从 SSL 输入流中读取 (Java)

Question

我正在尝试使用经过身份验证的 SSL 连接和在下面的类中定义的一些控制消息在客户端和服务器之间编写一个简单的协议：

public class KeyExchangeProtcolMsgs {
    public static final String reqStr = "#REQ_KM";
    public static final String nonceStr = "#NONCE_END";
    public static final String ackStr = "#ACK_KM";
}

client.java

        // Connect to the server
        cSock = (SSLSocket) fact.createSocket(this.remoteHost, this.remotePort);
        // Create the streams to send out data as well as read data
        OutputStream out = cSock.getOutputStream();
        InputStream in = cSock.getInputStream();
        // Generate client nonce
        byte[] clientNonceB = CryptographyUtils.generateRandomNumber();
        // Send the nonce and the request for a key from the server
        // First, send the keying material request to the server
        System.out.println("[I] SSL client written " + KeyExchangeProtcolMsgs.reqStr);
        out.write(CryptographyUtils.toByteArray(KeyExchangeProtcolMsgs.reqStr)); // <== Successfully written to the server
        // Next, send the generated nonce (by the client)
        System.out.println("[I] SSL client written nonce ");
        System.out.println(new String(clientNonceB, "UTF-8"));
        out.write(clientNonceB);
        // Finally, send the ending string
        System.out.println("[I] SSL client written " + KeyExchangeProtcolMsgs.nonceStr);
        out.write(CryptographyUtils.toByteArray(KeyExchangeProtcolMsgs.nonceStr));
        // Wait for the response from the server containing the key
        int ch = 0;
        String responseStr = "";
        while ((responseStr.contains(KeyExchangeProtcolMsgs.ackStr) == false) && (responseStr.contains(KeyExchangeProtcolMsgs.nonceStr) == false)) {
            ch = in.read();
            responseStr = responseStr + (char) ch;
            System.out.println("[I] SSL client read " + responseStr);
        }
        // Display read information from server
        System.out.println("[I] SSL client read " + responseStr);
        // Check if the server nonce contains the starting and end messages of the protocol

            String serverNonceStr = responseStr.substring(KeyExchangeProtcolMsgs.ackStr.length(), responseStr.length() - KeyExchangeProtcolMsgs.nonceStr.length());
            // Compute the key by xor-ing the client and server nonce and applying AES
            // on the resulting string
            clientKeyingMaterial = new SecretKeySpec(CryptographyUtils.xorStrings(clientNonceB, CryptographyUtils.toByteArray(serverNonceStr)), "AES");
            return clientKeyingMaterial;

server.java

        System.out.println("[I] SSL server listening");

        SSLSocket sslSock = (SSLSocket) sSock.accept();
        sslSock.startHandshake();

        System.out.println("[I] SSL server starting handshake");

        // Process if principal checks out
        if (isEndEntity(sslSock.getSession())) {
            // Create the streams to send out data as well as read data
            OutputStream out = sslSock.getOutputStream();
            InputStream in = sslSock.getInputStream();
            // Wait and read the client's nonce
            int ch = 0;
            String requestStr = "";
            while ((requestStr.contains(KeyExchangeProtcolMsgs.reqStr) == false) && (requestStr.contains(KeyExchangeProtcolMsgs.nonceStr) == false)) {
                ch = in.read();
                requestStr = requestStr + (char) ch;
                System.out.println("[I] SSL server received " + requestStr);
            }

            System.out.println("[I] SSL server received " + requestStr);
         }

服务器端的循环在发送 KeyExchangeProtcolMsgs.reqStr/#REQ_KM 后立即退出，但不等待实际的 nonce 和结束消息 KeyExchangeProtcolMsgs.nonceStr/#NONCE_END强>.

为什么在客户端发送最后一条消息之前，服务器端while循环就退出了？

Answer 1

因为只要requestStr包含KeyExchangeProtcolMsgs.reqStr，requestStr.contains(KeyExchangeProtcolMsgs.reqStr)就变成true，所以requestStr.contains(KeyExchangeProtcolMsgs.reqStr) == false变成true == false，也就是false，所以while循环中的整个测试变成false ，因此执行会退出 while 循环。

有几种方法可以解决这个问题，最简单的方法是使用两个 while 循环。第一个循环直到requestStr 是KeyExchangeProtcolMsgs.reqStr，第二个循环累积随机数直到它以KeyExchangeProtcolMsgs.nonceStr 结束。像这样的：

        String requestStr = "";
        while (!requestStr.equals(KeyExchangeProtcolMsgs.reqStr)) {
            ch = in.read();
            requestStr = requestStr + (char) ch;
        }

        System.out.println("[I] SSL server received " + requestStr);

        String nonceStr = "";
        while (!requestStr.endsWith(KeyExchangeProtcolMsgs.nonceStr)) {
            ch = in.read();
            nonceStr = nonceStr + (char) ch;
        }

        // Whack #NONCE_END from the end to get just the nonce.

        nonceStr = nonceStr.substring(0, nonceStr.length() - KeyExchangeProtcolMsgs.nonceStr.length());

        System.out.println("[I] SSL server received " + nonceStr);

这没有经过测试，但应该很接近。

您可以通过保留某种状态指示器来使用单个 while 循环来做到这一点，这样您就知道何时累积 reqStr 以及何时累积 nonceStr，但我认为像这样拆分它是清洁工。