kriegaex/BootstrapAgent.java

badabapidas · 2021-03-24T12:34:34Z

Hi I was trying this sample but with the mentioned version I am getitng a compilation error in the below line
ClassInjector.UsingInstrumentation.Target.BOOTSTRAP

As it seems like Target is private but in the documentation its stil saying its public. So I am confused here. Can you please help me here.

kriegaex · 2021-03-24T16:04:32Z

If you want help, I need details. Which Java version? Which ByteBuddy version? Where ist your exception stack trace?

I remember I tried that with Java 8. Please confirm that it works with Java 8 and ByteBudy 1.10.10 or greater. With Java 9+ there might be JVM restrictions which stop that from working, I am not sure.

badabapidas · 2021-03-25T04:37:29Z

I am using Java 8, Bytebuddy version 1.10.9 as you mentioned in the top. I am getting compile time dependency

ClassInjector.UsingInstrumentation
  .of(tempDirectory, ClassInjector.UsingInstrumentation.**Target**.BOOTSTRAP, instrumentation)
  .inject(Collections.singletonMap(new TypeDescription.ForLoadedType(MyInterceptor.class),

Its saying Target filed can not be found. Not sure why in my case it could not found the Target field. Not sure if the issue with IDE which should not be the cases usually, I am using eclipse.

kriegaex · 2021-03-25T08:08:19Z

Sorry, your problem must be a different one. This enum Target exists and was public since version 0.6 and still exists in 1.10.22. Do you have a Maven project or did you just set up everything manually in Eclipse? If Maven, show me your POM. If only Eclipse, show me your project configuration files or a screenshot of the libraries in your classpath. I also want to see the original compile error (textual copy or screenshot), not just you describing an error, showing me a copy of my own code instead of your side of the situation.

May I ask about your background and development experience? For how long have you been programming in Java? How much experience do you have in using Eclipse?

badabapidas · 2021-03-25T10:06:25Z

I have tried both the ways (gradle project and manually setup a new eclipse project). Gradle file is shown as below

I created a project and added netbuddy libraries and then used the exact code from here. Thats it.

For error please refer the below

Java in use
openjdk version "1.8.0_261"
OpenJDK Runtime Environment (Zulu 8.47.0.16-SA-win64) (build 1.8.0_261-b09)
OpenJDK 64-Bit Server VM (Zulu 8.47.0.16-SA-win64) (build 25.261-b09, mixed mode)

I have 7 years of development experience in java.

kriegaex · 2021-03-25T10:37:40Z

Hard to see what is wrong. Some more questions:

Please show me your imports.
Is your JDK really a JDK or a JRE?
Did you try adding /bin/tools.jar to your classpath?

The easiest would be to zip the whole project incl. Eclipse files and upload it so I can inspect it. I am working in IntelliJ, but I have Eclipse here too. I just do not want to recreate your project from scratch, speculating what might be the problem. I prefer to try your exact setup (except for the path to the JDK, maybe, mine is a bit older).

badabapidas · 2021-03-25T10:59:45Z

I have uploaded this project in my github. Please let me know if you are facing any issue accessing the same.

To your points

Please show me your imports.

import net.bytebuddy.agent.ByteBuddyAgent;
import net.bytebuddy.agent.builder.AgentBuilder;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.dynamic.ClassFileLocator;
import net.bytebuddy.dynamic.loading.ClassInjector;
import net.bytebuddy.implementation.MethodDelegation;
import net.bytebuddy.implementation.bind.annotation.SuperCall;
import net.bytebuddy.matcher.ElementMatchers;

import java.io.File;
import java.lang.instrument.Instrumentation;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.file.Files;
import java.util.Collections;
import java.util.concurrent.Callable;

Is your JDK really a JDK or a JRE?

Tried with both no success.

Did you try adding /bin/tools.jar to your classpath?

I have not tried this

Please let me know if you need more details.

kriegaex · 2021-03-25T11:43:29Z

I cloned your project into my IntelliJ IDEA, imported Gradle and set JDK 8 as runtime environment. I got strange JNI errors about language levels for bytecode not matching, so I added this to your Gradle build file:

compileJava {
  sourceCompatibility = '1.8'
  targetCompatibility = '1.8'
}

That works for me again, just like in my own Maven build. Please note however, that Java 9+ is more complicated and I do not really understand the code in raphw/byte-buddy#697.

badabapidas · 2021-03-25T12:24:04Z

Thanks for all the effort and your time. But for me after adding the mentioned block in the build script could not resolve the error. Now I am not sure if eclipse has some configuration issue may be I will try with other IDE.

