add DRBG reseed boundary test

Author: JeremiahM37

tests/api/test_random.c

@@ -94,6 +94,67 @@ int test_wc_RNG_GenerateBlock_Reseed(void)
     return EXPECT_RESULT();
 }
 
+int test_wc_RNG_ReseedBoundary(void)
+{
+    EXPECT_DECLS;
+#if defined(HAVE_HASHDRBG) && !defined(CUSTOM_RAND_GENERATE_BLOCK) && \
+    !defined(HAVE_FIPS) && !defined(HAVE_SELFTEST)
+    WC_RNG rng;
+    byte   out[32];
+    int    drbgChecked = 0;
+
+    XMEMSET(&rng, 0, sizeof(WC_RNG));
+    ExpectIntEQ(wc_InitRng(&rng), 0);
+
+#ifndef NO_SHA256
+    if (rng.drbgType == WC_DRBG_SHA256) {
+        struct DRBG_internal* drbg = (struct DRBG_internal*)rng.drbg;
+        if (drbg != NULL && rng.status == WC_DRBG_OK) {
+        #ifdef WORD64_AVAILABLE
+            word64 startCtr = drbg->reseedCtr;
+        #else
+            word32 startCtr = drbg->reseedCtr;
+        #endif
+            ExpectIntEQ(wc_RNG_GenerateBlock(&rng, out, sizeof(out)), 0);
+            if (drbg->reseedCtr == startCtr + 1) {
+                drbg->reseedCtr = WC_RESEED_INTERVAL - 1;
+                ExpectIntEQ(wc_RNG_GenerateBlock(&rng, out, sizeof(out)), 0);
+                ExpectTrue(drbg->reseedCtr == WC_RESEED_INTERVAL);
+                ExpectIntEQ(wc_RNG_GenerateBlock(&rng, out, sizeof(out)), 0);
+                ExpectTrue(drbg->reseedCtr == 2);
+                drbgChecked = 1;
+            }
+        }
+    }
+#endif
+#ifdef WOLFSSL_DRBG_SHA512
+    if (!drbgChecked && rng.drbgType == WC_DRBG_SHA512) {
+        struct DRBG_SHA512_internal* drbg =
+            (struct DRBG_SHA512_internal*)rng.drbg512;
+        if (drbg != NULL && rng.status == WC_DRBG_OK) {
+            word64 startCtr = drbg->reseedCtr;
+            ExpectIntEQ(wc_RNG_GenerateBlock(&rng, out, sizeof(out)), 0);
+            if (drbg->reseedCtr == startCtr + 1) {
+                drbg->reseedCtr = WC_RESEED_INTERVAL - 1;
+                ExpectIntEQ(wc_RNG_GenerateBlock(&rng, out, sizeof(out)), 0);
+                ExpectTrue(drbg->reseedCtr == WC_RESEED_INTERVAL);
+                ExpectIntEQ(wc_RNG_GenerateBlock(&rng, out, sizeof(out)), 0);
+                ExpectTrue(drbg->reseedCtr == 2);
+                drbgChecked = 1;
+            }
+        }
+    }
+#endif
+    /* Ensure the test actually exercised a DRBG; a silently-skipped body
+     * (e.g. due to an unrecognised drbgType) would otherwise pass with no
+     * coverage. */
+    ExpectIntEQ(drbgChecked, 1);
+
+    DoExpectIntEQ(wc_FreeRng(&rng), 0);
+#endif
+    return EXPECT_RESULT();
+}
+
 int test_wc_RNG_GenerateBlock(void)
 {
     EXPECT_DECLS;

tests/api/test_random.h

@@ -26,6 +26,7 @@
 
 int test_wc_InitRng(void);
 int test_wc_RNG_GenerateBlock_Reseed(void);
+int test_wc_RNG_ReseedBoundary(void);
 int test_wc_RNG_GenerateBlock(void);
 int test_wc_RNG_GenerateByte(void);
 int test_wc_InitRngNonce(void);
@@ -40,6 +41,7 @@ int test_wc_RNG_HealthTest_SHA512(void);
 #define TEST_RANDOM_DECLS                                           \
     TEST_DECL_GROUP("random", test_wc_InitRng),                     \
     TEST_DECL_GROUP("random", test_wc_RNG_GenerateBlock_Reseed),    \
+    TEST_DECL_GROUP("random", test_wc_RNG_ReseedBoundary),          \
     TEST_DECL_GROUP("random", test_wc_RNG_GenerateBlock),           \
     TEST_DECL_GROUP("random", test_wc_RNG_GenerateByte),            \
     TEST_DECL_GROUP("random", test_wc_InitRngNonce),                \