安全性增強項目

Android 14

Every Android release includes dozens of security enhancements to protect users. Here are some of the major security enhancements available in Android 14:

• Hardware-assisted AddressSanitizer (HWASan), introduced in Android 10, is a memory error detection tool similar to AddressSanitizer. Android 14 brings significant improvements to HWASan. Learn how it helps prevent bugs from making it into Android releases, HWAddressSanitizer
• In Android 14, starting with apps that share location data with third-parties, the system runtime permission dialog now includes a clickable section that highlights the app's data-sharing practices, including information such as why an app may decide to share data with third parties.
• Android 12 introduced an option to disable 2G support at the modem level, which protects users from the inherent security risk from 2G's obsolete security model. Recognizing how critical disabling 2G could be for enterprise customers, Android 14 enables this security feature in Android Enterprise, introducing support for IT admins to restrict the ability of a managed device to downgrade to 2G connectivity.
• Added support to reject null-ciphered cellular connections, ensuring that circuit-switched voice and SMS traffic is always encrypted and protected from passive over-the-air interception. Learn more about Android's program to harden cellular connectivity.
• Added support for multiple IMEIs
• Since Android 14, AES-HCTR2 is the preferred mode of filenames encryption for devices with accelerated cryptography instructions.
• Cellular connectivity
• Documentation added for Android Safety Center
• If your app targets Android 14 and uses Dynamic Code Loading (DCL), all dynamically-loaded files must be marked as read-only. Otherwise, the system throws an exception. We recommend that apps avoid dynamically loading code whenever possible, as doing so greatly increases the risk that an app can be compromised by code injection or code tampering.

Check out our full AOSP release notes and the Android Developer features and changes list.

Android 13

Every Android release includes dozens of security enhancements to protect users. Here are some of the major security enhancements available in Android 13:

• Android 13 adds multi-document presentation support. This new Presentation Session interface enables an app to do a multi-document presentation, something which isn't possible with the existing API. For further information, refer to Identity Credential
• In Android 13, intents originating from external apps are delivered to an exported component if and only if the intents match their declared intent-filter elements.
• Open Mobile API (OMAPI) is a standard API used to communicate with a device's Secure Element. Before Android 13, only apps and framework modules had access to this interface. By converting it to a vendor stable interface, HAL modules are also capable of communicating with the secure elements through the OMAPI service. For more information, see OMAPI Vendor Stable Interface.
• As of Android 13-QPR, shared UIDs are deprecated. Users of Android 13 or higher should put the line `android:sharedUserMaxSdkVersion="32"` in their manifest. This entry prevents new users from getting a shared UID. For further information on UIDs, see App signing.
• Android 13 added support Keystore symmetric cryptographic primitives such as AES (Advanced Encryption Standard), HMAC (Keyed-Hash Message Authentication Code), and asymmetric cryptographic algorithms (including Elliptic Curve, RSA2048, RSA4096, and Curve 25519)
• Android 13 (API level 33) and higher supports a runtime permission for sending non-exempt notifications from an app. This gives users control over which permission notifications they see.
• Added per-use prompt for apps requesting access to all device logs, giving users the ability to allow or deny access.
• introduced the Android Virtualization Framework (AVF), which brings together different hypervisors under one framework with standardized APIs. It provides secure and private execution environments for executing workloads isolated by hypervisor.
• Introduced APK signature scheme v3.1 All new key rotations that use apksigner use the v3.1 signature scheme by default to target rotation for Android 13 and higher.

Check out our full AOSP release notes and the Android Developer features and changes list.

