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Diffstat (limited to 'src/resolve/resolved-dns-packet.c')
-rw-r--r--src/resolve/resolved-dns-packet.c406
1 files changed, 321 insertions, 85 deletions
diff --git a/src/resolve/resolved-dns-packet.c b/src/resolve/resolved-dns-packet.c
index 9bd08eeec2..9a5223ef01 100644
--- a/src/resolve/resolved-dns-packet.c
+++ b/src/resolve/resolved-dns-packet.c
@@ -58,6 +58,7 @@ int dns_packet_new(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
p->size = p->rindex = DNS_PACKET_HEADER_SIZE;
p->allocated = a;
p->protocol = protocol;
+ p->opt_start = p->opt_size = (size_t) -1;
p->n_ref = 1;
*ret = p;
@@ -65,20 +66,18 @@ int dns_packet_new(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
return 0;
}
-int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled) {
- DnsPacket *p;
- DnsPacketHeader *h;
- int r;
+void dns_packet_set_flags(DnsPacket *p, bool dnssec_checking_disabled, bool truncated) {
- assert(ret);
+ DnsPacketHeader *h;
- r = dns_packet_new(&p, protocol, mtu);
- if (r < 0)
- return r;
+ assert(p);
h = DNS_PACKET_HEADER(p);
- if (protocol == DNS_PROTOCOL_LLMNR)
+ switch(p->protocol) {
+ case DNS_PROTOCOL_LLMNR:
+ assert(!truncated);
+
h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
0 /* opcode */,
0 /* c */,
@@ -88,17 +87,23 @@ int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu, bool
0 /* ad */,
0 /* cd */,
0 /* rcode */));
- else if (protocol == DNS_PROTOCOL_MDNS)
- h->flags = htobe16(DNS_PACKET_MAKE_FLAGS(0 /* qr */,
- 0 /* opcode */,
- 0 /* aa */,
- 0 /* tc */,
- 0 /* rd (ask for recursion) */,
- 0 /* ra */,
- 0 /* ad */,
- 0 /* cd */,
- 0 /* rcode */));
- else
+ 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 */,
@@ -108,6 +113,23 @@ int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu, bool
0 /* ad */,
dnssec_checking_disabled /* cd */,
0 /* rcode */));
+ }
+}
+
+int dns_packet_new_query(DnsPacket **ret, DnsProtocol protocol, size_t mtu, bool dnssec_checking_disabled) {
+ DnsPacket *p;
+ int r;
+
+ assert(ret);
+
+ r = dns_packet_new(&p, protocol, mtu);
+ 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;
@@ -132,6 +154,7 @@ static void dns_packet_free(DnsPacket *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);
@@ -149,6 +172,8 @@ DnsPacket *dns_packet_unref(DnsPacket *p) {
assert(p->n_ref > 0);
+ dns_packet_unref(p->more);
+
if (p->n_ref == 1)
dns_packet_free(p);
else
@@ -185,6 +210,7 @@ int dns_packet_validate_reply(DnsPacket *p) {
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)
@@ -225,6 +251,7 @@ int dns_packet_validate_query(DnsPacket *p) {
return -EBADMSG;
switch (p->protocol) {
+
case DNS_PROTOCOL_LLMNR:
/* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */
if (DNS_PACKET_QDCOUNT(p) != 1)
@@ -412,10 +439,15 @@ int dns_packet_append_raw_string(DnsPacket *p, const void *s, size_t size, size_
return 0;
}
-int dns_packet_append_label(DnsPacket *p, const char *d, size_t l, size_t *start) {
+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);
@@ -428,18 +460,14 @@ int dns_packet_append_label(DnsPacket *p, const char *d, size_t l, size_t *start
*(w++) = (uint8_t) l;
- if (p->canonical_form) {
+ 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++) {
- if (d[i] >= 'A' && d[i] <= 'Z')
- w[i] = (uint8_t) (d[i] - 'A' + 'a');
- else
- w[i] = (uint8_t) d[i];
- }
+ 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
@@ -453,6 +481,7 @@ int dns_packet_append_name(
DnsPacket *p,
const char *name,
bool allow_compression,
+ bool canonical_candidate,
size_t *start) {
size_t saved_size;
@@ -466,11 +495,10 @@ int dns_packet_append_name(
saved_size = p->size;
- while (*name) {
- _cleanup_free_ char *s = NULL;
+ while (!dns_name_is_root(name)) {
+ const char *z = name;
char label[DNS_LABEL_MAX];
size_t n = 0;
- int k;
