4260. [security] Insufficient testing when parsing a message allowed

records with an incorrect class to be be accepted,
                        triggering a REQUIRE failure when those records
                        were subsequently cached. (CVE-2015-8000) [RT #4098]

(cherry picked from commit c8821d124c)

CHANGES

@@ -1,3 +1,8 @@
+4260.	[security]	Insufficient testing when parsing a message allowed
+			records with an incorrect class to be be accepted,
+			triggering a REQUIRE failure when those records
+			were subsequently cached. (CVE-2015-8000) [RT #4098]
+
 4258.	[bug]		Limit rndc query message sizes to 32 KiB. This should
 			not break any legitimate rndc commands, but will
 			prevent a rogue rndc query from allocating too

bin/tests/system/start.pl

@@ -68,6 +68,7 @@ my $NAMED = $ENV{'NAMED'};
 my $LWRESD = $ENV{'LWRESD'};
 my $DIG = $ENV{'DIG'};
 my $PERL = $ENV{'PERL'};
+my $PYTHON = $ENV{'PYTHON'};
 
 # Start the server(s)
 
@@ -226,7 +227,9 @@ sub start_server {
 		$pid_file = "lwresd.pid";
 	} elsif ($server =~ /^ans/) {
 		$cleanup_files = "{ans.run}";
-                if (-e "$testdir/$server/ans.pl") {
+                if (-e "$testdir/$server/ans.py") {
+                        $command = "$PYTHON ans.py 10.53.0.$' 5300";
+                } elsif (-e "$testdir/$server/ans.pl") {
                         $command = "$PERL ans.pl";
                 } else {
                         $command = "$PERL $topdir/ans.pl 10.53.0.$'";

doc/arm/notes.xml

@@ -40,6 +40,15 @@
   <section xml:id="relnotes_security"><info><title>Security Fixes</title></info>
 
     <itemizedlist>
+      <listitem>
+	<para>
+	  Insufficient testing when parsing a message allowed
+	  records with an incorrect class to be be accepted,
+	  triggering a REQUIRE failure when those records
+	  were subsequently cached.  This flaw is disclosed
+	  in CVE-2015-8000. [RT #4098]
+	</para>
+      </listitem>
       <listitem>
 	<para>
 	  An incorrect boundary check in the OPENPGPKEY rdatatype

lib/dns/include/dns/message.h

@@ -15,8 +15,6 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id$ */
-
 #ifndef DNS_MESSAGE_H
 #define DNS_MESSAGE_H 1
 
@@ -216,6 +214,8 @@ struct dns_message {
 	unsigned int			verify_attempted : 1;
 	unsigned int			free_query : 1;
 	unsigned int			free_saved : 1;
+	unsigned int			tkey : 1;
+	unsigned int			rdclass_set : 1;
 
 	unsigned int			opt_reserved;
 	unsigned int			sig_reserved;
@@ -1380,6 +1380,15 @@ dns_message_buildopt(dns_message_t *msg, dns_rdataset_t **opt,
  * \li	 other.
  */
 
+void
+dns_message_setclass(dns_message_t *msg, dns_rdataclass_t rdclass);
+/*%<
+ * Set the expected class of records in the response.
+ *
+ * Requires:
+ * \li   msg be a valid message with parsing intent.
+ */
+
 ISC_LANG_ENDDECLS
 
 #endif /* DNS_MESSAGE_H */

lib/dns/message.c

@@ -438,6 +438,8 @@ msginit(dns_message_t *m) {
 	m->saved.base = NULL;
 	m->saved.length = 0;
 	m->free_saved = 0;
+	m->tkey = 0;
+	m->rdclass_set = 0;
 	m->querytsig = NULL;
 }
 
@@ -1088,12 +1090,18 @@ getquestions(isc_buffer_t *source, dns_message_t *msg, dns_decompress_t *dctx,
 		 * If this class is different than the one we already read,
 		 * this is an error.
 		 */
-		if (msg->state == DNS_SECTION_ANY) {
-			msg->state = DNS_SECTION_QUESTION;
+		if (msg->rdclass_set == 0) {
 			msg->rdclass = rdclass;
+			msg->rdclass_set = 1;
 		} else if (msg->rdclass != rdclass)
 			DO_FORMERR;
 
