Use official APIs to load dynamic resources

app/shared/src/main/java/com/topjohnwu/magisk/StubApk.java

@@ -1,14 +1,20 @@
 package com.topjohnwu.magisk;
 
 import static android.os.Build.VERSION.SDK_INT;
+import static android.os.ParcelFileDescriptor.MODE_READ_ONLY;
 
 import android.app.Activity;
 import android.content.Context;
 import android.content.Intent;
 import android.content.pm.ApplicationInfo;
 import android.content.res.AssetManager;
+import android.content.res.Resources;
+import android.content.res.loader.ResourcesLoader;
+import android.content.res.loader.ResourcesProvider;
+import android.os.ParcelFileDescriptor;
 
 import java.io.File;
+import java.io.IOException;
 import java.lang.reflect.Method;
 import java.util.Map;
 
@@ -50,12 +56,21 @@ public class StubApk {
         return new File(getDynDir(info), "update.apk");
     }
 
-    public static void addAssetPath(AssetManager asset, String path) {
+    public static void addAssetPath(Resources res, String path) {
-        try {
+        if (SDK_INT >= 30) {
-            if (addAssetPath == null)
+            try (var fd = ParcelFileDescriptor.open(new File(path), MODE_READ_ONLY)) {
-                addAssetPath = AssetManager.class.getMethod("addAssetPath", String.class);
+                var loader = new ResourcesLoader();
-            addAssetPath.invoke(asset, path);
+                loader.addProvider(ResourcesProvider.loadFromApk(fd));
-        } catch (Exception ignored) {}
+                res.addLoaders(loader);
+            } catch (IOException ignored) {}
+        } else {
+            AssetManager asset = res.getAssets();
+            try {
+                if (addAssetPath == null)
+                    addAssetPath = AssetManager.class.getMethod("addAssetPath", String.class);
+                addAssetPath.invoke(asset, path);
+            } catch (Exception ignored) {}
+        }
     }
 
     public static void restartProcess(Activity activity) {

app/src/main/java/com/topjohnwu/magisk/core/Hacks.kt

@@ -18,7 +18,7 @@ import com.topjohnwu.magisk.di.AppContext
 
 lateinit var AppApkPath: String
 
-fun AssetManager.addAssetPath(path: String) = StubApk.addAssetPath(this, path)
+fun Resources.addAssetPath(path: String) = StubApk.addAssetPath(this, path)
 
 fun Context.wrap(): Context = if (this is PatchedContext) this else PatchedContext(this)
 
@@ -32,17 +32,18 @@ private class PatchedContext(base: Context) : ContextWrapper(base) {
 fun Resources.patch(): Resources {
     syncLocale()
     if (isRunningAsStub)
-        assets.addAssetPath(AppApkPath)
+        addAssetPath(AppApkPath)
     return this
 }
 
 fun createNewResources(): Resources {
     val asset = AssetManager::class.java.newInstance()
-    asset.addAssetPath(AppApkPath)
     val config = Configuration(AppContext.resources.configuration)
     val metrics = DisplayMetrics()
     metrics.setTo(AppContext.resources.displayMetrics)
-    return Resources(asset, metrics, config)
+    val res = Resources(asset, metrics, config)
+    res.addAssetPath(AppApkPath)
+    return res
 }
 
 fun Class<*>.cmp(pkg: String) =

stub/src/main/java/com/topjohnwu/magisk/DownloadActivity.java

@@ -12,8 +12,14 @@ import android.app.AlertDialog;
 import android.app.ProgressDialog;
 import android.content.Context;
 import android.content.Intent;
+import android.content.res.loader.ResourcesLoader;
+import android.content.res.loader.ResourcesProvider;
 import android.os.AsyncTask;
+import android.os.Build;
 import android.os.Bundle;
+import android.os.ParcelFileDescriptor;
+import android.system.Os;
+import android.system.OsConstants;
 import android.util.Log;
 import android.view.ContextThemeWrapper;
 
@@ -27,6 +33,7 @@ import java.io.ByteArrayInputStream;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.io.OutputStream;
 
 import javax.crypto.Cipher;
 import javax.crypto.CipherInputStream;
@@ -66,7 +73,9 @@ public class DownloadActivity extends Activity {
         dynLoad = !getPackageName().equals(BuildConfig.APPLICATION_ID);
 
         // Inject resources
-        loadResources();
+        try {
+            loadResources();
+        } catch (Exception ignored) {}
 
         ProviderInstaller.install(this);
 
@@ -140,21 +149,35 @@ public class DownloadActivity extends Activity {
         }
     }
 
-    private void loadResources() {
+    private void decryptResources(OutputStream out) throws Exception {
-        File apk = new File(getCacheDir(), "res.apk");
+        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
-        try {
+        SecretKey key = new SecretKeySpec(Bytes.key(), "AES");
-            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
+        IvParameterSpec iv = new IvParameterSpec(Bytes.iv());
-            SecretKey key = new SecretKeySpec(Bytes.key(), "AES");
+        cipher.init(Cipher.DECRYPT_MODE, key, iv);
-            IvParameterSpec iv = new IvParameterSpec(Bytes.iv());
+        var is = new CipherInputStream(new ByteArrayInputStream(Bytes.res()), cipher);
-            cipher.init(Cipher.DECRYPT_MODE, key, iv);
+        try (is; out) {
-            var is = new CipherInputStream(new ByteArrayInputStream(Bytes.res()), cipher);
+            APKInstall.transfer(is, out);
-            var out = new FileOutputStream(apk);
-            try (is; out) {
-                APKInstall.transfer(is, out);
-            }
-            StubApk.addAssetPath(getResources().getAssets(), apk.getPath());
-        } catch (Exception ignored) {
         }
     }
 
+    private void loadResources() throws Exception {
+        if (Build.VERSION.SDK_INT >= 30) {
+            var fd = Os.memfd_create("res.apk", 0);
+            try {
+                decryptResources(new FileOutputStream(fd));
+                Os.lseek(fd, 0, OsConstants.SEEK_SET);
+                try (var pfd = ParcelFileDescriptor.dup(fd)) {
+                    var loader = new ResourcesLoader();
+                    loader.addProvider(ResourcesProvider.loadFromApk(pfd));
+                    getResources().addLoaders(loader);
+                }
+            } finally {
+                Os.close(fd);
+            }
+        } else {
+            File apk = new File(getCacheDir(), "res.apk");
+            decryptResources(new FileOutputStream(apk));
+            StubApk.addAssetPath(getResources(), apk.getPath());
+        }
+    }
 }