一种有效管控APP隐私权限的解决方案

小咪咪 2022-10-23 15:27 190阅读 0赞

## 引言 ##

诸如读写外置存储、读取联系人、发短信等隐私权限，android在6.0系统开始进行动态授权。但在我国，仅向用户提示授权框还不够，工信部在19年11月初发布了专项整治App八类侵权行为审明 ,其文明确治理以下八类问题：

1.私自收集个人信息；  
2.超范围收集个人信息；  
3.私自共享给第三方用户信息；  
4.强制用户使用定向推送功能；  
5.不给权限不让用；  
6.频繁申请权限；  
7.过度索取权限；  
8.为用户账号注销设置障碍。

很不幸，网报通告批评：我司老版本APP中审明了隐私权限，但在隐私文档中并未进行有效说明。收到通告，团队立马对权限进行了扫描，发现APP在AndroidManifest中审明了三项隐私权限，但实际过程并未使用(有些冤大头)。我相信很多团队跟我们面临同个问题，多团队开发下，权限引入问题没有一个有效监管机制。为避免类似问题再次发生，本文给出一个简单有效的代码编译层拦截方案。

在说方案原理之前，我们先假定检测方案是扫描APP AndroidManifest.xml文件中审明的和用户有关的隐私权限，再比对隐私文档以及实际使用场景，进行判别。面对检测方案，我们给出解决思路：

在编译阶段processApplicationManifest task运行后，对Merged Manifest Log文件进行扫描,如果用到了新权限，抛出打包错误，直至问题解决；

## 源码简阅 ##

Android Gradle Plugin在编译APP后，会在build/outputs/logs目录下生成名为【manifest-merger-$\{variantname\}-report.txt】文本文件。  
以AGP 3.5.0源码为例，简单分析下ProcessApplicationManifest任务是如何产生Merged Manifest Log文件的。

package com.android.build.gradle.tasks;
    
    /** A task that processes the manifest */
    @CacheableTask
    public abstract class ProcessApplicationManifest extends ManifestProcessorTask {
        @Override
        @Internal
        protected boolean getIncremental() {
            return true;
        }
    
        @Override
        protected void doFullTaskAction() throws IOException {
            ... ...
                        MergingReport mergingReport =
                        ManifestHelperKt.mergeManifestsForApplication(
                                getMainManifest(),
                                getManifestOverlays(),
                                computeFullProviderList(compatibleScreenManifestForSplit),
                                navigationXmls,
                                getFeatureName(),
                                moduleMetadata == null
                                        ? getPackageOverride()
                                        : moduleMetadata.getApplicationId(),
                                moduleMetadata == null
                                        ? apkData.getVersionCode()
                                        : Integer.parseInt(moduleMetadata.getVersionCode()),
                                moduleMetadata == null
                                        ? apkData.getVersionName()
                                        : moduleMetadata.getVersionName(),
                                getMinSdkVersion(),
                                getTargetSdkVersion(),
                                getMaxSdkVersion(),
                                manifestOutputFile.getAbsolutePath(),
                                // no aapt friendly merged manifest file necessary for applications.
                                null /* aaptFriendlyManifestOutputFile */,
                                metadataFeatureManifestOutputFile.getAbsolutePath(),
                                bundleManifestOutputFile.getAbsolutePath(),
                                instantAppManifestOutputFile != null
                                        ? instantAppManifestOutputFile.getAbsolutePath()
                                        : null,
                                ManifestMerger2.MergeType.APPLICATION,
                                variantConfiguration.getManifestPlaceholders(),
                                getOptionalFeatures(),
                                getReportFile(),   
                                LoggerWrapper.getLogger(ProcessApplicationManifest.class));
            ... ...
        }
    
        public static class CreationAction
                extends AnnotationProcessingTaskCreationAction<ProcessApplicationManifest> {
    
            private File reportFile;
    
            @Override
            public void preConfigure(@NonNull String taskName) {
                super.preConfigure(taskName);
                
                //这里就【manifest-merger-${variantname}-report.txt】文件
                reportFile =
                        FileUtils.join(
                                variantScope.getGlobalScope().getOutputsDir(),
                                "logs",
                                "manifest-merger-"
                                        + variantScope.getVariantConfiguration().getBaseName()
                                        + "-report.txt");
            }
         }   
    }

通过代码，可以发现ProcessApplicationManifest是交给ManifestHelperKt.mergeManifestsForApplication方法对所有Manifest进行合并处理的，并且Log保存在【manifest-merger-$\{variantname\}-report.txt】文件中。

package com.android.build.gradle.internal.tasks.manifest
    
    /** Invoke the Manifest Merger version 2.  */
    fun mergeManifestsForApplication(
        mainManifest: File,
        manifestOverlays: List<File>,
        dependencies: List<ManifestProvider>,
        navigationFiles: List<File>,
        featureName: String?,
        packageOverride: String?,
        versionCode: Int,
        versionName: String?,
        minSdkVersion: String?,
        targetSdkVersion: String?,
        maxSdkVersion: Int?,
        outManifestLocation: String,
        outAaptSafeManifestLocation: String?,
        outMetadataFeatureManifestLocation: String?,
        outBundleManifestLocation: String?,
        outInstantAppManifestLocation: String?,
        mergeType: ManifestMerger2.MergeType,
        placeHolders: Map<String, Any>,
        optionalFeatures: Collection<ManifestMerger2.Invoker.Feature>,
        reportFile: File?,
        logger: ILogger
    ): MergingReport {
    
