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Merge pull request #21264 from medhefgo/boot-lto
[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 "string-table.h"
13 #include "strv.h"
14 #include "unaligned.h"
15 #include "utf8.h"
16 #include "util.h"
17
18 #define EDNS0_OPT_DO (1<<15)
19
20 assert_cc(DNS_PACKET_SIZE_START > DNS_PACKET_HEADER_SIZE);
21
22 typedef struct DnsPacketRewinder {
23 DnsPacket *packet;
24 size_t saved_rindex;
25 } DnsPacketRewinder;
26
27 static void rewind_dns_packet(DnsPacketRewinder *rewinder) {
28 if (rewinder->packet)
29 dns_packet_rewind(rewinder->packet, rewinder->saved_rindex);
30 }
31
32 #define REWINDER_INIT(p) { \
33 .packet = (p), \
34 .saved_rindex = (p)->rindex, \
35 }
36 #define CANCEL_REWINDER(rewinder) do { (rewinder).packet = NULL; } while (0)
37
38 int dns_packet_new(
39 DnsPacket **ret,
40 DnsProtocol protocol,
41 size_t min_alloc_dsize,
42 size_t max_size) {
43
44 DnsPacket *p;
45 size_t a;
46
47 assert(ret);
48 assert(max_size >= DNS_PACKET_HEADER_SIZE);
49
50 if (max_size > DNS_PACKET_SIZE_MAX)
51 max_size = DNS_PACKET_SIZE_MAX;
52
53 /* The caller may not check what is going to be truly allocated, so do not allow to
54 * allocate a DNS packet bigger than DNS_PACKET_SIZE_MAX.
55 */
56 if (min_alloc_dsize > DNS_PACKET_SIZE_MAX)
57 return log_error_errno(SYNTHETIC_ERRNO(EFBIG),
58 "Requested packet data size too big: %zu",
59 min_alloc_dsize);
60
61 /* When dns_packet_new() is called with min_alloc_dsize == 0, allocate more than the
62 * absolute minimum (which is the dns packet header size), to avoid
63 * resizing immediately again after appending the first data to the packet.
64 */
65 if (min_alloc_dsize < DNS_PACKET_HEADER_SIZE)
66 a = DNS_PACKET_SIZE_START;
67 else
68 a = min_alloc_dsize;
69
70 /* round up to next page size */
71 a = PAGE_ALIGN(ALIGN(sizeof(DnsPacket)) + a) - ALIGN(sizeof(DnsPacket));
72
73 /* make sure we never allocate more than useful */
74 if (a > max_size)
75 a = max_size;
76
77 p = malloc0(ALIGN(sizeof(DnsPacket)) + a);
78 if (!p)
79 return -ENOMEM;
80
81 *p = (DnsPacket) {
82 .n_ref = 1,
83 .protocol = protocol,
84 .size = DNS_PACKET_HEADER_SIZE,
85 .rindex = DNS_PACKET_HEADER_SIZE,
86 .allocated = a,
87 .max_size = max_size,
88 .opt_start = SIZE_MAX,
89 .opt_size = SIZE_MAX,
90 };
91
92 *ret = p;
93
94 return 0;
95 }
96
97 void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated) {
98
99 DnsPacketHeader *h;
100
101 assert(p);
102
103 h = DNS_PACKET_HEADER(p);
104
105 switch(p->protocol) {
106 case DNS_PROTOCOL_LLMNR:
107 assert(!truncated);
108
109 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
110 0 /* opcode */,
111 0 /* c */,
112 0 /* tc */,
113 0 /* t */,
114 0 /* ra */,
115 0 /* ad */,
116 0 /* cd */,
117 0 /* rcode */));
118 break;
119
120 case DNS_PROTOCOL_MDNS:
121 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
122 0 /* opcode */,
123 0 /* aa */,
124 truncated /* tc */,
125 0 /* rd (ask for recursion) */,
126 0 /* ra */,
127 0 /* ad */,
128 0 /* cd */,
129 0 /* rcode */));
130 break;
131
132 default:
133 assert(!truncated);
134
135 h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
136 0 /* opcode */,
137 0 /* aa */,
138 0 /* tc */,
139 1 /* rd (ask for recursion) */,
140 0 /* ra */,
141 0 /* ad */,
142 dnssec_checking_disabled /* cd */,
143 0 /* rcode */));
144 }
145 }
146
147 int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t min_alloc_dsize, bool dnssec_checking_disabled) {
148 DnsPacket *p;
149 int r;
150
151 assert(ret);
152
153 r = dns_packet_new(&p, protocol, min_alloc_dsize, DNS_PACKET_SIZE_MAX);
154 if (r < 0)
155 return r;
156
157 /* Always set the TC bit to 0 initially.
158 * If there are multiple packets later, we'll update the bit shortly before sending.
159 */
160 dns_packet_set_flags(p, dnssec_checking_disabled, false);
161
162 *ret = p;
163 return 0;
164 }
165
166 int dns_packet_dup(DnsPacket **ret, DnsPacket *p) {
167 DnsPacket *c;
168 int r;
169
170 assert(ret);
171 assert(p);
172
173 r = dns_packet_validate(p);
174 if (r < 0)
175 return r;
176
177 c = malloc(ALIGN(sizeof(DnsPacket)) + p->size);
178 if (!c)
179 return -ENOMEM;
180
181 *c = (DnsPacket) {
182 .n_ref = 1,
183 .protocol = p->protocol,
184 .size = p->size,
185 .rindex = DNS_PACKET_HEADER_SIZE,
186 .allocated = p->size,
187 .max_size = p->max_size,
188 .opt_start = SIZE_MAX,
189 .opt_size = SIZE_MAX,
190 };
191
192 memcpy(DNS_PACKET_DATA(c), DNS_PACKET_DATA(p), p->size);
193
194 *ret = c;
195 return 0;
196 }
197
198 DnsPacket *dns_packet_ref(DnsPacket *p) {
199
200 if (!p)
201 return NULL;
202
203 assert(!p->on_stack);
204
205 assert(p->n_ref > 0);
206 p->n_ref++;
207 return p;
208 }
209
210 static void dns_packet_free(DnsPacket *p) {
211 char *s;
212
213 assert(p);
214
215 dns_question_unref(p->question);
216 dns_answer_unref(p->answer);
217 dns_resource_record_unref(p->opt);
218
219 while ((s = hashmap_steal_first_key(p->names)))
220 free(s);
221 hashmap_free(p->names);
222
223 free(p->_data);
224
225 if (!p->on_stack)
226 free(p);
227 }
228
229 DnsPacket *dns_packet_unref(DnsPacket *p) {
230 if (!p)
231 return NULL;
232
233 assert(p->n_ref > 0);
234
235 dns_packet_unref(p->more);
236
237 if (p->n_ref == 1)
238 dns_packet_free(p);
239 else
240 p->n_ref--;
241
242 return NULL;
243 }
244
245 int dns_packet_validate(DnsPacket *p) {
246 assert(p);
247
248 if (p->size < DNS_PACKET_HEADER_SIZE)
249 return -EBADMSG;
250
251 if (p->size > DNS_PACKET_SIZE_MAX)
252 return -EBADMSG;
253
254 return 1;
255 }
256
257 int dns_packet_validate_reply(DnsPacket *p) {
258 int r;
259
260 assert(p);
261
262 r = dns_packet_validate(p);
263 if (r < 0)
264 return r;
265
266 if (DNS_PACKET_QR(p) != 1)
267 return 0;
268
269 if (DNS_PACKET_OPCODE(p) != 0)
270 return -EBADMSG;
271
272 switch (p->protocol) {
273
274 case DNS_PROTOCOL_LLMNR:
275 /* RFC 4795, Section 2.1.1. says to discard all replies with QDCOUNT != 1 */
276 if (DNS_PACKET_QDCOUNT(p) != 1)
277 return -EBADMSG;
278
279 break;
280
281 case DNS_PROTOCOL_MDNS:
282 /* RFC 6762, Section 18 */
283 if (DNS_PACKET_RCODE(p) != 0)
284 return -EBADMSG;
285
286 break;
287
288 default:
289 break;
290 }
291
292 return 1;
293 }
294
295 int dns_packet_validate_query(DnsPacket *p) {
296 int r;
297
298 assert(p);
299
300 r = dns_packet_validate(p);
301 if (r < 0)
302 return r;
303
304 if (DNS_PACKET_QR(p) != 0)
305 return 0;
306
307 if (DNS_PACKET_OPCODE(p) != 0)
308 return -EBADMSG;
309
310 if (DNS_PACKET_TC(p))
311 return -EBADMSG;
312
313 switch (p->protocol) {
314
315 case DNS_PROTOCOL_LLMNR:
316 case DNS_PROTOCOL_DNS:
317 /* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */
318 if (DNS_PACKET_QDCOUNT(p) != 1)
319 return -EBADMSG;
320
321 /* RFC 4795, Section 2.1.1. says to discard all queries with ANCOUNT != 0 */
322 if (DNS_PACKET_ANCOUNT(p) > 0)
323 return -EBADMSG;
324
325 /* RFC 4795, Section 2.1.1. says to discard all queries with NSCOUNT != 0 */
326 if (DNS_PACKET_NSCOUNT(p) > 0)
327 return -EBADMSG;
328
329 break;
330
331 case DNS_PROTOCOL_MDNS:
332 /* RFC 6762, Section 18 specifies that messages with non-zero RCODE
333 * must be silently ignored, and that we must ignore the values of
334 * AA, RD, RA, AD, and CD bits. */
335 if (DNS_PACKET_RCODE(p) != 0)
336 return -EBADMSG;
337
338 break;
339
340 default:
341 break;
342 }
343
344 return 1;
345 }
346
347 static int dns_packet_extend(DnsPacket *p, size_t add, void **ret, size_t *start) {
348 assert(p);
349
350 if (p->size + add > p->allocated) {
351 size_t a, ms;
352
353 a = PAGE_ALIGN((p->size + add) * 2);
354
355 ms = dns_packet_size_max(p);
