Merge pull request #944 from NLnetLabs/disable-edns-do

wcawijngaards · web-flow · commit 5c6c57ed8988 · 2023-10-12T14:04:29.000+02:00
Disable EDNS DO
diff --git a/daemon/worker.c b/daemon/worker.c
@@ -543,6 +543,8 @@ answer_norec_from_cache(struct worker* worker, struct query_info* qinfo,
 	edns->udp_size = EDNS_ADVERTISED_SIZE;
 	edns->ext_rcode = 0;
 	edns->bits &= EDNS_DO;
+	if(worker->env.cfg->disable_edns_do && (edns->bits & EDNS_DO))
+		edns->edns_present = 0;
 	if(!inplace_cb_reply_cache_call(&worker->env, qinfo, NULL, msg->rep,
 		(int)(flags&LDNS_RCODE_MASK), edns, repinfo, worker->scratchpad,
 		worker->env.now_tv))
@@ -703,6 +705,8 @@ answer_from_cache(struct worker* worker, struct query_info* qinfo,
 		edns->udp_size = EDNS_ADVERTISED_SIZE;
 		edns->ext_rcode = 0;
 		edns->bits &= EDNS_DO;
+		if(worker->env.cfg->disable_edns_do && (edns->bits & EDNS_DO))
+			edns->edns_present = 0;
 		if(!inplace_cb_reply_servfail_call(&worker->env, qinfo, NULL, rep,
 			LDNS_RCODE_SERVFAIL, edns, repinfo, worker->scratchpad,
 			worker->env.now_tv))
@@ -743,6 +747,8 @@ answer_from_cache(struct worker* worker, struct query_info* qinfo,
 	edns->udp_size = EDNS_ADVERTISED_SIZE;
 	edns->ext_rcode = 0;
 	edns->bits &= EDNS_DO;
+	if(worker->env.cfg->disable_edns_do && (edns->bits & EDNS_DO))
+		edns->edns_present = 0;
 	*alias_rrset = NULL; /* avoid confusion if caller set it to non-NULL */
 	if((worker->daemon->use_response_ip || worker->daemon->use_rpz) &&
 		!partial_rep && !apply_respip_action(worker, qinfo, cinfo, rep,
diff --git a/doc/example.conf.in b/doc/example.conf.in
@@ -683,6 +683,11 @@ server:
 	# that set CD but cannot validate themselves.
 	# ignore-cd-flag: no
 
+	# Disable the DO flag in outgoing requests. It is helpful for upstream
+	# devices that cannot handle DNSSEC information. But do not enable it
+	# otherwise, because it would stop DNSSEC validation.
+	# disable-edns-do: no
+
 	# Serve expired responses from cache, with serve-expired-reply-ttl in
 	# the response, and then attempt to fetch the data afresh.
 	# serve-expired: no
diff --git a/doc/unbound.conf.5.in b/doc/unbound.conf.5.in
@@ -1302,6 +1302,20 @@ servers that set the CD flag but cannot validate DNSSEC themselves are
 the clients, and then Unbound provides them with DNSSEC protection.
 The default value is "no".
 .TP
+.B disable\-edns\-do: \fI<yes or no>
+Disable the EDNS DO flag in upstream requests.
+It breaks DNSSEC validation for Unbound's clients.
+This results in the upstream name servers to not include DNSSEC records in
+their replies and could be helpful for devices that cannot handle DNSSEC
+information.
+When the option is enabled, clients that set the DO flag receive no EDNS
+record in the response to indicate the lack of support to them.
+If this option is enabled but Unbound is already configured for DNSSEC
+validation (i.e., the validator module is enabled; default) this option is
+implicitly turned off with a warning as to not break DNSSEC validation in
+Unbound.
+Default is no.
