diff options
Diffstat (limited to '')
| -rw-r--r-- | src/resolve/resolved-dns-packet.c | 2380 |
1 files changed, 2380 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c new file mode 100644 index 0000000..572271b --- /dev/null +++ b/src/resolve/resolved-dns-packet.c @@ -0,0 +1,2380 @@ +/* SPDX-License-Identifier: LGPL-2.1+ */ + +#if HAVE_GCRYPT +#include <gcrypt.h> +#endif + +#include "alloc-util.h" +#include "dns-domain.h" +#include "resolved-dns-packet.h" +#include "string-table.h" +#include "strv.h" +#include "unaligned.h" +#include "utf8.h" +#include "util.h" + +#define EDNS0_OPT_DO (1<<15) + +assert_cc(DNS_PACKET_SIZE_START > DNS_PACKET_HEADER_SIZE) + +typedef struct DnsPacketRewinder { + DnsPacket *packet; + size_t saved_rindex; +} DnsPacketRewinder; + +static void rewind_dns_packet(DnsPacketRewinder *rewinder) { + if (rewinder->packet) + dns_packet_rewind(rewinder->packet, rewinder->saved_rindex); +} + +#define INIT_REWINDER(rewinder, p) do { rewinder.packet = p; rewinder.saved_rindex = p->rindex; } while (0) +#define CANCEL_REWINDER(rewinder) do { rewinder.packet = NULL; } while (0) + +int dns_packet_new( + DnsPacket **ret, + DnsProtocol protocol, + size_t min_alloc_dsize, + size_t max_size) { + + DnsPacket *p; + size_t a; + + assert(ret); + assert(max_size >= DNS_PACKET_HEADER_SIZE); + + if (max_size > DNS_PACKET_SIZE_MAX) + max_size = DNS_PACKET_SIZE_MAX; + + /* The caller may not check what is going to be truly allocated, so do not allow to + * allocate a DNS packet bigger than DNS_PACKET_SIZE_MAX. + */ + if (min_alloc_dsize > DNS_PACKET_SIZE_MAX) + return log_error_errno(SYNTHETIC_ERRNO(EFBIG), + "Requested packet data size too big: %zu", + min_alloc_dsize); + + /* When dns_packet_new() is called with min_alloc_dsize == 0, allocate more than the + * absolute minimum (which is the dns packet header size), to avoid + * resizing immediately again after appending the first data to the packet. + */ + if (min_alloc_dsize < DNS_PACKET_HEADER_SIZE) + a = DNS_PACKET_SIZE_START; + else + a = min_alloc_dsize; + + /* round up to next page size */ + a = PAGE_ALIGN(ALIGN(sizeof(DnsPacket)) + a) - ALIGN(sizeof(DnsPacket)); + + /* make sure we never allocate more than useful */ + if (a > max_size) + a = max_size; + + p = malloc0(ALIGN(sizeof(DnsPacket)) + a); + if (!p) + return -ENOMEM; + + p->size = p->rindex = DNS_PACKET_HEADER_SIZE; + p->allocated = a; + p->max_size = max_size; + p->protocol = protocol; + p->opt_start = p->opt_size = (size_t) -1; + p->n_ref = 1; + + *ret = p; + + return 0; +} + +void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated) { + + DnsPacketHeader *h; + + assert(p); + + h = DNS_PACKET_HEADER(p); + + switch(p->protocol) { + case DNS_PROTOCOL_LLMNR: + assert(!truncated); + + h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */, + 0 /* opcode */, + 0 /* c */, + 0 /* tc */, + 0 /* t */, + 0 /* ra */, + 0 /* ad */, + 0 /* cd */, + 0 /* rcode */)); + break; + + case DNS_PROTOCOL_MDNS: + h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */, + 0 /* opcode */, + 0 /* aa */, + truncated /* tc */, + 0 /* rd (ask for recursion) */, + 0 /* ra */, + 0 /* ad */, + 0 /* cd */, + 0 /* rcode */)); + break; + + default: + assert(!truncated); + + h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */, + 0 /* opcode */, + 0 /* aa */, + 0 /* tc */, + 1 /* rd (ask for recursion) */, + 0 /* ra */, + 0 /* ad */, + dnssec_checking_disabled /* cd */, + 0 /* rcode */)); + } +} + +int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t min_alloc_dsize, bool dnssec_checking_disabled) { + DnsPacket *p; + int r; + + assert(ret); + + r = dns_packet_new(&p, protocol, min_alloc_dsize, DNS_PACKET_SIZE_MAX); + if (r < 0) + return r; + + /* Always set the TC bit to 0 initially. + * If there are multiple packets later, we'll update the bit shortly before sending. + */ + dns_packet_set_flags(p, dnssec_checking_disabled, false); + + *ret = p; + return 0; +} + +DnsPacket *dns_packet_ref(DnsPacket *p) { + + if (!p) + return NULL; + + assert(!p->on_stack); + + assert(p->n_ref > 0); + p->n_ref++; + return p; +} + +static void dns_packet_free(DnsPacket *p) { + char *s; + + assert(p); + + dns_question_unref(p->question); + dns_answer_unref(p->answer); + dns_resource_record_unref(p->opt); + + while ((s = hashmap_steal_first_key(p->names))) + free(s); + hashmap_free(p->names); + + free(p->_data); + + if (!p->on_stack) + free(p); +} + +DnsPacket *dns_packet_unref(DnsPacket *p) { + if (!p) + return NULL; + + assert(p->n_ref > 0); + + dns_packet_unref(p->more); + + if (p->n_ref == 1) + dns_packet_free(p); + else + p->n_ref--; + + return NULL; +} + +int dns_packet_validate(DnsPacket *p) { + assert(p); + + if (p->size < DNS_PACKET_HEADER_SIZE) + return -EBADMSG; + + if (p->size > DNS_PACKET_SIZE_MAX) + return -EBADMSG; + + return 1; +} + +int dns_packet_validate_reply(DnsPacket *p) { + int r; + + assert(p); + + r = dns_packet_validate(p); + if (r < 0) + return r; + + if (DNS_PACKET_QR(p) != 1) + return 0; + + if (DNS_PACKET_OPCODE(p) != 0) + return -EBADMSG; + + switch (p->protocol) { + + case DNS_PROTOCOL_LLMNR: + /* RFC 4795, Section 2.1.1. says to discard all replies with QDCOUNT != 1 */ + if (DNS_PACKET_QDCOUNT(p) != 1) + return -EBADMSG; + + break; + + case DNS_PROTOCOL_MDNS: + /* RFC 6762, Section 18 */ + if (DNS_PACKET_RCODE(p) != 0) + return -EBADMSG; + + break; + + default: + break; + } + + return 1; +} + +int dns_packet_validate_query(DnsPacket *p) { + int r; + + assert(p); + + r = dns_packet_validate(p); + if (r < 0) + return r; + + if (DNS_PACKET_QR(p) != 0) + return 0; + + if (DNS_PACKET_OPCODE(p) != 0) + return -EBADMSG; + + if (DNS_PACKET_TC(p)) + return -EBADMSG; + + switch (p->protocol) { + + case DNS_PROTOCOL_LLMNR: + case DNS_PROTOCOL_DNS: + /* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */ + if (DNS_PACKET_QDCOUNT(p) != 1) + return -EBADMSG; + + /* RFC 4795, Section 2.1.1. says to discard all queries with ANCOUNT != 0 */ + if (DNS_PACKET_ANCOUNT(p) > 0) + return -EBADMSG; + + /* RFC 4795, Section 2.1.1. says to discard all queries with NSCOUNT != 0 */ + if (DNS_PACKET_NSCOUNT(p) > 0) + return -EBADMSG; + + break; + + case DNS_PROTOCOL_MDNS: + /* RFC 6762, Section 18 */ + if (DNS_PACKET_AA(p) != 0 || + DNS_PACKET_RD(p) != 