diff options
| -rw-r--r-- | src/resolve/resolved-dns-dnssec.c | 2 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-dnssec.h | 11 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-server.c | 20 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-server.h | 12 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-transaction.c | 75 |
5 files changed, 106 insertions, 14 deletions
diff --git a/src/resolve/resolved-dns-dnssec.c b/src/resolve/resolved-dns-dnssec.c index 14fa58c544..a856f0717e 100644 --- a/src/resolve/resolved-dns-dnssec.c +++ b/src/resolve/resolved-dns-dnssec.c @@ -1197,6 +1197,7 @@ int dnssec_test_nsec(DnsAnswer *answer, DnsResourceKey *key, DnssecNsecResult *r static const char* const dnssec_mode_table[_DNSSEC_MODE_MAX] = { [DNSSEC_NO] = "no", + [DNSSEC_DOWNGRADE_OK] = "downgrade-ok", [DNSSEC_YES] = "yes", }; DEFINE_STRING_TABLE_LOOKUP(dnssec_mode, DnssecMode); @@ -1211,5 +1212,6 @@ static const char* const dnssec_result_table[_DNSSEC_RESULT_MAX] = { [DNSSEC_UNSIGNED] = "unsigned", [DNSSEC_FAILED_AUXILIARY] = "failed-auxiliary", [DNSSEC_NSEC_MISMATCH] = "nsec-mismatch", + [DNSSEC_INCOMPATIBLE_SERVER] = "incompatible-server", }; DEFINE_STRING_TABLE_LOOKUP(dnssec_result, DnssecResult); diff --git a/src/resolve/resolved-dns-dnssec.h b/src/resolve/resolved-dns-dnssec.h index 9ad20c8c69..d7aecbce13 100644 --- a/src/resolve/resolved-dns-dnssec.h +++ b/src/resolve/resolved-dns-dnssec.h @@ -32,7 +32,14 @@ enum DnssecMode { /* No DNSSEC validation is done */ DNSSEC_NO, - /* Validate locally, if the server knows DO, but if not, don't. Don't trust the AD bit */ + /* Validate locally, if the server knows DO, but if not, + * don't. Don't trust the AD bit. If the server doesn't do + * DNSSEC properly, downgrade to non-DNSSEC operation. Of + * course, we then are vulnerable to a downgrade attack, but + * that's life and what is configured. */ + DNSSEC_DOWNGRADE_OK, + + /* Insist on DNSSEC server support, and rather fail than downgrading. */ DNSSEC_YES, _DNSSEC_MODE_MAX, @@ -54,6 +61,8 @@ enum DnssecResult { DNSSEC_UNSIGNED, DNSSEC_FAILED_AUXILIARY, DNSSEC_NSEC_MISMATCH, + DNSSEC_INCOMPATIBLE_SERVER, + _DNSSEC_RESULT_MAX, _DNSSEC_RESULT_INVALID = -1 }; diff --git a/src/resolve/resolved-dns-server.c b/src/resolve/resolved-dns-server.c index d565f99c09..b0db5bbb16 100644 --- a/src/resolve/resolved-dns-server.c +++ b/src/resolve/resolved-dns-server.c @@ -228,9 +228,11 @@ void dns_server_packet_received(DnsServer *s, DnsServerFeatureLevel features, us assert(s); if (features == DNS_SERVER_FEATURE_LEVEL_LARGE) { - /* even if we successfully receive a reply to a request announcing - support for large packets, that does not mean we can necessarily - receive large packets. */ + /* Even if we successfully receive a reply to a + request announcing support for large packets, that + does not mean we can necessarily receive large + packets. */ + if (s->verified_features < DNS_SERVER_FEATURE_LEVEL_LARGE - 1) { s->verified_features = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); @@ -278,6 +280,17 @@ void dns_server_packet_failed(DnsServer *s, DnsServerFeatureLevel features) { s->n_failed_attempts = (unsigned) -1; } +void dns_server_packet_rrsig_missing(DnsServer *s) { + _cleanup_free_ char *ip = NULL; + assert(s); + assert(s->manager); + + in_addr_to_string(s->family, &s->address, &ip); + log_warning("DNS server %s does not augment replies with RRSIG records, DNSSEC not available.", strna(ip)); + + s->rrsig_missing = true; +} + static bool dns_server_grace_period_expired(DnsServer *s) { usec_t ts; @@ -307,6 +320,7 @@ DnsServerFeatureLevel dns_server_possible_features(DnsServer *s) { s->possible_features = DNS_SERVER_FEATURE_LEVEL_BEST; s->n_failed_attempts = 0; s->verified_usec = 0; + s->rrsig_missing = false; in_addr_to_string(s->family, &s->address, &ip); log_info("Grace period over, resuming full feature set for DNS server %s", strna(ip)); diff --git a/src/resolve/resolved-dns-server.h b/src/resolve/resolved-dns-server.h index b07fc3af3d..3011904bfd 100644 --- a/src/resolve/resolved-dns-server.h +++ b/src/resolve/resolved-dns-server.h @@ -61,8 +61,6 @@ struct DnsServer { int family; union in_addr_union address; - bool marked:1; - usec_t resend_timeout; usec_t max_rtt; @@ -73,6 +71,15 @@ struct DnsServer { usec_t verified_usec; usec_t features_grace_period_usec; + /* Indicates whether responses are augmented with RRSIG by + * server or not. Note that this is orthogonal to the feature + * level stuff, as it's only information describing