From bfb027fecdcb0229eb515982f8293825f3ae2627 Mon Sep 17 00:00:00 2001
From: Evan Hunt <each@isc.org>
Date: Tue, 3 Mar 2026 14:00:38 -0800
Subject: [PATCH 1/8] Disable recursion for non-IN classes

Force recursion off, and set allow-recursion/allow-recursion-on ACLs
to none, for views with a class other than IN. Log a configuration
warning if recursion is explicitly enabled for a non-IN view.

This addresses YWH-PGM40640-74 and YWH-PGM40640-75 by preventing any
attempt at recursive processing in a class-CHAOS view, ensuring that
server addresses used for recursive queries and received in recursive
responses are of the expected format.

Fixes: isc-projects/bind9#5780
Fixes: isc-projects/bind9#5781
---
 bin/named/server.c                            | 37 +++++--------------
 bin/tests/system/checkconf/tests.sh           |  1 +
 .../nohintswarn_bindchaos/ns1/named.conf.j2   | 23 ------------
 .../tests_nohintswarn_bindchaos.py            | 25 -------------
 bin/tests/system/resolver/tests.sh            |  8 ++--
 lib/isccfg/check.c                            | 21 +++++++++--
 6 files changed, 33 insertions(+), 82 deletions(-)
 delete mode 100644 bin/tests/system/nohintswarn_bindchaos/ns1/named.conf.j2
 delete mode 100644 bin/tests/system/nohintswarn_bindchaos/tests_nohintswarn_bindchaos.py

diff --git a/bin/named/server.c b/bin/named/server.c
index e9f2329b7c..1a98450e81 100644
--- a/bin/named/server.c
+++ b/bin/named/server.c
@@ -3926,7 +3926,8 @@ configure_view(dns_view_t *view, dns_viewlist_t *viewlist, cfg_obj_t *config,
 	obj = NULL;
 	result = named_config_get(maps, "recursion", &obj);
 	INSIST(result == ISC_R_SUCCESS);
-	view->recursion = cfg_obj_asboolean(obj);
+	view->recursion = (view->rdclass == dns_rdataclass_in &&
+			   cfg_obj_asboolean(obj));
 
 	max_cache_size = configure_max_cache_size(view, maps);
 
@@ -4543,35 +4544,13 @@ configure_view(dns_view_t *view, dns_viewlist_t *viewlist, cfg_obj_t *config,
 	/*
 	 * We have default root hints for class IN if we need them.
 	 * Each view gets its own rootdb so a priming response only
-	 * writes into that view's copy.
+	 * writes into that view's copy.  Other classes don't support
+	 * recursion and don't need hints.
 	 */
 	if (view->rdclass == dns_rdataclass_in && view->rootdb == NULL) {
 		CHECK(configure_rootdb(view, NULL));
 	}
 
-	/*
-	 * If we still have no root hints, this is a non-IN view with no
-	 * "hints zone" configured.  Issue a warning, except if this
-	 * is a root server.  Root servers never need to consult
-	 * their hints, so it's no point requiring users to configure
-	 * them.
-	 */
-	if (view->rootdb == NULL) {
-		dns_zone_t *rootzone = NULL;
-		(void)dns_view_findzone(view, dns_rootname, DNS_ZTFIND_EXACT,
-					&rootzone);
-		if (rootzone != NULL) {
-			dns_zone_detach(&rootzone);
-		} else if (strcmp(view->name, "_bind") != 0 ||
-			   view->rdclass != dns_rdataclass_chaos)
-		{
-			isc_log_write(NAMED_LOGCATEGORY_GENERAL,
-				      NAMED_LOGMODULE_SERVER, ISC_LOG_WARNING,
-				      "no root hints for view '%s'",
-				      view->name);
-		}
-	}
-
 	/*
 	 * Configure the view's transports (DoT/DoH)
 	 */
@@ -4794,9 +4773,11 @@ configure_view(dns_view_t *view, dns_viewlist_t *viewlist, cfg_obj_t *config,
 	CHECK(configure_view_acl(vconfig, config, "allow-proxy-on", NULL,
 				 aclctx, isc_g_mctx, &view->proxyonacl));
 
-	if (strcmp(view->name, "_bind") != 0 &&
-	    view->rdclass != dns_rdataclass_chaos)
-	{
+	if (view->rdclass != dns_rdataclass_in) {
+		view->recursion = false;
+		dns_acl_none(isc_g_mctx, &view->recursionacl);
+		dns_acl_none(isc_g_mctx, &view->recursiononacl);
+	} else {
 		CHECK(configure_view_acl(vconfig, config, "allow-recursion",
 					 NULL, aclctx, isc_g_mctx,
 					 &view->recursionacl));
diff --git a/bin/tests/system/checkconf/tests.sh b/bin/tests/system/checkconf/tests.sh
index 69d96b7ea8..f927d78919 100644
--- a/bin/tests/system/checkconf/tests.sh
+++ b/bin/tests/system/checkconf/tests.sh
@@ -515,6 +515,7 @@ $CHECKCONF -l good.conf \
   | grep -v "is not implemented" \
   | grep -v "is not recommended" \
   | grep -v "no longer exists" \
+  | grep -v "recursion will be disabled" \
   | grep -v "is obsolete" >checkconf.out$n || ret=1
 diff good.zonelist checkconf.out$n >diff.out$n || ret=1
 if [ $ret -ne 0 ]; then
diff --git a/bin/tests/system/nohintswarn_bindchaos/ns1/named.conf.j2 b/bin/tests/system/nohintswarn_bindchaos/ns1/named.conf.j2
deleted file mode 100644
index 57389c0521..0000000000
--- a/bin/tests/system/nohintswarn_bindchaos/ns1/named.conf.j2
+++ /dev/null
@@ -1,23 +0,0 @@
-options {
-        port @PORT@;
-        pid-file "named.pid";
-        listen-on { 10.53.0.1; };
-};
-
-key rndc_key {
-        secret "1234abcd8765";
-        algorithm @DEFAULT_HMAC@;
-};
-
-controls {
-        inet 10.53.0.1 port @CONTROLPORT@ allow { any; } keys { rndc_key; };
-};
-
-view _bind {
-};
-
-view foo {
-};
-
-view bar ch {
-};
diff --git a/bin/tests/system/nohintswarn_bindchaos/tests_nohintswarn_bindchaos.py b/bin/tests/system/nohintswarn_bindchaos/tests_nohintswarn_bindchaos.py
deleted file mode 100644
index bb788d1708..0000000000
--- a/bin/tests/system/nohintswarn_bindchaos/tests_nohintswarn_bindchaos.py
+++ /dev/null
@@ -1,25 +0,0 @@
-# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
-#
-# SPDX-License-Identifier: MPL-2.0
-#
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0.  If a copy of the MPL was not distributed with this
-# file, you can obtain one at https://mozilla.org/MPL/2.0/.
-#
-# See the COPYRIGHT file distributed with this work for additional
-# information regarding copyright ownership.
-
-import isctest
-
-
-def test_nohintswarn_bindchaos(ns1):
-    found = True
-    try:
-        with ns1.watch_log_from_start(timeout=1) as watcher:
-            watcher.wait_for_line("no root hints for view '_bind'")
-    except isctest.log.watchlog.WatchLogTimeout:
-        found = False
-    assert found is False
-
-    with ns1.watch_log_from_start() as watcher:
-        watcher.wait_for_line("no root hints for view 'bar'")
diff --git a/bin/tests/system/resolver/tests.sh b/bin/tests/system/resolver/tests.sh
index 18893edd69..06ef98f697 100755
--- a/bin/tests/system/resolver/tests.sh
+++ b/bin/tests/system/resolver/tests.sh
@@ -783,10 +783,12 @@ if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
 
