安全性增強項目

Android 會持續改善安全性功能和服務。請參閱左側導覽面板中各版本的強化功能清單。

Android 14

每個 Android 版本都包含數十項安全性強化功能，可保護使用者。以下列舉 Android 14 提供的一些主要安全性強化功能：

  • 在 Android 10 中推出的 Hardware-assisted AddressSanitizer (HWASan) 是一款記憶體錯誤偵測工具，類似 AddressSanitizer。Android 14 為 HWASan 帶來顯著改善。瞭解如何防止錯誤進入 Android 版本，HWAddressSanitizer
  • 在 Android 14 中，如果應用程式會與第三方分享位置資料，系統執行階段權限對話方塊現在會包含可點選的部分，醒目顯示應用程式的資料分享做法，包括應用程式決定與第三方分享資料的原因等資訊。
  • Android 12 推出了在數據機層級停用 2G 支援的選項，可保護使用者免於 2G 過時安全性模型的固有安全性風險。由於禁用 2G 對企業客戶來說至關重要，Android 14 會在 Android Enterprise 中啟用這項安全防護功能，為 IT 管理員提供支援，以便限制受管理裝置降級至 2G 連線。
  • 新增支援功能，可拒絕空值加密的行動網路連線，確保電路交換語音和簡訊流量一律加密，並受到保護，避免遭到被動式無線攔截。進一步瞭解 Android 的行動網路連線強化計畫。
  • 新增對多個 IMEI 的支援
  • 自 Android 14 起，如果裝置支援加速加密指令，則 AES-HCTR2 是檔案名稱加密的首選模式。
  • 行動網路連線能力
  • 新增 Android 安全中心說明文件
  • 如果您的應用程式指定 Android 14 為目標版本，並且使用動態程式碼載入 (DCL)，則所有動態載入的檔案都必須標示為唯讀。否則系統會擲回例外狀況。我們建議應用程式盡量避免使用動態載入程式碼，否則應用程式很可能會因為程式碼插入或竄改程式碼而無法正常運作。

請參閱完整的 AOSP 版本資訊，以及 Android 開發人員的功能和變更清單。

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

Every Android release includes dozens of security enhancements to protect users. For a list of some of the major security enhancements available in Android 11, see the Android Release Notes.

Android 10

Every Android release includes dozens of security enhancements to protect users. Android 10 includes several security and privacy enhancements. See the Android 10 release notes for a complete list of changes in Android 10.

Security

BoundsSanitizer

Android 10 deploys BoundsSanitizer (BoundSan) in Bluetooth and codecs. BoundSan uses UBSan's bounds sanitizer. This mitigation is enabled on a per-module level. It helps keep critical components of Android secure and shouldn't be disabled. BoundSan is enabled in the following codecs:

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

Execute-only memory

By default, executable code sections for AArch64 system binaries are marked execute-only (nonreadable) as a hardening mitigation against just-in-time code reuse attacks. Code that mixes data and code together and code that purposefully inspects these sections (without first remapping the memory segments as readable) no longer functions. Apps with a target SDK of Android 10 (API level 29 or higher) are impacted if the app attempts to read code sections of execute-only memory (XOM) enabled system libraries in memory without first marking the section as readable.

Extended access

Trust agents, the underlying mechanism used by tertiary authentication mechanisms such as Smart Lock, can only extend unlock in Android 10. Trust agents can no longer unlock a locked device and can only keep a device unlocked for a maximum of four hours.

Face authentication

Face authentication allows users to unlock their device simply by looking at the front of their device. Android 10 adds support for a new face authentication stack that can securely process camera frames, preserving security and privacy during face authentication on supported hardware. Android 10 also provides an easy way for security-compliant implementations to enable app integration for transactions such as online banking or other services.

Integer Overflow Sanitization

Android 10 enables Integer Overflow Sanitization (IntSan) in software codecs. Ensure that playback performance is acceptable for any codecs that aren't supported in the device's hardware. IntSan is enabled in the following codecs:

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

Modular system components

Android 10 modularizes some Android system components and enables them to be updated outside of the normal Android release cycle. Some modules include:

OEMCrypto

Android 10 uses OEMCrypto API version 15.

Scudo

Scudo is a dynamic user-mode memory allocator designed to be more resilient against heap-related vulnerabilities. It provides the standard C allocation and deallocation primitives, as well as the C++ primitives.

ShadowCallStack

ShadowCallStack (SCS) is an LLVM instrumentation mode that protects against return address overwrites (like stack buffer overflows) by saving a function's return address to a separately allocated ShadowCallStack instance in the function prolog of nonleaf functions and loading the return address from the ShadowCallStack instance in the function epilog.