responses, + * and has no effect on how the questions are asked. */ + bool rrsig_missing:1; + + /* Used when GC'ing old DNS servers when configuration changes. */ + bool marked:1; + /* If linked is set, then this server appears in the servers linked list */ bool linked:1; LIST_FIELDS(DnsServer, servers); @@ -95,6 +102,7 @@ void dns_server_move_back_and_unmark(DnsServer *s); void dns_server_packet_received(DnsServer *s, DnsServerFeatureLevel features, usec_t rtt, size_t size); void dns_server_packet_lost(DnsServer *s, DnsServerFeatureLevel features, usec_t usec); void dns_server_packet_failed(DnsServer *s, DnsServerFeatureLevel features); +void dns_server_packet_rrsig_missing(DnsServer *s); DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr); diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c index 2875330812..5933e0e462 100644 --- a/src/resolve/resolved-dns-transaction.c +++ b/src/resolve/resolved-dns-transaction.c @@ -478,10 +478,19 @@ static void dns_transaction_process_dnssec(DnsTransaction *t) { return; } + 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, refuse operation. */ + 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_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; } @@ -1001,7 +1010,7 @@ static int dns_transaction_make_packet(DnsTransaction *t) { if (t->sent) return 0; - r = dns_packet_new_query(&p, t->scope->protocol, 0, t->scope->dnssec_mode == DNSSEC_YES); + r = dns_packet_new_query(&p, t->scope->protocol, 0, t->scope->dnssec_mode != DNSSEC_NO); if (r < 0) return r; @@ -1336,9 +1345,14 @@ int dns_transaction_request_dnssec_keys(DnsTransaction *t) { * - For other queries with no matching response RRs, and no NSEC/NSEC3, the SOA RR */ - if (t->scope->dnssec_mode != DNSSEC_YES) + if (t->scope->dnssec_mode == DNSSEC_NO) return 0; + if (t->current_features < DNS_SERVER_FEATURE_LEVEL_DO) + return 0; /* Server doesn't do DNSSEC, there's no point in requesting any RRs then. */ + if (t->server && t->server->rrsig_missing) + return 0; /* Server handles DNSSEC requests, but isn't augmenting responses with RRSIGs. No point in trying DNSSEC then. */ + DNS_ANSWER_FOREACH(rr, t->answer) { if (dns_type_is_pseudo(rr->key->type)) @@ -1682,7 +1696,7 @@ static int dns_transaction_requires_rrsig(DnsTransaction *t, DnsResourceRecord * /* 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_YES) + if (t->scope->dnssec_mode == DNSSEC_NO) return false; if (dns_type_is_pseudo(rr->key->type)) @@ -1819,7 +1833,7 @@ static int dns_transaction_requires_nsec(DnsTransaction *t) { /* Checks if we need to insist on NSEC/NSEC3 RRs for proving * this negative reply */ - if (t->scope->dnssec_mode != DNSSEC_YES) + if (t->scope->dnssec_mode == DNSSEC_NO) return false; if (dns_type_is_pseudo(t->key->type)) @@ -1932,6 +1946,17 @@ static int dns_transaction_dnskey_authenticated(DnsTransaction *t, DnsResourceRe 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)); +} + int dns_transaction_validate_dnssec(DnsTransaction *t) { _cleanup_(dns_answer_unrefp) DnsAnswer *validated = NULL; bool dnskeys_finalized = false; @@ -1945,7 +1970,7 @@ int dns_transaction_validate_dnssec(DnsTransaction *t) { * t->validated_keys, let's see which RRs we can now * authenticate with that. */ - if (t->scope->dnssec_mode != DNSSEC_YES) + if (t->scope->dnssec_mode == DNSSEC_NO) return 0; /* Already validated */ @@ -1963,6 +1988,13 @@ int dns_transaction_validate_dnssec(DnsTransaction *t) { if (t->answer_source != DNS_TRANSACTION_NETWORK) return 0; + if (t->current_features < DNS_SERVER_FEATURE_LEVEL_DO || + (t->server && t->server->rrsig_missing)) { + /* The server does not support DNSSEC, or doesn't augment responses with RRSIGs. */ + t->answer_dnssec_result = DNSSEC_INCOMPATIBLE_SERVER; + return 0; + } + log_debug("Validating response from transaction %" PRIu16 " (%s).", t->id, dns_transaction_key_string(t)); /* First see if there are DNSKEYs we already known a validated DS for. */ @@ -2037,6 +2069,33 @@ int dns_transaction_validate_dnssec(DnsTransaction *t) { changed = true; break; } + + 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); + + if (t->scope->dnssec_mode == DNSSEC_DOWNGRADE_OK) { + + /* Downgrading is OK? If so, just consider the information unsigned */ + + r = dns_answer_move_by_key(&validated, &t->answer, rr->key, 0); + if (r < 0) + return r; + + t->scope->manager->n_dnssec_insecure++; + changed = true; + break; + } + + /* Otherwise, fail */ + t->answer_dnssec_result = DNSSEC_INCOMPATIBLE_SERVER; + return 0; + } } if (IN_SET(result, |