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Merge pull request #23881 from keszybz/kernel-install-strikes-yet-again
[thirdparty/systemd.git] / src / resolve / resolved-dns-packet.c
1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
2
3 #if HAVE_GCRYPT
4 # include <gcrypt.h>
5 #endif
6
7 #include "alloc-util.h"
8 #include "dns-domain.h"
9 #include "memory-util.h"
10 #include "resolved-dns-packet.h"
11 #include "set.h"
12 #include "stdio-util.h"
13 #include "string-table.h"
14 #include "strv.h"
15 #include "unaligned.h"
16 #include "utf8.h"
17 #include "util.h"
18
19 #define EDNS0_OPT_DO (1<<15)
20
21 assert_cc(DNS_PACKET_SIZE_START > DNS_PACKET_HEADER_SIZE);
22
23 typedef struct DnsPacketRewinder {
24 DnsPacket *packet;
25 size_t saved_rindex;
26 } DnsPacketRewinder;
27
28 static void rewind_dns_packet(DnsPacketRewinder *rewinder) {
29 if (rewinder->packet)
30 dns_packet_rewind(rewinder->packet, rewinder->saved_rindex);
31 }
32
33 #define REWINDER_INIT(p) { \
34 .packet = (p), \
35 .saved_rindex = (p)->rindex, \
36 }
37 #define CANCEL_REWINDER(rewinder) do { (rewinder).packet = NULL; } while (0)
38
39 int dns_packet_new(
40 DnsPacket **ret,
41 DnsProtocol protocol,
42 size_t min_alloc_dsize,
43 size_t max_size) {
44
45 DnsPacket *p;
46 size_t a;
47
48 assert(ret);
49 assert(max_size >= DNS_PACKET_HEADER_SIZE);
50
51 if (max_size > DNS_PACKET_SIZE_MAX)
52 max_size = DNS_PACKET_SIZE_MAX;
53
54 /* The caller may not check what is going to be truly allocated, so do not allow to
55 * allocate a DNS packet bigger than DNS_PACKET_SIZE_MAX.
56 */
57 if (min_alloc_dsize > DNS_PACKET_SIZE_MAX)
58 return log_error_errno(SYNTHETIC_ERRNO(EFBIG),
59 "Requested packet data size too big: %zu",
60 min_alloc_dsize);
61
62 /* When dns_packet_new() is called with min_alloc_dsize == 0, allocate more than the
63 * absolute minimum (which is the dns packet header size), to avoid
64 * resizing immediately again after appending the first data to the packet.
65 */
66 if (min_alloc_dsize < DNS_PACKET_HEADER_SIZE)
67 a = DNS_PACKET_SIZE_START;
68 else
69 a = min_alloc_dsize;
70
71 /* round up to next page size */
72 a = PAGE_ALIGN(ALIGN(sizeof(DnsPacket)) + a) - ALIGN(sizeof(DnsPacket));
73
74 /* make sure we never allocate more than useful */
75 if (a > max_size)
76 a = max_size;
77
78 p = malloc0(ALIGN(sizeof(DnsPacket)) + a);
79 if (!p)
80 return -ENOMEM;
81
82 *p = (DnsPacket) {
83 .n_ref = 1,
84 .protocol = protocol,
85 .size = DNS_PACKET_HEADER_SIZE,
86 .rindex = DNS_PACKET_HEADER_SIZE,
87 .allocated = a,
88 .max_size = max_size,
89 .opt_start = SIZE_MAX,
90 .opt_size = SIZE_MAX,
91 };
92
93 *ret = p;
94
95 return 0;
96 }
97
98 void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated) {
99
100 DnsPacketHeader *h;
101
102 assert(p);
103
104 h = DNS_PACKET_HEADER(p);
105
106 switch (p->protocol) {
107 case DNS_PROTOCOL_LLMNR:
108 assert(!truncated);
109
110 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
111 0 /* opcode */,
112 0 /* c */,
113 0 /* tc */,
114 0 /* t */,
115 0 /* ra */,
116 0 /* ad */,
117 0 /* cd */,
118 0 /* rcode */));
119 break;
120
121 case DNS_PROTOCOL_MDNS:
122 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
123 0 /* opcode */,
124 0 /* aa */,
125 truncated /* tc */,
126 0 /* rd (ask for recursion) */,
127 0 /* ra */,
128 0 /* ad */,
129 0 /* cd */,
130 0 /* rcode */));
131 break;
132
133 default:
134 assert(!truncated);
135
136 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
137 0 /* opcode */,
138 0 /* aa */,
139 0 /* tc */,
140 1 /* rd (ask for recursion) */,
141 0 /* ra */,
142 0 /* ad */,
143 dnssec_checking_disabled /* cd */,
144 0 /* rcode */));
145 }
146 }
147
148 int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t min_alloc_dsize, bool dnssec_checking_disabled) {
149 DnsPacket *p;
150 int r;
151
152 assert(ret);
153
154 r = dns_packet_new(&p, protocol, min_alloc_dsize, DNS_PACKET_SIZE_MAX);
155 if (r < 0)
156 return r;
157
158 /* Always set the TC bit to 0 initially.
159 * If there are multiple packets later, we'll update the bit shortly before sending.
160 */
161 dns_packet_set_flags(p, dnssec_checking_disabled, false);
162
163 *ret = p;
164 return 0;
165 }
166
167 int dns_packet_dup(DnsPacket **ret, DnsPacket *p) {
168 DnsPacket *c;
169 int r;
170
171 assert(ret);
172 assert(p);
173
174 r = dns_packet_validate(p);
175 if (r < 0)
176 return r;
177
178 c = malloc(ALIGN(sizeof(DnsPacket)) + p->size);
179 if (!c)
180 return -ENOMEM;
181
182 *c = (DnsPacket) {
183 .n_ref = 1,
184 .protocol = p->protocol,
185 .size = p->size,
186 .rindex = DNS_PACKET_HEADER_SIZE,
187 .allocated = p->size,
188 .max_size = p->max_size,
189 .opt_start = SIZE_MAX,
190 .opt_size = SIZE_MAX,
191 };
192
193 memcpy(DNS_PACKET_DATA(c), DNS_PACKET_DATA(p), p->size);
194
195 *ret = c;
196 return 0;
197 }
198
199 DnsPacket *dns_packet_ref(DnsPacket *p) {
200
201 if (!p)
202 return NULL;
203
204 assert(!p->on_stack);
205
206 assert(p->n_ref > 0);
207 p->n_ref++;
208 return p;
209 }
210
211 static void dns_packet_free(DnsPacket *p) {
212 char *s;
213
214 assert(p);
215
216 dns_question_unref(p->question);
217 dns_answer_unref(p->answer);
218 dns_resource_record_unref(p->opt);
219
220 while ((s = hashmap_steal_first_key(p->names)))
221 free(s);
222 hashmap_free(p->names);
223
224 free(p->_data);
225
226 if (!p->on_stack)
227 free(p);
228 }
229
230 DnsPacket *dns_packet_unref(DnsPacket *p) {
231 if (!p)
232 return NULL;
233
234 assert(p->n_ref > 0);
235
236 dns_packet_unref(p->more);
237
238 if (p->n_ref == 1)
239 dns_packet_free(p);
240 else
241 p->n_ref--;
242
243 return NULL;
244 }
245
246 int dns_packet_validate(DnsPacket *p) {
247 assert(p);
248
249 if (p->size < DNS_PACKET_HEADER_SIZE)
250 return -EBADMSG;
251
252 if (p->size > DNS_PACKET_SIZE_MAX)
253 return -EBADMSG;
254
255 return 1;
256 }
257
258 int dns_packet_validate_reply(DnsPacket *p) {
259 int r;
260
261 assert(p);
262
263 r = dns_packet_validate(p);
264 if (r < 0)
265 return r;
266
267 if (DNS_PACKET_QR(p) != 1)
268 return 0;
269
270 if (DNS_PACKET_OPCODE(p) != 0)
271 return -EBADMSG;
272
273 switch (p->protocol) {
274
275 case DNS_PROTOCOL_LLMNR:
276 /* RFC 4795, Section 2.1.1. says to discard all replies with QDCOUNT != 1 */
277 if (DNS_PACKET_QDCOUNT(p) != 1)
278 return -EBADMSG;
279
280 break;
281
282 case DNS_PROTOCOL_MDNS:
283 /* RFC 6762, Section 18 */
284 if (DNS_PACKET_RCODE(p) != 0)
285 return -EBADMSG;
286
287 break;
288
289 default:
290 break;
291 }
292
293 return 1;
294 }
295
296 int dns_packet_validate_query(DnsPacket *p) {
297 int r;
298
299 assert(p);
300
301 r = dns_packet_validate(p);
302 if (r < 0)
303 return r;
304
305 if (DNS_PACKET_QR(p) != 0)
306 return 0;
307
308 if (DNS_PACKET_OPCODE(p) != 0)
309 return -EBADMSG;
310
311 if (DNS_PACKET_TC(p))
312 return -EBADMSG;
313
314 switch (p->protocol) {
315
316 case DNS_PROTOCOL_LLMNR:
317 case DNS_PROTOCOL_DNS:
318 /* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */
319 if (DNS_PACKET_QDCOUNT(p) != 1)
320 return -EBADMSG;
321
322 /* RFC 4795, Section 2.1.1. says to discard all queries with ANCOUNT != 0 */
323 if (DNS_PACKET_ANCOUNT(p) > 0)
324 return -EBADMSG;
325
326 /* RFC 4795, Section 2.1.1. says to discard all queries with NSCOUNT != 0 */
327 if (DNS_PACKET_NSCOUNT(p) > 0)
328 return -EBADMSG;
329
330 break;
331
332 case DNS_PROTOCOL_MDNS:
333 /* RFC 6762, Section 18 specifies that messages with non-zero RCODE
334 * must be silently ignored, and that we must ignore the values of
335 * AA, RD, RA, AD, and CD bits. */
336 if (DNS_PACKET_RCODE(p) != 0)
337 return -EBADMSG;
338
339 break;
340
341 default:
342 break;
343 }
344
345 return 1;
