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 /* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
  69 #define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096
  70
  71 #define DNS_PACKET_SIZE_START 512
  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
  80         /* Parsed data */
  81         DnsQuestion *question;
  82         DnsAnswer *answer;
  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         bool extracted;
  92         bool refuse_compression;
  93 };
  94
  95 static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
  96         if (_unlikely_(!p))
  97                 return NULL;
  98
  99         if (p->_data)
 100                 return p->_data;
 101
 102         return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
 103 }
 104
 105 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
 106 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
 107 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
 108 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
 109 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
 110 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
 111 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
 112 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
 113 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
 114 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
 115 #define DNS_PACKET_RCODE(p) (be16toh(DNS_PACKET_HEADER(p)->flags) & 15)
 116
 117 /* LLMNR defines some bits differently */
 118 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 119 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 120
 121 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 122 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 123 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 124 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 125
 126 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 127         (((uint16_t) !!(qr) << 15) |                                    \
 128          ((uint16_t) ((opcode) & 15) << 11) |                           \
 129          ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
 130          ((uint16_t) !!(tc) << 9) |                                     \
 131          ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
 132          ((uint16_t) !!(ra) << 7) |                                     \
 133          ((uint16_t) !!(ad) << 5) |                                     \
 134          ((uint16_t) !!(cd) << 4) |                                     \
 135          ((uint16_t) ((rcode) & 15)))
 136
 137 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 138         return
 139                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 140                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 141                 (unsigned) DNS_PACKET_ARCOUNT(p);
 142 }
 143
 144 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 145 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 146
 147 DnsPacket *dns_packet_ref(DnsPacket *p);
 148 DnsPacket *dns_packet_unref(DnsPacket *p);
 149
 150 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 151
 152 int dns_packet_validate(DnsPacket *p);
 153 int dns_packet_validate_reply(DnsPacket *p);
 154 int dns_packet_validate_query(DnsPacket *p);
 155
 156 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 157 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 158 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 159 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 160 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 161 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
 162 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, size_t *start);
 163 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, size_t *start);
 164 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
 165 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start);
 166 int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start);
 167
 168 void dns_packet_truncate(DnsPacket *p, size_t sz);
 169
 170 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
 171 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
 172 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
 173 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
 174 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
 175 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
 176 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
 177 int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
 178 int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start);
 179 int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start);
 180
 181 void dns_packet_rewind(DnsPacket *p, size_t idx);
 182
 183 int dns_packet_skip_question(DnsPacket *p);
 184 int dns_packet_extract(DnsPacket *p);
 185
 186 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
 187         /* Never cache data originating from localhost, under the
 188          * assumption, that it's coming from a locally DNS forwarder
 189          * or server, that is caching on its own. */
 190
 191         return in_addr_is_localhost(p->family, &p->sender) == 0;
 192 }
 193
 194 enum {
 195         DNS_RCODE_SUCCESS = 0,
 196         DNS_RCODE_FORMERR = 1,
 197         DNS_RCODE_SERVFAIL = 2,
 198         DNS_RCODE_NXDOMAIN = 3,
 199         DNS_RCODE_NOTIMP = 4,
 200         DNS_RCODE_REFUSED = 5,
 201         DNS_RCODE_YXDOMAIN = 6,
 202         DNS_RCODE_YXRRSET = 7,
 203         DNS_RCODE_NXRRSET = 8,
 204         DNS_RCODE_NOTAUTH = 9,
 205         DNS_RCODE_NOTZONE = 10,
 206         DNS_RCODE_BADVERS = 16,
 207         DNS_RCODE_BADSIG = 16, /* duplicate value! */
 208         DNS_RCODE_BADKEY = 17,
 209         DNS_RCODE_BADTIME = 18,
 210         DNS_RCODE_BADMODE = 19,
 211         DNS_RCODE_BADNAME = 20,
 212         DNS_RCODE_BADALG = 21,
 213         DNS_RCODE_BADTRUNC = 22,
 214         _DNS_RCODE_MAX_DEFINED
 215 };
 216
 217 const char* dns_rcode_to_string(int i) _const_;
 218 int dns_rcode_from_string(const char *s) _pure_;
 219
 220 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 221 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 222
 223 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 224 #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 } })
 225
 226 #define DNSKEY_FLAG_ZONE_KEY (UINT16_C(1) << 8)
 227 #define DNSKEY_FLAG_SEP      (UINT16_C(1) << 0)
 228
 229 /* http://tools.ietf.org/html/rfc4034#appendix-A.1 and
 230  * https://www.iana.org/assignments/dns-sec-alg-numbers/dns-sec-alg-numbers.xhtml */
 231 enum {
 232         DNSSEC_ALGORITHM_RSAMD5 = 1,
 233         DNSSEC_ALGORITHM_DH,
 234         DNSSEC_ALGORITHM_DSA,
 235         DNSSEC_ALGORITHM_ECC,
 236         DNSSEC_ALGORITHM_RSASHA1,
 237         DNSSEC_ALGORITHM_DSA_NSEC3_SHA1,
 238         DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1,
 239         DNSSEC_ALGORITHM_RSASHA256 = 8,  /* RFC 5702 */
 240         DNSSEC_ALGORITHM_RSASHA512 = 10, /* RFC 5702 */
 241         DNSSEC_ALGORITHM_INDIRECT = 252,
 242         DNSSEC_ALGORITHM_PRIVATEDNS,
 243         DNSSEC_ALGORITHM_PRIVATEOID,
 244         _DNSSEC_ALGORITHM_MAX_DEFINED
 245 };
 246
 247 const char* dnssec_algorithm_to_string(int i) _const_;
 248 int dnssec_algorithm_from_string(const char *s) _pure_;
 249
 250 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family) {
 251
 252         /* Converts a protocol + family into a flags field as used in queries */
 253
 254         switch (protocol) {
 255         case DNS_PROTOCOL_DNS:
 256                 return SD_RESOLVED_DNS;
 257
 258         case DNS_PROTOCOL_LLMNR:
 259                 return family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4;
 260
 261         default:
 262                 break;
 263         }
 264
 265         return 0;
 266 }