if (allow_compression)
n = PTR_TO_SIZE(hashmap_get(p->names, name));
@@ -486,32 +514,23 @@ int dns_packet_append_name(
}
}
- s = strdup(name);
- if (!s) {
- r = -ENOMEM;
- goto fail;
- }
-
r = dns_label_unescape(&name, label, sizeof(label));
if (r < 0)
goto fail;
- if (p->protocol == DNS_PROTOCOL_DNS)
- k = dns_label_apply_idna(label, r, label, sizeof(label));
- else
- k = dns_label_undo_idna(label, r, label, sizeof(label));
- if (k < 0) {
- r = k;
- goto fail;
- }
- if (k > 0)
- r = k;
-
- r = dns_packet_append_label(p, label, r, &n);
+ 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;
@@ -548,7 +567,7 @@ int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *k, size_t *start)
saved_size = p->size;
- r = dns_packet_append_name(p, DNS_RESOURCE_KEY_NAME(k), true, NULL);
+ r = dns_packet_append_name(p, DNS_RESOURCE_KEY_NAME(k), true, true, NULL);
if (r < 0)
goto fail;
@@ -570,7 +589,7 @@ fail:
return r;
}
-static int dns_packet_append_type_window(DnsPacket *p, uint8_t window, uint8_t length, uint8_t *types, size_t *start) {
+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;
@@ -611,7 +630,6 @@ static int dns_packet_append_types(DnsPacket *p, Bitmap *types, size_t *start) {
int r;
assert(p);
- assert(types);
saved_size = p->size;
@@ -627,15 +645,16 @@ static int dns_packet_append_types(DnsPacket *p, Bitmap *types, size_t *start) {
}
window = n >> 8;
-
entry = n & 255;
bitmaps[entry / 8] |= 1 << (7 - (entry % 8));
}
- r = dns_packet_append_type_window(p, window, entry / 8 + 1, bitmaps, NULL);
- if (r < 0)
- goto fail;
+ 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;
@@ -647,7 +666,7 @@ fail:
}
/* Append the OPT pseudo-RR described in RFC6891 */
-int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start) {
+int dns_packet_append_opt(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start) {
size_t saved_size;
int r;
@@ -655,6 +674,11 @@ int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, bool edns0_do,
/* we must never advertise supported packet size smaller than the legacy max */
assert(max_udp_size >= DNS_PACKET_UNICAST_SIZE_MAX);
+ if (p->opt_start != (size_t) -1)
+ return -EBUSY;
+
+ assert(p->opt_size == (size_t) -1);
+
saved_size = p->size;
/* empty name */
@@ -683,10 +707,48 @@ int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, bool edns0_do,
goto fail;
/* RDLENGTH */
- r = dns_packet_append_uint16(p, 0, NULL);
+
+ if (edns0_do) {
+ /* If DO is on, also append RFC6975 Algorithm data */
+
+ static const uint8_t rfc6975[] = {
+
+ 0, 5, /* OPTION_CODE: DAU */
+ 0, 6, /* LIST_LENGTH */
+ DNSSEC_ALGORITHM_RSASHA1,
+ DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1,
+ DNSSEC_ALGORITHM_RSASHA256,
+ DNSSEC_ALGORITHM_RSASHA512,
+ DNSSEC_ALGORITHM_ECDSAP256SHA256,
+ DNSSEC_ALGORITHM_ECDSAP384SHA384,
+
+ 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;
@@ -697,6 +759,27 @@ fail:
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, size_t *start, size_t *rdata_start) {
size_t saved_size, rdlength_offset, end, rdlength, rds;
int r;
@@ -736,14 +819,14 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
if (r < 0)
goto fail;
- r = dns_packet_append_name(p, rr->srv.name, true, NULL);
+ r = dns_packet_append_name(p, rr->srv.name, true, 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, NULL);
+ r = dns_packet_append_name(p, rr->ptr.name, true, false, NULL);
break;
case DNS_TYPE_HINFO:
@@ -786,11 +869,11 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
break;
case DNS_TYPE_SOA:
- r = dns_packet_append_name(p, rr->soa.mname, true, NULL);
+ 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, NULL);
+ r = dns_packet_append_name(p, rr->soa.rname, true, false, NULL);
if (r < 0)
goto fail;
@@ -818,7 +901,7 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
if (r < 0)
goto fail;
