Merge branch '779-named-checkconf-crashes-in-parser-c' into 'master'

Resolve "named-checkconf crashes in parser.c"

Closes #779

See merge request !1234

CHANGES

+5112.	[bug]		Named/named-checkconf could dump core if there was
+			a missing masters clause and a bad notify clause.
+			[GL #779]
+
 5111.	[bug]		Occluded DNSKEY records could make it into the
 			delegating NSEC/NSEC3 bitmap. [GL #742]

bin/tests/system/checkconf/bad-stub-masters-dialup.conf

+controls { /* empty */ };
+options {
+	query-source address 10.53.0.2;
+	notify-source 10.53.0.2;
+	transfer-source 10.53.0.2;
+	port 5300;
+	pid-file "named.pid";
+	listen-on { 10.53.0.2; };
+	listen-on-v6 { none; };
+	heartbeat-interval 2;
+	recursion no;
+};
+zone "." {
+	type hint;
+	file "hint";
+};
+zone "example." {
+	type stub;
+	dialup notify;
+	notify no;
+	file "example.bk";
+	// masters { 10.53.0.1; };
+};

lib/bind9/check.c

@@ -2434,10 +2434,10 @@ check_zoneconf(const cfg_obj_t *zconfig, const cfg_obj_t *voptions,
 	if (ztype == CFG_ZONE_MASTER || ztype == CFG_ZONE_SLAVE ||
 	    ztype == CFG_ZONE_STUB)
 	{
-		const cfg_obj_t *dialup = NULL;
-		(void)cfg_map_get(zoptions, "dialup", &dialup);
-		if (dialup != NULL && cfg_obj_isstring(dialup)) {
-			const char *str = cfg_obj_asstring(dialup);
+		obj = NULL;
+		(void)cfg_map_get(zoptions, "dialup", &obj);
+		if (obj != NULL && cfg_obj_isstring(obj)) {
+			const char *str = cfg_obj_asstring(obj);
 			for (i = 0;
 			     i < sizeof(dialups) / sizeof(dialups[0]);
 			     i++)