346 }
347
348 static int dns_packet_extend(DnsPacket *p, size_t add, void **ret, size_t *start) {
349 assert(p);
350
351 if (p->size + add > p->allocated) {
352 size_t a, ms;
353
354 a = PAGE_ALIGN((p->size + add) * 2);
355
356 ms = dns_packet_size_max(p);
357 if (a > ms)
358 a = ms;
359
360 if (p->size + add > a)
361 return -EMSGSIZE;
362
363 if (p->_data) {
364 void *d;
365
366 d = realloc(p->_data, a);
367 if (!d)
368 return -ENOMEM;
369
370 p->_data = d;
371 } else {
372 p->_data = malloc(a);
373 if (!p->_data)
374 return -ENOMEM;
375
376 memcpy(p->_data, (uint8_t*) p + ALIGN(sizeof(DnsPacket)), p->size);
377 memzero((uint8_t*) p->_data + p->size, a - p->size);
378 }
379
380 p->allocated = a;
381 }
382
383 if (start)
384 *start = p->size;
385
386 if (ret)
387 *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->size;
388
389 p->size += add;
390 return 0;
391 }
392
393 void dns_packet_truncate(DnsPacket *p, size_t sz) {
394 char *s;
395 void *n;
396
397 assert(p);
398
399 if (p->size <= sz)
400 return;
401
402 HASHMAP_FOREACH_KEY(n, s, p->names) {
403
404 if (PTR_TO_SIZE(n) < sz)
405 continue;
406
407 hashmap_remove(p->names, s);
408 free(s);
409 }
410
411 p->size = sz;
412 }
413
414 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t l, size_t *start) {
415 void *q;
416 int r;
417
418 assert(p);
419
420 r = dns_packet_extend(p, l, &q, start);
421 if (r < 0)
422 return r;
423
424 memcpy_safe(q, d, l);
425 return 0;
426 }
427
428 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start) {
429 void *d;
430 int r;
431
432 assert(p);
433
434 r = dns_packet_extend(p, sizeof(uint8_t), &d, start);
435 if (r < 0)
436 return r;
437
438 ((uint8_t*) d)[0] = v;
439
440 return 0;
441 }
442
443 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start) {
444 void *d;
445 int r;
446
447 assert(p);
448
449 r = dns_packet_extend(p, sizeof(uint16_t), &d, start);
450 if (r < 0)
451 return r;
452
453 unaligned_write_be16(d, v);
454
455 return 0;
456 }
457
458 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start) {
459 void *d;
460 int r;
461
462 assert(p);
463
464 r = dns_packet_extend(p, sizeof(uint32_t), &d, start);
465 if (r < 0)
466 return r;
467
468 unaligned_write_be32(d, v);
469
470 return 0;
471 }
472
473 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start) {
474 assert(p);
475 assert(s);
476
477 return dns_packet_append_raw_string(p, s, strlen(s), start);
478 }
479
480 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start) {
481 void *d;
482 int r;
483
484 assert(p);
485 assert(s || size == 0);
486
487 if (size > 255)
488 return -E2BIG;
489
490 r = dns_packet_extend(p, 1 + size, &d, start);
491 if (r < 0)
492 return r;
493
494 ((uint8_t*) d)[0] = (uint8_t) size;
495
496 memcpy_safe(((uint8_t*) d) + 1, s, size);
497
498 return 0;
499 }
500
501 int dns_packet_append_label(DnsPacket *p, const char *d, size_t l, bool canonical_candidate, size_t *start) {
502 uint8_t *w;
503 int r;
504
505 /* Append a label to a packet. Optionally, does this in DNSSEC
506 * canonical form, if this label is marked as a candidate for
507 * it, and the canonical form logic is enabled for the
508 * packet */
509
510 assert(p);
511 assert(d);
512
513 if (l > DNS_LABEL_MAX)
514 return -E2BIG;
515
516 r = dns_packet_extend(p, 1 + l, (void**) &w, start);
517 if (r < 0)
518 return r;
519
520 *(w++) = (uint8_t) l;
521
522 if (p->canonical_form && canonical_candidate)
523 /* Generate in canonical form, as defined by DNSSEC
524 * RFC 4034, Section 6.2, i.e. all lower-case. */
525 for (size_t i = 0; i < l; i++)
526 w[i] = (uint8_t) ascii_tolower(d[i]);
527 else
528 /* Otherwise, just copy the string unaltered. This is
529 * essential for DNS-SD, where the casing of labels
530 * matters and needs to be retained. */
531 memcpy(w, d, l);
532
533 return 0;
534 }
535
536 int dns_packet_append_name(
537 DnsPacket *p,
538 const char *name,
539 bool allow_compression,
540 bool canonical_candidate,
541 size_t *start) {
542
543 size_t saved_size;
544 int r;
545
546 assert(p);
547 assert(name);
548
549 if (p->refuse_compression)
550 allow_compression = false;
551
552 saved_size = p->size;
553
554 while (!dns_name_is_root(name)) {
555 const char *z = name;
556 char label[DNS_LABEL_MAX];
557 size_t n = 0;
558
559 if (allow_compression)
560 n = PTR_TO_SIZE(hashmap_get(p->names, name));
561 if (n > 0) {
562 assert(n < p->size);
563
564 if (n < 0x4000) {
565 r = dns_packet_append_uint16(p, 0xC000 | n, NULL);
566 if (r < 0)
567 goto fail;
568
569 goto done;
570 }
571 }
572
573 r = dns_label_unescape(&name, label, sizeof label, 0);
574 if (r < 0)
575 goto fail;
576
577 r = dns_packet_append_label(p, label, r, canonical_candidate, &n);
578 if (r < 0)
579 goto fail;
580
581 if (allow_compression) {
582 _cleanup_free_ char *s = NULL;
583
584 s = strdup(z);
585 if (!s) {
586 r = -ENOMEM;
587 goto fail;
588 }
589
590 r = hashmap_ensure_put(&p->names, &dns_name_hash_ops, s, SIZE_TO_PTR(n));
591 if (r < 0)
592 goto fail;
593
594 TAKE_PTR(s);
595 }
596 }
597
598 r = dns_packet_append_uint8(p, 0, NULL);
599 if (r < 0)
600 return r;
601
602 done:
603 if (start)
604 *start = saved_size;
605
606 return 0;
607
608 fail:
609 dns_packet_truncate(p, saved_size);
610 return r;
611 }
612
613 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *k, const DnsAnswerFlags flags, size_t *start) {
614 size_t saved_size;
615 uint16_t class;
616 int r;
617
618 assert(p);
619 assert(k);
620
621 saved_size = p->size;
622
623 r = dns_packet_append_name(p, dns_resource_key_name(k), true, true, NULL);
624 if (r < 0)
625 goto fail;
626
627 r = dns_packet_append_uint16(p, k->type, NULL);
628 if (r < 0)
629 goto fail;
630
631 class = flags & DNS_ANSWER_CACHE_FLUSH ? k->class | MDNS_RR_CACHE_FLUSH_OR_QU : k->class;
632 r = dns_packet_append_uint16(p, class, NULL);
633 if (r < 0)
634 goto fail;
635
636 if (start)
637 *start = saved_size;
638
639 return 0;
640
641 fail:
642 dns_packet_truncate(p, saved_size);
643 return r;
644 }
645
646 static int dns_packet_append_type_window(DnsPacket *p, uint8_t window, uint8_t length, const uint8_t *types, size_t *start) {
647 size_t saved_size;
648 int r;
649
650 assert(p);
651 assert(types);
652 assert(length > 0);
653
654 saved_size = p->size;
655
656 r = dns_packet_append_uint8(p, window, NULL);
657 if (r < 0)
658 goto fail;
659
660 r = dns_packet_append_uint8(p, length, NULL);
661 if (r < 0)
662 goto fail;
663
664 r = dns_packet_append_blob(p, types, length, NULL);
665 if (r < 0)
666 goto fail;
667
668 if (start)
669 *start = saved_size;
670
671 return 0;
672 fail:
673 dns_packet_truncate(p, saved_size);
674 return r;
675 }
676
677 static int dns_packet_append_types(DnsPacket *p, Bitmap *types, size_t *start) {
678 uint8_t window = 0;
679 uint8_t entry = 0;
680 uint8_t bitmaps[32] = {};
681 unsigned n;
682 size_t saved_size;
683 int r;
684
685 assert(p);
686
687 saved_size = p->size;
688
689 BITMAP_FOREACH(n, types) {
690 assert(n <= 0xffff);
691
692 if ((n >> 8) != window && bitmaps[entry / 8] != 0) {
693 r = dns_packet_append_type_window(p, window, entry / 8 + 1, bitmaps, NULL);
694 if (r < 0)
695 goto fail;
696
697 zero(bitmaps);
698 }
699
700 window = n >> 8;
701 entry = n & 255;
702
703 bitmaps[entry / 8] |= 1 << (7 - (entry % 8));
704 }
705
706 if (bitmaps[entry / 8] != 0) {
707 r = dns_packet_append_type_window(p, window, entry / 8 + 1, bitmaps, NULL);
708 if (r < 0)
709 goto fail;
710 }
711
712 if (start)
713 *start = saved_size;
714
715 return 0;
716 fail:
717 dns_packet_truncate(p, saved_size);
718 return r;
719 }
720
721 /* Append the OPT pseudo-RR described in RFC6891 */
722 int dns_packet_append_opt(
