安全性：將javax.mail.Message寫入帶加密的文件

Question

我有一個應該寫入文件系統的'javax.mail.Message'對象。我使用版本爲1.5.5的javax.mail（com.sun.mail）

javax.mail.Message message = buildMessage(...); 
message.writeTo(new FileOutputStream("message.plain")); 

現在將消息寫入文件。但是我怎麼能加密&解密這個文件？我在下面發表我的例子，但是這段代碼失敗了。

我的示例代碼：

static byte[] salt = new byte[8]; 
static { 
    SecureRandom random = new SecureRandom(); 
    random.nextBytes(salt); 
} 

public final void test() throws Exception { 
    Message message = buildTestMessage(...); 

    SecretKey secret = encode(message, new FileOutputStream("test.encrypted"), "".toCharArray()); 
    Message message2 = decode(new FileInputStream("test.encrypted"), "".toCharArray()); 

    // out sth. like from@domain <--> null 
    System.out.println(message.getFrom()[0] + " <--> " + message2.getFrom()); 

} 

private Message decode(
     InputStream mailFileInputStream, char[] password) throws NoSuchAlgorithmException, NoSuchPaddingException, 
     InvalidKeyException, MessagingException, IOException, InvalidKeySpecException { 
    /* Derive the key, given password and salt. */ 
    SecretKeyFactory factory = SecretKeyFactory.getInstance("PBEWithHmacSHA256AndAES_128"); 
    KeySpec spec = new PBEKeySpec(password, salt, 65536, 256); 
    SecretKey tmp = factory.generateSecret(spec); 
    SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "PBEWithHmacSHA256AndAES_128"); 

    Cipher cipher = Cipher.getInstance("PBEWithHmacSHA256AndAES_128"); 
    cipher.init(Cipher.DECRYPT_MODE, secret);  

    InputStream is = new CipherInputStream(mailFileInputStream, cipher); 
    Properties props = new Properties(); 
    Session session = Session.getDefaultInstance(props, null); 

    Message message = new MimeMessage(session, is); 
    return message; 
} 

static SecretKey encode(
     Message message, 
     FileOutputStream out, 
     char[] password) throws Exception { 

    /* Derive the key, given password and salt. */ 
    SecretKeyFactory factory = SecretKeyFactory.getInstance("PBEWithHmacSHA256AndAES_128"); 
    KeySpec spec = new PBEKeySpec(password, salt, 65536, 256); 
    SecretKey tmp = factory.generateSecret(spec); 
    SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "PBEWithHmacSHA256AndAES_128"); 

    Cipher cipher = Cipher.getInstance("PBEWithHmacSHA256AndAES_128"); 
    cipher.init(Cipher.ENCRYPT_MODE, secret); 

    OutputStream cos = new CipherOutputStream(out, cipher); 
    message.writeTo(cos); 
    cos.close(); 

    return secret; 
} 

附加：給予好評，我的問題，我紀念你的答案被接受。我有一個問題禁令，沒有任何問題留在我的問題上或沒有留意！

Answer 1

import java.io.ByteArrayInputStream; 
import java.io.ByteArrayOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.security.InvalidAlgorithmParameterException; 
import java.security.InvalidKeyException; 
import java.security.NoSuchAlgorithmException; 
import java.security.SecureRandom; 
import java.security.spec.InvalidKeySpecException; 
import java.security.spec.KeySpec; 
import java.util.Base64; 
import java.util.Date; 
import java.util.Optional; 

import javax.crypto.BadPaddingException; 
import javax.crypto.Cipher; 
import javax.crypto.IllegalBlockSizeException; 
import javax.crypto.NoSuchPaddingException; 
import javax.crypto.SecretKey; 
import javax.crypto.SecretKeyFactory; 
import javax.crypto.spec.IvParameterSpec; 
import javax.crypto.spec.PBEKeySpec; 
import javax.crypto.spec.SecretKeySpec; 
import javax.mail.Message; 
import javax.mail.MessagingException; 
import javax.mail.Multipart; 
import javax.mail.Session; 
import javax.mail.internet.InternetAddress; 
import javax.mail.internet.MimeBodyPart; 
import javax.mail.internet.MimeMessage; 
import javax.mail.internet.MimeMultipart; 