356 if (a > ms)
357 a = ms;
358
359 if (p->size + add > a)
360 return -EMSGSIZE;
361
362 if (p->_data) {
363 void *d;
364
365 d = realloc(p->_data, a);
366 if (!d)
367 return -ENOMEM;
368
369 p->_data = d;
370 } else {
371 p->_data = malloc(a);
372 if (!p->_data)
373 return -ENOMEM;
374
375 memcpy(p->_data, (uint8_t*) p + ALIGN(sizeof(DnsPacket)), p->size);
376 memzero((uint8_t*) p->_data + p->size, a - p->size);
377 }
378
379 p->allocated = a;
380 }
381
382 if (start)
383 *start = p->size;
384
385 if (ret)
386 *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->size;
387
388 p->size += add;
389 return 0;
390 }
391
392 void dns_packet_truncate(DnsPacket *p, size_t sz) {
393 char *s;
394 void *n;
395
396 assert(p);
397
398 if (p->size <= sz)
399 return;
400
401 HASHMAP_FOREACH_KEY(n, s, p->names) {
402
403 if (PTR_TO_SIZE(n) < sz)
404 continue;
405
406 hashmap_remove(p->names, s);
407 free(s);
408 }
409
410 p->size = sz;
411 }
412
413 int dns_packet_append_blob(DnsPacket *p, const void *d, size_t l, size_t *start) {
414 void *q;
415 int r;
416
417 assert(p);
418
419 r = dns_packet_extend(p, l, &q, start);
420 if (r < 0)
421 return r;
422
423 memcpy_safe(q, d, l);
424 return 0;
425 }
426
427 int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start) {
428 void *d;
429 int r;
430
431 assert(p);
432
433 r = dns_packet_extend(p, sizeof(uint8_t), &d, start);
434 if (r < 0)
435 return r;
436
437 ((uint8_t*) d)[0] = v;
438
439 return 0;
440 }
441
442 int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start) {
443 void *d;
444 int r;
445
446 assert(p);
447
448 r = dns_packet_extend(p, sizeof(uint16_t), &d, start);
449 if (r < 0)
450 return r;
451
452 unaligned_write_be16(d, v);
453
454 return 0;
455 }
456
457 int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start) {
458 void *d;
459 int r;
460
461 assert(p);
462
463 r = dns_packet_extend(p, sizeof(uint32_t), &d, start);
464 if (r < 0)
465 return r;
466
467 unaligned_write_be32(d, v);
468
469 return 0;
470 }
471
472 int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start) {
473 assert(p);
474 assert(s);
475
476 return dns_packet_append_raw_string(p, s, strlen(s), start);
477 }
478
479 int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start) {
480 void *d;
481 int r;
482
483 assert(p);
484 assert(s || size == 0);
485
486 if (size > 255)
487 return -E2BIG;
488
489 r = dns_packet_extend(p, 1 + size, &d, start);
490 if (r < 0)
491 return r;
492
493 ((uint8_t*) d)[0] = (uint8_t) size;
494
495 memcpy_safe(((uint8_t*) d) + 1, s, size);
496
497 return 0;
498 }
499
500 int dns_packet_append_label(DnsPacket *p, const char *d, size_t l, bool canonical_candidate, size_t *start) {
501 uint8_t *w;
502 int r;
503
504 /* Append a label to a packet. Optionally, does this in DNSSEC
505 * canonical form, if this label is marked as a candidate for
506 * it, and the canonical form logic is enabled for the
507 * packet */
508
509 assert(p);
510 assert(d);
511
512 if (l > DNS_LABEL_MAX)
513 return -E2BIG;
514
515 r = dns_packet_extend(p, 1 + l, (void**) &w, start);
516 if (r < 0)
517 return r;
518
519 *(w++) = (uint8_t) l;
520
521 if (p->canonical_form && canonical_candidate)
522 /* Generate in canonical form, as defined by DNSSEC
523 * RFC 4034, Section 6.2, i.e. all lower-case. */
524 for (size_t i = 0; i < l; i++)
525 w[i] = (uint8_t) ascii_tolower(d[i]);
526 else
527 /* Otherwise, just copy the string unaltered. This is
528 * essential for DNS-SD, where the casing of labels
529 * matters and needs to be retained. */
530 memcpy(w, d, l);
531
532 return 0;
533 }
534
535 int dns_packet_append_name(
536 DnsPacket *p,
537 const char *name,
538 bool allow_compression,
539 bool canonical_candidate,
540 size_t *start) {
541
542 size_t saved_size;
543 int r;
544
545 assert(p);
546 assert(name);
547
548 if (p->refuse_compression)
549 allow_compression = false;
550
551 saved_size = p->size;
552
553 while (!dns_name_is_root(name)) {
554 const char *z = name;
555 char label[DNS_LABEL_MAX];
556 size_t n = 0;
557
558 if (allow_compression)
559 n = PTR_TO_SIZE(hashmap_get(p->names, name));
560 if (n > 0) {
561 assert(n < p->size);
562
563 if (n < 0x4000) {
564 r = dns_packet_append_uint16(p, 0xC000 | n, NULL);
565 if (r < 0)
566 goto fail;
567
568 goto done;
569 }
570 }
571
572 r = dns_label_unescape(&name, label, sizeof label, 0);
573 if (r < 0)
574 goto fail;
575
576 r = dns_packet_append_label(p, label, r, canonical_candidate, &n);
577 if (r < 0)
578 goto fail;
579
580 if (allow_compression) {
581 _cleanup_free_ char *s = NULL;
582
583 s = strdup(z);
584 if (!s) {
585 r = -ENOMEM;
586 goto fail;
587 }
588
589 r = hashmap_ensure_put(&p->names, &dns_name_hash_ops, s, SIZE_TO_PTR(n));
590 if (r < 0)
591 goto fail;
592
593 TAKE_PTR(s);
594 }
595 }
596
597 r = dns_packet_append_uint8(p, 0, NULL);
598 if (r < 0)
599 return r;
600
601 done:
602 if (start)
603 *start = saved_size;
604
605 return 0;
606
607 fail:
608 dns_packet_truncate(p, saved_size);
609 return r;
610 }
611
612 int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *k, const DnsAnswerFlags flags, size_t *start) {
613 size_t saved_size;
614 uint16_t class;
615 int r;
616
617 assert(p);
618 assert(k);
619
620 saved_size = p->size;
621
622 r = dns_packet_append_name(p, dns_resource_key_name(k), true, true, NULL);
623 if (r < 0)
624 goto fail;
625
626 r = dns_packet_append_uint16(p, k->type, NULL);
627 if (r < 0)
628 goto fail;
629
630 class = flags & DNS_ANSWER_CACHE_FLUSH ? k->class | MDNS_RR_CACHE_FLUSH_OR_QU : k->class;
631 r = dns_packet_append_uint16(p, class, NULL);
632 if (r < 0)
633 goto fail;
634
635 if (start)
636 *start = saved_size;
637
638 return 0;
639
640 fail:
641 dns_packet_truncate(p, saved_size);
642 return r;
643 }
644
645 static int dns_packet_append_type_window(DnsPacket *p, uint8_t window, uint8_t length, const uint8_t *types, size_t *start) {
646 size_t saved_size;
647 int r;
648
649 assert(p);
650 assert(types);
651 assert(length > 0);
652
653 saved_size = p->size;
654
655 r = dns_packet_append_uint8(p, window, NULL);
656 if (r < 0)
657 goto fail;
658
659 r = dns_packet_append_uint8(p, length, NULL);
660 if (r < 0)
661 goto fail;
662
663 r = dns_packet_append_blob(p, types, length, NULL);
664 if (r < 0)
665 goto fail;
666
667 if (start)
668 *start = saved_size;
669
670 return 0;
671 fail:
672 dns_packet_truncate(p, saved_size);
673 return r;
674 }
675
676 static int dns_packet_append_types(DnsPacket *p, Bitmap *types, size_t *start) {
677 uint8_t window = 0;
678 uint8_t entry = 0;
679 uint8_t bitmaps[32] = {};
680 unsigned n;
681 size_t saved_size;
682 int r;
683
684 assert(p);
685
686 saved_size = p->size;
687
688 BITMAP_FOREACH(n, types) {
689 assert(n <= 0xffff);
690
691 if ((n >> 8) != window && bitmaps[entry / 8] != 0) {
692 r = dns_packet_append_type_window(p, window, entry / 8 + 1, bitmaps, NULL);
693 if (r < 0)
694 goto fail;
695
696 zero(bitmaps);
697 }
698
699 window = n >> 8;
700 entry = n & 255;
701
702 bitmaps[entry / 8] |= 1 << (7 - (entry % 8));
703 }
704
705 if (bitmaps[entry / 8] != 0) {
706 r = dns_packet_append_type_window(p, window, entry / 8 + 1, bitmaps, NULL);
707 if (r < 0)
708 goto fail;
709 }
710
711 if (start)
712 *start = saved_size;
713
714 return 0;
715 fail:
716 dns_packet_truncate(p, saved_size);
717 return r;
718 }
719
720 /* Append the OPT pseudo-RR described in RFC6891 */
721 int dns_packet_append_opt(
722 DnsPacket *p,
723 uint16_t max_udp_size,
724 bool edns0_do,
725 bool include_rfc6975,
726 const char *nsid,
727 int rcode,
728 size_t *ret_start) {
729
730 size_t saved_size;
