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attack-surface.md

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Attack Surface Analysis for jenkinsci/jenkins

Attack Surface: Vulnerable Plugins

  • Description: Jenkins plugins, while extending functionality, can contain critical security vulnerabilities like remote code execution (RCE), authentication bypasses, or significant information disclosure.
  • Jenkins Contribution: Jenkins' plugin architecture relies on third-party code, increasing the attack surface and potential for vulnerabilities within the Jenkins ecosystem.
  • Example: A plugin with an unauthenticated RCE vulnerability allows attackers to execute arbitrary code on the Jenkins server simply by sending a crafted request.
  • Impact: Full compromise of the Jenkins server, data breaches, unauthorized access to connected systems, and complete disruption of CI/CD pipelines.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Mandatory Plugin Updates: Implement a strict policy for regularly updating plugins to the latest versions, prioritizing security updates.
    • Automated Vulnerability Scanning: Integrate automated plugin vulnerability scanning into your Jenkins management process.
    • Plugin Whitelisting: Restrict plugin installations to a pre-approved list of trusted and regularly vetted plugins.
    • Minimize Plugin Usage: Reduce the number of installed plugins to the absolute minimum required functionality to decrease the attack surface.
    • Security Monitoring & Alerts: Actively monitor plugin security advisories and set up alerts for newly discovered vulnerabilities in used plugins.

Attack Surface: Script Injection in Pipelines

  • Description: Jenkins Pipelines, using Groovy scripts, are vulnerable to script injection when user-controlled input or external data is not properly sanitized. This allows attackers to execute arbitrary code on the Jenkins master or agents.
  • Jenkins Contribution: Jenkins' "Pipeline as Code" feature, while powerful, inherently involves dynamic script execution, creating a direct pathway for injection vulnerabilities if not secured.
  • Example: A pipeline takes a user-provided branch name and uses it unsanitized in a shell command. An attacker injects malicious shell commands within the branch name, leading to command execution on the Jenkins agent.
  • Impact: Remote code execution on Jenkins master or agents, allowing for complete system takeover, data exfiltration, and manipulation of the CI/CD process.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Strict Input Sanitization: Implement rigorous input sanitization and validation for all user-provided data and external data used in Pipeline scripts.
    • Secure Scripting Practices: Avoid dynamic script evaluation with user input. Use parameterized builds with caution and validate parameters thoroughly.
    • Principle of Least Privilege for Pipelines: Run pipeline scripts with the minimum necessary permissions, avoiding execution as root or with overly broad credentials.
    • Static Pipeline Analysis: Use static analysis tools to automatically scan Jenkinsfile definitions for potential script injection vulnerabilities.
    • Code Review for Pipelines: Mandate code reviews for all Jenkinsfile changes to identify and prevent injection vulnerabilities before deployment.

Attack Surface: Unsecured Jenkins Remoting

  • Description: The Jenkins remoting protocol (JNLP or SSH) used for communication between master and agents can be exploited if not properly secured. This includes unencrypted communication, deserialization vulnerabilities, and agent impersonation.
  • Jenkins Contribution: Jenkins' distributed architecture relies on remoting, and historically, default configurations might have been insecure (e.g., unencrypted JNLP). Vulnerabilities in the remoting protocol itself are direct Jenkins weaknesses.
  • Example: Unencrypted JNLP communication allows network attackers to intercept credentials or inject malicious commands. Deserialization vulnerabilities in older JNLP versions allow RCE by sending crafted serialized objects.
  • Impact: Remote code execution on master or agents, agent hijacking, man-in-the-middle attacks, and unauthorized access to the Jenkins environment and connected systems.
  • Risk Severity: High to Critical
  • Mitigation Strategies:
    • Enforce JNLP-over-HTTPS or SSH: Mandatory configuration to use JNLP-over-HTTPS or SSH for all agent communication to ensure encryption.
    • Disable Unnecessary JNLP Ports: Disable the JNLP port if not actively used or restrict access via firewalls.
    • Regularly Update Jenkins Core and Agents: Keep both Jenkins master and agents updated to patch remoting protocol vulnerabilities, including deserialization issues.
    • Agent-to-Master Security Hardening: Configure agent-to-master security settings to limit agent capabilities and restrict outbound connections from agents.
    • Strong Agent Authentication: Implement robust agent authentication mechanisms to prevent unauthorized agents from connecting.

Attack Surface: Insufficient Access Control

  • Description: Weak or misconfigured Role-Based Access Control (RBAC) in Jenkins can grant excessive privileges to users, leading to unauthorized access to sensitive configurations, jobs, credentials, and functionalities.
  • Jenkins Contribution: Jenkins' flexible RBAC system, if not carefully planned and implemented, can easily result in overly permissive access, directly exposing Jenkins resources.
  • Example: Granting "Administer" permissions to a large number of users, or allowing developers "Job/Configure" access when they only need "Job/Read," enabling them to modify critical build processes or inject malicious code.
  • Impact: Unauthorized modification of Jenkins configurations, jobs, and pipelines, access to sensitive credentials, escalation of privileges, and potential system compromise.
  • Risk Severity: High
  • Mitigation Strategies:
    • Principle of Least Privilege: Strictly adhere to the principle of least privilege when assigning roles and permissions in Jenkins.
    • Role-Based Access Control Planning: Carefully plan and define roles and permissions based on job functions and responsibilities.
    • Regular Access Control Audits: Conduct periodic audits of user permissions and role assignments to identify and rectify any over-permissioning.
    • Granular Permissions using Matrix-Based Security: Utilize Jenkins' matrix-based security to fine-tune permissions at a granular level, controlling access to specific jobs and resources.
    • External Authentication and Authorization Integration: Integrate Jenkins with external identity providers (LDAP, Active Directory, OAuth) for centralized user management and consistent access policies.

Attack Surface: Default Credentials

  • Description: Jenkins instances left with default administrative credentials are critically vulnerable, allowing immediate and complete takeover by attackers.
  • Jenkins Contribution: Jenkins' initial setup, if not properly secured, can leave default credentials active, a direct and easily exploitable vulnerability in a new or misconfigured Jenkins instance.
  • Example: An attacker attempts to log in using common default credentials like "admin/admin" and gains full administrative access to the Jenkins server.
  • Impact: Complete compromise of the Jenkins server, full administrative control, data breaches, and total disruption of CI/CD pipelines.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Mandatory Password Change on First Login: Enforce immediate password change for the administrative user during the initial Jenkins setup.
    • Disable Default Accounts: If possible, disable or remove default administrative accounts after creating secure replacements.
    • Strong Password Policies: Implement and enforce strong password policies for all Jenkins users, including administrators.
    • Regular Security Scanning for Default Credentials: Include checks for default credentials in regular security scans of the Jenkins instance.
    • Security Awareness Training: Train administrators and users on the critical importance of changing default credentials and maintaining strong passwords.