Alibaba Cloud DNS：Android端HTTPS（含SNI）業務情境"IP直連"方案說明

概述

HTTPS是一種通過電腦網路進行安全通訊的傳輸協議，經由HTTP進行通訊，利用SSL/TLS建立全通道，加密資料包。HTTPS使用的主要目的是提供對網站伺服器的身份認證，同時保護交換資料的隱私與完整性，TLS是傳輸層加密協議，前身是SSL協議。HTTPS下有兩種業務情境普通情境和SNI情境，SNI（Server Name Indication）是用來改善伺服器與用戶端SSL（Secure Socket Layer）和TLS（Transport Layer Security）的擴充，主要解決一台伺服器能夠提供多個網域名稱服務 (DNS)的情況。

• 普通情境

普通情境使用“IP直連”對開發人員來說很方便，直接將請求URL中的Host替換成IP，在執行認證驗證時將IP再替換成原來的網域名稱即可。

• SNI情境

SNI（單IP多HTTPS認證）情境下，針對HttpsURLConnection介面，開發人員需要定製SSLSocketFactory，在createSocket時通過移動解析HTTPDNS Android SDK提供的API替換為網域名稱解析後的IP後，並需要對 SNI/HostNameVerify進行配置。

實踐方案

• HTTPS下普通情境解決方案

針對“domain不匹配”的問題，可以採用hook認證校正的解決方案，將IP直接替換成原來的網域名稱，再執行證 書驗證。

此樣本針對HttpURLConnection

try {
      //使用者如果使用ipv6的IP地址進行替換請求URL中的Host，需要對ipv6地址加上“[]”。
      //例如：https://[2400:3200:xxx:1]/path
      String url = "https://124.239.XX.XX/?sprefer=sypc00";
      HttpsURLConnection connection = (HttpsURLConnection) new URL(url).openConnection();

      connection.setRequestProperty("Host", "m.taobao.com");
      connection.setHostnameVerifier(new HostnameVerifier() {

      /*
       * 關於這個介面的說明，官方有文檔描述：
       * This is an extended verification option that implementers can provide.
       * It is to be used during a handshake if the URL's hostname does not match the
       * peer's identification hostname.
       *
       * 使用移動解析HTTPDNS Android SDK後URL裡設定的hostname不是遠端主機名稱（如：m.taobao.com），與憑證發行的域不匹配，
       * Android HttpsURLConnection提供了回調介面讓使用者來處理這種定製化情境。
       * 在確認移動解析HTTPDNS Android SDK返回的來源站點IP與Session攜帶的IP資訊一致後，您可以在回調方法中將待驗證網域名稱替換為原來的真實網域名稱進行驗證。
       *
       */

        @Override
        public boolean verify(String hostname, SSLSession session) {
             return HttpsURLConnection.getDefaultHostnameVerifier().verify("m.taobao.com", session);
        }
    }); 
    connection.connect();
     } catch (Exception e) {
           e.printStackTrace();
     } finally { 
   }

• HTTPS下SNI情境解決方案

class TlsSniSocketFactory extends SSLSocketFactory {
    private final String TAG = TlsSniSocketFactory.class.getSimpleName();
    HostnameVerifier hostnameVerifier = HttpsURLConnection.getDefaultHostnameVerifier();
    private HttpsURLConnection conn;

    public TlsSniSocketFactory(HttpsURLConnection conn) {
        this.conn = conn;
    }

    @Override
    public Socket createSocket() throws IOException {
        return null;
    }

    @Override
    public Socket createSocket(String host, int port) throws IOException, UnknownHostException {
        return null;
    }

    @Override
    public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException, UnknownHostException {
        return null;
    }

    @Override
    public Socket createSocket(InetAddress host, int port) throws IOException {
        return null;
    }

    @Override
    public Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {
        return null;
    }

    // TLS layer
    @Override
    public String[] getDefaultCipherSuites() {
        return new String[0];
    }

    @Override
    public String[] getSupportedCipherSuites() {
        return new String[0];
    }

    @Override
    public Socket createSocket(Socket plainSocket, String host, int port, boolean autoClose) throws IOException {
        String peerHost = this.conn.getRequestProperty("Host");
        if (peerHost == null){           
            peerHost = host;
        }

        Log.i(TAG, "customized createSocket. host: " + peerHost);
        InetAddress address = plainSocket.getInetAddress();

        if (autoClose) {
            // we don't need the plainSocket
            plainSocket.close();
        }
        // create and connect SSL socket, but don't do hostname/certificate verification yet
        SSLCertificateSocketFactory sslSocketFactory = (SSLCertificateSocketFactory) SSLCertificateSocketFactory.getDefault(0);
        SSLSocket ssl = (SSLSocket) sslSocketFactory.createSocket(address, port);