Android 12

Every Android release includes dozens of security enhancements to protect users. Here are some of the major security enhancements available in Android 12:

• Android 12 introduces the BiometricManager.Strings API, which provides localized strings for apps that use BiometricPrompt for authentication. These strings are intended to be device-aware and provide more specificity about which authentication types might be used. Android 12 also includes support for under-display fingerprint sensors
• Support added for under-display fingerprint sensors
• Introduction of the Fingerprint Android Interface Definition Language (AIDL)
• Support for new Face AIDL
• Introduction of Rust as a language for platform development
• The option for users to grant access only to their approximate location added
• Added Privacy indicators on the status bar when an app is using the camera or microphone
• Android's Private Compute Core (PCC)
• Added an option to disable 2G support

Android 11

每個 Android 版本都包含數十項安全性強化功能，可保護使用者。如需 Android 11 中提供的部分主要安全性強化功能清單，請參閱 Android 版本資訊。

Android 10

每個 Android 版本都包含數十項安全性強化功能，可保護使用者。Android 10 包含多項安全性和隱私權強化功能。如需 Android 10 的完整變更清單，請參閱 Android 10 版本資訊。

安全性

BoundsSanitizer

Android 10 會在藍牙和編解碼器中部署 BoundsSanitizer (BoundSan)。BoundSan 使用 UBSan 的邊界消毒工具。這項緩解措施會在每個模組層級啟用。這有助於確保 Android 的重要元件安全無虞，因此不應停用。在下列編解碼中啟用 BoundSan：

• libFLAC
• libavcdec
• libavcenc
• libhevcdec
• libmpeg2
• libopus
• libvpx
• libspeexresampler
• libvorbisidec
• libaac
• libxaac

僅執行記憶體

根據預設，AArch64 系統二進位檔的可執行程式碼區段會標示為「僅供執行」(不可讀取)，以便針對即時程式碼重複使用攻擊採取強化措施。將資料和程式碼混合在一起的程式碼，以及有意檢查這些區段 (不先將記憶體區段重新對應為可讀) 的程式碼，都無法運作。如果應用程式嘗試讀取記憶體中僅執行記憶體 (XOM) 啟用的系統程式庫的程式碼區段，而未先將該區段標示為可讀，就會影響到目標 SDK 為 Android 10 (API 級別 29 以上) 的應用程式。

額外存取權

信任的代理程式是第三方驗證機制 (例如 Smart Lock) 使用的基礎機制，只能在 Android 10 中延長解鎖時間。信任的代理程式無法再解鎖已鎖定的裝置，最多只能讓裝置保持解鎖狀態四小時。

臉孔驗證

臉部驗證：使用者只要看著裝置正面，即可解鎖裝置。Android 10 新增了臉部辨識堆疊支援功能，可安全處理相機影格，在支援的硬體上進行臉部辨識時，保護安全性和隱私權。Android 10 也為符合安全性規定的實作方式，提供簡單的方法，讓應用程式整合線上銀行或其他服務等交易。

整數溢位清理

Android 10 會在軟體編碼器中啟用整數溢位清理 (IntSan)。確保播放效能可接受任何裝置硬體不支援的編解碼。在下列編解碼中啟用 IntSan：

• libFLAC
• libavcdec
• libavcenc
• libhevcdec
• libmpeg2
• libopus
• libvpx
• libspeexresampler
• libvorbisidec

模組化系統元件

Android 10 將部分 Android 系統元件模組化，讓這些元件能夠在 Android 的正常發布週期外進行更新。部分模組包括：

• Android 執行階段
• Conscrypt
• DNS 解析器
• DocumentsUI
• ExtServices
• 媒體
• ModuleMetadata
• 網路
• PermissionController
• 時區資料

OEMCrypto

Android 10 使用 OEMCrypto API 15 版。

Scudo

Scudo 是動態使用者模式記憶體配置器，旨在更能抵禦堆積相關的安全漏洞。它提供標準 C 配置和解除配置基本功能，以及 C++ 基本功能。

ShadowCallStack

ShadowCallStack (SCS) 是 LLVM 檢測模式，可在非葉節點函式的函式 prolog 中，將函式的回傳位址儲存至個別配置的 ShadowCallStack 例項，並從函式 epilog 中的 ShadowCallStack 例項載入回傳位址，藉此防止回傳位址覆寫 (例如堆疊緩衝區溢位)。

