Security Hardening

Secure Azure resources following Zero Trust principles.

Security Principles

1. Zero Trust — Never trust, always verify
2. Least Privilege — Minimum required permissions
3. Defense in Depth — Multiple security layers
4. Encryption Everywhere — At rest and in transit

Security Services

MCP Tools (Preferred)

When Azure MCP is enabled:

Key Vault:

• azure__keyvault with command keyvault_list — List Key Vaults
• azure__keyvault with command keyvault_secret_list — List secrets
• azure__keyvault with command keyvault_secret_get — Get secret value
• azure__keyvault with command keyvault_key_list — List keys
• azure__keyvault with command keyvault_certificate_list — List certificates

RBAC:

• azure__role with command role_assignment_list — List role assignments
• azure__role with command role_definition_list — List role definitions

CLI Quick Reference

# Key Vault
az keyvault list --output table
az keyvault secret list --vault-name VAULT --output table

# RBAC
az role assignment list --output table

# Managed Identity
az identity list --output table

Identity and Access

Checklist

• [ ] Use managed identities (no credentials in code)
• [ ] Enable MFA for all users
• [ ] Apply least privilege RBAC
• [ ] Use Microsoft Entra ID for authentication
• [ ] SQL Server: Entra-only auth — NEVER generate administratorLogin or administratorLoginPassword anywhere in Bicep, including inside conditional branches (see sql-database/auth.md)
• [ ] Review access regularly

Managed Identity

# App Service
az webapp identity assign --name APP -g RG

# Container Apps
az containerapp identity assign --name APP -g RG --system-assigned

# Function App
az functionapp identity assign --name APP -g RG

Grant Access

# Grant Key Vault access
az role assignment create \
  --role "Key Vault Secrets User" \
  --assignee IDENTITY_PRINCIPAL_ID \
  --scope /subscriptions/SUB/resourceGroups/RG/providers/Microsoft.KeyVault/vaults/VAULT

Permissions Required to Grant Roles

⚠️ Important: To assign RBAC roles to identities, you need a role with the Microsoft.Authorization/roleAssignments/write permission.

Common Scenario: Granting Storage Blob Data Owner to a Web App's managed identity

# You need User Access Administrator (or Owner) on the Storage Account to run this:
az role assignment create \
  --role "Storage Blob Data Owner" \
  --assignee WEBAPP_PRINCIPAL_ID \
  --scope /subscriptions/SUB/resourceGroups/RG/providers/Microsoft.Storage/storageAccounts/ACCOUNT

If you encounter AuthorizationFailed errors when assigning roles, you likely need the User Access Administrator role at the target scope.

RBAC Best Practices

# Grant minimal role at resource scope
az role assignment create \
  --role "Storage Blob Data Reader" \
  --assignee PRINCIPAL_ID \
  --scope /subscriptions/SUB/resourceGroups/RG/providers/Microsoft.Storage/storageAccounts/ACCOUNT

Network Security

Checklist

• [ ] Use private endpoints for PaaS services
• [ ] Configure NSGs on all subnets
• [ ] Disable public endpoints where possible
• [ ] Enable DDoS protection
• [ ] Use Azure Firewall or NVA

Private Endpoints

# Create private endpoint for storage
az network private-endpoint create \
  --name myEndpoint -g RG \
  --vnet-name VNET --subnet SUBNET \
  --private-connection-resource-id STORAGE_ID \
  --group-id blob \
  --connection-name myConnection

NSG Rules

# Deny all inbound by default, allow only required traffic
az network nsg rule create \
  --nsg-name NSG -g RG \
  --name AllowHTTPS \
  --priority 100 \
  --destination-port-ranges 443 \
  --access Allow

Best Practices

1. Default deny — Block all traffic by default, allow only required
2. Segment networks — Use subnets and NSGs to isolate workloads
3. Private endpoints — Use for all PaaS services in production
4. Service endpoints — Alternative to private endpoints for simpler scenarios
5. Azure Firewall — Centralize egress traffic control

Data Protection

Checklist

• [ ] Enable encryption at rest (default for most Azure services)
• [ ] Use TLS 1.2+ for transit
• [ ] Store secrets in Key Vault
• [ ] Enable soft delete for Key Vault
• [ ] Use customer-managed keys (CMK) for sensitive data

Key Vault Security

# Enable soft delete and purge protection
az keyvault update \
  --name VAULT -g RG \
  --enable-soft-delete true \
  --enable-purge-protection true

# Enable RBAC permission model
az keyvault update \
  --name VAULT -g RG \
  --enable-rbac-authorization true

Best Practices

1. Never store secrets in code — Use Key Vault or managed identity
2. Rotate secrets regularly — Set expiration dates and automate rotation
3. Enable soft delete — Protect against accidental deletion
4. Enable purge protection — Prevent permanent deletion during retention
5. Use RBAC for Key Vault — Prefer over access policies
6. Customer-managed keys — For sensitive data requiring key control

Monitoring and Defender

Checklist

• [ ] Enable Microsoft Defender for Cloud
• [ ] Configure diagnostic logging
• [ ] Set up security alerts
• [ ] Enable audit logging

Microsoft Defender for Cloud

# Enable Defender plans
az security pricing create \
  --name VirtualMachines \
  --tier Standard

Security Assessment

Use Microsoft Defender for Cloud for:

• Security score
• Recommendations
• Compliance assessment
• Threat detection

Best Practices

1. Enable Defender — For all production workloads
2. Review security score — Address high-priority recommendations
3. Configure alerts — Set up notifications for security events
4. Diagnostic logs — Enable for all resources, send to Log Analytics
5. Audit logging — Track administrative actions and access

Azure Identity SDK

All Azure SDKs use their language's Identity library for credential-free authentication. Use DefaultAzureCredential for local development only; in production, use ManagedIdentityCredential or another deterministic credential — see auth-best-practices.md. Rust uses DeveloperToolsCredential as it doesn't have a DefaultAzureCredential equivalent.

For Key Vault SDK examples, see: Key Vault Reference

For Storage SDK examples, see: Storage Reference

Further Reading

• Key Vault documentation
• Managed identities documentation
• Azure RBAC documentation
• Microsoft Defender for Cloud