Inherited roles¶

Introduction¶

An inherited role is a way to create a new role which infers permissions from two or more non-inherited roles. Once an inherited role is created, it can be treated as any other role i.e. can be given in X-Hasura-Role session variable.

Inherited roles are useful when you need to define multiple permission rules (may be overlapping) on schema objects and also for greater modularity in role management.

Creating inherited roles¶

Console

CLI

API

Go to the Settings tab (⚙) on the console and click on Inherited Roles.

To add a new inherited role, edit the metadata/inherited_roles.yaml file adding the inherited role definition like this:

- role_name: sample_inherited_role
  role_set:
    - user
    - editor

Apply the metadata by running:

hasura metadata apply

You can add a inherited role using the add_inherited_role metadata API:

POST /v1/metadata HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
  "type": "add_inherited_role",
  "args": {
     "role_name":"sample_inherited_role",
     "role_set":[
        "user",
        "editor"
     ]
  }
}

How is the permission of the inherited role inferred?¶

A select permission is comprised of the following things:

1. Columns accessible to the role
2. Row selection filter
3. Limit
4. Allow aggregation
5. Scalar computed fields accessible to the role

Suppose there are two roles, role1 gives access to column C1 with row filter P1 and role2 gives access to columns C1 and C2 with row filter P2. Consider the following GraphQL query executed with an inherited role comprised of role1 and role2:

query {
  T {
    C1
    C2
  }
}

The above GraphQL query will be translated to the following SQL query.

select (case when (P1 or P2) then C1 else null end) as C1,
       (case when P2 then C2 else null end) as C2
from T
where (P1 or P2)

The other parameters of the select permission will be combined in the following manner:

1. Limit - Maximum of the limits will be the limit of the inherited role
2. Allow aggregations - If any of the role allows aggregation, then the inherited role will allow aggregation
3. Scalar computed fields - same as table column fields, as in the above example

Examples¶

Let’s take the example of an users table with the following columns:

1. id - Int - Primary key
2. name - Text
3. email - Text

There are two roles defined namely employee and manager.

1. User role - The user role will be able to access all columns of their row when the session variable X-Hasura-User-Id is equal to the id.
2. Anonymous role - The anonymous role will be able to access only the id and name columns of all the users.

Let’s create a new inherited role called user_anonymous_inherited_role which inherits from the user and the anonymous roles.

1. Executing the query as user role

POST /v1/graphql HTTP/1.1
Content-Type: application/json
X-Hasura-Role: user
X-Hasura-User-Id: 1

query {
   users {
     id
     name
     email
   }
 }

2. Executing the query as anonymous role

POST /v1/graphql HTTP/1.1
Content-Type: application/json
X-Hasura-Role: anonymous

query {
   users {
     id
     name
   }
 }

3. Executing the query as user_anonymous_inherited_role role

POST /v1/graphql HTTP/1.1
Content-Type: application/json
X-Hasura-Role: user_anonymous_inherited_role
X-Hasura-User-Id: 1

query {
  users {
    id
    name
    email
  }
}

In the response of the query being executed with the user_anonymous_inherited_role role, there are 3 rows returned and if we compare that to the queries executed as the user and anonymous roles, the results are unioned in the inherited role. But some of the fields have null values despite the value in the database not being null. This can only happen with inherited roles when a column doesn’t have permission in the particular row. In the above example, we see that the email of “Bob” and “Sam” is null but a non null value for “Alice”, this is because the “Alice” row is executed as the user role and the other rows are executed as the anonymous role which is why is why the value is null.

4. Suppose we have two tables users and authors and similarly two roles user and author are defined. The user role doesn’t have permission to query the authors table and the author role doesn’t have permission to query the users table. With only the user and the author role, we won’t be able to construct a query which fetches data from both the tables. This can be solved by creating an inherited role out of user and author which can query both the tables in a single query.

POST /v1/graphql HTTP/1.1
Content-Type: application/json
X-Hasura-Role: user_authors_inherited_role
X-Hasura-User-Id: 1

query {
  users {
    id
    name
    email
  }
  authors {
    id
    name
    followers
  }
}

Present limitations¶

Currently, inherited roles are supported only for Postgres read queries and subscriptions. The following features are not supported for inherited roles yet:

1. Mutations
2. Actions
3. Remote schemas