RCODE as referring to the immediate look-up we do, i.e. the first element of a
1016 * CNAME/DNAME chain. This way, we uniformly handle CNAME/DNAME chains, regardless if the DNS server
1017 * incorrectly implements RCODE, whether DNSSEC is in use, or whether the DNS server only supplied us with an
1018 * incomplete CNAME/DNAME chain.
1020 * Or in other words: if we get at least one positive reply in a message we patch NXDOMAIN to become SUCCESS,
1021 * and then rely on the CNAME chasing logic to figure out that there's actually a CNAME error with a new
1024 if (t
->answer_rcode
!= DNS_RCODE_NXDOMAIN
)
1027 r
= dns_transaction_has_positive_answer(t
, NULL
);
1031 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1035 void dns_transaction_process_reply(DnsTransaction
*t
, DnsPacket
*p
, bool encrypted
) {
1036 bool retry_with_tcp
= false;
1042 assert(t
->scope
->manager
);
1044 if (t
->state
!= DNS_TRANSACTION_PENDING
)
1047 /* Note that this call might invalidate the query. Callers
1048 * should hence not attempt to access the query or transaction
1049 * after calling this function. */
1051 log_debug("Processing incoming packet of size %zu on transaction %" PRIu16
" (rcode=%s).",
1053 t
->id
, FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)));
1055 switch (t
->scope
->protocol
) {
1057 case DNS_PROTOCOL_LLMNR
:
1058 /* For LLMNR we will not accept any packets from other interfaces */
1060 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
1063 if (p
->family
!= t
->scope
->family
)
1066 /* Tentative packets are not full responses but still
1067 * useful for identifying uniqueness conflicts during
1069 if (DNS_PACKET_LLMNR_T(p
)) {
1070 dns_transaction_tentative(t
, p
);
1076 case DNS_PROTOCOL_MDNS
:
1077 /* For mDNS we will not accept any packets from other interfaces */
1079 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
1082 if (p
->family
!= t
->scope
->family
)
1087 case DNS_PROTOCOL_DNS
:
1088 /* Note that we do not need to verify the
1089 * addresses/port numbers of incoming traffic, as we
1090 * invoked connect() on our UDP socket in which case
1091 * the kernel already does the needed verification for
1096 assert_not_reached();
1099 if (t
->received
!= p
)
1100 DNS_PACKET_REPLACE(t
->received
, dns_packet_ref(p
));
1102 t
->answer_source
= DNS_TRANSACTION_NETWORK
;
1104 if (p
->ipproto
== IPPROTO_TCP
) {
1105 if (DNS_PACKET_TC(p
)) {
1106 /* Truncated via TCP? Somebody must be fucking with us */
1107 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1111 if (DNS_PACKET_ID(p
) != t
->id
) {
1112 /* Not the reply to our query? Somebody must be fucking with us */
1113 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1118 switch (t
->scope
->protocol
) {
1120 case DNS_PROTOCOL_DNS
:
1124 IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_FORMERR
, DNS_RCODE_SERVFAIL
, DNS_RCODE_NOTIMP
)) {
1126 /* Request failed, immediately try again with reduced features */
1128 if (t
->current_feature_level
<= DNS_SERVER_FEATURE_LEVEL_UDP
) {
1130 /* This was already at UDP feature level? If so, it doesn't make sense to downgrade
1131 * this transaction anymore, but let's see if it might make sense to send the request
1132 * to a different DNS server instead. If not let's process the response, and accept the
1133 * rcode. Note that we don't retry on TCP, since that's a suitable way to mitigate
1134 * packet loss, but is not going to give us better rcodes should we actually have
1135 * managed to get them already at UDP level. */
1137 if (dns_transaction_limited_retry(t
))
1140 /* Give up, accept the rcode */
1141 log_debug("Server returned error: %s", FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)));
1145 /* SERVFAIL can happen for many reasons and may be transient.
1146 * To avoid unnecessary downgrades retry once with the initial level.
1147 * Check for clamp_feature_level_servfail having an invalid value as a sign that this is the
1148 * first attempt to downgrade. If so, clamp to the current value so that the transaction
1149 * is retried without actually downgrading. If the next try also fails we will downgrade by
1150 * hitting the else branch below. */
1151 if (DNS_PACKET_RCODE(p
) == DNS_RCODE_SERVFAIL
&&
1152 t
->clamp_feature_level_servfail
< 0) {
1153 t
->clamp_feature_level_servfail
= t
->current_feature_level
;
1154 log_debug("Server returned error %s, retrying transaction.",
1155 FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)));
1157 /* Reduce this feature level by one and try again. */
1158 switch (t
->current_feature_level
) {
1159 case DNS_SERVER_FEATURE_LEVEL_TLS_DO
:
1160 t
->clamp_feature_level_servfail
= DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
;
1162 case DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
+ 1:
1163 /* Skip plain TLS when TLS is not supported */
1164 t
->clamp_feature_level_servfail
= DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
- 1;
1167 t
->clamp_feature_level_servfail
= t
->current_feature_level
- 1;
1170 log_debug("Server returned error %s, retrying transaction with reduced feature level %s.",
1171 FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)),
1172 dns_server_feature_level_to_string(t
->clamp_feature_level_servfail
));
1175 dns_transaction_retry(t
, false /* use the same server */);
1179 if (DNS_PACKET_RCODE(p
) == DNS_RCODE_REFUSED
) {
1180 /* This server refused our request? If so, try again, use a different server */
1181 log_debug("Server returned REFUSED, switching servers, and retrying.");
1183 if (dns_transaction_limited_retry(t
))
1189 if (DNS_PACKET_TC(p
))
1190 dns_server_packet_truncated(t
->server
, t
->current_feature_level
);
1194 case DNS_PROTOCOL_LLMNR
:
1195 case DNS_PROTOCOL_MDNS
:
1196 dns_scope_packet_received(t
->scope
, p
->timestamp
- t
->start_usec
);
1200 assert_not_reached();
1203 if (DNS_PACKET_TC(p
)) {
1205 /* Truncated packets for mDNS are not allowed. Give up immediately. */
1206 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
) {
1207 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1211 /* Response was truncated, let's try again with good old TCP */
1212 log_debug("Reply truncated, retrying via TCP.");
1213 retry_with_tcp
= true;
1215 } else if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1216 DNS_PACKET_IS_FRAGMENTED(p
)) {
1218 /* Report the fragment size, so that we downgrade from LARGE to regular EDNS0 if needed */
1220 dns_server_packet_udp_fragmented(t
->server
, dns_packet_size_unfragmented(p
));
1222 if (t
->current_feature_level
> DNS_SERVER_FEATURE_LEVEL_UDP
) {
1223 /* Packet was fragmented. Let's retry with TCP to avoid fragmentation attack
1224 * issues. (We don't do that on the lowest feature level however, since crappy DNS
1225 * servers often do not implement TCP, hence falling back to TCP on fragmentation is
1226 * counter-productive there.) */
1228 log_debug("Reply fragmented, retrying via TCP. (Largest fragment size: %zu; Datagram size: %zu)",
1229 p
->fragsize
, p
->size
);
1230 retry_with_tcp
= true;
1234 if (retry_with_tcp
) {
1235 r
= dns_transaction_emit_tcp(t
);
1237 /* No servers found? Damn! */
1238 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
1241 if (r
== -EOPNOTSUPP
) {
1242 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
1243 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
1247 /* On LLMNR, if we cannot connect to the host,
1248 * we immediately give up */
1249 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1252 /* On DNS, couldn't send? Try immediately again, with a new server */
1253 if (dns_transaction_limited_retry(t
))
1256 /* No new server to try, give up */
1257 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1263 /* After the superficial checks, actually parse the message. */
1264 r
= dns_packet_extract(p
);
1267 dns_server_packet_invalid(t
->server
, t
->current_feature_level
);
1269 r
= dns_transaction_maybe_restart(t
);
1272 if (r
> 0) /* Transaction got restarted... */
1276 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1280 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1282 DNS_PACKET_RCODE(p
) == DNS_RCODE_NXDOMAIN
&&
1283 p
->opt
&& !DNS_PACKET_DO(p
) &&
1284 DNS_SERVER_FEATURE_LEVEL_IS_EDNS0(t
->current_feature_level
) &&
1285 DNS_SERVER_FEATURE_LEVEL_IS_UDP(t
->current_feature_level
) &&
1286 t
->scope
->dnssec_mode
!= DNSSEC_YES
) {
1288 /* Some captive portals are special in that the Aruba/Datavalet hardware will miss
1289 * replacing the packets with the local server IP to point to the authenticated side
1290 * of the network if EDNS0 is enabled. Instead they return NXDOMAIN, with DO bit set
1291 * to zero... nothing to see here, yet respond with the captive portal IP, when using
1292 * the more simple UDP level.
