foodfight.c

#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <stdint.h>
#include <unistd.h>
#include <stddef.h>
#include <stdbool.h>
#include <signal.h>

#include <jni.h>

static void go(jint (*JNI_CreateJavaVM)(JavaVM**, JNIEnv**, void*), int (*JNI_OnLoad)(JavaVM *)) {
    JavaVM *jvm = NULL;
    JNIEnv *env = NULL;
    JavaVMOption opt[4];
 
    opt[0].optionString = "-Djava.class.path=/data/local/tmp/food.apk";
    opt[1].optionString = "-agentlib:jdwp=transport=dt_android_adb,suspend=n,server=y";
    opt[2].optionString = "-Djava.library.path=/data/local/tmp";
    opt[3].optionString = "-verbose:jni";

    JavaVMInitArgs args = {
        .version = JNI_VERSION_1_6,
        .options = opt,
        .nOptions = 4,
        .ignoreUnrecognized = JNI_FALSE
    };
    printf("Creating Java VM\n");
    JNI_CreateJavaVM(&jvm, &env, &args);
    printf("Waiting for a debugger\n");
    raise(SIGTRAP);
    printf("Calling JNI_OnLoad\n");
    jint result = JNI_OnLoad(jvm);
    printf("Done with status code %d; destroying JVM\n", result);
    (*jvm)->DestroyJavaVM(jvm);
}

int main(int argc, const char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "usage: %s [path]\n", argv[0]);
        return -1;
    }

    void *handle = dlopen(argv[1], RTLD_NOW | RTLD_LOCAL);
    if (handle == NULL) {
        fprintf(stderr, "error loading `%s`\n", argv[1]);
        return -1;
    } else {
        fprintf(stderr, "loaded `%s`\n", argv[1]);
    }

    int (*JNI_OnLoad)(JavaVM *) = dlsym(handle, "JNI_OnLoad");
    if (JNI_OnLoad == NULL) {
        fprintf(stderr, "couldn't find JNI_OnLoad\n");
        return -1;
    }

    // load Dalvik
    void *dalvik = dlopen("libdvm.so", RTLD_NOW);
    if (dalvik == NULL) {
        fprintf(stderr, "error loading libdvm\n");
        return -1;
    } else {
        fprintf(stderr, "loaded libdvm.so\n");
    }

    jint (*JNI_CreateJavaVM)(JavaVM**, JNIEnv**, void*) = dlsym(dalvik, "JNI_CreateJavaVM");
    if (JNI_CreateJavaVM == NULL) {
        fprintf(stderr, "couldn't find JNI_CreateJavaVM\n");
        return -1;
    }

    go(JNI_CreateJavaVM, JNI_OnLoad);
    dlclose(handle);
    dlclose(dalvik);
    return 0;
}