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ASM 字节码插桩：隐私合规方法检测!

news 2025/7/11 16:30:25

1.前言

近两年来工信部对于应用的隐私合规安全问题愈加重视，对 Android 平台的管控程度也要比 IOS 平台严格很多，很多不合规的应用也先后被下架要求整改。笔者就曾遇到过加班整改隐私合规的问题，隐私合规问题主要针对两个方面。

在用户同意隐私协议之前不能收集用户隐私数据，例如 IMEI、AndroidId、MAC 等

在用户同意隐私协议之后，收集用户数据行为在对应场景不能超频。比如一分钟不能超过 3 次获取 IMEI

针对上述两个方面，有以下措施来针对

通过静态扫描，收集项目中（自有代码 + 三方 sdk）使用隐私合规相关 api 的相关代码

通过 ASM 插桩，在调用隐私合规 api 之前插入代码，记录运行时的方法调用链和当前时间

hook 隐私合规 api，替换字节码指令将调用链指向工具类，在未同意隐私协议之前，不调用相关的 api

2.实现

2.1 注解和工具类

通过定义注解和工具类，用来定义要处理哪些隐私合规相关的方法，目前笔者已经处理了大部分，请放心食用

2.1.1 注解

/*** 收集和注解匹配的方法* visitMethodInsn(int opcode, String owner, String name,String desc)** ======如果 originName 和 originDesc 传""，逻辑会在插件中处理=====*/
@Retention(RetentionPolicy.CLASS)
@Target({ElementType.METHOD})
public @interface AsmMethodReplace {/*** 指令操作码*/int targetMethodOpcode();/*** 方法所有者类*/String targetClass();/*** 方法名称*/String targetName() default "";/*** 方法描述符*/String targetDesc() default "";/*** 是否进行 hook*/boolean hook() default false;}

该注解用来匹配调用隐私合规 api 的字节码指令，例如通过 ASM 调用 getImei 的字节码指令为methodVisitor.visitMethodInsn(INVOKEVIRTUAL, "android/telephony/TelephonyManager", "getImei", "()Ljava/lang/String;", false);。targetName 属性和 targetDesc 可以不赋值，这里做了取巧的处理，会根据工具类的 method name 和method descriptor 推断出调用隐私合规方法的字节码指令，这块后面插件会处理。最后的 hook 属性表示是否 hook 掉原始的调用链，将调用指向工具类中的方法。

2.1.2 工具类

上述注解可以用在任何地方，笔者将常用的隐私合规的方法聚合起来，方法工具类中统一处理，例如处理 IMEI 的逻辑如下：

@RequiresApi(api = Build.VERSION_CODES.O)
@AsmMethodReplace(targetMethodOpcode = OPCODE_INVOKEVIRTUAL, targetClass = CLASS_NAME_TELEPHONYMANAGER,hook = true)
public static String getImei(TelephonyManager telephonyManager) {if (!checkAgreePrivacy("getImei")) {Log.e(TAG, TIP);return "";}if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {Log.i(TAG, "getImei-SDK_INT above android Q");return "";}return telephonyManager.getImei();
}

如果还没有同意隐私协议，直接 return “”，否者走正常的调用方法。同时，通过工具类

   @Overrideprotected void attachBaseContext(Context base) {super.attachBaseContext(base);ConfigGlobal.getInstance().setStoreDirectory(base.getExternalCacheDir().getAbsolutePath());}

设置存储调用堆栈和时间的文件路径。

2.2 插件处理

gradle 插件的基本使用在这里就不赘述了，这里主要是两方面的处理

编译时扫描代码，处理有定义特定注解的方法，分析字节码指令，收集所有需要处理的隐私合规相关 api 相关的信息

再次扫描，根据第一次扫描收集到的信息，判断当前类是否含有调用隐私合规 api 的字节码指令，如果有，在该类中注入一个写文件方法及在隐私合规 api 调用指令之前插入写文件的字节码指令，用来记录调用堆栈和频次。

