- Fix #397: [Feature request] add new type always_null to local-zone

similar to always_nxdomain.

doc/Changelog

@@ -1,3 +1,7 @@
+12 January 2021: Wouter
+	- Fix #397: [Feature request] add new type always_null to local-zone
+	  similar to always_nxdomain.
+
 8 January 2021: Wouter
 	- Merge PR #391 from fhriley: Add start_time to reply callbacks so
 	  modules can compute the response time.

doc/example.conf.in

@@ -706,6 +706,7 @@ server:
 	# o inform_redirect redirects queries and logs client IP address
 	# o always_transparent, always_refuse, always_nxdomain, resolve in
 	#   that way but ignore local data for that name
+	# o always_null returns 0.0.0.0 or ::0 for any name in the zone.
 	# o noview breaks out of that view towards global local-zones.
 	#
 	# defaults are localhost address, reverse for 127.0.0.1 and ::1

doc/unbound.conf.5.in

@@ -1231,7 +1231,7 @@ address space are not validated.  This is usually required whenever
 Configure a local zone. The type determines the answer to give if
 there is no match from local\-data. The types are deny, refuse, static,
 transparent, redirect, nodefault, typetransparent, inform, inform_deny,
-inform_redirect, always_transparent, always_refuse, always_nxdomain, noview,
+inform_redirect, always_transparent, always_refuse, always_nxdomain, always_null, noview,
 and are explained below. After that the default settings are listed. Use
 local\-data: to enter data into the local zone. Answers for local zones
 are authoritative DNS answers. By default the zones are class IN.
@@ -1305,6 +1305,11 @@ Like refuse, but ignores local data and refuses the query.
 \h'5'\fIalways_nxdomain\fR
 Like static, but ignores local data and returns nxdomain for the query.
 .TP 10
+\h'5'\fIalways_null\fR
+Always returns 0.0.0.0 or ::0 for every name in the zone.  Like redirect
+with zero data for A and AAAA.  Ignores local data in the zone.  Used for
+some block lists.
+.TP 10
 \h'5'\fInoview\fR
 Breaks out of that view and moves towards the global local zones for answer
 to the query.  If the view first is no, it'll resolve normally.  If view first

services/localzone.c

@@ -1558,6 +1558,46 @@ local_zones_zone_answer(struct local_zone* z, struct module_env* env,
 		|| lz_type == local_zone_always_transparent) {
 		/* no NODATA or NXDOMAINS for this zone type */
 		return 0;
+	} else if(lz_type == local_zone_always_null) {
+		/* 0.0.0.0 or ::0 or noerror/nodata for this zone type,
+		 * used for blocklists. */
+		if(qinfo->qtype == LDNS_RR_TYPE_A ||
+			qinfo->qtype == LDNS_RR_TYPE_AAAA) {
+			struct ub_packed_rrset_key lrr;
+			struct packed_rrset_data d;
+			time_t rr_ttl = 3600;
+			size_t rr_len = 0;
+			uint8_t rr_data[2+16] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
+			uint8_t* rr_datas = rr_data;
+			memset(&lrr, 0, sizeof(lrr));
+			memset(&d, 0, sizeof(d));
+			lrr.entry.data = &d;
+			lrr.rk.dname = qinfo->qname;
+			lrr.rk.dname_len = qinfo->qname_len;
+			lrr.rk.type = htons(qinfo->qtype);
+			lrr.rk.rrset_class = htons(qinfo->qclass);
+			if(qinfo->qtype == LDNS_RR_TYPE_A) {
+				rr_len = 4;
+				sldns_write_uint16(rr_data, rr_len);
+				rr_len += 2;
+			} else {
+				rr_len = 16;
+				sldns_write_uint16(rr_data, rr_len);
+				rr_len += 2;
+			}
+			d.ttl = rr_ttl;
+			d.count = 1;
+			d.rr_len = &rr_len;
+			d.rr_data = &rr_datas;
+			d.rr_ttl = &rr_ttl;
+			return local_encode(qinfo, env, edns, repinfo, buf, temp,
+				&lrr, 1, LDNS_RCODE_NOERROR);
+		} else {
+			local_error_encode(qinfo, env, edns, repinfo, buf,
+				temp, LDNS_RCODE_NOERROR,
+				(LDNS_RCODE_NOERROR|BIT_AA));
+		}
+		return 1;
 	}
 	/* else lz_type == local_zone_transparent */
 