723 DnsPacket *p,
724 uint16_t max_udp_size,
725 bool edns0_do,
726 bool include_rfc6975,
727 const char *nsid,
728 int rcode,
729 size_t *ret_start) {
730
731 size_t saved_size;
732 int r;
733
734 assert(p);
735 /* we must never advertise supported packet size smaller than the legacy max */
736 assert(max_udp_size >= DNS_PACKET_UNICAST_SIZE_MAX);
737 assert(rcode >= 0);
738 assert(rcode <= _DNS_RCODE_MAX);
739
740 if (p->opt_start != SIZE_MAX)
741 return -EBUSY;
742
743 assert(p->opt_size == SIZE_MAX);
744
745 saved_size = p->size;
746
747 /* empty name */
748 r = dns_packet_append_uint8(p, 0, NULL);
749 if (r < 0)
750 return r;
751
752 /* type */
753 r = dns_packet_append_uint16(p, DNS_TYPE_OPT, NULL);
754 if (r < 0)
755 goto fail;
756
757 /* class: maximum udp packet that can be received */
758 r = dns_packet_append_uint16(p, max_udp_size, NULL);
759 if (r < 0)
760 goto fail;
761
762 /* extended RCODE and VERSION */
763 r = dns_packet_append_uint16(p, ((uint16_t) rcode & 0x0FF0) << 4, NULL);
764 if (r < 0)
765 goto fail;
766
767 /* flags: DNSSEC OK (DO), see RFC3225 */
768 r = dns_packet_append_uint16(p, edns0_do ? EDNS0_OPT_DO : 0, NULL);
769 if (r < 0)
770 goto fail;
771
772 if (edns0_do && include_rfc6975) {
773 /* If DO is on and this is requested, also append RFC6975 Algorithm data. This is supposed to
774 * be done on queries, not on replies, hencer callers should turn this off when finishing off
775 * replies. */
776
777 static const uint8_t rfc6975[] = {
778
779 0, 5, /* OPTION_CODE: DAU */
780 #if PREFER_OPENSSL || (HAVE_GCRYPT && GCRYPT_VERSION_NUMBER >= 0x010600)
781 0, 7, /* LIST_LENGTH */
782 #else
783 0, 6, /* LIST_LENGTH */
784 #endif
785 DNSSEC_ALGORITHM_RSASHA1,
786 DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1,
787 DNSSEC_ALGORITHM_RSASHA256,
788 DNSSEC_ALGORITHM_RSASHA512,
789 DNSSEC_ALGORITHM_ECDSAP256SHA256,
790 DNSSEC_ALGORITHM_ECDSAP384SHA384,
791 #if PREFER_OPENSSL || (HAVE_GCRYPT && GCRYPT_VERSION_NUMBER >= 0x010600)
792 DNSSEC_ALGORITHM_ED25519,
793 #endif
794
795 0, 6, /* OPTION_CODE: DHU */
796 0, 3, /* LIST_LENGTH */
797 DNSSEC_DIGEST_SHA1,
798 DNSSEC_DIGEST_SHA256,
799 DNSSEC_DIGEST_SHA384,
800
801 0, 7, /* OPTION_CODE: N3U */
802 0, 1, /* LIST_LENGTH */
803 NSEC3_ALGORITHM_SHA1,
804 };
805
806 r = dns_packet_append_uint16(p, sizeof(rfc6975), NULL); /* RDLENGTH */
807 if (r < 0)
808 goto fail;
809
810 r = dns_packet_append_blob(p, rfc6975, sizeof(rfc6975), NULL); /* the payload, as defined above */
811
812 } else if (nsid) {
813
814 if (strlen(nsid) > UINT16_MAX - 4) {
815 r = -E2BIG;
816 goto fail;
817 }
818
819 r = dns_packet_append_uint16(p, 4 + strlen(nsid), NULL); /* RDLENGTH */
820 if (r < 0)
821 goto fail;
822
823 r = dns_packet_append_uint16(p, 3, NULL); /* OPTION-CODE: NSID */
824 if (r < 0)
825 goto fail;
826
827 r = dns_packet_append_uint16(p, strlen(nsid), NULL); /* OPTION-LENGTH */
828 if (r < 0)
829 goto fail;
830
831 r = dns_packet_append_blob(p, nsid, strlen(nsid), NULL);
832 } else
833 r = dns_packet_append_uint16(p, 0, NULL);
834 if (r < 0)
835 goto fail;
836
837 DNS_PACKET_HEADER(p)->arcount = htobe16(DNS_PACKET_ARCOUNT(p) + 1);
838
839 p->opt_start = saved_size;
840 p->opt_size = p->size - saved_size;
841
842 if (ret_start)
843 *ret_start = saved_size;
844
845 return 0;
846
847 fail:
848 dns_packet_truncate(p, saved_size);
849 return r;
850 }
851
852 int dns_packet_truncate_opt(DnsPacket *p) {
853 assert(p);
854
855 if (p->opt_start == SIZE_MAX) {
856 assert(p->opt_size == SIZE_MAX);
857 return 0;
858 }
859
860 assert(p->opt_size != SIZE_MAX);
861 assert(DNS_PACKET_ARCOUNT(p) > 0);
862
863 if (p->opt_start + p->opt_size != p->size)
864 return -EBUSY;
865
866 dns_packet_truncate(p, p->opt_start);
867 DNS_PACKET_HEADER(p)->arcount = htobe16(DNS_PACKET_ARCOUNT(p) - 1);
868 p->opt_start = p->opt_size = SIZE_MAX;
869
870 return 1;
871 }
872
873 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, const DnsAnswerFlags flags, size_t *start, size_t *rdata_start) {
874
875 size_t saved_size, rdlength_offset, end, rdlength, rds;
876 uint32_t ttl;
877 int r;
878
879 assert(p);
880 assert(rr);
881
882 saved_size = p->size;
883
884 r = dns_packet_append_key(p, rr->key, flags, NULL);
885 if (r < 0)
886 goto fail;
887
888 ttl = flags & DNS_ANSWER_GOODBYE ? 0 : rr->ttl;
889 r = dns_packet_append_uint32(p, ttl, NULL);
890 if (r < 0)
891 goto fail;
892
893 /* Initially we write 0 here */
894 r = dns_packet_append_uint16(p, 0, &rdlength_offset);
895 if (r < 0)
896 goto fail;
897
898 rds = p->size - saved_size;
899
900 switch (rr->unparsable ? _DNS_TYPE_INVALID : rr->key->type) {
901
902 case DNS_TYPE_SRV:
903 r = dns_packet_append_uint16(p, rr->srv.priority, NULL);
904 if (r < 0)
905 goto fail;
906
907 r = dns_packet_append_uint16(p, rr->srv.weight, NULL);
908 if (r < 0)
909 goto fail;
910
911 r = dns_packet_append_uint16(p, rr->srv.port, NULL);
912 if (r < 0)
913 goto fail;
914
915 /* RFC 2782 states "Unless and until permitted by future standards
916 * action, name compression is not to be used for this field." */
917 r = dns_packet_append_name(p, rr->srv.name, false, true, NULL);
918 break;
919
920 case DNS_TYPE_PTR:
921 case DNS_TYPE_NS:
922 case DNS_TYPE_CNAME:
923 case DNS_TYPE_DNAME:
924 r = dns_packet_append_name(p, rr->ptr.name, true, true, NULL);
925 break;
926
927 case DNS_TYPE_HINFO:
928 r = dns_packet_append_string(p, rr->hinfo.cpu, NULL);
929 if (r < 0)
930 goto fail;
931
932 r = dns_packet_append_string(p, rr->hinfo.os, NULL);
933 break;
934
935 case DNS_TYPE_SPF: /* exactly the same as TXT */
936 case DNS_TYPE_TXT:
937
938 if (!rr->txt.items) {
939 /* RFC 6763, section 6.1 suggests to generate
940 * single empty string for an empty array. */
941
942 r = dns_packet_append_raw_string(p, NULL, 0, NULL);
943 if (r < 0)
944 goto fail;
945 } else
946 LIST_FOREACH(items, i, rr->txt.items) {
947 r = dns_packet_append_raw_string(p, i->data, i->length, NULL);
948 if (r < 0)
949 goto fail;
950 }
951
952 r = 0;
953 break;
954
955 case DNS_TYPE_A:
956 r = dns_packet_append_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
957 break;
958
959 case DNS_TYPE_AAAA:
960 r = dns_packet_append_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
961 break;
962
963 case DNS_TYPE_SOA:
964 r = dns_packet_append_name(p, rr->soa.mname, true, true, NULL);
965 if (r < 0)
966 goto fail;
967
968 r = dns_packet_append_name(p, rr->soa.rname, true, true, NULL);
969 if (r < 0)
970 goto fail;
971
972 r = dns_packet_append_uint32(p, rr->soa.serial, NULL);
973 if (r < 0)
974 goto fail;
975
976 r = dns_packet_append_uint32(p, rr->soa.refresh, NULL);
977 if (r < 0)
978 goto fail;
979
980 r = dns_packet_append_uint32(p, rr->soa.retry, NULL);
981 if (r < 0)
982 goto fail;
983
984 r = dns_packet_append_uint32(p, rr->soa.expire, NULL);
985 if (r < 0)
986 goto fail;
987
988 r = dns_packet_append_uint32(p, rr->soa.minimum, NULL);
989 break;
990
991 case DNS_TYPE_MX:
992 r = dns_packet_append_uint16(p, rr->mx.priority, NULL);
993 if (r < 0)
994 goto fail;
995
996 r = dns_packet_append_name(p, rr->mx.exchange, true, true, NULL);
997 break;
998
999 case DNS_TYPE_LOC:
1000 r = dns_packet_append_uint8(p, rr->loc.version, NULL);
1001 if (r < 0)
1002 goto fail;
1003
1004 r = dns_packet_append_uint8(p, rr->loc.size, NULL);
1005 if (r < 0)
1006 goto fail;
1007
1008 r = dns_packet_append_uint8(p, rr->loc.horiz_pre, NULL);
1009 if (r < 0)
1010 goto fail;
1011
1012 r = dns_packet_append_uint8(p, rr->loc.vert_pre, NULL);
1013 if (r < 0)
1014 goto fail;
1015
1016 r = dns_packet_append_uint32(p, rr->loc.latitude, NULL);
1017 if (r < 0)
1018 goto fail;
1019
