debian-mirror-gitlab/doc/development/graphql_guide/authorization.md

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GraphQL Authorization

Authorizations can be applied in these places:

• Types:
  • Objects (all classes descending from ::Types::BaseObject)
  • Enums (all classes descending from ::Types::BaseEnum)
• Resolvers:
  • Field resolvers (all classes descending from ::Types::BaseResolver)
  • Mutations (all classes descending from ::Types::BaseMutation)
• Fields (all fields declared using the field DSL method)

Authorizations cannot be specified for abstract types (interfaces and unions). Abstract types delegate to their member types. Basic built in scalars (such as integers) do not have authorizations.

Our authorization system uses the same DeclarativePolicy system as throughout the rest of the application.

• For single values (such as Query.project), if the currently authenticated user fails the authorization, the field resolves to null.
• For collections (such as Project.issues), the collection is filtered to exclude the objects that the user's authorization checks failed against. This process of filtering (also known as redaction) happens after pagination, so some pages may be smaller than the requested page size, due to redacted objects being removed.

Also see authorizing resources in a mutation.

NOTE: The best practice is to load only what the currently authenticated user is allowed to view with our existing finders first, without relying on authorization to filter the records. This minimizes database queries and unnecessary authorization checks of the loaded records. It also avoids situations, such as short pages, which can expose the presence of confidential resources.

See authorization_spec.rb for examples of all the authorization schemes discussed here.

Type authorization

Authorize a type by passing an ability to the authorize method. All fields with the same type is authorized by checking that the currently authenticated user has the required ability.

For example, the following authorization ensures that the currently authenticated user can only see projects that they have the read_project ability for (so long as the project is returned in a field that uses Types::ProjectType):

module Types
  class ProjectType < BaseObject
    authorize :read_project
  end
end

You can also authorize against multiple abilities, in which case all of the ability checks must pass.

For example, the following authorization ensures that the currently authenticated user must have read_project and another_ability abilities to see a project:

module Types
  class ProjectType < BaseObject
    authorize [:read_project, :another_ability]
  end
end

Resolver authorization

Resolvers can have their own authorizations, which can be applied either to the parent object or to the resolved values.

An example of a resolver that authorizes against the parent is Resolvers::BoardListsResolver, which requires that the parent satisfy :read_list before it runs.

An example which authorizes against the resolved resource is Resolvers::Ci::ConfigResolver, which requires that the resolved value satisfy :read_pipeline.

To authorize against the parent, the resolver must opt in (because this was not the default value initially), by declaring this with authorizes_object!:

module Resolvers
  class MyResolver < BaseResolver
    authorizes_object!

    authorize :some_permission
  end
end

To authorize against the resolved value, the resolver must apply the authorization at some point, typically by using #authorized_find!(**args):

module Resolvers
  class MyResolver < BaseResolver
    authorize :some_permission

    def resolve(**args)
      authorized_find!(**args) # calls find_object
    end

    def find_object(id:)
      MyThing.find(id)
    end
  end
end

Of the two approaches, authorizing the object is more efficient, because it helps avoid unnecessary queries.

Field authorization

Fields can be authorized with the authorize option.

Fields authorization is checked against the current object, and authorization happens before resolution, which means that fields do not have access to the resolved resource. If you need to apply an authorization check to a field, you probably want to add authorization to the resolver, or ideally to the type.

For example, the following authorization ensures that the authenticated user must have administrator level access to the project to view the secretName field:

module Types
  class ProjectType < BaseObject
    field :secret_name, ::GraphQL::Types::String, null: true, authorize: :owner_access
  end
end

In this example, we use field authorization (such as Ability.allowed?(current_user, :read_transactions, bank_account)) to avoid a more expensive query:

module Types
  class BankAccountType < BaseObject
    field :transactions, ::Types::TransactionType.connection_type, null: true,
      authorize: :read_transactions
  end
end

Field authorization is recommended for:

• Scalar fields (strings, booleans, or numbers) that should have different levels of access controls to other fields.
• Object and collection fields where an access check can be applied to the parent to save the field resolution, and avoid individual policy checks on each resolved object.

Field authorization does not replace object level checks, unless the object precisely matches the access level of the parent project. For example, issues can be confidential, independent of the access level of the parent. Therefore, we should not use field authorization for Project.issue.

You can also authorize fields against multiple abilities. Pass the abilities as an array instead of as a single value:

module Types
  class MyType < BaseObject
    field :hidden_field, ::GraphQL::Types::Int,
      null: true,
      authorize: [:owner_access, :another_ability]
  end
end

The field authorization on MyType.hiddenField implies the following tests:

Ability.allowed?(current_user, :owner_access, object_of_my_type) &&
    Ability.allowed?(current_user, :another_ability, object_of_my_type)

Type and Field authorizations together

Authorizations are cumulative. In other words, the currently authenticated user may need to pass authorization requirements on both a field and a field's type.

In the following simplified example the currently authenticated user needs both first_permission on the user and second_permission on the issue to see the author of the issue.

class UserType
  authorize :first_permission
end

class IssueType
  field :author, UserType, authorize: :second_permission
end

The combination of the object authorization on UserType and the field authorization on IssueType.author implies the following tests:

Ability.allowed?(current_user, :second_permission, issue) &&
  Ability.allowed?(current_user, :first_permission, issue.author)