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Client Configuration

The following are topics for configuring the client from the client API.

Page Contents

Enabling SSL/TLS for TCP Traffic Between the Client and the SOCKS Server

You can enable SSL/TLS for TCP traffic between the client and the SOCKS server under the following condition:

  • The SOCKS server accepts SSL/TLS connections.

By default, SSL/TLS for TCP traffic between the client and the SOCKS server is disabled. To enable SSL/TLS for TCP traffic between the client and the SOCKS server, you will need to have the property socksClient.ssl.enabled set to true. In addition, you will need to have the property socksClient.ssl.trustStoreFile to specify the SOCKS server's key store file used as a trust store (this file would need to be created by Java's keytool utility). Also, you will need to have the property socksClient.ssl.trustStorePassword to specify the password for the SOCKS server's trust store file.

API example:

package com.example;

import com.github.jh3nd3rs0n.jargyle.client.HostResolver;
import com.github.jh3nd3rs0n.jargyle.client.NetObjectFactory;

import java.io.IOException;

import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.net.Socket;

public class ClientApp {
    public static void main(String[] args) throws IOException {
        System.setProperty("socksServerUri.scheme", "socks5");
        System.setProperty("socksServerUri.host", "jargyle.net");
        System.setProperty("socksServerUri.port", "1234");
        System.setProperty("socksClient.ssl.enabled", "true");
        System.setProperty("socksClient.ssl.trustStoreFile", "jargyle.jks");
        System.setProperty("socksClient.ssl.trustStorePassword", "password");
        NetObjectFactory netObjectFactory = NetObjectFactory.newInstance();
        // ...
    }
}

If the SOCKS server wants the client to authenticate using SSL/TLS, you will need to have the property socksClient.ssl.keyStoreFile to specify the client's key store file (this file would need to be created by Java's keytool utility). Also, you will need to have the property socksClient.ssl.keyStorePassword to specify the password for the client's key store file.

API example:

package com.example;

import com.github.jh3nd3rs0n.jargyle.client.HostResolver;
import com.github.jh3nd3rs0n.jargyle.client.NetObjectFactory;

import java.io.IOException;

import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.net.Socket;

public class ClientApp {
    public static void main(String[] args) throws IOException {
        System.setProperty("socksServerUri.scheme", "socks5");
        System.setProperty("socksServerUri.host", "jargyle.net");
        System.setProperty("socksServerUri.port", "1234");
        System.setProperty("socksClient.ssl.enabled", "true");
        System.setProperty("socksClient.ssl.keyStoreFile", "client.jks");
        System.setProperty("socksClient.ssl.keyStorePassword", "drowssap");
        System.setProperty("socksClient.ssl.trustStoreFile", "jargyle.jks");
        System.setProperty("socksClient.ssl.trustStorePassword", "password");
        NetObjectFactory netObjectFactory = NetObjectFactory.newInstance();
        // ...
    }
}

Enabling DTLS for UDP Traffic Between the Client and the SOCKS Server

You can enable DTLS for UDP traffic between the client and the SOCKS server under the following condition:

  • The SOCKS server accepts DTLS connections.

By default, DTLS for UDP traffic between the client and the SOCKS server is disabled. To enable DTLS for UDP traffic between the client and the SOCKS server, you will need to have the property socksClient.dtls.enabled set to true. In addition, you will need to have the property socksClient.dtls.trustStoreFile to specify the SOCKS server's key store file used as a trust store (this file would need to be created by Java's keytool utility). Also, you will need to have the property socksClient.dtls.trustStorePassword to specify the password for the SOCKS server's trust store file.

API example:

package com.example;

import com.github.jh3nd3rs0n.jargyle.client.HostResolver;
import com.github.jh3nd3rs0n.jargyle.client.NetObjectFactory;

import java.io.IOException;

import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.net.Socket;

public class ClientApp {
    public static void main(String[] args) throws IOException {
        System.setProperty("socksServerUri.scheme", "socks5");
        System.setProperty("socksServerUri.host", "jargyle.net");
        System.setProperty("socksServerUri.port", "1234");
        System.setProperty("socksClient.dtls.enabled", "true");
        System.setProperty("socksClient.dtls.trustStoreFile", "jargyle.jks");
        System.setProperty("socksClient.dtls.trustStorePassword", "password");
        NetObjectFactory netObjectFactory = NetObjectFactory.newInstance();
        // ...
    }
}

Accessing the SOCKS Server Using SOCKS5 Authentication

The client has the following SOCKS5 authentication methods to choose from when accessing the SOCKS5 server:

  • NO_AUTHENTICATION_REQUIRED: No authentication required
  • GSSAPI: GSS-API authentication
  • USERNAME_PASSWORD: Username password authentication

From the API, you can have one or more of the aforementioned authentication methods set in the property socksClient.socks5.methods as a comma separated list.

