8293779: redundant checking in AESCrypt.makeSessionKey() method

Reviewed-by: djelinski, hchao, mullan

Author: XueleiFan

src/java.base/share/classes/com/sun/crypto/provider/AESCrypt.java

@@ -86,9 +86,9 @@ void init(boolean decrypting, String algorithm, byte[] key)
             throw new InvalidKeyException
                 ("Wrong algorithm: AES or Rijndael required");
         }
-        if (!isKeySizeValid(key.length)) {
-            throw new InvalidKeyException("Invalid AES key length: " +
-                key.length + " bytes");
+
+        if (key == null) {      // Unlikely, but just double check it.
+            throw new InvalidKeyException("Empty key");
         }
 
         if (!MessageDigest.isEqual(key, lastKey)) {
@@ -602,13 +602,11 @@ private void implDecryptBlock(byte[] in, int inOffset,
      * @exception InvalidKeyException  If the key is invalid.
      */
     private void makeSessionKey(byte[] k) throws InvalidKeyException {
-        if (k == null) {
-            throw new InvalidKeyException("Empty key");
-        }
         if (!isKeySizeValid(k.length)) {
-             throw new InvalidKeyException("Invalid AES key length: " +
-                                           k.length + " bytes");
+            throw new InvalidKeyException("Invalid AES key length: " +
+                    k.length + " bytes");
         }
+
         int ROUNDS          = getRounds(k.length);
         int ROUND_KEY_COUNT = (ROUNDS + 1) * 4;
 
@@ -696,7 +694,6 @@ private void makeSessionKey(byte[] k) throws InvalidKeyException {
         sessionK = new int[][] { expandedKe, expandedKd };
     }
 
-
     /**
      * Return The number of rounds for a given Rijndael keysize.
      *