add unit test for NULL SHAKE parameters

Author: rlm2002

tests/api/test_evp_digest.c

@@ -368,6 +368,22 @@ int test_wolfSSL_EVP_DigestFinalXOF(void)
     ExpectIntEQ(sz, 16);
     ExpectIntEQ(EVP_MD_CTX_cleanup(&mdCtx), WOLFSSL_SUCCESS);
     #endif
+
+    /* NULL size pointer on the non-XOF Final must not crash;
+     * defaults to 32 / 16 bytes for SHAKE256 / SHAKE128. */
+    wolfSSL_EVP_MD_CTX_init(&mdCtx);
+    ExpectIntEQ(EVP_DigestInit(&mdCtx, EVP_shake256()), WOLFSSL_SUCCESS);
+    ExpectIntEQ(EVP_DigestUpdate(&mdCtx, data, 1), WOLFSSL_SUCCESS);
+    ExpectIntEQ(EVP_DigestFinal(&mdCtx, shake, NULL), WOLFSSL_SUCCESS);
+    ExpectIntEQ(EVP_MD_CTX_cleanup(&mdCtx), WOLFSSL_SUCCESS);
+
+    #if defined(WOLFSSL_SHAKE128)
+    wolfSSL_EVP_MD_CTX_init(&mdCtx);
+    ExpectIntEQ(EVP_DigestInit(&mdCtx, EVP_shake128()), WOLFSSL_SUCCESS);
+    ExpectIntEQ(EVP_DigestUpdate(&mdCtx, data, 1), WOLFSSL_SUCCESS);
+    ExpectIntEQ(EVP_DigestFinal(&mdCtx, shake, NULL), WOLFSSL_SUCCESS);
+    ExpectIntEQ(EVP_MD_CTX_cleanup(&mdCtx), WOLFSSL_SUCCESS);
+    #endif
 #endif
     return EXPECT_RESULT();
 }