diff options
Diffstat (limited to 'src/resolve/resolved-dns-query.c')
| -rw-r--r-- | src/resolve/resolved-dns-query.c | 1299 |
1 files changed, 1299 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-query.c b/src/resolve/resolved-dns-query.c new file mode 100644 index 0000000..7eb6b97 --- /dev/null +++ b/src/resolve/resolved-dns-query.c @@ -0,0 +1,1299 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include "alloc-util.h" +#include "dns-domain.h" +#include "dns-type.h" +#include "event-util.h" +#include "glyph-util.h" +#include "hostname-util.h" +#include "local-addresses.h" +#include "resolved-dns-query.h" +#include "resolved-dns-synthesize.h" +#include "resolved-etc-hosts.h" +#include "string-util.h" + +#define QUERIES_MAX 2048 +#define AUXILIARY_QUERIES_MAX 64 +#define CNAME_REDIRECTS_MAX 16 + +assert_cc(AUXILIARY_QUERIES_MAX < UINT8_MAX); +assert_cc(CNAME_REDIRECTS_MAX < UINT8_MAX); + +static int dns_query_candidate_new(DnsQueryCandidate **ret, DnsQuery *q, DnsScope *s) { + DnsQueryCandidate *c; + + assert(ret); + assert(q); + assert(s); + + c = new(DnsQueryCandidate, 1); + if (!c) + return -ENOMEM; + + *c = (DnsQueryCandidate) { + .n_ref = 1, + .query = q, + .scope = s, + }; + + LIST_PREPEND(candidates_by_query, q->candidates, c); + LIST_PREPEND(candidates_by_scope, s->query_candidates, c); + + *ret = c; + return 0; +} + +static void dns_query_candidate_stop(DnsQueryCandidate *c) { + DnsTransaction *t; + + assert(c); + + /* Detach all the DnsTransactions attached to this query */ + + while ((t = set_steal_first(c->transactions))) { + set_remove(t->notify_query_candidates, c); + set_remove(t->notify_query_candidates_done, c); + dns_transaction_gc(t); + } +} + +static DnsQueryCandidate* dns_query_candidate_unlink(DnsQueryCandidate *c) { + assert(c); + + /* Detach this DnsQueryCandidate from the Query and Scope objects */ + + if (c->query) { + LIST_REMOVE(candidates_by_query, c->query->candidates, c); + c->query = NULL; + } + + if (c->scope) { + LIST_REMOVE(candidates_by_scope, c->scope->query_candidates, c); + c->scope = NULL; + } + + return c; +} + +static DnsQueryCandidate* dns_query_candidate_free(DnsQueryCandidate *c) { + if (!c) + return NULL; + + dns_query_candidate_stop(c); + dns_query_candidate_unlink(c); + + set_free(c->transactions); + dns_search_domain_unref(c->search_domain); + + return mfree(c); +} + +DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(DnsQueryCandidate, dns_query_candidate, dns_query_candidate_free); + +static int dns_query_candidate_next_search_domain(DnsQueryCandidate *c) { + DnsSearchDomain *next; + + assert(c); + + if (c->search_domain && c->search_domain->linked) + next = c->search_domain->domains_next; + else + next = dns_scope_get_search_domains(c->scope); + + for (;;) { + if (!next) /* We hit the end of the list */ + return 0; + + if (!next->route_only) + break; + + /* Skip over route-only domains */ + next = next->domains_next; + } + + dns_search_domain_unref(c->search_domain); + c->search_domain = dns_search_domain_ref(next); + + return 1; +} + +static int dns_query_candidate_add_transaction( + DnsQueryCandidate *c, + DnsResourceKey *key, + DnsPacket *bypass) { + + _cleanup_(dns_transaction_gcp) DnsTransaction *t = NULL; + int r; + + assert(c); + assert(c->query); /* We shan't add transactions to a candidate that has been detached already */ + + if (key) { + /* Regular lookup with a resource key */ + assert(!bypass); + + t = dns_scope_find_transaction(c->scope, key, c->query->flags); + if (!t) { + r = dns_transaction_new(&t, c->scope, key, NULL, c->query->flags); + if (r < 0) + return r; + } else if (set_contains(c->transactions, t)) + return 0; + } else { + /* "Bypass" lookup with a query packet */ + assert(bypass); + + r = dns_transaction_new(&t, c->scope, NULL, bypass, c->query->flags); + if (r < 0) + return r; + } + + r = set_ensure_allocated(&t->notify_query_candidates_done, NULL); + if (r < 0) + return r; + + r = set_ensure_put(&t->notify_query_candidates, NULL, c); + if (r < 0) + return r; + + r = set_ensure_put(&c->transactions, NULL, t); + if (r < 0) { + (void) set_remove(t->notify_query_candidates, c); + return r; + } + + TAKE_PTR(t); + return 1; +} + +static int dns_query_candidate_go(DnsQueryCandidate *c) { + _unused_ _cleanup_(dns_query_candidate_unrefp) DnsQueryCandidate *keep_c = NULL; + DnsTransaction *t; + int r; + unsigned n = 0; + + assert(c); + + /* Let's keep a reference to the query while we're operating */ + keep_c = dns_query_candidate_ref(c); + + /* Start the transactions