src/resolve/resolved-dns-packet.h

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 #pragma once
   4
   5 /***
   6   This file is part of systemd.
   7
   8   Copyright 2014 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22  ***/
  23
  24 #include <netinet/ip.h>
  25 #include <netinet/udp.h>
  26
  27 #include "hashmap.h"
  28 #include "in-addr-util.h"
  29 #include "macro.h"
  30 #include "sparse-endian.h"
  31
  32 typedef struct DnsPacketHeader DnsPacketHeader;
  33 typedef struct DnsPacket DnsPacket;
  34
  35 #include "resolved-def.h"
  36 #include "resolved-dns-answer.h"
  37 #include "resolved-dns-question.h"
  38 #include "resolved-dns-rr.h"
  39
  40 typedef enum DnsProtocol {
  41         DNS_PROTOCOL_DNS,
  42         DNS_PROTOCOL_MDNS,
  43         DNS_PROTOCOL_LLMNR,
  44         _DNS_PROTOCOL_MAX,
  45         _DNS_PROTOCOL_INVALID = -1
  46 } DnsProtocol;
  47
  48 struct DnsPacketHeader {
  49         uint16_t id;
  50         be16_t flags;
  51         be16_t qdcount;
  52         be16_t ancount;
  53         be16_t nscount;
  54         be16_t arcount;
  55 };
  56
  57 #define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader)
  58 #define UDP_PACKET_HEADER_SIZE (sizeof(struct iphdr) + sizeof(struct udphdr))
  59
  60 /* The various DNS protocols deviate in how large a packet can grow,
  61    but the TCP transport has a 16bit size field, hence that appears to
  62    be the absolute maximum. */
  63 #define DNS_PACKET_SIZE_MAX 0xFFFF
  64
  65 /* RFC 1035 say 512 is the maximum, for classic unicast DNS */
  66 #define DNS_PACKET_UNICAST_SIZE_MAX 512
  67
  68 #define DNS_PACKET_SIZE_START 512
  69
  70 struct DnsPacket {
  71         int n_ref;
  72         DnsProtocol protocol;
  73         size_t size, allocated, rindex;
  74         void *_data; /* don't access directly, use DNS_PACKET_DATA()! */
  75         Hashmap *names; /* For name compression */
  76
  77         /* Parsed data */
  78         DnsQuestion *question;
  79         DnsAnswer *answer;
  80
  81         /* Packet reception metadata */
  82         int ifindex;
  83         int family, ipproto;
  84         union in_addr_union sender, destination;
  85         uint16_t sender_port, destination_port;
  86         uint32_t ttl;
  87
  88         bool extracted;
  89         bool refuse_compression;
  90 };
  91
  92 static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
  93         if (_unlikely_(!p))
  94                 return NULL;
  95
  96         if (p->_data)
  97                 return p->_data;
  98
  99         return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
 100 }
 101
 102 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
 103 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
 104 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
 105 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
 106 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
 107 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
 108 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
 109 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
 110 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
 111 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
 112 #define DNS_PACKET_RCODE(p) (be16toh(DNS_PACKET_HEADER(p)->flags) & 15)
 113
 114 /* LLMNR defines some bits differently */
 115 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 116 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 117
 118 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 119 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 120 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 121 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 122
 123 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 124         (((uint16_t) !!(qr) << 15) |                                    \
 125          ((uint16_t) ((opcode) & 15) << 11) |                           \
 126          ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
 127          ((uint16_t) !!(tc) << 9) |                                     \
 128          ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
 129          ((uint16_t) !!(ra) << 7) |                                     \
 130          ((uint16_t) !!(ad) << 5) |                                     \
 131          ((uint16_t) !!(cd) << 4) |                                     \
 132          ((uint16_t) ((rcode) & 15)))
 133
 134 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 135         return
 136                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 137                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 138                 (unsigned) DNS_PACKET_ARCOUNT(p);
 139 }
 140
 141 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 142 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 143
