1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
7 #include "alloc-util.h"
8 #include "dns-domain.h"
9 #include "memory-util.h"
10 #include "resolved-dns-packet.h"
12 #include "string-table.h"
14 #include "unaligned.h"
18 #define EDNS0_OPT_DO (1<<15)
20 assert_cc(DNS_PACKET_SIZE_START
> DNS_PACKET_HEADER_SIZE
);
22 typedef struct DnsPacketRewinder
{
27 static void rewind_dns_packet(DnsPacketRewinder
*rewinder
) {
29 dns_packet_rewind(rewinder
->packet
, rewinder
->saved_rindex
);
32 #define INIT_REWINDER(rewinder, p) do { rewinder.packet = p; rewinder.saved_rindex = p->rindex; } while (0)
33 #define CANCEL_REWINDER(rewinder) do { rewinder.packet = NULL; } while (0)
38 size_t min_alloc_dsize
,
45 assert(max_size
>= DNS_PACKET_HEADER_SIZE
);
47 if (max_size
> DNS_PACKET_SIZE_MAX
)
48 max_size
= DNS_PACKET_SIZE_MAX
;
50 /* The caller may not check what is going to be truly allocated, so do not allow to
51 * allocate a DNS packet bigger than DNS_PACKET_SIZE_MAX.
53 if (min_alloc_dsize
> DNS_PACKET_SIZE_MAX
)
54 return log_error_errno(SYNTHETIC_ERRNO(EFBIG
),
55 "Requested packet data size too big: %zu",
58 /* When dns_packet_new() is called with min_alloc_dsize == 0, allocate more than the
59 * absolute minimum (which is the dns packet header size), to avoid
60 * resizing immediately again after appending the first data to the packet.
62 if (min_alloc_dsize
< DNS_PACKET_HEADER_SIZE
)
63 a
= DNS_PACKET_SIZE_START
;
67 /* round up to next page size */
68 a
= PAGE_ALIGN(ALIGN(sizeof(DnsPacket
)) + a
) - ALIGN(sizeof(DnsPacket
));
70 /* make sure we never allocate more than useful */
74 p
= malloc0(ALIGN(sizeof(DnsPacket
)) + a
);
81 .size
= DNS_PACKET_HEADER_SIZE
,
82 .rindex
= DNS_PACKET_HEADER_SIZE
,
85 .opt_start
= SIZE_MAX
,
94 void dns_packet_set_flags(DnsPacket
*p
, bool dnssec_checking_disabled
, bool truncated
) {
100 h
= DNS_PACKET_HEADER(p
);
102 switch(p
->protocol
) {
103 case DNS_PROTOCOL_LLMNR
:
106 h
->flags
= htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
117 case DNS_PROTOCOL_MDNS
:
118 h
->flags
= htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
122 0 /* rd (ask for recursion) */,
132 h
->flags
= htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
136 1 /* rd (ask for recursion) */,
139 dnssec_checking_disabled
/* cd */,
144 int dns_packet_new_query(DnsPacket
**ret
, DnsProtocol protocol
, size_t min_alloc_dsize
, bool dnssec_checking_disabled
) {
150 r
= dns_packet_new(&p
, protocol
, min_alloc_dsize
, DNS_PACKET_SIZE_MAX
);
154 /* Always set the TC bit to 0 initially.
155 * If there are multiple packets later, we'll update the bit shortly before sending.
157 dns_packet_set_flags(p
, dnssec_checking_disabled
, false);
163 int dns_packet_dup(DnsPacket
**ret
, DnsPacket
*p
) {
170 r
= dns_packet_validate(p
);
174 c
= malloc(ALIGN(sizeof(DnsPacket
)) + p
->size
);
180 .protocol
= p
->protocol
,
182 .rindex
= DNS_PACKET_HEADER_SIZE
,
183 .allocated
= p
->size
,
184 .max_size
= p
->max_size
,
185 .opt_start
= SIZE_MAX
,
186 .opt_size
= SIZE_MAX
,
189 memcpy(DNS_PACKET_DATA(c
), DNS_PACKET_DATA(p
), p
->size
);
195 DnsPacket
*dns_packet_ref(DnsPacket
*p
) {
200 assert(!p
->on_stack
);
202 assert(p
->n_ref
> 0);
207 static void dns_packet_free(DnsPacket
*p
) {
212 dns_question_unref(p
->question
);
213 dns_answer_unref(p
->answer
);
214 dns_resource_record_unref(p
->opt
);
216 while ((s
= hashmap_steal_first_key(p
->names
)))
218 hashmap_free(p
->names
);
226 DnsPacket
*dns_packet_unref(DnsPacket
*p
) {
230 assert(p
->n_ref
> 0);
232 dns_packet_unref(p
->more
);
242 int dns_packet_validate(DnsPacket
*p
) {
245 if (p
->size
< DNS_PACKET_HEADER_SIZE
)
248 if (p
->size
> DNS_PACKET_SIZE_MAX
)
254 int dns_packet_validate_reply(DnsPacket
*p
) {
259 r
= dns_packet_validate(p
);
263 if (DNS_PACKET_QR(p
) != 1)
266 if (DNS_PACKET_OPCODE(p
) != 0)
269 switch (p
->protocol
) {
271 case DNS_PROTOCOL_LLMNR
:
272 /* RFC 4795, Section 2.1.1. says to discard all replies with QDCOUNT != 1 */
273 if (DNS_PACKET_QDCOUNT(p
) != 1)
278 case DNS_PROTOCOL_MDNS
:
279 /* RFC 6762, Section 18 */
280 if (DNS_PACKET_RCODE(p
) != 0)
292 int dns_packet_validate_query(DnsPacket
*p
) {
297 r
= dns_packet_validate(p
);
301 if (DNS_PACKET_QR(p
) != 0)
304 if (DNS_PACKET_OPCODE(p
) != 0)
307 if (DNS_PACKET_TC(p
))
310 switch (p
->protocol
) {
312 case DNS_PROTOCOL_LLMNR
:
313 case DNS_PROTOCOL_DNS
:
314 /* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */
315 if (DNS_PACKET_QDCOUNT(p
) != 1)
318 /* RFC 4795, Section 2.1.1. says to discard all queries with ANCOUNT != 0 */
319 if (DNS_PACKET_ANCOUNT(p
) > 0)
322 /* RFC 4795, Section 2.1.1. says to discard all queries with NSCOUNT != 0 */
323 if (DNS_PACKET_NSCOUNT(p
) > 0)
328 case DNS_PROTOCOL_MDNS
:
329 /* RFC 6762, Section 18 specifies that messages with non-zero RCODE
330 * must be silently ignored, and that we must ignore the values of
331 * AA, RD, RA, AD, and CD bits. */
332 if (DNS_PACKET_RCODE(p
) != 0)
344 static int dns_packet_extend(DnsPacket
*p
, size_t add
, void **ret
, size_t *start
) {
347 if (p
->size
+ add
> p
->allocated
) {
350 a
= PAGE_ALIGN((p
->size
+ add
) * 2);
352 ms
= dns_packet_size_max(p
);
356 if (p
->size
+ add
> a
)
362 d
= realloc(p
->_data
, a
);
368 p
->_data
= malloc(a
);
372 memcpy(p
->_data
, (uint8_t*) p
+ ALIGN(sizeof(DnsPacket
)), p
->size
);
373 memzero((uint8_t*) p
->_data
+ p
->size
, a
- p
->size
);
383 *ret
= (uint8_t*) DNS_PACKET_DATA(p
) + p
->size
;