that are not started yet */ + SET_FOREACH(t, c->transactions) { + if (t->state != DNS_TRANSACTION_NULL) + continue; + + r = dns_transaction_go(t); + if (r < 0) + return r; + + n++; + } + + /* If there was nothing to start, then let's proceed immediately */ + if (n == 0) + dns_query_candidate_notify(c); + + return 0; +} + +static DnsTransactionState dns_query_candidate_state(DnsQueryCandidate *c) { + DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS; + DnsTransaction *t; + + assert(c); + + if (c->error_code != 0) + return DNS_TRANSACTION_ERRNO; + + SET_FOREACH(t, c->transactions) + + switch (t->state) { + + case DNS_TRANSACTION_NULL: + /* If there's a NULL transaction pending, then + * this means not all transactions where + * started yet, and we were called from within + * the stackframe that is supposed to start + * remaining transactions. In this case, + * simply claim the candidate is pending. */ + + case DNS_TRANSACTION_PENDING: + case DNS_TRANSACTION_VALIDATING: + /* If there's one transaction currently in + * VALIDATING state, then this means there's + * also one in PENDING state, hence we can + * return PENDING immediately. */ + return DNS_TRANSACTION_PENDING; + + case DNS_TRANSACTION_SUCCESS: + state = t->state; + break; + + default: + if (state != DNS_TRANSACTION_SUCCESS) + state = t->state; + + break; + } + + return state; +} + +static int dns_query_candidate_setup_transactions(DnsQueryCandidate *c) { + DnsQuestion *question; + DnsResourceKey *key; + int n = 0, r; + + assert(c); + assert(c->query); /* We shan't add transactions to a candidate that has been detached already */ + + dns_query_candidate_stop(c); + + if (c->query->question_bypass) { + /* If this is a bypass query, then pass the original query packet along to the transaction */ + + assert(dns_question_size(c->query->question_bypass->question) == 1); + + if (!dns_scope_good_key(c->scope, dns_question_first_key(c->query->question_bypass->question))) + return 0; + + r = dns_query_candidate_add_transaction(c, NULL, c->query->question_bypass); + if (r < 0) + goto fail; + + return 1; + } + + question = dns_query_question_for_protocol(c->query, c->scope->protocol); + + /* Create one transaction per question key */ + DNS_QUESTION_FOREACH(key, question) { + _cleanup_(dns_resource_key_unrefp) DnsResourceKey *new_key = NULL; + DnsResourceKey *qkey; + + if (c->search_domain) { + r = dns_resource_key_new_append_suffix(&new_key, key, c->search_domain->name); + if (r < 0) + goto fail; + + qkey = new_key; + } else + qkey = key; + + if (!dns_scope_good_key(c->scope, qkey)) + continue; + + r = dns_query_candidate_add_transaction(c, qkey, NULL); + if (r < 0) + goto fail; + + n++; + } + + return n; + +fail: + dns_query_candidate_stop(c); + return r; +} + +void dns_query_candidate_notify(DnsQueryCandidate *c) { + DnsTransactionState state; + int r; + + assert(c); + + if (!c->query) /* This candidate has been abandoned, do nothing. */ + return; + + state = dns_query_candidate_state(c); + + if (DNS_TRANSACTION_IS_LIVE(state)) + return; + + if (state != DNS_TRANSACTION_SUCCESS && c->search_domain) { + + r = dns_query_candidate_next_search_domain(c); + if (r < 0) + goto fail; + + if (r > 0) { + /* OK, there's another search domain to try, let's do so. */ + + r = dns_query_candidate_setup_transactions(c); + if (r < 0) + goto fail; + + if (r > 0) { + /* New transactions where queued. Start them and wait */ + + r = dns_query_candidate_go(c); + if (r < 0) + goto fail; + + return; + } + } + + } + + dns_query_ready(c->query); + return; + +fail: + c->error_code = log_warning_errno(r, "Failed to follow search domains: %m"); + dns_query_ready(c->query); +} + +static void dns_query_stop(DnsQuery *q) { + assert(q); + + event_source_disable(q->timeout_event_source); + + LIST_FOREACH(candidates_by_query, c, q->candidates) + dns_query_candidate_stop(c); +} + +static void dns_query_unlink_candidates(DnsQuery *q) { + assert(q); + + while (q->candidates) + /* Here we drop *our* references to each of the candidates. If we had the only reference, the + * DnsQueryCandidate object will be freed. */ + dns_query_candidate_unref(dns_query_candidate_unlink(q->candidates)); +} + +static void dns_query_reset_answer(DnsQuery *q) { + assert(q); + + q->answer = dns_answer_unref(q->answer); + q->answer_rcode = 0; + q->answer_dnssec_result = _DNSSEC_RESULT_INVALID; + q->answer_errno = 0; + q->answer_query_flags = 0; + q->answer_protocol = _DNS_PROTOCOL_INVALID; + q->answer_family = AF_UNSPEC; + q->answer_search_domain = dns_search_domain_unref(q->answer_search_domain); + q->answer_full_packet = dns_packet_unref(q->answer_full_packet); +} + +DnsQuery *dns_query_free(DnsQuery *q) { + if (!q) + return NULL; + + q->timeout_event_source = sd_event_source_disable_unref(q->timeout_event_source); + + while (q->auxiliary_queries) + dns_query_free(q->auxiliary_queries); + + if (q->auxiliary_for) { + assert(q->auxiliary_for->n_auxiliary_queries > 0); + q->auxiliary_for->n_auxiliary_queries--; + LIST_REMOVE(auxiliary_queries, q->auxiliary_for->auxiliary_queries, q); + } + + dns_query_unlink_candidates(q); + + dns_question_unref(q->question_idna); + dns_question_unref(q->question_utf8); + dns_packet_unref(q->question_bypass); + dns_question_unref(q->collected_questions); + + dns_query_reset_answer(q); + + sd_bus_message_unref(q->bus_request); + sd_bus_track_unref(q->bus_track); + + if (q->varlink_request) { + varlink_set_userdata(q->varlink_request, NULL); + varlink_unref(q->varlink_request); + } + + if (q->request_packet) + hashmap_remove_value(q->stub_listener_extra ? + q->stub_listener_extra->queries_by_packet : + q->manager->stub_queries_by_packet, + q->request_packet, + q); + + dns_packet_unref(q->request_packet); + dns_answer_unref(q->reply_answer); + dns_answer_unref(q->reply_authoritative); + dns_answer_unref(q->reply_additional); + + if (q->request_stream) { + /* Detach the stream from our query, in case something else keeps a reference to it. */ + (void) set_remove(q->request_stream->queries, q); + q->request_stream = dns_stream_unref(q->request_stream); + } + + free(q->request_address_string); + + if (q->manager) { + LIST_REMOVE(queries, q->manager->dns_queries, q); + q->manager->n_dns_queries--; + } + + return mfree(q); +} + +int dns_query_new( + Manager *m, + DnsQuery **ret, + DnsQuestion *question_utf8, + DnsQuestion *question_idna, + DnsPacket *question_bypass, + int ifindex, + uint64_t flags) { + + _cleanup_(dns_query_freep) DnsQuery *q = NULL; + char key_str[DNS_RESOURCE_KEY_STRING_MAX]; + DnsResourceKey *key; + int r; + + assert(m); + + if (question_bypass) { + /* It's either a "bypass" query, or a regular one, but can't be both. */ + if (question_utf8 || question_idna) + return -EINVAL; + + } else { + bool good = false; + + /* This (primarily) checks two things: + * + * 1. That the question is not empty + * 2. That all RR keys in the question objects are for the same domain + * + * Or in other words, a single DnsQuery object may be used to look up A+AAAA combination for + * the same domain name, or SRV+TXT (for DNS-SD services), but not for unrelated lookups. */ + + if (dns_question_size(question_utf8) > 0) { + r = dns_question_is_valid_for_query(question_utf8); + if (r < 0) + return r; + if (r == 0) + return -EINVAL; + + good = true; + } + + /* If the IDNA and UTF8 questions are the same, merge their references */ + r = dns_question_is_equal(question_idna, question_utf8); + if (r < 0) + return r; + if (r > 0) + question_idna = question_utf8; + else { + if (dns_question_size(question_idna) > 0) { + r = dns_question_is_valid_for_query(question_idna); + if (r < 0) + return r; + if (r == 0) + return -EINVAL; + + good = true; + } + } + + if (!good) /* don't allow empty queries */ + return -EINVAL; + } + + if (m->n_dns_queries >= QUERIES_MAX) + return -EBUSY; + + q = new(DnsQuery, 1); + if (!q) + return -ENOMEM; + + *q = (DnsQuery) { + .question_utf8 = dns_question_ref(question_utf8), + .question_idna = dns_question_ref(question_idna), + .question_bypass = dns_packet_ref(question_bypass), + .ifindex = ifindex, + .flags = flags, + .answer_dnssec_result = _DNSSEC_RESULT_INVALID, + .answer_protocol = _DNS_PROTOCOL_INVALID, + .answer_family = AF_UNSPEC, + }; + + if (question_bypass) { + DNS_QUESTION_FOREACH(key, question_bypass->question) + log_debug("Looking up bypass packet for %s.", + dns_resource_key_to_string(key, key_str, sizeof key_str)); + } else { + /* First dump UTF8 question */ + DNS_QUESTION_FOREACH(key, question_utf8) + log_debug("Looking up RR for %s.", + dns_resource_key_to_string(key, key_str, sizeof key_str)); + + /* And then dump the IDNA question, but only what hasn't been dumped already through the UTF8 question. */ + DNS_QUESTION_FOREACH(key, question_idna) { + r = dns_question_contains_key(question_utf8, key); + if (r < 0) + return r; + if (r > 0) + continue; + + log_debug("Looking up IDNA RR for %s.", + dns_resource_key_to_string(key, key_str, sizeof key_str)); + } + } + + LIST_PREPEND(queries, m->dns_queries, q); + m->n_dns_queries++; + q->manager = m; + + if (ret) + *ret = q; + + TAKE_PTR(q); + return 0; +} + +int dns_query_make_auxiliary(DnsQuery *q, DnsQuery *auxiliary_for) { + assert(q); + assert(auxiliary_for); + + /* Ensure that the query is not auxiliary yet, and + * nothing else is auxiliary to it either */ + assert(!q->auxiliary_for); + assert(!q->auxiliary_queries); + + /* Ensure that the unit we shall be made auxiliary for isn't + * auxiliary itself */ + assert(!auxiliary_for->auxiliary_for); + + if (auxiliary_for->n_auxiliary_queries >= AUXILIARY_QUERIES_MAX) + return -EAGAIN; + + LIST_PREPEND(auxiliary_queries, auxiliary_for->auxiliary_queries, q); + q->auxiliary_for = auxiliary_for; + + auxiliary_for->n_auxiliary_queries++; + return 0; +} + +void dns_query_complete(DnsQuery *q, DnsTransactionState state) { + assert(q); + assert(!DNS_TRANSACTION_IS_LIVE(state)); + assert(DNS_TRANSACTION_IS_LIVE(q->state)); + + /* Note that this call might invalidate the query. Callers should hence not attempt to access the + * query or transaction after calling this function. */ + + q->state = state; + + (void) manager_monitor_send(q->manager, q->state, q->answer_rcode, q->answer_errno, q->question_idna, q->question_utf8, q->question_bypass, q->collected_questions, q->answer); + + dns_query_stop(q); + if (q->complete) + q->complete(q); +} + +static int on_query_timeout(sd_event_source *s, usec_t usec, void *userdata) { + DnsQuery *q = ASSERT_PTR(userdata); + + assert(s); + + dns_query_complete(q, DNS_TRANSACTION_TIMEOUT); + return 0; +} + +static int dns_query_add_candidate(DnsQuery *q, DnsScope *s) { + _cleanup_(dns_query_candidate_unrefp) DnsQueryCandidate *c = NULL; + int r; + + assert(q); + assert(s); + + r = dns_query_candidate_new(&c, q, s); + if (r < 0) + return r; + + /* If this a single-label domain on DNS, we might append a suitable search domain first. */ + if (!FLAGS_SET(q->flags, SD_RESOLVED_NO_SEARCH) && + dns_scope_name_wants_search_domain(s, dns_question_first_name(q->question_idna))) { + /* OK, we want a search domain now. Let's find one for this scope */ + + r = dns_query_candidate_next_search_domain(c); + if (r < 0) + return r; + } + + r = dns_query_candidate_setup_transactions(c); + if (r < 0) + return r; + + TAKE_PTR(c); + return 0; +} + +static int dns_query_synthesize_reply(DnsQuery *q, DnsTransactionState *state) { + _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL; + int r; + + assert(q); + assert(state); + + /* Tries to synthesize localhost RR replies (and others) where appropriate. Note that this is done *after* the + * the normal lookup finished. The data from the network hence takes precedence over the data we + * synthesize. (But note that many scopes refuse to resolve certain domain names) */ + + if (!IN_SET(*state, + DNS_TRANSACTION_RCODE_FAILURE, + DNS_TRANSACTION_NO_SERVERS, + DNS_TRANSACTION_TIMEOUT, + DNS_TRANSACTION_ATTEMPTS_MAX_REACHED, + DNS_TRANSACTION_NETWORK_DOWN, + DNS_TRANSACTION_NOT_FOUND)) + return 0; + + if (FLAGS_SET(q->flags, SD_RESOLVED_NO_SYNTHESIZE)) + return 0; + + r = dns_synthesize_answer( + q->manager, + q->question_bypass ? q->question_bypass->question : q->question_utf8, + q->ifindex, + &answer); + if (r == -ENXIO) { + /* If we get ENXIO this tells us to generate NXDOMAIN unconditionally. */ + + dns_query_reset_answer(q); + q->answer_rcode = DNS_RCODE_NXDOMAIN; + q->answer_protocol = dns_synthesize_protocol(q->flags); + q->answer_family = dns_synthesize_family(q->flags); + q->answer_query_flags = SD_RESOLVED_AUTHENTICATED|SD_RESOLVED_CONFIDENTIAL|SD_RESOLVED_SYNTHETIC; + *state = DNS_TRANSACTION_RCODE_FAILURE; + + return 0; + } + if (r <= 0) + return r; + + dns_query_reset_answer(q); + + q->answer = TAKE_PTR(answer); + q->answer_rcode = DNS_RCODE_SUCCESS; + q->answer_protocol = dns_synthesize_protocol(q->flags); + q->answer_family = dns_synthesize_family(q->flags); + q->answer_query_flags = SD_RESOLVED_AUTHENTICATED|SD_RESOLVED_CONFIDENTIAL|SD_RESOLVED_SYNTHETIC; + + *state = DNS_TRANSACTION_SUCCESS; + + return 1; +} + +static int dns_query_try_etc_hosts(DnsQuery *q) { + _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL; + int r; + + assert(q); + + /* Looks in /etc/hosts for matching entries. Note that this is done *before* the normal lookup is + * done. The data from /etc/hosts hence takes precedence over the network. */ + + if (FLAGS_SET(q->flags, SD_RESOLVED_NO_SYNTHESIZE)) + return 0; + + r = manager_etc_hosts_lookup( + q->manager, + q->question_bypass ? q->question_bypass->question : q->question_utf8, + &answer); + if (r <= 