AttributeExt provides additional access control for rails model attributes.

Date-granular history for specified model fields. Compact & easy to query.

An association extension for attr_json

Active Record extention to sanitize your inputspec.

Views and controls for audited records

Logs of model changes, including nested attributes.

Opinionated app strategy used for authentication & role-based authorization.

A rails authentication and authorization engine that reduces clutter in your controllers and views. Includes aliased link_to and button_to helpers that return an empty string if the current user is not permitted to follow the link. ...

Devise + Omniauth Authentication encapsulated in an Engine. Uses Devise. Parts taken from perens-instant-user and sso-devise-omniauth-provider

Authentication via JWT (with encryption)

Auth for your Rails application

Bushido support for Authlogic

Cloudfuji support for Authlogic

AuthNetReceiver is an endpoint and processor for Authorize.Net Silent Post transactions

Rails engine to add IndieAuth authentication endpoint functionality

A description of a really simple authorization plugin for Rails.

A gem for rails giving vast flexibility in authorization management.

Minimalistic authorization library for Ruby on Rails applications.

Authorization that includes basic authorization and 3 social authorization with Latvia social network draugiem.lv, facebook.com and twitter.com.

A simple authentication provider for Ruby/Rails app. Designed for mobile clients and is compatible with the OAuth 2.0 specification.