Image Security Scanner

Scan and secure Docker images for production deployment.

Quick Start

Scan an image:

docker scan myapp:latest
# or
trivy image myapp:latest

Instructions

Step 1: Choose Scanning Tool

Docker Scan (built-in):

docker scan myapp:latest

Trivy (comprehensive):

trivy image myapp:latest

Grype (fast):

grype myapp:latest

Snyk (detailed):

snyk container test myapp:latest

Step 2: Run Security Scan

Basic scan:

docker scan myapp:latest

Detailed scan with Trivy:

trivy image --severity HIGH,CRITICAL myapp:latest

Scan with JSON output:

trivy image -f json -o results.json myapp:latest

Step 3: Analyze Results

Review findings by severity:

• CRITICAL: Immediate action required
• HIGH: Fix soon
• MEDIUM: Plan to fix
• LOW: Monitor

Common vulnerabilities:

• Outdated base image
• Vulnerable packages
• Known CVEs
• Misconfigurations

Step 4: Fix Vulnerabilities

Update base image:

# Before
FROM node:18-alpine3.17

# After
FROM node:18-alpine3.18

Update packages:

RUN apk upgrade --no-cache
# or
RUN apt-get update && apt-get upgrade -y

Remove vulnerable packages:

RUN apk del vulnerable-package

Use distroless for minimal attack surface:

FROM gcr.io/distroless/nodejs18-debian11

Step 5: Implement Security Best Practices

Run as non-root:

USER nobody
# or
RUN adduser -D appuser
USER appuser

Remove unnecessary tools:

RUN apk del apk-tools

Use read-only filesystem:

# In docker-compose or k8s
read_only: true

Add security labels:

LABEL security.scan-date="2024-01-15"
LABEL security.scanner="trivy"

Step 6: Verify Fixes

Re-scan after fixes:

docker build -t myapp:latest .
trivy image myapp:latest

Compare before/after:

# Before: 15 HIGH, 5 CRITICAL
# After: 2 HIGH, 0 CRITICAL

Scanning Patterns

CI/CD Integration:

# GitHub Actions
- name: Scan image
  run: |
    docker build -t myapp:${{ github.sha }} .
    trivy image --exit-code 1 --severity CRITICAL myapp:${{ github.sha }}

Pre-deployment scan:

#!/bin/bash
IMAGE=$1
trivy image --severity HIGH,CRITICAL $IMAGE
if [ $? -ne 0 ]; then
  echo "Security vulnerabilities found!"
  exit 1
fi

Scheduled scans:

# Cron job to scan running images
0 2 * * * trivy image --severity HIGH,CRITICAL $(docker images -q)

Security Hardening

Minimal base image:

FROM alpine:3.18
# or
FROM gcr.io/distroless/static-debian11

No secrets in image:

# Bad
ENV API_KEY=secret123

# Good
# Pass at runtime
docker run -e API_KEY=$API_KEY myapp

Health checks:

HEALTHCHECK --interval=30s --timeout=3s \
  CMD curl -f http://localhost:8080/health || exit 1

Limit capabilities:

docker run --cap-drop=ALL --cap-add=NET_BIND_SERVICE myapp

Common Vulnerabilities

Outdated base image:

# Vulnerable
FROM node:16-alpine

# Fixed
FROM node:18-alpine3.18

Exposed secrets:

# Vulnerable
COPY .env .

# Fixed
# Use runtime secrets

Running as root:

# Vulnerable
CMD ["node", "server.js"]

# Fixed
USER node
CMD ["node", "server.js"]

Unnecessary packages:

# Vulnerable
RUN apk add curl wget git vim

# Fixed
RUN apk add --no-cache curl

Scanning Tools Comparison

Docker Scan:

• Built into Docker
• Uses Snyk backend
• Easy to use
• Limited free scans

Trivy:

• Open source
• Fast and accurate
• Multiple output formats
• CI/CD friendly

Grype:

• Open source
• Very fast
• Good accuracy
• Simple CLI

Snyk:

• Commercial (free tier)
• Detailed reports
• Fix recommendations
• IDE integration

Advanced

For production deployments:

• Implement image signing
• Use admission controllers
• Set up continuous scanning
• Monitor runtime security
• Implement security policies