diff options
Diffstat (limited to 'src/resolve/resolved-dns-transaction.c')
| -rw-r--r-- | src/resolve/resolved-dns-transaction.c | 3670 |
1 files changed, 3670 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c new file mode 100644 index 0000000..8ff5653 --- /dev/null +++ b/src/resolve/resolved-dns-transaction.c @@ -0,0 +1,3670 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include "sd-messages.h" + +#include "af-list.h" +#include "alloc-util.h" +#include "dns-domain.h" +#include "errno-list.h" +#include "errno-util.h" +#include "fd-util.h" +#include "glyph-util.h" +#include "random-util.h" +#include "resolved-dns-cache.h" +#include "resolved-dns-transaction.h" +#include "resolved-dnstls.h" +#include "resolved-llmnr.h" +#include "string-table.h" + +#define TRANSACTIONS_MAX 4096 +#define TRANSACTION_TCP_TIMEOUT_USEC (10U*USEC_PER_SEC) + +/* After how much time to repeat classic DNS requests */ +#define DNS_TIMEOUT_USEC (SD_RESOLVED_QUERY_TIMEOUT_USEC / DNS_TRANSACTION_ATTEMPTS_MAX) + +static void dns_transaction_reset_answer(DnsTransaction *t) { + assert(t); + + t->received = dns_packet_unref(t->received); + t->answer = dns_answer_unref(t->answer); + t->answer_rcode = 0; + t->answer_dnssec_result = _DNSSEC_RESULT_INVALID; + t->answer_source = _DNS_TRANSACTION_SOURCE_INVALID; + t->answer_query_flags = 0; + t->answer_nsec_ttl = UINT32_MAX; + t->answer_errno = 0; +} + +static void dns_transaction_flush_dnssec_transactions(DnsTransaction *t) { + DnsTransaction *z; + + assert(t); + + while ((z = set_steal_first(t->dnssec_transactions))) { + set_remove(z->notify_transactions, t); + set_remove(z->notify_transactions_done, t); + dns_transaction_gc(z); + } +} + +static void dns_transaction_close_connection( + DnsTransaction *t, + bool use_graveyard) { /* Set use_graveyard = false when you know the connection is already + * dead, for example because you got a connection error back from the + * kernel. In that case there's no point in keeping the fd around, + * hence don't. */ + int r; + + assert(t); + + if (t->stream) { + /* Let's detach the stream from our transaction, in case something else keeps a reference to it. */ + LIST_REMOVE(transactions_by_stream, t->stream->transactions, t); + + /* Remove packet in case it's still in the queue */ + dns_packet_unref(ordered_set_remove(t->stream->write_queue, t->sent)); + + t->stream = dns_stream_unref(t->stream); + } + + t->dns_udp_event_source = sd_event_source_disable_unref(t->dns_udp_event_source); + + /* If we have a UDP socket where we sent a packet, but never received one, then add it to the socket + * graveyard, instead of closing it right away. That way it will stick around for a moment longer, + * and the reply we might still get from the server will be eaten up instead of resulting in an ICMP + * port unreachable error message. */ + + /* Skip the graveyard stuff when we're shutting down, since that requires running event loop */ + if (!t->scope->manager->event || sd_event_get_state(t->scope->manager->event) == SD_EVENT_FINISHED) + use_graveyard = false; + + if (use_graveyard && t->dns_udp_fd >= 0 && t->sent && !t->received) { + r = manager_add_socket_to_graveyard(t->scope->manager, t->dns_udp_fd); + if (r < 0) + log_debug_errno(r, "Failed to add UDP socket to graveyard, closing immediately: %m"); + else + TAKE_FD(t->dns_udp_fd); + } + + t->dns_udp_fd = safe_close(t->dns_udp_fd); +} + +static void dns_transaction_stop_timeout(DnsTransaction *t) { + assert(t); + + t->timeout_event_source = sd_event_source_disable_unref(t->timeout_event_source); +} + +DnsTransaction* dns_transaction_free(DnsTransaction *t) { + DnsQueryCandidate *c; + DnsZoneItem *i; + DnsTransaction *z; + + if (!t) + return NULL; + + log_debug("Freeing transaction %" PRIu16 ".", t->id); + + dns_transaction_close_connection(t, true); + dns_transaction_stop_timeout(t); + + dns_packet_unref(t->sent); + dns_transaction_reset_answer(t); + + dns_server_unref(t->server); + + if (t->scope) { + if (t->key) { + DnsTransaction *first; + + first = hashmap_get(t->scope->transactions_by_key, t->key); + LIST_REMOVE(transactions_by_key, first, t); + if (first) + hashmap_replace(t->scope->transactions_by_key, first->key, first); + else + hashmap_remove(t->scope->transactions_by_key, t->key); + } + + LIST_REMOVE(transactions_by_scope, t->scope->transactions, t); + + if (t->id != 0) + hashmap_remove(t->scope->manager->dns_transactions, UINT_TO_PTR(t->id)); + } + + while ((c = set_steal_first(t->notify_query_candidates))) + set_remove(c->transactions, t); + set_free(t->notify_query_candidates); + + while ((c = set_steal_first(t->notify_query_candidates_done))) + set_remove(c->transactions, t); + set_free(t->notify_query_candidates_done); + + while ((i = set_steal_first(t->notify_zone_items))) + i->probe_transaction = NULL; + set_free(t->notify_zone_items); + + while ((i = set_steal_first(t->notify_zone_items_done))) + i->probe_transaction = NULL; + set_free(t->notify_zone_items_done); + + while ((z = set_steal_first(t->notify_transactions))) + set_remove(z->dnssec_transactions, t); + set_free(t->notify_transactions); + + while ((z = set_steal_first(t->notify_transactions_done))) + set_remove(z->dnssec_transactions, t); + set_free(t->notify_transactions_done); + + dns_transaction_flush_dnssec_transactions(t); + set_free(t->dnssec_transactions); + + dns_answer_unref(t->validated_keys); + dns_resource_key_unref(t->key); + dns_packet_unref(t->bypass); + + return mfree(t); +} + +DEFINE_TRIVIAL_CLEANUP_FUNC(DnsTransaction*, dns_transaction_free); + +DnsTransaction* dns_transaction_gc(DnsTransaction *t) { + assert(t); + + /* Returns !NULL if we can't gc yet. */ + + if (t->block_gc > 0) + return t; + + if (set_isempty(t->notify_query_candidates) && + set_isempty(t->notify_query_candidates_done) && + set_isempty(t->notify_zone_items) && + set_isempty(t->notify_zone_items_done) && + set_isempty(t->notify_transactions) && + set_isempty(t->notify_transactions_done)) + return dns_transaction_free(t); + + return t; +} + +static uint16_t pick_new_id(Manager *m) { + uint16_t new_id; + + /* Find a fresh, unused transaction id. Note that this loop is bounded because there's a limit on the + * number of transactions, and it's much lower than the space of IDs. */ + + assert_cc(TRANSACTIONS_MAX < 0xFFFF); + + do + random_bytes(&new_id, sizeof(new_id)); + while (new_id == 0 || + hashmap_get(m->dns_transactions, UINT_TO_PTR(new_id))); + + return new_id; +} + +static int key_ok( + DnsScope *scope, + DnsResourceKey *key) { + + /* Don't allow looking up invalid or pseudo RRs */ + if (!dns_type_is_valid_query(key->type)) + return -EINVAL; + if (dns_type_is_obsolete(key->type)) + return -EOPNOTSUPP; + + /* We only support the IN class */ + if (!IN_SET(key->class, DNS_CLASS_IN, DNS_CLASS_ANY)) + return -EOPNOTSUPP; + + /* Don't allows DNSSEC RRs to be looked up via LLMNR/mDNS. They don't really make sense + * there, and it speeds up our queries if we refuse this early */ + if (scope->protocol != DNS_PROTOCOL_DNS && + dns_type_is_dnssec(key->type)) + return -EOPNOTSUPP; + + return 0; +} + +int dns_transaction_new( + DnsTransaction **ret, + DnsScope *s, + DnsResourceKey *key, + DnsPacket *bypass, + uint64_t query_flags) { + + _cleanup_(dns_transaction_freep) DnsTransaction *t = NULL; + int r; + + assert(ret); + assert(s); + + if (key) { + assert(!bypass); + + r = key_ok(s, key); + if (r < 0) + return r; + } else { + DnsResourceKey *qk; + assert(bypass); + + r = dns_packet_validate_query(bypass); + if (r < 0) + return r; + + DNS_QUESTION_FOREACH(qk, bypass->question) { + r = key_ok(s, qk); + if (r < 0) + return r; + } + } + + if (hashmap_size(s->manager->dns_transactions) >= TRANSACTIONS_MAX) + return -EBUSY; + + r = hashmap_ensure_allocated(&s->manager->dns_transactions, NULL); + if (r < 0) + return r; + + if (key) { + r = hashmap_ensure_allocated(&s->transactions_by_key, &dns_resource_key_hash_ops); + if (r < 0) + return r; + } + + t = new(DnsTransaction, 1); + if (!t) + return -ENOMEM; + + *t = (DnsTransaction) { + .dns_udp_fd = -EBADF, + .answer_source = _DNS_TRANSACTION_SOURCE_INVALID, + .answer_dnssec_result = _DNSSEC_RESULT_INVALID, + .answer_nsec_ttl = UINT32_MAX, + .key = dns_resource_key_ref(key), + .query_flags = query_flags, + .bypass = dns_packet_ref(bypass), + .current_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID, + .clamp_feature_level_servfail = _DNS_SERVER_FEATURE_LEVEL_INVALID, + .id = pick_new_id(s->manager), + }; + + r = hashmap_put(s->manager->dns_transactions, UINT_TO_PTR(t->id), t); + if (r < 0) { + t->id = 0; + return r; + } + + if (t->key) { + DnsTransaction *first; + + first = hashmap_get(s->transactions_by_key, t->key); + LIST_PREPEND(transactions_by_key, first, t); + + r = hashmap_replace(s->transactions_by_key, first->key, first); + if (r < 0) { + LIST_REMOVE(transactions_by_key, first, t); + return r; + } + } + + LIST_PREPEND(transactions_by_scope, s->transactions, t); + t->scope = s; + + s->manager->n_transactions_total++; + + if (ret) + *ret = t; + + TAKE_PTR(t); + return 0; +} + +static void dns_transaction_shuffle_id(DnsTransaction *t) { + uint16_t new_id; + assert(t); + + /* Pick a new ID for this transaction. */ + + new_id = pick_new_id(t->scope->manager); + assert_se(hashmap_remove_and_put(t->scope->manager->dns_transactions, UINT_TO_PTR(t->id), UINT_TO_PTR(new_id), t) >= 0); + + log_debug("Transaction %" PRIu16 " is now %" PRIu16 ".", t->id, new_id); + t->id = new_id; + + /* Make sure we generate a new packet with the new ID */ + t->sent = dns_packet_unref(t->sent); +} + +static void dns_transaction_tentative(DnsTransaction *t, DnsPacket *p) { + char key_str[DNS_RESOURCE_KEY_STRING_MAX]; + DnsZoneItem *z; + + assert(t); + assert(p); + assert(t->scope->protocol == DNS_PROTOCOL_LLMNR); + + if (manager_packet_from_local_address(t->scope->manager, p) != 0) + return; + + log_debug("Transaction %" PRIu16 " for <%s> on scope %s on %s/%s got tentative packet from %s.", + t->id, + dns_resource_key_to_string(dns_transaction_key(t), key_str, sizeof key_str), + dns_protocol_to_string(t->scope->protocol), + t->scope->link ? t->scope->link->ifname : "*", + af_to_name_short(t->scope->family), + IN_ADDR_TO_STRING(p->family, &p->sender)); + + /* RFC 4795, Section 4.1 says that the peer with the + * lexicographically smaller IP address loses */ + if (memcmp(&p->sender, &p->destination, FAMILY_ADDRESS_SIZE(p->family)) >= 0) { + log_debug("Peer has lexicographically larger IP address and thus lost in the conflict."); + return; + } + + log_debug("We have the lexicographically larger IP address and thus lost in the conflict."); + + t->block_gc++; + + while ((z = set_first(t->notify_zone_items))) { + /* First, make sure the zone item drops the reference + * to us */ + dns_zone_item_probe_stop(z); + + /* Secondly, report this as conflict, so that we might + * look for a different hostname */ + dns_zone_item_conflict(z); + } + t->block_gc--; + + dns_transaction_gc(t); +} + +void dns_transaction_complete(DnsTransaction *t, DnsTransactionState state) { + DnsQueryCandidate *c; + DnsZoneItem *z; + DnsTransaction *d; + const char *st; + char key_str[DNS_RESOURCE_KEY_STRING_MAX]; + + assert(t); + assert(!DNS_TRANSACTION_IS_LIVE(state)); + + if (state == DNS_TRANSACTION_DNSSEC_FAILED) { + dns_resource_key_to_string(dns_transaction_key(t), key_str, sizeof key_str); + + log_struct(LOG_NOTICE, + "MESSAGE_ID=" SD_MESSAGE_DNSSEC_FAILURE_STR, + LOG_MESSAGE("DNSSEC validation failed for question %s: %s", + key_str, dnssec_result_to_string(t->answer_dnssec_result)), + "DNS_TRANSACTION=%" PRIu16, t->id, + "DNS_QUESTION=%s", key_str, + "DNSSEC_RESULT=%s", dnssec_result_to_string(t->answer_dnssec_result), + "DNS_SERVER=%s", strna(dns_server_string_full(t->server)), + "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(t->server->possible_feature_level)); + } + + /* Note that this call might invalidate the query. Callers + * should hence not attempt to access the query or transaction + * after calling this function. */ + + if (state == DNS_TRANSACTION_ERRNO) + st = errno_to_name(t->answer_errno); + else + st = dns_transaction_state_to_string(state); + + log_debug("%s transaction %" PRIu16 " for <%s> on scope %s on %s/%s now complete with <%s> from %s (%s; %s).", + t->bypass ? "Bypass" : "Regular", + t->id, + dns_resource_key_to_string(dns_transaction_key(t), key_str, sizeof key_str), + dns_protocol_to_string(t->scope->protocol), + t->scope->link ? t->scope->link->ifname : "*", + af_to_name_short(t->scope->family), + st, + t->answer_source < 0 ? "none" : dns_transaction_source_to_string(t->answer_source), + FLAGS_SET(t->query_flags, SD_RESOLVED_NO_VALIDATE) ? "not validated" : + (FLAGS_SET(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED) ? "authenticated" : "unsigned"), + FLAGS_SET(t->answer_query_flags, SD_RESOLVED_CONFIDENTIAL) ? "confidential" : "non-confidential"); + + t->state = state; + + dns_transaction_close_connection(t, true); + dns_transaction_stop_timeout(t); + + /* Notify all queries that are interested, but make sure the + * transaction isn't freed while we are still looking at it */ + t->block_gc++; + + SET_FOREACH_MOVE(c, t->notify_query_candidates_done, t->notify_query_candidates) + dns_query_candidate_notify(c); + SWAP_TWO(t->notify_query_candidates, t->notify_query_candidates_done); + + SET_FOREACH_MOVE(z, t->notify_zone_items_done, t->notify_zone_items) + dns_zone_item_notify(z); + SWAP_TWO(t->notify_zone_items, t->notify_zone_items_done); + if (t->probing && t->state == DNS_TRANSACTION_ATTEMPTS_MAX_REACHED) + (void) dns_scope_announce(t->scope, false); + + SET_FOREACH_MOVE(d, t->notify_transactions_done, t->notify_transactions) + dns_transaction_notify(d, t); + SWAP_TWO(t->notify_transactions, t->notify_transactions_done); + + t->block_gc--; + dns_transaction_gc(t); +} + +static