389 void dns_packet_truncate(DnsPacket
*p
, size_t sz
) {
398 HASHMAP_FOREACH_KEY(n
, s
, p
->names
) {
400 if (PTR_TO_SIZE(n
) < sz
)
403 hashmap_remove(p
->names
, s
);
410 int dns_packet_append_blob(DnsPacket
*p
, const void *d
, size_t l
, size_t *start
) {
416 r
= dns_packet_extend(p
, l
, &q
, start
);
420 memcpy_safe(q
, d
, l
);
424 int dns_packet_append_uint8(DnsPacket
*p
, uint8_t v
, size_t *start
) {
430 r
= dns_packet_extend(p
, sizeof(uint8_t), &d
, start
);
434 ((uint8_t*) d
)[0] = v
;
439 int dns_packet_append_uint16(DnsPacket
*p
, uint16_t v
, size_t *start
) {
445 r
= dns_packet_extend(p
, sizeof(uint16_t), &d
, start
);
449 unaligned_write_be16(d
, v
);
454 int dns_packet_append_uint32(DnsPacket
*p
, uint32_t v
, size_t *start
) {
460 r
= dns_packet_extend(p
, sizeof(uint32_t), &d
, start
);
464 unaligned_write_be32(d
, v
);
469 int dns_packet_append_string(DnsPacket
*p
, const char *s
, size_t *start
) {
473 return dns_packet_append_raw_string(p
, s
, strlen(s
), start
);
476 int dns_packet_append_raw_string(DnsPacket
*p
, const void *s
, size_t size
, size_t *start
) {
481 assert(s
|| size
== 0);
486 r
= dns_packet_extend(p
, 1 + size
, &d
, start
);
490 ((uint8_t*) d
)[0] = (uint8_t) size
;
492 memcpy_safe(((uint8_t*) d
) + 1, s
, size
);
497 int dns_packet_append_label(DnsPacket
*p
, const char *d
, size_t l
, bool canonical_candidate
, size_t *start
) {
501 /* Append a label to a packet. Optionally, does this in DNSSEC
502 * canonical form, if this label is marked as a candidate for
503 * it, and the canonical form logic is enabled for the
509 if (l
> DNS_LABEL_MAX
)
512 r
= dns_packet_extend(p
, 1 + l
, (void**) &w
, start
);
516 *(w
++) = (uint8_t) l
;
518 if (p
->canonical_form
&& canonical_candidate
) {
521 /* Generate in canonical form, as defined by DNSSEC
522 * RFC 4034, Section 6.2, i.e. all lower-case. */
524 for (i
= 0; i
< l
; i
++)
525 w
[i
] = (uint8_t) ascii_tolower(d
[i
]);
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. */
535 int dns_packet_append_name(
538 bool allow_compression
,
539 bool canonical_candidate
,
548 if (p
->refuse_compression
)
549 allow_compression
= false;
551 saved_size
= p
->size
;
553 while (!dns_name_is_root(name
)) {
554 const char *z
= name
;
555 char label
[DNS_LABEL_MAX
];
558 if (allow_compression
)
559 n
= PTR_TO_SIZE(hashmap_get(p
->names
, name
));
564 r
= dns_packet_append_uint16(p
, 0xC000 | n
, NULL
);
572 r
= dns_label_unescape(&name
, label
, sizeof label
, 0);
576 r
= dns_packet_append_label(p
, label
, r
, canonical_candidate
, &n
);
580 if (allow_compression
) {
581 _cleanup_free_
char *s
= NULL
;
589 r
= hashmap_ensure_put(&p
->names
, &dns_name_hash_ops
, s
, SIZE_TO_PTR(n
));
597 r
= dns_packet_append_uint8(p
, 0, NULL
);
608 dns_packet_truncate(p
, saved_size
);
612 int dns_packet_append_key(DnsPacket
*p
, const DnsResourceKey
*k
, const DnsAnswerFlags flags
, size_t *start
) {
620 saved_size
= p
->size
;
622 r
= dns_packet_append_name(p
, dns_resource_key_name(k
), true, true, NULL
);
626 r
= dns_packet_append_uint16(p
, k
->type
, NULL
);
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
);
641 dns_packet_truncate(p
, saved_size
);
645 static int dns_packet_append_type_window(DnsPacket
*p
, uint8_t window
, uint8_t length
, const uint8_t *types
, size_t *start
) {
653 saved_size
= p
->size
;
655 r
= dns_packet_append_uint8(p
, window
, NULL
);
659 r
= dns_packet_append_uint8(p
, length
, NULL
);
663 r
= dns_packet_append_blob(p
, types
, length
, NULL
);
672 dns_packet_truncate(p
, saved_size
);
676 static int dns_packet_append_types(DnsPacket
*p
, Bitmap
*types
, size_t *start
) {
679 uint8_t bitmaps
[32] = {};
686 saved_size
= p
->size
;
688 BITMAP_FOREACH(n
, types
) {
691 if ((n
>> 8) != window
&& bitmaps
[entry
/ 8] != 0) {
692 r
= dns_packet_append_type_window(p
, window
, entry
/ 8 + 1, bitmaps
, NULL
);
702 bitmaps
[entry
/ 8] |= 1 << (7 - (entry
% 8));
705 if (bitmaps
[entry
/ 8] != 0) {
706 r
= dns_packet_append_type_window(p
, window
, entry
/ 8 + 1, bitmaps
, NULL
);
716 dns_packet_truncate(p
, saved_size
);
720 /* Append the OPT pseudo-RR described in RFC6891 */
721 int dns_packet_append_opt(
723 uint16_t max_udp_size
,
725 bool include_rfc6975
,
734 /* we must never advertise supported packet size smaller than the legacy max */
735 assert(max_udp_size
>= DNS_PACKET_UNICAST_SIZE_MAX
);
737 assert(rcode
<= _DNS_RCODE_MAX
);
739 if (p
->opt_start
!= SIZE_MAX
)
742 assert(p
->opt_size
== SIZE_MAX
);
744 saved_size
= p
->size
;
747 r
= dns_packet_append_uint8(p
, 0, NULL
);
752 r
= dns_packet_append_uint16(p
, DNS_TYPE_OPT
, NULL
);
756 /* class: maximum udp packet that can be received */
757 r
= dns_packet_append_uint16(p
, max_udp_size
, NULL
);
761 /* extended RCODE and VERSION */
762 r
= dns_packet_append_uint16(p
, ((uint16_t) rcode
& 0x0FF0) << 4, NULL
);
766 /* flags: DNSSEC OK (DO), see RFC3225 */
767 r
= dns_packet_append_uint16(p
, edns0_do
? EDNS0_OPT_DO
: 0, NULL
);
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
776 static const uint8_t rfc6975
[] = {
778 0, 5, /* OPTION_CODE: DAU */
779 #if HAVE_GCRYPT && GCRYPT_VERSION_NUMBER >= 0x010600
780 0, 7, /* LIST_LENGTH */
782 0, 6, /* LIST_LENGTH */
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 HAVE_GCRYPT && GCRYPT_VERSION_NUMBER >= 0x010600
791 DNSSEC_ALGORITHM_ED25519
,
794 0, 6, /* OPTION_CODE: DHU */
795 0, 3, /* LIST_LENGTH */
797 DNSSEC_DIGEST_SHA256
,
798 DNSSEC_DIGEST_SHA384
,
800 0, 7, /* OPTION_CODE: N3U */
