Enforce presence of query section in reply.

git-svn-id: file:///svn/unbound/trunk@1018 be551aaa-1e26-0410-a405-d3ace91eadb9

doc/Changelog

@@ -1,3 +1,13 @@
+25 March 2008: Wouter
+	- implemented check that for NXDOMAIN and NOERROR answers a query
+	  section must be present in the reply (by the scrubber). And it must
+	  be equal to the question sent, at least lowercase folded.
+	  Previously this feature happened because the cache code refused
+	  to store such messages. However blocking by the scrubber makes 
+	  sure nothing gets into the RRset cache. Also, this looks like a
+	  timeout (instead of an allocation failure) and this retries are
+	  done (which is useful in a spoofing situation).
+
 7 March 2008: Wouter
 	- -C config feature for harvest program. 
 	- harvest handles CNAMEs too.

iterator/iter_scrub.c

@@ -564,6 +564,14 @@ scrub_message(ldns_buffer* pkt, struct msg_parse* msg,
 	if( !(msg->flags&BIT_QR) )
 		return 0;
 	
+	/* make sure that a query is echoed back when NOERROR or NXDOMAIN */
+	/* this is not required for basic operation but is a forgery 
+	 * resistance (security) feature */
+	if((FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR ||
+		FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN) &&
+		msg->qdcount == 0)
+		return 0;
+
 	/* if a query is echoed back, make sure it is correct. Otherwise,
 	 * this may be not a reply to our query. */
 	if(msg->qdcount == 1) {

testdata/iter_req_qname.rpl

@@ -0,0 +1,91 @@
+; config options
+stub-zone:
+	name: "."
+	stub-addr: 193.0.14.129 	# K.ROOT-SERVERS.NET.
+CONFIG_END
+
+SCENARIO_BEGIN Test a query name in the reply is required by resolver
+
+; 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
+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.
+; always the same reply since we cannot match anything from the qsection.
+RANGE_BEGIN 0 100
+	ADDRESS 1.2.3.4
+ENTRY_BEGIN
+MATCH opcode
+ADJUST copy_id
+REPLY QR NOERROR
+SECTION QUESTION
+; no query section!
+; 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
+SECTION QUESTION
+www.example.com. IN A
+ENTRY_END
+
+; recursion happens here.
+
+; the query name is echoed properly to *our* client
+STEP 10 CHECK_ANSWER
+ENTRY_BEGIN
+MATCH all
+REPLY QR RD RA SERVFAIL
+SECTION QUESTION
+www.example.com. IN A
+ENTRY_END
+
+SCENARIO_END