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attack-surface.md

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Attack Surface Analysis for jenkinsci/jenkins

Attack Surface: 1. Unsafe Script Execution (Groovy)

  • Description: Execution of arbitrary code, often through Groovy scripts, within the Jenkins environment. This remains the most significant and direct attack vector within Jenkins.
  • How Jenkins Contributes: Jenkins' core functionality allows and often encourages the execution of Groovy scripts in numerous contexts: build steps, pipeline definitions, system configuration, and even within some plugins. This inherent design choice is the primary contributor.
  • Example: An attacker injects a malicious Groovy script into a build parameter (if parameters are not properly validated) that executes a system command to exfiltrate data or install a backdoor. Alternatively, a malicious script could be injected into a Pipeline definition if source control is compromised.
  • Impact: Complete compromise of the Jenkins master server, including access to all builds, artifacts, credentials, and potentially connected systems (via those credentials or build agents). Data loss, system destruction, lateral movement to other systems.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Script Security Plugin: Mandatory. Enable the "sandbox" feature to severely restrict the capabilities of scripts. This is the single most important mitigation.
    • Approval Process: Implement a mandatory approval process for all Groovy scripts, especially those running outside the sandbox. This requires a knowledgeable administrator to review and approve scripts before execution.
    • Parameterized Builds (with Validation): Favor parameterized builds with strict input validation over inline Groovy scripts. Validate all user-supplied input to prevent script injection.
    • External Scripts (Version Controlled): Store scripts in a secure, version-controlled repository (e.g., Git) and load them into Jenkins builds. This provides better auditing, control, and prevents direct modification within Jenkins.
    • Developer Training: Mandatory training for developers on secure Groovy scripting practices. Focus on the dangers of untrusted input, proper sanitization techniques, and the principle of least privilege.
    • Regular Audits: Perform regular, scheduled audits of existing scripts for potential vulnerabilities and adherence to security best practices.

Attack Surface: 2. Plugin Vulnerabilities

  • Description: Exploitation of security flaws in installed Jenkins plugins. This is a direct consequence of Jenkins' plugin architecture.
  • How Jenkins Contributes: Jenkins' extensibility through plugins is a core feature, but it directly introduces the risk of vulnerabilities within those plugins. Jenkins itself provides the mechanism for plugin installation and execution.
  • Example: An outdated version of a widely used plugin contains a known Remote Code Execution (RCE) vulnerability. An attacker exploits this vulnerability (published in a CVE) to gain control of the Jenkins server.
  • Impact: Varies significantly depending on the specific plugin and the nature of the vulnerability. Can range from information disclosure to complete system compromise (RCE).
  • Risk Severity: High to Critical (depending on the plugin and vulnerability)
  • Mitigation Strategies:
    • Automated Plugin Updates: Implement automated updates for all plugins. This is crucial to minimize the window of vulnerability.
    • Plugin Vetting: Before installing any plugin, carefully evaluate its reputation, maintenance status (is it actively maintained?), and security track record. Check for known vulnerabilities (CVEs).
    • Plugin Removal: Immediately remove any unused or unnecessary plugins to reduce the attack surface.
    • Vulnerability Scanning: Use a dedicated plugin vulnerability scanning tool that integrates with Jenkins to automatically identify vulnerable plugins.
    • Security Advisories: Subscribe to Jenkins security advisories and plugin-specific vulnerability announcements. Act immediately on any reported vulnerabilities.

Attack Surface: 3. Credential Exposure (within Jenkins)

  • Description: Leakage or misuse of credentials stored within the Jenkins environment.
  • How Jenkins Contributes: Jenkins is designed to store and manage credentials for accessing various systems and services (build tools, source control, deployment targets). This inherent functionality creates the risk of exposure if not managed correctly.
  • Example: A build script inadvertently logs a sensitive credential to the console output, which is then accessible to users with build log viewing permissions. Or, a credential is not properly scoped and is accessible to more builds/users than necessary.
  • Impact: Compromise of connected systems and services, data breaches, unauthorized access to sensitive information. The impact depends on the compromised credential.
  • Risk Severity: High to Critical
  • Mitigation Strategies:
    • Jenkins Credentials Plugin: Mandatory use of the Jenkins Credentials plugin to manage credentials securely. Never store credentials directly in build scripts or configuration files.
    • Least Privilege (Credentials): Use credentials with the absolute minimum necessary privileges. Avoid using overly permissive credentials.
    • Credential Rotation: Implement a policy of regular credential rotation, especially for sensitive systems and services.
    • Secret Masking: Utilize Jenkins' secret masking features to prevent credentials from being displayed in build logs or console output.
    • Access Control (Credentials): Strictly control access to credentials within Jenkins based on user roles and permissions. Use the principle of least privilege.
    • External Secret Management (Integration): Strongly consider integrating Jenkins with an external secret management system (e.g., HashiCorp Vault, AWS Secrets Manager) for enhanced security and centralized management.

Attack Surface: 4. Unsecured API Access

  • Description: Unauthorized access or control via Jenkins' REST API. This is a direct attack surface of the Jenkins application itself.
  • How Jenkins Contributes: Jenkins provides a built-in REST API for programmatic interaction. This API, if not properly secured, is a direct entry point for attackers.
  • Example: An attacker uses the Jenkins API, without requiring authentication (due to misconfiguration), to trigger malicious builds, modify system configurations, or retrieve sensitive information (like stored credentials).
  • Impact: Unauthorized actions, data breaches, complete system compromise, depending on the specific API endpoint accessed and the permissions granted.
  • Risk Severity: High
  • Mitigation Strategies:
    • Authentication (Mandatory): Require authentication for all API access. Disable anonymous API access completely.
    • API Tokens (Scoped): Use API tokens with limited, specific permissions instead of full user credentials. Restrict the token's scope to the absolute minimum necessary actions.
    • IP Whitelisting: Restrict API access to a specific, trusted set of IP addresses or networks.
    • Rate Limiting: Implement rate limiting on API calls to prevent brute-force attacks and denial-of-service attempts.
    • Monitoring: Actively monitor API usage for suspicious activity, unusual access patterns, and unauthorized access attempts.