+.TP
 .B serve\-expired: \fI<yes or no>
 If enabled, Unbound attempts to serve old responses from cache with a
 TTL of \fBserve\-expired\-reply\-ttl\fR in the response without waiting for the
diff --git a/iterator/iterator.c b/iterator/iterator.c
@@ -2875,7 +2875,8 @@ processQueryTargets(struct module_qstate* qstate, struct iter_qstate* iq,
 		/* unset CD if to forwarder(RD set) and not dnssec retry
 		 * (blacklist nonempty) and no trust-anchors are configured
 		 * above the qname or on the first attempt when dnssec is on */
-		EDNS_DO| ((iq->chase_to_rd||(iq->chase_flags&BIT_RD)!=0)&&
+		(qstate->env->cfg->disable_edns_do?0:EDNS_DO)|
+		((iq->chase_to_rd||(iq->chase_flags&BIT_RD)!=0)&&
 		!qstate->blacklist&&(!iter_qname_indicates_dnssec(qstate->env,
 		&iq->qinfo_out)||target->attempts==1)?0:BIT_CD),
 		iq->dnssec_expected, iq->caps_fallback || is_caps_whitelisted(
diff --git a/services/mesh.c b/services/mesh.c
@@ -1197,6 +1197,8 @@ mesh_do_callback(struct mesh_state* m, int rcode, struct reply_info* rep,
 		r->edns.udp_size = EDNS_ADVERTISED_SIZE;
 		r->edns.ext_rcode = 0;
 		r->edns.bits &= EDNS_DO;
+		if(m->s.env->cfg->disable_edns_do && (r->edns.bits&EDNS_DO))
+			r->edns.edns_present = 0;
 
 		if(!inplace_cb_reply_call(m->s.env, &m->s.qinfo, &m->s, rep,
 			LDNS_RCODE_NOERROR, &r->edns, NULL, m->s.region, start_time) ||
@@ -1372,6 +1374,8 @@ mesh_send_reply(struct mesh_state* m, int rcode, struct reply_info* rep,
 		r->edns.udp_size = EDNS_ADVERTISED_SIZE;
 		r->edns.ext_rcode = 0;
 		r->edns.bits &= EDNS_DO;
+		if(m->s.env->cfg->disable_edns_do && (r->edns.bits&EDNS_DO))
+			r->edns.edns_present = 0;
 		m->s.qinfo.qname = r->qname;
 		m->s.qinfo.local_alias = r->local_alias;
 
diff --git a/smallapp/unbound-checkconf.c b/smallapp/unbound-checkconf.c
@@ -707,6 +707,23 @@ morechecks(struct config_file* cfg)
 		cfg->auto_trust_anchor_file_list, cfg->chrootdir, cfg);
 	check_chroot_filelist_wild("trusted-keys-file",
 		cfg->trusted_keys_file_list, cfg->chrootdir, cfg);
+	if(cfg->disable_edns_do && strstr(cfg->module_conf, "validator")
+		&& (cfg->trust_anchor_file_list
+		|| cfg->trust_anchor_list
+		|| cfg->auto_trust_anchor_file_list
+		|| cfg->trusted_keys_file_list)) {
+		char* key = NULL;
+		if(cfg->auto_trust_anchor_file_list)
+			key = cfg->auto_trust_anchor_file_list->str;
+		if(!key && cfg->trust_anchor_file_list)
+			key = cfg->trust_anchor_file_list->str;
+		if(!key && cfg->trust_anchor_list)
+			key = cfg->trust_anchor_list->str;
+		if(!key && cfg->trusted_keys_file_list)
+			key = cfg->trusted_keys_file_list->str;
+		if(!key) key = "";
+		fatal_exit("disable-edns-do does not allow DNSSEC to work, but the validator module uses a trust anchor %s, turn off disable-edns-do or disable validation", key);
+	}
 #ifdef USE_IPSECMOD
 	if(cfg->ipsecmod_enabled && strstr(cfg->module_conf, "ipsecmod")) {
 		/* only check hook if enabled */
diff --git a/testcode/fake_event.c b/testcode/fake_event.c
@@ -1249,7 +1249,7 @@ struct serviced_query* outnet_serviced_query(struct outside_network* outnet,
 		edns.edns_version = EDNS_ADVERTISED_VERSION;
 		edns.udp_size = EDNS_ADVERTISED_SIZE;
 		edns.bits = 0;
-		if(dnssec)
+		if((dnssec & EDNS_DO))
 			edns.bits = EDNS_DO;
 		edns.padding_block_size = 0;
 		edns.cookie_present = 0;
diff --git a/testdata/disable_edns_do.rpl b/testdata/disable_edns_do.rpl
@@ -0,0 +1,164 @@
+; config options
+; The island of trust is at example.com
+server:
+	target-fetch-policy: "0 0 0 0 0"
+	qname-minimisation: "no"
+	trust-anchor-signaling: no
+	minimal-responses: no
+	disable-edns-do: yes
+
+stub-zone:
+	name: "."
+	stub-addr: 193.0.14.129 	# K.ROOT-SERVERS.NET.
+CONFIG_END
+
+SCENARIO_BEGIN Test lookup with disable-edns-do
+
+; K.ROOT-SERVERS.NET.
+RANGE_BEGIN 0 100
+	ADDRESS 193.0.14.129 
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+. IN NS
+SECTION ANSWER
+. IN NS	K.ROOT-SERVERS.NET.
