Attaching a remote host process in ByteBuddy - byte-buddy

Question

I am new to ByteBuddy and trying to setup instrumentation for a process running on a remote process.
My remote process is started with -XX:+StartAttachListener.
Created a simple Maven project with the following in the pom.
<dependency>
<groupId>net.bytebuddy</groupId>
<artifactId>byte-buddy-agent</artifactId>
<version>1.10.7</version>
</dependency>
<!-- https://mvnrepository.com/artifact/net.bytebuddy/byte-buddy -->
<dependency>
<groupId>net.bytebuddy</groupId>
<artifactId>byte-buddy</artifactId>
<version>1.10.7</version>
</dependency>
Created an agent class with a premain method.
public class Agent {
public static void premain(String args, Instrumentation instrumentation) {
System.out.println("Premain");
File file ;
try {
file = (new File("Agent.jar"));
ByteBuddyAgent.attach(file,"18467");
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
Questions:-
Do I need to generate Agent.jar here? Or else, it comes with byte-buddy?
ByteBuddyAgent.attach doesn't take the remote hostname. How can I define the remote host process to attach? Or else, byte buddy should be running in the same host where the Java process in running.
The below example to run the agent along with the jar under test.
java -javaagent:/path/to/agent.jar -cp jar-under-test.jar Foo.Main
How to run the agent attacher as a separate process to attach the java agent to a java process running on a remote host?

Answer 1

Remote attachment in Java is only possible not only from the same host but also only from the same OS user. This is meant as a security mechanism as it would otherwise be fairly simple to take over any Java process from a remote location.
Byte Buddy simply provides wrappers around it. You can use byte-buddy-agent.jar as your agent and attach it either to your own process (ByteBuddyAgent.install()) or to a remote one ByteBuddyAgent.attach(pid, new File("byte-buddy-agent.jar")). An instance of Instrumentation is then available via Installer class to the entire Java process. Adding byte-buddy-agent.jar to the command line has the same effect for that process.