手機(jī)系統(tǒng)外文翻譯--深入理解安卓系統(tǒng)的安全性.doc

畢業(yè)設(shè)計(jì)（論文）譯文及原稿譯文題目 深入理解安卓系統(tǒng)的安全性 原稿題目 Understanding Android Security 原稿出處 Security & Privacy, IEEE.2009,7 深入理解安卓系統(tǒng)的安全性下一代開放操作系統(tǒng)的主流將不會(huì)在桌面上，但是將會(huì)出現(xiàn)在我們每天攜帶的手機(jī)上。這些開放性的環(huán)境將會(huì)帶領(lǐng)這些新的應(yīng)用可能集成這些已經(jīng)存在的在線服務(wù)，當(dāng)然隨著日以具增的數(shù)據(jù)與服務(wù)在手機(jī)上的支持，手機(jī)上的安全缺陷也越發(fā)明顯。下一代操作系統(tǒng)本質(zhì)在于是否提供一個(gè)完整綜合的安全平臺(tái)。由開放手機(jī)聯(lián)盟（open Handset Alliance 谷歌領(lǐng)導(dǎo)）所開發(fā)的android 系統(tǒng)是一個(gè)被廣泛看好的一個(gè)手機(jī)開源系統(tǒng)，該系統(tǒng)提供一個(gè)基本的操作系統(tǒng)，一個(gè)中間件應(yīng)用層，一個(gè)java開發(fā)工具和一個(gè)系統(tǒng)應(yīng)用收集器（collection of system applications ）。盡管android SDK自2007年就發(fā)布了，但是第一部android 手機(jī)卻在2008年10月才誕生。自從這時(shí)起谷歌開起了自己的時(shí)代，T-Mobile的G1的制造商臺(tái)灣 HTC估算G1的發(fā)貨量在2008年底已經(jīng)超過100萬(wàn)部。據(jù)業(yè)內(nèi)人士預(yù)期該G1手機(jī)的銷量將會(huì)在2009年繼續(xù)保持。不久的將來(lái)其他許多手機(jī)供應(yīng)商要計(jì)劃支持這個(gè)系統(tǒng)。一個(gè)圍繞android龐大的開發(fā)者社區(qū)已經(jīng)建立，同時(shí)很多新的產(chǎn)品和應(yīng)用已經(jīng)可以在android上使用。一個(gè)Android的主要賣點(diǎn)是它使開發(fā)人員無(wú)縫把在線服務(wù)擴(kuò)展到手機(jī)。這方面最明顯的例子是谷歌的緊密集成Gmail，日歷和聯(lián)系人Web應(yīng)用程序通過該系統(tǒng)。用戶只需提供一個(gè)android用戶名和密碼，其手機(jī)自動(dòng)同步與谷歌的服務(wù)。其他廠商正在迅速適應(yīng)自己的現(xiàn)有的即時(shí)通訊，社交網(wǎng)絡(luò)和游戲服務(wù)。Android和許多企業(yè)尋找新途徑來(lái)整合他們的自己已有的業(yè)務(wù)到android上。傳統(tǒng)的臺(tái)式機(jī)和服務(wù)器的操作系統(tǒng)一直在努力進(jìn)行安全功能的集成。這些個(gè)人和商業(yè)應(yīng)用在單一平臺(tái)的很出色，然而這一塊業(yè)務(wù)一個(gè)手機(jī)平臺(tái)上像android上不是很有用。它給了許多研究人員希望。Android沒有停在為其他平臺(tái)體用應(yīng)用支持：應(yīng)用的執(zhí)行依賴于頂層JAVA中間件，這個(gè)中間件運(yùn)行在嵌入式Linux 內(nèi)核之上。所以開發(fā)人員要把他們的應(yīng)用部署到Android必須使用其自定義的用戶界面環(huán)境。此外，android系統(tǒng)應(yīng)用限制各應(yīng)用相互調(diào)用API協(xié)作，并且對(duì)方為自己的用戶應(yīng)用進(jìn)行身份驗(yàn)證。盡管這些應(yīng)用有一定的安全特性，我們一些有經(jīng)驗(yàn)的開發(fā)人員開發(fā)android應(yīng)用人士透露，設(shè)計(jì)安全應(yīng)用程序并不總是直線前進(jìn)的。Android使用一個(gè)簡(jiǎn)單的許可標(biāo)簽分配模式限制訪問的資源，但其他應(yīng)用程序的原因必要性和便利，其設(shè)計(jì)師們?cè)黾恿死Щ髮?duì)這個(gè)系統(tǒng)。本文試圖對(duì)Android的安全的復(fù)雜性進(jìn)行講解，并注意一些可能的發(fā)展缺陷以及應(yīng)用程序的安全。我們通過嘗試得出一些經(jīng)驗(yàn)教訓(xùn)，希望對(duì)未來(lái)的安全有用。Android Application Android應(yīng)用程序框架對(duì)開發(fā)者來(lái)說(shuō)是一個(gè)強(qiáng)制架構(gòu)。它沒有一個(gè)main（）函數(shù)功能或單一入口點(diǎn)執(zhí)行，相反，開發(fā)人員必須在設(shè)計(jì)方面的應(yīng)用組件。我們開發(fā)的應(yīng)用對(duì)android的sdk的幫助的APIExample Application。 我們開發(fā)了一個(gè)描述如何創(chuàng)建android的應(yīng)用。有興趣的讀者可以去我們的站點(diǎn)下載讓我們考慮一個(gè)基于位置的社交網(wǎng)絡(luò)應(yīng)用，其中手機(jī)用戶可以通過本應(yīng)用發(fā)現(xiàn)他們的朋友們位置。我們進(jìn)行功能拆分，分成兩個(gè)應(yīng)用程序：一個(gè)用于跟蹤查看朋友和?？此麄?。如圖1所示，F(xiàn)riendTracker應(yīng)用包括跟蹤的組件specifc朋友的位置（例如，通過一個(gè)Web服務(wù)），儲(chǔ)存地理坐標(biāo)，并分享這些合作統(tǒng)籌與其他應(yīng)用程序。然后用戶使用友情查看器應(yīng)用程序來(lái)檢索地理坐標(biāo)和儲(chǔ)存在地圖上查看朋友。這兩個(gè)應(yīng)用程序包含的多個(gè)組件包括展示自己任務(wù)，他們組件是由他們組件類型所決定的。 。一個(gè)Android 開發(fā)者選擇從根據(jù)不同的組件類型組件的目的決定 （如與一個(gè)用戶或存儲(chǔ)數(shù)據(jù)接口）。圖1。例如Android應(yīng)用程序。FriendTracker和FriendViewer應(yīng)用由多個(gè)不同類型的組件，每個(gè)提供一個(gè)不同的組功能。Activity提供一個(gè)用戶界面，Service執(zhí)行后臺(tái)處理，Content提供存儲(chǔ)，Broadcast receiver接收機(jī)其他應(yīng)用程序的信息。 Component Types android系通定義了4種組件類型。 Activity 組件定義應(yīng)用程序的用戶界面。通常，應(yīng)用程序開發(fā)者定義每一個(gè)活動(dòng)“畫面?！盇ctivity可以自己開始，也可能通過傳遞和返回值。在一時(shí)間只有一個(gè)鍵盤的系統(tǒng)Activity可以進(jìn)行處理，在這個(gè)時(shí)候所有其他的Activity都會(huì)被暫停。Service組件執(zhí)行后臺(tái)處理。當(dāng)一個(gè)活動(dòng)需要進(jìn)行一些操作，在用戶界面消失以后（如下載一個(gè)文件或播放音樂），它通常采取此種動(dòng)作特殊設(shè)計(jì)的服務(wù)。開發(fā)人員還可以在系統(tǒng)啟動(dòng)使用特殊的守護(hù)進(jìn)程，Service通常定義一個(gè)遠(yuǎn)程過程調(diào)用（RPC），其他系統(tǒng)組件可以用來(lái)傳送接口命令和檢索數(shù)據(jù)，以及注冊(cè)一個(gè)回調(diào)函數(shù)。