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Permission Queries

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Permission queries allow you to express permissions by leveraging the power of GraphQL queries. This combination is a powerful concept and provides a great tool to express even complex permission scenarios in a simple form.

#The Graphcool permission schema

#Overview

All available queries in the GraphQL permission schema are derived from the available types and relations in your data model. The permisson schema leverages the familiar and powerful filter system that allows you to define very specific permissions.

For every type Type in your data model, the field SomeTypeExists(filter: TypeFilter): Boolean! is part of the permission schema. SomeTypeExists returns true only if the given filters match at least one existing Type node.

As an example, consider the following type definitions:

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type Post @model {
  id: ID! @isUnique # read-only (managed by Graphcool)
  title: String!
  author: User! @relation(name: "UsersPosts") 
}

type User @model {
  id: ID! @isUnique # read-only (managed by Graphcool)
  name: String!
  posts: [Post!]! @relation(name: "UsersPosts") 
}

The Query type from generated permission schema will look as follows:

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type Query {
  SomePostExists(filter: PostFilter, orderBy: PostOrderBy, skip: Int, after: String, before: String, first: Int, last: Int): Boolean!
  SomeUserExists(filter: UserFilter, orderBy: UserOrderBy, skip: Int, after: String, before: String, first: Int, last: Int): Boolean!
}

The PostFilter and UserFilter as well as PostOrderBy and UserOrderBy types are similar to the ones in the regular GraphQL API.

#Accessing the permission schema

Every Graphcool service comes with a dedicated endpoint for the permission schema. This endpoint is of the following form:

https://api.graph.cool/simple/v1/__SERVICE_ID__/permissions

To access it, you need to set the Authorization header in the request. Here is a sample request against the example schema above:

curl 'https://api.graph.cool/simple/v1/__SERVICE_ID__/permissions' \
-H 'Authorization: Bearer __PLATFORM_TOKEN__' \
-H 'Content-Type: application/json' \
-d '{"query":"{\n  SomePostExists\n}"}' 

#The execution and evaluation of permission queries

The execution of permission queries differs for read and write operations:

For read operations, all matching permission queries are executed and evaluated for every single node that is part of the response. For all write operations, all matching permission queries are executed and evaluated before the pending operation.

A permission query grants permission to an operation if and only if all top-level fields return true.

#Available GraphQL variables for permission queries

Depending on the pending operation, several GraphQL variables are available that can be used to influence the behaviour of a permission query.

You can't specify the values for these variables. You can only use the variables in the query itself.

#Custom variables

  • $now: DateTime! the current time as a DateTime

The $now variable is not available yet.

#Variables for type permissions

  • $node_id: ID! the id of the current node

  • $node_scalar the value of a scalar field on an existing node

  • $user_id: ID! the id of the authenticated user

  • $input_scalar the value of an input argument of a given mutation

#Variables for relation permissions

  • $leftType_id: ID!, $rightType_id: ID! the ids of the nodes to be connected or disconnected

For example, a relation with the two fields users: [User!]! and post: Post, will result in these variables:

  • usersUser_id: ID!
  • postPost_id: ID!

#Common authorization patterns

Permission queries can be used to express all common authorization patterns like role-based authorization, access control lists and ownership derived access. For more information check the full guide.

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