attack-surface.md

Attack Surface Analysis for jenkinsci/pipeline-model-definition-plugin

Attack Surface: Script Injection via script Block

• Description: Execution of arbitrary Groovy code within the Jenkins master or agent context due to insufficient input sanitization or validation within script blocks in declarative pipelines.
• Pipeline-Model-Definition-Plugin Contribution: The plugin's declarative syntax, while aiming for structure, still allows embedding Groovy code in script blocks. This feature, if misused, becomes a direct vector for script injection.
• Example: A pipeline takes a user-provided parameter userInput. The pipeline includes a script block that directly uses this parameter:

  pipeline {
      agent any
      parameters {
          string(name: 'userInput', defaultValue: '', description: 'Enter input')
      }
      stages {
          stage('Example') {
              steps {
                  script {
                      println "User input: ${params.userInput}"
                      // Vulnerable code:
                      evaluate(params.userInput)
                  }
              }
          }
      }
  }

  If a user provides malicious Groovy code as userInput, the evaluate() function will execute it.
• Impact: Full compromise of the Jenkins master or agent, depending on where the script executes. Attackers can gain complete control, steal secrets, modify configurations, or launch further attacks.
• Risk Severity: Critical
• Mitigation Strategies:
  • Avoid script blocks when possible: Utilize declarative steps and plugins instead of raw Groovy scripting.
  • Input Sanitization: Never directly use user-provided input (parameters, environment variables) in script blocks without rigorous sanitization and validation.
  • Principle of Least Privilege: Run pipelines with the minimum necessary permissions.
  • Code Review: Thoroughly review any script blocks for potential injection vulnerabilities.
  • Static Analysis: Use static analysis tools to detect potential script injection risks in pipeline definitions.

Attack Surface: Command Injection via sh and powershell Steps

• Description: Execution of arbitrary shell commands on the Jenkins agent due to insufficient sanitization of user-provided input used within sh or powershell steps.
• Pipeline-Model-Definition-Plugin Contribution: The plugin provides sh and powershell steps as core functionalities within declarative pipelines, making command execution readily available. If input to these steps is not handled carefully, it opens the door to command injection.
• Example: A pipeline takes a parameter fileName. The pipeline uses sh step to process this file:

  pipeline {
      agent any
      parameters {
          string(name: 'fileName', defaultValue: '', description: 'Enter file name')
      }
      stages {
          stage('Example') {
              steps {
                  sh "cat ${params.fileName}" // Vulnerable code
              }
          }
      }
  }

  If a user provides a malicious filename like ; rm -rf /, the sh command becomes cat ; rm -rf /, leading to command injection.
• Impact: Compromise of the Jenkins agent. Attackers can execute arbitrary commands, potentially gaining access to sensitive data on the agent, modifying files, or using the agent as a pivot point for further attacks.
• Risk Severity: High
• Mitigation Strategies:
  • Input Sanitization and Escaping: Properly sanitize and escape user-provided input before using it in sh or powershell commands. Use parameterized queries or safe command construction methods provided by scripting languages.
  • Avoid String Interpolation: Prefer safer methods of command construction that avoid direct string interpolation of user input.
  • Principle of Least Privilege (Agent): Run agents with minimal necessary privileges to limit the impact of command injection.
  • Command Whitelisting (where feasible): Restrict the commands that can be executed within sh or powershell steps to a predefined whitelist.

Attack Surface: Parameter Injection

• Description: Exploiting pipeline parameters to inject malicious input that is then processed unsafely within the pipeline, leading to script injection, command injection, or other vulnerabilities.
• Pipeline-Model-Definition-Plugin Contribution: The plugin heavily relies on parameters for user input and pipeline configuration within declarative pipelines. If pipelines are not designed with security in mind, parameters become a primary entry point for malicious input.
• Example: A pipeline parameter buildCommand is intended to specify a build command. However, it's directly used in a sh step without validation:

  pipeline {
      agent any
      parameters {
          string(name: 'buildCommand', defaultValue: 'mvn clean install', description: 'Build command')
      }
      stages {
          stage('Build') {
              steps {
                  sh "${params.buildCommand}" // Vulnerable code
              }
          }
      }
  }

