Script approval and sandbox in Jenkins - Commands & Configuration

Introduction

Sometimes Jenkins runs scripts that need special permission to keep your system safe. Script approval and sandbox help control which scripts can run automatically and which need manual approval.

When you add a new Groovy script to a Jenkins pipeline and it uses commands Jenkins does not trust by default

When you want to prevent unsafe scripts from running automatically in your Jenkins jobs

When you want to allow safe scripts to run without manual approval by using the sandbox mode

When you need to approve specific scripts or script signatures manually to allow them to run

When you want to keep your Jenkins environment secure while still allowing custom automation

Commands

This command runs a Groovy script on Jenkins using the Jenkins CLI. If the script uses unapproved methods, Jenkins will block it and require approval.

Terminal

java -jar jenkins-cli.jar -s http://localhost:8080 groovy = < script.groovy

Expected Output

ERROR: Scripts not permitted to use method java.lang.Runtime exec java.lang.String

Please approve this signature in the script approval page.

This command approves a specific script signature manually via Jenkins script approval REST API, allowing scripts using this method to run.

Terminal

curl -X POST http://localhost:8080/scriptApproval/approve -d 'signature=method java.lang.Runtime exec java.lang.String' --user admin:admin123

Expected Output

Approved signature: method java.lang.Runtime exec java.lang.String

→

-X POST - Send data to approve the script signature

→

--user admin:admin123 - Authenticate as admin to approve scripts

Run the same Groovy script again after approval. Now it should run without errors because the script signature is approved.

Terminal

java -jar jenkins-cli.jar -s http://localhost:8080 groovy = < script.groovy

Expected Output

Script executed successfully.

Key Concept

If you remember nothing else from this pattern, remember: Jenkins blocks unsafe scripts until you approve their signatures or run them in sandbox mode.

Common Mistakes

Trying to run a Groovy script with unapproved methods without approving them first

Jenkins blocks the script for security, causing errors and stopping the job

Manually approve the script signatures in Jenkins script approval or run the script in sandbox mode if safe

Approving all scripts blindly without checking their safety

This can allow unsafe scripts to run and harm your Jenkins environment

Review each script signature carefully before approving to keep Jenkins secure

Summary

Run Groovy scripts in Jenkins and watch for script approval errors.

Approve script signatures manually to allow safe scripts to run.

Use sandbox mode to run scripts safely without manual approval.

Practice

1. What is the main purpose of script approval in Jenkins?

easy

A. To automatically run all scripts without restrictions

B. To protect Jenkins by allowing admins to approve unsafe scripts before execution

C. To speed up the build process by skipping script checks

D. To disable all scripts in Jenkins

Solution

1. Step 1: Understand script approval role

   Script approval is designed to protect Jenkins by controlling which scripts can run.

2. Step 2: Identify admin involvement

   Admins review and approve scripts to prevent unsafe code from running.

3. Final Answer:

   To protect Jenkins by allowing admins to approve unsafe scripts before execution -> Option B

4. Quick Check:

   Script approval = Admin review for safety [OK]

Hint: Script approval means admin checks scripts before running [OK]

Common Mistakes:

• Thinking scripts run automatically without checks
• Confusing script approval with disabling scripts
• Assuming script approval speeds up builds

2. Which of the following is the correct way to enable sandbox mode in a Jenkins Pipeline script?

easy

A. Check the 'Use Groovy Sandbox' option in the Pipeline script configuration

B. Use @Sandbox annotation at the top of the script

C. Add sandbox=true inside the Jenkinsfile

D. Enable sandbox mode in Jenkins global settings only

Solution

1. Step 1: Identify sandbox enabling method

   Sandbox mode is enabled by checking the 'Use Groovy Sandbox' box in the Pipeline script configuration.

2. Step 2: Verify other options

   Annotations or code inside Jenkinsfile do not enable sandbox; global settings do not control this per script.

3. Final Answer:

   Check the 'Use Groovy Sandbox' option in the Pipeline script configuration -> Option A

4. Quick Check:

   Sandbox enabled via checkbox in script config [OK]

Hint: Sandbox mode is a checkbox in Pipeline script config [OK]

Common Mistakes:

• Trying to enable sandbox with code annotations
• Assuming sandbox is a global-only setting
• Adding sandbox flags inside Jenkinsfile

3. Given this Jenkins Pipeline snippet running with sandbox enabled:

node {
  def result = sh(script: 'echo Hello', returnStdout: true).trim()
  echo result
}

What will be the output?

medium

A. No output because sandbox blocks shell commands

B. Syntax error due to sandbox

C. result

D. Hello

Solution

1. Step 1: Analyze the sh step

   sh(script: 'echo Hello', returnStdout: true).trim() executes 'echo Hello', captures stdout, trims to 'Hello', assigns to result.

2. Step 2: Analyze echo step

   echo result prints the value of result ('Hello'). In Jenkins Pipeline, the echo step prints variable values directly. Sandbox allows whitelisted steps like sh and echo.

3. Final Answer:

   Hello -> Option D

4. Quick Check:

   sh captures stdout, echo prints var value [OK]

Hint: In Pipeline, echo result prints result's value [OK]

Common Mistakes:

• Thinking echo prints literal 'result' like shell
• Believing sandbox blocks whitelisted sh commands
• Expecting syntax error from sandbox

4. You wrote a Jenkins Pipeline script that uses a method not whitelisted in the sandbox. The build fails with a script approval error. What should you do to fix this?

medium

A. Restart Jenkins to clear the error

B. Remove sandbox mode and run the script without restrictions

C. Ask the Jenkins admin to approve the method in the script approval page

D. Rewrite the script to avoid using any methods

Solution

1. Step 1: Understand script approval error cause

   The error occurs because the method is not approved in Jenkins script approval.

2. Step 2: Fix by admin approval

   The correct fix is to have the Jenkins admin approve the method via the script approval UI.

3. Final Answer:

   Ask the Jenkins admin to approve the method in the script approval page -> Option C

4. Quick Check:

   Approval needed for unapproved methods [OK]

Hint: Unapproved methods need admin approval, not disabling sandbox [OK]

Common Mistakes:

• Disabling sandbox instead of approving scripts
• Trying to remove methods instead of approval
• Restarting Jenkins does not fix approval errors

5. You want to run a custom Groovy script in Jenkins Pipeline that uses a non-whitelisted method and also requires sandbox protection. Which approach correctly balances safety and functionality?

hard

A. Run the script with sandbox enabled and request admin approval for the method

B. Disable sandbox and run the script directly to avoid approval delays

C. Rewrite the script to avoid all non-whitelisted methods, ignoring sandbox

D. Run the script outside Jenkins and import results to avoid sandbox issues

Solution

1. Step 1: Understand sandbox and approval roles

   Sandbox protects Jenkins by restricting unsafe code; approval allows safe exceptions.

2. Step 2: Balance safety and functionality

   Enabling sandbox with admin approval keeps Jenkins safe while allowing needed methods.

3. Final Answer:

   Run the script with sandbox enabled and request admin approval for the method -> Option A

4. Quick Check:

   Sandbox + approval = safe and functional scripts [OK]

Hint: Use sandbox plus admin approval for safe custom scripts [OK]

Common Mistakes:

• Disabling sandbox risking Jenkins security
• Avoiding needed methods by rewriting scripts unnecessarily
• Running scripts outside Jenkins complicates workflow