void dns_transaction_complete_errno(DnsTransaction *t, int error) { + assert(t); + assert(error != 0); + + t->answer_errno = abs(error); + dns_transaction_complete(t, DNS_TRANSACTION_ERRNO); +} + +static int dns_transaction_pick_server(DnsTransaction *t) { + DnsServer *server; + + assert(t); + assert(t->scope->protocol == DNS_PROTOCOL_DNS); + + /* Pick a DNS server and a feature level for it. */ + + server = dns_scope_get_dns_server(t->scope); + if (!server) + return -ESRCH; + + /* If we changed the server invalidate the feature level clamping, as the new server might have completely + * different properties. */ + if (server != t->server) + t->clamp_feature_level_servfail = _DNS_SERVER_FEATURE_LEVEL_INVALID; + + t->current_feature_level = dns_server_possible_feature_level(server); + + /* Clamp the feature level if that is requested. */ + if (t->clamp_feature_level_servfail != _DNS_SERVER_FEATURE_LEVEL_INVALID && + t->current_feature_level > t->clamp_feature_level_servfail) + t->current_feature_level = t->clamp_feature_level_servfail; + + log_debug("Using feature level %s for transaction %u.", dns_server_feature_level_to_string(t->current_feature_level), t->id); + + if (server == t->server) + return 0; + + dns_server_unref(t->server); + t->server = dns_server_ref(server); + + t->n_picked_servers ++; + + log_debug("Using DNS server %s for transaction %u.", strna(dns_server_string_full(t->server)), t->id); + + return 1; +} + +static void dns_transaction_retry(DnsTransaction *t, bool next_server) { + int r; + + assert(t); + + /* Retries the transaction as it is, possibly on a different server */ + + if (next_server && t->scope->protocol == DNS_PROTOCOL_DNS) + log_debug("Retrying transaction %" PRIu16 ", after switching servers.", t->id); + else + log_debug("Retrying transaction %" PRIu16 ".", t->id); + + /* Before we try again, switch to a new server. */ + if (next_server) + dns_scope_next_dns_server(t->scope, t->server); + + r = dns_transaction_go(t); + if (r < 0) + dns_transaction_complete_errno(t, r); +} + +static bool dns_transaction_limited_retry(DnsTransaction *t) { + assert(t); + + /* If we haven't tried all different servers yet, let's try again with a different server */ + + if (t->n_picked_servers >= dns_scope_get_n_dns_servers(t->scope)) + return false; + + dns_transaction_retry(t, /* next_server= */ true); + return true; +} + +static int dns_transaction_maybe_restart(DnsTransaction *t) { + int r; + + assert(t); + + /* Restarts the transaction, under a new ID if the feature level of the server changed since we first + * tried, without changing DNS server. Returns > 0 if the transaction was restarted, 0 if not. */ + + if (!t->server) + return 0; + + if (t->current_feature_level <= dns_server_possible_feature_level(t->server)) + return 0; + + /* The server's current feature level is lower than when we sent the original query. We learnt something from + the response or possibly an auxiliary DNSSEC response that we didn't know before. We take that as reason to + restart the whole transaction. This is a good idea to deal with servers that respond rubbish if we include + OPT RR or DO bit. One of these cases is documented here, for example: + https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ + + log_debug("Server feature level is now lower than when we began our transaction. Restarting with new ID."); + dns_transaction_shuffle_id(t); + + r = dns_transaction_go(t); + if (r < 0) + return r; + + return 1; +} + +static void on_transaction_stream_error(DnsTransaction *t, int error) { + assert(t); + + dns_transaction_close_connection(t, true); + + if (ERRNO_IS_DISCONNECT(error)) { + if (t->scope->protocol == DNS_PROTOCOL_LLMNR) { + /* If the LLMNR/TCP connection failed, the host doesn't support LLMNR, and we cannot answer the + * question on this scope. */ + dns_transaction_complete(t, DNS_TRANSACTION_NOT_FOUND); + return; + } + + dns_transaction_retry(t, true); + return; + } + if (error != 0) + dns_transaction_complete_errno(t, error); +} + +static int dns_transaction_on_stream_packet(DnsTransaction *t, DnsStream *s, DnsPacket *p) { + bool encrypted; + + assert(t); + assert(s); + assert(p); + + encrypted = s->encrypted; + + dns_transaction_close_connection(t, true); + + if (dns_packet_validate_reply(p) <= 0) { + log_debug("Invalid TCP reply packet."); + dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); + return 0; + } + + dns_scope_check_conflicts(t->scope, p); + + t->block_gc++; + dns_transaction_process_reply(t, p, encrypted); + t->block_gc--; + + /* If the response wasn't useful, then complete the transition + * now. After all, we are the worst feature set now with TCP + * sockets, and there's really no point in retrying. */ + if (t->state == DNS_TRANSACTION_PENDING) + dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); + else + dns_transaction_gc(t); + + return 0; +} + +static int on_stream_complete(DnsStream *s, int error) { + assert(s); + + if (ERRNO_IS_DISCONNECT(error) && s->protocol != DNS_PROTOCOL_LLMNR) { + log_debug_errno(error, "Connection failure for DNS TCP stream: %m"); + + if (s->transactions) { + DnsTransaction *t; + + t = s->transactions; + dns_server_packet_lost(t->server, IPPROTO_TCP, t->current_feature_level); + } + } + + if (error != 0) { + /* First, detach the stream from the server. Otherwise, transactions attached to this stream + * may be restarted by on_transaction_stream_error() below with this stream. */ + dns_stream_detach(s); + + /* Do not use LIST_FOREACH() here, as + * on_transaction_stream_error() + * -> dns_transaction_complete_errno() + * -> dns_transaction_free() + * may free multiple transactions in the list. */ + DnsTransaction *t; + while ((t = s->transactions)) + on_transaction_stream_error(t, error); + } + + return 0; +} + +static int on_stream_packet(DnsStream *s, DnsPacket *p) { + DnsTransaction *t; + + assert(s); + assert(s->manager); + assert(p); + + t = hashmap_get(s->manager->dns_transactions, UINT_TO_PTR(DNS_PACKET_ID(p))); + if (t && t->stream == s) /* Validate that the stream we got this on actually is the stream the + * transaction was using. */ + return dns_transaction_on_stream_packet(t, s, p); + + /* Ignore incorrect transaction id as an old transaction can have been canceled. */ + log_debug("Received unexpected TCP reply packet with id %" PRIu16 ", ignoring.", DNS_PACKET_ID(p)); + return 0; +} + +static uint16_t dns_transaction_port(DnsTransaction *t) { + assert(t); + + if (t->server->port > 0) + return t->server->port; + + return DNS_SERVER_FEATURE_LEVEL_IS_TLS(t->current_feature_level) ? 853 : 53; +} + +static int dns_transaction_emit_tcp(DnsTransaction *t) { + usec_t stream_timeout_usec = DNS_STREAM_DEFAULT_TIMEOUT_USEC; + _cleanup_(dns_stream_unrefp) DnsStream *s = NULL; + _cleanup_close_ int fd = -EBADF; + union sockaddr_union sa; + DnsStreamType type; + int r; + + assert(t); + assert(t->sent); + + dns_transaction_close_connection(t, true); + + switch (t->scope->protocol) { + + case DNS_PROTOCOL_DNS: + r = dns_transaction_pick_server(t); + if (r < 0) + return r; + + if (manager_server_is_stub(t->scope->manager, t->server)) + return -ELOOP; + + if (!t->bypass) { + if (!dns_server_dnssec_supported(t->server) && dns_type_is_dnssec(dns_transaction_key(t)->type)) + return -EOPNOTSUPP; + + r = dns_server_adjust_opt(t->server, t->sent, t->current_feature_level); + if (r < 0) + return r; + } + + if (t->server->stream && (DNS_SERVER_FEATURE_LEVEL_IS_TLS(t->current_feature_level) == t->server->stream->encrypted)) + s = dns_stream_ref(t->server->stream); + else + fd = dns_scope_socket_tcp(t->scope, AF_UNSPEC, NULL, t->server, dns_transaction_port(t), &sa); + + /* Lower timeout in DNS-over-TLS opportunistic mode. In environments where DoT is blocked + * without ICMP response overly long delays when contacting DoT servers are nasty, in + * particular if multiple DNS servers are defined which we try in turn and all are + * blocked. Hence, substantially lower the timeout in that case. */ + if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(t->current_feature_level) && + dns_server_get_dns_over_tls_mode(t->server) == DNS_OVER_TLS_OPPORTUNISTIC) + stream_timeout_usec = DNS_STREAM_OPPORTUNISTIC_TLS_TIMEOUT_USEC; + + type = DNS_STREAM_LOOKUP; + break; + + case DNS_PROTOCOL_LLMNR: + /* When we already received a reply to this (but it was truncated), send to its sender address */ + if (t->received) + fd = dns_scope_socket_tcp(t->scope, t->received->family, &t->received->sender, NULL, t->received->sender_port, &sa); + else { + union in_addr_union address; + int family = AF_UNSPEC; + + /* Otherwise, try to talk to the owner of a + * the IP address, in case this is a reverse + * PTR lookup */ + + r = dns_name_address(dns_resource_key_name(dns_transaction_key(t)), &family, &address); + if (r < 0) + return r; + if (r == 0) + return -EINVAL; + if (family != t->scope->family) + return -ESRCH; + + fd = dns_scope_socket_tcp(t->scope, family, &address, NULL, LLMNR_PORT, &sa); + } + + type = DNS_STREAM_LLMNR_SEND; + break; + + default: + return -EAFNOSUPPORT; + } + + if (!s) { + if (fd < 0) + return fd; + + r = dns_stream_new(t->scope->manager, &s, type, t->scope->protocol, fd, &sa, + on_stream_packet, on_stream_complete, stream_timeout_usec); + if (r < 0) + return r; + + fd = -EBADF; + +#if ENABLE_DNS_OVER_TLS + if (t->scope->protocol == DNS_PROTOCOL_DNS && + DNS_SERVER_FEATURE_LEVEL_IS_TLS(t->current_feature_level)) { + + assert(t->server); + r = dnstls_stream_connect_tls(s, t->server); + if (r < 0) + return r; + } +#endif + + if (t->server) { + dns_server_unref_stream(t->server); + s->server = dns_server_ref(t->server); + t->server->stream = dns_stream_ref(s); + } + + /* The interface index is difficult to determine if we are + * connecting to the local host, hence fill this in right away + * instead of determining it from the socket */ + s->ifindex = dns_scope_ifindex(t->scope); + } + + t->stream = TAKE_PTR(s); + LIST_PREPEND(transactions_by_stream, t->stream->transactions, t); + + r = dns_stream_write_packet(t->stream, t->sent); + if (r < 0) { + dns_transaction_close_connection(t, /* use_graveyard= */ false); + return r; + } + + dns_transaction_reset_answer(t); + + t->tried_stream = true; + + return 0; +} + +static void dns_transaction_cache_answer(DnsTransaction *t) { + assert(t); + + /* For mDNS we cache whenever we get the packet, rather than + * in each transaction. */ + if (!IN_SET(t->scope->protocol, DNS_PROTOCOL_DNS, DNS_PROTOCOL_LLMNR)) + return; + + /* Caching disabled? */ + if (t->scope->manager->enable_cache == DNS_CACHE_MODE_NO) + return; + + /* If validation is turned off for this transaction, but DNSSEC is on, then let's not cache this */ + if (FLAGS_SET(t->query_flags, SD_RESOLVED_NO_VALIDATE) && t->scope->dnssec_mode != DNSSEC_NO) + return; + + /* Packet from localhost? */ + if (!t->scope->manager->cache_from_localhost && + in_addr_is_localhost(t->received->family, &t->received->sender) != 0) + return; + + dns_cache_put(&t->scope->cache, + t->scope->manager->enable_cache, + t->scope->protocol, + dns_transaction_key(t), + t->answer_rcode, + t->answer, + DNS_PACKET_CD(t->received) ? t->received : NULL, /* only cache full packets with CD on, + * since our use case for caching them + * is "bypass" mode which is only + * enabled for CD packets. */ + t->answer_query_flags, + t->answer_dnssec_result, + t->answer_nsec_ttl, + t->received->family, + &t->received->sender, + t->scope->manager->stale_retention_usec); +} + +static bool dns_transaction_dnssec_is_live(DnsTransaction *t) { + DnsTransaction *dt; + + assert(t); + + SET_FOREACH(dt, t->dnssec_transactions) + if (DNS_TRANSACTION_IS_LIVE(dt->state)) + return true; + + return false; +} + +static int dns_transaction_dnssec_ready(DnsTransaction *t) { + DnsTransaction *dt; + int r; + + assert(t); + + /* Checks whether the auxiliary DNSSEC transactions of our transaction have completed, or are still + * ongoing. Returns 0, if we aren't ready for the DNSSEC validation, positive if we are. */ + + SET_FOREACH(dt, t->dnssec_transactions) { + + switch (dt->state) { + + case DNS_TRANSACTION_NULL: + case DNS_TRANSACTION_PENDING: + case DNS_TRANSACTION_VALIDATING: + /* Still ongoing */ + return 0; + + case DNS_TRANSACTION_RCODE_FAILURE: + if (!IN_SET(dt->answer_rcode, DNS_RCODE_NXDOMAIN, DNS_RCODE_SERVFAIL)) { + log_debug("Auxiliary DNSSEC RR query failed with rcode=%s.", FORMAT_DNS_RCODE(dt->answer_rcode)); + goto fail; + } + + /* Fall-through: NXDOMAIN/SERVFAIL is good enough for us. This is because some DNS servers + * erroneously return NXDOMAIN/SERVFAIL for empty non-terminals (Akamai...) or missing DS + * records (Facebook), and we need to handle that nicely, when asking for parent SOA or similar + * RRs to make unsigned proofs. */ + + case DNS_TRANSACTION_SUCCESS: + /* All good. */ + break; + + case DNS_TRANSACTION_DNSSEC_FAILED: + /* We handle DNSSEC failures different from other errors, as we care about the DNSSEC + * validation result */ + + log_debug("Auxiliary DNSSEC RR query failed validation: %s", dnssec_result_to_string(dt->answer_dnssec_result)); + t->answer_dnssec_result = dt->answer_dnssec_result; /* Copy error code over */ + dns_transaction_complete(t, DNS_TRANSACTION_DNSSEC_FAILED); + return 0; + + default: + log_debug("Auxiliary DNSSEC RR query failed with %s", dns_transaction_state_to_string(dt->state)); + goto fail; + } + } + + /* All is ready, we can go and validate */ + return 1; + +fail: + /* Some auxiliary DNSSEC transaction failed for some reason. Maybe we learned something about the + * server due to