WPA3 和 Wi-Fi Enhanced Open

Android 10 新增了 Wi-Fi Protected Access 3 (WPA3) 和 Wi-Fi Enhanced Open 安全標準支援，可提供更完善的隱私權，並抵禦已知的攻擊。

隱私權

指定 Android 9 以下版本時的應用程式存取權

如果應用程式在 Android 10 以上版本上執行，但指定 Android 9 (API 級別 28) 以下版本，平台會套用以下行為：

• 如果應用程式為 ACCESS_FINE_LOCATION 或 ACCESS_COARSE_LOCATION 宣告 <uses-permission> 元素，系統會在安裝期間自動為 ACCESS_BACKGROUND_LOCATION 新增 <uses-permission> 元素。
• 如果應用程式要求 ACCESS_FINE_LOCATION 或 ACCESS_COARSE_LOCATION，系統會自動將 ACCESS_BACKGROUND_LOCATION 新增至要求。

背景活動限制

自 Android 10 起，系統會限制從背景啟動活動。這項行為異動可減少使用者遭受的干擾，讓使用者更能掌控螢幕上顯示的內容。只要您的應用程式是因使用者互動而啟動活動，就很可能不會受到這些限制的影響。
如要進一步瞭解從背景啟動活動的建議替代方案，請參閱指南，瞭解如何在應用程式中向使用者發出時間敏感事件的警示。

相機中繼資料

Android 10 會變更 getCameraCharacteristics() 方法預設傳回的資訊廣度。具體來說，應用程式必須具備 CAMERA 權限，才能存取這個方法的傳回值中可能包含的裝置專屬中繼資料。
如要進一步瞭解這些異動，請參閱「需要權限的攝影機欄位」一節。

剪貼簿資料

除非您的應用程式是預設的輸入法編輯器 (IME)，或是目前有焦點的應用程式，否則無法在 Android 10 以上版本存取剪貼簿資料。

裝置定位功能

為讓使用者進一步控管應用程式對位置資訊的存取權，Android 10 推出了 ACCESS_BACKGROUND_LOCATION 權限。
與 ACCESS_FINE_LOCATION 和 ACCESS_COARSE_LOCATION 權限不同，ACCESS_BACKGROUND_LOCATION 權限只會影響應用程式在背景執行時對位置資訊的存取權。除非符合下列任一條件，否則系統會視為應用程式在背景存取位置資訊：

• 屬於應用程式的活動會顯示在畫面上。
• 應用程式正在執行前景服務，且已宣告 location 的前景服務類型。
  如要為應用程式中的服務宣告前景服務類型，請將應用程式的 targetSdkVersion 或 compileSdkVersion 設為 29 以上。進一步瞭解前景服務如何繼續執行使用者啟動的動作，而這些動作需要存取位置資訊。

外部儲存空間

根據預設，指定 Android 10 以上版本為目標版本的應用程式會取得外部儲存空間的限定範圍存取權，或稱為限定範圍儲存空間。這類應用程式可以在外部儲存裝置中查看下列類型的檔案，無須要求任何儲存空間相關使用者權限：

• 應用程式專屬目錄中的檔案，可透過 getExternalFilesDir() 存取。
• 應用程式從媒體庫建立的相片、影片和音訊片段。

如要進一步瞭解限定範圍儲存空間，以及如何分享、存取及修改儲存在外部儲存裝置中的檔案，請參閱如何管理外部儲存空間中的檔案和存取及修改媒體檔案的指南。

MAC 位址隨機化

在搭載 Android 10 以上版本的裝置上，系統會根據預設傳送隨機 MAC 位址。
如果您的應用程式處理企業用途，平台會提供與 MAC 位址相關的多項作業 API：