801 0, 1, /* LIST_LENGTH */
802 NSEC3_ALGORITHM_SHA1
,
805 r
= dns_packet_append_uint16(p
, sizeof(rfc6975
), NULL
); /* RDLENGTH */
809 r
= dns_packet_append_blob(p
, rfc6975
, sizeof(rfc6975
), NULL
); /* the payload, as defined above */
813 if (strlen(nsid
) > UINT16_MAX
- 4) {
818 r
= dns_packet_append_uint16(p
, 4 + strlen(nsid
), NULL
); /* RDLENGTH */
822 r
= dns_packet_append_uint16(p
, 3, NULL
); /* OPTION-CODE: NSID */
826 r
= dns_packet_append_uint16(p
, strlen(nsid
), NULL
); /* OPTION-LENGTH */
830 r
= dns_packet_append_blob(p
, nsid
, strlen(nsid
), NULL
);
832 r
= dns_packet_append_uint16(p
, 0, NULL
);
836 DNS_PACKET_HEADER(p
)->arcount
= htobe16(DNS_PACKET_ARCOUNT(p
) + 1);
838 p
->opt_start
= saved_size
;
839 p
->opt_size
= p
->size
- saved_size
;
842 *ret_start
= saved_size
;
847 dns_packet_truncate(p
, saved_size
);
851 int dns_packet_truncate_opt(DnsPacket
*p
) {
854 if (p
->opt_start
== SIZE_MAX
) {
855 assert(p
->opt_size
== SIZE_MAX
);
859 assert(p
->opt_size
!= SIZE_MAX
);
860 assert(DNS_PACKET_ARCOUNT(p
) > 0);
862 if (p
->opt_start
+ p
->opt_size
!= p
->size
)
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
;
872 int dns_packet_append_rr(DnsPacket
*p
, const DnsResourceRecord
*rr
, const DnsAnswerFlags flags
, size_t *start
, size_t *rdata_start
) {
874 size_t saved_size
, rdlength_offset
, end
, rdlength
, rds
;
881 saved_size
= p
->size
;
883 r
= dns_packet_append_key(p
, rr
->key
, flags
, NULL
);
887 ttl
= flags
& DNS_ANSWER_GOODBYE
? 0 : rr
->ttl
;
888 r
= dns_packet_append_uint32(p
, ttl
, NULL
);
892 /* Initially we write 0 here */
893 r
= dns_packet_append_uint16(p
, 0, &rdlength_offset
);
897 rds
= p
->size
- saved_size
;
899 switch (rr
->unparsable
? _DNS_TYPE_INVALID
: rr
->key
->type
) {
902 r
= dns_packet_append_uint16(p
, rr
->srv
.priority
, NULL
);
906 r
= dns_packet_append_uint16(p
, rr
->srv
.weight
, NULL
);
910 r
= dns_packet_append_uint16(p
, rr
->srv
.port
, NULL
);
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
);
923 r
= dns_packet_append_name(p
, rr
->ptr
.name
, true, true, NULL
);
927 r
= dns_packet_append_string(p
, rr
->hinfo
.cpu
, NULL
);
931 r
= dns_packet_append_string(p
, rr
->hinfo
.os
, NULL
);
934 case DNS_TYPE_SPF
: /* exactly the same as TXT */
937 if (!rr
->txt
.items
) {
938 /* RFC 6763, section 6.1 suggests to generate
939 * single empty string for an empty array. */
941 r
= dns_packet_append_raw_string(p
, NULL
, 0, NULL
);
947 LIST_FOREACH(items
, i
, rr
->txt
.items
) {
948 r
= dns_packet_append_raw_string(p
, i
->data
, i
->length
, NULL
);
958 r
= dns_packet_append_blob(p
, &rr
->a
.in_addr
, sizeof(struct in_addr
), NULL
);
962 r
= dns_packet_append_blob(p
, &rr
->aaaa
.in6_addr
, sizeof(struct in6_addr
), NULL
);
966 r
= dns_packet_append_name(p
, rr
->soa
.mname
, true, true, NULL
);
970 r
= dns_packet_append_name(p
, rr
->soa
.rname
, true, true, NULL
);
974 r
= dns_packet_append_uint32(p
, rr
->soa
.serial
, NULL
);
978 r
= dns_packet_append_uint32(p
, rr
->soa
.refresh
, NULL
);
982 r
= dns_packet_append_uint32(p
, rr
->soa
.retry
, NULL
);
986 r
= dns_packet_append_uint32(p
, rr
->soa
.expire
, NULL
);
990 r
= dns_packet_append_uint32(p
, rr
->soa
.minimum
, NULL
);
994 r
= dns_packet_append_uint16(p
, rr
->mx
.priority
, NULL
);
998 r
= dns_packet_append_name(p
, rr
->mx
.exchange
, true, true, NULL
);
1002 r
= dns_packet_append_uint8(p
, rr
->loc
.version
, NULL
);
1006 r
= dns_packet_append_uint8(p
, rr
->loc
.size
, NULL
);
1010 r
= dns_packet_append_uint8(p
, rr
->loc
.horiz_pre
, NULL
);
1014 r
= dns_packet_append_uint8(p
, rr
->loc
.vert_pre
, NULL
);
1018 r
= dns_packet_append_uint32(p
, rr
->loc
.latitude
, NULL
);
1022 r
= dns_packet_append_uint32(p
, rr
->loc
.longitude
, NULL
);
1026 r
= dns_packet_append_uint32(p
, rr
->loc
.altitude
, NULL
);
1030 r
= dns_packet_append_uint16(p
, rr
->ds
.key_tag
, NULL
);
1034 r
= dns_packet_append_uint8(p
, rr
->ds
.algorithm
, NULL
);
1038 r
= dns_packet_append_uint8(p
, rr
->ds
.digest_type
, NULL
);
1042 r
= dns_packet_append_blob(p
, rr
->ds
.digest
, rr
->ds
.digest_size
, NULL
);
1045 case DNS_TYPE_SSHFP
:
1046 r
= dns_packet_append_uint8(p
, rr
->sshfp
.algorithm
, NULL
);
1050 r
= dns_packet_append_uint8(p
, rr
->sshfp
.fptype
, NULL
);
1054 r
= dns_packet_append_blob(p
, rr
->sshfp
.fingerprint
, rr
->sshfp
.fingerprint_size
, NULL
);
1057 case DNS_TYPE_DNSKEY
:
1058 r
= dns_packet_append_uint16(p
, rr
->dnskey
.flags
, NULL
);
1062 r
= dns_packet_append_uint8(p
, rr
->dnskey
.protocol
, NULL
);
1066 r
= dns_packet_append_uint8(p
, rr
->dnskey
.algorithm
, NULL
);
1070 r
= dns_packet_append_blob(p
, rr
->dnskey
.key
, rr
->dnskey
.key_size
, NULL
);
1073 case DNS_TYPE_RRSIG
:
1074 r
= dns_packet_append_uint16(p
, rr
->rrsig
.type_covered
, NULL
);
1078 r
= dns_packet_append_uint8(p
, rr
->rrsig
.algorithm
, NULL
);
1082 r
= dns_packet_append_uint8(p
, rr
->rrsig
.labels
, NULL
);
1086 r
= dns_packet_append_uint32(p
, rr
->rrsig
.original_ttl
, NULL
);
1090 r
= dns_packet_append_uint32(p
, rr
->rrsig
.expiration
, NULL
);
1094 r
= dns_packet_append_uint32(p
, rr
->rrsig
.inception
, NULL
);
1098 r
= dns_packet_append_uint16(p
, rr
->rrsig
.key_tag
, NULL
);
1102 r
= dns_packet_append_name(p
, rr
->rrsig
.signer
, false, true, NULL
);
1106 r
= dns_packet_append_blob(p
, rr
->rrsig
.signature
, rr
->rrsig
.signature_size
, NULL
);
1110 r
= dns_packet_append_name(p
, rr
->nsec
.next_domain_name
, false, false, NULL
