Add REST API for creating an account

The method is available to apps with a token obtained via the client
credentials grant. It creates a user and account records, as well as
an access token for the app that initiated the request. The user is
unconfirmed, and an e-mail is sent as usual.

The method returns the access token, which the app should save for
later. The REST API is not available to users with unconfirmed
accounts, so the app must be smart to wait for the user to click a
link in their e-mail inbox.

The method is rate-limited by IP to 5 requests per 30 minutes.

app/controllers/api/base_controller.rb

@@ -68,7 +68,7 @@ class Api::BaseController < ApplicationController
   end
 
   def require_user!
-    if current_user && !current_user.disabled?
+    if current_user && !current_user.disabled? && current_user.confirmed?
       set_user_activity
     elsif current_user
       render json: { error: 'Your login is currently disabled' }, status: 403

app/controllers/api/v1/accounts_controller.rb

@@ -1,13 +1,14 @@
 # frozen_string_literal: true
 
 class Api::V1::AccountsController < Api::BaseController
-  before_action -> { authorize_if_got_token! :read, :'read:accounts' }, except: [:follow, :unfollow, :block, :unblock, :mute, :unmute]
+  before_action -> { authorize_if_got_token! :read, :'read:accounts' }, except: [:create, :follow, :unfollow, :block, :unblock, :mute, :unmute]
   before_action -> { doorkeeper_authorize! :follow, :'write:follows' }, only: [:follow, :unfollow]
   before_action -> { doorkeeper_authorize! :follow, :'write:mutes' }, only: [:mute, :unmute]
   before_action -> { doorkeeper_authorize! :follow, :'write:blocks' }, only: [:block, :unblock]
+  before_action -> { doorkeeper_authorize! }, only: [:create]
 
-  before_action :require_user!, except: [:show]
-  before_action :set_account
+  before_action :require_user!, except: [:show, :create]
+  before_action :set_account, except: [:create]
   before_action :check_account_suspension, only: [:show]
 
   respond_to :json
@@ -16,6 +17,16 @@ class Api::V1::AccountsController < Api::BaseController
     render json: @account, serializer: REST::AccountSerializer
   end
 
+  def create
+    token    = AppSignUpService.new.call(doorkeeper_token.application, account_params)
+    response = Doorkeeper::OAuth::TokenResponse.new(token)
+
+    headers.merge!(response.headers)
+
+    self.response_body = Oj.dump(response.body)
+    self.status        = response.status
+  end
+
   def follow
     FollowService.new.call(current_user.account, @account, reblogs: truthy_param?(:reblogs))
 
@@ -62,4 +73,8 @@ class Api::V1::AccountsController < Api::BaseController
   def check_account_suspension
     gone if @account.suspended?
   end
+
+  def account_params
+    params.permit(:username, :email, :password)
+  end
 end

app/services/app_sign_up_service.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class AppSignUpService < BaseService
+  def call(app, params)
+    return unless allowed_registrations?
+
+    user_params    = params.slice(:email, :password)
+    account_params = params.slice(:username)
+    user           = User.create!(user_params.merge(password_confirmation: user_params[:password], account_attributes: account_params))
+
+    Doorkeeper::AccessToken.create!(application: app,
+                                    resource_owner_id: user.id,
+                                    scopes: app.scopes,
+                                    expires_in: Doorkeeper.configuration.access_token_expires_in,
+                                    use_refresh_token: Doorkeeper.configuration.refresh_token_enabled?)
+  end
+
+  private
+
+  def allowed_registrations?
+    Setting.open_registrations && !Rails.configuration.x.single_user_mode
+  end
+end

config/initializers/rack_attack.rb

@@ -57,6 +57,10 @@ class Rack::Attack
     req.authenticated_user_id if req.post? && req.path.start_with?('/api/v1/media')
   end
 
+  throttle('throttle_api_sign_up', limit: 5, period: 30.minutes) do |req|
+    req.ip if req.post? && req.path == '/api/v1/accounts'
+  end
+
   throttle('protected_paths', limit: 25, period: 5.minutes) do |req|
     req.ip if req.post? && req.path =~ PROTECTED_PATHS_REGEX
   end

config/routes.rb

@@ -328,7 +328,7 @@ Rails.application.routes.draw do
         resources :relationships, only: :index
       end
 
-      resources :accounts, only: [:show] do
+      resources :accounts, only: [:create, :show] do
         resources :statuses, only: :index, controller: 'accounts/statuses'
         resources :followers, only: :index, controller: 'accounts/follower_accounts'
         resources :following, only: :index, controller: 'accounts/following_accounts'

spec/services/app_sign_up_service_spec.rb

@@ -0,0 +1,41 @@
+require 'rails_helper'
+
+RSpec.describe AppSignUpService, type: :service do
+  let(:app) { Fabricate(:application, scopes: 'read write') }
+  let(:good_params) { { username: 'alice', password: '12345678', email: 'good@email.com' } }
+
+  subject { described_class.new }
+
+  describe '#call' do
+    it 'returns nil when registrations are closed' do
+      Setting.open_registrations = false
+      expect(subject.call(app, good_params)).to be_nil
+    end
+
+    it 'raises an error when params are missing' do
+      expect { subject.call(app, {}) }.to raise_error ActiveRecord::RecordInvalid
+    end
+
+    it 'creates an unconfirmed user with access token' do
+      access_token = subject.call(app, good_params)
+      expect(access_token).to_not be_nil
+      user = User.find_by(id: access_token.resource_owner_id)
+      expect(user).to_not be_nil
+      expect(user.confirmed?).to be false
+    end
+
+    it 'creates access token with the app\'s scopes' do
+      access_token = subject.call(app, good_params)
+      expect(access_token).to_not be_nil
+      expect(access_token.scopes.to_s).to eq 'read write'
+    end
+
+    it 'creates an account' do
+      access_token = subject.call(app, good_params)
+      expect(access_token).to_not be_nil
+      user = User.find_by(id: access_token.resource_owner_id)
+      expect(user).to_not be_nil
+      expect(user.account).to_not be_nil
+    end
+  end
+end