Doorkeeper is an OAuth 2 provider for Rails and Grape.

Doorkeeper is an OAuth 2 provider for Rails.

Generic, Configurable OmniAuth Strategy for OAuth2 providers

Warden strategy for OAuth provider

Makes it easy(er) to make an oauth provider.

Simple OAuth 2.0 provider toolkit

There are plenty of gems out there that deal with being an OAuth2 "consumer", where you redirect users to an OAuth2 "provider", allowing you to hand off authentication to a separate service. There are also plenty of gems that set you up as your own OAuth2 provider. ***BUT***, what happens when you want to separate your "authentication" server from your "resource" server? This gem is meant to be used on an API "resource" server, where you want to accept OAuth Access Tokens from a client, and validate them against a separate "authentication" server. This communication is outside the scope of the official OAuth 2 spec, but there is a need for it anyway.

A Rails Engine that allow the site to act as an OAuth provider

Wechat oauth2 provider for sorcery

Couchbase OAuth2 Provider using Couchbase

OAuth2 Provider, extracted from api.hashblue.com

Rack middleware for OAuth2 Provider Server Based on Couchdb

A simple implementation of provider protocols of oAuth 2.0 (right now just AssertionProfile).

Leash allows you to build an OAuth2 provider for a closed set of trusted client apps. It can support multiple user roles and is designed to handle high load.

Rails3 engine that adds OAuth2 Provider support to any application built with Devise authentication

Configurable Strategy for One ID OAuth2 provider

Rails 4 engine that adds OAuth2 Provider support to any application built with Devise authentication

Flexible, ORM-agnostic, fully customizable and simple OAuth2 provider support for Grape APIs

OAuth3 (backwards compatible with OAuth2) authentication strategy for connecting to any OAuth2 / OAuth3 provider in Ruby / Sinatra / etc

A Rails plugin to OAuth v2.0 enable your rails application. This plugin implements v09 of the OAuth2 draft spec http://tools.ietf.org/html/draft-ietf-oauth-v2-09.