731 int r;
732
733 assert(p);
734 /* we must never advertise supported packet size smaller than the legacy max */
735 assert(max_udp_size >= DNS_PACKET_UNICAST_SIZE_MAX);
736 assert(rcode >= 0);
737 assert(rcode <= _DNS_RCODE_MAX);
738
739 if (p->opt_start != SIZE_MAX)
740 return -EBUSY;
741
742 assert(p->opt_size == SIZE_MAX);
743
744 saved_size = p->size;
745
746 /* empty name */
747 r = dns_packet_append_uint8(p, 0, NULL);
748 if (r < 0)
749 return r;
750
751 /* type */
752 r = dns_packet_append_uint16(p, DNS_TYPE_OPT, NULL);
753 if (r < 0)
754 goto fail;
755
756 /* class: maximum udp packet that can be received */
757 r = dns_packet_append_uint16(p, max_udp_size, NULL);
758 if (r < 0)
759 goto fail;
760
761 /* extended RCODE and VERSION */
762 r = dns_packet_append_uint16(p, ((uint16_t) rcode & 0x0FF0) << 4, NULL);
763 if (r < 0)
764 goto fail;
765
766 /* flags: DNSSEC OK (DO), see RFC3225 */
767 r = dns_packet_append_uint16(p, edns0_do ? EDNS0_OPT_DO : 0, NULL);
768 if (r < 0)
769 goto fail;
770
771 if (edns0_do && include_rfc6975) {
772 /* If DO is on and this is requested, also append RFC6975 Algorithm data. This is supposed to
773 * be done on queries, not on replies, hencer callers should turn this off when finishing off
774 * replies. */
775
776 static const uint8_t rfc6975[] = {
777
778 0, 5, /* OPTION_CODE: DAU */
779 #if PREFER_OPENSSL || (HAVE_GCRYPT && GCRYPT_VERSION_NUMBER >= 0x010600)
780 0, 7, /* LIST_LENGTH */
781 #else
782 0, 6, /* LIST_LENGTH */
783 #endif
784 DNSSEC_ALGORITHM_RSASHA1,
785 DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1,
786 DNSSEC_ALGORITHM_RSASHA256,
787 DNSSEC_ALGORITHM_RSASHA512,
788 DNSSEC_ALGORITHM_ECDSAP256SHA256,
789 DNSSEC_ALGORITHM_ECDSAP384SHA384,
790 #if PREFER_OPENSSL || (HAVE_GCRYPT && GCRYPT_VERSION_NUMBER >= 0x010600)
791 DNSSEC_ALGORITHM_ED25519,
792 #endif
793
794 0, 6, /* OPTION_CODE: DHU */
795 0, 3, /* LIST_LENGTH */
796 DNSSEC_DIGEST_SHA1,
797 DNSSEC_DIGEST_SHA256,
798 DNSSEC_DIGEST_SHA384,
799
800 0, 7, /* OPTION_CODE: N3U */
801 0, 1, /* LIST_LENGTH */
802 NSEC3_ALGORITHM_SHA1,
803 };
804
805 r = dns_packet_append_uint16(p, sizeof(rfc6975), NULL); /* RDLENGTH */
806 if (r < 0)
807 goto fail;
808
809 r = dns_packet_append_blob(p, rfc6975, sizeof(rfc6975), NULL); /* the payload, as defined above */
810
811 } else if (nsid) {
812
813 if (strlen(nsid) > UINT16_MAX - 4) {
814 r = -E2BIG;
815 goto fail;
816 }
817
818 r = dns_packet_append_uint16(p, 4 + strlen(nsid), NULL); /* RDLENGTH */
819 if (r < 0)
820 goto fail;
821
822 r = dns_packet_append_uint16(p, 3, NULL); /* OPTION-CODE: NSID */
823 if (r < 0)
824 goto fail;
825
826 r = dns_packet_append_uint16(p, strlen(nsid), NULL); /* OPTION-LENGTH */
827 if (r < 0)
828 goto fail;
829
830 r = dns_packet_append_blob(p, nsid, strlen(nsid), NULL);
831 } else
832 r = dns_packet_append_uint16(p, 0, NULL);
833 if (r < 0)
834 goto fail;
835
836 DNS_PACKET_HEADER(p)->arcount = htobe16(DNS_PACKET_ARCOUNT(p) + 1);
837
838 p->opt_start = saved_size;
839 p->opt_size = p->size - saved_size;
840
841 if (ret_start)
842 *ret_start = saved_size;
843
844 return 0;
845
846 fail:
847 dns_packet_truncate(p, saved_size);
848 return r;
849 }
850
851 int dns_packet_truncate_opt(DnsPacket *p) {
852 assert(p);
853
854 if (p->opt_start == SIZE_MAX) {
855 assert(p->opt_size == SIZE_MAX);
856 return 0;
857 }
858
859 assert(p->opt_size != SIZE_MAX);
860 assert(DNS_PACKET_ARCOUNT(p) > 0);
861
862 if (p->opt_start + p->opt_size != p->size)
863 return -EBUSY;
864
865 dns_packet_truncate(p, p->opt_start);
866 DNS_PACKET_HEADER(p)->arcount = htobe16(DNS_PACKET_ARCOUNT(p) - 1);
867 p->opt_start = p->opt_size = SIZE_MAX;
868
869 return 1;
870 }
871
872 int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, const DnsAnswerFlags flags, size_t *start, size_t *rdata_start) {
873
874 size_t saved_size, rdlength_offset, end, rdlength, rds;
875 uint32_t ttl;
876 int r;
877
878 assert(p);
879 assert(rr);
880
881 saved_size = p->size;
882
883 r = dns_packet_append_key(p, rr->key, flags, NULL);
884 if (r < 0)
885 goto fail;
886
887 ttl = flags & DNS_ANSWER_GOODBYE ? 0 : rr->ttl;
888 r = dns_packet_append_uint32(p, ttl, NULL);
889 if (r < 0)
890 goto fail;
891
892 /* Initially we write 0 here */
893 r = dns_packet_append_uint16(p, 0, &rdlength_offset);
894 if (r < 0)
895 goto fail;
896
897 rds = p->size - saved_size;
898
899 switch (rr->unparsable ? _DNS_TYPE_INVALID : rr->key->type) {
900
901 case DNS_TYPE_SRV:
902 r = dns_packet_append_uint16(p, rr->srv.priority, NULL);
903 if (r < 0)
904 goto fail;
905
906 r = dns_packet_append_uint16(p, rr->srv.weight, NULL);
907 if (r < 0)
908 goto fail;
909
910 r = dns_packet_append_uint16(p, rr->srv.port, NULL);
911 if (r < 0)
912 goto fail;
913
914 /* RFC 2782 states "Unless and until permitted by future standards
915 * action, name compression is not to be used for this field." */
916 r = dns_packet_append_name(p, rr->srv.name, false, true, NULL);
917 break;
918
919 case DNS_TYPE_PTR:
920 case DNS_TYPE_NS:
921 case DNS_TYPE_CNAME:
922 case DNS_TYPE_DNAME:
923 r = dns_packet_append_name(p, rr->ptr.name, true, true, NULL);
924 break;
925
926 case DNS_TYPE_HINFO:
927 r = dns_packet_append_string(p, rr->hinfo.cpu, NULL);
928 if (r < 0)
929 goto fail;
930
931 r = dns_packet_append_string(p, rr->hinfo.os, NULL);
932 break;
933
934 case DNS_TYPE_SPF: /* exactly the same as TXT */
935 case DNS_TYPE_TXT:
936
937 if (!rr->txt.items) {
938 /* RFC 6763, section 6.1 suggests to generate
939 * single empty string for an empty array. */
940
941 r = dns_packet_append_raw_string(p, NULL, 0, NULL);
942 if (r < 0)
943 goto fail;
944 } else {
945 DnsTxtItem *i;
946
947 LIST_FOREACH(items, i, rr->txt.items) {
948 r = dns_packet_append_raw_string(p, i->data, i->length, NULL);
949 if (r < 0)
950 goto fail;
951 }
952 }
953
954 r = 0;
955 break;
956
957 case DNS_TYPE_A:
958 r = dns_packet_append_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
959 break;
960
961 case DNS_TYPE_AAAA:
962 r = dns_packet_append_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
963 break;
964
965 case DNS_TYPE_SOA:
966 r = dns_packet_append_name(p, rr->soa.mname, true, true, NULL);
967 if (r < 0)
968 goto fail;
969
970 r = dns_packet_append_name(p, rr->soa.rname, true, true, NULL);
971 if (r < 0)
972 goto fail;
973
974 r = dns_packet_append_uint32(p, rr->soa.serial, NULL);
975 if (r < 0)
976 goto fail;
977
978 r = dns_packet_append_uint32(p, rr->soa.refresh, NULL);
979 if (r < 0)
980 goto fail;
981
982 r = dns_packet_append_uint32(p, rr->soa.retry, NULL);
983 if (r < 0)
984 goto fail;
985
986 r = dns_packet_append_uint32(p, rr->soa.expire, NULL);
987 if (r < 0)
988 goto fail;
989
990 r = dns_packet_append_uint32(p, rr->soa.minimum, NULL);
991 break;
992
993 case DNS_TYPE_MX:
994 r = dns_packet_append_uint16(p, rr->mx.priority, NULL);
995 if (r < 0)
996 goto fail;
997
998 r = dns_packet_append_name(p, rr->mx.exchange, true, true, NULL);
999 break;
1000
1001 case DNS_TYPE_LOC:
1002 r = dns_packet_append_uint8(p, rr->loc.version, NULL);
1003 if (r < 0)
1004 goto fail;
1005
1006 r = dns_packet_append_uint8(p, rr->loc.size, NULL);
1007 if (r < 0)
1008 goto fail;
1009
1010 r = dns_packet_append_uint8(p, rr->loc.horiz_pre, NULL);
1011 if (r < 0)
1012 goto fail;
1013
1014 r = dns_packet_append_uint8(p, rr->loc.vert_pre, NULL);
1015 if (r < 0)
1016 goto fail;
1017
1018 r = dns_packet_append_uint32(p, rr->loc.latitude, NULL);
1019 if (r < 0)
1020 goto fail;
1021
1022 r = dns_packet_append_uint32(p, rr->loc.longitude, NULL);
1023 if (r < 0)
1024 goto fail;
1025
