Entropy - fix off by ones in continuous testing

rep_cnt is count of contiguous bytes with same value.
First ever sample must set count to 1.

Wasn't filling the cache up completely.
Off by one in check for initial fill.

Author: SparkiDev

wolfcrypt/src/random.c

@@ -1124,6 +1124,16 @@ static word64 Entropy_GetSample(void)
     word64 now;
     word64 ret;
 
+#ifdef HAVE_FIPS
+    /* First sample must be disregard when in FIPS. */
+    if (entropy_last_time == 0) {
+        /* Get sample which triggers CAST in FIPS mode. */
+        Entropy_MemUse();
+        /* Start entropy time after CASTs. */
+        entropy_last_time = Entropy_TimeHiRes();
+    }
+#endif
+
     /* Use memory such that it will take an unpredictable amount of time. */
     Entropy_MemUse();
 
@@ -1225,6 +1235,7 @@ static int Entropy_HealthTest_Repetition(byte noise)
     if (!rep_have_prev) {
         rep_prev_noise = noise;
         rep_have_prev = 1;
+        rep_cnt = 1;
     }
     /* Check whether this sample matches last. */
     else if (noise == rep_prev_noise) {
@@ -1308,7 +1319,8 @@ static int Entropy_HealthTest_Proportion(byte noise)
 {
     int ret = 0;
 
-    /* Need at least 512-1 samples to test with. */
+    /* Need 511 samples in queue to test with - keep adding while we have less.
+     */
     if (prop_total < PROP_WINDOW_SIZE - 1) {
         /* Store sample at last position in circular queue. */
         prop_samples[prop_last++] = noise;
@@ -1318,19 +1330,18 @@ static int Entropy_HealthTest_Proportion(byte noise)
         prop_total++;
     }
     else {
+        /* We have 511 samples in queue. */
         /* Get first value in queue - value to test. */
         byte val = (byte)prop_samples[prop_first];
-        /* Store new sample in queue. */
+
+        /* Store new sample at end of queue - 512 samples in queue. */
         prop_samples[prop_last] = noise;
-        /* Update first index now that we have removed in from the queue. */
-        prop_first = (prop_first + 1) % PROP_WINDOW_SIZE;
         /* Update last index now that we have added new sample to queue. */
         prop_last = (prop_last + 1) % PROP_WINDOW_SIZE;
-        /* Removed sample from queue - remove count. */
-        prop_cnt[val]--;
         /* Added sample to queue - add count. */
         prop_cnt[noise]++;
-        /* Check whether removed value has too many repetitions in queue. */
+
+        /* Check whether first value has too many repetitions in queue. */
         if (prop_cnt[val] >= PROP_CUTOFF) {
         #ifdef WOLFSSL_DEBUG_ENTROPY_MEMUSE
             fprintf(stderr, "PROPORTION FAILED: %d %d\n", val, prop_cnt[val]);
@@ -1339,6 +1350,13 @@ static int Entropy_HealthTest_Proportion(byte noise)
             /* Error code returned. */
             ret = ENTROPY_APT_E;
         }
+        else {
+            /* Return to 511 samples in queue. */
+            /* Update first index to remove first sample from the queue. */
+            prop_first = (prop_first + 1) % PROP_WINDOW_SIZE;
+            /* Removed first sample from queue - remove count. */
+            prop_cnt[val]--;
+        }
     }
 
     return ret;