0 || + DNS_PACKET_RA(p) != 0 || + DNS_PACKET_AD(p) != 0 || + DNS_PACKET_CD(p) != 0 || + DNS_PACKET_RCODE(p) != 0) + return -EBADMSG; + + break; + + default: + break; + } + + return 1; +} + +static int dns_packet_extend(DnsPacket *p, size_t add, void **ret, size_t *start) { + assert(p); + + if (p->size + add > p->allocated) { + size_t a, ms; + + a = PAGE_ALIGN((p->size + add) * 2); + + ms = dns_packet_size_max(p); + if (a > ms) + a = ms; + + if (p->size + add > a) + return -EMSGSIZE; + + if (p->_data) { + void *d; + + d = realloc(p->_data, a); + if (!d) + return -ENOMEM; + + p->_data = d; + } else { + p->_data = malloc(a); + if (!p->_data) + return -ENOMEM; + + memcpy(p->_data, (uint8_t*) p + ALIGN(sizeof(DnsPacket)), p->size); + memzero((uint8_t*) p->_data + p->size, a - p->size); + } + + p->allocated = a; + } + + if (start) + *start = p->size; + + if (ret) + *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->size; + + p->size += add; + return 0; +} + +void dns_packet_truncate(DnsPacket *p, size_t sz) { + Iterator i; + char *s; + void *n; + + assert(p); + + if (p->size <= sz) + return; + + HASHMAP_FOREACH_KEY(n, s, p->names, i) { + + if (PTR_TO_SIZE(n) < sz) + continue; + + hashmap_remove(p->names, s); + free(s); + } + + p->size = sz; +} + +int dns_packet_append_blob(DnsPacket *p, const void *d, size_t l, size_t *start) { + void *q; + int r; + + assert(p); + + r = dns_packet_extend(p, l, &q, start); + if (r < 0) + return r; + + memcpy_safe(q, d, l); + return 0; +} + +int dns_packet_append_uint8(DnsPacket *p, uint8_t v, size_t *start) { + void *d; + int r; + + assert(p); + + r = dns_packet_extend(p, sizeof(uint8_t), &d, start); + if (r < 0) + return r; + + ((uint8_t*) d)[0] = v; + + return 0; +} + +int dns_packet_append_uint16(DnsPacket *p, uint16_t v, size_t *start) { + void *d; + int r; + + assert(p); + + r = dns_packet_extend(p, sizeof(uint16_t), &d, start); + if (r < 0) + return r; + + unaligned_write_be16(d, v); + + return 0; +} + +int dns_packet_append_uint32(DnsPacket *p, uint32_t v, size_t *start) { + void *d; + int r; + + assert(p); + + r = dns_packet_extend(p, sizeof(uint32_t), &d, start); + if (r < 0) + return r; + + unaligned_write_be32(d, v); + + return 0; +} + +int dns_packet_append_string(DnsPacket *p, const char *s, size_t *start) { + assert(p); + assert(s); + + return dns_packet_append_raw_string(p, s, strlen(s), start); +} + +int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_t *start) { + void *d; + int r; + + assert(p); + assert(s || size == 0); + + if (size > 255) + return -E2BIG; + + r = dns_packet_extend(p, 1 + size, &d, start); + if (r < 0) + return r; + + ((uint8_t*) d)[0] = (uint8_t) size; + + memcpy_safe(((uint8_t*) d) + 1, s, size); + + return 0; +} + +int dns_packet_append_label(DnsPacket *p, const char *d, size_t l, bool canonical_candidate, size_t *start) { + uint8_t *w; + int r; + + /* Append a label to a packet. Optionally, does this in DNSSEC + * canonical form, if this label is marked as a candidate for + * it, and the canonical form logic is enabled for the + * packet */ + + assert(p); + assert(d); + + if (l > DNS_LABEL_MAX) + return -E2BIG; + + r = dns_packet_extend(p, 1 + l, (void**) &w, start); + if (r < 0) + return r; + + *(w++) = (uint8_t) l; + + if (p->canonical_form && canonical_candidate) { + size_t i; + + /* Generate in canonical form, as defined by DNSSEC + * RFC 4034, Section 6.2, i.e. all lower-case. */ + + for (i = 0; i < l; i++) + w[i] = (uint8_t) ascii_tolower(d[i]); + } else + /* Otherwise, just copy the string unaltered. This is + * essential for DNS-SD, where the casing of labels + * matters and needs to be retained. */ + memcpy(w, d, l); + + return 0; +} + +int dns_packet_append_name( + DnsPacket *p, + const char *name, + bool allow_compression, + bool canonical_candidate, + size_t *start) { + + size_t saved_size; + int r; + + assert(p); + assert(name); + + if (p->refuse_compression) + allow_compression = false; + + saved_size = p->size; + + while (!dns_name_is_root(name)) { + const char *z = name; + char label[DNS_LABEL_MAX]; + size_t n = 0; + + if (allow_compression) + n = PTR_TO_SIZE(hashmap_get(p->names, name)); + if (n > 0) { + assert(n < p->size); + + if (n < 0x4000) { + r = dns_packet_append_uint16(p, 0xC000 | n, NULL); + if (r < 0) + goto fail; + + goto done; + } + } + + r = dns_label_unescape(&name, label, sizeof label, 0); + if (r < 0) + goto fail; + + r = dns_packet_append_label(p, label, r, canonical_candidate, &n); + if (r < 0) + goto fail; + + if (allow_compression) { + _cleanup_free_ char *s = NULL; + + s = strdup(z); + if (!s) { + r = -ENOMEM; + goto fail; + } + + r = hashmap_ensure_allocated(&p->names, &dns_name_hash_ops); + if (r < 0) + goto fail; + + r = hashmap_put(p->names, s, SIZE_TO_PTR(n)); + if (r < 0) + goto fail; + + s = NULL; + } + } + + r = dns_packet_append_uint8(p, 0, NULL); + if (r < 0) + return r; + +done: + if (start) + *start = saved_size; + + return 0; + +fail: + dns_packet_truncate(p, saved_size); + return r; +} + +int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *k, const DnsAnswerFlags flags, size_t *start) { + size_t saved_size; + uint16_t class; + int r; + + assert(p); + assert(k); + + saved_size = p->size; + + r = dns_packet_append_name(p, dns_resource_key_name(k), true, true, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint16(p, k->type, NULL); + if (r < 0) + goto fail; + + class = flags & DNS_ANSWER_CACHE_FLUSH ? k->class | MDNS_RR_CACHE_FLUSH : k->class; + r = dns_packet_append_uint16(p, class, NULL); + if (r < 0) + goto fail; + + if (start) + *start = saved_size; + + return 0; + +fail: + dns_packet_truncate(p, saved_size); + return r; +} + +static int dns_packet_append_type_window(DnsPacket *p, uint8_t window, uint8_t length, const uint8_t *types, size_t *start) { + size_t saved_size; + int r; + + assert(p); + assert(types); + assert(length > 0); + + saved_size = p->size; + + r = dns_packet_append_uint8(p, window, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, length, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_blob(p, types, length, NULL); + if (r < 0) + goto fail; + + if (start) + *start = saved_size; + + return 0; +fail: + dns_packet_truncate(p, saved_size); + return r; +} + +static int