 144 DnsPacket *dns_packet_ref(DnsPacket *p);
 145 DnsPacket *dns_packet_unref(DnsPacket *p);
 146
 147 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 148
 149 int dns_packet_validate(DnsPacket *p);
 150 int dns_packet_validate_reply(DnsPacket *p);
 151 int dns_packet_validate_query(DnsPacket *p);
 152
 153 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 154 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 155 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 156 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 157 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 158 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
 159 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, size_t *start);
 160 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, size_t *start);
 161 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
 162 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start);
 163 int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, size_t *start);
 164
 165 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
 166 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
 167 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
 168 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
 169 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
 170 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
 171 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
 172 int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
 173 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start);
 174 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start);
 175
 176 void dns_packet_rewind(DnsPacket *p, size_t idx);
 177
 178 int dns_packet_skip_question(DnsPacket *p);
 179 int dns_packet_extract(DnsPacket *p);
 180
 181 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
 182         /* Never cache data originating from localhost, under the
 183          * assumption, that it's coming from a locally DNS forwarder
 184          * or server, that is caching on its own. */
 185
 186         return in_addr_is_localhost(p->family, &p->sender) == 0;
 187 }
 188
 189 enum {
 190         DNS_RCODE_SUCCESS = 0,
 191         DNS_RCODE_FORMERR = 1,
 192         DNS_RCODE_SERVFAIL = 2,
 193         DNS_RCODE_NXDOMAIN = 3,
 194         DNS_RCODE_NOTIMP = 4,
 195         DNS_RCODE_REFUSED = 5,
 196         DNS_RCODE_YXDOMAIN = 6,
 197         DNS_RCODE_YXRRSET = 7,
 198         DNS_RCODE_NXRRSET = 8,
 199         DNS_RCODE_NOTAUTH = 9,
 200         DNS_RCODE_NOTZONE = 10,
 201         DNS_RCODE_BADVERS = 16,
 202         DNS_RCODE_BADSIG = 16, /* duplicate value! */
 203         DNS_RCODE_BADKEY = 17,
 204         DNS_RCODE_BADTIME = 18,
 205         DNS_RCODE_BADMODE = 19,
 206         DNS_RCODE_BADNAME = 20,
 207         DNS_RCODE_BADALG = 21,
 208         DNS_RCODE_BADTRUNC = 22,
 209         _DNS_RCODE_MAX_DEFINED
 210 };
 211
 212 const char* dns_rcode_to_string(int i) _const_;
 213 int dns_rcode_from_string(const char *s) _pure_;
 214
 215 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 216 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 217
 218 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 219 #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 } })
 220
 221 #define DNSKEY_FLAG_ZONE_KEY (1u << 8)
 222 #define DNSKEY_FLAG_SEP      (1u << 0)
 223
 224 static inline uint16_t dnskey_to_flags(const DnsResourceRecord *rr) {
 225         return (rr->dnskey.zone_key_flag * DNSKEY_FLAG_ZONE_KEY |
 226                 rr->dnskey.sep_flag * DNSKEY_FLAG_SEP);
 227 }
 228
 229 /* http://tools.ietf.org/html/rfc4034#appendix-A.1 */
 230 enum {
 231         DNSSEC_ALGORITHM_RSAMD5 = 1,
 232         DNSSEC_ALGORITHM_DH,
 233         DNSSEC_ALGORITHM_DSA,
 234         DNSSEC_ALGORITHM_ECC,
 235         DNSSEC_ALGORITHM_RSASHA1,
 236         DNSSEC_ALGORITHM_DSA_NSEC3_SHA1,
 237         DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1,
 238         DNSSEC_ALGORITHM_INDIRECT = 252,
 239         DNSSEC_ALGORITHM_PRIVATEDNS,
 240         DNSSEC_ALGORITHM_PRIVATEOID,
 241         _DNSSEC_ALGORITHM_MAX_DEFINED
 242 };
 243
 244 const char* dnssec_algorithm_to_string(int i) _const_;
 245 int dnssec_algorithm_from_string(const char *s) _pure_;
 246
 247 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family) {
 248
 249         /* Converts a protocol + family into a flags field as used in queries */
 250
 251         switch (protocol) {
 252         case DNS_PROTOCOL_DNS:
 253                 return SD_RESOLVED_DNS;
 254
 255         case DNS_PROTOCOL_LLMNR:
 256                 return family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4;
 257
 258         default:
 259                 break;
 260         }
 261
 262         return 0;
 263 }