From f5016d88dd5a9c651162c137ecade04da72a4705 Mon Sep 17 00:00:00 2001
From: Steffen Jaeckel <s@jaeckel.eu>
Date: Wed, 16 Sep 2015 23:51:57 +0200
Subject: [PATCH] Prevent undefined behavior

Don't call XMEMCPY() in case info (the source parameter to memcpy) is NULL
as this would trigger UB
---
 src/misc/hkdf/hkdf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/misc/hkdf/hkdf.c b/src/misc/hkdf/hkdf.c
index b6f24a0..3682bf8 100644
--- a/src/misc/hkdf/hkdf.c
+++ b/src/misc/hkdf/hkdf.c
@@ -61,7 +61,9 @@ int hkdf_expand(int hash_idx, const unsigned char *info, unsigned long infolen,
    if (T == NULL) {
       return CRYPT_MEM;
    }
-   XMEMCPY(T + hashsize, info, infolen);
+   if (info != NULL) {
+      XMEMCPY(T + hashsize, info, infolen);
+   }
 
    /* HMAC data T(1) doesn't include a previous hash value */
    dat    = T    + hashsize;