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 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) & 15);
 130 }
 131
 132 /* LLMNR defines some bits differently */
 133 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 134 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 135
 136 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 137 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 138 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 139 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 140
 141 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 142         (((uint16_t) !!(qr) << 15) |                                    \
 143          ((uint16_t) ((opcode) & 15) << 11) |                           \
 144          ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
 145          ((uint16_t) !!(tc) << 9) |                                     \
 146          ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
 147          ((uint16_t) !!(ra) << 7) |                                     \
 148          ((uint16_t) !!(ad) << 5) |                                     \
 149          ((uint16_t) !!(cd) << 4) |                                     \
 150          ((uint16_t) ((rcode) & 15)))
 151
 152 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 153         return
 154                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 155                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 156                 (unsigned) DNS_PACKET_ARCOUNT(p);
 157 }
 158
 159 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 160 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled);
 161
 162 void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated);
 163
 164 DnsPacket *dns_packet_ref(DnsPacket *p);
 165 DnsPacket *dns_packet_unref(DnsPacket *p);
 166
 167 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 168
 169 int dns_packet_validate(DnsPacket *p);
 170 int dns_packet_validate_reply(DnsPacket *p);
 171 int dns_packet_validate_query(DnsPacket *p);
 172
 173 int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key);
 174
 175 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 176 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 177 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 178 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 179 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 180 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
 181 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, bool canonical_candidate, size_t *start);
 182 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, bool canonical_candidate, size_t *start);
 183 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
 184 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start);
 185 int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, int rcode, size_t *start);
 186 int dns_packet_append_question(DnsPacket *p, DnsQuestion *q);
 187 int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a);
 188
 189 void dns_packet_truncate(DnsPacket *p, size_t sz);
 190 int dns_packet_truncate_opt(DnsPacket *p);
 191
 192 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
 193 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
 194 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
 195 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
 196 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
 197 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
 198 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
 199 int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
 200 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, bool *ret_cache_flush, size_t *start);
 201 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, bool *ret_cache_flush, size_t *start);
 202
 203 void dns_packet_rewind(DnsPacket *p, size_t idx);
 204
 205 int dns_packet_skip_question(DnsPacket *p);
 206 int dns_packet_extract(DnsPacket *p);
 207
 208 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
 209         /* Never cache data originating from localhost, under the
 210          * assumption, that it's coming from a locally DNS forwarder
 211          * or server, that is caching on its own. */
 212
 213         return in_addr_is_localhost(p->family, &p->sender) == 0;
 214 }
 215
 216 /* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */
 217 enum {
 218         DNS_RCODE_SUCCESS = 0,
 219         DNS_RCODE_FORMERR = 1,
 220         DNS_RCODE_SERVFAIL = 2,
 221         DNS_RCODE_NXDOMAIN = 3,
 222         DNS_RCODE_NOTIMP = 4,
 223         DNS_RCODE_REFUSED = 5,
 224         DNS_RCODE_YXDOMAIN = 6,
 225         DNS_RCODE_YXRRSET = 7,
 226         DNS_RCODE_NXRRSET = 8,
 227         DNS_RCODE_NOTAUTH = 9,
 228         DNS_RCODE_NOTZONE = 10,
 229         DNS_RCODE_BADVERS = 16,
 230         DNS_RCODE_BADSIG = 16, /* duplicate value! */
 231         DNS_RCODE_BADKEY = 17,
 232         DNS_RCODE_BADTIME = 18,
 233         DNS_RCODE_BADMODE = 19,
 234         DNS_RCODE_BADNAME = 20,
 235         DNS_RCODE_BADALG = 21,
 236         DNS_RCODE_BADTRUNC = 22,
 237         _DNS_RCODE_MAX_DEFINED,
 238         _DNS_RCODE_MAX = 4095 /* 4 bit rcode in the header plus 8 bit rcode in OPT, makes 12 bit */
 239 };
 240
 241 const char* dns_rcode_to_string(int i) _const_;
 242 int dns_rcode_from_string(const char *s) _pure_;
 243
 244 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 245 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 246
 247 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 248 #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 } })
 249
 250 #define MDNS_MULTICAST_IPV4_ADDRESS  ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
 251 #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 } })
 252
 253 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
 254         uint64_t f;
 255
 256         /* Converts a protocol + family into a flags field as used in queries and responses */
 257
 258         f = authenticated ? SD_RESOLVED_AUTHENTICATED : 0;
 259
 260         switch (protocol) {
 261         case DNS_PROTOCOL_DNS:
 262                 return f|SD_RESOLVED_DNS;
 263
 264         case DNS_PROTOCOL_LLMNR:
 265                 return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);
 266
 267         case DNS_PROTOCOL_MDNS:
 268                 return f|(family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4);
 269
 270         default:
 271                 return f;
 272         }
 273 }