Content組件存儲(chǔ)和共享數(shù)據(jù) 用關(guān)系數(shù)據(jù)庫(kù)接口。每個(gè)Content供應(yīng)者都有一個(gè)關(guān)聯(lián)的“權(quán)限”來(lái)形容它的內(nèi)容包含。其他組件使用時(shí)作為一個(gè)handle執(zhí)行SQL查詢（如的SELECT，INSERT或DELETE內(nèi)容。雖然Content供應(yīng)者通常存儲(chǔ)把數(shù)值放在數(shù)據(jù)庫(kù)記錄中，數(shù)據(jù)檢索是實(shí)現(xiàn)特殊的例子，文件也同時(shí)通過內(nèi)容提供商共享接口。Broadcast receiver該組件作為為從郵件信箱發(fā)送信息給他應(yīng)用程序。通常，廣播消息的應(yīng)用程序代碼隱含的目的地。因此，廣播接收器訂閱這些目的地接收發(fā)送給它的消息。應(yīng)用程序代碼也可以解決明確廣播接收機(jī)包括命名空間分配。圖1顯示了FriendTracker和FriendViewer應(yīng)用所包含的不同的組件類型。開發(fā)者組件使用一個(gè)主要定義文件（也用于定義權(quán)限，稍后介紹）。上有一個(gè)應(yīng)用程序的組件的數(shù)量沒有限制定義每種類型，但作為習(xí)慣，一組件應(yīng)具有相同的名稱該應(yīng)用程序。通常情況下，這是作為在FriendViewer activity中進(jìn)行注冊(cè)。這一動(dòng)作通常指示主activity作為該系統(tǒng)應(yīng)用程序啟動(dòng)器用于啟動(dòng)用戶界面;然而，如果需要啟動(dòng)特定的activity，開發(fā)者需要者在選擇配置manifest 信息來(lái)實(shí)現(xiàn)這一個(gè)功能。在在FriendTracker應(yīng)用，例如，F(xiàn)riendTrackerControl活動(dòng)被標(biāo)記為主用戶界面的啟動(dòng)點(diǎn)。在這種情況下，我們保留名稱“FriendTracker”為服務(wù)執(zhí)行的核心組成部分的應(yīng)用程序邏輯。在FriendTracker應(yīng)用包含四種類型的組件。在FriendTracker服務(wù)搜尋調(diào)查外部服務(wù)并發(fā)現(xiàn)好友的位置。在我們的示例代碼中，位置是我們隨機(jī)生成的，但直接通過網(wǎng)絡(luò)連接組件接口的服務(wù)。該FriendProvider Content 提供保持最新的朋友地理坐標(biāo)，F(xiàn)riendTrackerControl活動(dòng)用于啟動(dòng)和用戶界面停止跟蹤好友功能，該系統(tǒng)一旦啟動(dòng) BootReceiver通知從廣播系統(tǒng)啟動(dòng)。該FriendViewer應(yīng)用主要是顯示有關(guān)好友的位置的信息。每個(gè)啟動(dòng)的FriendViewer將會(huì)列出了所有的朋友和他們的地理坐標(biāo)，F(xiàn)riendMap顯示他們?cè)诘貓D上的位置。FriendReceiver將會(huì)等待接收附近的手機(jī)發(fā)送的消息這個(gè)消息來(lái)一個(gè)所指定的朋友。盡管我們可以在這些組件內(nèi)放置在FriendTracker應(yīng)用，但是我們?nèi)匀粍?chuàng)建了一個(gè)單獨(dú)的應(yīng)用程序來(lái)展示跨應(yīng)用的溝通。此外，通過分離程序功能和接口，我們可以創(chuàng)建不同的顯示和功能，可選用戶界面是，許多應(yīng)用程序可以重用這些來(lái)自FriendTracker的功能。Component Interaction該組件交互的主要機(jī)制是一個(gè)intent ，這是一個(gè)簡(jiǎn)單的消息對(duì)象，其中包含一個(gè)目的地組件的地址和數(shù)據(jù)。 Android的API定義了他的方法中傳入intent ，并使用該信息來(lái)啟動(dòng)一個(gè)activity例如開始一個(gè)activity(startActivity(intent)，啟動(dòng)服務(wù)（startService（intent）和廣播信息（sendBroadcast（intent）。Android框架來(lái)通知這些方法的調(diào)用開始執(zhí)行在目標(biāo)應(yīng)用程序代碼。這個(gè)過程中內(nèi)部組件通信稱為一個(gè)動(dòng)作。簡(jiǎn)單地說(shuō)， Intent對(duì)象定義的“Intent”以執(zhí)行“action”。Android的一個(gè)最強(qiáng)大的特點(diǎn)是允許的多種intent尋址機(jī)制。開發(fā)人員可以解決一個(gè)目標(biāo)組件使用其應(yīng)用的空間，他們也可以指定一個(gè)隱含的名稱。在后一種情況下，系統(tǒng)決定了一個(gè)action的最佳組件，通過考慮安裝的應(yīng)用程序和用戶的選擇 。這個(gè)隱含的名字被稱為動(dòng)作字符串因?yàn)樗厥獾念愋偷恼?qǐng)求動(dòng)作。例如一個(gè)view動(dòng)作字符串，在一個(gè)intent中和數(shù)據(jù)域指向一個(gè)圖像文件，系統(tǒng)將會(huì)直接指首選圖像瀏覽器、開發(fā)者也能使用動(dòng)作字符串進(jìn)行大量廣播發(fā)送和接收。在接收端的接收者，開發(fā)者使用一intent 過濾器來(lái)定制特殊的動(dòng)作字符串。Android系包括附加目標(biāo)的決議規(guī)則，但可選的數(shù)據(jù)操作字符串類型是最常見的。圖2顯示了組件之間的FriendTracker和FriendViewer應(yīng)用程序和組件的交互作用在應(yīng)用程序中定義為基礎(chǔ)的Android發(fā)布的一部分。在每一種情況下，發(fā)起一個(gè)組件與其他的溝通。為了簡(jiǎn)單起見，我們稱這個(gè)為件間通信（ICC）。在許多方面，ICC是類似于進(jìn)程間通信（IPC）在基于Unix的系統(tǒng)中。對(duì)于開發(fā)人員，ICC的功能相同無(wú)論目標(biāo)是在相同或不同的應(yīng)用與界定將在下文的安全規(guī)則中說(shuō)明。可用的ICC的動(dòng)作取決于目標(biāo)的組成部分。每個(gè)組件類型支持自己的類型例如，當(dāng)FriendViewer開始FriendMap的FriendMap活動(dòng)出現(xiàn)在屏幕上。服務(wù)組件支持啟動(dòng)，停止，并結(jié)合行動(dòng)，所以FriendTrackerControl活動(dòng)，例如，可以啟動(dòng)和停止FriendTracker服務(wù)在后臺(tái)運(yùn)行。Action的綁定組件之間建立連接，使啟動(dòng)執(zhí)行的服務(wù)定義的RPC。在我們的例子，F(xiàn)riendTracker結(jié)合到系統(tǒng)中的服務(wù)器位置的管理。