public class Stackoverflow { 

    private static final int keySize = 128; 
    static byte[] saltForThisRun = new byte[8]; 
    static { 
     SecureRandom random = new SecureRandom(); 
     random.nextBytes(saltForThisRun); 
    } 

    public static void main(
      String[] args) throws Exception { 
     Message message = buildTestMessage("from@null.org", new String[] { "to@null.org", "to2@null.org" }, 
       "Subject is needed here", Optional.of("This is just a text"), Optional.empty()); 

     char[] password = "password".toCharArray(); 
     String encryptedMsg = encrypt(password, saltForThisRun, message); 
     System.out.println("encryptedMsg: " + encryptedMsg); 
     Message message2 = decrypt(password, saltForThisRun, encryptedMsg); 

     // out sth. like from@domain <--> null 
     System.out.println(message.getFrom()[0] + " <--> " + message2.getFrom()[0]); 

    } 

    private static Message decrypt(
      char[] password, 
      byte[] salt, 
      String base64CipherText) throws EncryptionException { 
     try { 
      SecretKey secretKey = generateKey(password, salt, keySize); 
      byte[] initializationVector = createInitializationVector(keySize); 

      Cipher aesCipherForDecryption = Cipher.getInstance("AES/CBC/PKCS5PADDING"); 

      aesCipherForDecryption.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(initializationVector)); 
      byte[] decryptedByteCipherText = Base64.getDecoder().decode(base64CipherText); 
      byte[] byteDecryptedMessage = aesCipherForDecryption.doFinal(decryptedByteCipherText); 
      return createMessageFromBytes(byteDecryptedMessage); 
     } catch (IllegalStateException | InvalidKeyException | InvalidAlgorithmParameterException 
       | NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeySpecException 
       | IllegalBlockSizeException | BadPaddingException | MessagingException e) { 
      throw new EncryptionException(String.format("Unable to enrypt message due to: %s", e.getMessage()), e); 
     } 
    } 

    /** 
    * 
    * @param password 
    * @param salt 
    * @param message 
    * @param charArray 
    * @return Base64 encoded CipherText 
    * @throws EncryptionException 
    *    If sth. goes wrong 
    */ 
    private static String encrypt(
      char[] password, 
      byte[] salt, 
      Message message) throws EncryptionException { 
     try { 
      /** 
      * Step 1. Generate an AES key with password and salt 
      * 
      */ 
      SecretKey secretKey = generateKey(password, salt, keySize); 
      System.out.println(secretKey.getEncoded().length); 

      /** 
      * Step 2. Generate an Initialization Vector (IV) 
      * a. Use SecureRandom to generate random bits 
      * The size of the IV matches the blocksize of the cipher (e.g. 128 bits for AES) 
      * b. Construct the appropriate IvParameterSpec object for the data to pass to Cipher's init() method 
      */ 
      byte[] initializationVector = createInitializationVector(keySize); 

      /** 
      * Step 3. Create a Cipher by specifying the following parameters 
      * a. Algorithm name - here it is AES 
      * b. Mode - here it is CBC mode 
      * c. Padding - e.g. PKCS7 or PKCS5 
      * 
      * Must specify the mode explicitly as most JCE providers default to ECB mode!! 
      */ 
      Cipher aesCipherForEncryption = Cipher.getInstance("AES/CBC/PKCS5PADDING"); 

      /** 
      * Step 4. Initialize the Cipher for Encryption 
      */ 
      aesCipherForEncryption.init(Cipher.ENCRYPT_MODE, secretKey, new IvParameterSpec(initializationVector)); 