2.2.1 模版代码

下面这块代码是我们在自定义 gradle 插件时常用的模版代码，供大家使用

abstract class BaseTransform extends Transform {AbstractExecutorService executorService = ForkJoinPool.commonPool()private List<Callable<Void>> taskList = new ArrayList<>()protected Project projectBaseTransform(Project project) {this.project = project}@OverrideString getName() {return getClass().simpleName}@OverrideSet<QualifiedContent.ContentType> getInputTypes() {return TransformManager.CONTENT_CLASS}@OverrideSet<? super QualifiedContent.Scope> getScopes() {return TransformManager.SCOPE_FULL_PROJECT}@Overrideboolean isIncremental() {return true}@Overridevoid transform(TransformInvocation transformInvocation) throws TransformException, InterruptedException, IOException {super.transform(transformInvocation)println("transform start--------------->")if (firstTransform()) {printCopyRight()}onTransformStart(transformInvocation)def startTime = System.currentTimeMillis()def inputs = transformInvocation.inputsdef outputProvider = transformInvocation.outputProviderdef context = transformInvocation.contextdef isIncremental = transformInvocation.isIncremental()if (!isIncremental) {outputProvider.deleteAll()}//1
//        inputs.each { input ->
//            input.jarInputs.each { JarInput jarInput ->
//                forEachJar(jarInput, outputProvider, context, isIncremental)
//            }
//
//            input.directoryInputs.each { DirectoryInput dirInput ->
//                forEachDir(dirInput, outputProvider, context, isIncremental)
//            }
//        }//3inputs.each { input ->input.jarInputs.each { jarInput ->submitTask(new Runnable() {@Overridevoid run() {forEachJar(jarInput, outputProvider, context, isIncremental)}})}input.directoryInputs.each { DirectoryInput dirInput ->submitTask(new Runnable() {@Overridevoid run() {forEachDir(dirInput, outputProvider, context, isIncremental)}})}}def futures = executorService.invokeAll(taskList)futures.each { it ->it.get()}onTransformEnd(transformInvocation)println(getName() + "transform end--------------->" + "duration : " + (System.currentTimeMillis() - startTime) + " ms")}void submitTask(Runnable runnable) {taskList.add(new Callable<Void>() {@OverrideVoid call() throws Exception {runnable.run()return null}})}void forEachDir(DirectoryInput directoryInput, TransformOutputProvider outputProvider, Context context, boolean isIncremental) {def inputDir = directoryInput.fileFile dest = outputProvider.getContentLocation(directoryInput.name,directoryInput.contentTypes,directoryInput.scopes,Format.DIRECTORY)println "directoryInputPath:" + directoryInput.file.absolutePathprintln "destPath:" + dest.absolutePathdef srcDirPath = inputDir.absolutePathdef destDirPath = dest.absolutePathdef temporaryDir = context.temporaryDirFileUtils.forceMkdir(dest)Logger.info("srcDirPath:${srcDirPath}, destDirPath:${destDirPath}")if (isIncremental) {directoryInput.getChangedFiles().each { entry ->def classFile = entry.keyswitch (entry.value) {case Status.NOTCHANGED:Logger.info("处理 class： " + classFile.absoluteFile + " NOTCHANGED")breakcase Status.REMOVED:Logger.info("处理 class： " + classFile.absoluteFile + " REMOVED")//最终文件应该存放的路径def destFilePath = classFile.absolutePath.replace(srcDirPath, destDirPath)def destFile = File(destFilePath)if (destFile.exists()) {destFile.delete()}breakcase Status.ADDED:case Status.CHANGED:Logger.info("处理 class： " + classFile.absoluteFile + " ADDED or CHANGED")modifyClassFile(classFile, srcDirPath, destDirPath, temporaryDir)breakdefault:break}}} else {com.android.utils.FileUtils.getAllFiles(inputDir).each { File file ->modifyClassFile(file, srcDirPath, destDirPath, temporaryDir)}}}void modifyClassFile(classFile, srcDirPath, destDirPath, temporaryDir) {Logger.info("处理 class： " + classFile.absoluteFile)//目标路径def destFilePath = classFile.absolutePath.replace(srcDirPath, destDirPath)def destFile = new File(destFilePath)if (destFile.exists()) {destFile.delete()}Logger.info("处理 class：destFile" + destFile.absoluteFile)String className = CommonUtil.path2ClassName(classFile.absolutePath.replace(srcDirPath + File.separator, ""))Logger.info("处理 className： " + className)File modifyFile = nullif (CommonUtil.isLegalClass(classFile) && shouldHookClass(className)) {modifyFile = getModifyFile(classFile, temporaryDir, className)}if (modifyFile == null) {modifyFile = classFile}FileUtils.copyFile(modifyFile, destFile)}File getModifyFile(File classFile, File temporaryDir, String className) {byte[] sourceBytes = IOUtils.toByteArray(new FileInputStream(classFile))def tempFile = new File(temporaryDir, CommonUtil.generateClassFileName(classFile))if (tempFile.exists()) {FileUtils.forceDelete(tempFile)}def modifyBytes = modifyClass(className, sourceBytes)if (modifyBytes == null) {modifyBytes = sourceBytes}tempFile.createNewFile()def fos = new FileOutputStream(tempFile)fos.write(modifyBytes)fos.flush()IOUtils.closeQuietly(fos)return tempFile}void forEachJar(JarInput jarInput, TransformOutputProvider outputProvider, Context context, boolean isIncremental) {Logger.info("jarInput:" + jarInput.file)File destFile = outputProvider.getContentLocation(//防止同名被覆盖CommonUtil.generateJarFileName(jarInput.file), jarInput.contentTypes, jarInput.scopes, Format.JAR)//增量编译处理if (isIncremental) {Status status = jarInput.statusswitch (status) {case Status.NOTCHANGED:Logger.info("处理 jar： " + jarInput.file.absoluteFile + " NotChanged")//Do nothingreturncase Status.REMOVED:Logger.info("处理 jar： " + jarInput.file.absoluteFile + " REMOVED")if (destFile.exists()) {FileUtils.forceDelete(destFile)}returncase Status.ADDED:case Status.CHANGED:Logger.info("处理 jar： " + jarInput.file.absoluteFile + " ADDED or CHANGED")break}}if (destFile.exists()) {FileUtils.forceDelete(destFile)}CommonUtil.isLegalJar(jarInput.file) ? transformJar(jarInput.file, context.getTemporaryDir(), destFile): FileUtils.copyFile(jarInput.file, destFile)}def transformJar(File jarFile, File temporaryDir, File destFile) {Logger.info("处理 jar： " + jarFile.absoluteFile)File tempOutputJarFile = new File(temporaryDir, CommonUtil.generateJarFileName(jarFile))if (tempOutputJarFile.exists()) {FileUtils.forceDelete(tempOutputJarFile)}JarOutputStream jarOutputStream = new JarOutputStream(new FileOutputStream(tempOutputJarFile))JarFile inputJarFile = new JarFile(jarFile, false)try {def entries = inputJarFile.entries()while (entries.hasMoreElements()) {def jarEntry = entries.nextElement()def entryName = jarEntry.getName()def inputStream = inputJarFile.getInputStream(jarEntry)try {byte[] sourceByteArray = IOUtils.toByteArray(inputStream)def modifiedByteArray = nullif (!jarEntry.isDirectory() && CommonUtil.isLegalClass(entryName)) {String className = CommonUtil.path2ClassName(entryName)if (shouldHookClass(className)) {modifiedByteArray = modifyClass(className, sourceByteArray)}}if (modifiedByteArray == null) {modifiedByteArray = sourceByteArray}jarOutputStream.putNextEntry(new JarEntry(entryName))jarOutputStream.write(modifiedByteArray)jarOutputStream.closeEntry()} finally {IOUtils.closeQuietly(inputStream)}}} finally {jarOutputStream.flush()IOUtils.closeQuietly(jarOutputStream)IOUtils.closeQuietly(inputJarFile)}FileUtils.copyFile(tempOutputJarFile, destFile)}private byte[] modifyClass(String className, byte[] sourceBytes) {byte[] classBytesCodetry {classBytesCode = hookClassInner(className, sourceBytes)} catch (Throwable e) {e.printStackTrace()classBytesCode = nullprintln "throw exception when modify class ${className}"}return classBytesCode}/*** 打印日志信息*/static void printCopyRight() {println()println '#######################################################################'println '##########                                                    'println '##########                欢迎使用隐私合规处理插件'println '##########                                                    'println '#######################################################################'println '##########                                                    'println '##########                 插件配置参数                         'println '##########                                                    'println '##########                -isDebug: ' + PrivacyGlobalConfig.isDebugprintln '##########                -handleAnnotationName: ' + PrivacyGlobalConfig.handleAnnotationNameprintln '##########                -exclude: ' + PrivacyGlobalConfig.excludeprintln '##########                                                    'println '##########                                                    'println '##########                                                    'println '#######################################################################'println()}protected boolean firstTransform() {return false}boolean shouldHookClass(String className) {def excludes = PrivacyGlobalConfig.excludeif (excludes != null) {for (String string : excludes) {if (className.startsWith(string)) {return false}}}return shouldHookClassInner(className)}protected abstract boolean shouldHookClassInner(String className)protected abstract byte[] hookClassInner(String className, byte[] bytes)protected abstract void onTransformStart(TransformInvocation transformInvocation)protected abstract void onTransformEnd(TransformInvocation transformInvocation)
}