dns_packet_append_types(DnsPacket *p, Bitmap *types, size_t *start) { + Iterator i; + uint8_t window = 0; + uint8_t entry = 0; + uint8_t bitmaps[32] = {}; + unsigned n; + size_t saved_size; + int r; + + assert(p); + + saved_size = p->size; + + BITMAP_FOREACH(n, types, i) { + assert(n <= 0xffff); + + if ((n >> 8) != window && bitmaps[entry / 8] != 0) { + r = dns_packet_append_type_window(p, window, entry / 8 + 1, bitmaps, NULL); + if (r < 0) + goto fail; + + zero(bitmaps); + } + + window = n >> 8; + entry = n & 255; + + bitmaps[entry / 8] |= 1 << (7 - (entry % 8)); + } + + if (bitmaps[entry / 8] != 0) { + r = dns_packet_append_type_window(p, window, entry / 8 + 1, bitmaps, NULL); + if (r < 0) + goto fail; + } + + if (start) + *start = saved_size; + + return 0; +fail: + dns_packet_truncate(p, saved_size); + return r; +} + +/* Append the OPT pseudo-RR described in RFC6891 */ +int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, int rcode, size_t *start) { + size_t saved_size; + int r; + + assert(p); + /* we must never advertise supported packet size smaller than the legacy max */ + assert(max_udp_size >= DNS_PACKET_UNICAST_SIZE_MAX); + assert(rcode >= 0); + assert(rcode <= _DNS_RCODE_MAX); + + if (p->opt_start != (size_t) -1) + return -EBUSY; + + assert(p->opt_size == (size_t) -1); + + saved_size = p->size; + + /* empty name */ + r = dns_packet_append_uint8(p, 0, NULL); + if (r < 0) + return r; + + /* type */ + r = dns_packet_append_uint16(p, DNS_TYPE_OPT, NULL); + if (r < 0) + goto fail; + + /* class: maximum udp packet that can be received */ + r = dns_packet_append_uint16(p, max_udp_size, NULL); + if (r < 0) + goto fail; + + /* extended RCODE and VERSION */ + r = dns_packet_append_uint16(p, ((uint16_t) rcode & 0x0FF0) << 4, NULL); + if (r < 0) + goto fail; + + /* flags: DNSSEC OK (DO), see RFC3225 */ + r = dns_packet_append_uint16(p, edns0_do ? EDNS0_OPT_DO : 0, NULL); + if (r < 0) + goto fail; + + /* RDLENGTH */ + if (edns0_do && !DNS_PACKET_QR(p)) { + /* If DO is on and this is not a reply, also append RFC6975 Algorithm data */ + + static const uint8_t rfc6975[] = { + + 0, 5, /* OPTION_CODE: DAU */ +#if HAVE_GCRYPT && GCRYPT_VERSION_NUMBER >= 0x010600 + 0, 7, /* LIST_LENGTH */ +#else + 0, 6, /* LIST_LENGTH */ +#endif + DNSSEC_ALGORITHM_RSASHA1, + DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1, + DNSSEC_ALGORITHM_RSASHA256, + DNSSEC_ALGORITHM_RSASHA512, + DNSSEC_ALGORITHM_ECDSAP256SHA256, + DNSSEC_ALGORITHM_ECDSAP384SHA384, +#if HAVE_GCRYPT && GCRYPT_VERSION_NUMBER >= 0x010600 + DNSSEC_ALGORITHM_ED25519, +#endif + + 0, 6, /* OPTION_CODE: DHU */ + 0, 3, /* LIST_LENGTH */ + DNSSEC_DIGEST_SHA1, + DNSSEC_DIGEST_SHA256, + DNSSEC_DIGEST_SHA384, + + 0, 7, /* OPTION_CODE: N3U */ + 0, 1, /* LIST_LENGTH */ + NSEC3_ALGORITHM_SHA1, + }; + + r = dns_packet_append_uint16(p, sizeof(rfc6975), NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_blob(p, rfc6975, sizeof(rfc6975), NULL); + } else + r = dns_packet_append_uint16(p, 0, NULL); + if (r < 0) + goto fail; + + DNS_PACKET_HEADER(p)->arcount = htobe16(DNS_PACKET_ARCOUNT(p) + 1); + + p->opt_start = saved_size; + p->opt_size = p->size - saved_size; + + if (start) + *start = saved_size; + + return 0; + +fail: + dns_packet_truncate(p, saved_size); + return r; +} + +int dns_packet_truncate_opt(DnsPacket *p) { + assert(p); + + if (p->opt_start == (size_t) -1) { + assert(p->opt_size == (size_t) -1); + return 0; + } + + assert(p->opt_size != (size_t) -1); + assert(DNS_PACKET_ARCOUNT(p) > 0); + + if (p->opt_start + p->opt_size != p->size) + return -EBUSY; + + dns_packet_truncate(p, p->opt_start); + DNS_PACKET_HEADER(p)->arcount = htobe16(DNS_PACKET_ARCOUNT(p) - 1); + p->opt_start = p->opt_size = (size_t) -1; + + return 1; +} + +int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, const DnsAnswerFlags flags, size_t *start, size_t *rdata_start) { + + size_t saved_size, rdlength_offset, end, rdlength, rds; + uint32_t ttl; + int r; + + assert(p); + assert(rr); + + saved_size = p->size; + + r = dns_packet_append_key(p, rr->key, flags, NULL); + if (r < 0) + goto fail; + + ttl = flags & DNS_ANSWER_GOODBYE ? 0 : rr->ttl; + r = dns_packet_append_uint32(p, ttl, NULL); + if (r < 0) + goto fail; + + /* Initially we write 0 here */ + r = dns_packet_append_uint16(p, 0, &rdlength_offset); + if (r < 0) + goto fail; + + rds = p->size - saved_size; + + switch (rr->unparseable ? _DNS_TYPE_INVALID : rr->key->type) { + + case DNS_TYPE_SRV: + r = dns_packet_append_uint16(p, rr->srv.priority, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint16(p, rr->srv.weight, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint16(p, rr->srv.port, NULL); + if (r < 0) + goto fail; + + /* RFC 2782 states "Unless and until permitted by future standards + * action, name compression is not to be used for this field." */ + r = dns_packet_append_name(p, rr->srv.name, false, false, NULL); + break; + + case DNS_TYPE_PTR: + case DNS_TYPE_NS: + case DNS_TYPE_CNAME: + case DNS_TYPE_DNAME: + r = dns_packet_append_name(p, rr->ptr.name, true, false, NULL); + break; + + case DNS_TYPE_HINFO: + r = dns_packet_append_string(p, rr->hinfo.cpu, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_string(p, rr->hinfo.os, NULL); + break; + + case DNS_TYPE_SPF: /* exactly the same as TXT */ + case DNS_TYPE_TXT: + + if (!rr->txt.items) { + /* RFC 6763, section 6.1 suggests to generate + * single empty string for an empty array. */ + + r = dns_packet_append_raw_string(p, NULL, 0, NULL); + if (r < 0) + goto fail; + } else { + DnsTxtItem *i; + + LIST_FOREACH(items, i, rr->txt.items) { + r = dns_packet_append_raw_string(p, i->data, i->length, NULL); + if (r < 0) + goto fail; + } + } + + r = 0; + break; + + case DNS_TYPE_A: + r = dns_packet_append_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL); + break; + + case DNS_TYPE_AAAA: + r = dns_packet_append_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL); + break; + + case DNS_TYPE_SOA: + r = dns_packet_append_name(p, rr->soa.mname, true, false, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_name(p, rr->soa.rname, true, false, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->soa.serial, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->soa.refresh, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->soa.retry, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->soa.expire, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->soa.minimum, NULL); + break; + + case