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Address race in dns_tsigkey_find()

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Restart the process with a write lock if we discover an expired key
while holding the read lock.

(cherry picked from commit d2ba96488e)
This commit is contained in:
Mark Andrews 2023-06-29 09:15:38 +10:00 committed by Michał Kępień
parent 75677d375e
commit f46a81932f
No known key found for this signature in database
1 changed files with 14 additions and 8 deletions
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22
lib/dns/tsig.c
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@ -1757,8 +1757,9 @@ isc_result_t
dns_tsigkey_find(dns_tsigkey_t **tsigkey, const dns_name_t *name,
const dns_name_t *algorithm, dns_tsig_keyring_t *ring) {
dns_tsigkey_t *key;
isc_stdtime_t now;
isc_result_t result;
isc_rwlocktype_t locktype = isc_rwlocktype_read;
isc_stdtime_t now;
REQUIRE(tsigkey != NULL);
REQUIRE(*tsigkey == NULL);
@ -1770,25 +1771,30 @@ dns_tsigkey_find(dns_tsigkey_t **tsigkey, const dns_name_t *name,
RWUNLOCK(&ring->lock, isc_rwlocktype_write);
isc_stdtime_get(&now);
RWLOCK(&ring->lock, isc_rwlocktype_read);
again:
RWLOCK(&ring->lock, locktype);
key = NULL;
result = dns_rbt_findname(ring->keys, name, 0, NULL, (void *)&key);
if (result == DNS_R_PARTIALMATCH || result == ISC_R_NOTFOUND) {
RWUNLOCK(&ring->lock, isc_rwlocktype_read);
RWUNLOCK(&ring->lock, locktype);
return (ISC_R_NOTFOUND);
}
if (algorithm != NULL && !dns_name_equal(key->algorithm, algorithm)) {
RWUNLOCK(&ring->lock, isc_rwlocktype_read);
RWUNLOCK(&ring->lock, locktype);
return (ISC_R_NOTFOUND);
}
if (key->inception != key->expire && isc_serial_lt(key->expire, now)) {
/*
* The key has expired.
*/
RWUNLOCK(&ring->lock, isc_rwlocktype_read);
RWLOCK(&ring->lock, isc_rwlocktype_write);
if (locktype == isc_rwlocktype_read) {
RWUNLOCK(&ring->lock, locktype);
locktype = isc_rwlocktype_write;
goto again;
}
remove_fromring(key);
RWUNLOCK(&ring->lock, isc_rwlocktype_write);
RWUNLOCK(&ring->lock, locktype);
return (ISC_R_NOTFOUND);
}
#if 0
@ -1803,7 +1809,7 @@ dns_tsigkey_find(dns_tsigkey_t **tsigkey, const dns_name_t *name,
}
#endif /* if 0 */
isc_refcount_increment(&key->refs);
RWUNLOCK(&ring->lock, isc_rwlocktype_read);
RWUNLOCK(&ring->lock, locktype);
adjust_lru(key);
*tsigkey = key;
return (ISC_R_SUCCESS);