2.2.2 注解处理 transform

收集和处理具有特定注解的字节码指令,给下一个 transform 使用

@Override
byte[] hookClassInner(String className, byte[] bytes) {ClassReader cr = new ClassReader(bytes)ClassNode classNode = new ClassNode()cr.accept(classNode, 0)classNode.methods.each { methodNode ->//编译期注解methodNode.invisibleAnnotations.each { annotationNode ->if (PrivacyGlobalConfig.getHandleAnnotationName() == annotationNode.desc) {collectPrivacyMethod(annotationNode, methodNode, cr.className)}}}return bytes
}/*** 收集注解和注解关联的方法* @param annotationNode 注解信息* @param methodNode 方法信息*/
static collectPrivacyMethod(AnnotationNode annotationNode, MethodNode methodNode, String className) {List<Object> values = annotationNode.valuesLogger.info("annotation values : ${values}")MethodReplaceItem item = new MethodReplaceItem(values, methodNode, CommonUtil.getClassInternalName(className))PrivacyGlobalConfig.methodReplaceItemList.offer(item)Logger.info("collectPrivacyMethod success: ${item}")println("collectPrivacyMethod success: ${item}")
}

MethodReplaceItem中封装了收集到的字节码属性，同时会根据注解关联方法的字节码指令推断出想要处理的隐私合规 api 的字节码指令。

MethodReplaceItem(List<Object> annotationPair, MethodNode methodNode, String owner) {replaceOpcode = Opcodes.INVOKESTATICreplaceClass = ownerreplaceMethod = methodNode.namereplaceDesc = methodNode.descfor (int i = 0; i < annotationPair.size(); i = i + 2) {def key = annotationPair[i]def value = annotationPair[i + 1]if (key == "targetMethodOpcode") {targetOpcode = value} else if (key == "targetClass") {targetOwner = value} else if (key == "targetName") {targetMethod = value} else if (key == "targetDesc") {targetDesc = value}else if(key == "hook"){willHook = value}}Logger.info("=====targetOpcode:${targetOpcode},targetOwner:${targetOwner} , replaceDesc${replaceDesc}")if (isEmpty(targetMethod)) {targetMethod = replaceMethod}if (isEmpty(targetDesc)) {//静态方法，oriDesc 跟 targetDesc 一样if (targetOpcode == Opcodes.INVOKESTATIC) {targetDesc = replaceDesc} else {//非静态方法，约定第一个参数是实例类名，oriDesc 比 targetDesc 少一个参数，处理一下// (Landroid/telephony/TelephonyManager;)Ljava/lang/String ->  ()Ljava/lang/Stringdef param = replaceDesc.split('\)')[0] + ")"def result = replaceDesc.split('\)')[1]def index = replaceDesc.indexOf(targetOwner)if (index != -1) {param = "(" + param.substring(index + targetOwner.length() + 1)}Logger.info("index::: ${index}")targetDesc = param + result}}
}

