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[9.18] fix: usr: return SERVFAIL for a too long CNAME chain

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When cutting a long CNAME chain, named was returning NOERROR 
instead of SERVFAIL (alongside with a partial answer). This
has been fixed.

Closes #4449

Backport of MR !9090

Merge branch 'backport-4449-return-servfail-for-a-long-cname-chain-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!9204
This commit is contained in:
Arаm Sаrgsyаn 2024-07-31 16:29:24 +00:00
commit f7de909b98
4 changed files with 54 additions and 7 deletions
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14
bin/tests/system/chain/tests.sh
View file

@ -439,11 +439,21 @@ if [ $ret != 0 ]; then echo_i "failed"; fi
status=$((status + ret))
n=$((n + 1))
echo_i "checking CNAME loops are detected ($n)"
echo_i "checking CNAME loops are detected (resolver) ($n)"
ret=0
$RNDCCMD 10.53.0.7 null --- start test$n --- 2>&1 | sed 's/^/ns7 /' | cat_i
$DIG $DIGOPTS @10.53.0.7 loop.example >dig.out.test$n
grep "status: NOERROR" dig.out.test$n >/dev/null || ret=1
grep "status: SERVFAIL" dig.out.test$n >/dev/null || ret=1
grep "ANSWER: 0" dig.out.test$n >/dev/null || ret=1
if [ $ret != 0 ]; then echo_i "failed"; fi
status=$((status + ret))
n=$((n + 1))
echo_i "checking CNAME loops are detected (auth) ($n)"
ret=0
$DIG $DIGOPTS @10.53.0.2 loop.example >dig.out.test$n
grep "status: SERVFAIL" dig.out.test$n >/dev/null || ret=1
grep "max. restarts reached" dig.out.test$n >/dev/null || ret=1
grep "ANSWER: 17" dig.out.test$n >/dev/null || ret=1
if [ $ret != 0 ]; then echo_i "failed"; fi
status=$((status + ret))

3
bin/tests/system/resolver/ans3/ans.pl
View file

@ -102,6 +102,9 @@ sub handleQuery {
$packet->push("answer",
new Net::DNS::RR($qname .
" 300 CNAME goodcname.example.org"));
} elsif ($qname =~ /^longcname/) {
$cname = $qname =~ s/longcname/longcnamex/r;
$packet->push("answer", new Net::DNS::RR($qname . " 300 CNAME " . $cname));
} elsif ($qname =~ /^nodata\.example\.net$/i) {
$packet->header->aa(1);
} elsif ($qname =~ /^nxdomain\.example\.net$/i) {

11
bin/tests/system/resolver/tests.sh
View file

@ -222,6 +222,17 @@ if [ -x "${RESOLVE}" ]; then
status=$((status + ret))
fi
n=$((n + 1))
echo_i "checking long CNAME chain target filtering (deny) ($n)"
ret=0
dig_with_opts +tcp longcname1.example.net @10.53.0.1 a >dig.out.ns1.test${n} || ret=1
grep -F "status: SERVFAIL" dig.out.ns1.test${n} >/dev/null || ret=1
grep -F "max. restarts reached" dig.out.ns1.test${n} >/dev/null || ret=1
lines=$(grep -F "CNAME" dig.out.ns1.test${n} | wc -l)
test ${lines:-1} -eq 17 || ret=1
if [ $ret != 0 ]; then echo_i "failed"; fi
status=$((status + ret))
n=$((n + 1))
echo_i "checking DNAME target filtering (deny) ($n)"
ret=0

33
lib/ns/query.c
View file

@ -11910,7 +11910,7 @@ isc_result_t
ns_query_done(query_ctx_t *qctx) {
isc_result_t result = ISC_R_UNSET;
const dns_namelist_t *secs = qctx->client->message->sections;
bool nodetach;
bool nodetach, partial_result_with_servfail = false;
CCTRACE(ISC_LOG_DEBUG(3), "ns_query_done");
@ -11944,13 +11944,36 @@ ns_query_done(query_ctx_t *qctx) {
/*
* Do we need to restart the query (e.g. for CNAME chaining)?
*/
if (qctx->want_restart && qctx->client->query.restarts < MAX_RESTARTS) {
qctx->client->query.restarts++;
return (ns__query_start(qctx));
if (qctx->want_restart) {
if (qctx->client->query.restarts < MAX_RESTARTS) {
qctx->client->query.restarts++;
return (ns__query_start(qctx));
} else {
/*
* This is e.g. a long CNAME chain which we cut short.
*/
qctx->client->query.attributes |=
NS_QUERYATTR_PARTIALANSWER;
qctx->client->message->rcode = dns_rcode_servfail;
qctx->result = DNS_R_SERVFAIL;
/*
* Send the answer back with a SERVFAIL result even
* if recursion was requested.
*/
partial_result_with_servfail = true;
ns_client_extendederror(qctx->client, 0,
"max. restarts reached");
ns_client_log(qctx->client, NS_LOGCATEGORY_CLIENT,
NS_LOGMODULE_QUERY, ISC_LOG_INFO,
"query iterations limit reached");
}
}
if (qctx->result != ISC_R_SUCCESS &&
(!PARTIALANSWER(qctx->client) || WANTRECURSION(qctx->client) ||
(!PARTIALANSWER(qctx->client) ||
(WANTRECURSION(qctx->client) && !partial_result_with_servfail) ||
qctx->result == DNS_R_DROP))
{
if (qctx->result == DNS_R_DUPLICATE ||