Skip to content

Latest commit

 

History

History
466 lines (410 loc) · 19.4 KB

sec-design.md

File metadata and controls

466 lines (410 loc) · 19.4 KB

BUSINESS POSTURE

The Termux project aims to provide a powerful and accessible terminal emulator and Linux environment for Android devices.

  • Business Priorities and Goals:

    • Provide a free and open-source terminal emulator for Android.
    • Offer a complete Linux environment on Android without requiring rooting.
    • Empower users with command-line tools for development, system administration, and general computing tasks on mobile devices.
    • Maintain user privacy and security within the Termux environment.
    • Foster a community around the Termux project and encourage contributions.

  • Business Risks:

    • Security vulnerabilities in the application or provided packages could compromise user devices and data.
    • Dependence on volunteer developers and maintainers can lead to slow updates or project stagnation.
    • Changes in Android OS or Google Play Store policies could break Termux functionality or distribution.
    • Competition from other terminal emulators or alternative mobile computing solutions.
    • Misuse of Termux for malicious activities due to its powerful capabilities.

SECURITY POSTURE

  • Security Controls:

    • security control: Open-source codebase (publicly auditable on GitHub). Implemented: GitHub Repository.
    • security control: Use of standard Linux packages and tools. Implemented: Termux environment.
    • security control: Android permission model restricting access to device resources. Implemented: Android OS.
    • security control: Regular updates of packages within the Termux environment. Implemented: pkg package manager.
    • security control: Distribution through reputable app stores (Google Play, F-Droid). Implemented: App store distribution channels.

  • Accepted Risks:

    • accepted risk: Reliance on upstream package security. Risk accepted due to the nature of providing a Linux environment.
    • accepted risk: Potential for user misconfiguration leading to security issues within the Termux environment. Risk accepted as Termux provides a powerful and flexible environment.
    • accepted risk: Vulnerabilities in open-source dependencies. Risk mitigated by regular updates and community scrutiny.

  • Recommended Security Controls:

    • security control: Automated security scanning of the Termux application code (SAST/DAST).
    • security control: Dependency vulnerability scanning for packages included in the Termux environment.
    • security control: Implement reproducible builds to ensure build integrity and prevent supply chain attacks.
    • security control: User education and documentation on secure usage of Termux, including best practices for permissions and package management.

  • Security Requirements:

    • Authentication:
      • Requirement: Termux itself does not require user authentication to access the terminal environment.
      • Requirement: Authentication to external services (SSH, web servers) should be handled by standard Linux tools within Termux.
    • Authorization:
      • Requirement: Termux should respect Android's permission model to control access to device resources.
      • Requirement: Within the Termux environment, standard Linux file permissions should be enforced.
      • Requirement: Consider implementing optional fine-grained permission control for Termux features if feasible and beneficial.
    • Input Validation:
      • Requirement: Input to Termux commands should be validated to prevent command injection vulnerabilities. This is primarily the responsibility of the underlying Linux tools and shell.
      • Requirement: Ensure proper handling of user input in any Termux-specific components or scripts.
    • Cryptography:
      • Requirement: Utilize standard cryptographic libraries provided by the Android OS and Linux environment for secure communication and data handling within Termux.
      • Requirement: Ensure proper configuration and usage of cryptographic tools (e.g., SSH, GnuPG) within the Termux environment.

DESIGN

C4 CONTEXT

graph LR
    subgraph "Android Device"
        A["Termux App"]
    end
    B["Android User"]
    C["Android OS"]
    D["Package Repositories (Termux, Debian, etc.)"]
    E["External Storage"]
    F["Network (Internet, Local Network)"]