Understand android security the next generation of open operating systems wont be on desktops or mainframes but on the small mobile devices we carry every day. The openness of these new environments will lead to new applications and markets and will enable greater integration with existing online services. However, as the importance of the data and services our cell phones support increases, so too do the opportunities for vulnerability. Its essential that this next generation of platforms provide a comprehensive and usable security infrastructure.Developed by the Open Handset Alliance (visibly led by Google), Android is a widely anticipated open source operating system for mobile devices that provides a base operating system, an application middleware layer, a Java software development kit (SDK), and a collection of system applications. Although the Android SDK has been available since late 2007, the frst publicly available Android-ready “G1” phone debuted in late October 2008. Since then, Androids growth has been phenomenal: TMobiles G1 manufacturer HTC estimates shipment volumes of more than 1 million phones by the end of 2008, and industry insiders expect public adoption to increase steeply in 2009. Many other cell phone providers have either promised or plan to support it in the near future.A large community of developers has organized around Android, and many new products and applications are now available for it. One of Androids chief selling points is that it lets developers seamlessly .extend online services to phones. The most visible example of this feature isunsurprisinglythe tight integration of Googles Gmail, Calendar, and Contacts Web applications with system utilities. Android users simply supply a username and password, and their phones automatically synchronize with Google services. Other vendors are rapidly adapting their existing instant messaging, social networks, and gaming services to Android, and many enterprises are looking for ways to integrate their own internal operations (such as inventory management, purchasing, receiving, and so forth) into it as well.Traditional desktop and server operating systems have struggled to securely integrate such personal and business applications and services on a single platform; although doing so on a mobile platform such as Android remains nontrivial, many researchers hope it provides a clean slate devoid of the complications that legacy software can cause. Android doesnt ofcially support applications eloped for other platforms: applications execute on top of a Java middleware layer running on an embedded Linux kernel, so developers wishing to port their application to Android must use its custom user interface environment. Additionally, Android restricts application interaction to its special APIs by running each application as its own user identity. Although this controlled interaction has several benefcial security features, our experiences developing Android applications have revealed that designing secure forward. Android uses a simple permission label assignment model to restrict access to resources and other applications, but for reasons of necessity and convenience, its designers have added several potentially confusing refnements as the system has evolved.This article attempts to unmask the complexity of Android security and note some possible development pitfalls that occur when defning an applications security. We conclude by attempting to draw some lessons and identify opportunities for future enhancements that should aid in clarity and correctness.Android Applications The Android application framework forces a structure on developers. It doesnt have a main() function or single entry point for executioninstead, developers