this failure, and the feature level is now different? Let's see and restart the + * transaction if so. If not, let's propagate the auxiliary failure. + * + * This is particularly relevant if an auxiliary request figured out that DNSSEC doesn't work, and we + * are in permissive DNSSEC mode, and thus should restart things without DNSSEC magic. */ + r = dns_transaction_maybe_restart(t); + if (r < 0) + return r; + if (r > 0) + return 0; /* don't validate just yet, we restarted things */ + + t->answer_dnssec_result = DNSSEC_FAILED_AUXILIARY; + dns_transaction_complete(t, DNS_TRANSACTION_DNSSEC_FAILED); + return 0; +} + +static void dns_transaction_process_dnssec(DnsTransaction *t) { + int r; + + assert(t); + + /* Are there ongoing DNSSEC transactions? If so, let's wait for them. */ + r = dns_transaction_dnssec_ready(t); + if (r < 0) + goto fail; + if (r == 0) /* We aren't ready yet (or one of our auxiliary transactions failed, and we shouldn't validate now */ + return; + + /* See if we learnt things from the additional DNSSEC transactions, that we didn't know before, and better + * restart the lookup immediately. */ + r = dns_transaction_maybe_restart(t); + if (r < 0) + goto fail; + if (r > 0) /* Transaction got restarted... */ + return; + + /* All our auxiliary DNSSEC transactions are complete now. Try + * to validate our RRset now. */ + r = dns_transaction_validate_dnssec(t); + if (r == -EBADMSG) { + dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); + return; + } + if (r < 0) + goto fail; + + if (t->answer_dnssec_result == DNSSEC_INCOMPATIBLE_SERVER && + t->scope->dnssec_mode == DNSSEC_YES) { + + /* We are not in automatic downgrade mode, and the server is bad. Let's try a different server, maybe + * that works. */ + + if (dns_transaction_limited_retry(t)) + return; + + /* OK, let's give up, apparently all servers we tried didn't work. */ + dns_transaction_complete(t, DNS_TRANSACTION_DNSSEC_FAILED); + return; + } + + if (!IN_SET(t->answer_dnssec_result, + _DNSSEC_RESULT_INVALID, /* No DNSSEC validation enabled */ + DNSSEC_VALIDATED, /* Answer is signed and validated successfully */ + DNSSEC_UNSIGNED, /* Answer is right-fully unsigned */ + DNSSEC_INCOMPATIBLE_SERVER)) { /* Server does not do DNSSEC (Yay, we are downgrade attack vulnerable!) */ + dns_transaction_complete(t, DNS_TRANSACTION_DNSSEC_FAILED); + return; + } + + if (t->answer_dnssec_result == DNSSEC_INCOMPATIBLE_SERVER) + dns_server_warn_downgrade(t->server); + + dns_transaction_cache_answer(t); + + if (t->answer_rcode == DNS_RCODE_SUCCESS) + dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS); + else + dns_transaction_complete(t, DNS_TRANSACTION_RCODE_FAILURE); + + return; + +fail: + dns_transaction_complete_errno(t, r); +} + +static int dns_transaction_has_positive_answer(DnsTransaction *t, DnsAnswerFlags *flags) { + int r; + + assert(t); + + /* Checks whether the answer is positive, i.e. either a direct + * answer to the question, or a CNAME/DNAME for it */ + + r = dns_answer_match_key(t->answer, dns_transaction_key(t), flags); + if (r != 0) + return r; + + r = dns_answer_find_cname_or_dname(t->answer, dns_transaction_key(t), NULL, flags); + if (r != 0) + return r; + + return false; +} + +static int dns_transaction_fix_rcode(DnsTransaction *t) { + int r; + + assert(t); + + /* Fix up the RCODE to SUCCESS if we get at least one matching RR in a response. Note that this contradicts the + * DNS RFCs a bit. Specifically, RFC 6604 Section 3 clarifies that the RCODE shall say something about a + * CNAME/DNAME chain element coming after the last chain element contained in the message, and not the first + * one included. However, it also indicates that not all DNS servers implement this correctly. Moreover, when + * using DNSSEC we usually only can prove the first element of a CNAME/DNAME chain anyway, hence let's settle + * on always processing the RCODE as referring to the immediate look-up we do, i.e. the first element of a + * CNAME/DNAME chain. This way, we uniformly handle CNAME/DNAME chains, regardless if the DNS server + * incorrectly implements RCODE, whether DNSSEC is in use, or whether the DNS server only supplied us with an + * incomplete CNAME/DNAME chain. + * + * Or in other words: if we get at least one positive reply in a message we patch NXDOMAIN to become SUCCESS, + * and then rely on the CNAME chasing logic to figure out that there's actually a CNAME error with a new + * lookup. */ + + if (t->answer_rcode != DNS_RCODE_NXDOMAIN) + return 0; + + r = dns_transaction_has_positive_answer(t, NULL); + if (r <= 0) + return r; + + t->answer_rcode = DNS_RCODE_SUCCESS; + return 0; +} + +void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p, bool encrypted) { + bool retry_with_tcp = false; + int r; + + assert(t); + assert(p); + assert(t->scope); + assert(t->scope->manager); + + if (t->state != DNS_TRANSACTION_PENDING) + return; + + /* Increment the total failure counter only when it is the first attempt at querying and the upstream + * server returns a failure response code. This ensures a more accurate count of the number of queries + * that received a failure response code, as it doesn't consider retries. */ + + if (t->n_attempts == 1 && !IN_SET(DNS_PACKET_RCODE(p), DNS_RCODE_SUCCESS, DNS_RCODE_NXDOMAIN)) + t->scope->manager->n_failure_responses_total++; + + /* Note that this call might invalidate the query. Callers + * should hence not attempt to access the query or transaction + * after calling this function. */ + + log_debug("Processing incoming packet of size %zu on transaction %" PRIu16" (rcode=%s).", + p->size, + t->id, FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p))); + + switch (t->scope->protocol) { + + case DNS_PROTOCOL_LLMNR: + /* For LLMNR we will not accept any packets from other interfaces */ + + if (p->ifindex != dns_scope_ifindex(t->scope)) + return; + + if (p->family != t->scope->family) + return; + + /* Tentative packets are not full responses but still + * useful for identifying uniqueness conflicts during + * probing. */ + if (DNS_PACKET_LLMNR_T(p)) { + dns_transaction_tentative(t, p); + return; + } + + break; + + case DNS_PROTOCOL_MDNS: + /* For mDNS we will not accept any packets from other interfaces */ + + if (p->ifindex != dns_scope_ifindex(t->scope)) + return; + + if (p->family != t->scope->family) + return; + + break; + + case DNS_PROTOCOL_DNS: + /* Note that we do not need to verify the + * addresses/port numbers of incoming traffic, as we + * invoked connect() on our UDP socket in which case + * the kernel already does the needed verification for + * us. */ + break; + + default: + assert_not_reached(); + } + + if (t->received != p) + DNS_PACKET_REPLACE(t->received, dns_packet_ref(p)); + + t->answer_source = DNS_TRANSACTION_NETWORK; + + if (p->ipproto == IPPROTO_TCP) { + if (DNS_PACKET_TC(p)) { + /* Truncated via TCP? Somebody must be fucking with us */ + dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); + return; + } + + if (DNS_PACKET_ID(p) != t->id) { + /* Not the reply to our query? Somebody must be fucking with us */ + dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); + return; + } + } + + switch (t->scope->protocol) { + + case DNS_PROTOCOL_DNS: + assert(t->server); + + if (!t->bypass && + IN_SET(DNS_PACKET_RCODE(p), DNS_RCODE_FORMERR, DNS_RCODE_SERVFAIL, DNS_RCODE_NOTIMP)) { + + /* Request failed, immediately try again with reduced features */ + + if (t->current_feature_level <= DNS_SERVER_FEATURE_LEVEL_UDP) { + + /* This was already at UDP feature level? If so, it doesn't make sense to downgrade + * this transaction anymore, but let's see if it might make sense to send the request + * to a different DNS server instead. If not let's process the response, and accept the + * rcode. Note that we don't retry on TCP, since that's a suitable way to mitigate + * packet loss, but is not going to give us better rcodes should we actually have + * managed to get them already at UDP level. */ + + if (dns_transaction_limited_retry(t)) + return; + + /* Give up, accept the rcode */ + log_debug("Server returned error: %s", FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p))); + break; + } + + /* SERVFAIL can happen for many reasons and may be transient. + * To avoid unnecessary downgrades retry once with the initial level. + * Check for clamp_feature_level_servfail having an invalid value as a sign that this is the + * first attempt to downgrade. If so, clamp to the current value so that the transaction + * is retried without actually downgrading. If the next try also fails we will downgrade by + * hitting the else branch below. */ + if (DNS_PACKET_RCODE(p) == DNS_RCODE_SERVFAIL && + t->clamp_feature_level_servfail < 0) { + t->clamp_feature_level_servfail = t->current_feature_level; + log_debug("Server returned error %s, retrying transaction.", + FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p))); + } else { + /* Reduce this feature level by one and try again. */ + switch (t->current_feature_level) { + case DNS_SERVER_FEATURE_LEVEL_TLS_DO: + t->clamp_feature_level_servfail = DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN; + break; + case DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN + 1: + /* Skip plain TLS when TLS is not supported */ + t->clamp_feature_level_servfail = DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN - 1; + break; + default: + t->clamp_feature_level_servfail = t->current_feature_level - 1; + } + + log_debug("Server returned error %s, retrying transaction with reduced feature level %s.", + FORMAT_DNS_RCODE(DNS_PACKET_RCODE(p)), + dns_server_feature_level_to_string(t->clamp_feature_level_servfail)); + } + + dns_transaction_retry(t, false /* use the same server */); + return; + } + + if (DNS_PACKET_RCODE(p) == DNS_RCODE_REFUSED) { + /* This server refused our request? If so, try again, use a different server */ + log_debug("Server returned REFUSED, switching servers, and retrying."); + + if (dns_transaction_limited_retry(t)) + return; + + break; + } + + if (DNS_PACKET_TC(p)) + dns_server_packet_truncated(t->server, t->current_feature_level); + + break; + + case DNS_PROTOCOL_LLMNR: + case DNS_PROTOCOL_MDNS: + dns_scope_packet_received(t->scope, p->timestamp - t->start_usec); + break; + + default: + assert_not_reached(); + } + + if (DNS_PACKET_TC(p)) { + + /* Truncated packets for mDNS are not allowed. Give up immediately. */ + if (t->scope->protocol == DNS_PROTOCOL_MDNS) { + dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); + return; + } + + /* Response was truncated, let's try again with good old TCP */ + log_debug("Reply truncated, retrying via TCP."); + retry_with_tcp = true; + + } else if (t->scope->protocol == DNS_PROTOCOL_DNS && + DNS_PACKET_IS_FRAGMENTED(p)) { + + /* Report the fragment size, so that we downgrade from LARGE to regular EDNS0 if needed */ + if (t->server) + dns_server_packet_udp_fragmented(t->server, dns_packet_size_unfragmented(p)); + + if (t->current_feature_level > DNS_SERVER_FEATURE_LEVEL_UDP) { + /* Packet was fragmented. Let's retry with TCP to avoid fragmentation attack + * issues. (We don't do that on the lowest feature level however, since crappy DNS + * servers often do not implement TCP, hence falling back to TCP on fragmentation is + * counter-productive there.) */ + + log_debug("Reply fragmented, retrying via TCP. (Largest fragment size: %zu; Datagram size: %zu)", + p->fragsize, p->size); + retry_with_tcp = true; + } + } + + if (retry_with_tcp) { + r = dns_transaction_emit_tcp(t); + if (r == -ESRCH) { + /* No servers found? Damn! */ + dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS); + return; + } + if (r == -EOPNOTSUPP) { + /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */ + dns_transaction_complete(t, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED); + return; + } + if (r < 0) { + /* On LLMNR, if we cannot connect to the host, + * we immediately give up */ + if (t->scope->protocol != DNS_PROTOCOL_DNS) + goto fail; + + /* On DNS, couldn't send? Try immediately again, with a new server */ + if (dns_transaction_limited_retry(t)) + return; + + /* No new server to try, give up */ + dns_transaction_complete(t, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED); + } + + return; + } + + /* After the superficial checks, actually parse the message. */ + r = dns_packet_extract(p); + if (r < 0) { + if (t->server) { + dns_server_packet_invalid(t->server, t->current_feature_level); + + r = dns_transaction_maybe_restart(t); + if (r < 0) + goto fail; + if (r > 0) /* Transaction got restarted... */ + return; + } + + dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); + return; + } + + if (t->server) { + /* Report that we successfully received a valid packet with a good rcode after we initially got a bad + * rcode and subsequently downgraded the protocol */ + + if (IN_SET(DNS_PACKET_RCODE(p), DNS_RCODE_SUCCESS, DNS_RCODE_NXDOMAIN) && + t->clamp_feature_level_servfail != _DNS_SERVER_FEATURE_LEVEL_INVALID) + dns_server_packet_rcode_downgrade(t->server, t->clamp_feature_level_servfail); + + /* Report that the OPT RR was missing */ + if (!p->opt) + dns_server_packet_bad_opt(t->server, t->current_feature_level); + + /* Report that the server didn't copy our query DO bit from request to response */ + if (DNS_PACKET_DO(t->sent) && !DNS_PACKET_DO(t->received)) + dns_server_packet_do_off(t->server, t->current_feature_level); + + /* Report that we successfully received a packet. We keep track of the largest packet + * size/fragment size we got. Which is useful for announcing the EDNS(0) packet size we can + * receive to our server. */ + dns_server_packet_received(t->server, p->ipproto, t->current_feature_level, dns_packet_size_unfragmented(p)); + } + + /* See