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
,
820 dns_transaction_key(t
),
823 DNS_PACKET_CD(t
->received
) ? t
->received
: NULL
, /* only cache full packets with CD on,
824 * since our usecase for caching them
825 * is "bypass" mode which is only
826 * enabled for CD packets. */
827 t
->answer_query_flags
,
828 t
->answer_dnssec_result
,
831 &t
->received
->sender
);
834 static bool dns_transaction_dnssec_is_live(DnsTransaction
*t
) {
839 SET_FOREACH(dt
, t
->dnssec_transactions
)
840 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
846 static int dns_transaction_dnssec_ready(DnsTransaction
*t
) {
852 /* Checks whether the auxiliary DNSSEC transactions of our transaction have completed, or are still
853 * ongoing. Returns 0, if we aren't ready for the DNSSEC validation, positive if we are. */
855 SET_FOREACH(dt
, t
->dnssec_transactions
) {
859 case DNS_TRANSACTION_NULL
:
860 case DNS_TRANSACTION_PENDING
:
861 case DNS_TRANSACTION_VALIDATING
:
865 case DNS_TRANSACTION_RCODE_FAILURE
:
866 if (!IN_SET(dt
->answer_rcode
, DNS_RCODE_NXDOMAIN
, DNS_RCODE_SERVFAIL
)) {
867 log_debug("Auxiliary DNSSEC RR query failed with rcode=%s.", FORMAT_DNS_RCODE(dt
->answer_rcode
));
871 /* Fall-through: NXDOMAIN/SERVFAIL is good enough for us. This is because some DNS servers
872 * erroneously return NXDOMAIN/SERVFAIL for empty non-terminals (Akamai...) or missing DS
873 * records (Facebook), and we need to handle that nicely, when asking for parent SOA or similar
874 * RRs to make unsigned proofs. */
876 case DNS_TRANSACTION_SUCCESS
:
880 case DNS_TRANSACTION_DNSSEC_FAILED
:
881 /* We handle DNSSEC failures different from other errors, as we care about the DNSSEC
882 * validation result */
884 log_debug("Auxiliary DNSSEC RR query failed validation: %s", dnssec_result_to_string(dt
->answer_dnssec_result
));
885 t
->answer_dnssec_result
= dt
->answer_dnssec_result
; /* Copy error code over */
886 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
890 log_debug("Auxiliary DNSSEC RR query failed with %s", dns_transaction_state_to_string(dt
->state
));
895 /* All is ready, we can go and validate */
899 /* Some auxiliary DNSSEC transaction failed for some reason. Maybe we learned something about the
900 * server due to this failure, and the feature level is now different? Let's see and restart the
901 * transaction if so. If not, let's propagate the auxiliary failure.
903 * This is particularly relevant if an auxiliary request figured out that DNSSEC doesn't work, and we
904 * are in permissive DNSSEC mode, and thus should restart things without DNSSEC magic. */
905 r
= dns_transaction_maybe_restart(t
);
909 return 0; /* don't validate just yet, we restarted things */
911 t
->answer_dnssec_result
= DNSSEC_FAILED_AUXILIARY
;
912 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
916 static void dns_transaction_process_dnssec(DnsTransaction
*t
) {
921 /* Are there ongoing DNSSEC transactions? If so, let's wait for them. */
922 r
= dns_transaction_dnssec_ready(t
);
925 if (r
== 0) /* We aren't ready yet (or one of our auxiliary transactions failed, and we shouldn't validate now */
928 /* See if we learnt things from the additional DNSSEC transactions, that we didn't know before, and better
929 * restart the lookup immediately. */
930 r
= dns_transaction_maybe_restart(t
);
933 if (r
> 0) /* Transaction got restarted... */
936 /* All our auxiliary DNSSEC transactions are complete now. Try
937 * to validate our RRset now. */
938 r
= dns_transaction_validate_dnssec(t
);
940 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
946 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
&&
947 t
->scope
->dnssec_mode
== DNSSEC_YES
) {
949 /* We are not in automatic downgrade mode, and the server is bad. Let's try a different server, maybe
952 if (dns_transaction_limited_retry(t
))
955 /* OK, let's give up, apparently all servers we tried didn't work. */
956 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
960 if (!IN_SET(t
->answer_dnssec_result
,
961 _DNSSEC_RESULT_INVALID
, /* No DNSSEC validation enabled */
962 DNSSEC_VALIDATED
, /* Answer is signed and validated successfully */
963 DNSSEC_UNSIGNED
, /* Answer is right-fully unsigned */
964 DNSSEC_INCOMPATIBLE_SERVER
)) { /* Server does not do DNSSEC (Yay, we are downgrade attack vulnerable!) */
965 dns_transaction_complete(t
, DNS_TRANSACTION_DNSSEC_FAILED
);
969 if (t
->answer_dnssec_result
== DNSSEC_INCOMPATIBLE_SERVER
)
970 dns_server_warn_downgrade(t
->server
);
972 dns_transaction_cache_answer(t
);
974 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
975 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
977 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
982 dns_transaction_complete_errno(t
, r
);
985 static int dns_transaction_has_positive_answer(DnsTransaction
*t
, DnsAnswerFlags
*flags
) {
990 /* Checks whether the answer is positive, i.e. either a direct
991 * answer to the question, or a CNAME/DNAME for it */
993 r
= dns_answer_match_key(t
->answer
, dns_transaction_key(t
), flags
);
997 r
= dns_answer_find_cname_or_dname(t
->answer
, dns_transaction_key(t
), NULL
, flags
);
1004 static int dns_transaction_fix_rcode(DnsTransaction
*t
) {
1009 /* Fix up the RCODE to SUCCESS if we get at least one matching RR in a response. Note that this contradicts the
1010 * DNS RFCs a bit. Specifically, RFC 6604 Section 3 clarifies that the RCODE shall say something about a
1011 * CNAME/DNAME chain element coming after the last chain element contained in the message, and not the first
1012 * one included. However, it also indicates that not all DNS servers implement this correctly. Moreover, when
1013 * using DNSSEC we usually only can prove the first element of a CNAME/DNAME chain anyway, hence let's settle
1014 * on always processing the RCODE as referring to the immediate look-up we do, i.e. the first element of a
1015 * CNAME/DNAME chain. This way, we uniformly handle CNAME/DNAME chains, regardless if the DNS server
1016 * incorrectly implements RCODE, whether DNSSEC is in use, or whether the DNS server only supplied us with an
1017 * incomplete CNAME/DNAME chain.
1019 * Or in other words: if we get at least one positive reply in a message we patch NXDOMAIN to become SUCCESS,
1020 * and then rely on the CNAME chasing logic to figure out that there's actually a CNAME error with a new
1023 if (t
->answer_rcode
!= DNS_RCODE_NXDOMAIN
)
1026 r
= dns_transaction_has_positive_answer(t
, NULL
);
1030 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1034 void dns_transaction_process_reply(DnsTransaction
*t
, DnsPacket
*p
, bool encrypted
) {
1035 bool retry_with_tcp
= false;
1041 assert(t
->scope
->manager
);
1043 if (t
->state
!= DNS_TRANSACTION_PENDING
)
1046 /* Note that this call might invalidate the query. Callers
1047 * should hence not attempt to access the query or transaction
1048 * after calling this function. */
1050 log_debug("Processing incoming packet of size %zu on transaction %" PRIu16
" (rcode=%s).",
1052 t
->id
, FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)));
1054 switch (t
->scope
->protocol
) {
1056 case DNS_PROTOCOL_LLMNR
:
1057 /* For LLMNR we will not accept any packets from other interfaces */
1059 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
1062 if (p
->family
!= t
->scope
->family
)
1065 /* Tentative packets are not full responses but still
1066 * useful for identifying uniqueness conflicts during
1068 if (DNS_PACKET_LLMNR_T(p
)) {
1069 dns_transaction_tentative(t
, p
);
1075 case DNS_PROTOCOL_MDNS
:
1076 /* For mDNS we will not accept any packets from other interfaces */
1078 if (p
->ifindex
!= dns_scope_ifindex(t
->scope
))
1081 if (p
->family
!= t
->scope
->family
)
1086 case DNS_PROTOCOL_DNS
:
1087 /* Note that we do not need to verify the
1088 * addresses/port numbers of incoming traffic, as we
1089 * invoked connect() on our UDP socket in which case
1090 * the kernel already does the needed verification for
1095 assert_not_reached();
1098 if (t
->received
!= p
)
1099 DNS_PACKET_REPLACE(t
->received
, dns_packet_ref(p
));
1101 t
->answer_source
= DNS_TRANSACTION_NETWORK
;
1103 if (p
->ipproto
== IPPROTO_TCP
) {
1104 if (DNS_PACKET_TC(p
)) {
1105 /* Truncated via TCP? Somebody must be fucking with us */
1106 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1110 if (DNS_PACKET_ID(p
) != t
->id
) {
1111 /* Not the reply to our query? Somebody must be fucking with us */
1112 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1117 switch (t
->scope
->protocol
) {
1119 case DNS_PROTOCOL_DNS
:
1123 IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_FORMERR
, DNS_RCODE_SERVFAIL
, DNS_RCODE_NOTIMP
)) {
1125 /* Request failed, immediately try again with reduced features */
1127 if (t
->current_feature_level
<= DNS_SERVER_FEATURE_LEVEL_UDP
) {
1129 /* This was already at UDP feature level? If so, it doesn't make sense to downgrade
1130 * this transaction anymore, but let's see if it might make sense to send the request
1131 * to a different DNS server instead. If not let's process the response, and accept the
1132 * rcode. Note that we don't retry on TCP, since that's a suitable way to mitigate
1133 * packet loss, but is not going to give us better rcodes should we actually have
1134 * managed to get them already at UDP level. */
1136 if (dns_transaction_limited_retry(t
))
1139 /* Give up, accept the rcode */
1140 log_debug("Server returned error: %s", FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)));
1144 /* SERVFAIL can happen for many reasons and may be transient.
1145 * To avoid unnecessary downgrades retry once with the initial level.