Anyway thank you.

kriegaex · 2021-03-25T13:30:37Z

I never use Gradle, always Maven. And 90% I use IDEA, not Eclipse. But normally Maven projects in Eclipse work fairly well. I have no Gradle experience and saw that my Eclipse 2021-03 could not import the Gradle project, there were error messages during import related to Gradle. Directly opening the Eclipse project showed missing Byte Buddy dependencies. Anyway, as soon as I added them as external JARs from my local Maven repository, everything works like a charm in Eclipse too. I think you are not so much struggling with Byte Buddy but with your Eclipse and Gradle configuration.

parmar-tejas · 2024-01-11T11:31:35Z

The provided code intercepts the connect method of the HttpURLConnection class in Java 8. However, when attempting to run the same code with Java 17, it results in an error provided below.
please provide any solutions or suggestion.

CODE :

package com.bytebuddy.bytebuddydemo.test;

import net.bytebuddy.agent.ByteBuddyAgent;
import net.bytebuddy.agent.builder.AgentBuilder;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.dynamic.ClassFileLocator;
import net.bytebuddy.dynamic.loading.ClassInjector;
import net.bytebuddy.implementation.MethodDelegation;
import net.bytebuddy.implementation.bind.annotation.Origin;
import net.bytebuddy.implementation.bind.annotation.SuperCall;
import net.bytebuddy.matcher.ElementMatchers;

import java.io.File;
import java.lang.instrument.Instrumentation;
import java.lang.reflect.Method;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.file.Files;
import java.util.Collections;
import java.util.concurrent.Callable;

public class Test {
	public static void main(String[] args) throws Exception {
		premain(null, ByteBuddyAgent.install());
		HttpURLConnection urlConnection = (HttpURLConnection) new URL("http://www.google.com").openConnection();
		System.out.println(urlConnection.getRequestMethod());
		System.out.println(urlConnection.getResponseCode());
	}

	public static void premain(String arg, Instrumentation instrumentation) throws Exception {
		File tempDirectory = Files.createTempDirectory("tmp").toFile();
		ClassInjector.UsingInstrumentation
				.of(tempDirectory, ClassInjector.UsingInstrumentation.Target.BOOTSTRAP, instrumentation)
				.inject(Collections.singletonMap(new TypeDescription.ForLoadedType(MyInterceptor.class),
						ClassFileLocator.ForClassLoader.read(MyInterceptor.class)));
		new AgentBuilder.Default().ignore(ElementMatchers.nameStartsWith("net.bytebuddy."))
				.with(new AgentBuilder.InjectionStrategy.UsingInstrumentation(instrumentation, tempDirectory))
				.type(ElementMatchers.nameEndsWith(".HttpURLConnection"))
				.transform((builder, typeDescription, classLoader, module) -> builder
						.method(ElementMatchers.named("connect")).intercept(MethodDelegation.to(MyInterceptor.class)))
				.installOn(instrumentation);
	}

	public static class MyInterceptor {
		public static void intercept(@SuperCall Callable<?> zuper, @Origin Method method) throws Exception {
			System.out.println("Intercepted!");
			System.out.println("method :: !" + method);
			zuper.call();

		}
	}
}

ERROR :

Java HotSpot(TM) 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
Java HotSpot(TM) 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
Exception in thread "main" java.lang.ExceptionInInitializerError
at java.base/sun.net.www.protocol.http.Handler.openConnection(Handler.java:62)
at java.base/sun.net.www.protocol.http.Handler.openConnection(Handler.java:57)
at java.base/java.net.URL.openConnection(URL.java:1094)
at com.JavaAgent.Agent.Test.main(Test.java:26)
Caused by: java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at java.base/sun.net.www.protocol.http.HttpURLConnection.(HttpURLConnection.java:435)
... 4 more
Caused by: java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at net.bytebuddy.dynamic.Nexus.initialize(Nexus.java:143)
... 9 more
Caused by: java.lang.IllegalStateException: Cannot load injected class
at net.bytebuddy.dynamic.loading.ClassInjector$UsingInstrumentation.injectRaw(ClassInjector.java:2498)
at net.bytebuddy.dynamic.loading.ClassInjector$AbstractBase.inject(ClassInjector.java:118)
at net.bytebuddy.agent.builder.AgentBuilder$InitializationStrategy$SelfInjection$Dispatcher$InjectingInitializer.onLoad(AgentBuilder.java:3855)
... 14 more
Caused by: java.lang.ClassNotFoundException: sun/net/www/protocol/http/HttpURLConnection$auxiliary$vcxnSSGw
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:467)
at net.bytebuddy.dynamic.loading.ClassInjector$UsingInstrumentation.injectRaw(ClassInjector.java:2487)
... 16 more