DNS_TYPE_MX: + r = dns_packet_append_uint16(p, rr->mx.priority, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_name(p, rr->mx.exchange, true, false, NULL); + break; + + case DNS_TYPE_LOC: + r = dns_packet_append_uint8(p, rr->loc.version, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->loc.size, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->loc.horiz_pre, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->loc.vert_pre, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->loc.latitude, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->loc.longitude, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->loc.altitude, NULL); + break; + + case DNS_TYPE_DS: + r = dns_packet_append_uint16(p, rr->ds.key_tag, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->ds.algorithm, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->ds.digest_type, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_blob(p, rr->ds.digest, rr->ds.digest_size, NULL); + break; + + case DNS_TYPE_SSHFP: + r = dns_packet_append_uint8(p, rr->sshfp.algorithm, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->sshfp.fptype, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_blob(p, rr->sshfp.fingerprint, rr->sshfp.fingerprint_size, NULL); + break; + + case DNS_TYPE_DNSKEY: + r = dns_packet_append_uint16(p, rr->dnskey.flags, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->dnskey.protocol, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->dnskey.algorithm, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_blob(p, rr->dnskey.key, rr->dnskey.key_size, NULL); + break; + + case DNS_TYPE_RRSIG: + r = dns_packet_append_uint16(p, rr->rrsig.type_covered, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->rrsig.algorithm, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->rrsig.labels, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->rrsig.original_ttl, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->rrsig.expiration, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint32(p, rr->rrsig.inception, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint16(p, rr->rrsig.key_tag, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_name(p, rr->rrsig.signer, false, true, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_blob(p, rr->rrsig.signature, rr->rrsig.signature_size, NULL); + break; + + case DNS_TYPE_NSEC: + r = dns_packet_append_name(p, rr->nsec.next_domain_name, false, false, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_types(p, rr->nsec.types, NULL); + if (r < 0) + goto fail; + + break; + + case DNS_TYPE_NSEC3: + r = dns_packet_append_uint8(p, rr->nsec3.algorithm, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->nsec3.flags, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint16(p, rr->nsec3.iterations, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->nsec3.salt_size, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_blob(p, rr->nsec3.salt, rr->nsec3.salt_size, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->nsec3.next_hashed_name_size, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_blob(p, rr->nsec3.next_hashed_name, rr->nsec3.next_hashed_name_size, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_types(p, rr->nsec3.types, NULL); + if (r < 0) + goto fail; + + break; + + case DNS_TYPE_TLSA: + r = dns_packet_append_uint8(p, rr->tlsa.cert_usage, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->tlsa.selector, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_uint8(p, rr->tlsa.matching_type, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_blob(p, rr->tlsa.data, rr->tlsa.data_size, NULL); + break; + + case DNS_TYPE_CAA: + r = dns_packet_append_uint8(p, rr->caa.flags, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_string(p, rr->caa.tag, NULL); + if (r < 0) + goto fail; + + r = dns_packet_append_blob(p, rr->caa.value, rr->caa.value_size, NULL); + break; + + case DNS_TYPE_OPT: + case DNS_TYPE_OPENPGPKEY: + case _DNS_TYPE_INVALID: /* unparseable */ + default: + + r = dns_packet_append_blob(p, rr->generic.data, rr->generic.data_size, NULL); + break; + } + if (r < 0) + goto fail; + + /* Let's calculate the actual data size and update the field */ + rdlength = p->size - rdlength_offset - sizeof(uint16_t); + if (rdlength > 0xFFFF) { + r = -ENOSPC; + goto fail; + } + + end = p->size; + p->size = rdlength_offset; + r = dns_packet_append_uint16(p, rdlength, NULL); + if (r < 0) + goto fail; + p->size = end; + + if (start) + *start = saved_size; + + if (rdata_start) + *rdata_start = rds; + + return 0; + +fail: + dns_packet_truncate(p, saved_size); + return r; +} + +int dns_packet_append_question(DnsPacket *p, DnsQuestion *q) { + DnsResourceKey *key; + int r; + + assert(p); + + DNS_QUESTION_FOREACH(key, q) { + r = dns_packet_append_key(p, key, 0, NULL); + if (r < 0) + return r; + } + + return 0; +} + +int dns_packet_append_answer(DnsPacket *p, DnsAnswer *a) { + DnsResourceRecord *rr; + DnsAnswerFlags flags; + int r; + + assert(p); + + DNS_ANSWER_FOREACH_FLAGS(rr, flags, a) { + r = dns_packet_append_rr(p, rr, flags, NULL, NULL); + if (r < 0) + return r; + } + + return 0; +} + +int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) { + assert(p); + + if (p->rindex + sz > p->size) + return -EMSGSIZE; + + if (ret) + *ret = (uint8_t*) DNS_PACKET_DATA(p) + p->rindex; + + if (start) + *start = p->rindex; + + p->rindex += sz; + return 0; +} + +void dns_packet_rewind(DnsPacket *p, size_t idx) { + assert(p); + assert(idx <= p->size); + assert(idx >= DNS_PACKET_HEADER_SIZE); + + p->rindex = idx; +} + +int dns_packet_read_blob(DnsPacket *p, void *d, size_t sz, size_t *start) { + const void *q; + int r; + + assert(p); + assert(d); + + r = dns_packet_read(p, sz, &q, start); + if (r < 0) + return r; + + memcpy(d, q, sz); + return 0; +} + +static int dns_packet_read_memdup( + DnsPacket *p, size_t size, + void **ret, size_t *ret_size, + size_t *ret_start) { + + const void *src; + size_t start; + int r; + + assert(p); + assert(ret); + + r = dns_packet_read(p, size, &src, &start); + if (r < 0) + return