1146 * Check for clamp_feature_level_servfail having an invalid value as a sign that this is the
1147 * first attempt to downgrade. If so, clamp to the current value so that the transaction
1148 * is retried without actually downgrading. If the next try also fails we will downgrade by
1149 * hitting the else branch below. */
1150 if (DNS_PACKET_RCODE(p
) == DNS_RCODE_SERVFAIL
&&
1151 t
->clamp_feature_level_servfail
< 0) {
1152 t
->clamp_feature_level_servfail
= t
->current_feature_level
;
1153 log_debug("Server returned error %s, retrying transaction.",
1154 FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)));
1156 /* Reduce this feature level by one and try again. */
1157 switch (t
->current_feature_level
) {
1158 case DNS_SERVER_FEATURE_LEVEL_TLS_DO
:
1159 t
->clamp_feature_level_servfail
= DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
;
1161 case DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
+ 1:
1162 /* Skip plain TLS when TLS is not supported */
1163 t
->clamp_feature_level_servfail
= DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN
- 1;
1166 t
->clamp_feature_level_servfail
= t
->current_feature_level
- 1;
1169 log_debug("Server returned error %s, retrying transaction with reduced feature level %s.",
1170 FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)),
1171 dns_server_feature_level_to_string(t
->clamp_feature_level_servfail
));
1174 dns_transaction_retry(t
, false /* use the same server */);
1178 if (DNS_PACKET_RCODE(p
) == DNS_RCODE_REFUSED
) {
1179 /* This server refused our request? If so, try again, use a different server */
1180 log_debug("Server returned REFUSED, switching servers, and retrying.");
1182 if (dns_transaction_limited_retry(t
))
1188 if (DNS_PACKET_TC(p
))
1189 dns_server_packet_truncated(t
->server
, t
->current_feature_level
);
1193 case DNS_PROTOCOL_LLMNR
:
1194 case DNS_PROTOCOL_MDNS
:
1195 dns_scope_packet_received(t
->scope
, p
->timestamp
- t
->start_usec
);
1199 assert_not_reached();
1202 if (DNS_PACKET_TC(p
)) {
1204 /* Truncated packets for mDNS are not allowed. Give up immediately. */
1205 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
) {
1206 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1210 /* Response was truncated, let's try again with good old TCP */
1211 log_debug("Reply truncated, retrying via TCP.");
1212 retry_with_tcp
= true;
1214 } else if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1215 DNS_PACKET_IS_FRAGMENTED(p
)) {
1217 /* Report the fragment size, so that we downgrade from LARGE to regular EDNS0 if needed */
1219 dns_server_packet_udp_fragmented(t
->server
, dns_packet_size_unfragmented(p
));
1221 if (t
->current_feature_level
> DNS_SERVER_FEATURE_LEVEL_UDP
) {
1222 /* Packet was fragmented. Let's retry with TCP to avoid fragmentation attack
1223 * issues. (We don't do that on the lowest feature level however, since crappy DNS
1224 * servers often do not implement TCP, hence falling back to TCP on fragmentation is
1225 * counter-productive there.) */
1227 log_debug("Reply fragmented, retrying via TCP. (Largest fragment size: %zu; Datagram size: %zu)",
1228 p
->fragsize
, p
->size
);
1229 retry_with_tcp
= true;
1233 if (retry_with_tcp
) {
1234 r
= dns_transaction_emit_tcp(t
);
1236 /* No servers found? Damn! */
1237 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
1240 if (r
== -EOPNOTSUPP
) {
1241 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
1242 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
1246 /* On LLMNR, if we cannot connect to the host,
1247 * we immediately give up */
1248 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1251 /* On DNS, couldn't send? Try immediately again, with a new server */
1252 if (dns_transaction_limited_retry(t
))
1255 /* No new server to try, give up */
1256 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1262 /* After the superficial checks, actually parse the message. */
1263 r
= dns_packet_extract(p
);
1266 dns_server_packet_invalid(t
->server
, t
->current_feature_level
);
1268 r
= dns_transaction_maybe_restart(t
);
1271 if (r
> 0) /* Transaction got restarted... */
1275 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1279 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1281 DNS_PACKET_RCODE(p
) == DNS_RCODE_NXDOMAIN
&&
1282 p
->opt
&& !DNS_PACKET_DO(p
) &&
1283 DNS_SERVER_FEATURE_LEVEL_IS_EDNS0(t
->current_feature_level
) &&
1284 DNS_SERVER_FEATURE_LEVEL_IS_UDP(t
->current_feature_level
) &&
1285 t
->scope
->dnssec_mode
!= DNSSEC_YES
) {
1287 /* Some captive portals are special in that the Aruba/Datavalet hardware will miss
1288 * replacing the packets with the local server IP to point to the authenticated side
1289 * of the network if EDNS0 is enabled. Instead they return NXDOMAIN, with DO bit set
1290 * to zero... nothing to see here, yet respond with the captive portal IP, when using
1291 * the more simple UDP level.
1293 * Common portal names that fail like so are:
1294 * secure.datavalet.io
1295 * securelogin.arubanetworks.com
1296 * securelogin.networks.mycompany.com
1298 * Thus retry NXDOMAIN RCODES with a lower feature level.
1300 * Do not lower the server's tracked feature level, as the captive portal should not
1301 * be lying for the wider internet (e.g. _other_ queries were observed fine with
1302 * EDNS0 on these networks, post auth), i.e. let's just lower the level transaction's
1305 * This is reported as https://github.com/dns-violations/dns-violations/blob/master/2018/DVE-2018-0001.md
1308 t
->clamp_feature_level_nxdomain
= DNS_SERVER_FEATURE_LEVEL_UDP
;
1310 log_debug("Server returned error %s in EDNS0 mode, retrying transaction with reduced feature level %s (DVE-2018-0001 mitigation)",
1311 FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p
)),
1312 dns_server_feature_level_to_string(t
->clamp_feature_level_nxdomain
));
1314 dns_transaction_retry(t
, false /* use the same server */);
1319 /* Report that we successfully received a valid packet with a good rcode after we initially got a bad
1320 * rcode and subsequently downgraded the protocol */
1322 if (IN_SET(DNS_PACKET_RCODE(p
), DNS_RCODE_SUCCESS
, DNS_RCODE_NXDOMAIN
) &&
1323 t
->clamp_feature_level_servfail
!= _DNS_SERVER_FEATURE_LEVEL_INVALID
)
1324 dns_server_packet_rcode_downgrade(t
->server
, t
->clamp_feature_level_servfail
);
1326 /* Report that the OPT RR was missing */
1328 dns_server_packet_bad_opt(t
->server
, t
->current_feature_level
);
1330 /* Report that the server didn't copy our query DO bit from request to response */
1331 if (DNS_PACKET_DO(t
->sent
) && !DNS_PACKET_DO(t
->received
))
1332 dns_server_packet_do_off(t
->server
, t
->current_feature_level
);
1334 /* Report that we successfully received a packet. We keep track of the largest packet
1335 * size/fragment size we got. Which is useful for announcing the EDNS(0) packet size we can
1336 * receive to our server. */
1337 dns_server_packet_received(t
->server
, p
->ipproto
, t
->current_feature_level
, dns_packet_size_unfragmented(p
));
1340 /* See if we know things we didn't know before that indicate we better restart the lookup immediately. */
1341 r
= dns_transaction_maybe_restart(t
);
1344 if (r
> 0) /* Transaction got restarted... */
1347 /* When dealing with protocols other than mDNS only consider responses with equivalent query section
1348 * to the request. For mDNS this check doesn't make sense, because the section 6 of RFC6762 states
1349 * that "Multicast DNS responses MUST NOT contain any questions in the Question Section". */
1350 if (t
->scope
->protocol
!= DNS_PROTOCOL_MDNS
) {
1351 r
= dns_packet_is_reply_for(p
, dns_transaction_key(t
));
1355 dns_transaction_complete(t
, DNS_TRANSACTION_INVALID_REPLY
);
1360 /* Install the answer as answer to the transaction. We ref the answer twice here: the main `answer`
1361 * field is later replaced by the DNSSEC validated subset. The 'answer_auxiliary' field carries the
1362 * original complete record set, including RRSIG and friends. We use this when passing data to
1363 * clients that ask for DNSSEC metadata. */
1364 DNS_ANSWER_REPLACE(t
->answer
, dns_answer_ref(p
->answer
));
1365 t
->answer_rcode
= DNS_PACKET_RCODE(p
);
1366 t
->answer_dnssec_result
= _DNSSEC_RESULT_INVALID
;
1367 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
1368 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
, encrypted
);
1370 r
= dns_transaction_fix_rcode(t
);
1374 /* Block GC while starting requests for additional DNSSEC RRs */
1376 r
= dns_transaction_request_dnssec_keys(t
);
1379 /* Maybe the transaction is ready for GC'ing now? If so, free it and return. */
1380 if (!dns_transaction_gc(t
))
1383 /* Requesting additional keys might have resulted in this transaction to fail, since the auxiliary
1384 * request failed for some reason. If so, we are not in pending state anymore, and we should exit
1386 if (t
->state
!= DNS_TRANSACTION_PENDING
)
1391 /* There are DNSSEC transactions pending now. Update the state accordingly. */
1392 t
->state
= DNS_TRANSACTION_VALIDATING
;
1393 dns_transaction_close_connection(t
, true);
1394 dns_transaction_stop_timeout(t
);
1398 dns_transaction_process_dnssec(t
);
1402 dns_transaction_complete_errno(t
, r
);
1405 static int on_dns_packet(sd_event_source
*s
, int fd
, uint32_t revents
, void *userdata
) {
1406 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1407 DnsTransaction
*t
= ASSERT_PTR(userdata
);
1412 r
= manager_recv(t
->scope
->manager
, fd
, DNS_PROTOCOL_DNS
, &p
);
1413 if (ERRNO_IS_DISCONNECT(r
)) {
1416 /* UDP connection failures get reported via ICMP and then are possibly delivered to us on the
1417 * next recvmsg(). Treat this like a lost packet. */
1419 log_debug_errno(r
, "Connection failure for DNS UDP packet: %m");
1420 assert_se(sd_event_now(t
->scope
->manager
->event
, CLOCK_BOOTTIME
, &usec
) >= 0);
1421 dns_server_packet_lost(t
->server
, IPPROTO_UDP
, t
->current_feature_level
);
1423 dns_transaction_close_connection(t
, /* use_graveyard = */ false);
1425 if (dns_transaction_limited_retry(t
)) /* Try a different server */
1428 dns_transaction_complete_errno(t
, r
);
1432 dns_transaction_complete_errno(t
, r
);
1436 /* Spurious wakeup without any data */
1439 r
= dns_packet_validate_reply(p
);
1441 log_debug_errno(r
, "Received invalid DNS packet as response, ignoring: %m");
1445 log_debug("Received inappropriate DNS packet as response, ignoring.");
1449 if (DNS_PACKET_ID(p
) != t
->id
) {
1450 log_debug("Received packet with incorrect transaction ID, ignoring.");
1454 dns_transaction_process_reply(t
, p
, false);
1458 static int dns_transaction_emit_udp(DnsTransaction
*t
) {
1463 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
) {
1465 r
= dns_transaction_pick_server(t
);
1469 if (manager_server_is_stub(t