+SECTION ADDITIONAL
+K.ROOT-SERVERS.NET.	IN	A	193.0.14.129
+ENTRY_END
+
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+www.example.com. IN A
+SECTION AUTHORITY
+com.	IN NS	a.gtld-servers.net.
+SECTION ADDITIONAL
+a.gtld-servers.net.	IN 	A	192.5.6.30
+ENTRY_END
+RANGE_END
+
+; a.gtld-servers.net.
+RANGE_BEGIN 0 100
+	ADDRESS 192.5.6.30
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+com. IN NS
+SECTION ANSWER
+com.    IN NS   a.gtld-servers.net.
+SECTION ADDITIONAL
+a.gtld-servers.net.     IN      A       192.5.6.30
+ENTRY_END
+
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+www.example.com. IN A
+SECTION AUTHORITY
+example.com.	IN NS	ns.example.com.
+SECTION ADDITIONAL
+ns.example.com.		IN 	A	1.2.3.4
+ENTRY_END
+RANGE_END
+
+; ns.example.com.
+RANGE_BEGIN 0 100
+	ADDRESS 1.2.3.4
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+example.com. IN NS
+SECTION ANSWER
+example.com.    IN NS   ns.example.com.
+example.com.    3600    IN      RRSIG   NS 3 2 3600 20070926134150 20070829134150 2854 example.com. MC0CFQCN+qHdJxoI/2tNKwsb08pra/G7aAIUAWA5sDdJTbrXA1/3OaesGBAO3sI= ;{id = 2854}
+SECTION ADDITIONAL
+ns.example.com.         IN      A       1.2.3.4
+ns.example.com. 3600    IN      RRSIG   A 3 3 3600 20070926135752 20070829135752 2854 example.com. MC0CFQCMSWxVehgOQLoYclB9PIAbNP229AIUeH0vNNGJhjnZiqgIOKvs1EhzqAo= ;{id = 2854}
+ENTRY_END
+
+; response to DNSKEY priming query
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+example.com. IN DNSKEY
+SECTION ANSWER
+example.com.    3600    IN      DNSKEY  256 3 3 ALXLUsWqUrY3JYER3T4TBJII s70j+sDS/UT2QRp61SE7S3E EXopNXoFE73JLRmvpi/UrOO/Vz4Se 6wXv/CYCKjGw06U4WRgR YXcpEhJROyNapmdIKSx hOzfLVE1gqA0PweZR8d tY3aNQSRn3sPpwJr6Mi /PqQKAMMrZ9ckJpf1+b QMOOvxgzz2U1GS18b3y ZKcgTMEaJzd/GZYzi/B N2DzQ0MsrSwYXfsNLFO Bbs8PJMW4LYIxeeOe6rUgkWOF 7CC9Dh/dduQ1QrsJhmZAEFfd6ByYV+ ;{id = 2854 (zsk), size = 1688b}
+example.com.    3600    IN      RRSIG   DNSKEY 3 2 3600 20070926134802 20070829134802 2854 example.com. MCwCFG1yhRNtTEa3Eno2zhVVuy2EJX3wAhQeLyUp6+UXcpC5qGNu9tkrTEgPUg== ;{id = 2854}
+SECTION AUTHORITY
+example.com.	IN NS	ns.example.com.
+example.com.    3600    IN      RRSIG   NS 3 2 3600 20070926134150 20070829134150 2854 example.com. MC0CFQCN+qHdJxoI/2tNKwsb08pra/G7aAIUAWA5sDdJTbrXA1/3OaesGBAO3sI= ;{id = 2854}
+SECTION ADDITIONAL
+ns.example.com.		IN 	A	1.2.3.4
+ns.example.com. 3600    IN      RRSIG   A 3 3 3600 20070926135752 20070829135752 2854 example.com. MC0CFQCMSWxVehgOQLoYclB9PIAbNP229AIUeH0vNNGJhjnZiqgIOKvs1EhzqAo= ;{id = 2854}
+ENTRY_END
+
+; response to query of interest, when sent with EDNS DO
+ENTRY_BEGIN
+MATCH opcode qtype qname DO
+ADJUST copy_id
+REPLY QR AA DO NOERROR
+SECTION QUESTION
+www.example.com. IN A
+SECTION ANSWER
+www.example.com. IN A	10.20.30.40
+ns.example.com. 3600    IN      RRSIG   A 3 3 3600 20070926134150 20070829134150 2854 example.com. MC0CFQCQMyTjn7WWwpwAR1LlVeLpRgZGuQIUCcJDEkwAuzytTDRlYK7nIMwH1CM= ;{id = 2854}
+SECTION AUTHORITY
+example.com.	IN NS	ns.example.com.