1026 r = dns_packet_append_uint32(p, rr->loc.altitude, NULL);
1027 break;
1028
1029 case DNS_TYPE_DS:
1030 r = dns_packet_append_uint16(p, rr->ds.key_tag, NULL);
1031 if (r < 0)
1032 goto fail;
1033
1034 r = dns_packet_append_uint8(p, rr->ds.algorithm, NULL);
1035 if (r < 0)
1036 goto fail;
1037
1038 r = dns_packet_append_uint8(p, rr->ds.digest_type, NULL);
1039 if (r < 0)
1040 goto fail;
1041
1042 r = dns_packet_append_blob(p, rr->ds.digest, rr->ds.digest_size, NULL);
1043 break;
1044
1045 case DNS_TYPE_SSHFP:
1046 r = dns_packet_append_uint8(p, rr->sshfp.algorithm, NULL);
1047 if (r < 0)
1048 goto fail;
1049
1050 r = dns_packet_append_uint8(p, rr->sshfp.fptype, NULL);
1051 if (r < 0)
1052 goto fail;
1053
1054 r = dns_packet_append_blob(p, rr->sshfp.fingerprint, rr->sshfp.fingerprint_size, NULL);
1055 break;
1056
1057 case DNS_TYPE_DNSKEY:
1058 r = dns_packet_append_uint16(p, rr->dnskey.flags, NULL);
1059 if (r < 0)
1060 goto fail;
1061
1062 r = dns_packet_append_uint8(p, rr->dnskey.protocol, NULL);
1063 if (r < 0)
1064 goto fail;
1065
1066 r = dns_packet_append_uint8(p, rr->dnskey.algorithm, NULL);
1067 if (r < 0)
1068 goto fail;
1069
1070 r = dns_packet_append_blob(p, rr->dnskey.key, rr->dnskey.key_size, NULL);
1071 break;
1072
1073 case DNS_TYPE_RRSIG:
1074 r = dns_packet_append_uint16(p, rr->rrsig.type_covered, NULL);
1075 if (r < 0)
1076 goto fail;
1077
1078 r = dns_packet_append_uint8(p, rr->rrsig.algorithm, NULL);
1079 if (r < 0)
1080 goto fail;
1081
1082 r = dns_packet_append_uint8(p, rr->rrsig.labels, NULL);
1083 if (r < 0)
1084 goto fail;
1085
1086 r = dns_packet_append_uint32(p, rr->rrsig.original_ttl, NULL);
1087 if (r < 0)
1088 goto fail;
1089
1090 r = dns_packet_append_uint32(p, rr->rrsig.expiration, NULL);
1091 if (r < 0)
1092 goto fail;
1093
1094 r = dns_packet_append_uint32(p, rr->rrsig.inception, NULL);
1095 if (r < 0)
1096 goto fail;
1097
1098 r = dns_packet_append_uint16(p, rr->rrsig.key_tag, NULL);
1099 if (r < 0)
1100 goto fail;
1101
1102 r = dns_packet_append_name(p, rr->rrsig.signer, false, true, NULL);
1103 if (r < 0)
1104 goto fail;
1105
1106 r = dns_packet_append_blob(p, rr->rrsig.signature, rr->rrsig.signature_size, NULL);
1107 break;
1108
1109 case DNS_TYPE_NSEC:
1110 r = dns_packet_append_name(p, rr->nsec.next_domain_name, false, false, NULL);
1111 if (r < 0)
1112 goto fail;
1113
1114 r = dns_packet_append_types(p, rr->nsec.types, NULL);
1115 if (r < 0)
1116 goto fail;
1117
1118 break;
1119
1120 case DNS_TYPE_NSEC3:
1121 r = dns_packet_append_uint8(p, rr->nsec3.algorithm, NULL);
1122 if (r < 0)
1123 goto fail;
1124
1125 r = dns_packet_append_uint8(p, rr->nsec3.flags, NULL);
1126 if (r < 0)
1127 goto fail;
1128
1129 r = dns_packet_append_uint16(p, rr->nsec3.iterations, NULL);
1130 if (r < 0)
1131 goto fail;
1132
1133 r = dns_packet_append_uint8(p, rr->nsec3.salt_size, NULL);
1134 if (r < 0)
1135 goto fail;
1136
1137 r = dns_packet_append_blob(p, rr->nsec3.salt, rr->nsec3.salt_size, NULL);
1138 if (r < 0)
1139 goto fail;
1140
1141 r = dns_packet_append_uint8(p, rr->nsec3.next_hashed_name_size, NULL);
1142 if (r < 0)
1143 goto fail;
1144
1145 r = dns_packet_append_blob(p, rr->nsec3.next_hashed_name, rr->nsec3.next_hashed_name_size, NULL);
1146 if (r < 0)
1147 goto fail;
1148
1149 r = dns_packet_append_types(p, rr->nsec3.types, NULL);
1150 if (r < 0)
1151 goto fail;
1152
1153 break;
1154
1155 case DNS_TYPE_TLSA:
1156 r = dns_packet_append_uint8(p, rr->tlsa.cert_usage, NULL);
1157 if (r < 0)
1158 goto fail;
1159
1160 r = dns_packet_append_uint8(p, rr->tlsa.selector, NULL);
1161 if (r < 0)
1162 goto fail;
1163
1164 r = dns_packet_append_uint8(p, rr->tlsa.matching_type, NULL);
1165 if (r < 0)
1166 goto fail;
1167
1168 r = dns_packet_append_blob(p, rr->tlsa.data, rr->tlsa.data_size, NULL);
1169 break;
1170
1171 case DNS_TYPE_CAA:
1172 r = dns_packet_append_uint8(p, rr->caa.flags, NULL);
1173 if (r < 0)
1174 goto fail;
1175
1176 r = dns_packet_append_string(p, rr->caa.tag, NULL);
1177 if (r < 0)
1178 goto fail;
1179
1180 r = dns_packet_append_blob(p, rr->caa.value, rr->caa.value_size, NULL);
1181 break;
1182
1183 case DNS_TYPE_OPT:
1184 case DNS_TYPE_OPENPGPKEY:
1185 case _DNS_TYPE_INVALID: /* unparsable */
1186 default:
1187
1188 r = dns_packet_append_blob(p, rr->generic.data, rr->generic.data_size, NULL);
1189 break;
1190 }
1191 if (r < 0)
1192 goto fail;
1193
1194 /* Let's calculate the actual data size and update the field */
1195 rdlength = p->size - rdlength_offset - sizeof(uint16_t);
1196 if (rdlength > 0xFFFF) {
1197 r = -ENOSPC;
1198 goto fail;
1199 }
1200
1201 end = p->size;
1202 p->size = rdlength_offset;
1203 r = dns_packet_append_uint16(p, rdlength, NULL);
1204 if (r < 0)
1205 goto fail;
1206 p->size = end;
1207
1208 if (start)
1209 *start = saved_size;
1210
1211 if (rdata_start)
1212 *rdata_start = rds;
1213
1214 return 0;
1215
1216 fail:
1217 dns_packet_truncate(p, saved_size);
1218 return r;
1219 }
1220
1221 int dns_packet_append_question(DnsPacket *p, DnsQuestion *q) {
1222 DnsResourceKey *key;
1223 int r;
1224
1225 assert(p);
1226
1227 DNS_QUESTION_FOREACH(key, q) {
1228 r = dns_packet_append_key(p, key, 0, NULL);
1229 if (r < 0)
1230 return r;
1231 }
1232
1233 return 0;
1234 }
1235
1236 int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a, unsigned *completed) {
1237 DnsResourceRecord *rr;
1238 DnsAnswerFlags flags;
1239 int r;
1240
1241 assert(p);
1242
1243 DNS_ANSWER_FOREACH_FLAGS(rr, flags, a) {
1244 r = dns_packet_append_rr(p, rr, flags, NULL, NULL);
1245 if (r < 0)
1246 return r;
1247
1248 if (completed)
1249 (*completed)++;
1250 }
1251
1252 return 0;
1253 }
1254
1255 int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) {
1256 assert(p);
1257
1258 if (p->rindex + sz > p->size)
1259 return -EMSGSIZE;
1260
1261 if (ret)
1262 *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->rindex;
1263
1264 if (start)
1265 *start = p->rindex;
1266
1267 p->rindex += sz;
1268 return 0;
1269 }
1270
1271 void dns_packet_rewind(DnsPacket *p, size_t idx) {
1272 assert(p);
1273 assert(idx <= p->size);
1274 assert(idx >= DNS_PACKET_HEADER_SIZE);
1275
1276 p->rindex = idx;
1277 }
1278
1279 int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start) {
1280 const void *q;
1281 int r;
1282
1283 assert(p);
1284 assert(d);
1285
1286 r = dns_packet_read(p, sz, &q, start);
1287 if (r < 0)
1288 return r;
1289
1290 memcpy(d, q, sz);
1291 return 0;
1292 }
1293
1294 static int dns_packet_read_memdup(
1295 DnsPacket *p, size_t size,
1296 void **ret, size_t *ret_size,
1297 size_t *ret_start) {
1298
1299 const void *src;
1300 size_t start;
1301 int r;
1302
1303 assert(p);
1304 assert(ret);
1305
1306 r = dns_packet_read(p, size, &src, &start);
1307 if (r < 0)
1308 return r;
1309
1310 if (size <= 0)
1311 *ret = NULL;
1312 else {
1313 void *copy;
1314
1315 copy = memdup(src, size);
1316 if (!copy)
1317 return -ENOMEM;
1318
1319 *ret = copy;
1320 }
1321
1322 if (ret_size)
1323 *ret_size = size;
1324 if (ret_start)
1325 *ret_start = start;
1326
1327 return 0;
1328 }
1329
1330 int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start) {
1331 const void *d;
1332 int r;
1333
1334 assert(p);
1335
1336 r = dns_packet_read(p, sizeof(uint8_t), &d, start);
1337 if (r < 0)
1338 return r;
1339
1340 *ret = ((uint8_t*) d)[0];
1341 return 0;
1342 }
1343
1344 int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start) {
1345 const void *d;
1346 int r;
1347
1348 assert(p);
1349
1350 r = dns_packet_read(p, sizeof(uint16_t), &d, start);
1351 if (r < 0)
1352 return r;
1353
1354 if (ret)
1355 *ret = unaligned_read_be16(d);
1356
1357 return 0;
1358 }