);
1114 r
= dns_packet_append_types(p
, rr
->nsec
.types
, NULL
);
1120 case DNS_TYPE_NSEC3
:
1121 r
= dns_packet_append_uint8(p
, rr
->nsec3
.algorithm
, NULL
);
1125 r
= dns_packet_append_uint8(p
, rr
->nsec3
.flags
, NULL
);
1129 r
= dns_packet_append_uint16(p
, rr
->nsec3
.iterations
, NULL
);
1133 r
= dns_packet_append_uint8(p
, rr
->nsec3
.salt_size
, NULL
);
1137 r
= dns_packet_append_blob(p
, rr
->nsec3
.salt
, rr
->nsec3
.salt_size
, NULL
);
1141 r
= dns_packet_append_uint8(p
, rr
->nsec3
.next_hashed_name_size
, NULL
);
1145 r
= dns_packet_append_blob(p
, rr
->nsec3
.next_hashed_name
, rr
->nsec3
.next_hashed_name_size
, NULL
);
1149 r
= dns_packet_append_types(p
, rr
->nsec3
.types
, NULL
);
1156 r
= dns_packet_append_uint8(p
, rr
->tlsa
.cert_usage
, NULL
);
1160 r
= dns_packet_append_uint8(p
, rr
->tlsa
.selector
, NULL
);
1164 r
= dns_packet_append_uint8(p
, rr
->tlsa
.matching_type
, NULL
);
1168 r
= dns_packet_append_blob(p
, rr
->tlsa
.data
, rr
->tlsa
.data_size
, NULL
);
1172 r
= dns_packet_append_uint8(p
, rr
->caa
.flags
, NULL
);
1176 r
= dns_packet_append_string(p
, rr
->caa
.tag
, NULL
);
1180 r
= dns_packet_append_blob(p
, rr
->caa
.value
, rr
->caa
.value_size
, NULL
);
1184 case DNS_TYPE_OPENPGPKEY
:
1185 case _DNS_TYPE_INVALID
: /* unparsable */
1188 r
= dns_packet_append_blob(p
, rr
->generic
.data
, rr
->generic
.data_size
, NULL
);
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) {
1202 p
->size
= rdlength_offset
;
1203 r
= dns_packet_append_uint16(p
, rdlength
, NULL
);
1209 *start
= saved_size
;
1217 dns_packet_truncate(p
, saved_size
);
1221 int dns_packet_append_question(DnsPacket
*p
, DnsQuestion
*q
) {
1222 DnsResourceKey
*key
;
1227 DNS_QUESTION_FOREACH(key
, q
) {
1228 r
= dns_packet_append_key(p
, key
, 0, NULL
);
1236 int dns_packet_append_answer(DnsPacket
*p
, DnsAnswer
*a
, unsigned *completed
) {
1237 DnsResourceRecord
*rr
;
1238 DnsAnswerFlags flags
;
1243 DNS_ANSWER_FOREACH_FLAGS(rr
, flags
, a
) {
1244 r
= dns_packet_append_rr(p
, rr
, flags
, NULL
, NULL
);
1255 int dns_packet_read(DnsPacket
*p
, size_t sz
, const void **ret
, size_t *start
) {
1258 if (p
->rindex
+ sz
> p
->size
)
1262 *ret
= (uint8_t*) DNS_PACKET_DATA(p
) + p
->rindex
;
1271 void dns_packet_rewind(DnsPacket
*p
, size_t idx
) {
1273 assert(idx
<= p
->size
);
1274 assert(idx
>= DNS_PACKET_HEADER_SIZE
);
1279 int dns_packet_read_blob(DnsPacket
*p
, void *d
, size_t sz
, size_t *start
) {
1286 r
= dns_packet_read(p
, sz
, &q
, start
);
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
) {
1306 r
= dns_packet_read(p
, size
, &src
, &start
);
1315 copy
= memdup(src
, size
);
1330 int dns_packet_read_uint8(DnsPacket
*p
, uint8_t *ret
, size_t *start
) {
1336 r
= dns_packet_read(p
, sizeof(uint8_t), &d
, start
);
1340 *ret
= ((uint8_t*) d
)[0];
1344 int dns_packet_read_uint16(DnsPacket
*p
, uint16_t *ret
, size_t *start
) {
1350 r
= dns_packet_read(p
, sizeof(uint16_t), &d
, start
);
1355 *ret
= unaligned_read_be16(d
);
1360 int dns_packet_read_uint32(DnsPacket
*p
, uint32_t *ret
, size_t *start
) {
1366 r
= dns_packet_read(p
, sizeof(uint32_t), &d
, start
);
1370 *ret
= unaligned_read_be32(d
);
1375 int dns_packet_read_string(DnsPacket
*p
, char **ret
, size_t *start
) {
1376 _cleanup_(rewind_dns_packet
) DnsPacketRewinder rewinder
;
1383 INIT_REWINDER(rewinder
, p
);
1385 r
= dns_packet_read_uint8(p
, &c
, NULL
);
1389 r
= dns_packet_read(p
, c
, &d
, NULL
);
1393 if (memchr(d
, 0, c
))
1400 if (!utf8_is_valid(t
)) {
1408 *start
= rewinder
.saved_rindex
;
1409 CANCEL_REWINDER(rewinder
);
1414 int dns_packet_read_raw_string(DnsPacket
*p
, const void **ret
, size_t *size
, size_t *start
) {
1415 _cleanup_(rewind_dns_packet
) DnsPacketRewinder rewinder
;
1420 INIT_REWINDER(rewinder
, p
);
1422 r
= dns_packet_read_uint8(p
, &c
, NULL
);
1426 r
= dns_packet_read(p
, c
, ret
, NULL
);
1433 *start
= rewinder
.saved_rindex
;
1434 CANCEL_REWINDER(rewinder
);
1439 int dns_packet_read_name(
1442 bool allow_compression
,
1443 size_t *ret_start
) {
1445 _cleanup_(rewind_dns_packet
) DnsPacketRewinder rewinder
;
1446 size_t after_rindex
= 0, jump_barrier
;
1447 _cleanup_free_
char *name
= NULL
;
1454 INIT_REWINDER(rewinder
, p
);
1455 jump_barrier
= p
->rindex
;
1457 if (p
->refuse_compression
)
1458 allow_compression
= false;
1463 r
= dns_packet_read_uint8(p
, &c
, NULL
);
1474 r
= dns_packet_read(p
, c
, (const void**) &label
, NULL
);
1478 if (!GREEDY_REALLOC(name
, n
+ !first
+ DNS_LABEL_ESCAPED_MAX
))
1486 r
= dns_label_escape(label
, c
, name
+ n
, DNS_LABEL_ESCAPED_MAX
);
1492 } else if (allow_compression
&& FLAGS_SET(c
, 0xc0)) {
1496 r
= dns_packet_read_uint8(p
, &d
, NULL
);
1500 ptr
= (uint16_t) (c
& ~0xc0) << 8 | (uint16_t) d
;
1501 if (ptr
< DNS_PACKET_HEADER_SIZE
|| ptr
>= jump_barrier
)
1504 if (after_rindex
== 0)
1505 after_rindex
= p
->rindex
;
1507 /* Jumps are limited to a "prior occurrence" (RFC-1035 4.1.4) */
1514 if (!GREEDY_REALLOC(name
, n
+ 1))
1519 if (after_rindex
!= 0)
1520 p
->rindex
= after_rindex
;
1523 *ret
= TAKE_PTR(name
);
1525 *ret_start
= rewinder
.saved_rindex
;
1527 CANCEL_REWINDER(rewinder
);
1532 static int dns_packet_read_type_window(DnsPacket
*p
, Bitmap
**types
, size_t *start
) {
1535 const uint8_t *bitmap
;
1539 _cleanup_(rewind_dns_packet
) DnsPacketRewinder rewinder
;
1544 INIT_REWINDER(rewinder
, p
);
1546 r
= bitmap_ensure_allocated(types
);
1550 r
= dns_packet_read_uint8(p
, &window
, NULL
);
1554 r