0) + return r; + + dns_query_reset_answer(q); + + q->answer = TAKE_PTR(answer); + q->answer_rcode = DNS_RCODE_SUCCESS; + q->answer_protocol = dns_synthesize_protocol(q->flags); + q->answer_family = dns_synthesize_family(q->flags); + q->answer_query_flags = SD_RESOLVED_AUTHENTICATED|SD_RESOLVED_CONFIDENTIAL|SD_RESOLVED_SYNTHETIC; + + return 1; +} + +int dns_query_go(DnsQuery *q) { + DnsScopeMatch found = DNS_SCOPE_NO; + DnsScope *first = NULL; + int r; + + assert(q); + + if (q->state != DNS_TRANSACTION_NULL) + return 0; + + r = dns_query_try_etc_hosts(q); + if (r < 0) + return r; + if (r > 0) { + dns_query_complete(q, DNS_TRANSACTION_SUCCESS); + return 1; + } + + LIST_FOREACH(scopes, s, q->manager->dns_scopes) { + DnsScopeMatch match; + + match = dns_scope_good_domain(s, q); + assert(match >= 0); + if (match > found) { /* Does this match better? If so, remember how well it matched, and the first one + * that matches this well */ + found = match; + first = s; + } + } + + if (found == DNS_SCOPE_NO) { + DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS; + + r = dns_query_synthesize_reply(q, &state); + if (r < 0) + return r; + + dns_query_complete(q, state); + return 1; + } + + r = dns_query_add_candidate(q, first); + if (r < 0) + goto fail; + + LIST_FOREACH(scopes, s, first->scopes_next) { + DnsScopeMatch match; + + match = dns_scope_good_domain(s, q); + assert(match >= 0); + if (match < found) + continue; + + r = dns_query_add_candidate(q, s); + if (r < 0) + goto fail; + } + + dns_query_reset_answer(q); + + r = event_reset_time_relative( + q->manager->event, + &q->timeout_event_source, + CLOCK_BOOTTIME, + SD_RESOLVED_QUERY_TIMEOUT_USEC, + 0, on_query_timeout, q, + 0, "query-timeout", true); + if (r < 0) + goto fail; + + q->state = DNS_TRANSACTION_PENDING; + q->block_ready++; + + /* Start the transactions */ + LIST_FOREACH(candidates_by_query, c, q->candidates) { + r = dns_query_candidate_go(c); + if (r < 0) { + q->block_ready--; + goto fail; + } + } + + q->block_ready--; + dns_query_ready(q); + + return 1; + +fail: + dns_query_stop(q); + return r; +} + +static void dns_query_accept(DnsQuery *q, DnsQueryCandidate *c) { + DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS; + bool has_authenticated = false, has_non_authenticated = false, has_confidential = false, has_non_confidential = false; + DnssecResult dnssec_result_authenticated = _DNSSEC_RESULT_INVALID, dnssec_result_non_authenticated = _DNSSEC_RESULT_INVALID; + DnsTransaction *t; + int r; + + assert(q); + + if (!c) { + r = dns_query_synthesize_reply(q, &state); + if (r < 0) + goto fail; + + dns_query_complete(q, state); + return; + } + + if (c->error_code != 0) { + /* If the candidate had an error condition of its own, start with that. */ + state = DNS_TRANSACTION_ERRNO; + q->answer = dns_answer_unref(q->answer); + q->answer_rcode = 0; + q->answer_dnssec_result = _DNSSEC_RESULT_INVALID; + q->answer_query_flags = 0; + q->answer_errno = c->error_code; + q->answer_full_packet = dns_packet_unref(q->answer_full_packet); + } + + SET_FOREACH(t, c->transactions) { + + switch (t->state) { + + case DNS_TRANSACTION_SUCCESS: { + /* We found a successful reply, merge it into the answer */ + + if (state == DNS_TRANSACTION_SUCCESS) { + r = dns_answer_extend(&q->answer, t->answer); + if (r < 0) + goto fail; + + q->answer_query_flags |= dns_transaction_source_to_query_flags(t->answer_source); + } else { + /* Override non-successful previous answers */ + DNS_ANSWER_REPLACE(q->answer, dns_answer_ref(t->answer)); + q->answer_query_flags = dns_transaction_source_to_query_flags(t->answer_source); + } + + q->answer_rcode = t->answer_rcode; + q->answer_errno = 0; + + DNS_PACKET_REPLACE(q->answer_full_packet, dns_packet_ref(t->received)); + + if (FLAGS_SET(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED)) { + has_authenticated = true; + dnssec_result_authenticated = t->answer_dnssec_result; + } else { + has_non_authenticated = true; + dnssec_result_non_authenticated = t->answer_dnssec_result; + } + + if (FLAGS_SET(t->answer_query_flags, SD_RESOLVED_CONFIDENTIAL)) + has_confidential = true; + else + has_non_confidential = true; + + state = DNS_TRANSACTION_SUCCESS; + break; + } + + case DNS_TRANSACTION_NULL: + case DNS_TRANSACTION_PENDING: + case DNS_TRANSACTION_VALIDATING: + case DNS_TRANSACTION_ABORTED: + /* Ignore transactions that didn't complete */ + continue; + + default: + /* Any kind of failure? Store the data away, if there's nothing stored yet. */ + if (state == DNS_TRANSACTION_SUCCESS) + continue; + + /* If