->scope
->manager
, t
->server
))
1472 if (t
->current_feature_level
< DNS_SERVER_FEATURE_LEVEL_UDP
|| DNS_SERVER_FEATURE_LEVEL_IS_TLS(t
->current_feature_level
))
1473 return -EAGAIN
; /* Sorry, can't do UDP, try TCP! */
1475 if (!t
->bypass
&& !dns_server_dnssec_supported(t
->server
) && dns_type_is_dnssec(dns_transaction_key(t
)->type
))
1478 if (r
> 0 || t
->dns_udp_fd
< 0) { /* Server changed, or no connection yet. */
1481 dns_transaction_close_connection(t
, true);
1483 /* Before we allocate a new UDP socket, let's process the graveyard a bit to free some fds */
1484 manager_socket_graveyard_process(t
->scope
->manager
);
1486 fd
= dns_scope_socket_udp(t
->scope
, t
->server
);
1490 r
= sd_event_add_io(t
->scope
->manager
->event
, &t
->dns_udp_event_source
, fd
, EPOLLIN
, on_dns_packet
, t
);
1496 (void) sd_event_source_set_description(t
->dns_udp_event_source
, "dns-transaction-udp");
1501 r
= dns_server_adjust_opt(t
->server
, t
->sent
, t
->current_feature_level
);
1506 dns_transaction_close_connection(t
, true);
1508 r
= dns_scope_emit_udp(t
->scope
, t
->dns_udp_fd
, t
->server
? t
->server
->family
: AF_UNSPEC
, t
->sent
);
1512 dns_transaction_reset_answer(t
);
1517 static int on_transaction_timeout(sd_event_source
*s
, usec_t usec
, void *userdata
) {
1518 DnsTransaction
*t
= ASSERT_PTR(userdata
);
1522 if (t
->initial_jitter_scheduled
&& !t
->initial_jitter_elapsed
) {
1523 log_debug("Initial jitter phase for transaction %" PRIu16
" elapsed.", t
->id
);
1524 t
->initial_jitter_elapsed
= true;
1526 /* Timeout reached? Increase the timeout for the server used */
1527 switch (t
->scope
->protocol
) {
1529 case DNS_PROTOCOL_DNS
:
1531 dns_server_packet_lost(t
->server
, t
->stream
? IPPROTO_TCP
: IPPROTO_UDP
, t
->current_feature_level
);
1534 case DNS_PROTOCOL_LLMNR
:
1535 case DNS_PROTOCOL_MDNS
:
1536 dns_scope_packet_lost(t
->scope
, usec
- t
->start_usec
);
1540 assert_not_reached();
1543 log_debug("Timeout reached on transaction %" PRIu16
".", t
->id
);
1546 dns_transaction_retry(t
, /* next_server= */ true); /* try a different server, but given this means
1547 * packet loss, let's do so even if we already
1552 static int dns_transaction_setup_timeout(
1554 usec_t timeout_usec
/* relative */,
1555 usec_t next_usec
/* CLOCK_BOOTTIME */) {
1561 dns_transaction_stop_timeout(t
);
1563 r
= sd_event_add_time_relative(
1564 t
->scope
->manager
->event
,
1565 &t
->timeout_event_source
,
1568 on_transaction_timeout
, t
);
1572 (void) sd_event_source_set_description(t
->timeout_event_source
, "dns-transaction-timeout");
1574 t
->next_attempt_after
= next_usec
;
1575 t
->state
= DNS_TRANSACTION_PENDING
;
1579 static usec_t
transaction_get_resend_timeout(DnsTransaction
*t
) {
1583 switch (t
->scope
->protocol
) {
1585 case DNS_PROTOCOL_DNS
:
1587 /* When we do TCP, grant a much longer timeout, as in this case there's no need for us to quickly
1588 * resend, as the kernel does that anyway for us, and we really don't want to interrupt it in that
1591 return TRANSACTION_TCP_TIMEOUT_USEC
;
1593 return DNS_TIMEOUT_USEC
;
1595 case DNS_PROTOCOL_MDNS
:
1597 return MDNS_PROBING_INTERVAL_USEC
;
1599 /* See RFC 6762 Section 5.1 suggests that timeout should be a few seconds. */
1600 assert(t
->n_attempts
> 0);
1601 return (1 << (t
->n_attempts
- 1)) * USEC_PER_SEC
;
1603 case DNS_PROTOCOL_LLMNR
:
1604 return t
->scope
->resend_timeout
;
1607 assert_not_reached();
1611 static void dns_transaction_randomize_answer(DnsTransaction
*t
) {
1616 /* Randomizes the order of the answer array. This is done for all cached responses, so that we return
1617 * a different order each time. We do this only for DNS traffic, in order to do some minimal, crappy
1618 * load balancing. We don't do this for LLMNR or mDNS, since the order (preferring link-local
1619 * addresses, and such like) might have meaning there, and load balancing is pointless. */
1621 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
1624 /* No point in randomizing, if there's just one RR */
1625 if (dns_answer_size(t
->answer
) <= 1)
1628 r
= dns_answer_reserve_or_clone(&t
->answer
, 0);
1629 if (r
< 0) /* If this fails, just don't randomize, this is non-essential stuff after all */
1630 return (void) log_debug_errno(r
, "Failed to clone answer record, not randomizing RR order of answer: %m");
1632 dns_answer_randomize(t
->answer
);
1635 static int dns_transaction_prepare(DnsTransaction
*t
, usec_t ts
) {
1640 /* Returns 0 if dns_transaction_complete() has been called. In that case the transaction and query
1641 * candidate objects may have been invalidated and must not be accessed. Returns 1 if the transaction
1642 * has been prepared. */
1644 dns_transaction_stop_timeout(t
);
1646 if (!dns_scope_network_good(t
->scope
)) {
1647 dns_transaction_complete(t
, DNS_TRANSACTION_NETWORK_DOWN
);
1651 if (t
->n_attempts
>= TRANSACTION_ATTEMPTS_MAX(t
->scope
->protocol
)) {
1652 DnsTransactionState result
;
1654 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
)
1655 /* If we didn't find anything on LLMNR, it's not an error, but a failure to resolve
1657 result
= DNS_TRANSACTION_NOT_FOUND
;
1659 result
= DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
;
1661 dns_transaction_complete(t
, result
);
1665 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& t
->tried_stream
) {
1666 /* If we already tried via a stream, then we don't
1667 * retry on LLMNR. See RFC 4795, Section 2.7. */
1668 dns_transaction_complete(t
, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
);
1675 dns_transaction_reset_answer(t
);
1676 dns_transaction_flush_dnssec_transactions(t
);
1678 /* Check the trust anchor. Do so only on classic DNS, since DNSSEC does not apply otherwise. */
1679 if (t
->scope
->protocol
== DNS_PROTOCOL_DNS
&&
1680 !FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_TRUST_ANCHOR
)) {
1681 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, dns_transaction_key(t
), &t
->answer
);
1685 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1686 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1687 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
|SD_RESOLVED_CONFIDENTIAL
, true);
1688 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1692 if (dns_name_is_root(dns_resource_key_name(dns_transaction_key(t
))) &&
1693 dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
1695 /* Hmm, this is a request for the root DS? A DS RR doesn't exist in the root zone,
1696 * and if our trust anchor didn't know it either, this means we cannot do any DNSSEC
1699 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
1700 /* We are in downgrade mode. In this case, synthesize an unsigned empty
1701 * response, so that the any lookup depending on this one can continue
1702 * assuming there was no DS, and hence the root zone was unsigned. */
1704 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1705 t
->answer_source
= DNS_TRANSACTION_TRUST_ANCHOR
;
1706 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
1707 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_CONFIDENTIAL
, true);
1708 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1710 /* If we are not in downgrade mode, then fail the lookup, because we cannot
1711 * reasonably answer it. There might be DS RRs, but we don't know them, and
1712 * the DNS server won't tell them to us (and even if it would, we couldn't
1713 * validate and trust them. */
1714 dns_transaction_complete(t
, DNS_TRANSACTION_NO_TRUST_ANCHOR
);
1720 /* Check the zone. */
1721 if (!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_ZONE
)) {
1722 r
= dns_zone_lookup(&t
->scope
->zone
, dns_transaction_key(t
), dns_scope_ifindex(t
->scope
), &t
->answer
, NULL
, NULL
);
1726 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
1727 t
->answer_source
= DNS_TRANSACTION_ZONE
;
1728 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
|SD_RESOLVED_CONFIDENTIAL
, true);
1729 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1734 /* Check the cache. */
1735 if (!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_CACHE
)) {
1737 /* Before trying the cache, let's make sure we figured out a server to use. Should this cause
1738 * a change of server this might flush the cache. */
1739 (void) dns_scope_get_dns_server(t
->scope
);
1741 /* Let's then prune all outdated entries */
1742 dns_cache_prune(&t
->scope
->cache
);
1744 r
= dns_cache_lookup(
1746 dns_transaction_key(t
),
1751 &t
->answer_query_flags
,
1752 &t
->answer_dnssec_result
);
1756 dns_transaction_randomize_answer(t
);
1758 if (t
->bypass
&& t
->scope
->protocol
== DNS_PROTOCOL_DNS
&& !t
->received
)
1759 /* When bypass mode is on, do not use cached data unless it came with a full
1761 dns_transaction_reset_answer(t
);
1763 t
->answer_source
= DNS_TRANSACTION_CACHE
;
1764 if (t
->answer_rcode
== DNS_RCODE_SUCCESS
)
1765 dns_transaction_complete(t
, DNS_TRANSACTION_SUCCESS
);
1767 dns_transaction_complete(t
, DNS_TRANSACTION_RCODE_FAILURE
);
1773 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_NETWORK
)) {
1774 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SOURCE
);
1781 static int dns_packet_append_zone(DnsPacket
*p
, DnsTransaction
*t
, DnsResourceKey
*k
, unsigned *nscount
) {
1782 _cleanup_(dns_answer_unrefp
) DnsAnswer
*answer
= NULL
;
1790 if (k
->type
!= DNS_TYPE_ANY
)
1793 r
= dns_zone_lookup(&t
->scope
->zone
, k
, t
->scope
->link
->ifindex
, &answer
, NULL
, &tentative
);
1797 return dns_packet_append_answer(p
, answer
, nscount
);
1800 static int dns_transaction_make_packet_mdns(DnsTransaction
*t
) {
1801 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1802 _cleanup_set_free_ Set
*keys
= NULL
;
1803 unsigned qdcount
, ancount
= 0 /* avoid false maybe-uninitialized warning */, nscount
;
1804 bool add_known_answers
= false;
1809 assert(t
->scope
->protocol
== DNS_PROTOCOL_MDNS
);
1811 /* Discard any previously prepared packet, so we can start over and coalesce again */
1812 t
->sent
= dns_packet_unref(t
->sent
);
1814 /* First, create a dummy packet to calculate packet size. */
1815 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, false);
1819 r
= dns_packet_append_key(p
, dns_transaction_key(t
), 0, NULL
);
1825 if (dns_key_is_shared(dns_transaction_key(t
)))
1826 add_known_answers
= true;
1828 r
= dns_packet_append_zone(p
, t
, dns_transaction_key(t
), NULL
);
1832 /* Save appended keys */
1833 r
= set_ensure_put(&keys
, &dns_resource_key_hash_ops
, dns_transaction_key(t
));
1838 * For mDNS, we want to coalesce as many open queries in pending transactions into one single
1839 * query packet on the wire as possible. To achieve that, we iterate through all pending transactions
1840 * in our current scope, and see whether their timing constraints allow them to be sent.
