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Address races in dns_tsigkey_find()

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

2) Move incrementing the key reference inside the lock block of code.
This commit is contained in:
Mark Andrews 2023-06-29 09:15:38 +10:00 committed by Michał Kępień
parent 9074bfa38d
commit d2ba96488e
No known key found for this signature in database
1 changed files with 15 additions and 9 deletions
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24
lib/dns/tsig.c
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@ -1539,38 +1539,44 @@ isc_result_t
dns_tsigkey_find(dns_tsigkey_t **tsigkey, const dns_name_t *name,
const dns_name_t *algorithm, dns_tsigkeyring_t *ring) {
dns_tsigkey_t *key = NULL;
isc_stdtime_t now = isc_stdtime_now();
isc_result_t result;
isc_rwlocktype_t locktype = isc_rwlocktype_read;
isc_stdtime_t now = isc_stdtime_now();
REQUIRE(name != NULL);
REQUIRE(VALID_TSIGKEYRING(ring));
REQUIRE(tsigkey != NULL && *tsigkey == NULL);
RWLOCK(&ring->lock, isc_rwlocktype_read);
again:
RWLOCK(&ring->lock, locktype);
result = isc_hashmap_find(ring->keys, dns_name_hash(name), tkey_match,
name, (void **)&key);
if (result == ISC_R_NOTFOUND) {
RWUNLOCK(&ring->lock, isc_rwlocktype_read);
RWUNLOCK(&ring->lock, locktype);
return (result);
}
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;
key = NULL;
goto again;
}
rm_lru(key);
rm_hashmap(key);
RWUNLOCK(&ring->lock, isc_rwlocktype_write);
RWUNLOCK(&ring->lock, locktype);
return (ISC_R_NOTFOUND);
}
RWUNLOCK(&ring->lock, isc_rwlocktype_read);
adjust_lru(key);
dns_tsigkey_ref(key);
RWUNLOCK(&ring->lock, locktype);
adjust_lru(key);
*tsigkey = key;
return (ISC_R_SUCCESS);
}