1294 * Common portal names that fail like so are:
1295 * secure.datavalet.io
1296 * securelogin.arubanetworks.com
1297 * securelogin.networks.mycompany.com
1299 * Thus retry NXDOMAIN RCODES with a lower feature level.
1301 * Do not lower the server's tracked feature level, as the captive portal should not
1302 * be lying for the wider internet (e.g. _other_ queries were observed fine with
1303 * EDNS0 on these networks, post auth), i.e. let's just lower the level transaction's
1306 * This is reported as https://github.com/dns-violations/dns-violations/blob/master/2018/DVE-2018-0001.md
1309 t
->clamp_feature_level_nxdomain
= DNS_SERVER_FEATURE_LEVEL_UDP
;
1311 log_debug("Server returned error %s in EDNS0 mode, retrying transaction with reduced feature level %s (DVE-2018-0001 mitigation)",
1312 FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)),
1313 dns_server_feature_level_to_string(t
->clamp_feature_level_nxdomain
));
1315 dns_transaction_retry(t
, false /* use the same server */);
1320 /* Report that we successfully received a valid packet with a good rcode after we initially got a bad
1321 * rcode and subsequently downgraded the protocol */
1323 if (IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_SUCCESS
, DNS_RCODE_NXDOMAIN
) &&
1324 t
->clamp_feature_level_servfail
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
)
1325 dns_server_packet_rcode_downgrade(t
->server
, t
->clamp_feature_level_servfail
);
1327 /* Report that the OPT RR was missing */
1329 dns_server_packet_bad_opt(t
->server
, t
->current_feature_level
);
1331 /* Report that the server didn't copy our query DO bit from request to response */
1332 if (DNS_PACKET_DO(t
->sent
) && !DNS_PACKET_DO(t
->received
))
1333 dns_server_packet_do_off(t
->server
, t
->current_feature_level
);
1335 /* Report that we successfully received a packet. We keep track of the largest packet
1336 * size/fragment size we got. Which is useful for announcing the EDNS(0) packet size we can
1337 * receive to our server. */
1338 dns_server_packet_received(t
->server
, p
->ipproto
, t
->current_feature_level
, dns_packet_size_unfragmented(p
));
1341 /* See if we know things we didn't know before that indicate we better restart the lookup immediately. */
1342 r
= dns_transaction_maybe_restart(t
);
1345 if (r
> 0) /* Transaction got restarted... */
1348 /* When dealing with protocols other than mDNS only consider responses with equivalent query section
1349 * to the request. For mDNS this check doesn't make sense, because the section 6 of RFC6762 states
1350 * that "Multicast DNS responses MUST NOT contain any questions in the Question Section". */
1351 if (t
->scope
->protocol
!= DNS_PROTOCOL_MDNS
) {
1352 r
= dns_packet_is_reply_for(p
, dns_transaction_key(t
));
1356 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1361 /* Install the answer as answer to the transaction. We ref the answer twice here: the main `answer`
1362 * field is later replaced by the DNSSEC validated subset. The 'answer_auxiliary' field carries the
1363 * original complete record set, including RRSIG and friends. We use this when passing data to
1364 * clients that ask for DNSSEC metadata. */
1365 DNS_ANSWER_REPLACE(t
->answer
, dns_answer_ref(p
->answer
));
1366 t
->answer_rcode
= DNS_PACKET_RCODE(p
);
1367 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
1368 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
1369 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
, encrypted
);
1371 r
= dns_transaction_fix_rcode(t
);
1375 /* Block GC while starting requests for additional DNSSEC RRs */
1377 r
= dns_transaction_request_dnssec_keys(t
);
1380 /* Maybe the transaction is ready for GC'ing now? If so, free it and return. */
1381 if (!dns_transaction_gc(t
))
1384 /* Requesting additional keys might have resulted in this transaction to fail, since the auxiliary
1385 * request failed for some reason. If so, we are not in pending state anymore, and we should exit
1387 if (t
->state
!= DNS_TRANSACTION_PENDING
)
1392 /* There are DNSSEC transactions pending now. Update the state accordingly. */
1393 t
->state
= DNS_TRANSACTION_VALIDATING
;
1394 dns_transaction_close_connection(t
, true);
1395 dns_transaction_stop_timeout(t
);
1399 dns_transaction_process_dnssec(t
);
1403 dns_transaction_complete_errno(t
, r
);
1406 static int on_dns_packet(sd_event_source
*s
, int fd
, uint32_t revents
, void *userdata
) {
1407 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1408 DnsTransaction
*t
= ASSERT_PTR(userdata
);
1413 r
= manager_recv(t
->scope
->manager
, fd
, DNS_PROTOCOL_DNS
, &p
);
1414 if (ERRNO_IS_DISCONNECT(r
)) {
1417 /* UDP connection failures get reported via ICMP and then are possibly delivered to us on the
1418 * next recvmsg(). Treat this like a lost packet. */
1420 log_debug_errno(r
, "Connection failure for DNS UDP packet: %m");
1421 assert_se(sd_event_now(t
->scope
->manager
->event
, CLOCK_BOOTTIME
, &usec
) >= 0);
1422 dns_server_packet_lost(t
->server
, IPPROTO_UDP
, t
->current_feature_level
);
1424 dns_transaction_close_connection(t
, /* use_graveyard = */ false);
1426 if (dns_transaction_limited_retry(t
)) /* Try a different server */
1429 dns_transaction_complete_errno(t
, r
);
1433 dns_transaction_complete_errno(t
, r
);
1437 /* Spurious wakeup without any data */
1440 r
= dns_packet_validate_reply(p
);
1442 log_debug_errno(r
, "Received invalid DNS packet as response, ignoring: %m");
1446 log_debug("Received inappropriate DNS packet as response, ignoring.");
1450 if (DNS_PACKET_ID(p
) != t
->id
) {
1451 log_debug("Received packet with incorrect transaction ID, ignoring.");
1455 dns_transaction_process_reply(t
, p
, false);
1459 static int dns_transaction_emit_udp(DnsTransaction
*t
) {
1464 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
) {
1466 r
= dns_transaction_pick_server(t
);
1470 if (manager_server_is_stub(t
->scope
->manager
, t
->server
))
1473 if (t
->current_feature_level
< DNS_SERVER_FEATURE_LEVEL_UDP
|| DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
))
1474 return -EAGAIN
; /* Sorry, can't do UDP, try TCP! */
1476 if (!t
->bypass
&& !dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(dns_transaction_key(t
)->type
))
1479 if (r
> 0 || t
->dns_udp_fd
< 0) { /* Server changed, or no connection yet. */
1482 dns_transaction_close_connection(t
, true);
1484 /* Before we allocate a new UDP socket, let's process the graveyard a bit to free some fds */
1485 manager_socket_graveyard_process(t
->scope
->manager
);
1487 fd
= dns_scope_socket_udp(t
->scope
, t
->server
);
1491 r
= sd_event_add_io(t
->scope
->manager
->event
, &t
->dns_udp_event_source
, fd
, EPOLLIN
, on_dns_packet
, t
);
1497 (void) sd_event_source_set_description(t
->dns_udp_event_source
, "dns-transaction-udp");
1502 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
1507 dns_transaction_close_connection(t
, true);
1509 r
= dns_scope_emit_udp(t
->scope
, t
->dns_udp_fd
, t
->server
? t
->server
->family
: AF_UNSPEC
, t
->sent
);
1513 dns_transaction_reset_answer(t
);
1518 static int on_transaction_timeout(sd_event_source
*s
, usec_t usec
, void *userdata
) {
1519 DnsTransaction
*t
= ASSERT_PTR(userdata
);
1523 if (t
->initial_jitter_scheduled
&& !t
->initial_jitter_elapsed
) {
1524 log_debug("Initial jitter phase for transaction %" PRIu16
" elapsed.", t
->id
);
1525 t
->initial_jitter_elapsed
= true;
1527 /* Timeout reached? Increase the timeout for the server used */
1528 switch (t
->scope
->protocol
) {
1530 case DNS_PROTOCOL_DNS
:
1532 dns_server_packet_lost(t
->server
, t
->stream
? IPPROTO_TCP
: IPPROTO_UDP
, t
->current_feature_level
);
1535 case DNS_PROTOCOL_LLMNR
:
1536 case DNS_PROTOCOL_MDNS
:
1537 dns_scope_packet_lost(t
->scope
, usec
- t
->start_usec
);
1541 assert_not_reached();
1544 log_debug("Timeout reached on transaction %" PRIu16
".", t
->id
);
1547 dns_transaction_retry(t
, /* next_server= */ true); /* try a different server, but given this means
1548 * packet loss, let's do so even if we already
1553 static int dns_transaction_setup_timeout(
1555 usec_t timeout_usec
/* relative */,
1556 usec_t next_usec
/* CLOCK_BOOTTIME */) {
1562 dns_transaction_stop_timeout(t
);
1564 r
= sd_event_add_time_relative(
1565 t
->scope
->manager
->event
,
1566 &t
->timeout_event_source
,
1569 on_transaction_timeout
, t
);
1573 (void) sd_event_source_set_description(t
->timeout_event_source
, "dns-transaction-timeout");
1575 t
->next_attempt_after
= next_usec
;
1576 t
->state
= DNS_TRANSACTION_PENDING
;
1580 static usec_t
transaction_get_resend_timeout(DnsTransaction
*t
) {
1584 switch (t
