graphql-guard

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This gem provides a field-level authorization for graphql-ruby.

Contents

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
  <b>use GraphQL::Guard.new</b>
end

Now you can define guard for a field, which will check permissions before resolving the field:


QueryType = GraphQL::ObjectType.define do
  name "Query"

  <b>field :posts</b>, !types[PostType] do
    argument :user_id, !types.ID
    <b>guard ->(obj, args, ctx) {</b> args[:user_id] == ctx[:current_user].id <b>}</b>
    ...
  end
end

You can also define guard, which will be executed for every * field in the type:


PostType = GraphQL::ObjectType.define do
  name "Post"
  <b>guard ->(obj, args, ctx) {</b> ctx[:current_user].admin? <b>}</b>
  ...
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 <b>GraphqlPolicy</b>
  RULES = {
    QueryType => {
      <b>posts: ->(obj, args, ctx) {</b> args[:user_id] == ctx[:current_user].id <b>}</b>
    },
    PostType => {
      <b>'*': ->(obj, args, ctx) {</b> ctx[:current_user].admin? <b>}</b>
    }
  }

  def self.<b>guard(type, field)</b>
    RULES.dig(type, field)
  end
end

Pass this object to GraphQL::Guard:


Schema = GraphQL::Schema.define do
  query QueryType
  use GraphQL::Guard.new(<b>policy_object: GraphqlPolicy</b>)
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.
  4. Policy from the policy object on the type.

class <b>GraphqlPolicy</b>
  RULES = {
    PostType => {
      <b>'*': ->(obj, args, ctx) {</b> ctx[:current_user].admin? <b>}</b>,                           # <=== <b>4</b>
      <b>title: ->(obj, args, ctx) {</b> ctx[:current_user].admin? <b>}</b>                          # <=== <b>2</b>
    }
  }

  def self.guard(type, field)
    RULES.dig(type, field)
  end
end

PostType = GraphQL::ObjectType.define do
  name "Post"
  <b>guard ->(obj, args, ctx) {</b> ctx[:current_user].admin? <b>}</b>                               # <=== <b>3</b>
  <b>field :title</b>, !types.String, <b>guard: ->(obj, args, ctx) {</b> ctx[:current_user].admin? <b>}</b> # <=== <b>1</b>
end

Schema = GraphQL::Schema.define do
  query QueryType
  use GraphQL::Guard.new(<b>policy_object: GraphqlPolicy</b>)
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:


SchemaWithErrors = GraphQL::Schema.define do
  query QueryType
  use GraphQL::Guard.new(
    # Returns an error in the response
    <b>not_authorized: ->(type, field) { GraphQL::ExecutionError.new("Not authorized to access #{type}.#{field}") }</b>

    # By default it raises an error
    # not_authorized: ->(type, field) { raise GraphQL::Guard::NotAuthorizedError.new("#{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 { <b>posts</b>(user_id: 1) { id title } }")
# => {
#   "data" => <b>nil</b>,
#   "errors" => [{ "messages" => <b>"Not authorized to access Query.posts"</b>, "locations": { ... }, "path" => [<b>"posts"</b>] }]
# }

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 <b>Ability</b>
  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"
  <b>guard ->(post, args, ctx) { ctx[:current_ability].can?(:read, post) }</b>
  ...
end

# Pass the ability
GraphSchema.execute(query, context: { <b>current_ability: Ability.new(current_user)</b> })

Pundit


# Define a policy
class <b>PostPolicy</b> < 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"
  <b>guard ->(post, args, ctx) { PostPolicy.new(ctx[:current_user], post).show? }</b>
  ...
end

# Pass current_user
GraphSchema.execute(query, context: { <b>current_user: current_user</b> })

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
QueryType = GraphQL::ObjectType.define do
  name "Query"
  <b>field :posts</b>, !types[PostType], <b>guard ->(obj, args, ctx) {</b> ... <b>}</b>
end

# Your test
<b>require "graphql/guard/testing"</b>

posts = QueryType.<b>field_with_guard('posts')</b>
result = posts.<b>guard(obj, args, ctx)</b>
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"
  <b>field :posts</b>, !types[PostType]
end

# Your policy object
class <b>GraphqlPolicy</b>
  def self.<b>guard</b>(type, field)
    <b>->(obj, args, ctx) {</b> ... <b>}</b>
  end
end

# Your test
<b>require "graphql/guard/testing"</b>

posts = QueryType.<b>field_with_guard('posts', GraphqlPolicy)</b>
result = posts.<b>guard(obj, args, ctx)</b>
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.