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 /* The default size to use for allocation when we don't know how large
  64  * the packet will turn out to be. */
  65 #define DNS_PACKET_SIZE_START 512u
  66
  67 /* RFC 1035 say 512 is the maximum, for classic unicast DNS */
  68 #define DNS_PACKET_UNICAST_SIZE_MAX 512u
  69
  70 /* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
  71 #define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096u
  72
  73 struct DnsPacket {
  74         int n_ref;
  75         DnsProtocol protocol;
  76         size_t size, allocated, rindex;
  77         void *_data; /* don't access directly, use DNS_PACKET_DATA()! */
  78         Hashmap *names; /* For name compression */
  79         size_t opt_start, opt_size;
  80
  81         /* Parsed data */
  82         DnsQuestion *question;
  83         DnsAnswer *answer;
  84         DnsResourceRecord *opt;
  85
  86         /* Packet reception metadata */
  87         int ifindex;
  88         int family, ipproto;
  89         union in_addr_union sender, destination;
  90         uint16_t sender_port, destination_port;
  91         uint32_t ttl;
  92
  93         /* For support of truncated packets */
  94         DnsPacket *more;
  95
  96         bool on_stack:1;
  97         bool extracted:1;
  98         bool refuse_compression:1;
  99         bool canonical_form:1;
 100 };
 101
 102 static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
 103         if (_unlikely_(!p))
 104                 return NULL;
 105
 106         if (p->_data)
 107                 return p->_data;
 108
 109         return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
 110 }
 111
 112 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
 113 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
 114 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
 115 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
 116 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
 117 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
 118 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
 119 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
 120 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
 121 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
 122
 123 #define DNS_PACKET_FLAG_TC (UINT16_C(1) << 9)
 124
 125 static inline uint16_t DNS_PACKET_RCODE(DnsPacket *p) {
 126         uint16_t rcode;
 127
 128         if (p->opt)
 129                 rcode = (uint16_t) (p->opt->ttl >> 24);
 130         else
 131                 rcode = 0;
 132
 133         return rcode | (be16toh(DNS_PACKET_HEADER(p)->flags) & 0xF);
 134 }
 135
 136 static inline uint16_t DNS_PACKET_PAYLOAD_SIZE_MAX(DnsPacket *p) {
 137
 138         /* Returns the advertised maximum datagram size for replies, or the DNS default if there's nothing defined. */
 139
 140         if (p->opt)
 141                 return MAX(DNS_PACKET_UNICAST_SIZE_MAX, p->opt->key->class);
 142
 143         return DNS_PACKET_UNICAST_SIZE_MAX;
 144 }
 145
 146 static inline bool DNS_PACKET_DO(DnsPacket *p) {
 147         if (!p->opt)
 148                 return false;
 149
 150         return !!(p->opt->ttl & (1U << 15));
 151 }
 152
 153 static inline bool DNS_PACKET_VERSION_SUPPORTED(DnsPacket *p) {
 154         /* Returns true if this packet is in a version we support. Which means either non-EDNS or EDNS(0), but not EDNS
 155          * of any newer versions */
 156
 157         if (!p->opt)
 158                 return true;
 159
 160         return DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(p->opt);
 161 }
 162
 163 /* LLMNR defines some bits differently */
 164 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 165 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 166
 167 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 168 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 169 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 170 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 171
 172 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 173         (((uint16_t) !!(qr) << 15) |                                    \
 174          ((uint16_t) ((opcode) & 15) << 11) |                           \
 175          ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
 176          ((uint16_t) !!(tc) << 9) |                                     \
 177          ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
 178          ((uint16_t) !!(ra) << 7) |                                     \
 179          ((uint16_t) !!(ad) << 5) |                                     \
 180          ((uint16_t) !!(cd) << 4) |                                     \
 181          ((uint16_t) ((rcode) & 15)))
 182
 183 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 184         return
 185                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 186                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 187                 (unsigned) DNS_PACKET_ARCOUNT(p);
 188 }
 189
 190 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t min_alloc_dsize);