->scope
->protocol
) {
1586 case DNS_PROTOCOL_DNS
:
1588 /* When we do TCP, grant a much longer timeout, as in this case there's no need for us to quickly
1589 * resend, as the kernel does that anyway for us, and we really don't want to interrupt it in that
1592 return TRANSACTION_TCP_TIMEOUT_USEC
;
1594 return DNS_TIMEOUT_USEC
;
1596 case DNS_PROTOCOL_MDNS
:
1598 return MDNS_PROBING_INTERVAL_USEC
;
1600 /* See RFC 6762 Section 5.1 suggests that timeout should be a few seconds. */
1601 assert(t
->n_attempts
> 0);
1602 return (1 << (t
->n_attempts
- 1)) * USEC_PER_SEC
;
1604 case DNS_PROTOCOL_LLMNR
:
1605 return t
->scope
->resend_timeout
;
1608 assert_not_reached();
1612 static void dns_transaction_randomize_answer(DnsTransaction
*t
) {
1617 /* Randomizes the order of the answer array. This is done for all cached responses, so that we return
1618 * a different order each time. We do this only for DNS traffic, in order to do some minimal, crappy
1619 * load balancing. We don't do this for LLMNR or mDNS, since the order (preferring link-local
1620 * addresses, and such like) might have meaning there, and load balancing is pointless. */
1622 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1625 /* No point in randomizing, if there's just one RR */
1626 if (dns_answer_size(t
->answer
) <= 1)
1629 r
= dns_answer_reserve_or_clone(&t
->answer
, 0);
1630 if (r
< 0) /* If this fails, just don't randomize, this is non-essential stuff after all */
1631 return (void) log_debug_errno(r
, "Failed to clone answer record, not randomizing RR order of answer: %m");
1633 dns_answer_randomize(t
->answer
);
1636 static int dns_transaction_prepare(DnsTransaction
*t
, usec_t ts
) {
1641 /* Returns 0 if dns_transaction_complete() has been called. In that case the transaction and query
1642 * candidate objects may have been invalidated and must not be accessed. Returns 1 if the transaction
1643 * has been prepared. */
1645 dns_transaction_stop_timeout(t
);
1647 if (!dns_scope_network_good(t
->scope
)) {
1648 dns_transaction_complete(t
, DNS_TRANSACTION_NETWORK_DOWN
);
1652 if (t
->n_attempts
>= TRANSACTION_ATTEMPTS_MAX(t
->scope
->protocol
)) {
1653 DnsTransactionState result
;
1655 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
)
1656 /* If we didn't find anything on LLMNR, it's not an error, but a failure to resolve
1658 result
= DNS_TRANSACTION_NOT_FOUND
;
1660 result
= DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
;
1662 dns_transaction_complete(t
, result
);
1666 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& t
->tried_stream
) {
1667 /* If we already tried via a stream, then we don't
1668 * retry on LLMNR. See RFC 4795, Section 2.7. */
1669 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1676 dns_transaction_reset_answer(t
);
1677 dns_transaction_flush_dnssec_transactions(t
);
1679 /* Check the trust anchor. Do so only on classic DNS, since DNSSEC does not apply otherwise. */
1680 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1681 !FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_TRUST_ANCHOR
)) {
1682 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, dns_transaction_key(t
), &t
->answer
);
1686 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1687 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1688 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
|SD_RESOLVED_CONFIDENTIAL
, true);
1689 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1693 if (dns_name_is_root(dns_resource_key_name(dns_transaction_key(t
))) &&
1694 dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
1696 /* Hmm, this is a request for the root DS? A DS RR doesn't exist in the root zone,
1697 * and if our trust anchor didn't know it either, this means we cannot do any DNSSEC
1700 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
1701 /* We are in downgrade mode. In this case, synthesize an unsigned empty
1702 * response, so that the any lookup depending on this one can continue
1703 * assuming there was no DS, and hence the root zone was unsigned. */
1705 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1706 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1707 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
1708 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
, true);
1709 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1711 /* If we are not in downgrade mode, then fail the lookup, because we cannot
1712 * reasonably answer it. There might be DS RRs, but we don't know them, and
1713 * the DNS server won't tell them to us (and even if it would, we couldn't
1714 * validate and trust them. */
1715 dns_transaction_complete(t
, DNS_TRANSACTION_NO_TRUST_ANCHOR
);
1721 /* Check the zone. */
1722 if (!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_ZONE
)) {
1723 r
= dns_zone_lookup(&t
->scope
->zone
, dns_transaction_key(t
), dns_scope_ifindex(t
->scope
), &t
->answer
, NULL
, NULL
);
1727 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1728 t
->answer_source
= DNS_TRANSACTION_ZONE
;
1729 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
|SD_RESOLVED_CONFIDENTIAL
, true);
1730 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1735 /* Check the cache. */
1736 if (!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_CACHE
)) {
1738 /* Before trying the cache, let's make sure we figured out a server to use. Should this cause
1739 * a change of server this might flush the cache. */
1740 (void) dns_scope_get_dns_server(t
->scope
);
1742 /* Let's then prune all outdated entries */
1743 dns_cache_prune(&t
->scope
->cache
);
1745 r
= dns_cache_lookup(
1747 dns_transaction_key(t
),
1752 &t
->answer_query_flags
,
1753 &t
->answer_dnssec_result
);
1757 dns_transaction_randomize_answer(t
);
1759 if (t
->bypass
&& t
->scope
->protocol
== DNS_PROTOCOL_DNS
&& !t
->received
)
1760 /* When bypass mode is on, do not use cached data unless it came with a full
1762 dns_transaction_reset_answer(t
);
1764 t
->answer_source
= DNS_TRANSACTION_CACHE
;
1765 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
1766 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1768 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
1774 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_NETWORK
)) {
1775 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SOURCE
);
1782 static int dns_packet_append_zone(DnsPacket
*p
, DnsTransaction
*t
, DnsResourceKey
*k
, unsigned *nscount
) {
1783 _cleanup_(dns_answer_unrefp
) DnsAnswer
*answer
= NULL
;
1791 if (k
->type
!= DNS_TYPE_ANY
)
1794 r
= dns_zone_lookup(&t
->scope
->zone
, k
, t
->scope
->link
->ifindex
, &answer
, NULL
, &tentative
);
1798 return dns_packet_append_answer(p
, answer
, nscount
);
1801 static int dns_transaction_make_packet_mdns(DnsTransaction
*t
) {
1802 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1803 _cleanup_set_free_ Set
*keys
= NULL
;
1804 unsigned qdcount
, ancount
= 0 /* avoid false maybe-uninitialized warning */, nscount
;
1805 bool add_known_answers
= false;
1810 assert(t
->scope
->protocol
== DNS_PROTOCOL_MDNS
);
1812 /* Discard any previously prepared packet, so we can start over and coalesce again */
1813 t
->sent
= dns_packet_unref(t
->sent
);
1815 /* First, create a dummy packet to calculate packet size. */
1816 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, false);
1820 r
= dns_packet_append_key(p
, dns_transaction_key(t
), 0, NULL
);
1826 if (dns_key_is_shared(dns_transaction_key(t
)))
1827 add_known_answers
= true;
1829 r
= dns_packet_append_zone(p
, t
, dns_transaction_key(t
), NULL
);
1833 /* Save appended keys */
1834 r
= set_ensure_put(&keys
, &dns_resource_key_hash_ops
, dns_transaction_key(t
));
1839 * For mDNS, we want to coalesce as many open queries in pending transactions into one single
1840 * query packet on the wire as possible. To achieve that, we iterate through all pending transactions
1841 * in our current scope, and see whether their timing constraints allow them to be sent.
1844 assert_se(sd_event_now(t
->scope
->manager
->event
, CLOCK_BOOTTIME
, &ts
) >= 0);
1846 for (bool restart
= true; restart
;) {
1848 LIST_FOREACH(transactions_by_scope
, other
, t
->scope
->transactions
) {
1849 size_t saved_packet_size
;
1850 bool append
= false;
1852 /* Skip ourselves */
1856 if (other
->state
!= DNS_TRANSACTION_PENDING
)
1859 if (other
->next_attempt_after
> ts
)
1862 if (!set_contains(keys
, dns_transaction_key(other
))) {
1863 r
= dns_packet_append_key(p
, dns_transaction_key(other
), 0, &saved_packet_size
);
1864 /* If we can't stuff more questions into the packet, just give up.
