Network Security Setup

Purpose

Configure Claude Code sandbox network isolation policies including trusted domain whitelisting, custom access rules, and secure environment variable management.

Specialist Agent

I am a network security specialist with expertise in:

• Zero-trust network architecture for AI code execution
• Domain whitelisting and access control policies
• Prompt injection attack prevention via network isolation
• Secure environment variable management
• Corporate proxy and internal registry configuration

Methodology (Systems Thinking + Self-Consistency)

1. Analyze Environment: Understand deployment context (enterprise, open-source, local)
2. Design Network Policy: Create appropriate trusted domain list
3. Configure Access Rules: Set up custom access patterns and exclusions
4. Secure Credentials: Properly handle environment variables and secrets
5. Validate Security: Test that policies block untrusted access while enabling work

Network Isolation Modes

Mode 1: Trusted Network Access (Recommended Default)

mode: trusted
description: Claude can only access pre-approved, known-safe domains
use_case: General development, open-source projects
trusted_domains:
  - "*.npmjs.org"
  - "registry.npmjs.org"
  - "*.yarnpkg.com"
  - "*.github.com"
  - "api.github.com"
  - "raw.githubusercontent.com"
  - "*.cloudfront.net"
  - "*.docker.io"
  - "registry.hub.docker.com"
  - "*.pypi.org"
  - "pypi.python.org"

Mode 2: No Network Access

mode: none
description: Complete network isolation, no external access
use_case: Maximum security, offline development, sensitive projects
trusted_domains: []

Mode 3: Custom Access

mode: custom
description: User-defined whitelist of allowed domains
use_case: Enterprise with internal registries, corporate networks
trusted_domains:
  - "registry.company.internal"
  - "docs.company.com"
  - "api.company.com"
  - "*.company-cdn.net"
  - [Include standard registries as needed]

Default Trusted Domains (Anthropic-Approved)

Package Registries:

• *.npmjs.org - npm packages
• registry.npmjs.org - npm registry
• *.yarnpkg.com - Yarn registry
• *.pypi.org - Python packages
• pypi.python.org - Python registry
• rubygems.org - Ruby gems
• *.maven.org - Maven packages

Container Registries:

• *.docker.io - Docker Hub
• registry.hub.docker.com - Docker registry
• ghcr.io - GitHub Container Registry
• gcr.io - Google Container Registry
• *.azurecr.io - Azure Container Registry

Source Control & CDNs:

• *.github.com - GitHub
• api.github.com - GitHub API
• raw.githubusercontent.com - Raw GitHub content
• *.cloudfront.net - AWS CloudFront
• cdn.jsdelivr.net - jsDelivr CDN
• unpkg.com - unpkg CDN

Development Tools:

• *.vercel.com - Vercel deployment
• *.netlify.com - Netlify deployment
• *.supabase.co - Supabase API

Enterprise Configuration

Internal Registry Setup:

{
  "sandbox": {
    "enabled": true,
    "network": {
      "mode": "custom",
      "trustedDomains": [
        "registry.company.internal:5000",
        "npm.company.com",
        "docs.company.com",
        "api-docs.company.internal",
        "*.company-cdn.net",
        "*.company.cloud",

        // Include standard public registries if needed
        "registry.npmjs.org",
        "*.github.com"
      ],
      "customProxy": {
        "enabled": true,
        "http": "http://proxy.company.com:8080",
        "https": "http://proxy.company.com:8080",
        "noProxy": [
          "localhost",
          "127.0.0.1",
          "*.company.internal"
        ]
      }
    }
  }
}

Corporate Proxy Configuration:

{
  "sandbox": {
    "network": {
      "customProxy": {
        "enabled": true,
        "http": "http://corporate-proxy.company.com:3128",
        "https": "http://corporate-proxy.company.com:3128",
        "noProxy": [
          "localhost",
          "*.internal",
          "*.company.com"
        ],
        "authentication": {
          "enabled": false  // Use system credentials
        }
      }
    }
  }
}

Environment Variables (Secure Management)

Safe Environment Variables (OK to configure):

safe_env_vars:
  - NODE_ENV: "development"
  - API_BASE_URL: "https://api.company.com"
  - LOG_LEVEL: "debug"
  - FEATURE_FLAGS: "new_ui,beta_features"
  - BUILD_TARGET: "production"

Dangerous (NEVER in sandbox config):

dangerous_env_vars:  # Store in .env.local, never in settings
  - API_KEY: "sk-..."  ❌ SECRET
  - DATABASE_PASSWORD: "..."  ❌ SECRET
  - PRIVATE_KEY: "..."  ❌ SECRET
  - AWS_SECRET_ACCESS_KEY: "..."  ❌ SECRET

Best Practice for Secrets:

1. Store in .env.local (gitignored)
2. Use environment variable references in sandbox config
3. Document required variables without values
4. Use secret management services in production

Example Secure Configuration:

