Extensible security first OAuth 2.0 and OpenID Connect SDK for Go.
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ORY Fosite - Security-first OAuth2 framework

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The security first OAuth2 & OpenID Connect framework for Go. Built simple, powerful and extensible. This library implements peer-reviewed IETF RFC6749, counterfeits weaknesses covered in peer-reviewed IETF RFC6819 and countermeasures various database attack scenarios, keeping your application safe when that hacker penetrates or leaks your database. OpenID Connect is implemented according to OpenID Connect Core 1.0 incorporating errata set 1 and includes all flows: code, implicit, hybrid.

This library considered and implemented:

OAuth2 and OpenID Connect are difficult protocols. If you want quick wins, we strongly encourage you to look at Hydra. Hydra is a secure, high performance, cloud native OAuth2 and OpenID Connect service that integrates with every authentication method imaginable and is built on top of Fosite.

Table of Contents


Fosite was written because our OAuth2 and OpenID Connect service Hydra required a secure and extensible OAuth2 library. We had to realize that nothing matching our requirements was out there, so we decided to build it ourselves.

API Stability

The core public API is almost stable as most changes will only touch the inner workings.

We strongly encourage vendoring fosite using dep or comparable tools.


The example does not have nice visuals but it should give you an idea of what you can do with Fosite and a few lines of code.

Authorize Code Grant

You can run this minimalistic example by doing

go get
cd $GOPATH/src/
dep ensure
go install

There should be a server listening on localhost:3846. You can check out the example's source code here.

A word on quality

We tried to set up as many tests as possible and test for as many cases covered in the RFCs as possible. But we are only human. Please, feel free to add tests for the various cases defined in the OAuth2 RFCs 6749 and 6819 or any other cases that improve the tests.

Everyone writing an RFC conform test that breaks with the current implementation, will receive a place in the Hall of Fame!

A word on security

Please be aware that Fosite only secures parts of your server side security. You still need to secure your apps and clients, keep your tokens safe, prevent CSRF attacks, ensure database security, use valid and strong TLS certificates and much more. If you need any help or advice feel free to contact our security staff through our website!

We have given the various specifications, especially OAuth 2.0 Threat Model and Security Considerations, a very close look and included everything we thought was in the scope of this framework. Here is a complete list of things we implemented in Fosite:

Additionally, we added these safeguards:

  • Enforcing random states: Without a random-looking state or OpenID Connect nonce the request will fail.
  • Advanced Token Validation: Tokens are layouted as <key>.<signature> where <signature> is created using HMAC-SHA256 using a global secret. This is what a token can look like: /tgBeUhWlAT8tM8Bhmnx+Amf8rOYOUhrDi3pGzmjP7c=.BiV/Yhma+5moTP46anxMT6cWW8gz5R5vpC9RbpwSDdM=

Sections below Section 5 that are not covered in the list above should be reviewed by you. If you think that a specific section should be something that is covered in Fosite, feel free to create an issue. Please be aware that OpenID Connect requires specific knowledge of the identity provider, which is why Fosite only implements core requirements and most things must be implemented by you (for example prompt, max_age, ui_locales, id_token_hint, user authentication, session management, ...).

It is strongly encouraged to use the handlers shipped with Fosite as they follow the specs and are well tested.

A word on extensibility

Fosite is extensible ... because OAuth2 is an extensible and flexible framework. Fosite let's you register custom token and authorize endpoint handlers with the security that the requests have been validated against the OAuth2 specs beforehand. You can easily extend Fosite's capabilities. For example, if you want to provide OpenID Connect on top of your OAuth2 stack, that's no problem. Or custom assertions, what ever you like and as long as it is secure. ;)


Go 1.11+ must be installed on your system and it is required that you have set up your GOPATH environment variable.

go get -u

We recommend to use dep to mitigate compatibility breaks that come with new api versions.


There is an API documentation available at


Fosite has three strategies for matching scopes. You can replace the default scope strategy if you need a custom one by implementing fosite.ScopeStrategy.

Using the composer, setting a strategy is easy:

import ""

var config = &fosite.Config{
ScopeStrategy: fosite.HierarchicScopeStrategy,

Note: To issue refresh tokens with any of the grants, you need to include the offline scope in the OAuth2 request. This can be modified by the RefreshTokenScopes compose configuration. When set to an empty array, all grants will issue refresh tokens.