1020 r = dns_packet_append_uint32(p, rr->loc.longitude, NULL);
1021 if (r < 0)
1022 goto fail;
1023
1024 r = dns_packet_append_uint32(p, rr->loc.altitude, NULL);
1025 break;
1026
1027 case DNS_TYPE_DS:
1028 r = dns_packet_append_uint16(p, rr->ds.key_tag, NULL);
1029 if (r < 0)
1030 goto fail;
1031
1032 r = dns_packet_append_uint8(p, rr->ds.algorithm, NULL);
1033 if (r < 0)
1034 goto fail;
1035
1036 r = dns_packet_append_uint8(p, rr->ds.digest_type, NULL);
1037 if (r < 0)
1038 goto fail;
1039
1040 r = dns_packet_append_blob(p, rr->ds.digest, rr->ds.digest_size, NULL);
1041 break;
1042
1043 case DNS_TYPE_SSHFP:
1044 r = dns_packet_append_uint8(p, rr->sshfp.algorithm, NULL);
1045 if (r < 0)
1046 goto fail;
1047
1048 r = dns_packet_append_uint8(p, rr->sshfp.fptype, NULL);
1049 if (r < 0)
1050 goto fail;
1051
1052 r = dns_packet_append_blob(p, rr->sshfp.fingerprint, rr->sshfp.fingerprint_size, NULL);
1053 break;
1054
1055 case DNS_TYPE_DNSKEY:
1056 r = dns_packet_append_uint16(p, rr->dnskey.flags, NULL);
1057 if (r < 0)
1058 goto fail;
1059
1060 r = dns_packet_append_uint8(p, rr->dnskey.protocol, NULL);
1061 if (r < 0)
1062 goto fail;
1063
1064 r = dns_packet_append_uint8(p, rr->dnskey.algorithm, NULL);
1065 if (r < 0)
1066 goto fail;
1067
1068 r = dns_packet_append_blob(p, rr->dnskey.key, rr->dnskey.key_size, NULL);
1069 break;
1070
1071 case DNS_TYPE_RRSIG:
1072 r = dns_packet_append_uint16(p, rr->rrsig.type_covered, NULL);
1073 if (r < 0)
1074 goto fail;
1075
1076 r = dns_packet_append_uint8(p, rr->rrsig.algorithm, NULL);
1077 if (r < 0)
1078 goto fail;
1079
1080 r = dns_packet_append_uint8(p, rr->rrsig.labels, NULL);
1081 if (r < 0)
1082 goto fail;
1083
1084 r = dns_packet_append_uint32(p, rr->rrsig.original_ttl, NULL);
1085 if (r < 0)
1086 goto fail;
1087
1088 r = dns_packet_append_uint32(p, rr->rrsig.expiration, NULL);
1089 if (r < 0)
1090 goto fail;
1091
1092 r = dns_packet_append_uint32(p, rr->rrsig.inception, NULL);
1093 if (r < 0)
1094 goto fail;
1095
1096 r = dns_packet_append_uint16(p, rr->rrsig.key_tag, NULL);
1097 if (r < 0)
1098 goto fail;
1099
1100 r = dns_packet_append_name(p, rr->rrsig.signer, false, true, NULL);
1101 if (r < 0)
1102 goto fail;
1103
1104 r = dns_packet_append_blob(p, rr->rrsig.signature, rr->rrsig.signature_size, NULL);
1105 break;
1106
1107 case DNS_TYPE_NSEC:
1108 r = dns_packet_append_name(p, rr->nsec.next_domain_name, false, false, NULL);
1109 if (r < 0)
1110 goto fail;
1111
1112 r = dns_packet_append_types(p, rr->nsec.types, NULL);
1113 if (r < 0)
1114 goto fail;
1115
1116 break;
1117
1118 case DNS_TYPE_NSEC3:
1119 r = dns_packet_append_uint8(p, rr->nsec3.algorithm, NULL);
1120 if (r < 0)
1121 goto fail;
1122
1123 r = dns_packet_append_uint8(p, rr->nsec3.flags, NULL);
1124 if (r < 0)
1125 goto fail;
1126
1127 r = dns_packet_append_uint16(p, rr->nsec3.iterations, NULL);
1128 if (r < 0)
1129 goto fail;
1130
1131 r = dns_packet_append_uint8(p, rr->nsec3.salt_size, NULL);
1132 if (r < 0)
1133 goto fail;
1134
1135 r = dns_packet_append_blob(p, rr->nsec3.salt, rr->nsec3.salt_size, NULL);
1136 if (r < 0)
1137 goto fail;
1138
1139 r = dns_packet_append_uint8(p, rr->nsec3.next_hashed_name_size, NULL);
1140 if (r < 0)
1141 goto fail;
1142
1143 r = dns_packet_append_blob(p, rr->nsec3.next_hashed_name, rr->nsec3.next_hashed_name_size, NULL);
1144 if (r < 0)
1145 goto fail;
1146
1147 r = dns_packet_append_types(p, rr->nsec3.types, NULL);
1148 if (r < 0)
1149 goto fail;
1150
1151 break;
1152
1153 case DNS_TYPE_TLSA:
1154 r = dns_packet_append_uint8(p, rr->tlsa.cert_usage, NULL);
1155 if (r < 0)
1156 goto fail;
1157
1158 r = dns_packet_append_uint8(p, rr->tlsa.selector, NULL);
1159 if (r < 0)
1160 goto fail;
1161
1162 r = dns_packet_append_uint8(p, rr->tlsa.matching_type, NULL);
1163 if (r < 0)
1164 goto fail;
1165
1166 r = dns_packet_append_blob(p, rr->tlsa.data, rr->tlsa.data_size, NULL);
1167 break;
1168
1169 case DNS_TYPE_CAA:
1170 r = dns_packet_append_uint8(p, rr->caa.flags, NULL);
1171 if (r < 0)
1172 goto fail;
1173
1174 r = dns_packet_append_string(p, rr->caa.tag, NULL);
1175 if (r < 0)
1176 goto fail;
1177
1178 r = dns_packet_append_blob(p, rr->caa.value, rr->caa.value_size, NULL);
1179 break;
1180
1181 case DNS_TYPE_OPT:
1182 case DNS_TYPE_OPENPGPKEY:
1183 case _DNS_TYPE_INVALID: /* unparsable */
1184 default:
1185
1186 r = dns_packet_append_blob(p, rr->generic.data, rr->generic.data_size, NULL);
1187 break;
1188 }
1189 if (r < 0)
1190 goto fail;
1191
1192 /* Let's calculate the actual data size and update the field */
1193 rdlength = p->size - rdlength_offset - sizeof(uint16_t);
1194 if (rdlength > 0xFFFF) {
1195 r = -ENOSPC;
1196 goto fail;
1197 }
1198
1199 end = p->size;
1200 p->size = rdlength_offset;
1201 r = dns_packet_append_uint16(p, rdlength, NULL);
1202 if (r < 0)
1203 goto fail;
1204 p->size = end;
1205
1206 if (start)
1207 *start = saved_size;
1208
1209 if (rdata_start)
1210 *rdata_start = rds;
1211
1212 return 0;
1213
1214 fail:
1215 dns_packet_truncate(p, saved_size);
1216 return r;
1217 }
1218
1219 int dns_packet_append_question(DnsPacket *p, DnsQuestion *q) {
1220 DnsResourceKey *key;
1221 int r;
1222
1223 assert(p);
1224
1225 DNS_QUESTION_FOREACH(key, q) {
1226 r = dns_packet_append_key(p, key, 0, NULL);
1227 if (r < 0)
1228 return r;
1229 }
1230
1231 return 0;
1232 }
1233
1234 int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a, unsigned *completed) {
1235 DnsResourceRecord *rr;
1236 DnsAnswerFlags flags;
1237 int r;
1238
1239 assert(p);
1240
1241 DNS_ANSWER_FOREACH_FLAGS(rr, flags, a) {
1242 r = dns_packet_append_rr(p, rr, flags, NULL, NULL);
1243 if (r < 0)
1244 return r;
1245
1246 if (completed)
1247 (*completed)++;
1248 }
1249
1250 return 0;
1251 }
1252
1253 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) {
1254 assert(p);
1255 assert(p->rindex <= p->size);
1256
1257 if (sz > p->size - p->rindex)
1258 return -EMSGSIZE;
1259
1260 if (ret)
1261 *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->rindex;
1262
1263 if (start)
1264 *start = p->rindex;
1265
1266 p->rindex += sz;
1267 return 0;
1268 }
1269
1270 void dns_packet_rewind(DnsPacket *p, size_t idx) {
1271 assert(p);
1272 assert(idx <= p->size);
1273 assert(idx >= DNS_PACKET_HEADER_SIZE);
1274
1275 p->rindex = idx;
1276 }
1277
1278 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start) {
1279 const void *q;
1280 int r;
1281
1282 assert(p);
1283 assert(d);
1284
1285 r = dns_packet_read(p, sz, &q, start);
1286 if (r < 0)
1287 return r;
1288
1289 memcpy(d, q, sz);
1290 return 0;
1291 }
1292
1293 static int dns_packet_read_memdup(
1294 DnsPacket *p, size_t size,
1295 void **ret, size_t *ret_size,
1296 size_t *ret_start) {
1297
1298 const void *src;
1299 size_t start;
1300 int r;
1301
1302 assert(p);
1303 assert(ret);
1304
1305 r = dns_packet_read(p, size, &src, &start);
1306 if (r < 0)
1307 return r;
1308
1309 if (size <= 0)
1310 *ret = NULL;
1311 else {
1312 void *copy;
1313
1314 copy = memdup(src, size);
1315 if (!copy)
1316 return -ENOMEM;
1317
1318 *ret = copy;
1319 }
1320
1321 if (ret_size)
1322 *ret_size = size;
1323 if (ret_start)
1324 *ret_start = start;
1325
1326 return 0;
1327 }
1328
1329 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start) {
1330 const void *d;
1331 int r;
1332
1333 assert(p);
1334
1335 r = dns_packet_read(p, sizeof(uint8_t), &d, start);
1336 if (r < 0)
1337 return r;
1338
1339 *ret = ((uint8_t*) d)[0];
1340 return 0;
1341 }
1342
1343 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start) {
1344 const void *d;
1345 int r;
1346
1347 assert(p);
1348
1349 r = dns_packet_read(p, sizeof(uint16_t), &d, start);
1350 if (r < 0)
1351 return r;
1352
1353 if (ret)