@@ -1762,6 +1802,7 @@ const char* local_zone_type2str(enum localzone_type t)
 		case local_zone_always_nxdomain: return "always_nxdomain";
 		case local_zone_always_nodata: return "always_nodata";
 		case local_zone_always_deny: return "always_deny";
+		case local_zone_always_null: return "always_null";
 		case local_zone_noview: return "noview";
 		case local_zone_invalid: return "invalid";
 	}
@@ -1798,6 +1839,8 @@ int local_zone_str2type(const char* type, enum localzone_type* t)
 		*t = local_zone_always_nodata;
 	else if(strcmp(type, "always_deny") == 0)
 		*t = local_zone_always_deny;
+	else if(strcmp(type, "always_null") == 0)
+		*t = local_zone_always_null;
 	else if(strcmp(type, "noview") == 0)
 		*t = local_zone_noview;
 	else if(strcmp(type, "nodefault") == 0)

services/localzone.h

@@ -96,6 +96,9 @@ enum localzone_type {
 	local_zone_always_nodata,
 	/** drop query, even when there is local data */
 	local_zone_always_deny,
+	/** answer with 0.0.0.0 or ::0 or noerror/nodata, even when there is
+	 * local data */
+	local_zone_always_null,
 	/** answer not from the view, but global or no-answer */
 	local_zone_noview,
 	/** Invalid type, cannot be used to generate answer */

testdata/localdata.rpl

@@ -35,6 +35,9 @@ server:
 	local-zone: "redirect.top." redirect
 	local-data: "redirect.top. A 20.30.40.54"
 
+	; null zone
+	local-zone: "null.top." always_null
+
 	; create implicit data in the IN domain as well
 	local-data: "a.a.implicit. A 20.30.41.50"
 	local-data: "b.a.implicit. A 20.30.42.50"
@@ -355,4 +358,36 @@ SECTION ANSWER
 www.redirect.top. IN A 20.30.40.54
 ENTRY_END
 
+; always_null zone
+STEP 60 QUERY
+ENTRY_BEGIN
+SECTION QUESTION
+null.top. IN A
+ENTRY_END
+STEP 61 CHECK_ANSWER
+ENTRY_BEGIN
+MATCH all
+REPLY QR RA AA NOERROR
+SECTION QUESTION
+null.top. IN A
+SECTION ANSWER
+null.top. IN A 0.0.0.0
+ENTRY_END
+
+; always_null zone AAAA
+STEP 62 QUERY
+ENTRY_BEGIN
+SECTION QUESTION
+foo.null.top. IN AAAA
+ENTRY_END
+STEP 63 CHECK_ANSWER
+ENTRY_BEGIN
+MATCH all
+REPLY QR RA AA NOERROR
+SECTION QUESTION
+foo.null.top. IN AAAA
+SECTION ANSWER
+foo.null.top. IN AAAA ::0
+ENTRY_END
+
 SCENARIO_END

util/configparser.y

@@ -2030,6 +2030,7 @@ server_local_zone: VAR_LOCAL_ZONE STRING_ARG STRING_ARG
 		   && strcmp($3, "always_transparent")!=0
 		   && strcmp($3, "always_refuse")!=0
 		   && strcmp($3, "always_nxdomain")!=0
+		   && strcmp($3, "always_null")!=0
 		   && strcmp($3, "noview")!=0
 		   && strcmp($3, "inform")!=0 && strcmp($3, "inform_deny")!=0
 		   && strcmp($3, "inform_redirect") != 0
@@ -2038,8 +2039,8 @@ server_local_zone: VAR_LOCAL_ZONE STRING_ARG STRING_ARG
 				"refuse, redirect, transparent, "
 				"typetransparent, inform, inform_deny, "
 				"inform_redirect, always_transparent, "
-				"always_refuse, always_nxdomain, noview "
+				"always_refuse, always_nxdomain, always_null, "
-				", nodefault or ipset");
+				"noview, nodefault or ipset");
 			free($2);
 			free($3);
 		} else if(strcmp($3, "nodefault")==0) {