I made a java agent with bytebuddy. It works well untill target application load classes form uRLConnection.getInputStream. The target app works well without attachment the agent, but shows exception [java.lang.ClassNotFoundException] when the agent attached. this is app's classloading line.
return this.getClass().getClassLoader().loadClass(string) //string points the name of a byte array.
In the application, the classes is provided in the form of byte array from the uRLConnection.getInputStream at runtime and the application loads those at runtime. The eclipst stacktrace:
[Byte Buddy] COMPLETE client [app.m@7dc3712, null, loaded=false]
Exception in thread "main" java.lang.NoClassDefFoundError: kh
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at app.m.loadClass(m.java:22)
at java.lang.ClassLoader.loadClass(Unknown Source)
at app.appletviewer.b(appletviewer.java:1176)
at app.appletviewer.a(appletviewer.java:454)
at Launcher.main(Launcher.java:43)
Caused by: java.lang.ClassNotFoundException: kh
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at app.u.loadClass(u.java:79)
at java.lang.ClassLoader.findSystemClass(Unknown Source)
at app.m.loadClass(m.java:30)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 7 more
My agent is:
try {
new AgentBuilder.Default()
.with(new AgentBuilder.InitializationStrategy.SelfInjection.Eager())
.with(AgentBuilder.Listener.StreamWriting.toSystemError())
.type((ElementMatchers.any()))
.transform((builder, typeDescription, classLoader, module) -> builder
.method(ElementMatchers.any())
.intercept(Advice.to(MyAdviser.class))
).installOn(instrumentation);
} catch (Exception e) {
return;
}
I also tried
.transform(new AgentBuilder.Transformer.ForAdvice()
.include(MyAdviser.class.getClassLoader())
.advice(ElementMatchers.any(), MyAdviser.class.getName()))
But it doesn't seem to be attached.