• 取得隨機化 MAC 位址：裝置擁有者應用程式和設定檔擁有者應用程式可以呼叫 getRandomizedMacAddress()，擷取指派給特定網路的隨機化 MAC 位址。
• 取得實際的原廠 MAC 位址：裝置擁有者應用程式可以呼叫 getWifiMacAddress()，擷取裝置的實際硬體 MAC 位址。這個方法適合用於追蹤裝置機隊。

無法重設的裝置 ID

自 Android 10 起，應用程式必須具備 READ_PRIVILEGED_PHONE_STATE 特權才能存取裝置的無法重設 ID，包括 IMEI 和序號。

• Build
  • getSerial()
• TelephonyManager
  • getImei()
  • getDeviceId()
  • getMeid()
  • getSimSerialNumber()
  • getSubscriberId()

如果您的應用程式沒有權限，但您仍嘗試要求有關不可重設 ID 的資訊，平台的回應會因目標 SDK 版本而異：

• 如果應用程式指定 Android 10 以上版本，就會發生 SecurityException。
• 如果應用程式指定 Android 9 (API 級別 28) 以下版本，且應用程式具有 READ_PHONE_STATE 權限，則該方法會傳回 null 或預留位置資料。否則會發生 SecurityException。

體能活動辨識

Android 10 為需要偵測使用者步數或分類使用者體能活動 (例如步行、騎單車或在車輛中移動) 的應用程式，推出 android.permission.ACTIVITY_RECOGNITION 執行階段權限。這項功能可讓使用者瞭解「設定」中如何使用裝置感應器資料。
Google Play 服務中的部分程式庫 (例如 Activity Recognition API 和 Google Fit API) 只有在使用者授予應用程式此權限時，才會提供結果。
裝置上唯一需要您宣告這項權限的內建感應器，就是步數計數器和步數偵測器感應器。
如果應用程式指定 Android 9 (API 級別 28) 以下版本，且滿足下列所有條件，系統會視需要自動授予應用程式 android.permission.ACTIVITY_RECOGNITION 權限：

• 資訊清單檔案包含 com.google.android.gms.permission.ACTIVITY_RECOGNITION 權限。
• 資訊清單檔案不含 android.permission.ACTIVITY_RECOGNITION 權限。

如果系統自動授予 android.permission.ACTIVITY_RECOGNITION 權限，則在您將應用程式更新為指定 Android 10 後，應用程式會保留該權限。不過，使用者隨時可以在系統設定中撤銷這項權限。

/proc/net 檔案系統限制

在搭載 Android 10 以上版本的裝置上，應用程式無法存取 /proc/net，其中包含裝置網路狀態的相關資訊。需要存取這類資訊的應用程式 (例如 VPN) 應使用 NetworkStatsManager 或 ConnectivityManager 類別。

已從 UI 中移除權限群組

自 Android 10 起，應用程式無法在 UI 中查詢權限分組方式。

移除聯絡人親和力

自 Android 10 起，平台不會追蹤聯絡人親和力資訊。因此，如果您的應用程式對使用者的聯絡人進行搜尋，結果不會依互動頻率排序。
ContactsProvider 指南包含一則通知，說明從 Android 10 開始，所有裝置上已淘汰的特定欄位和方法。

限制存取畫面內容

為保護使用者的螢幕內容，Android 10 會變更 READ_FRAME_BUFFER、CAPTURE_VIDEO_OUTPUT 和 CAPTURE_SECURE_VIDEO_OUTPUT 權限的範圍，防止未經許可存取裝置的螢幕內容。自 Android 10 起，這些權限僅限簽名存取。
需要存取裝置畫面內容的應用程式應使用 MediaProjection API，該 API 會顯示提示，要求使用者提供同意聲明。

USB 裝置序號

如果應用程式指定 Android 10 以上版本，除非使用者授予應用程式存取 USB 裝置或配件的權限，否則應用程式無法讀取序號。
如要進一步瞭解如何使用 USB 裝置，請參閱設定 USB 主機的指南。

