attack-tree.md

Attack Tree Analysis for caddyserver/caddy

Objective: Attacker's Goal: To compromise the application served by Caddy by exploiting vulnerabilities or weaknesses within Caddy itself.

Attack Tree Visualization

Compromise Application via Caddy [ROOT GOAL] ├───[OR]─ Exploit Caddy Configuration Vulnerabilities [HIGH RISK PATH] │ ├───[OR]─ Improper Certificate Management │ │ ├───[OR]─ Private Key Exposure (e.g., insecure storage, misconfigured permissions) [CRITICAL NODE] │ ├───[OR]─ Exposed Admin API [HIGH RISK PATH] [CRITICAL NODE] │ │ ├───[AND]─ Admin API Enabled on Publicly Accessible Interface [CRITICAL NODE] │ │ ├───[AND]─ Weak or Default Admin API Authentication │ │ │ ├───[OR]─ Default API Token Used (if applicable, though Caddy generates random tokens) [CRITICAL NODE] │ │ ├───[AND]─ Admin API Vulnerabilities (e.g., Injection, Authentication Bypass - less likely in Caddy core, but possible in plugins) [CRITICAL NODE] │ ├───[OR]─ Misconfigured Reverse Proxy [HIGH RISK PATH] │ │ ├───[AND]─ Proxying to Internal Services without Proper Access Control [HIGH RISK PATH] ├───[OR]─ Exploit Caddy Software Vulnerabilities [HIGH RISK PATH] │ ├───[OR]─ Exploiting Known Caddy Core Vulnerabilities (CVEs) [HIGH RISK PATH] [CRITICAL NODE] │ │ ├───[AND]─ Using Outdated Caddy Version with Known Vulnerabilities [HIGH RISK PATH] [CRITICAL NODE] │ ├───[OR]─ Exploiting Vulnerabilities in Caddy Plugins/Modules [HIGH RISK PATH] │ │ ├───[AND]─ Using Vulnerable or Outdated Plugins [HIGH RISK PATH] │ │ ├───[AND]─ Zero-Day Vulnerabilities in Plugins (possible, especially in less popular plugins) [CRITICAL NODE] │ ├───[OR]─ Dependency Vulnerabilities [HIGH RISK PATH] │ │ ├───[OR]─ Vulnerabilities in Go Libraries Used by Caddy [HIGH RISK PATH] │ │ ├───[OR]─ Vulnerabilities in System Libraries (OS level dependencies) [HIGH RISK PATH] ├───[OR]─ Resource Exhaustion Attacks on Caddy [HIGH RISK PATH] │ ├───[OR]─ Denial of Service (DoS) Attacks [HIGH RISK PATH] │ │ ├───[AND]─ HTTP Flood Attacks (e.g., SYN flood, HTTP GET/POST flood) [HIGH RISK PATH]

Attack Tree Path: 1. Exploit Caddy Configuration Vulnerabilities [HIGH RISK PATH]:

• Attack Vector: This path encompasses vulnerabilities arising from insecure or incorrect configuration of Caddy server. Misconfigurations can expose sensitive functionalities or weaken security controls.
• Breakdown of Sub-Vectors:

  • Improper Certificate Management:

    • Private Key Exposure [CRITICAL NODE]:
      • Attack Description: If the private key used for TLS/HTTPS is exposed due to insecure storage, weak file permissions, or other vulnerabilities, an attacker can compromise the entire TLS infrastructure.
      • Consequences: Man-in-the-Middle attacks, decryption of encrypted traffic, server impersonation, complete loss of confidentiality and integrity for HTTPS connections.
      • Actionable Insight: Securely store private keys with appropriate file system permissions and access controls.
      • Mitigation: Use hardware security modules (HSMs) or key management systems (KMS) for enhanced key protection in sensitive environments.

