java - 使用 Windows 通过 TCP 流发送由 key 编码的字符串 BadPaddingException

Question

我认为我在使用 writeUTF() 和 readUTF() 方法通过 TCP 连接发送加密字符串时遇到了特定于 Windows 操作系统 (Windows 7) 的问题。

客户端和服务器首先使用私钥-公钥对建立连接。然后他们就用于进一步通信的共享 key 达成一致。当由共享 key 加密并通过 writeUTF() 和 readUTF() 发送的字符串填充错误时，就会出现此问题。第一个发生的情况是使用 writeUTF() 方法从服务器向客户端发送加密确认。

这个问题只是偶尔出现!有时，程序可以顺利地完成，没有任何错误，但有时会抛出 BadPaddingException ，指出“给定的最终 block 未正确填充”在客户端:

            byte[] byteDecriptedAck = decryptCipher.doFinal(encryptedAck.getBytes());

和服务器端:

            byte[] byteDecriptedAck = decryptCipher.doFinal(encryptedPassword.getBytes());

在 OSX 操作系统上运行代码时不会出现此问题。因此，我认为这与windows如何表示UTF字符串、写入UTF字符串或读取UTF字符串有关。

我对解决这个问题感到不知所措。任何帮助将非常感激。

谢谢

客户端建立连接的代码:

private void establishConnection() {
    try {
        int numBytesPubKey = in.readInt();
        byte[] bytesPubKey = new byte[numBytesPubKey];
        in.readFully(bytesPubKey, 0, numBytesPubKey);

        //get public key from server
        X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(bytesPubKey);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PublicKey pubKey = keyFactory.generatePublic(pubKeySpec);

        //generate secret key for communicating
        KeyGenerator keyGen = KeyGenerator.getInstance("AES");
        keyGen.init(128); //key size
        SecretKey secretKey = keyGen.generateKey();
        byte[] encodedSecretKey = secretKey.getEncoded();

        //use public key to encode message containing secret key to send to server
        encryptCipher = Cipher.getInstance("RSA");
        encryptCipher.init(Cipher.ENCRYPT_MODE, pubKey);
        byte[] cipherData = encryptCipher.doFinal(encodedSecretKey);

        //send secret key to server encoded by servers public key
        out.writeInt(cipherData.length);
        out.write(cipherData, 0, cipherData.length);

        //read acknowledge from server
        SecretKeySpec secretKeySpec = new SecretKeySpec(encodedSecretKey,"AES");

        String encryptedAck = in.readUTF();
        decryptCipher = Cipher.getInstance("AES");
        decryptCipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
        byte[] byteDecriptedAck = decryptCipher.doFinal(encryptedAck.getBytes());

        if(!(new String(byteDecriptedAck).equals("ACK"))) {
            System.err.println("Server acknowledgement corrupted. Terminate communications.");
            System.exit(1);
        }

        //send password to server

        encryptCipher = Cipher.getInstance("AES");
        encryptCipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
        byte[] cipheredPassword = encryptCipher.doFinal("password".getBytes());
        out.writeUTF(new String(cipheredPassword));

    } catch (Exception e) {
        System.err.println(e.getMessage());
        e.printStackTrace();
    }
}

服务器端建立连接的代码:

private void establishConnection() {
    try {
        //generate public/private key pair for communicating with initially
        KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
        SecureRandom random = SecureRandom.getInstance("SHA1PRNG", "SUN");
        keyGen.initialize(1024, random);

        KeyPair pair = keyGen.generateKeyPair();
        PrivateKey privKey = pair.getPrivate();
        PublicKey pubKey = pair.getPublic();

        //send public key to client
        byte[] bytesPubKey = pubKey.getEncoded();
        out.writeInt(bytesPubKey.length);
        out.write(bytesPubKey, 0, bytesPubKey.length);

        //read in secret key to use for further communications
        int numBytesSecretKey = in.readInt();
        byte[] bytesSecretKey = new byte[numBytesSecretKey];
        in.readFully(bytesSecretKey, 0, numBytesSecretKey);

        decryptCipher = Cipher.getInstance("RSA");
        decryptCipher.init(Cipher.DECRYPT_MODE, privKey, decryptCipher.getParameters());
        byte[] byteDecriptedSecretKey = decryptCipher.doFinal(bytesSecretKey);
        SecretKeySpec secretKeySpec = new SecretKeySpec(byteDecriptedSecretKey,"AES");

        //send back acknowledgment encoded with secret key: ACK
        encryptCipher = Cipher.getInstance("AES");
        encryptCipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);
        byte[] cipheredACK = encryptCipher.doFinal("ACK".getBytes());

        out.writeUTF(new String(cipheredACK));

        //read password from client
        String encryptedPassword = in.readUTF();
        decryptCipher = Cipher.getInstance("AES");
        decryptCipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
        byte[] byteDecriptedAck = decryptCipher.doFinal(encryptedPassword.getBytes());

        if(!(new String(byteDecriptedAck).equals("password"))) {
            System.err.println("Access Denied. Client password incorrect. Terminate communications.");
            System.exit(1);
        } else {
            System.err.println("Access Granted.");
        } 
    } catch (Exception e) {
        e.printStackTrace();
    }
} 

Answer 1

byte[] cipheredACK = encryptCipher.doFinal("ACK".getBytes());
out.writeUTF(new String(cipheredACK));

那是行不通的。 UTF 和 String 用于字符数据。这里有原始字节，不能被解释为文本。

将它们作为二进制数据发送:

out.write(cipheredACK);

您看到 OS X 和 Windows 之间存在差异的原因是，您在将字节强制转换为字符串时没有指定字符编码，因此它变得特定于平台。如果这确实是字符数据，您可以将字符集传递给构造函数以使其与平台无关。但就您而言，它无论如何都不是字符数据，因此只需使用字节即可。

另外，为什么不直接使用 SSL？