r; + + if (size <= 0) + *ret = NULL; + else { + void *copy; + + copy = memdup(src, size); + if (!copy) + return -ENOMEM; + + *ret = copy; + } + + if (ret_size) + *ret_size = size; + if (ret_start) + *ret_start = start; + + return 0; +} + +int dns_packet_read_uint8(DnsPacket *p, uint8_t *ret, size_t *start) { + const void *d; + int r; + + assert(p); + + r = dns_packet_read(p, sizeof(uint8_t), &d, start); + if (r < 0) + return r; + + *ret = ((uint8_t*) d)[0]; + return 0; +} + +int dns_packet_read_uint16(DnsPacket *p, uint16_t *ret, size_t *start) { + const void *d; + int r; + + assert(p); + + r = dns_packet_read(p, sizeof(uint16_t), &d, start); + if (r < 0) + return r; + + *ret = unaligned_read_be16(d); + + return 0; +} + +int dns_packet_read_uint32(DnsPacket *p, uint32_t *ret, size_t *start) { + const void *d; + int r; + + assert(p); + + r = dns_packet_read(p, sizeof(uint32_t), &d, start); + if (r < 0) + return r; + + *ret = unaligned_read_be32(d); + + return 0; +} + +int dns_packet_read_string(DnsPacket *p, char **ret, size_t *start) { + _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder; + const void *d; + char *t; + uint8_t c; + int r; + + assert(p); + INIT_REWINDER(rewinder, p); + + r = dns_packet_read_uint8(p, &c, NULL); + if (r < 0) + return r; + + r = dns_packet_read(p, c, &d, NULL); + if (r < 0) + return r; + + if (memchr(d, 0, c)) + return -EBADMSG; + + t = strndup(d, c); + if (!t) + return -ENOMEM; + + if (!utf8_is_valid(t)) { + free(t); + return -EBADMSG; + } + + *ret = t; + + if (start) + *start = rewinder.saved_rindex; + CANCEL_REWINDER(rewinder); + + return 0; +} + +int dns_packet_read_raw_string(DnsPacket *p, const void **ret, size_t *size, size_t *start) { + _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder; + uint8_t c; + int r; + + assert(p); + INIT_REWINDER(rewinder, p); + + r = dns_packet_read_uint8(p, &c, NULL); + if (r < 0) + return r; + + r = dns_packet_read(p, c, ret, NULL); + if (r < 0) + return r; + + if (size) + *size = c; + if (start) + *start = rewinder.saved_rindex; + CANCEL_REWINDER(rewinder); + + return 0; +} + +int dns_packet_read_name( + DnsPacket *p, + char **_ret, + bool allow_compression, + size_t *start) { + + _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder; + size_t after_rindex = 0, jump_barrier; + _cleanup_free_ char *ret = NULL; + size_t n = 0, allocated = 0; + bool first = true; + int r; + + assert(p); + assert(_ret); + INIT_REWINDER(rewinder, p); + jump_barrier = p->rindex; + + if (p->refuse_compression) + allow_compression = false; + + for (;;) { + uint8_t c, d; + + r = dns_packet_read_uint8(p, &c, NULL); + if (r < 0) + return r; + + if (c == 0) + /* End of name */ + break; + else if (c <= 63) { + const char *label; + + /* Literal label */ + r = dns_packet_read(p, c, (const void**) &label, NULL); + if (r < 0) + return r; + + if (!GREEDY_REALLOC(ret, allocated, n + !first + DNS_LABEL_ESCAPED_MAX)) + return -ENOMEM; + + if (first) + first = false; + else + ret[n++] = '.'; + + r = dns_label_escape(label, c, ret + n, DNS_LABEL_ESCAPED_MAX); + if (r < 0) + return r; + + n += r; + continue; + } else if (allow_compression && (c & 0xc0) == 0xc0) { + uint16_t ptr; + + /* Pointer */ + r = dns_packet_read_uint8(p, &d, NULL); + if (r < 0) + return r; + + ptr = (uint16_t) (c & ~0xc0) << 8 | (uint16_t) d; + if (ptr < DNS_PACKET_HEADER_SIZE || ptr >= jump_barrier) + return -EBADMSG; + + if (after_rindex == 0) + after_rindex = p->rindex; + + /* Jumps are limited to a "prior occurrence" (RFC-1035 4.1.4) */ + jump_barrier = ptr; + p->rindex = ptr; + } else + return -EBADMSG; + } + + if (!GREEDY_REALLOC(ret, allocated, n + 1)) + return -ENOMEM; + + ret[n] = 0; + + if (after_rindex != 0) + p->rindex= after_rindex; + + *_ret = TAKE_PTR(ret); + + if (start) + *start = rewinder.saved_rindex; + CANCEL_REWINDER(rewinder); + + return 0; +} + +static int dns_packet_read_type_window(DnsPacket *p, Bitmap **types, size_t *start) { + uint8_t window; + uint8_t length; + const uint8_t *bitmap; + uint8_t bit = 0; + unsigned i; + bool found = false; + _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder; + int r; + + assert(p); + assert(types); + INIT_REWINDER(rewinder, p); + + r = bitmap_ensure_allocated(types); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &window, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &length, NULL); + if (r < 0) + return r; + + if (length == 0 || length > 32) + return -EBADMSG; + + r = dns_packet_read(p, length, (const void **)&bitmap, NULL); + if (r < 0) + return r; + + for (i = 0; i < length; i++) { + uint8_t bitmask = 1 << 7; + + if (!bitmap[i]) { + found = false; + bit += 8; + continue; + } + + found = true; + + for (; bitmask; bit++, bitmask >>= 1) + if (bitmap[i] & bitmask) { + uint16_t n; + + n = (uint16_t) window << 8 | (uint16_t) bit; + + /* Ignore pseudo-types. see RFC4034 section 4.1.2 */ + if (dns_type_is_pseudo(n)) + continue; + + r = bitmap_set(*types, n); + if (r < 0) + return r; + } + } + + if (!found) + return -EBADMSG; + + if (start) + *start = rewinder.saved_rindex; + CANCEL_REWINDER(rewinder); + + return 0; +} + +static int dns_packet_read_type_windows(DnsPacket *p, Bitmap **types, size_t size, size_t *start) { + _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder; + int r; + + INIT_REWINDER(rewinder, p); + + while (p->rindex < rewinder.saved_rindex + size) { + r = dns_packet_read_type_window(p, types, NULL); + if (r < 0) + return r; + + /* don't read past end of current RR */ + if (p->rindex > rewinder.saved_rindex + size) + return -EBADMSG; + } + + if (p->rindex != rewinder.saved_rindex + size) + return -EBADMSG; + + if (start) + *start = rewinder.saved_rindex; + CANCEL_REWINDER(rewinder); + + return 0; +} + +int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, bool *ret_cache_flush, size_t *start) { + _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder; + _cleanup_free_ char *name = NULL; + bool cache_flush = false; + uint16_t class, type; + DnsResourceKey *key; + int r; + + assert(p); + assert(ret); + INIT_REWINDER(rewinder, p); + + r = dns_packet_read_name(p, &name, true, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint16(p, &type, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint16(p, &class, NULL); + if (r < 