 n=$((n + 1))
-echo_i "checking NXDOMAIN is returned when querying non existing domain in CH class ($n)"
+echo_i "checking REFUSED is returned when querying non existing domain in CH class ($n)"
 ret=0
-dig_with_opts @10.53.0.1 id.hostname txt ch >dig.ns1.out.${n} || ret=1
-grep "status: NXDOMAIN" dig.ns1.out.${n} >/dev/null || ret=1
+dig_with_opts @10.53.0.1 hostname.chaostest txt ch >dig.ns1.out.1.${n} || ret=1
+grep "status: NOERROR" dig.ns1.out.1.${n} >/dev/null || ret=1
+dig_with_opts @10.53.0.1 id.hostname txt ch >dig.ns1.out.2.${n} || ret=1
+grep "status: REFUSED" dig.ns1.out.2.${n} >/dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
 
diff --git a/lib/isccfg/check.c b/lib/isccfg/check.c
index 232d4d1890..2995319627 100644
--- a/lib/isccfg/check.c
+++ b/lib/isccfg/check.c
@@ -2869,13 +2869,17 @@ check_mirror_zone_notify(const cfg_obj_t *zoptions, const char *znamestr) {
  */
 static bool
 check_recursion(const cfg_obj_t *config, const cfg_obj_t *voptions,
-		const cfg_obj_t *goptions, cfg_aclconfctx_t *aclctx,
-		isc_mem_t *mctx) {
+		dns_rdataclass_t vclass, const cfg_obj_t *goptions,
+		cfg_aclconfctx_t *aclctx, isc_mem_t *mctx) {
 	dns_acl_t *acl = NULL;
 	const cfg_obj_t *obj;
 	isc_result_t result = ISC_R_SUCCESS;
 	bool retval = true;
 
+	if (vclass != dns_rdataclass_in) {
+		return false;
+	}
+
 	/*
 	 * Check the "recursion" option first.
 	 */
@@ -3827,7 +3831,7 @@ isccfg_check_zoneconf(const cfg_obj_t *zconfig, const cfg_obj_t *voptions,
 	 * contradicts the purpose of the former.
 	 */
 	if (ztype == CFG_ZONE_MIRROR &&
-	    !check_recursion(config, voptions, goptions, aclctx, mctx))
+	    !check_recursion(config, voptions, zclass, goptions, aclctx, mctx))
 	{
 		cfg_obj_log(zoptions, ISC_LOG_ERROR,
 			    "zone '%s': mirror zones cannot be used if "
@@ -5646,6 +5650,17 @@ check_viewconf(const cfg_obj_t *config, const cfg_obj_t *voptions,
 
 	cfg_aclconfctx_create(mctx, &aclctx);
 
+	if (vclass != dns_rdataclass_in) {
+		if (check_recursion(config, voptions, dns_rdataclass_in,
+				    options, aclctx, mctx))
+		{
+			cfg_obj_log(opts, ISC_LOG_WARNING,
+				    "recursion will be disabled for "
+				    "non-IN view '%s'",
+				    viewname);
+		}
+	}
+
 	if (voptions != NULL) {
 		(void)cfg_map_get(voptions, "zone", &zones);
 	} else {

From 6ba5e87a08a0ec38efbbfc2cedef71660221778f Mon Sep 17 00:00:00 2001
From: Evan Hunt <each@isc.org>
Date: Wed, 4 Mar 2026 13:24:52 -0800
Subject: [PATCH 2/8] Disable UPDATE and NOTIFY for non-IN classes

Return NOTIMP for UPDATE and NOTIFY requests received for views with a
class other than IN.  Only QUERY is now supported for non-IN views such
as CHAOS.

When running dns dns_rdata_tostruct() with types that are only defined
for class IN, ensure that the class is correct before proceeding.

Add an assertion that any zone being updated is of class IN. (Note
that previously, a DLZ zone could have its class value set incorrectly
to NONE; this has been fixed.)

This addresses YWH-PGM40640-70 and YWH-PGM40640-73 (as well as any
similar problems that might have occurred in the future) by minimizing
the code paths that can be reached by rdata classes other than IN, so it
is safe for the implementation to assume that rdatatypes that are only
defined for class IN, such as SVCB or WKS, have been parsed and
validated, and not accepted as unknown/opaque data.

Fixes: isc-projects/bind9#5777
Fixes: isc-projects/bind9#5779
---
 bin/named/server.c |  1 +
 lib/dns/adb.c      |  5 +++--
 lib/ns/client.c    |  8 ++++++++
 lib/ns/update.c    | 42 ++++++++++++++++++++++--------------------
 4 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/bin/named/server.c b/bin/named/server.c
index 1a98450e81..d584c1249e 100644
--- a/bin/named/server.c
+++ b/bin/named/server.c
@@ -1715,6 +1715,7 @@ dlzconfigure_callback(dns_view_t *view, dns_dlzdb_t *dlzdb, dns_zone_t *zone) {
 	dns_name_t *origin = dns_zone_getorigin(zone);
 	dns_rdataclass_t zclass = view->rdclass;
 
+	dns_zone_setclass(zone, zclass);
 	RETERR(dns_zonemgr_managezone(named_g_server->zonemgr, zone));
 
 	dns_zone_setstats(zone, named_g_server->zonestats);
diff --git a/lib/dns/adb.c b/lib/dns/adb.c
index f51b2a8821..758f0d8187 100644
--- a/lib/dns/adb.c
+++ b/lib/dns/adb.c
@@ -566,6 +566,9 @@ import_rdataset(dns_adbname_t *adbname, dns_rdataset_t *rdataset,
 
 	rdtype = rdataset->type;
 
+	REQUIRE(rdataset->rdclass == dns_rdataclass_in);
+	REQUIRE(dns_rdatatype_isaddr(rdtype));
+
 	switch (rdataset->trust) {
 	case dns_trust_glue:
 	case dns_trust_additional:
@@ -584,8 +587,6 @@ import_rdataset(dns_adbname_t *adbname, dns_rdataset_t *rdataset,
 		rdataset->ttl = ttlclamp(rdataset->ttl);
 	}
 