  • Exposed Admin API [HIGH RISK PATH] [CRITICAL NODE]:

    • Attack Description: Caddy's Admin API allows for runtime configuration changes and management. If exposed to unauthorized access, it provides a direct path to server compromise.
    • Breakdown of Sub-Vectors:

      • Admin API Enabled on Publicly Accessible Interface [CRITICAL NODE]:

        • Attack Description: If the Admin API is configured to listen on a public network interface (instead of localhost), it becomes accessible from the internet.
        • Consequences: Full server control, configuration manipulation, access to secrets, potential for remote code execution via plugins or modules through API calls.
        • Actionable Insight: Ensure Admin API is only accessible on localhost or a restricted network interface. Use -admin flag or admin directive with specific bind address.
        • Mitigation: Implement network segmentation and firewall rules to restrict access to the Admin API.

      • Weak or Default Admin API Authentication:

        • Default API Token Used (if applicable, though Caddy generates random tokens) [CRITICAL NODE]:
          • Attack Description: If a default or easily guessable API token is used (less likely in Caddy due to random generation, but possible if tokens are not rotated or reused across deployments), attackers can bypass authentication.
          • Consequences: Full server control as described above for exposed Admin API.
          • Actionable Insight: Rotate Admin API tokens regularly. Consider disabling or customizing token-based authentication if not needed.
          • Mitigation: Implement stronger authentication mechanisms if available in future Caddy versions or through plugins.

      • Admin API Vulnerabilities (e.g., Injection, Authentication Bypass - less likely in Caddy core, but possible in plugins) [CRITICAL NODE]:

        • Attack Description: Vulnerabilities within the Admin API itself (in core Caddy or plugins) could allow attackers to bypass authentication, inject commands, or gain unauthorized access.
        • Consequences: Full server control as described above for exposed Admin API.
        • Actionable Insight: Keep Caddy and its plugins up-to-date to patch any known vulnerabilities in the Admin API.
        • Mitigation: Regularly audit and penetration test the Admin API, especially if using custom plugins or extensions.

  • Misconfigured Reverse Proxy [HIGH RISK PATH]:

    • Attack Description: Incorrectly configured reverse proxy settings can lead to security breaches, especially when proxying to internal services.
    • Breakdown of Sub-Vectors:
      • Proxying to Internal Services without Proper Access Control [HIGH RISK PATH]:
        • Attack Description: If Caddy proxies requests to internal services without proper authentication or authorization checks, external attackers can gain unauthorized access to these internal resources.
        • Consequences: Access to internal services, data breaches, lateral movement within the network, exposure of sensitive internal applications and data.
        • Actionable Insight: Implement proper authentication and authorization mechanisms for backend services. Ensure Caddy only proxies requests to authorized services.
        • Mitigation: Use network segmentation and firewalls to restrict access to internal services from Caddy and other external sources.

Attack Tree Path: 2. Exploit Caddy Software Vulnerabilities [HIGH RISK PATH]:

• Attack Vector: Exploiting vulnerabilities in the Caddy server software itself, including the core server, plugins, and dependencies.
• Breakdown of Sub-Vectors:

  • Exploiting Known Caddy Core Vulnerabilities (CVEs) [HIGH RISK PATH] [CRITICAL NODE]:

    • Attack Description: Exploiting publicly known vulnerabilities (CVEs) in the Caddy core software.

    • Breakdown of Sub-Vectors:

      • Using Outdated Caddy Version with Known Vulnerabilities [HIGH RISK PATH] [CRITICAL NODE]:
        • Attack Description: Running an outdated version of Caddy that is vulnerable to known CVEs.
        • Consequences: Remote Code Execution, Denial of Service, or other impacts depending on the specific CVE. Full server compromise is a likely outcome for many server-side vulnerabilities.
        • Actionable Insight: Regularly update Caddy to the latest stable version to patch known vulnerabilities. Subscribe to security advisories.
        • Mitigation: Implement automated update mechanisms for Caddy and its dependencies.