1359
1360 int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start) {
1361 const void *d;
1362 int r;
1363
1364 assert(p);
1365
1366 r = dns_packet_read(p, sizeof(uint32_t), &d, start);
1367 if (r < 0)
1368 return r;
1369
1370 *ret = unaligned_read_be32(d);
1371
1372 return 0;
1373 }
1374
1375 int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start) {
1376 assert(p);
1377
1378 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1379 const void *d;
1380 char *t;
1381 uint8_t c;
1382 int r;
1383
1384 r = dns_packet_read_uint8(p, &c, NULL);
1385 if (r < 0)
1386 return r;
1387
1388 r = dns_packet_read(p, c, &d, NULL);
1389 if (r < 0)
1390 return r;
1391
1392 if (memchr(d, 0, c))
1393 return -EBADMSG;
1394
1395 t = strndup(d, c);
1396 if (!t)
1397 return -ENOMEM;
1398
1399 if (!utf8_is_valid(t)) {
1400 free(t);
1401 return -EBADMSG;
1402 }
1403
1404 *ret = t;
1405
1406 if (start)
1407 *start = rewinder.saved_rindex;
1408 CANCEL_REWINDER(rewinder);
1409
1410 return 0;
1411 }
1412
1413 int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start) {
1414 assert(p);
1415
1416 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1417 uint8_t c;
1418 int r;
1419
1420 r = dns_packet_read_uint8(p, &c, NULL);
1421 if (r < 0)
1422 return r;
1423
1424 r = dns_packet_read(p, c, ret, NULL);
1425 if (r < 0)
1426 return r;
1427
1428 if (size)
1429 *size = c;
1430 if (start)
1431 *start = rewinder.saved_rindex;
1432 CANCEL_REWINDER(rewinder);
1433
1434 return 0;
1435 }
1436
1437 int dns_packet_read_name(
1438 DnsPacket *p,
1439 char **ret,
1440 bool allow_compression,
1441 size_t *ret_start) {
1442
1443 assert(p);
1444
1445 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1446 size_t after_rindex = 0, jump_barrier = p->rindex;
1447 _cleanup_free_ char *name = NULL;
1448 bool first = true;
1449 size_t n = 0;
1450 int r;
1451
1452 if (p->refuse_compression)
1453 allow_compression = false;
1454
1455 for (;;) {
1456 uint8_t c, d;
1457
1458 r = dns_packet_read_uint8(p, &c, NULL);
1459 if (r < 0)
1460 return r;
1461
1462 if (c == 0)
1463 /* End of name */
1464 break;
1465 else if (c <= 63) {
1466 const char *label;
1467
1468 /* Literal label */
1469 r = dns_packet_read(p, c, (const void**) &label, NULL);
1470 if (r < 0)
1471 return r;
1472
1473 if (!GREEDY_REALLOC(name, n + !first + DNS_LABEL_ESCAPED_MAX))
1474 return -ENOMEM;
1475
1476 if (first)
1477 first = false;
1478 else
1479 name[n++] = '.';
1480
1481 r = dns_label_escape(label, c, name + n, DNS_LABEL_ESCAPED_MAX);
1482 if (r < 0)
1483 return r;
1484
1485 n += r;
1486 continue;
1487 } else if (allow_compression && FLAGS_SET(c, 0xc0)) {
1488 uint16_t ptr;
1489
1490 /* Pointer */
1491 r = dns_packet_read_uint8(p, &d, NULL);
1492 if (r < 0)
1493 return r;
1494
1495 ptr = (uint16_t) (c & ~0xc0) << 8 | (uint16_t) d;
1496 if (ptr < DNS_PACKET_HEADER_SIZE || ptr >= jump_barrier)
1497 return -EBADMSG;
1498
1499 if (after_rindex == 0)
1500 after_rindex = p->rindex;
1501
1502 /* Jumps are limited to a "prior occurrence" (RFC-1035 4.1.4) */
1503 jump_barrier = ptr;
1504 p->rindex = ptr;
1505 } else
1506 return -EBADMSG;
1507 }
1508
1509 if (!GREEDY_REALLOC(name, n + 1))
1510 return -ENOMEM;
1511
1512 name[n] = 0;
1513
1514 if (after_rindex != 0)
1515 p->rindex= after_rindex;
1516
1517 if (ret)
1518 *ret = TAKE_PTR(name);
1519 if (ret_start)
1520 *ret_start = rewinder.saved_rindex;
1521
1522 CANCEL_REWINDER(rewinder);
1523
1524 return 0;
1525 }
1526
1527 static int dns_packet_read_type_window(DnsPacket *p, Bitmap **types, size_t *start) {
1528 assert(p);
1529 assert(types);
1530
1531 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1532 uint8_t window, length;
1533 const uint8_t *bitmap;
1534 uint8_t bit = 0;
1535 bool found = false;
1536 int r;
1537
1538 r = bitmap_ensure_allocated(types);
1539 if (r < 0)
1540 return r;
1541
1542 r = dns_packet_read_uint8(p, &window, NULL);
1543 if (r < 0)
1544 return r;
1545
1546 r = dns_packet_read_uint8(p, &length, NULL);
1547 if (r < 0)
1548 return r;
1549
1550 if (length == 0 || length > 32)
1551 return -EBADMSG;
1552
1553 r = dns_packet_read(p, length, (const void **)&bitmap, NULL);
1554 if (r < 0)
1555 return r;
1556
1557 for (uint8_t i = 0; i < length; i++) {
1558 uint8_t bitmask = 1 << 7;
1559
1560 if (!bitmap[i]) {
1561 found = false;
1562 bit += 8;
1563 continue;
1564 }
1565
1566 found = true;
1567
1568 for (; bitmask; bit++, bitmask >>= 1)
1569 if (bitmap[i] & bitmask) {
1570 uint16_t n;
1571
1572 n = (uint16_t) window << 8 | (uint16_t) bit;
1573
1574 /* Ignore pseudo-types. see RFC4034 section 4.1.2 */
1575 if (dns_type_is_pseudo(n))
1576 continue;
1577
1578 r = bitmap_set(*types, n);
1579 if (r < 0)
1580 return r;
1581 }
1582 }
1583
1584 if (!found)
1585 return -EBADMSG;
1586
1587 if (start)
1588 *start = rewinder.saved_rindex;
1589 CANCEL_REWINDER(rewinder);
1590
1591 return 0;
1592 }
1593
1594 static int dns_packet_read_type_windows(DnsPacket *p, Bitmap **types, size_t size, size_t *start) {
1595 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1596 int r;
1597
1598 while (p->rindex < rewinder.saved_rindex + size) {
1599 r = dns_packet_read_type_window(p, types, NULL);
1600 if (r < 0)
1601 return r;
1602
1603 /* don't read past end of current RR */
1604 if (p->rindex > rewinder.saved_rindex + size)
1605 return -EBADMSG;
1606 }
1607
1608 if (p->rindex != rewinder.saved_rindex + size)
1609 return -EBADMSG;
1610
1611 if (start)
1612 *start = rewinder.saved_rindex;
1613 CANCEL_REWINDER(rewinder);
1614
1615 return 0;
1616 }
1617
1618 int dns_packet_read_key(
1619 DnsPacket *p,
1620 DnsResourceKey **ret,
1621 bool *ret_cache_flush_or_qu,
1622 size_t *ret_start) {
1623
1624 assert(p);
1625
1626 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1627 _cleanup_free_ char *name = NULL;
1628 bool cache_flush_or_qu = false;
1629 uint16_t class, type;
1630 int r;
1631
1632 r = dns_packet_read_name(p, &name, true, NULL);
1633 if (r < 0)
1634 return r;
1635
1636 r = dns_packet_read_uint16(p, &type, NULL);
1637 if (r < 0)
1638 return r;
1639
1640 r = dns_packet_read_uint16(p, &class, NULL);
1641 if (r < 0)
1642 return r;
1643
1644 if (p->protocol == DNS_PROTOCOL_MDNS) {
1645 /* See RFC6762, sections 5.4 and 10.2 */
1646
1647 if (type != DNS_TYPE_OPT && (class & MDNS_RR_CACHE_FLUSH_OR_QU)) {
1648 class &= ~MDNS_RR_CACHE_FLUSH_OR_QU;
1649 cache_flush_or_qu = true;
1650 }
1651 }
1652
1653 if (ret) {
1654 DnsResourceKey *key;
1655
1656 key = dns_resource_key_new_consume(class, type, name);
1657 if (!key)
1658 return -ENOMEM;
1659
1660 TAKE_PTR(name);
1661 *ret = key;
1662 }
1663
1664 if (ret_cache_flush_or_qu)
1665 *ret_cache_flush_or_qu = cache_flush_or_qu;
1666 if (ret_start)
1667 *ret_start = rewinder.saved_rindex;
1668
1669 CANCEL_REWINDER(rewinder);
1670 return 0;
1671 }
1672
1673 static bool loc_size_ok(uint8_t size) {
1674 uint8_t m = size >> 4, e = size & 0xF;
1675
1676 return m <= 9 && e <= 9 && (m > 0 || e == 0);
1677 }
1678
1679 int dns_packet_read_rr(
1680 DnsPacket *p,
1681 DnsResourceRecord **ret,
1682 bool *ret_cache_flush,
1683 size_t *ret_start) {
1684
1685 assert(p);
1686
1687 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
1688 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
1689 _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
1690 size_t offset;
1691 uint16_t rdlength;
1692 bool cache_flush;
1693 int r;
1694
1695 r = dns_packet_read_key(p, &key, &cache_flush, NULL);
1696 if (r < 0)
1697 return r;
1698
1699 if (!dns_class_is_valid_rr(key->class) || !dns_type_is_valid_rr(key->type))
1700 return -EBADMSG;
1701