= dns_packet_read_uint8(p
, &length
, NULL
);
1558 if (length
== 0 || length
> 32)
1561 r
= dns_packet_read(p
, length
, (const void **)&bitmap
, NULL
);
1565 for (i
= 0; i
< length
; i
++) {
1566 uint8_t bitmask
= 1 << 7;
1576 for (; bitmask
; bit
++, bitmask
>>= 1)
1577 if (bitmap
[i
] & bitmask
) {
1580 n
= (uint16_t) window
<< 8 | (uint16_t) bit
;
1582 /* Ignore pseudo-types. see RFC4034 section 4.1.2 */
1583 if (dns_type_is_pseudo(n
))
1586 r
= bitmap_set(*types
, n
);
1596 *start
= rewinder
.saved_rindex
;
1597 CANCEL_REWINDER(rewinder
);
1602 static int dns_packet_read_type_windows(DnsPacket
*p
, Bitmap
**types
, size_t size
, size_t *start
) {
1603 _cleanup_(rewind_dns_packet
) DnsPacketRewinder rewinder
;
1606 INIT_REWINDER(rewinder
, p
);
1608 while (p
->rindex
< rewinder
.saved_rindex
+ size
) {
1609 r
= dns_packet_read_type_window(p
, types
, NULL
);
1613 /* don't read past end of current RR */
1614 if (p
->rindex
> rewinder
.saved_rindex
+ size
)
1618 if (p
->rindex
!= rewinder
.saved_rindex
+ size
)
1622 *start
= rewinder
.saved_rindex
;
1623 CANCEL_REWINDER(rewinder
);
1628 int dns_packet_read_key(
1630 DnsResourceKey
**ret
,
1631 bool *ret_cache_flush_or_qu
,
1632 size_t *ret_start
) {
1634 _cleanup_(rewind_dns_packet
) DnsPacketRewinder rewinder
;
1635 _cleanup_free_
char *name
= NULL
;
1636 bool cache_flush_or_qu
= false;
1637 uint16_t class, type
;
1641 INIT_REWINDER(rewinder
, p
);
1643 r
= dns_packet_read_name(p
, &name
, true, NULL
);
1647 r
= dns_packet_read_uint16(p
, &type
, NULL
);
1651 r
= dns_packet_read_uint16(p
, &class, NULL
);
1655 if (p
->protocol
== DNS_PROTOCOL_MDNS
) {
1656 /* See RFC6762, sections 5.4 and 10.2 */
1658 if (type
!= DNS_TYPE_OPT
&& (class & MDNS_RR_CACHE_FLUSH_OR_QU
)) {
1659 class &= ~MDNS_RR_CACHE_FLUSH_OR_QU
;
1660 cache_flush_or_qu
= true;
1665 DnsResourceKey
*key
;
1667 key
= dns_resource_key_new_consume(class, type
, name
);
1675 if (ret_cache_flush_or_qu
)
1676 *ret_cache_flush_or_qu
= cache_flush_or_qu
;
1678 *ret_start
= rewinder
.saved_rindex
;
1680 CANCEL_REWINDER(rewinder
);
1684 static bool loc_size_ok(uint8_t size
) {
1685 uint8_t m
= size
>> 4, e
= size
& 0xF;
1687 return m
<= 9 && e
<= 9 && (m
> 0 || e
== 0);
1690 int dns_packet_read_rr(
1692 DnsResourceRecord
**ret
,
1693 bool *ret_cache_flush
,
1694 size_t *ret_start
) {
1696 _cleanup_(dns_resource_record_unrefp
) DnsResourceRecord
*rr
= NULL
;
1697 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*key
= NULL
;
1698 _cleanup_(rewind_dns_packet
) DnsPacketRewinder rewinder
;
1706 INIT_REWINDER(rewinder
, p
);
1708 r
= dns_packet_read_key(p
, &key
, &cache_flush
, NULL
);
1712 if (!dns_class_is_valid_rr(key
->class) || !dns_type_is_valid_rr(key
->type
))
1715 rr
= dns_resource_record_new(key
);
1719 r
= dns_packet_read_uint32(p
, &rr
->ttl
, NULL
);
1723 /* RFC 2181, Section 8, suggests to
1724 * treat a TTL with the MSB set as a zero TTL. */
1725 if (rr
->ttl
& UINT32_C(0x80000000))
1728 r
= dns_packet_read_uint16(p
, &rdlength
, NULL
);
1732 if (p
->rindex
+ rdlength
> p
->size
)
1737 switch (rr
->key
->type
) {
1740 r
= dns_packet_read_uint16(p
, &rr
->srv
.priority
, NULL
);
1743 r
= dns_packet_read_uint16(p
, &rr
->srv
.weight
, NULL
);
1746 r
= dns_packet_read_uint16(p
, &rr
->srv
.port
, NULL
);
1749 r
= dns_packet_read_name(p
, &rr
->srv
.name
, true, NULL
);
1754 case DNS_TYPE_CNAME
:
1755 case DNS_TYPE_DNAME
:
1756 r
= dns_packet_read_name(p
, &rr
->ptr
.name
, true, NULL
);
1759 case DNS_TYPE_HINFO
:
1760 r
= dns_packet_read_string(p
, &rr
->hinfo
.cpu
, NULL
);
1764 r
= dns_packet_read_string(p
, &rr
->hinfo
.os
, NULL
);
1767 case DNS_TYPE_SPF
: /* exactly the same as TXT */
1769 if (rdlength
<= 0) {
1770 r
= dns_txt_item_new_empty(&rr
->txt
.items
);
1774 DnsTxtItem
*last
= NULL
;
1776 while (p
->rindex
< offset
+ rdlength
) {
1781 r
= dns_packet_read_raw_string(p
, &data
, &sz
, NULL
);
1785 i
= malloc0(offsetof(DnsTxtItem
, data
) + sz
+ 1); /* extra NUL byte at the end */
1789 memcpy(i
->data
, data
, sz
);
1792 LIST_INSERT_AFTER(items
, rr
->txt
.items
, last
, i
);
1801 r
= dns_packet_read_blob(p
, &rr
->a
.in_addr
, sizeof(struct in_addr
), NULL
);
1805 r
= dns_packet_read_blob(p
, &rr
->aaaa
.in6_addr
, sizeof(struct in6_addr
), NULL
);
1809 r
= dns_packet_read_name(p
, &rr
->soa
.mname
, true, NULL
);
1813 r
= dns_packet_read_name(p
, &rr
->soa
.rname
, true, NULL
);
1817 r
= dns_packet_read_uint32(p
, &rr
->soa
.serial
, NULL
);
1821 r
= dns_packet_read_uint32(p
, &rr
->soa
.refresh
, NULL
);
1825 r
= dns_packet_read_uint32(p
, &rr
->soa
.retry
, NULL
);
1829 r
= dns_packet_read_uint32(p
, &rr
->soa
.expire
, NULL
);
1833 r
= dns_packet_read_uint32(p
, &rr
->soa
.minimum
, NULL
);
1837 r
= dns_packet_read_uint16(p
, &rr
->mx
.priority
, NULL
);
1841 r
= dns_packet_read_name(p
, &rr
->mx
.exchange
, true, NULL
);
1844 case DNS_TYPE_LOC
: {
1848 r
= dns_packet_read_uint8(p
, &t
, &pos
);
1853 rr
->loc
.version
= t
;
1855 r
= dns_packet_read_uint8(p
, &rr
->loc
.size
, NULL
);
1859 if (!loc_size_ok(rr
->loc
.size
))
1862 r
= dns_packet_read_uint8(p
, &rr
->loc
.horiz_pre
, NULL
);
1866 if (!loc_size_ok(rr
->loc
.horiz_pre
))
1869 r
= dns_packet_read_uint8(p
, &rr
->loc
.vert_pre
, NULL
);
1873 if (!loc_size_ok(rr
->loc
.vert_pre
))
1876 r
= dns_packet_read_uint32(p
, &rr
->loc
.latitude
, NULL
);
1880 r
= dns_packet_read_uint32(p
, &rr
->loc
.longitude
, NULL
);
1884 r
= dns_packet_read_uint32(p
, &rr
->loc
.altitude
, NULL