    • Zero-Day Vulnerabilities in Caddy Core [CRITICAL NODE]:

      • Attack Description: Exploiting previously unknown vulnerabilities (zero-days) in the Caddy core.
      • Consequences: Similar to known CVEs, potentially Remote Code Execution and full server compromise.
      • Actionable Insight: Implement proactive security measures like Web Application Firewall (WAF) and Intrusion Detection/Prevention Systems (IDS/IPS) to detect and mitigate potential zero-day exploits.
      • Mitigation: Follow security best practices for web server hardening and defense in depth.

  • Exploiting Vulnerabilities in Caddy Plugins/Modules [HIGH RISK PATH]:

    • Attack Description: Exploiting vulnerabilities in Caddy plugins or modules. Plugins often have less rigorous security review than the core server.
    • Breakdown of Sub-Vectors:

      • Using Vulnerable or Outdated Plugins [HIGH RISK PATH]:

        • Attack Description: Using plugins with known vulnerabilities or running outdated versions of plugins.
        • Consequences: Similar to core vulnerabilities, potential for Remote Code Execution, Denial of Service, or other impacts depending on the plugin vulnerability.
        • Actionable Insight: Regularly update Caddy plugins to the latest versions. Only use trusted and actively maintained plugins.
        • Mitigation: Audit and review plugins for potential security vulnerabilities before deployment.

      • Zero-Day Vulnerabilities in Plugins (possible, especially in less popular plugins) [CRITICAL NODE]:

        • Attack Description: Exploiting previously unknown vulnerabilities (zero-days) in Caddy plugins.
        • Consequences: Similar to known plugin vulnerabilities, potential for Remote Code Execution.
        • Actionable Insight: Minimize the number of plugins used and only use essential plugins from reputable sources.
        • Mitigation: Monitor plugin security advisories and communities for reported vulnerabilities.

  • Dependency Vulnerabilities [HIGH RISK PATH]:

    • Attack Description: Exploiting vulnerabilities in the software libraries that Caddy depends on.
    • Breakdown of Sub-Vectors:

      • Vulnerabilities in Go Libraries Used by Caddy [HIGH RISK PATH]:

        • Attack Description: Vulnerabilities in Go libraries that Caddy uses internally.
        • Consequences: Depends on the vulnerability, could range from Denial of Service to memory corruption, potentially Remote Code Execution.
        • Actionable Insight: Regularly update Caddy and rebuild from source to incorporate updated Go libraries with security patches.
        • Mitigation: Use dependency scanning tools to identify and mitigate vulnerabilities in Caddy's dependencies.

      • Vulnerabilities in System Libraries (OS level dependencies) [HIGH RISK PATH]:

        • Attack Description: Vulnerabilities in system libraries provided by the operating system that Caddy relies on.
        • Consequences: Depends on the OS vulnerability, could lead to privilege escalation, system compromise, Remote Code Execution.
        • Actionable Insight: Keep the operating system and system libraries up-to-date with security patches.
        • Mitigation: Implement automated patching and vulnerability management for the underlying operating system.

Attack Tree Path: 3. Resource Exhaustion Attacks on Caddy [HIGH RISK PATH]:

• Attack Vector: Overwhelming Caddy with requests or consuming excessive resources to cause service disruption or unavailability.
• Breakdown of Sub-Vectors:
  • Denial of Service (DoS) Attacks [HIGH RISK PATH]:
    • Attack Description: Attacks aimed at making the Caddy-served application unavailable to legitimate users.
    • Breakdown of Sub-Vectors:
      • HTTP Flood Attacks (e.g., SYN flood, HTTP GET/POST flood) [HIGH RISK PATH]:
        • Attack Description: Flooding the server with a high volume of HTTP requests (SYN, GET, POST, etc.) to exhaust resources and prevent legitimate requests from being processed.
        • Consequences: Service unavailability, application downtime, impact on business operations.
        • Actionable Insight: Implement rate limiting, connection limits, and request size limits in Caddy configuration or using a WAF.
        • Mitigation: Use CDN and DDoS mitigation services to absorb and filter malicious traffic.