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Process NSID and DNS COOKIE options when returning BADVERS

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This will help identify the broken server if we happen to break
EDNS version negotiation.  It will also help protect the client
from spoofed BADVERSION responses.
This commit is contained in:
Mark Andrews 2024-10-25 14:43:03 +11:00
parent 488f0f876d
commit 0d9cab1555
1 changed files with 23 additions and 11 deletions
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34
lib/ns/client.c
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@ -1580,17 +1580,6 @@ process_opt(ns_client_t *client, dns_rdataset_t *opt) {
* XXXRTH need library support for this!
*/
client->ednsversion = (opt->ttl & 0x00FF0000) >> 16;
if (client->ednsversion > DNS_EDNS_VERSION) {
ns_stats_increment(client->manager->sctx->nsstats,
ns_statscounter_badednsver);
result = ns_client_addopt(client, client->message,
&client->opt);
if (result == ISC_R_SUCCESS) {
result = DNS_R_BADVERS;
}
ns_client_error(client, result);
return result;
}
/* Check for NSID request */
result = dns_rdataset_first(opt);
@ -1602,6 +1591,17 @@ process_opt(ns_client_t *client, dns_rdataset_t *opt) {
while (isc_buffer_remaininglength(&optbuf) >= 4) {
optcode = isc_buffer_getuint16(&optbuf);
optlen = isc_buffer_getuint16(&optbuf);
/*
* When returning BADVERSION, only process
* DNS_OPT_NSID or DNS_OPT_COOKIE options.
*/
if (client->ednsversion > DNS_EDNS_VERSION &&
optcode != DNS_OPT_NSID &&
optcode != DNS_OPT_COOKIE)
{
isc_buffer_forward(&optbuf, optlen);
continue;
}
switch (optcode) {
case DNS_OPT_NSID:
if (!WANTNSID(client)) {
@ -1683,6 +1683,18 @@ process_opt(ns_client_t *client, dns_rdataset_t *opt) {
}
}
if (client->ednsversion > DNS_EDNS_VERSION) {
ns_stats_increment(client->manager->sctx->nsstats,
ns_statscounter_badednsver);
result = ns_client_addopt(client, client->message,
&client->opt);
if (result == ISC_R_SUCCESS) {
result = DNS_R_BADVERS;
}
ns_client_error(client, result);
return result;
}
ns_stats_increment(client->manager->sctx->nsstats,
ns_statscounter_edns0in);
client->attributes |= NS_CLIENTATTR_WANTOPT;