- r = dns_packet_append_name(p, rr->mx.exchange, true, NULL);
+ r = dns_packet_append_name(p, rr->mx.exchange, true, false, NULL);
break;
case DNS_TYPE_LOC:
@@ -922,7 +1005,7 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
if (r < 0)
goto fail;
- r = dns_packet_append_name(p, rr->rrsig.signer, false, NULL);
+ r = dns_packet_append_name(p, rr->rrsig.signer, false, true, NULL);
if (r < 0)
goto fail;
@@ -930,7 +1013,7 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
break;
case DNS_TYPE_NSEC:
- r = dns_packet_append_name(p, rr->nsec.next_domain_name, false, NULL);
+ r = dns_packet_append_name(p, rr->nsec.next_domain_name, false, false, NULL);
if (r < 0)
goto fail;
@@ -939,6 +1022,7 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
goto fail;
break;
+
case DNS_TYPE_NSEC3:
r = dns_packet_append_uint8(p, rr->nsec3.algorithm, NULL);
if (r < 0)
@@ -973,6 +1057,8 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
goto fail;
break;
+
+ case DNS_TYPE_OPT:
case _DNS_TYPE_INVALID: /* unparseable */
default:
@@ -985,7 +1071,7 @@ int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *star
/* Let's calculate the actual data size and update the field */
rdlength = p->size - rdlength_offset - sizeof(uint16_t);
if (rdlength > 0xFFFF) {
- r = ENOSPC;
+ r = -ENOSPC;
goto fail;
}
@@ -1009,7 +1095,6 @@ fail:
return r;
}
-
int dns_packet_read(DnsPacket *p, size_t sz, const void **ret, size_t *start) {
assert(p);
@@ -1419,7 +1504,7 @@ fail:
return r;
}
-int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
+int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, bool *ret_cache_flush, size_t *start) {
_cleanup_free_ char *name = NULL;
bool cache_flush = false;
uint16_t class, type;
@@ -1447,7 +1532,7 @@ int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
if (p->protocol == DNS_PROTOCOL_MDNS) {
/* See RFC6762, Section 10.2 */
- if (class & MDNS_RR_CACHE_FLUSH) {
+ if (type != DNS_TYPE_OPT && (class & MDNS_RR_CACHE_FLUSH)) {
class &= ~MDNS_RR_CACHE_FLUSH;
cache_flush = true;
}
@@ -1459,11 +1544,11 @@ int dns_packet_read_key(DnsPacket *p, DnsResourceKey **ret, size_t *start) {
goto fail;
}
- key->cache_flush = cache_flush;
-
name = NULL;
*ret = key;
+ if (ret_cache_flush)
+ *ret_cache_flush = cache_flush;
if (start)
*start = saved_rindex;
@@ -1479,11 +1564,12 @@ static bool loc_size_ok(uint8_t size) {
return m <= 9 && e <= 9 && (m > 0 || e == 0);
}
-int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
+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;
size_t saved_rindex, offset;
uint16_t rdlength;
+ bool cache_flush;
int r;
assert(p);
@@ -1491,12 +1577,12 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
saved_rindex = p->rindex;
- r = dns_packet_read_key(p, &key, NULL);
+ r = dns_packet_read_key(p, &key, &cache_flush, NULL);
if (r < 0)
goto fail;
- if (key->class == DNS_CLASS_ANY ||
- key->type == DNS_TYPE_ANY) {
+ if (!dns_class_is_valid_rr(key->class)||
+ !dns_type_is_valid_rr(key->type)) {
r = -EBADMSG;
goto fail;
}
@@ -1511,6 +1597,11 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
if (r < 0)
goto fail;
+ /* 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)
goto fail;
@@ -1544,10 +1635,6 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
r = dns_packet_read_name(p, &rr->ptr.name, true, NULL);
break;
- case DNS_TYPE_OPT: /* we only care about the header */
- r = 0;
- break;
-
case DNS_TYPE_HINFO:
r = dns_packet_read_string(p, &rr->hinfo.cpu, NULL);
if (r < 0)
@@ -1725,6 +1812,7 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
}
break;
+
case DNS_TYPE_SSHFP:
r = dns_packet_read_uint8(p, &rr->sshfp.algorithm, NULL);
if (r < 0)
@@ -1822,7 +1910,7 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
case DNS_TYPE_NSEC: {
/*
- * RFC6762, section 18.14 explicly states mDNS should use name compression.
