resolved: partially implement RFC5011 Trust Anchor support

With this patch resolved will properly handle revoked keys, but not
augment the locally configured trust anchor database with newly learned
keys.

Specifically, resolved now refuses validating RRsets with
revoked keys, and it will remove revoked keys from the configured trust
anchors (only until reboot).

This patch does not add logic for adding new keys to the set of trust
anchors. This is a deliberate decision as this only can work with
persistent disk storage, and would result in a different update logic
for stateful and stateless systems.  Since we have to support stateless
systems anyway, and don't want to encourage two independent upgrade
paths we focus on upgrading the trust anchor database via the usual OS
upgrade logic.

Whenever a trust anchor entry is found revoked and removed from the
trust anchor a recognizable log message is written, encouraging the user
to update the trust anchor or update his operating system.
This commit is contained in:
Lennart Poettering 2016-01-04 20:38:21 +01:00
parent 85aeaccc10
commit 0c85702874
9 changed files with 307 additions and 27 deletions

View File

@ -524,6 +524,92 @@ int dns_answer_remove_by_key(DnsAnswer **a, const DnsResourceKey *key) {
return 1;
}
int dns_answer_remove_by_rr(DnsAnswer **a, DnsResourceRecord *rm) {
bool found = false, other = false;
DnsResourceRecord *rr;
unsigned i;
int r;
assert(a);
assert(rm);
/* Remove all entries matching the specified RR from *a */
DNS_ANSWER_FOREACH(rr, *a) {
r = dns_resource_record_equal(rr, rm);
if (r < 0)
return r;
if (r > 0)
found = true;
else
other = true;
if (found && other)
break;
}
if (!found)
return 0;
if (!other) {
*a = dns_answer_unref(*a); /* Return NULL for the empty answer */
return 1;
}
if ((*a)->n_ref > 1) {
_cleanup_(dns_answer_unrefp) DnsAnswer *copy = NULL;
DnsAnswerFlags flags;
int ifindex;
copy = dns_answer_new((*a)->n_rrs);
if (!copy)
return -ENOMEM;
DNS_ANSWER_FOREACH_FULL(rr, ifindex, flags, *a) {
r = dns_resource_record_equal(rr, rm);
if (r < 0)
return r;
if (r > 0)
continue;
r = dns_answer_add_raw(copy, rr, ifindex, flags);
if (r < 0)
return r;
}
dns_answer_unref(*a);
*a = copy;
copy = NULL;
return 1;
}
/* Only a single reference, edit in-place */
i = 0;
for (;;) {
if (i >= (*a)->n_rrs)
break;
r = dns_resource_record_equal((*a)->items[i].rr, rm);
if (r < 0)
return r;
if (r > 0) {
/* Kill this entry */
dns_resource_record_unref((*a)->items[i].rr);
memmove((*a)->items + i, (*a)->items + i + 1, sizeof(DnsAnswerItem) * ((*a)->n_rrs - i - 1));
(*a)->n_rrs --;
continue;
} else
/* Keep this entry */
i++;
}
return 1;
}
int dns_answer_copy_by_key(DnsAnswer **a, DnsAnswer *source, const DnsResourceKey *key, DnsAnswerFlags or_flags) {
DnsResourceRecord *rr_source;
int ifindex_source, r;

View File

@ -77,6 +77,8 @@ int dns_answer_reserve(DnsAnswer **a, unsigned n_free);
int dns_answer_reserve_or_clone(DnsAnswer **a, unsigned n_free);
int dns_answer_remove_by_key(DnsAnswer **a, const DnsResourceKey *key);
int dns_answer_remove_by_rr(DnsAnswer **a, DnsResourceRecord *rr);
int dns_answer_copy_by_key(DnsAnswer **a, DnsAnswer *source, const DnsResourceKey *key, DnsAnswerFlags or_flags);
int dns_answer_move_by_key(DnsAnswer **to, DnsAnswer **from, const DnsResourceKey *key, DnsAnswerFlags or_flags);

