wolfSSL
Entropy - fix off by ones in continuous testing
Description
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.
Testing
./configure --disable-shared --enable-entropy-memuse
Checklist
- [ ] added tests
- [ ] updated/added doxygen
- [ ] updated appropriate READMEs
- [ ] Updated manual and documentation
@SparkiDev can you rebase this on master please so you get the updates to the workflow file? There are known issues with Ubuntu mirrors at the moment so the following has been added to the workflow file to update the repositories list after VM creation. Unfortunately your PR workflow file is missing the updates:
LATEST:
37 - name: install_multilib
38 run: |
39 export DEBIAN_FRONTEND=noninteractive
40 sudo apt-get update
41 sudo apt-get install -y gcc-multilib
Your branch:
37 - name: install_multilib
38 run: sudo apt-get install -y gcc-multilib
I did notice a new behavior with this update, one now has to call wolfCrypt_Init() two times, once to "prime the entropy source" and then a second time to get a successful init. The first call seems to fail 100% of the time with ENTROPY_APT_E = -295, /* Entropy Adaptive Proportion Test failed */ at least on the system I am using to gather noise samples.
Do we want to look into that more or is that expected?
Since we're making a change anyway, now might be a good time to address that longer initial time slice we were seeing during startup sequences due the SHA3-256 Conditional Algorithm Self Test (CAST) on initial priming of the entropy pool, here is a tentitive patch to address that if you care to include it (no obligation):
diff --git a/wolfcrypt/src/random.c b/wolfcrypt/src/random.c
index 822f069f7..650945fc4 100644
--- a/wolfcrypt/src/random.c
+++ b/wolfcrypt/src/random.c
@@ -1086,7 +1086,15 @@ static word64 Entropy_GetSample(void)
word64 now;
word64 ret;
+ /* If zero we know this is the very first call */
+ if (entropy_last_time == 0) {
+ Entropy_MemUse(); /* do INITIAL work to trigger the CAST in FIPS mode */
+ entropy_last_time = Entropy_TimeHiRes(); /* Exclude CAST time from first
+ * sample */
+ }
+
/* Use memory such that it will take an unpredictable amount of time. */
+ /* All other times just do 'the work' */
Entropy_MemUse();