2.2.3 合规方法处理 transform

再次扫描整个项目，根据在上一个 transform 中收集到的要处理的隐私合规的 api，遍历字节码指令，当匹配上时，在当前的类中注入写文件的方法，同时在调用隐私合规的字节码指令前插入写文件的字节码指令，用来记录。

@Override
byte[] hookClassInner(String className, byte[] bytes) {Logger.info("${getName()} modifyClassInner--------------->")def findHookPoint = falseMap<MethodNode, InsertInsnPoint> collectMap = new HashMap<>()ClassReader cr = new ClassReader(bytes)ClassNode classNode = new ClassNode()cr.accept(classNode, ClassReader.EXPAND_FRAMES)classNode.methods.each { methodNode ->//过滤掉含有特定注解的方法if (isNotHookMethod(cr.className, methodNode)) {methodNode.instructions.each { insnNode ->//判断字节码能否匹配def methodReplaceItem = searchHookPoint(insnNode)if (methodReplaceItem != null) {//判断是否需要 hook 掉当前指令def inject = methodReplaceItem.willHook//记录隐私合规 api 所在的类及方法logHookPoint(classNode.name, methodReplaceItem, methodNode, insnNode.opcode, insnNode.owner, insnNode.name, insnNode.desc, inject)if (inject) {//hookinjectInsn(insnNode, methodReplaceItem)}//插入写文件方法指令，收集调用隐私方法的堆栈collectInsertInsn(insnNode, methodNode, classNode, collectMap, inject)findHookPoint = true}}}}if (!collectMap.isEmpty() && findHookPoint) {//插入写文件指令，用来展示堆栈信息collectMap.each { key, value ->key.instructions.insert(value.hookInsnNode, value.instList)}//插入 writeToFile 方法ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS)classNode.accept(cw)insertWriteToFileMethod(cw)return cw.toByteArray()}return bytes
}

在 collectInsertInsn 方法中，通过 throwable 来收集当前的堆栈

/*** 收集 在调用特定的方法前插入调用写入文件的方法的指令* @param insnNode* @param methodNode* @param classNode* @param collectMap*/
static void collectInsertInsn(insnNode, methodNode, classNode, collectMap, Inject) {def className = classNode.namedef methodName = methodNode.namedef methodDesc = methodNode.descdef owner = nulldef name = nulldef desc = nullif (insnNode instanceof MethodInsnNode) {owner = insnNode.ownername = insnNode.namedesc = insnNode.desc}//------logStringBuilder lintLog = new StringBuilder()lintLog.append(className)lintLog.append("  ->  ")lintLog.append(methodName)lintLog.append("  ->  ")lintLog.append(methodDesc)lintLog.append("\r\n")lintLog.append(owner)lintLog.append("  ->  ")lintLog.append(name)lintLog.append("  ->  ")lintLog.append(desc)//------要插入字节码指令lintLog.append("\r\n")InsnList insnList = new InsnList()insnList.add(new LdcInsnNode(lintLog.toString()))insnList.add(new TypeInsnNode(Opcodes.NEW, "java/lang/Throwable"))insnList.add(new InsnNode(Opcodes.DUP))insnList.add(new MethodInsnNode(Opcodes.INVOKESPECIAL, "java/lang/Throwable", "<init>", "()V", false))insnList.add(new MethodInsnNode(Opcodes.INVOKESTATIC, className, writeToFileMethodName, writeToFileMethodDesc))println "插入指令完成 =---------->"collectMap.put(methodNode, new InsertInsnPoint(insnList, insnNode))
}

最终，在项目编译完成之后，会在项目的根目录下生成 replaceInsn.txt 文件，记录包含隐私合规 api 的类和相关方法。

当项目运行起来之后，会在设置的路径中（笔者设置在 getExternalCacheDir 中）生成 privacy_log.txt 文件，里面会记录隐私合规 api 的调用堆栈和时间，根据该调用链，我们就可以快速定位是哪一块业务执行了敏感操作。

3.总结

通过 ASM + gradle plugin ，能够排查出大部分的隐私合规问题。有什么不足之处，也请读者多多提意见和建议。

源码地址

https://github.com/season-max/asm_hook.git