        try {
    
            //ManifestMerger2是 manifest-merger库提供的辅助类
            val manifestMergerInvoker = ManifestMerger2.newMerger(mainManifest, logger, mergeType)
                .setPlaceHolderValues(placeHolders)
                .addFlavorAndBuildTypeManifests(*manifestOverlays.toTypedArray())
                .addManifestProviders(dependencies)
                .addNavigationFiles(navigationFiles)
                .withFeatures(*optionalFeatures.toTypedArray())
                .setMergeReportFile(reportFile)
                .setFeatureName(featureName)
    
            if (mergeType == ManifestMerger2.MergeType.APPLICATION) {
                manifestMergerInvoker.withFeatures(ManifestMerger2.Invoker.Feature.REMOVE_TOOLS_DECLARATIONS)
            }
    
    
            if (outAaptSafeManifestLocation != null) {
                manifestMergerInvoker.withFeatures(ManifestMerger2.Invoker.Feature.MAKE_AAPT_SAFE)
            }
    
            setInjectableValues(
                manifestMergerInvoker,
                packageOverride, versionCode, versionName,
                minSdkVersion, targetSdkVersion, maxSdkVersion
            )
            
            //关注这里的调用
            val mergingReport = manifestMergerInvoker.merge()
            //省略其他对merge结果处理代码
            ... ...
            return mergingReport
        } catch (e: ManifestMerger2.MergeFailureException) {
            // TODO: unacceptable.
            throw RuntimeException(e)
        }
    }
    接着看manifestMergerInvoker.merge()的实现
    
    package com.android.manifmerger;
    
    /**
     * merges android manifest files, idempotent.
     */
    @Immutable
    public class ManifestMerger2 {
        public static class Invoker<T extends Invoker<T>>{
    
            @NonNull
            public MergingReport merge() throws MergeFailureException {
    
                // provide some free placeholders values.
                ImmutableMap<ManifestSystemProperty, Object> systemProperties = mSystemProperties.build();
                ... ...
                FileStreamProvider fileStreamProvider = mFileStreamProvider != null
                        ? mFileStreamProvider : new FileStreamProvider();
                ManifestMerger2 manifestMerger =
                        new ManifestMerger2(
                                mLogger,
                                mMainManifestFile,
                                mLibraryFilesBuilder.build(),
                                mFlavorsAndBuildTypeFiles.build(),
                                mFeaturesBuilder.build(),
                                mPlaceholders.build(),
                                new MapBasedKeyBasedValueResolver<ManifestSystemProperty>(
                                        systemProperties),
                                mMergeType,
                                mDocumentType,
                                Optional.fromNullable(mReportFile),
                                mFeatureName,
                                fileStreamProvider,
                                mNavigationFilesBuilder.build());
                //调用下面的 private MergingReport merge()方法               
                return manifestMerger.merge();
            }
        }
    
    
        /**
         * Perform high level ordering of files merging and delegates actual merging to
         * {@link XmlDocument#merge(XmlDocument, com.android.manifmerger.MergingReport.Builder)}
         *
         * @return the merging activity report.
         * @throws MergeFailureException if the merging cannot be completed (for instance, if xml
         * files cannot be loaded).
         */
        @NonNull
        private MergingReport merge() throws MergeFailureException {
            // initiate a new merging report
            MergingReport.Builder mergingReportBuilder = new MergingReport.Builder(mLogger);
            //一系列merge manifest规则处理
            ... ...
            MergingReport mergingReport = mergingReportBuilder.build();
    
            if (mReportFile.isPresent()) {
                writeReport(mergingReport);
            }
            return mergingReport;
        }
    
        //最终写入Log文件方法
        /**
         * Creates the merging report file.
         * @param mergingReport the merging activities report to serialize.
         */
        private void writeReport(@NonNull MergingReport mergingReport) {
            FileWriter fileWriter = null;
                    ... ... 
                    fileWriter = new FileWriter(mReportFile.get());
                    mergingReport.getActions().log(fileWriter);
        } 
    }

到目前为止,从代码层面看到了Log文件是如何生成的。

## 方案实现 ##

【manifest-merger-$\{variantname\}-report.txt】文件大致内容如下：

-- Merging decision tree log ---
    manifest
    ADDED from /somepath/AndroidManifest.xml:x:x-xx:xx
    MERGED from [dependencies sdk] /somepath/AndroidManifest.xml:x:x-xx:xx
    INJECTED from /somepath/AndroidManifest.xml:x:x-xx:xx
    ...
    uses-permission#android.permission.INTERNET
    方案代码实现很简单：
    
