diff options
Diffstat (limited to 'src/resolve/resolved-dns-packet.c')
| -rw-r--r-- | src/resolve/resolved-dns-packet.c | 83 |
1 files changed, 64 insertions, 19 deletions
diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c index b7907bb511..ea0be56d98 100644 --- a/src/resolve/resolved-dns-packet.c +++ b/src/resolve/resolved-dns-packet.c @@ -264,6 +264,7 @@ int dns_packet_validate_query(DnsPacket *p) { switch (p->protocol) { case DNS_PROTOCOL_LLMNR: + case DNS_PROTOCOL_DNS: /* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */ if (DNS_PACKET_QDCOUNT(p) != 1) return -EBADMSG; @@ -676,13 +677,15 @@ fail: } /* Append the OPT pseudo-RR described in RFC6891 */ -int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start) { +int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, int rcode, size_t *start) { size_t saved_size; int r; assert(p); /* we must never advertise supported packet size smaller than the legacy max */ assert(max_udp_size >= DNS_PACKET_UNICAST_SIZE_MAX); + assert(rcode >= 0); + assert(rcode <= _DNS_RCODE_MAX); if (p->opt_start != (size_t) -1) return -EBUSY; @@ -701,13 +704,13 @@ int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, si if (r < 0) goto fail; - /* maximum udp packet that can be received */ + /* class: maximum udp packet that can be received */ r = dns_packet_append_uint16(p, max_udp_size, NULL); if (r < 0) goto fail; /* extended RCODE and VERSION */ - r = dns_packet_append_uint16(p, 0, NULL); + r = dns_packet_append_uint16(p, ((uint16_t) rcode & 0x0FF0) << 4, NULL); if (r < 0) goto fail; @@ -717,9 +720,8 @@ int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, si goto fail; /* RDLENGTH */ - - if (edns0_do) { - /* If DO is on, also append RFC6975 Algorithm data */ + if (edns0_do & !DNS_PACKET_QR(p)) { + /* If DO is on and this is not a reply, also append RFC6975 Algorithm data */ static const uint8_t rfc6975[] = { @@ -750,7 +752,6 @@ int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, si r = dns_packet_append_blob(p, rfc6975, sizeof(rfc6975), NULL); } else r = dns_packet_append_uint16(p, 0, NULL); - if (r < 0) goto fail; @@ -791,6 +792,7 @@ int dns_packet_truncate_opt(DnsPacket *p) { } int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start) { + size_t saved_size, rdlength_offset, end, rdlength, rds; int r; @@ -1134,6 +1136,36 @@ fail: return r; } +int dns_packet_append_question(DnsPacket *p, DnsQuestion *q) { + DnsResourceKey *key; + int r; + + assert(p); + + DNS_QUESTION_FOREACH(key, q) { + r = dns_packet_append_key(p, key, NULL); + if (r < 0) + return r; + } + + return 0; +} + +int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a) { + DnsResourceRecord *rr; + int r; + + assert(p); + + DNS_ANSWER_FOREACH(rr, a) { + r = dns_packet_append_rr(p, rr, NULL, NULL); + if (r < 0) + return r; + } + + return 0; +} + int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) { assert(p); @@ -2029,8 +2061,10 @@ static bool opt_is_good(DnsResourceRecord *rr, bool *rfc6975) { assert(rr->key->type == DNS_TYPE_OPT); /* Check that the version is 0 */ - if (((rr->ttl >> 16) & UINT32_C(0xFF)) != 0) - return false; + if (((rr->ttl >> 16) & UINT32_C(0xFF)) != 0) { + *rfc6975 = false; + return true; /* if it's not version 0, it's OK, but we will ignore the OPT field contents */ + } p = rr->opt.data; l = rr->opt.data_size; @@ -2153,16 +2187,27 @@ int dns_packet_extract(DnsPacket *p) { continue; } - if (has_rfc6975) { - /* If the OPT RR contains RFC6975 algorithm data, then this is indication that - * the server just copied the OPT it got from us (which contained that data) - * back into the reply. If so, then it doesn't properly support EDNS, as - * RFC6975 makes it very clear that the algorithm data should only be contained - * in questions, never in replies. Crappy Belkin routers copy the OPT data for - * example, hence let's detect this so that we downgrade early. */ - log_debug("OPT RR contained RFC6975 data, ignoring."); - bad_opt = true; - continue; + if (DNS_PACKET_QR(p)) { + /* Additional checks for responses */ + + if (!DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(rr)) { + /* If this is a reply and we don't know the EDNS version then something + * is weird... */ + log_debug("EDNS version newer that our request, bad server."); + return -EBADMSG; + } + + if (has_rfc6975) { + /* If the OPT RR contains RFC6975 algorithm data, then this is indication that + * the server just copied the OPT it got from us (which contained that data) + * back into the reply. If so, then it doesn't properly support EDNS, as + * RFC6975 makes it very clear that the algorithm data should only be contained + * in questions, never in replies. Crappy Belkin routers copy the OPT data for + * example, hence let's detect this so that we downgrade early. */ + log_debug("OPT RR contained RFC6975 data, ignoring."); + bad_opt = true; + continue; + } } p->opt = dns_resource_record_ref(rr); |