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Authorization

The NATS server supports authorization using subject-level permissions on a per-user basis. Permission-based authorization is available with multi-user authentication via the users list.

Each permission specifies the subjects the user can publish to and subscribe to. The parser is generous at understanding what the intent is, so both arrays and singletons are processed. For more complex configuration, you can specify a permission object which explicitly allows or denies subjects. The specified subjects can specify wildcards. Permissions can make use of variables.

You configure authorization by creating a permissions entry in the authorization object.

Permissions Configuration Map

The permissions map specify subjects that can be subscribed to or published by the specified client.

Permission Map

The permission map provides additional properties for configuring a permissions map. Instead of providing a list of subjects that are allowed, the permission map allows you to explicitly list subjects you want toallow or deny:

Important Note NATS Authorizations can be allow lists, deny lists, or both. It is important to not break request/reply patterns. In some cases (as shown below) you need to add rules as above with Alice and Bob for the _INBOX.> pattern. If an unauthorized client publishes or attempts to subscribe to a subject that has not been allow listed, the action fails and is logged at the server, and an error message is returned to the client.

Example

Here is an example authorization configuration that uses variables which defines four users, three of whom are assigned explicit permissions.

authorization {
  ADMIN = {
    publish = ">"
    subscribe = ">"
  }
  REQUESTOR = {
    publish = ["req.a", "req.b"]
    subscribe = "_INBOX.>"
  }
  RESPONDER = {
    subscribe = ["req.a", "req.b"]
    publish = "_INBOX.>"
  }
  DEFAULT_PERMISSIONS = {
    publish = "SANDBOX.*"
    subscribe = ["PUBLIC.>", "_INBOX.>"]
  }
  users = [
    {user: admin,   password: $ADMIN_PASS, permissions: $ADMIN}
    {user: client,  password: $CLIENT_PASS, permissions: $REQUESTOR}
    {user: service,  password: $SERVICE_PASS, permissions: $RESPONDER}
    {user: other, password: $OTHER_PASS}
  ]
}

DEFAULT_PERMISSIONS is a special permissions name. If defined, it applies to all users that don't have specific permissions set.

• admin has ADMIN permissions and can publish/subscribe on any subject. We use the wildcard > to match any subject.

• client is a REQUESTOR and can publish requests on subjects req.a or req.b, and subscribe to anything that is a response (_INBOX.>).

• service is a RESPONDER to req.a and req.b requests, so it needs to be able to subscribe to the request subjects and respond to client's that can publish requests to req.a and req.b. The reply subject is an inbox. Typically inboxes start with the prefix _INBOX. followed by a generated string. The _INBOX.> subject matches all subjects that begin with _INBOX..

• other has no permissions granted and therefore inherits the default permission set. You set the inherited default permissions by assigning them to the default_permissions entry inside of the authorization configuration block.

Note that in the above example, any client with permissions to subscribe to _INBOX.> can receive all responses published. More sensitive installations will want to add or subset the prefix to further limit subjects that a client can subscribe. Alternatively, Accounts allow complete isolation limiting what members of an account can see.

Here's another example, where the allow and deny options are specified:

authorization: {
    users = [
        {
            user: admin
            password: secret
            permissions: {
                publish: ">"
                subscribe: ">"
            }
        }
        { 
            user: test
            password: test
            permissions: {
                publish: {
                    deny: ">"
                }, 
                subscribe: {
                    allow: "client.>"
                }
            }
        }
    ]
}