WPA3 and Wi-Fi Enhanced Open

Android 10 adds support for the Wi-Fi Protected Access 3 (WPA3) and Wi-Fi Enhanced Open security standards to provide better privacy and robustness against known attacks.

Privacy

App access when targeting Android 9 or lower

If your app runs on Android 10 or higher but targets Android 9 (API level 28) or lower, the platform applies the following behavior:

  • If your app declares a <uses-permission> element for either ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION, the system automatically adds a <uses-permission> element for ACCESS_BACKGROUND_LOCATION during installation.
  • If your app requests either ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION, the system automatically adds ACCESS_BACKGROUND_LOCATION to the request.

Background activity restrictions

Starting in Android 10, the system places restrictions on starting activities from the background. This behavior change helps minimize interruptions for the user and keeps the user more in control of what's shown on their screen. As long as your app starts activities as a direct result of user interaction, your app most likely isn't affected by these restrictions.
To learn more about the recommended alternative to starting activities from the background, see the guide on how to alert users of time-sensitive events in your app.

Camera metadata

Android 10 changes the breadth of information that the getCameraCharacteristics() method returns by default. In particular, your app must have the CAMERA permission in order to access potentially device-specific metadata that is included in this method's return value.
To learn more about these changes, see the section about camera fields that require permission.

Clipboard data

Unless your app is the default input method editor (IME) or is the app that currently has focus, your app cannot access clipboard data on Android 10 or higher.

Device location

To support the additional control that users have over an app's access to location information, Android 10 introduces the ACCESS_BACKGROUND_LOCATION permission.
Unlike the ACCESS_FINE_LOCATION and ACCESS_COARSE_LOCATION permissions, the ACCESS_BACKGROUND_LOCATION permission only affects an app's access to location when it runs in the background. An app is considered to be accessing location in the background unless one of the following conditions is satisfied:

  • An activity belonging to the app is visible.
  • The app is running a foreground service that has declared a foreground service type of location.
    To declare the foreground service type for a service in your app, set your app's targetSdkVersion or compileSdkVersion to 29 or higher. Learn more about how foreground services can continue user-initiated actions that require access to location.

External storage

By default, apps targeting Android 10 and higher are given scoped access into external storage, or scoped storage. Such apps can see the following types of files within an external storage device without needing to request any storage-related user permissions:

To learn more about scoped storage, as well as how to share, access, and modify files that are saved on external storage devices, see the guides on how to manage files in external storage and access and modify media files.

MAC address randomization

On devices that run Android 10 or higher, the system transmits randomized MAC addresses by default.
If your app handles an enterprise use case, the platform provides APIs for several operations related to MAC addresses:

  • Obtain randomized MAC address: Device owner apps and profile owner apps can retrieve the randomized MAC address assigned to a specific network by calling getRandomizedMacAddress().
  • Obtain actual, factory MAC address: Device owner apps can retrieve a device's actual hardware MAC address by calling getWifiMacAddress(). This method is useful for tracking fleets of devices.

Non-resettable device identifiers

Starting in Android 10, apps must have the READ_PRIVILEGED_PHONE_STATE privileged permission in order to access the device's non-resettable identifiers, which include both IMEI and serial number.

If your app doesn't have the permission and you try asking for information about non-resettable identifiers anyway, the platform's response varies based on target SDK version:

  • If your app targets Android 10 or higher, a SecurityException occurs.
  • If your app targets Android 9 (API level 28) or lower, the method returns null or placeholder data if the app has the READ_PHONE_STATE permission. Otherwise, a SecurityException occurs.

Physical activity recognition

Android 10 introduces the android.permission.ACTIVITY_RECOGNITION runtime permission for apps that need to detect the user's step count or classify the user's physical activity, such as walking, biking, or moving in a vehicle. This is designed to give users visibility of how device sensor data is used in Settings.
Some libraries within Google Play services, such as the Activity Recognition API and the Google Fit API, don't provide results unless the user has granted your app this permission.
The only built-in sensors on the device that require you to declare this permission are the step counter and step detector sensors.
If your app targets Android 9 (API level 28) or lower, the system auto-grants the android.permission.ACTIVITY_RECOGNITION permission to your app, as needed, if your app satisfies each of the following conditions:

  • The manifest file includes the com.google.android.gms.permission.ACTIVITY_RECOGNITION permission.
  • The manifest file doesn't include the android.permission.ACTIVITY_RECOGNITION permission.

If the system-auto grants the android.permission.ACTIVITY_RECOGNITION permission, your app retains the permission after you update your app to target Android 10. However, the user can revoke this permission at any time in system settings.

/proc/net filesystem restrictions

On devices that run Android 10 or higher, apps cannot access /proc/net, which includes information about a device's network state. Apps that need access to this information, such as VPNs, should use the NetworkStatsManager or ConnectivityManager class.

