From cc917b541f353c71353a826568d4becdf8d66293 Mon Sep 17 00:00:00 2001
From: Jakub Jelen <jjelen@redhat.com>
Date: Thu, 7 Nov 2019 13:45:24 +0100
Subject: [PATCH] asn1: Avoid calling malloc with 0 argument

Caused problems reported by oss-fuzz

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=18758
---
 src/libopensc/asn1.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/libopensc/asn1.c b/src/libopensc/asn1.c
index 4e95fe78..299de5b2 100644
--- a/src/libopensc/asn1.c
+++ b/src/libopensc/asn1.c
@@ -1500,10 +1500,12 @@ static int asn1_decode_entry(sc_context_t *ctx,struct sc_asn1_entry *entry,
 			/* Allocate buffer if needed */
 			if (entry->flags & SC_ASN1_ALLOC) {
 				u8 **buf = (u8 **) parm;
-				*buf = malloc(objlen);
-				if (*buf == NULL) {
-					r = SC_ERROR_OUT_OF_MEMORY;
-					break;
+				if (objlen > 0) {
+					*buf = malloc(objlen);
+					if (*buf == NULL) {
+						r = SC_ERROR_OUT_OF_MEMORY;
+						break;
+					}
 				}
 				c = *len = objlen;
 				parm = *buf;