Add toString() to WolfCryptRandom, init fixes for serialization

src/main/java/com/wolfssl/provider/jce/WolfCryptRandom.java

@@ -44,10 +44,7 @@ public final class WolfCryptRandom extends SecureRandomSpi {
      * Create new WolfCryptRandom object
      */
     public WolfCryptRandom() {
-
-        this.rng = new Rng();
-        this.rng.init();
-
+        checkRngInitialized();
         log("initialized new object");
     }
 
@@ -69,19 +66,45 @@ protected synchronized byte[] engineGenerateSeed(int numBytes)
                 Rng.RNG_MAX_BLOCK_LEN);
         }
 
+        checkRngInitialized();
+
         return rng.generateBlock(numBytes);
     }
 
     @Override
     protected synchronized void engineNextBytes(byte[] bytes) {
 
+        if (bytes == null) {
+            throw new NullPointerException("Input byte[] should not be null");
+        }
+
+        checkRngInitialized();
+
         rng.generateBlock(bytes);
     }
 
     @Override
     protected synchronized void engineSetSeed(byte[] seed) {
+
+        if (seed == null) {
+            throw new NullPointerException("Input seed[] should not be null");
+        }
+
         /* wolfCrypt reseeds internally automatically */
         log("setSeed() not supported by wolfJCE");
+
+    }
+
+    /**
+     * Initialize the RNG if needed (null). This handles cases where the object
+     * was created through deserialization, reflection, etc. and the
+     * constructor was not called.
+     */
+    private void checkRngInitialized() {
+        if (this.rng == null) {
+            this.rng = new Rng();
+            this.rng.init();
+        }
     }
 
     private void log(String msg) {
@@ -138,12 +161,25 @@ private synchronized void writeObject(ObjectOutputStream out)
     private synchronized void readObject(ObjectInputStream in)
         throws IOException, ClassNotFoundException {
 
-        if (rng == null) {
-            this.rng = new Rng();
-            this.rng.init();
-        }
-
         in.defaultReadObject();
+
+        checkRngInitialized();
+    }
+
+    @Override
+    public String toString() {
+        /* Native wolfCrypt DRBG details:
+         *     Hash_DRBG = DRBG implementation
+         *     SHA-256 = hash function used in Hash_DRBG implementation
+         *     128 = security strength in bits
+         *     reseed_only = NIST implementation default, prediction resistance
+         *     not enabled for every generate call, only when explicitly
+         *     reseeded.
+         *
+         * This output format matches other JCE providers, some callers
+         * may expect this format.
+         */
+        return "Hash_DRBG,SHA-256,128,reseed_only";
     }
 }
 

src/test/java/com/wolfssl/provider/jce/test/WolfCryptRandomTest.java

@@ -36,6 +36,12 @@
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.LinkedBlockingQueue;
 
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+
 import java.security.Security;
 import java.security.Provider;
 import java.security.SecureRandom;
@@ -345,5 +351,92 @@ public void testGenerateSeedWithZeroArgument()
         assertNotNull(seed);
         assertEquals(0, seed.length);
     }
+
+    @Test
+    public void testSerializationDeserialization()
+        throws NoSuchProviderException, NoSuchAlgorithmException,
+               IOException, ClassNotFoundException {
+
+        /* Create original SecureRandom instance */
+        SecureRandom orig = SecureRandom.getInstance("HashDRBG", "wolfJCE");
+        assertNotNull(orig);
+
+        /* Serialize the SecureRandom instance */
+        byte[] serialized = serialize(orig);
+        assertNotNull(serialized);
+        assertTrue(serialized.length > 0);
+
+        /* Deserialize the SecureRandom instance */
+        SecureRandom copy = deserialize(serialized);
+        assertNotNull(copy);
+
+        /* Test that both original and deserialized instances can generate
+         * random numbers without throwing NullPointerException.
+         * This test would fail without the lazy loading fix in
+         * WolfCryptRandom.engineNextBytes() and engineGenerateSeed() */
+        byte[] origBytes = new byte[32];
+        byte[] copyBytes = new byte[32];
+
+        /* This should not throw NullPointerException */
+        orig.nextBytes(origBytes);
+        copy.nextBytes(copyBytes);
+
+        /* Also test generateSeed() to ensure it works after deserialization */
+        byte[] origSeed = orig.generateSeed(16);
+        byte[] copySeed = copy.generateSeed(16);
+
+        assertNotNull(origSeed);
+        assertNotNull(copySeed);
+        assertEquals(16, origSeed.length);
+        assertEquals(16, copySeed.length);
+
+        /* Verify we got actual random data */
+        assertNotNull(origBytes);
+        assertNotNull(copyBytes);
+        assertEquals(32, origBytes.length);
+        assertEquals(32, copyBytes.length);
+
+        /* Random bytes should not be all zeros */
+        boolean origHasNonZero = false;
+        boolean copyHasNonZero = false;
+        for (int i = 0; i < 32; i++) {
+            if (origBytes[i] != 0) {
+                origHasNonZero = true;
+            }
+            if (copyBytes[i] != 0) {
+                copyHasNonZero = true;
+            }
+        }
+        assertTrue("Original random bytes should not be all zeros",
+            origHasNonZero);
+        assertTrue("Deserialized random bytes should not be all zeros",
+            copyHasNonZero);
+
+        /* The two instances should generate different random sequences */
+        assertFalse("Original and deserialized instances should generate " +
+            "different random sequences", Arrays.equals(origBytes, copyBytes));
+    }
+
+    /*
+     * Serialize a SecureRandom object to byte array
+     */
+    private byte[] serialize(SecureRandom sr) throws IOException {
+        try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
+             ObjectOutputStream oos = new ObjectOutputStream(bos)) {
+            oos.writeObject(sr);
+            return bos.toByteArray();
+        }
+    }
+
+    /*
+     * Deserialize a SecureRandom object from byte array
+     */
+    private SecureRandom deserialize(byte[] serialized)
+        throws IOException, ClassNotFoundException {
+        try (ByteArrayInputStream bis = new ByteArrayInputStream(serialized);
+             ObjectInputStream ois = new ObjectInputStream(bis)) {
+            return (SecureRandom) ois.readObject();
+        }
+    }
 }