Pretender

As an admin, there are times you want to see exactly what another user sees. Meet Pretender.

• Easily switch between users
• Minimal code changes
• Plays nicely with Action Cable and auditing tools

:boom: Rock on

Pretender is flexible and lightweight - less than 100 lines of code :-)

Works with any authentication system - Devise, Authlogic, and Sorcery to name a few.

:tangerine: Battle-tested at Instacart

Installation

Add this line to your application’s Gemfile:

gem "pretender"

And add this to your ApplicationController:

class ApplicationController < ActionController::Base
  impersonates :user
end

How It Works

Sign in as another user with:

impersonate_user(user)

The current_user method now returns the impersonated user.

You can access the true user with:

true_user

And stop impersonating with:

stop_impersonating_user

Sample Implementation

Create a controller

class UsersController < ApplicationController
  before_action :require_admin! # your authorization method

  def index
    @users = User.order(:id)
  end

  def impersonate
    user = User.find(params[:id])
    impersonate_user(user)
    redirect_to root_path
  end

  def stop_impersonating
    stop_impersonating_user
    redirect_to root_path
  end
end

Add routes

resources :users, only: [:index] do
  post :impersonate, on: :member
  post :stop_impersonating, on: :collection
end

Create an index view

<ul>
  <% @users.each do |user| %>
    <li>Sign in as <%= link_to user.name, impersonate_user_path(user), method: :post %></li>
  <% end %>
</ul>

And show when someone is signed in as another user in your application layout

<% if current_user != true_user %>
  You (<%= true_user.name %>) are signed in as <%= current_user.name %>
  <%= link_to "Back to admin", stop_impersonating_users_path, method: :post %>
<% end %>

Audits

If you keep audit logs with a library like Audited, make sure it uses the true user.

Audited.current_user_method = :true_user

Action Cable

And add this to your ApplicationCable::Connection:

module ApplicationCable
  class Connection < ActionCable::Connection::Base
    identified_by :current_user, :true_user
    impersonates :user

    def connect
      self.current_user = find_verified_user
      reject_unauthorized_connection unless current_user
    end

    private

    def find_verified_user
      env["warden"].user # for Devise
    end
  end
end

The current_user method now returns the impersonated user in channels.

Configuration

Pretender is super flexible. You can change the names of methods and even impersonate multiple roles at the same time. Here’s the default configuration.

impersonates :user,
             method: :current_user,
             with: ->(id) { User.find_by(id: id) }

Mold it to fit your application.

impersonates :account,
             method: :authenticated_account,
             with: ->(id) { EnterpriseAccount.find_by(id: id) }

This creates three methods:

true_account
impersonate_account
stop_impersonating_account

History

View the changelog

Contributing

Everyone is encouraged to help improve this project. Here are a few ways you can help:

• Report bugs
• Fix bugs and submit pull requests
• Write, clarify, or fix documentation
• Suggest or add new features

To get started with development:

git clone https://github.com/ankane/pretender.git
cd pretender
bundle install
bundle exec rake test