    1.自定义一个Extension，列出暂禁用的权限；
    2.实现相应Plugin和Task；
    
    Extension定义可以如下所示：
    
    host{
           //明确暂禁用的权限列表
           forbiddenPermissions = ['android.permission.GET_ACCOUNTS',
                                'android.permission.SEND_SMS',
                                'android.permission.CALL_PHONE',
                                'android.permission.BLUETOOTH',
                                 ... ...] 
    }
    Plugin简单示例：
    
    public  class HostPlugin implements Plugin<Project> {
        @Override
        final void apply(Project project) {
            if (!project.getPlugins().hasPlugin('com.android.application') && !project.getPlugins().hasPlugin('com.android.library')) {
                throw new GradleException('apply plugin: \'com.android.application\' or apply plugin: \'com.android.library\' is required')
            }
            HostExtension hostExtension = project.getExtensions().create('host', HostExtension.class)
            
            project.afterEvaluate {
                def variants = null;
                if (project.plugins.hasPlugin('com.android.application')) {
                    variants = android.getApplicationVariants()
                } else if (project.plugins.hasPlugin('com.android.library')) {
                    variants = android.getLibraryVariants()
                }
                variants?.all { BaseVariant variant ->
                   MergeHostManifestTask taskConfiguration=  new MergeHostManifestTask.CreationAction()
                   project.getTasks().create(taskConfiguration.getName(), taskConfiguration.getType(), taskConfiguration)
                }
            }
        }   
    }
    Task简单示例：
    
    import org.gradle.util.GFileUtils
    import com.android.utils.FileUtils
    
    class MergeHostManifestTask extends DefaultTask {
    
        List<String> forbiddenPermissions //禁用的权限列表
    
        VariantScope scope
    
        @TaskAction
        def doFullTaskAction() {
    
            File logFile = FileUtils.join(
                    scope.getGlobalScope().getOutputsDir(),
                    "logs",
                    "manifest-permissions-validate-"
                            + scope.getVariantConfiguration().getBaseName()
                            + "-report.txt")
            GFileUtils.mkdirs(logFile.getParentFile())
            GFileUtils.deleteQuietly(logFile)  
    
            checkHostManifest(forbiddenPermissions,logFile,scope)
            if (logFile.exists() && logFile.length() > 0) {
                throw new GradleException("Has forbidden permissions in host, please check it in file ${logFile.getAbsolutePath()}")
            }              
        }    
    
        /**
         * 检测host manifest 是否含有禁用权限列表
         * @param forbiddenPermissions
         * @param logFile
         * @param variantScope
         */
        public static void checkHostManifest(List<String> forbiddenPermissions, File logFile, def variantScope) {
            if (forbiddenPermissions == null || forbiddenPermissions.isEmpty()) {
                return
            }
    
            File reportFile =
                    FileUtils.join(
                            variantScope.getGlobalScope().getOutputsDir(),
                            "logs",
                            "manifest-merger-"
                                    + variantScope.getVariantConfiguration().getBaseName()
                                    + "-report.txt")
    
            if (!reportFile.exists()) {
                return
            }
    
            reportFile.withReader { reader ->
                String line
                while ((line = reader.readLine()) != null) {
                    forbiddenPermissions.each { p ->
                        if (line.contains("uses-permission#${p.trim()}")) {
                            logFile.append("${p.trim()}\n")
                            logFile.append(reader.readLine())
                            logFile.append("\n")
                        }
                    }
                }
            }
        }
    
        public static class CreationAction
                extends TaskConfiguration<MergeHostManifestTask> {
    
            BaseVariant variant
    
            Project project
    
            public CreationAction(Project project,BaseVariant variant){
                this.project= project
                this.variant=variant
            }
    
            @Override
            void execute(MergeHostManifestTask task) {
                ... ...
                HostExtension hostExtension = project.getExtensions().findByType(HostExtension.class)
                task.forbiddenPermissions = hostExtension.getForbiddenPermissions()
                task.scope= variant.getMetaClass().getProperty(variant, 'variantData').getScope()
                task.dependsOn getProcessManifestTask()
            }
    
           private Task getProcessManifestTaskCompat() {
            try {
                //>=3.3.0
                String taskName = variant.getMetaClass().getProperty(variant, 'variantData').getScope().getTaskContainer().getProcessManifestTask().getName()
                return project.getTasks().findByName(taskName)
            } catch (Exception e) {
    
            }
        }
    }

如果APP或其依赖的SDK,有引入禁用权限，则会抛出编译异常，生成的【manifest-permissions-validate-$\{variantname\}-report.txt】文件内容类似以下所示：

android.permission.SEND_SMS
    ADDED from /../app/src/main/AndroidManifest.xml:9:5-67
    android.permission.BLUETOOTH
    ADDED from /../app/src/main/AndroidManifest.xml:11:5-68

## 结束语 ##

关于隐私权限列表，相关部门也未给允一个完整的列表，建议团队把所有未在隐私文档中描述的动态权限都作为禁用权限，直至隐私文档同步。

## 参考 ##

1.Android Gradle Plugin：https://android.googlesource.com/platform/tools/base/+/studio-master-dev/build-system/gradle-core

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