Use GNU tar format

app/src/main/java/com/topjohnwu/magisk/utils/TarEntry.java

@@ -3,6 +3,7 @@ package com.topjohnwu.magisk.utils;
 import org.kamranzafar.jtar.TarHeader;
 
 import java.io.File;
+import java.util.Arrays;
 
 public class TarEntry extends org.kamranzafar.jtar.TarEntry {
 
@@ -10,10 +11,6 @@ public class TarEntry extends org.kamranzafar.jtar.TarEntry {
         super(file, entryName);
     }
 
-    public TarEntry(byte[] headerBuf) {
-        super(headerBuf);
-    }
-
     /*
     * Workaround missing java.nio.file.attribute.PosixFilePermission
     * Simply just assign a default permission to the file
@@ -21,7 +18,47 @@ public class TarEntry extends org.kamranzafar.jtar.TarEntry {
 
     @Override
     public void extractTarHeader(String entryName) {
-        int permissions = file.isDirectory() ? 040755 : 0100644;
+        int permissions = file.isDirectory() ? 000755 : 000644;
         header = TarHeader.createHeader(entryName, file.length(), file.lastModified() / 1000, file.isDirectory(), permissions);
+        header.userName = new StringBuffer("");
+        header.groupName = header.userName;
+    }
+
+    /*
+    * Rewrite the header to GNU format
+    * */
+
+    @Override
+    public void writeEntryHeader(byte[] outbuf) {
+        super.writeEntryHeader(outbuf);
+
+        System.arraycopy("ustar  \0".getBytes(), 0, outbuf, 257, TarHeader.USTAR_MAGICLEN);
+        getOctalBytes(header.mode, outbuf, 100, TarHeader.MODELEN);
+        getOctalBytes(header.userId, outbuf, 108, TarHeader.UIDLEN);
+        getOctalBytes(header.groupId, outbuf, 116, TarHeader.GIDLEN);
+        getOctalBytes(header.size, outbuf, 124, TarHeader.SIZELEN);
+        getOctalBytes(header.modTime, outbuf, 136, TarHeader.MODTIMELEN);
+        Arrays.fill(outbuf, 148, 148 + TarHeader.CHKSUMLEN, (byte) ' ');
+        Arrays.fill(outbuf, 329, 329 + TarHeader.USTAR_DEVLEN, (byte) '\0');
+        Arrays.fill(outbuf, 337, 337 + TarHeader.USTAR_DEVLEN, (byte) '\0');
+
+        // Recalculate checksum
+        getOctalBytes(computeCheckSum(outbuf), outbuf, 148, TarHeader.CHKSUMLEN);
+    }
+
+    /*
+    * Proper octal to ASCII conversion
+    * */
+
+    private void getOctalBytes(long value, byte[] buf, int offset, int length) {
+        int idx = length - 1;
+
+        buf[offset + idx] = 0;
+        --idx;
+
+        for (long val = value; idx >= 0; --idx) {
+            buf[offset + idx] = (byte) ((byte) '0' + (byte) (val & 7));
+            val = val >> 3;
+        }
     }
 }

app/src/main/java/com/topjohnwu/magisk/utils/ZipUtils.java

@@ -127,9 +127,7 @@ public class ZipUtils {
 
                     // Patch binary XML with new package name
                     pkg = Utils.genPackageName("com.", UNHIDE_PKG_NAME.length - 1);
-                    for (int i = 0; i < pkg.length(); ++i) {
-                        xml[offset + i] = (byte) pkg.charAt(i);
-                    }
+                    System.arraycopy(pkg.getBytes(), 0, xml, offset, pkg.length());
                     dest.write(xml);
                 } else {
                     while((size = source.read(buffer)) != -1) {