must design applications in terms of components. Example Application.We developed a pair of applications to help describe how Android applications operate. Interested readers can download the source code from our web sitepttp://android_sec_tutorial.html).Lets consider a location-sensitive social networking application for mobile phones in which users can discover their friendslocations. We split the functionality into two applications: one for tracking friends and one for viewing them. As Figure 1 shows, the FriendTracker application consists of components specifc to tracking friend locations (for example, via a Web service), storing geographic coordinates, and sharing those coordinates with other applications. The user then uses the FriendViewer application to retrieve the stored geographic coordinates and view friends on a map.Both applications contain multiple components for performing their respective tasks; the components themselves are classifed by their component types. An Android developer chooses from predefned component types depending on the components purpose (such as interfacing with a user or storing data).Component TypesAndroid defnes four component types:Activity components defne an applications user interface. Typically, an application developer defnes one activity per “screen.” Activities start each other, possibly passing and returning values. Only one activity on the system has keyboard and ocessing focus at a time; all others are suspended.Service components perform background processing. When an activity needs to perform some operation that must continue after the user interface disappears (such as download a fle or play music), it commonly starts a service specifcally designed for that action. The developer can also use services as application-specifc daemons, possibly starting on boot. Services often define an interface for Remote Procedure Call (RPC) that other system components can use to send commands and retrieve data, as well as register callbacks. Content provider components store and share data using a relational database interface. Each content provider has an associated “authority” describing the content it contains. Other components use the authority name as a handle to perform SQL queries (such as SELECT, INSERT, or DELETE) to read and write content. Although content providers typically store values in database records, data retrieval is implementation-specifcfor example, fles are also shared through content provider interfaces.Broadcast receiver components act as mailboxes for messages from other applications. Commonly, application code broadcasts messages to an implicit destination. Broadcast receivers thus sub-scribe to such destinations to receive the messages sent to it. Application code can also address a broadcast receiver explicitly by including the namespace assigned to its containing application. Figure 1 shows the FriendTrack-er and FriendViewer applications containing the diferent component types. The developer specifes components using a manifest fle (also used to defne policy as described later). There are no restrictions on the number of components an application defnes for each type, but as a convention, one component has the same name as the application. Frequently, this is an activity, as in the FriendViewer application. This activity usually indicates the primary activity that the system application launcher uses to start the user interface; however, the specifc activity cho-sen on launch