+example.com.    3600    IN      RRSIG   NS 3 2 3600 20070926134150 20070829134150 2854 example.com. MC0CFQCN+qHdJxoI/2tNKwsb08pra/G7aAIUAWA5sDdJTbrXA1/3OaesGBAO3sI= ;{id = 2854}
+SECTION ADDITIONAL
+ns.example.com.		IN 	A	1.2.3.4
+www.example.com.        3600    IN      RRSIG   A 3 3 3600 20070926134150 20070829134150 2854 example.com. MC0CFC99iE9K5y2WNgI0gFvBWaTi9wm6AhUAoUqOpDtG5Zct+Qr9F3mSdnbc6V4= ;{id = 2854}
+ENTRY_END
+
+; response to query of interest, when sent without DO
+ENTRY_BEGIN
+MATCH opcode qtype qname
+ADJUST copy_id
+REPLY QR AA NOERROR
+SECTION QUESTION
+www.example.com. IN A
+SECTION ANSWER
+www.example.com. IN A	10.20.30.40
+SECTION AUTHORITY
+example.com.	IN NS	ns.example.com.
+SECTION ADDITIONAL
+ns.example.com.		IN 	A	1.2.3.4
+ENTRY_END
+RANGE_END
+
+STEP 1 QUERY
+ENTRY_BEGIN
+REPLY RD DO
+SECTION QUESTION
+www.example.com. IN A
+ENTRY_END
+
+; recursion happens here.
+STEP 10 CHECK_ANSWER
+ENTRY_BEGIN
+MATCH all
+REPLY QR RD RA NOERROR
+SECTION QUESTION
+www.example.com. IN A
+SECTION ANSWER
+www.example.com. IN A	10.20.30.40
+SECTION AUTHORITY
+example.com.	IN NS	ns.example.com.
+SECTION ADDITIONAL
+ns.example.com.		IN 	A	1.2.3.4
+ENTRY_END
+
+SCENARIO_END
diff --git a/util/config_file.c b/util/config_file.c
@@ -271,6 +271,7 @@ config_create(void)
 	cfg->val_permissive_mode = 0;
 	cfg->aggressive_nsec = 1;
 	cfg->ignore_cd = 0;
+	cfg->disable_edns_do = 0;
 	cfg->serve_expired = 0;
 	cfg->serve_expired_ttl = 0;
 	cfg->serve_expired_ttl_reset = 0;
@@ -691,6 +692,7 @@ int config_set_option(struct config_file* cfg, const char* opt,
 	else S_YNO("val-permissive-mode:", val_permissive_mode)
 	else S_YNO("aggressive-nsec:", aggressive_nsec)
 	else S_YNO("ignore-cd-flag:", ignore_cd)
+	else S_YNO("disable-edns-do:", disable_edns_do)
 	else if(strcmp(opt, "serve-expired:") == 0)
 	{ IS_YES_OR_NO; cfg->serve_expired = (strcmp(val, "yes") == 0);
 	  SERVE_EXPIRED = cfg->serve_expired; }
@@ -1150,6 +1152,7 @@ config_get_option(struct config_file* cfg, const char* opt,
 	else O_YNO(opt, "val-permissive-mode", val_permissive_mode)
 	else O_YNO(opt, "aggressive-nsec", aggressive_nsec)
 	else O_YNO(opt, "ignore-cd-flag", ignore_cd)
+	else O_YNO(opt, "disable-edns-do", disable_edns_do)
 	else O_YNO(opt, "serve-expired", serve_expired)
 	else O_DEC(opt, "serve-expired-ttl", serve_expired_ttl)
 	else O_YNO(opt, "serve-expired-ttl-reset", serve_expired_ttl_reset)
diff --git a/util/config_file.h b/util/config_file.h
@@ -409,6 +409,8 @@ struct config_file {
 	int aggressive_nsec;
 	/** ignore the CD flag in incoming queries and refuse them bogus data */
 	int ignore_cd;
+	/** disable EDNS DO flag in outgoing requests */
+	int disable_edns_do;
 	/** serve expired entries and prefetch them */
 	int serve_expired;
 	/** serve expired entries until TTL after expiration */
diff --git a/util/configlexer.lex b/util/configlexer.lex
@@ -403,6 +403,7 @@ val-clean-additional{COLON}	{ YDVAR(1, VAR_VAL_CLEAN_ADDITIONAL) }
 val-permissive-mode{COLON}	{ YDVAR(1, VAR_VAL_PERMISSIVE_MODE) }
 aggressive-nsec{COLON}		{ YDVAR(1, VAR_AGGRESSIVE_NSEC) }
 ignore-cd-flag{COLON}		{ YDVAR(1, VAR_IGNORE_CD_FLAG) }
