Move cipher logic out of backup and restore components

app/src/main/java/com/stevesoltys/backup/security/CipherUtil.java

@@ -0,0 +1,57 @@
+package com.stevesoltys.backup.security;
+
+import javax.crypto.*;
+import javax.crypto.spec.IvParameterSpec;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.spec.InvalidKeySpecException;
+
+/**
+ * A utility class for encrypting and decrypting data using a {@link Cipher}.
+ *
+ * @author Steve Soltys
+ */
+public class CipherUtil {
+
+    /**
+     * The cipher algorithm.
+     */
+    public static final String CIPHER_ALGORITHM = "AES/CFB/PKCS5Padding";
+
+    /**
+     * Encrypts the given payload using a key generated from the provided password and salt.
+     *
+     * @param payload  The payload.
+     * @param password The password.
+     * @param salt     The salt.
+     */
+    public static byte[] encrypt(byte[] payload, String password, byte[] salt) throws NoSuchPaddingException,
+            NoSuchAlgorithmException, InvalidKeySpecException, BadPaddingException, IllegalBlockSizeException,
+            InvalidAlgorithmParameterException, InvalidKeyException {
+
+        SecretKey secretKey = KeyGenerator.generate(password, salt);
+        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
+        cipher.init(Cipher.ENCRYPT_MODE, secretKey, new IvParameterSpec(salt));
+
+        return cipher.doFinal(payload);
+    }
+
+    /**
+     * Decrypts the given payload using a key generated from the provided password and salt.
+     *
+     * @param payload  The payload.
+     * @param password The password.
+     * @param salt     The salt.
+     */
+    public static byte[] decrypt(byte[] payload, String password, byte[] salt) throws NoSuchPaddingException,
+            NoSuchAlgorithmException, InvalidKeySpecException, BadPaddingException, IllegalBlockSizeException,
+            InvalidAlgorithmParameterException, InvalidKeyException {
+
+        SecretKey secretKey = KeyGenerator.generate(password, salt);
+        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
+        cipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(salt));
+
+        return cipher.doFinal(payload);
+    }
+}

app/src/main/java/com/stevesoltys/backup/transport/component/provider/ContentProviderBackupComponent.java

@@ -6,19 +6,15 @@ import android.content.pm.PackageInfo;
 import android.os.ParcelFileDescriptor;
 import android.util.Base64;
 import android.util.Log;
-import com.stevesoltys.backup.security.KeyGenerator;
+import com.stevesoltys.backup.security.CipherUtil;
 import com.stevesoltys.backup.transport.component.BackupComponent;
 import libcore.io.IoUtils;
 import org.apache.commons.io.IOUtils;
 
-import javax.crypto.Cipher;
-import javax.crypto.SecretKey;
-import javax.crypto.spec.IvParameterSpec;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipOutputStream;
@@ -262,14 +258,12 @@ public class ContentProviderBackupComponent implements BackupComponent {
 
                 try {
                     if (configuration.getPassword() != null && !configuration.getPassword().isEmpty()) {
-                        SecretKey secretKey = KeyGenerator.generate(configuration.getPassword(), backupState.getSalt());
-
-                        Cipher cipher = Cipher.getInstance(ContentProviderBackupConstants.CIPHER_ALGORITHM);
-                        cipher.init(Cipher.ENCRYPT_MODE, secretKey, new IvParameterSpec(backupState.getSalt()));
 
                         byte[] payload = Arrays.copyOfRange(buffer, 0, dataSize);
-                        byte[] encryptedBuffer = cipher.doFinal(payload);
+                        String password = configuration.getPassword();
-                        outputStream.write(encryptedBuffer);
+                        byte[] salt = backupState.getSalt();
+
+                        outputStream.write(CipherUtil.encrypt(payload, password, salt));
 
                     } else {
                         outputStream.write(buffer, 0, dataSize);

app/src/main/java/com/stevesoltys/backup/transport/component/provider/ContentProviderBackupConstants.java

@@ -3,9 +3,7 @@ package com.stevesoltys.backup.transport.component.provider;
 /**
  * @author Steve Soltys
  */
-public class ContentProviderBackupConstants {
+class ContentProviderBackupConstants {
-
-    static final String CIPHER_ALGORITHM = "AES/CFB/PKCS5Padding";
 
     static final String SALT_FILE_PATH = "salt";
 }

app/src/main/java/com/stevesoltys/backup/transport/component/provider/ContentProviderRestoreComponent.java

@@ -9,6 +9,7 @@ import android.os.ParcelFileDescriptor;
 import android.util.Base64;
 import android.util.Log;
 import com.android.internal.util.Preconditions;
+import com.stevesoltys.backup.security.CipherUtil;
 import com.stevesoltys.backup.security.KeyGenerator;
 import com.stevesoltys.backup.transport.component.RestoreComponent;
 import libcore.io.IoUtils;
@@ -179,14 +180,11 @@ public class ContentProviderRestoreComponent implements RestoreComponent {
     private byte[] readBackupData(ZipInputStream inputStream) throws Exception {
         byte[] backupData = Streams.readFullyNoClose(inputStream);
 
-        if (configuration.getPassword() != null && !configuration.getPassword().isEmpty() &&
+        String password = configuration.getPassword();
-                restoreState.getSalt() != null) {
+        byte[] salt = restoreState.getSalt();
 
-            SecretKey secretKey = KeyGenerator.generate(configuration.getPassword(), restoreState.getSalt());
+        if (password != null && !password.isEmpty() && salt != null) {
-
+            backupData = CipherUtil.decrypt(backupData, password, salt);
-            Cipher cipher = Cipher.getInstance(ContentProviderBackupConstants.CIPHER_ALGORITHM);
-            cipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(restoreState.getSalt()));
-            backupData = cipher.doFinal(backupData);
         }
 
         return backupData;