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Secure service invocation with access control

When one app calls another over service invocation, Catalyst routes the request and authenticates the caller by its ID. By default, any app in a Catalyst project can invoke any other app. Service-invocation access control lets you lock this down: you declare which caller apps may invoke a target app — and which methods — and Catalyst denies everything else.

Access control is expressed as an access control list (ACL) inside a Catalyst Configuration resource that you attach to the target app. Unlike workflow access policies, there is no dedicated access-policy command — you manage a Configuration with the diagrid configuration commands (or a YAML manifest) and attach it to an app with diagrid appid update.

How access control works​

A Configuration's accessControl block has two parts:

  • defaultAction — the global default, allow or deny, applied when no caller policy matches.
  • policies — a list of per-caller rules. Each names a caller appId and can narrow access to specific operations (request paths and HTTP verbs).

Catalyst evaluates the caller's authenticated ID against these rules at the service-invocation boundary, before the request reaches the target app. A denied call is rejected with 403 Forbidden, and the target app never sees it.

Three behaviors to keep in mind:

  • No access control means open. If the target app has no Configuration with an accessControl block, every app in the project can invoke it. Attaching a deny-by-default configuration is what turns enforcement on.
  • Most specific rule wins. A matching operations rule takes precedence over the caller's defaultAction, which takes precedence over the global defaultAction.
  • IDs are authenticated, not asserted. A caller cannot spoof another app's ID — Catalyst authenticates it cryptographically during service invocation, so an allow-list is a real trust boundary.

Create and attach a policy​

The fastest way to create a policy is with the --default-action and --policy flags:

diagrid configuration create order-app-acl \
  --project my-project \
  --default-action deny \
  --policy orchestrator-app:allow \
  --policy reporting-app:allow

This creates a deny-by-default configuration that allows only orchestrator-app and reporting-app. Attach it to the target app so it takes effect on inbound traffic:

diagrid appid update order-app --project my-project --app-config order-app-acl

Now any other app that tries to invoke order-app is rejected with 403 Forbidden. The --policy appID:action flag is all-or-nothing per caller — it allows or denies every method. To restrict callers to specific methods, define the configuration as a YAML manifest.

Fine-grained rules with a YAML manifest​

To grant access to specific paths and verbs, declare operations on a caller and apply the manifest:

# order-app-acl.yaml
apiVersion: dapr.io/v1alpha1
kind: Configuration
metadata:
  name: order-app-acl
spec:
  accessControl:
    defaultAction: deny
    policies:
      - appId: orchestrator-app
        operations:
          - name: /orders
            httpVerb: ["POST"]
            action: allow
          - name: /orders/*
            httpVerb: ["GET"]
            action: allow
diagrid apply -f order-app-acl.yaml --project my-project
diagrid appid update order-app --project my-project --app-config order-app-acl

diagrid apply creates the configuration or replaces it in place, so you can re-run it as you iterate on the manifest. Here orchestrator-app can POST /orders and GET any /orders/{id} on order-app, and nothing else — every other caller and method is denied. Match the request path with name: an exact path like /orders, a single-segment wildcard like /orders/*, or a multi-segment wildcard like /orders/**/items. Set httpVerb to the methods the rule covers, or ["*"] for any method.

Start from deny by default​

For the strictest posture, apply a configuration whose global default is deny with no caller policies, then attach it. Every cross-app call to the target app is denied until you add an allow rule:

# deny-all.yaml
apiVersion: dapr.io/v1alpha1
kind: Configuration
metadata:
  name: order-app-acl
spec:
  accessControl:
    defaultAction: deny
diagrid apply -f deny-all.yaml --project my-project
diagrid appid update order-app --project my-project --app-config order-app-acl

From this baseline, layer in callers by editing the manifest and re-running diagrid apply -f. Apply one configuration per target app and keep its accessControl rules scoped to that app's callers.

Manage configurations​

List the configurations in a project:

diagrid configuration list --project my-project

Inspect a configuration, including its full ACL:

diagrid configuration get order-app-acl --project my-project -o yaml

Update a configuration with flags. The flags replace the corresponding fields, so the example below replaces all caller policies with a single grant for orchestrator-app:

diagrid configuration update order-app-acl \
  --project my-project \
  --policy orchestrator-app:allow

To change fine-grained rules, edit the YAML manifest and re-run diagrid apply -f order-app-acl.yaml. To stop enforcing access control, delete the configuration:

diagrid configuration delete order-app-acl --project my-project

Verify a policy​

To confirm a policy is enforced, invoke the target app from a caller that no rule allows. The caller receives a 403 Forbidden and the request never reaches order-app. Calls that match an allow rule continue to succeed.

note

Access control changes take 10–15 seconds to propagate after you apply the configuration or attach it to an app. If a caller is allowed or denied unexpectedly, wait and retry, and confirm the ID in the policy exactly matches the caller's ID (case-sensitive).

Next steps​

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