if we know things we didn't know before that indicate we better restart the lookup immediately. */ + r = dns_transaction_maybe_restart(t); + if (r < 0) + goto fail; + if (r > 0) /* Transaction got restarted... */ + return; + + /* When dealing with protocols other than mDNS only consider responses with equivalent query section + * to the request. For mDNS this check doesn't make sense, because the section 6 of RFC6762 states + * that "Multicast DNS responses MUST NOT contain any questions in the Question Section". */ + if (t->scope->protocol != DNS_PROTOCOL_MDNS) { + r = dns_packet_is_reply_for(p, dns_transaction_key(t)); + if (r < 0) + goto fail; + if (r == 0) { + dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); + return; + } + } + + /* Install the answer as answer to the transaction. We ref the answer twice here: the main `answer` + * field is later replaced by the DNSSEC validated subset. The 'answer_auxiliary' field carries the + * original complete record set, including RRSIG and friends. We use this when passing data to + * clients that ask for DNSSEC metadata. */ + DNS_ANSWER_REPLACE(t->answer, dns_answer_ref(p->answer)); + t->answer_rcode = DNS_PACKET_RCODE(p); + t->answer_dnssec_result = _DNSSEC_RESULT_INVALID; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED, false); + SET_FLAG(t->answer_query_flags, SD_RESOLVED_CONFIDENTIAL, encrypted); + + r = dns_transaction_fix_rcode(t); + if (r < 0) + goto fail; + + /* Block GC while starting requests for additional DNSSEC RRs */ + t->block_gc++; + r = dns_transaction_request_dnssec_keys(t); + t->block_gc--; + + /* Maybe the transaction is ready for GC'ing now? If so, free it and return. */ + if (!dns_transaction_gc(t)) + return; + + /* Requesting additional keys might have resulted in this transaction to fail, since the auxiliary + * request failed for some reason. If so, we are not in pending state anymore, and we should exit + * quickly. */ + if (t->state != DNS_TRANSACTION_PENDING) + return; + if (r < 0) + goto fail; + if (r > 0) { + /* There are DNSSEC transactions pending now. Update the state accordingly. */ + t->state = DNS_TRANSACTION_VALIDATING; + dns_transaction_close_connection(t, true); + dns_transaction_stop_timeout(t); + return; + } + + dns_transaction_process_dnssec(t); + return; + +fail: + dns_transaction_complete_errno(t, r); +} + +static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) { + _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; + DnsTransaction *t = ASSERT_PTR(userdata); + int r; + + assert(t->scope); + + r = manager_recv(t->scope->manager, fd, DNS_PROTOCOL_DNS, &p); + if (r < 0) { + if (ERRNO_IS_DISCONNECT(r)) { + usec_t usec; + + /* UDP connection failures get reported via ICMP and then are possibly delivered to us on the + * next recvmsg(). Treat this like a lost packet. */ + + log_debug_errno(r, "Connection failure for DNS UDP packet: %m"); + assert_se(sd_event_now(t->scope->manager->event, CLOCK_BOOTTIME, &usec) >= 0); + dns_server_packet_lost(t->server, IPPROTO_UDP, t->current_feature_level); + + dns_transaction_close_connection(t, /* use_graveyard = */ false); + + if (dns_transaction_limited_retry(t)) /* Try a different server */ + return 0; + } + dns_transaction_complete_errno(t, r); + return 0; + } + if (r == 0) + /* Spurious wakeup without any data */ + return 0; + + r = dns_packet_validate_reply(p); + if (r < 0) { + log_debug_errno(r, "Received invalid DNS packet as response, ignoring: %m"); + return 0; + } + if (r == 0) { + log_debug("Received inappropriate DNS packet as response, ignoring."); + return 0; + } + + if (DNS_PACKET_ID(p) != t->id) { + log_debug("Received packet with incorrect transaction ID, ignoring."); + return 0; + } + + dns_transaction_process_reply(t, p, false); + return 0; +} + +static int dns_transaction_emit_udp(DnsTransaction *t) { + int r; + + assert(t); + + if (t->scope->protocol == DNS_PROTOCOL_DNS) { + + r = dns_transaction_pick_server(t); + if (r < 0) + return r; + + if (manager_server_is_stub(t->scope->manager, t->server)) + return -ELOOP; + + if (t->current_feature_level < DNS_SERVER_FEATURE_LEVEL_UDP || DNS_SERVER_FEATURE_LEVEL_IS_TLS(t->current_feature_level)) + return -EAGAIN; /* Sorry, can't do UDP, try TCP! */ + + if (!t->bypass && !dns_server_dnssec_supported(t->server) && dns_type_is_dnssec(dns_transaction_key(t)->type)) + return -EOPNOTSUPP; + + if (r > 0 || t->dns_udp_fd < 0) { /* Server changed, or no connection yet. */ + int fd; + + dns_transaction_close_connection(t, true); + + /* Before we allocate a new UDP socket, let's process the graveyard a bit to free some fds */ + manager_socket_graveyard_process(t->scope->manager); + + fd = dns_scope_socket_udp(t->scope, t->server); + if (fd < 0) + return fd; + + r = sd_event_add_io(t->scope->manager->event, &t->dns_udp_event_source, fd, EPOLLIN, on_dns_packet, t); + if (r < 0) { + safe_close(fd); + return r; + } + + (void) sd_event_source_set_description(t->dns_udp_event_source, "dns-transaction-udp"); + t->dns_udp_fd = fd; + } + + if (!t->bypass) { + r = dns_server_adjust_opt(t->server, t->sent, t->current_feature_level); + if (r < 0) + return r; + } + } else + dns_transaction_close_connection(t, true); + + r = dns_scope_emit_udp(t->scope, t->dns_udp_fd, t->server ? t->server->family : AF_UNSPEC, t->sent); + if (r < 0) + return r; + + dns_transaction_reset_answer(t); + + return 0; +} + +static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdata) { + DnsTransaction *t = ASSERT_PTR(userdata); + + assert(s); + + t->seen_timeout = true; + + if (t->initial_jitter_scheduled && !t->initial_jitter_elapsed) { + log_debug("Initial jitter phase for transaction %" PRIu16 " elapsed.", t->id); + t->initial_jitter_elapsed = true; + } else { + /* Timeout reached? Increase the timeout for the server used */ + switch (t->scope->protocol) { + + case DNS_PROTOCOL_DNS: + assert(t->server); + dns_server_packet_lost(t->server, t->stream ? IPPROTO_TCP : IPPROTO_UDP, t->current_feature_level); + break; + + case DNS_PROTOCOL_LLMNR: + case DNS_PROTOCOL_MDNS: + dns_scope_packet_lost(t->scope, usec - t->start_usec); + break; + + default: + assert_not_reached(); + } + + log_debug("Timeout reached on transaction %" PRIu16 ".", t->id); + } + + dns_transaction_retry(t, /* next_server= */ true); /* try a different server, but given this means + * packet loss, let's do so even if we already + * tried a bunch */ + return 0; +} + +static int dns_transaction_setup_timeout( + DnsTransaction *t, + usec_t timeout_usec /* relative */, + usec_t next_usec /* CLOCK_BOOTTIME */) { + + int r; + + assert(t); + + dns_transaction_stop_timeout(t); + + r = sd_event_add_time_relative( + t->scope->manager->event, + &t->timeout_event_source, + CLOCK_BOOTTIME, + timeout_usec, 0, + on_transaction_timeout, t); + if (r < 0) + return r; + + (void) sd_event_source_set_description(t->timeout_event_source, "dns-transaction-timeout"); + + t->next_attempt_after = next_usec; + t->state = DNS_TRANSACTION_PENDING; + return 0; +} + +static usec_t transaction_get_resend_timeout(DnsTransaction *t) { + assert(t); + assert(t->scope); + + switch (t->scope->protocol) { + + case DNS_PROTOCOL_DNS: + + /* When we do TCP, grant a much longer timeout, as in this case there's no need for us to quickly + * resend, as the kernel does that anyway for us, and we really don't want to interrupt it in that + * needlessly. */ + if (t->stream) + return TRANSACTION_TCP_TIMEOUT_USEC; + + return DNS_TIMEOUT_USEC; + + case DNS_PROTOCOL_MDNS: + if (t->probing) + return MDNS_PROBING_INTERVAL_USEC; + + /* See RFC 6762 Section 5.1 suggests that timeout should be a few seconds. */ + assert(t->n_attempts > 0); + return (1 << (t->n_attempts - 1)) * USEC_PER_SEC; + + case DNS_PROTOCOL_LLMNR: + return t->scope->resend_timeout; + + default: + assert_not_reached(); + } +} + +static void dns_transaction_randomize_answer(DnsTransaction *t) { + int r; + + assert(t); + + /* Randomizes the order of the answer array. This is done for all cached responses, so that we return + * a different order each time. We do this only for DNS traffic, in order to do some minimal, crappy + * load balancing. We don't do this for LLMNR or mDNS, since the order (preferring link-local + * addresses, and such like) might have meaning there, and load balancing is pointless. */ + + if (t->scope->protocol != DNS_PROTOCOL_DNS) + return; + + /* No point in randomizing, if there's just one RR */ + if (dns_answer_size(t->answer) <= 1) + return; + + r = dns_answer_reserve_or_clone(&t->answer, 0); + if (r < 0) /* If this fails, just don't randomize, this is non-essential stuff after all */ + return (void) log_debug_errno(r, "Failed to clone answer record, not randomizing RR order of answer: %m"); + + dns_answer_randomize(t->answer); +} + +static int dns_transaction_prepare(DnsTransaction *t, usec_t ts) { + int r; + + assert(t); + + /* Returns 0 if dns_transaction_complete() has been called. In that case the transaction and query + * candidate objects may have been invalidated and must not be accessed. Returns 1 if the transaction + * has been prepared. */ + + dns_transaction_stop_timeout(t); + + if (t->n_attempts == 1 && t->seen_timeout) + t->scope->manager->n_timeouts_total++; + + if (!dns_scope_network_good(t->scope)) { + dns_transaction_complete(t, DNS_TRANSACTION_NETWORK_DOWN); + return 0; + } + + if (t->n_attempts >= TRANSACTION_ATTEMPTS_MAX(t->scope->protocol)) { + DnsTransactionState result; + + if (t->scope->protocol == DNS_PROTOCOL_LLMNR) + /* If we didn't find anything on LLMNR, it's not an error, but a failure to resolve + * the name. */ + result = DNS_TRANSACTION_NOT_FOUND; + else + result = DNS_TRANSACTION_ATTEMPTS_MAX_REACHED; + + dns_transaction_complete(t, result); + return 0; + } + + if (t->scope->protocol == DNS_PROTOCOL_LLMNR && t->tried_stream) { + /* If we already tried via a stream, then we don't + * retry on LLMNR. See RFC 4795, Section 2.7. */ + dns_transaction_complete(t, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED); + return 0; + } + + t->n_attempts++; + t->start_usec = ts; + + dns_transaction_reset_answer(t); + dns_transaction_flush_dnssec_transactions(t); + + /* Check the trust anchor. Do so only on classic DNS, since DNSSEC does not apply otherwise. */ + if (t->scope->protocol == DNS_PROTOCOL_DNS && + !FLAGS_SET(t->query_flags, SD_RESOLVED_NO_TRUST_ANCHOR)) { + r = dns_trust_anchor_lookup_positive(&t->scope->manager->trust_anchor, dns_transaction_key(t), &t->answer); + if (r < 0) + return r; + if (r > 0) { + t->answer_rcode = DNS_RCODE_SUCCESS; + t->answer_source = DNS_TRANSACTION_TRUST_ANCHOR; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED|SD_RESOLVED_CONFIDENTIAL, true); + dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS); + return 0; + } + + if (dns_name_is_root(dns_resource_key_name(dns_transaction_key(t))) && + dns_transaction_key(t)->type == DNS_TYPE_DS) { + + /* Hmm, this is a request for the root DS? A DS RR doesn't exist in the root zone, + * and if our trust anchor didn't know it either, this means we cannot do any DNSSEC + * logic anymore. */ + + if (t->scope->dnssec_mode == DNSSEC_ALLOW_DOWNGRADE) { + /* We are in downgrade mode. In this case, synthesize an unsigned empty + * response, so that the any lookup depending on this one can continue + * assuming there was no DS, and hence the root zone was unsigned. */ + + t->answer_rcode = DNS_RCODE_SUCCESS; + t->answer_source = DNS_TRANSACTION_TRUST_ANCHOR; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED, false); + SET_FLAG(t->answer_query_flags, SD_RESOLVED_CONFIDENTIAL, true); + dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS); + } else + /* If we are not in downgrade mode, then fail the lookup, because we cannot + * reasonably answer it. There might be DS RRs, but we don't know them, and + * the DNS server won't tell them to us (and even if it would, we couldn't + * validate and trust them. */ + dns_transaction_complete(t, DNS_TRANSACTION_NO_TRUST_ANCHOR); + + return 0; + } + } + + /* Check the zone. */ + if (!FLAGS_SET(t->query_flags, SD_RESOLVED_NO_ZONE)) { + r = dns_zone_lookup(&t->scope->zone, dns_transaction_key(t), dns_scope_ifindex(t->scope), &t->answer, NULL, NULL); + if (r < 0) + return r; + if (r > 0) { + t->answer_rcode = DNS_RCODE_SUCCESS; + t->answer_source = DNS_TRANSACTION_ZONE; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED|SD_RESOLVED_CONFIDENTIAL, true); + dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS); + return 0; + } + } + + /* Check the cache. */ + if (!FLAGS_SET(t->query_flags, SD_RESOLVED_NO_CACHE)) { + + /* Before trying the cache, let's make sure we figured out a server to use. Should this cause + * a change of server this might flush the cache. */ + (void) dns_scope_get_dns_server(t->scope); + + /* Let's then prune all outdated entries */ + dns_cache_prune(&t->scope->cache); + + /* For the initial attempt or when no stale data is requested, disable serve stale + * and answer the question from the cache (honors ttl property). + * On the second attempt, if StaleRetentionSec is greater than zero, + * try to answer the question using stale date (honors until property) */ + uint64_t query_flags = t->query_flags; + if (t->n_attempts == 1 || t->scope->manager->stale_retention_usec == 0) + query_flags |= SD_RESOLVED_NO_STALE; + + r = dns_cache_lookup( + &t->scope->cache, + dns_transaction_key(t), + query_flags, + &t->answer_rcode, + &t->answer, + &t->received, + &t->answer_query_flags, + &t->answer_dnssec_result); + if (r < 0) + return r; + if (r > 0) { + dns_transaction_randomize_answer(t); + + if (t->bypass && t->scope->protocol == DNS_PROTOCOL_DNS && !t->received) + /* When bypass mode is on, do not