0) + return r; + + if (p->protocol == DNS_PROTOCOL_MDNS) { + /* See RFC6762, Section 10.2 */ + + if (type != DNS_TYPE_OPT && (class & MDNS_RR_CACHE_FLUSH)) { + class &= ~MDNS_RR_CACHE_FLUSH; + cache_flush = true; + } + } + + key = dns_resource_key_new_consume(class, type, name); + if (!key) + return -ENOMEM; + + name = NULL; + *ret = key; + + if (ret_cache_flush) + *ret_cache_flush = cache_flush; + if (start) + *start = rewinder.saved_rindex; + CANCEL_REWINDER(rewinder); + + return 0; +} + +static bool loc_size_ok(uint8_t size) { + uint8_t m = size >> 4, e = size & 0xF; + + return m <= 9 && e <= 9 && (m > 0 || e == 0); +} + +int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, bool *ret_cache_flush, size_t *start) { + _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; + _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL; + _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder; + size_t offset; + uint16_t rdlength; + bool cache_flush; + int r; + + assert(p); + assert(ret); + + INIT_REWINDER(rewinder, p); + + r = dns_packet_read_key(p, &key, &cache_flush, NULL); + if (r < 0) + return r; + + if (!dns_class_is_valid_rr(key->class) || !dns_type_is_valid_rr(key->type)) + return -EBADMSG; + + rr = dns_resource_record_new(key); + if (!rr) + return -ENOMEM; + + r = dns_packet_read_uint32(p, &rr->ttl, NULL); + if (r < 0) + return r; + + /* RFC 2181, Section 8, suggests to + * treat a TTL with the MSB set as a zero TTL. */ + if (rr->ttl & UINT32_C(0x80000000)) + rr->ttl = 0; + + r = dns_packet_read_uint16(p, &rdlength, NULL); + if (r < 0) + return r; + + if (p->rindex + rdlength > p->size) + return -EBADMSG; + + offset = p->rindex; + + switch (rr->key->type) { + + case DNS_TYPE_SRV: + r = dns_packet_read_uint16(p, &rr->srv.priority, NULL); + if (r < 0) + return r; + r = dns_packet_read_uint16(p, &rr->srv.weight, NULL); + if (r < 0) + return r; + r = dns_packet_read_uint16(p, &rr->srv.port, NULL); + if (r < 0) + return r; + r = dns_packet_read_name(p, &rr->srv.name, true, NULL); + break; + + case DNS_TYPE_PTR: + case DNS_TYPE_NS: + case DNS_TYPE_CNAME: + case DNS_TYPE_DNAME: + r = dns_packet_read_name(p, &rr->ptr.name, true, NULL); + break; + + case DNS_TYPE_HINFO: + r = dns_packet_read_string(p, &rr->hinfo.cpu, NULL); + if (r < 0) + return r; + + r = dns_packet_read_string(p, &rr->hinfo.os, NULL); + break; + + case DNS_TYPE_SPF: /* exactly the same as TXT */ + case DNS_TYPE_TXT: + if (rdlength <= 0) { + r = dns_txt_item_new_empty(&rr->txt.items); + if (r < 0) + return r; + } else { + DnsTxtItem *last = NULL; + + while (p->rindex < offset + rdlength) { + DnsTxtItem *i; + const void *data; + size_t sz; + + r = dns_packet_read_raw_string(p, &data, &sz, NULL); + if (r < 0) + return r; + + i = malloc0(offsetof(DnsTxtItem, data) + sz + 1); /* extra NUL byte at the end */ + if (!i) + return -ENOMEM; + + memcpy(i->data, data, sz); + i->length = sz; + + LIST_INSERT_AFTER(items, rr->txt.items, last, i); + last = i; + } + } + + r = 0; + break; + + case DNS_TYPE_A: + r = dns_packet_read_blob(p, &rr->a.in_addr, sizeof(struct in_addr), NULL); + break; + + case DNS_TYPE_AAAA: + r = dns_packet_read_blob(p, &rr->aaaa.in6_addr, sizeof(struct in6_addr), NULL); + break; + + case DNS_TYPE_SOA: + r = dns_packet_read_name(p, &rr->soa.mname, true, NULL); + if (r < 0) + return r; + + r = dns_packet_read_name(p, &rr->soa.rname, true, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint32(p, &rr->soa.serial, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint32(p, &rr->soa.refresh, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint32(p, &rr->soa.retry, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint32(p, &rr->soa.expire, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint32(p, &rr->soa.minimum, NULL); + break; + + case DNS_TYPE_MX: + r = dns_packet_read_uint16(p, &rr->mx.priority, NULL); + if (r < 0) + return r; + + r = dns_packet_read_name(p, &rr->mx.exchange, true, NULL); + break; + + case DNS_TYPE_LOC: { + uint8_t t; + size_t pos; + + r = dns_packet_read_uint8(p, &t, &pos); + if (r < 0) + return r; + + if (t == 0) { + rr->loc.version = t; + + r = dns_packet_read_uint8(p, &rr->loc.size, NULL); + if (r < 0) + return r; + + if (!loc_size_ok(rr->loc.size)) + return -EBADMSG; + + r = dns_packet_read_uint8(p, &rr->loc.horiz_pre, NULL); + if (r < 0) + return r; + + if (!loc_size_ok(rr->loc.horiz_pre)) + return -EBADMSG; + + r = dns_packet_read_uint8(p, &rr->loc.vert_pre, NULL); + if (r < 0) + return r; + + if (!loc_size_ok(rr->loc.vert_pre)) + return -EBADMSG; + + r = dns_packet_read_uint32(p, &rr->loc.latitude, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint32(p, &rr->loc.longitude, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint32(p, &rr->loc.altitude, NULL); + if (r < 0) + return r; + + break; + } else { + dns_packet_rewind(p, pos); + rr->unparseable = true; + goto unparseable; + } + } + + case DNS_TYPE_DS: + r = dns_packet_read_uint16(p, &rr->ds.key_tag, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &rr->ds.algorithm, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &rr->ds.digest_type, NULL); + if (r < 0) + return r; + + if (rdlength < 4) + return -EBADMSG; + + r = dns_packet_read_memdup(p, rdlength - 4, + &rr->ds.digest, &rr->ds.digest_size, + NULL); + if (r < 0) + return r; + + if (rr->ds.digest_size <= 0) + /* the accepted size depends on the algorithm, but for now + just ensure that the value is greater than zero */ + return -EBADMSG; + + break; + + case DNS_TYPE_SSHFP: + r = dns_packet_read_uint8(p, &rr->sshfp.algorithm, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &rr->sshfp.fptype, NULL); + if (r < 0) + return r; + + if (rdlength < 2) + return -EBADMSG; + + r = dns_packet_read_memdup(p, rdlength - 2, + &rr->sshfp.fingerprint, &rr->sshfp.fingerprint_size, + NULL); + + if (rr->sshfp.fingerprint_size <= 0) + /* the accepted size depends on the algorithm, but for now + just ensure that the value is greater than zero */ + return -EBADMSG; + + break; + + case DNS_TYPE_DNSKEY: + r = dns_packet_read_uint16(p, &rr->dnskey.flags, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &rr->dnskey.protocol, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &rr->dnskey.algorithm, NULL); + if (r < 0) + return