Wi-Fi

以 Android 10 以上版本為目標版本的應用程式無法啟用或停用 Wi-Fi。WifiManager.setWifiEnabled() 方法一律會傳回 false。
如果您需要提示使用者啟用及停用 Wi-Fi，請使用設定面板。

限制直接存取已設定的 Wi-Fi 網路

為保護使用者隱私，系統應用程式和裝置政策控制器 (DPC) 才能手動設定 Wi-Fi 網路清單。特定 DPC 可以是裝置擁有者或設定檔擁有者。
如果應用程式指定 Android 10 以上版本，且不是系統應用程式或 DPC，則下列方法不會傳回實用的資料：

• getConfiguredNetworks() 方法一律會傳回空白清單。
• 每個會傳回整數值的網路作業方法 (addNetwork() 和 updateNetwork()) 一律會傳回 -1。
• 每個會傳回布林值的網路作業 (removeNetwork()、reassociate()、enableNetwork()、disableNetwork()、reconnect() 和 disconnect()) 一律會傳回 false。

Android 9

Every Android release includes dozens of security enhancements to protect users. For a list of some of the major security enhancements available in Android 9, see the Android Release Notes.

Android 8

Every Android release includes dozens of security enhancements to protect users. Here are some of the major security enhancements available in Android 8.0:

• Encryption. Added support to evict key in work profile.
• Verified Boot. Added Android Verified Boot (AVB). Verified Boot codebase supporting rollback protection for use in boot loaders added to AOSP. Recommend bootloader support for rollback protection for the HLOS. Recommend boot loaders can only be unlocked by user physically interacting with the device.
• Lock screen. Added support for using tamper-resistant hardware to verify lock screen credential.
• KeyStore. Required key attestation for all devices that ship with Android 8.0+. Added ID attestation support to improve Zero Touch Enrollment.
• Sandboxing. More tightly sandboxed many components using Project Treble's standard interface between framework and device-specific components. Applied seccomp filtering to all untrusted apps to reduce the kernel's attack surface. WebView is now run in an isolated process with very limited access to the rest of the system.
• Kernel hardening. Implemented hardened usercopy, PAN emulation, read-only after init, and KASLR.
• Userspace hardening. Implemented CFI for the media stack. App overlays can no longer cover system-critical windows and users have a way to dismiss them.
• Streaming OS update. Enabled updates on devices that are are low on disk space.
• Install unknown apps. Users must grant permission to install apps from a source that isn't a first-party app store.
• Privacy. Android ID (SSAID) has a different value for each app and each user on the device. For web browser apps, Widevine Client ID returns a different value for each app package name and web origin. net.hostname is now empty and the dhcp client no longer sends a hostname. android.os.Build.SERIAL has been replaced with the Build.SERIAL API which is protected behind a user-controlled permission. Improved MAC address randomization in some chipsets.

Android 7

Every Android release includes dozens of security enhancements to protect users. Here are some of the major security enhancements available in Android 7.0:

• File-based encryption. Encrypting at the file level, instead of encrypting the entire storage area as a single unit, better isolates and protects individual users and profiles (such as personal and work) on a device.
• Direct Boot. Enabled by file-based encryption, Direct Boot allows certain apps such as alarm clock and accessibility features to run when device is powered on but not unlocked.
• Verified Boot. Verified Boot is now strictly enforced to prevent compromised devices from booting; it supports error correction to improve reliability against non-malicious data corruption.
• SELinux. Updated SELinux configuration and increased seccomp coverage further locks down the Application Sandbox and reduces attack surface.
• Library load-order randomization and improved ASLR. Increased randomness makes some code-reuse attacks less reliable.
• Kernel hardening. Added additional memory protection for newer kernels by marking portions of kernel memory as read-only, restricting kernel access to userspace addresses and further reducing the existing attack surface.
• APK signature scheme v2. Introduced a whole-file signature scheme that improves verification speed and strengthens integrity guarantees.
• Trusted CA store. To make it easier for apps to control access to their secure network traffic, user-installed certificate authorities and those installed through Device Admin APIs are no longer trusted by default for apps targeting API Level 24+. Additionally, all new Android devices must ship with the same trusted CA store.
• Network Security Config. Configure network security and TLS through a declarative configuration file.