use cached data unless it came with a full + * packet. */ + dns_transaction_reset_answer(t); + else { + if (t->n_attempts > 1 && !FLAGS_SET(query_flags, SD_RESOLVED_NO_STALE)) { + + if (t->answer_rcode == DNS_RCODE_SUCCESS) { + if (t->seen_timeout) + t->scope->manager->n_timeouts_served_stale_total++; + else + t->scope->manager->n_failure_responses_served_stale_total++; + } + + char key_str[DNS_RESOURCE_KEY_STRING_MAX]; + log_debug("Serve Stale response rcode=%s for %s", + FORMAT_DNS_RCODE(t->answer_rcode), + dns_resource_key_to_string(dns_transaction_key(t), key_str, sizeof key_str)); + } + + t->answer_source = DNS_TRANSACTION_CACHE; + if (t->answer_rcode == DNS_RCODE_SUCCESS) + dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS); + else + dns_transaction_complete(t, DNS_TRANSACTION_RCODE_FAILURE); + return 0; + } + } + } + + if (FLAGS_SET(t->query_flags, SD_RESOLVED_NO_NETWORK)) { + dns_transaction_complete(t, DNS_TRANSACTION_NO_SOURCE); + return 0; + } + + return 1; +} + +static int dns_packet_append_zone(DnsPacket *p, DnsTransaction *t, DnsResourceKey *k, unsigned *nscount) { + _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL; + bool tentative; + int r; + + assert(p); + assert(t); + assert(k); + + if (k->type != DNS_TYPE_ANY) + return 0; + + r = dns_zone_lookup(&t->scope->zone, k, t->scope->link->ifindex, &answer, NULL, &tentative); + if (r < 0) + return r; + + return dns_packet_append_answer(p, answer, nscount); +} + +static int mdns_make_dummy_packet(DnsTransaction *t, DnsPacket **ret_packet, Set **ret_keys) { + _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; + _cleanup_set_free_ Set *keys = NULL; + bool add_known_answers = false; + unsigned qdcount; + usec_t ts; + int r; + + assert(t); + assert(t->scope); + assert(t->scope->protocol == DNS_PROTOCOL_MDNS); + assert(ret_packet); + assert(ret_keys); + + r = dns_packet_new_query(&p, t->scope->protocol, 0, false); + if (r < 0) + return r; + + r = dns_packet_append_key(p, dns_transaction_key(t), 0, NULL); + if (r < 0) + return r; + + qdcount = 1; + + if (dns_key_is_shared(dns_transaction_key(t))) + add_known_answers = true; + + r = dns_packet_append_zone(p, t, dns_transaction_key(t), NULL); + if (r < 0) + return r; + + /* Save appended keys */ + r = set_ensure_put(&keys, &dns_resource_key_hash_ops, dns_transaction_key(t)); + if (r < 0) + return r; + + assert_se(sd_event_now(t->scope->manager->event, CLOCK_BOOTTIME, &ts) >= 0); + + LIST_FOREACH(transactions_by_scope, other, t->scope->transactions) { + + /* Skip ourselves */ + if (other == t) + continue; + + if (other->state != DNS_TRANSACTION_PENDING) + continue; + + if (other->next_attempt_after > ts) + continue; + + if (!set_contains(keys, dns_transaction_key(other))) { + size_t saved_packet_size; + + r = dns_packet_append_key(p, dns_transaction_key(other), 0, &saved_packet_size); + /* If we can't stuff more questions into the packet, just give up. + * One of the 'other' transactions will fire later and take care of the rest. */ + if (r == -EMSGSIZE) + break; + if (r < 0) + return r; + + r = dns_packet_append_zone(p, t, dns_transaction_key(other), NULL); + if (r == -EMSGSIZE) { + dns_packet_truncate(p, saved_packet_size); + break; + } + if (r < 0) + return r; + + r = set_ensure_put(&keys, &dns_resource_key_hash_ops, dns_transaction_key(other)); + if (r < 0) + return r; + } + + r = dns_transaction_prepare(other, ts); + if (r < 0) + return r; + if (r == 0) + /* In this case, not only this transaction, but multiple transactions may be + * freed. Hence, we need to restart the loop. */ + return -EAGAIN; + + usec_t timeout = transaction_get_resend_timeout(other); + r = dns_transaction_setup_timeout(other, timeout, usec_add(ts, timeout)); + if (r < 0) + return r; + + if (dns_key_is_shared(dns_transaction_key(other))) + add_known_answers = true; + + qdcount++; + if (qdcount >= UINT16_MAX) + break; + } + + DNS_PACKET_HEADER(p)->qdcount = htobe16(qdcount); + + /* Append known answers section if we're asking for any shared record */ + if (add_known_answers) { + r = dns_cache_export_shared_to_packet(&t->scope->cache, p, ts, 0); + if (r < 0) + return r; + } + + *ret_packet = TAKE_PTR(p); + *ret_keys = TAKE_PTR(keys); + return add_known_answers; +} + +static int dns_transaction_make_packet_mdns(DnsTransaction *t) { + _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL, *dummy = NULL; + _cleanup_set_free_ Set *keys = NULL; + bool add_known_answers; + DnsResourceKey *k; + unsigned c; + int r; + + assert(t); + assert(t->scope->protocol == DNS_PROTOCOL_MDNS); + + /* Discard any previously prepared packet, so we can start over and coalesce again */ + t->sent = dns_packet_unref(t->sent); + + /* First, create a dummy packet to calculate the number of known answers to be appended in the first packet. */ + for (;;) { + r = mdns_make_dummy_packet(t, &dummy, &keys); + if (r == -EAGAIN) + continue; + if (r < 0) + return r; + + add_known_answers = r; + break; + } + + /* Then, create actual packet. */ + r = dns_packet_new_query(&p, t->scope->protocol, 0, false); + if (r < 0) + return r; + + /* Questions */ + c = 0; + SET_FOREACH(k, keys) { + r = dns_packet_append_key(p, k, 0, NULL); + if (r < 0) + return r; + c++; + } + DNS_PACKET_HEADER(p)->qdcount = htobe16(c); + + /* Known answers */ + if (add_known_answers) { + usec_t ts; + + assert_se(sd_event_now(t->scope->manager->event, CLOCK_BOOTTIME, &ts) >= 0); + + r = dns_cache_export_shared_to_packet(&t->scope->cache, p, ts, be16toh(DNS_PACKET_HEADER(dummy)->ancount)); + if (r < 0) + return r; + } + + /* Authorities */ + c = 0; + SET_FOREACH(k, keys) { + r = dns_packet_append_zone(p, t, k, &c); + if (r < 0) + return r; + } + DNS_PACKET_HEADER(p)->nscount = htobe16(c); + + t->sent = TAKE_PTR(p); + return 0; +} + +static int dns_transaction_make_packet(DnsTransaction *t) { + _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; + int r; + + assert(t); + + if (t->scope->protocol == DNS_PROTOCOL_MDNS) + return dns_transaction_make_packet_mdns(t); + + if (t->sent) + return 0; + + if (t->bypass && t->bypass->protocol == t->scope->protocol) { + /* If bypass logic is enabled and the protocol if the original packet and our scope match, + * take the original packet, copy it, and patch in our new ID */ + r = dns_packet_dup(&p, t->bypass); + if (r < 0) + return r; + } else { + r = dns_packet_new_query( + &p, t->scope->protocol, + /* min_alloc_dsize = */ 0, + /* dnssec_cd = */ !FLAGS_SET(t->query_flags, SD_RESOLVED_NO_VALIDATE) && + t->scope->dnssec_mode != DNSSEC_NO); + if (r < 0) + return r; + + r = dns_packet_append_key(p, dns_transaction_key(t), 0, NULL); + if (r < 0) + return r; + + DNS_PACKET_HEADER(p)->qdcount = htobe16(1); + } + + DNS_PACKET_HEADER(p)->id = t->id; + + t->sent = TAKE_PTR(p); + return 0; +} + +int dns_transaction_go(DnsTransaction *t) { + usec_t ts; + int r; + char key_str[DNS_RESOURCE_KEY_STRING_MAX]; + + assert(t); + + /* Returns > 0 if the transaction is now pending, returns 0 if could be processed immediately and has + * finished now. In the latter case, the transaction and query candidate objects must not be accessed. + */ + + assert_se(sd_event_now(t->scope->manager->event, CLOCK_BOOTTIME, &ts) >= 0); + + r = dns_transaction_prepare(t, ts); + if (r <= 0) + return r; + + log_debug("Firing %s transaction %" PRIu16 " for <%s> scope %s on %s/%s (validate=%s).", + t->bypass ? "bypass" : "regular", + t->id, + dns_resource_key_to_string(dns_transaction_key(t), key_str, sizeof key_str), + dns_protocol_to_string(t->scope->protocol), + t->scope->link ? t->scope->link->ifname : "*", + af_to_name_short(t->scope->family), + yes_no(!FLAGS_SET(t->query_flags, SD_RESOLVED_NO_VALIDATE))); + + if (!t->initial_jitter_scheduled && + IN_SET(t->scope->protocol, DNS_PROTOCOL_LLMNR, DNS_PROTOCOL_MDNS)) { + usec_t jitter; + + /* RFC 4795 Section 2.7 suggests all LLMNR queries should be delayed by a random time from 0 to + * JITTER_INTERVAL. + * RFC 6762 Section 8.1 suggests initial probe queries should be delayed by a random time from + * 0 to 250ms. */ + + t->initial_jitter_scheduled = true; + t->n_attempts = 0; + + switch (t->scope->protocol) { + + case DNS_PROTOCOL_LLMNR: + jitter = random_u64_range(LLMNR_JITTER_INTERVAL_USEC); + break; + + case DNS_PROTOCOL_MDNS: + if (t->probing) + jitter = random_u64_range(MDNS_PROBING_INTERVAL_USEC); + else + jitter = 0; + break; + default: + assert_not_reached(); + } + + r = dns_transaction_setup_timeout(t, jitter, ts); + if (r < 0) + return r; + + log_debug("Delaying %s transaction %" PRIu16 " for " USEC_FMT "us.", + dns_protocol_to_string(t->scope->protocol), + t->id, + jitter); + return 1; + } + + /* Otherwise, we need to ask the network */ + r = dns_transaction_make_packet(t); + if (r < 0) + return r; + + if (t->scope->protocol == DNS_PROTOCOL_LLMNR && + (dns_name_endswith(dns_resource_key_name(dns_transaction_key(t)), "in-addr.arpa") > 0 || + dns_name_endswith(dns_resource_key_name(dns_transaction_key(t)), "ip6.arpa") > 0)) { + + /* RFC 4795, Section 2.4. says reverse lookups shall + * always be made via TCP on LLMNR */ + r = dns_transaction_emit_tcp(t); + } else { + /* Try via UDP, and if that fails due to large size or lack of + * support try via TCP */ + r = dns_transaction_emit_udp(t); + if (r == -EMSGSIZE) + log_debug("Sending query via TCP since it is too large."); + else if (r == -EAGAIN) + log_debug("Sending query via TCP since UDP isn't supported or DNS-over-TLS is selected."); + else if (r == -EPERM) + log_debug("Sending query via TCP since UDP is blocked."); + if (IN_SET(r, -EMSGSIZE, -EAGAIN, -EPERM)) + r = dns_transaction_emit_tcp(t); + } + if (r == -ELOOP) { + if (t->scope->protocol != DNS_PROTOCOL_DNS) + return r; + + /* One of our own stub listeners */ + log_debug_errno(r, "Detected that specified DNS server is our own extra listener, switching DNS servers."); + + dns_scope_next_dns_server(t->scope, t->server); + + if (dns_scope_get_dns_server(t->scope) == t->server) { + log_debug_errno(r, "Still pointing to extra listener after switching DNS servers, refusing operation."); + dns_transaction_complete(t, DNS_TRANSACTION_STUB_LOOP); + return 0; + } + + return dns_transaction_go(t); + } + if (r == -ESRCH) { + /* No servers to send this to? */ + dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS); + return 0; + } + if (r == -EOPNOTSUPP) { + /* Tried to ask for DNSSEC RRs, on a server that doesn't do DNSSEC */ + dns_transaction_complete(t, DNS_TRANSACTION_RR_TYPE_UNSUPPORTED); + return 0; + } + if (t->scope->protocol == DNS_PROTOCOL_LLMNR && ERRNO_IS_NEG_DISCONNECT(r)) { + /* On LLMNR, if we cannot connect to a host via TCP when doing reverse lookups. This means we cannot + * answer this request with this protocol. */ + dns_transaction_complete(t, DNS_TRANSACTION_NOT_FOUND); + return 0; + } + if (r < 0) { + if (t->scope->protocol != DNS_PROTOCOL_DNS) + return r; + + /* Couldn't send? Try immediately again, with a new server */ + dns_scope_next_dns_server(t->scope, t->server); + + return dns_transaction_go(t); + } + + usec_t timeout = transaction_get_resend_timeout(t); + r = dns_transaction_setup_timeout(t, timeout, usec_add(ts, timeout)); + if (r < 0) + return r; + + return 1; +} + +static int dns_transaction_find_cyclic(DnsTransaction *t, DnsTransaction *aux) { + DnsTransaction *n; + int r; + + assert(t); + assert(aux); + + /* Try to find cyclic dependencies between transaction objects */ + + if (t == aux) + return 1; + + SET_FOREACH(n, aux->dnssec_transactions) { + r = dns_transaction_find_cyclic(t, n); + if (r != 0) + return r; + } + + return 0; +} + +static int dns_transaction_add_dnssec_transaction(DnsTransaction *t, DnsResourceKey *key, DnsTransaction **ret) { + _cleanup_(dns_transaction_gcp) DnsTransaction *aux = NULL; + int r; + + assert(t); + assert(ret); + assert(key); + + aux = dns_scope_find_transaction(t->scope, key, t->query_flags); + if (!aux) { + r = dns_transaction_new(&aux, t->scope, key, NULL, t->query_flags); + if (r < 0) + return r; + } else { + if (set_contains(t->dnssec_transactions, aux)) { + *ret = aux; + return 0; + } + + r = dns_transaction_find_cyclic(t, aux); + if (r < 0) + return r; + if (r > 0) { + char s[DNS_RESOURCE_KEY_STRING_MAX], saux[DNS_RESOURCE_KEY_STRING_MAX]; + + return log_debug_errno(SYNTHETIC_ERRNO(ELOOP), + "Potential cyclic dependency, refusing to add transaction %" PRIu16 " (%s) as dependency for %" PRIu16 " (%s).", + aux->id, + dns_resource_key_to_string(dns_transaction_key(t), s, sizeof s), + t->id, + dns_resource_key_to_string(dns_transaction_key(aux), saux, sizeof saux)); + } + } + + r = set_ensure_allocated(&aux->notify_transactions_done, NULL); + if (r < 0) + return r; + + r = set_ensure_put(&t->dnssec_transactions, NULL, aux); + if (r < 0) + return r; + + r = set_ensure_put(&aux->notify_transactions, NULL, t); + if (r < 0) { + (void) set_remove(t->dnssec_transactions, aux); + return r; + } + + *ret = TAKE_PTR(aux); + return 1; +} + +static int dns_transaction_request_dnssec_rr(DnsTransaction *t, DnsResourceKey *key) { + _cleanup_(dns_answer_unrefp) DnsAnswer *a = NULL; + DnsTransaction *aux; + int r; + + assert(t); + assert(key); + + /* Try to get the data from the trust anchor */ + r = dns_trust_anchor_lookup_positive(&t->scope->manager->trust_anchor, key, &a); + if (r < 0) + return r; + if (r > 0) { + r = dns_answer_extend(&t->validated_keys, a); + if (r < 0) + return r; + + return 0; + } + + /* This didn't work, ask for it via the network/cache then. */ + r = dns_transaction_add_dnssec_transaction(t, key, &aux); + if (r == -ELOOP) /* This would result in a cyclic dependency */ + return 0; + if (r < 0) + return r; + + if (aux->state == DNS_TRANSACTION_NULL) { + r = dns_transaction_go(aux); + if (r < 