      /** 
      * Step 5. Encrypt the Data 
      * a. Declare/Initialize the Data. Here the data is of type String 
      * b. Convert the Input Text to Bytes 
      * c. Encrypt the bytes using doFinal method 
      */ 
      byte[] byteCipherText = updateCipherWithMessage(aesCipherForEncryption, message); 
      return new String(Base64.getEncoder().encode(byteCipherText)); 

     } catch (IllegalBlockSizeException | BadPaddingException | IOException | MessagingException 
       | InvalidKeyException | InvalidAlgorithmParameterException | NoSuchAlgorithmException 
       | NoSuchPaddingException | InvalidKeySpecException e) { 
      throw new EncryptionException(String.format("Unable to enrypt message due to: %s", e.getMessage()), e); 
     } 

    } 

    private static MimeMessage createMessageFromBytes(
      byte[] decodedBytes) throws MessagingException { 
     InputStream is = new ByteArrayInputStream(decodedBytes); 
     Session session = null; 
     return new MimeMessage(session, is); 
    } 

    private static byte[] updateCipherWithMessage(
      Cipher cipher, 
      Message message) throws IOException, MessagingException, IllegalBlockSizeException, BadPaddingException { 
     ByteArrayOutputStream os = new ByteArrayOutputStream(); 
     try { 
      message.writeTo(os); 
      return cipher.doFinal(os.toByteArray()); 
     } finally { 
      os.close(); 
     } 
    } 

    private static byte[] createInitializationVector(
      int keyLength) { 
     // Save the IV bytes or send it in plaintext with the encrypted data so you can decrypt the data later 
     byte[] iv = new byte[keyLength/8]; 

     SecureRandom prng = new SecureRandom(); 
     prng.nextBytes(iv); 
     return iv; 
    } 

    private static SecretKey generateKey(
      char[] password, 
      byte[] salt, 
      int keySize) throws InvalidKeySpecException, NoSuchAlgorithmException { 
     int nIterations = 65536; 
     SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1"); 
     KeySpec spec = new PBEKeySpec(password, salt, nIterations, keySize); 
     SecretKey tmp = factory.generateSecret(spec); 
     return new SecretKeySpec(tmp.getEncoded(), "AES"); 
    } 

    private static Message buildTestMessage(
      String from, 
      String[] to, 
      String subject, 
      Optional<String> text, 
      Optional<String> html) throws Exception { 
     String replyto = from; 
     Session session = null; 
     Message message = new MimeMessage(session); 
     Multipart multiPart = new MimeMultipart("alternative"); 

     try { 

      if (text.isPresent()) { 
       MimeBodyPart textPart = new MimeBodyPart(); 
       textPart.setText(text.get(), "utf-8"); 
       multiPart.addBodyPart(textPart); 
      } 
      if (html.isPresent()) { 
       MimeBodyPart htmlPart = new MimeBodyPart(); 
       htmlPart.setContent(html, "text/html; charset=utf-8"); 
       multiPart.addBodyPart(htmlPart); 
      } 

      message.setContent(multiPart); 

      if (from != null) { 
       message.setFrom(new InternetAddress(from)); 
      } else 
       message.setFrom(); 

      if (replyto != null) 
       message.setReplyTo(new InternetAddress[] { new InternetAddress(replyto) }); 
      else 
       message.setReplyTo(new InternetAddress[] { new InternetAddress(from) }); 

      InternetAddress[] toAddresses = new InternetAddress[to.length]; 
      for (int i = 0; i < toAddresses.length; i++) { 
       toAddresses[i] = new InternetAddress(to[i]); 
      } 
      message.setRecipients(Message.RecipientType.TO, toAddresses); 
      message.setSubject(subject); 
      message.setSentDate(new Date()); 

      return message; 

     } catch (Exception e) { 
      e.printStackTrace(); 
      System.out.println("Exception: " + e.getMessage()); 
      throw e; 

     } 

    } 

}