Tenant Isolation

Tenant isolation network policies ensure that workloads running in different tenant namespaces cannot communicate with each other. This is a critical security boundary in the MATIH multi-tenant architecture, preventing data leakage and unauthorized access between tenant environments.

Isolation Model

The MATIH platform supports two tenant isolation levels:

Level	Network Isolation	Compute Isolation	Data Isolation
Namespace-isolated	NetworkPolicy per namespace	Shared nodes, resource quotas	Separate databases/schemas
Dedicated	NetworkPolicy + dedicated nodes	Dedicated node pool	Dedicated database instances

Default Deny Policy

Each tenant namespace starts with a default deny-all policy:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-all
  namespace: tenant-acme
spec:
  podSelector: {}
  policyTypes:
    - Ingress
    - Egress
  ingress: []
  egress: []

This ensures that no traffic flows to or from the tenant namespace until explicit allow rules are created.

Tenant-to-Shared-Service Access

Tenant workloads can access shared platform services through explicit egress rules:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-shared-services
  namespace: tenant-acme
spec:
  podSelector: {}
  policyTypes:
    - Egress
  egress:
    # DNS
    - to:
        - namespaceSelector: {}
          podSelector:
            matchLabels:
              k8s-app: kube-dns
      ports:
        - protocol: UDP
          port: 53
 
    # API Gateway
    - to:
        - namespaceSelector:
            matchLabels:
              name: matih-system
          podSelector:
            matchLabels:
              app: api-gateway
      ports:
        - protocol: TCP
          port: 8080
 
    # AI Service
    - to:
        - namespaceSelector:
            matchLabels:
              name: matih-data-plane
          podSelector:
            matchLabels:
              app: ai-service
      ports:
        - protocol: TCP
          port: 8000

Cross-Tenant Denial

The critical isolation rule prevents any tenant from reaching another tenant namespace:

Source	Destination	Allowed
tenant-acme	tenant-acme	Yes (intra-namespace)
tenant-acme	tenant-beta	No (blocked)
tenant-acme	matih-system	Limited (API Gateway only)
tenant-acme	matih-data-plane	Limited (shared services only)
tenant-acme	matih-monitoring	No
matih-data-plane	tenant-acme	Limited (ingress controller only)

Ingress to Tenant Services

Tenant-specific services receive traffic only through the dedicated tenant ingress controller:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-tenant-ingress
  namespace: tenant-acme
spec:
  podSelector:
    matchLabels:
      app: tenant-frontend
  policyTypes:
    - Ingress
  ingress:
    - from:
        - namespaceSelector:
            matchLabels:
              name: tenant-acme
          podSelector:
            matchLabels:
              app: ingress-nginx
      ports:
        - protocol: TCP
          port: 3000

Label Requirements

Tenant isolation depends on correct namespace labels:

Label	Purpose	Example
`name`	Namespace name reference	`name: tenant-acme`
`matih.io/tenant-id`	Tenant identifier	`matih.io/tenant-id: acme`
`matih.io/namespace-type`	Namespace category	`matih.io/namespace-type: tenant`
`matih.io/isolation-level`	Isolation tier	`matih.io/isolation-level: namespace`

Provisioning Integration

Network policies are created automatically during tenant provisioning:

Tenant Service creates the namespace with required labels
Default deny policy is applied
Shared service egress rules are created
Tenant ingress policy is created
Connectivity is validated

Verification

Tenant isolation can be verified using the validation script:

./scripts/tools/validate-tenant-ingress.sh --tenant acme

Troubleshooting

Issue	Symptom	Resolution
Tenant cannot access AI service	Connection timeout	Verify egress rule to matih-data-plane
Cross-tenant data leak	Unauthorized namespace access	Check default-deny policy exists
Missing namespace labels	Policies not matching	Verify namespace labels with expected values
Ingress not working	Tenant frontend unreachable	Check ingress controller pod labels

Egress Policies Autoscaling