1843 assert_se(sd_event_now(t
->scope
->manager
->event
, CLOCK_BOOTTIME
, &ts
) >= 0);
1845 for (bool restart
= true; restart
;) {
1847 LIST_FOREACH(transactions_by_scope
, other
, t
->scope
->transactions
) {
1848 size_t saved_packet_size
;
1849 bool append
= false;
1851 /* Skip ourselves */
1855 if (other
->state
!= DNS_TRANSACTION_PENDING
)
1858 if (other
->next_attempt_after
> ts
)
1861 if (!set_contains(keys
, dns_transaction_key(other
))) {
1862 r
= dns_packet_append_key(p
, dns_transaction_key(other
), 0, &saved_packet_size
);
1863 /* If we can't stuff more questions into the packet, just give up.
1864 * One of the 'other' transactions will fire later and take care of the rest. */
1870 r
= dns_packet_append_zone(p
, t
, dns_transaction_key(other
), NULL
);
1879 r
= dns_transaction_prepare(other
, ts
);
1884 dns_packet_truncate(p
, saved_packet_size
);
1886 /* In this case, not only this transaction, but multiple transactions may be
1887 * freed. Hence, we need to restart the loop. */
1892 usec_t timeout
= transaction_get_resend_timeout(other
);
1893 r
= dns_transaction_setup_timeout(other
, timeout
, usec_add(ts
, timeout
));
1897 if (dns_key_is_shared(dns_transaction_key(other
)))
1898 add_known_answers
= true;
1901 r
= set_ensure_put(&keys
, &dns_resource_key_hash_ops
, dns_transaction_key(other
));
1907 if (qdcount
>= UINT16_MAX
)
1912 /* Append known answer section if we're asking for any shared record */
1913 if (add_known_answers
) {
1914 r
= dns_cache_export_shared_to_packet(&t
->scope
->cache
, p
, ts
, 0);
1918 ancount
= be16toh(DNS_PACKET_HEADER(p
)->ancount
);
1921 /* Then, create actual packet. */
1922 p
= dns_packet_unref(p
);
1923 r
= dns_packet_new_query(&p
, t
->scope
->protocol
, 0, false);
1929 SET_FOREACH(k
, keys
) {
1930 r
= dns_packet_append_key(p
, k
, 0, NULL
);
1934 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(qdcount
);
1937 if (add_known_answers
) {
1938 r
= dns_cache_export_shared_to_packet(&t
->scope
->cache
, p
, ts
, ancount
);
1945 SET_FOREACH(k
, keys
) {
1946 r
= dns_packet_append_zone(p
, t
, k
, &nscount
);
1950 DNS_PACKET_HEADER(p
)->nscount
= htobe16(nscount
);
1952 t
->sent
= TAKE_PTR(p
);
1956 static int dns_transaction_make_packet(DnsTransaction
*t
) {
1957 _cleanup_(dns_packet_unrefp
) DnsPacket
*p
= NULL
;
1962 if (t
->scope
->protocol
== DNS_PROTOCOL_MDNS
)
1963 return dns_transaction_make_packet_mdns(t
);
1968 if (t
->bypass
&& t
->bypass
->protocol
== t
->scope
->protocol
) {
1969 /* If bypass logic is enabled and the protocol if the original packet and our scope match,
1970 * take the original packet, copy it, and patch in our new ID */
1971 r
= dns_packet_dup(&p
, t
->bypass
);
1975 r
= dns_packet_new_query(
1976 &p
, t
->scope
->protocol
,
1977 /* min_alloc_dsize = */ 0,
1978 /* dnssec_cd = */ !FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) &&
1979 t
->scope
->dnssec_mode
!= DNSSEC_NO
);
1983 r
= dns_packet_append_key(p
, dns_transaction_key(t
), 0, NULL
);
1987 DNS_PACKET_HEADER(p
)->qdcount
= htobe16(1);
1990 DNS_PACKET_HEADER(p
)->id
= t
->id
;
1992 t
->sent
= TAKE_PTR(p
);
1996 int dns_transaction_go(DnsTransaction
*t
) {
1999 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
2003 /* Returns > 0 if the transaction is now pending, returns 0 if could be processed immediately and has
2004 * finished now. In the latter case, the transaction and query candidate objects must not be accessed.
2007 assert_se(sd_event_now(t
->scope
->manager
->event
, CLOCK_BOOTTIME
, &ts
) >= 0);
2009 r
= dns_transaction_prepare(t
, ts
);
2013 log_debug("Firing %s transaction %" PRIu16
" for <%s> scope %s on %s/%s (validate=%s).",
2014 t
->bypass
? "bypass" : "regular",
2016 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
),
2017 dns_protocol_to_string(t
->scope
->protocol
),
2018 t
->scope
->link
? t
->scope
->link
->ifname
: "*",
2019 af_to_name_short(t
->scope
->family
),
2020 yes_no(!FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
)));
2022 if (!t
->initial_jitter_scheduled
&&
2023 IN_SET(t
->scope
->protocol
, DNS_PROTOCOL_LLMNR
, DNS_PROTOCOL_MDNS
)) {
2026 /* RFC 4795 Section 2.7 suggests all LLMNR queries should be delayed by a random time from 0 to
2028 * RFC 6762 Section 8.1 suggests initial probe queries should be delayed by a random time from
2031 t
->initial_jitter_scheduled
= true;
2034 switch (t
->scope
->protocol
) {
2036 case DNS_PROTOCOL_LLMNR
:
2037 jitter
= random_u64_range(LLMNR_JITTER_INTERVAL_USEC
);
2040 case DNS_PROTOCOL_MDNS
:
2042 jitter
= random_u64_range(MDNS_PROBING_INTERVAL_USEC
);
2047 assert_not_reached();
2050 r
= dns_transaction_setup_timeout(t
, jitter
, ts
);
2054 log_debug("Delaying %s transaction %" PRIu16
" for " USEC_FMT
"us.",
2055 dns_protocol_to_string(t
->scope
->protocol
),
2061 /* Otherwise, we need to ask the network */
2062 r
= dns_transaction_make_packet(t
);
2066 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&&
2067 (dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), "in-addr.arpa") > 0 ||
2068 dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), "ip6.arpa") > 0)) {
2070 /* RFC 4795, Section 2.4. says reverse lookups shall
2071 * always be made via TCP on LLMNR */
2072 r
= dns_transaction_emit_tcp(t
);
2074 /* Try via UDP, and if that fails due to large size or lack of
2075 * support try via TCP */
2076 r
= dns_transaction_emit_udp(t
);
2078 log_debug("Sending query via TCP since it is too large.");
2079 else if (r
== -EAGAIN
)
2080 log_debug("Sending query via TCP since UDP isn't supported or DNS-over-TLS is selected.");
2081 if (IN_SET(r
, -EMSGSIZE
, -EAGAIN
))
2082 r
= dns_transaction_emit_tcp(t
);
2085 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2088 /* One of our own stub listeners */
2089 log_debug_errno(r
, "Detected that specified DNS server is our own extra listener, switching DNS servers.");
2091 dns_scope_next_dns_server(t
->scope
, t
->server
);
2093 if (dns_scope_get_dns_server(t
->scope
) == t
->server
) {
2094 log_debug_errno(r
, "Still pointing to extra listener after switching DNS servers, refusing operation.");
2095 dns_transaction_complete(t
, DNS_TRANSACTION_STUB_LOOP
);
2099 return dns_transaction_go(t
);
2102 /* No servers to send this to? */
2103 dns_transaction_complete(t
, DNS_TRANSACTION_NO_SERVERS
);
2106 if (r
== -EOPNOTSUPP
) {
2107 /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */
2108 dns_transaction_complete(t
, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
);
2111 if (t
->scope
->protocol
== DNS_PROTOCOL_LLMNR
&& ERRNO_IS_DISCONNECT(r
)) {
2112 /* On LLMNR, if we cannot connect to a host via TCP when doing reverse lookups. This means we cannot
2113 * answer this request with this protocol. */
2114 dns_transaction_complete(t
, DNS_TRANSACTION_NOT_FOUND
);
2118 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2121 /* Couldn't send? Try immediately again, with a new server */
2122 dns_scope_next_dns_server(t
->scope
, t
->server
);
2124 return dns_transaction_go(t
);
2127 usec_t timeout
= transaction_get_resend_timeout(t
);
2128 r
= dns_transaction_setup_timeout(t
, timeout
, usec_add(ts
, timeout
));
2135 static int dns_transaction_find_cyclic(DnsTransaction
*t
, DnsTransaction
*aux
) {
2142 /* Try to find cyclic dependencies between transaction objects */
2147 SET_FOREACH(n
, aux
->dnssec_transactions
) {
2148 r
= dns_transaction_find_cyclic(t
, n
);
2156 static int dns_transaction_add_dnssec_transaction(DnsTransaction
*t
, DnsResourceKey
*key
, DnsTransaction
**ret
) {
2157 _cleanup_(dns_transaction_gcp
) DnsTransaction
*aux
= NULL
;
2164 aux
= dns_scope_find_transaction(t
->scope
, key
, t
->query_flags
);
2166 r
= dns_transaction_new(&aux
, t
->scope
, key
, NULL
, t
->query_flags
);
2170 if (set_contains(t
->dnssec_transactions
, aux
)) {
2175 r
= dns_transaction_find_cyclic(t
, aux
);
2179 char s
[DNS_RESOURCE_KEY_STRING_MAX
], saux
[DNS_RESOURCE_KEY_STRING_MAX
];
2181 return log_debug_errno(SYNTHETIC_ERRNO(ELOOP
),
