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Systemd/src/resolve/resolved-dns-rr.h
Lennart Poettering b30bf55d5c resolved: respond to local resolver requests on 127.0.0.53:53 
In order to improve compatibility with local clients that speak DNS directly
(and do not use NSS or our bus API) listen locally on 127.0.0.53:53 and process
any queries made that way.

Note that resolved does not implement a full DNS server on this port, but
simply enough to allow normal, local clients to resolve RRs through resolved.
Specifically it does not implement queries without the RD bit set (these are
requests where recursive lookups are explicitly disabled), and neither queries
with DNSSEC DO set in combination with DNSSEC CD (i.e. DNSSEC lookups with
validation turned off). It also refuses zone transfers and obsolete RR types.
All lookups done this way will be rejected with a clean error code, so that the
client side can repeat the query with a reduced feature set.

The code will set the DNSSEC AD flag however, depending on whether the data
resolved has been validated (or comes from a local, trusted source).

Lookups made via this mechanisms are propagated to LLMNR and mDNS as necessary,
but this is only partially useful as DNS packets cannot carry IP scope data
(i.e. the ifindex), and hence link-local addresses returned cannot be used
properly (and given that LLMNR/mDNS are mostly about link-local communication
this is quite a limitation). Also, given that DNS tends to use IDNA for
non-ASCII names, while LLMNR/mDNS uses UTF-8 lookups cannot be mapped 1:1.

In general this should improve compatibility with clients bypassing NSS but
it is highly recommended for clients to instead use NSS or our native bus API.

This patch also beefs up the DnsStream logic, as it reuses the code for local
TCP listening. DnsStream now provides proper reference counting for its
objects.

In order to avoid feedback loops resolved will no silently ignore 127.0.0.53
specified as DNS server when reading configuration.

resolved listens on 127.0.0.53:53 instead of 127.0.0.1:53 in order to leave
the latter free for local, external DNS servers or forwarders.

This also changes the "etc.conf" tmpfiles snippet to create a symlink from
/etc/resolv.conf to /usr/lib/systemd/resolv.conf by default, thus making this
stub the default mode of operation if /etc is not populated.
2016-06-21 14:15:23 +02:00