Android 6

Every Android release includes dozens of security enhancements to protect users. Here are some of the major security enhancements available in Android 6.0:

• Runtime Permissions. Apps request permissions at runtime instead of being granted at App install time. Users can toggle permissions on and off for both M and pre-M apps.
• Verified Boot. A set of cryptographic checks of system software are conducted prior to execution to ensure the phone is healthy from the bootloader all the way up to the operating system.
• Hardware-Isolated Security. New Hardware Abstraction Layer (HAL) used by Fingerprint API, Lockscreen, Device Encryption, and Client Certificates to protect keys against kernel compromise and/or local physical attacks
• Fingerprints. Devices can now be unlocked with just a touch. Developers can also take advantage of new APIs to use fingerprints to lock and unlock encryption keys.
• SD Card Adoption. Removable media can be adopted to a device and expand available storage for app local data, photos, videos, etc., but still be protected by block-level encryption.
• Clear Text Traffic. Developers can use a new StrictMode to make sure their app doesn't use cleartext.
• System Hardening. Hardening of the system via policies enforced by SELinux. This offers better isolation between users, IOCTL filtering, reduce threat of exposed services, further tightening of SELinux domains, and extremely limited /proc access.
• USB Access Control: Users must confirm to allow USB access to files, storage, or other functionality on the phone. Default is now charge only with access to storage requiring explicit approval from the user.

Android 5

5.0

Every Android release includes dozens of security enhancements to protect users. Here are some of the major security enhancements available in Android 5.0:

• Encrypted by default. On devices that ship with L out-of-the-box, full disk encryption is enabled by default to improve protection of data on lost or stolen devices. Devices that update to L can be encrypted in Settings > Security .
• Improved full disk encryption. The user password is protected against brute-force attacks using scrypt and, where available, the key is bound to the hardware keystore to prevent off-device attacks. As always, the Android screen lock secret and the device encryption key are not sent off the device or exposed to any application.
• Android sandbox reinforced with SELinux . Android now requires SELinux in enforcing mode for all domains. SELinux is a mandatory access control (MAC) system in the Linux kernel used to augment the existing discretionary access control (DAC) security model. This new layer provides additional protection against potential security vulnerabilities.
• Smart Lock. Android now includes trustlets that provide more flexibility for unlocking devices. For example, trustlets can allow devices to be unlocked automatically when close to another trusted device (through NFC, Bluetooth) or being used by someone with a trusted face.
• Multi user, restricted profile, and guest modes for phones and tablets. Android now provides for multiple users on phones and includes a guest mode that can be used to provide easy temporary access to your device without granting access to your data and apps.
• Updates to WebView without OTA. WebView can now be updated independent of the framework and without a system OTA. This allows for faster response to potential security issues in WebView.
• Updated cryptography for HTTPS and TLS/SSL. TLSv1.2 and TLSv1.1 is now enabled, Forward Secrecy is now preferred, AES-GCM is now enabled, and weak cipher suites (MD5, 3DES, and export cipher suites) are now disabled. See https://developer.android.com/reference/javax/net/ssl/SSLSocket.html for more details.
• non-PIE linker support removed. Android now requires all dynamically linked executables to support PIE (position-independent executables). This enhances Android's address space layout randomization (ASLR) implementation.
• FORTIFY_SOURCE improvements. The following libc functions now implement FORTIFY_SOURCE protections: stpcpy(), stpncpy(), read(), recvfrom(), FD_CLR(), FD_SET(), and FD_ISSET(). This provides protection against memory-corruption vulnerabilities involving those functions.
• Security Fixes. Android 5.0 also includes fixes for Android-specific vulnerabilities. Information about these vulnerabilities has been provided to Open Handset Alliance members, and fixes are available in Android Open Source Project. To improve security, some devices with earlier versions of Android may also include these fixes.