-	REQUIRE(dns_rdatatype_isaddr(rdtype));
-
 	DNS_RDATASET_FOREACH(rdataset) {
 		/* FIXME: Move to a separate function */
 		dns_adbnamehooklist_t *hookhead = NULL;
diff --git a/lib/ns/client.c b/lib/ns/client.c
index 7a4fd19771..2faf971041 100644
--- a/lib/ns/client.c
+++ b/lib/ns/client.c
@@ -2459,6 +2459,10 @@ ns_client_request_continue(void *arg) {
 		break;
 	case dns_opcode_update:
 		CTRACE("update");
+		if (client->inner.view->rdclass != dns_rdataclass_in) {
+			ns_client_error(client, DNS_R_NOTIMP);
+			break;
+		}
 #ifdef HAVE_DNSTAP
 		dns_dt_send(client->inner.view, DNS_DTTYPE_UQ,
 			    &client->inner.peeraddr,
@@ -2472,6 +2476,10 @@ ns_client_request_continue(void *arg) {
 		break;
 	case dns_opcode_notify:
 		CTRACE("notify");
+		if (client->inner.view->rdclass != dns_rdataclass_in) {
+			ns_client_error(client, DNS_R_NOTIMP);
+			break;
+		}
 		ns_client_settimeout(client, 60);
 		ns_notify_start(client, client->inner.handle);
 		break;
diff --git a/lib/ns/update.c b/lib/ns/update.c
index 93240ca250..b5ea582879 100644
--- a/lib/ns/update.c
+++ b/lib/ns/update.c
@@ -966,7 +966,9 @@ ssu_checkrr(void *data, rr_t *rr) {
 		RUNTIME_CHECK(result == ISC_R_SUCCESS);
 		target = &ptr.ptr;
 	}
-	if (rr->rdata.type == dns_rdatatype_srv) {
+	if (rr->rdata.rdclass == dns_rdataclass_in &&
+	    rr->rdata.type == dns_rdatatype_srv)
+	{
 		result = dns_rdata_tostruct(&rr->rdata, &srv, NULL);
 		RUNTIME_CHECK(result == ISC_R_SUCCESS);
 		target = &srv.target;
@@ -1311,7 +1313,10 @@ replaces_p(dns_rdata_t *update_rr, dns_rdata_t *db_rr) {
 			return true;
 		}
 	}
-	if (db_rr->type == dns_rdatatype_wks) {
+
+	if (db_rr->rdclass == dns_rdataclass_in &&
+	    db_rr->type == dns_rdatatype_wks)
+	{
 		/*
 		 * Compare the address and protocol fields only.  These
 		 * form the first five bytes of the RR data.  Do a
@@ -1451,9 +1456,8 @@ add_rr_prepare_action(void *data, rr_t *rr) {
  * 'rdata', and 'ttl', respectively.
  */
 static void
-get_current_rr(dns_rdataclass_t zoneclass, dns_name_t *name, dns_rdata_t *rdata,
-	       dns_rdatatype_t *covers, dns_ttl_t *ttl,
-	       dns_rdataclass_t *update_class) {
+get_current_rr(dns_name_t *name, dns_rdata_t *rdata, dns_rdatatype_t *covers,
+	       dns_ttl_t *ttl, dns_rdataclass_t *update_class) {
 	dns_rdataset_t *rdataset;
 	isc_result_t result;
 	rdataset = ISC_LIST_HEAD(name->list);
@@ -1466,7 +1470,7 @@ get_current_rr(dns_rdataclass_t zoneclass, dns_name_t *name, dns_rdata_t *rdata,
 	dns_rdataset_current(rdataset, rdata);
 	INSIST(dns_rdataset_next(rdataset) == ISC_R_NOMORE);
 	*update_class = rdata->rdclass;
-	rdata->rdclass = zoneclass;
+	rdata->rdclass = dns_rdataclass_in;
 }
 
 /*%
@@ -1562,7 +1566,6 @@ send_update(ns_client_t *client, dns_zone_t *zone) {
 	dns_message_t *request = client->message;
 	isc_mem_t *mctx = client->manager->mctx;
 	dns_aclenv_t *env = client->manager->aclenv;
-	dns_rdataclass_t zoneclass;
 	dns_rdatatype_t covers;
 	dns_name_t *zonename = NULL;
 	unsigned int *maxbytype = NULL;
@@ -1574,11 +1577,13 @@ send_update(ns_client_t *client, dns_zone_t *zone) {
 
 	CHECK(dns_zone_getdb(zone, &db));
 	zonename = dns_db_origin(db);
-	zoneclass = dns_db_class(db);
 	dns_zone_getssutable(zone, &ssutable);
 	options = dns_zone_getoptions(zone);
 	dns_db_currentversion(db, &ver);
 
+	/* Updates are only supported for class IN. */
+	INSIST(dns_zone_getclass(zone) == dns_rdataclass_in);
+
 	/*
 	 * Update message processing can leak record existence information
 	 * so check that we are allowed to query this zone.  Additionally,
@@ -1623,13 +1628,12 @@ send_update(ns_client_t *client, dns_zone_t *zone) {
 		dns_rdataclass_t update_class;
 
 		INSIST(ssutable == NULL || update < maxbytypelen);
-		get_current_rr(zoneclass, name, &rdata, &covers, &ttl,
-			       &update_class);
+		get_current_rr(name, &rdata, &covers, &ttl, &update_class);
 
 		if (!dns_name_issubdomain(name, zonename)) {
 			FAILC(DNS_R_NOTZONE, "update RR is outside zone");
 		}
-		if (update_class == zoneclass) {
+		if (update_class == dns_rdataclass_in) {
 			/*
 			 * Check for meta-RRs.  The RFC2136 pseudocode says
 			 * check for ANY|AXFR|MAILA|MAILB, but the text adds
@@ -1643,6 +1647,7 @@ send_update(ns_client_t *client, dns_zone_t *zone) {
 				CLEANUP(DNS_R_REFUSED);
 			}
 			if ((options & DNS_ZONEOPT_CHECKSVCB) != 0 &&
+			    rdata.rdclass == dns_rdataclass_in &&
 			    rdata.type == dns_rdatatype_svcb)
 			{
 				result = dns_rdata_checksvcb(name, &rdata);
@@ -1731,7 +1736,6 @@ send_update(ns_client_t *client, dns_zone_t *zone) {
 			}
 
 			if (update_class == dns_rdataclass_any &&
-			    zoneclass == dns_rdataclass_in &&
 			    (rdata.type == dns_rdatatype_ptr ||
 			     rdata.type == dns_rdatatype_srv))
 			{
@@ -2629,7 +2633,6 @@ update_action(void *arg) {
 	isc_mem_t *mctx = client->manager->mctx;
 	dns_rdatatype_t covers;
 	dns_message_t *request = client->message;
-	dns_rdataclass_t zoneclass;
 	dns_name_t *zonename = NULL;
 	dns_fixedname_t tmpnamefixed;
 	dns_name_t *tmpname = NULL;
@@ -2646,9 +2649,10 @@ update_action(void *arg) {
 
 	CHECK(dns_zone_getdb(zone, &db));
 	zonename = dns_db_origin(db);
-	zoneclass = dns_db_class(db);
 	options = dns_zone_getoptions(zone);
 
+	INSIST(dns_zone_getclass(zone) == dns_rdataclass_in);
+
 	is_inline = (!dns_zone_israw(zone) && dns_zone_issecure(zone));
 	is_maintain = (dns_zone_getkasp(zone) != NULL) && !dns_zone_israw(zone);
 	is_signing = is_inline || is_maintain;
@@ -2669,8 +2673,7 @@ update_action(void *arg) {
 		dns_rdataclass_t update_class;
 		bool flag;
 
-		get_current_rr(zoneclass, name, &rdata, &covers, &ttl,
-			       &update_class);
+		get_current_rr(name, &rdata, &covers, &ttl, &update_class);
 
 		if (ttl != 0) {
 			PREREQFAILC(DNS_R_FORMERR,
@@ -2733,7 +2736,7 @@ update_action(void *arg) {
 						"prerequisite not satisfied");
 				}
 			}
-		} else if (update_class == zoneclass) {
+		} else if (update_class == dns_rdataclass_in) {
 			/* "temp<rr.name, rr.type> += rr;" */
 			temp_append(&temp, name, &rdata);
 		} else {
@@ -2784,10 +2787,9 @@ update_action(void *arg) {
 
 		INSIST(ssutable == NULL || maxidx < maxbytypelen);
 
-		get_current_rr(zoneclass, name, &rdata, &covers, &ttl,
-			       &update_class);
+		get_current_rr(name, &rdata, &covers, &ttl, &update_class);
 
-		if (update_class == zoneclass) {
+		if (update_class == dns_rdataclass_in) {
 			/*
 			 * RFC1123 doesn't allow MF and MD in master files.
 			 */

From 967776d94dc2cd13a7243352e70c318422052e1e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
Date: Wed, 4 Mar 2026 10:46:58 +0100
Subject: [PATCH 3/8] Validate DNS message CLASS early in request processing

Reject requests with unsupported or misused CLASS values before
further processing.  Only IN, CH, HS, RESERVED0 (for DNS Cookies),
ANY (for TKEY negotiation), and NONE (for DNS UPDATE) are accepted;
all other classes return NOTIMP.  Misuse of NONE or ANY outside
their allowed contexts returns FORMERR.

