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Threat Model Analysis for rust-lang/mdbook

Threat: Malicious Markdown Injection via Source Repository Compromise (Direct Impact on mdBook)

  • Description: An attacker gains unauthorized write access to the Git repository. They directly modify the Markdown source files processed by mdBook, injecting malicious content. Crucially, this includes injecting content designed to exploit potential vulnerabilities within mdBook's Markdown parser or HTML rendering process, even if those vulnerabilities are subtle. This goes beyond simply adding malicious links; it involves crafting Markdown that could, for example, trigger unexpected behavior in how mdBook handles specific Markdown syntax or interacts with enabled HTML features. The attacker might also modify book.toml to point to malicious resources or alter build settings in a way that directly impacts mdBook's operation.

  • Impact:

    • Users visiting the generated website may be redirected to phishing sites, have their data stolen, or have malware installed.
    • Reputation damage.
    • Potential for data exfiltration if the injected content can interact with mdBook's internal state or access files during the build process.
    • Website defacement or rendering it unusable.

  • Affected mdBook Component:

    • Markdown Parser: (Specifically, vulnerabilities in the parser's handling of edge cases, complex syntax, or interaction with enabled HTML).
    • HTML Sanitization (if applicable): If mdBook performs any HTML sanitization after Markdown parsing, vulnerabilities in this process.
    • Configuration File (book.toml) Parser: If malicious configurations are injected that directly affect mdBook's build process.
    • File System Interaction: (Reading source files and writing output files, potentially manipulated by malicious book.toml settings).

  • Risk Severity: Critical

  • Mitigation Strategies:

    • Strict Repository Access Control: Multi-factor authentication, least privilege, branch protection rules (mandatory code reviews).
    • Code Reviews: Mandatory, thorough code reviews for all changes, focusing on potentially dangerous Markdown constructs.
    • Secure Development Environment: Secure workstations and secure coding practices for developers.
    • Git Hooks: Pre-commit/pre-receive hooks to scan for suspicious patterns (e.g., unusual HTML tags, complex nested Markdown).
    • Regular Security Audits: Of the repository and build process.
    • Fuzz Testing of mdBook: Directly test mdBook's parser with a wide range of malformed and edge-case Markdown inputs to identify potential vulnerabilities. This is a mitigation for the mdBook developers, not just users.
    • Input validation: Validate all input, including markdown files.

Threat: Malicious Preprocessor Execution

  • Description: An attacker modifies the book.toml file to include a malicious preprocessor. mdBook executes this preprocessor as part of its build process. The preprocessor has the full privileges of the user running mdBook and can execute arbitrary code on the build system.

  • Impact:

    • Complete compromise of the build system.
    • Injection of arbitrary content into the generated website through direct manipulation of mdBook's input.
    • Data theft from the build system.
    • Potential for lateral movement.

  • Affected mdBook Component:

    • Preprocessor System: (The core component that loads and executes preprocessors).
    • Configuration File (book.toml) Parser:
    • File System Interaction: (Reading and writing files, as controlled by the preprocessor).
    • Process Execution: (Spawning and managing preprocessor processes – this is a direct part of mdBook).

  • Risk Severity: Critical

  • Mitigation Strategies:

    • Avoid Custom Preprocessors: The strongest mitigation.
    • Thorough Preprocessor Vetting: Extremely careful code audit of any custom preprocessors. Treat them as untrusted code.
    • Sandboxing: Run preprocessors in a sandboxed environment (e.g., Docker). This is a best practice, not a built-in mdBook feature, but it's crucial for mitigating this threat.
    • Strict Repository Access Control: (As above).
    • Code Reviews: (As above).
    • Input validation: Validate all input, including data from preprocessors.

Threat: Plugin-Related Vulnerabilities (Direct mdBook Execution)

  • Description: An attacker leverages a malicious or vulnerable mdBook plugin. Since plugins are executed directly by mdBook as part of its build process, a compromised plugin can have significant impact. The plugin could exploit vulnerabilities in mdBook's API or directly manipulate the build process.

  • Impact:

    • Similar to preprocessors: potential for complete compromise of the build system.
    • Injection of arbitrary content through direct interaction with mdBook's internal state.
    • Data theft or system compromise.

  • Affected mdBook Component:

    • Plugin System: (The core component that loads and executes plugins).
    • API exposed to plugins: (Vulnerabilities in the API could be exploited).
    • File System Interaction: (If the plugin interacts with the file system, controlled by mdBook).
    • Process Execution: (If the plugin executes external commands, initiated by mdBook).

  • Risk Severity: High to Critical (depending on the plugin's capabilities and the nature of the vulnerability)

  • Mitigation Strategies:

    • Avoid Unnecessary Plugins: Only use essential, well-vetted plugins.
    • Thorough Plugin Vetting: Extremely careful code audit of all plugins. Treat them as untrusted code.
    • Sandboxing: Consider sandboxing plugins (e.g., Docker) if they require significant privileges.
    • Use Well-Maintained Plugins: Prefer reputable, actively maintained plugins.
    • Regular Plugin Updates: Keep plugins up-to-date.
    • Input validation: Validate all input, including data from plugins.