summaryrefslogtreecommitdiff
path: root/src/grp-resolve/systemd-resolved/resolved-dns-packet.h
blob: 0bf34d270ce909798a9e1f1ed064a9173d636f73 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
#pragma once

/***
  This file is part of systemd.

  Copyright 2014 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/

#include <netinet/ip.h>
#include <netinet/udp.h>

#include "hashmap.h"
#include "in-addr-util.h"
#include "macro.h"
#include "sparse-endian.h"

typedef struct DnsPacketHeader DnsPacketHeader;
typedef struct DnsPacket DnsPacket;

#include "resolved-def.h"
#include "resolved-dns-answer.h"
#include "resolved-dns-question.h"
#include "resolved-dns-rr.h"

typedef enum DnsProtocol {
        DNS_PROTOCOL_DNS,
        DNS_PROTOCOL_MDNS,
        DNS_PROTOCOL_LLMNR,
        _DNS_PROTOCOL_MAX,
        _DNS_PROTOCOL_INVALID = -1
} DnsProtocol;

struct DnsPacketHeader {
        uint16_t id;
        be16_t flags;
        be16_t qdcount;
        be16_t ancount;
        be16_t nscount;
        be16_t arcount;
};

#define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader)
#define UDP_PACKET_HEADER_SIZE (sizeof(struct iphdr) + sizeof(struct udphdr))

/* The various DNS protocols deviate in how large a packet can grow,
   but the TCP transport has a 16bit size field, hence that appears to
   be the absolute maximum. */
#define DNS_PACKET_SIZE_MAX 0xFFFF

/* RFC 1035 say 512 is the maximum, for classic unicast DNS */
#define DNS_PACKET_UNICAST_SIZE_MAX 512

/* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
#define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096

#define DNS_PACKET_SIZE_START 512

struct DnsPacket {
        int n_ref;
        DnsProtocol protocol;
        size_t size, allocated, rindex;
        void *_data; /* don't access directly, use DNS_PACKET_DATA()! */
        Hashmap *names; /* For name compression */
        size_t opt_start, opt_size;

        /* Parsed data */
        DnsQuestion *question;
        DnsAnswer *answer;
        DnsResourceRecord *opt;

        /* Packet reception metadata */
        int ifindex;
        int family, ipproto;
        union in_addr_union sender, destination;
        uint16_t sender_port, destination_port;
        uint32_t ttl;

        /* For support of truncated packets */
        DnsPacket *more;

        bool on_stack:1;
        bool extracted:1;
        bool refuse_compression:1;
        bool canonical_form:1;
};

static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
        if (_unlikely_(!p))
                return NULL;

        if (p->_data)
                return p->_data;

        return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
}

#define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
#define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
#define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
#define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
#define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
#define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
#define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
#define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
#define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
#define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)

static inline uint16_t DNS_PACKET_RCODE(DnsPacket *p) {
        uint16_t rcode;

        if (p->opt)
                rcode = (uint16_t) (p->opt->ttl >> 24);
        else
                rcode = 0;

        return rcode | (be16toh(DNS_PACKET_HEADER(p)->flags) & 15);
}

/* LLMNR defines some bits differently */
#define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
#define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)

#define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
#define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
#define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
#define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)

#define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
        (((uint16_t) !!(qr) << 15) |                                    \
         ((uint16_t) ((opcode) & 15) << 11) |                           \
         ((uint16_t) !!(aa) << 10) |                /* on LLMNR: c */   \
         ((uint16_t) !!(tc) << 9) |                                     \
         ((uint16_t) !!(rd) << 8) |                 /* on LLMNR: t */   \
         ((uint16_t) !!(ra) << 7) |                                     \
         ((uint16_t) !!(ad) << 5) |                                     \
         ((uint16_t) !!(cd) << 4) |                                     \
         ((uint16_t) ((rcode) & 15)))

static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
        return
                (unsigned) DNS_PACKET_ANCOUNT(p) +
                (unsigned) DNS_PACKET_NSCOUNT(p) +
                (unsigned) DNS_PACKET_ARCOUNT(p);
}

int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t mtu);
int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled);

void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated);

DnsPacket *dns_packet_ref(DnsPacket *p);
DnsPacket *dns_packet_unref(DnsPacket *p);

DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);

int dns_packet_validate(DnsPacket *p);
int dns_packet_validate_reply(DnsPacket *p);
int dns_packet_validate_query(DnsPacket *p);

int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key);

int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, bool canonical_candidate, size_t *start);
int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, bool canonical_candidate, size_t *start);
int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start, size_t *rdata_start);
int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start);

void dns_packet_truncate(DnsPacket *p, size_t sz);
int dns_packet_truncate_opt(DnsPacket *p);

int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, bool *ret_cache_flush, size_t *start);
int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, bool *ret_cache_flush, size_t *start);

void dns_packet_rewind(DnsPacket *p, size_t idx);

int dns_packet_skip_question(DnsPacket *p);
int dns_packet_extract(DnsPacket *p);

static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
        /* Never cache data originating from localhost, under the
         * assumption, that it's coming from a locally DNS forwarder
         * or server, that is caching on its own. */

        return in_addr_is_localhost(p->family, &p->sender) == 0;
}

/* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */
enum {
        DNS_RCODE_SUCCESS = 0,
        DNS_RCODE_FORMERR = 1,
        DNS_RCODE_SERVFAIL = 2,
        DNS_RCODE_NXDOMAIN = 3,
        DNS_RCODE_NOTIMP = 4,
        DNS_RCODE_REFUSED = 5,
        DNS_RCODE_YXDOMAIN = 6,
        DNS_RCODE_YXRRSET = 7,
        DNS_RCODE_NXRRSET = 8,
        DNS_RCODE_NOTAUTH = 9,
        DNS_RCODE_NOTZONE = 10,
        DNS_RCODE_BADVERS = 16,
        DNS_RCODE_BADSIG = 16, /* duplicate value! */
        DNS_RCODE_BADKEY = 17,
        DNS_RCODE_BADTIME = 18,
        DNS_RCODE_BADMODE = 19,
        DNS_RCODE_BADNAME = 20,
        DNS_RCODE_BADALG = 21,
        DNS_RCODE_BADTRUNC = 22,
        _DNS_RCODE_MAX_DEFINED
};

const char* dns_rcode_to_string(int i) _const_;
int dns_rcode_from_string(const char *s) _pure_;

const char* dns_protocol_to_string(DnsProtocol p) _const_;
DnsProtocol dns_protocol_from_string(const char *s) _pure_;

#define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
#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 } })

#define MDNS_MULTICAST_IPV4_ADDRESS  ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
#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 } })

static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
        uint64_t f;

        /* Converts a protocol + family into a flags field as used in queries and responses */

        f = authenticated ? SD_RESOLVED_AUTHENTICATED : 0;

        switch (protocol) {
        case DNS_PROTOCOL_DNS:
                return f|SD_RESOLVED_DNS;

        case DNS_PROTOCOL_LLMNR:
                return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);

        case DNS_PROTOCOL_MDNS:
                return family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4;

        default:
                break;
        }

        return 0;
}