给OkHttp Client添加socks代理

Okhttp的使用没有httpClient广泛，网上关于Okhttp设置代理的方法很少，这篇文章完整介绍了需要注意的方方面面。

上一篇博客中介绍了socks代理的入口是创建java.net.Socket时传入一个java.net.Porxy对象。 OkHttp client通过OkHttpClient.Builder创建，可以通过定制javax.net.ssl.SSLSocketFactory和java.net.SocketFactory来实现socks代理。

定制SocketFactory

JDK中默认的是java.net.DefaultSocketFactory,它是包可见的，没法扩展，所以只能用java.net.SocketFactory扩展，没有什么其他好的招数，这个过程其实有点繁琐。

public class ProxySocketFactory extends SocketFactory {

    private ProxyConfigProvider proxyConfigProvider;

    public ProxySocketFactory(ProxyConfigProvider proxyConfigProvider) {
        this.proxyConfigProvider = proxyConfigProvider;
    }

    @Override
    public Socket createSocket() throws IOException {
        ProxyConfig proxyConfig = proxyConfigProvider.getProxyConfig();
        if (proxyConfig != null) {
            return new Socket(proxyConfig.getProxy());
        } else {
            return new Socket();
        }
    }

    public Socket createSocket(String host, int port)
            throws IOException, UnknownHostException {
        Socket socket = createSocket();
        try {
            socket.connect(new InetSocketAddress(host, port));
        } catch (IOException e) {
            socket.close();
            throw e;
        }
        return socket;
    }

    public Socket createSocket(InetAddress address, int port)
            throws IOException {
        Socket socket = createSocket();
        try {
            socket.connect(new InetSocketAddress(address, port));
        } catch (IOException e) {
            socket.close();
            throw e;
        }
        return socket;
    }

    public Socket createSocket(String host, int port,
                               InetAddress clientAddress, int clientPort)
            throws IOException, UnknownHostException {
        Socket socket = createSocket();
        try {
            socket.bind(new InetSocketAddress(clientAddress, clientPort));
            socket.connect(new InetSocketAddress(host, port));
        } catch (IOException e) {
            socket.close();
            throw e;
        }
        return socket;
    }

    public Socket createSocket(InetAddress address, int port,
                               InetAddress clientAddress, int clientPort)
            throws IOException {
        Socket socket = createSocket();
        try {
            socket.bind(new InetSocketAddress(clientAddress, clientPort));
            socket.connect(new InetSocketAddress(address, port));
        } catch (IOException e) {
            socket.close();
            throw e;
        }
        return socket;
    }
}

上面代码这么长，并不是随便写的，也省不了。我参考了DefaultSocketFactory里面创建Socket对象的各个构造函数，保证了ProxySocketFactory的跟DefaultSocketFactory对应方法的行为完全一致，只是在创建socket时用了代理而已。简单一句话：只要传入了IP地址和端口，就会直接发起连接。

对SSL socket工厂的定制同样繁琐。不是简单的继承（继承搞不定），而是采用包装模式，用原来的SSLSocketFactory来实现与代理无关的方法。

public class ProxySSLSocketFactory extends SSLSocketFactory {
    private ProxyConfigProvider configProvider;
    private SSLSocketFactory socketFactory;

    public ProxySSLSocketFactory(ProxyConfigProvider configProvider, SSLSocketFactory socketFactory) {
        this.configProvider = configProvider;
        this.socketFactory = socketFactory;
    }

    @Override
    public String[] getDefaultCipherSuites() {
        return socketFactory.getDefaultCipherSuites();
    }

    @Override
    public String[] getSupportedCipherSuites() {
        return socketFactory.getSupportedCipherSuites();
    }

    public Socket createSocket()
            throws IOException {
        ProxyConfig proxyConfig = configProvider.getProxyConfig();
        if (proxyConfig != null) {
            return new Socket(proxyConfig.getProxy());
        } else {
            return new Socket();
        }
    }

    public Socket createSocket(String host, int port)
            throws IOException {
        Socket socket = createSocket();
        try {
            return socketFactory.createSocket(socket, host, port, true);
        } catch (IOException e) {
            socket.close();
            throw e;
        }
    }

    public Socket createSocket(Socket s, String host,
                               int port, boolean autoClose)
            throws IOException {
        //TODO 无法代理
        return socketFactory.createSocket(s, host, port, autoClose);
    }