1354 *ret = unaligned_read_be16(d);
1355
1356 return 0;
1357 }
1358
1359 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start) {
1360 const void *d;
1361 int r;
1362
1363 assert(p);
1364
1365 r = dns_packet_read(p, sizeof(uint32_t), &d, start);
1366 if (r < 0)
1367 return r;
1368
1369 *ret = unaligned_read_be32(d);
1370
1371 return 0;
1372 }
1373
1374 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start) {
1375 assert(p);
1376
1377 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1378 const void *d;
1379 char *t;
1380 uint8_t c;
1381 int r;
1382
1383 r = dns_packet_read_uint8(p, &c, NULL);
1384 if (r < 0)
1385 return r;
1386
1387 r = dns_packet_read(p, c, &d, NULL);
1388 if (r < 0)
1389 return r;
1390
1391 if (memchr(d, 0, c))
1392 return -EBADMSG;
1393
1394 t = memdup_suffix0(d, c);
1395 if (!t)
1396 return -ENOMEM;
1397
1398 if (!utf8_is_valid(t)) {
1399 free(t);
1400 return -EBADMSG;
1401 }
1402
1403 *ret = t;
1404
1405 if (start)
1406 *start = rewinder.saved_rindex;
1407 CANCEL_REWINDER(rewinder);
1408
1409 return 0;
1410 }
1411
1412 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start) {
1413 assert(p);
1414
1415 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1416 uint8_t c;
1417 int r;
1418
1419 r = dns_packet_read_uint8(p, &c, NULL);
1420 if (r < 0)
1421 return r;
1422
1423 r = dns_packet_read(p, c, ret, NULL);
1424 if (r < 0)
1425 return r;
1426
1427 if (size)
1428 *size = c;
1429 if (start)
1430 *start = rewinder.saved_rindex;
1431 CANCEL_REWINDER(rewinder);
1432
1433 return 0;
1434 }
1435
1436 int dns_packet_read_name(
1437 DnsPacket *p,
1438 char **ret,
1439 bool allow_compression,
1440 size_t *ret_start) {
1441
1442 assert(p);
1443
1444 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1445 size_t after_rindex = 0, jump_barrier = p->rindex;
1446 _cleanup_free_ char *name = NULL;
1447 bool first = true;
1448 size_t n = 0;
1449 int r;
1450
1451 if (p->refuse_compression)
1452 allow_compression = false;
1453
1454 for (;;) {
1455 uint8_t c, d;
1456
1457 r = dns_packet_read_uint8(p, &c, NULL);
1458 if (r < 0)
1459 return r;
1460
1461 if (c == 0)
1462 /* End of name */
1463 break;
1464 else if (c <= 63) {
1465 const char *label;
1466
1467 /* Literal label */
1468 r = dns_packet_read(p, c, (const void**) &label, NULL);
1469 if (r < 0)
1470 return r;
1471
1472 if (!GREEDY_REALLOC(name, n + !first + DNS_LABEL_ESCAPED_MAX))
1473 return -ENOMEM;
1474
1475 if (first)
1476 first = false;
1477 else
1478 name[n++] = '.';
1479
1480 r = dns_label_escape(label, c, name + n, DNS_LABEL_ESCAPED_MAX);
1481 if (r < 0)
1482 return r;
1483
1484 n += r;
1485 continue;
1486 } else if (allow_compression && FLAGS_SET(c, 0xc0)) {
1487 uint16_t ptr;
1488
1489 /* Pointer */
1490 r = dns_packet_read_uint8(p, &d, NULL);
1491 if (r < 0)
1492 return r;
1493
1494 ptr = (uint16_t) (c & ~0xc0) << 8 | (uint16_t) d;
1495 if (ptr < DNS_PACKET_HEADER_SIZE || ptr >= jump_barrier)
1496 return -EBADMSG;
1497
1498 if (after_rindex == 0)
1499 after_rindex = p->rindex;
1500
1501 /* Jumps are limited to a "prior occurrence" (RFC-1035 4.1.4) */
1502 jump_barrier = ptr;
1503 p->rindex = ptr;
1504 } else
1505 return -EBADMSG;
1506 }
1507
1508 if (!GREEDY_REALLOC(name, n + 1))
1509 return -ENOMEM;
1510
1511 name[n] = 0;
1512
1513 if (after_rindex != 0)
1514 p->rindex= after_rindex;
1515
1516 if (ret)
1517 *ret = TAKE_PTR(name);
1518 if (ret_start)
1519 *ret_start = rewinder.saved_rindex;
1520
1521 CANCEL_REWINDER(rewinder);
1522
1523 return 0;
1524 }
1525
1526 static int dns_packet_read_type_window(DnsPacket *p, Bitmap **types, size_t *start) {
1527 assert(p);
1528 assert(types);
1529
1530 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1531 uint8_t window, length;
1532 const uint8_t *bitmap;
1533 uint8_t bit = 0;
1534 bool found = false;
1535 int r;
1536
1537 r = bitmap_ensure_allocated(types);
1538 if (r < 0)
1539 return r;
1540
1541 r = dns_packet_read_uint8(p, &window, NULL);
1542 if (r < 0)
1543 return r;
1544
1545 r = dns_packet_read_uint8(p, &length, NULL);
1546 if (r < 0)
1547 return r;
1548
1549 if (length == 0 || length > 32)
1550 return -EBADMSG;
1551
1552 r = dns_packet_read(p, length, (const void **)&bitmap, NULL);
1553 if (r < 0)
1554 return r;
1555
1556 for (uint8_t i = 0; i < length; i++) {
1557 uint8_t bitmask = 1 << 7;
1558
1559 if (!bitmap[i]) {
1560 found = false;
1561 bit += 8;
1562 continue;
1563 }
1564
1565 found = true;
1566
1567 for (; bitmask; bit++, bitmask >>= 1)
1568 if (bitmap[i] & bitmask) {
1569 uint16_t n;
1570
1571 n = (uint16_t) window << 8 | (uint16_t) bit;
1572
1573 /* Ignore pseudo-types. see RFC4034 section 4.1.2 */
1574 if (dns_type_is_pseudo(n))
1575 continue;
1576
1577 r = bitmap_set(*types, n);
1578 if (r < 0)
1579 return r;
1580 }
1581 }
1582
1583 if (!found)
1584 return -EBADMSG;
1585
1586 if (start)
1587 *start = rewinder.saved_rindex;
1588 CANCEL_REWINDER(rewinder);
1589
1590 return 0;
1591 }
1592
1593 static int dns_packet_read_type_windows(DnsPacket *p, Bitmap **types, size_t size, size_t *start) {
1594 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1595 int r;
1596
1597 while (p->rindex - rewinder.saved_rindex < size) {
1598 r = dns_packet_read_type_window(p, types, NULL);
1599 if (r < 0)
1600 return r;
1601
1602 assert(p->rindex >= rewinder.saved_rindex);
1603
1604 /* don't read past end of current RR */
1605 if (p->rindex - rewinder.saved_rindex > size)
1606 return -EBADMSG;
1607 }
1608
1609 if (p->rindex - rewinder.saved_rindex != size)
1610 return -EBADMSG;
1611
1612 if (start)
1613 *start = rewinder.saved_rindex;
1614 CANCEL_REWINDER(rewinder);
1615
1616 return 0;
1617 }
1618
1619 int dns_packet_read_key(
1620 DnsPacket *p,
1621 DnsResourceKey **ret,
1622 bool *ret_cache_flush_or_qu,
1623 size_t *ret_start) {
1624
1625 assert(p);
1626
1627 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1628 _cleanup_free_ char *name = NULL;
1629 bool cache_flush_or_qu = false;
1630 uint16_t class, type;
1631 int r;
1632
1633 r = dns_packet_read_name(p, &name, true, NULL);
1634 if (r < 0)
1635 return r;
1636
1637 r = dns_packet_read_uint16(p, &type, NULL);
1638 if (r < 0)
1639 return r;
1640
1641 r = dns_packet_read_uint16(p, &class, NULL);
1642 if (r < 0)
1643 return r;
1644
1645 if (p->protocol == DNS_PROTOCOL_MDNS) {
1646 /* See RFC6762, sections 5.4 and 10.2 */
1647
1648 if (type != DNS_TYPE_OPT && (class & MDNS_RR_CACHE_FLUSH_OR_QU)) {
1649 class &= ~MDNS_RR_CACHE_FLUSH_OR_QU;
1650 cache_flush_or_qu = true;
1651 }
1652 }
1653
1654 if (ret) {
1655 DnsResourceKey *key;
1656
1657 key = dns_resource_key_new_consume(class, type, name);
1658 if (!key)
1659 return -ENOMEM;
1660
1661 TAKE_PTR(name);
1662 *ret = key;
1663 }
1664
1665 if (ret_cache_flush_or_qu)
1666 *ret_cache_flush_or_qu = cache_flush_or_qu;
1667 if (ret_start)
1668 *ret_start = rewinder.saved_rindex;
1669
1670 CANCEL_REWINDER(rewinder);
1671 return 0;
1672 }
1673
1674 static bool loc_size_ok(uint8_t size) {
1675 uint8_t m = size >> 4, e = size & 0xF;
1676
1677 return m <= 9 && e <= 9 && (m > 0 || e == 0);
1678 }
1679
1680 int dns_packet_read_rr(
1681 DnsPacket *p,
1682 DnsResourceRecord **ret,
1683 bool *ret_cache_flush,
1684 size_t *ret_start) {
1685
1686 assert(p);
1687
1688 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1689 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
1690 _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
1691 size_t offset;
1692 uint16_t rdlength;
1693 bool cache_flush;
1694 int r;
1695
1696 r = dns_packet_read_key(p, &key, &cache_flush, NULL);
1697 if (r < 0)
1698 return r;
1699
1700 if (!dns_class_is_valid_rr(key->class) || !dns_type_is_valid_rr(key->type))