r; + + if (rdlength < 4) + return -EBADMSG; + + r = dns_packet_read_memdup(p, rdlength - 4, + &rr->dnskey.key, &rr->dnskey.key_size, + NULL); + + if (rr->dnskey.key_size <= 0) + /* the accepted size depends on the algorithm, but for now + just ensure that the value is greater than zero */ + return -EBADMSG; + + break; + + case DNS_TYPE_RRSIG: + r = dns_packet_read_uint16(p, &rr->rrsig.type_covered, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &rr->rrsig.algorithm, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &rr->rrsig.labels, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint32(p, &rr->rrsig.original_ttl, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint32(p, &rr->rrsig.expiration, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint32(p, &rr->rrsig.inception, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint16(p, &rr->rrsig.key_tag, NULL); + if (r < 0) + return r; + + r = dns_packet_read_name(p, &rr->rrsig.signer, false, NULL); + if (r < 0) + return r; + + if (rdlength + offset < p->rindex) + return -EBADMSG; + + r = dns_packet_read_memdup(p, offset + rdlength - p->rindex, + &rr->rrsig.signature, &rr->rrsig.signature_size, + NULL); + + if (rr->rrsig.signature_size <= 0) + /* the accepted size depends on the algorithm, but for now + just ensure that the value is greater than zero */ + return -EBADMSG; + + break; + + case DNS_TYPE_NSEC: { + + /* + * RFC6762, section 18.14 explictly states mDNS should use name compression. + * This contradicts RFC3845, section 2.1.1 + */ + + bool allow_compressed = p->protocol == DNS_PROTOCOL_MDNS; + + r = dns_packet_read_name(p, &rr->nsec.next_domain_name, allow_compressed, NULL); + if (r < 0) + return r; + + r = dns_packet_read_type_windows(p, &rr->nsec.types, offset + rdlength - p->rindex, NULL); + + /* We accept empty NSEC bitmaps. The bit indicating the presence of the NSEC record itself + * is redundant and in e.g., RFC4956 this fact is used to define a use for NSEC records + * without the NSEC bit set. */ + + break; + } + case DNS_TYPE_NSEC3: { + uint8_t size; + + r = dns_packet_read_uint8(p, &rr->nsec3.algorithm, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &rr->nsec3.flags, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint16(p, &rr->nsec3.iterations, NULL); + if (r < 0) + return r; + + /* this may be zero */ + r = dns_packet_read_uint8(p, &size, NULL); + if (r < 0) + return r; + + r = dns_packet_read_memdup(p, size, &rr->nsec3.salt, &rr->nsec3.salt_size, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &size, NULL); + if (r < 0) + return r; + + if (size <= 0) + return -EBADMSG; + + r = dns_packet_read_memdup(p, size, + &rr->nsec3.next_hashed_name, &rr->nsec3.next_hashed_name_size, + NULL); + if (r < 0) + return r; + + r = dns_packet_read_type_windows(p, &rr->nsec3.types, offset + rdlength - p->rindex, NULL); + + /* empty non-terminals can have NSEC3 records, so empty bitmaps are allowed */ + + break; + } + + case DNS_TYPE_TLSA: + r = dns_packet_read_uint8(p, &rr->tlsa.cert_usage, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &rr->tlsa.selector, NULL); + if (r < 0) + return r; + + r = dns_packet_read_uint8(p, &rr->tlsa.matching_type, NULL); + if (r < 0) + return r; + + if (rdlength < 3) + return -EBADMSG; + + r = dns_packet_read_memdup(p, rdlength - 3, + &rr->tlsa.data, &rr->tlsa.data_size, + NULL); + + if (rr->tlsa.data_size <= 0) + /* the accepted size depends on the algorithm, but for now + just ensure that the value is greater than zero */ + return -EBADMSG; + + break; + + case DNS_TYPE_CAA: + r = dns_packet_read_uint8(p, &rr->caa.flags, NULL); + if (r < 0) + return r; + + r = dns_packet_read_string(p, &rr->caa.tag, NULL); + if (r < 0) + return r; + + if (rdlength + offset < p->rindex) + return -EBADMSG; + + r = dns_packet_read_memdup(p, + rdlength + offset - p->rindex, + &rr->caa.value, &rr->caa.value_size, NULL); + + break; + + case DNS_TYPE_OPT: /* we only care about the header of OPT for now. */ + case DNS_TYPE_OPENPGPKEY: + default: + unparseable: + r = dns_packet_read_memdup(p, rdlength, &rr->generic.data, &rr->generic.data_size, NULL); + + break; + } + if (r < 0) + return r; + if (p->rindex != offset + rdlength) + return -EBADMSG; + + *ret = TAKE_PTR(rr); + + if (ret_cache_flush) + *ret_cache_flush = cache_flush; + if (start) + *start = rewinder.saved_rindex; + CANCEL_REWINDER(rewinder); + + return 0; +} + +static bool opt_is_good(DnsResourceRecord *rr, bool *rfc6975) { + const uint8_t* p; + bool found_dau_dhu_n3u = false; + size_t l; + + /* Checks whether the specified OPT RR is well-formed and whether it contains RFC6975 data (which is not OK in + * a reply). */ + + assert(rr); + assert(rr->key->type == DNS_TYPE_OPT); + + /* Check that the version is 0 */ + if (((rr->ttl >> 16) & UINT32_C(0xFF)) != 0) { + *rfc6975 = false; + return true; /* if it's not version 0, it's OK, but we will ignore the OPT field contents */ + } + + p = rr->opt.data; + l = rr->opt.data_size; + while (l > 0) { + uint16_t option_code, option_length; + + /* At least four bytes for OPTION-CODE and OPTION-LENGTH are required */ + if (l < 4U) + return false; + + option_code = unaligned_read_be16(p); + option_length = unaligned_read_be16(p + 2); + + if (l < option_length + 4U) + return false; + + /* RFC 6975 DAU, DHU or N3U fields found. */ + if (IN_SET(option_code, 5, 6, 7)) + found_dau_dhu_n3u = true; + + p += option_length + 4U; + l -= option_length + 4U; + } + + *rfc6975 = found_dau_dhu_n3u; + return true; +} + +static int dns_packet_extract_question(DnsPacket *p, DnsQuestion **ret_question) { + _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL; + unsigned n, i; + int r; + + n = DNS_PACKET_QDCOUNT(p); + if (n > 0) { + question = dns_question_new(n); + if (!question) + return -ENOMEM; + + for (i = 0; i < n; i++) { + _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL; + bool cache_flush; + + r = dns_packet_read_key(p, &key, &cache_flush, NULL); + if (r < 0) + return r; + + if (cache_flush) + return -EBADMSG; + + if (!dns_type_is_valid_query(key->type)) + return -EBADMSG; + + r = dns_question_add(question, key); + if (r < 0) + return r; + } + } + + *ret_question = TAKE_PTR(question); + + return 0; +} + +static int dns_packet_extract_answer(DnsPacket *p, DnsAnswer **ret_answer) { + _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL; + unsigned n, i; + _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *previous = NULL; + bool bad_opt = false; + int r; + + n = DNS_PACKET_RRCOUNT(p); + if (n == 0) + return 0; + + answer = dns_answer_new(n); + if (!answer) + return -ENOMEM; + + for (i = 0; i < n; i++) { + _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; + bool cache_flush = false; + + r = dns_packet_read_rr(p, &rr, &cache_flush, NULL); + if (r < 0) + return r; + + /* Try to reduce memory usage a bit */ + if (previous) + dns_resource_key_reduce(&rr->key, &previous->key); + + if (rr->key->type == DNS_TYPE_OPT) { + bool has_rfc6975; + + if (p->opt || bad_opt) { + /* Multiple OPT RRs? if so, let's ignore all, because there's + * something wrong with the server, and if one is valid we wouldn't + * know which one. */ + log_debug("Multiple OPT RRs detected, ignoring all."); + bad_opt = true; + continue; + } + + if (!dns_name_is_root(dns_resource_key_name(rr->key))) { + /* If the OPT RR is not owned by the root domain, then it is bad, + * let's ignore it. */ + log_debug("OPT RR is not owned by root domain, ignoring."); + bad_opt = true; + continue; + } + + if (i < DNS_PACKET_ANCOUNT(p) + DNS_PACKET_NSCOUNT(p)) { + /* OPT RR is in the wrong section? Some Belkin routers do this. This + * is a hint the EDNS implementation is borked, like the Belkin one + * is, hence ignore it. */ + log_debug("OPT RR in wrong section, ignoring."); + bad_opt = true; + continue; + } + + if (!opt_is_good(rr, &has_rfc6975)) { + log_debug("Malformed OPT RR, ignoring."); + bad_opt = true; + continue; + } + + if (DNS_PACKET_QR(p)) { + /* Additional checks for responses */ + + if (!DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(rr)) { + /* If this is a reply and we don't know the EDNS version + * then something is weird... */ + log_debug("EDNS version newer that our request, bad server."); + return -EBADMSG; + } + + if (has_rfc6975) { + /* If the OPT RR contains RFC6975 algorithm data, then this + * is indication that the server just copied the OPT it got + * from us (which contained that data) back into the reply. + * If so, then it doesn't properly support EDNS, as RFC6975 + * makes it very clear that the algorithm data should only + * be contained in questions, never in replies. Crappy + * Belkin routers copy the OPT data for example, hence let's + * detect this so that we downgrade early. */ + log_debug("OPT RR contained RFC6975 data, ignoring."); + bad_opt = true; + continue; + } + } + + p->opt = dns_resource_record_ref(rr); + } else { + /* According to RFC 4795, section 2.9. only the RRs from the Answer section + * shall be cached. Hence mark only those RRs as cacheable by default, but + * not the ones from the Additional or Authority sections. */ + DnsAnswerFlags flags = + (i < DNS_PACKET_ANCOUNT(p) ? DNS_ANSWER_CACHEABLE : 0) | + (p->protocol == DNS_PROTOCOL_MDNS && !cache_flush ? DNS_ANSWER_SHARED_OWNER : 0); + + r = dns_answer_add(answer, rr, p->ifindex, flags); + if (r < 0) + return r; + } + + /* Remember this RR, so that we potentically can merge it's ->key object with the + * next RR. Note that we only do this if we actually decided to keep the RR around. + */ + dns_resource_record_unref(previous); + previous = dns_resource_record_ref(rr); + } + + if (bad_opt) + p->opt = dns_resource_record_unref(p->opt); + + *ret_answer = TAKE_PTR(answer); + + return 0; +} + +int dns_packet_extract(DnsPacket *p) { + _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL; + _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL; + _cleanup_(rewind_dns_packet) DnsPacketRewinder rewinder = {}; + int r; + + if (p->extracted) + return 0; + + INIT_REWINDER(rewinder, p); + dns_packet_rewind(p, DNS_PACKET_HEADER_SIZE); + + r = dns_packet_extract_question(p, &question); + if (r < 0) + return r; + + r = dns_packet_extract_answer(p, &answer); + if (r < 0) + return r; + + p->question = TAKE_PTR(question); + p->answer = TAKE_PTR(answer); + + p->extracted = true; + + /* no CANCEL, always rewind */ + return 0; +} + +int dns_packet_is_reply_for(DnsPacket *p, const DnsResourceKey *key) { + int r; + + assert(p); + assert(key); + + /* Checks if the specified packet is a reply for the specified + * key and the specified key is the only one in the question + * section. */ + + if (DNS_PACKET_QR(p) != 1) + return 0; + + /* Let's unpack the packet, if that hasn't happened yet. */ + r = dns_packet_extract(p); + if (r < 0) + return r; + + if (!p->question) + return 0; + + if (p->question->n_keys != 1) + return 0; + + return dns_resource_key_equal(p->question->keys[0], key); +} + +static void dns_packet_hash_func(const DnsPacket *s, struct siphash *state) { + assert(s); + + siphash24_compress(&s->size, sizeof(s->size), state); + siphash24_compress(DNS_PACKET_DATA((DnsPacket*) s), s->size, state); +} + +static int dns_packet_compare_func(const DnsPacket *x, const DnsPacket *y) { + int r; + + r = CMP(x->size, y->size); + if (r != 0) + return r; + + return memcmp(DNS_PACKET_DATA((DnsPacket*) x), DNS_PACKET_DATA((DnsPacket*) y), x->size); +} + +DEFINE_HASH_OPS(dns_packet_hash_ops, DnsPacket, dns_packet_hash_func, dns_packet_compare_func); + +static const char* const dns_rcode_table[_DNS_RCODE_MAX_DEFINED] = { + [DNS_RCODE_SUCCESS] = "SUCCESS", + [DNS_RCODE_FORMERR] = "FORMERR", + [DNS_RCODE_SERVFAIL] = "SERVFAIL", + [DNS_RCODE_NXDOMAIN] = "NXDOMAIN", + [DNS_RCODE_NOTIMP] = "NOTIMP", + [DNS_RCODE_REFUSED] = "REFUSED", + [DNS_RCODE_YXDOMAIN] = "YXDOMAIN", + [DNS_RCODE_YXRRSET] = "YRRSET", + [DNS_RCODE_NXRRSET] = "NXRRSET", + [DNS_RCODE_NOTAUTH] = "NOTAUTH", + [DNS_RCODE_NOTZONE] = "NOTZONE", + [DNS_RCODE_BADVERS] = "BADVERS", + [DNS_RCODE_BADKEY] = "BADKEY", + [DNS_RCODE_BADTIME] = "BADTIME", + [DNS_RCODE_BADMODE] = "BADMODE", + [DNS_RCODE_BADNAME] = "BADNAME", + [DNS_RCODE_BADALG] = "BADALG", + [DNS_RCODE_BADTRUNC] = "BADTRUNC", + [DNS_RCODE_BADCOOKIE] = "BADCOOKIE", +}; +DEFINE_STRING_TABLE_LOOKUP(dns_rcode, int); + +static const char* const dns_protocol_table[_DNS_PROTOCOL_MAX] = { + [DNS_PROTOCOL_DNS] = "dns", + [DNS_PROTOCOL_MDNS] = "mdns", + [DNS_PROTOCOL_LLMNR] = "llmnr", +}; +DEFINE_STRING_TABLE_LOOKUP(dns_protocol, DnsProtocol); |