API example:

package com.example;

import com.github.jh3nd3rs0n.jargyle.client.HostResolver;
import com.github.jh3nd3rs0n.jargyle.client.NetObjectFactory;

import java.io.IOException;

import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.net.Socket;

public class ClientApp {
    public static void main(String[] args) throws IOException {
        System.setProperty("socksServerUri.scheme", "socks5");
        System.setProperty("socksServerUri.host", "jargyle.net");
        System.setProperty("socksServerUri.port", "1234");
        System.setProperty(
            "socksClient.socks5.methods", 
            "NO_AUTHENTICATION_REQUIRED,GSSAPI");
        NetObjectFactory netObjectFactory = NetObjectFactory.newInstance();
        // ...
    }
}

If not set, the default value for the property socksClient.socks5.methods is set to NO_AUTHENTICATION_REQUIRED.

Accessing the SOCKS Server Using No Authentication

Because the default value for the property socksClient.socks5.methods is set to NO_AUTHENTICATION_REQUIRED, it is not required for NO_AUTHENTICATION_REQUIRED to be included in the property socksClient.socks5.methods.

However, if other authentication methods are to be used in addition to NO_AUTHENTICATION_REQUIRED, NO_AUTHENTICATION_REQUIRED must be included in the property socksClient.socks5.methods

API example:

package com.example;

import com.github.jh3nd3rs0n.jargyle.client.HostResolver;
import com.github.jh3nd3rs0n.jargyle.client.NetObjectFactory;

import java.io.IOException;

import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.net.Socket;

public class ClientApp {
    public static void main(String[] args) throws IOException {
        System.setProperty("socksServerUri.scheme", "socks5");
        System.setProperty("socksServerUri.host", "jargyle.net");
        System.setProperty("socksServerUri.port", "1234");
        System.setProperty(
            "socksClient.socks5.methods", 
            "NO_AUTHENTICATION_REQUIRED,GSSAPI,USERNAME_PASSWORD");
        NetObjectFactory netObjectFactory = NetObjectFactory.newInstance();
        // ...
    }
}

Accessing the SOCKS Server Using Username Password Authentication

To access the SOCKS server using username password authentication, you will need to have the property socksClient.socks5.methods to have USERNAME_PASSWORD included. You will also need to have the properties socksClient.socks5.userpassmethod.username and socksClient.socks5.userpassmethod.password respectively specify the username and password for the SOCKS5 server.

API example:

package com.example;

import com.github.jh3nd3rs0n.jargyle.client.HostResolver;
import com.github.jh3nd3rs0n.jargyle.client.NetObjectFactory;

import java.io.IOException;

import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.net.Socket;

public class ClientApp {
    public static void main(String[] args) throws IOException {
        System.setProperty("socksServerUri.scheme", "socks5");
        System.setProperty("socksServerUri.host", "jargyle.net");
        System.setProperty("socksServerUri.port", "1234");
        System.setProperty(
            "socksClient.socks5.methods", "USERNAME_PASSWORD");
        System.setProperty(
            "socksClient.socks5.userpassmethod.username", 
            "Aladdin");
        System.setProperty(
            "socksClient.socks5.userpassmethod.password",
            "opensesame");
        NetObjectFactory netObjectFactory = NetObjectFactory.newInstance();
        // ...
    }
}

Accessing the SOCKS Server Using GSS-API Authentication

To access the SOCKS server using GSS-API authentication, you will need to have the property socksClient.socks5.methods to have GSSAPI included. You will also need to specify Java system properties to use a security mechanism that implements the GSS-API (for example, Kerberos is a security mechanism that implements the GSS-API) and you will also need to specify the GSS-API service name for the SOCKS5 server.

The following is a sufficient example of using the Kerberos security mechanism:

API example:

package com.example;

import com.github.jh3nd3rs0n.jargyle.client.HostResolver;
import com.github.jh3nd3rs0n.jargyle.client.NetObjectFactory;

import java.io.IOException;

import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.net.Socket;

public class ClientApp {
    public static void main(String[] args) throws IOException {
        System.setProperty(
            "javax.security.auth.useSubjectCredsOnly", "false");
        System.setProperty(
            "java.security.auth.login.config", "login.conf");
        System.setProperty("java.security.krb5.conf", "krb5.conf");
        System.setProperty("socksServerUri.scheme", "socks5");
        System.setProperty("socksServerUri.host", "jargyle.net");
        System.setProperty("socksServerUri.port", "1234");
        System.setProperty("socksClient.socks5.methods", "GSSAPI");
        System.setProperty(
            "socksClient.socks5.gssapimethod.serviceName",
            "rcmd/jargyle.net");
        NetObjectFactory netObjectFactory = NetObjectFactory.newInstance();
        // ...
    }
}

The Java system property javax.security.auth.useSubjectCredsOnly with the value false disables JAAS-based authentication to obtain the credentials directly and lets the underlying security mechanism obtain them instead.

The Java system property java.security.auth.login.config with the value login.conf provides a JAAS configuration file for the underlying security mechanism.

login.conf:

com.sun.security.jgss.initiate {
  com.sun.security.auth.module.Krb5LoginModule required
  principal="alice"
  useKeyTab=true
  keyTab="alice.keytab"
  storeKey=true;
};

In login.conf, alice is a principal that is created by a Kerberos administrator.