);
1890 dns_packet_rewind(p
, pos
);
1891 rr
->unparsable
= true;
1897 r
= dns_packet_read_uint16(p
, &rr
->ds
.key_tag
, NULL
);
1901 r
= dns_packet_read_uint8(p
, &rr
->ds
.algorithm
, NULL
);
1905 r
= dns_packet_read_uint8(p
, &rr
->ds
.digest_type
, NULL
);
1912 r
= dns_packet_read_memdup(p
, rdlength
- 4,
1913 &rr
->ds
.digest
, &rr
->ds
.digest_size
,
1918 if (rr
->ds
.digest_size
<= 0)
1919 /* the accepted size depends on the algorithm, but for now
1920 just ensure that the value is greater than zero */
1925 case DNS_TYPE_SSHFP
:
1926 r
= dns_packet_read_uint8(p
, &rr
->sshfp
.algorithm
, NULL
);
1930 r
= dns_packet_read_uint8(p
, &rr
->sshfp
.fptype
, NULL
);
1937 r
= dns_packet_read_memdup(p
, rdlength
- 2,
1938 &rr
->sshfp
.fingerprint
, &rr
->sshfp
.fingerprint_size
,
1941 if (rr
->sshfp
.fingerprint_size
<= 0)
1942 /* the accepted size depends on the algorithm, but for now
1943 just ensure that the value is greater than zero */
1948 case DNS_TYPE_DNSKEY
:
1949 r
= dns_packet_read_uint16(p
, &rr
->dnskey
.flags
, NULL
);
1953 r
= dns_packet_read_uint8(p
, &rr
->dnskey
.protocol
, NULL
);
1957 r
= dns_packet_read_uint8(p
, &rr
->dnskey
.algorithm
, NULL
);
1964 r
= dns_packet_read_memdup(p
, rdlength
- 4,
1965 &rr
->dnskey
.key
, &rr
->dnskey
.key_size
,
1968 if (rr
->dnskey
.key_size
<= 0)
1969 /* the accepted size depends on the algorithm, but for now
1970 just ensure that the value is greater than zero */
1975 case DNS_TYPE_RRSIG
:
1976 r
= dns_packet_read_uint16(p
, &rr
->rrsig
.type_covered
, NULL
);
1980 r
= dns_packet_read_uint8(p
, &rr
->rrsig
.algorithm
, NULL
);
1984 r
= dns_packet_read_uint8(p
, &rr
->rrsig
.labels
, NULL
);
1988 r
= dns_packet_read_uint32(p
, &rr
->rrsig
.original_ttl
, NULL
);
1992 r
= dns_packet_read_uint32(p
, &rr
->rrsig
.expiration
, NULL
);
1996 r
= dns_packet_read_uint32(p
, &rr
->rrsig
.inception
, NULL
);
2000 r
= dns_packet_read_uint16(p
, &rr
->rrsig
.key_tag
, NULL
);
2004 r
= dns_packet_read_name(p
, &rr
->rrsig
.signer
, false, NULL
);
2008 if (rdlength
+ offset
< p
->rindex
)
2011 r
= dns_packet_read_memdup(p
, offset
+ rdlength
- p
->rindex
,
2012 &rr
->rrsig
.signature
, &rr
->rrsig
.signature_size
,
2015 if (rr
->rrsig
.signature_size
<= 0)
2016 /* the accepted size depends on the algorithm, but for now
2017 just ensure that the value is greater than zero */
2022 case DNS_TYPE_NSEC
: {
2025 * RFC6762, section 18.14 explicitly states mDNS should use name compression.
2026 * This contradicts RFC3845, section 2.1.1
2029 bool allow_compressed
= p
->protocol
== DNS_PROTOCOL_MDNS
;
2031 r
= dns_packet_read_name(p
, &rr
->nsec
.next_domain_name
, allow_compressed
, NULL
);
2035 r
= dns_packet_read_type_windows(p
, &rr
->nsec
.types
, offset
+ rdlength
- p
->rindex
, NULL
);
2037 /* We accept empty NSEC bitmaps. The bit indicating the presence of the NSEC record itself
2038 * is redundant and in e.g., RFC4956 this fact is used to define a use for NSEC records
2039 * without the NSEC bit set. */
2043 case DNS_TYPE_NSEC3
: {
2046 r
= dns_packet_read_uint8(p
, &rr
->nsec3
.algorithm
, NULL
);
2050 r
= dns_packet_read_uint8(p
, &rr
->nsec3
.flags
, NULL
);
2054 r
= dns_packet_read_uint16(p
, &rr
->nsec3
.iterations
, NULL
);
2058 /* this may be zero */
2059 r
= dns_packet_read_uint8(p
, &size
, NULL
);
2063 r
= dns_packet_read_memdup(p
, size
, &rr
->nsec3
.salt
, &rr
->nsec3
.salt_size
, NULL
);
2067 r
= dns_packet_read_uint8(p
, &size
, NULL
);
2074 r
= dns_packet_read_memdup(p
, size
,
2075 &rr
->nsec3
.next_hashed_name
, &rr
->nsec3
.next_hashed_name_size
,
2080 r
= dns_packet_read_type_windows(p
, &rr
->nsec3
.types
, offset
+ rdlength
- p
->rindex
, NULL
);
2082 /* empty non-terminals can have NSEC3 records, so empty bitmaps are allowed */
2088 r
= dns_packet_read_uint8(p
, &rr
->tlsa
.cert_usage
, NULL
);
2092 r
= dns_packet_read_uint8(p
, &rr
->tlsa
.selector
, NULL
);
2096 r
= dns_packet_read_uint8(p
, &rr
->tlsa
.matching_type
, NULL
);
2103 r
= dns_packet_read_memdup(p
, rdlength
- 3,
2104 &rr
->tlsa
.data
, &rr
->tlsa
.data_size
,
2107 if (rr
->tlsa
.data_size
<= 0)
2108 /* the accepted size depends on the algorithm, but for now
2109 just ensure that the value is greater than zero */
2115 r
= dns_packet_read_uint8(p
, &rr
->caa
.flags
, NULL
);
2119 r
= dns_packet_read_string(p
, &rr
->caa
.tag
, NULL
);
2123 if (rdlength
+ offset
< p
->rindex
)
2126 r
= dns_packet_read_memdup(p
,
2127 rdlength
+ offset
- p
->rindex
,
2128 &rr
->caa
.value
, &rr
->caa
.value_size
, NULL
);
2132 case DNS_TYPE_OPT
: /* we only care about the header of OPT for now. */
2133 case DNS_TYPE_OPENPGPKEY
:
2136 r
= dns_packet_read_memdup(p
, rdlength
, &rr
->generic
.data
, &rr
->generic
.data_size
, NULL
);
2142 if (p
->rindex
!= offset
+ rdlength
)
2146 *ret
= TAKE_PTR(rr
);
2147 if (ret_cache_flush
)
2148 *ret_cache_flush
= cache_flush
;
2150 *ret_start
= rewinder
.saved_rindex
;
2152 CANCEL_REWINDER(rewinder
);
2156 static bool opt_is_good(DnsResourceRecord
*rr
, bool *rfc6975
) {
2158 bool found_dau_dhu_n3u
= false;
2161 /* Checks whether the specified OPT RR is well-formed and whether it contains RFC6975 data (which is not OK in
2165 assert(rr
->key
->type
== DNS_TYPE_OPT
);
2167 /* Check that the version is 0 */
2168 if (((rr
->ttl
>> 16) & UINT32_C(0xFF)) != 0) {
2170 return true; /* if it's not version 0, it's OK, but we will ignore the OPT field contents */
2174 l
= rr
->opt
.data_size
;
2176 uint16_t option_code
, option_length