This adds further protection against bugs of the same general class
as YWH-PGM40640-70 and YWH-PGM40640-73.
---
 bin/tests/system/unknown/tests.sh | 17 ++++++----
 lib/ns/client.c                   | 55 ++++++++++++++++++++++++-------
 2 files changed, 55 insertions(+), 17 deletions(-)

diff --git a/bin/tests/system/unknown/tests.sh b/bin/tests/system/unknown/tests.sh
index eb61f21f28..cbc2943f17 100644
--- a/bin/tests/system/unknown/tests.sh
+++ b/bin/tests/system/unknown/tests.sh
@@ -25,6 +25,11 @@ dig_cmd() {
   "$DIG" $DIGOPTS "$@" | grep -v '^;'
 }
 
+dig_full() {
+  # shellcheck disable=SC2086
+  "$DIG" $DIGOPTS "$@"
+}
+
 n=$((n + 1))
 echo_i "querying for various representations of an IN A record ($n)"
 for i in 1 2 3 4 5 6 7 8 9 10 11 12; do
@@ -81,8 +86,8 @@ n=$((n + 1))
 echo_i "querying for various representations of a CLASS10 TYPE1 record ($n)"
 for i in 1 2; do
   ret=0
-  dig_cmd +short @10.53.0.1 a$i.example a class10 >dig.out.$i.test$n
-  echo '\# 4 0A000001' | diff - dig.out.$i.test$n || ret=1
+  dig_full @10.53.0.1 a$i.example a class10 >dig.out.$i.test$n
+  grep -q "NOTIMP" dig.out.$i.test$n || ret=1
   if [ $ret != 0 ]; then
     echo_i "#$i failed"
   fi
@@ -93,8 +98,8 @@ n=$((n + 1))
 echo_i "querying for various representations of a CLASS10 TXT record ($n)"
 for i in 1 2 3 4; do
   ret=0
-  dig_cmd +short @10.53.0.1 txt$i.example txt class10 >dig.out.$i.test$n
-  echo '"hello"' | diff - dig.out.$i.test$n || ret=1
+  dig_full @10.53.0.1 txt$i.example txt class10 >dig.out.$i.test$n
+  grep -q "NOTIMP" dig.out.$i.test$n || ret=1
   if [ $ret != 0 ]; then
     echo_i "#$i failed"
   fi
@@ -105,8 +110,8 @@ n=$((n + 1))
 echo_i "querying for various representations of a CLASS10 TYPE123 record ($n)"
 for i in 1 2; do
   ret=0
-  dig_cmd +short @10.53.0.1 unk$i.example type123 class10 >dig.out.$i.test$n
-  echo '\# 1 00' | diff - dig.out.$i.test$n || ret=1
+  dig_full @10.53.0.1 unk$i.example type123 class10 >dig.out.$i.test$n
+  grep -q "NOTIMP" dig.out.$i.test$n || ret=1
   if [ $ret != 0 ]; then
     echo_i "#$i failed"
   fi
diff --git a/lib/ns/client.c b/lib/ns/client.c
index 2faf971041..7a48d613af 100644
--- a/lib/ns/client.c
+++ b/lib/ns/client.c
@@ -42,6 +42,7 @@
 #include <dns/dispatch.h>
 #include <dns/dnstap.h>
 #include <dns/edns.h>
+#include <dns/enumclass.h>
 #include <dns/message.h>
 #include <dns/peer.h>
 #include <dns/rcode.h>
@@ -2082,7 +2083,9 @@ ns_client_request(isc_nmhandle_t *handle, isc_result_t eresult,
 		}
 	}
 
-	if (client->message->rdclass == 0) {
+	char classbuf[DNS_RDATACLASS_FORMATSIZE];
+	switch (client->message->rdclass) {
+	case dns_rdataclass_reserved0:
 		if ((client->inner.attributes & NS_CLIENTATTR_WANTCOOKIE) !=
 			    0 &&
 		    client->message->opcode == dns_opcode_query &&
@@ -2102,12 +2105,46 @@ ns_client_request(isc_nmhandle_t *handle, isc_result_t eresult,
 			return;
 		}
 
+		ns_client_dumpmessage(client,
+				      "message class could not be determined");
+		ns_client_error(client, notimp ? DNS_R_NOTIMP : DNS_R_FORMERR);
+		return;
+	case dns_rdataclass_in:
+		break;
+	case dns_rdataclass_chaos:
+		break;
+	case dns_rdataclass_hs:
+		break;
+	case dns_rdataclass_none:
+		if (client->message->opcode != dns_opcode_update) {
+			ns_client_dumpmessage(client,
+					      "message class NONE can be only "
+					      "used in DNS updates");
+			ns_client_error(client, DNS_R_FORMERR);
+			return;
+		}
+		break;
+	case dns_rdataclass_any:
+		/*
+		 * Required for TKEY negotiation.
+		 */
+		if (client->message->tkey == 0) {
+			ns_client_dumpmessage(client,
+					      "message class ANY can be only "
+					      "used for TKEY negotiation");
+			ns_client_error(client, DNS_R_FORMERR);
+			return;
+		}
+		break;
+	default:
+		dns_rdataclass_format(client->message->rdclass, classbuf,
+				      sizeof(classbuf));
+		ns_client_dumpmessage(client, NULL);
 		ns_client_log(client, NS_LOGCATEGORY_CLIENT,
 			      NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(1),
-			      "message class could not be determined");
-		ns_client_dumpmessage(client, "message class could not be "
-					      "determined");
-		ns_client_error(client, notimp ? DNS_R_NOTIMP : DNS_R_FORMERR);
+			      "invalid message class: %s", classbuf);
+
+		ns_client_error(client, DNS_R_NOTIMP);
 		return;
 	}
 
@@ -2192,9 +2229,6 @@ ns_client_request_continue(void *arg) {
 				      "SIG(0) checks quota reached");
 
 			if (can_log_sigchecks_quota()) {
-				ns_client_log(client, NS_LOGCATEGORY_CLIENT,
-					      NS_LOGMODULE_CLIENT, ISC_LOG_INFO,
-					      "SIG(0) checks quota reached");
 				ns_client_dumpmessage(
 					client, "SIG(0) checks quota reached");
 			}
@@ -2204,12 +2238,11 @@ ns_client_request_continue(void *arg) {
 			dns_rdataclass_format(client->message->rdclass,
 					      classname, sizeof(classname));
 
+			ns_client_dumpmessage(client, NULL);
 			ns_client_log(client, NS_LOGCATEGORY_CLIENT,
 				      NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(1),
 				      "no matching view in class '%s'",
 				      classname);
-			ns_client_dumpmessage(client,
-					      "no matching view in class");
 		}
 
 		dns_ede_add(&client->edectx, DNS_EDE_PROHIBITED, NULL);
@@ -2843,7 +2876,7 @@ ns_client_dumpmessage(ns_client_t *client, const char *reason) {
 	int len = 1024;
 	isc_result_t result;
 
-	if (!isc_log_wouldlog(ISC_LOG_DEBUG(1))) {
+	if (!isc_log_wouldlog(ISC_LOG_DEBUG(1)) || reason == NULL) {
 		return;
 	}
 

From 71221a1402ceaef3a1554801515dbbb6dfcee134 Mon Sep 17 00:00:00 2001
From: Mark Andrews <marka@isc.org>
Date: Wed, 4 Mar 2026 10:00:56 +1100
Subject: [PATCH 4/8] Reject meta-classes in UPDATE and NOTIFY messages

NOTIFY and UPDATE messages must specify a data class in the
QUESTION/ZONE section.  NONE and ANY are meta-classes and not
appropriate here.  Return FORMERR if either is used.