Android 4 以下版本

Every Android release includes dozens of security enhancements to protect users. The following are some of the security enhancements available in Android 4.4:

• Android sandbox reinforced with SELinux. Android now uses SELinux in enforcing mode. SELinux is a mandatory access control (MAC) system in the Linux kernel used to augment the existing discretionary access control (DAC) based security model. This provides additional protection against potential security vulnerabilities.
• Per User VPN. On multi-user devices, VPNs are now applied per user. This can allow a user to route all network traffic through a VPN without affecting other users on the device.
• ECDSA Provider support in AndroidKeyStore. Android now has a keystore provider that allows use of ECDSA and DSA algorithms.
• Device Monitoring Warnings. Android provides users with a warning if any certificate has been added to the device certificate store that could allow monitoring of encrypted network traffic.
• FORTIFY_SOURCE. Android now supports FORTIFY_SOURCE level 2, and all code is compiled with these protections. FORTIFY_SOURCE has been enhanced to work with clang.
• Certificate Pinning. Android 4.4 detects and prevents the use of fraudulent Google certificates used in secure SSL/TLS communications.
• Security Fixes. Android 4.4 also includes fixes for Android-specific vulnerabilities. Information about these vulnerabilities has been provided to Open Handset Alliance members and fixes are available in Android Open Source Project. To improve security, some devices with earlier versions of Android may also include these fixes.

Every Android release includes dozens of security enhancements to protect users. The following are some of the security enhancements available in Android 4.3:

• Android sandbox reinforced with SELinux. This release strengthens the Android sandbox using the SELinux mandatory access control system (MAC) in the Linux kernel. SELinux reinforcement is invisible to users and developers, and adds robustness to the existing Android security model while maintaining compatibility with existing apps. To ensure continued compatibility this release allows the use of SELinux in a permissive mode. This mode logs any policy violations, but will not break apps or affect system behavior.
• No setuid or setgid programs. Added support for filesystem capabilities to Android system files and removed all setuid or setgid programs. This reduces root attack surface and the likelihood of potential security vulnerabilities.
• ADB authentication. Starting in Android 4.2.2, connections to ADB are authenticated with an RSA keypair. This prevents unauthorized use of ADB where the attacker has physical access to a device.
• Restrict Setuid from Android Apps. The /system partition is now mounted nosuid for zygote-spawned processes, preventing Android apps from executing setuid programs. This reduces root attack surface and the likelihood of potential security vulnerabilities.
• Capability bounding. Android zygote and ADB now use prctl(PR_CAPBSET_DROP) to drop unnecessary capabilities prior to executing apps. This prevents Android apps and apps launched from the shell from acquiring privileged capabilities.
• AndroidKeyStore Provider. Android now has a keystore provider that allows apps to create exclusive use keys. This provides apps with an API to create or store private keys that cannot be used by other apps.
• KeyChain isBoundKeyAlgorithm. Keychain API now provides a method (isBoundKeyType) that allows apps to confirm that system-wide keys are bound to a hardware root of trust for the device. This provides a place to create or store private keys that can't be exported off the device, even in the event of a root compromise.
• NO_NEW_PRIVS. Android zygote now uses prctl(PR_SET_NO_NEW_PRIVS) to block addition of new privileges prior to execution app code. This prevents Android apps from performing operations that can elevate privileges through execve. (This requires Linux kernel version 3.5 or greater).
• FORTIFY_SOURCE enhancements. Enabled FORTIFY_SOURCE on Android x86 and MIPS and fortified strchr(), strrchr(), strlen(), and umask() calls. This can detect potential memory corruption vulnerabilities or unterminated string constants.
• Relocation protections. Enabled read only relocations (relro) for statically linked executables and removed all text relocations in Android code. This provides defense in depth against potential memory corruption vulnerabilities.
• Improved EntropyMixer. EntropyMixer now writes entropy at shutdown or reboot, in addition to periodic mixing. This allows retention of all entropy generated while devices are powered on, and is especially useful for devices that are rebooted immediately after provisioning.
• Security fixes. Android 4.3 also includes fixes for Android-specific vulnerabilities. Information about these vulnerabilities has been provided to Open Handset Alliance members and fixes are available in Android Open Source Project. To improve security, some devices with earlier versions of Android may also include these fixes.