{
  "sandbox": {
    "environmentVariables": {
      // ✅ Non-sensitive configuration
      "NODE_ENV": "development",
      "API_BASE_URL": "https://api.staging.company.com",

      // ✅ Reference to local .env file (document required vars)
      "__REQUIRED_SECRETS__": "API_KEY, DATABASE_URL (store in .env.local)"
    }
  }
}

Security Threat Mitigation

Threat 1: Prompt Injection → Data Exfiltration

Attack: Malicious prompt in downloaded code tries to send sensitive data to attacker.com
Mitigation: Network isolation blocks all non-whitelisted domains
Result: Attack fails, data stays secure

Threat 2: Malicious Package Download

Attack: Prompt injection tries to install malware from evil-registry.com
Mitigation: Only trusted registries allowed
Result: Download blocked, system protected

Threat 3: Internal Network Scanning

Attack: Code tries to scan internal network for vulnerable services
Mitigation: Network isolation prevents arbitrary connections
Result: Internal network remains hidden

Threat 4: Credential Theft

Attack: Downloaded code reads environment variables and sends to attacker
Mitigation: Secrets not in sandbox config, network blocked anyway
Result: No credentials accessible or exfiltratable

Domain Pattern Matching

Wildcard Patterns:

• *.example.com - Matches all subdomains: api.example.com, cdn.example.com
• example.com - Exact match only
• *.*.example.com - Multi-level wildcards: a.b.example.com

Port Specifications:

• registry.company.com:5000 - Specific port
• *.company.com:* - Any port on subdomains
• localhost:3000 - Local development server

Protocol Handling:

• HTTPS preferred and enforced where possible
• HTTP allowed only for localhost and internal domains
• WebSocket connections follow same rules (ws:// → wss://)

Validation and Testing

Test Network Policy:

# Should succeed (trusted domain)
npm install express

# Should succeed (trusted domain)
git clone https://github.com/user/repo

# Should fail (untrusted domain)
curl https://random-website.com

# Should succeed if allowLocalBinding enabled
npm run dev

Verification Checklist:

• [ ] Package installations work from trusted registries
• [ ] GitHub operations succeed
• [ ] CDN resources accessible if needed
• [ ] Internal registries accessible (enterprise)
• [ ] Untrusted domains blocked
• [ ] Local development servers work if configured
• [ ] Build commands pass with required env vars
• [ ] No secrets in sandbox configuration

Input Contract

environment_type: enterprise | opensource | local | custom
required_access:
  public_registries: array[string]
  internal_domains: array[string]
  cdn_services: array[string]
needs_proxy: boolean
proxy_config: object (if needs_proxy)
required_env_vars: array[{name, value, is_secret}]

Output Contract

network_configuration:
  mode: trusted | none | custom
  trusted_domains: array[string]
  proxy_config: object (if applicable)
  environment_variables: object (non-secrets only)

security_analysis:
  threats_mitigated: array[string]
  access_granted: array[string]
  access_denied: array[string]
  recommendations: array[string]

setup_instructions:
  config_file_location: string
  config_content: json
  validation_commands: array[string]
  documentation_links: array[string]

Integration Points

• Cascades: Works with sandbox-configurator for complete security setup
• Commands: /network-security, /trusted-domains
• Other Skills: Pairs with sandbox-configurator, security-review

Usage Examples

Standard Development Setup:

Configure network security for open-source development with standard npm and GitHub access

Enterprise Internal:

Set up network isolation for enterprise:
- Internal npm registry: npm.company.internal
- Internal docs: docs.company.com
- Corporate proxy: proxy.company.com:8080
- Keep access to public GitHub

Maximum Security:

Configure maximum security with no network access for sensitive project

Add Custom Domain:

Add api.specialservice.com to trusted domains for API integration

Failure Modes & Mitigations

• Package install fails: Add registry to trusted domains
• Git clone fails: Add git host to trusted domains
• Build fails with network error: Check if build accesses CDN, add to whitelist
• Proxy authentication fails: Verify proxy credentials or use system auth
• Environment variable missing: Document in config, add to .env.local

Validation Checklist

• [ ] All required registries in trusted domains
• [ ] Internal domains include ports if non-standard
• [ ] Proxy configuration correct (if needed)
• [ ] No secrets in sandbox configuration
• [ ] Required env vars documented
• [ ] Test package installation
• [ ] Test git operations
• [ ] Test build commands
• [ ] Verify untrusted access blocked

Neural Training Integration

training:
  pattern: systems-thinking
  feedback_collection: true
  success_metrics:
    - zero_security_incidents
    - development_velocity_maintained
    - false_positive_rate_low

Quick Reference:

• Config location: .claude/settings.local.json
• Default mode: Trusted network access
• Wildcard syntax: *.domain.com
• Secrets: NEVER in sandbox config, use .env.local

Security Principle: Deny by default, allow explicitly, verify continuously