JCE: code review fixes, cleanup

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

@@ -237,6 +237,10 @@ public class WolfCryptKeyAgreement extends KeyAgreementSpi {
                 }
 
                 tmp = this.dh.makeSharedSecret(this.dh);
+                if (tmp == null) {
+                    throw new RuntimeException("Error when creating DH " +
+                            "shared secret");
+                }
                 
                 if ((sharedSecret.length - offset) < tmp.length) {
                     zeroArray(tmp);
@@ -256,6 +260,10 @@ public class WolfCryptKeyAgreement extends KeyAgreementSpi {
             case WC_ECDH:
 
                 tmp = this.ecPrivate.makeSharedSecret(this.ecPublic);
+                if (tmp == null) {
+                    throw new RuntimeException("Error when creating ECDH " +
+                            "shared secret");
+                }
 
                 if ((sharedSecret.length - offset) < tmp.length) {
                     zeroArray(tmp);

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

@@ -161,7 +161,7 @@ public class WolfCryptKeyPairGenerator extends KeyPairGeneratorSpi {
                         "Invalid parameters, either p or g is null");
                 }
 
-                if (debug.DEBUG)
+                if ((this.dhP != null) && debug.DEBUG)
                     log("init with spec, prime len: " + this.dhP.length);
 
                 break;

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

@@ -111,7 +111,11 @@ public class WolfCryptMac extends MacSpi {
         byte[] out = this.hmac.doFinal();
 
         if (debug.DEBUG)
+            if (out != null) {
                 log("final digest generated, len: " + out.length);
+            } else {
+                log("final digest was null");
+            }
 
         return out;
     }

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

@@ -433,8 +433,13 @@ public class WolfCryptSignature extends SignatureSpi {
         rng.free();
         rng.releaseNativeStruct();
 
-        if (debug.DEBUG)
+        if (debug.DEBUG) {
+            if (signature != null) {
                 log("generated signature, len: " + signature.length);
+            } else {
+                log("generated signature was null");
+            }
+        }
 
         return signature;
     }
@@ -560,9 +565,12 @@ public class WolfCryptSignature extends SignatureSpi {
                 break;
         }
 
-        if (debug.DEBUG)
+        if (debug.DEBUG) {
+            if (sigBytes != null) {
                 log("finished verify of sig len: " + sigBytes.length +
                     ", verified: " + verified);
+            }
+        }
 
         return verified;
     }