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         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 static inline uint16_t DNS_PACKET_RCODE(DnsPacket *p) {
 124         uint16_t rcode;
 125
 126         if (p->opt)
 127                 rcode = (uint16_t) (p->opt->ttl >> 24);
 128         else
 129                 rcode = 0;
 130
 131         return rcode | (be16toh(DNS_PACKET_HEADER(p)->flags) & 15);
 132 }
 133
 134 /* LLMNR defines some bits differently */
 135 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
 136 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
 137
 138 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
 139 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
 140 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
 141 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
 142
 143 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
 144         (((uint16_t) !!(qr) << 15) |                                    \
 145          ((uint16_t) ((opcode) & 15) << 11) |                           \
 146          ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
 147          ((uint16_t) !!(tc) << 9) |                                     \
 148          ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
 149          ((uint16_t) !!(ra) << 7) |                                     \
 150          ((uint16_t) !!(ad) << 5) |                                     \
 151          ((uint16_t) !!(cd) << 4) |                                     \
 152          ((uint16_t) ((rcode) & 15)))
 153
 154 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
 155         return
 156                 (unsigned) DNS_PACKET_ANCOUNT(p) +
 157                 (unsigned) DNS_PACKET_NSCOUNT(p) +
 158                 (unsigned) DNS_PACKET_ARCOUNT(p);
 159 }
 160
 161 int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t mtu);
 162 int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled);
 163
 164 void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated);
 165
 166 DnsPacket *dns_packet_ref(DnsPacket *p);
 167 DnsPacket *dns_packet_unref(DnsPacket *p);
 168
 169 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
 170
 171 int dns_packet_validate(DnsPacket *p);
 172 int dns_packet_validate_reply(DnsPacket *p);
 173 int dns_packet_validate_query(DnsPacket *p);
 174
 175 int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key);
 176
 177 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
 178 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
 179 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
 180 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
 181 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
 182 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
 183 int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, bool canonical_candidate, size_t *start);
 184 int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, bool canonical_candidate, size_t *start);
 185 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
 186 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start);
 187 int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start);
 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 };
 239
 240 const char* dns_rcode_to_string(int i) _const_;
 241 int dns_rcode_from_string(const char *s) _pure_;
 242
 243 const char* dns_protocol_to_string(DnsProtocol p) _const_;
 244 DnsProtocol dns_protocol_from_string(const char *s) _pure_;
 245
 246 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
 247 #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 } })
 248
 249 #define MDNS_MULTICAST_IPV4_ADDRESS  ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
 250 #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 } })
 251
 252 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
 253         uint64_t f;
 254
 255         /* Converts a protocol + family into a flags field as used in queries and responses */
 256
 257         f = authenticated ? SD_RESOLVED_AUTHENTICATED : 0;
 258
 259         switch (protocol) {
 260         case DNS_PROTOCOL_DNS:
 261                 return f|SD_RESOLVED_DNS;
 262
 263         case DNS_PROTOCOL_LLMNR:
 264                 return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);
 265
 266         case DNS_PROTOCOL_MDNS:
 267                 return family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4;
 268
 269         default:
 270                 break;
 271         }
 272
 273         return 0;
 274 }