From 958d6377e303ee944fe10c0f1741f04632a0d3bf Mon Sep 17 00:00:00 2001
From: topjohnwu <topjohnwu@gmail.com>
Date: Fri, 26 Oct 2018 02:50:45 -0400
Subject: [PATCH] Improve XML string matching code

---
 .../com/topjohnwu/magisk/asyncs/PatchAPK.java | 68 ++++++++-----------
 1 file changed, 28 insertions(+), 40 deletions(-)

diff --git a/app/src/full/java/com/topjohnwu/magisk/asyncs/PatchAPK.java b/app/src/full/java/com/topjohnwu/magisk/asyncs/PatchAPK.java
index a3b3c818c..7fa140bc3 100644
--- a/app/src/full/java/com/topjohnwu/magisk/asyncs/PatchAPK.java
+++ b/app/src/full/java/com/topjohnwu/magisk/asyncs/PatchAPK.java
@@ -17,25 +17,32 @@ import com.topjohnwu.superuser.io.SuFileOutputStream;
 import com.topjohnwu.utils.JarMap;
 import com.topjohnwu.utils.SignAPK;
 
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.CharBuffer;
 import java.security.SecureRandom;
 import java.util.jar.JarEntry;
 
 public class PatchAPK {
 
+    public static final String LOWERALPHA = "abcdefghijklmnopqrstuvwxyz";
+    public static final String UPPERALPHA = LOWERALPHA.toUpperCase();
+    public static final String ALPHA = LOWERALPHA + UPPERALPHA;
+    public static final String DIGITS = "0123456789";
+    public static final String ALPHANUM = ALPHA + DIGITS;
+    public static final String ALPHANUMDOTS = ALPHANUM + "............";
+
     private static String genPackageName(String prefix, int length) {
         StringBuilder builder = new StringBuilder(length);
         builder.append(prefix);
         length -= prefix.length();
         SecureRandom random = new SecureRandom();
-        String base = "abcdefghijklmnopqrstuvwxyz";
-        String alpha = base + base.toUpperCase();
-        String full = alpha + "0123456789..........";
-        char next, prev = '\0';
+        char next, prev = '.';
         for (int i = 0; i < length; ++i) {
-            if (prev == '.' || i == length - 1 || i == 0) {
-                next = alpha.charAt(random.nextInt(alpha.length()));
+            if (prev == '.' || i == length - 1) {
+                next = ALPHA.charAt(random.nextInt(ALPHA.length()));
             } else {
-                next = full.charAt(random.nextInt(full.length()));
+                next = ALPHANUMDOTS.charAt(random.nextInt(ALPHANUMDOTS.length()));
             }
             builder.append(next);
             prev = next;
@@ -43,48 +50,30 @@ public class PatchAPK {
         return builder.toString();
     }
 
-    private static int findOffset(byte buf[], byte pattern[]) {
+    private static boolean findAndPatch(byte xml[], String a, String b) {
+        if (a.length() != b.length())
+            return false;
+        char[] from = a.toCharArray(), to = b.toCharArray();
+        CharBuffer buf = ByteBuffer.wrap(xml).order(ByteOrder.LITTLE_ENDIAN).asCharBuffer();
         int offset = -1;
-        for (int i = 0; i < buf.length - pattern.length; ++i) {
+        for (int i = 0; i < buf.length() - from.length; ++i) {
             boolean match = true;
-            for (int j = 0; j < pattern.length; ++j) {
-                if (buf[i + j] != pattern[j]) {
+            for (int j = 0; j < from.length; ++j) {
+                if (buf.get(i + j) != from[j]) {
                     match = false;
                     break;
                 }
             }
-            if (match) {
+            // Make sure it is null terminated
+            if (match && buf.get(i + from.length) == '\0') {
                 offset = i;
                 break;
             }
         }
-        return offset;
-    }
-
-    /* It seems that AAPT sometimes generate another type of string format */
-    private static boolean fallbackPatch(byte xml[], String from, String to) {
-
-        byte[] target = new byte[from.length() * 2 + 2];
-        for (int i = 0; i < from.length(); ++i) {
-            target[i * 2] = (byte) from.charAt(i);
-        }
-        int offset = findOffset(xml, target);
         if (offset < 0)
             return false;
-        byte[] dest = new byte[target.length - 2];
-        for (int i = 0; i < to.length(); ++i) {
-            dest[i * 2] = (byte) to.charAt(i);
-        }
-        System.arraycopy(dest, 0, xml, offset, dest.length);
-        return true;
-    }
-
-    private static boolean findAndPatch(byte xml[], String from, String to) {
-        byte target[] = (from + '\0').getBytes();
-        int offset = findOffset(xml, target);
-        if (offset < 0)
-            return fallbackPatch(xml, from, to);
-        System.arraycopy(to.getBytes(), 0, xml, offset, to.length());
+        buf.position(offset);
+        buf.put(to);
         return true;
     }
 
@@ -123,9 +112,8 @@ public class PatchAPK {
             JarEntry je = apk.getJarEntry(Const.ANDROID_MANIFEST);
             byte xml[] = apk.getRawData(je);
 
-            if (!findAndPatch(xml, from, to))
-                return false;
-            if (!findAndPatch(xml, from + ".provider", to + ".provider"))
+            if (!findAndPatch(xml, from, to) ||
+                    !findAndPatch(xml, from + ".provider", to + ".provider"))
                 return false;
 
             // Write in changes