there's already an authenticated negative reply stored, then prefer that over any unauthenticated one */ + if (FLAGS_SET(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED) && + !FLAGS_SET(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED)) + continue; + + DNS_ANSWER_REPLACE(q->answer, dns_answer_ref(t->answer)); + q->answer_rcode = t->answer_rcode; + q->answer_dnssec_result = t->answer_dnssec_result; + q->answer_query_flags = t->answer_query_flags | dns_transaction_source_to_query_flags(t->answer_source); + q->answer_errno = t->answer_errno; + DNS_PACKET_REPLACE(q->answer_full_packet, dns_packet_ref(t->received)); + + state = t->state; + break; + } + } + + if (state == DNS_TRANSACTION_SUCCESS) { + SET_FLAG(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED, has_authenticated && !has_non_authenticated); + SET_FLAG(q->answer_query_flags, SD_RESOLVED_CONFIDENTIAL, has_confidential && !has_non_confidential); + q->answer_dnssec_result = FLAGS_SET(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED) ? dnssec_result_authenticated : dnssec_result_non_authenticated; + } + + q->answer_protocol = c->scope->protocol; + q->answer_family = c->scope->family; + + dns_search_domain_unref(q->answer_search_domain); + q->answer_search_domain = dns_search_domain_ref(c->search_domain); + + r = dns_query_synthesize_reply(q, &state); + if (r < 0) + goto fail; + + dns_query_complete(q, state); + return; + +fail: + q->answer_errno = -r; + dns_query_complete(q, DNS_TRANSACTION_ERRNO); +} + +void dns_query_ready(DnsQuery *q) { + DnsQueryCandidate *bad = NULL; + bool pending = false; + + assert(q); + assert(DNS_TRANSACTION_IS_LIVE(q->state)); + + /* Note that this call might invalidate the query. Callers + * should hence not attempt to access the query or transaction + * after calling this function, unless the block_ready + * counter was explicitly bumped before doing so. */ + + if (q->block_ready > 0) + return; + + LIST_FOREACH(candidates_by_query, c, q->candidates) { + DnsTransactionState state; + + state = dns_query_candidate_state(c); + switch (state) { + + case DNS_TRANSACTION_SUCCESS: + /* One of the candidates is successful, + * let's use it, and copy its data out */ + dns_query_accept(q, c); + return; + + case DNS_TRANSACTION_NULL: + case DNS_TRANSACTION_PENDING: + case DNS_TRANSACTION_VALIDATING: + /* One of the candidates is still going on, + * let's maybe wait for it */ + pending = true; + break; + + default: + /* Any kind of failure */ + bad = c; + break; + } + } + + if (pending) + return; + + dns_query_accept(q, bad); +} + +static int dns_query_collect_question(DnsQuery *q, DnsQuestion *question) { + _cleanup_(dns_question_unrefp) DnsQuestion *merged = NULL; + int r; + + assert(q); + + if (dns_question_size(question) == 0) + return 0; + + /* When redirecting, save the first element in the chain, for informational purposes when monitoring */ + r = dns_question_merge(q->collected_questions, question, &merged); + if (r < 0) + return r; + + dns_question_unref(q->collected_questions); + q->collected_questions = TAKE_PTR(merged); + + return 0; +} + +static int dns_query_cname_redirect(DnsQuery *q, const DnsResourceRecord *cname) { + _cleanup_(dns_question_unrefp) DnsQuestion *nq_idna = NULL, *nq_utf8 = NULL; + int r, k; + + assert(q); + + if (q->n_cname_redirects >= CNAME_REDIRECTS_MAX) + return -ELOOP; + q->n_cname_redirects++; + + r = dns_question_cname_redirect(q->question_idna, cname, &nq_idna); + if (r < 0) + return r; + if (r > 0) + log_debug("Following CNAME/DNAME %s %s %s.", + dns_question_first_name(q->question_idna), + special_glyph(SPECIAL_GLYPH_ARROW_RIGHT), + dns_question_first_name(nq_idna)); + + k = dns_question_is_equal(q->question_idna, q->question_utf8); + if (k < 0) + return k; + if (k > 0) { + /* Same question? Shortcut new question generation */ + nq_utf8 = dns_question_ref(nq_idna); + k = r; + } else { + k = dns_question_cname_redirect(q->question_utf8, cname, &nq_utf8); + if (k < 0) + return k; + if (k > 0) + log_debug("Following UTF8 CNAME/DNAME %s %s %s.", + dns_question_first_name(q->question_utf8), + special_glyph(SPECIAL_GLYPH_ARROW_RIGHT), + dns_question_first_name(nq_utf8)); + } + + if (r == 0 && k == 0) /* No actual cname happened? */ + return -ELOOP; + + if (q->answer_protocol == DNS_PROTOCOL_DNS) + /* Don't permit CNAME redirects from unicast DNS to LLMNR or MulticastDNS, so that global resources + * cannot invade the local namespace. The opposite way we permit: local names may redirect to global + * ones. */ + q->flags &= ~(SD_RESOLVED_LLMNR|SD_RESOLVED_MDNS); /* mask away the local protocols */ + + /* Turn off searching for the new name */ + q->flags |= SD_RESOLVED_NO_SEARCH; + + r = dns_query_collect_question(q, q->question_idna); + if (r < 0) + return r; + r = dns_query_collect_question(q, q->question_utf8); + if (r < 0) + return r; + + /* Install the redirected question */ + dns_question_unref(q->question_idna); + q->question_idna = TAKE_PTR(nq_idna); + + dns_question_unref(q->question_utf8); + q->question_utf8 = TAKE_PTR(nq_utf8); + + dns_query_unlink_candidates(q); + + /* Note that we do *not* reset the answer here, because the answer we previously got might already + * include everything we need, let's check that first */ + + q->state = DNS_TRANSACTION_NULL; + + return 0; +} + +int dns_query_process_cname_one(DnsQuery *q) { + _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *cname = NULL; + DnsQuestion *question; + DnsResourceRecord *rr; + bool full_match = true; + DnsResourceKey *k; + int r; + + assert(q); + + /* Processes a CNAME redirect if there's one. Returns one of three values: + * + * CNAME_QUERY_MATCH → direct RR match, caller should just use the RRs in this answer (and not + * bother with any CNAME/DNAME stuff) + * + * CNAME_QUERY_NOMATCH → no match at all, neither direct nor CNAME/DNAME, caller might decide to + * restart query or take things as NODATA reply. + * + * CNAME_QUERY_CNAME → no direct RR match, but a CNAME/DNAME match that we now followed for one step. + * + * The function might also return a failure, in particular -ELOOP if we encountered too many + * CNAMEs/DNAMEs in a chain or if following CNAMEs/DNAMEs was turned off. + * + * Note that this function doesn't actually restart the query. The caller can decide to do that in + * case of CNAME_QUERY_CNAME, though. */ + + if (!IN_SET(q->state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_NULL)) + return DNS_QUERY_NOMATCH; + + question = dns_query_question_for_protocol(q, q->answer_protocol); + + /* Small reminder: our question will consist of one or more RR keys that match in name, but not in + * record type. Specifically, when we do an address lookup the question will typically consist of one + * A and one AAAA key lookup for the same domain name. When we get a response from a server we need + * to check if the answer answers all our questions to use it. Note that a response of CNAME/DNAME + * can answer both an A and the AAAA question for us, but an A/AAAA response only the relevant + * type. + * + * Hence we first check of the answers we collected are sufficient to answer all our questions + * directly. If one question wasn't answered we go on, waiting for more replies. However, if there's + * a CNAME/DNAME response we use it, and redirect to it, regardless if it was a response to the A or + * the AAAA query. */ + + DNS_QUESTION_FOREACH(k, question) { + bool match = false; + + DNS_ANSWER_FOREACH(rr, q->answer) { + r = dns_resource_key_match_rr(k, rr, DNS_SEARCH_DOMAIN_NAME(q->answer_search_domain)); + if (r < 0) + return r; + if (r > 0) { + match = true; /* Yay, we found an RR that matches the key we are looking for */ + break; + } + } + + if (!match) { + /* Hmm. :-( there's no response for this key. This doesn't match. */ + full_match = false; + break; + } + } + + if (full_match) + return DNS_QUERY_MATCH; /* The answer can answer our question in full, no need to follow CNAMEs/DNAMEs */ + + /* Let's see if there is a CNAME/DNAME to match. This case is simpler: we accept the CNAME/DNAME that + * matches any of our questions. */ + DNS_ANSWER_FOREACH(rr, q->answer) { + r = dns_question_matches_cname_or_dname(question, rr, DNS_SEARCH_DOMAIN_NAME(q->answer_search_domain)); + if (r < 0) + return r; + if (r > 0 && !cname) + cname = dns_resource_record_ref(rr); + } + + if (!cname) + return DNS_QUERY_NOMATCH; /* No match and no CNAME/DNAME to follow */ + + if (q->flags & SD_RESOLVED_NO_CNAME) + return -ELOOP; + + if (!FLAGS_SET(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED)) + q->previous_redirect_unauthenticated = true; + if (!FLAGS_SET(q->answer_query_flags, SD_RESOLVED_CONFIDENTIAL)) + q->previous_redirect_non_confidential = true; + if (!FLAGS_SET(q->answer_query_flags, SD_RESOLVED_SYNTHETIC)) + q->previous_redirect_non_synthetic = true; + + /* OK, let's actually follow the CNAME */ + r = dns_query_cname_redirect(q, cname); + if (r < 0) + return r; + + return DNS_QUERY_CNAME; /* Tell caller that we did a single CNAME/DNAME redirection step */ +} + +int