1701 return -EBADMSG;
1702
1703 rr = dns_resource_record_new(key);
1704 if (!rr)
1705 return -ENOMEM;
1706
1707 r = dns_packet_read_uint32(p, &rr->ttl, NULL);
1708 if (r < 0)
1709 return r;
1710
1711 /* RFC 2181, Section 8, suggests to
1712 * treat a TTL with the MSB set as a zero TTL. */
1713 if (rr->ttl & UINT32_C(0x80000000))
1714 rr->ttl = 0;
1715
1716 r = dns_packet_read_uint16(p, &rdlength, NULL);
1717 if (r < 0)
1718 return r;
1719
1720 if (rdlength > p->size - p->rindex)
1721 return -EBADMSG;
1722
1723 offset = p->rindex;
1724
1725 switch (rr->key->type) {
1726
1727 case DNS_TYPE_SRV:
1728 r = dns_packet_read_uint16(p, &rr->srv.priority, NULL);
1729 if (r < 0)
1730 return r;
1731 r = dns_packet_read_uint16(p, &rr->srv.weight, NULL);
1732 if (r < 0)
1733 return r;
1734 r = dns_packet_read_uint16(p, &rr->srv.port, NULL);
1735 if (r < 0)
1736 return r;
1737 r = dns_packet_read_name(p, &rr->srv.name, true, NULL);
1738 break;
1739
1740 case DNS_TYPE_PTR:
1741 case DNS_TYPE_NS:
1742 case DNS_TYPE_CNAME:
1743 case DNS_TYPE_DNAME:
1744 r = dns_packet_read_name(p, &rr->ptr.name, true, NULL);
1745 break;
1746
1747 case DNS_TYPE_HINFO:
1748 r = dns_packet_read_string(p, &rr->hinfo.cpu, NULL);
1749 if (r < 0)
1750 return r;
1751
1752 r = dns_packet_read_string(p, &rr->hinfo.os, NULL);
1753 break;
1754
1755 case DNS_TYPE_SPF: /* exactly the same as TXT */
1756 case DNS_TYPE_TXT:
1757 if (rdlength <= 0) {
1758 r = dns_txt_item_new_empty(&rr->txt.items);
1759 if (r < 0)
1760 return r;
1761 } else {
1762 DnsTxtItem *last = NULL;
1763
1764 while (p->rindex - offset < rdlength) {
1765 DnsTxtItem *i;
1766 const void *data;
1767 size_t sz;
1768
1769 r = dns_packet_read_raw_string(p, &data, &sz, NULL);
1770 if (r < 0)
1771 return r;
1772
1773 i = malloc0(offsetof(DnsTxtItem, data) + sz + 1); /* extra NUL byte at the end */
1774 if (!i)
1775 return -ENOMEM;
1776
1777 memcpy(i->data, data, sz);
1778 i->length = sz;
1779
1780 LIST_INSERT_AFTER(items, rr->txt.items, last, i);
1781 last = i;
1782 }
1783 }
1784
1785 r = 0;
1786 break;
1787
1788 case DNS_TYPE_A:
1789 r = dns_packet_read_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
1790 break;
1791
1792 case DNS_TYPE_AAAA:
1793 r = dns_packet_read_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
1794 break;
1795
1796 case DNS_TYPE_SOA:
1797 r = dns_packet_read_name(p, &rr->soa.mname, true, NULL);
1798 if (r < 0)
1799 return r;
1800
1801 r = dns_packet_read_name(p, &rr->soa.rname, true, NULL);
1802 if (r < 0)
1803 return r;
1804
1805 r = dns_packet_read_uint32(p, &rr->soa.serial, NULL);
1806 if (r < 0)
1807 return r;
1808
1809 r = dns_packet_read_uint32(p, &rr->soa.refresh, NULL);
1810 if (r < 0)
1811 return r;
1812
1813 r = dns_packet_read_uint32(p, &rr->soa.retry, NULL);
1814 if (r < 0)
1815 return r;
1816
1817 r = dns_packet_read_uint32(p, &rr->soa.expire, NULL);
1818 if (r < 0)
1819 return r;
1820
1821 r = dns_packet_read_uint32(p, &rr->soa.minimum, NULL);
1822 break;
1823
1824 case DNS_TYPE_MX:
1825 r = dns_packet_read_uint16(p, &rr->mx.priority, NULL);
1826 if (r < 0)
1827 return r;
1828
1829 r = dns_packet_read_name(p, &rr->mx.exchange, true, NULL);
1830 break;
1831
1832 case DNS_TYPE_LOC: {
1833 uint8_t t;
1834 size_t pos;
1835
1836 r = dns_packet_read_uint8(p, &t, &pos);
1837 if (r < 0)
1838 return r;
1839
1840 if (t == 0) {
1841 rr->loc.version = t;
1842
1843 r = dns_packet_read_uint8(p, &rr->loc.size, NULL);
1844 if (r < 0)
1845 return r;
1846
1847 if (!loc_size_ok(rr->loc.size))
1848 return -EBADMSG;
1849
1850 r = dns_packet_read_uint8(p, &rr->loc.horiz_pre, NULL);
1851 if (r < 0)
1852 return r;
1853
1854 if (!loc_size_ok(rr->loc.horiz_pre))
1855 return -EBADMSG;
1856
1857 r = dns_packet_read_uint8(p, &rr->loc.vert_pre, NULL);
1858 if (r < 0)
1859 return r;
1860
1861 if (!loc_size_ok(rr->loc.vert_pre))
1862 return -EBADMSG;
1863
1864 r = dns_packet_read_uint32(p, &rr->loc.latitude, NULL);
1865 if (r < 0)
1866 return r;
1867
1868 r = dns_packet_read_uint32(p, &rr->loc.longitude, NULL);
1869 if (r < 0)
1870 return r;
1871
1872 r = dns_packet_read_uint32(p, &rr->loc.altitude, NULL);
1873 if (r < 0)
1874 return r;
1875
1876 break;
1877 } else {
1878 dns_packet_rewind(p, pos);
1879 rr->unparsable = true;
1880 goto unparsable;
1881 }
1882 }
1883
1884 case DNS_TYPE_DS:
1885 r = dns_packet_read_uint16(p, &rr->ds.key_tag, NULL);
1886 if (r < 0)
1887 return r;
1888
1889 r = dns_packet_read_uint8(p, &rr->ds.algorithm, NULL);
1890 if (r < 0)
1891 return r;
1892
1893 r = dns_packet_read_uint8(p, &rr->ds.digest_type, NULL);
1894 if (r < 0)
1895 return r;
1896
1897 if (rdlength < 4)
1898 return -EBADMSG;
1899
1900 r = dns_packet_read_memdup(p, rdlength - 4,
1901 &rr->ds.digest, &rr->ds.digest_size,
1902 NULL);
1903 if (r < 0)
1904 return r;
1905
1906 if (rr->ds.digest_size <= 0)
1907 /* the accepted size depends on the algorithm, but for now
1908 just ensure that the value is greater than zero */
1909 return -EBADMSG;
1910
1911 break;
1912
1913 case DNS_TYPE_SSHFP:
1914 r = dns_packet_read_uint8(p, &rr->sshfp.algorithm, NULL);
1915 if (r < 0)
1916 return r;
1917
1918 r = dns_packet_read_uint8(p, &rr->sshfp.fptype, NULL);
1919 if (r < 0)
1920 return r;
1921
1922 if (rdlength < 2)
1923 return -EBADMSG;
1924
1925 r = dns_packet_read_memdup(p, rdlength - 2,
1926 &rr->sshfp.fingerprint, &rr->sshfp.fingerprint_size,
1927 NULL);
1928
1929 if (rr->sshfp.fingerprint_size <= 0)
1930 /* the accepted size depends on the algorithm, but for now
1931 just ensure that the value is greater than zero */
1932 return -EBADMSG;
1933
1934 break;
1935
1936 case DNS_TYPE_DNSKEY:
1937 r = dns_packet_read_uint16(p, &rr->dnskey.flags, NULL);
1938 if (r < 0)
1939 return r;
1940
1941 r = dns_packet_read_uint8(p, &rr->dnskey.protocol, NULL);
1942 if (r < 0)
1943 return r;
1944
1945 r = dns_packet_read_uint8(p, &rr->dnskey.algorithm, NULL);
1946 if (r < 0)
1947 return r;
1948
1949 if (rdlength < 4)
1950 return -EBADMSG;
1951
1952 r = dns_packet_read_memdup(p, rdlength - 4,
1953 &rr->dnskey.key, &rr->dnskey.key_size,
1954 NULL);
1955
1956 if (rr->dnskey.key_size <= 0)
1957 /* the accepted size depends on the algorithm, but for now
1958 just ensure that the value is greater than zero */
1959 return -EBADMSG;
1960
1961 break;
1962
1963 case DNS_TYPE_RRSIG:
1964 r = dns_packet_read_uint16(p, &rr->rrsig.type_covered, NULL);
1965 if (r < 0)
1966 return r;
1967
1968 r = dns_packet_read_uint8(p, &rr->rrsig.algorithm, NULL);
1969 if (r < 0)
1970 return r;
1971
1972 r = dns_packet_read_uint8(p, &rr->rrsig.labels, NULL);
1973 if (r < 0)
1974 return r;
1975
1976 r = dns_packet_read_uint32(p, &rr->rrsig.original_ttl, NULL);
1977 if (r < 0)
1978 return r;
1979
1980 r = dns_packet_read_uint32(p, &rr->rrsig.expiration, NULL);
1981 if (r < 0)
1982 return r;
1983
1984 r = dns_packet_read_uint32(p, &rr->rrsig.inception, NULL);
1985 if (r < 0)
1986 return r;
1987
1988 r = dns_packet_read_uint16(p, &rr->rrsig.key_tag, NULL);
1989 if (r < 0)
1990 return r;
1991
1992 r = dns_packet_read_name(p, &rr->rrsig.signer, false, NULL);
1993 if (r < 0)
1994 return r;
1995
1996 if (rdlength < p->rindex - offset)
1997 return -EBADMSG;
1998
1999 r = dns_packet_read_memdup(p, offset + rdlength - p->rindex,
2000 &rr->rrsig.signature, &rr->rrsig.signature_size,
2001 NULL);
2002
2003 if (rr->rrsig.signature_size <= 0)
2004 /* the accepted size depends on the algorithm, but for now
2005 just ensure that the value is greater than zero */
2006 return -EBADMSG;
2007
2008 break;
2009
2010 case DNS_TYPE_NSEC: {
2011
2012 /*
2013 * RFC6762, section 18.14 explicitly states mDNS should use name compression.
