From 6d27eb7f64324e137de6b36842ac79bc94951974 Mon Sep 17 00:00:00 2001
From: topjohnwu <topjohnwu@gmail.com>
Date: Mon, 31 Dec 2018 15:53:24 +0800
Subject: [PATCH] Dynamic load updated APK for patching

Magisk Manager sometimes updates the code for patching the APK due to several changes.
When an old manager tries to patch an updated APK using its internal methods, it is
sometimes incomplete, or simply won't work at all.

This commit exposes an API that can be dynamically loaded from an old app to invoke the
updated patchAPK method from the downloaded new APK.
---
 app/src/full/java/a/a.java                    |  5 ++++-
 .../topjohnwu/magisk/utils/DownloadApp.java   | 14 +++++++++++---
 .../com/topjohnwu/magisk/utils/PatchAPK.java  | 19 +++++++------------
 3 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/app/src/full/java/a/a.java b/app/src/full/java/a/a.java
index e2481e07e..b97ad15e2 100644
--- a/app/src/full/java/a/a.java
+++ b/app/src/full/java/a/a.java
@@ -1,10 +1,13 @@
 package a;
 
 import com.topjohnwu.core.utils.BootSigner;
+import com.topjohnwu.magisk.utils.PatchAPK;
 
 import androidx.annotation.Keep;
 
 @Keep
 public class a extends BootSigner {
-    /* stub */
+    public static boolean patchAPK(String in, String out, String pkg) {
+        return PatchAPK.patch(in, out, pkg);
+    }
 }
diff --git a/app/src/full/java/com/topjohnwu/magisk/utils/DownloadApp.java b/app/src/full/java/com/topjohnwu/magisk/utils/DownloadApp.java
index f08090f30..9436f6897 100644
--- a/app/src/full/java/com/topjohnwu/magisk/utils/DownloadApp.java
+++ b/app/src/full/java/com/topjohnwu/magisk/utils/DownloadApp.java
@@ -19,6 +19,8 @@ import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.FileOutputStream;
 
+import dalvik.system.DexClassLoader;
+
 public class DownloadApp {
 
     public static void upgrade(String name) {
@@ -72,10 +74,16 @@ public class DownloadApp {
                 progress.update();
                 patched = new File(apk.getParent(), "patched.apk");
                 try {
-                    JarMap jarMap = PatchAPK.patch(apk.getPath(), app.getPackageName());
-                    SignAPK.sign(jarMap, new BufferedOutputStream(new FileOutputStream(patched)));
+                    // Try using the new APK to patch itself
+                    ClassLoader loader = new DexClassLoader(apk.getPath(),
+                            apk.getParent(), null, ClassLoader.getSystemClassLoader());
+                    loader.loadClass("a.a")
+                            .getMethod("patchAPK", String.class, String.class, String.class)
+                            .invoke(null, apk.getPath(), patched.getPath(), app.getPackageName());
                 } catch (Exception e) {
-                    return;
+                    e.printStackTrace();
+                    // Fallback to use the current implementation
+                    PatchAPK.patch(apk.getPath(), patched.getPath(), app.getPackageName());
                 }
             }
             APKInstall.install(app, patched);
diff --git a/app/src/full/java/com/topjohnwu/magisk/utils/PatchAPK.java b/app/src/full/java/com/topjohnwu/magisk/utils/PatchAPK.java
index c8bd1d32c..17ca8d9b0 100644
--- a/app/src/full/java/com/topjohnwu/magisk/utils/PatchAPK.java
+++ b/app/src/full/java/com/topjohnwu/magisk/utils/PatchAPK.java
@@ -102,14 +102,8 @@ public class PatchAPK {
         File repack = new File(app.getFilesDir(), "patched.apk");
         String pkg = genPackageName("com.", BuildConfig.APPLICATION_ID.length());
 
-        try {
-            JarMap apk;
-            if ((apk = patch(app.getPackageCodePath(), pkg)) == null)
-                return false;
-            SignAPK.sign(apk, new BufferedOutputStream(new FileOutputStream(repack)));
-        } catch (Exception e) {
+        if (!patch(app.getPackageCodePath(), repack.getPath(), pkg))
             return false;
-        }
 
         // Install the application
         repack.setReadable(true, false);
@@ -123,23 +117,24 @@ public class PatchAPK {
         return true;
     }
 
-    public static JarMap patch(String apk, String pkg) {
+    public static boolean patch(String in, String out, String pkg) {
         try {
-            JarMap jar = new JarMap(apk);
+            JarMap jar = new JarMap(in);
             JarEntry je = jar.getJarEntry(Const.ANDROID_MANIFEST);
             byte xml[] = jar.getRawData(je);
 
             if (!findAndPatch(xml, BuildConfig.APPLICATION_ID, pkg) ||
                     !findAndPatch(xml, R.string.app_name, R.string.re_app_name))
-                return null;
+                return false;
 
             // Write in changes
             jar.getOutputStream(je).write(xml);
-            return jar;
+            SignAPK.sign(jar, new BufferedOutputStream(new FileOutputStream(out)));
         } catch (Exception e) {
             e.printStackTrace();
-            return null;
+            return false;
         }
+        return true;
     }
 
     public static void hideManager() {