View File

@ -79,9 +79,9 @@ static void initialize_libgcrypt(void) {
gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
}
uint16_t dnssec_keytag(DnsResourceRecord *dnskey) {
uint16_t dnssec_keytag(DnsResourceRecord *dnskey, bool mask_revoke) {
const uint8_t *p;
uint32_t sum;
uint32_t sum, f;
size_t i;
/* The algorithm from RFC 4034, Appendix B. */
@ -89,8 +89,12 @@ uint16_t dnssec_keytag(DnsResourceRecord *dnskey) {
assert(dnskey);
assert(dnskey->key->type == DNS_TYPE_DNSKEY);
sum = (uint32_t) dnskey->dnskey.flags +
((((uint32_t) dnskey->dnskey.protocol) << 8) + (uint32_t) dnskey->dnskey.algorithm);
f = (uint32_t) dnskey->dnskey.flags;
if (mask_revoke)
f &= ~DNSKEY_FLAG_REVOKE;
sum = f + ((((uint32_t) dnskey->dnskey.protocol) << 8) + (uint32_t) dnskey->dnskey.algorithm);
p = dnskey->dnskey.key;
@ -494,7 +498,7 @@ static int algorithm_to_gcrypt_md(uint8_t algorithm) {
int dnssec_verify_rrset(
DnsAnswer *a,
DnsResourceKey *key,
const DnsResourceKey *key,
DnsResourceRecord *rrsig,
DnsResourceRecord *dnskey,
usec_t realtime,
@ -653,7 +657,7 @@ finish:
return r;
}
int dnssec_rrsig_match_dnskey(DnsResourceRecord *rrsig, DnsResourceRecord *dnskey) {
int dnssec_rrsig_match_dnskey(DnsResourceRecord *rrsig, DnsResourceRecord *dnskey, bool revoked_ok) {
assert(rrsig);
assert(dnskey);
@ -670,14 +674,14 @@ int dnssec_rrsig_match_dnskey(DnsResourceRecord *rrsig, DnsResourceRecord *dnske
return 0;
if ((dnskey->dnskey.flags & DNSKEY_FLAG_ZONE_KEY) == 0)
return 0;
if ((dnskey->dnskey.flags & DNSKEY_FLAG_REVOKE))
if (!revoked_ok && (dnskey->dnskey.flags & DNSKEY_FLAG_REVOKE))
return 0;
if (dnskey->dnskey.protocol != 3)
return 0;
if (dnskey->dnskey.algorithm != rrsig->rrsig.algorithm)
return 0;
if (dnssec_keytag(dnskey) != rrsig->rrsig.key_tag)
if (dnssec_keytag(dnskey, false) != rrsig->rrsig.key_tag)
return 0;
return dns_name_equal(DNS_RESOURCE_KEY_NAME(dnskey->key), rrsig->rrsig.signer);
@ -739,7 +743,7 @@ static int dnssec_fix_rrset_ttl(DnsAnswer *a, const DnsResourceKey *key, DnsReso
int dnssec_verify_rrset_search(
DnsAnswer *a,
DnsResourceKey *key,
const DnsResourceKey *key,
DnsAnswer *validated_dnskeys,
usec_t realtime,
DnssecResult *result) {
@ -778,7 +782,7 @@ int dnssec_verify_rrset_search(
continue;
/* Is this a DNSKEY RR that matches they key of our RRSIG? */
r = dnssec_rrsig_match_dnskey(rrsig, dnskey);
r = dnssec_rrsig_match_dnskey(rrsig, dnskey, false);
if (r < 0)
return r;
if (r == 0)
@ -958,7 +962,7 @@ static int digest_to_gcrypt_md(uint8_t algorithm) {
}
}
int dnssec_verify_dnskey(DnsResourceRecord *dnskey, DnsResourceRecord *ds) {
int dnssec_verify_dnskey(DnsResourceRecord *dnskey, DnsResourceRecord *ds, bool mask_revoke) {
char owner_name[DNSSEC_CANONICAL_HOSTNAME_MAX];
gcry_md_hd_t md = NULL;
size_t hash_size;
@ -976,12 +980,14 @@ int dnssec_verify_dnskey(DnsResourceRecord *dnskey, DnsResourceRecord *ds) {
return -EINVAL;
if ((dnskey->dnskey.flags & DNSKEY_FLAG_ZONE_KEY) == 0)
return -EKEYREJECTED;
if (!mask_revoke && (dnskey->dnskey.flags & DNSKEY_FLAG_REVOKE))
return -EKEYREJECTED;
if (dnskey->dnskey.protocol != 3)
return -EKEYREJECTED;
if (dnskey->dnskey.algorithm != ds->ds.algorithm)
return 0;
if (dnssec_keytag(dnskey) != ds->ds.key_tag)
if (dnssec_keytag(dnskey, mask_revoke) != ds->ds.key_tag)
return 0;
initialize_libgcrypt();
@ -1005,7 +1011,10 @@ int dnssec_verify_dnskey(DnsResourceRecord *dnskey, DnsResourceRecord *ds) {
return -EIO;
gcry_md_write(md, owner_name, r);
md_add_uint16(md, dnskey->dnskey.flags);
if (mask_revoke)
md_add_uint16(md, dnskey->dnskey.flags & ~DNSKEY_FLAG_REVOKE);
else
md_add_uint16(md, dnskey->dnskey.flags);
md_add_uint8(md, dnskey->dnskey.protocol);
md_add_uint8(md, dnskey->dnskey.algorithm);
gcry_md_write(md, dnskey->dnskey.key, dnskey->dnskey.key_size);
@ -1050,7 +1059,9 @@ int dnssec_verify_dnskey_search(DnsResourceRecord *dnskey, DnsAnswer *validated_
if (r == 0)
continue;
r = dnssec_verify_dnskey(dnskey, ds);
r = dnssec_verify_dnskey(dnskey, ds, false);
if (r == -EKEYREJECTED)
return 0; /* The DNSKEY is revoked or otherwise invalid, we won't bless it */
if (r < 0)
return r;
if (r > 0)

