Parent Epic: #250 - Implement Automated Docker Image Vulnerability Scanning

Overview

Implement a GitHub Actions workflow that uses Trivy to scan Docker images for vulnerabilities. This initial implementation uses a hardcoded list of images and provides immediate security coverage while Phase 2 makes it dynamic.

Goals

• Create GitHub Actions workflow for Trivy scanning
• Scan all project Docker images for HIGH/CRITICAL vulnerabilities
• Run scans on push, PR, and periodically
• Fail builds when vulnerabilities detected
• Generate actionable vulnerability reports

Docker Images to Scan

Project-built (build first, then scan):

1. torrust-tracker-deployer/provisioned-instance:latest
2. torrust-tracker-deployer/ssh-server:latest

Third-party (direct scan):
3. torrust/tracker:develop
4. mysql:8.0
5. grafana/grafana:11.4.0
6. prom/prometheus:v3.0.1

Implementation Phases

Phase 1: Workflow File Creation

• Create .github/workflows/docker-security-scan.yml
• Configure workflow triggers (push to main, pull_request, schedule)
• Set up job structure for parallel scanning

Phase 2: Project Image Scanning

• Build provisioned-instance and ssh-server images
• Run Trivy scanner on built images
• Configure severity filter (HIGH, CRITICAL)

Phase 3: Third-Party Image Scanning

• Scan torrust/tracker:develop
• Scan mysql:8.0
• Scan grafana/grafana:11.4.0
• Scan prom/prometheus:v3.0.1

Phase 4: Results Upload

• Generate SARIF format reports
• Upload to GitHub Security tab
• Configure exit-code: 1 for failures

Phase 5: Testing & Documentation

• Test workflow on PR
• Add workflow badge to README
• Document in security guidelines

Acceptance Criteria

Quality Checks:

• Workflow YAML passes yamllint
• No syntax errors in workflow file

Functional Requirements:

• All 6 images scanned successfully
• Vulnerabilities displayed in GitHub Security tab
• Build fails when HIGH/CRITICAL vulnerabilities found
• Workflow runs on: push to main, PRs, weekly schedule
• Badge shows workflow status in README

Testing:

• Manual test: create PR to trigger workflow
• Verify SARIF uploads to Security tab
• Verify build fails with vulnerable image

Documentation:

• README.md updated with workflow badge
• Security documentation references workflow

Estimated effort: 2-4 hours

Full specification: docs/issues/implement-basic-trivy-scanning-workflow.md