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/udp.h>
  25 #include <netinet/ip.h>
  26
  27 #include "macro.h"
  28 #include "sparse-endian.h"
  29 #include "hashmap.h"
  30 #include "in-addr-util.h"
  31
  32 typedef struct DnsPacketHeader DnsPacketHeader;
  33 typedef struct DnsPacket DnsPacket;
  34
  35 #include "resolved-dns-rr.h"
  36 #include "resolved-dns-question.h"
  37 #include "resolved-dns-answer.h"
  38 #include "resolved-def.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 meta data */
  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 };
  90
  91 static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
  92         if (_unlikely_(!p))
  93                 return NULL;
  94
  95         if (p->_data)
  96                 return p->_data;
  97
  98         return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
  99 }
 100
 101 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
 102 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
 103 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
 104 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
 105 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
 106 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
 107 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
 108 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
 109 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
 110 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
 111 #define DNS_PACKET_RCODE(p) (be16toh(DNS_PACKET_HEADER(p)->flags) & 15)
 112
 113 /* LLMNR defines some bits differently */
 114 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 115 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 116
 117 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 118 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 119 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 120 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 121
 122 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 123         (((uint16_t) !!qr << 15) |  \
 124          ((uint16_t) (opcode & 15) << 11) | \
 125          ((uint16_t) !!aa << 10) | \
 126          ((uint16_t) !!tc << 9) | \
 127          ((uint16_t) !!rd << 8) | \
 128          ((uint16_t) !!ra << 7) | \
 129          ((uint16_t) !!ad << 5) | \
 130          ((uint16_t) !!cd << 4) | \
 131          ((uint16_t) (rcode & 15)))
 132
 133 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 134         return
 135                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 136                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 137                 (unsigned) DNS_PACKET_ARCOUNT(p);
 138 }
 139
 140 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 141 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 142
 143 DnsPacket *dns_packet_ref(DnsPacket *p);
 144 DnsPacket *dns_packet_unref(DnsPacket *p);
 145
 146 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 147
 148 int dns_packet_validate(DnsPacket *p);
 149 int dns_packet_validate_reply(DnsPacket *p);
 150 int dns_packet_validate_query(DnsPacket *p);
 151
 152 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 153 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 154 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 155 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 156 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 157 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, size_t *start);
 158 int dns_packet_append_name(DnsPacket *p, const char *name,
 159                            bool allow_compression, size_t *start);
 160 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
 161 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start);
 162
 163 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
 164 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
 165 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
 166 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
 167 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
 168 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
 169 int dns_packet_read_name(DnsPacket *p, char **ret,
 170                          bool allow_compression, size_t *start);
 171 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start);
 172 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start);
 173
 174 void dns_packet_rewind(DnsPacket *p, size_t idx);
 175
 176 int dns_packet_skip_question(DnsPacket *p);
 177 int dns_packet_extract(DnsPacket *p);
 178
 179 enum {
 180         DNS_RCODE_SUCCESS = 0,
 181         DNS_RCODE_FORMERR = 1,
 182         DNS_RCODE_SERVFAIL = 2,
 183         DNS_RCODE_NXDOMAIN = 3,
 184         DNS_RCODE_NOTIMP = 4,
 185         DNS_RCODE_REFUSED = 5,
 186         DNS_RCODE_YXDOMAIN = 6,
 187         DNS_RCODE_YXRRSET = 7,
 188         DNS_RCODE_NXRRSET = 8,
 189         DNS_RCODE_NOTAUTH = 9,
 190         DNS_RCODE_NOTZONE = 10,
 191         DNS_RCODE_BADVERS = 16,
 192         DNS_RCODE_BADSIG = 16, /* duplicate value! */
 193         DNS_RCODE_BADKEY = 17,
 194         DNS_RCODE_BADTIME = 18,
 195         DNS_RCODE_BADMODE = 19,
 196         DNS_RCODE_BADNAME = 20,
 197         DNS_RCODE_BADALG = 21,
 198         DNS_RCODE_BADTRUNC = 22,
 199         _DNS_RCODE_MAX_DEFINED
 200 };
 201
 202 const char* dns_rcode_to_string(int i) _const_;
 203 int dns_rcode_from_string(const char *s) _pure_;
 204
 205 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 206 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 207
 208 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 209 #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 } })
 210
 211 #define DNSKEY_FLAG_ZONE_KEY (1u << 8)
 212 #define DNSKEY_FLAG_SEP      (1u << 0)
 213
 214 static inline uint16_t dnskey_to_flags(const DnsResourceRecord *rr) {
 215         return (rr->dnskey.zone_key_flag * DNSKEY_FLAG_ZONE_KEY |
 216                 rr->dnskey.sep_flag * DNSKEY_FLAG_SEP);
 217 }
 218
 219 /* http://tools.ietf.org/html/rfc4034#appendix-A.1 */
 220 enum {
 221         DNSSEC_ALGORITHM_RSAMD5 = 1,
 222         DNSSEC_ALGORITHM_DH,
 223         DNSSEC_ALGORITHM_DSA,
 224         DNSSEC_ALGORITHM_ECC,
 225         DNSSEC_ALGORITHM_RSASHA1,
 226         DNSSEC_ALGORITHM_DSA_NSEC3_SHA1,
 227         DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1,
 228         DNSSEC_ALGORITHM_INDIRECT = 252,
 229         DNSSEC_ALGORITHM_PRIVATEDNS,
 230         DNSSEC_ALGORITHM_PRIVATEOID,
 231         _DNSSEC_ALGORITHM_MAX_DEFINED
 232 };
 233
 234 const char* dnssec_algorithm_to_string(int i) _const_;
 235 int dnssec_algorithm_from_string(const char *s) _pure_;
 236
 237 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family) {
 238
 239         /* Converts a protocol + family into a flags field as used in queries */
 240
 241         if (protocol == DNS_PROTOCOL_DNS)
 242                 return SD_RESOLVED_DNS;
 243
 244         if (protocol == DNS_PROTOCOL_LLMNR)
 245                 return family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4;
 246
 247         return 0;
 248 }