android apk 防止反編譯技術(shù)第一篇-加殼技術(shù)
做android framework方面的工作將近三年的時間了,現(xiàn)在公司讓做一下android apk安全方面的研究,于是最近就在網(wǎng)上找大量的資料來學(xué)習(xí)?,F(xiàn)在將最近學(xué)習(xí)成果做一下整理總結(jié)。學(xué)習(xí)的這些成果我會做成一個系列慢慢寫出來與大家分享,共同進步。這篇主要講apk的加殼技術(shù),廢話不多說了直接進入正題。
一、加殼技術(shù)原理
所謂apk的加殼技術(shù)和pc exe的加殼原理一樣,就是在程序的外面再包裹上另外一段代碼,保護里面的代碼不被非法修改或反編譯,在程序運行的時候優(yōu)先取得程序的控制權(quán)做一些我們自己想做的工作。(哈哈,跟病毒的原理差不多)
PC exe的加殼原理如下:
二、android apk加殼實現(xiàn)
要想實現(xiàn)加殼需要解決的技術(shù)點如下:
(1)怎么第一時間執(zhí)行我們的加殼程序?
首先根據(jù)上面的原理我們在apk中要想優(yōu)先取得程序的控制權(quán)作為android apk的開發(fā)人員都知道Application會被系統(tǒng)第一時間調(diào)用而我們的程序也會放在這里執(zhí)行。
(2)怎么將我們的加殼程序和原有的android apk文件合并到一起?
我們知道android apk最終會打包生成dex文件,我們可以將我們的程序生成dex文件后,將我們要進行加殼的apk和我們dex文件合并成一個文件,然后修改dex文件頭中的checksum、signature 和file_size的信息,并且要附加加殼的apk的長度信息在dex文件中,以便我們進行解殼保證原來apk的正常運行。加完殼后整個文件的結(jié)構(gòu)如下:
(3)怎么將原來的apk正常的運行起來?
按照(2)中的合并方式在當(dāng)我們的程序首先運行起來后,逆向讀取dex文件獲取原來的apk文件通過DexClassLoader動態(tài)加載。
具體實現(xiàn)如下:
(1)修改原來apk的AndroidMainfest.xml文件,假如原來apk的AndroidMainfest.xml文件內(nèi)容如下:
1. <application
2. android:icon="@drawable/ic_launcher"
3. android:label="@string/app_name"
4. android:theme="@style/AppTheme" android:name="com.android.MyApplication" >
5. </application>
修改后的內(nèi)容如下:
1. <application
2. android:icon="@drawable/ic_launcher"
3. android:label="@string/app_name"
4. android:theme="@style/AppTheme" android:name="com.android.shellApplication" >
5. <meta-data android:name="APPLICATION_CLASS_NAME" android:value="com.android.MyApplication"/>
6. </application>
com.android.shellApplication這個就是我們的程序的的application的名稱,而
7. <meta-data android:name="APPLICATION_CLASS_NAME" android:value="com.android.MyApplication"/>
是原來的apk的application名稱。
(2)合并文件代碼實現(xiàn)如下:
?
