From 4e1b719236f9a10dce836591bf37d360f752c57a Mon Sep 17 00:00:00 2001
From: David Garske <david@wolfssl.com>
Date: Fri, 14 Nov 2025 09:40:56 -0800
Subject: [PATCH] Improve wc_HmacUpdate to return early if input length == 0.
 Fixes QAT issue with HKDF test.

---
 wolfcrypt/src/hmac.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/wolfcrypt/src/hmac.c b/wolfcrypt/src/hmac.c
index caf7e142a..e7e23387f 100644
--- a/wolfcrypt/src/hmac.c
+++ b/wolfcrypt/src/hmac.c
@@ -814,6 +814,9 @@ int wc_HmacUpdate(Hmac* hmac, const byte* msg, word32 length)
     if (hmac == NULL || (msg == NULL && length > 0)) {
         return BAD_FUNC_ARG;
     }
+    if (length == 0) {
+        return 0; /* nothing to do, return success */
+    }
 
 #ifdef WOLF_CRYPTO_CB
     if (hmac->devId != INVALID_DEVID) {