    public Socket createSocket(InetAddress address, int port)
            throws IOException {
        Socket socket = createSocket();
        try {
            return socketFactory.createSocket(socket, address.getHostAddress(), port, true);
        } catch (IOException e) {
            socket.close();
            throw e;
        }
    }

    public Socket createSocket(String host, int port,
                               InetAddress clientAddress, int clientPort)
            throws IOException {
        Socket socket = createSocket();
        try {
            socket.bind(new InetSocketAddress(clientAddress, clientPort));
            return socketFactory.createSocket(socket, host, port, true);
        } catch (IOException e) {
            socket.close();
            throw e;
        }
    }

    public Socket createSocket(InetAddress address, int port,
                               InetAddress clientAddress, int clientPort)
            throws IOException {
        Socket socket = createSocket();
        try {
            socket.bind(new InetSocketAddress(clientAddress, clientPort));
            return socketFactory.createSocket(socket, address.getHostAddress(), port, true);
        } catch (IOException e) {
            socket.close();
            throw e;
        }
    }
}

注意，其中有一个方法是无法使用代理的：Socket createSocket(Socket s, String host,int port, boolean autoClose)，因为传入的已经是一个创建好的Socket，所以使用这个方法，要注意你的组件有没有用到这个方法，如果用到了，代理的功能需要在这个方法的调用者那一层去实现。我测试OkHttp client是没有用到这个方法的。

创建OkHttpClient对象

两个工厂类设计好了之后，下面就是运用他们创建OkHttpClient对象。

    public OkHttpClient buildOkHttpClient() {
        OkHttpClient httpClient = new OkHttpClient.Builder()
                .sslSocketFactory(new ProxySSLSocketFactory(proxyProvider, NOP_TLSV12_SSL_CONTEXT.getSocketFactory()), NOP_TRUST_MANAGER)
                .socketFactory(new ProxySocketFactory(proxyProvider))
                .hostnameVerifier(NOP_HOSTNAME_VERIFIER)
                .connectTimeout(DEFAULT_CONNECTION_TIMEOUT, TimeUnit.SECONDS)
                .writeTimeout(DEFAULT_CONNECTION_TIMEOUT, TimeUnit.SECONDS)
                .readTimeout(DEFAULT_CONNECTION_TIMEOUT, TimeUnit.SECONDS)                
                .addInterceptor(new OkHttpProxyInterceptor())
                .build();
        return httpClient;
    }

上面的方法注意两行：

.sslSocketFactory(xxx)
.socketFactory(xxx)

其他代码，有对超时的设置.xxxTimeout()，这里不赘述，还有对https请求证书的设置以及对socks密码的设置，稍后详解

设置https需要注意的地方

NOP_TRUST_MANAGER对象设置为信任任何证书：

    public static final X509TrustManager NOP_TRUST_MANAGER = new X509TrustManager() {
        @Override
        public void checkClientTrusted(X509Certificate[] x509Certificates, String s)
                throws CertificateException {
        }

        @Override
        public void checkServerTrusted(X509Certificate[] x509Certificates, String s)
                throws CertificateException {
        }

        @Override
        public X509Certificate[] getAcceptedIssuers() {
            return new X509Certificate[0];
        }
    };

NOP_HOSTNAME_VERIFIER对象设置为信任任何域名：

    public static final HostnameVerifier NOP_HOSTNAME_VERIFIER = new HostnameVerifier() {
        @Override
        public boolean verify(String s, SSLSession sslSession) {
            return true;
        }
    };

https的协议版本可能不支持TLSv1

上面两条设置网上很多文档都会介绍，重点需要关注的是NOP_TLSV12_SSL_CONTEXT对象。

干货来了：JDK使用的HTTPS协议版本参考这里-diagnosing-tls,-ssl,-and-https，可以看到在JDK7以前，默认都是TLSv1，JDK8才默认采用TLSv1.2，而很多较新的网站都已经禁用HTTPS使用TLSv1握手了，认为这个协议已经不够安全（例如，我在给minio-java client添加proxy支持时，发现minio-server就这么干的）。所以你用java去发起HTTPS连接经常会出现SSL相关的异常，大部分异常信息根本看不懂。

所以，需要在代码里面指定https使用TLSv1.2：

    static {
        try {
            NOP_TLSV12_SSL_CONTEXT = SSLContext.getInstance("TLSv1.2");
            NOP_TLSV12_SSL_CONTEXT.init(null, new TrustManager[]{NOP_TRUST_MANAGER}, new java.security.SecureRandom());
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (KeyManagementException e) {
            e.printStackTrace();
        }
    }