  An attacker could set buildCommand to mvn clean install && malicious_command to inject and execute arbitrary commands.
• Impact: Varies depending on how the injected parameter is used. Can range from command injection on agents to script injection on the master, leading to system compromise or data breaches.
• Risk Severity: High to Critical (depending on the context of parameter usage)
• Mitigation Strategies:
  • Parameter Validation: Strictly validate all pipeline parameters against expected formats and values. Reject invalid input.
  • Input Sanitization: Sanitize parameter values before using them in scripts or commands.
  • Treat Parameters as Untrusted: Always treat parameters as potentially malicious user input and handle them with caution.
  • Use Parameter Types Wisely: Utilize specific parameter types (e.g., choice, boolean) to restrict input options and reduce the attack surface compared to free-form string parameters.

Attack Surface: Agent Misconfiguration leading to Sensitive Data Exposure

• Description: Pipelines processing sensitive data being executed on unintended or less secure Jenkins agents due to misconfiguration of the agent directive in declarative pipelines, leading to potential data exposure.
• Pipeline-Model-Definition-Plugin Contribution: The agent directive is a core feature of declarative pipelines, allowing specification of where pipelines should run. Misconfiguration here directly leads to pipelines running in potentially vulnerable environments.
• Example: A pipeline designed to handle confidential customer data is mistakenly configured to run on a shared, less secure agent due to an incorrect label in the agent directive:

  pipeline {
      agent { label 'incorrect-agent-label' } // Misconfiguration - points to less secure agent
      stages {
          // ... pipeline steps processing sensitive data ...
      }
  }

  This could expose sensitive customer data processed by the pipeline to a less secure environment, increasing the risk of unauthorized access or data breaches.
• Impact: Information disclosure, exposure of sensitive data to less secure environments, potential data breaches, compliance violations.
• Risk Severity: High
• Mitigation Strategies:
  • Careful Agent Labeling and Configuration: Accurately configure agent labels and rigorously test pipeline agent directives to ensure pipelines are directed to the intended, secure agents.
  • Agent Security Hardening: Harden all Jenkins agents, and especially dedicate specific, highly secured agents for pipelines processing sensitive data.
  • Regular Agent Audits: Periodically audit agent configurations and pipeline agent directives, particularly for pipelines handling sensitive information, to ensure correct and secure assignments.
  • Principle of Least Privilege (Agents): Grant agents only the necessary permissions and access, and strictly segregate agents based on the sensitivity of the pipelines they execute.

Attack Surface: Tool Misconfiguration and Use of Vulnerable Tools Exposing Agents

• Description: Exploiting vulnerabilities arising from misconfigured or vulnerable tools specified using the tools directive in declarative pipelines, potentially leading to agent compromise.
• Pipeline-Model-Definition-Plugin Contribution: The tools directive allows pipelines to declare required tools (JDK, Maven, etc.). Misconfiguration or vulnerabilities in the tool setup process or the tools themselves can be exploited, directly impacting the agent.
• Example: A pipeline specifies an outdated and vulnerable version of a build tool using the tools directive:

  pipeline {
      agent any
      tools {
          maven 'vulnerable-maven-version' // Misconfiguration - using outdated, vulnerable version
      }
      stages {
          // ... pipeline steps using Maven ...
      }
  }

  If the specified Maven version has known vulnerabilities, the agent running the pipeline becomes vulnerable to exploits targeting that Maven version.
• Impact: Compromise of the Jenkins agent if a vulnerable tool is exploited. Attackers could leverage tool vulnerabilities to gain unauthorized access to the agent, execute arbitrary code, or steal sensitive information.
• Risk Severity: High
• Mitigation Strategies:
  • Use Latest Tool Versions: Always use the latest stable and security-patched versions of tools.
  • Tool Version Management and Enforcement: Implement a robust tool version management strategy and enforce the use of approved and secure tool versions within pipelines.
  • Tool Source Verification and Integrity Checks: Verify the integrity and authenticity of tool installations to prevent the introduction of compromised or malicious tools.
  • Regular Vulnerability Scanning of Tools: Regularly scan installed tools for known vulnerabilities and implement a process for patching or updating vulnerable tools promptly.
  • Agent Isolation and Monitoring: Isolate agents as much as possible and implement robust monitoring to detect and respond to any suspicious activity potentially related to tool exploitation.