0) + return r; + } + + return 1; +} + +static int dns_transaction_negative_trust_anchor_lookup(DnsTransaction *t, const char *name) { + int r; + + assert(t); + + /* Check whether the specified name is in the NTA + * database, either in the global one, or the link-local + * one. */ + + r = dns_trust_anchor_lookup_negative(&t->scope->manager->trust_anchor, name); + if (r != 0) + return r; + + if (!t->scope->link) + return 0; + + return link_negative_trust_anchor_lookup(t->scope->link, name); +} + +static int dns_transaction_has_negative_answer(DnsTransaction *t) { + int r; + + assert(t); + + /* Checks whether the answer is negative, and lacks NSEC/NSEC3 + * RRs to prove it */ + + r = dns_transaction_has_positive_answer(t, NULL); + if (r < 0) + return r; + if (r > 0) + return false; + + /* Is this key explicitly listed as a negative trust anchor? + * If so, it's nothing we need to care about */ + r = dns_transaction_negative_trust_anchor_lookup(t, dns_resource_key_name(dns_transaction_key(t))); + if (r < 0) + return r; + return !r; +} + +static int dns_transaction_is_primary_response(DnsTransaction *t, DnsResourceRecord *rr) { + int r; + + assert(t); + assert(rr); + + /* Check if the specified RR is the "primary" response, + * i.e. either matches the question precisely or is a + * CNAME/DNAME for it. */ + + r = dns_resource_key_match_rr(dns_transaction_key(t), rr, NULL); + if (r != 0) + return r; + + return dns_resource_key_match_cname_or_dname(dns_transaction_key(t), rr->key, NULL); +} + +static bool dns_transaction_dnssec_supported(DnsTransaction *t) { + assert(t); + + /* Checks whether our transaction's DNS server is assumed to be compatible with DNSSEC. Returns false as soon + * as we changed our mind about a server, and now believe it is incompatible with DNSSEC. */ + + if (t->scope->protocol != DNS_PROTOCOL_DNS) + return false; + + /* If we have picked no server, then we are working from the cache or some other source, and DNSSEC might well + * be supported, hence return true. */ + if (!t->server) + return true; + + /* Note that we do not check the feature level actually used for the transaction but instead the feature level + * the server is known to support currently, as the transaction feature level might be lower than what the + * server actually supports, since we might have downgraded this transaction's feature level because we got a + * SERVFAIL earlier and wanted to check whether downgrading fixes it. */ + + return dns_server_dnssec_supported(t->server); +} + +static bool dns_transaction_dnssec_supported_full(DnsTransaction *t) { + DnsTransaction *dt; + + assert(t); + + /* Checks whether our transaction our any of the auxiliary transactions couldn't do DNSSEC. */ + + if (!dns_transaction_dnssec_supported(t)) + return false; + + SET_FOREACH(dt, t->dnssec_transactions) + if (!dns_transaction_dnssec_supported(dt)) + return false; + + return true; +} + +int dns_transaction_request_dnssec_keys(DnsTransaction *t) { + DnsResourceRecord *rr; + + int r; + + assert(t); + + /* + * Retrieve all auxiliary RRs for the answer we got, so that + * we can verify signatures or prove that RRs are rightfully + * unsigned. Specifically: + * + * - For RRSIG we get the matching DNSKEY + * - For DNSKEY we get the matching DS + * - For unsigned SOA/NS we get the matching DS + * - For unsigned CNAME/DNAME/DS we get the parent SOA RR + * - For other unsigned RRs we get the matching SOA RR + * - For SOA/NS queries with no matching response RR, and no NSEC/NSEC3, the DS RR + * - For DS queries with no matching response RRs, and no NSEC/NSEC3, the parent's SOA RR + * - For other queries with no matching response RRs, and no NSEC/NSEC3, the SOA RR + */ + + if (FLAGS_SET(t->query_flags, SD_RESOLVED_NO_VALIDATE) || t->scope->dnssec_mode == DNSSEC_NO) + return 0; + if (t->answer_source != DNS_TRANSACTION_NETWORK) + return 0; /* We only need to validate stuff from the network */ + if (!dns_transaction_dnssec_supported(t)) + return 0; /* If we can't do DNSSEC anyway there's no point in getting the auxiliary RRs */ + + DNS_ANSWER_FOREACH(rr, t->answer) { + + if (dns_type_is_pseudo(rr->key->type)) + continue; + + /* If this RR is in the negative trust anchor, we don't need to validate it. */ + r = dns_transaction_negative_trust_anchor_lookup(t, dns_resource_key_name(rr->key)); + if (r < 0) + return r; + if (r > 0) + continue; + + switch (rr->key->type) { + + case DNS_TYPE_RRSIG: { + /* For each RRSIG we request the matching DNSKEY */ + _cleanup_(dns_resource_key_unrefp) DnsResourceKey *dnskey = NULL; + + /* If this RRSIG is about a DNSKEY RR and the + * signer is the same as the owner, then we + * already have the DNSKEY, and we don't have + * to look for more. */ + if (rr->rrsig.type_covered == DNS_TYPE_DNSKEY) { + r = dns_name_equal(rr->rrsig.signer, dns_resource_key_name(rr->key)); + if (r < 0) + return r; + if (r > 0) + continue; + } + + /* If the signer is not a parent of our + * original query, then this is about an + * auxiliary RRset, but not anything we asked + * for. In this case we aren't interested, + * because we don't want to request additional + * RRs for stuff we didn't really ask for, and + * also to avoid request loops, where + * additional RRs from one transaction result + * in another transaction whose additional RRs + * point back to the original transaction, and + * we deadlock. */ + r = dns_name_endswith(dns_resource_key_name(dns_transaction_key(t)), rr->rrsig.signer); + if (r < 0) + return r; + if (r == 0) + continue; + + dnskey = dns_resource_key_new(rr->key->class, DNS_TYPE_DNSKEY, rr->rrsig.signer); + if (!dnskey) + return -ENOMEM; + + log_debug("Requesting DNSKEY to validate transaction %" PRIu16" (%s, RRSIG with key tag: %" PRIu16 ").", + t->id, dns_resource_key_name(rr->key), rr->rrsig.key_tag); + r = dns_transaction_request_dnssec_rr(t, dnskey); + if (r < 0) + return r; + break; + } + + case DNS_TYPE_DNSKEY: { + /* For each DNSKEY we request the matching DS */ + _cleanup_(dns_resource_key_unrefp) DnsResourceKey *ds = NULL; + + /* If the DNSKEY we are looking at is not for + * zone we are interested in, nor any of its + * parents, we aren't interested, and don't + * request it. After all, we don't want to end + * up in request loops, and want to keep + * additional traffic down. */ + + r = dns_name_endswith(dns_resource_key_name(dns_transaction_key(t)), dns_resource_key_name(rr->key)); + if (r < 0) + return r; + if (r == 0) + continue; + + ds = dns_resource_key_new(rr->key->class, DNS_TYPE_DS, dns_resource_key_name(rr->key)); + if (!ds) + return -ENOMEM; + + log_debug("Requesting DS to validate transaction %" PRIu16" (%s, DNSKEY with key tag: %" PRIu16 ").", + t->id, dns_resource_key_name(rr->key), dnssec_keytag(rr, false)); + r = dns_transaction_request_dnssec_rr(t, ds); + if (r < 0) + return r; + + break; + } + + case DNS_TYPE_SOA: + case DNS_TYPE_NS: { + _cleanup_(dns_resource_key_unrefp) DnsResourceKey *ds = NULL; + + /* For an unsigned SOA or NS, try to acquire + * the matching DS RR, as we are at a zone cut + * then, and whether a DS exists tells us + * whether the zone is signed. Do so only if + * this RR matches our original question, + * however. */ + + r = dns_resource_key_match_rr(dns_transaction_key(t), rr, NULL); + if (r < 0) + return r; + if (r == 0) { + /* Hmm, so this SOA RR doesn't match our original question. In this case, maybe this is + * a negative reply, and we need the SOA RR's TTL in order to cache a negative entry? + * If so, we need to validate it, too. */ + + r = dns_answer_match_key(t->answer, dns_transaction_key(t), NULL); + if (r < 0) + return r; + if (r > 0) /* positive reply, we won't need the SOA and hence don't need to validate + * it. */ + continue; + + /* Only bother with this if the SOA/NS RR we are looking at is actually a parent of + * what we are looking for, otherwise there's no value in it for us. */ + r = dns_name_endswith(dns_resource_key_name(dns_transaction_key(t)), dns_resource_key_name(rr->key)); + if (r < 0) + return r; + if (r == 0) + continue; + } + + r = dnssec_has_rrsig(t->answer, rr->key); + if (r < 0) + return r; + if (r > 0) + continue; + + ds = dns_resource_key_new(rr->key->class, DNS_TYPE_DS, dns_resource_key_name(rr->key)); + if (!ds) + return -ENOMEM; + + log_debug("Requesting DS to validate transaction %" PRIu16 " (%s, unsigned SOA/NS RRset).", + t->id, dns_resource_key_name(rr->key)); + r = dns_transaction_request_dnssec_rr(t, ds); + if (r < 0) + return r; + + break; + } + + case DNS_TYPE_DS: + case DNS_TYPE_CNAME: + case DNS_TYPE_DNAME: { + _cleanup_(dns_resource_key_unrefp) DnsResourceKey *soa = NULL; + const char *name; + + /* CNAMEs and DNAMEs cannot be located at a + * zone apex, hence ask for the parent SOA for + * unsigned CNAME/DNAME RRs, maybe that's the + * apex. But do all that only if this is + * actually a response to our original + * question. + * + * Similar for DS RRs, which are signed when + * the parent SOA is signed. */ + + r = dns_transaction_is_primary_response(t, rr); + if (r < 0) + return r; + if (r == 0) + continue; + + r = dnssec_has_rrsig(t->answer, rr->key); + if (r < 0) + return r; + if (r > 0) + continue; + + r = dns_answer_has_dname_for_cname(t->answer, rr); + if (r < 0) + return r; + if (r > 0) + continue; + + name = dns_resource_key_name(rr->key); + r = dns_name_parent(&name); + if (r < 0) + return r; + if (r == 0) + continue; + + soa = dns_resource_key_new(rr->key->class, DNS_TYPE_SOA, name); + if (!soa) + return -ENOMEM; + + log_debug("Requesting parent SOA to validate transaction %" PRIu16 " (%s, unsigned CNAME/DNAME/DS RRset).", + t->id, dns_resource_key_name(rr->key)); + r = dns_transaction_request_dnssec_rr(t, soa); + if (r < 0) + return r; + + break; + } + + default: { + _cleanup_(dns_resource_key_unrefp) DnsResourceKey *soa = NULL; + + /* For other unsigned RRsets (including + * NSEC/NSEC3!), look for proof the zone is + * unsigned, by requesting the SOA RR of the + * zone. However, do so only if they are + * directly relevant to our original + * question. */ + + r = dns_transaction_is_primary_response(t, rr); + if (r < 0) + return r; + if (r == 0) + continue; + + r = dnssec_has_rrsig(t->answer, rr->key); + if (r < 0) + return r; + if (r > 0) + continue; + + soa = dns_resource_key_new(rr->key->class, DNS_TYPE_SOA, dns_resource_key_name(rr->key)); + if (!soa) + return -ENOMEM; + + log_debug("Requesting SOA to validate transaction %" PRIu16 " (%s, unsigned non-SOA/NS RRset <%s>).", + t->id, dns_resource_key_name(rr->key), dns_resource_record_to_string(rr)); + r = dns_transaction_request_dnssec_rr(t, soa); + if (r < 0) + return r; + break; + }} + } + + /* Above, we requested everything necessary to validate what + * we got. Now, let's request what we need to validate what we + * didn't get... */ + + r = dns_transaction_has_negative_answer(t); + if (r < 0) + return r; + if (r > 0) { + const char *name, *signed_status; + uint16_t type = 0; + + name = dns_resource_key_name(dns_transaction_key(t)); + signed_status = dns_answer_contains_nsec_or_nsec3(t->answer) ? "signed" : "unsigned"; + + /* If this was a SOA or NS request, then check if there's a DS RR for the same domain. Note that this + * could also be used as indication that we are not at a zone apex, but in real world setups there are + * too many broken DNS servers (Hello, incapdns.net!) where non-terminal zones return NXDOMAIN even + * though they have further children. If this was a DS request, then it's signed when the parent zone + * is signed, hence ask the parent SOA in that case. If this was any other RR then ask for the SOA RR, + * to see if that is signed. */ + + if (dns_transaction_key(t)->type == DNS_TYPE_DS) { + r = dns_name_parent(&name); + if (r > 0) { + type = DNS_TYPE_SOA; + log_debug("Requesting parent SOA (%s %s) to validate transaction %" PRIu16 " (%s, %s empty DS response).", + special_glyph(SPECIAL_GLYPH_ARROW_RIGHT), name, t->id, + dns_resource_key_name(dns_transaction_key(t)), signed_status); + } else + name = NULL; + + } else if (IN_SET(dns_transaction_key(t)->type, DNS_TYPE_SOA, DNS_TYPE_NS)) { + + type = DNS_TYPE_DS; + log_debug("Requesting DS (%s %s) to validate transaction %" PRIu16 " (%s, %s empty SOA/NS response).", + special_glyph(SPECIAL_GLYPH_ARROW_RIGHT), name, t->id, name, signed_status); + + } else { + type = DNS_TYPE_SOA; + log_debug("Requesting SOA (%s %s) to validate transaction %" PRIu16 " (%s, %s empty non-SOA/NS/DS response).", + special_glyph(SPECIAL_GLYPH_ARROW_RIGHT), name, t->id, name, signed_status); + } + + if (name) { + _cleanup_(dns_resource_key_unrefp) DnsResourceKey *soa = NULL; + + soa = dns_resource_key_new(dns_transaction_key(t)->class, type, name); + if (!soa) + return -ENOMEM; + + r = dns_transaction_request_dnssec_rr(t, soa); + if (r < 0) + return r; + } + } + + return dns_transaction_dnssec_is_live(t); +} + +void dns_transaction_notify(DnsTransaction *t, DnsTransaction *source) { + assert(t); + assert(source); + + /* Invoked whenever any of our auxiliary DNSSEC transactions completed its work. If the state is still PENDING, + we are still in the loop that adds further DNSSEC transactions, hence don't check if we are ready yet. If + the state is VALIDATING however, we should check if we are complete now. */ + + if (t->state == DNS_TRANSACTION_VALIDATING) + dns_transaction_process_dnssec(t); +} + +static int dns_transaction_validate_dnskey_by_ds(DnsTransaction *t) { + DnsAnswerItem *item; + int r; + + assert(t); + + /* Add all DNSKEY RRs from the answer that are validated by DS + * RRs from the list of validated keys to the list of + * validated keys. */ + + DNS_ANSWER_FOREACH_ITEM(item, t->answer) { + + r = dnssec_verify_dnskey_by_ds_search(item->rr, t->validated_keys); + if (r < 0) + return r; + if (r == 0) + continue; + + /* If so, the DNSKEY is validated too. */ + r = dns_answer_add_extend(&t->validated_keys, item->rr, item->ifindex, item->flags|DNS_ANSWER_AUTHENTICATED, item->rrsig); + if (r < 0) + return r; + } + + return 0; +} + +static int dns_transaction_requires_rrsig(DnsTransaction *t, DnsResourceRecord *rr) { + int r; + + assert(t); + assert(rr); + + /* Checks if the RR we are looking for must be signed with an + * RRSIG. This is used for positive responses. */ + + if (t->scope->dnssec_mode == DNSSEC_NO) + return false; + + if (dns_type_is_pseudo(rr->key->type)) + return -EINVAL; + + r = dns_transaction_negative_trust_anchor_lookup(t, dns_resource_key_name(rr->key)); + if (r < 0) + return r; + if (r > 0) + return false; + + switch (rr->key->type) { + + case DNS_TYPE_RRSIG: + /* RRSIGs are the signatures themselves, they need no signing. */ + return false; + + case DNS_TYPE_SOA: + case DNS_TYPE_NS: { + DnsTransaction *dt; + + /* For SOA or NS RRs we look for a matching DS transaction */ + + SET_FOREACH(dt, t->dnssec_transactions) { + + if (dns_transaction_key(dt)->class != rr->key->class) + continue; + if (dns_transaction_key(dt)->type != DNS_TYPE_DS) + continue; + + r = dns_name_equal(dns_resource_key_name(dns_transaction_key(dt)), dns_resource_key_name(rr->key)); + if (r < 0) + return r; + if (r == 0) + continue; + + /* We found a DS transactions for the SOA/NS + * RRs we are looking at. If it discovered signed DS + * RRs, then we need to be signed, too. */ + + if (!FLAGS_SET(dt->answer_query_flags, SD_RESOLVED_AUTHENTICATED)) + return false; + + return dns_answer_match_key(dt->answer, dns_transaction_key(dt), NULL); + } + + /* We found nothing that proves this is safe to leave + * this unauthenticated, hence ask inist on + * authentication. */ + return true; + } + + case DNS_TYPE_DS: + case DNS_TYPE_CNAME: + case DNS_TYPE_DNAME: { + const char *parent = NULL; + DnsTransaction *dt; + + /* + * CNAME/DNAME RRs cannot be located at a zone apex, hence look directly for the parent SOA. + * + * DS RRs are signed if the parent is signed, hence also look at the parent SOA + */ + + SET_FOREACH(dt, t->dnssec_transactions) { + + if (dns_transaction_key(dt)->class != rr->key->class) + continue; + if (dns_transaction_key(dt)->type != DNS_TYPE_SOA) + continue; + + if (!parent) { + parent = dns_resource_key_name(rr->key); + r = dns_name_parent(&parent); + if (r < 0) + return r; + if (r == 0) { + if (rr->key->type == DNS_TYPE_DS) + return true; + + /* A CNAME/DNAME without a parent? That's sooo weird. */ + return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG), + "Transaction %" PRIu16 " claims CNAME/DNAME at root. Refusing.", t->id); + } + } + + r = dns_name_equal(dns_resource_key_name(dns_transaction_key(dt)), parent); + if (r < 0) + return r; + if (r == 0) + continue; + + return FLAGS_SET(dt->answer_query_flags, SD_RESOLVED_AUTHENTICATED); + } + + return true; + } + + default: { + DnsTransaction *dt; + + /* Any other kind of RR (including DNSKEY/NSEC/NSEC3). Let's see if our SOA lookup was authenticated */ + + SET_FOREACH(dt, t->dnssec_transactions) { + + if (dns_transaction_key(dt)->class != rr->key->class) + continue; + if (dns_transaction_key(dt)->type != DNS_TYPE_SOA) + continue; + + r = dns_name_equal(dns_resource_key_name(dns_transaction_key(dt)), dns_resource_key_name(rr->key)); + if (r < 0) + return r; + if (r == 0) + continue; + + /* We found the transaction that was supposed to find the SOA RR for us. It was + * successful, but found no RR for us. This means we are not at a zone cut. In this + * case, we require authentication if the SOA lookup was authenticated too. */ + return FLAGS_SET(dt->answer_query_flags, SD_RESOLVED_AUTHENTICATED); + } + + return true; + }} +} + +static int dns_transaction_in_private_tld(DnsTransaction *t, const DnsResourceKey *key) { + DnsTransaction *dt; + const char *tld; + int r; + + /* If DNSSEC downgrade mode is on, checks whether the + * specified RR is one level below a TLD we have proven not to + * exist. In such a case we assume that this is a private + * domain, and permit it. + * + * This detects cases like the Fritz!Box router networks. Each + * Fritz!Box router serves a private "fritz.box" zone, in the + * non-existing TLD "box". Requests for the "fritz.box" domain + * are served by the router itself, while requests for the + * "box" domain will result in NXDOMAIN. + * + * Note that this logic is unable to detect cases where a + * router serves a private DNS zone directly under + * non-existing TLD. In such a case we cannot detect whether + * the TLD is supposed to exist or not, as all requests we + * make for it will be answered by the router's zone, and not + * by the root zone. */ + + assert(t); + + if (t->scope->dnssec_mode != DNSSEC_ALLOW_DOWNGRADE) + return false; /* In strict DNSSEC mode what doesn't exist, doesn't exist */ + + tld = dns_resource_key_name(key); + r = dns_name_parent(&tld); + if (r < 0) + return r; + if (r == 0) + return false; /* Already the root domain */ + + if (!dns_name_is_single_label(tld)) + return false; + + SET_FOREACH(dt, t->dnssec_transactions) { + + if (dns_transaction_key(dt)->class != key->class) + continue; + + r = dns_name_equal(dns_resource_key_name(dns_transaction_key(dt)), tld); + if (r < 0) + return r; + if (r == 0) + continue; + + /* We found an auxiliary lookup we did for the TLD. If + * that returned with NXDOMAIN, we know the TLD didn't + * exist, and hence this might be a private zone. */ + + return dt->answer_rcode == DNS_RCODE_NXDOMAIN; + } + + return false; +} + +static int dns_transaction_requires_nsec(DnsTransaction *t) { + char key_str[DNS_RESOURCE_KEY_STRING_MAX]; + DnsTransaction *dt; + const char *name; + uint16_t type = 0; + int r; + + assert(t); + + /* Checks if we need to insist on NSEC/NSEC3 RRs for proving + * this negative reply */ + + if (t->scope->dnssec_mode == DNSSEC_NO) + return false; + + if (dns_type_is_pseudo(dns_transaction_key(t)->type)) + return -EINVAL; + + r = dns_transaction_negative_trust_anchor_lookup(t, dns_resource_key_name(dns_transaction_key(t))); + if (r < 0) + return r; + if (r > 0) + return false; + + r = dns_transaction_in_private_tld(t, dns_transaction_key(t)); + if (r < 0) + return r; + if (r > 0) { + /* The lookup is from a TLD that is proven not to + * exist, and we are in downgrade mode, hence ignore + * that fact that we didn't get any NSEC RRs. */ + + log_info("Detected a negative query %s in a private DNS zone, permitting unsigned response.", + dns_resource_key_to_string(dns_transaction_key(t), key_str, sizeof key_str)); + return false; + } + + name = dns_resource_key_name(dns_transaction_key(t)); + + if (dns_transaction_key(t)->type == DNS_TYPE_DS) { + + /* We got a negative reply for this DS lookup? DS RRs are signed when their parent zone is signed, + * hence check the parent SOA in this case. */ + + r = dns_name_parent(&name); + if (r < 0) + return r; + if (r == 0) + return true; + + type = DNS_TYPE_SOA; + + } else if (IN_SET(dns_transaction_key(t)->type, DNS_TYPE_SOA, DNS_TYPE_NS)) + /* We got a negative reply for this SOA/NS lookup? If so, check if there's a DS RR for this */ + type = DNS_TYPE_DS; + else + /* For all other negative replies, check for the SOA lookup */ + type = DNS_TYPE_SOA; + + /* For all other RRs we check the SOA on the same level to see + * if it's signed. */ + + SET_FOREACH(dt, t->dnssec_transactions) { + + if (dns_transaction_key(dt)->class != dns_transaction_key(t)->class) + continue; + if (dns_transaction_key(dt)->type != type) + continue; + + r = dns_name_equal(dns_resource_key_name(dns_transaction_key(dt)), name); + if (r < 0) + return r; + if (r == 0) + continue; + + return FLAGS_SET(dt->answer_query_flags, SD_RESOLVED_AUTHENTICATED); + } + + /* If in doubt, require NSEC/NSEC3 */ + return true; +} + +static int dns_transaction_dnskey_authenticated(DnsTransaction *t, DnsResourceRecord *rr) { + DnsResourceRecord *rrsig; + bool found = false; + int r; + + /* Checks whether any of the DNSKEYs used for the RRSIGs for + * the specified RRset is authenticated (i.e. has a matching + * DS RR). */ + + r = dns_transaction_negative_trust_anchor_lookup(t, dns_resource_key_name(rr->key)); + if (r < 0) + return r; + if (r > 0) + return false; + + DNS_ANSWER_FOREACH(rrsig, t->answer) { + DnsTransaction *dt; + + r = dnssec_key_match_rrsig(rr->key, rrsig); + if (r < 0) + return r; + if (r == 0) + continue; + + SET_FOREACH(dt, t->dnssec_transactions) { + + if (dns_transaction_key(dt)->class != rr->key->class) + continue; + + if (dns_transaction_key(dt)->type == DNS_TYPE_DNSKEY) { + + r = dns_name_equal(dns_resource_key_name(dns_transaction_key(dt)), rrsig->rrsig.signer); + if (r < 0) + return r; + if (r == 0) + continue; + + /* OK, we found an auxiliary DNSKEY lookup. If that lookup is authenticated, + * report this. */ + + if (FLAGS_SET(dt->answer_query_flags, SD_RESOLVED_AUTHENTICATED)) + return true; + + found = true; + + } else if (dns_transaction_key(dt)->type == DNS_TYPE_DS) { + + r = dns_name_equal(dns_resource_key_name(dns_transaction_key(dt)), rrsig->rrsig.signer); + if (r < 0) + return r; + if (r == 0) + continue; + + /* OK, we found an auxiliary DS lookup. If that lookup is authenticated and + * non-zero, we won! */ + + if (!FLAGS_SET(dt->answer_query_flags, SD_RESOLVED_AUTHENTICATED)) + return false; + + return dns_answer_match_key(dt->answer, dns_transaction_key(dt), NULL); + } + } + } + + return found ? false : -ENXIO; +} + +static int dns_transaction_known_signed(DnsTransaction *t, DnsResourceRecord *rr) { + assert(t); + assert(rr); + + /* We know that the root domain is signed, hence if it appears + * not to be signed, there's a problem with the DNS server */ + + return rr->key->class == DNS_CLASS_IN && + dns_name_is_root(dns_resource_key_name(rr->key)); +} + +static int dns_transaction_check_revoked_trust_anchors(DnsTransaction *t) { + DnsResourceRecord *rr; + int r; + + assert(t); + + /* Maybe warn the user that we encountered a revoked DNSKEY + * for a key from our trust anchor. Note that we don't care + * whether the DNSKEY can be authenticated or not. It's + * sufficient if it is self-signed. */ + + DNS_ANSWER_FOREACH(rr, t->answer) { + r = dns_trust_anchor_check_revoked(&t->scope->manager->trust_anchor, rr, t->answer); + if (r < 0) + return r; + } + + return 0; +} + +static int dns_transaction_invalidate_revoked_keys(DnsTransaction *t) { + bool changed; + int r; + + assert(t); + + /* Removes all DNSKEY/DS objects from t->validated_keys that + * our trust anchors database considers revoked. */ + + do { + DnsResourceRecord *rr; + + changed = false; + + DNS_ANSWER_FOREACH(rr, t->validated_keys) { + r = dns_trust_anchor_is_revoked(&t->scope->manager->trust_anchor, rr); + if (r < 0) + return r; + if (r > 0) { + r = dns_answer_remove_by_rr(&t->validated_keys, rr); + if (r < 0) + return r; + + assert(r > 0); + changed = true; + break; + } + } + } while (changed); + + return 0; +} + +static int dns_transaction_copy_validated(DnsTransaction *t) { + DnsTransaction *dt; + int r; + + assert(t); + + /* Copy all validated RRs from the auxiliary DNSSEC transactions into our set of validated RRs */ + + SET_FOREACH(dt, t->dnssec_transactions) { + + if (DNS_TRANSACTION_IS_LIVE(dt->state)) + continue; + + if (!FLAGS_SET(dt->answer_query_flags, SD_RESOLVED_AUTHENTICATED)) + continue; + + r = dns_answer_extend(&t->validated_keys, dt->answer); + if (r < 0) + return r; + } + + return 0; +} + +typedef enum { + DNSSEC_PHASE_DNSKEY, /* Phase #1, only validate DNSKEYs */ + DNSSEC_PHASE_NSEC, /* Phase #2, only validate NSEC+NSEC3 */ + DNSSEC_PHASE_ALL, /* Phase #3, validate everything else */ +} Phase; + +static int dnssec_validate_records( + DnsTransaction *t, + Phase phase, + bool *have_nsec, + unsigned *nvalidations, + DnsAnswer **validated) { + + DnsResourceRecord *rr; + int r; + + assert(nvalidations); + + /* Returns negative on error, 0 if validation failed, 1 to restart validation, 2 when finished. */ + + DNS_ANSWER_FOREACH(rr, t->answer) { + _unused_ _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr_ref = dns_resource_record_ref(rr); + DnsResourceRecord *rrsig = NULL; + DnssecResult result; + + switch (rr->key->type) { + case DNS_TYPE_RRSIG: + continue; + + case DNS_TYPE_DNSKEY: + /* We validate DNSKEYs only in the DNSKEY and ALL phases */ + if (phase == DNSSEC_PHASE_NSEC) + continue; + break; + + case DNS_TYPE_NSEC: + case DNS_TYPE_NSEC3: + *have_nsec = true; + + /* We validate NSEC/NSEC3 only in the NSEC and ALL phases */ + if (phase == DNSSEC_PHASE_DNSKEY) + continue; + break; + + default: + /* We validate all other RRs only in the ALL phases */ + if (phase != DNSSEC_PHASE_ALL) + continue; + } + + r = dnssec_verify_rrset_search( + t->answer, + rr->key, + t->validated_keys, + USEC_INFINITY, + &result, + &rrsig); + if (r < 0) + return r; + *nvalidations += r; + + log_debug("Looking at %s: %s", strna(dns_resource_record_to_string(rr)), dnssec_result_to_string(result)); + + if (result == DNSSEC_VALIDATED) { + assert(rrsig); + + if (rr->key->type == DNS_TYPE_DNSKEY) { + /* If we just validated a DNSKEY RRset, then let's add these keys to + * the set of validated keys for this transaction. */ + + r = dns_answer_copy_by_key(&t->validated_keys, t->answer, rr->key, DNS_ANSWER_AUTHENTICATED, rrsig); + if (r < 0) + return r; + + /* Some of the DNSKEYs we just added might already have been revoked, + * remove them again in that case. */ + r = dns_transaction_invalidate_revoked_keys(t); + if (r < 0) + return r; + } + + /* Add the validated RRset to the new list of validated RRsets, and remove it from + * the unvalidated RRsets. We mark the