    B -- Uses --> A
    A -- Relies on --> C
    A -- Downloads Packages from --> D
    A -- Accesses --> E
    A -- Communicates with --> F

    style A fill:#f9f,stroke:#333,stroke-width:2px
Loading
  • Context Diagram Elements:
      • Name: Termux App
      • Type: Software System
      • Description: The Termux application, providing a terminal emulator and Linux environment on Android.
      • Responsibilities:
        • Emulate a terminal interface.
        • Provide a Linux-like environment on Android.
        • Manage packages and software installations.
        • Allow users to run command-line tools and applications.
      • Security controls:
        • Android permission model.
        • Open-source codebase.
        • Package management system for updates.
      • Name: Android User
      • Type: Person
      • Description: A user who interacts with the Termux application on their Android device.
      • Responsibilities:
        • Install and configure the Termux application.
        • Use the terminal emulator to run commands and applications.
        • Manage files and data within the Termux environment.
      • Security controls:
        • User awareness and responsible usage of the terminal environment.
        • Management of Android device security settings.
      • Name: Android OS
      • Type: Software System
      • Description: The underlying Android operating system that Termux runs on.
      • Responsibilities:
        • Provide the runtime environment for Termux.
        • Enforce system-level security policies and permissions.
        • Manage device resources and hardware.
      • Security controls:
        • Android permission model.
        • Security updates and patches.
        • Sandboxing of applications.
      • Name: Package Repositories (Termux, Debian, etc.)
      • Type: External System
      • Description: Online repositories that host software packages that can be installed within the Termux environment.
      • Responsibilities:
        • Store and distribute software packages.
        • Provide package metadata and dependencies.
        • Ensure package integrity (checksums, signatures).
      • Security controls:
        • HTTPS for package downloads.
        • Package signing and verification.
        • Repository security measures.
      • Name: External Storage
      • Type: External System
      • Description: The Android device's external storage (SD card, shared storage) that Termux can access.
      • Responsibilities:
        • Store user files and data.
        • Provide persistent storage for the Termux environment.
      • Security controls:
        • Android file permissions.
        • User management of file access.
        • Potential encryption of external storage by Android OS.
      • Name: Network (Internet, Local Network)
      • Type: External System
      • Description: Networks that the Android device is connected to, allowing Termux to communicate with external systems.
      • Responsibilities:
        • Provide network connectivity for Termux.
        • Enable communication with remote servers and services.
      • Security controls:
        • Network security protocols (HTTPS, SSH).
        • Firewall and network security configurations on the user's network.
        • Android network permissions.

C4 CONTAINER

graph LR
    subgraph "Android Device"
        subgraph "Termux App Container"
            A["Termux Application"]
            B["Terminal Emulator"]
            C["Package Manager (pkg)"]
            D["Core Utilities (shell, coreutils)"]
        end
    end
    E["Android OS"]
    F["Package Repositories"]
    G["File System (Android Storage)"]
    H["Network Interfaces"]

    A -- Uses --> B
    A -- Uses --> C
    A -- Uses --> D
    B -- Uses --> D
    C -- Downloads from --> F
    D -- Accesses --> G
    A -- Uses --> E
    A -- Uses --> H
    B -- Communicates with --> H

    style A fill:#f9f,stroke:#333,stroke-width:2px
    style "Termux App Container" fill:#ccf,stroke:#333,stroke-width:2px,stroke-dasharray: 5 5
Loading
  • Container Diagram Elements:
      • Name: Termux Application
      • Type: Container - Android Application
      • Description: The main Termux Android application package, acting as the entry point and orchestrator.
      • Responsibilities:
        • Manage application lifecycle on Android.
        • Integrate with Android OS services.
        • Provide user interface and settings.
        • Coordinate terminal emulation and package management.
      • Security controls:
        • Android application sandboxing.
        • Application signing.
        • Regular updates through app stores.
      • Name: Terminal Emulator
      • Type: Container - Software Component
      • Description: The component responsible for emulating a terminal interface, handling user input and output.
      • Responsibilities:
        • Render terminal display.
        • Process user input (keyboard, touch).
        • Interact with the underlying shell and core utilities.
        • Manage terminal sessions.
      • Security controls:
        • Input validation (to prevent escape sequences vulnerabilities).
        • Secure handling of terminal data.
      • Name: Package Manager (pkg)
      • Type: Container - Software Component
      • Description: The package manager used to install, update, and remove software packages within the Termux environment.
      • Responsibilities:
        • Download packages from repositories.
        • Resolve package dependencies.
        • Install and uninstall software.
        • Manage package updates.
      • Security controls:
        • HTTPS for package downloads.
        • Package signature verification.
        • Repository security policies.
      • Name: Core Utilities (shell, coreutils)
      • Type: Container - Software Component
      • Description: The core Linux utilities and shell (e.g., bash, zsh, coreutils) that provide the fundamental command-line environment.
      • Responsibilities:
        • Execute user commands.
        • Provide basic command-line tools (ls, cp, mv, etc.).
        • Manage processes and file system interactions.
      • Security controls:
        • Standard Linux security mechanisms (file permissions, process isolation).
        • Security updates for core utilities packages.
      • Name: Android OS
      • Type: Container - Operating System
      • Description: The underlying Android operating system.
      • Responsibilities:
        • Provide system calls and APIs for Termux.
        • Manage resources and security policies.
      • Security controls:
        • Android security features (sandboxing, permissions).
        • OS-level security updates.
      • Name: Package Repositories
      • Type: Container - External System
      • Description: Remote servers hosting software packages.
      • Responsibilities:
        • Host and distribute packages.
        • Maintain package metadata.
      • Security controls:
        • Repository security measures.
        • HTTPS.
        • Package signing.
      • Name: File System (Android Storage)
      • Type: Container - Data Store
      • Description: The Android device's file system, used for storing Termux files and user data.
      • Responsibilities:
        • Persistent storage for Termux environment.
        • File access and management.
      • Security controls:
        • Android file permissions.
        • User data encryption (optional Android feature).
      • Name: Network Interfaces
      • Type: Container - Infrastructure
      • Description: Android's network interfaces, allowing Termux to communicate over networks.
      • Responsibilities:
        • Network connectivity for Termux.
      • Security controls:
        • Android network permissions.
        • Device network security settings.