- public class ShellTool {
 - /**
 - * @param args
 - */
 - public static void main(String[] args) {
 - // TODO Auto-generated method stub
 - try {
 - File payloadSrcFile = new File("payload.apk");//我們要加殼的apk文件
 - File unShellDexFile = new File("classes.dex");//我們的程序生成的dex文件
 - byte[] payloadArray = encrpt(readFileBytes(payloadSrcFile));
 - byte[] unShellDexArray = readFileBytes(unShellDexFile);
 - int payloadLen = payloadArray.length;
 - int unShellDexLen = unShellDexArray.length;
 - int totalLen = payloadLen + unShellDexLen +4;
 - byte[] newdex = new byte[totalLen];
 - //添加我們程序的dex
 - System.arraycopy(unShellDexArray, 0, newdex, 0, unShellDexLen);
 - //添加要加殼的apk文件
 - System.arraycopy(payloadArray, 0, newdex, unShellDexLen,
 - payloadLen);
 - //添加apk文件長度
 - System.arraycopy(intToByte(payloadLen), 0, newdex, totalLen-4, 4);
 - //修改DEX file size文件頭
 - fixFileSizeHeader(newdex);
 - //修改DEX SHA1 文件頭
 - fixSHA1Header(newdex);
 - //修改DEX CheckSum文件頭
 - fixCheckSumHeader(newdex);
 - String str = "outdir/classes.dex";
 - File file = new File(str);
 - if (!file.exists()) {
 - file.createNewFile();
 - }
 - FileOutputStream localFileOutputStream = new FileOutputStream(str);
 - localFileOutputStream.write(newdex);
 - localFileOutputStream.flush();
 - localFileOutputStream.close();
 - } catch (Exception e) {
 - // TODO Auto-generated catch block
 - e.printStackTrace();
 - }
 - }
 - //直接返回數(shù)據(jù),讀者可以添加自己加密方法
 - private static byte[] encrpt(byte[] srcdata){
 - return srcdata;
 - }
 - private static void fixCheckSumHeader(byte[] dexBytes) {
 - Adler32 adler = new Adler32();
 - adler.update(dexBytes, 12, dexBytes.length - 12);
 - long value = adler.getValue();
 - int va = (int) value;
 - byte[] newcs = intToByte(va);
 - byte[] recs = new byte[4];
 - for (int i = 0; i < 4; i++) {
 - recs[i] = newcs[newcs.length - 1 - i];
 - System.out.println(Integer.toHexString(newcs[i]));
 - }
 - System.arraycopy(recs, 0, dexBytes, 8, 4);
 - System.out.println(Long.toHexString(value));
 - System.out.println();
 - }
 - public static byte[] intToByte(int number) {
 - byte[] b = new byte[4];
 - for (int i = 3; i >= 0; i--) {
 - b[i] = (byte) (number % 256);
 - number >>= 8;
 - }
 - return b;
 - }
 - private static void fixSHA1Header(byte[] dexBytes)
 - throws NoSuchAlgorithmException {
 - MessageDigest md = MessageDigest.getInstance("SHA-1");
 - md.update(dexBytes, 32, dexBytes.length - 32);
 - byte[] newdt = md.digest();
 - System.arraycopy(newdt, 0, dexBytes, 12, 20);
 - String hexstr = "";
 - for (int i = 0; i < newdt.length; i++) {
 - hexstr += Integer.toString((newdt[i] & 0xff) + 0x100, 16)
 - .substring(1);
 - }
 - System.out.println(hexstr);
 - }
 - private static void fixFileSizeHeader(byte[] dexBytes) {
 - byte[] newfs = intToByte(dexBytes.length);
 - System.out.println(Integer.toHexString(dexBytes.length));
 - byte[] refs = new byte[4];
 - for (int i = 0; i < 4; i++) {
 - refs[i] = newfs[newfs.length - 1 - i];
 - System.out.println(Integer.toHexString(newfs[i]));
 - }
 - System.arraycopy(refs, 0, dexBytes, 32, 4);
 - }
 - private static byte[] readFileBytes(File file) throws IOException {
 - byte[] arrayOfByte = new byte[1024];
 - ByteArrayOutputStream localByteArrayOutputStream = new ByteArrayOutputStream();
 - FileInputStream fis = new FileInputStream(file);
 - while (true) {
 - int i = fis.read(arrayOfByte);
 - if (i != -1) {
 - localByteArrayOutputStream.write(arrayOfByte, 0, i);
 - } else {
 - return localByteArrayOutputStream.toByteArray();
 - }
 - }