Rejecting messages with a query class of NONE addresses YWH-PGM40640-72,
YWH-PGM40640-82, and YWH-PGM40640-83.  Rejecting messages with a query
class of ANY addresses YWH-PGM40640-87, YWH-PGM40640-88, and
YWH-PGM40640-117.

Fixes: isc-projects/bind9#5778
Fixes: isc-projects/bind9#5782
Fixes: isc-projects/bind9#5783
Fixes: isc-projects/bind9#5797
Fixes: isc-projects/bind9#5798
Fixes: isc-projects/bind9#5853
---
 lib/dns/message.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/lib/dns/message.c b/lib/dns/message.c
index 1a7181b105..2dc904c3f1 100644
--- a/lib/dns/message.c
+++ b/lib/dns/message.c
@@ -972,6 +972,17 @@ getquestions(isc_buffer_t *source, dns_message_t *msg, dns_decompress_t dctx,
 		rdtype = isc_buffer_getuint16(source);
 		rdclass = isc_buffer_getuint16(source);
 
+		/*
+		 * Notify and update messages need to specify the data class.
+		 */
+		if ((msg->opcode == dns_opcode_update ||
+		     msg->opcode == dns_opcode_notify) &&
+		    (rdclass == dns_rdataclass_none ||
+		     rdclass == dns_rdataclass_any))
+		{
+			DO_ERROR(DNS_R_FORMERR);
+		}
+
 		/*
 		 * If this class is different than the one we already read,
 		 * this is an error.

From 787b9bc45097b59812b0128cf6172d70105d9d18 Mon Sep 17 00:00:00 2001
From: Evan Hunt <each@isc.org>
Date: Tue, 17 Mar 2026 13:24:43 -0700
Subject: [PATCH 5/8] Skip "deny-answer-address" for non-IN addresses

Ensure that we don't attempt an ACL match for answer addresses
when handling a class-CHAOS zone. This is an additional line of
defense for YWH-PGM40640-74.
---
 lib/dns/resolver.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lib/dns/resolver.c b/lib/dns/resolver.c
index 50f88209dd..7410431284 100644
--- a/lib/dns/resolver.c
+++ b/lib/dns/resolver.c
@@ -6825,6 +6825,13 @@ is_answeraddress_allowed(dns_view_t *view, dns_name_t *name,
 		return true;
 	}
 
+	/*
+	 * deny-answer-address doesn't apply to non-IN classes.
+	 */
+	if (rdataset->rdclass != dns_rdataclass_in) {
+		return true;
+	}
+
 	/*
 	 * Otherwise, search the filter list for a match for each
 	 * address record.  If a match is found, the address should be

From dd4af20dc8235b861b745abd651daa0d5e55e09d Mon Sep 17 00:00:00 2001
From: Evan Hunt <each@isc.org>
Date: Tue, 17 Mar 2026 13:45:11 -0700
Subject: [PATCH 6/8] Test CHAOS view recursion behavior

Check that recursive and forward queries to views of type CHAOS
are REFUSED, but that authoritative queries are answered correctly.
---
 bin/tests/system/checkconf/tests.sh           | 11 ++++
 .../checkconf/warn-chaos-recursion.conf       | 12 +++++
 bin/tests/system/class/ns1/chaos.db.in        |  4 ++
 bin/tests/system/class/ns1/named.conf.j2      | 31 +++++++++++
 bin/tests/system/class/ns2/example.db.in      |  6 +++
 bin/tests/system/class/ns2/localhost.db.in    |  6 +++
 bin/tests/system/class/ns2/named.conf.j2      | 42 +++++++++++++++
 bin/tests/system/class/ns3/named.conf.j2      | 28 ++++++++++
 bin/tests/system/class/setup.sh               | 19 +++++++
 bin/tests/system/class/tests_class_chaos.py   | 54 +++++++++++++++++++
 bin/tests/system/isctest/check.py             |  4 ++
 11 files changed, 217 insertions(+)
 create mode 100644 bin/tests/system/checkconf/warn-chaos-recursion.conf
 create mode 100644 bin/tests/system/class/ns1/chaos.db.in
 create mode 100644 bin/tests/system/class/ns1/named.conf.j2
 create mode 100644 bin/tests/system/class/ns2/example.db.in
 create mode 100644 bin/tests/system/class/ns2/localhost.db.in
 create mode 100644 bin/tests/system/class/ns2/named.conf.j2
 create mode 100644 bin/tests/system/class/ns3/named.conf.j2
 create mode 100644 bin/tests/system/class/setup.sh
 create mode 100644 bin/tests/system/class/tests_class_chaos.py

diff --git a/bin/tests/system/checkconf/tests.sh b/bin/tests/system/checkconf/tests.sh
index f927d78919..330da510e3 100644
--- a/bin/tests/system/checkconf/tests.sh
+++ b/bin/tests/system/checkconf/tests.sh
@@ -739,5 +739,16 @@ if [ $ret != 0 ]; then
 fi
 status=$((status + ret))
 