1702 rr = dns_resource_record_new(key);
1703 if (!rr)
1704 return -ENOMEM;
1705
1706 r = dns_packet_read_uint32(p, &rr->ttl, NULL);
1707 if (r < 0)
1708 return r;
1709
1710 /* RFC 2181, Section 8, suggests to
1711 * treat a TTL with the MSB set as a zero TTL. */
1712 if (rr->ttl & UINT32_C(0x80000000))
1713 rr->ttl = 0;
1714
1715 r = dns_packet_read_uint16(p, &rdlength, NULL);
1716 if (r < 0)
1717 return r;
1718
1719 if (p->rindex + rdlength > p->size)
1720 return -EBADMSG;
1721
1722 offset = p->rindex;
1723
1724 switch (rr->key->type) {
1725
1726 case DNS_TYPE_SRV:
1727 r = dns_packet_read_uint16(p, &rr->srv.priority, NULL);
1728 if (r < 0)
1729 return r;
1730 r = dns_packet_read_uint16(p, &rr->srv.weight, NULL);
1731 if (r < 0)
1732 return r;
1733 r = dns_packet_read_uint16(p, &rr->srv.port, NULL);
1734 if (r < 0)
1735 return r;
1736 r = dns_packet_read_name(p, &rr->srv.name, true, NULL);
1737 break;
1738
1739 case DNS_TYPE_PTR:
1740 case DNS_TYPE_NS:
1741 case DNS_TYPE_CNAME:
1742 case DNS_TYPE_DNAME:
1743 r = dns_packet_read_name(p, &rr->ptr.name, true, NULL);
1744 break;
1745
1746 case DNS_TYPE_HINFO:
1747 r = dns_packet_read_string(p, &rr->hinfo.cpu, NULL);
1748 if (r < 0)
1749 return r;
1750
1751 r = dns_packet_read_string(p, &rr->hinfo.os, NULL);
1752 break;
1753
1754 case DNS_TYPE_SPF: /* exactly the same as TXT */
1755 case DNS_TYPE_TXT:
1756 if (rdlength <= 0) {
1757 r = dns_txt_item_new_empty(&rr->txt.items);
1758 if (r < 0)
1759 return r;
1760 } else {
1761 DnsTxtItem *last = NULL;
1762
1763 while (p->rindex < offset + rdlength) {
1764 DnsTxtItem *i;
1765 const void *data;
1766 size_t sz;
1767
1768 r = dns_packet_read_raw_string(p, &data, &sz, NULL);
1769 if (r < 0)
1770 return r;
1771
1772 i = malloc0(offsetof(DnsTxtItem, data) + sz + 1); /* extra NUL byte at the end */
1773 if (!i)
1774 return -ENOMEM;
1775
1776 memcpy(i->data, data, sz);
1777 i->length = sz;
1778
1779 LIST_INSERT_AFTER(items, rr->txt.items, last, i);
1780 last = i;
1781 }
1782 }
1783
1784 r = 0;
1785 break;
1786
1787 case DNS_TYPE_A:
1788 r = dns_packet_read_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL);
1789 break;
1790
1791 case DNS_TYPE_AAAA:
1792 r = dns_packet_read_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL);
1793 break;
1794
1795 case DNS_TYPE_SOA:
1796 r = dns_packet_read_name(p, &rr->soa.mname, true, NULL);
1797 if (r < 0)
1798 return r;
1799
1800 r = dns_packet_read_name(p, &rr->soa.rname, true, NULL);
1801 if (r < 0)
1802 return r;
1803
1804 r = dns_packet_read_uint32(p, &rr->soa.serial, NULL);
1805 if (r < 0)
1806 return r;
1807
1808 r = dns_packet_read_uint32(p, &rr->soa.refresh, NULL);
1809 if (r < 0)
1810 return r;
1811
1812 r = dns_packet_read_uint32(p, &rr->soa.retry, NULL);
1813 if (r < 0)
1814 return r;
1815
1816 r = dns_packet_read_uint32(p, &rr->soa.expire, NULL);
1817 if (r < 0)
1818 return r;
1819
1820 r = dns_packet_read_uint32(p, &rr->soa.minimum, NULL);
1821 break;
1822
1823 case DNS_TYPE_MX:
1824 r = dns_packet_read_uint16(p, &rr->mx.priority, NULL);
1825 if (r < 0)
1826 return r;
1827
1828 r = dns_packet_read_name(p, &rr->mx.exchange, true, NULL);
1829 break;
1830
1831 case DNS_TYPE_LOC: {
1832 uint8_t t;
1833 size_t pos;
1834
1835 r = dns_packet_read_uint8(p, &t, &pos);
1836 if (r < 0)
1837 return r;
1838
1839 if (t == 0) {
1840 rr->loc.version = t;
1841
1842 r = dns_packet_read_uint8(p, &rr->loc.size, NULL);
1843 if (r < 0)
1844 return r;
1845
1846 if (!loc_size_ok(rr->loc.size))
1847 return -EBADMSG;
1848
1849 r = dns_packet_read_uint8(p, &rr->loc.horiz_pre, NULL);
1850 if (r < 0)
1851 return r;
1852
1853 if (!loc_size_ok(rr->loc.horiz_pre))
1854 return -EBADMSG;
1855
1856 r = dns_packet_read_uint8(p, &rr->loc.vert_pre, NULL);
1857 if (r < 0)
1858 return r;
1859
1860 if (!loc_size_ok(rr->loc.vert_pre))
1861 return -EBADMSG;
1862
1863 r = dns_packet_read_uint32(p, &rr->loc.latitude, NULL);
1864 if (r < 0)
1865 return r;
1866
1867 r = dns_packet_read_uint32(p, &rr->loc.longitude, NULL);
1868 if (r < 0)
1869 return r;
1870
1871 r = dns_packet_read_uint32(p, &rr->loc.altitude, NULL);
1872 if (r < 0)
1873 return r;
1874
1875 break;
1876 } else {
1877 dns_packet_rewind(p, pos);
1878 rr->unparsable = true;
1879 goto unparsable;
1880 }
1881 }
1882
1883 case DNS_TYPE_DS:
1884 r = dns_packet_read_uint16(p, &rr->ds.key_tag, NULL);
1885 if (r < 0)
1886 return r;
1887
1888 r = dns_packet_read_uint8(p, &rr->ds.algorithm, NULL);
1889 if (r < 0)
1890 return r;
1891
1892 r = dns_packet_read_uint8(p, &rr->ds.digest_type, NULL);
1893 if (r < 0)
1894 return r;
1895
1896 if (rdlength < 4)
1897 return -EBADMSG;
1898
1899 r = dns_packet_read_memdup(p, rdlength - 4,
1900 &rr->ds.digest, &rr->ds.digest_size,
1901 NULL);
1902 if (r < 0)
1903 return r;
1904
1905 if (rr->ds.digest_size <= 0)
1906 /* the accepted size depends on the algorithm, but for now
1907 just ensure that the value is greater than zero */
1908 return -EBADMSG;
1909
1910 break;
1911
1912 case DNS_TYPE_SSHFP:
1913 r = dns_packet_read_uint8(p, &rr->sshfp.algorithm, NULL);
1914 if (r < 0)
1915 return r;
1916
1917 r = dns_packet_read_uint8(p, &rr->sshfp.fptype, NULL);
1918 if (r < 0)
1919 return r;
1920
1921 if (rdlength < 2)
1922 return -EBADMSG;
1923
1924 r = dns_packet_read_memdup(p, rdlength - 2,
1925 &rr->sshfp.fingerprint, &rr->sshfp.fingerprint_size,
1926 NULL);
1927
1928 if (rr->sshfp.fingerprint_size <= 0)
1929 /* the accepted size depends on the algorithm, but for now
1930 just ensure that the value is greater than zero */
1931 return -EBADMSG;
1932
1933 break;
1934
1935 case DNS_TYPE_DNSKEY:
1936 r = dns_packet_read_uint16(p, &rr->dnskey.flags, NULL);
1937 if (r < 0)
1938 return r;
1939
1940 r = dns_packet_read_uint8(p, &rr->dnskey.protocol, NULL);
1941 if (r < 0)
1942 return r;
1943
1944 r = dns_packet_read_uint8(p, &rr->dnskey.algorithm, NULL);
1945 if (r < 0)
1946 return r;
1947
1948 if (rdlength < 4)
1949 return -EBADMSG;
1950
1951 r = dns_packet_read_memdup(p, rdlength - 4,
1952 &rr->dnskey.key, &rr->dnskey.key_size,
1953 NULL);
1954
1955 if (rr->dnskey.key_size <= 0)
1956 /* the accepted size depends on the algorithm, but for now
1957 just ensure that the value is greater than zero */
1958 return -EBADMSG;
1959
1960 break;
1961
1962 case DNS_TYPE_RRSIG:
1963 r = dns_packet_read_uint16(p, &rr->rrsig.type_covered, NULL);
1964 if (r < 0)
1965 return r;
1966
1967 r = dns_packet_read_uint8(p, &rr->rrsig.algorithm, NULL);
1968 if (r < 0)
1969 return r;
1970
1971 r = dns_packet_read_uint8(p, &rr->rrsig.labels, NULL);
1972 if (r < 0)
1973 return r;
1974
1975 r = dns_packet_read_uint32(p, &rr->rrsig.original_ttl, NULL);
1976 if (r < 0)
1977 return r;
1978
1979 r = dns_packet_read_uint32(p, &rr->rrsig.expiration, NULL);
1980 if (r < 0)
1981 return r;
1982
1983 r = dns_packet_read_uint32(p, &rr->rrsig.inception, NULL);
1984 if (r < 0)
1985 return r;
1986
1987 r = dns_packet_read_uint16(p, &rr->rrsig.key_tag, NULL);
1988 if (r < 0)
1989 return r;
1990
1991 r = dns_packet_read_name(p, &rr->rrsig.signer, false, NULL);
1992 if (r < 0)
1993 return r;
1994
1995 if (rdlength + offset < p->rindex)
1996 return -EBADMSG;
1997
1998 r = dns_packet_read_memdup(p, offset + rdlength - p->rindex,
1999 &rr->rrsig.signature, &rr->rrsig.signature_size,
2000 NULL);
2001
2002 if (rr->rrsig.signature_size <= 0)
2003 /* the accepted size depends on the algorithm, but for now
2004 just ensure that the value is greater than zero */
2005 return -EBADMSG;
2006
2007 break;
2008
2009 case DNS_TYPE_NSEC: {
2010
2011 /*
2012 * RFC6762, section 18.14 explicitly states mDNS should use name compression.