2182 "Potential cyclic dependency, refusing to add transaction %" PRIu16
" (%s) as dependency for %" PRIu16
" (%s).",
2184 dns_resource_key_to_string(dns_transaction_key(t
), s
, sizeof s
),
2186 dns_resource_key_to_string(dns_transaction_key(aux
), saux
, sizeof saux
));
2190 r
= set_ensure_allocated(&aux
->notify_transactions_done
, NULL
);
2194 r
= set_ensure_put(&t
->dnssec_transactions
, NULL
, aux
);
2198 r
= set_ensure_put(&aux
->notify_transactions
, NULL
, t
);
2200 (void) set_remove(t
->dnssec_transactions
, aux
);
2204 *ret
= TAKE_PTR(aux
);
2208 static int dns_transaction_request_dnssec_rr(DnsTransaction
*t
, DnsResourceKey
*key
) {
2209 _cleanup_(dns_answer_unrefp
) DnsAnswer
*a
= NULL
;
2210 DnsTransaction
*aux
;
2216 /* Try to get the data from the trust anchor */
2217 r
= dns_trust_anchor_lookup_positive(&t
->scope
->manager
->trust_anchor
, key
, &a
);
2221 r
= dns_answer_extend(&t
->validated_keys
, a
);
2228 /* This didn't work, ask for it via the network/cache then. */
2229 r
= dns_transaction_add_dnssec_transaction(t
, key
, &aux
);
2230 if (r
== -ELOOP
) /* This would result in a cyclic dependency */
2235 if (aux
->state
== DNS_TRANSACTION_NULL
) {
2236 r
= dns_transaction_go(aux
);
2244 static int dns_transaction_negative_trust_anchor_lookup(DnsTransaction
*t
, const char *name
) {
2249 /* Check whether the specified name is in the NTA
2250 * database, either in the global one, or the link-local
2253 r
= dns_trust_anchor_lookup_negative(&t
->scope
->manager
->trust_anchor
, name
);
2257 if (!t
->scope
->link
)
2260 return link_negative_trust_anchor_lookup(t
->scope
->link
, name
);
2263 static int dns_transaction_has_negative_answer(DnsTransaction
*t
) {
2268 /* Checks whether the answer is negative, and lacks NSEC/NSEC3
2269 * RRs to prove it */
2271 r
= dns_transaction_has_positive_answer(t
, NULL
);
2277 /* Is this key explicitly listed as a negative trust anchor?
2278 * If so, it's nothing we need to care about */
2279 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(dns_transaction_key(t
)));
2285 static int dns_transaction_is_primary_response(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2291 /* Check if the specified RR is the "primary" response,
2292 * i.e. either matches the question precisely or is a
2293 * CNAME/DNAME for it. */
2295 r
= dns_resource_key_match_rr(dns_transaction_key(t
), rr
, NULL
);
2299 return dns_resource_key_match_cname_or_dname(dns_transaction_key(t
), rr
->key
, NULL
);
2302 static bool dns_transaction_dnssec_supported(DnsTransaction
*t
) {
2305 /* Checks whether our transaction's DNS server is assumed to be compatible with DNSSEC. Returns false as soon
2306 * as we changed our mind about a server, and now believe it is incompatible with DNSSEC. */
2308 if (t
->scope
->protocol
!= DNS_PROTOCOL_DNS
)
2311 /* If we have picked no server, then we are working from the cache or some other source, and DNSSEC might well
2312 * be supported, hence return true. */
2316 /* Note that we do not check the feature level actually used for the transaction but instead the feature level
2317 * the server is known to support currently, as the transaction feature level might be lower than what the
2318 * server actually supports, since we might have downgraded this transaction's feature level because we got a
2319 * SERVFAIL earlier and wanted to check whether downgrading fixes it. */
2321 return dns_server_dnssec_supported(t
->server
);
2324 static bool dns_transaction_dnssec_supported_full(DnsTransaction
*t
) {
2329 /* Checks whether our transaction our any of the auxiliary transactions couldn't do DNSSEC. */
2331 if (!dns_transaction_dnssec_supported(t
))
2334 SET_FOREACH(dt
, t
->dnssec_transactions
)
2335 if (!dns_transaction_dnssec_supported(dt
))
2341 int dns_transaction_request_dnssec_keys(DnsTransaction
*t
) {
2342 DnsResourceRecord
*rr
;
2349 * Retrieve all auxiliary RRs for the answer we got, so that
2350 * we can verify signatures or prove that RRs are rightfully
2351 * unsigned. Specifically:
2353 * - For RRSIG we get the matching DNSKEY
2354 * - For DNSKEY we get the matching DS
2355 * - For unsigned SOA/NS we get the matching DS
2356 * - For unsigned CNAME/DNAME/DS we get the parent SOA RR
2357 * - For other unsigned RRs we get the matching SOA RR
2358 * - For SOA/NS queries with no matching response RR, and no NSEC/NSEC3, the DS RR
2359 * - For DS queries with no matching response RRs, and no NSEC/NSEC3, the parent's SOA RR
2360 * - For other queries with no matching response RRs, and no NSEC/NSEC3, the SOA RR
2363 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) || t
->scope
->dnssec_mode
== DNSSEC_NO
)
2365 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
2366 return 0; /* We only need to validate stuff from the network */
2367 if (!dns_transaction_dnssec_supported(t
))
2368 return 0; /* If we can't do DNSSEC anyway there's no point in getting the auxiliary RRs */
2370 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
2372 if (dns_type_is_pseudo(rr
->key
->type
))
2375 /* If this RR is in the negative trust anchor, we don't need to validate it. */
2376 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2382 switch (rr
->key
->type
) {
2384 case DNS_TYPE_RRSIG
: {
2385 /* For each RRSIG we request the matching DNSKEY */
2386 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*dnskey
= NULL
;
2388 /* If this RRSIG is about a DNSKEY RR and the
2389 * signer is the same as the owner, then we
2390 * already have the DNSKEY, and we don't have
2391 * to look for more. */
2392 if (rr
->rrsig
.type_covered
== DNS_TYPE_DNSKEY
) {
2393 r
= dns_name_equal(rr
->rrsig
.signer
, dns_resource_key_name(rr
->key
));
2400 /* If the signer is not a parent of our
2401 * original query, then this is about an
2402 * auxiliary RRset, but not anything we asked
2403 * for. In this case we aren't interested,
2404 * because we don't want to request additional
2405 * RRs for stuff we didn't really ask for, and
2406 * also to avoid request loops, where
2407 * additional RRs from one transaction result
2408 * in another transaction whose additional RRs
2409 * point back to the original transaction, and
2411 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), rr
->rrsig
.signer
);
2417 dnskey
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DNSKEY
, rr
->rrsig
.signer
);
2421 log_debug("Requesting DNSKEY to validate transaction %" PRIu16
" (%s, RRSIG with key tag: %" PRIu16
").",
2422 t
->id
, dns_resource_key_name(rr
->key
), rr
->rrsig
.key_tag
);
2423 r
= dns_transaction_request_dnssec_rr(t
, dnskey
);
2429 case DNS_TYPE_DNSKEY
: {
2430 /* For each DNSKEY we request the matching DS */
2431 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
2433 /* If the DNSKEY we are looking at is not for
2434 * zone we are interested in, nor any of its
2435 * parents, we aren't interested, and don't
2436 * request it. After all, we don't want to end
2437 * up in request loops, and want to keep
2438 * additional traffic down. */
2440 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), dns_resource_key_name(rr
->key
));
2446 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
2450 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, DNSKEY with key tag: %" PRIu16
").",
2451 t
->id
, dns_resource_key_name(rr
->key
), dnssec_keytag(rr
, false));
2452 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2461 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*ds
= NULL
;
2463 /* For an unsigned SOA or NS, try to acquire
2464 * the matching DS RR, as we are at a zone cut
2465 * then, and whether a DS exists tells us
2466 * whether the zone is signed. Do so only if
2467 * this RR matches our original question,
2470 r
= dns_resource_key_match_rr(dns_transaction_key(t
), rr
, NULL
);
2474 /* Hmm, so this SOA RR doesn't match our original question. In this case, maybe this is
2475 * a negative reply, and we need the SOA RR's TTL in order to cache a negative entry?