 191 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t min_alloc_dsize, bool dnssec_checking_disabled);
 192
 193 void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated);
 194
 195 DnsPacket *dns_packet_ref(DnsPacket *p);
 196 DnsPacket *dns_packet_unref(DnsPacket *p);
 197
 198 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 199
 200 int dns_packet_validate(DnsPacket *p);
 201 int dns_packet_validate_reply(DnsPacket *p);
 202 int dns_packet_validate_query(DnsPacket *p);
 203
 204 int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key);
 205
 206 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 207 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 208 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 209 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 210 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 211 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
 212 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, bool canonical_candidate, size_t *start);
 213 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, bool canonical_candidate, size_t *start);
 214 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, const DnsAnswerFlags flags, size_t *start);
 215 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, const DnsAnswerFlags flags, size_t *start, size_t *rdata_start);
 216 int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, int rcode, size_t *start);
 217 int dns_packet_append_question(DnsPacket *p, DnsQuestion *q);
 218 int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a);
 219
 220 void dns_packet_truncate(DnsPacket *p, size_t sz);
 221 int dns_packet_truncate_opt(DnsPacket *p);
 222
 223 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
 224 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
 225 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
 226 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
 227 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
 228 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
 229 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
 230 int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
 231 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, bool *ret_cache_flush, size_t *start);
 232 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, bool *ret_cache_flush, size_t *start);
 233
 234 void dns_packet_rewind(DnsPacket *p, size_t idx);
 235
 236 int dns_packet_skip_question(DnsPacket *p);
 237 int dns_packet_extract(DnsPacket *p);
 238
 239 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
 240         /* Never cache data originating from localhost, under the
 241          * assumption, that it's coming from a locally DNS forwarder
 242          * or server, that is caching on its own. */
 243
 244         return in_addr_is_localhost(p->family, &p->sender) == 0;
 245 }
 246
 247 /* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */
 248 enum {
 249         DNS_RCODE_SUCCESS = 0,
 250         DNS_RCODE_FORMERR = 1,
 251         DNS_RCODE_SERVFAIL = 2,
 252         DNS_RCODE_NXDOMAIN = 3,
 253         DNS_RCODE_NOTIMP = 4,
 254         DNS_RCODE_REFUSED = 5,
 255         DNS_RCODE_YXDOMAIN = 6,
 256         DNS_RCODE_YXRRSET = 7,
 257         DNS_RCODE_NXRRSET = 8,
 258         DNS_RCODE_NOTAUTH = 9,
 259         DNS_RCODE_NOTZONE = 10,
 260         DNS_RCODE_BADVERS = 16,
 261         DNS_RCODE_BADSIG = 16, /* duplicate value! */
 262         DNS_RCODE_BADKEY = 17,
 263         DNS_RCODE_BADTIME = 18,
 264         DNS_RCODE_BADMODE = 19,
 265         DNS_RCODE_BADNAME = 20,
 266         DNS_RCODE_BADALG = 21,
 267         DNS_RCODE_BADTRUNC = 22,
 268         DNS_RCODE_BADCOOKIE = 23,
 269         _DNS_RCODE_MAX_DEFINED,
 270         _DNS_RCODE_MAX = 4095 /* 4 bit rcode in the header plus 8 bit rcode in OPT, makes 12 bit */
 271 };
 272
 273 const char* dns_rcode_to_string(int i) _const_;
 274 int dns_rcode_from_string(const char *s) _pure_;
 275
 276 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 277 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 278
 279 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 280 #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 } })
 281
 282 #define MDNS_MULTICAST_IPV4_ADDRESS  ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
 283 #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 } })
 284
 285 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
 286         uint64_t f;
 287
 288         /* Converts a protocol + family into a flags field as used in queries and responses */
 289
 290         f = authenticated ? SD_RESOLVED_AUTHENTICATED : 0;
 291
 292         switch (protocol) {
 293         case DNS_PROTOCOL_DNS:
 294                 return f|SD_RESOLVED_DNS;
 295
 296         case DNS_PROTOCOL_LLMNR:
 297                 return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);
 298
 299         case DNS_PROTOCOL_MDNS:
 300                 return f|(family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4);
 301
 302         default:
 303                 return f;
 304         }
 305 }