kriegaex · 2024-01-12T01:45:05Z

@parmar-tejas, I played around with it for a while and was able to get it working. Please try the updated version.

Thanks to @raphw and @wu-sheng for the inspiration in Byte Buddy issue #697.

Try it on JDoodle.

parmar-tejas · 2024-01-14T08:43:38Z

@kriegaex , Yes its working now. Thank you so much !!

Ch35Tnut · 2024-01-16T08:02:01Z

hi, @kriegaex , I've tried your demo, it works. But i want to enhance java.lang.String? It not works. jdk is 1.8.0_301, bytebuddy is 1.14.11。Could you give me some advice？

Input

someting

Expected output

String Intercepted!
hello something world

Actually output

 hello something world

My code

package org.example;

import net.bytebuddy.agent.ByteBuddyAgent;
import net.bytebuddy.agent.builder.AgentBuilder;
import net.bytebuddy.dynamic.ClassFileLocator;
import net.bytebuddy.dynamic.loading.ClassInjector;
import net.bytebuddy.implementation.MethodDelegation;
import net.bytebuddy.implementation.bind.annotation.SuperCall;
import net.bytebuddy.matcher.ElementMatchers;

import java.lang.instrument.Instrumentation;
import java.util.Collections;
import java.util.Scanner;
import java.util.concurrent.Callable;
import static net.bytebuddy.matcher.ElementMatchers.none;
public class BootstrapStringAgent {
    public static void main(String[] args) throws Exception {
        premain(null, ByteBuddyAgent.install());
        while(true) {
            String input = new Scanner(System.in).nextLine();
            String hello = "hello ";
            hello = hello.concat(input);
            hello = hello.concat(" world");
            System.out.println(hello);
        }
        //Object urlConnection = new URL("http://www.baidu.com").openConnection();
        //System.out.println(urlConnection.getClass().getMethod("getRequestMethod").invoke(urlConnection));
    }

    public static void premain(String arg, Instrumentation instrumentation) throws Exception {
        ClassInjector.UsingUnsafe.Factory factory = ClassInjector.UsingUnsafe.Factory.resolve(instrumentation);
        factory.make(null, null).injectRaw(
                Collections.singletonMap(
                        BootstrapStringAgent.MyStringInterceptor.class.getName(),
                        ClassFileLocator.ForClassLoader.read(MyStringInterceptor.class)
                )
        );
        AgentBuilder agentBuilder = new AgentBuilder.Default();
        agentBuilder = agentBuilder.with(new AgentBuilder.InjectionStrategy.UsingUnsafe.OfFactory(factory));
        agentBuilder
                .ignore(none())
                .assureReadEdgeFromAndTo(instrumentation, Class.forName("java.lang.String"))
                .assureReadEdgeFromAndTo(instrumentation, MyStringInterceptor.class)
                .with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
                .with(AgentBuilder.Listener.StreamWriting.toSystemOut())
                .ignore(ElementMatchers.nameStartsWith("net.bytebuddy"))
                .type(ElementMatchers.named("java.lang.String"))
                .transform((builder, typeDescription, classLoader, module, protectionDomain) -> builder
                        .method(ElementMatchers.named("concat"))
                        .intercept(MethodDelegation.to(MyStringInterceptor.class))
                )
                .installOn(instrumentation);
    }

    public static class MyStringInterceptor {
        public static String intercept(@SuperCall Callable<String> zuper) throws Exception {
            System.out.println("String Intercepted!");
            return zuper.call();
        }
    }
}

kriegaex · 2024-01-17T09:05:11Z

The String class cannot be transformed like this. It is already loaded when your application starts, i.e. you literally have a bootstrapping problem here with JRE classes on the bootstrap classpath. In order to modify String, you need to instrument the JRE class and write it to disk, then prepend the path or JAR containing any patched JRE classes to the bootstrap class path when starting the JRE. On JDK 8 there is one way to do that, on 9+ it works differently.