+		/*
+		 * Is this a TKEY query?
+		 */
+		if (rdtype == dns_rdatatype_tkey)
+			msg->tkey = 1;
+
 		/*
 		 * Can't ask the same question twice.
 		 */
@@ -1238,12 +1246,12 @@ getsection(isc_buffer_t *source, dns_message_t *msg, dns_decompress_t *dctx,
 		 * If there was no question section, we may not yet have
 		 * established a class.  Do so now.
 		 */
-		if (msg->state == DNS_SECTION_ANY &&
+		if (msg->rdclass_set == 0 &&
 		    rdtype != dns_rdatatype_opt &&	/* class is UDP SIZE */
 		    rdtype != dns_rdatatype_tsig &&	/* class is ANY */
 		    rdtype != dns_rdatatype_tkey) {	/* class is undefined */
 			msg->rdclass = rdclass;
-			msg->state = DNS_SECTION_QUESTION;
+			msg->rdclass_set = 1;
 		}
 
 		/*
@@ -1253,13 +1261,23 @@ getsection(isc_buffer_t *source, dns_message_t *msg, dns_decompress_t *dctx,
 		if (msg->opcode != dns_opcode_update
 		    && rdtype != dns_rdatatype_tsig
 		    && rdtype != dns_rdatatype_opt
-		    && rdtype != dns_rdatatype_dnskey /* in a TKEY query */
+		    && rdtype != dns_rdatatype_key /* in a TKEY query */
 		    && rdtype != dns_rdatatype_sig /* SIG(0) */
 		    && rdtype != dns_rdatatype_tkey /* Win2000 TKEY */
 		    && msg->rdclass != dns_rdataclass_any
 		    && msg->rdclass != rdclass)
 			DO_FORMERR;
 
+		/*
+		 * If this is not a TKEY query/response then the KEY
+		 * record's class needs to match.
+		 */
+		if (msg->opcode != dns_opcode_update && !msg->tkey &&
+		    rdtype == dns_rdatatype_key &&
+		    msg->rdclass != dns_rdataclass_any &&
+		    msg->rdclass != rdclass)
+			DO_FORMERR;
+
 		/*
 		 * Special type handling for TSIG, OPT, and TKEY.
 		 */
@@ -1375,6 +1393,10 @@ getsection(isc_buffer_t *source, dns_message_t *msg, dns_decompress_t *dctx,
 				skip_name_search = ISC_TRUE;
 				skip_type_search = ISC_TRUE;
 				issigzero = ISC_TRUE;
+			} else {
+				if (msg->rdclass != dns_rdataclass_any &&
+				    msg->rdclass != rdclass)
+					DO_FORMERR;
 			}
 		} else
 			covers = 0;
@@ -1619,6 +1641,7 @@ dns_message_parse(dns_message_t *msg, isc_buffer_t *source,
 	msg->counts[DNS_SECTION_ADDITIONAL] = isc_buffer_getuint16(source);
 
 	msg->header_ok = 1;
+	msg->state = DNS_SECTION_QUESTION;
 
 	/*
 	 * -1 means no EDNS.
@@ -3608,3 +3631,15 @@ dns_message_buildopt(dns_message_t *message, dns_rdataset_t **rdatasetp,
 		dns_message_puttemprdatalist(message, &rdatalist);
 	return (result);
 }
+
+void
+dns_message_setclass(dns_message_t *msg, dns_rdataclass_t rdclass) {
+
+	REQUIRE(DNS_MESSAGE_VALID(msg));
+	REQUIRE(msg->from_to_wire == DNS_MESSAGE_INTENTPARSE);
+	REQUIRE(msg->state == DNS_SECTION_ANY);
+	REQUIRE(msg->rdclass_set == 0);
+
+	msg->rdclass = rdclass;
+	msg->rdclass_set = 1;
+}

lib/dns/resolver.c

@@ -7403,8 +7403,11 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
 		}
 	}
 
+	dns_message_setclass(message, res->rdclass);
+
 	if ((options & DNS_FETCHOPT_TCP) == 0)
 		dns_adb_plainresponse(fctx->adb, query->addrinfo);
+
 	result = dns_message_parse(message, &devent->buffer, 0);
 	if (result != ISC_R_SUCCESS) {
 		FCTXTRACE3("message failed to parse", result);
@@ -7477,6 +7480,12 @@ resquery_response(isc_task_t *task, isc_event_t *event) {
 	 */
 	log_packet(message, ISC_LOG_DEBUG(10), res->mctx);
 
+	if (message->rdclass != res->rdclass) {
+		resend = ISC_TRUE;
+		FCTXTRACE("bad class");
+		goto done;
+	}
+
 	/*
 	 * Process receive opt record.
 	 */

lib/dns/xfrin.c

@@ -1221,6 +1221,8 @@ xfrin_recv_done(isc_task_t *task, isc_event_t *ev) {
 	msg->tsigctx = xfr->tsigctx;
 	xfr->tsigctx = NULL;
 
+	dns_message_setclass(msg, xfr->rdclass);
+
 	if (xfr->nmsg > 0)
 		msg->tcp_continuation = 1;