Crypto: refactor the Cipher class.

Include the hmac in the cipher class.
Derive keys on class creation instead of on encrypt/decrypt.

app/src/main/java/com/etesync/syncadapter/journalmanager/BaseManager.java

@@ -1,5 +1,8 @@
 package com.etesync.syncadapter.journalmanager;
 
+import com.etesync.syncadapter.App;
+import com.etesync.syncadapter.GsonHelper;
+
 import org.apache.commons.codec.Charsets;
 
 import java.io.ByteArrayOutputStream;
@@ -7,9 +10,6 @@ import java.io.IOException;
 import java.net.HttpURLConnection;
 import java.util.logging.Level;
 
-import com.etesync.syncadapter.App;
-import com.etesync.syncadapter.GsonHelper;
-
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.Setter;
@@ -19,8 +19,6 @@ import okhttp3.OkHttpClient;
 import okhttp3.Request;
 import okhttp3.Response;
 
-import static com.etesync.syncadapter.journalmanager.Crypto.hmac;
-
 abstract class BaseManager {
     final static protected MediaType JSON = MediaType.parse("application/json; charset=utf-8");
 
@@ -77,12 +75,14 @@ abstract class BaseManager {
 
         public String getContent(String keyBase64) {
             // FIXME: probably cache encryption object
-            return new String(new Crypto.Cipher().decrypt(keyBase64, content), Charsets.UTF_8);
+            Crypto.Cipher cipher = new Crypto.Cipher(keyBase64, null);
+            return new String(cipher.decrypt(content), Charsets.UTF_8);
         }
 
         void setContent(String keyBase64, String content) {
             // FIXME: probably cache encryption object
-            this.content = new Crypto.Cipher().encrypt(keyBase64, content.getBytes(Charsets.UTF_8));
+            Crypto.Cipher cipher = new Crypto.Cipher(keyBase64, null);
+            this.content = cipher.encrypt(content.getBytes(Charsets.UTF_8));
         }
 
         byte[] calculateHmac(String keyBase64, String uuid) {
@@ -99,7 +99,9 @@ abstract class BaseManager {
                 return "DEADBEEFDEADBEEFDEADBEEFDEADBEEF".getBytes();
             }
 
-            return hmac(keyBase64, hashContent.toByteArray());
+            // FIXME: probably cache encryption object
+            Crypto.Cipher cipher = new Crypto.Cipher(keyBase64, null);
+            return cipher.hmac(hashContent.toByteArray());
         }
 
         protected Base() {

app/src/main/java/com/etesync/syncadapter/journalmanager/Crypto.java

@@ -31,32 +31,22 @@ public class Crypto {
         return Base64.encodeToString(SCrypt.generate(password.getBytes(Charsets.UTF_8), salt.getBytes(Charsets.UTF_8), 16384, 8, 1, keySize), Base64.NO_WRAP);
     }
 
-    private static byte[] hmac256(byte[] keyByte, byte[] data) {
-        HMac hmac = new HMac(new SHA256Digest());
-        KeyParameter key = new KeyParameter(keyByte);
-        byte[] ret = new byte[hmac.getMacSize()];
-        hmac.init(key);
-        hmac.update(data, 0, data.length);
-        hmac.doFinal(ret, 0);
-        return ret;
-    }
-
-    static byte[] hmac(String keyBase64, byte[] data) {
-        byte[] derivedKey = hmac256("hmac".getBytes(Charsets.UTF_8), Base64.decode(keyBase64, Base64.NO_WRAP));
-        return hmac256(derivedKey, data);
-    }
-
     static class Cipher {
         private SecureRandom _random = null;
-
-        Cipher() {
+        private final byte[] cipherKey;
+        private final byte[] hmacKey;
+
+        Cipher(String keyBase64, String salt) {
+            byte[] derivedKey; // FIXME use salt = hmac256(salt.getBytes(Charsets.UTF_8), Base64.decode(keyBase64, Base64.NO_WRAP));
+            derivedKey = Base64.decode(keyBase64, Base64.NO_WRAP);
+            cipherKey = hmac256("aes".getBytes(Charsets.UTF_8), derivedKey);
+            hmacKey = hmac256("hmac".getBytes(Charsets.UTF_8), derivedKey);
         }
 
         private static final int blockSize = 16; // AES's block size in bytes
 
-        private BufferedBlockCipher getCipher(String keyBase64, byte[] iv, boolean encrypt) {
-            byte[] derivedKey = hmac256("aes".getBytes(Charsets.UTF_8), Base64.decode(keyBase64, Base64.NO_WRAP));
-            KeyParameter key = new KeyParameter(derivedKey);
+        private BufferedBlockCipher getCipher(byte[] iv, boolean encrypt) {
+            KeyParameter key = new KeyParameter(cipherKey);
             CipherParameters params = new ParametersWithIV(key, iv);
 
             BlockCipherPadding padding = new PKCS7Padding();
@@ -68,11 +58,11 @@ public class Crypto {
             return cipher;
         }
 
-        byte[] decrypt(String keyBase64, byte[] _data) {
+        byte[] decrypt(byte[] _data) {
             byte[] iv = Arrays.copyOfRange(_data, 0, blockSize);
             byte[] data = Arrays.copyOfRange(_data, blockSize, _data.length);
 
-            BufferedBlockCipher cipher = getCipher(keyBase64, iv, false);
+            BufferedBlockCipher cipher = getCipher(iv, false);
 
             byte[] buf = new byte[cipher.getOutputSize(data.length)];
             int len = cipher.processBytes(data, 0, data.length, buf, 0);
@@ -91,11 +81,11 @@ public class Crypto {
             return out;
         }
 
-        byte[] encrypt(String keyBase64, byte[] data) {
+        byte[] encrypt(byte[] data) {
             byte[] iv = new byte[blockSize];
             getRandom().nextBytes(iv);
 
-            BufferedBlockCipher cipher = getCipher(keyBase64, iv, true);
+            BufferedBlockCipher cipher = getCipher(iv, true);
 
             byte[] buf = new byte[cipher.getOutputSize(data.length) + blockSize];
             System.arraycopy(iv, 0, buf, 0, iv.length);
@@ -111,12 +101,26 @@ public class Crypto {
             return buf;
         }
 
+        byte[] hmac(byte[] data) {
+            return hmac256(hmacKey, data);
+        }
+
         private SecureRandom getRandom() {
             if (_random == null) {
                 _random = new SecureRandom();
             }
             return _random;
         }
+
+        private static byte[] hmac256(byte[] keyByte, byte[] data) {
+            HMac hmac = new HMac(new SHA256Digest());
+            KeyParameter key = new KeyParameter(keyByte);
+            byte[] ret = new byte[hmac.getMacSize()];
+            hmac.init(key);
+            hmac.update(data, 0, data.length);
+            hmac.doFinal(ret, 0);
+            return ret;
+        }
     }
 
     static String sha256(String base) {