Android provides a multi-layered security model described in the Android Security Overview. Each update to Android includes dozens of security enhancements to protect users. The following are some of the security enhancements introduced in Android 4.2:

• App verification: Users can choose to enable Verify Apps and have apps screened by an app verifier, prior to installation. App verification can alert the user if they try to install an app that might be harmful; if an app is especially bad, it can block installation.
• More control of premium SMS: Android provides a notification if an app attempts to send SMS to a short code that uses premium services that might cause additional charges. The user can choose whether to allow the app to send the message or block it.
• Always-on VPN: VPN can be configured so that apps won't have access to the network until a VPN connection is established. This prevents apps from sending data across other networks.
• Certificate pinning: The Android core libraries now support certificate pinning. Pinned domains receive a certificate validation failure if the certificate doesn't chain to a set of expected certificates. This protects against possible compromise of certificate authorities.
• Improved display of Android permissions: Permissions are organized into groups that are more easily understood by users. During review of the permissions, the user can click on the permission to see more detailed information about the permission.
• installd hardening: The installd daemon does not run as the root user, reducing potential attack surface for root privilege escalation.
• init script hardening: init scripts now apply O_NOFOLLOW semantics to prevent symlink related attacks.
• FORTIFY_SOURCE: Android now implements FORTIFY_SOURCE. This is used by system libraries and apps to prevent memory corruption.
• ContentProvider default configuration: Apps that target API level 17 have export set to false by default for each Content Provider, reducing default attack surface for apps.
• Cryptography: Modified the default implementations of SecureRandom and Cipher.RSA to use OpenSSL. Added SSL Socket support for TLSv1.1 and TLSv1.2 using OpenSSL 1.0.1
• Security fixes: Upgraded open source libraries with security fixes include WebKit, libpng, OpenSSL, and LibXML. Android 4.2 also includes fixes for Android-specific vulnerabilities. Information about these vulnerabilities has been provided to Open Handset Alliance members and fixes are available in Android Open Source Project. To improve security, some devices with earlier versions of Android may also include these fixes.

Android 提供多層式安全模型，詳情請參閱 Android 安全性總覽。每個 Android 更新都包含數十項安全性強化功能，可保護使用者。以下是 Android 1.5 至 4.1 版本中推出的部分安全性強化功能：

Android 1.5

• 使用 ProPolice 防止堆疊緩衝區溢位 (-fstack-protector)
• 使用 safe_iop 減少整數溢位
• OpenBSD dlmalloc 的擴充功能，可防止雙重 free() 漏洞和區塊合併攻擊。因此，攻擊者常會利用堆積毀損問題，發動區塊整合攻擊。
• OpenBSD calloc，可防止記憶體配置期間整數溢位

Android 2.3

• 格式字串安全漏洞防護機制 (-Wformat-security -Werror=format-security)
• 硬體層級的從不執行 (NX) 功能，可防止在堆疊和堆積上執行程式碼
• 使用 Linux mmap_min_addr 緩解空值指標解參照權限升級問題 (在 Android 4.1 中進一步強化)

Android 4.0

位址空間配置隨機載入 (ASLR)，用於隨機產生記憶體中的關鍵位置

Android 4.1

• PIE (位置無關可執行檔) 支援
• 唯讀重新安置 / 立即繫結 (-Wl,-z,relro -Wl,-z,now)
• 啟用 dmesg_restrict (避免洩漏核心位址)
• 啟用 kptr_restrict (避免核心位址外洩)