Ensure that both the MD and key have been initialised before attempting to

create an HMAC

Inspired by BoringSSL commit 2fe7f2d0d9a6fcc75b4e594eeec306cc55acd594
Reviewed-by: NRichard Levitte <levitte@openssl.org>

crypto/hmac/hmac.c

@@ -71,8 +71,14 @@ int HMAC_Init_ex(HMAC_CTX *ctx, const void *key, int len,
     if (md != NULL) {
         reset = 1;
         ctx->md = md;
-    } else
+    } else if(ctx->md) {
         md = ctx->md;
+    } else {
+        return 0;
+    }
+
+    if(!ctx->key_init && key == NULL)
+        return 0;
 
     if (key != NULL) {
         reset = 1;
@@ -94,6 +100,7 @@ int HMAC_Init_ex(HMAC_CTX *ctx, const void *key, int len,
         if (ctx->key_length != HMAC_MAX_MD_CBLOCK)
             memset(&ctx->key[ctx->key_length], 0,
                    HMAC_MAX_MD_CBLOCK - ctx->key_length);
+        ctx->key_init = 1;
     }
 
     if (reset) {
@@ -129,6 +136,8 @@ int HMAC_Init(HMAC_CTX *ctx, const void *key, int len, const EVP_MD *md)
 
 int HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, size_t len)
 {
+    if(!ctx->key_init)
+        return 0;
     return EVP_DigestUpdate(&ctx->md_ctx, data, len);
 }
 
@@ -137,6 +146,9 @@ int HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len)
     unsigned int i;
     unsigned char buf[EVP_MAX_MD_SIZE];
 
+    if(!ctx->key_init)
+        goto err;
+
     if (!EVP_DigestFinal_ex(&ctx->md_ctx, buf, &i))
         goto err;
     if (!EVP_MD_CTX_copy_ex(&ctx->md_ctx, &ctx->o_ctx))
@@ -155,6 +167,8 @@ void HMAC_CTX_init(HMAC_CTX *ctx)
     EVP_MD_CTX_init(&ctx->i_ctx);
     EVP_MD_CTX_init(&ctx->o_ctx);
     EVP_MD_CTX_init(&ctx->md_ctx);
+    ctx->key_init = 0;
+    ctx->md = NULL;
 }
 
 int HMAC_CTX_copy(HMAC_CTX *dctx, HMAC_CTX *sctx)
@@ -166,8 +180,11 @@ int HMAC_CTX_copy(HMAC_CTX *dctx, HMAC_CTX *sctx)
         goto err;
     if (!EVP_MD_CTX_copy_ex(&dctx->md_ctx, &sctx->md_ctx))
         goto err;
-    memcpy(dctx->key, sctx->key, HMAC_MAX_MD_CBLOCK);
-    dctx->key_length = sctx->key_length;
+    dctx->key_init = sctx->key_init;
+    if(sctx->key_init) {
+        memcpy(dctx->key, sctx->key, HMAC_MAX_MD_CBLOCK);
+        dctx->key_length = sctx->key_length;
+    }
     dctx->md = sctx->md;
     return 1;
  err:

crypto/hmac/hmac.h

@@ -75,6 +75,7 @@ typedef struct hmac_ctx_st {
     EVP_MD_CTX o_ctx;
     unsigned int key_length;
     unsigned char key[HMAC_MAX_MD_CBLOCK];
+    int key_init;
 } HMAC_CTX;
 
 # define HMAC_size(e)    (EVP_MD_size((e)->md))