From f38a321e64e700407554c2aa55f26d97b6f349d9 Mon Sep 17 00:00:00 2001
From: Takashi Kojo <kojo@wolfsssl.com>
Date: Wed, 22 Nov 2017 06:53:52 +0900
Subject: [PATCH] HMAC_Init_ex with NULL key to recover Hmac initial state

---
 src/ssl.c              | 14 ++++++++++----
 wolfssl/openssl/hmac.h |  2 ++
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/ssl.c b/src/ssl.c
index bd6c131ba..d713fb323 100644
--- a/src/ssl.c
+++ b/src/ssl.c
@@ -24645,7 +24645,7 @@ int wolfSSL_HMAC_CTX_Init(WOLFSSL_HMAC_CTX* ctx)
 int wolfSSL_HMAC_Init_ex(WOLFSSL_HMAC_CTX* ctx, const void* key,
                              int keylen, const EVP_MD* type, WOLFSSL_ENGINE* e)
 {
-    WOLFSSL_ENTER("wolfSSL_HMAC_Init_ex()");
+    WOLFSSL_ENTER("wolfSSL_HMAC_Init_ex");
 
     /* WOLFSSL_ENGINE not used, call wolfSSL_HMAC_Init */
     (void)e;
@@ -24805,10 +24805,16 @@ int wolfSSL_HMAC_Init(WOLFSSL_HMAC_CTX* ctx, const void* key, int keylen,
                 wc_HmacFree(&ctx->hmac);
                 return WOLFSSL_FAILURE;
             }
+            XMEMCPY((byte *)&ctx->save_key, (const byte*)key, (word32)keylen);
+            ctx->save_len = keylen;
+        }
+        /* OpenSSL compat, no error */
+    } else if(ctx->type) {
+        WOLFSSL_MSG("recover hmac");
+        if (wc_HmacInit(&ctx->hmac, NULL, INVALID_DEVID) == 0) {
+            wc_HmacSetKey(&ctx->hmac, ctx->type, (byte *)&ctx->save_key,
+                                                        (word32)ctx->save_len);
         }
-    } else {
-        WOLFSSL_MSG("no key or keylen");
-        return WOLFSSL_FAILURE;
     }
 
     return WOLFSSL_SUCCESS;
diff --git a/wolfssl/openssl/hmac.h b/wolfssl/openssl/hmac.h
index d78cfda59..37a78d154 100644
--- a/wolfssl/openssl/hmac.h
+++ b/wolfssl/openssl/hmac.h
@@ -53,6 +53,8 @@ WOLFSSL_API unsigned char* wolfSSL_HMAC(const WOLFSSL_EVP_MD* evp_md,
 typedef struct WOLFSSL_HMAC_CTX {
     Hmac hmac;
     int  type;
+    byte save_key[HMAC_BLOCK_SIZE]; /* save initial hmac after wc_HmacSetKey */
+    word32 save_len;
 } WOLFSSL_HMAC_CTX;