[英]ByteBuddy attach to a local running process
我正在嘗試使用 ByteBuddy 附加到在我的計算機上運行的正在運行的進程。 我希望在我附加到正在運行的程序時,我的代理將導致加載的類被重新加載並顯示我的 Transformer 的打印語句。
相反,當我停止附加到的正在運行的進程時,我會看到一些來自 Transformer 的打印語句,用於某些 JDK 類。
代碼貼在下面:
import net.bytebuddy.ByteBuddy;
import net.bytebuddy.agent.ByteBuddyAgent;
import net.bytebuddy.dynamic.loading.ClassReloadingStrategy;
import net.bytebuddy.implementation.FixedValue;
import java.io.*;
import static net.bytebuddy.matcher.ElementMatchers.named;
public class Thief {
public static void main(String[] args) throws Throwable {
String pid = "86476"; // <-- modify this to attach to any java process running on your computer
System.out.println(new Thief().guessSecurityCode(pid));
}
public String guessSecurityCode(final String pid) throws Throwable {
File jarFile = createAgent();
ByteBuddyAgent.attach(jarFile, pid);
return "0000";
}
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 Throwable {
writeFile("Agent.java", generateSimpleAgent());
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");
}
}
僅添加轉換器不會導致重新加載已加載的類。 默認情況下,您的轉換器只會看到新加載的類,因此您在退出時看到某些類的原因是這些類之前沒有使用過,而是專門為關閉過程加載的。
要重新轉換類,您首先必須使用addTransformer(yourTransformer, true)
進行注冊,然后使用要轉換的類調用retransformClasses
。 注意getAllLoadedClasses和getInitiatedClasses(ClassLoader)
的存在
作為附加說明,我強烈不鼓勵采用將 Java 代理作為源代碼字符串嵌入的方法,需要將它們寫入臨時文件,調用編譯器並最終創建 jar 文件。 您可以輕松地將 Agent 類集成到您的普通源代碼中。 然后,要生成僅包含 Agent 類的 jar 文件,您只需將現有的.class
文件從應用程序的代碼庫復制到 Agent jar。 對於簡單的情況,您可以同時使您的應用程序 jar 文件成為有效的代理 jar 文件,並且只需使用該文件而無需任何額外的復制步驟。
此外,請記住, ClassFileTransformer
應始終為所有未更改的類返回null
。 返回原始類文件字節在語義上是相同的,但它需要調用方額外的努力才能發現您沒有更改它。 對於將為每個加載的類調用的代碼,但通常只對少數感興趣(或只想打印信息而不更改任何內容),這樣的性能問題很重要。
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