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#pragma once
/***
This file is part of systemd.
Copyright 2014 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <netinet/in.h>
#include "bitmap.h"
#include "dns-type.h"
#include "hashmap.h"
#include "in-addr-util.h"
#include "list.h"
#include "string-util.h"
typedef struct DnsResourceKey DnsResourceKey;
typedef struct DnsResourceRecord DnsResourceRecord;
typedef struct DnsTxtItem DnsTxtItem;
/* DNSKEY RR flags */
#define DNSKEY_FLAG_SEP (UINT16_C(1) << 0)
#define DNSKEY_FLAG_REVOKE (UINT16_C(1) << 7)
#define DNSKEY_FLAG_ZONE_KEY (UINT16_C(1) << 8)
/* mDNS RR flags */
#define MDNS_RR_CACHE_FLUSH (UINT16_C(1) << 15)
/* DNSSEC algorithm identifiers, see
* http://tools.ietf.org/html/rfc4034#appendix-A.1 and
* https://www.iana.org/assignments/dns-sec-alg-numbers/dns-sec-alg-numbers.xhtml */
enum {
DNSSEC_ALGORITHM_RSAMD5 = 1,
DNSSEC_ALGORITHM_DH,
DNSSEC_ALGORITHM_DSA,
DNSSEC_ALGORITHM_ECC,
DNSSEC_ALGORITHM_RSASHA1,
DNSSEC_ALGORITHM_DSA_NSEC3_SHA1,
DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1,
DNSSEC_ALGORITHM_RSASHA256 = 8, /* RFC 5702 */
DNSSEC_ALGORITHM_RSASHA512 = 10, /* RFC 5702 */
DNSSEC_ALGORITHM_ECC_GOST = 12, /* RFC 5933 */
DNSSEC_ALGORITHM_ECDSAP256SHA256 = 13, /* RFC 6605 */
DNSSEC_ALGORITHM_ECDSAP384SHA384 = 14, /* RFC 6605 */
DNSSEC_ALGORITHM_INDIRECT = 252,
DNSSEC_ALGORITHM_PRIVATEDNS,
DNSSEC_ALGORITHM_PRIVATEOID,
_DNSSEC_ALGORITHM_MAX_DEFINED
};
/* DNSSEC digest identifiers, see
* https://www.iana.org/assignments/ds-rr-types/ds-rr-types.xhtml */
enum {
DNSSEC_DIGEST_SHA1 = 1,
DNSSEC_DIGEST_SHA256 = 2, /* RFC 4509 */
DNSSEC_DIGEST_GOST_R_34_11_94 = 3, /* RFC 5933 */
DNSSEC_DIGEST_SHA384 = 4, /* RFC 6605 */
_DNSSEC_DIGEST_MAX_DEFINED
};
/* DNSSEC NSEC3 hash algorithms, see
* https://www.iana.org/assignments/dnssec-nsec3-parameters/dnssec-nsec3-parameters.xhtml */
enum {
NSEC3_ALGORITHM_SHA1 = 1,
_NSEC3_ALGORITHM_MAX_DEFINED
};
struct DnsResourceKey {
unsigned n_ref; /* (unsigned -1) for const keys, see below */
uint16_t class, type;
char *_name; /* don't access directly, use dns_resource_key_name()! */
};
/* Creates a temporary resource key. This is only useful to quickly
* look up something, without allocating a full DnsResourceKey object
* for it. Note that it is not OK to take references to this kind of
* resource key object. */
#define DNS_RESOURCE_KEY_CONST(c, t, n) \
((DnsResourceKey) { \
.n_ref = (unsigned) -1, \
.class = c, \
.type = t, \
._name = (char*) n, \
})
struct DnsTxtItem {
size_t length;
LIST_FIELDS(DnsTxtItem, items);
uint8_t data[];
};
struct DnsResourceRecord {
unsigned n_ref;
DnsResourceKey *key;
char *to_string;
uint32_t ttl;
usec_t expiry; /* RRSIG signature expiry */
/* How many labels to strip to determine "signer" of the RRSIG (aka, the zone). -1 if not signed. */
unsigned n_skip_labels_signer;
/* How many labels to strip to determine "synthesizing source" of this RR, i.e. the wildcard's immediate parent. -1 if not signed. */
unsigned n_skip_labels_source;
bool unparseable:1;
bool wire_format_canonical:1;
void *wire_format;
size_t wire_format_size;
size_t wire_format_rdata_offset;
union {
struct {
void *data;
size_t data_size;
} generic, opt;
struct {
uint16_t priority;
uint16_t weight;
uint16_t port;
char *name;
} srv;
struct {
char *name;
} ptr, ns, cname, dname;
struct {
char *cpu;
char *os;
} hinfo;
struct {
DnsTxtItem *items;
} txt, spf;
struct {
struct in_addr in_addr;
} a;
struct {
struct in6_addr in6_addr;
} aaaa;
struct {
char *mname;
char *rname;
uint32_t serial;
uint32_t refresh;
uint32_t retry;
uint32_t expire;
uint32_t minimum;
} soa;
struct {
uint16_t priority;
char *exchange;
} mx;
/* https://tools.ietf.org/html/rfc1876 */
struct {
uint8_t version;
uint8_t size;
uint8_t horiz_pre;
uint8_t vert_pre;
uint32_t latitude;
uint32_t longitude;
uint32_t altitude;
} loc;
/* https://tools.ietf.org/html/rfc4255#section-3.1 */
struct {
uint8_t algorithm;
uint8_t fptype;
void *fingerprint;
size_t fingerprint_size;
} sshfp;
/* http://tools.ietf.org/html/rfc4034#section-2.1 */
struct {
uint16_t flags;
uint8_t protocol;
uint8_t algorithm;
void* key;
size_t key_size;
} dnskey;
/* http://tools.ietf.org/html/rfc4034#section-3.1 */
struct {
uint16_t type_covered;
uint8_t algorithm;
uint8_t labels;
uint32_t original_ttl;
uint32_t expiration;
uint32_t inception;
uint16_t key_tag;
char *signer;
void *signature;
size_t signature_size;
} rrsig;
/* https://tools.ietf.org/html/rfc4034#section-4.1 */
struct {
char *next_domain_name;
Bitmap *types;
} nsec;
/* https://tools.ietf.org/html/rfc4034#section-5.1 */
struct {
uint16_t key_tag;
uint8_t algorithm;
uint8_t digest_type;
void *digest;
size_t digest_size;
} ds;
struct {
uint8_t algorithm;
uint8_t flags;
