Not able to attach through oracle forms GUI object using dll injection and JNI

Question

Under one of my project I need to read VTextField GUI object of running oracle forms application, and set new value in it, I am able to inject my DLL into application and i am able to attach thorugh the current thread below is my code for this

JNIEnv* env;
JavaVM *jvm = NULL;
jsize jvm_count = 0;
jint res = 0;
#ifdef __STATIC_LIB_JVM
    res = JNI_GetCreatedJavaVMs(&jvm, 1, &jvm_count);
#else
{
    HINSTANCE hLibJVM;
    typedef jint(JNICALL GetCreatedJavaVMs_t)(JavaVM**, jsize, jsize*);
    GetCreatedJavaVMs_t *MyGetCreatedJavaVMs;
    hLibJVM = LoadLibrary(L"jvm.dll");
    MyGetCreatedJavaVMs = (GetCreatedJavaVMs_t*)GetProcAddress(hLibJVM,  "JNI_GetCreatedJavaVMs");
    res = MyGetCreatedJavaVMs(&jvm, 1, &jvm_count);
}
#endif
if (res == 0)
{
    if (jvm_count == 0)
    {
        jvm = NULL;
    }
}
else jvm = NULL;
bool mustDetach = false;
//jint retval = jvm->GetEnv((void**)&env, JNI_VERSION_1_6);
jint retval = jvm->GetEnv((void**)&env, JNI_VERSION_1_6);

if (retval == JNI_EDETACHED)
{
    JavaVMAttachArgs args;
    args.version = JNI_VERSION_1_6;
    args.name = NULL;
    args.group = NULL;
    retval = jvm->AttachCurrentThread((void**)&env, &args);
    mustDetach = true; // to clean up afterwards
}
else{
    fprintf(JNIStatus, "JNI is not processing\n"); // should never happen
}
if (retval != JNI_OK){
    fprintf(JNIStatus, "JNI is not ok\n"); // should never happen
}
else{
fprintf(JNIStatus, "JNI is  ok\n"); // should never happen
}
if (retval>=0)
    fprintf(JNIStatus, "Attachcurrentthread was successfull\n"); 

here i am getting output as Attach current thread was successful, but after this when i am trying to find class using below code , system is not able to find class for this

char* strin;
strin = "abcdef";
jstring str = env->NewStringUTF(strin);
jfieldID fid;
jclass clazz = env->FindClass("oracle/forms/ui/VTextField");
if (clazz == NULL) {
    fprintf(JNIStatus, "Can't find class %s", clazz);
}

Even i thought of that it because of local reference , but i tried to make jclass ob ject as global reference also but no luck :(

/* Create a global reference */
jclass clazzLUSCore = (_jclass*)env->NewGlobalRef(clazz);

/* The local reference is no longer useful */
env->DeleteLocalRef(clazz);

/* Is the global reference created successfully? */
if (clazzLUSCore == NULL) {
    fprintf(JNIStatus, "Error - clazzLUSCore is still null when it is suppose to be global\n");
}

I am newbie in c++, please help me on this , i am not able to find running application class , I need to attain this without accessing server code.

As per @michael comment, i tried to add this but its throwing exception i think. so not able to get class name

   JavaVM* gJvm = nullptr;
   static jobject gClassLoader;
   static jmethodID gFindClassMethod;

    JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *pjvm, void *reserved) {
     gJvm = pjvm;  // cache the JavaVM pointer
     auto env = getEnv();
     //replace with one of your classes in the line below
     auto randomClass = env->FindClass("oracle/forms/ui/VTextField");
     jclass classClass = env->GetObjectClass(randomClass);
     auto classLoaderClass = env->FindClass("java/lang/ClassLoader");
     auto getClassLoaderMethod = env->GetMethodID(classClass, "getClassLoader",
    "()Ljava/lang/ClassLoader;");
      gClassLoader = env->CallObjectMethod(randomClass, getClassLoaderMethod);
     gFindClassMethod = env->GetMethodID(classLoaderClass, "findClass",
    "(Ljava/lang/String;)Ljava/lang/Class;");

return JNI_VERSION_1_6;
    }

  jclass findClass(const char* name) {
   return static_cast<jclass>(getEnv()->CallObjectMethod(gClassLoader, gFindClassMethod, getEnv()->NewStringUTF(name)));

}

JNIEnv* getEnv() {
 JNIEnv *env;
 int status = gJvm->GetEnv((void**)&env, JNI_VERSION_1_6);
 if (status < 0) {
    status = gJvm->AttachCurrentThread((void**)&env, NULL);
    if (status < 0) {
        return nullptr;
    }
 }
 return env;

}

Answer 1

You need to get the correct class loader.

1. Use the Win32 FindWindow API to get a HWND for the main window of the application. You may use the Spy++ tool to get the exact properties of that window.
2. Dynamically load the jawt.dll, using the Win32 LoadLibrary API. That DLL is typically located in the parent directory of the directory containing the jvm.dll. Exemple :

C:\Program Files (x86)\Java\jre1.8.0_73\bin\jawt.dll
C:\Program Files (x86)\Java\jre1.8.0_73\bin\client\jvm.dll

You have many ways to get the LoadLibrary call to succeed:

• just use "jawt.dll"
• get the path of the already loaded jvm.dll, using GetModuleFileName and build a new path with it.
• get the path of the current executable (should be java.exe) passing a NULL module handle to GetModuleFileName. You should get the bin path.

Once you successfully loaded jawt.dll, use GetProcAdress to get the _JAWT_GetAWT@8 function, and call it. Exemple:

// error checking committed (for clarity...)
typedef jboolean (JNICALL * PGETAWT)(JNIEnv* env, JAWT* awt);
PGETAWT pGetAWT = (PGETAWT)GetProcAddress( hModJAWT, "_JAWT_GetAWT@8" );
JAWT jawt;
jawt.version = JAWT_VERSION_1_4;
pGetAWT( env, &jawt );

Now, you are able to call the wonderful GetComponent API:

jobject jObjMainWindow = jawt->GetComponent( env, (void*)hWndOfTheMainOracleWindow );

Then, use JNI to obtain the jclass of that main window, and then call the getClassLoader method of the Class Class.

With that Class Loader, FindClass should work much better.