From: Mark Andrews <marka@isc.org>
Date: Wed, 15 Jul 2020 16:07:51 +1000
Subject: Always keep a copy of the message

Origin: https://gitlab.isc.org/isc-projects/bind9/commit/6ed167ad0a647dff20c8cb08c944a7967df2d415
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2020-8622

this allows it to be available even when dns_message_parse()
returns a error.
---
 lib/dns/message.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/lib/dns/message.c b/lib/dns/message.c
index ac637a2..39ed80f 100644
--- a/lib/dns/message.c
+++ b/lib/dns/message.c
@@ -1679,6 +1679,19 @@ dns_message_parse(dns_message_t *msg, isc_buffer_t *source,
 	msg->header_ok = 0;
 	msg->question_ok = 0;
 
+	if ((options & DNS_MESSAGEPARSE_CLONEBUFFER) == 0) {
+		isc_buffer_usedregion(&origsource, &msg->saved);
+	} else {
+		msg->saved.length = isc_buffer_usedlength(&origsource);
+		msg->saved.base = isc_mem_get(msg->mctx, msg->saved.length);
+		if (msg->saved.base == NULL) {
+			return (ISC_R_NOMEMORY);
+		}
+		memmove(msg->saved.base, isc_buffer_base(&origsource),
+			msg->saved.length);
+		msg->free_saved = 1;
+	}
+
 	isc_buffer_remainingregion(source, &r);
 	if (r.length < DNS_MESSAGE_HEADERLEN)
 		return (ISC_R_UNEXPECTEDEND);
@@ -1754,17 +1767,6 @@ dns_message_parse(dns_message_t *msg, isc_buffer_t *source,
 	}
 
  truncated:
-	if ((options & DNS_MESSAGEPARSE_CLONEBUFFER) == 0)
-		isc_buffer_usedregion(&origsource, &msg->saved);
-	else {
-		msg->saved.length = isc_buffer_usedlength(&origsource);
-		msg->saved.base = isc_mem_get(msg->mctx, msg->saved.length);
-		if (msg->saved.base == NULL)
-			return (ISC_R_NOMEMORY);
-		memmove(msg->saved.base, isc_buffer_base(&origsource),
-			msg->saved.length);
-		msg->free_saved = 1;
-	}
 
 	if (ret == ISC_R_UNEXPECTEDEND && ignore_tc)
 		return (DNS_R_RECOVERABLE);