From ed9abf94b3167a1a61b5da163e9b07b06c8a457b Mon Sep 17 00:00:00 2001
From: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Date: Sun, 6 Sep 2020 09:35:49 +1200
Subject: [PATCH] utils/asn1: avoid undefined behaviour warning

UBSAN does not like an int >= 1<<24 being shifted left.
We check the overflow in the very next line.

Credit to OSS-Fuzz.

REF: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=25436

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Fri Sep 11 05:05:59 UTC 2020 on sn-devel-184
---
 lib/util/asn1.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/util/asn1.c b/lib/util/asn1.c
index 6b1b4bc2877f..9ab9e1b08449 100644
--- a/lib/util/asn1.c
+++ b/lib/util/asn1.c
@@ -1071,7 +1071,11 @@ bool asn1_read_enumerated(struct asn1_data *data, int *v)
 		if (!asn1_read_uint8(data, &b)) {
 			return false;
 		}
-		*v = (*v << 8) + b;
+		/*
+		 * To please/fool the Undefined Behaviour Sanitizer we cast to
+		 * unsigned for the left shift.
+		 */
+		*v = ((unsigned int)*v << 8) + b;
 	}
 	return asn1_end_tag(data);
 }