File 0667-crypto-hmac_low_level-only-call-HMAC-once-not-twice.patch of Package erlang

From 289fa8314a865695af31aa6a44dd0e42f7a034ec Mon Sep 17 00:00:00 2001
From: Mikael Pettersson <mikael.pettersson@klarna.com>
Date: Thu, 19 Nov 2020 13:07:12 +0100
Subject: [PATCH 3/4] crypto: hmac_low_level(): only call HMAC() once, not
 twice

This reinstates logic from the removed hmac_nif().
---
 lib/crypto/c_src/hmac.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/lib/crypto/c_src/hmac.c b/lib/crypto/c_src/hmac.c
index 193902c481..3ea7c1f5dc 100644
--- a/lib/crypto/c_src/hmac.c
+++ b/lib/crypto/c_src/hmac.c
@@ -233,18 +233,19 @@ int hmac_low_level(ErlNifEnv* env, const EVP_MD *md,
 {
     unsigned int size_int;
     size_t size;
+    unsigned char buff[EVP_MAX_MD_SIZE];
 
-    /* Find the needed space */
     if (HMAC(md,
              key_bin.data, (int)key_bin.size,
              text.data, text.size,
-             NULL, &size_int) == NULL)
+             buff, &size_int) == NULL)
         {
-            *return_term = EXCP_ERROR(env, "Get HMAC size failed");
+            *return_term = EXCP_ERROR(env, "HMAC sign failed");
             return 0;
         }
 
     size = (size_t)size_int; /* Otherwise "size" is unused in 0.9.8.... */
+    ASSERT(0 < size && size <= EVP_MAX_MD_SIZE);
     if (!enif_alloc_binary(size, ret_bin))
         {
             *return_term = EXCP_ERROR(env, "Alloc binary");
@@ -252,15 +253,7 @@ int hmac_low_level(ErlNifEnv* env, const EVP_MD *md,
         }
     *ret_bin_alloc = 1;
 
-    /* And do the real HMAC calc */
-    if (HMAC(md,
-             key_bin.data, (int)key_bin.size,
-             text.data, text.size,
-             ret_bin->data, &size_int) == NULL)
-        {
-            *return_term = EXCP_ERROR(env, "HMAC sign failed");
-            return 0;
-        }
+    memcpy(ret_bin->data, buff, size);
                     
     return 1;
 }
-- 
2.26.2