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Authentication

Virtual MCP implements a two-boundary authentication model that separates client authentication from backend authentication, giving you centralized control over access while supporting diverse backend requirements.

Two-boundary authentication model​

Boundary 1 (Incoming): Clients authenticate to Virtual MCP using the mechanism defined in the MCP specification. This is your organization's identity layer.

Boundary 2 (Outgoing): Virtual MCP obtains appropriate credentials for each backend. Each backend API receives a token or credential scoped to its requirements.

Incoming authentication​

Configure how clients authenticate to Virtual MCP.

Anonymous (development only)​

No authentication required. Use only for local development.

spec:
  incomingAuth:
    type: anonymous

OIDC authentication​

Validate tokens from an external identity provider.

Kubernetes service account tokens​

Authenticate using Kubernetes service account tokens for in-cluster clients.

Outgoing authentication​

Configure how Virtual MCP authenticates to backend MCP servers. Outgoing authentication is configured through MCPExternalAuthConfig resources.

When using discovery mode, Virtual MCP checks each backend MCPServer's externalAuthConfigRef to determine how to authenticate. If a backend has no auth config, Virtual MCP uses the specified default.

spec:
  outgoingAuth:
    source: discovered
    default:
      type: discovered

External auth config reference​

Reference an MCPExternalAuthConfig resource for specific backends:

spec:
  outgoingAuth:
    source: inline
    backends:
      github:
        type: external_auth_config_ref
        externalAuthConfigRef:
          name: github-auth

The MCPExternalAuthConfig resource defines the actual authentication strategy:

  • Token exchange: Exchange the client's token for a backend-specific token using RFC 8693
  • Header injection: Inject a static header value (such as an API key)

Authorization with Cedar​

Add fine-grained authorization using Cedar policies:

See Cedar policies for policy syntax.

Token caching​

Virtual MCP caches exchanged tokens to reduce latency and load on identity providers:

spec:
  tokenCache:
    provider: memory
    memory:
      maxEntries: 1000
      ttlOffset: 5m # Refresh 5 minutes before expiry

Example: Complete authentication setup​