1865 * One of the 'other' transactions will fire later and take care of the rest. */
1871 r
= dns_packet_append_zone(p
, t
, dns_transaction_key(other
), NULL
);
1880 r
= dns_transaction_prepare(other
, ts
);
1885 dns_packet_truncate(p
, saved_packet_size
);
1887 /* In this case, not only this transaction, but multiple transactions may be
1888 * freed. Hence, we need to restart the loop. */
1893 usec_t timeout
= transaction_get_resend_timeout(other
);
1894 r
= dns_transaction_setup_timeout(other
, timeout
, usec_add(ts
, timeout
));
1898 if (dns_key_is_shared(dns_transaction_key(other
)))
1899 add_known_answers
= true;
1902 r
= set_ensure_put(&keys
, &dns_resource_key_hash_ops
, dns_transaction_key(other
));
1908 if (qdcount
>= UINT16_MAX
)
1913 /* Append known answer section if we're asking for any shared record */
1914 if (add_known_answers
) {
1915 r
= dns_cache_export_shared_to_packet(&t
->scope
->cache
, p
, ts
, 0);
1919 ancount
= be16toh(DNS_PACKET_HEADER(p
)->ancount
);
1922 /* Then, create actual packet. */
1923 p
= dns_packet_unref(p
);
1924 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, false);
1930 SET_FOREACH(k
, keys
) {
1931 r
= dns_packet_append_key(p
, k
, 0, NULL
);
1935 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(qdcount
);
1938 if (add_known_answers
) {
1939 r
= dns_cache_export_shared_to_packet(&t
->scope
->cache
, p
, ts
, ancount
);
1946 SET_FOREACH(k
, keys
) {
1947 r
= dns_packet_append_zone(p
, t
, k
, &nscount
);
1951 DNS_PACKET_HEADER(p
)->nscount
= htobe16(nscount
);
1953 t
->sent
= TAKE_PTR(p
);
1957 static int dns_transaction_make_packet(DnsTransaction
*t
) {
1958 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1963 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
)
1964 return dns_transaction_make_packet_mdns(t
);
1969 if (t
->bypass
&& t
->bypass
->protocol
== t
->scope
->protocol
) {
1970 /* If bypass logic is enabled and the protocol if the original packet and our scope match,
1971 * take the original packet, copy it, and patch in our new ID */
1972 r
= dns_packet_dup(&p
, t
->bypass
);
1976 r
= dns_packet_new_query(
1977 &p
, t
->scope
->protocol
,
1978 /* min_alloc_dsize = */ 0,
1979 /* dnssec_cd = */ !FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) &&
1980 t
->scope
->dnssec_mode
!= DNSSEC_NO
);
1984 r
= dns_packet_append_key(p
, dns_transaction_key(t
), 0, NULL
);
1988 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(1);
1991 DNS_PACKET_HEADER(p
)->id
= t
->id
;
1993 t
->sent
= TAKE_PTR(p
);
1997 int dns_transaction_go(DnsTransaction
*t
) {
2000 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
2004 /* Returns > 0 if the transaction is now pending, returns 0 if could be processed immediately and has
2005 * finished now. In the latter case, the transaction and query candidate objects must not be accessed.
2008 assert_se(sd_event_now(t
->scope
->manager
->event
, CLOCK_BOOTTIME
, &ts
) >= 0);
2010 r
= dns_transaction_prepare(t
, ts
);
2014 log_debug("Firing %s transaction %" PRIu16
" for <%s> scope %s on %s/%s (validate=%s).",
2015 t
->bypass
? "bypass" : "regular",
2017 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
),
2018 dns_protocol_to_string(t
->scope
->protocol
),
2019 t
->scope
->link
? t
->scope
->link
->ifname
: "*",
2020 af_to_name_short(t
->scope
->family
),
2021 yes_no(!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
)));
2023 if (!t
->initial_jitter_scheduled
&&
2024 IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_LLMNR
, DNS_PROTOCOL_MDNS
)) {
2027 /* RFC 4795 Section 2.7 suggests all LLMNR queries should be delayed by a random time from 0 to
2029 * RFC 6762 Section 8.1 suggests initial probe queries should be delayed by a random time from
2032 t
->initial_jitter_scheduled
= true;
2035 switch (t
->scope
->protocol
) {
2037 case DNS_PROTOCOL_LLMNR
:
2038 jitter
= random_u64_range(LLMNR_JITTER_INTERVAL_USEC
);
2041 case DNS_PROTOCOL_MDNS
:
2043 jitter
= random_u64_range(MDNS_PROBING_INTERVAL_USEC
);
2048 assert_not_reached();
2051 r
= dns_transaction_setup_timeout(t
, jitter
, ts
);
2055 log_debug("Delaying %s transaction %" PRIu16
" for " USEC_FMT
"us.",
2056 dns_protocol_to_string(t
->scope
->protocol
),
2062 /* Otherwise, we need to ask the network */
2063 r
= dns_transaction_make_packet(t
);
2067 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&&
2068 (dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), "in-addr.arpa") > 0 ||
2069 dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), "ip6.arpa") > 0)) {
2071 /* RFC 4795, Section 2.4. says reverse lookups shall
2072 * always be made via TCP on LLMNR */
2073 r
= dns_transaction_emit_tcp(t
);
2075 /* Try via UDP, and if that fails due to large size or lack of
2076 * support try via TCP */
2077 r
= dns_transaction_emit_udp(t
);
2079 log_debug("Sending query via TCP since it is too large.");
2080 else if (r
== -EAGAIN
)
2081 log_debug("Sending query via TCP since UDP isn't supported or DNS-over-TLS is selected.");
2082 if (IN_SET(r
, -EMSGSIZE
, -EAGAIN
))
2083 r
= dns_transaction_emit_tcp(t
);
2086 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2089 /* One of our own stub listeners */
2090 log_debug_errno(r
, "Detected that specified DNS server is our own extra listener, switching DNS servers.");
2092 dns_scope_next_dns_server(t
->scope
, t
->server
);
2094 if (dns_scope_get_dns_server(t
->scope
) == t
->server
) {
2095 log_debug_errno(r
, "Still pointing to extra listener after switching DNS servers, refusing operation.");
2096 dns_transaction_complete(t
, DNS_TRANSACTION_STUB_LOOP
);
2100 return dns_transaction_go(t
);
2103 /* No servers to send this to? */
2104 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
2107 if (r
== -EOPNOTSUPP
) {
2108 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
2109 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
2112 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& ERRNO_IS_DISCONNECT(r
)) {
2113 /* On LLMNR, if we cannot connect to a host via TCP when doing reverse lookups. This means we cannot
2114 * answer this request with this protocol. */
2115 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
2119 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2122 /* Couldn't send? Try immediately again, with a new server */
2123 dns_scope_next_dns_server(t
->scope
, t
->server
);
2125 return dns_transaction_go(t
);
2128 usec_t timeout
= transaction_get_resend_timeout(t
);
2129 r
= dns_transaction_setup_timeout(t
, timeout
, usec_add(ts
, timeout
));
2136 static int dns_transaction_find_cyclic(DnsTransaction
*t
, DnsTransaction
*aux
) {
2143 /* Try to find cyclic dependencies between transaction objects */
2148 SET_FOREACH(n
, aux
->dnssec_transactions
) {
2149 r
= dns_transaction_find_cyclic(t
, n
);
2157 static int dns_transaction_add_dnssec_transaction(DnsTransaction
*t
, DnsResourceKey
*key
, DnsTransaction
**ret
) {
2158 _cleanup_(dns_transaction_gcp
) DnsTransaction
*aux
= NULL
;
2165 aux
= dns_scope_find_transaction(t
->scope
, key
, t
->query_flags
);
2167 r
= dns_transaction_new(&aux
, t
->scope
, key
, NULL
, t
->query_flags
);
2171 if (set_contains(t
->dnssec_transactions
, aux
)) {
2176 r
= dns_transaction_find_cyclic(t
, aux
);
2180 char s
[DNS_RESOURCE_KEY_STRING_MAX
], saux
[DNS_RESOURCE_KEY_STRING_MAX
];
2182 return log_debug_errno(SYNTHETIC_ERRNO(ELOOP
),
2183 "Potential cyclic dependency, refusing to add transaction %" PRIu16
" (%s) as dependency for %" PRIu16
" (%s).",
2185 dns_resource_key_to_string(dns_transaction_key(t
), s
, sizeof s
),
2187 dns_resource_key_to_string(dns_transaction_key(aux
), saux
, sizeof saux
));
2191 r
= set_ensure_allocated(&aux
->notify_transactions_done
, NULL
);
2195 r
= set_ensure_put(&t
->dnssec_transactions
, NULL
, aux
);
2199 r
= set_ensure_put(&aux
->notify_transactions
, NULL
, t
);
2201 (void) set_remove(t
->dnssec_transactions
, aux
);
2205 *ret
= TAKE_PTR(aux
);
2209 static int dns_transaction_request_dnssec_rr(DnsTransaction
*t
, DnsResourceKey
*key
) {
2210 _cleanup_(dns_answer_unrefp
) DnsAnswer
*a
= NULL
;
2211 DnsTransaction
*aux
;
2217 /* Try to get the data from the trust anchor */
2218 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, key
, &a
);
2222 r
= dns_answer_extend(&t
->validated_keys
, a
);
2229 /* This didn't work, ask for it via the network/cache then. */
2230 r
= dns_transaction_add_dnssec_transaction(t
, key
, &aux
);
2231 if (r
== -ELOOP
) /* This would result in a cyclic dependency */
2236 if (aux
->state
== DNS_TRANSACTION_NULL
) {
2237 r
= dns_transaction_go(aux
);
2245 static int dns_transaction_negative_trust_anchor_lookup(DnsTransaction
*t
, const char *name
) {
2250 /* Check whether the specified name is in the NTA
2251 * database, either in the global one, or the link-local
2254 r
= dns_trust_anchor_lookup_negative(&t
->scope
->manager
->trust_anchor
, name
);
2258 if (!t
->scope
->link
)
2261 return link_negative_trust_anchor_lookup(t
->scope
->link
, name
);
2264 static int dns_transaction_has_negative_answer(DnsTransaction
*t
) {
2269 /* Checks whether the answer is negative, and lacks NSEC/NSEC3
2270 * RRs to prove it */
2272 r
= dns_transaction_has_positive_answer(t
, NULL
);
2278 /* Is this key explicitly listed as a negative trust anchor?
