Line data Source code
1 : /* SPDX-License-Identifier: LGPL-2.1+ */
2 : #pragma once
3 :
4 : #include <netinet/ip.h>
5 : #include <netinet/udp.h>
6 :
7 : #include "hashmap.h"
8 : #include "in-addr-util.h"
9 : #include "macro.h"
10 : #include "sparse-endian.h"
11 :
12 : typedef struct DnsPacketHeader DnsPacketHeader;
13 : typedef struct DnsPacket DnsPacket;
14 :
15 : #include "resolved-def.h"
16 : #include "resolved-dns-answer.h"
17 : #include "resolved-dns-question.h"
18 : #include "resolved-dns-rr.h"
19 :
20 : typedef enum DnsProtocol {
21 : DNS_PROTOCOL_DNS,
22 : DNS_PROTOCOL_MDNS,
23 : DNS_PROTOCOL_LLMNR,
24 : _DNS_PROTOCOL_MAX,
25 : _DNS_PROTOCOL_INVALID = -1
26 : } DnsProtocol;
27 :
28 : struct DnsPacketHeader {
29 : uint16_t id;
30 : be16_t flags;
31 : be16_t qdcount;
32 : be16_t ancount;
33 : be16_t nscount;
34 : be16_t arcount;
35 : };
36 :
37 : #define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader)
38 : #define UDP_PACKET_HEADER_SIZE (sizeof(struct iphdr) + sizeof(struct udphdr))
39 :
40 : /* The various DNS protocols deviate in how large a packet can grow,
41 : * but the TCP transport has a 16bit size field, hence that appears to
42 : * be the absolute maximum. */
43 : #define DNS_PACKET_SIZE_MAX 0xFFFFu
44 :
45 : /* The default size to use for allocation when we don't know how large
46 : * the packet will turn out to be. */
47 : #define DNS_PACKET_SIZE_START 512u
48 :
49 : /* RFC 1035 say 512 is the maximum, for classic unicast DNS */
50 : #define DNS_PACKET_UNICAST_SIZE_MAX 512u
51 :
52 : /* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
53 : #define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096u
54 :
55 : struct DnsPacket {
56 : unsigned n_ref;
57 : DnsProtocol protocol;
58 : size_t size, allocated, rindex, max_size;
59 : void *_data; /* don't access directly, use DNS_PACKET_DATA()! */
60 : Hashmap *names; /* For name compression */
61 : size_t opt_start, opt_size;
62 :
63 : /* Parsed data */
64 : DnsQuestion *question;
65 : DnsAnswer *answer;
66 : DnsResourceRecord *opt;
67 :
68 : /* Packet reception metadata */
69 : int ifindex;
70 : int family, ipproto;
71 : union in_addr_union sender, destination;
72 : uint16_t sender_port, destination_port;
73 : uint32_t ttl;
74 :
75 : /* For support of truncated packets */
76 : DnsPacket *more;
77 :
78 : bool on_stack:1;
79 : bool extracted:1;
80 : bool refuse_compression:1;
81 : bool canonical_form:1;
82 : };
83 :
84 10583 : static inline uint8_t* DNS_PACKET_DATA(DnsPacket *p) {
85 10583 : if (_unlikely_(!p))
86 0 : return NULL;
87 :
88 10583 : if (p->_data)
89 2927 : return p->_data;
90 :
91 7656 : return ((uint8_t*) p) + ALIGN(sizeof(DnsPacket));
92 : }
93 :
94 : #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
95 : #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
96 : #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
97 : #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
98 : #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
99 : #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
100 : #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
101 : #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
102 : #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
103 : #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
104 :
105 : #define DNS_PACKET_FLAG_TC (UINT16_C(1) << 9)
106 :
107 0 : static inline uint16_t DNS_PACKET_RCODE(DnsPacket *p) {
108 : uint16_t rcode;
109 :
110 0 : if (p->opt)
111 0 : rcode = (uint16_t) (p->opt->ttl >> 24);
112 : else
113 0 : rcode = 0;
114 :
115 0 : return rcode | (be16toh(DNS_PACKET_HEADER(p)->flags) & 0xF);
116 : }
117 :
118 : static inline uint16_t DNS_PACKET_PAYLOAD_SIZE_MAX(DnsPacket *p) {
119 :
120 : /* Returns the advertised maximum size for replies, or the DNS default if there's nothing defined. */
121 :
