From 8e09649351e9e8143b4bd0b76bcbd2cfb4d2f281 Mon Sep 17 00:00:00 2001
From: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Date: Fri, 21 Aug 2020 17:23:17 +1200
Subject: [PATCH] CVE-2020-14383: s4/dns: do not crash when additional data not
 found
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Found by Francis Brosnan Blázquez <francis@aspl.es>.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14472
BUG: https://bugzilla.samba.org/show_bug.cgi?id=12795

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Jeremy Allison <jra@samba.org>

Autobuild-User(master): Douglas Bagnall <dbagnall@samba.org>
Autobuild-Date(master): Mon Aug 24 00:21:41 UTC 2020 on sn-devel-184

(based on commit df98e7db04c901259dd089e20cd557bdbdeaf379)
---
 source4/rpc_server/dnsserver/dcerpc_dnsserver.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/source4/rpc_server/dnsserver/dcerpc_dnsserver.c b/source4/rpc_server/dnsserver/dcerpc_dnsserver.c
index ec610168266..88efc01f154 100644
--- a/source4/rpc_server/dnsserver/dcerpc_dnsserver.c
+++ b/source4/rpc_server/dnsserver/dcerpc_dnsserver.c
@@ -1859,8 +1859,8 @@ static WERROR dnsserver_enumerate_records(struct dnsserver_state *dsstate,
 	/* Add any additional records */
 	if (select_flag & DNS_RPC_VIEW_ADDITIONAL_DATA) {
 		for (i=0; i<add_count; i++) {
-			struct dnsserver_zone *z2;
-
+			struct dnsserver_zone *z2 = NULL;
+			struct ldb_message *msg = NULL;
 			/* Search all the available zones for additional name */
 			for (z2 = dsstate->zones; z2; z2 = z2->next) {
 				char *encoded_name;
@@ -1877,6 +1877,7 @@ static WERROR dnsserver_enumerate_records(struct dnsserver_state *dsstate,
 					continue;
 				}
 				if (res->count == 1) {
+					msg = res->msgs[0];
 					break;
 				} else {
 					TALLOC_FREE(res);
@@ -1892,7 +1893,7 @@ static WERROR dnsserver_enumerate_records(struct dnsserver_state *dsstate,
 			}
 			status = dns_fill_records_array(tmp_ctx, NULL, DNS_TYPE_A,
 							select_flag, rname,
-							res->msgs[0], 0, recs,
+							msg, 0, recs,
 							NULL, NULL);
 			TALLOC_FREE(rname);
 			TALLOC_FREE(res);
-- 
2.29.2