# graphql-guard
[](https://travis-ci.org/exAspArk/graphql-guard)
[](https://coveralls.io/github/exAspArk/graphql-guard)
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[](https://rubygems.org/gems/graphql-guard)
[](https://rubygems.org/gems/graphql-guard)
This gem provides a field-level authorization for [graphql-ruby](https://github.com/rmosolgo/graphql-ruby).
## Contents
* [Usage](#usage)
* [Inline policies](#inline-policies)
* [Policy object](#policy-object)
* [Priority order](#priority-order)
* [Integration](#integration)
* [CanCanCan](#cancancan)
* [Pundit](#pundit)
* [Error handling](#error-handling)
* [Schema masking](#schema-masking)
* [Installation](#installation)
* [Testing](#testing)
* [Development](#development)
* [Contributing](#contributing)
* [License](#license)
* [Code of Conduct](#code-of-conduct)
## Usage
Define a GraphQL schema:
```ruby
# 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
Schema.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
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 }
...
end
end
You can also define `guard`, which will be executed for every `*` field in the type:
PostType = GraphQL::ObjectType.define do
name "Post"
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`:
Schema = GraphQL::Schema.define do
query QueryType
use GraphQL::Guard.new(policy_object: GraphqlPolicy)
end
When using a policy object, you may want to allow [introspection queries](http://graphql.org/learn/introspection/) 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:
1. Inline policy on the field.
2. Policy from the policy object on the field.
3. Inline policy on the type.
2. 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
PostType = GraphQL::ObjectType.define do
name "Post"
guard ->(obj, args, ctx) { ctx[:current_user].admin? } # <=== 3
field :title, !types.String, guard: ->(obj, args, ctx) { ctx[:current_user].admin? } # <=== 1
end
Schema = GraphQL::Schema.define do
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
PostType = GraphQL::ObjectType.define do
name "Post"
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
PostType = GraphQL::ObjectType.define do
name "Post"
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:
SchemaWithErrors = 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`:
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
Schema = GraphQL::Schema.define do
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:
PostType = GraphQL::ObjectType.define do
name "Post"
field :id, !types.ID
field :title, types.String 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:
```ruby
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
QueryType = GraphQL::ObjectType.define do
name "Query"
field :posts, !types[!PostType], 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
QueryType = GraphQL::ObjectType.define do
name "Query"
field :posts, !types[!PostType]
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](https://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](http://contributor-covenant.org) code of conduct.
## License
The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).
## 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](https://github.com/exAspArk/graphql-guard/blob/master/CODE_OF_CONDUCT.md).