122 : if (p->ipproto == IPPROTO_TCP) /* we ignore EDNS(0) size data on TCP, like everybody else */
123 : return DNS_PACKET_SIZE_MAX;
124 :
125 : if (p->opt)
126 : return MAX(DNS_PACKET_UNICAST_SIZE_MAX, p->opt->key->class);
127 :
128 : return DNS_PACKET_UNICAST_SIZE_MAX;
129 : }
130 :
131 : static inline bool DNS_PACKET_DO(DnsPacket *p) {
132 : if (!p->opt)
133 : return false;
134 :
135 : return !!(p->opt->ttl & (1U << 15));
136 : }
137 :
138 : static inline bool DNS_PACKET_VERSION_SUPPORTED(DnsPacket *p) {
139 : /* Returns true if this packet is in a version we support. Which means either non-EDNS or EDNS(0), but not EDNS
140 : * of any newer versions */
141 :
142 : if (!p->opt)
143 : return true;
144 :
145 : return DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(p->opt);
146 : }
147 :
148 : /* LLMNR defines some bits differently */
149 : #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
150 : #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
151 :
152 : #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
153 : #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
154 : #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
155 : #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
156 :
157 : #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
158 : (((uint16_t) !!(qr) << 15) | \
159 : ((uint16_t) ((opcode) & 15) << 11) | \
160 : ((uint16_t) !!(aa) << 10) | /* on LLMNR: c */ \
161 : ((uint16_t) !!(tc) << 9) | \
162 : ((uint16_t) !!(rd) << 8) | /* on LLMNR: t */ \
163 : ((uint16_t) !!(ra) << 7) | \
164 : ((uint16_t) !!(ad) << 5) | \
165 : ((uint16_t) !!(cd) << 4) | \
166 : ((uint16_t) ((rcode) & 15)))
167 :
168 0 : static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket *p) {
169 : return
170 0 : (unsigned) DNS_PACKET_ANCOUNT(p) +
171 0 : (unsigned) DNS_PACKET_NSCOUNT(p) +
172 0 : (unsigned) DNS_PACKET_ARCOUNT(p);
173 : }
174 :
175 : int dns_packet_new(DnsPacket **p, DnsProtocol protocol, size_t min_alloc_dsize, size_t max_size);
176 : int dns_packet_new_query(DnsPacket **p, DnsProtocol protocol, size_t min_alloc_dsize, bool dnssec_checking_disabled);
177 :
178 : void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated);
179 :
180 : DnsPacket *dns_packet_ref(DnsPacket *p);
181 : DnsPacket *dns_packet_unref(DnsPacket *p);
182 :
183 1017 : DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket*, dns_packet_unref);
184 :
185 : int dns_packet_validate(DnsPacket *p);
186 : int dns_packet_validate_reply(DnsPacket *p);
187 : int dns_packet_validate_query(DnsPacket *p);
188 :
189 : int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key);
190 :
191 : int dns_packet_append_blob(DnsPacket *p, const void *d, size_t sz, size_t *start);
192 : int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start);
193 : int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start);
194 : int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start);
195 : int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start);
196 : int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start);
197 : int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, bool canonical_candidate, size_t *start);
198 : int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, bool canonical_candidate, size_t *start);
199 : int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, const DnsAnswerFlags flags, size_t *start);
200 : int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, const DnsAnswerFlags flags, size_t *start, size_t *rdata_start);
201 : int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, int rcode, size_t *start);
202 : int dns_packet_append_question(DnsPacket *p, DnsQuestion *q);
203 : int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a);
204 :
205 : void dns_packet_truncate(DnsPacket *p, size_t sz);
206 : int dns_packet_truncate_opt(DnsPacket *p);
207 :
208 : int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start);