2279 * If so, it's nothing we need to care about */
2280 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(dns_transaction_key(t
)));
2286 static int dns_transaction_is_primary_response(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2292 /* Check if the specified RR is the "primary" response,
2293 * i.e. either matches the question precisely or is a
2294 * CNAME/DNAME for it. */
2296 r
= dns_resource_key_match_rr(dns_transaction_key(t
), rr
, NULL
);
2300 return dns_resource_key_match_cname_or_dname(dns_transaction_key(t
), rr
->key
, NULL
);
2303 static bool dns_transaction_dnssec_supported(DnsTransaction
*t
) {
2306 /* Checks whether our transaction's DNS server is assumed to be compatible with DNSSEC. Returns false as soon
2307 * as we changed our mind about a server, and now believe it is incompatible with DNSSEC. */
2309 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2312 /* If we have picked no server, then we are working from the cache or some other source, and DNSSEC might well
2313 * be supported, hence return true. */
2317 /* Note that we do not check the feature level actually used for the transaction but instead the feature level
2318 * the server is known to support currently, as the transaction feature level might be lower than what the
2319 * server actually supports, since we might have downgraded this transaction's feature level because we got a
2320 * SERVFAIL earlier and wanted to check whether downgrading fixes it. */
2322 return dns_server_dnssec_supported(t
->server
);
2325 static bool dns_transaction_dnssec_supported_full(DnsTransaction
*t
) {
2330 /* Checks whether our transaction our any of the auxiliary transactions couldn't do DNSSEC. */
2332 if (!dns_transaction_dnssec_supported(t
))
2335 SET_FOREACH(dt
, t
->dnssec_transactions
)
2336 if (!dns_transaction_dnssec_supported(dt
))
2342 int dns_transaction_request_dnssec_keys(DnsTransaction
*t
) {
2343 DnsResourceRecord
*rr
;
2350 * Retrieve all auxiliary RRs for the answer we got, so that
2351 * we can verify signatures or prove that RRs are rightfully
2352 * unsigned. Specifically:
2354 * - For RRSIG we get the matching DNSKEY
2355 * - For DNSKEY we get the matching DS
2356 * - For unsigned SOA/NS we get the matching DS
2357 * - For unsigned CNAME/DNAME/DS we get the parent SOA RR
2358 * - For other unsigned RRs we get the matching SOA RR
2359 * - For SOA/NS queries with no matching response RR, and no NSEC/NSEC3, the DS RR
2360 * - For DS queries with no matching response RRs, and no NSEC/NSEC3, the parent's SOA RR
2361 * - For other queries with no matching response RRs, and no NSEC/NSEC3, the SOA RR
2364 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) || t
->scope
->dnssec_mode
== DNSSEC_NO
)
2366 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
2367 return 0; /* We only need to validate stuff from the network */
2368 if (!dns_transaction_dnssec_supported(t
))
2369 return 0; /* If we can't do DNSSEC anyway there's no point in getting the auxiliary RRs */
2371 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
2373 if (dns_type_is_pseudo(rr
->key
->type
))
2376 /* If this RR is in the negative trust anchor, we don't need to validate it. */
2377 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2383 switch (rr
->key
->type
) {
2385 case DNS_TYPE_RRSIG
: {
2386 /* For each RRSIG we request the matching DNSKEY */
2387 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*dnskey
= NULL
;
2389 /* If this RRSIG is about a DNSKEY RR and the
2390 * signer is the same as the owner, then we
2391 * already have the DNSKEY, and we don't have
2392 * to look for more. */
2393 if (rr
->rrsig
.type_covered
== DNS_TYPE_DNSKEY
) {
2394 r
= dns_name_equal(rr
->rrsig
.signer
, dns_resource_key_name(rr
->key
));
2401 /* If the signer is not a parent of our
2402 * original query, then this is about an
2403 * auxiliary RRset, but not anything we asked
2404 * for. In this case we aren't interested,
2405 * because we don't want to request additional
2406 * RRs for stuff we didn't really ask for, and
2407 * also to avoid request loops, where
2408 * additional RRs from one transaction result
2409 * in another transaction whose additional RRs
2410 * point back to the original transaction, and
2412 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), rr
->rrsig
.signer
);
2418 dnskey
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DNSKEY
, rr
->rrsig
.signer
);
2422 log_debug("Requesting DNSKEY to validate transaction %" PRIu16
" (%s, RRSIG with key tag: %" PRIu16
").",
2423 t
->id
, dns_resource_key_name(rr
->key
), rr
->rrsig
.key_tag
);
2424 r
= dns_transaction_request_dnssec_rr(t
, dnskey
);
2430 case DNS_TYPE_DNSKEY
: {
2431 /* For each DNSKEY we request the matching DS */
2432 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
2434 /* If the DNSKEY we are looking at is not for
2435 * zone we are interested in, nor any of its
2436 * parents, we aren't interested, and don't
2437 * request it. After all, we don't want to end
2438 * up in request loops, and want to keep
2439 * additional traffic down. */
2441 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), dns_resource_key_name(rr
->key
));
2447 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
2451 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, DNSKEY with key tag: %" PRIu16
").",
2452 t
->id
, dns_resource_key_name(rr
->key
), dnssec_keytag(rr
, false));
2453 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2462 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
2464 /* For an unsigned SOA or NS, try to acquire
2465 * the matching DS RR, as we are at a zone cut
2466 * then, and whether a DS exists tells us
2467 * whether the zone is signed. Do so only if
2468 * this RR matches our original question,
2471 r
= dns_resource_key_match_rr(dns_transaction_key(t
), rr
, NULL
);
2475 /* Hmm, so this SOA RR doesn't match our original question. In this case, maybe this is
2476 * a negative reply, and we need the SOA RR's TTL in order to cache a negative entry?
