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Docker Sandbox Scanning

Run security scans in an isolated Docker environment for maximum safety.

Why Use Sandbox?​

Protect your host system from potentially malicious code:

  • ✅ Isolated execution - Code runs in containerized environment
  • ✅ Resource limits - CPU, memory, and time constraints
  • ✅ Network isolation - No external network access
  • ✅ Read-only filesystem - Cannot modify host files
  • ✅ Enhanced scanning - Uses external tools (Trivy, Checkov, GitLeaks)

Setup​

docker pull ongjin/security-scanner-mcp:latest
docker tag ongjin/security-scanner-mcp:latest security-scanner-mcp:latest

Or Build from Source​

npm run docker:build

Note: Building takes 5-10 minutes and creates a ~500MB image with:

  • Trivy v0.50.4
  • GitLeaks v8.18.4
  • Checkov (Python-based)

Usage​

Basic Sandbox Scan​

Me: Scan this code in a sandbox

const apiKey = "AIzaSyC1234567890abcdef";
const query = `SELECT * FROM users WHERE id = ${userId}`;

Claude will call scan-in-sandbox which:

  1. Writes code to temporary file
  2. Launches Docker container
  3. Runs all scanners inside container
  4. Returns results as JSON
  5. Cleans up container

Scan Untrusted Code​

Me: This code looks suspicious, scan it safely

[paste potentially malicious code]

Security Configuration​

Default Settings​

Memory Limit: 512MB
CPU Limit: 0.5 cores
Timeout: 30 seconds
Network: Disabled
Filesystem: Read-only (except /tmp)
Capabilities: Dropped (no-new-privileges)

Customizable Options​

You can adjust these through environment variables:

SANDBOX_MEMORY=1g \
SANDBOX_CPU=1.0 \
SANDBOX_TIMEOUT=60000 \
scan-in-sandbox

Scanners Available in Sandbox​

Built-in Scanners​

  • Secret detection
  • SQL/NoSQL/Command injection
  • XSS vulnerabilities
  • Cryptographic issues
  • Authentication problems
  • Path traversal

External Tools (Docker only)​

  • GitLeaks: Enhanced secret detection with entropy analysis
  • Trivy: IaC and container vulnerability scanning
  • Checkov: Infrastructure as Code security analysis

Docker Container Details​

Base Image​

FROM node:20-alpine

Security Hardening​

# Non-root user
RUN addgroup -g 1001 scanner && \
    adduser -D -u 1001 -G scanner scanner

# Read-only root filesystem
# No new privileges
# Dropped capabilities
# Network disabled

Installed Tools​

# Verify tools are installed
docker run security-scanner-mcp:latest sh -c "
  trivy --version &&
  gitleaks version &&
  checkov --version
"

Results Format​

Sandbox scan returns comprehensive JSON:

{
  "success": true,
  "language": "javascript",
  "filename": "code.js",
  "issuesCount": 3,
  "issues": [
    {
      "type": "Google API Key",
      "severity": "critical",
      "message": "Google API Key is hardcoded",
      "fix": "Use environment variables",
      "line": 1,
      "metadata": {
        "tool": "gitleaks",
        "ruleId": "google-api-key",
        "entropy": 4.2
      }
    }
  ],
  "summary": {
    "critical": 1,
    "high": 1,
    "medium": 1,
    "low": 0
  }
}

Performance Considerations​

Container Startup​

  • First run: ~2-3 seconds (cold start)
  • Subsequent runs: ~1 second (cached)

Scan Duration​

  • Small files (under 100 lines): Less than 5 seconds
  • Medium files (100-500 lines): 5-15 seconds
  • Large files (over 500 lines): 15-30 seconds

Resource Usage​

  • Memory: Approximately 100-200MB per scan
  • CPU: Minimal (0.1-0.5 cores)
  • Disk: Temporary files cleaned automatically

Troubleshooting​

Container Not Found​

# Check if image exists
docker images | grep security-scanner-mcp

# Pull if missing
docker pull ongjin/security-scanner-mcp:latest

Permission Denied​

# Add user to docker group
sudo usermod -aG docker $USER

# Restart shell

Timeout Issues​

# Increase timeout (ms)
SANDBOX_TIMEOUT=60000 scan-in-sandbox

Best Practices​

  1. Use for untrusted code: Always scan code from unknown sources
  2. Regular image updates: Pull latest security updates monthly
  3. Monitor resource usage: Prevent abuse with limits
  4. Cleanup: Containers are auto-removed, but check periodically
  5. Network isolation: Keep network disabled unless required

Advanced Configuration​

Custom Docker Image​

FROM security-scanner-mcp:latest

# Add custom scanners
RUN pip3 install custom-scanner

# Add custom rules
COPY custom-rules.yaml /app/rules/

Integration with CI/CD​

# GitHub Actions example
- name: Scan Code in Sandbox
  run: |
    docker pull ongjin/security-scanner-mcp:latest
    docker run --rm \
      -v ${{ github.workspace }}:/code:ro \
      security-scanner-mcp:latest \
      scan /code

Next Steps​