;
2178 /* At least four bytes for OPTION-CODE and OPTION-LENGTH are required */
2182 option_code
= unaligned_read_be16(p
);
2183 option_length
= unaligned_read_be16(p
+ 2);
2185 if (l
< option_length
+ 4U)
2188 /* RFC 6975 DAU, DHU or N3U fields found. */
2189 if (IN_SET(option_code
, 5, 6, 7))
2190 found_dau_dhu_n3u
= true;
2192 p
+= option_length
+ 4U;
2193 l
-= option_length
+ 4U;
2196 *rfc6975
= found_dau_dhu_n3u
;
2200 static int dns_packet_extract_question(DnsPacket
*p
, DnsQuestion
**ret_question
) {
2201 _cleanup_(dns_question_unrefp
) DnsQuestion
*question
= NULL
;
2205 n
= DNS_PACKET_QDCOUNT(p
);
2207 question
= dns_question_new(n
);
2211 _cleanup_set_free_ Set
*keys
= NULL
; /* references to keys are kept by Question */
2213 keys
= set_new(&dns_resource_key_hash_ops
);
2217 r
= set_reserve(keys
, n
* 2); /* Higher multipliers give slightly higher efficiency through
2218 * hash collisions, but the gains quickly drop off after 2. */
2222 for (i
= 0; i
< n
; i
++) {
2223 _cleanup_(dns_resource_key_unrefp
) DnsResourceKey
*key
= NULL
;
2226 r
= dns_packet_read_key(p
, &key
, &qu
, NULL
);
2230 if (!dns_type_is_valid_query(key
->type
))
2233 r
= set_put(keys
, key
);
2237 /* Already in the Question, let's skip */
2240 r
= dns_question_add_raw(question
, key
, qu
? DNS_QUESTION_WANTS_UNICAST_REPLY
: 0);
2246 *ret_question
= TAKE_PTR(question
);
2251 static int dns_packet_extract_answer(DnsPacket
*p
, DnsAnswer
**ret_answer
) {
2252 _cleanup_(dns_answer_unrefp
) DnsAnswer
*answer
= NULL
;
2254 _cleanup_(dns_resource_record_unrefp
) DnsResourceRecord
*previous
= NULL
;
2255 bool bad_opt
= false;
2258 n
= DNS_PACKET_RRCOUNT(p
);
2262 answer
= dns_answer_new(n
);
2266 for (i
= 0; i
< n
; i
++) {
2267 _cleanup_(dns_resource_record_unrefp
) DnsResourceRecord
*rr
= NULL
;
2268 bool cache_flush
= false;
2271 if (p
->rindex
== p
->size
&& p
->opt
) {
2272 /* If we reached the end of the packet already, but there are still more RRs
2273 * declared, then that's a corrupt packet. Let's accept the packet anyway, since it's
2274 * apparently a common bug in routers. Let's however suppress OPT support in this
2275 * case, so that we force the rest of the logic into lowest DNS baseline support. Or
2276 * to say this differently: if the DNS server doesn't even get the RR counts right,
2277 * it's highly unlikely it gets EDNS right. */
2278 log_debug("More resource records declared in packet than included, suppressing OPT.");
2283 r
= dns_packet_read_rr(p
, &rr
, &cache_flush
, &start
);
2287 /* Try to reduce memory usage a bit */
2289 dns_resource_key_reduce(&rr
->key
, &previous
->key
);
2291 if (rr
->key
->type
== DNS_TYPE_OPT
) {
2294 if (p
->opt
|| bad_opt
) {
2295 /* Multiple OPT RRs? if so, let's ignore all, because there's
2296 * something wrong with the server, and if one is valid we wouldn't
2297 * know which one. */
2298 log_debug("Multiple OPT RRs detected, ignoring all.");
2303 if (!dns_name_is_root(dns_resource_key_name(rr
->key
))) {
2304 /* If the OPT RR is not owned by the root domain, then it is bad,
2305 * let's ignore it. */
2306 log_debug("OPT RR is not owned by root domain, ignoring.");
2311 if (i
< DNS_PACKET_ANCOUNT(p
) + DNS_PACKET_NSCOUNT(p
)) {
2312 /* OPT RR is in the wrong section? Some Belkin routers do this. This
2313 * is a hint the EDNS implementation is borked, like the Belkin one
2314 * is, hence ignore it. */
2315 log_debug("OPT RR in wrong section, ignoring.");
2320 if (!opt_is_good(rr
, &has_rfc6975
)) {
2321 log_debug("Malformed OPT RR, ignoring.");
2326 if (DNS_PACKET_QR(p
)) {
2327 /* Additional checks for responses */
2329 if (!DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(rr
))
2330 /* If this is a reply and we don't know the EDNS version
2331 * then something is weird... */
2332 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG
),
2333 "EDNS version newer that our request, bad server.");
2336 /* If the OPT RR contains RFC6975 algorithm data, then this
2337 * is indication that the server just copied the OPT it got
2338 * from us (which contained that data) back into the reply.
2339 * If so, then it doesn't properly support EDNS, as RFC6975
2340 * makes it very clear that the algorithm data should only
2341 * be contained in questions, never in replies. Crappy
2342 * Belkin routers copy the OPT data for example, hence let's
2343 * detect this so that we downgrade early. */
2344 log_debug("OPT RR contains RFC6975 data, ignoring.");
2350 p
->opt
= dns_resource_record_ref(rr
);
2351 p
->opt_start
= start
;
2352 assert(p
->rindex
>= start
);
2353 p
->opt_size
= p
->rindex
- start
;
2355 DnsAnswerFlags flags
= 0;
2357 if (p
->protocol
== DNS_PROTOCOL_MDNS
&& !cache_flush
)
2358 flags
|= DNS_ANSWER_SHARED_OWNER
;
2360 /* According to RFC 4795, section 2.9. only the RRs from the Answer section shall be
2361 * cached. Hence mark only those RRs as cacheable by default, but not the ones from
2362 * the Additional or Authority sections. */
2363 if (i
< DNS_PACKET_ANCOUNT(p
))
2364 flags
|= DNS_ANSWER_CACHEABLE
|DNS_ANSWER_SECTION_ANSWER
;
2365 else if (i
< DNS_PACKET_ANCOUNT(p
) + DNS_PACKET_NSCOUNT(p
))
2366 flags
|= DNS_ANSWER_SECTION_AUTHORITY
;
2368 flags
|= DNS_ANSWER_SECTION_ADDITIONAL
;
2370 r
= dns_answer_add(answer
, rr
, p
->ifindex
, flags
, NULL
);
2375 /* Remember this RR, so that we can potentially merge its ->key object with the
2376 * next RR. Note that we only do this if we actually decided to keep the RR around.