2476 * If so, we need to validate it, too. */
2478 r
= dns_answer_match_key(t
->answer
, dns_transaction_key(t
), NULL
);
2481 if (r
> 0) /* positive reply, we won't need the SOA and hence don't need to validate
2485 /* Only bother with this if the SOA/NS RR we are looking at is actually a parent of
2486 * what we are looking for, otherwise there's no value in it for us. */
2487 r
= dns_name_endswith(dns_resource_key_name(dns_transaction_key(t
)), dns_resource_key_name(rr
->key
));
2494 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2500 ds
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_DS
, dns_resource_key_name(rr
->key
));
2504 log_debug("Requesting DS to validate transaction %" PRIu16
" (%s, unsigned SOA/NS RRset).",
2505 t
->id
, dns_resource_key_name(rr
->key
));
2506 r
= dns_transaction_request_dnssec_rr(t
, ds
);
2514 case DNS_TYPE_CNAME
:
2515 case DNS_TYPE_DNAME
: {
2516 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2519 /* CNAMEs and DNAMEs cannot be located at a
2520 * zone apex, hence ask for the parent SOA for
2521 * unsigned CNAME/DNAME RRs, maybe that's the
2522 * apex. But do all that only if this is
2523 * actually a response to our original
2526 * Similar for DS RRs, which are signed when
2527 * the parent SOA is signed. */
2529 r
= dns_transaction_is_primary_response(t
, rr
);
2535 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2541 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
2547 name
= dns_resource_key_name(rr
->key
);
2548 r
= dns_name_parent(&name
);
2554 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, name
);
2558 log_debug("Requesting parent SOA to validate transaction %" PRIu16
" (%s, unsigned CNAME/DNAME/DS RRset).",
2559 t
->id
, dns_resource_key_name(rr
->key
));
2560 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2568 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2570 /* For other unsigned RRsets (including
2571 * NSEC/NSEC3!), look for proof the zone is
2572 * unsigned, by requesting the SOA RR of the
2573 * zone. However, do so only if they are
2574 * directly relevant to our original
2577 r
= dns_transaction_is_primary_response(t
, rr
);
2583 r
= dnssec_has_rrsig(t
->answer
, rr
->key
);
2589 soa
= dns_resource_key_new(rr
->key
->class, DNS_TYPE_SOA
, dns_resource_key_name(rr
->key
));
2593 log_debug("Requesting SOA to validate transaction %" PRIu16
" (%s, unsigned non-SOA/NS RRset <%s>).",
2594 t
->id
, dns_resource_key_name(rr
->key
), dns_resource_record_to_string(rr
));
2595 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2602 /* Above, we requested everything necessary to validate what
2603 * we got. Now, let's request what we need to validate what we
2606 r
= dns_transaction_has_negative_answer(t
);
2610 const char *name
, *signed_status
;
2613 name
= dns_resource_key_name(dns_transaction_key(t
));
2614 signed_status
= dns_answer_contains_nsec_or_nsec3(t
->answer
) ? "signed" : "unsigned";
2616 /* If this was a SOA or NS request, then check if there's a DS RR for the same domain. Note that this
2617 * could also be used as indication that we are not at a zone apex, but in real world setups there are
2618 * too many broken DNS servers (Hello, incapdns.net!) where non-terminal zones return NXDOMAIN even
2619 * though they have further children. If this was a DS request, then it's signed when the parent zone
2620 * is signed, hence ask the parent SOA in that case. If this was any other RR then ask for the SOA RR,
2621 * to see if that is signed. */
2623 if (dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
2624 r
= dns_name_parent(&name
);
2626 type
= DNS_TYPE_SOA
;
2627 log_debug("Requesting parent SOA (%s %s) to validate transaction %" PRIu16
" (%s, %s empty DS response).",
2628 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT
), name
, t
->id
,
2629 dns_resource_key_name(dns_transaction_key(t
)), signed_status
);
2633 } else if (IN_SET(dns_transaction_key(t
)->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
)) {
2636 log_debug("Requesting DS (%s %s) to validate transaction %" PRIu16
" (%s, %s empty SOA/NS response).",
2637 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT
), name
, t
->id
, name
, signed_status
);
2640 type
= DNS_TYPE_SOA
;
2641 log_debug("Requesting SOA (%s %s) to validate transaction %" PRIu16
" (%s, %s empty non-SOA/NS/DS response).",
2642 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT
), name
, t
->id
, name
, signed_status
);
2646 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*soa
= NULL
;
2648 soa
= dns_resource_key_new(dns_transaction_key(t
)->class, type
, name
);
2652 r
= dns_transaction_request_dnssec_rr(t
, soa
);
2658 return dns_transaction_dnssec_is_live(t
);
2661 void dns_transaction_notify(DnsTransaction
*t
, DnsTransaction
*source
) {
2665 /* Invoked whenever any of our auxiliary DNSSEC transactions completed its work. If the state is still PENDING,
2666 we are still in the loop that adds further DNSSEC transactions, hence don't check if we are ready yet. If
2667 the state is VALIDATING however, we should check if we are complete now. */
2669 if (t
->state
== DNS_TRANSACTION_VALIDATING
)
2670 dns_transaction_process_dnssec(t
);
2673 static int dns_transaction_validate_dnskey_by_ds(DnsTransaction
*t
) {
2674 DnsAnswerItem
*item
;
2679 /* Add all DNSKEY RRs from the answer that are validated by DS
2680 * RRs from the list of validated keys to the list of
2681 * validated keys. */
2683 DNS_ANSWER_FOREACH_ITEM(item
, t
->answer
) {
2685 r
= dnssec_verify_dnskey_by_ds_search(item
->rr
, t
->validated_keys
);
2691 /* If so, the DNSKEY is validated too. */
2692 r
= dns_answer_add_extend(&t
->validated_keys
, item
->rr
, item
->ifindex
, item
->flags
|DNS_ANSWER_AUTHENTICATED
, item
->rrsig
);
2700 static int dns_transaction_requires_rrsig(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2706 /* Checks if the RR we are looking for must be signed with an
2707 * RRSIG. This is used for positive responses. */
2709 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2712 if (dns_type_is_pseudo(rr
->key
->type
))
2715 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2721 switch (rr
->key
->type
) {
2723 case DNS_TYPE_RRSIG
:
2724 /* RRSIGs are the signatures themselves, they need no signing. */
2731 /* For SOA or NS RRs we look for a matching DS transaction */
2733 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2735 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2737 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_DS
)
2740 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), dns_resource_key_name(rr
->key
));
2746 /* We found a DS transactions for the SOA/NS
2747 * RRs we are looking at. If it discovered signed DS
2748 * RRs, then we need to be signed, too. */
2750 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
2753 return dns_answer_match_key(dt
->answer
, dns_transaction_key(dt
), NULL
);
2756 /* We found nothing that proves this is safe to leave
2757 * this unauthenticated, hence ask inist on
2758 * authentication. */
2763 case DNS_TYPE_CNAME
:
2764 case DNS_TYPE_DNAME
: {
2765 const char *parent
= NULL
;
2769 * CNAME/DNAME RRs cannot be located at a zone apex, hence look directly for the parent SOA.
2771 * DS RRs are signed if the parent is signed, hence also look at the parent SOA
2774 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2776 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2778 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_SOA
)
2782 parent
= dns_resource_key_name(rr
->key
);
2783 r
= dns_name_parent(&parent
);
2787 if (rr
->key
->type
== DNS_TYPE_DS
)
2790 /* A CNAME/DNAME without a parent? That's sooo weird. */
2791 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG
),
2792 "Transaction %" PRIu16
" claims CNAME/DNAME at root. Refusing.", t
->id
);
2796 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), parent
);
2802 return FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2811 /* Any other kind of RR (including DNSKEY/NSEC/NSEC3). Let's see if our SOA lookup was authenticated */
2813 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2815 if (dns_transaction_key(dt
)->class != rr
->key
->class)
2817 if (dns_transaction_key(dt
)->type
!= DNS_TYPE_SOA
)
2820 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), dns_resource_key_name(rr
->key
));
2826 /* We found the transaction that was supposed to find the SOA RR for us. It was
2827 * successful, but found no RR for us. This means we are not at a zone cut. In this
2828 * case, we require authentication if the SOA lookup was authenticated too. */
2829 return FLAGS_SET(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2836 static int dns_transaction_in_private_tld(DnsTransaction
*t
, const DnsResourceKey
*key
) {
2841 /* If DNSSEC downgrade mode is on, checks whether the
2842 * specified RR is one level below a TLD we have proven not to
2843 * exist. In such a case we assume that this is a private
2844 * domain, and permit it.
2846 * This detects cases like the Fritz!Box router networks. Each
2847 * Fritz!Box router serves a private "fritz.box" zone, in the
2848 * non-existing TLD "box". Requests for the "fritz.box" domain
2849 * are served by the router itself, while requests for the
2850 * "box" domain will result in NXDOMAIN.