        // enable TLSv1.1/1.2 if available
        ssl.setEnabledProtocols(ssl.getSupportedProtocols());

       // set up SNI before the handshake
       if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
            Log.i(TAG, "Setting SNI hostname");
            sslSocketFactory.setHostname(ssl, peerHost);
       } else {
            Log.d(TAG, "No documented SNI support on Android <4.2, trying with reflection");
            try {
                 java.lang.reflect.Method setHostnameMethod = ssl.getClass().getMethod("setHostname", String.class);
                 setHostnameMethod.invoke(ssl, peerHost);
            } catch (Exception e) {
                 Log.w(TAG, "SNI not useable", e);
            }
        }

        // verify hostname and certificate
        SSLSession session = ssl.getSession();

        if (!hostnameVerifier.verify(peerHost, session)){
            throw new SSLPeerUnverifiedException("Cannot verify hostname: " + peerHost);
        }

       Log.i(TAG, "Established " + session.getProtocol() + " connection with " + session.getPeerHost() +
                " using " + session.getCipherSuite());

        return ssl;
    }
}

public void recursiveRequest(String path, String reffer) {
    URL url = null;
    try {
          url = new URL(path);
          conn = (HttpsURLConnection) url.openConnection();
          String ip = dnsResolver.getIPV4ByHost(url.getHost());
          //使用者如果使用ipv6的IP地址進行替換請求URL中的Host，需要對ipv6地址加上“[]”。
          //例如：https://[2400:3200:xxx:1]/path
          if (ip != null) {
               // 通過移動解析HTTPDNS Android SDK擷取IP成功，進行URL替換和HOST頭設定
               Log.d(TAG, "get IP: " + ip + " for host: " + url.getHost() + "from pdns resolver success!");
               String newUrl = path.replaceFirst(url.getHost(), ip);
               conn = (HttpsURLConnection) new URL(newUrl).openConnection();
               // 設定HTTP要求標頭Host域
               conn.setRequestProperty("Host", url.getHost());
            }
            conn.setConnectTimeout(30000);
            conn.setReadTimeout(30000);
            conn.setInstanceFollowRedirects(false);
            TlsSniSocketFactory sslSocketFactory = new TlsSniSocketFactory(conn);
            conn.setSSLSocketFactory(sslSocketFactory);
            conn.setHostnameVerifier(new HostnameVerifier() {
            /*
             * 關於這個介面的說明，官方有文檔描述：
             * This is an extended verification option that implementers can provide.
             * It is to be used during a handshake if the URL's hostname does not match the
             * peer's identification hostname.
             *
             * 使用移動解析HTTPDNS Android SDK後URL裡設定的hostname不是遠端主機名稱（如：m.taobao.com），與憑證發行的域不匹配，
             * Android HttpsURLConnection提供了回調介面讓使用者來處理這種定製化情境。
             * 在確認移動解析HTTPDNS Android SDK返回的來源站點IP與Session攜帶的IP資訊一致後，您可以在回調方法中將待驗證網域名稱替換為原來的真實網域名稱進行驗證。
             *
             */
            @Override
            public boolean verify(String hostname, SSLSession session) {
                String host = conn.getRequestProperty("Host");
                if (null == host) {
                    host = conn.getURL().getHost();
                }
                return HttpsURLConnection.getDefaultHostnameVerifier().verify(host, session);
             }
         });
         int code = conn.getResponseCode();// Network block
         if (needRedirect(code)) {
             //臨時重新導向和永久重新導向location的大小寫有區分
             String location = conn.getHeaderField("Location");
             if (location == null) {
                 location = conn.getHeaderField("location");
             }
             if (!(location.startsWith("http://") || location.startsWith("https://"))) {
                 //某些時候會省略host，只返回後面的path，所以需要補全url
                 URL originalUrl = new URL(path);
                 location = originalUrl.getProtocol() + "://"+originalUrl.getHost() + location;
             }
             recursiveRequest(location, path);
         } else {
            // redirect finish.
            DataInputStream dis = new DataInputStream(conn.getInputStream());
            int len;
            byte[] buff = new byte[4096];
            StringBuilder response = new StringBuilder();
            while ((len = dis.read(buff)) != -1) {
                response.append(new String(buff, 0, len));
            }
            Log.d(TAG, "Response: " + response.toString());
         }
    } catch (MalformedURLException e) {
        Log.w(TAG, "recursiveRequest MalformedURLException");
    } catch (IOException e) {
        Log.w(TAG, "recursiveRequest IOException");
    } catch (Exception e) {
        Log.w(TAG, "unknow exception");
    } finally {
        if (conn != null) {
            conn.disconnect();
        }
    }
}