+n=$((n + 1))
+echo_i "check 'recursion yes;' is warned and disabled in a non-IN view ($n)"
+ret=0
+$CHECKCONF warn-chaos-recursion.conf >checkconf.out$n 2>&1 || ret=1
+grep -F "recursion will be disabled" checkconf.out$n >/dev/null || ret=1
+if [ $ret != 0 ]; then
+  echo_i "failed"
+  ret=1
+fi
+status=$((status + ret))
+
 echo_i "exit status: $status"
 [ $status -eq 0 ] || exit 1
diff --git a/bin/tests/system/checkconf/warn-chaos-recursion.conf b/bin/tests/system/checkconf/warn-chaos-recursion.conf
new file mode 100644
index 0000000000..01965102a4
--- /dev/null
+++ b/bin/tests/system/checkconf/warn-chaos-recursion.conf
@@ -0,0 +1,12 @@
+options {
+	directory ".";
+};
+
+view chaos ch {
+        match-clients { any; };
+        recursion yes;
+        zone "." {
+                type hint;
+                file "chaos.hints";
+        };
+};
diff --git a/bin/tests/system/class/ns1/chaos.db.in b/bin/tests/system/class/ns1/chaos.db.in
new file mode 100644
index 0000000000..43ca58ffa8
--- /dev/null
+++ b/bin/tests/system/class/ns1/chaos.db.in
@@ -0,0 +1,4 @@
+.                  CH NS ns.root.
+ns.root.           CH A ns.root. 1
+ns.root.           CH AAAA \# 1 00
+
diff --git a/bin/tests/system/class/ns1/named.conf.j2 b/bin/tests/system/class/ns1/named.conf.j2
new file mode 100644
index 0000000000..76f85fc6c9
--- /dev/null
+++ b/bin/tests/system/class/ns1/named.conf.j2
@@ -0,0 +1,31 @@
+options {
+	query-source address 10.53.0.1;
+	notify-source 10.53.0.1;
+	transfer-source 10.53.0.1;
+	port @PORT@;
+	pid-file "named.pid";
+	listen-on { 10.53.0.1; };
+	listen-on-v6 { none; };
+};
+
+key rndc_key {
+	secret "1234abcd8765";
+	algorithm @DEFAULT_HMAC@;
+};
+
+controls {
+	inet 10.53.0.1 port @CONTROLPORT@ allow { any; } keys { rndc_key; };
+};
+
+view chaos ch {
+	match-clients { any; };
+	recursion yes;
+	zone "." {
+		type hint;
+		file "chaos.db";
+	};
+	zone "version.bind" {
+		type primary;
+		database "_builtin version";
+	};
+};
diff --git a/bin/tests/system/class/ns2/example.db.in b/bin/tests/system/class/ns2/example.db.in
new file mode 100644
index 0000000000..a658ddbd89
--- /dev/null
+++ b/bin/tests/system/class/ns2/example.db.in
@@ -0,0 +1,6 @@
+$TTL 300
+@ CH SOA ns.example. hostmaster.example. 1 3600 1200 604800 300
+@ CH NS ns.example.
+ns CH TXT "ns"
+a CH A target.example. 1
+target CH TXT "target"
diff --git a/bin/tests/system/class/ns2/localhost.db.in b/bin/tests/system/class/ns2/localhost.db.in
new file mode 100644
index 0000000000..baa5f74862
--- /dev/null
+++ b/bin/tests/system/class/ns2/localhost.db.in
@@ -0,0 +1,6 @@
+$ORIGIN 1.0.0.127.in-addr.arpa.
+$TTL 300
+@ IN SOA ns hostmaster 1 3600 900 604800 300
+@ IN NS ns
+ns IN A 127.0.0.1
+@ IN KX 10 target.example.
diff --git a/bin/tests/system/class/ns2/named.conf.j2 b/bin/tests/system/class/ns2/named.conf.j2
new file mode 100644
index 0000000000..5618c15216
--- /dev/null
+++ b/bin/tests/system/class/ns2/named.conf.j2
@@ -0,0 +1,42 @@
+options {
+	directory ".";
+	query-source address 10.53.0.2;
+	notify-source 10.53.0.2;
+	transfer-source 10.53.0.2;
+	port @PORT@;
+	pid-file "named.pid";
+	listen-on { 10.53.0.2; };
+	listen-on-v6 { none; };
+};
+
+key rndc_key {
+	secret "1234abcd8765";
+	algorithm @DEFAULT_HMAC@;
+};
+
+controls {
+	inet 10.53.0.2 port @CONTROLPORT@ allow { any; } keys { rndc_key; };
+};
+
+view default {
+	match-clients { any; };
+	recursion no;
+        dnssec-validation no;
+	zone "1.0.0.127.in-addr.arpa." {
+		type primary;
+		file "localhost.db";
+		update-policy {
+			grant * tcp-self . ANY;
+		};
+	};
+};
+
+view chaos ch {
+	match-clients { any; };
+	recursion no;
+	zone example {
+		type primary;
+		file "example.db";
+		allow-update { any; };
+	};
+};
diff --git a/bin/tests/system/class/ns3/named.conf.j2 b/bin/tests/system/class/ns3/named.conf.j2
new file mode 100644
index 0000000000..3016333aad
--- /dev/null
+++ b/bin/tests/system/class/ns3/named.conf.j2
@@ -0,0 +1,28 @@
+options {
+	directory ".";
+	query-source address 10.53.0.3;
+	notify-source 10.53.0.3;
+	transfer-source 10.53.0.3;
+	port @PORT@;
+	pid-file "named.pid";
+	listen-on { 10.53.0.3; };
+	listen-on-v6 { none; };
+};
+
+key rndc_key {
+	secret "1234abcd8765";
+	algorithm @DEFAULT_HMAC@;
+};
+
+controls {
+	inet 10.53.0.3 port @CONTROLPORT@ allow { any; } keys { rndc_key; };
+};
+
+view chaos ch {
+	match-clients { any; };
+	recursion yes;
+        dnssec-validation no;
+        forward only;
+        forwarders port @PORT@ { 10.53.0.2; };
+        deny-answer-addresses { 0.0.0.0/0; ::/0; };
+};
diff --git a/bin/tests/system/class/setup.sh b/bin/tests/system/class/setup.sh
new file mode 100644
index 0000000000..c70a2f8290
--- /dev/null
+++ b/bin/tests/system/class/setup.sh
@@ -0,0 +1,19 @@
+#!/bin/sh -e
+
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# SPDX-License-Identifier: MPL-2.0
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0.  If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+# shellcheck source=conf.sh
+. ../conf.sh
+
+cp ns1/chaos.db.in ns1/chaos.db
+cp ns2/example.db.in ns2/example.db
+cp ns2/localhost.db.in ns2/localhost.db
diff --git a/bin/tests/system/class/tests_class_chaos.py b/bin/tests/system/class/tests_class_chaos.py
new file mode 100644
index 0000000000..5b4fef9ae4
--- /dev/null
+++ b/bin/tests/system/class/tests_class_chaos.py
@@ -0,0 +1,54 @@
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# SPDX-License-Identifier: MPL-2.0
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0.  If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+
+import dns.opcode
+import pytest
+
+import isctest
+
+pytestmark = pytest.mark.extra_artifacts(
+    [
+        "*/*.db",
+    ]
+)
+
+
+def test_chaos_recursion():
+    msg = isctest.query.create("foo.example.", "TXT", qclass="CH")
+    res = isctest.query.udp(msg, "10.53.0.1")
+    isctest.check.refused(res)
+
+
+def test_chaos_auth():
+    msg = isctest.query.create("a.example.", "A", qclass="CH")
+    res = isctest.query.udp(msg, "10.53.0.2")
+    isctest.check.noerror(res)
+
+
+def test_chaos_forward():
+    msg = isctest.query.create("a.example.", "A", qclass="CH")
+    res = isctest.query.udp(msg, "10.53.0.3")
+    isctest.check.refused(res)
+
+
+def test_chaos_notify():
+    msg = isctest.query.create("example.", "SOA", qclass="CH", rd=False, dnssec=False)
+    msg.set_opcode(dns.opcode.NOTIFY)
+    msg.flags = dns.opcode.to_flags(dns.opcode.NOTIFY)
+    res = isctest.query.udp(msg, "10.53.0.2")
+    isctest.check.notimp(res)
+
+
+def test_query_class_none():
+    msg = isctest.query.create("example.", "A", qclass="NONE")
+    res = isctest.query.udp(msg, "10.53.0.2")
+    isctest.check.formerr(res)
diff --git a/bin/tests/system/isctest/check.py b/bin/tests/system/isctest/check.py
index 7c5e30c4e1..f723dd95c0 100644
--- a/bin/tests/system/isctest/check.py
+++ b/bin/tests/system/isctest/check.py
@@ -47,6 +47,10 @@ def servfail(message: dns.message.Message) -> None:
     rcode(message, dns.rcode.SERVFAIL)
 
 
+def formerr(message: dns.message.Message) -> None:
+    rcode(message, dns.rcode.FORMERR)
+
+
 def adflag(message: dns.message.Message) -> None:
     assert (message.flags & dns.flags.AD) != 0, str(message)
 

From 3b596adbd21a8cf04478464b2a012d15b0349453 Mon Sep 17 00:00:00 2001
From: Evan Hunt <each@isc.org>
Date: Tue, 17 Mar 2026 13:45:11 -0700
Subject: [PATCH 7/8] Test UPDATE behavior in CHAOS and other non-IN classes