+disable-edns-do{COLON}		{ YDVAR(1, VAR_DISABLE_EDNS_DO) }
 serve-expired{COLON}		{ YDVAR(1, VAR_SERVE_EXPIRED) }
 serve-expired-ttl{COLON}	{ YDVAR(1, VAR_SERVE_EXPIRED_TTL) }
 serve-expired-ttl-reset{COLON}	{ YDVAR(1, VAR_SERVE_EXPIRED_TTL_RESET) }
diff --git a/util/configparser.y b/util/configparser.y
@@ -199,7 +199,7 @@ extern struct config_parser_state* cfg_parser;
 %token VAR_INTERFACE_ACTION VAR_INTERFACE_VIEW VAR_INTERFACE_TAG
 %token VAR_INTERFACE_TAG_ACTION VAR_INTERFACE_TAG_DATA
 %token VAR_PROXY_PROTOCOL_PORT VAR_STATISTICS_INHIBIT_ZERO
-%token VAR_HARDEN_UNKNOWN_ADDITIONAL
+%token VAR_HARDEN_UNKNOWN_ADDITIONAL VAR_DISABLE_EDNS_DO
 
 %%
 toplevelvars: /* empty */ | toplevelvars toplevelvar ;
@@ -333,7 +333,7 @@ content_server: server_num_threads | server_verbosity | server_port |
 	server_tcp_reuse_timeout | server_tcp_auth_query_timeout |
 	server_interface_automatic_ports | server_ede |
 	server_proxy_protocol_port | server_statistics_inhibit_zero |
-	server_harden_unknown_additional
+	server_harden_unknown_additional | server_disable_edns_do
 	;
 stubstart: VAR_STUB_ZONE
 	{
@@ -2061,6 +2061,15 @@ server_ignore_cd_flag: VAR_IGNORE_CD_FLAG STRING_ARG
 		free($2);
 	}
 	;
+server_disable_edns_do: VAR_DISABLE_EDNS_DO STRING_ARG
+	{
+		OUTYY(("P(server_disable_edns_do:%s)\n", $2));
+		if(strcmp($2, "yes") != 0 && strcmp($2, "no") != 0)
+			yyerror("expected yes or no.");
+		else cfg_parser->cfg->disable_edns_do = (strcmp($2, "yes")==0);
+		free($2);
+	}
+	;
 server_serve_expired: VAR_SERVE_EXPIRED STRING_ARG
 	{
 		OUTYY(("P(server_serve_expired:%s)\n", $2));
diff --git a/util/data/msgencode.c b/util/data/msgencode.c
@@ -1012,8 +1012,10 @@ reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep,
 	ede_size = calc_ede_option_size(edns, &ede_txt_size);
 	if(sldns_buffer_capacity(pkt) < udpsize)
 		udpsize = sldns_buffer_capacity(pkt);
+	if(!edns || !edns->edns_present) {
+		attach_edns = 0;
 	/* EDEs are optional, try to fit anything else before them */
-	if(udpsize < LDNS_HEADER_SIZE + edns_field_size - ede_size) {
+	} else if(udpsize < LDNS_HEADER_SIZE + edns_field_size - ede_size) {
 		/* packet too small to contain edns, omit it. */
 		attach_edns = 0;
 	} else {
diff --git a/validator/val_anchor.c b/validator/val_anchor.c
@@ -1322,3 +1322,24 @@ anchor_has_keytag(struct val_anchors* anchors, uint8_t* name, int namelabs,
 	free(taglist);
 	return 0;
 }
+
+struct trust_anchor*
+anchors_find_any_noninsecure(struct val_anchors* anchors)
+{
+	struct trust_anchor* ta, *next;
+	lock_basic_lock(&anchors->lock);
+	ta=(struct trust_anchor*)rbtree_first(anchors->tree);
+	while((rbnode_type*)ta != RBTREE_NULL) {
+		next = (struct trust_anchor*)rbtree_next(&ta->node);
+		lock_basic_lock(&ta->lock);
+		if(ta->numDS != 0 || ta->numDNSKEY != 0) {
+			/* not an insecurepoint */
+			lock_basic_unlock(&anchors->lock);
+			return ta;
+		}
+		lock_basic_unlock(&ta->lock);
+		ta = next;
+	}
+	lock_basic_unlock(&anchors->lock);
+	return NULL;
+}
diff --git a/validator/val_anchor.h b/validator/val_anchor.h
diff --git a/validator/validator.c b/validator/validator.c
