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android中是如何对包进行解析--解析ContentProvider_android解析 app 发送的数据包

作者：喵喵爱编程 | 2024-07-24 10:23:59

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android解析 app 发送的数据包

如果了解过android的启动流程，我们知道android在启动的时候会去解析/data/system和/data/app下已经存在的apk。

那么是从哪里开始对这些包进行解析的呢？

1.

  1. public static final IPackageManager main(Context context, Installer installer,
  2.             boolean factoryTest, boolean onlyCore) {
  3.         PackageManagerService m = new PackageManagerService(context, installer,
  4.                 factoryTest, onlyCore);
  5.         ServiceManager.addService("package", m);
  6.         return m;
  7.     }
android在启动的时候，会根据init.rc配置文件去执行PackageManagerService中的main方法。

该方法的操作很简单，就是生成一个PackageManagerService的对象，然后加载到ServiceManager进程中进行管理。

从这里我们就可以看出，ServiceManager进程就是用来管理android中Framework层的一些系统Service。


2.

main方法中代码很少，那么PackageManagerService是在哪里解析包的呢？

实际上在new一个PackageManagerService对象的时候，就对已存在的apk进行了解析。

下面我们对/data/app/下的apk解析过程做一个分析。

  1. synchronized (mPackages) {
  2.             mHandlerThread.start();
  3.             mHandler = new PackageHandler(mHandlerThread.getLooper());
  4.  
  5.             File dataDir = Environment.getDataDirectory();
  6.             mAppDataDir = new File(dataDir, "data");
  7.             mAppInstallDir = new File(dataDir, "app");
  8.             mAppLibInstallDir = new File(dataDir, "app-lib");
  9.             mAsecInternalPath = new File(dataDir, "app-asec").getPath();
  10.             mUserAppDataDir = new File(dataDir, "user");
  11.             mDrmAppPrivateInstallDir = new File(dataDir, "app-private");
  12.  
  13.             sUserManager = new UserManagerService(context, this,
  14.                     mInstallLock, mPackages);
在这里对android的一些路径进行了获取，这里我们就看到android默认的用户安装路径mAppInstallDir就是/data/app/。

知道用户的apk所在路径，下面就可以去遍历该路径下的所有apk，然后进行解析。

  1.             if (!mOnlyCore) {
  2.                 EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,
  3.                         SystemClock.uptimeMillis());
  4.                 mAppInstallObserver = new AppDirObserver(
  5.                     mAppInstallDir.getPath(), OBSERVER_EVENTS, false);
  6.                 mAppInstallObserver.startWatching();
  7.                 scanDirLI(mAppInstallDir, 0, scanMode, 0);
  8.     
  9.                 mDrmAppInstallObserver = new AppDirObserver(
  10.                     mDrmAppPrivateInstallDir.getPath(), OBSERVER_EVENTS, false);
  11.                 mDrmAppInstallObserver.startWatching();
  12.                 scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,
  13.                         scanMode, 0);

通过上面的scanDirLI方法，对/data/app/下面的apk进行遍历。 
  1.     private void scanDirLI(File dir, int flags, int scanMode, long currentTime) {
  2.         String[] files = dir.list();
  3.         if (files == null) {
  4.             Log.d(TAG, "No files in app dir " + dir);
  5.             return;
  6.         }
  7.  
  8.         if (DEBUG_PACKAGE_SCANNING) {
  9.             Log.d(TAG, "Scanning app dir " + dir);
  10.         }
  11.  
  12.         int i;
  13.         for (i=0; i<files.length; i++) {
  14.             File file = new File(dir, files[i]);
  15.             if (!isPackageFilename(files[i])) {
  16.                 // Ignore entries which are not apk's
  17.                 continue;
  18.             }
  19.             PackageParser.Package pkg = scanPackageLI(file,
  20.                     flags|PackageParser.PARSE_MUST_BE_APK, scanMode, currentTime, null);
  21.             // Don't mess around with apps in system partition.
  22.             if (pkg == null && (flags & PackageParser.PARSE_IS_SYSTEM) == 0 &&
  23.                     mLastScanError == PackageManager.INSTALL_FAILED_INVALID_APK) {
  24.                 // Delete the apk
  25.                 Slog.w(TAG, "Cleaning up failed install of " + file);
  26.                 file.delete();
  27.             }
  28.         }
  29.     }
通过dir.list()我们得到/data/app/下所有的文件名，然后在后面的for循环中逐个判断是否是*.apk文件，如果是，就调用scanPackageLI进行解析；