View File

@ -72,18 +72,18 @@ enum DnssecResult {
/* The longest digest we'll ever generate, of all digest algorithms we support */
#define DNSSEC_HASH_SIZE_MAX (MAX(20, 32))
int dnssec_rrsig_match_dnskey(DnsResourceRecord *rrsig, DnsResourceRecord *dnskey);
int dnssec_rrsig_match_dnskey(DnsResourceRecord *rrsig, DnsResourceRecord *dnskey, bool revoked_ok);
int dnssec_key_match_rrsig(const DnsResourceKey *key, DnsResourceRecord *rrsig);
int dnssec_verify_rrset(DnsAnswer *answer, DnsResourceKey *key, DnsResourceRecord *rrsig, DnsResourceRecord *dnskey, usec_t realtime, DnssecResult *result);
int dnssec_verify_rrset_search(DnsAnswer *answer, DnsResourceKey *key, DnsAnswer *validated_dnskeys, usec_t realtime, DnssecResult *result);
int dnssec_verify_rrset(DnsAnswer *answer, const DnsResourceKey *key, DnsResourceRecord *rrsig, DnsResourceRecord *dnskey, usec_t realtime, DnssecResult *result);
int dnssec_verify_rrset_search(DnsAnswer *answer, const DnsResourceKey *key, DnsAnswer *validated_dnskeys, usec_t realtime, DnssecResult *result);
int dnssec_verify_dnskey(DnsResourceRecord *dnskey, DnsResourceRecord *ds);
int dnssec_verify_dnskey(DnsResourceRecord *dnskey, DnsResourceRecord *ds, bool mask_revoke);
int dnssec_verify_dnskey_search(DnsResourceRecord *dnskey, DnsAnswer *validated_ds);
int dnssec_has_rrsig(DnsAnswer *a, const DnsResourceKey *key);
uint16_t dnssec_keytag(DnsResourceRecord *dnskey);
uint16_t dnssec_keytag(DnsResourceRecord *dnskey, bool mask_revoke);
int dnssec_canonicalize(const char *n, char *buffer, size_t buffer_max);

