src/resolve/resolved-dns-packet.h

   1 #pragma once
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2014 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20  ***/
  21
  22 #include <netinet/ip.h>
  23 #include <netinet/udp.h>
  24
  25 #include "hashmap.h"
  26 #include "in-addr-util.h"
  27 #include "macro.h"
  28 #include "sparse-endian.h"
  29
  30 typedef struct DnsPacketHeader DnsPacketHeader;
  31 typedef struct DnsPacket DnsPacket;
  32
  33 #include "resolved-def.h"
  34 #include "resolved-dns-answer.h"
  35 #include "resolved-dns-question.h"
  36 #include "resolved-dns-rr.h"
  37
  38 typedef enum DnsProtocol {
  39         DNS_PROTOCOL_DNS,
  40         DNS_PROTOCOL_MDNS,
  41         DNS_PROTOCOL_LLMNR,
  42         _DNS_PROTOCOL_MAX,
  43         _DNS_PROTOCOL_INVALID = -1
  44 } DnsProtocol;
  45
  46 struct DnsPacketHeader {
  47         uint16_t id;
  48         be16_t flags;
  49         be16_t qdcount;
  50         be16_t ancount;
  51         be16_t nscount;
  52         be16_t arcount;
  53 };
  54
  55 #define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader)
  56 #define UDP_PACKET_HEADER_SIZE (sizeof(struct iphdr) + sizeof(struct udphdr))
  57
  58 /* The various DNS protocols deviate in how large a packet can grow,
  59    but the TCP transport has a 16bit size field, hence that appears to
  60    be the absolute maximum. */
  61 #define DNS_PACKET_SIZE_MAX 0xFFFF
  62
  63 /* RFC 1035 say 512 is the maximum, for classic unicast DNS */
  64 #define DNS_PACKET_UNICAST_SIZE_MAX 512
  65
  66 /* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
  67 #define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096
  68
  69 #define DNS_PACKET_SIZE_START 512
  70
  71 struct DnsPacket {
  72         int n_ref;
  73         DnsProtocol protocol;
  74         size_t size, allocated, rindex;
  75         void *_data; /* don't access directly, use DNS_PACKET_DATA()! */
  76         Hashmap *names; /* For name compression */
  77         size_t opt_start, opt_size;
  78
  79         /* Parsed data */
  80         DnsQuestion *question;
  81         DnsAnswer *answer;
  82         DnsResourceRecord *opt;
  83
  84         /* Packet reception metadata */
  85         int ifindex;
  86         int family, ipproto;
  87         union in_addr_union sender, destination;
  88         uint16_t sender_port, destination_port;
  89         uint32_t ttl;
  90
  91         /* For support of truncated packets */
  92         DnsPacket *more;
  93
  94         bool on_stack:1;
  95         bool extracted:1;
  96         bool refuse_compression:1;
  97         bool canonical_form:1;
  98 };
  99
 100 static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
 101         if (_unlikely_(!p))
 102                 return NULL;
 103
 104         if (p->_data)
 105                 return p->_data;
 106
 107         return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
 108 }
 109
 110 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
 111 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
 112 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
 113 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
 114 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
 115 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
 116 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
 117 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
 118 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
 119 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
 120
 121 #define DNS_PACKET_FLAG_TC (UINT16_C(1) << 9)
 122
 123 static inline uint16_t DNS_PACKET_RCODE(DnsPacket *p) {
 124         uint16_t rcode;
 125
 126         if (p->opt)
 127                 rcode = (uint16_t) (p->opt->ttl >> 24);
 128         else
 129                 rcode = 0;
 130
 131         return rcode | (be16toh(DNS_PACKET_HEADER(p)->flags) & 0xF);
 132 }
 133
 134 static inline uint16_t DNS_PACKET_PAYLOAD_SIZE_MAX(DnsPacket *p) {
 135
 136         /* Returns the advertised maximum datagram size for replies, or the DNS default if there's nothing defined. */
 137
 138         if (p->opt)
 139                 return MAX(DNS_PACKET_UNICAST_SIZE_MAX, p->opt->key->class);
 140
 141         return DNS_PACKET_UNICAST_SIZE_MAX;
 142 }
 143
 144 static inline bool DNS_PACKET_DO(DnsPacket *p) {
 145         if (!p->opt)
 146                 return false;
 147
 148         return !!(p->opt->ttl & (1U << 15));
 149 }
 150
 151 static inline bool DNS_PACKET_VERSION_SUPPORTED(DnsPacket *p) {
 152         /* Returns true if this packet is in a version we support. Which means either non-EDNS or EDNS(0), but not EDNS
 153          * of any newer versions */
 154
 155         if (!p->opt)
 156                 return true;
 157
 158         return DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(p->opt);
 159 }
 160
 161 /* LLMNR defines some bits differently */
 162 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 163 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 164
 165 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 166 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 167 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 168 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 169
 170 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 171         (((uint16_t) !!(qr) << 15) |                                    \
 172          ((uint16_t) ((opcode) & 15) << 11) |                           \
 173          ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
 174          ((uint16_t) !!(tc) << 9) |                                     \