2014 * This contradicts RFC3845, section 2.1.1
2015 */
2016
2017 bool allow_compressed = p->protocol == DNS_PROTOCOL_MDNS;
2018
2019 r = dns_packet_read_name(p, &rr->nsec.next_domain_name, allow_compressed, NULL);
2020 if (r < 0)
2021 return r;
2022
2023 if (rdlength < p->rindex - offset)
2024 return -EBADMSG;
2025
2026 r = dns_packet_read_type_windows(p, &rr->nsec.types, offset + rdlength - p->rindex, NULL);
2027
2028 /* We accept empty NSEC bitmaps. The bit indicating the presence of the NSEC record itself
2029 * is redundant and in e.g., RFC4956 this fact is used to define a use for NSEC records
2030 * without the NSEC bit set. */
2031
2032 break;
2033 }
2034 case DNS_TYPE_NSEC3: {
2035 uint8_t size;
2036
2037 r = dns_packet_read_uint8(p, &rr->nsec3.algorithm, NULL);
2038 if (r < 0)
2039 return r;
2040
2041 r = dns_packet_read_uint8(p, &rr->nsec3.flags, NULL);
2042 if (r < 0)
2043 return r;
2044
2045 r = dns_packet_read_uint16(p, &rr->nsec3.iterations, NULL);
2046 if (r < 0)
2047 return r;
2048
2049 /* this may be zero */
2050 r = dns_packet_read_uint8(p, &size, NULL);
2051 if (r < 0)
2052 return r;
2053
2054 r = dns_packet_read_memdup(p, size, &rr->nsec3.salt, &rr->nsec3.salt_size, NULL);
2055 if (r < 0)
2056 return r;
2057
2058 r = dns_packet_read_uint8(p, &size, NULL);
2059 if (r < 0)
2060 return r;
2061
2062 if (size <= 0)
2063 return -EBADMSG;
2064
2065 r = dns_packet_read_memdup(p, size,
2066 &rr->nsec3.next_hashed_name, &rr->nsec3.next_hashed_name_size,
2067 NULL);
2068 if (r < 0)
2069 return r;
2070
2071 if (rdlength < p->rindex - offset)
2072 return -EBADMSG;
2073
2074 r = dns_packet_read_type_windows(p, &rr->nsec3.types, offset + rdlength - p->rindex, NULL);
2075
2076 /* empty non-terminals can have NSEC3 records, so empty bitmaps are allowed */
2077
2078 break;
2079 }
2080
2081 case DNS_TYPE_TLSA:
2082 r = dns_packet_read_uint8(p, &rr->tlsa.cert_usage, NULL);
2083 if (r < 0)
2084 return r;
2085
2086 r = dns_packet_read_uint8(p, &rr->tlsa.selector, NULL);
2087 if (r < 0)
2088 return r;
2089
2090 r = dns_packet_read_uint8(p, &rr->tlsa.matching_type, NULL);
2091 if (r < 0)
2092 return r;
2093
2094 if (rdlength < 3)
2095 return -EBADMSG;
2096
2097 r = dns_packet_read_memdup(p, rdlength - 3,
2098 &rr->tlsa.data, &rr->tlsa.data_size,
2099 NULL);
2100
2101 if (rr->tlsa.data_size <= 0)
2102 /* the accepted size depends on the algorithm, but for now
2103 just ensure that the value is greater than zero */
2104 return -EBADMSG;
2105
2106 break;
2107
2108 case DNS_TYPE_CAA:
2109 r = dns_packet_read_uint8(p, &rr->caa.flags, NULL);
2110 if (r < 0)
2111 return r;
2112
2113 r = dns_packet_read_string(p, &rr->caa.tag, NULL);
2114 if (r < 0)
2115 return r;
2116
2117 if (rdlength < p->rindex - offset)
2118 return -EBADMSG;
2119
2120 r = dns_packet_read_memdup(p,
2121 rdlength + offset - p->rindex,
2122 &rr->caa.value, &rr->caa.value_size, NULL);
2123
2124 break;
2125
2126 case DNS_TYPE_OPT: /* we only care about the header of OPT for now. */
2127 case DNS_TYPE_OPENPGPKEY:
2128 default:
2129 unparsable:
2130 r = dns_packet_read_memdup(p, rdlength, &rr->generic.data, &rr->generic.data_size, NULL);
2131
2132 break;
2133 }
2134 if (r < 0)
2135 return r;
2136 if (p->rindex - offset != rdlength)
2137 return -EBADMSG;
2138
2139 if (ret)
2140 *ret = TAKE_PTR(rr);
2141 if (ret_cache_flush)
2142 *ret_cache_flush = cache_flush;
2143 if (ret_start)
2144 *ret_start = rewinder.saved_rindex;
2145
2146 CANCEL_REWINDER(rewinder);
2147 return 0;
2148 }
2149
2150 static bool opt_is_good(DnsResourceRecord *rr, bool *rfc6975) {
2151 const uint8_t* p;
2152 bool found_dau_dhu_n3u = false;
2153 size_t l;
2154
2155 /* Checks whether the specified OPT RR is well-formed and whether it contains RFC6975 data (which is not OK in
2156 * a reply). */
2157
2158 assert(rr);
2159 assert(rr->key->type == DNS_TYPE_OPT);
2160
2161 /* Check that the version is 0 */
2162 if (((rr->ttl >> 16) & UINT32_C(0xFF)) != 0) {
2163 *rfc6975 = false;
2164 return true; /* if it's not version 0, it's OK, but we will ignore the OPT field contents */
2165 }
2166
2167 p = rr->opt.data;
2168 l = rr->opt.data_size;
2169 while (l > 0) {
2170 uint16_t option_code, option_length;
2171
2172 /* At least four bytes for OPTION-CODE and OPTION-LENGTH are required */
2173 if (l < 4U)
2174 return false;
2175
2176 option_code = unaligned_read_be16(p);
2177 option_length = unaligned_read_be16(p + 2);
2178
2179 if (l < option_length + 4U)
2180 return false;
2181
2182 /* RFC 6975 DAU, DHU or N3U fields found. */
2183 if (IN_SET(option_code, 5, 6, 7))
2184 found_dau_dhu_n3u = true;
2185
2186 p += option_length + 4U;
2187 l -= option_length + 4U;
2188 }
2189
2190 *rfc6975 = found_dau_dhu_n3u;
2191 return true;
2192 }
2193
2194 static int dns_packet_extract_question(DnsPacket *p, DnsQuestion **ret_question) {
2195 _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
2196 unsigned n;
2197 int r;
2198
2199 n = DNS_PACKET_QDCOUNT(p);
2200 if (n > 0) {
2201 question = dns_question_new(n);
2202 if (!question)
2203 return -ENOMEM;
2204
2205 _cleanup_set_free_ Set *keys = NULL; /* references to keys are kept by Question */
2206
2207 keys = set_new(&dns_resource_key_hash_ops);
2208 if (!keys)
2209 return log_oom();
2210
2211 r = set_reserve(keys, n * 2); /* Higher multipliers give slightly higher efficiency through
2212 * hash collisions, but the gains quickly drop off after 2. */
2213 if (r < 0)
2214 return r;
2215
2216 for (unsigned i = 0; i < n; i++) {
2217 _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
2218 bool qu;
2219
2220 r = dns_packet_read_key(p, &key, &qu, NULL);
2221 if (r < 0)
2222 return r;
2223
2224 if (!dns_type_is_valid_query(key->type))
2225 return -EBADMSG;
2226
2227 r = set_put(keys, key);
2228 if (r < 0)
2229 return r;
2230 if (r == 0)
2231 /* Already in the Question, let's skip */
2232 continue;
2233
2234 r = dns_question_add_raw(question, key, qu ? DNS_QUESTION_WANTS_UNICAST_REPLY : 0);
2235 if (r < 0)
2236 return r;
2237 }
2238 }
2239
2240 *ret_question = TAKE_PTR(question);
2241
2242 return 0;
2243 }
2244
2245 static int dns_packet_extract_answer(DnsPacket *p, DnsAnswer **ret_answer) {
2246 _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
2247 unsigned n;
2248 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *previous = NULL;
2249 bool bad_opt = false;
2250 int r;
2251
2252 n = DNS_PACKET_RRCOUNT(p);
2253 if (n == 0)
2254 return 0;
2255
2256 answer = dns_answer_new(n);
2257 if (!answer)
2258 return -ENOMEM;
2259
2260 for (unsigned i = 0; i < n; i++) {
2261 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
2262 bool cache_flush = false;
2263 size_t start;
2264
2265 if (p->rindex == p->size && p->opt) {
2266 /* If we reached the end of the packet already, but there are still more RRs
2267 * declared, then that's a corrupt packet. Let's accept the packet anyway, since it's
2268 * apparently a common bug in routers. Let's however suppress OPT support in this
2269 * case, so that we force the rest of the logic into lowest DNS baseline support. Or
2270 * to say this differently: if the DNS server doesn't even get the RR counts right,
2271 * it's highly unlikely it gets EDNS right. */
2272 log_debug("More resource records declared in packet than included, suppressing OPT.");
2273 bad_opt = true;
2274 break;
2275 }
2276
2277 r = dns_packet_read_rr(p, &rr, &cache_flush, &start);
2278 if (r < 0)
2279 return r;
2280
2281 /* Try to reduce memory usage a bit */
2282 if (previous)
2283 dns_resource_key_reduce(&rr->key, &previous->key);
2284
2285 if (rr->key->type == DNS_TYPE_OPT) {
2286 bool has_rfc6975;
2287
2288 if (p->opt || bad_opt) {
2289 /* Multiple OPT RRs? if so, let's ignore all, because there's
2290 * something wrong with the server, and if one is valid we wouldn't
2291 * know which one. */
2292 log_debug("Multiple OPT RRs detected, ignoring all.");
2293 bad_opt = true;
2294 continue;
2295 }
2296
2297 if (!dns_name_is_root(dns_resource_key_name(rr->key))) {
2298 /* If the OPT RR is not owned by the root domain, then it is bad,
2299 * let's ignore it. */
2300 log_debug("OPT RR is not owned by root domain, ignoring.");
2301 bad_opt = true;
2302 continue;
2303 }
2304
2305 if (i < DNS_PACKET_ANCOUNT(p) + DNS_PACKET_NSCOUNT(p)) {
2306 /* OPT RR is in the wrong section? Some Belkin routers do this. This
2307 * is a hint the EDNS implementation is borked, like the Belkin one
2308 * is, hence ignore it. */
2309 log_debug("OPT RR in wrong section, ignoring.");
2310 bad_opt = true;
2311 continue;
2312 }
2313
2314 if (!opt_is_good(rr, &has_rfc6975)) {
2315 log_debug("Malformed OPT RR, ignoring.");
2316 bad_opt = true;
2317 continue;
2318 }
2319
2320 if (DNS_PACKET_QR(p)) {
2321 /* Additional checks for responses */
2322
2323 if (!DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(rr))
2324 /* If this is a reply and we don't know the EDNS version
2325 * then something is weird... */
2326 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
2327 "EDNS version newer that our request, bad server.");
2328
2329 if (has_rfc6975) {
2330 /* If the OPT RR contains RFC6975 algorithm data, then this
2331 * is indication that the server just copied the OPT it got
2332 * from us (which contained that data) back into the reply.
2333 * If so, then it doesn't properly support EDNS, as RFC6975
2334 * makes it very clear that the algorithm data should only
2335 * be contained in questions, never in replies. Crappy
2336 * Belkin routers copy the OPT data for example, hence let's
2337 * detect this so that we downgrade early. */
2338 log_debug("OPT RR contains RFC6975 data, ignoring.");
2339 bad_opt = true;
2340 continue;
2341 }
2342 }
2343
2344 p->opt = dns_resource_record_ref(rr);
2345 p->opt_start = start;
2346 assert(p->rindex >= start);
2347 p->opt_size = p->rindex - start;
2348 } else {
2349 DnsAnswerFlags flags = 0;
2350
2351 if (p->protocol == DNS_PROTOCOL_MDNS && !cache_flush)
2352 flags |= DNS_ANSWER_SHARED_OWNER;
2353
2354 /* According to RFC 4795, section 2.9. only the RRs from the Answer section shall be
2355 * cached. Hence mark only those RRs as cacheable by default, but not the ones from
2356 * the Additional or Authority sections.
2357 * This restriction does not apply to mDNS records (RFC 6762). */
2358 if (i < DNS_PACKET_ANCOUNT(p))
2359 flags |= DNS_ANSWER_CACHEABLE|DNS_ANSWER_SECTION_ANSWER;
2360 else if (i < DNS_PACKET_ANCOUNT(p) + DNS_PACKET_NSCOUNT(p))
2361 flags |= DNS_ANSWER_SECTION_AUTHORITY;
2362 else {
2363 flags |= DNS_ANSWER_SECTION_ADDITIONAL;
2364 if (p->protocol == DNS_PROTOCOL_MDNS)
2365 flags |= DNS_ANSWER_CACHEABLE;
2366 }
2367
2368 r = dns_answer_add(answer, rr, p->ifindex, flags, NULL);
2369 if (r < 0)
2370 return r;
2371 }
2372
2373 /* Remember this RR, so that we can potentially merge its ->key object with the
2374 * next RR. Note that we only do this if we actually decided to keep the RR around.