DEPLOYMENT

Deployment Architecture: App Store Distribution

graph LR
    A["Developer"] --> B["Build System (GitHub Actions)"]
    B --> C["Termux APK Artifact"]
    C --> D{ "Google Play Store / F-Droid" }
    D --> E["Android User Devices"]

    style D fill:#ccf,stroke:#333,stroke-width:2px,stroke-dasharray: 5 5
Loading
  • Deployment Diagram Elements:
      • Name: Developer
      • Type: Person/Role
      • Description: Software developers contributing to the Termux project.
      • Responsibilities:
        • Write and maintain Termux code.
        • Commit code changes to the GitHub repository.
      • Security controls:
        • Secure coding practices.
        • Code review process.
        • Access control to the code repository.
      • Name: Build System (GitHub Actions)
      • Type: Infrastructure - CI/CD
      • Description: Automated build system (e.g., GitHub Actions) used to compile and package Termux.
      • Responsibilities:
        • Automate the build process.
        • Compile code, run tests, and create APK artifacts.
        • Potentially perform security checks during build.
      • Security controls:
        • Secure CI/CD pipeline configuration.
        • Access control to CI/CD system.
        • Build artifact signing.
      • Name: Termux APK Artifact
      • Type: Artifact - Software Package
      • Description: The compiled Android Application Package (APK) file for Termux.
      • Responsibilities:
        • Contain the complete Termux application.
        • Be installable on Android devices.
      • Security controls:
        • Application signing.
        • Integrity checks (checksums).
      • Name: Google Play Store / F-Droid
      • Type: Infrastructure - App Store
      • Description: App stores used to distribute Termux to Android users.
      • Responsibilities:
        • Host and distribute the Termux APK.
        • Verify application integrity (Google Play Protect).
        • Provide update mechanisms.
      • Security controls:
        • App store security scanning.
        • Developer account verification.
        • User reviews and ratings.
      • Name: Android User Devices
      • Type: Infrastructure - End User Devices
      • Description: Android devices where users install and run the Termux application.
      • Responsibilities:
        • Run the Termux application.
        • Provide the runtime environment.
      • Security controls:
        • Device security settings.
        • Android OS security features.
        • User responsibility for device security.