Besides: String is also final, which is why it resists mocking because it cannot be subclassed. But the final modifier can also be removed while instrumenting the JRE as explained above. Whether that makes any sense, is another question. But I have done it experimentally a few years ago, and it worked.

All of this is very advanced and I recommend not to do it. The question is also, what the real-world use case would be. The better alternative probably is to instument the classes calling the JRE methods you are interested in, e.g. String::concat. That should be easier, and you can then replace the method call result in the caller rather than the callee.

From now on, please no more hijacking of this gist for new questions. This is not a support channel. If you have any questions, please ask your question on Stack Overflow with a full MCVE.

Ch35Tnut · 2024-01-18T03:22:59Z

@kriegaex Thank you very much for your suggestion. I have previously enhanced the String class using ASM. Seeing that ByteBuddy is more convenient to use, I'm interested in trying to modify String with ByteBuddy.

The question is also, what the real-world use case would be.

A real-world use case for this is IAST . If I want to trace the method invocation chain triggered by a specific request to detect potential security risks, I need to track the input parameters and return values of String::concat, similar to the example below:

public class SqlController {
    @RequestMapping("/sql-test")
    public String sqlTest(@RequestParam String name){
        String sql = "select id from user where name = '";
        sql = sql.concat(name);
        sql = sql.concat("'");
        return SqlUtil.exec(sql);
}

The data flow process is as follows:

somebody -> select id from user where name = 'somebody -> select id from user where name = 'somebody'

Finally, thank you again for your suggestion.

kriegaex · 2024-01-18T04:50:51Z

I have previously enhanced the String class using ASM.

How? Where is your MCVE? Just show your ASM solution (on StackOverflow, not here) as a point of departure for how to transform that into an equivalent solution using another tool.

Regarding your example, it looks as if there is absolutely no need to instrument the String class, and I doubt that your ASM solution did. Otherwise, you would already know how to bootstrap it. Probably, you instrumented the calls in sqlTest, which is easy to replicate with BB.

If you ask me, BB is also too complicated for this approach. I suggest to use Eclipse AspectJ, which has special syntax for intercepting method or constructor calls, field access and many more. Spoiler: I am the current AspectJ maintainer.

From now on no more follow-up discussion here about your use case! Like I said, ask a Stack Overflow question with a proper reproducer for what you want to port to BB or AspectJ.

Ch35Tnut · 2024-01-18T11:29:51Z

How? Where is your MCVE? Just show your ASM solution (on StackOverflow, not here) as a point of departure for how to transform that into an equivalent solution using another tool.

Just to prove that using ASM can enhance Java. lang.String. Here is my demo.
I've tried on HttpURLConnection, it's not works on JDK17, maybe it's appropriate to answer that question.
Thank you for your help. And let me know that if I have any problems next time, I should use StackOverFlow instead of Gist.

kriegaex · 2024-01-18T13:44:05Z

Thanks for proving that your agent has absolutely no effect.

I cloned the project, built it and then put it on the JVM command line with -javaagent:.../EnhanceStringAgent-1.0-SNAPSHOT.jar, running this sample program:

public class App {
  public static void main(String[] args) {
    System.out.println("Hello ".concat("world!"));
  }
}

The console log says:

Enhance: java/lang/String
Hello world!

I.e., the agent starts, of course, but the transformer never does anything. And why would it? Class String was loaded before already. Like I said, your agent should instrument the caller, not the callee in this case.

Ch35Tnut · 2024-01-18T15:16:43Z

It works on me. Just want you to know that I'm not lying.And this strategy has been proven in Project.

That's so weird. I know the Class String was loaded before already. So it need to be retransformed, like this:

Class[] classes = instrumentation.getAllLoadedClasses();
for (Class clazz : classes) {
    if (instrumentation.isModifiableClass(clazz)) {
        instrumentation.retransformClasses(clazz);
    }
}

My sample program bellows , your sample program wokrs on my agent too.

public class Main {
    public static void main(String[] args) {
        while (true){
            String input = new Scanner(System.in).nextLine();
            System.out.println(input.concat(", hello!"));
        }
    }
}

Input:

ssss

Output

Enhance String::concat
ssss, hello!