RRset as authenticated and cacheable. */ + r = dns_answer_move_by_key(validated, &t->answer, rr->key, DNS_ANSWER_AUTHENTICATED|DNS_ANSWER_CACHEABLE, rrsig); + if (r < 0) + return r; + + manager_dnssec_verdict(t->scope->manager, DNSSEC_SECURE, rr->key); + + /* Exit the loop, we dropped something from the answer, start from the beginning */ + return 1; + } + + /* If we haven't read all DNSKEYs yet a negative result of the validation is irrelevant, as + * there might be more DNSKEYs coming. Similar, if we haven't read all NSEC/NSEC3 RRs yet, + * we cannot do positive wildcard proofs yet, as those require the NSEC/NSEC3 RRs. */ + if (phase != DNSSEC_PHASE_ALL) + continue; + + if (result == DNSSEC_VALIDATED_WILDCARD) { + bool authenticated = false; + const char *source; + + assert(rrsig); + + /* This RRset validated, but as a wildcard. This means we need + * to prove via NSEC/NSEC3 that no matching non-wildcard RR exists. */ + + /* First step, determine the source of synthesis */ + r = dns_resource_record_source(rrsig, &source); + if (r < 0) + return r; + + r = dnssec_test_positive_wildcard(*validated, + dns_resource_key_name(rr->key), + source, + rrsig->rrsig.signer, + &authenticated); + + /* Unless the NSEC proof showed that the key really doesn't exist something is off. */ + if (r == 0) + result = DNSSEC_INVALID; + else { + r = dns_answer_move_by_key( + validated, + &t->answer, + rr->key, + authenticated ? (DNS_ANSWER_AUTHENTICATED|DNS_ANSWER_CACHEABLE) : 0, + rrsig); + if (r < 0) + return r; + + manager_dnssec_verdict(t->scope->manager, authenticated ? DNSSEC_SECURE : DNSSEC_INSECURE, rr->key); + + /* Exit the loop, we dropped something from the answer, start from the beginning */ + return 1; + } + } + + if (result == DNSSEC_NO_SIGNATURE) { + r = dns_transaction_requires_rrsig(t, rr); + if (r < 0) + return r; + if (r == 0) { + /* Data does not require signing. In that case, just copy it over, + * but remember that this is by no means authenticated. */ + r = dns_answer_move_by_key( + validated, + &t->answer, + rr->key, + 0, + NULL); + if (r < 0) + return r; + + manager_dnssec_verdict(t->scope->manager, DNSSEC_INSECURE, rr->key); + return 1; + } + + r = dns_transaction_known_signed(t, rr); + if (r < 0) + return r; + if (r > 0) { + /* This is an RR we know has to be signed. If it isn't this means + * the server is not attaching RRSIGs, hence complain. */ + + dns_server_packet_rrsig_missing(t->server, t->current_feature_level); + + if (t->scope->dnssec_mode == DNSSEC_ALLOW_DOWNGRADE) { + + /* Downgrading is OK? If so, just consider the information unsigned */ + + r = dns_answer_move_by_key(validated, &t->answer, rr->key, 0, NULL); + if (r < 0) + return r; + + manager_dnssec_verdict(t->scope->manager, DNSSEC_INSECURE, rr->key); + return 1; + } + + /* Otherwise, fail */ + t->answer_dnssec_result = DNSSEC_INCOMPATIBLE_SERVER; + return 0; + } + + r = dns_transaction_in_private_tld(t, rr->key); + if (r < 0) + return r; + if (r > 0) { + char s[DNS_RESOURCE_KEY_STRING_MAX]; + + /* The data is from a TLD that is proven not to exist, and we are in downgrade + * mode, hence ignore the fact that this was not signed. */ + + log_info("Detected RRset %s is in a private DNS zone, permitting unsigned RRs.", + dns_resource_key_to_string(rr->key, s, sizeof s)); + + r = dns_answer_move_by_key(validated, &t->answer, rr->key, 0, NULL); + if (r < 0) + return r; + + manager_dnssec_verdict(t->scope->manager, DNSSEC_INSECURE, rr->key); + return 1; + } + } + + /* https://datatracker.ietf.org/doc/html/rfc6840#section-5.2 */ + if (result == DNSSEC_UNSUPPORTED_ALGORITHM) { + r = dns_answer_move_by_key(validated, &t->answer, rr->key, 0, NULL); + if (r < 0) + return r; + + manager_dnssec_verdict(t->scope->manager, DNSSEC_INSECURE, rr->key); + return 1; + } + + if (IN_SET(result, + DNSSEC_MISSING_KEY, + DNSSEC_SIGNATURE_EXPIRED)) { + + r = dns_transaction_dnskey_authenticated(t, rr); + if (r < 0 && r != -ENXIO) + return r; + if (r == 0) { + /* The DNSKEY transaction was not authenticated, this means there's + * no DS for this, which means it's OK if no keys are found for this signature. */ + + r = dns_answer_move_by_key(validated, &t->answer, rr->key, 0, NULL); + if (r < 0) + return r; + + manager_dnssec_verdict(t->scope->manager, DNSSEC_INSECURE, rr->key); + return 1; + } + } + + r = dns_transaction_is_primary_response(t, rr); + if (r < 0) + return r; + if (r > 0) { + /* Look for a matching DNAME for this CNAME */ + r = dns_answer_has_dname_for_cname(t->answer, rr); + if (r < 0) + return r; + if (r == 0) { + /* Also look among the stuff we already validated */ + r = dns_answer_has_dname_for_cname(*validated, rr); + if (r < 0) + return r; + } + + if (r == 0) { + if (IN_SET(result, + DNSSEC_INVALID, + DNSSEC_SIGNATURE_EXPIRED, + DNSSEC_NO_SIGNATURE)) + manager_dnssec_verdict(t->scope->manager, DNSSEC_BOGUS, rr->key); + else /* DNSSEC_MISSING_KEY, DNSSEC_UNSUPPORTED_ALGORITHM, + or DNSSEC_TOO_MANY_VALIDATIONS */ + manager_dnssec_verdict(t->scope->manager, DNSSEC_INDETERMINATE, rr->key); + + /* This is a primary response to our question, and it failed validation. + * That's fatal. */ + t->answer_dnssec_result = result; + return 0; + } + + /* This is a primary response, but we do have a DNAME RR + * in the RR that can replay this CNAME, hence rely on + * that, and we can remove the CNAME in favour of it. */ + } + + /* This is just some auxiliary data. Just remove the RRset and continue. */ + r = dns_answer_remove_by_key(&t->answer, rr->key); + if (r < 0) + return r; + + /* We dropped something from the answer, start from the beginning. */ + return 1; + } + + return 2; /* Finito. */ +} + +int dns_transaction_validate_dnssec(DnsTransaction *t) { + _cleanup_(dns_answer_unrefp) DnsAnswer *validated = NULL; + Phase phase; + DnsAnswerFlags flags; + int r; + char key_str[DNS_RESOURCE_KEY_STRING_MAX]; + + assert(t); + + /* We have now collected all DS and DNSKEY RRs in t->validated_keys, let's see which RRs we can now + * authenticate with that. */ + + if (FLAGS_SET(t->query_flags, SD_RESOLVED_NO_VALIDATE) || t->scope->dnssec_mode == DNSSEC_NO) + return 0; + + /* Already validated */ + if (t->answer_dnssec_result != _DNSSEC_RESULT_INVALID) + return 0; + + /* Our own stuff needs no validation */ + if (IN_SET(t->answer_source, DNS_TRANSACTION_ZONE, DNS_TRANSACTION_TRUST_ANCHOR)) { + t->answer_dnssec_result = DNSSEC_VALIDATED; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED, true); + return 0; + } + + /* Cached stuff is not affected by validation. */ + if (t->answer_source != DNS_TRANSACTION_NETWORK) + return 0; + + if (!dns_transaction_dnssec_supported_full(t)) { + /* The server does not support DNSSEC, or doesn't augment responses with RRSIGs. */ + t->answer_dnssec_result = DNSSEC_INCOMPATIBLE_SERVER; + log_debug("Not validating response for %" PRIu16 ", used server feature level does not support DNSSEC.", t->id); + return 0; + } + + log_debug("Validating response from transaction %" PRIu16 " (%s).", + t->id, + dns_resource_key_to_string(dns_transaction_key(t), key_str, sizeof key_str)); + + /* First, see if this response contains any revoked trust + * anchors we care about */ + r = dns_transaction_check_revoked_trust_anchors(t); + if (r < 0) + return r; + + /* Third, copy all RRs we acquired successfully from auxiliary RRs over. */ + r = dns_transaction_copy_validated(t); + if (r < 0) + return r; + + /* Second, see if there are DNSKEYs we already know a + * validated DS for. */ + r = dns_transaction_validate_dnskey_by_ds(t); + if (r < 0) + return r; + + /* Fourth, remove all DNSKEY and DS RRs again that our trust + * anchor says are revoked. After all we might have marked + * some keys revoked above, but they might still be lingering + * in our validated_keys list. */ + r = dns_transaction_invalidate_revoked_keys(t); + if (r < 0) + return r; + + phase = DNSSEC_PHASE_DNSKEY; + for (unsigned nvalidations = 0;;) { + bool have_nsec = false; + + r = dnssec_validate_records(t, phase, &have_nsec, &nvalidations, &validated); + if (r <= 0) + return r; + + if (nvalidations > DNSSEC_VALIDATION_MAX) { + /* This reply requires an onerous number of signature validations to verify. Let's + * not waste our time trying, as this shouldn't happen for well-behaved domains + * anyway. */ + t->answer_dnssec_result = DNSSEC_TOO_MANY_VALIDATIONS; + return 0; + } + + /* Try again as long as we managed to achieve something */ + if (r == 1) + continue; + + if (phase == DNSSEC_PHASE_DNSKEY && have_nsec) { + /* OK, we processed all DNSKEYs, and there are NSEC/NSEC3 RRs, look at those now. */ + phase = DNSSEC_PHASE_NSEC; + continue; + } + + if (phase != DNSSEC_PHASE_ALL) { + /* OK, we processed all DNSKEYs and NSEC/NSEC3 RRs, look at all the rest now. + * Note that in this third phase we start to remove RRs we couldn't validate. */ + phase = DNSSEC_PHASE_ALL; + continue; + } + + /* We're done */ + break; + } + + DNS_ANSWER_REPLACE(t->answer, TAKE_PTR(validated)); + + /* At this point the answer only contains validated + * RRsets. Now, let's see if it actually answers the question + * we asked. If so, great! If it doesn't, then see if + * NSEC/NSEC3 can prove this. */ + r = dns_transaction_has_positive_answer(t, &flags); + if (r > 0) { + /* Yes, it answers the question! */ + + if (flags & DNS_ANSWER_AUTHENTICATED) { + /* The answer is fully authenticated, yay. */ + t->answer_dnssec_result = DNSSEC_VALIDATED; + t->answer_rcode = DNS_RCODE_SUCCESS; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED, true); + } else { + /* The answer is not fully authenticated. */ + t->answer_dnssec_result = DNSSEC_UNSIGNED; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED, false); + } + + } else if (r == 0) { + DnssecNsecResult nr; + bool authenticated = false; + + /* Bummer! Let's check NSEC/NSEC3 */ + r = dnssec_nsec_test(t->answer, dns_transaction_key(t), &nr, &authenticated, &t->answer_nsec_ttl); + if (r < 0) + return r; + + switch (nr) { + + case DNSSEC_NSEC_NXDOMAIN: + /* NSEC proves the domain doesn't exist. Very good. */ + log_debug("Proved NXDOMAIN via NSEC/NSEC3 for transaction %u (%s)", t->id, key_str); + t->answer_dnssec_result = DNSSEC_VALIDATED; + t->answer_rcode = DNS_RCODE_NXDOMAIN; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED, authenticated); + + manager_dnssec_verdict(t->scope->manager, authenticated ? DNSSEC_SECURE : DNSSEC_INSECURE, dns_transaction_key(t)); + break; + + case DNSSEC_NSEC_NODATA: + /* NSEC proves that there's no data here, very good. */ + log_debug("Proved NODATA via NSEC/NSEC3 for transaction %u (%s)", t->id, key_str); + t->answer_dnssec_result = DNSSEC_VALIDATED; + t->answer_rcode = DNS_RCODE_SUCCESS; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED, authenticated); + + manager_dnssec_verdict(t->scope->manager, authenticated ? DNSSEC_SECURE : DNSSEC_INSECURE, dns_transaction_key(t)); + break; + + case DNSSEC_NSEC_OPTOUT: + /* NSEC3 says the data might not be signed */ + log_debug("Data is NSEC3 opt-out via NSEC/NSEC3 for transaction %u (%s)", t->id, key_str); + t->answer_dnssec_result = DNSSEC_UNSIGNED; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED, false); + + manager_dnssec_verdict(t->scope->manager, DNSSEC_INSECURE, dns_transaction_key(t)); + break; + + case DNSSEC_NSEC_NO_RR: + /* No NSEC data? Bummer! */ + + r = dns_transaction_requires_nsec(t); + if (r < 0) + return r; + if (r > 0) { + t->answer_dnssec_result = DNSSEC_NO_SIGNATURE; + manager_dnssec_verdict(t->scope->manager, DNSSEC_BOGUS, dns_transaction_key(t)); + } else { + t->answer_dnssec_result = DNSSEC_UNSIGNED; + SET_FLAG(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED, false); + manager_dnssec_verdict(t->scope->manager, DNSSEC_INSECURE, dns_transaction_key(t)); + } + + break; + + case DNSSEC_NSEC_UNSUPPORTED_ALGORITHM: + /* We don't know the NSEC3 algorithm used? */ + t->answer_dnssec_result = DNSSEC_UNSUPPORTED_ALGORITHM; + manager_dnssec_verdict(t->scope->manager, DNSSEC_INDETERMINATE, dns_transaction_key(t)); + break; + + case DNSSEC_NSEC_FOUND: + case DNSSEC_NSEC_CNAME: + /* NSEC says it needs to be there, but we couldn't find it? Bummer! */ + t->answer_dnssec_result = DNSSEC_NSEC_MISMATCH; + manager_dnssec_verdict(t->scope->manager, DNSSEC_BOGUS, dns_transaction_key(t)); + break; + + default: + assert_not_reached(); + } + } + + return 1; +} + +static const char* const dns_transaction_state_table[_DNS_TRANSACTION_STATE_MAX] = { + [DNS_TRANSACTION_NULL] = "null", + [DNS_TRANSACTION_PENDING] = "pending", + [DNS_TRANSACTION_VALIDATING] = "validating", + [DNS_TRANSACTION_RCODE_FAILURE] = "rcode-failure", + [DNS_TRANSACTION_SUCCESS] = "success", + [DNS_TRANSACTION_NO_SERVERS] = "no-servers", + [DNS_TRANSACTION_TIMEOUT] = "timeout", + [DNS_TRANSACTION_ATTEMPTS_MAX_REACHED] = "attempts-max-reached", + [DNS_TRANSACTION_INVALID_REPLY] = "invalid-reply", + [DNS_TRANSACTION_ERRNO] = "errno", + [DNS_TRANSACTION_ABORTED] = "aborted", + [DNS_TRANSACTION_DNSSEC_FAILED] = "dnssec-failed", + [DNS_TRANSACTION_NO_TRUST_ANCHOR] = "no-trust-anchor", + [DNS_TRANSACTION_RR_TYPE_UNSUPPORTED] = "rr-type-unsupported", + [DNS_TRANSACTION_NETWORK_DOWN] = "network-down", + [DNS_TRANSACTION_NOT_FOUND] = "not-found", + [DNS_TRANSACTION_NO_SOURCE] = "no-source", + [DNS_TRANSACTION_STUB_LOOP] = "stub-loop", +}; +DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state, DnsTransactionState); + +static const char* const dns_transaction_source_table[_DNS_TRANSACTION_SOURCE_MAX] = { + [DNS_TRANSACTION_NETWORK] = "network", + [DNS_TRANSACTION_CACHE] = "cache", + [DNS_TRANSACTION_ZONE] = "zone", + [DNS_TRANSACTION_TRUST_ANCHOR] = "trust-anchor", +}; +DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source, DnsTransactionSource); |