BUILD

graph LR
    A["Developer"] --> B["Code Repository (GitHub)"]
    B --> C["Build System (GitHub Actions)"]
    C --> D["Security Checks (SAST, Linters)"]
    D --> E["Compilation & Packaging"]
    E --> F["Artifact Signing"]
    F --> G["Termux APK Artifact"]

    subgraph "Build System (GitHub Actions)"
        direction TB
        C
        D
        E
        F
    end
    style "Build System (GitHub Actions)" fill:#ccf,stroke:#333,stroke-width:2px,stroke-dasharray: 5 5
Loading
  • Build Process Elements:
      • Name: Developer
      • Type: Role
      • Description: Software developers writing and contributing code.
      • Responsibilities:
        • Write secure and functional code.
        • Follow coding standards and best practices.
        • Submit code changes via pull requests.
      • Security controls:
        • Secure development training.
        • Code review process.
        • Access control to code repository.
      • Name: Code Repository (GitHub)
      • Type: Tool - Version Control
      • Description: GitHub repository hosting the Termux source code.
      • Responsibilities:
        • Store and manage source code.
        • Track code changes and versions.
        • Facilitate collaboration among developers.
      • Security controls:
        • Access control (authentication, authorization).
        • Audit logging.
        • Branch protection.
      • Name: Build System (GitHub Actions)
      • Type: Tool - CI/CD
      • Description: GitHub Actions workflow for automated building and testing.
      • Responsibilities:
        • Automate build process.
        • Run tests and security checks.
        • Package the application.
      • Security controls:
        • Secure workflow configuration.
        • Secret management for signing keys.
        • Isolation of build environments.
      • Name: Security Checks (SAST, Linters)
      • Type: Tool - Security Scanning
      • Description: Static Application Security Testing (SAST) tools and linters integrated into the build process.
      • Responsibilities:
        • Automatically scan code for potential security vulnerabilities and code quality issues.
        • Provide feedback to developers.
        • Enforce coding standards.
      • Security controls:
        • Regularly updated security rules and vulnerability databases.
        • Configuration of scanning tools for relevant checks.
      • Name: Compilation & Packaging
      • Type: Process - Build Step
      • Description: Steps to compile source code and package it into an APK.
      • Responsibilities:
        • Compile native code (if any).
        • Package resources and assets.
        • Create the APK file.
      • Security controls:
        • Use of trusted build tools and toolchains.
        • Dependency management and vulnerability scanning of dependencies.
      • Name: Artifact Signing
      • Type: Process - Build Step
      • Description: Signing the APK artifact with a digital signature.
      • Responsibilities:
        • Ensure the integrity and authenticity of the APK.
        • Allow Android to verify the application's origin.
      • Security controls:
        • Secure storage and management of signing keys.
        • Protection of signing process from unauthorized access.
      • Name: Termux APK Artifact
      • Type: Artifact - Software Package
      • Description: The final Termux Android Application Package (APK) ready for distribution.
      • Responsibilities:
        • Be the distributable package for Termux.
      • Security controls:
        • Digital signature.
        • Integrity checksums.

RISK ASSESSMENT

  • Critical Business Processes:

    • Providing a functional and reliable terminal emulator and Linux environment on Android.
    • Maintaining the open-source nature and community around the project.
    • Ensuring user privacy and security within the Termux environment.
    • Distributing Termux through trusted channels (app stores).

  • Data to Protect and Sensitivity:

    • User commands and input within the terminal: Medium sensitivity. Could contain personal or sensitive information depending on user activity.
    • Files and data stored within the Termux environment: High sensitivity. Can include user documents, code, configuration files, and potentially credentials.
    • Application code and build artifacts: Medium sensitivity. Protecting against tampering and unauthorized modification is important for maintaining trust and preventing supply chain attacks.
    • Developer credentials and signing keys: High sensitivity. Compromise could lead to unauthorized code changes or malicious application releases.

QUESTIONS & ASSUMPTIONS

  • Questions:

    • What specific SAST/DAST tools and linters are currently used or planned for use in the Termux build process?
    • Are reproducible builds currently implemented or planned for Termux?
    • What is the process for managing and rotating signing keys for the Termux APK?
    • Are there specific security guidelines or training for Termux developers?
    • Is there a formal security incident response plan for Termux?

  • Assumptions:

    • BUSINESS POSTURE: The primary goal is to provide a free and open-source tool for users, with a focus on functionality and community rather than direct revenue generation.
    • SECURITY POSTURE: Security is a significant concern for the project, and efforts are made to maintain a secure application, but resources may be limited due to the volunteer-driven nature of the project.
    • DESIGN: The build process is automated using GitHub Actions, and distribution primarily occurs through app stores like Google Play Store and F-Droid. The project relies on standard Linux security practices within the Termux environment.