Magisk/stub/src/main/java/com/topjohnwu/magisk/InjectAPK.java

package com.topjohnwu.magisk;

import android.app.AppComponentFactory;
import android.app.Application;
import android.content.ContentResolver;
import android.content.Context;
import android.content.ContextWrapper;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Build;
import android.util.Log;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Field;

import io.michaelrocks.paranoid.Obfuscate;

@Obfuscate
public class InjectAPK {

    static Object componentFactory;

    private static DelegateComponentFactory getComponentFactory() {
        return (DelegateComponentFactory) componentFactory;
    }

    @SuppressWarnings("ResultOfMethodCallIgnored")
    static Application setup(Context context) {
        // Get ContextImpl
        while (context instanceof ContextWrapper) {
            context = ((ContextWrapper) context).getBaseContext();
        }

        File apk = DynAPK.current(context);
        File update = DynAPK.update(context);
        if (update.exists())
            update.renameTo(apk);
        if (!apk.exists()) {
            // Try copying APK
            Uri uri = new Uri.Builder().scheme("content")
                    .authority("com.topjohnwu.magisk.provider")
                    .encodedPath("apk_file").build();
            ContentResolver resolver = context.getContentResolver();
            try (InputStream src = resolver.openInputStream(uri)) {
                if (src != null) {
                    try (OutputStream out = new FileOutputStream(apk)) {
                        byte[] buf = new byte[4096];
                        for (int read; (read = src.read(buf)) >= 0;) {
                            out.write(buf, 0, read);
                        }
                    }
                }
            } catch (Exception ignored) {}
        }
        if (apk.exists()) {
            ClassLoader cl = new InjectedClassLoader(apk);
            PackageManager pm = context.getPackageManager();
            PackageInfo pkgInfo = pm.getPackageArchiveInfo(apk.getPath(), 0);
            try {
                return createApp(context, cl, pkgInfo.applicationInfo);
            } catch (Exception e) {
                Log.e(InjectAPK.class.getSimpleName(), "", e);
                apk.delete();
            }
            // fallthrough
        }

        ClassLoader cl = new RedirectClassLoader();
        try {
            setClassLoader(context, cl);
            if (Build.VERSION.SDK_INT >= 28) {
                getComponentFactory().loader = cl;
            }
        } catch (Exception e) {
            Log.e(InjectAPK.class.getSimpleName(), "", e);
        }

        return null;
    }

    private static Application createApp(Context context, ClassLoader cl, ApplicationInfo info)
            throws ReflectiveOperationException {
        // Create the receiver Application
        Object app = cl.loadClass(info.className)
                .getConstructor(Object.class)
                .newInstance(DynAPK.pack(dynData()));

        // Create the receiver component factory
        Object factory = null;
        if (Build.VERSION.SDK_INT >= 28) {
            factory = cl.loadClass(info.appComponentFactory).newInstance();
        }

        setClassLoader(context, cl);

        // Finally, set variables
        if (Build.VERSION.SDK_INT >= 28) {
            getComponentFactory().loader = cl;
            getComponentFactory().receiver = (AppComponentFactory) factory;
        }

        return (Application) app;
    }

    // Replace LoadedApk mClassLoader
    private static void setClassLoader(Context impl, ClassLoader cl)
            throws NoSuchFieldException, IllegalAccessException {
        Field mInfo = impl.getClass().getDeclaredField("mPackageInfo");
        mInfo.setAccessible(true);
        Object loadedApk = mInfo.get(impl);
        Field mcl = loadedApk.getClass().getDeclaredField("mClassLoader");
        mcl.setAccessible(true);
        mcl.set(loadedApk, cl);
    }

    private static DynAPK.Data dynData() {
        DynAPK.Data data = new DynAPK.Data();
        data.version = BuildConfig.STUB_VERSION;
        data.classToComponent = Mapping.inverseMap;
        return data;
    }

}