dns_query_process_cname_many(DnsQuery *q) { + int r; + + assert(q); + + /* Follows CNAMEs through the current packet: as long as the current packet can fulfill our + * redirected CNAME queries we keep going, and restart the query once the current packet isn't good + * enough anymore. It's a wrapper around dns_query_process_cname_one() and returns the same values, + * but with extended semantics. Specifically: + * + * DNS_QUERY_MATCH → as above + * + * DNS_QUERY_CNAME → we ran into a CNAME/DNAME redirect that we could not answer from the current + * message, and thus restarted the query to resolve it. + * + * DNS_QUERY_NOMATCH → we reached the end of CNAME/DNAME chain, and there are no direct matches nor a + * CNAME/DNAME match. i.e. this is a NODATA case. + * + * Note that this function will restart the query for the caller if needed, and that's the case + * DNS_QUERY_CNAME is returned. + */ + + r = dns_query_process_cname_one(q); + if (r != DNS_QUERY_CNAME) + return r; /* The first redirect is special: if it doesn't answer the question that's no + * reason to restart the query, we just accept this as a NODATA answer. */ + + for (;;) { + r = dns_query_process_cname_one(q); + if (r < 0 || r == DNS_QUERY_MATCH) + return r; + if (r == DNS_QUERY_NOMATCH) { + /* OK, so we followed one or more CNAME/DNAME RR but the existing packet can't answer + * this. Let's restart the query hence, with the new question. Why the different + * handling than the first chain element? Because if the server answers a direct + * question with an empty answer then this is a NODATA response. But if it responds + * with a CNAME chain that ultimately is incomplete (i.e. a non-empty but truncated + * CNAME chain) then we better follow up ourselves and ask for the rest of the + * chain. This is particular relevant since our cache will store CNAME/DNAME + * redirects that we learnt about for lookups of certain DNS types, but later on we + * can reuse this data even for other DNS types, but in that case need to follow up + * with the final lookup of the chain ourselves with the RR type we ourselves are + * interested in. */ + r = dns_query_go(q); + if (r < 0) + return r; + + return DNS_QUERY_CNAME; + } + + /* So we found a CNAME that the existing packet already answers, again via a CNAME, let's + * continue going then. */ + assert(r == DNS_QUERY_CNAME); + } +} + +DnsQuestion* dns_query_question_for_protocol(DnsQuery *q, DnsProtocol protocol) { + assert(q); + + if (q->question_bypass) + return q->question_bypass->question; + + switch (protocol) { + + case DNS_PROTOCOL_DNS: + return q->question_idna; + + case DNS_PROTOCOL_MDNS: + case DNS_PROTOCOL_LLMNR: + return q->question_utf8; + + default: + return NULL; + } +} + +const char *dns_query_string(DnsQuery *q) { + const char *name; + int r; + + /* Returns a somewhat useful human-readable lookup key string for this query */ + + if (q->question_bypass) + return dns_question_first_name(q->question_bypass->question); + + if (q->request_address_string) + return q->request_address_string; + + if (q->request_address_valid) { + r = in_addr_to_string(q->request_family, &q->request_address, &q->request_address_string); + if (r >= 0) + return q->request_address_string; + } + + name = dns_question_first_name(q->question_utf8); + if (name) + return name; + + return dns_question_first_name(q->question_idna); +} + +bool dns_query_fully_authenticated(DnsQuery *q) { + assert(q); + + return FLAGS_SET(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED) && !q->previous_redirect_unauthenticated; +} + +bool dns_query_fully_confidential(DnsQuery *q) { + assert(q); + + return FLAGS_SET(q->answer_query_flags, SD_RESOLVED_CONFIDENTIAL) && !q->previous_redirect_non_confidential; +} + +bool dns_query_fully_authoritative(DnsQuery *q) { + assert(q); + + /* We are authoritative for everything synthetic (except if a previous CNAME/DNAME) wasn't + * synthetic. (Note: SD_RESOLVED_SYNTHETIC is reset on each CNAME/DNAME, hence the explicit check for + * previous synthetic DNAME/CNAME redirections.) */ + if ((q->answer_query_flags & SD_RESOLVED_SYNTHETIC) && !q->previous_redirect_non_synthetic) + return true; + + /* We are also authoritative for everything coming only from the trust anchor and the local + * zones. (Note: the SD_RESOLVED_FROM_xyz flags we merge on each redirect, hence no need to + * explicitly check previous redirects here.) */ + return (q->answer_query_flags & SD_RESOLVED_FROM_MASK & ~(SD_RESOLVED_FROM_TRUST_ANCHOR | SD_RESOLVED_FROM_ZONE)) == 0; +} |