uint16_t iterations;
void *salt;
size_t salt_size;
void *next_hashed_name;
size_t next_hashed_name_size;
Bitmap *types;
} nsec3;
/* https://tools.ietf.org/html/draft-ietf-dane-protocol-23 */
struct {
uint8_t cert_usage;
uint8_t selector;
uint8_t matching_type;
void *data;
size_t data_size;
} tlsa;
/* https://tools.ietf.org/html/rfc6844 */
struct {
uint8_t flags;
char *tag;
void *value;
size_t value_size;
} caa;
};
};
static inline const void* DNS_RESOURCE_RECORD_RDATA(DnsResourceRecord *rr) {
if (!rr)
return NULL;
if (!rr->wire_format)
return NULL;
assert(rr->wire_format_rdata_offset <= rr->wire_format_size);
return (uint8_t*) rr->wire_format + rr->wire_format_rdata_offset;
}
static inline size_t DNS_RESOURCE_RECORD_RDATA_SIZE(DnsResourceRecord *rr) {
if (!rr)
return 0;
if (!rr->wire_format)
return 0;
assert(rr->wire_format_rdata_offset <= rr->wire_format_size);
return rr->wire_format_size - rr->wire_format_rdata_offset;
}
static inline uint8_t DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(DnsResourceRecord *rr) {
assert(rr);
assert(rr->key->type == DNS_TYPE_OPT);
return ((rr->ttl >> 16) & 0xFF) == 0;
}
DnsResourceKey* dns_resource_key_new(uint16_t class, uint16_t type, const char *name);
DnsResourceKey* dns_resource_key_new_redirect(const DnsResourceKey *key, const DnsResourceRecord *cname);
int dns_resource_key_new_append_suffix(DnsResourceKey **ret, DnsResourceKey *key, char *name);
DnsResourceKey* dns_resource_key_new_consume(uint16_t class, uint16_t type, char *name);
DnsResourceKey* dns_resource_key_ref(DnsResourceKey *key);
DnsResourceKey* dns_resource_key_unref(DnsResourceKey *key);
const char* dns_resource_key_name(const DnsResourceKey *key);
bool dns_resource_key_is_address(const DnsResourceKey *key);
int dns_resource_key_equal(const DnsResourceKey *a, const DnsResourceKey *b);
int dns_resource_key_match_rr(const DnsResourceKey *key, DnsResourceRecord *rr, const char *search_domain);
int dns_resource_key_match_cname_or_dname(const DnsResourceKey *key, const DnsResourceKey *cname, const char *search_domain);
int dns_resource_key_match_soa(const DnsResourceKey *key, const DnsResourceKey *soa);
/* _DNS_{CLASS,TYPE}_STRING_MAX include one byte for NUL, which we use for space instead below.
* DNS_HOSTNAME_MAX does not include the NUL byte, so we need to add 1. */
#define DNS_RESOURCE_KEY_STRING_MAX (_DNS_CLASS_STRING_MAX + _DNS_TYPE_STRING_MAX + DNS_HOSTNAME_MAX + 1)
char* dns_resource_key_to_string(const DnsResourceKey *key, char *buf, size_t buf_size);
ssize_t dns_resource_record_payload(DnsResourceRecord *rr, void **out);
DEFINE_TRIVIAL_CLEANUP_FUNC(DnsResourceKey*, dns_resource_key_unref);
static inline bool dns_key_is_shared(const DnsResourceKey *key) {
return IN_SET(key->type, DNS_TYPE_PTR);
}
bool dns_resource_key_reduce(DnsResourceKey **a, DnsResourceKey **b);
DnsResourceRecord* dns_resource_record_new(DnsResourceKey *key);
DnsResourceRecord* dns_resource_record_new_full(uint16_t class, uint16_t type, const char *name);
DnsResourceRecord* dns_resource_record_ref(DnsResourceRecord *rr);
DnsResourceRecord* dns_resource_record_unref(DnsResourceRecord *rr);
int dns_resource_record_new_reverse(DnsResourceRecord **ret, int family, const union in_addr_union *address, const char *name);
int dns_resource_record_new_address(DnsResourceRecord **ret, int family, const union in_addr_union *address, const char *name);
int dns_resource_record_equal(const DnsResourceRecord *a, const DnsResourceRecord *b);
const char* dns_resource_record_to_string(DnsResourceRecord *rr);
DnsResourceRecord *dns_resource_record_copy(DnsResourceRecord *rr);
DEFINE_TRIVIAL_CLEANUP_FUNC(DnsResourceRecord*, dns_resource_record_unref);
int dns_resource_record_to_wire_format(DnsResourceRecord *rr, bool canonical);
int dns_resource_record_signer(DnsResourceRecord *rr, const char **ret);
int dns_resource_record_source(DnsResourceRecord *rr, const char **ret);
int dns_resource_record_is_signer(DnsResourceRecord *rr, const char *zone);
int dns_resource_record_is_synthetic(DnsResourceRecord *rr);
int dns_resource_record_clamp_ttl(DnsResourceRecord **rr, uint32_t max_ttl);
DnsTxtItem *dns_txt_item_free_all(DnsTxtItem *i);
bool dns_txt_item_equal(DnsTxtItem *a, DnsTxtItem *b);
DnsTxtItem *dns_txt_item_copy(DnsTxtItem *i);
void dns_resource_record_hash_func(const void *i, struct siphash *state);
extern const struct hash_ops dns_resource_key_hash_ops;
extern const struct hash_ops dns_resource_record_hash_ops;
int dnssec_algorithm_to_string_alloc(int i, char **ret);
int dnssec_algorithm_from_string(const char *s) _pure_;
int dnssec_digest_to_string_alloc(int i, char **ret);
int dnssec_digest_from_string(const char *s) _pure_;
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