2013 * This contradicts RFC3845, section 2.1.1
2014 */
2015
2016 bool allow_compressed = p->protocol == DNS_PROTOCOL_MDNS;
2017
2018 r = dns_packet_read_name(p, &rr->nsec.next_domain_name, allow_compressed, NULL);
2019 if (r < 0)
2020 return r;
2021
2022 r = dns_packet_read_type_windows(p, &rr->nsec.types, offset + rdlength - p->rindex, NULL);
2023
2024 /* We accept empty NSEC bitmaps. The bit indicating the presence of the NSEC record itself
2025 * is redundant and in e.g., RFC4956 this fact is used to define a use for NSEC records
2026 * without the NSEC bit set. */
2027
2028 break;
2029 }
2030 case DNS_TYPE_NSEC3: {
2031 uint8_t size;
2032
2033 r = dns_packet_read_uint8(p, &rr->nsec3.algorithm, NULL);
2034 if (r < 0)
2035 return r;
2036
2037 r = dns_packet_read_uint8(p, &rr->nsec3.flags, NULL);
2038 if (r < 0)
2039 return r;
2040
2041 r = dns_packet_read_uint16(p, &rr->nsec3.iterations, NULL);
2042 if (r < 0)
2043 return r;
2044
2045 /* this may be zero */
2046 r = dns_packet_read_uint8(p, &size, NULL);
2047 if (r < 0)
2048 return r;
2049
2050 r = dns_packet_read_memdup(p, size, &rr->nsec3.salt, &rr->nsec3.salt_size, NULL);
2051 if (r < 0)
2052 return r;
2053
2054 r = dns_packet_read_uint8(p, &size, NULL);
2055 if (r < 0)
2056 return r;
2057
2058 if (size <= 0)
2059 return -EBADMSG;
2060
2061 r = dns_packet_read_memdup(p, size,
2062 &rr->nsec3.next_hashed_name, &rr->nsec3.next_hashed_name_size,
2063 NULL);
2064 if (r < 0)
2065 return r;
2066
2067 r = dns_packet_read_type_windows(p, &rr->nsec3.types, offset + rdlength - p->rindex, NULL);
2068
2069 /* empty non-terminals can have NSEC3 records, so empty bitmaps are allowed */
2070
2071 break;
2072 }
2073
2074 case DNS_TYPE_TLSA:
2075 r = dns_packet_read_uint8(p, &rr->tlsa.cert_usage, NULL);
2076 if (r < 0)
2077 return r;
2078
2079 r = dns_packet_read_uint8(p, &rr->tlsa.selector, NULL);
2080 if (r < 0)
2081 return r;
2082
2083 r = dns_packet_read_uint8(p, &rr->tlsa.matching_type, NULL);
2084 if (r < 0)
2085 return r;
2086
2087 if (rdlength < 3)
2088 return -EBADMSG;
2089
2090 r = dns_packet_read_memdup(p, rdlength - 3,
2091 &rr->tlsa.data, &rr->tlsa.data_size,
2092 NULL);
2093
2094 if (rr->tlsa.data_size <= 0)
2095 /* the accepted size depends on the algorithm, but for now
2096 just ensure that the value is greater than zero */
2097 return -EBADMSG;
2098
2099 break;
2100
2101 case DNS_TYPE_CAA:
2102 r = dns_packet_read_uint8(p, &rr->caa.flags, NULL);
2103 if (r < 0)
2104 return r;
2105
2106 r = dns_packet_read_string(p, &rr->caa.tag, NULL);
2107 if (r < 0)
2108 return r;
2109
2110 if (rdlength + offset < p->rindex)
2111 return -EBADMSG;
2112
2113 r = dns_packet_read_memdup(p,
2114 rdlength + offset - p->rindex,
2115 &rr->caa.value, &rr->caa.value_size, NULL);
2116
2117 break;
2118
2119 case DNS_TYPE_OPT: /* we only care about the header of OPT for now. */
2120 case DNS_TYPE_OPENPGPKEY:
2121 default:
2122 unparsable:
2123 r = dns_packet_read_memdup(p, rdlength, &rr->generic.data, &rr->generic.data_size, NULL);
2124
2125 break;
2126 }
2127 if (r < 0)
2128 return r;
2129 if (p->rindex != offset + rdlength)
2130 return -EBADMSG;
2131
2132 if (ret)
2133 *ret = TAKE_PTR(rr);
2134 if (ret_cache_flush)
2135 *ret_cache_flush = cache_flush;
2136 if (ret_start)
2137 *ret_start = rewinder.saved_rindex;
2138
2139 CANCEL_REWINDER(rewinder);
2140 return 0;
2141 }
2142
2143 static bool opt_is_good(DnsResourceRecord *rr, bool *rfc6975) {
2144 const uint8_t* p;
2145 bool found_dau_dhu_n3u = false;
2146 size_t l;
2147
2148 /* Checks whether the specified OPT RR is well-formed and whether it contains RFC6975 data (which is not OK in
2149 * a reply). */
2150
2151 assert(rr);
2152 assert(rr->key->type == DNS_TYPE_OPT);
2153
2154 /* Check that the version is 0 */
2155 if (((rr->ttl >> 16) & UINT32_C(0xFF)) != 0) {
2156 *rfc6975 = false;
2157 return true; /* if it's not version 0, it's OK, but we will ignore the OPT field contents */
2158 }
2159
2160 p = rr->opt.data;
2161 l = rr->opt.data_size;
2162 while (l > 0) {
2163 uint16_t option_code, option_length;
2164
2165 /* At least four bytes for OPTION-CODE and OPTION-LENGTH are required */
2166 if (l < 4U)
2167 return false;
2168
2169 option_code = unaligned_read_be16(p);
2170 option_length = unaligned_read_be16(p + 2);
2171
2172 if (l < option_length + 4U)
2173 return false;
2174
2175 /* RFC 6975 DAU, DHU or N3U fields found. */
2176 if (IN_SET(option_code, 5, 6, 7))
2177 found_dau_dhu_n3u = true;
2178
2179 p += option_length + 4U;
2180 l -= option_length + 4U;
2181 }
2182
2183 *rfc6975 = found_dau_dhu_n3u;
2184 return true;
2185 }
2186
2187 static int dns_packet_extract_question(DnsPacket *p, DnsQuestion **ret_question) {
2188 _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
2189 unsigned n;
2190 int r;
2191
2192 n = DNS_PACKET_QDCOUNT(p);
2193 if (n > 0) {
2194 question = dns_question_new(n);
2195 if (!question)
2196 return -ENOMEM;
2197
2198 _cleanup_set_free_ Set *keys = NULL; /* references to keys are kept by Question */
2199
2200 keys = set_new(&dns_resource_key_hash_ops);
2201 if (!keys)
2202 return log_oom();
2203
2204 r = set_reserve(keys, n * 2); /* Higher multipliers give slightly higher efficiency through
2205 * hash collisions, but the gains quickly drop off after 2. */
2206 if (r < 0)
2207 return r;
2208
2209 for (unsigned i = 0; i < n; i++) {
2210 _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
2211 bool qu;
2212
2213 r = dns_packet_read_key(p, &key, &qu, NULL);
2214 if (r < 0)
2215 return r;
2216
2217 if (!dns_type_is_valid_query(key->type))
2218 return -EBADMSG;
2219
2220 r = set_put(keys, key);
2221 if (r < 0)
2222 return r;
2223 if (r == 0)
2224 /* Already in the Question, let's skip */
2225 continue;
2226
2227 r = dns_question_add_raw(question, key, qu ? DNS_QUESTION_WANTS_UNICAST_REPLY : 0);
2228 if (r < 0)
2229 return r;
2230 }
2231 }
2232
2233 *ret_question = TAKE_PTR(question);
2234
2235 return 0;
2236 }
2237
2238 static int dns_packet_extract_answer(DnsPacket *p, DnsAnswer **ret_answer) {
2239 _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
2240 unsigned n;
2241 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *previous = NULL;
2242 bool bad_opt = false;
2243 int r;
2244
2245 n = DNS_PACKET_RRCOUNT(p);
2246 if (n == 0)
2247 return 0;
2248
2249 answer = dns_answer_new(n);
2250 if (!answer)
2251 return -ENOMEM;
2252
2253 for (unsigned i = 0; i < n; i++) {
2254 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
2255 bool cache_flush = false;
2256 size_t start;
2257
2258 if (p->rindex == p->size && p->opt) {
2259 /* If we reached the end of the packet already, but there are still more RRs
2260 * declared, then that's a corrupt packet. Let's accept the packet anyway, since it's
2261 * apparently a common bug in routers. Let's however suppress OPT support in this
2262 * case, so that we force the rest of the logic into lowest DNS baseline support. Or
2263 * to say this differently: if the DNS server doesn't even get the RR counts right,
2264 * it's highly unlikely it gets EDNS right. */
2265 log_debug("More resource records declared in packet than included, suppressing OPT.");
2266 bad_opt = true;
2267 break;
2268 }
2269
2270 r = dns_packet_read_rr(p, &rr, &cache_flush, &start);
2271 if (r < 0)
2272 return r;
2273
2274 /* Try to reduce memory usage a bit */
2275 if (previous)
2276 dns_resource_key_reduce(&rr->key, &previous->key);
2277
2278 if (rr->key->type == DNS_TYPE_OPT) {
2279 bool has_rfc6975;
2280
2281 if (p->opt || bad_opt) {
2282 /* Multiple OPT RRs? if so, let's ignore all, because there's
2283 * something wrong with the server, and if one is valid we wouldn't
2284 * know which one. */
2285 log_debug("Multiple OPT RRs detected, ignoring all.");
2286 bad_opt = true;
2287 continue;
2288 }
2289
2290 if (!dns_name_is_root(dns_resource_key_name(rr->key))) {
2291 /* If the OPT RR is not owned by the root domain, then it is bad,
2292 * let's ignore it. */
2293 log_debug("OPT RR is not owned by root domain, ignoring.");
2294 bad_opt = true;
2295 continue;
2296 }
2297
2298 if (i < DNS_PACKET_ANCOUNT(p) + DNS_PACKET_NSCOUNT(p)) {
2299 /* OPT RR is in the wrong section? Some Belkin routers do this. This
2300 * is a hint the EDNS implementation is borked, like the Belkin one
2301 * is, hence ignore it. */
2302 log_debug("OPT RR in wrong section, ignoring.");
2303 bad_opt = true;
2304 continue;
2305 }
2306
2307 if (!opt_is_good(rr, &has_rfc6975)) {
2308 log_debug("Malformed OPT RR, ignoring.");
2309 bad_opt = true;
2310 continue;
2311 }
2312
2313 if (DNS_PACKET_QR(p)) {
2314 /* Additional checks for responses */
2315
2316 if (!DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(rr))
2317 /* If this is a reply and we don't know the EDNS version
2318 * then something is weird... */
2319 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
2320 "EDNS version newer that our request, bad server.");
2321
2322 if (has_rfc6975) {
2323 /* If the OPT RR contains RFC6975 algorithm data, then this
2324 * is indication that the server just copied the OPT it got
2325 * from us (which contained that data) back into the reply.
2326 * If so, then it doesn't properly support EDNS, as RFC6975
2327 * makes it very clear that the algorithm data should only
2328 * be contained in questions, never in replies. Crappy
2329 * Belkin routers copy the OPT data for example, hence let's
2330 * detect this so that we downgrade early. */
2331 log_debug("OPT RR contains RFC6975 data, ignoring.");
2332 bad_opt = true;
2333 continue;
2334 }
2335 }
2336
2337 p->opt = dns_resource_record_ref(rr);
2338 p->opt_start = start;
2339 assert(p->rindex >= start);
2340 p->opt_size = p->rindex - start;
2341 } else {
2342 DnsAnswerFlags flags = 0;
2343
2344 if (p->protocol == DNS_PROTOCOL_MDNS && !cache_flush)
2345 flags |= DNS_ANSWER_SHARED_OWNER;
2346
2347 /* According to RFC 4795, section 2.9. only the RRs from the Answer section shall be
2348 * cached. Hence mark only those RRs as cacheable by default, but not the ones from
2349 * the Additional or Authority sections. */
2350 if (i < DNS_PACKET_ANCOUNT(p))
2351 flags |= DNS_ANSWER_CACHEABLE|DNS_ANSWER_SECTION_ANSWER;
2352 else if (i < DNS_PACKET_ANCOUNT(p) + DNS_PACKET_NSCOUNT(p))
2353 flags |= DNS_ANSWER_SECTION_AUTHORITY;
2354 else
2355 flags |= DNS_ANSWER_SECTION_ADDITIONAL;
2356
2357 r = dns_answer_add(answer, rr, p->ifindex, flags, NULL);
2358 if (r < 0)
2359 return r;
2360 }
2361
2362 /* Remember this RR, so that we can potentially merge its ->key object with the
2363 * next RR. Note that we only do this if we actually decided to keep the RR around.