如果不是，就继续循环，寻找下一个apk文件。


下面进入scanPackageLI

  1.     private PackageParser.Package scanPackageLI(File scanFile,
  2.             int parseFlags, int scanMode, long currentTime, UserHandle user) {
  3.         mLastScanError = PackageManager.INSTALL_SUCCEEDED;
  4.         String scanPath = scanFile.getPath();
  5.         parseFlags |= mDefParseFlags;
  6.         PackageParser pp = new PackageParser(scanPath);
  7.         pp.setSeparateProcesses(mSeparateProcesses);
  8.         pp.setOnlyCoreApps(mOnlyCore);
  9.         final PackageParser.Package pkg = pp.parsePackage(scanFile,
  10.                 scanPath, mMetrics, parseFlags);
  11.         if (pkg == null) {
  12.             mLastScanError = pp.getParseError();
  13.             return null;
  14.         }
  15.         PackageSetting ps = null;
  16.         PackageSetting updatedPkg;

scanPackageLI返回PackageParser.Package类型的值，里面存储了对应apk的解析出来的信息。 

  1. final PackageParser.Package pkg = pp.parsePackage(scanFile,
  2.                 scanPath, mMetrics, parseFlags);
这里就是去解析apk文件，从scanpackageLI的代码看出pp实际是一个PackageParser对象。


3. PackageParser.java

上面的pp.parsePackage会调用如下：

  1.         try {
  2.             // XXXX todo: need to figure out correct configuration.
  3.             pkg = parsePackage(res, parser, flags, errorText);
  4.         } catch (Exception e) {
  5.             errorException = e;
  6.             mParseError = PackageManager.INSTALL_PARSE_FAILED_UNEXPECTED_EXCEPTION;
  7.         }

这里调用重载的parsePackage方法。

在这里面回去分析AndroidManifest.xml文件，当获取到application标签时，回去解析下面存在的控件。

  1.             if (tagName.equals("application")) {
  2.                 if (foundApp) {
  3.                     if (RIGID_PARSER) {
  4.                         outError[0] = "<manifest> has more than one <application>";
  5.                         mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
  6.                         return null;
  7.                     } else {
  8.                         Slog.w(TAG, "<manifest> has more than one <application>");
  9.                         XmlUtils.skipCurrentTag(parser);
  10.                         continue;
  11.                     }
  12.                 }
  13.  
  14.                 foundApp = true;
  15.                 if (!parseApplication(pkg, res, parser, attrs, flags, outError)) {
  16.                     return null;
  17.                 }
parseApplication就是去解析标签<application>中的资源。

下面我们来看一下parseApplication是怎么解析provider的。

  1.        while ((type = parser.next()) != XmlPullParser.END_DOCUMENT
  2.                 && (type != XmlPullParser.END_TAG || parser.getDepth() > innerDepth)) {
  3.             if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {
  4.                 continue;
  5.             }
  6.  
  7.             String tagName = parser.getName();
  8.             if (tagName.equals("activity")) {
  9.                 Activity a = parseActivity(owner, res, parser, attrs, flags, outError, false,
  10.                         hardwareAccelerated);
  11.                 if (a == null) {
  12.                     mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
  13.                     return false;
  14.                 }
  15.  
  16.                 owner.activities.add(a);
  17.  
  18.             } else if (tagName.equals("receiver")) {
  19.                 Activity a = parseActivity(owner, res, parser, attrs, flags, outError, true, false);
  20.                 if (a == null) {
  21.                     mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
  22.                     return false;
  23.                 }
  24.  
  25.                 owner.receivers.add(a);
  26.  
  27.             } else if (tagName.equals("service")) {
  28.                 Service s = parseService(owner, res, parser, attrs, flags, outError);
  29.                 if (s == null) {
  30.                     mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
  31.                     return false;
  32.                 }
  33.  
  34.                 owner.services.add(s);
  35.  
  36.             } else if (tagName.equals("provider")) {
  37.                 Provider p = parseProvider(owner, res, parser, attrs, flags, outError);
  38.                 if (p == null) {
  39.                     mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
  40.                     return false;
  41.                 }
  42.  
  43.                 owner.providers.add(p);
  44.  
  45.             }