2477 * If so, we need to validate it, too. */
2479 r
= dns_answer_match_key(t
->answer
, dns_transaction_key(t
), NULL
);
2482 if (r
> 0) /* positive reply, we won't need the SOA and hence don't need to validate
2486 /* Only bother with this if the SOA/NS RR we are looking at is actually a parent of
2487 * what we are looking for, otherwise there's no value in it for us. */
2488 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), dns_resource_key_name(rr
->key
));
2495 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2501 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
2505 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, unsigned SOA/NS RRset).",
2506 t
->id
, dns_resource_key_name(rr
->key
));
2507 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2515 case DNS_TYPE_CNAME
:
2516 case DNS_TYPE_DNAME
: {
2517 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2520 /* CNAMEs and DNAMEs cannot be located at a
2521 * zone apex, hence ask for the parent SOA for
2522 * unsigned CNAME/DNAME RRs, maybe that's the
2523 * apex. But do all that only if this is
2524 * actually a response to our original
2527 * Similar for DS RRs, which are signed when
2528 * the parent SOA is signed. */
2530 r
= dns_transaction_is_primary_response(t
, rr
);
2536 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2542 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
2548 name
= dns_resource_key_name(rr
->key
);
2549 r
= dns_name_parent(&name
);
2555 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, name
);
2559 log_debug("Requesting parent SOA to validate transaction %" PRIu16
" (%s, unsigned CNAME/DNAME/DS RRset).",
2560 t
->id
, dns_resource_key_name(rr
->key
));
2561 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2569 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2571 /* For other unsigned RRsets (including
2572 * NSEC/NSEC3!), look for proof the zone is
2573 * unsigned, by requesting the SOA RR of the
2574 * zone. However, do so only if they are
2575 * directly relevant to our original
2578 r
= dns_transaction_is_primary_response(t
, rr
);
2584 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2590 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, dns_resource_key_name(rr
->key
));
2594 log_debug("Requesting SOA to validate transaction %" PRIu16
" (%s, unsigned non-SOA/NS RRset <%s>).",
2595 t
->id
, dns_resource_key_name(rr
->key
), dns_resource_record_to_string(rr
));
2596 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2603 /* Above, we requested everything necessary to validate what
2604 * we got. Now, let's request what we need to validate what we
2607 r
= dns_transaction_has_negative_answer(t
);
2611 const char *name
, *signed_status
;
2614 name
= dns_resource_key_name(dns_transaction_key(t
));
2615 signed_status
= dns_answer_contains_nsec_or_nsec3(t
->answer
) ? "signed" : "unsigned";
2617 /* If this was a SOA or NS request, then check if there's a DS RR for the same domain. Note that this
2618 * could also be used as indication that we are not at a zone apex, but in real world setups there are
2619 * too many broken DNS servers (Hello, incapdns.net!) where non-terminal zones return NXDOMAIN even
2620 * though they have further children. If this was a DS request, then it's signed when the parent zone
2621 * is signed, hence ask the parent SOA in that case. If this was any other RR then ask for the SOA RR,
2622 * to see if that is signed. */
2624 if (dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
2625 r
= dns_name_parent(&name
);
2627 type
= DNS_TYPE_SOA
;
2628 log_debug("Requesting parent SOA (%s %s) to validate transaction %" PRIu16
" (%s, %s empty DS response).",
2629 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT
), name
, t
->id
,
2630 dns_resource_key_name(dns_transaction_key(t
)), signed_status
);
2634 } else if (IN_SET(dns_transaction_key(t
)->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
)) {
2637 log_debug("Requesting DS (%s %s) to validate transaction %" PRIu16
" (%s, %s empty SOA/NS response).",
2638 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT
), name
, t
->id
, name
, signed_status
);
2641 type
= DNS_TYPE_SOA
;
2642 log_debug("Requesting SOA (%s %s) to validate transaction %" PRIu16
" (%s, %s empty non-SOA/NS/DS response).",
2643 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT
), name
, t
->id
, name
, signed_status
);
2647 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2649 soa
= dns_resource_key_new(dns_transaction_key(t
)->class, type
, name
);
2653 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2659 return dns_transaction_dnssec_is_live(t
);
2662 void dns_transaction_notify(DnsTransaction
*t
, DnsTransaction
*source
) {
2666 /* Invoked whenever any of our auxiliary DNSSEC transactions completed its work. If the state is still PENDING,
2667 we are still in the loop that adds further DNSSEC transactions, hence don't check if we are ready yet. If
2668 the state is VALIDATING however, we should check if we are complete now. */
2670 if (t
->state
== DNS_TRANSACTION_VALIDATING
)
2671 dns_transaction_process_dnssec(t
);
2674 static int dns_transaction_validate_dnskey_by_ds(DnsTransaction
*t
) {
2675 DnsAnswerItem
*item
;
2680 /* Add all DNSKEY RRs from the answer that are validated by DS
2681 * RRs from the list of validated keys to the list of
2682 * validated keys. */
2684 DNS_ANSWER_FOREACH_ITEM(item
, t
->answer
) {
2686 r
= dnssec_verify_dnskey_by_ds_search(item
->rr
, t
->validated_keys
);
2692 /* If so, the DNSKEY is validated too. */
2693 r
= dns_answer_add_extend(&t
->validated_keys
, item
->rr
, item
->ifindex
, item
->flags
|DNS_ANSWER_AUTHENTICATED
, item
->rrsig
);
2701 static int dns_transaction_requires_rrsig(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2707 /* Checks if the RR we are looking for must be signed with an
2708 * RRSIG. This is used for positive responses. */
2710 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2713 if (dns_type_is_pseudo(rr
->key
->type
))
2716 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2722 switch (rr
->key
->type
) {
2724 case DNS_TYPE_RRSIG
:
2725 /* RRSIGs are the signatures themselves, they need no signing. */
2732 /* For SOA or NS RRs we look for a matching DS transaction */
2734 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2736 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2738 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_DS
)
2741 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), dns_resource_key_name(rr
->key
));
2747 /* We found a DS transactions for the SOA/NS
2748 * RRs we are looking at. If it discovered signed DS
2749 * RRs, then we need to be signed, too. */
2751 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
2754 return dns_answer_match_key(dt
->answer
, dns_transaction_key(dt
), NULL
);
2757 /* We found nothing that proves this is safe to leave
2758 * this unauthenticated, hence ask inist on
2759 * authentication. */
2764 case DNS_TYPE_CNAME
:
2765 case DNS_TYPE_DNAME
: {
2766 const char *parent
= NULL
;
2770 * CNAME/DNAME RRs cannot be located at a zone apex, hence look directly for the parent SOA.
2772 * DS RRs are signed if the parent is signed, hence also look at the parent SOA
2775 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2777 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2779 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_SOA
)
2783 parent
= dns_resource_key_name(rr
->key
);
2784 r
= dns_name_parent(&parent
);
2788 if (rr
->key
->type
== DNS_TYPE_DS
)
2791 /* A CNAME/DNAME without a parent? That's sooo weird. */
2792 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG
),
2793 "Transaction %" PRIu16
" claims CNAME/DNAME at root. Refusing.", t
->id
);
2797 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), parent
);
2803 return FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2812 /* Any other kind of RR (including DNSKEY/NSEC/NSEC3). Let's see if our SOA lookup was authenticated */
2814 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2816 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2818 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_SOA
)
2821 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), dns_resource_key_name(rr
->key
));
2827 /* We found the transaction that was supposed to find the SOA RR for us. It was
2828 * successful, but found no RR for us. This means we are not at a zone cut. In this
2829 * case, we require authentication if the SOA lookup was authenticated too. */
2830 return FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2837 static int dns_transaction_in_private_tld(DnsTransaction
*t
, const DnsResourceKey
*key
) {
2842 /* If DNSSEC downgrade mode is on, checks whether the
2843 * specified RR is one level below a TLD we have proven not to
2844 * exist. In such a case we assume that this is a private
2845 * domain, and permit it.
2847 * This detects cases like the Fritz!Box router networks. Each
2848 * Fritz!Box router serves a private "fritz.box" zone, in the
2849 * non-existing TLD "box". Requests for the "fritz.box" domain
2850 * are served by the router itself, while requests for the
2851 * "box" domain will result in NXDOMAIN.
