OpenStack Hardening Explained: The Security Functions of Keystone, Neutron, and Barbican

OpenStack is a powerful open-source cloud computing platform that provides infrastructure-as-a-service (IaaS) capabilities. As it gains widespread adoption in both enterprise and public cloud environments, security has become a central focus. Ensuring a hardened OpenStack deployment means understanding and leveraging its core components not just for functionality, but also for security. Three key services—Keystone, Neutron, and Barbican—play critical roles in establishing a secure OpenStack environment. 

This article explores the security functions of these services, explaining how they contribute to a hardened, enterprise-grade cloud infrastructure. 

Keystone: Identity, Authentication, and Authorization 

Keystone is the identity service for OpenStack. It provides a central authentication mechanism and manages users, roles, and service endpoints. In a hardened OpenStack deployment, Keystone is the gatekeeper and the foundation of all security. 

Security Functions of Keystone 

Authentication and Tokens

Keystone supports multiple authentication methods, including username/password, token-based, and federation (SAML, OpenID Connect). It issues authentication tokens, which are used to validate access to other OpenStack services. 

Tokens can be: 

• UUID tokens: Simple, unique identifiers. 

• Fernet tokens: Lightweight, non-persistent, encrypted tokens offering better performance and security. 

• OAuth2 or JWT: For more advanced use cases such as multi-cloud identity federation. 

A hardened Keystone deployment prefers Fernet tokens due to their statelessness and encrypted nature. 

Role-Based Access Control (RBAC): 

Keystone enforces RBAC through policies. Each user is assigned roles within projects (tenants), and policies determine what actions roles can perform. 

Administrators can define custom policies for fine-grained access control. For example, only users with the “admin” role may delete instances, while “read-only” roles may only view resources. 

Federation and External Identity Providers: 

To support large-scale enterprise use cases, Keystone can federate with external identity providers such as LDAP or Active Directory. This centralizes identity management, improves user accountability, and supports Single Sign-On (SSO). 

Endpoint Filtering and Scoping: 

Keystone supports scoped tokens that restrict access to a specific project, domain, or system. This ensures users can only operate within their intended boundaries, limiting the blast radius in the event of a breach. 

Hardening Tips for Keystone: 

• Use TLS/SSL for all Keystone API endpoints. 

• Prefer Fernet tokens over UUID for better scalability and security. 

• Regularly rotate Fernet keys and credentials. 

• Enable multi-factor authentication (MFA) for administrative access. 

• Minimize user privileges via least-privilege principles. 

Neutron: Securing the Network Layer 

Neutron is OpenStack’s networking service. It provides “networking-as-a-service” including layer-2 and layer-3 networking, IP address management, firewalls, load balancing, and VPN-as-a-service. In terms of security, Neutron is critical because the network layer is a major attack vector. 

Security Functions of Neutron 

Security Groups and Firewall Rules: 

Neutron allows administrators to define security groups that function like virtual firewalls, controlling inbound and outbound traffic to instances. 

For example, a default security group may only allow SSH and HTTP from specific IP ranges, blocking all other traffic. 

Security groups are stateful, meaning return traffic for an allowed connection is automatically permitted. 

Port Security and Anti-Spoofing: 

Neutron supports port security extensions that prevent MAC and IP spoofing by ensuring traffic from a VM matches the assigned addresses. 

This helps mitigate risks of man-in-the-middle (MITM) and ARP poisoning attacks inside a multi-tenant environment. 

Isolation via Tenant Networks: 

Neutron supports network segmentation using VLANs, VXLANs, or GRE tunnels. Each tenant gets isolated networks, ensuring that one tenant’s traffic is not visible to another. 

Firewall-as-a-Service (FWaaS): 

Neutron can deploy virtual firewalls for more complex traffic filtering, although this service is often replaced with third-party solutions in production. 

Distributed Virtual Routers and Load Balancers: 

Network services such as routers, NAT, and load balancers can be deployed in a distributed way. When secured properly, this minimizes bottlenecks and single points of failure. 

Hardening Tips for Neutron: 

• Apply default-deny policies in all security groups. 

• Use port security and enable anti-spoofing features. 

• Encrypt data in transit between nodes using IPsec or TLS. 

• Segment management, data, and control traffic on separate VLANs. 

• Monitor traffic logs for anomalies and unauthorized scans. 

Barbican: Secret Management 

Barbican is OpenStack’s secret management service. It is responsible for storing and retrieving secrets such as passwords, encryption keys, certificates, and token signing keys. 

In a hardened OpenStack setup, Barbican provides centralized, auditable control over sensitive cryptographic material. 

Security Functions of Barbican 

Secure Secret Storage: 

Barbican allows services and users to securely store and retrieve secrets via REST APIs. Secrets can include: 

• TLS private keys 

• API tokens 

• Image signing keys 

• Encrypted volume keys 

Barbican stores these secrets in backends such as Hardware Security Modules (HSMs), KMIP-compatible systems, or encrypted software backends. 

Key Management with Key Encryption Keys (KEKs): 

To protect stored secrets, Barbican encrypts them using KEKs, which are securely stored and rotated. This enables defense-in-depth, especially in multi-tenant environments. 

Integration with Cinder and Glance: 

Barbican integrates with Cinder (block storage) and Glance (image service) to provide encryption at rest. For example: 

• Cinder can use Barbican to store volume encryption keys. 

• Glance can store image signing keys in Barbican to validate image authenticity. 

Access Control and Audit Logging: 

Access to secrets is strictly controlled via Keystone. Only authorized users and services can access specific secrets. Barbican also supports detailed audit logging for regulatory compliance and forensic analysis. 

Hardening Tips for Barbican: 

• Use HSM-backed key storage for high security environments. 

• Enforce RBAC policies to restrict secret access. 

• Enable TLS for all API traffic. 

• Rotate KEKs regularly and track secret access logs. 

• Limit secret TTL (time to live) when possible. 

Conclusion: Building a Hardened OpenStack Cloud 

Hardening an OpenStack environment is a multi-layered process that involves securing authentication (Keystone), network traffic (Neutron), and secrets (Barbican). Each component plays a pivotal role: 

• Keystone ensures only authenticated, authorized users can access cloud services. 

• Neutron isolates tenant networks and enforces strict traffic control at the instance level. 

• Barbican manages sensitive cryptographic material safely and efficiently. 

Combined with good operational hygiene, patching, and monitoring, these services form a robust foundation for building a secure OpenStack cloud. 

For organizations deploying OpenStack in production, understanding and configuring these components properly is essential. With proper hardening practices, OpenStack can offer not just flexibility and scale—but also enterprise-grade security.

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