Permission groups removed from UI

As of Android 10, apps cannot look up how permissions are grouped in the UI.

Removal of contacts affinity

Starting in Android 10, the platform doesn't keep track of contacts affinity information. As a result, if your app conducts a search on the user's contacts, the results aren't ordered by frequency of interaction.
The guide about ContactsProvider contains a notice describing the specific fields and methods that are obsolete on all devices starting in Android 10.

Restricted access to screen contents

To protect users' screen contents, Android 10 prevents silent access to the device's screen contents by changing the scope of the READ_FRAME_BUFFER, CAPTURE_VIDEO_OUTPUT, and CAPTURE_SECURE_VIDEO_OUTPUT permissions. As of Android 10, these permissions are signature-access only.
Apps that need to access the device's screen contents should use the MediaProjection API, which displays a prompt asking the user to provide consent.

USB device serial number

If your app targets Android 10 or higher, your app cannot read the serial number until the user has granted your app permission to access the USB device or accessory.
To learn more about working with USB devices, see the guide on how to configure USB hosts.

Wi-Fi

Apps targeting Android 10 or higher cannot enable or disable Wi-Fi. The WifiManager.setWifiEnabled() method always returns false.
If you need to prompt users to enable and disable Wi-Fi, use a settings panel.

Restrictions on direct access to configured Wi-Fi networks

To protect user privacy, manual configuration of the list of Wi-Fi networks is restricted to system apps and device policy controllers (DPCs). A given DPC can be either the device owner or the profile owner.
If your app targets Android 10 or higher, and it isn't a system app or a DPC, then the following methods don't return useful data:

Android 9

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 9 中提供的部分主要安全性增強功能清單，請參閱 Android 版本資訊。

Android 8

每個 Android 版本都包含數十項安全性強化功能，可保護使用者。以下列舉 Android 8.0 提供的一些主要安全性強化功能：

  • 加密。新增支援在工作資料夾中移除鍵的功能。
  • 驗證開機程序。新增 Android 驗證開機程序 (AVB)。已驗證的 Boot 程式碼庫，可在 AOSP 中新增用於開機載入器的回溯保護機制。建議為 HLOS 提供復原保護機制的啟動載入程式支援。建議使用者必須透過實體互動才能解鎖啟動載入程式。
  • 螢幕鎖定。新增使用防竄改硬體驗證鎖定螢幕憑證的支援功能。
  • KeyStore。針對搭載 Android 8.0 以上版本的所有裝置，必須進行金鑰認證。新增ID 認證支援功能，以改善零接觸註冊程序。
  • 採用沙箱機制。使用 Project Treble 的標準介面，在架構和裝置專屬元件之間，為許多元件提供更嚴密的沙箱。將 seccomp 篩選功能套用至所有不受信任的應用程式，以減少核心的受攻擊面。WebView 目前會在隔離程序中執行，對系統其他部分的存取權非常有限。
  • 核心強化。實作強化的 usercopy、PAN 模擬、啟動後唯讀，以及 KASLR。
  • 使用者空間強化。為媒體堆疊實作 CFI。應用程式疊加層無法再覆蓋系統重要視窗，使用者可以關閉疊加層。
  • 串流 OS 更新。在磁碟空間不足的裝置上啟用更新。
  • 安裝不明應用程式。使用者必須授予權限，才能從非第一方應用程式商店的來源安裝應用程式。
  • 隱私權。每個應用程式和裝置上的每位使用者，都有不同的 Android ID (SSAID) 值。針對網頁瀏覽器應用程式，Widevine 用戶端 ID 會針對每個應用程式套件名稱和網頁來源傳回不同的值。net.hostname 現已空白，且 DHCP 用戶端不再傳送主機名稱。android.os.Build.SERIAL 已改為 Build.SERIAL API，並受到使用者控管的權限保護。改善部分晶片組的 MAC 位址隨機化功能。

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

每個 Android 版本都包含數十項安全性強化功能，可保護使用者。以下是 Android 6.0 提供的一些主要安全性強化功能：

  • 執行階段權限。應用程式會在執行階段要求權限，而非在應用程式安裝期間授予權限。使用者可以為 M 版和 M 版以下的應用程式開啟或關閉權限。
  • 驗證開機程序。系統軟體會在執行前進行一連串加密編譯檢查，確保手機從啟動載入程式到作業系統的整個過程都正常運作。
  • 硬體隔離安全性。Fingerprint API、鎖定畫面、裝置加密和用戶端憑證所使用的新硬體抽象層 (HAL)，可保護金鑰免於遭受核心竄改和/或本機物理攻擊
  • 指紋。裝置現在只要輕觸一下即可解鎖。開發人員也可以利用新的 API，使用指紋鎖定及解鎖加密金鑰。
  • SD 卡採用率。可移除媒體可採用至裝置，並為應用程式本機資料、相片、影片等擴充可用儲存空間，但仍受區塊層級加密保護。
  • 明文流量。開發人員可以使用新的 StrictMode，確保應用程式不會使用明文。
  • 強化系統安全性。透過 SELinux 強制執行的政策強化系統。這可提供更佳的使用者隔離、IOCTL 篩選、減少暴露服務的威脅、進一步加強 SELinux 網域，以及極為有限的 /proc 存取權。
  • USB 存取權控管：使用者必須確認允許 USB 存取手機上的檔案、儲存空間或其他功能。預設值現在為「僅收費」，且需要使用者明確核准才能存取儲存空間。