is marked by meta information in the manifest. In the FriendTracker application, for example, the FriendTrackerControl activity is marked as the main user interface entry point. In this case, we reserved the name “FriendTracker” for the service component performing the core application logic.The FriendTracker application contains each of the four component types. The FriendTracker service polls an external service to discover friends locations. In our example code, we generate locaFriendTracker application BootReceiver Broadcast receiver ActivityFriendTracker FriendProvider Content provider Service FriendTracker control FriendViewer application FriendReceiver Broadcast receiver Activity FriendTracker Activity FriendViewer Figure 1. Example Android application. The FriendTracker and FriendViewer applications consist of multiple components of different types, each of which provides a different set of functionalities. Activities provide a user interface, services execute background processing, content providers are data storage facilities, and broadcast receivers act as mailboxes for messages from other applications.tions randomly, but extending the component to interface with a Web service is straightforward. The FriendProvider content provider maintains the most recent geographic coordinates for friends, the FriendTrackerControl activity defnes a user interface for starting and stopping the tracking functionality, and the BootReceiver broadcast receiver obtains a notifcation from the system once it boots (the application uses this to utomatically start the FriendTracker service).The FriendViewer application bis primarily concerned with showing information about friends locations. The FriendViewer activity lists all friends and their geographic coordinates, and the FriendMap activity displays them on a map. The FriendReceiver broadcast receiver waits for messages that indicate the physical phone is near a particular friend and displays a message to the user upon such an event. Although we could have placed these components within the FriendTracker application, we created a separate application to demonstrate cross-application communication. dditionally, by separating the tracking and user interface logic, we can create alternative user interfaces with different displays and featuresthat is, many applications can reuse the logic performed in FriendTracker.Component Interaction The primary mechanism for component interaction is an intent, which is simply a message object containing a destination component address and data. The Android API defnes methods that accept intents, and uses that information to start activities (startActivity(Intent), start services (startService (Intent), and broadcast messages (sendBroadcast(Intent). The invocation of these methods tells the Android framework to begin executing code in the target application. This process of intercomponent communication is known as an action. Simply put, an intent object defnes the “intent” to perform an “action.”O(jiān)ne of Androids most powerful features is the fexibility allowed by its intent-addressing mechanism. Although developers can uniquely address a target component using its applications namespace, they can also specify an implicit name. In the latter case, the system determines the best component for an action by considering the set of installed applications and user choices. The implicit name is called an action string because it specifes the type of requested actionfor ex