View File

@ -1497,7 +1497,7 @@ int dns_transaction_request_dnssec_keys(DnsTransaction *t) {
if (!ds)
return -ENOMEM;
log_debug("Requesting DS to validate transaction %" PRIu16" (%s, DNSKEY with key tag: %" PRIu16 ").", t->id, DNS_RESOURCE_KEY_NAME(rr->key), dnssec_keytag(rr));
log_debug("Requesting DS to validate transaction %" PRIu16" (%s, DNSKEY with key tag: %" PRIu16 ").", t->id, DNS_RESOURCE_KEY_NAME(rr->key), dnssec_keytag(rr, false));
r = dns_transaction_request_dnssec_rr(t, ds);
if (r < 0)
return r;
@ -2119,6 +2119,14 @@ int dns_transaction_validate_dnssec(DnsTransaction *t) {
r = dns_answer_copy_by_key(&t->validated_keys, t->answer, rr->key, DNS_ANSWER_AUTHENTICATED);
if (r < 0)
return r;
/* Maybe warn the user that we
* encountered a revoked
* DNSKEY for a key from our
* trust anchor */
r = dns_trust_anchor_check_revoked(&t->scope->manager->trust_anchor, t->answer, rr->key);
if (r < 0)
return r;
}
/* Add the validated RRset to the new