 - }
 - }
 
(3)在我們的程序中加載運行原來的apk文件,代碼如下:
- public class shellApplication extends Application {
 - private static final String appkey = "APPLICATION_CLASS_NAME";
 - private String apkFileName;
 - private String odexPath;
 - private String libPath;
 - protected void attachBaseContext(Context base) {
 - super.attachBaseContext(base);
 - try {
 - File odex = this.getDir("payload_odex", MODE_PRIVATE);
 - File libs = this.getDir("payload_lib", MODE_PRIVATE);
 - odexPath = odex.getAbsolutePath();
 - libPath = libs.getAbsolutePath();
 - apkFileName = odex.getAbsolutePath() + "/payload.apk";
 - File dexFile = new File(apkFileName);
 - if (!dexFile.exists())
 - dexFile.createNewFile();
 - // 讀取程序classes.dex文件
 - byte[] dexdata = this.readDexFileFromApk();
 - // 分離出解殼后的apk文件已用于動態(tài)加載
 - this.splitPayLoadFromDex(dexdata);
 - // 配置動態(tài)加載環(huán)境
 - Object currentActivityThread = RefInvoke.invokeStaticMethod(
 - "android.app.ActivityThread", "currentActivityThread",
 - new Class[] {}, new Object[] {});
 - String packageName = this.getPackageName();
 - HashMap mPackages = (HashMap) RefInvoke.getFieldOjbect(
 - "android.app.ActivityThread", currentActivityThread,
 - "mPackages");
 - WeakReference wr = (WeakReference) mPackages.get(packageName);
 - DexClassLoader dLoader = new DexClassLoader(apkFileName, odexPath,
 - libPath, (ClassLoader) RefInvoke.getFieldOjbect(
 - "android.app.LoadedApk", wr.get(), "mClassLoader"));
 - RefInvoke.setFieldOjbect("android.app.LoadedApk", "mClassLoader",
 - wr.get(), dLoader);
 - } catch (Exception e) {
 - // TODO Auto-generated catch block
 - e.printStackTrace();
 - }
 - }
 - public void onCreate() {
 - {
 - // 如果源應(yīng)用配置有Appliction對象,則替換為源應(yīng)用Applicaiton,以便不影響源程序邏輯。
 - String appClassName = null;
 - try {
 - ApplicationInfo ai = this.getPackageManager()
 - .getApplicationInfo(this.getPackageName(),
 - PackageManager.GET_META_DATA);
 - Bundle bundle = ai.metaData;
 - if (bundle != null
 - && bundle.containsKey("APPLICATION_CLASS_NAME")) {
 - appClassName = bundle.getString("APPLICATION_CLASS_NAME");
 - } else {
 - return;
 - }
 - } catch (NameNotFoundException e) {
 - // TODO Auto-generated catch block
 - e.printStackTrace();
 - }
 - Object currentActivityThread = RefInvoke.invokeStaticMethod(
 - "android.app.ActivityThread", "currentActivityThread",
 - new Class[] {}, new Object[] {});
 - Object mBoundApplication = RefInvoke.getFieldOjbect(
 - "android.app.ActivityThread", currentActivityThread,
 - "mBoundApplication");
 - Object loadedApkInfo = RefInvoke.getFieldOjbect(
 - "android.app.ActivityThread$AppBindData",
 - mBoundApplication, "info");
 - RefInvoke.setFieldOjbect("android.app.LoadedApk", "mApplication",
 - loadedApkInfo, null);
 - Object oldApplication = RefInvoke.getFieldOjbect(
 - "android.app.ActivityThread", currentActivityThread,
 - "mInitialApplication");
 - ArrayList<Application> mAllApplications = (ArrayList<Application>) RefInvoke
 - .getFieldOjbect("android.app.ActivityThread",
 - currentActivityThread, "mAllApplications");
 - mAllApplications.remove(oldApplication);
 - ApplicationInfo appinfo_In_LoadedApk = (ApplicationInfo) RefInvoke
 - .getFieldOjbect("android.app.LoadedApk", loadedApkInfo,
 - "mApplicationInfo");
 - ApplicationInfo appinfo_In_AppBindData = (ApplicationInfo) RefInvoke
 - .getFieldOjbect("android.app.ActivityThread$AppBindData",
 - mBoundApplication, "appInfo");
 - appinfo_In_LoadedApk.className = appClassName;
 - appinfo_In_AppBindData.className = appClassName;
