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attack-surface.md

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Attack Surface Analysis for termux/termux-app

Attack Surface: Arbitrary Command Execution via User Input

  • Description: The application allows user-supplied input to be directly or indirectly interpreted as commands within the Termux environment.
    • How Termux-App Contributes: Termux provides the command-line interface and execution environment, making this attack possible. This is the core functionality of Termux.
    • Example: An application feature allows users to enter a "custom script path" which is then passed to a Termux command like bash /sdcard/Download/[user_input]. An attacker could input a malicious command.
    • Impact: Complete compromise of the Termux environment, potential sandbox escape, data exfiltration, device damage, use of the device in malicious activities.
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Developer:
        • Strict Whitelisting: Never directly execute user input. Use a strict whitelist of allowed commands and arguments. Pre-define all necessary operations.
        • Input Sanitization (secondary): Sanitize input to remove dangerous characters.
        • Avoid User Input: Redesign the application to eliminate the need for user-provided commands.
      • User:
        • Be extremely cautious about any application that requests command-line input when using Termux.

Attack Surface: Malicious Package Installation (Unofficial Repositories)

  • Description: Users add third-party, untrusted package repositories to Termux and install packages from them.
    • How Termux-App Contributes: Termux's package management system allows the addition of arbitrary repositories. This is a core feature of Termux's package management.
    • Example: A user adds a repository and installs a package containing a backdoor.
    • Impact: Compromise of the Termux environment, data theft, malware, potential sandbox escape.
    • Risk Severity: High
    • Mitigation Strategies:
      • Developer:
        • Application-Managed Packages: Pre-install required packages from the official repository. Prevent users from adding other repositories.
        • User Education: Warn users about the dangers of unofficial repositories.
      • User:
        • Only use the official Termux repositories.

Attack Surface: Exploitation of Outdated Packages

  • Description: Known vulnerabilities in outdated packages within the Termux environment are exploited.
    • How Termux-App Contributes: Termux relies on a package management system, and users may not keep packages updated. This is inherent to any system with package management.
    • Example: An attacker exploits a known vulnerability in an outdated version of a package like openssh.
    • Impact: Compromise of the Termux environment, data theft, malware, potential sandbox escape.
    • Risk Severity: High
    • Mitigation Strategies:
      • Developer:
        • Managed Updates (critical packages): Enforce minimum versions and automate updates for critical packages (with consent).
        • Reminders: Remind users to update Termux packages.
      • User:
        • Regularly run pkg update && pkg upgrade in Termux.

Attack Surface: Termux:API Abuse

  • Description: Malicious scripts within Termux leverage the termux-api package to access sensitive Android APIs.
    • How Termux-App Contributes: Termux provides the termux-api package, bridging Termux and Android. This is a specific feature of Termux.
    • Example: A script uses termux-api to access location, contacts, and camera.
    • Impact: Privacy violation, data theft, surveillance.
    • Risk Severity: High
    • Mitigation Strategies:
      • Developer:
        • Minimal Permissions: Request only necessary Android permissions.
        • API Usage Audit: Review termux-api usage for security.
        • Uninstall if Unnecessary: Ensure termux-api is not installed if not needed.
      • User:
        • Be cautious about granting permissions to apps using Termux.
        • Uninstall termux-api: pkg uninstall termux-api if not needed.

Attack Surface: Compromised Script Execution (Application-Relied Scripts)

  • Description: Application relies on scripts in Termux, and these are modified by an attacker.
    • How Termux-App Contributes: Termux provides the environment where these scripts are stored and executed. This is a direct consequence of using Termux for scripting.
    • Example: An attacker replaces an application's script with a malicious version.
    • Impact: Compromised application functionality, data theft, further attacks.
    • Risk Severity: High
    • Mitigation Strategies:
      • Developer:
        • Integrity Checks: Use checksums or signatures for scripts. Verify before execution.
        • Secure Storage: Protect scripts from modification.
        • Regular Audits: Audit scripts for vulnerabilities.
      • User:
        • Be cautious about modifying application scripts in Termux.

Attack Surface: Insecure Inter-Process Communication (IPC)

  • Description: The main Android application communicates with the Termux environment using an insecure IPC mechanism.
    • How Termux-App Contributes: The very act of integrating with Termux necessitates IPC, making this a Termux-integration-specific risk.
    • Example: The application sends commands to Termux via unencrypted intents, which an attacker intercepts.
    • Impact: Compromise of the Termux environment, data exfiltration.
    • Risk Severity: High
    • Mitigation Strategies:
      • Developer:
        • Secure IPC: Use authenticated, encrypted IPC (e.g., bound services).
        • Input Validation (both sides): Validate data sent to and from Termux.
      • User: (Limited mitigation; primarily a developer responsibility.)