动态附加Java代理不起作用

Question

我为编码挑战编写了以下代码。该程序的目的是将程序启动后附加到另一个Java过程并加载仪器引擎。这通常是在Java中通过在您的代理JAR文件中实现AgentMain方法来完成的。我在下面的代码中生成了所有这些内容：

在运行玩具程序的JVM上看到错误，并且线索是由于某种原因认为代理类文件名是代理$ 1。我评论了我对字节带纸的使用情况，只是尝试使用内置库加载代理文件，但仍然失败。

heartbeat : 373 pid = 21992
heartbeat : 374 pid = 21992
Exception in thread "Attach Listener" 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.instrument/sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:491)
    at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndCallAgentmain(InstrumentationImpl.java:513)
Caused by: java.lang.NoClassDefFoundError: Agent$1
    at Agent.agentmain(Agent.java:8)
    ... 6 more
Caused by: java.lang.ClassNotFoundException: Agent$1
    ... 7 more
Agent failed to start!

import com.sun.tools.attach.VirtualMachine;
import net.bytebuddy.ByteBuddy;
import net.bytebuddy.agent.ByteBuddyAgent;
import net.bytebuddy.dynamic.loading.ClassReloadingStrategy;
import net.bytebuddy.implementation.FixedValue;

import java.io.*;
import java.lang.instrument.Instrumentation;

import static net.bytebuddy.matcher.ElementMatchers.named;

public class Thief {

    public static void main(String[] args) throws Exception {
        Thief thief = new Thief();

        VirtualMachine jvm = VirtualMachine.attach("21992");
        File agentFile = new File("agent.jar");
        jvm.loadAgent(agentFile.getAbsolutePath());

        //thief.guessSecurityCode("24472");
    }

    public String guessSecurityCode(final String pid) throws Exception {
        File jarFile = createAgent();
        ByteBuddyAgent.attach(jarFile, pid);
        return "0000";
    }

    private static String generateSimpleAgent2() {

        return  "import java.lang.instrument.ClassFileTransformer;" + "\n" +
                "import java.lang.instrument.Instrumentation;" + "\n" +
                "import java.security.ProtectionDomain;" + "\n" +
                "\n\n" +
                "public class Agent {" +"\n" +
                "    public static void agentmain(String argument, Instrumentation inst) {" +"\n" +
                "    }" +"\n" +
                "}" +"\n";
    }

    private static String generateSimpleAgent() {

        return  "import java.lang.instrument.ClassFileTransformer;" + "\n" +
                "import java.lang.instrument.Instrumentation;" + "\n" +
                "import java.security.ProtectionDomain;" + "\n" +
                "\n\n" +
                "public class Agent {" +"\n" +
                "    public static void agentmain(String argument, Instrumentation inst) {" +"\n" +
                "        inst.addTransformer(new ClassFileTransformer() {" +"\n" +
                "            @Override" +"\n" +
                "            public byte[] transform(" +"\n" +
                "                ClassLoader loader," +"\n" +
                "                String className," +"\n" +
                "                Class<?> classBeingRedefined," +"\n" +
                "                ProtectionDomain protectionDomain," +"\n" +
                "                byte[] classFileBuffer) {" +"\n" +
                "            System.out.println(\"transform on : \" +className);" +"\n" +
                "            return classFileBuffer;" +"\n" +
                "            }" +"\n" +
                "        });" +"\n" +
                "    }" +"\n" +
                "}" +"\n";
    }

    private static String generateAgentManifest() {
        return  String.join("\n", "Agent-Class: Agent",
                "Can-Retransform-Classes: true",
                "Can-Redefine-Classes: true",
                "Premain-Class: Agent"
        );
    }

    private static String generateAgentManifest2() {
        return  String.join("\n",
                "Manifest-Version: 1.0",
                "Agent-Class: Agent",
                "Permissions: all-permissions"
        );
    }

    private static String generateTransformer() {
        return String.join("\n",
                "import java.lang.instrument.ClassFileTransformer;",
                "import java.security.ProtectionDomain;",
                "import java.util.Arrays;",
                "public class Transformer implements ClassFileTransformer {",
                "    public byte[] transform(ClassLoader loader, String className, Class<?> cls, ProtectionDomain dom, byte[] buf) {",
                "        return null;",
                "    }",
                "}"
        );
    }

    private static void writeFile(String path, String data) throws IOException {
        final PrintWriter out = new PrintWriter(path);
        out.print(data);
        out.close();
    }

    private static void runCommand(String cmd) throws Exception {
        System.out.println("[commmand] " + cmd);
        String s;
        Process p = Runtime.getRuntime().exec(cmd);
        BufferedReader out = new BufferedReader(new InputStreamReader(p.getInputStream()));
        while ((s = out.readLine()) != null) {
            System.out.println("[out] " + s);
        }
        out = new BufferedReader(new InputStreamReader(p.getErrorStream()));
        while ((s = out.readLine()) != null) {
            System.out.println("[err] " + s);
        }
        p.waitFor();
        System.out.println("[exit status] " + p.exitValue());
        p.destroy();
    }

    private static File createAgent() throws Exception {
        writeFile("Agent.java", generateSimpleAgent2());
        writeFile("Transformer.java", generateTransformer());
        writeFile("manifest.mf", generateAgentManifest2());
        runCommand("javac Agent.java Transformer.java");
        runCommand("jar -cfm agent.jar manifest.mf Agent.class Transformer.class");
        return new File("agent.jar");
    }
}

有人知道我在这里做错了吗？

Answer 1

使用generatesImpleagent2（），它起作用。它不会以相同的方式失败，就像您在 ewramner 的答案下的评论中所说的那样。那应该给你一个线索。此外，如果您只是阅读异常并相信它告诉您的内容，那么您就会知道该怎么做。再次：

java.lang.ClassNotFoundException: Agent$1

ie，generatesImpleagent（）创建两个类文件，一个用于代理本身，一个用于匿名类。这正是 javac 有望做的。只需检查输出目录，您就会看到它。只需将丢失的类文件添加到JAR上并感到高兴：

runCommand("jar -cfm agent.jar manifest.mf Agent.class Agent$1.class Transformer.class");

现在，具有匿名变压器类的代理也可以工作。我测试了它。

Answer 2

代理$ 1是一个匿名类，因此它必须是您在这里创建的一个：

new ClassFileTransformer() { ... }

关于为什么找不到它以及如何修复它我不知道，也许您可​​以生成一个真实的名字命名在引用之前，上课？