Also in login.conf, alice.keytab is a keytab file also created by a Kerberos administrator that contains the aforementioned principal and its respective encrypted key.

The Java system property java.security.krb5.conf with the value krb5.conf provides the Kerberos configuration file that points to the Kerberos Key Distribution Center (KDC) for authentication.

krb5.conf:

[libdefaults]
    kdc_realm = JARGYLE.NET
    default_realm = JARGYLE.NET
    udp_preference_limit = 4096
    kdc_tcp_port = 4444
    kdc_udp_port = 4444

[realms]
    JARGYLE.NET = {
        kdc = jargyle.net:4444
    }

In krb5.conf, a KDC is defined as running at the address jargyle.net on port 4444 with its realm as JARGYLE.NET. (In a production environment, the address jargyle.net should be replaced by the actual address or name of the machine of where the KDC resides. Also, in a production environment, the realm JARGYLE.NET should be replaced by an actual realm provided by a Kerberos administrator.)

The property socksClient.socks5.gssapimethod.serviceName with the value rcmd/jargyle.net is the GSS-API service name (or the Kerberos service principal) for the SOCKS server residing at the address jargyle.net. (In a production environment, the address jargyle.net should be replaced by the name of the machine of where the SOCKS server resides.)

Resolving Host Names From the SOCKS5 Server

By default, host name resolution from the SOCKS5 server occurs only when a Socket is created with a host name and port number.

API example:

package com.example;

import com.github.jh3nd3rs0n.jargyle.client.HostResolver;
import com.github.jh3nd3rs0n.jargyle.client.NetObjectFactory;

import java.io.IOException;

import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.net.Socket;

public class ClientApp {
    public static void main(String[] args) throws IOException {
        System.setProperty("socksServerUri.scheme", "socks5");
        System.setProperty("socksServerUri.host", "jargyle.net");
        System.setProperty("socksServerUri.port", "1234");
        NetObjectFactory netObjectFactory = NetObjectFactory.newInstance();
        Socket socket = netObjectFactory.newSocket("google.com", 443);
        // ...
    }
}

The client API comes with a HostResolver object to resolve host names. By default, the HostResolver object resolves host names through the local system. To enable the HostResolver object to have the host names resolved from the SOCKS5 server instead, you would need to set the property socksClient.socks5.useResolveCommand set to true. This property can only be used if the SOCKS5 server supports the SOCKS5 RESOLVE command.

API example:

package com.example;

import com.github.jh3nd3rs0n.jargyle.client.HostResolver;
import com.github.jh3nd3rs0n.jargyle.client.NetObjectFactory;

import java.io.IOException;

import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;

public class ClientApp {
    public static void main(String[] args) throws IOException {
        System.setProperty("socksServerUri.scheme", "socks5");
        System.setProperty("socksServerUri.host", "jargyle.net");
        System.setProperty("socksServerUri.port", "1234");
        NetObjectFactory netObjectFactory = NetObjectFactory.newInstance();
        HostResolver hostResolver = netObjectFactory.newHostResolver();
        InetAddress inetAddress = hostResolver.resolve("google.com");
        Socket socket = netObjectFactory.newSocket(inetAddress, 443);
        // ...
    }
}

Routing Traffic Through a Specified Chain of SOCKS Servers

You can have the client route traffic through a specified chain of SOCKS servers. To do this, you will need to create a chain of SocksClient objects with each SocksClient object specifying a SOCKS server.

API example:

package com.example;

import com.github.jh3nd3rs0n.jargyle.client.HostResolver;
import com.github.jh3nd3rs0n.jargyle.client.NetObjectFactory;
import com.github.jh3nd3rs0n.jargyle.client.Properties;
import com.github.jh3nd3rs0n.jargyle.client.Scheme;
import com.github.jh3nd3rs0n.jargyle.client.SocksClient;

import java.io.IOException;

import java.net.DatagramSocket;
import java.net.ServerSocket;
import java.net.Socket;

public class ClientApp {
    public static void main(String[] args) throws IOException {
        SocksClient socksClient1 = Scheme.SOCKS5
            .newSocksServerUri("betabeta.net", "3456")
            .newSocksClient(Properties.of());
        SocksClient socksClient2 = Scheme.SOCKS5
            .newSocksServerUri("alphaalpha.net", "2345")
            .newSocksClient(Properties.of(), socksClient1);
        SocksClient socksClient3 = Scheme.SOCKS5
            .newSocksServerUri("jargyle.net", "1234")
            .newSocksClient(Properties.of(), socksClient2);
        NetObjectFactory netObjectFactory = 
            socksClient3.newSocksNetObjectFactory();
        // ...
    }
}

The known limitations of routing traffic through a specified chain of SOCKS servers include the following:

  • Only TCP traffic can be routed through the chain. The client will attempt to route any UDP traffic through the last SOCKS server of the chain.