File bind-9.16.27-0001-CVE-2021-25220.patch of Package bind.29534

Index: bind-9.16.6/lib/dns/resolver.c
===================================================================
--- bind-9.16.6.orig/lib/dns/resolver.c
+++ bind-9.16.6/lib/dns/resolver.c
@@ -62,6 +62,8 @@
 #include <dns/stats.h>
 #include <dns/tsig.h>
 #include <dns/validator.h>
+#include <dns/zone.h>
+
 #ifdef WANT_QUERYTRACE
 #define RTRACE(m)                                                             \
 	isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,                     \
@@ -334,6 +336,8 @@ struct fetchctx {
 	dns_fetch_t *qminfetch;
 	dns_rdataset_t qminrrset;
 	dns_name_t qmindcname;
+	dns_fixedname_t fwdfname;
+	dns_name_t *fwdname;
 
 	/*%
 	 * The number of events we're waiting for.
@@ -3708,6 +3712,7 @@ fctx_getaddresses(fetchctx_t *fctx, bool
 		if (result == ISC_R_SUCCESS) {
 			fwd = ISC_LIST_HEAD(forwarders->fwdrs);
 			fctx->fwdpolicy = forwarders->fwdpolicy;
+			dns_name_copynf(domain, fctx->fwdname);
 			if (fctx->fwdpolicy == dns_fwdpolicy_only &&
 			    isstrictsubdomain(domain, &fctx->domain))
 			{
@@ -5004,6 +5009,9 @@ fctx_create(dns_resolver_t *res, const d
 	fctx->restarts = 0;
 	fctx->querysent = 0;
 	fctx->referrals = 0;
+
+	fctx->fwdname = dns_fixedname_initname(&fctx->fwdfname);
+
 	TIME_NOW(&fctx->start);
 	fctx->timeouts = 0;
 	fctx->lamecount = 0;
@@ -5065,6 +5073,7 @@ fctx_create(dns_resolver_t *res, const d
 					   fname, &forwarders);
 		if (result == ISC_R_SUCCESS) {
 			fctx->fwdpolicy = forwarders->fwdpolicy;
+			dns_name_copynf(fname, fctx->fwdname);
 		}
 
 		if (fctx->fwdpolicy != dns_fwdpolicy_only) {
@@ -6914,6 +6923,107 @@ mark_related(dns_name_t *name, dns_rdata
 	}
 }
 