2852 * Note that this logic is unable to detect cases where a
2853 * router serves a private DNS zone directly under
2854 * non-existing TLD. In such a case we cannot detect whether
2855 * the TLD is supposed to exist or not, as all requests we
2856 * make for it will be answered by the router's zone, and not
2857 * by the root zone. */
2861 if (t
->scope
->dnssec_mode
!= DNSSEC_ALLOW_DOWNGRADE
)
2862 return false; /* In strict DNSSEC mode what doesn't exist, doesn't exist */
2864 tld
= dns_resource_key_name(key
);
2865 r
= dns_name_parent(&tld
);
2869 return false; /* Already the root domain */
2871 if (!dns_name_is_single_label(tld
))
2874 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2876 if (dns_transaction_key(dt
)->class != key
->class)
2879 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), tld
);
2885 /* We found an auxiliary lookup we did for the TLD. If
2886 * that returned with NXDOMAIN, we know the TLD didn't
2887 * exist, and hence this might be a private zone. */
2889 return dt
->answer_rcode
== DNS_RCODE_NXDOMAIN
;
2895 static int dns_transaction_requires_nsec(DnsTransaction
*t
) {
2896 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
2904 /* Checks if we need to insist on NSEC/NSEC3 RRs for proving
2905 * this negative reply */
2907 if (t
->scope
->dnssec_mode
== DNSSEC_NO
)
2910 if (dns_type_is_pseudo(dns_transaction_key(t
)->type
))
2913 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(dns_transaction_key(t
)));
2919 r
= dns_transaction_in_private_tld(t
, dns_transaction_key(t
));
2923 /* The lookup is from a TLD that is proven not to
2924 * exist, and we are in downgrade mode, hence ignore
2925 * that fact that we didn't get any NSEC RRs. */
2927 log_info("Detected a negative query %s in a private DNS zone, permitting unsigned response.",
2928 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
));
2932 name
= dns_resource_key_name(dns_transaction_key(t
));
2934 if (dns_transaction_key(t
)->type
== DNS_TYPE_DS
) {
2936 /* We got a negative reply for this DS lookup? DS RRs are signed when their parent zone is signed,
2937 * hence check the parent SOA in this case. */
2939 r
= dns_name_parent(&name
);
2945 type
= DNS_TYPE_SOA
;
2947 } else if (IN_SET(dns_transaction_key(t
)->type
, DNS_TYPE_SOA
, DNS_TYPE_NS
))
2948 /* We got a negative reply for this SOA/NS lookup? If so, check if there's a DS RR for this */
2951 /* For all other negative replies, check for the SOA lookup */
2952 type
= DNS_TYPE_SOA
;
2954 /* For all other RRs we check the SOA on the same level to see
2955 * if it's signed. */
2957 SET_FOREACH(dt
, t
->dnssec_transactions
) {
2959 if (dns_transaction_key(dt
)->class != dns_transaction_key(t
)->class)
2961 if (dns_transaction_key(dt
)->type
!= type
)
2964 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), name
);
2970 return FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
);
2973 /* If in doubt, require NSEC/NSEC3 */
2977 static int dns_transaction_dnskey_authenticated(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
2978 DnsResourceRecord
*rrsig
;
2982 /* Checks whether any of the DNSKEYs used for the RRSIGs for
2983 * the specified RRset is authenticated (i.e. has a matching
2986 r
= dns_transaction_negative_trust_anchor_lookup(t
, dns_resource_key_name(rr
->key
));
2992 DNS_ANSWER_FOREACH(rrsig
, t
->answer
) {
2995 r
= dnssec_key_match_rrsig(rr
->key
, rrsig
);
3001 SET_FOREACH(dt
, t
->dnssec_transactions
) {
3003 if (dns_transaction_key(dt
)->class != rr
->key
->class)
3006 if (dns_transaction_key(dt
)->type
== DNS_TYPE_DNSKEY
) {
3008 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), rrsig
->rrsig
.signer
);
3014 /* OK, we found an auxiliary DNSKEY lookup. If that lookup is authenticated,
3017 if (FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
3022 } else if (dns_transaction_key(dt
)->type
== DNS_TYPE_DS
) {
3024 r
= dns_name_equal(dns_resource_key_name(dns_transaction_key(dt
)), rrsig
->rrsig
.signer
);
3030 /* OK, we found an auxiliary DS lookup. If that lookup is authenticated and
3031 * non-zero, we won! */
3033 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
3036 return dns_answer_match_key(dt
->answer
, dns_transaction_key(dt
), NULL
);
3041 return found
? false : -ENXIO
;
3044 static int dns_transaction_known_signed(DnsTransaction
*t
, DnsResourceRecord
*rr
) {
3048 /* We know that the root domain is signed, hence if it appears
3049 * not to be signed, there's a problem with the DNS server */
3051 return rr
->key
->class == DNS_CLASS_IN
&&
3052 dns_name_is_root(dns_resource_key_name(rr
->key
));
3055 static int dns_transaction_check_revoked_trust_anchors(DnsTransaction
*t
) {
3056 DnsResourceRecord
*rr
;
3061 /* Maybe warn the user that we encountered a revoked DNSKEY
3062 * for a key from our trust anchor. Note that we don't care
3063 * whether the DNSKEY can be authenticated or not. It's
3064 * sufficient if it is self-signed. */
3066 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
3067 r
= dns_trust_anchor_check_revoked(&t
->scope
->manager
->trust_anchor
, rr
, t
->answer
);
3075 static int dns_transaction_invalidate_revoked_keys(DnsTransaction
*t
) {
3081 /* Removes all DNSKEY/DS objects from t->validated_keys that
3082 * our trust anchors database considers revoked. */
3085 DnsResourceRecord
*rr
;
3089 DNS_ANSWER_FOREACH(rr
, t
->validated_keys
) {
3090 r
= dns_trust_anchor_is_revoked(&t
->scope
->manager
->trust_anchor
, rr
);
3094 r
= dns_answer_remove_by_rr(&t
->validated_keys
, rr
);
3108 static int dns_transaction_copy_validated(DnsTransaction
*t
) {
3114 /* Copy all validated RRs from the auxiliary DNSSEC transactions into our set of validated RRs */
3116 SET_FOREACH(dt
, t
->dnssec_transactions
) {
3118 if (DNS_TRANSACTION_IS_LIVE(dt
->state
))
3121 if (!FLAGS_SET(dt
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
))
3124 r
= dns_answer_extend(&t
->validated_keys
, dt
->answer
);
3133 DNSSEC_PHASE_DNSKEY
, /* Phase #1, only validate DNSKEYs */
3134 DNSSEC_PHASE_NSEC
, /* Phase #2, only validate NSEC+NSEC3 */
3135 DNSSEC_PHASE_ALL
, /* Phase #3, validate everything else */
3138 static int dnssec_validate_records(
3142 DnsAnswer
**validated
) {
3144 DnsResourceRecord
*rr
;
3147 /* Returns negative on error, 0 if validation failed, 1 to restart validation, 2 when finished. */
3149 DNS_ANSWER_FOREACH(rr
, t
->answer
) {
3150 _unused_
_cleanup_(dns_resource_record_unrefp
) DnsResourceRecord
*rr_ref
= dns_resource_record_ref(rr
);
3151 DnsResourceRecord
*rrsig
= NULL
;
3152 DnssecResult result
;
3154 switch (rr
->key
->type
) {
3155 case DNS_TYPE_RRSIG
:
3158 case DNS_TYPE_DNSKEY
:
3159 /* We validate DNSKEYs only in the DNSKEY and ALL phases */
3160 if (phase
== DNSSEC_PHASE_NSEC
)
3165 case DNS_TYPE_NSEC3
:
3168 /* We validate NSEC/NSEC3 only in the NSEC and ALL phases */
3169 if (phase
== DNSSEC_PHASE_DNSKEY
)
3174 /* We validate all other RRs only in the ALL phases */
3175 if (phase
!= DNSSEC_PHASE_ALL
)
3179 r
= dnssec_verify_rrset_search(
3189 log_debug("Looking at %s: %s", strna(dns_resource_record_to_string(rr
)), dnssec_result_to_string(result
));
3191 if (result
== DNSSEC_VALIDATED
) {
3194 if (rr
->key
->type
== DNS_TYPE_DNSKEY
) {
3195 /* If we just validated a DNSKEY RRset, then let's add these keys to
3196 * the set of validated keys for this transaction. */
3198 r
= dns_answer_copy_by_key(&t
->validated_keys
, t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
, rrsig
);
3202 /* Some of the DNSKEYs we just added might already have been revoked,
3203 * remove them again in that case. */
3204 r
= dns_transaction_invalidate_revoked_keys(t
);
3209 /* Add the validated RRset to the new list of validated RRsets, and remove it from
3210 * the unvalidated RRsets. We mark the RRset as authenticated and cacheable. */
3211 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
, rrsig
);
3215 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_SECURE
, rr
->key
);
3217 /* Exit the loop, we dropped something from the answer, start from the beginning */
3221 /* If we haven't read all DNSKEYs yet a negative result of the validation is irrelevant, as
3222 * there might be more DNSKEYs coming. Similar, if we haven't read all NSEC/NSEC3 RRs yet,
3223 * we cannot do positive wildcard proofs yet, as those require the NSEC/NSEC3 RRs. */
3224 if (phase
!= DNSSEC_PHASE_ALL
)
3227 if (result
== DNSSEC_VALIDATED_WILDCARD
) {
3228 bool authenticated
= false;
3233 /* This RRset validated, but as a wildcard. This means we need
3234 * to prove via NSEC/NSEC3 that no matching non-wildcard RR exists. */
3236 /* First step, determine the source of synthesis */
3237 r
= dns_resource_record_source(rrsig
, &source
);
3241 r
= dnssec_test_positive_wildcard(*validated
,
3242 dns_resource_key_name(rr
->key
),
3244 rrsig
->rrsig
.signer
,
3247 /* Unless the NSEC proof showed that the key really doesn't exist something is off. */
3249 result
= DNSSEC_INVALID
;
3251 r
= dns_answer_move_by_key(
3255 authenticated
? (DNS_ANSWER_AUTHENTICATED
|DNS_ANSWER_CACHEABLE
) : 0,
3260 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, rr
->key
);
3262 /* Exit the loop, we dropped something from the answer, start from the beginning */
3267 if (result
== DNSSEC_NO_SIGNATURE
) {
3268 r
= dns_transaction_requires_rrsig(t
, rr
);
3272 /* Data does not require signing. In that case, just copy it over,
3273 * but remember that this is by no means authenticated. */
3274 r
= dns_answer_move_by_key(
3283 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3287 r
= dns_transaction_known_signed(t
, rr
);
3291 /* This is an RR we know has to be signed. If it isn't this means
3292 * the server is not attaching RRSIGs, hence complain. */
3294 dns_server_packet_rrsig_missing(t
->server
, t
->current_feature_level
);
3296 if (t
->scope
->dnssec_mode
== DNSSEC_ALLOW_DOWNGRADE
) {
3298 /* Downgrading is OK? If so, just consider the information unsigned */
3300 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3304 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3308 /* Otherwise, fail */
3309 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
3313 r
= dns_transaction_in_private_tld(t
, rr
->key
);
3317 char s
[DNS_RESOURCE_KEY_STRING_MAX
];
3319 /* The data is from a TLD that is proven not to exist, and we are in downgrade
3320 * mode, hence ignore the fact that this was not signed. */
3322 log_info("Detected RRset %s is in a private DNS zone, permitting unsigned RRs.",
3323 dns_resource_key_to_string(rr
->key
, s
, sizeof s
));
3325 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3329 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3336 DNSSEC_SIGNATURE_EXPIRED
,
3337 DNSSEC_UNSUPPORTED_ALGORITHM
)) {
3339 r
= dns_transaction_dnskey_authenticated(t
, rr
);
3340 if (r
< 0 && r
!= -ENXIO
)
3343 /* The DNSKEY transaction was not authenticated, this means there's
3344 * no DS for this, which means it's OK if no keys are found for this signature. */
3346 r
= dns_answer_move_by_key(validated
, &t
->answer
, rr
->key
, 0, NULL
);
3350 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, rr
->key
);
3355 r
= dns_transaction_is_primary_response(t
, rr
);
3359 /* Look for a matching DNAME for this CNAME */
3360 r
= dns_answer_has_dname_for_cname(t
->answer
, rr
);
3364 /* Also look among the stuff we already validated */
3365 r
= dns_answer_has_dname_for_cname(*validated
, rr
);
3373 DNSSEC_SIGNATURE_EXPIRED
,
3374 DNSSEC_NO_SIGNATURE
))
3375 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, rr
->key
);
3376 else /* DNSSEC_MISSING_KEY or DNSSEC_UNSUPPORTED_ALGORITHM */
3377 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, rr
->key
);
3379 /* This is a primary response to our question, and it failed validation.
