graphql-guard
This gem provides a field-level authorization for graphql-ruby.
Contents
- Usage
- Inline policies
- Policy object
- Priority order
- Integration
- CanCanCan
- Pundit
- Error handling
- Schema masking
- Installation
- Testing
- Development
- Contributing
- License
- Code of Conduct
Usage
Define a GraphQL schema:
# Define a type
class PostType < GraphQL::Schema::Object
field :id, ID, null: false
field :title, String, null: true
end
# Define a query
class QueryType < GraphQL::Schema::Object
field :posts, [PostType], null: false do
argument :user_id, ID, required: true
end
def posts(user_id:)
Post.where(user_id: user_id)
end
end
# Define a schema
class Schema < GraphQL::Schema
use GraphQL::Execution::Interpreter
use GraphQL::Analysis::AST
query QueryType
end
# Execute query
Schema.execute(query, variables: { userId: 1 }, context: { current_user: current_user })
Inline policies
Add GraphQL::Guard
to your schema:
class Schema < GraphQL::Schema use GraphQL::Execution::Interpreter use GraphQL::Analysis::AST query QueryType use GraphQL::Guard.new end
Now you can define guard
for a field, which will check permissions before resolving the field:
class QueryType < GraphQL::Schema::Object field :posts, [PostType], null: false do argument :user_id, ID, required: true guard ->(obj, args, ctx) { args[:user_id] == ctx[:current_user].id } end ... end
You can also define guard
, which will be executed for every *
field in the type:
class PostType < GraphQL::Schema::Object guard ->(obj, args, ctx) { ctx[:current_user].admin? } ... end
If guard
block returns nil
or false
, then it'll raise a GraphQL::Guard::NotAuthorizedError
error.
Policy object
Alternatively, it's possible to extract and 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 => { '*': ->(obj, args, ctx) { ctx[:current_user].admin? } } } def self.guard(type, field) RULES.dig(type, field) end end
Pass this object to GraphQL::Guard
:
class Schema < GraphQL::Schema use GraphQL::Execution::Interpreter use GraphQL::Analysis::AST query QueryType use GraphQL::Guard.new(policy_object: GraphqlPolicy) end
When using a policy object, you may want to allow introspection queries to skip authorization. A simple way to avoid having to whitelist every introspection type in the RULES
hash of your policy object is to check the type
parameter in the guard
method:
def self.guard(type, field) type.introspection? ? ->(_obj, _args, _ctx) { true } : RULES.dig(type, field) # or "false" to restrict an access 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 => { '*': ->(obj, args, ctx) { ctx[:current_user].admin? }, # <=== 4 title: ->(obj, args, ctx) { ctx[:current_user].admin? } # <=== 2 } } def self.guard(type, field) RULES.dig(type, field) end end class PostType < GraphQL::Schema::Object guard ->(obj, args, ctx) { ctx[:current_user].admin? } # <=== 3 field :title, String, null: true, guard: ->(obj, args, ctx) { ctx[:current_user].admin? } # <=== 1 end class Schema < GraphQL::Schema use GraphQL::Execution::Interpreter use GraphQL::Analysis::AST query QueryType use GraphQL::Guard.new(policy_object: GraphqlPolicy) end
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 if user.admin? can :manage, :all else can :read, Post, author_id: user.id end end end # Use the ability in your guard class PostType < GraphQL::Schema::Object guard ->(post, args, ctx) { ctx[:current_ability].can?(:read, post) } ... end # Pass the ability Schema.execute(query, context: { current_ability: Ability.new(current_user) })
Pundit
# Define a policy class PostPolicy < ApplicationPolicy def show? user.admin? || record.author_id == user.id end end # Use the ability in your guard class PostType < GraphQL::Schema::Object guard ->(post, args, ctx) { PostPolicy.new(ctx[:current_user], post).show? } ... end # Pass current_user Schema.execute(query, context: { current_user: current_user })
Error handling
By default GraphQL::Guard
raises a GraphQL::Guard::NotAuthorizedError
exception if access to the field is not authorized.
You can change this behavior, by passing custom not_authorized
lambda. For example:
class SchemaWithErrors < GraphQL::Schema use GraphQL::Execution::Interpreter use GraphQL::Analysis::AST query QueryType use GraphQL::Guard.new( # By default it raises an error # not_authorized: ->(type, field) do # raise GraphQL::Guard::NotAuthorizedError.new("#{type}.#{field}") # end # Returns an error in the response not_authorized: ->(type, field) do GraphQL::ExecutionError.new("Not authorized to access #{type}.#{field}") end ) end
In this case executing a query will continue, but return nil
for not authorized field and also an array of errors
:
SchemaWithErrors.execute("query { posts(user_id: 1) { id title } }") # => { # "data" => nil, # "errors" => [{ # "messages" => "Not authorized to access Query.posts", # "locations": { "line" => 1, "column" => 9 }, # "path" => ["posts"] # }] # }
In more advanced cases, you may want not to return errors
only for some unauthorized fields. Simply return nil
if user is not authorized to access the field. You can achieve it, for example, by placing the logic into your PolicyObject
:
class GraphqlPolicy RULES = { PostType => { '*': { guard: ->(obj, args, ctx) { ... }, not_authorized: ->(type, field) { GraphQL::ExecutionError.new("Not authorized to access #{type}.#{field}") } } title: { guard: ->(obj, args, ctx) { ... }, not_authorized: ->(type, field) { nil } # simply return nil if not authorized, no errors } } } def self.guard(type, field) RULES.dig(type, field, :guard) end def self.not_authorized_handler(type, field) RULES.dig(type, field, :not_authorized) || RULES.dig(type, :'*', :not_authorized) end end class Schema < GraphQL::Schema use GraphQL::Execution::Interpreter use GraphQL::Analysis::AST query QueryType mutation MutationType use GraphQL::Guard.new( policy_object: GraphqlPolicy, not_authorized: ->(type, field) { handler = GraphqlPolicy.not_authorized_handler(type, field) handler.call(type, field) } ) end
Schema masking
It's possible to hide fields from being introspectable and accessible based on the context. For example:
class PostType < GraphQL::Schema::Object field :id, ID, null: false field :title, String, null: true do # The field "title" is accessible only for beta testers mask ->(ctx) { ctx[:current_user].beta_tester? } 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
Testing
It's possible to test fields with guard
in isolation:
# Your type class QueryType < GraphQL::Schema::Object field :posts, [PostType], null: false, guard ->(obj, args, ctx) { ... } end # Your test require "graphql/guard/testing" posts = QueryType.field_with_guard('posts') result = posts.guard(obj, args, ctx) expect(result).to eq(true)
If you would like to test your fields with policy objects:
# Your type class QueryType < GraphQL::Schema::Object field :posts, [PostType], null: false end # Your policy object class GraphqlPolicy def self.guard(type, field) ->(obj, args, ctx) { ... } end end # Your test require "graphql/guard/testing" posts = QueryType.field_with_guard('posts', GraphqlPolicy) result = posts.guard(obj, args, ctx) expect(result).to eq(true)
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.