Send various UPDATE requests that are known to have caused
crashes previously with deliberately misconfigured non-IN
zones; confirm that UPDATE is not processed.
---
 bin/named/server.c                           |  1 -
 bin/tests/system/class/ns2/localhost.db.in   |  5 +
 bin/tests/system/class/tests_class_update.py | 96 ++++++++++++++++++++
 3 files changed, 101 insertions(+), 1 deletion(-)
 create mode 100644 bin/tests/system/class/tests_class_update.py

diff --git a/bin/named/server.c b/bin/named/server.c
index d584c1249e..7f3f0162a5 100644
--- a/bin/named/server.c
+++ b/bin/named/server.c
@@ -4775,7 +4775,6 @@ configure_view(dns_view_t *view, dns_viewlist_t *viewlist, cfg_obj_t *config,
 				 aclctx, isc_g_mctx, &view->proxyonacl));
 
 	if (view->rdclass != dns_rdataclass_in) {
-		view->recursion = false;
 		dns_acl_none(isc_g_mctx, &view->recursionacl);
 		dns_acl_none(isc_g_mctx, &view->recursiononacl);
 	} else {
diff --git a/bin/tests/system/class/ns2/localhost.db.in b/bin/tests/system/class/ns2/localhost.db.in
index baa5f74862..a50e5167a9 100644
--- a/bin/tests/system/class/ns2/localhost.db.in
+++ b/bin/tests/system/class/ns2/localhost.db.in
@@ -3,4 +3,9 @@ $TTL 300
 @ IN SOA ns hostmaster 1 3600 900 604800 300
 @ IN NS ns
 ns IN A 127.0.0.1
+
 @ IN KX 10 target.example.
+@ IN PX 10 map822.example. mapx400.example.
+@ IN NSAP 0x47000580ffff0000000001e133ffffff00016200
+@ IN NSAP-PTR target.example.
+@ in EID \# 01 aa
diff --git a/bin/tests/system/class/tests_class_update.py b/bin/tests/system/class/tests_class_update.py
new file mode 100644
index 0000000000..e53bbc77ea
--- /dev/null
+++ b/bin/tests/system/class/tests_class_update.py
@@ -0,0 +1,96 @@
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# SPDX-License-Identifier: MPL-2.0
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0.  If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+import socket
+import struct
+
+from dns import rdataclass, rdatatype, update
+
+import pytest
+
+import isctest
+
+pytestmark = pytest.mark.extra_artifacts(
+    [
+        "*/*.db",
+    ]
+)
+
+
+def encode_name(name: str) -> bytes:
+    out = b""
+    for label in name.rstrip(".").split("."):
+        out += bytes([len(label)]) + label.encode("ascii")
+    return out + b"\x00"
+
+
+@pytest.mark.parametrize(
+    "rdtype,rdclass,ttl,rdata",
+    [
+        (rdatatype.SRV, rdataclass.NONE, 0, b"\x00"),
+        (rdatatype.KX, rdataclass.NONE, 0, b""),
+        (rdatatype.PX, rdataclass.NONE, 0, b""),
+        (rdatatype.NSAP, rdataclass.NONE, 0, b""),
+        (rdatatype.NSAP_PTR, rdataclass.NONE, 0, b""),
+        (31, rdataclass.NONE, 0, b""),  # dnspython doesn't define type EID
+    ],
+)
+def test_class_invalid(rdtype, rdclass, ttl, rdata, named_port):
+    # these update messages are badly formatted, so we construct
+    # them manually instead of using dnspython.
+
+    # opcode=UPDATE, 1 RRset in ZONE, 1 RRset in UPDATE
+    header = struct.pack("!HHHHHH", 0, 0x2800, 1, 0, 1, 0)
+
+    # ZONE section: QNAME=<zone>, QTYPE=SOA, QCLASS=ANY
+    zone_q = encode_name("1.0.0.127.in-addr.arpa") + struct.pack("!HH", 6, 255)
+
+    # UPDATE section RR:
+    update_rr = (
+        encode_name("1.0.0.127.in-addr.arpa")
+        + struct.pack("!HHIH", rdtype, rdclass, ttl, len(rdata))
+        + rdata
+    )
+
+    m = header + zone_q + update_rr
+    packet = struct.pack("!H", len(m)) + m
+
+    with socket.create_connection(
+        ("10.53.0.2", named_port), source_address=("127.0.0.1", 0), timeout=2.0
+    ) as s:
+        s.sendall(packet)
+        try:
+            rwire = s.recv(4096)
+            res = dns.message.from_wire(rwire)
+            isctest.check.formerr(res)
+        except Exception:  # pylint: disable=broad-except
+            pass
+
+    # check the server is answering
+    msg = isctest.query.create("1.0.0.127.in-addr.arpa", "SRV")
+    res = isctest.query.udp(msg, "10.53.0.2")
+    isctest.check.noerror(res)
+    isctest.check.rr_count_eq(res.answer, 0)
+
+
+@pytest.mark.parametrize(
+    "rdtype,rdata",
+    [
+        (rdatatype.SVCB, "\\# 02 0000"),
+        (rdatatype.WKS, "\\# 02 4142"),
+        (rdatatype.WKS, "\\# 02 4344"),
+    ],
+)
+def test_class_chaosupdate(rdtype, rdata):
+    up = update.UpdateMessage("example.", rdclass=rdataclass.CHAOS)
+    up.add("foo.example.", 300, rdtype, rdata)
+    res = isctest.query.tcp(up, "10.53.0.2")
+    isctest.check.notimp(res)

From bb24573580b96fc659ab186000b0da4370fd64e3 Mon Sep 17 00:00:00 2001
From: Evan Hunt <each@isc.org>
Date: Mon, 9 Mar 2026 15:50:04 +1100
Subject: [PATCH 8/8] Test server behavior when sending various UPDATE requests

Send update messages for zones with CLASS0, ANY and NONE.  The class
ANY UPDATE also attempts to delete a KX record in an existing IN
class zone to trigger a REQUIRE.

Test that the server is still running.
---
 bin/tests/system/class/tests_class_update.py | 45 +++++++++++++++++++-
 bin/tests/system/nsupdate/setup.sh           |  1 +
 bin/tests/system/nsupdate/tests.sh           | 20 +++------
 bin/tests/system/packet.pl                   | 25 +++++++++--
 4 files changed, 71 insertions(+), 20 deletions(-)

diff --git a/bin/tests/system/class/tests_class_update.py b/bin/tests/system/class/tests_class_update.py
index e53bbc77ea..30e3ba6d2a 100644
--- a/bin/tests/system/class/tests_class_update.py
+++ b/bin/tests/system/class/tests_class_update.py
@@ -12,7 +12,7 @@
 import socket
 import struct
 
-from dns import rdataclass, rdatatype, update
+from dns import message, rdataclass, rdatatype, update
 
