sec-design-deep-analysis.md

Okay, let's perform a deep security analysis of Gollum based on the provided design review.

1. Objective, Scope, and Methodology

• Objective: To conduct a thorough security analysis of Gollum's key components, identify potential vulnerabilities, and propose actionable mitigation strategies. The analysis will focus on the application's architecture, data flow, and interaction with external systems (Git, web server). We aim to identify weaknesses that could lead to unauthorized access, data breaches, data loss, or denial of service.
• Scope: The analysis will cover the Gollum application itself, its interaction with the Git repository, the web server configuration (as described in the design review), and the build process. We will not delve into the security of the underlying operating system, network infrastructure (beyond the firewall), or the internal security of Git itself (assuming Git is correctly configured and up-to-date). We will also focus on the "Dedicated Server" deployment model.
• Methodology:
  1. Component Analysis: We will break down Gollum into its core components (as identified in the C4 diagrams) and analyze the security implications of each.
  2. Data Flow Analysis: We will trace the flow of data through the system, identifying potential points of vulnerability.
  3. Threat Modeling: We will use the identified business risks and security posture to identify specific threats.
  4. Vulnerability Identification: Based on the component analysis, data flow analysis, and threat modeling, we will identify potential vulnerabilities.
  5. Mitigation Recommendations: For each identified vulnerability, we will propose specific, actionable mitigation strategies. These will be tailored to Gollum and its architecture.

2. Component Security Analysis

• User (Person):

  • Security Implications: The user's security posture directly impacts the wiki's security. Weak passwords, compromised accounts, or lack of two-factor authentication (2FA) on the Git hosting provider or web server can lead to unauthorized access.
  • Threats: Account takeover, unauthorized access to wiki content, unauthorized modification/deletion of content.
  • Mitigation:
    • Strongly enforce the use of strong, unique passwords for web server authentication.
    • Mandate 2FA for access to the web server and the Git repository (if using a hosting provider).
    • Educate users on phishing and other social engineering attacks.
    • Implement account lockout policies on the web server to prevent brute-force attacks.

• Web Server (e.g., Nginx, Apache):

  • Security Implications: This is the primary point of entry for external users and a critical security component. Misconfiguration, vulnerabilities in the web server software, or weak authentication can expose the entire wiki.
  • Threats:
    • Web Server Exploits: Vulnerabilities in Nginx/Apache could allow attackers to gain control of the server.
    • Misconfiguration: Incorrectly configured virtual hosts, directory listings, or exposed server status pages can leak information or provide attack vectors.
    • Authentication Bypass: Weak or misconfigured authentication can allow unauthorized access.
    • Denial of Service (DoS): The web server is susceptible to DoS attacks, making the wiki unavailable.
  • Mitigation:
    • Hardening:
      • Keep Nginx/Apache up-to-date with the latest security patches.
      • Disable unnecessary modules.
      • Configure strong TLS/SSL settings (disable weak ciphers, use HSTS).
      • Use a non-root user to run the web server process.
      • Restrict file system access for the web server user.
      • Disable server signature (e.g., server_tokens off; in Nginx).
      • Prevent directory listing (e.g., autoindex off; in Nginx).
    • Authentication:
      • Implement robust authentication (HTTP Basic Auth, OAuth, or a dedicated authentication service). Prioritize OAuth if possible for better security and user experience.
      • Use strong password policies and account lockout mechanisms.
    • DoS Protection:
      • Configure rate limiting (e.g., limit_req in Nginx) to mitigate DoS attacks.
      • Use a Web Application Firewall (WAF) to filter malicious traffic.
    • Regular Security Audits: Conduct regular security audits of the web server configuration.