+ * RFC6762, section 18.14 explictly states mDNS should use name compression.
* This contradicts RFC3845, section 2.1.1
*/
@@ -1887,6 +1975,8 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
break;
}
+
+ case DNS_TYPE_OPT: /* we only care about the header of OPT for now. */
default:
unparseable:
r = dns_packet_read_memdup(p, rdlength, &rr->generic.data, &rr->generic.size, NULL);
@@ -1904,6 +1994,8 @@ int dns_packet_read_rr(DnsPacket *p, DnsResourceRecord **ret, size_t *start) {
*ret = rr;
rr = NULL;
+ if (ret_cache_flush)
+ *ret_cache_flush = cache_flush;
if (start)
*start = saved_rindex;
@@ -1913,6 +2005,48 @@ fail:
return r;
}
+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)
+ return false;
+
+ p = rr->opt.data;
+ l = rr->opt.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;
+}
+
int dns_packet_extract(DnsPacket *p) {
_cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
@@ -1936,11 +2070,22 @@ int dns_packet_extract(DnsPacket *p) {
for (i = 0; i < n; i++) {
_cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
+ bool cache_flush;
- r = dns_packet_read_key(p, &key, NULL);
+ r = dns_packet_read_key(p, &key, &cache_flush, NULL);
if (r < 0)
goto finish;
+ if (cache_flush) {
+ r = -EBADMSG;
+ goto finish;
+ }
+
+ if (!dns_type_is_valid_query(key->type)) {
+ r = -EBADMSG;
+ goto finish;
+ }
+
r = dns_question_add(question, key);
if (r < 0)
goto finish;
@@ -1949,6 +2094,9 @@ int dns_packet_extract(DnsPacket *p) {
n = DNS_PACKET_RRCOUNT(p);
if (n > 0) {
+ DnsResourceRecord *previous = NULL;
+ bool bad_opt = false;
+
answer = dns_answer_new(n);
if (!answer) {
r = -ENOMEM;
@@ -1957,15 +2105,79 @@ int dns_packet_extract(DnsPacket *p) {
for (i = 0; i < n; i++) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
+ bool cache_flush;
- r = dns_packet_read_rr(p, &rr, NULL);
+ r = dns_packet_read_rr(p, &rr, &cache_flush, NULL);
if (r < 0)
goto finish;
- r = dns_answer_add(answer, rr, p->ifindex);
- if (r < 0)
- goto finish;
+ /* 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 qis 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 (has_rfc6975) {
+ /* 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 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. */
+
+ r = dns_answer_add(answer, rr, p->ifindex,
+ (i < DNS_PACKET_ANCOUNT(p) ? DNS_ANSWER_CACHEABLE : 0) |
+ (p->protocol == DNS_PROTOCOL_MDNS && !cache_flush ? DNS_ANSWER_SHARED_OWNER : 0));
+ if (r < 0)
+ goto finish;
+ }
}
+
+ if (bad_opt)
+ p->opt = dns_resource_record_unref(p->opt);
}
p->question = question;
@@ -1983,6 +2195,30 @@ finish:
return r;
}
+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->n_keys != 1)
+ return 0;
+
+ return dns_resource_key_equal(p->question->keys[0], key);
+}
+
static const char* const dns_rcode_table[_DNS_RCODE_MAX_DEFINED] = {
[DNS_RCODE_SUCCESS] = "SUCCESS",
[DNS_RCODE_FORMERR] = "FORMERR",
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-03 05:18:07 +0000