 import pytest
 
@@ -35,6 +35,7 @@ def encode_name(name: str) -> bytes:
 @pytest.mark.parametrize(
     "rdtype,rdclass,ttl,rdata",
     [
+        (rdatatype.SRV, rdataclass.NONE, 0, b"\x00\x00\x00\x00\x00\x00\x01"),
         (rdatatype.SRV, rdataclass.NONE, 0, b"\x00"),
         (rdatatype.KX, rdataclass.NONE, 0, b""),
         (rdatatype.PX, rdataclass.NONE, 0, b""),
@@ -69,7 +70,7 @@ def test_class_invalid(rdtype, rdclass, ttl, rdata, named_port):
         s.sendall(packet)
         try:
             rwire = s.recv(4096)
-            res = dns.message.from_wire(rwire)
+            res = message.from_wire(rwire)
             isctest.check.formerr(res)
         except Exception:  # pylint: disable=broad-except
             pass
@@ -94,3 +95,43 @@ def test_class_chaosupdate(rdtype, rdata):
     up.add("foo.example.", 300, rdtype, rdata)
     res = isctest.query.tcp(up, "10.53.0.2")
     isctest.check.notimp(res)
+
+
+def test_class_undefined(ns2):
+    up = update.UpdateMessage(".", rdclass=257)
+    up.present(".", 0)
+    up.answer[0].rdclass = rdataclass.NONE
+    with ns2.watch_log_from_here() as watcher:
+        res = isctest.query.tcp(up, "10.53.0.2")
+        isctest.check.notimp(res)
+        watcher.wait_for_line("invalid message class: CLASS257")
+
+
+def test_class_zero(ns2):
+    up = update.UpdateMessage(".", rdclass=0)
+    up.present(".", 0)
+    up.answer[0].rdclass = rdataclass.NONE
+    with ns2.watch_log_from_here() as watcher:
+        res = isctest.query.tcp(up, "10.53.0.2")
+        isctest.check.formerr(res)
+        watcher.wait_for_line("message class could not be determined")
+
+
+def test_class_any(ns2):
+    up = update.UpdateMessage(".", rdclass=rdataclass.ANY)
+    up.present(".", 0)
+    up.answer[0].rdclass = rdataclass.NONE
+    with ns2.watch_log_from_here() as watcher:
+        res = isctest.query.tcp(up, "10.53.0.2")
+        isctest.check.formerr(res)
+        watcher.wait_for_line("message parsing failed: FORMERR")
+
+
+def test_class_none(ns2):
+    up = update.UpdateMessage(".", rdclass=rdataclass.NONE)
+    up.present(".", 0)
+    up.answer[0].rdclass = rdataclass.NONE
+    with ns2.watch_log_from_here() as watcher:
+        res = isctest.query.tcp(up, "10.53.0.2")
+        isctest.check.formerr(res)
+        watcher.wait_for_line("message parsing failed: FORMERR")
diff --git a/bin/tests/system/nsupdate/setup.sh b/bin/tests/system/nsupdate/setup.sh
index 299330773a..9d27b20a76 100644
--- a/bin/tests/system/nsupdate/setup.sh
+++ b/bin/tests/system/nsupdate/setup.sh
@@ -35,6 +35,7 @@ update.nil              IN SOA  ns1.example.nil. hostmaster.example.nil. (
                                 3600       ; minimum (1 hour)
                                 )
 update.nil.             NS      ns1.update.nil.
+update.nil.             KX      0 .
 ns1.update.nil.         A       10.53.0.2
 ns2.update.nil.		AAAA	::1
 EOF
diff --git a/bin/tests/system/nsupdate/tests.sh b/bin/tests/system/nsupdate/tests.sh
index 7a77faea6b..d71136c563 100755
--- a/bin/tests/system/nsupdate/tests.sh
+++ b/bin/tests/system/nsupdate/tests.sh
@@ -485,8 +485,10 @@ grep "status: NOERROR" dig.out.ns1.$n >/dev/null || ret=1
 n=$((n + 1))
 ret=0
 echo_i "check that TYPE=0 update is handled ($n)"
+nextpart ns1/named.run >/dev/null
 echo "a0e4280000010000000100000000060001c00c000000fe000000000000" \
-  | $PERL ../packet.pl -a 10.53.0.1 -p ${PORT} -t tcp >/dev/null || ret=1
+  | $PERL ../packet.pl -a 10.53.0.1 -p ${PORT} -t tcp -b >/dev/null || ret=1
+wait_for_log 2 "message parsing failed: FORMERR" ns1/named.run || ret=1
 $DIG $DIGOPTS +tcp version.bind txt ch @10.53.0.1 >dig.out.ns1.$n || ret=1
 grep "status: NOERROR" dig.out.ns1.$n >/dev/null || ret=1
 [ $ret = 0 ] || {
@@ -497,20 +499,10 @@ grep "status: NOERROR" dig.out.ns1.$n >/dev/null || ret=1
 n=$((n + 1))
 ret=0
 echo_i "check that TYPE=0 additional data is handled ($n)"
+nextpart ns1/named.run >/dev/null
 echo "a0e4280000010000000000010000060001c00c000000fe000000000000" \
-  | $PERL ../packet.pl -a 10.53.0.1 -p ${PORT} -t tcp >/dev/null || ret=1
-$DIG $DIGOPTS +tcp version.bind txt ch @10.53.0.1 >dig.out.ns1.$n || ret=1
-grep "status: NOERROR" dig.out.ns1.$n >/dev/null || ret=1
-[ $ret = 0 ] || {
-  echo_i "failed"
-  status=1
-}
-
-n=$((n + 1))
-ret=0
-echo_i "check that update to undefined class is handled ($n)"
-echo "a0e4280000010001000000000000060101c00c000000fe000000000000" \
-  | $PERL ../packet.pl -a 10.53.0.1 -p ${PORT} -t tcp >/dev/null || ret=1
+  | $PERL ../packet.pl -a 10.53.0.1 -p ${PORT} -t tcp -b >/dev/null || ret=1
+wait_for_log 2 "message parsing failed: FORMERR" ns1/named.run || ret=1
 $DIG $DIGOPTS +tcp version.bind txt ch @10.53.0.1 >dig.out.ns1.$n || ret=1
 grep "status: NOERROR" dig.out.ns1.$n >/dev/null || ret=1
 [ $ret = 0 ] || {
diff --git a/bin/tests/system/packet.pl b/bin/tests/system/packet.pl
index 900a0c071e..afb9f4784d 100644
--- a/bin/tests/system/packet.pl
+++ b/bin/tests/system/packet.pl
@@ -40,6 +40,7 @@
 # -p <port>:     specify port
 # -t <protocol>: specify UDP or TCP
 # -r <num>:      send packet <num> times
+# -b:		 blocking io
 # -d:            dump response packets
 #
 # If not specified, address defaults to 127.0.0.1, port to 53, protocol
@@ -51,6 +52,8 @@ use strict;
 use Getopt::Std;
 use IO::File;
 use IO::Socket;
+use Net::DNS;
+use Net::DNS::Packet;
 
 sub usage {
     print ("Usage: packet.pl [-a address] [-d] [-p port] [-t (tcp|udp)] [-r <repeats>] [file]\n");
@@ -61,8 +64,6 @@ my $sock;
 my $proto;
 
 sub dumppacket {
-    use Net::DNS;
-    use Net::DNS::Packet;
 
     my $rin;
     my $rout;
@@ -96,7 +97,7 @@ sub dumppacket {
 }
 
 my %options={};
-getopts("a:dp:t:r:", \%options);
+getopts("a:bdp:t:r:", \%options);
 
 my $addr = "127.0.0.1";
 $addr = $options{a} if defined $options{a};
@@ -111,6 +112,8 @@ usage if ($proto !~ /^(udp|tcp)$/);
 my $repeats = 1;
 $repeats = $options{r} if defined $options{r};
 
+my $blocking = defined $options{b} ? 1 : 0;
+
 my $file = "STDIN";
 if (@ARGV >= 1) {
     my $filename = shift @ARGV;
@@ -132,8 +135,22 @@ my $len = length $data;
 my $output = unpack("H*", $data);
 print ("sending $repeats time(s): $output\n");
 
+
+if (defined $options{d}) {
+    my $request;
+    if ($Net::DNS::VERSION > 0.68) {
+        $request = new Net::DNS::Packet(\$data, 0);
+        $@ and die $@;
+    } else {
+        my $err;
+        ($request, $err) = new Net::DNS::Packet(\$data, 0);
+        $err and die $err;
+    }
+    $request->print;
+}
+
 $sock = IO::Socket::INET->new(PeerAddr => $addr, PeerPort => $port,
-				 Blocking => 0,
+				 Blocking => $blocking,
 				 Proto => $proto,) or die "$!";
 
 STDOUT->autoflush(1);