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 0xFFFFu
  62
  63 /* RFC 1035 say 512 is the maximum, for classic unicast DNS */
  64 #define DNS_PACKET_UNICAST_SIZE_MAX 512u
  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 4096u
  68
  69 struct DnsPacket {
  70         int n_ref;
  71         DnsProtocol protocol;
  72         size_t size, allocated, rindex;
  73         void *_data; /* don't access directly, use DNS_PACKET_DATA()! */
  74         Hashmap *names; /* For name compression */
  75         size_t opt_start, opt_size;
  76
  77         /* Parsed data */
  78         DnsQuestion *question;
  79         DnsAnswer *answer;
  80         DnsResourceRecord *opt;
  81
  82         /* Packet reception metadata */
  83         int ifindex;
  84         int family, ipproto;
  85         union in_addr_union sender, destination;
  86         uint16_t sender_port, destination_port;
  87         uint32_t ttl;
  88
  89         /* For support of truncated packets */
  90         DnsPacket *more;
  91
  92         bool on_stack:1;
  93         bool extracted:1;
  94         bool refuse_compression:1;
  95         bool canonical_form:1;
  96 };
  97
  98 static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
  99         if (_unlikely_(!p))
 100                 return NULL;
 101
 102         if (p->_data)
 103                 return p->_data;
 104
 105         return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
 106 }
 107
 108 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
 109 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
 110 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
 111 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
 112 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
 113 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
 114 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
 115 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
 116 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
 117 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
 118
 119 #define DNS_PACKET_FLAG_TC (UINT16_C(1) << 9)
 120
 121 static inline uint16_t DNS_PACKET_RCODE(DnsPacket *p) {
 122         uint16_t rcode;
 123
 124         if (p->opt)
 125                 rcode = (uint16_t) (p->opt->ttl >> 24);
 126         else
 127                 rcode = 0;
 128
 129         return rcode | (be16toh(DNS_PACKET_HEADER(p)->flags) & 0xF);
 130 }
 131
 132 static inline uint16_t DNS_PACKET_PAYLOAD_SIZE_MAX(DnsPacket *p) {
 133
 134         /* Returns the advertised maximum datagram size for replies, or the DNS default if there's nothing defined. */
 135
 136         if (p->opt)
 137                 return MAX(DNS_PACKET_UNICAST_SIZE_MAX, p->opt->key->class);
 138
 139         return DNS_PACKET_UNICAST_SIZE_MAX;
 140 }
 141
 142 static inline bool DNS_PACKET_DO(DnsPacket *p) {
 143         if (!p->opt)
 144                 return false;
 145
 146         return !!(p->opt->ttl & (1U << 15));
 147 }
 148
 149 static inline bool DNS_PACKET_VERSION_SUPPORTED(DnsPacket *p) {
 150         /* Returns true if this packet is in a version we support. Which means either non-EDNS or EDNS(0), but not EDNS
 151          * of any newer versions */
 152
 153         if (!p->opt)
 154                 return true;
 155
 156         return DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(p->opt);
 157 }
 158
 159 /* LLMNR defines some bits differently */
 160 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 161 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 162
 163 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 164 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 165 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 166 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 167
 168 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 169         (((uint16_t) !!(qr) << 15) |                                    \
 170          ((uint16_t) ((opcode) & 15) << 11) |                           \
 171          ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
 172          ((uint16_t) !!(tc) << 9) |                                     \
 173          ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
 174          ((uint16_t) !!(ra) << 7) |                                     \
 175          ((uint16_t) !!(ad) << 5) |                                     \
 176          ((uint16_t) !!(cd) << 4) |                                     \
 177          ((uint16_t) ((rcode) & 15)))
 178
 179 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 180         return
 181                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 182                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 183                 (unsigned) DNS_PACKET_ARCOUNT(p);
 184 }
 185
 186 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t min_alloc_dsize);
 187 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t min_alloc_dsize, bool dnssec_checking_disabled);
