Android Security Internals: An In-Depth Guide to Android's Security Architecture

Description

There are more than one billion Android devices in use today, each one a potential target. Unfortunately, many fundamental Android security features have been little more than a black box to all but the most elite security professionals—until now. In Android Security Internals, top Android security expert Nikolay Elenkov takes us under the hood of the Android security sys­tem. Elenkov describes Android security archi­tecture from the bottom up, delving into the imple­mentation of major security-related components and subsystems, like Binder IPC, permissions, cryptographic providers, and device administration. You’ll learn: –How Android permissions are declared, used, and enforced –How Android manages application packages and employs code signing to verify their authenticity –How Android implements the Java Cryptography Architecture (JCA) and Java Secure Socket Extension (JSSE) frameworks –About Android’s credential storage system and APIs, which let applications store cryptographic keys securely –About the online account management framework and how Google accounts integrate with Android –About the implementation of verified boot, disk encryption, lockscreen, and other device security features –How Android’s bootloader and recovery OS are used to perform full system updates, and how to obtain root access With its unprecedented level of depth and detail, Android Security Internals is a must-have for any security-minded Android developer. About the Author Brief Contents Contents in Detail Foreword Acknowledgments Introduction Who This Book Is For Prerequisites Android Versions How Is This Book Organized? Conventions Chapter 1: Android’s Security Model Android’s Architecture Linux Kernel Native User Space Dalvik VM Java Runtime Libraries System Services Inter-Process Communication Binder Android Framework Libraries Applications Android’s Security Model Application Sandboxing Permissions IPC Code Signing and Platform Keys Multi-User Support SELinux System Updates Verified Boot Summary Chapter 2: Permissions The Nature of Permissions Requesting Permissions Permission Management Permission Protection Levels Permission Assignment Permission Enforcement Kernel-Level Enforcement Native Daemon-Level Enforcement Framework-Level Enforcement System Permissions Signature Permissions Development Permissions Shared User ID Custom Permissions Public and Private Components Activity and Service Permissions Broadcast Permissions Content Provider Permissions Static Provider Permissions Dynamic Provider Permissions Pending Intents Summary Chapter 3: Package Management Android Application Package Format Code Signing Java Code Signing Android Code Signing APK Install Process Location of Application Packages and Data Active Components Installing a Local Package Updating a Package Installing Encrypted APKs Forward Locking Android 4.1 Forward Locking Implementation Encrypted Apps and Google Play Package Verification Android Support for Package Verification Google Play Implementation Summary Chapter 4: User Management Multi-User Support Overview Types of Users The Primary User (Owner) Secondary Users Restricted Profiles Guest User User Management Command-Line Tools User States and Related Broadcasts User Metadata The User List File User Metadata Files User System Directory Per-User Application Management Application Data Directories Application Sharing External Storage External Storage Implementations Multi-User External Storage External Storage Permissions Other Multi-User Features Summary Chapter 5: Cryptographic Providers JCA Provider Architecture Cryptographic Service Providers JCA Engine Classes Obtaining an Engine Class Instance Algorithm Names SecureRandom MessageDigest Signature Cipher Mac Key SecretKey and PBEKey PublicKey, PrivateKey, and KeyPair KeySpec KeyFactory SecretKeyFactory KeyPairGenerator KeyGenerator KeyAgreement KeyStore CertificateFactory and CertPath CertPathValidator and CertPathBuilder Android JCA Providers Harmony’s Crypto Provider Android’s Bouncy Castle Provider AndroidOpenSSL Provider OpenSSL Using a Custom Provider Spongy Castle Summary Chapter 6: Network Security and PKI PKI and SSL Overview Public Key Certificates Direct Trust and Private CAs Public Key Infrastructure Certificate Revocation JSSE Introduction Secure Sockets Peer Authentication Hostname Verification Android JSSE Implementation Certificate Management and Validation Certificate Blacklisting Reexamining the PKI Trust Model Summary Chapter 7: Credential Storage VPN and Wi-Fi EAP Credentials Authentication Keys and Certificates The System Credential Store Credential Storage Implementation The keystore Service Key Blob Versions and Types Access Restrictions keymaster Module and keystore Service Implementation Nexus 4 Hardware-Backed Implementation Framework Integration Public APIs The KeyChain API KeyChain API Implementation Controlling Access to the Keystore Android Keystore Provider Summary Chapter 8: Online Account Management Android Account Management Overview Account Management Implementation AccountManagerService and AccountManager Authenticator Modules The Authenticator Module Cache AccountManagerService Operations and Permissions The Accounts Database Multi-User Support Adding an Authenticator Module Google Accounts Support The Google Login Service Google Services Authentication and Authorization Google Play Services Summary Chapter 9: Enterprise Security Device Administration Implementation Adding a Device Administrator Enterprise Account Integration VPN Support PPTP L2TP/IPSec IPSec Xauth SSL-Based VPNs Legacy VPN Application-Based VPNs Multi-User Support Wi-Fi EAP EAP Authentication Methods Android Wi-Fi Architecture EAP Credentials Management Adding an EAP Network with WifiManager Summary Chapter 10: Device Security Controlling OS Boot-Up and Installation Bootloader Recovery Verified Boot dm-verity Overview Android Implementation Enabling Verified Boot Disk Encryption Cipher Mode Key Derivation Disk Encryption Password Changing the Disk Encryption Password Enabling Encryption Booting an Encrypted Device Screen Security Lockscreen Implementation Keyguard Unlock Methods Brute-Force Attack Protection Secure USB Debugging ADB Overview The Need for Secure ADB Securing ADB Secure ADB Implementation ADB Authentication Keys Verifying the Host Key Fingerprint Android Backup Android Backup Overview Backup File Format Backup Encryption Controlling Backup Scope Summary Chapter 11: NFC and Secure Elements NFC Overview Android NFC Support Reader/Writer Mode Peer-to-Peer Mode Card Emulation Mode Secure Elements SE Form Factors in Mobile Devices Accessing the Embedded SE Android SE Execution Environment UICC as a Secure Element Software Card Emulation Android 4.4 HCE Architecture APDU Routing Writing an HCE Service Security of HCE Applications Summary Chapter 12: SELinux SELinux Introduction SELinux Architecture Mandatory Access Control SELinux Modes Security Contexts Security Context Assignment and Persistence Security Policy Policy Statements Type Transition Rules Domain Transition Rules Access Vector Rules Android Implementation Kernel Changes Userspace Changes Device Policy Files Policy Event Logging Android 4.4 SELinux Policy Policy Overview Enforcing Domains Unconfined Domains App Domains Summary Chapter 13: System Updates and Root Access Bootloader Unlocking the Bootloader Fastboot Mode Recovery Stock Recovery Custom Recoveries Root Access Root Access on Engineering Builds Root Access on Production Builds Rooting by Changing the boot or system Image Rooting by Flashing an OTA Package Rooting via Exploits Summary Index Updates