+/*
+ * Returns true if 'name' is external to the namespace for which
+ * the server being queried can answer, either because it's not a
+ * subdomain or because it's below a forward declaration or a
+ * locally served zone.
+ */
+static inline bool
+name_external(const dns_name_t *name, dns_rdatatype_t type, fetchctx_t *fctx) {
+       isc_result_t result;
+       dns_forwarders_t *forwarders = NULL;
+       dns_fixedname_t fixed, zfixed;
+       dns_name_t *fname = dns_fixedname_initname(&fixed);
+       dns_name_t *zfname = dns_fixedname_initname(&zfixed);
+       dns_name_t *apex = NULL;
+       dns_name_t suffix;
+       dns_zone_t *zone = NULL;
+       unsigned int labels;
+       dns_namereln_t rel;
+
+       apex = ISFORWARDER(fctx->addrinfo) ? fctx->fwdname : &fctx->domain;
+
+       /*
+        * The name is outside the queried namespace.
+        */
+       rel = dns_name_fullcompare(name, apex, &(int){ 0 },
+                                  &(unsigned int){ 0U });
+       if (rel != dns_namereln_subdomain && rel != dns_namereln_equal) {
+               return (true);
+       }
+
+       /*
+        * If the record lives in the parent zone, adjust the name so we
+        * look for the correct zone or forward clause.
+        */
+       labels = dns_name_countlabels(name);
+       if (dns_rdatatype_atparent(type) && labels > 1U) {
+               dns_name_init(&suffix, NULL);
+               dns_name_getlabelsequence(name, 1, labels - 1, &suffix);
+               name = &suffix;
+       } else if (rel == dns_namereln_equal) {
+               /* If 'name' is 'apex', no further checking is needed. */
+               return (false);
+       }
+
+       /*
+        * If there is a locally served zone between 'apex' and 'name'
+        * then don't cache.
+        */
+       LOCK(&fctx->res->view->lock);
+       if (fctx->res->view->zonetable != NULL) {
+               unsigned int options = DNS_ZTFIND_NOEXACT | DNS_ZTFIND_MIRROR;
+               result = dns_zt_find(fctx->res->view->zonetable, name, options,
+                                    zfname, &zone);
+               if (zone != NULL) {
+                       dns_zone_detach(&zone);
+               }
+               if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
+                       if (dns_name_fullcompare(zfname, apex, &(int){ 0 },
+                                                &(unsigned int){ 0U }) ==
+                           dns_namereln_subdomain)
+                       {
+                               UNLOCK(&fctx->res->view->lock);
+                               return (true);
+                       }
+               }
+       }
+       UNLOCK(&fctx->res->view->lock);
+
+       /*
+        * Look for a forward declaration below 'name'.
+        */
+       result = dns_fwdtable_find(fctx->res->view->fwdtable, name, fname,
+                                  &forwarders);
+
+       if (ISFORWARDER(fctx->addrinfo)) {
+               /*
+                * See if the forwarder declaration is better.
+                */
+               if (result == ISC_R_SUCCESS) {
+                       return (!dns_name_equal(fname, fctx->fwdname));
+               }
+
+               /*
+                * If the lookup failed, the configuration must have
+                * changed: play it safe and don't cache.
+                */
+               return (true);
+       } else if (result == ISC_R_SUCCESS &&
+                  forwarders->fwdpolicy == dns_fwdpolicy_only &&
+                  !ISC_LIST_EMPTY(forwarders->fwdrs))
+       {
+               /*
+                * If 'name' is covered by a 'forward only' clause then we
+                * can't cache this repsonse.
+                */
+               return (true);
+       }
+
+       return (false);
+}
+
 static isc_result_t
 check_section(void *arg, const dns_name_t *addname, dns_rdatatype_t type,
 	      dns_section_t section) {
@@ -6939,7 +7049,7 @@ check_section(void *arg, const dns_name_
 	result = dns_message_findname(fctx->rmessage, section, addname,
 				      dns_rdatatype_any, 0, &name, NULL);
 	if (result == ISC_R_SUCCESS) {
-		external = !dns_name_issubdomain(name, &fctx->domain);
+		external = name_external(name, type, fctx);
 		if (type == dns_rdatatype_a) {
 			for (rdataset = ISC_LIST_HEAD(name->list);
 			     rdataset != NULL;
@@ -8518,6 +8628,13 @@ rctx_answer_scan(respctx_t *rctx) {
 
 		case dns_namereln_subdomain:
 			/*
+			* Don't accept DNAME from parent namespace.
+			*/
+			if (name_external(name, dns_rdatatype_dname, fctx)) {
+				continue;
+			}
+
+			/*
 			 * In-scope DNAME records must have at least
 			 * as many labels as the domain being queried.
 			 * They also must be less that qname's labels
@@ -8829,13 +8946,11 @@ rctx_authority_positive(respctx_t *rctx)
 	result = dns_message_firstname(fctx->rmessage, DNS_SECTION_AUTHORITY);
 	while (!done && result == ISC_R_SUCCESS) {
 		dns_name_t *name = NULL;
-		bool external;
 
 		dns_message_currentname(fctx->rmessage, DNS_SECTION_AUTHORITY,
 					&name);
-		external = !dns_name_issubdomain(name, &fctx->domain);
 
-		if (!external) {
+		if (!name_external(name, dns_rdatatype_ns, fctx)) {
 			dns_rdataset_t *rdataset = NULL;
 
 			/*
@@ -9219,7 +9334,10 @@ rctx_authority_dnssec(respctx_t *rctx) {
 		}
 
 		if (!dns_name_issubdomain(name, &fctx->domain)) {
-			/* Invalid name found; preserve it for logging later */
+			/*
+			 * Invalid name found; preserve it for logging
+			 * later.
+			 */
 			rctx->found_name = name;
 			rctx->found_type = ISC_LIST_HEAD(name->list)->type;
 			continue;
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