From fba89ae034c9cc4a85f9d8e24f78033fde940895 Mon Sep 17 00:00:00 2001
From: John Safranek <john@wolfssl.com>
Date: Thu, 20 Jun 2019 11:43:29 -0700
Subject: [PATCH] Random Cleanup 1. Remove redundant calls to the generate
 function when instantiating and reseeding the DRBG. 2. Added note to the
 apparently redundant extra call to the generate function when running the
 self test. This extra call is there to make sure the internal state is
 updating correctly as a part of the KAT. 3. Removed duplicate enable argument
 clause for rng from configure.ac.

---
 configure.ac           | 14 +-------------
 wolfcrypt/src/random.c | 10 +++++-----
 2 files changed, 6 insertions(+), 18 deletions(-)

diff --git a/configure.ac b/configure.ac
index 652f5dc88..d67f1ba4d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -380,6 +380,7 @@ then
 fi
 
 
+# RNG
 AC_ARG_ENABLE([rng],
     [AS_HELP_STRING([--enable-rng],[Enable compiling and using RNG (default: enabled)])],
     [ ENABLED_RNG=$enableval ],
@@ -420,19 +421,6 @@ AC_ARG_ENABLE([mcast],
     [ENABLED_MCAST=no])
 
 
-# RNG
-AC_ARG_ENABLE([rng],
-    [AS_HELP_STRING([--enable-rng],[Enable compiling and using RNG (default: enabled)])],
-    [ ENABLED_RNG=$enableval ],
-    [ ENABLED_RNG=yes ]
-    )
-
-if test "$ENABLED_RNG" = "no"
-then
-    AM_CFLAGS="$AM_CFLAGS -DWC_NO_RNG"
-fi
-
-
 # List of open source project defines using our openssl compatibility layer:
 # openssh (--enable-openssh)
 # nginix (--enable-nginx) WOLFSSL_NGINX
diff --git a/wolfcrypt/src/random.c b/wolfcrypt/src/random.c
index 4903ac9ea..8ccdd3de7 100644
--- a/wolfcrypt/src/random.c
+++ b/wolfcrypt/src/random.c
@@ -780,9 +780,6 @@ static int _InitRng(WC_RNG* rng, byte* nonce, word32 nonceSz,
                             seed + SEED_BLOCK_SZ, seedSz - SEED_BLOCK_SZ,
                             nonce, nonceSz, rng->heap, devId);
 
-            if (ret == DRBG_SUCCESS)
-                ret = Hash_DRBG_Generate(rng->drbg, NULL, 0);
-
             if (ret != DRBG_SUCCESS) {
             #if !defined(WOLFSSL_NO_MALLOC) || defined(WOLFSSL_STATIC_MEMORY)
                 XFREE(rng->drbg, rng->heap, DYNAMIC_TYPE_RNG);
@@ -908,8 +905,6 @@ int wc_RNG_GenerateBlock(WC_RNG* rng, byte* output, word32 sz)
             if (ret == DRBG_SUCCESS)
                 ret = Hash_DRBG_Reseed(rng->drbg, newSeed + SEED_BLOCK_SZ,
                                        SEED_SZ);
-            if (ret == DRBG_SUCCESS)
-                ret = Hash_DRBG_Generate(rng->drbg, NULL, 0);
             if (ret == DRBG_SUCCESS)
                 ret = Hash_DRBG_Generate(rng->drbg, output, sz);
 
@@ -1032,6 +1027,11 @@ int wc_RNG_HealthTest_ex(int reseed, const byte* nonce, word32 nonceSz,
         }
     }
 
+    /* This call to generate is prescribed by the NIST DRBGVS
+     * procedure. The results are thrown away. The known
+     * answer test checks the second block of DRBG out of
+     * the generator to ensure the internal state is updated
+     * as expected. */
     if (Hash_DRBG_Generate(drbg, output, outputSz) != 0) {
         goto exit_rng_ht;
     }