Maybe my config is useful.
build agent with IDEA:

add VM option on sample project, -javaagent:C:\Users\A\Desktop\Code\Java\EnhanceStringAgent-main\target\EnhanceStringAgent-1.0-SNAPSHOT.jar

RUN sample project ，console log:

kriegaex · 2024-01-18T16:46:06Z

OK, I noticed that it started working for me locally when I downgraded my runtime from JDK 17 to 8, 11 or even 16. So I upgraded your code to use the latest ASM v9.6 and also bumped the ASM API version 8 in your project to Opcodes.ASM9. Now, it also works on JDKs 17 to 21. That is a starting point. I do not have any more time tonight to look into this any further, but tomorrow maybe I can spare a little bit of time.

I guess, I did something similar a few years ago in my testing tool Sarek, which I never got around to promote, even though it is feature-complete. (Only the API is not so easy to use. But I am degressing.) Basically, I can already say that if it works with ASM, there is no reason to believe that it will not work with Byte Buddy, too.

kriegaex · 2024-01-19T03:50:02Z

@Ch35Tnut, what you want is possible, like I said yesterday. But you need to avoid the interceptor approach in favour of an advice-based one and also make sure that you do not alter the original method signature. Finally, you need to issue retransformation, just like your custom ASM agent does.

See https://gist.github.com/kriegaex/8228c8ba664c730157c2fef3c5fd78e7.

kriegaex/BootstrapAgent.java

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	package net.bytebuddy;

	import net.bytebuddy.agent.ByteBuddyAgent;
	import net.bytebuddy.agent.builder.AgentBuilder;
	import net.bytebuddy.dynamic.ClassFileLocator;
	import net.bytebuddy.dynamic.loading.ClassInjector;
	import net.bytebuddy.implementation.MethodDelegation;
	import net.bytebuddy.implementation.bind.annotation.SuperCall;
	import net.bytebuddy.matcher.ElementMatchers;

	import java.lang.instrument.Instrumentation;
	import java.net.URL;
	import java.util.Collections;
	import java.util.concurrent.Callable;

	import static net.bytebuddy.matcher.ElementMatchers.none;

	/**
	* Inspired by <a href="https://github.com/apache/skywalking">Apache SkyWalking</a>, specifically
	* <a href="https://github.com/apache/skywalking/blob/bc64c6a12770031478d29e2f19004796584374c9/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/bootstrap/BootstrapInstrumentBoost.java">
	* this class</a>. Discussed in <a href="https://github.com/raphw/byte-buddy/issues/697">Byte Buddy issue #697</a>.
	* <p>
	* Successfully tested on JDKs 8 to 21. Should print:
	* <pre>
	* Intercepted!
	* GET
	* </pre>
	*/
	public class BootstrapAgent {
	public static void main(String[] args) throws Exception {
	premain(null, ByteBuddyAgent.install());
	Object urlConnection = new URL("http://www.google.com").openConnection();
	System.out.println(urlConnection.getClass().getMethod("getRequestMethod").invoke(urlConnection));
	}

	public static void premain(String arg, Instrumentation instrumentation) throws Exception {
	ClassInjector.UsingUnsafe.Factory factory = ClassInjector.UsingUnsafe.Factory.resolve(instrumentation);
	factory.make(null, null).injectRaw(
	Collections.singletonMap(
	MyInterceptor.class.getName(),
	ClassFileLocator.ForClassLoader.read(MyInterceptor.class)
	)
	);
	AgentBuilder agentBuilder = new AgentBuilder.Default();
	agentBuilder = agentBuilder.with(new AgentBuilder.InjectionStrategy.UsingUnsafe.OfFactory(factory));
	agentBuilder
	.ignore(none())
	.assureReadEdgeFromAndTo(instrumentation, Class.forName("java.net.HttpURLConnection"))
	.assureReadEdgeFromAndTo(instrumentation, MyInterceptor.class)
	.ignore(ElementMatchers.nameStartsWith("net.bytebuddy."))
	.type(ElementMatchers.nameContains("HttpURLConnection"))
	.transform((builder, typeDescription, classLoader, module, protectionDomain) -> builder
	.method(ElementMatchers.named("getRequestMethod"))
	.intercept(MethodDelegation.to(MyInterceptor.class))
	)
	.installOn(instrumentation);
	}

	public static class MyInterceptor {
	public static String intercept(@SuperCall Callable<String> zuper) throws Exception {
	System.out.println("Intercepted!");
	return zuper.call();
	}
	}
	}

kriegaex/BootstrapAgent.java

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Input

Expected output

Actually output

My code

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