graphql-guard
This tiny gem provides a field-level authorization for graphql-ruby.
Contents
- Usage
- Priority order
- Error handling
- Integration
- Installation
- Development
- Contributing
- License
- Code of Conduct
Usage
Define a GraphQL schema:
# define a type
PostType = GraphQL::ObjectType.define do
name "Post"
field :id, !types.ID
field :title, !types.String
end
# define a query
QueryType = GraphQL::ObjectType.define do
name "Query"
field :posts, !types[PostType] do
argument :user_id, !types.ID
resolve ->(_obj, args, _ctx) { Post.where(user_id: args[:user_id]) }
end
end
# define a schema
Schema = GraphQL::Schema.define do
query QueryType
end
# execute query
GraphSchema.execute(query, variables: { user_id: 1 }, context: { current_user: current_user })
Inline policies
Add GraphQL::Guard
to your schema:
Schema = GraphQL::Schema.define do
query QueryType
use GraphQL::Guard.new # <======= ʘ‿ʘ
end
Now you can define guard
for a field, which will check permissions before resolving the field:
QueryType = GraphQL::ObjectType.define do
name "Query"
field :posts, !types[PostType] do
argument :user_id, !types.ID
guard ->(_obj, args, ctx) { args[:user_id] == ctx[:current_user].id } # <======= ʘ‿ʘ
...
end
end
You can also define guard
, which will be executed for all fields in the type:
PostType = GraphQL::ObjectType.define do
name "Post"
guard ->(_post, ctx) { ctx[:current_user].admin? } # <======= ʘ‿ʘ
...
end
If guard
block returns false
, then it'll raise a GraphQL::Guard::NotAuthorizedError
error.
Policy object
Alternatively, it's possible to describe all policies by using PORO (Plain Old Ruby Object), which should implement a guard
method. For example:
class GraphqlPolicy
RULES = {
QueryType => {
posts: ->(_obj, args, ctx) { args[:user_id] == ctx[:current_user].id }
},
PostType => {
'*': ->(_post, ctx) { ctx[:current_user].admin? }
}
}
def self.guard(type, field)
RULES.dig(type, field)
end
end
Pass this object to GraphQL::Guard
:
Schema = GraphQL::Schema.define do
query QueryType
use GraphQL::Guard.new(policy_object: GraphqlPolicy) # <======= ʘ‿ʘ
end
Priority order
GraphQL::Guard
will use the policy in the following order of priority:
- Inline policy on the field.
- Policy from the policy object on the field.
- Inline policy on the type.
- Policy from the policy object on the type.
class GraphqlPolicy
RULES = {
PostType => {
title: ->(_post, ctx) { ctx[:current_user].admin? }, # <======= 2
'*': ->(_post, ctx) { ctx[:current_user].admin? } # <======= 4
}
}
def self.guard(type, field)
RULES.dig(type, field)
end
end
PostType = GraphQL::ObjectType.define do
name "Post"
guard ->(_post, ctx) { ctx[:current_user].admin? } # <======= 3
field :title, !types.String, guard: ->(_post, _args, ctx) { ctx[:current_user].admin? } # <======= 1
end
Schema = GraphQL::Schema.define do
query QueryType
use GraphQL::Guard.new(policy_object: GraphqlPolicy)
end
Error handling
By default GraphQL::Guard
raises a GraphQL::Guard::NotAuthorizedError
exception if access to field is not authorized.
You can change this behavior, by passing custom not_authorized
lambda. For example:
SchemaWithoutExceptions = GraphQL::Schema.define do
query QueryType
use GraphQL::Guard.new(
# by default it raises an error
# not_authorized: ->(type, field) { raise GraphQL::Guard::NotAuthorizedError.new("#{type}.#{field}") }
# returns an error in the response
not_authorized: ->(type, field) { GraphQL::ExecutionError.new("Not authorized to access #{type}.#{field}") }
)
end
In this case executing a query will continue, but return nil
for not authorized field and also an array of errors
:
SchemaWithoutExceptions.execute("query { posts(user_id: 1) { id title } }")
# => {
# "data" => nil,
# "errors" => [{ "messages" => "Not authorized to access Query.posts", "locations": { ... }, "path" => ["posts"] }]
# }
Integration
You can simply reuse your existing policies if you really want. You don't need any monkey patches or magic for it ;)
CanCanCan
# define an ability
class Ability
include CanCan::Ability
def initialize(user)
user ||= User.new # guest user if not logged in
if user.admin?
can :manage, :all
else
can :read, Post, author_id: user.id
end
end
end
# use the ability in your guard policy object
class GraphqlPolicy
RULES = {
PostType => {
'*': ->(post, ctx) { ctx[:current_ability].can?(:read, post) },
}
}
def self.guard(type, field)
RULES.dig(type, field)
end
end
# pass the ability
GraphSchema.execute(query, context: { current_ability: Ability.new(current_user) })
Pundit
# define a policy
class PostPolicy < ApplicationPolicy
def show?
user.admin? || record. == user.id
end
end
# use the policy in your guard policy object
class GraphqlPolicy
RULES = {
PostType => {
'*': ->(post, ctx) { PostPolicy.new(ctx[:current_user], post).show? },
}
}
def self.guard(type, field)
RULES.dig(type, field)
end
end
Installation
Add this line to your application's Gemfile:
gem 'graphql-guard'
And then execute:
$ bundle
Or install it yourself as:
$ gem install graphql-guard
Development
After checking out the repo, run bin/setup
to install dependencies. Then, run rake spec
to run the tests. You can also run bin/console
for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run bundle exec rake install
. To release a new version, update the version number in version.rb
, and then run bundle exec rake release
, which will create a git tag for the version, push git commits and tags, and push the .gem
file to rubygems.org.
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/exAspArk/graphql-guard. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.
License
The gem is available as open source under the terms of the MIT License.
Code of Conduct
Everyone interacting in the Graphql::Guard project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.