Android 5

5.0

每個 Android 版本都包含數十項安全性強化功能，可保護使用者。以下是 Android 5.0 提供的一些主要安全性強化功能：

  • 預設為加密。在搭載 L 原生功能的裝置上，系統預設會啟用全磁碟加密功能，以便在裝置遺失或遭竊時，提升資料保護力。更新至 L 的裝置可在「設定」 >「安全性」中進行加密。
  • 改善全磁碟加密功能。使用者密碼可透過 scrypt 防禦暴力破解攻擊，如果可用，金鑰會繫結至硬體 KeyStore，以防範裝置外攻擊。一如往常，Android 螢幕鎖定機密和裝置加密金鑰不會傳送至裝置外部或公開給任何應用程式。
  • 使用 SELinux 強化 Android 沙箱。Android 現已要求所有網域都處於 SELinux 強制執行模式。SELinux 是 Linux 核心中的強制存取控制 (MAC) 系統，用於強化現有的自由選定存取控制 (DAC) 安全性模型。這個新層可提供額外防護，抵禦潛在的安全漏洞。
  • Smart Lock。Android 現已納入信任元件，可讓您更彈性地解鎖裝置。舉例來說，信任小工具可讓裝置在靠近另一個信任裝置 (透過 NFC、藍牙) 或由信任的臉孔使用時，自動解鎖。
  • 適用於手機和平板電腦的多使用者、受限設定檔和訪客模式。Android 現已支援手機上的多位使用者，並提供訪客模式，可讓使用者輕鬆存取裝置，而無須授予資料和應用程式的存取權。
  • 不透過 OTA 更新 WebView。WebView 現在可以獨立於架構更新，且無須系統 OTA。這樣一來，系統就能更快回應 WebView 中的潛在安全性問題。
  • 更新 HTTPS 和 TLS/SSL 的加密技術。目前已啟用 TLSv1.2 和 TLSv1.1，並將優先採用前向保密性，同時啟用 AES-GCM，並停用弱加密套件 (MD5、3DES 和匯出加密套件)。詳情請參閱 https://developer.android.com/reference/javax/net/ssl/SSLSocket.html。
  • 已移除非 PIE 連結器支援功能。Android 現已要求所有動態連結的執行檔都支援 PIE (位置無關執行檔)。這可強化 Android 的位址空間配置隨機載入 (ASLR) 實作方式。
  • FORTIFY_SOURCE 改善項目。下列 libc 函式現在實作 FORTIFY_SOURCE 保護功能：stpcpy()、stpncpy()、read()、recvfrom()、FD_CLR()、FD_SET() 和 FD_ISSET()。這可防範涉及這些函式的記憶體毀損漏洞。
  • 安全性修正項目。Android 5.0 也包含 Android 專屬漏洞的修正程式。我們已將這些安全漏洞的相關資訊提供給開放手持裝置聯盟成員，並在 Android 開放原始碼專案中提供修正程式。為提升安全性，部分搭載舊版 Android 的裝置也可能包含這些修正項目。

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 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 versions 1.5 through 4.1:

Android 1.5
  • ProPolice to prevent stack buffer overruns (-fstack-protector)
  • safe_iop to reduce integer overflows
  • Extensions to OpenBSD dlmalloc to prevent double free() vulnerabilities and to prevent chunk consolidation attacks. Chunk consolidation attacks are a common way to exploit heap corruption.
  • OpenBSD calloc to prevent integer overflows during memory allocation
Android 2.3
  • Format string vulnerability protections (-Wformat-security -Werror=format-security)
  • Hardware-based No eXecute (NX) to prevent code execution on the stack and heap
  • Linux mmap_min_addr to mitigate null pointer dereference privilege escalation (further enhanced in Android 4.1)
Android 4.0
Address Space Layout Randomization (ASLR) to randomize key locations in memory
Android 4.1
  • PIE (Position Independent Executable) support
  • Read-only relocations / immediate binding (-Wl,-z,relro -Wl,-z,now)
  • dmesg_restrict enabled (avoid leaking kernel addresses)
  • kptr_restrict enabled (avoid leaking kernel addresses)