2375 */
2376 DNS_RR_REPLACE(previous, dns_resource_record_ref(rr));
2377 }
2378
2379 if (bad_opt) {
2380 p->opt = dns_resource_record_unref(p->opt);
2381 p->opt_start = p->opt_size = SIZE_MAX;
2382 }
2383
2384 *ret_answer = TAKE_PTR(answer);
2385
2386 return 0;
2387 }
2388
2389 int dns_packet_extract(DnsPacket *p) {
2390 assert(p);
2391
2392 if (p->extracted)
2393 return 0;
2394
2395 _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
2396 _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
2397 _unused_ _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
2398 int r;
2399
2400 dns_packet_rewind(p, DNS_PACKET_HEADER_SIZE);
2401
2402 r = dns_packet_extract_question(p, &question);
2403 if (r < 0)
2404 return r;
2405
2406 r = dns_packet_extract_answer(p, &answer);
2407 if (r < 0)
2408 return r;
2409
2410 if (p->rindex < p->size) {
2411 log_debug("Trailing garbage in packet, suppressing OPT.");
2412 p->opt = dns_resource_record_unref(p->opt);
2413 p->opt_start = p->opt_size = SIZE_MAX;
2414 }
2415
2416 p->question = TAKE_PTR(question);
2417 p->answer = TAKE_PTR(answer);
2418 p->extracted = true;
2419
2420 /* no CANCEL, always rewind */
2421 return 0;
2422 }
2423
2424 int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key) {
2425 int r;
2426
2427 assert(p);
2428 assert(key);
2429
2430 /* Checks if the specified packet is a reply for the specified
2431 * key and the specified key is the only one in the question
2432 * section. */
2433
2434 if (DNS_PACKET_QR(p) != 1)
2435 return 0;
2436
2437 /* Let's unpack the packet, if that hasn't happened yet. */
2438 r = dns_packet_extract(p);
2439 if (r < 0)
2440 return r;
2441
2442 if (!p->question)
2443 return 0;
2444
2445 if (p->question->n_keys != 1)
2446 return 0;
2447
2448 return dns_resource_key_equal(dns_question_first_key(p->question), key);
2449 }
2450
2451 int dns_packet_patch_max_udp_size(DnsPacket *p, uint16_t max_udp_size) {
2452 assert(p);
2453 assert(max_udp_size >= DNS_PACKET_UNICAST_SIZE_MAX);
2454
2455 if (p->opt_start == SIZE_MAX) /* No OPT section, nothing to patch */
2456 return 0;
2457
2458 assert(p->opt_size != SIZE_MAX);
2459 assert(p->opt_size >= 5);
2460
2461 unaligned_write_be16(DNS_PACKET_DATA(p) + p->opt_start + 3, max_udp_size);
2462 return 1;
2463 }
2464
2465 static int patch_rr(DnsPacket *p, usec_t age) {
2466 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
2467 size_t ttl_index;
2468 uint32_t ttl;
2469 uint16_t type, rdlength;
2470 int r;
2471
2472 /* Patches the RR at the current rindex, subtracts the specified time from the TTL */
2473
2474 r = dns_packet_read_name(p, NULL, true, NULL);
2475 if (r < 0)
2476 return r;
2477
2478 r = dns_packet_read_uint16(p, &type, NULL);
2479 if (r < 0)
2480 return r;
2481
2482 r = dns_packet_read_uint16(p, NULL, NULL);
2483 if (r < 0)
2484 return r;
2485
2486 r = dns_packet_read_uint32(p, &ttl, &ttl_index);
2487 if (r < 0)
2488 return r;
2489
2490 if (type != DNS_TYPE_OPT) { /* The TTL of the OPT field is not actually a TTL, skip it */
2491 ttl = LESS_BY(ttl * USEC_PER_SEC, age) / USEC_PER_SEC;
2492 unaligned_write_be32(DNS_PACKET_DATA(p) + ttl_index, ttl);
2493 }
2494
2495 r = dns_packet_read_uint16(p, &rdlength, NULL);
2496 if (r < 0)
2497 return r;
2498
2499 r = dns_packet_read(p, rdlength, NULL, NULL);
2500 if (r < 0)
2501 return r;
2502
2503 CANCEL_REWINDER(rewinder);
2504 return 0;
2505 }
2506
2507 int dns_packet_patch_ttls(DnsPacket *p, usec_t timestamp) {
2508 assert(p);
2509 assert(timestamp_is_set(timestamp));
2510
2511 /* Adjusts all TTLs in the packet by subtracting the time difference between now and the specified timestamp */
2512
2513 _unused_ _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
2514 unsigned n;
2515 usec_t k;
2516 int r;
2517
2518 k = now(CLOCK_BOOTTIME);
2519 assert(k >= timestamp);
2520 k -= timestamp;
2521
2522 dns_packet_rewind(p, DNS_PACKET_HEADER_SIZE);
2523
2524 n = DNS_PACKET_QDCOUNT(p);
2525 for (unsigned i = 0; i < n; i++) {
2526 r = dns_packet_read_key(p, NULL, NULL, NULL);
2527 if (r < 0)
2528 return r;
2529 }
2530
2531 n = DNS_PACKET_RRCOUNT(p);
2532 for (unsigned i = 0; i < n; i++) {
2533
2534 /* DNS servers suck, hence the RR count is in many servers off. If we reached the end
2535 * prematurely, accept that, exit early */
2536 if (p->rindex == p->size)
2537 break;
2538
2539 r = patch_rr(p, k);
2540 if (r < 0)
2541 return r;
2542 }
2543
2544 return 0;
2545 }
2546
2547 static void dns_packet_hash_func(const DnsPacket *s, struct siphash *state) {
2548 assert(s);
2549
2550 siphash24_compress(&s->size, sizeof(s->size), state);
2551 siphash24_compress(DNS_PACKET_DATA((DnsPacket*) s), s->size, state);
2552 }
2553
2554 static int dns_packet_compare_func(const DnsPacket *x, const DnsPacket *y) {
2555 int r;
2556
2557 r = CMP(x->size, y->size);
2558 if (r != 0)
2559 return r;
2560
2561 return memcmp(DNS_PACKET_DATA((DnsPacket*) x), DNS_PACKET_DATA((DnsPacket*) y), x->size);
2562 }
2563
2564 DEFINE_HASH_OPS(dns_packet_hash_ops, DnsPacket, dns_packet_hash_func, dns_packet_compare_func);
2565
2566 bool dns_packet_equal(const DnsPacket *a, const DnsPacket *b) {
2567 return dns_packet_compare_func(a, b) == 0;
2568 }
2569
2570 int dns_packet_has_nsid_request(DnsPacket *p) {
2571 bool has_nsid = false;
2572 const uint8_t *d;
2573 size_t l;
2574
2575 assert(p);
2576
2577 if (!p->opt)
2578 return false;
2579
2580 d = p->opt->opt.data;
2581 l = p->opt->opt.data_size;
2582
2583 while (l > 0) {
2584 uint16_t code, length;
2585
2586 if (l < 4U)
2587 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
2588 "EDNS0 variable part has invalid size.");
2589
2590 code = unaligned_read_be16(d);
2591 length = unaligned_read_be16(d + 2);
2592
2593 if (l < 4U + length)
2594 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
2595 "Truncated option in EDNS0 variable part.");
2596
2597 if (code == 3) {
2598 if (has_nsid)
2599 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
2600 "Duplicate NSID option in EDNS0 variable part.");
2601
2602 if (length != 0)
2603 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
2604 "Non-empty NSID option in DNS request.");
2605
2606 has_nsid = true;
2607 }
2608
2609 d += 4U + length;
2610 l -= 4U + length;
2611 }
2612
2613 return has_nsid;
2614 }
2615
2616 size_t dns_packet_size_unfragmented(DnsPacket *p) {
2617 assert(p);
2618
2619 if (p->fragsize == 0) /* Wasn't fragmented */
2620 return p->size;
2621
2622 /* The fragment size (p->fragsize) covers the whole (fragmented) IP packet, while the regular packet
2623 * size (p->size) only covers the DNS part. Thus, subtract the UDP header from the largest fragment
2624 * size, in order to determine which size of DNS packet would have gone through without
2625 * fragmenting. */
2626
2627 return LESS_BY(p->fragsize, udp_header_size(p->family));
2628 }
2629
2630 static const char* const dns_rcode_table[_DNS_RCODE_MAX_DEFINED] = {
2631 [DNS_RCODE_SUCCESS] = "SUCCESS",
2632 [DNS_RCODE_FORMERR] = "FORMERR",
2633 [DNS_RCODE_SERVFAIL] = "SERVFAIL",
2634 [DNS_RCODE_NXDOMAIN] = "NXDOMAIN",
2635 [DNS_RCODE_NOTIMP] = "NOTIMP",
2636 [DNS_RCODE_REFUSED] = "REFUSED",
2637 [DNS_RCODE_YXDOMAIN] = "YXDOMAIN",
2638 [DNS_RCODE_YXRRSET] = "YRRSET",
2639 [DNS_RCODE_NXRRSET] = "NXRRSET",
2640 [DNS_RCODE_NOTAUTH] = "NOTAUTH",
2641 [DNS_RCODE_NOTZONE] = "NOTZONE",
2642 [DNS_RCODE_BADVERS] = "BADVERS",
2643 [DNS_RCODE_BADKEY] = "BADKEY",
2644 [DNS_RCODE_BADTIME] = "BADTIME",
2645 [DNS_RCODE_BADMODE] = "BADMODE",
2646 [DNS_RCODE_BADNAME] = "BADNAME",
2647 [DNS_RCODE_BADALG] = "BADALG",
2648 [DNS_RCODE_BADTRUNC] = "BADTRUNC",
2649 [DNS_RCODE_BADCOOKIE] = "BADCOOKIE",
2650 };
2651 DEFINE_STRING_TABLE_LOOKUP(dns_rcode, int);
2652
2653 const char *format_dns_rcode(int i, char buf[static DECIMAL_STR_MAX(int)]) {
2654 const char *p = dns_rcode_to_string(i);
2655 if (p)
2656 return p;
2657
2658 return snprintf_ok(buf, DECIMAL_STR_MAX(int), "%i", i);
2659 }
2660
2661 static const char* const dns_protocol_table[_DNS_PROTOCOL_MAX] = {
2662 [DNS_PROTOCOL_DNS] = "dns",
2663 [DNS_PROTOCOL_MDNS] = "mdns",
2664 [DNS_PROTOCOL_LLMNR] = "llmnr",
2665 };
2666 DEFINE_STRING_TABLE_LOOKUP(dns_protocol, DnsProtocol);
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