 175          ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
 176          ((uint16_t) !!(ra) << 7) |                                     \
 177          ((uint16_t) !!(ad) << 5) |                                     \
 178          ((uint16_t) !!(cd) << 4) |                                     \
 179          ((uint16_t) ((rcode) & 15)))
 180
 181 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 182         return
 183                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 184                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 185                 (unsigned) DNS_PACKET_ARCOUNT(p);
 186 }
 187
 188 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 189 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled);
 190
 191 void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated);
 192
 193 DnsPacket *dns_packet_ref(DnsPacket *p);
 194 DnsPacket *dns_packet_unref(DnsPacket *p);
 195
 196 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 197
 198 int dns_packet_validate(DnsPacket *p);
 199 int dns_packet_validate_reply(DnsPacket *p);
 200 int dns_packet_validate_query(DnsPacket *p);
 201
 202 int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key);
 203
 204 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 205 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 206 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 207 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 208 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 209 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
 210 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, bool canonical_candidate, size_t *start);
 211 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, bool canonical_candidate, size_t *start);
 212 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
 213 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start);
 214 int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, int rcode, size_t *start);
 215 int dns_packet_append_question(DnsPacket *p, DnsQuestion *q);
 216 int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a);
 217
 218 void dns_packet_truncate(DnsPacket *p, size_t sz);
 219 int dns_packet_truncate_opt(DnsPacket *p);
 220
 221 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
 222 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
 223 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
 224 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
 225 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
 226 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
 227 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
 228 int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
 229 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, bool *ret_cache_flush, size_t *start);
 230 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, bool *ret_cache_flush, size_t *start);
 231
 232 void dns_packet_rewind(DnsPacket *p, size_t idx);
 233
 234 int dns_packet_skip_question(DnsPacket *p);
 235 int dns_packet_extract(DnsPacket *p);
 236
 237 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
 238         /* Never cache data originating from localhost, under the
 239          * assumption, that it's coming from a locally DNS forwarder
 240          * or server, that is caching on its own. */
 241
 242         return in_addr_is_localhost(p->family, &p->sender) == 0;
 243 }
 244
 245 /* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */
 246 enum {
 247         DNS_RCODE_SUCCESS = 0,
 248         DNS_RCODE_FORMERR = 1,
 249         DNS_RCODE_SERVFAIL = 2,
 250         DNS_RCODE_NXDOMAIN = 3,
 251         DNS_RCODE_NOTIMP = 4,
 252         DNS_RCODE_REFUSED = 5,
 253         DNS_RCODE_YXDOMAIN = 6,
 254         DNS_RCODE_YXRRSET = 7,
 255         DNS_RCODE_NXRRSET = 8,
 256         DNS_RCODE_NOTAUTH = 9,
 257         DNS_RCODE_NOTZONE = 10,
 258         DNS_RCODE_BADVERS = 16,
 259         DNS_RCODE_BADSIG = 16, /* duplicate value! */
 260         DNS_RCODE_BADKEY = 17,
 261         DNS_RCODE_BADTIME = 18,
 262         DNS_RCODE_BADMODE = 19,
 263         DNS_RCODE_BADNAME = 20,
 264         DNS_RCODE_BADALG = 21,
 265         DNS_RCODE_BADTRUNC = 22,
 266         _DNS_RCODE_MAX_DEFINED,
 267         _DNS_RCODE_MAX = 4095 /* 4 bit rcode in the header plus 8 bit rcode in OPT, makes 12 bit */
 268 };
 269
 270 const char* dns_rcode_to_string(int i) _const_;
 271 int dns_rcode_from_string(const char *s) _pure_;
 272
 273 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 274 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 275
 276 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 277 #define LLMNR_MULTICAST_IPV6_ADDRESS ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x03 } })
 278
 279 #define MDNS_MULTICAST_IPV4_ADDRESS  ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
 280 #define MDNS_MULTICAST_IPV6_ADDRESS  ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfb } })
 281
 282 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
 283         uint64_t f;
 284
 285         /* Converts a protocol + family into a flags field as used in queries and responses */
 286
 287         f = authenticated ? SD_RESOLVED_AUTHENTICATED : 0;
 288
 289         switch (protocol) {
 290         case DNS_PROTOCOL_DNS:
 291                 return f|SD_RESOLVED_DNS;
 292
 293         case DNS_PROTOCOL_LLMNR:
 294                 return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);
 295
 296         case DNS_PROTOCOL_MDNS:
 297                 return f|(family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4);
 298
 299         default:
 300                 return f;
 301         }
 302 }