2378 dns_resource_record_unref(previous
);
2379 previous
= dns_resource_record_ref(rr
);
2383 p
->opt
= dns_resource_record_unref(p
->opt
);
2384 p
->opt_start
= p
->opt_size
= SIZE_MAX
;
2387 *ret_answer
= TAKE_PTR(answer
);
2392 int dns_packet_extract(DnsPacket
*p
) {
2393 _cleanup_(dns_question_unrefp
) DnsQuestion
*question
= NULL
;
2394 _cleanup_(dns_answer_unrefp
) DnsAnswer
*answer
= NULL
;
2395 _cleanup_(rewind_dns_packet
) DnsPacketRewinder rewinder
= {};
2401 INIT_REWINDER(rewinder
, p
);
2402 dns_packet_rewind(p
, DNS_PACKET_HEADER_SIZE
);
2404 r
= dns_packet_extract_question(p
, &question
);
2408 r
= dns_packet_extract_answer(p
, &answer
);
2412 if (p
->rindex
< p
->size
) {
2413 log_debug("Trailing garbage in packet, suppressing OPT.");
2414 p
->opt
= dns_resource_record_unref(p
->opt
);
2415 p
->opt_start
= p
->opt_size
= SIZE_MAX
;
2418 p
->question
= TAKE_PTR(question
);
2419 p
->answer
= TAKE_PTR(answer
);
2421 p
->extracted
= true;
2423 /* no CANCEL, always rewind */
2427 int dns_packet_is_reply_for(DnsPacket
*p
, const DnsResourceKey
*key
) {
2433 /* Checks if the specified packet is a reply for the specified
2434 * key and the specified key is the only one in the question
2437 if (DNS_PACKET_QR(p
) != 1)
2440 /* Let's unpack the packet, if that hasn't happened yet. */
2441 r
= dns_packet_extract(p
);
2448 if (p
->question
->n_keys
!= 1)
2451 return dns_resource_key_equal(dns_question_first_key(p
->question
), key
);
2454 int dns_packet_patch_max_udp_size(DnsPacket
*p
, uint16_t max_udp_size
) {
2456 assert(max_udp_size
>= DNS_PACKET_UNICAST_SIZE_MAX
);
2458 if (p
->opt_start
== SIZE_MAX
) /* No OPT section, nothing to patch */
2461 assert(p
->opt_size
!= SIZE_MAX
);
2462 assert(p
->opt_size
>= 5);
2464 unaligned_write_be16(DNS_PACKET_DATA(p
) + p
->opt_start
+ 3, max_udp_size
);
2468 static int patch_rr(DnsPacket
*p
, usec_t age
) {
2469 _cleanup_(rewind_dns_packet
) DnsPacketRewinder rewinder
;
2472 uint16_t type
, rdlength
;
2475 INIT_REWINDER(rewinder
, p
);
2477 /* Patches the RR at the current rindex, subtracts the specified time from the TTL */
2479 r
= dns_packet_read_name(p
, NULL
, true, NULL
);
2483 r
= dns_packet_read_uint16(p
, &type
, NULL
);
2487 r
= dns_packet_read_uint16(p
, NULL
, NULL
);
2491 r
= dns_packet_read_uint32(p
, &ttl
, &ttl_index
);
2495 if (type
!= DNS_TYPE_OPT
) { /* The TTL of the OPT field is not actually a TTL, skip it */
2496 ttl
= LESS_BY(ttl
* USEC_PER_SEC
, age
) / USEC_PER_SEC
;
2497 unaligned_write_be32(DNS_PACKET_DATA(p
) + ttl_index
, ttl
);
2500 r
= dns_packet_read_uint16(p
, &rdlength
, NULL
);
2504 r
= dns_packet_read(p
, rdlength
, NULL
, NULL
);
2508 CANCEL_REWINDER(rewinder
);
2512 int dns_packet_patch_ttls(DnsPacket
*p
, usec_t timestamp
) {
2513 _cleanup_(rewind_dns_packet
) DnsPacketRewinder rewinder
= {};
2519 assert(timestamp_is_set(timestamp
));
2521 /* Adjusts all TTLs in the packet by subtracting the time difference between now and the specified timestamp */
2523 k
= now(clock_boottime_or_monotonic());
2524 assert(k
>= timestamp
);
2527 INIT_REWINDER(rewinder
, p
);
2529 dns_packet_rewind(p
, DNS_PACKET_HEADER_SIZE
);
2531 n
= DNS_PACKET_QDCOUNT(p
);
2532 for (i
= 0; i
< n
; i
++) {
2533 r
= dns_packet_read_key(p
, NULL
, NULL
, NULL
);
2538 n
= DNS_PACKET_RRCOUNT(p
);
2539 for (i
= 0; i
< n
; i
++) {
2541 /* DNS servers suck, hence the RR count is in many servers off. If we reached the end
2542 * prematurely, accept that, exit early */
2543 if (p
->rindex
== p
->size
)
2554 static void dns_packet_hash_func(const DnsPacket
*s
, struct siphash
*state
) {
2557 siphash24_compress(&s
->size
, sizeof(s
->size
), state
);
2558 siphash24_compress(DNS_PACKET_DATA((DnsPacket
*) s
), s
->size
, state
);
2561 static int dns_packet_compare_func(const DnsPacket
*x
, const DnsPacket
*y
) {
2564 r
= CMP(x
->size
, y
->size
);
2568 return memcmp(DNS_PACKET_DATA((DnsPacket
*) x
), DNS_PACKET_DATA((DnsPacket
*) y
), x
->size
);
2571 DEFINE_HASH_OPS(dns_packet_hash_ops
, DnsPacket
, dns_packet_hash_func
, dns_packet_compare_func
);
2573 bool dns_packet_equal(const DnsPacket
*a
, const DnsPacket
*b
) {
2574 return dns_packet_compare_func(a
, b
) == 0;
2577 int dns_packet_has_nsid_request(DnsPacket
*p
) {
2578 bool has_nsid
= false;
2587 d
= p
->opt
->opt
.data
;
2588 l
= p
->opt
->opt
.data_size
;
2591 uint16_t code
, length
;
2594 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG
),
2595 "EDNS0 variable part has invalid size.");
2597 code
= unaligned_read_be16(d
);
2598 length
= unaligned_read_be16(d
+ 2);
2600 if (l
< 4U + length
)
2601 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG
),
2602 "Truncated option in EDNS0 variable part.");
2606 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG
),
2607 "Duplicate NSID option in EDNS0 variable part.");
2610 return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG
),
2611 "Non-empty NSID option in DNS request.");
2623 size_t dns_packet_size_unfragmented(DnsPacket
*p
) {
2626 if (p
->fragsize
== 0) /* Wasn't fragmented */
2629 /* The fragment size (p->fragsize) covers the whole (fragmented) IP packet, while the regular packet
2630 * size (p->size) only covers the DNS part. Thus, subtract the UDP header from the largest fragment
2631 * size, in order to determine which size of DNS packet would have gone through without
2634 return LESS_BY(p
->fragsize
, udp_header_size(p
->family
));
2637 static const char* const dns_rcode_table
[_DNS_RCODE_MAX_DEFINED
] = {
2638 [DNS_RCODE_SUCCESS
] = "SUCCESS",
2639 [DNS_RCODE_FORMERR
] = "FORMERR",
2640 [DNS_RCODE_SERVFAIL
] = "SERVFAIL",
2641 [DNS_RCODE_NXDOMAIN
] = "NXDOMAIN",
2642 [DNS_RCODE_NOTIMP
] = "NOTIMP",
2643 [DNS_RCODE_REFUSED
] = "REFUSED",
2644 [DNS_RCODE_YXDOMAIN
] = "YXDOMAIN",
2645 [DNS_RCODE_YXRRSET
] = "YRRSET",
2646 [DNS_RCODE_NXRRSET
] = "NXRRSET",
2647 [DNS_RCODE_NOTAUTH
] = "NOTAUTH",
2648 [DNS_RCODE_NOTZONE
] = "NOTZONE",
2649 [DNS_RCODE_BADVERS
] = "BADVERS",
2650 [DNS_RCODE_BADKEY
] = "BADKEY",
2651 [DNS_RCODE_BADTIME
] = "BADTIME",
2652 [DNS_RCODE_BADMODE
] = "BADMODE",
2653 [DNS_RCODE_BADNAME
] = "BADNAME",
2654 [DNS_RCODE_BADALG
] = "BADALG",
2655 [DNS_RCODE_BADTRUNC
] = "BADTRUNC",
2656 [DNS_RCODE_BADCOOKIE
] = "BADCOOKIE",
2658 DEFINE_STRING_TABLE_LOOKUP(dns_rcode
, int);
2660 static const char* const dns_protocol_table
[_DNS_PROTOCOL_MAX
] = {
2661 [DNS_PROTOCOL_DNS
] = "dns",
2662 [DNS_PROTOCOL_MDNS
] = "mdns",
2663 [DNS_PROTOCOL_LLMNR
] = "llmnr",
2665 DEFINE_STRING_TABLE_LOOKUP(dns_protocol
, DnsProtocol
);