实际上也可以通过：

System.setProperty("https.protocols","TLSv1.2");//在创建任何SSLSocketFactory之前调用

或者设置虚拟机参数：

-Dhttps.protocols=TLSv1.2,TLSv1.1,TLSv1

放在前面的协议会被优先选用

检测https支持的协议版本

如果出现SSL相关异常，但是又不确定是不是协议版本导致的，可以有几个工具进行检验：
nmap : nmap --script ssl-enum-ciphers -p 443 baidu.com,在我机器上看到：

PORT    STATE SERVICE
443/tcp open  https
| ssl-enum-ciphers: 
|   SSLv3: 
|     ciphers: 
|       TLS_ECDHE_RSA_WITH_RC4_128_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (secp256r1) - A
|       TLS_RSA_WITH_AES_128_CBC_SHA (rsa 2048) - A
|       TLS_RSA_WITH_AES_256_CBC_SHA (rsa 2048) - A
|       TLS_RSA_WITH_RC4_128_SHA (rsa 2048) - A
|     compressors: 
|       NULL
|     cipher preference: server
|     warnings: 
|       CBC-mode cipher in SSLv3 (CVE-2014-3566)
|   TLSv1.0: 
|     ciphers: 
|       TLS_ECDHE_RSA_WITH_RC4_128_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (secp256r1) - A
|       TLS_RSA_WITH_AES_128_CBC_SHA (rsa 2048) - A
|       TLS_RSA_WITH_AES_256_CBC_SHA (rsa 2048) - A
|       TLS_RSA_WITH_RC4_128_SHA (rsa 2048) - A
|     compressors: 
|       NULL
|     cipher preference: server
|   TLSv1.1: 
|     ciphers: 
|       TLS_ECDHE_RSA_WITH_RC4_128_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (secp256r1) - A
|       TLS_RSA_WITH_AES_128_CBC_SHA (rsa 2048) - A
|       TLS_RSA_WITH_AES_256_CBC_SHA (rsa 2048) - A
|       TLS_RSA_WITH_RC4_128_SHA (rsa 2048) - A
|     compressors: 
|       NULL
|     cipher preference: server
|     warnings: 
|       Weak cipher RC4 in TLSv1.1 or newer not needed for BEAST mitigation
|   TLSv1.2: 
|     ciphers: 
|       TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_RC4_128_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (secp256r1) - A
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (secp256r1) - A
|       TLS_RSA_WITH_AES_128_GCM_SHA256 (rsa 2048) - A
|       TLS_RSA_WITH_AES_256_GCM_SHA384 (rsa 2048) - A
|       TLS_RSA_WITH_AES_128_CBC_SHA256 (rsa 2048) - A
|       TLS_RSA_WITH_AES_128_CBC_SHA (rsa 2048) - A
|       TLS_RSA_WITH_AES_256_CBC_SHA256 (rsa 2048) - A
|       TLS_RSA_WITH_AES_256_CBC_SHA (rsa 2048) - A
|       TLS_RSA_WITH_RC4_128_SHA (rsa 2048) - A
|     compressors: 
|       NULL
|     cipher preference: server
|     warnings: 
|       Weak cipher RC4 in TLSv1.1 or newer not needed for BEAST mitigation
|_  least strength: A

设置Socks的用户名和密码

OkHttp提供了拦截器的机制okhttp3.Interceptor，可以定制http发起的流程。
设置密码有两种方式：一种是设置全局的，另一种是按线程隔离（也是就是按请求隔离），不同请求可以设置不同的用户名和密码，详细介绍以及部分代码见我的上一篇博客-给HttpClient添加Socks代理。
注意到上面代码有这么一行：

.addInterceptor(new OkHttpProxyInterceptor())

就是设置一个拦截器。

    private class OkHttpProxyInterceptor implements Interceptor {
        @Override
        public Response intercept(Chain chain) throws IOException {
            ProxyConfig proxyConfig = ProxyHttpClientBuilder.this.getProxyConfig();
            boolean clearCredentials = false;
            if (proxyConfig != null) {
                if (proxyConfig.getAuthentication() != null) {
                    ThreadLocalProxyAuthenticator.setCredentials(proxyConfig.getAuthentication());
                    clearCredentials = true;
                }
            }
            try {
                return chain.proceed(chain.request());
            } finally {
                if (clearCredentials) {
                    ThreadLocalProxyAuthenticator.clearCredentials();
                }
            }
        }
    }

ThreadLocalProxyAuthenticator,ProxyConfig等类见上一篇博客。