2853 * Note that this logic is unable to detect cases where a
2854 * router serves a private DNS zone directly under
2855 * non-existing TLD. In such a case we cannot detect whether
2856 * the TLD is supposed to exist or not, as all requests we
2857 * make for it will be answered by the router's zone, and not
2858 * by the root zone. */
2862 if (t
->scope
->dnssec_mode
!= DNSSEC_ALLOW_DOWNGRADE
)
2863 return false; /* In strict DNSSEC mode what doesn't exist, doesn't exist */
2865 tld
= dns_resource_key_name(key
);
2866 r
= dns_name_parent(&tld
);
2870 return false; /* Already the root domain */
2872 if (!dns_name_is_single_label(tld
))
2875 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2877 if (dns_transaction_key(dt
)->class != key
->class)
2880 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), tld
);
2886 /* We found an auxiliary lookup we did for the TLD. If
2887 * that returned with NXDOMAIN, we know the TLD didn't
2888 * exist, and hence this might be a private zone. */
2890 return dt
->answer_rcode
== DNS_RCODE_NXDOMAIN
;
2896 static int dns_transaction_requires_nsec(DnsTransaction
*t
) {
2897 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
2905 /* Checks if we need to insist on NSEC/NSEC3 RRs for proving
2906 * this negative reply */
2908 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2911 if (dns_type_is_pseudo(dns_transaction_key(t
)->type
))
2914 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(dns_transaction_key(t
)));
2920 r
= dns_transaction_in_private_tld(t
, dns_transaction_key(t
));
2924 /* The lookup is from a TLD that is proven not to
2925 * exist, and we are in downgrade mode, hence ignore
2926 * that fact that we didn't get any NSEC RRs. */
2928 log_info("Detected a negative query %s in a private DNS zone, permitting unsigned response.",
2929 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
));
2933 name
= dns_resource_key_name(dns_transaction_key(t
));
2935 if (dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
2937 /* We got a negative reply for this DS lookup? DS RRs are signed when their parent zone is signed,
2938 * hence check the parent SOA in this case. */
2940 r
= dns_name_parent(&name
);
2946 type
= DNS_TYPE_SOA
;
2948 } else if (IN_SET(dns_transaction_key(t
)->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
))
2949 /* We got a negative reply for this SOA/NS lookup? If so, check if there's a DS RR for this */
2952 /* For all other negative replies, check for the SOA lookup */
2953 type
= DNS_TYPE_SOA
;
2955 /* For all other RRs we check the SOA on the same level to see
2956 * if it's signed. */
2958 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2960 if (dns_transaction_key(dt
)->class != dns_transaction_key(t
)->class)
2962 if (dns_transaction_key(dt
)->type
!= type
)
2965 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), name
);
2971 return FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2974 /* If in doubt, require NSEC/NSEC3 */
2978 static int dns_transaction_dnskey_authenticated(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2979 DnsResourceRecord
*rrsig
;
2983 /* Checks whether any of the DNSKEYs used for the RRSIGs for
2984 * the specified RRset is authenticated (i.e. has a matching
2987 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2993 DNS_ANSWER_FOREACH(rrsig
, t
->answer
) {
2996 r
= dnssec_key_match_rrsig(rr
->key
, rrsig
);
3002 SET_FOREACH(dt
, t
->dnssec_transactions
) {
3004 if (dns_transaction_key(dt
)->class != rr
->key
->class)
3007 if (dns_transaction_key(dt
)->type
== DNS_TYPE_DNSKEY
) {
3009 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), rrsig
->rrsig
.signer
);
3015 /* OK, we found an auxiliary DNSKEY lookup. If that lookup is authenticated,
3018 if (FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
3023 } else if (dns_transaction_key(dt
)->type
== DNS_TYPE_DS
) {
3025 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), rrsig
->rrsig
.signer
);
3031 /* OK, we found an auxiliary DS lookup. If that lookup is authenticated and
3032 * non-zero, we won! */
3034 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
3037 return dns_answer_match_key(dt
->answer
, dns_transaction_key(dt
), NULL
);
3042 return found
? false : -ENXIO
;
3045 static int dns_transaction_known_signed(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
3049 /* We know that the root domain is signed, hence if it appears
3050 * not to be signed, there's a problem with the DNS server */
3052 return rr
->key
->class == DNS_CLASS_IN
&&
3053 dns_name_is_root(dns_resource_key_name(rr
->key
));
3056 static int dns_transaction_check_revoked_trust_anchors(DnsTransaction
*t
) {
3057 DnsResourceRecord
*rr
;
3062 /* Maybe warn the user that we encountered a revoked DNSKEY
3063 * for a key from our trust anchor. Note that we don't care
3064 * whether the DNSKEY can be authenticated or not. It's
3065 * sufficient if it is self-signed. */
3067 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
3068 r
= dns_trust_anchor_check_revoked(&t
->scope
->manager
->trust_anchor
, rr
, t
->answer
);
3076 static int dns_transaction_invalidate_revoked_keys(DnsTransaction
*t
) {
3082 /* Removes all DNSKEY/DS objects from t->validated_keys that
3083 * our trust anchors database considers revoked. */
3086 DnsResourceRecord
*rr
;
3090 DNS_ANSWER_FOREACH(rr
, t
->validated_keys
) {
3091 r
= dns_trust_anchor_is_revoked(&t
->scope
->manager
->trust_anchor
, rr
);
3095 r
= dns_answer_remove_by_rr(&t
->validated_keys
, rr
);
3109 static int dns_transaction_copy_validated(DnsTransaction
*t
) {
3115 /* Copy all validated RRs from the auxiliary DNSSEC transactions into our set of validated RRs */
3117 SET_FOREACH(dt
, t
->dnssec_transactions
) {
3119 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
3122 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
3125 r
= dns_answer_extend(&t
->validated_keys
, dt
->answer
);
3134 DNSSEC_PHASE_DNSKEY
, /* Phase #1, only validate DNSKEYs */
3135 DNSSEC_PHASE_NSEC
, /* Phase #2, only validate NSEC+NSEC3 */
3136 DNSSEC_PHASE_ALL
, /* Phase #3, validate everything else */
3139 static int dnssec_validate_records(
3143 DnsAnswer
**validated
) {
3145 DnsResourceRecord
*rr
;
3148 /* Returns negative on error, 0 if validation failed, 1 to restart validation, 2 when finished. */
3150 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
3151 _unused_
_cleanup_(dns_resource_record_unrefp
) DnsResourceRecord
*rr_ref
= dns_resource_record_ref(rr
);
3152 DnsResourceRecord
*rrsig
= NULL
;
3153 DnssecResult result
;
3155 switch (rr
->key
->type
) {
3156 case DNS_TYPE_RRSIG
:
3159 case DNS_TYPE_DNSKEY
:
3160 /* We validate DNSKEYs only in the DNSKEY and ALL phases */
3161 if (phase
== DNSSEC_PHASE_NSEC
)
3166 case DNS_TYPE_NSEC3
:
3169 /* We validate NSEC/NSEC3 only in the NSEC and ALL phases */
3170 if (phase
== DNSSEC_PHASE_DNSKEY
)
3175 /* We validate all other RRs only in the ALL phases */
3176 if (phase
!= DNSSEC_PHASE_ALL
)
3180 r
= dnssec_verify_rrset_search(
3190 log_debug("Looking at %s: %s", strna(dns_resource_record_to_string(rr
)), dnssec_result_to_string(result
));
3192 if (result
== DNSSEC_VALIDATED
) {
3195 if (rr
->key
->type
== DNS_TYPE_DNSKEY
) {
3196 /* If we just validated a DNSKEY RRset, then let's add these keys to
3197 * the set of validated keys for this transaction. */
3199 r
= dns_answer_copy_by_key(&t
->validated_keys
, t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
, rrsig
);
3203 /* Some of the DNSKEYs we just added might already have been revoked,
3204 * remove them again in that case. */
3205 r
= dns_transaction_invalidate_revoked_keys(t
);
3210 /* Add the validated RRset to the new list of validated RRsets, and remove it from
3211 * the unvalidated RRsets. We mark the RRset as authenticated and cacheable. */
3212 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
, rrsig
);
3216 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_SECURE
, rr
->key
);
3218 /* Exit the loop, we dropped something from the answer, start from the beginning */
3222 /* If we haven't read all DNSKEYs yet a negative result of the validation is irrelevant, as
3223 * there might be more DNSKEYs coming. Similar, if we haven't read all NSEC/NSEC3 RRs yet,
3224 * we cannot do positive wildcard proofs yet, as those require the NSEC/NSEC3 RRs. */
3225 if (phase
!= DNSSEC_PHASE_ALL
)
3228 if (result
== DNSSEC_VALIDATED_WILDCARD
) {
3229 bool authenticated
= false;
3234 /* This RRset validated, but as a wildcard. This means we need
3235 * to prove via NSEC/NSEC3 that no matching non-wildcard RR exists. */
3237 /* First step, determine the source of synthesis */
3238 r
= dns_resource_record_source(rrsig
, &source
);
3242 r
= dnssec_test_positive_wildcard(*validated
,
3243 dns_resource_key_name(rr
->key
),
3245 rrsig
->rrsig
.signer
,
3248 /* Unless the NSEC proof showed that the key really doesn't exist something is off. */
3250 result
= DNSSEC_INVALID
;
3252 r
= dns_answer_move_by_key(
3256 authenticated
? (DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
) : 0,
3261 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, rr
->key
);
3263 /* Exit the loop, we dropped something from the answer, start from the beginning */
3268 if (result
== DNSSEC_NO_SIGNATURE
) {
3269 r
= dns_transaction_requires_rrsig(t
, rr
);
3273 /* Data does not require signing. In that case, just copy it over,
3274 * but remember that this is by no means authenticated. */
3275 r
= dns_answer_move_by_key(
3284 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3288 r
= dns_transaction_known_signed(t
, rr
);
3292 /* This is an RR we know has to be signed. If it isn't this means
3293 * the server is not attaching RRSIGs, hence complain. */
3295 dns_server_packet_rrsig_missing(t
->server
, t
->current_feature_level
);
3297 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
3299 /* Downgrading is OK? If so, just consider the information unsigned */
3301 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3305 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3309 /* Otherwise, fail */
3310 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
3314 r
= dns_transaction_in_private_tld(t
, rr
->key
);
3318 char s
[DNS_RESOURCE_KEY_STRING_MAX
];
3320 /* The data is from a TLD that is proven not to exist, and we are in downgrade
3321 * mode, hence ignore the fact that this was not signed. */
3323 log_info("Detected RRset %s is in a private DNS zone, permitting unsigned RRs.",
3324 dns_resource_key_to_string(rr
->key
, s
, sizeof s
));
3326 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3330 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3335 /* https://datatracker.ietf.org/doc/html/rfc6840#section-5.2 */
3336 if (result
== DNSSEC_UNSUPPORTED_ALGORITHM
) {
3337 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3341 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3347 DNSSEC_SIGNATURE_EXPIRED
)) {
3349 r
= dns_transaction_dnskey_authenticated(t
, rr
);
3350 if (r
< 0 && r
!= -ENXIO
)
3353 /* The DNSKEY transaction was not authenticated, this means there's
3354 * no DS for this, which means it's OK if no keys are found for this signature. */
3356 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3360 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3365 r
= dns_transaction_is_primary_response(t
, rr
);
3369 /* Look for a matching DNAME for this CNAME */
3370 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
3374 /* Also look among the stuff we already validated */
3375 r
= dns_answer_has_dname_for_cname(*validated
, rr
);
3383 DNSSEC_SIGNATURE_EXPIRED
,
3384 DNSSEC_NO_SIGNATURE
))
3385 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, rr
->key
);
3386 else /* DNSSEC_MISSING_KEY or DNSSEC_UNSUPPORTED_ALGORITHM */
3387 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, rr
->key
);
3389 /* This is a primary response to our question, and it failed validation.