View File

@ -19,6 +19,8 @@
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <sd-messages.h>
#include "alloc-util.h"
#include "conf-files.h"
#include "def.h"
@ -28,6 +30,7 @@
#include "hexdecoct.h"
#include "parse-util.h"
#include "resolved-dns-trust-anchor.h"
#include "resolved-dns-dnssec.h"
#include "set.h"
#include "string-util.h"
#include "strv.h"
@ -413,3 +416,170 @@ int dns_trust_anchor_lookup_negative(DnsTrustAnchor *d, const char *name) {
return set_contains(d->negative_by_name, name);
}
static int dns_trust_anchor_remove_revoked(DnsTrustAnchor *d, DnsResourceRecord *rr) {
_cleanup_(dns_answer_unrefp) DnsAnswer *new_answer = NULL;
DnsAnswer *old_answer;
int r;
old_answer = hashmap_get(d->positive_by_key, rr->key);
if (!old_answer)
return 0;
new_answer = dns_answer_ref(old_answer);
r = dns_answer_remove_by_rr(&new_answer, rr);
if (r <= 0)
return r;
/* We found the key! Warn the user */
log_struct(LOG_WARNING,
LOG_MESSAGE_ID(SD_MESSAGE_DNSSEC_TRUST_ANCHOR_REVOKED),
LOG_MESSAGE("DNSSEC Trust anchor %s has been revoked. Please update the trust anchor, or upgrade your operating system."), strna(dns_resource_record_to_string(rr)),
"TRUST_ANCHOR=%s", dns_resource_record_to_string(rr),
NULL);
if (dns_answer_size(new_answer) <= 0) {
assert_se(hashmap_remove(d->positive_by_key, rr->key) == old_answer);
dns_answer_unref(old_answer);
return 1;
}
r = hashmap_replace(d->positive_by_key, new_answer->items[0].rr->key, new_answer);
if (r < 0)
return r;
new_answer = NULL;
dns_answer_unref(old_answer);
return 1;
}
static int dns_trust_anchor_check_revoked_one(DnsTrustAnchor *d, DnsResourceRecord *revoked_dnskey) {
DnsAnswer *a;
int r;
assert(d);
assert(revoked_dnskey);
assert(revoked_dnskey->key->type == DNS_TYPE_DNSKEY);
assert(revoked_dnskey->dnskey.flags & DNSKEY_FLAG_REVOKE);
a = hashmap_get(d->positive_by_key, revoked_dnskey->key);
if (a) {
DnsResourceRecord *anchor;
/* First, look for the precise DNSKEY in our trust anchor database */
DNS_ANSWER_FOREACH(anchor, a) {
if (anchor->dnskey.protocol != revoked_dnskey->dnskey.protocol)
continue;
if (anchor->dnskey.algorithm != revoked_dnskey->dnskey.algorithm)
continue;
if (anchor->dnskey.key_size != revoked_dnskey->dnskey.key_size)
continue;
if (((anchor->dnskey.flags ^ revoked_dnskey->dnskey.flags) | DNSKEY_FLAG_REVOKE) != DNSKEY_FLAG_REVOKE)
continue;
if (memcmp(anchor->dnskey.key, revoked_dnskey->dnskey.key, anchor->dnskey.key_size) != 0)
continue;
dns_trust_anchor_remove_revoked(d, anchor);
break;
}
}
a = hashmap_get(d->positive_by_key, &DNS_RESOURCE_KEY_CONST(revoked_dnskey->key->class, DNS_TYPE_DS, DNS_RESOURCE_KEY_NAME(revoked_dnskey->key)));
if (a) {
DnsResourceRecord *anchor;
/* Second, look for DS RRs matching this DNSKEY in our trust anchor database */
DNS_ANSWER_FOREACH(anchor, a) {
r = dnssec_verify_dnskey(revoked_dnskey, anchor, true);
if (r < 0)
return r;
if (r == 0)
continue;
dns_trust_anchor_remove_revoked(d, anchor);
break;
}
}
return 0;
}
static bool dns_trust_anchor_knows_domain(DnsTrustAnchor *d, const char *name) {
assert(d);
/* Returns true if there's an entry for the specified domain
* name in our trust anchor */
return
hashmap_contains(d->positive_by_key, &DNS_RESOURCE_KEY_CONST(DNS_CLASS_IN, DNS_TYPE_DNSKEY, name)) ||
hashmap_contains(d->positive_by_key, &DNS_RESOURCE_KEY_CONST(DNS_CLASS_IN, DNS_TYPE_DS, name));
}
int dns_trust_anchor_check_revoked(DnsTrustAnchor *d, DnsAnswer *rrs, const DnsResourceKey *key) {
DnsResourceRecord *dnskey;
int r;
assert(d);
assert(key);
/* Looks for self-signed DNSKEY RRs in "rrs" that have been revoked. */
if (key->type != DNS_TYPE_DNSKEY)
return 0;
DNS_ANSWER_FOREACH(dnskey, rrs) {
DnsResourceRecord *rrsig;
DnssecResult result;
r = dns_resource_key_equal(key, dnskey->key);
if (r < 0)
return r;
if (r == 0)
continue;
/* Is this DNSKEY revoked? */
if ((dnskey->dnskey.flags & DNSKEY_FLAG_REVOKE) == 0)
continue;
/* Could this be interesting to us at all? If not,
* there's no point in looking for and verifying a
* self-signed RRSIG. */
if (!dns_trust_anchor_knows_domain(d, DNS_RESOURCE_KEY_NAME(dnskey->key)))
continue;
/* Look for a self-signed RRSIG */
DNS_ANSWER_FOREACH(rrsig, rrs) {
if (rrsig->key->type != DNS_TYPE_RRSIG)
continue;
r = dnssec_rrsig_match_dnskey(rrsig, dnskey, true);
if (r < 0)
return r;
if (r == 0)
continue;
r = dnssec_verify_rrset(rrs, key, rrsig, dnskey, USEC_INFINITY, &result);
if (r < 0)
return r;
if (result != DNSSEC_VALIDATED)
continue;
/* Bingo! Now, act! */
r = dns_trust_anchor_check_revoked_one(d, dnskey);
if (r < 0)
return r;
}
}
return 0;
}