 - Application app = (Application) RefInvoke.invokeMethod(
 - "android.app.LoadedApk", "makeApplication", loadedApkInfo,
 - new Class[] { boolean.class, Instrumentation.class },
 - new Object[] { false, null });
 - RefInvoke.setFieldOjbect("android.app.ActivityThread",
 - "mInitialApplication", currentActivityThread, app);
 - HashMap mProviderMap = (HashMap) RefInvoke.getFieldOjbect(
 - "android.app.ActivityThread", currentActivityThread,
 - "mProviderMap");
 - Iterator it = mProviderMap.values().iterator();
 - while (it.hasNext()) {
 - Object providerClientRecord = it.next();
 - Object localProvider = RefInvoke.getFieldOjbect(
 - "android.app.ActivityThread$ProviderClientRecord",
 - providerClientRecord, "mLocalProvider");
 - RefInvoke.setFieldOjbect("android.content.ContentProvider",
 - "mContext", localProvider, app);
 - }
 - app.onCreate();
 - }
 - }
 - private void splitPayLoadFromDex(byte[] data) throws IOException {
 - byte[] apkdata = decrypt(data);
 - int ablen = apkdata.length;
 - byte[] dexlen = new byte[4];
 - System.arraycopy(apkdata, ablen - 4, dexlen, 0, 4);
 - ByteArrayInputStream bais = new ByteArrayInputStream(dexlen);
 - DataInputStream in = new DataInputStream(bais);
 - int readInt = in.readInt();
 - System.out.println(Integer.toHexString(readInt));
 - byte[] newdex = new byte[readInt];
 - System.arraycopy(apkdata, ablen - 4 - readInt, newdex, 0, readInt);
 - File file = new File(apkFileName);
 - try {
 - FileOutputStream localFileOutputStream = new FileOutputStream(file);
 - localFileOutputStream.write(newdex);
 - localFileOutputStream.close();
 - } catch (IOException localIOException) {
 - throw new RuntimeException(localIOException);
 - }
 - ZipInputStream localZipInputStream = new ZipInputStream(
 - new BufferedInputStream(new FileInputStream(file)));
 - while (true) {
 - ZipEntry localZipEntry = localZipInputStream.getNextEntry();
 - if (localZipEntry == null) {
 - localZipInputStream.close();
 - break;
 - }
 - String name = localZipEntry.getName();
 - if (name.startsWith("lib/") && name.endsWith(".so")) {
 - File storeFile = new File(libPath + "/"
 - + name.substring(name.lastIndexOf('/')));
 - storeFile.createNewFile();
 - FileOutputStream fos = new FileOutputStream(storeFile);
 - byte[] arrayOfByte = new byte[1024];
 - while (true) {
 - int i = localZipInputStream.read(arrayOfByte);
 - if (i == -1)
 - break;
 - fos.write(arrayOfByte, 0, i);
 - }
 - fos.flush();
 - fos.close();
 - }
 - localZipInputStream.closeEntry();
 - }
 - localZipInputStream.close();
 - }
 - private byte[] readDexFileFromApk() throws IOException {
 - ByteArrayOutputStream dexByteArrayOutputStream = new ByteArrayOutputStream();
 - ZipInputStream localZipInputStream = new ZipInputStream(
 - new BufferedInputStream(new FileInputStream(
 - this.getApplicationInfo().sourceDir)));
 - while (true) {
 - ZipEntry localZipEntry = localZipInputStream.getNextEntry();
 - if (localZipEntry == null) {
 - localZipInputStream.close();
 - break;
 - }
 - if (localZipEntry.getName().equals("classes.dex")) {
 - byte[] arrayOfByte = new byte[1024];
 - while (true) {
 - int i = localZipInputStream.read(arrayOfByte);
 - if (i == -1)
 - break;
 - dexByteArrayOutputStream.write(arrayOfByte, 0, i);
 - }
 - }
 - localZipInputStream.closeEntry();
 - }
 - localZipInputStream.close();
 - return dexByteArrayOutputStream.toByteArray();
 - }
 - // //直接返回數(shù)據(jù),讀者可以添加自己解密方法
 - private byte[] decrypt(byte[] data) {
 - return data;
 - }
 
















 
 
 






 
 
 
 