3391 t
->answer_dnssec_result
= result
;
3395 /* This is a primary response, but we do have a DNAME RR
3396 * in the RR that can replay this CNAME, hence rely on
3397 * that, and we can remove the CNAME in favour of it. */
3400 /* This is just some auxiliary data. Just remove the RRset and continue. */
3401 r
= dns_answer_remove_by_key(&t
->answer
, rr
->key
);
3405 /* We dropped something from the answer, start from the beginning. */
3409 return 2; /* Finito. */
3412 int dns_transaction_validate_dnssec(DnsTransaction
*t
) {
3413 _cleanup_(dns_answer_unrefp
) DnsAnswer
*validated
= NULL
;
3415 DnsAnswerFlags flags
;
3417 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
3421 /* We have now collected all DS and DNSKEY RRs in t->validated_keys, let's see which RRs we can now
3422 * authenticate with that. */
3424 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) || t
->scope
->dnssec_mode
== DNSSEC_NO
)
3427 /* Already validated */
3428 if (t
->answer_dnssec_result
!= _DNSSEC_RESULT_INVALID
)
3431 /* Our own stuff needs no validation */
3432 if (IN_SET(t
->answer_source
, DNS_TRANSACTION_ZONE
, DNS_TRANSACTION_TRUST_ANCHOR
)) {
3433 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3434 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, true);
3438 /* Cached stuff is not affected by validation. */
3439 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
3442 if (!dns_transaction_dnssec_supported_full(t
)) {
3443 /* The server does not support DNSSEC, or doesn't augment responses with RRSIGs. */
3444 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
3445 log_debug("Not validating response for %" PRIu16
", used server feature level does not support DNSSEC.", t
->id
);
3449 log_debug("Validating response from transaction %" PRIu16
" (%s).",
3451 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
));
3453 /* First, see if this response contains any revoked trust
3454 * anchors we care about */
3455 r
= dns_transaction_check_revoked_trust_anchors(t
);
3459 /* Third, copy all RRs we acquired successfully from auxiliary RRs over. */
3460 r
= dns_transaction_copy_validated(t
);
3464 /* Second, see if there are DNSKEYs we already know a
3465 * validated DS for. */
3466 r
= dns_transaction_validate_dnskey_by_ds(t
);
3470 /* Fourth, remove all DNSKEY and DS RRs again that our trust
3471 * anchor says are revoked. After all we might have marked
3472 * some keys revoked above, but they might still be lingering
3473 * in our validated_keys list. */
3474 r
= dns_transaction_invalidate_revoked_keys(t
);
3478 phase
= DNSSEC_PHASE_DNSKEY
;
3480 bool have_nsec
= false;
3482 r
= dnssec_validate_records(t
, phase
, &have_nsec
, &validated
);
3486 /* Try again as long as we managed to achieve something */
3490 if (phase
== DNSSEC_PHASE_DNSKEY
&& have_nsec
) {
3491 /* OK, we processed all DNSKEYs, and there are NSEC/NSEC3 RRs, look at those now. */
3492 phase
= DNSSEC_PHASE_NSEC
;
3496 if (phase
!= DNSSEC_PHASE_ALL
) {
3497 /* OK, we processed all DNSKEYs and NSEC/NSEC3 RRs, look at all the rest now.
3498 * Note that in this third phase we start to remove RRs we couldn't validate. */
3499 phase
= DNSSEC_PHASE_ALL
;
3507 DNS_ANSWER_REPLACE(t
->answer
, TAKE_PTR(validated
));
3509 /* At this point the answer only contains validated
3510 * RRsets. Now, let's see if it actually answers the question
3511 * we asked. If so, great! If it doesn't, then see if
3512 * NSEC/NSEC3 can prove this. */
3513 r
= dns_transaction_has_positive_answer(t
, &flags
);
3515 /* Yes, it answers the question! */
3517 if (flags
& DNS_ANSWER_AUTHENTICATED
) {
3518 /* The answer is fully authenticated, yay. */
3519 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3520 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3521 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, true);
3523 /* The answer is not fully authenticated. */
3524 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3525 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3528 } else if (r
== 0) {
3529 DnssecNsecResult nr
;
3530 bool authenticated
= false;
3532 /* Bummer! Let's check NSEC/NSEC3 */
3533 r
= dnssec_nsec_test(t
->answer
, dns_transaction_key(t
), &nr
, &authenticated
, &t
->answer_nsec_ttl
);
3539 case DNSSEC_NSEC_NXDOMAIN
:
3540 /* NSEC proves the domain doesn't exist. Very good. */
3541 log_debug("Proved NXDOMAIN via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3542 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3543 t
->answer_rcode
= DNS_RCODE_NXDOMAIN
;
3544 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, authenticated
);
3546 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, dns_transaction_key(t
));
3549 case DNSSEC_NSEC_NODATA
:
3550 /* NSEC proves that there's no data here, very good. */
3551 log_debug("Proved NODATA via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3552 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3553 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3554 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, authenticated
);
3556 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, dns_transaction_key(t
));
3559 case DNSSEC_NSEC_OPTOUT
:
3560 /* NSEC3 says the data might not be signed */
3561 log_debug("Data is NSEC3 opt-out via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3562 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3563 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3565 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, dns_transaction_key(t
));
3568 case DNSSEC_NSEC_NO_RR
:
3569 /* No NSEC data? Bummer! */
3571 r
= dns_transaction_requires_nsec(t
);
3575 t
->answer_dnssec_result
= DNSSEC_NO_SIGNATURE
;
3576 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, dns_transaction_key(t
));
3578 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3579 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3580 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, dns_transaction_key(t
));
3585 case DNSSEC_NSEC_UNSUPPORTED_ALGORITHM
:
3586 /* We don't know the NSEC3 algorithm used? */
3587 t
->answer_dnssec_result
= DNSSEC_UNSUPPORTED_ALGORITHM
;
3588 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, dns_transaction_key(t
));
3591 case DNSSEC_NSEC_FOUND
:
3592 case DNSSEC_NSEC_CNAME
:
3593 /* NSEC says it needs to be there, but we couldn't find it? Bummer! */
3594 t
->answer_dnssec_result
= DNSSEC_NSEC_MISMATCH
;
3595 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, dns_transaction_key(t
));
3599 assert_not_reached();
3606 static const char* const dns_transaction_state_table
[_DNS_TRANSACTION_STATE_MAX
] = {
3607 [DNS_TRANSACTION_NULL
] = "null",
3608 [DNS_TRANSACTION_PENDING
] = "pending",
3609 [DNS_TRANSACTION_VALIDATING
] = "validating",
3610 [DNS_TRANSACTION_RCODE_FAILURE
] = "rcode-failure",
3611 [DNS_TRANSACTION_SUCCESS
] = "success",
3612 [DNS_TRANSACTION_NO_SERVERS
] = "no-servers",
3613 [DNS_TRANSACTION_TIMEOUT
] = "timeout",
3614 [DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
] = "attempts-max-reached",
3615 [DNS_TRANSACTION_INVALID_REPLY
] = "invalid-reply",
3616 [DNS_TRANSACTION_ERRNO
] = "errno",
3617 [DNS_TRANSACTION_ABORTED
] = "aborted",
3618 [DNS_TRANSACTION_DNSSEC_FAILED
] = "dnssec-failed",
3619 [DNS_TRANSACTION_NO_TRUST_ANCHOR
] = "no-trust-anchor",
3620 [DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
] = "rr-type-unsupported",
3621 [DNS_TRANSACTION_NETWORK_DOWN
] = "network-down",
3622 [DNS_TRANSACTION_NOT_FOUND
] = "not-found",
3623 [DNS_TRANSACTION_NO_SOURCE
] = "no-source",
3624 [DNS_TRANSACTION_STUB_LOOP
] = "stub-loop",
3626 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state
, DnsTransactionState
);
3628 static const char* const dns_transaction_source_table
[_DNS_TRANSACTION_SOURCE_MAX
] = {
3629 [DNS_TRANSACTION_NETWORK
] = "network",
3630 [DNS_TRANSACTION_CACHE
] = "cache",
3631 [DNS_TRANSACTION_ZONE
] = "zone",
3632 [DNS_TRANSACTION_TRUST_ANCHOR
] = "trust-anchor",
3634 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source
, DnsTransactionSource
);