View File

@ -39,3 +39,5 @@ void dns_trust_anchor_flush(DnsTrustAnchor *d);
int dns_trust_anchor_lookup_positive(DnsTrustAnchor *d, const DnsResourceKey* key, DnsAnswer **answer);
int dns_trust_anchor_lookup_negative(DnsTrustAnchor *d, const char *name);
int dns_trust_anchor_check_revoked(DnsTrustAnchor *d, DnsAnswer *rrs, const DnsResourceKey *key);

View File

@ -107,10 +107,10 @@ static void test_dnssec_verify_rrset2(void) {
assert_se(dnskey->dnskey.key);
log_info("DNSKEY: %s", strna(dns_resource_record_to_string(dnskey)));
log_info("DNSKEY keytag: %u", dnssec_keytag(dnskey));
log_info("DNSKEY keytag: %u", dnssec_keytag(dnskey, false));
assert_se(dnssec_key_match_rrsig(nsec->key, rrsig) > 0);
assert_se(dnssec_rrsig_match_dnskey(rrsig, dnskey) > 0);
assert_se(dnssec_rrsig_match_dnskey(rrsig, dnskey, false) > 0);
answer = dns_answer_new(1);
assert_se(answer);
@ -186,10 +186,10 @@ static void test_dnssec_verify_rrset(void) {
assert_se(dnskey->dnskey.key);
log_info("DNSKEY: %s", strna(dns_resource_record_to_string(dnskey)));
log_info("DNSKEY keytag: %u", dnssec_keytag(dnskey));
log_info("DNSKEY keytag: %u", dnssec_keytag(dnskey, false));
assert_se(dnssec_key_match_rrsig(a->key, rrsig) > 0);
assert_se(dnssec_rrsig_match_dnskey(rrsig, dnskey) > 0);
assert_se(dnssec_rrsig_match_dnskey(rrsig, dnskey, false) > 0);
answer = dns_answer_new(1);
assert_se(answer);
@ -268,10 +268,10 @@ static void test_dnssec_verify_dns_key(void) {
assert_se(dnskey->dnskey.key);
log_info("DNSKEY: %s", strna(dns_resource_record_to_string(dnskey)));
log_info("DNSKEY keytag: %u", dnssec_keytag(dnskey));
log_info("DNSKEY keytag: %u", dnssec_keytag(dnskey, false));
assert_se(dnssec_verify_dnskey(dnskey, ds1) > 0);
assert_se(dnssec_verify_dnskey(dnskey, ds2) > 0);
assert_se(dnssec_verify_dnskey(dnskey, ds1, false) > 0);
assert_se(dnssec_verify_dnskey(dnskey, ds2, false) > 0);
}
static void test_dnssec_canonicalize_one(const char *original, const char *canonical, int r) {

View File

@ -87,6 +87,7 @@ _SD_BEGIN_DECLARATIONS;
#define SD_MESSAGE_BOOTCHART SD_ID128_MAKE(9f,26,aa,56,2c,f4,40,c2,b1,6c,77,3d,04,79,b5,18)
#define SD_MESSAGE_DNSSEC_FAILURE SD_ID128_MAKE(16,75,d7,f1,72,17,40,98,b1,10,8b,f8,c7,dc,8f,5d)
#define SD_MESSAGE_DNSSEC_TRUST_ANCHOR_REVOKED SD_ID128_MAKE(4d,44,08,cf,d0,d1,44,85,91,84,d1,e6,5d,7c,8a,65)
_SD_END_DECLARATIONS;