2364 */
2365 dns_resource_record_unref(previous);
2366 previous = dns_resource_record_ref(rr);
2367 }
2368
2369 if (bad_opt) {
2370 p->opt = dns_resource_record_unref(p->opt);
2371 p->opt_start = p->opt_size = SIZE_MAX;
2372 }
2373
2374 *ret_answer = TAKE_PTR(answer);
2375
2376 return 0;
2377 }
2378
2379 int dns_packet_extract(DnsPacket *p) {
2380 assert(p);
2381
2382 if (p->extracted)
2383 return 0;
2384
2385 _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
2386 _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
2387 _unused_ _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
2388 int r;
2389
2390 dns_packet_rewind(p, DNS_PACKET_HEADER_SIZE);
2391
2392 r = dns_packet_extract_question(p, &question);
2393 if (r < 0)
2394 return r;
2395
2396 r = dns_packet_extract_answer(p, &answer);
2397 if (r < 0)
2398 return r;
2399
2400 if (p->rindex < p->size) {
2401 log_debug("Trailing garbage in packet, suppressing OPT.");
2402 p->opt = dns_resource_record_unref(p->opt);
2403 p->opt_start = p->opt_size = SIZE_MAX;
2404 }
2405
2406 p->question = TAKE_PTR(question);
2407 p->answer = TAKE_PTR(answer);
2408 p->extracted = true;
2409
2410 /* no CANCEL, always rewind */
2411 return 0;
2412 }
2413
2414 int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key) {
2415 int r;
2416
2417 assert(p);
2418 assert(key);
2419
2420 /* Checks if the specified packet is a reply for the specified
2421 * key and the specified key is the only one in the question
2422 * section. */
2423
2424 if (DNS_PACKET_QR(p) != 1)
2425 return 0;
2426
2427 /* Let's unpack the packet, if that hasn't happened yet. */
2428 r = dns_packet_extract(p);
2429 if (r < 0)
2430 return r;
2431
2432 if (!p->question)
2433 return 0;
2434
2435 if (p->question->n_keys != 1)
2436 return 0;
2437
2438 return dns_resource_key_equal(dns_question_first_key(p->question), key);
2439 }
2440
2441 int dns_packet_patch_max_udp_size(DnsPacket *p, uint16_t max_udp_size) {
2442 assert(p);
2443 assert(max_udp_size >= DNS_PACKET_UNICAST_SIZE_MAX);
2444
2445 if (p->opt_start == SIZE_MAX) /* No OPT section, nothing to patch */
2446 return 0;
2447
2448 assert(p->opt_size != SIZE_MAX);
2449 assert(p->opt_size >= 5);
2450
2451 unaligned_write_be16(DNS_PACKET_DATA(p) + p->opt_start + 3, max_udp_size);
2452 return 1;
2453 }
2454
2455 static int patch_rr(DnsPacket *p, usec_t age) {
2456 _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
2457 size_t ttl_index;
2458 uint32_t ttl;
2459 uint16_t type, rdlength;
2460 int r;
2461
2462 /* Patches the RR at the current rindex, subtracts the specified time from the TTL */
2463
2464 r = dns_packet_read_name(p, NULL, true, NULL);
2465 if (r < 0)
2466 return r;
2467
2468 r = dns_packet_read_uint16(p, &type, NULL);
2469 if (r < 0)
2470 return r;
2471
2472 r = dns_packet_read_uint16(p, NULL, NULL);
2473 if (r < 0)
2474 return r;
2475
2476 r = dns_packet_read_uint32(p, &ttl, &ttl_index);
2477 if (r < 0)
2478 return r;
2479
2480 if (type != DNS_TYPE_OPT) { /* The TTL of the OPT field is not actually a TTL, skip it */
2481 ttl = LESS_BY(ttl * USEC_PER_SEC, age) / USEC_PER_SEC;
2482 unaligned_write_be32(DNS_PACKET_DATA(p) + ttl_index, ttl);
2483 }
2484
2485 r = dns_packet_read_uint16(p, &rdlength, NULL);
2486 if (r < 0)
2487 return r;
2488
2489 r = dns_packet_read(p, rdlength, NULL, NULL);
2490 if (r < 0)
2491 return r;
2492
2493 CANCEL_REWINDER(rewinder);
2494 return 0;
2495 }
2496
2497 int dns_packet_patch_ttls(DnsPacket *p, usec_t timestamp) {
2498 assert(p);
2499 assert(timestamp_is_set(timestamp));
2500
2501 /* Adjusts all TTLs in the packet by subtracting the time difference between now and the specified timestamp */
2502
2503 _unused_ _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = REWINDER_INIT(p);
2504 unsigned n;
2505 usec_t k;
2506 int r;
2507
2508 k = now(clock_boottime_or_monotonic());
2509 assert(k >= timestamp);
2510 k -= timestamp;
2511
2512 dns_packet_rewind(p, DNS_PACKET_HEADER_SIZE);
2513
2514 n = DNS_PACKET_QDCOUNT(p);
2515 for (unsigned i = 0; i < n; i++) {
2516 r = dns_packet_read_key(p, NULL, NULL, NULL);
2517 if (r < 0)
2518 return r;
2519 }
2520
2521 n = DNS_PACKET_RRCOUNT(p);
2522 for (unsigned i = 0; i < n; i++) {
2523
2524 /* DNS servers suck, hence the RR count is in many servers off. If we reached the end
2525 * prematurely, accept that, exit early */
2526 if (p->rindex == p->size)
2527 break;
2528
2529 r = patch_rr(p, k);
2530 if (r < 0)
2531 return r;
2532 }
2533
2534 return 0;
2535 }
2536
2537 static void dns_packet_hash_func(const DnsPacket *s, struct siphash *state) {
2538 assert(s);
2539
2540 siphash24_compress(&s->size, sizeof(s->size), state);
2541 siphash24_compress(DNS_PACKET_DATA((DnsPacket*) s), s->size, state);
2542 }
2543
2544 static int dns_packet_compare_func(const DnsPacket *x, const DnsPacket *y) {
2545 int r;
2546
2547 r = CMP(x->size, y->size);
2548 if (r != 0)
2549 return r;
2550
2551 return memcmp(DNS_PACKET_DATA((DnsPacket*) x), DNS_PACKET_DATA((DnsPacket*) y), x->size);
2552 }
2553
2554 DEFINE_HASH_OPS(dns_packet_hash_ops, DnsPacket, dns_packet_hash_func, dns_packet_compare_func);
2555
2556 bool dns_packet_equal(const DnsPacket *a, const DnsPacket *b) {
2557 return dns_packet_compare_func(a, b) == 0;
2558 }
2559
2560 int dns_packet_has_nsid_request(DnsPacket *p) {
2561 bool has_nsid = false;
2562 const uint8_t *d;
2563 size_t l;
2564
2565 assert(p);
2566
2567 if (!p->opt)
2568 return false;
2569
2570 d = p->opt->opt.data;
2571 l = p->opt->opt.data_size;
2572
2573 while (l > 0) {
2574 uint16_t code, length;
2575
2576 if (l < 4U)
2577 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
2578 "EDNS0 variable part has invalid size.");
2579
2580 code = unaligned_read_be16(d);
2581 length = unaligned_read_be16(d + 2);
2582
2583 if (l < 4U + length)
2584 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
2585 "Truncated option in EDNS0 variable part.");
2586
2587 if (code == 3) {
2588 if (has_nsid)
2589 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
2590 "Duplicate NSID option in EDNS0 variable part.");
2591
2592 if (length != 0)
2593 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
2594 "Non-empty NSID option in DNS request.");
2595
2596 has_nsid = true;
2597 }
2598
2599 d += 4U + length;
2600 l -= 4U + length;
2601 }
2602
2603 return has_nsid;
2604 }
2605
2606 size_t dns_packet_size_unfragmented(DnsPacket *p) {
2607 assert(p);
2608
2609 if (p->fragsize == 0) /* Wasn't fragmented */
2610 return p->size;
2611
2612 /* The fragment size (p->fragsize) covers the whole (fragmented) IP packet, while the regular packet
2613 * size (p->size) only covers the DNS part. Thus, subtract the UDP header from the largest fragment
2614 * size, in order to determine which size of DNS packet would have gone through without
2615 * fragmenting. */
2616
2617 return LESS_BY(p->fragsize, udp_header_size(p->family));
2618 }
2619
2620 static const char* const dns_rcode_table[_DNS_RCODE_MAX_DEFINED] = {
2621 [DNS_RCODE_SUCCESS] = "SUCCESS",
2622 [DNS_RCODE_FORMERR] = "FORMERR",
2623 [DNS_RCODE_SERVFAIL] = "SERVFAIL",
2624 [DNS_RCODE_NXDOMAIN] = "NXDOMAIN",
2625 [DNS_RCODE_NOTIMP] = "NOTIMP",
2626 [DNS_RCODE_REFUSED] = "REFUSED",
2627 [DNS_RCODE_YXDOMAIN] = "YXDOMAIN",
2628 [DNS_RCODE_YXRRSET] = "YRRSET",
2629 [DNS_RCODE_NXRRSET] = "NXRRSET",
2630 [DNS_RCODE_NOTAUTH] = "NOTAUTH",
2631 [DNS_RCODE_NOTZONE] = "NOTZONE",
2632 [DNS_RCODE_BADVERS] = "BADVERS",
2633 [DNS_RCODE_BADKEY] = "BADKEY",
2634 [DNS_RCODE_BADTIME] = "BADTIME",
2635 [DNS_RCODE_BADMODE] = "BADMODE",
2636 [DNS_RCODE_BADNAME] = "BADNAME",
2637 [DNS_RCODE_BADALG] = "BADALG",
2638 [DNS_RCODE_BADTRUNC] = "BADTRUNC",
2639 [DNS_RCODE_BADCOOKIE] = "BADCOOKIE",
2640 };
2641 DEFINE_STRING_TABLE_LOOKUP(dns_rcode, int);
2642
2643 static const char* const dns_protocol_table[_DNS_PROTOCOL_MAX] = {
2644 [DNS_PROTOCOL_DNS] = "dns",
2645 [DNS_PROTOCOL_MDNS] = "mdns",
2646 [DNS_PROTOCOL_LLMNR] = "llmnr",
2647 };
2648 DEFINE_STRING_TABLE_LOOKUP(dns_protocol, DnsProtocol);
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