PBKDF2 computation speedup (15-40%)

This commit contains some optimizations in PKCS5_PBKDF2_HMAC() and
HMAC_CTX_copy() functions which together makes PBKDF2 computations
faster by 15-40% according to my measurements made on x64 Linux with
both asm optimized and no-asm versions of SHA1, SHA256 and SHA512.

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1708)

1 files changed, 14 insertions, 9 deletions

diff --git a/crypto/hmac/hmac.c b/crypto/hmac/hmac.c
index ffca891db1..3952dd50ad 100644
--- a/crypto/hmac/hmac.c
+++ b/crypto/hmac/hmac.c
@@ -157,31 +157,36 @@ void HMAC_CTX_free(HMAC_CTX *ctx)
     }
 }
 
-int HMAC_CTX_reset(HMAC_CTX *ctx)
+static int hmac_ctx_alloc_mds(HMAC_CTX *ctx)
 {
-    hmac_ctx_cleanup(ctx);
     if (ctx->i_ctx == NULL)
         ctx->i_ctx = EVP_MD_CTX_new();
     if (ctx->i_ctx == NULL)
-        goto err;
+        return 0;
     if (ctx->o_ctx == NULL)
         ctx->o_ctx = EVP_MD_CTX_new();
     if (ctx->o_ctx == NULL)
-        goto err;
+        return 0;
     if (ctx->md_ctx == NULL)
         ctx->md_ctx = EVP_MD_CTX_new();
     if (ctx->md_ctx == NULL)
-        goto err;
-    ctx->md = NULL;
+        return 0;
     return 1;
- err:
+}
+
+int HMAC_CTX_reset(HMAC_CTX *ctx)
+{
     hmac_ctx_cleanup(ctx);
-    return 0;
+    if (!hmac_ctx_alloc_mds(ctx)) {
+        hmac_ctx_cleanup(ctx);
+        return 0;
+    }
+    return 1;
 }
 
 int HMAC_CTX_copy(HMAC_CTX *dctx, HMAC_CTX *sctx)
 {
-    if (!HMAC_CTX_reset(dctx))
+    if (!hmac_ctx_alloc_mds(dctx))
         goto err;
     if (!EVP_MD_CTX_copy_ex(dctx->i_ctx, sctx->i_ctx))
         goto err;