我们看到上面会根据获取到不同的标签文件去解析不同的东西。

当我们的标签是provider时，就会调用parseProvider去解析。解析完成后就会把得到的Provider加入到owner.provider中。


  1.     private Provider parseProvider(Package owner, Resources res,
  2.             XmlPullParser parser, AttributeSet attrs, int flags, String[] outError)
  3.             throws XmlPullParserException, IOException {
  4.         TypedArray sa = res.obtainAttributes(attrs,
  5.                 com.android.internal.R.styleable.AndroidManifestProvider);
  6.  
  7.         if (mParseProviderArgs == null) {
  8.             mParseProviderArgs = new ParseComponentArgs(owner, outError,
  9.                     com.android.internal.R.styleable.AndroidManifestProvider_name,
  10.                     com.android.internal.R.styleable.AndroidManifestProvider_label,
  11.                     com.android.internal.R.styleable.AndroidManifestProvider_icon,
  12.                     com.android.internal.R.styleable.AndroidManifestProvider_logo,
  13.                     mSeparateProcesses,
  14.                     com.android.internal.R.styleable.AndroidManifestProvider_process,
  15.                     com.android.internal.R.styleable.AndroidManifestProvider_description,
  16.                     com.android.internal.R.styleable.AndroidManifestProvider_enabled);
  17.             mParseProviderArgs.tag = "<provider>";
  18.         }
  19.         
  20.         mParseProviderArgs.sa = sa;
  21.         mParseProviderArgs.flags = flags;
  22.         
  23.         Provider p = new Provider(mParseProviderArgs, new ProviderInfo());
  24.         if (outError[0] != null) {
  25.             sa.recycle();
  26.             return null;
  27.         }
  28.  
  29.         boolean providerExportedDefault = false;
  30.  
  31.         if (owner.applicationInfo.targetSdkVersion < Build.VERSION_CODES.JELLY_BEAN_MR1) {
  32.             // For compatibility, applications targeting API level 16 or lower
  33.             // should have their content providers exported by default, unless they
  34.             // specify otherwise.
  35.             providerExportedDefault = true;
  36.         }
  37.  
  38.         p.info.exported = sa.getBoolean(
  39.                 com.android.internal.R.styleable.AndroidManifestProvider_exported,
  40.                 providerExportedDefault);
  41.  
  42.         String cpname = sa.getNonConfigurationString(
  43.                 com.android.internal.R.styleable.AndroidManifestProvider_authorities, 0);
  44.  
  45.         p.info.isSyncable = sa.getBoolean(
  46.                 com.android.internal.R.styleable.AndroidManifestProvider_syncable,
  47.                 false);
  48.  
  49.         String permission = sa.getNonConfigurationString(
  50.                 com.android.internal.R.styleable.AndroidManifestProvider_permission, 0);
  51.         String str = sa.getNonConfigurationString(
  52.                 com.android.internal.R.styleable.AndroidManifestProvider_readPermission, 0);
  53.         if (str == null) {
  54.             str = permission;
  55.         }
  56.         if (str == null) {
  57.             p.info.readPermission = owner.applicationInfo.permission;
  58.         } else {
  59.             p.info.readPermission =
  60.                 str.length() > 0 ? str.toString().intern() : null;
  61.         }
  62.         str = sa.getNonConfigurationString(
  63.                 com.android.internal.R.styleable.AndroidManifestProvider_writePermission, 0);
  64.         if (str == null) {
  65.             str = permission;
  66.         }
  67.         if (str == null) {
  68.             p.info.writePermission = owner.applicationInfo.permission;
  69.         } else {
  70.             p.info.writePermission =
  71.                 str.length() > 0 ? str.toString().intern() : null;
  72.         }
  73.  
  74.         p.info.grantUriPermissions = sa.getBoolean(
  75.                 com.android.internal.R.styleable.AndroidManifestProvider_grantUriPermissions,
  76.                 false);
  77.  
  78.         p.info.multiprocess = sa.getBoolean(
  79.                 com.android.internal.R.styleable.AndroidManifestProvider_multiprocess,
  80.                 false);
  81.  
  82.         p.info.initOrder = sa.getInt(
  83.                 com.android.internal.R.styleable.AndroidManifestProvider_initOrder,
  84.                 0);
  85.  
  86.         p.info.flags = 0;
  87.  
  88.         if (sa.getBoolean(
  89.                 com.android.internal.R.styleable.AndroidManifestProvider_singleUser,
  90.                 false)) {
  91.             p.info.flags |= ProviderInfo.FLAG_SINGLE_USER;
  92.             if (p.info.exported) {
  93.                 Slog.w(TAG, "Provider exported request ignored due to singleUser: "
  94.                         + p.className + " at " + mArchiveSourcePath + " "
  95.                         + parser.getPositionDescription());
  96.                 p.info.exported = false;
  97.             }
  98.         }
  99.  
  100.         sa.recycle();
  101.  
  102.         if ((owner.applicationInfo.flags&ApplicationInfo.FLAG_CANT_SAVE_STATE) != 0) {
  103.             // A heavy-weight application can not have providers in its main process
  104.             // We can do direct compare because we intern all strings.
  105.             if (p.info.processName == owner.packageName) {
  106.                 outError[0] = "Heavy-weight applications can not have providers in main process";
  107.                 return null;
  108.             }
  109.         }
  110.         
  111.         if (cpname == null) {
  112.             outError[0] = "<provider> does not include authorities attribute";
  113.             return null;
  114.         }
  115.         p.info.authority = cpname.intern();
  116.  
  117.         if (!parseProviderTags(res, parser, attrs, p, outError)) {
  118.             return null;
  119.         }
  120.  
  121.         return p;
  122.     }

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