3381 t
->answer_dnssec_result
= result
;
3385 /* This is a primary response, but we do have a DNAME RR
3386 * in the RR that can replay this CNAME, hence rely on
3387 * that, and we can remove the CNAME in favour of it. */
3390 /* This is just some auxiliary data. Just remove the RRset and continue. */
3391 r
= dns_answer_remove_by_key(&t
->answer
, rr
->key
);
3395 /* We dropped something from the answer, start from the beginning. */
3399 return 2; /* Finito. */
3402 int dns_transaction_validate_dnssec(DnsTransaction
*t
) {
3403 _cleanup_(dns_answer_unrefp
) DnsAnswer
*validated
= NULL
;
3405 DnsAnswerFlags flags
;
3407 char key_str
[DNS_RESOURCE_KEY_STRING_MAX
];
3411 /* We have now collected all DS and DNSKEY RRs in t->validated_keys, let's see which RRs we can now
3412 * authenticate with that. */
3414 if (FLAGS_SET(t
->query_flags
, SD_RESOLVED_NO_VALIDATE
) || t
->scope
->dnssec_mode
== DNSSEC_NO
)
3417 /* Already validated */
3418 if (t
->answer_dnssec_result
!= _DNSSEC_RESULT_INVALID
)
3421 /* Our own stuff needs no validation */
3422 if (IN_SET(t
->answer_source
, DNS_TRANSACTION_ZONE
, DNS_TRANSACTION_TRUST_ANCHOR
)) {
3423 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3424 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, true);
3428 /* Cached stuff is not affected by validation. */
3429 if (t
->answer_source
!= DNS_TRANSACTION_NETWORK
)
3432 if (!dns_transaction_dnssec_supported_full(t
)) {
3433 /* The server does not support DNSSEC, or doesn't augment responses with RRSIGs. */
3434 t
->answer_dnssec_result
= DNSSEC_INCOMPATIBLE_SERVER
;
3435 log_debug("Not validating response for %" PRIu16
", used server feature level does not support DNSSEC.", t
->id
);
3439 log_debug("Validating response from transaction %" PRIu16
" (%s).",
3441 dns_resource_key_to_string(dns_transaction_key(t
), key_str
, sizeof key_str
));
3443 /* First, see if this response contains any revoked trust
3444 * anchors we care about */
3445 r
= dns_transaction_check_revoked_trust_anchors(t
);
3449 /* Third, copy all RRs we acquired successfully from auxiliary RRs over. */
3450 r
= dns_transaction_copy_validated(t
);
3454 /* Second, see if there are DNSKEYs we already know a
3455 * validated DS for. */
3456 r
= dns_transaction_validate_dnskey_by_ds(t
);
3460 /* Fourth, remove all DNSKEY and DS RRs again that our trust
3461 * anchor says are revoked. After all we might have marked
3462 * some keys revoked above, but they might still be lingering
3463 * in our validated_keys list. */
3464 r
= dns_transaction_invalidate_revoked_keys(t
);
3468 phase
= DNSSEC_PHASE_DNSKEY
;
3470 bool have_nsec
= false;
3472 r
= dnssec_validate_records(t
, phase
, &have_nsec
, &validated
);
3476 /* Try again as long as we managed to achieve something */
3480 if (phase
== DNSSEC_PHASE_DNSKEY
&& have_nsec
) {
3481 /* OK, we processed all DNSKEYs, and there are NSEC/NSEC3 RRs, look at those now. */
3482 phase
= DNSSEC_PHASE_NSEC
;
3486 if (phase
!= DNSSEC_PHASE_ALL
) {
3487 /* OK, we processed all DNSKEYs and NSEC/NSEC3 RRs, look at all the rest now.
3488 * Note that in this third phase we start to remove RRs we couldn't validate. */
3489 phase
= DNSSEC_PHASE_ALL
;
3497 DNS_ANSWER_REPLACE(t
->answer
, TAKE_PTR(validated
));
3499 /* At this point the answer only contains validated
3500 * RRsets. Now, let's see if it actually answers the question
3501 * we asked. If so, great! If it doesn't, then see if
3502 * NSEC/NSEC3 can prove this. */
3503 r
= dns_transaction_has_positive_answer(t
, &flags
);
3505 /* Yes, it answers the question! */
3507 if (flags
& DNS_ANSWER_AUTHENTICATED
) {
3508 /* The answer is fully authenticated, yay. */
3509 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3510 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
3511 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, true);
3513 /* The answer is not fully authenticated. */
3514 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3515 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3518 } else if (r
== 0) {
3519 DnssecNsecResult nr
;
3520 bool authenticated
= false;
3522 /* Bummer! Let's check NSEC/NSEC3 */
3523 r
= dnssec_nsec_test(t
->answer
, dns_transaction_key(t
), &nr
, &authenticated
, &t
->answer_nsec_ttl
);
3529 case DNSSEC_NSEC_NXDOMAIN
:
3530 /* NSEC proves the domain doesn't exist. Very good. */
3531 log_debug("Proved NXDOMAIN via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3532 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3533 t
->answer_rcode
= DNS_RCODE_NXDOMAIN
;
3534 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, authenticated
);
3536 manager_dnssec_verdict(t
->scope
->manager
, authenticated
? DNSSEC_SECURE
: DNSSEC_INSECURE
, dns_transaction_key(t
));
3539 case DNSSEC_NSEC_NODATA
:
3540 /* NSEC proves that there's no data here, very good. */
3541 log_debug("Proved NODATA via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3542 t
->answer_dnssec_result
= DNSSEC_VALIDATED
;
3543 t
->answer_rcode
= DNS_RCODE_SUCCESS
;
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_OPTOUT
:
3550 /* NSEC3 says the data might not be signed */
3551 log_debug("Data is NSEC3 opt-out via NSEC/NSEC3 for transaction %u (%s)", t
->id
, key_str
);
3552 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3553 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3555 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, dns_transaction_key(t
));
3558 case DNSSEC_NSEC_NO_RR
:
3559 /* No NSEC data? Bummer! */
3561 r
= dns_transaction_requires_nsec(t
);
3565 t
->answer_dnssec_result
= DNSSEC_NO_SIGNATURE
;
3566 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, dns_transaction_key(t
));
3568 t
->answer_dnssec_result
= DNSSEC_UNSIGNED
;
3569 SET_FLAG(t
->answer_query_flags
, SD_RESOLVED_AUTHENTICATED
, false);
3570 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INSECURE
, dns_transaction_key(t
));
3575 case DNSSEC_NSEC_UNSUPPORTED_ALGORITHM
:
3576 /* We don't know the NSEC3 algorithm used? */
3577 t
->answer_dnssec_result
= DNSSEC_UNSUPPORTED_ALGORITHM
;
3578 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_INDETERMINATE
, dns_transaction_key(t
));
3581 case DNSSEC_NSEC_FOUND
:
3582 case DNSSEC_NSEC_CNAME
:
3583 /* NSEC says it needs to be there, but we couldn't find it? Bummer! */
3584 t
->answer_dnssec_result
= DNSSEC_NSEC_MISMATCH
;
3585 manager_dnssec_verdict(t
->scope
->manager
, DNSSEC_BOGUS
, dns_transaction_key(t
));
3589 assert_not_reached();
3596 static const char* const dns_transaction_state_table
[_DNS_TRANSACTION_STATE_MAX
] = {
3597 [DNS_TRANSACTION_NULL
] = "null",
3598 [DNS_TRANSACTION_PENDING
] = "pending",
3599 [DNS_TRANSACTION_VALIDATING
] = "validating",
3600 [DNS_TRANSACTION_RCODE_FAILURE
] = "rcode-failure",
3601 [DNS_TRANSACTION_SUCCESS
] = "success",
3602 [DNS_TRANSACTION_NO_SERVERS
] = "no-servers",
3603 [DNS_TRANSACTION_TIMEOUT
] = "timeout",
3604 [DNS_TRANSACTION_ATTEMPTS_MAX_REACHED
] = "attempts-max-reached",
3605 [DNS_TRANSACTION_INVALID_REPLY
] = "invalid-reply",
3606 [DNS_TRANSACTION_ERRNO
] = "errno",
3607 [DNS_TRANSACTION_ABORTED
] = "aborted",
3608 [DNS_TRANSACTION_DNSSEC_FAILED
] = "dnssec-failed",
3609 [DNS_TRANSACTION_NO_TRUST_ANCHOR
] = "no-trust-anchor",
3610 [DNS_TRANSACTION_RR_TYPE_UNSUPPORTED
] = "rr-type-unsupported",
3611 [DNS_TRANSACTION_NETWORK_DOWN
] = "network-down",
3612 [DNS_TRANSACTION_NOT_FOUND
] = "not-found",
3613 [DNS_TRANSACTION_NO_SOURCE
] = "no-source",
3614 [DNS_TRANSACTION_STUB_LOOP
] = "stub-loop",
3616 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state
, DnsTransactionState
);
3618 static const char* const dns_transaction_source_table
[_DNS_TRANSACTION_SOURCE_MAX
] = {
3619 [DNS_TRANSACTION_NETWORK
] = "network",
3620 [DNS_TRANSACTION_CACHE
] = "cache",
3621 [DNS_TRANSACTION_ZONE
] = "zone",
3622 [DNS_TRANSACTION_TRUST_ANCHOR
] = "trust-anchor",
3624 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source
, DnsTransactionSource
);