209 : int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start);
210 : int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start);
211 : int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start);
212 : int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start);
213 : int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start);
214 : int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start);
215 : int dns_packet_read_name(DnsPacket *p, char **ret, bool allow_compression, size_t *start);
216 : int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, bool *ret_cache_flush, size_t *start);
217 : int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, bool *ret_cache_flush, size_t *start);
218 :
219 : void dns_packet_rewind(DnsPacket *p, size_t idx);
220 :
221 : int dns_packet_skip_question(DnsPacket *p);
222 : int dns_packet_extract(DnsPacket *p);
223 :
224 : static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket *p) {
225 : /* Never cache data originating from localhost, under the
226 : * assumption, that it's coming from a locally DNS forwarder
227 : * or server, that is caching on its own. */
228 :
229 : return in_addr_is_localhost(p->family, &p->sender) == 0;
230 : }
231 :
232 : /* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */
233 : enum {
234 : DNS_RCODE_SUCCESS = 0,
235 : DNS_RCODE_FORMERR = 1,
236 : DNS_RCODE_SERVFAIL = 2,
237 : DNS_RCODE_NXDOMAIN = 3,
238 : DNS_RCODE_NOTIMP = 4,
239 : DNS_RCODE_REFUSED = 5,
240 : DNS_RCODE_YXDOMAIN = 6,
241 : DNS_RCODE_YXRRSET = 7,
242 : DNS_RCODE_NXRRSET = 8,
243 : DNS_RCODE_NOTAUTH = 9,
244 : DNS_RCODE_NOTZONE = 10,
245 : DNS_RCODE_BADVERS = 16,
246 : DNS_RCODE_BADSIG = 16, /* duplicate value! */
247 : DNS_RCODE_BADKEY = 17,
248 : DNS_RCODE_BADTIME = 18,
249 : DNS_RCODE_BADMODE = 19,
250 : DNS_RCODE_BADNAME = 20,
251 : DNS_RCODE_BADALG = 21,
252 : DNS_RCODE_BADTRUNC = 22,
253 : DNS_RCODE_BADCOOKIE = 23,
254 : _DNS_RCODE_MAX_DEFINED,
255 : _DNS_RCODE_MAX = 4095 /* 4 bit rcode in the header plus 8 bit rcode in OPT, makes 12 bit */
256 : };
257 :
258 : const char* dns_rcode_to_string(int i) _const_;
259 : int dns_rcode_from_string(const char *s) _pure_;
260 :
261 : const char* dns_protocol_to_string(DnsProtocol p) _const_;
262 : DnsProtocol dns_protocol_from_string(const char *s) _pure_;
263 :
264 : #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
265 : #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 } })
266 :
267 : #define MDNS_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
268 : #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 } })
269 :
270 : extern const struct hash_ops dns_packet_hash_ops;
271 :
272 : static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol, int family, bool authenticated) {
273 : uint64_t f;
274 :
275 : /* Converts a protocol + family into a flags field as used in queries and responses */
276 :
277 : f = authenticated ? SD_RESOLVED_AUTHENTICATED : 0;
278 :
279 : switch (protocol) {
280 : case DNS_PROTOCOL_DNS:
281 : return f|SD_RESOLVED_DNS;
282 :
283 : case DNS_PROTOCOL_LLMNR:
284 : return f|(family == AF_INET6 ? SD_RESOLVED_LLMNR_IPV6 : SD_RESOLVED_LLMNR_IPV4);
285 :
286 : case DNS_PROTOCOL_MDNS:
287 : return f|(family == AF_INET6 ? SD_RESOLVED_MDNS_IPV6 : SD_RESOLVED_MDNS_IPV4);
288 :
289 : default:
290 : return f;
291 : }
292 : }
293 :
294 242 : static inline size_t dns_packet_size_max(DnsPacket *p) {
295 242 : assert(p);
296 :
297 : /* Why not insist on a fully initialized max_size during DnsPacket construction? Well, this way it's easy to
298 : * allocate a transient, throw-away DnsPacket on the stack by simple zero initialization, without having to
299 : * deal with explicit field initialization. */
300 :
301 242 : return p->max_size != 0 ? p->max_size : DNS_PACKET_SIZE_MAX;
302 : }
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