• Gollum Application (Ruby):

  • Security Implications: This component handles user input, renders markup, and interacts with the Git repository. Vulnerabilities here could lead to XSS, command injection, or unauthorized access to the Git repository.
  • Threats:
    • Cross-Site Scripting (XSS): If markup sanitization is flawed or bypassed, attackers could inject malicious JavaScript into wiki pages.
    • Command Injection: If user input is not properly sanitized before being passed to Git commands, attackers could execute arbitrary commands on the server.
    • Path Traversal: Attackers might try to manipulate file paths to access files outside the intended Git repository.
    • Denial of Service (DoS): Specially crafted input could cause the application to consume excessive resources, leading to a DoS.
    • Dependency Vulnerabilities: Vulnerabilities in Ruby gems used by Gollum could be exploited.
  • Mitigation:
    • Markup Sanitization:
      • Verify that the github-markup library (and any other markup rendering libraries) are configured securely and kept up-to-date.
      • Test the sanitization thoroughly with various attack payloads. Use a dedicated XSS testing tool.
      • Consider adding a Content Security Policy (CSP) to further mitigate XSS, even with robust sanitization. This is a defense-in-depth measure. A strict CSP can prevent the execution of inline scripts, even if they are injected.
    • Command Injection Prevention:
      • Never construct Git commands by directly concatenating user input. Use a Git library (like rugged in Ruby) that provides a safe API for interacting with Git repositories. This library should handle escaping and quoting appropriately. This is the most critical mitigation for command injection.
      • Validate all user-provided input (page names, commit messages, etc.) against a strict whitelist of allowed characters. Reject any input that contains potentially dangerous characters (e.g., semicolons, backticks, shell metacharacters).
    • Path Traversal Prevention:
      • Ensure that Gollum always uses absolute paths when accessing the Git repository.
      • Validate that any user-provided file paths are within the expected Git repository directory. Do not rely solely on relative paths.
    • DoS Prevention:
      • Implement input validation to limit the size and complexity of user input.
      • Consider using resource limits (e.g., ulimit in Linux) to prevent the Gollum process from consuming excessive CPU or memory.
    • Dependency Management:
      • Use a dependency management tool (like Bundler) to track and update dependencies.
      • Regularly run bundle audit to check for known vulnerabilities in dependencies.
      • Consider using a Software Composition Analysis (SCA) tool to automatically scan for vulnerable dependencies.
    • Input Validation:
      • Implement strict validation for all user inputs, including page names, content, and any other parameters. Use whitelisting where possible.

• Git Repository (Data Store):

  • Security Implications: This is where the wiki data is stored. Compromise of the repository could lead to data loss, modification, or theft.
  • Threats:
    • Unauthorized Access: If file system permissions are misconfigured, unauthorized users could directly access the Git repository.
    • Data Corruption: Accidental or malicious modification of the Git repository could lead to data loss.
    • Data Theft: Attackers could copy the entire Git repository, gaining access to the wiki content and history.
  • Mitigation:
    • File System Permissions:
      • Restrict access to the Git repository directory to only the user running the Gollum application (and potentially a backup user). Use the principle of least privilege.
      • Ensure that the Git repository is not directly accessible via the web server.
    • Backups:
      • Implement a robust backup strategy. Regularly back up the Git repository to a separate, secure location. Test the restoration process.
    • Git Configuration:
      • Ensure that Git is configured securely (e.g., disable unnecessary features, enable strong authentication if accessing the repository remotely).
    • Encryption at Rest (Optional):
      • If the wiki contains highly sensitive data, consider encrypting the Git repository at rest. This could be done using file system encryption (e.g., LUKS) or by storing encrypted files within the repository. This adds complexity and must be carefully managed.

3. Data Flow Analysis

1. User Request: The user sends an HTTPS request to the web server.
2. Web Server Handling: The web server terminates SSL/TLS, authenticates the user (if configured), and forwards the request to the Gollum application.
3. Gollum Processing: Gollum receives the request, parses it, and interacts with the Git repository to retrieve or update data. It uses github-markup (or similar) to render the markup into HTML.
4. Git Interaction: Gollum uses Git commands (ideally via a safe library like rugged) to read and write data to the Git repository.
5. Response: Gollum sends the rendered HTML back to the web server, which then sends it to the user.

Potential Vulnerability Points:

• Between User and Web Server: Lack of HTTPS, weak TLS configuration, man-in-the-middle attacks.
• Web Server: Vulnerabilities in the web server software, misconfiguration.
• Between Web Server and Gollum: If not using a secure connection (e.g., Unix socket or localhost with proper permissions), traffic could be intercepted.
• Gollum Application: XSS, command injection, path traversal, dependency vulnerabilities.
• Git Repository: Unauthorized access due to misconfigured file permissions.

4. Vulnerability Identification (Summary)

| Vulnerability Category | Specific Vulnerability | Component(s) Affected | Threat | Mitigation