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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.
pull/8820/head
Sean Parkinson 2025-05-30 08:47:18 +10:00
parent 50471342b3
commit c724c6560d
1 changed files with 34 additions and 15 deletions
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49
wolfcrypt/src/random.c
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@ -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) {
@ -1258,7 +1269,7 @@ static int Entropy_HealthTest_Repetition(byte noise)
/* SP800-90b 4.4.2 - Adaptive Proportion Test
* Note 10
* C = 1 + CRITBINOM(W, power(2,( -H)),1-alpha)
* alpa = 2^-30 = POWER(2,-30), H = 1, W = 512
* alpha = 2^-30 = POWER(2,-30), H = 1, W = 512
* C = 1 + CRITBINOM(512, 0.5, 1-POWER(2,-30)) = 1 + 324 = 325
*/
#define PROP_CUTOFF 325
@ -1308,8 +1319,9 @@ static int Entropy_HealthTest_Proportion(byte noise)
{
int ret = 0;
/* Need at least 512-1 samples to test with. */
if (prop_total < PROP_WINDOW_SIZE - 1) {
/* Need minimum samples in queue to test with - keep adding while we have
* less. */
if (prop_total < PROP_CUTOFF - 1) {
/* Store sample at last position in circular queue. */
prop_samples[prop_last++] = noise;
/* Update count of seen value based on new sample. */
@ -1318,27 +1330,32 @@ static int Entropy_HealthTest_Proportion(byte noise)
prop_total++;
}
else {
/* Get first value in queue - value to test. */
byte val = (byte)prop_samples[prop_first];
/* Store new sample in queue. */
/* We have at least a minimum set of samples in queue. */
/* Store new sample at end of 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. */
if (prop_cnt[val] >= PROP_CUTOFF) {
/* Check whether first value has too many repetitions in queue. */
if (prop_cnt[noise] >= PROP_CUTOFF) {
#ifdef WOLFSSL_DEBUG_ENTROPY_MEMUSE
fprintf(stderr, "PROPORTION FAILED: %d %d\n", val, prop_cnt[val]);
fprintf(stderr, "PROPORTION FAILED: %d %d\n", val, prop_cnt[noise]);
#endif
Entropy_HealthTest_Proportion_Reset();
/* Error code returned. */
ret = ENTROPY_APT_E;
}
else if (prop_total == PROP_WINDOW_SIZE) {
/* Return to 511 samples in queue. */
/* Get first value in queue - value to test. */
byte val = (byte)prop_samples[prop_first];
/* 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;
@ -1371,6 +1388,10 @@ static int Entropy_HealthTest_Startup(void)
#ifdef WOLFSSL_DEBUG_ENTROPY_MEMUSE
fprintf(stderr, "STARTUP HEALTH TEST\n");
#endif
/* Reset cached values before testing. */
Entropy_HealthTest_Reset();
/* Fill initial sample buffer with noise. */
Entropy_GetNoise(initial, ENTROPY_INITIAL_COUNT);
/* Health check initial noise. */
@ -1537,8 +1558,6 @@ int wc_Entropy_OnDemandTest(void)
}
if (ret == 0) {
/* Reset health test state for startup test. */
Entropy_HealthTest_Reset();
/* Perform startup tests. */
ret = Entropy_HealthTest_Startup();
}