PackageInstaller源码分析(二)

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最新推荐文章于 2025-03-22 16:05:31 发布

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分类专栏： Android安全文章标签： Android 源码权限安装过程

本文链接：https://blog.youkuaiyun.com/u010651541/article/details/52673895

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本文深入分析了Android的PackageInstaller组件在新App安装和App更新时的处理流程。首先，新App安装从installNewPackageLI()开始，涉及包名校验、扫描APK、更新设置及删除未安装完成的App。核心在于updateSettingsLI()更新系统设置文件。接着，App更新从replacePackageLI()开始，系统App更新会杀死应用进程并删除相关数据，然后更新设置；非系统App更新则删除旧App并接入新App信息。所有更新过程中，writeLPr()函数更新了权限相关文件，实现权限授予。

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上篇PackageInstaller源码分析(一)对PackageInstaller源码分析了一半，本篇接着分析，分别分析对于App更新和新App安装的处理。

一、新App的安装

新App的安装从installNewPackageLI()开始，我们查看其源码。

private void installNewPackageLI(PackageParser.Package pkg,
        int parseFlags, int scanFlags, UserHandle user,
        String installerPackageName, PackageInstalledInfo res) {

    ````

    boolean dataDirExists = getDataPathForPackage(pkg.packageName, 0).exists();
    synchronized(mPackages) {
        if (mSettings.mRenamedPackages.containsKey(pkgName)) {
            // A package with the same name is already installed, though
            // it has been renamed to an older name.  The package we
            // are trying to install should be installed as an update to
            // the existing one, but that has not been requested, so bail.
            res.setError(INSTALL_FAILED_ALREADY_EXISTS, "Attempt to re-install " + pkgName
                    + " without first uninstalling package running as "
                    + mSettings.mRenamedPackages.get(pkgName));
            return;
        }
        if (mPackages.containsKey(pkgName)) {
            // Don't allow installation over an existing package with the same name.
            res.setError(INSTALL_FAILED_ALREADY_EXISTS, "Attempt to re-install " + pkgName
                    + " without first uninstalling.");
            return;
        }
    }

    ````    

}

这段代码首先判断了是否建立了App的data数据目录。而后，对于要安装的app的包名若已存在的情况作了处理。对于包名已经存在，但是并非更新的情况，抛出异常。

紧接着，程序调用scanPackageLI()重新获取apk的Package结构，这个函数比较复杂，就是从apk中提取有用信息，这个和PackageInstaller源码分析(一)中PackageParser.Package parsed = PackageUtil.getPackageInfo(sourceFile)应该是非常类似的，后面再选择一个分析。而后，调用updateSettingsLI()将安装的App写入设置，最后判断App是否完整安装，若没有完整安装，则调用deletePackageLI()将未完整安装的App删除，包括建立的data目录和cache目录。关于这个，在此处不做分析，这些操作和卸载App一定的相似性。以下将分析安装app细节的核心函数updateSettingsLI()。

private void installNewPackageLI(PackageParser.Package pkg,
        int parseFlags, int scanFlags, UserHandle user,
        String installerPackageName, PackageInstalledInfo res) {

    ````

    try {
         PackageParser.Package newPackage = scanPackageLI(pkg, parseFlags, scanFlags,
                 System.currentTimeMillis(), user);

         updateSettingsLI(newPackage, installerPackageName, null, null, res);
         // delete the partially installed application. the data directory will have to be
         // restored if it was already existing
         if (res.returnCode != PackageManager.INSTALL_SUCCEEDED) {
             // remove package from internal structures.  Note that we want deletePackageX to
             // delete the package data and cache directories that it created in
             // scanPackageLocked, unless those directories existed before we even tried to
             // install.
             deletePackageLI(pkgName, UserHandle.ALL, false, null, null,
                     dataDirExists ? PackageManager.DELETE_KEEP_DATA : 0,
                             res.removedInfo, true);
         }

     } catch (PackageManagerException e) {
         res.setError("Package couldn't be installed in " + pkg.codePath, e);
     }
}

查看updateSettingsLI()源码，对mPackages的同步处理中，调用了Setting的writeLPr()方法。

private void updateSettingsLI(PackageParser.Package newPackage, 
        String installerPackageName,
        int[] allUsers, boolean[] perUserInstalled,
        PackageInstalledInfo res) {
      String pkgName = newPackage.packageName;
      synchronized (mPackages) {
          //write settings. the installStatus will be incomplete at this stage.