 188
 189 void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated);
 190
 191 DnsPacket *dns_packet_ref(DnsPacket *p);
 192 DnsPacket *dns_packet_unref(DnsPacket *p);
 193
 194 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 195
 196 int dns_packet_validate(DnsPacket *p);
 197 int dns_packet_validate_reply(DnsPacket *p);
 198 int dns_packet_validate_query(DnsPacket *p);
 199
 200 int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key);
 201
 202 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 203 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 204 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 205 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 206 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 207 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
 208 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, bool canonical_candidate, size_t *start);
 209 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, bool canonical_candidate, size_t *start);
 210 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, const DnsAnswerFlags flags, size_t *start);
 211 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, const DnsAnswerFlags flags, size_t *start, size_t *rdata_start);
 212 int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, int rcode, size_t *start);
 213 int dns_packet_append_question(DnsPacket *p, DnsQuestion *q);
 214 int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a);
 215
 216 void dns_packet_truncate(DnsPacket *p, size_t sz);
 217 int dns_packet_truncate_opt(DnsPacket *p);
 218
 219 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
 220 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
 221 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
 222 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
 223 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
 224 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
 225 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
 226 int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
 227 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, bool *ret_cache_flush, size_t *start);
 228 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, bool *ret_cache_flush, size_t *start);
 229
 230 void dns_packet_rewind(DnsPacket *p, size_t idx);
 231
 232 int dns_packet_skip_question(DnsPacket *p);
 233 int dns_packet_extract(DnsPacket *p);
 234
 235 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
 236         /* Never cache data originating from localhost, under the
 237          * assumption, that it's coming from a locally DNS forwarder
 238          * or server, that is caching on its own. */
 239
 240         return in_addr_is_localhost(p->family, &p->sender) == 0;
 241 }
 242
 243 /* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */
 244 enum {
 245         DNS_RCODE_SUCCESS = 0,
 246         DNS_RCODE_FORMERR = 1,
 247         DNS_RCODE_SERVFAIL = 2,
 248         DNS_RCODE_NXDOMAIN = 3,
 249         DNS_RCODE_NOTIMP = 4,
 250         DNS_RCODE_REFUSED = 5,
 251         DNS_RCODE_YXDOMAIN = 6,
 252         DNS_RCODE_YXRRSET = 7,
 253         DNS_RCODE_NXRRSET = 8,
 254         DNS_RCODE_NOTAUTH = 9,
 255         DNS_RCODE_NOTZONE = 10,
 256         DNS_RCODE_BADVERS = 16,
 257         DNS_RCODE_BADSIG = 16, /* duplicate value! */
 258         DNS_RCODE_BADKEY = 17,
 259         DNS_RCODE_BADTIME = 18,
 260         DNS_RCODE_BADMODE = 19,
 261         DNS_RCODE_BADNAME = 20,
 262         DNS_RCODE_BADALG = 21,
 263         DNS_RCODE_BADTRUNC = 22,
 264         DNS_RCODE_BADCOOKIE = 23,
 265         _DNS_RCODE_MAX_DEFINED,
 266         _DNS_RCODE_MAX = 4095 /* 4 bit rcode in the header plus 8 bit rcode in OPT, makes 12 bit */
 267 };
 268
 269 const char* dns_rcode_to_string(int i) _const_;
 270 int dns_rcode_from_string(const char *s) _pure_;
 271
 272 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 273 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 274
 275 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 276 #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 } })
 277
 278 #define MDNS_MULTICAST_IPV4_ADDRESS  ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
 279 #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 } })
 280
 281 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
 282         uint64_t f;
 283
 284         /* Converts a protocol + family into a flags field as used in queries and responses */
 285
 286         f = authenticated ? SD_RESOLVED_AUTHENTICATED : 0;
 287
 288         switch (protocol) {
 289         case DNS_PROTOCOL_DNS:
 290                 return f|SD_RESOLVED_DNS;
 291
 292         case DNS_PROTOCOL_LLMNR:
 293                 return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);
 294
 295         case DNS_PROTOCOL_MDNS:
 296                 return f|(family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4);
 297
 298         default:
 299                 return f;
 300         }
 301 }