This is the default strategy, and the safest one. It is best explained by looking at some examples:

  • users.* matches
  • users.* matches
  • matches
  • users does not match
  •* does not match
  • users.*.* does not match
  • users.*.* matches
  • users.*.* matches
  •* matches
  •* matches
  • users.write.* does not match
  • users.*.bar matches
  • users.*.bar does not

To request users.*, a client must have exactly users.* as granted scope.


This strategy is searching only for exact matches. It returns true iff the scope is granted.


This strategy is deprecated, use it with care. Again, it is best explained by looking at some examples:

  • users matches users
  • users matches
  • users matches
  • matches
  • matches
  • does not match users.write
  • does not match users.write.own


Fosite does not natively carry translations for error messages and hints, but offers an interface that allows the consumer to define catalog bundles and an implementation to translate. This is available through the MessageCatalog interface. The functions defined are self-explanatory. The DefaultMessageCatalog illustrates this. Compose config has been extended to take in an instance of the MessageCatalog.

Building translated files

There are three possible "message key" types:

  1. Value of RFC6749Error.ErrorField: This is a string like invalid_request and correlates to most errors produced by Fosite.
  2. Hint identifier passed into RFC6749Error.WithHintIDOrDefaultf: This func is not used extensively in Fosite but, in time, most WithHint and WithHintf will be replaced with this function.
  3. Free text string format passed into RFC6749Error.WithHint and RFC6749Error.WithHintf: This function is used in Fosite and Hydra extensively and any message catalog implementation can use the format string parameter as the message key.

An example of a message catalog can be seen in the i18n_test.go.

Generating the en messages file

This is a WIP at the moment, but effectively any scripting language can be used to generate this. It would need to traverse all files in the source code and extract the possible message identifiers based on the different message key types.


Instantiating fosite by hand can be painful. Therefore we created a few convenience helpers available through the compose package. It is strongly encouraged to use these well tested composers.

In this very basic example, we will instantiate fosite with all OpenID Connect and OAuth2 handlers enabled. Please refer to the example app for more details.

This little code snippet sets up a full-blown OAuth2 and OpenID Connect example.

package main

import ""
import ""
import ""

// This is the example storage that contains:
// * an OAuth2 Client with id "my-client" and secrets "foobar" and "foobaz" capable of all oauth2 and open id connect grant and response types.
// * a User for the resource owner password credentials grant type with username "peter" and password "secret".
// You will most likely replace this with your own logic once you set up a real world application.
var storage = storage.NewExampleStore()

// This secret is being used to sign access and refresh tokens as well as
// authorization codes. It must be exactly 32 bytes long.
var secret = []byte("my super secret signing password")

privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
panic("unable to create private key")

// check the api docs of fosite.Config for further configuration options
var config = &fosite.Config{
	AccessTokenLifespan: time.Minute * 30,
	// ...

var oauth2Provider = compose.ComposeAllEnabled(config, storage, secret, privateKey)

// The authorize endpoint is usually at "".
func authorizeHandlerFunc(rw http.ResponseWriter, req *http.Request) {
	// This context will be passed to all methods. It doesn't fulfill a real purpose in the standard library but could be used
	// to abort database lookups or similar things.
	ctx := req.Context()

	// Let's create an AuthorizeRequest object!
	// It will analyze the request and extract important information like scopes, response type and others.
	ar, err := oauth2Provider.NewAuthorizeRequest(ctx, req)
	if err != nil {
		oauth2Provider.WriteAuthorizeError(ctx, rw, ar, err)

	// Normally, this would be the place where you would check if the user is logged in and gives his consent.
	// We're simplifying things and just checking if the request includes a valid username and password
	if req.Form.Get("username") != "peter" {
		rw.Header().Set("Content-Type", "text/html;charset=UTF-8")
		rw.Write([]byte(`<h1>Login page</h1>`))
			<p>Howdy! This is the log in page. For this example, it is enough to supply the username.</p>
			<form method="post">
				<input type="text" name="username" /> <small>try peter</small><br>
				<input type="submit">

	// Now that the user is authorized, we set up a session. When validating / looking up tokens, we additionally get
	// the session. You can store anything you want in it.

	// The session will be persisted by the store and made available when e.g. validating tokens or handling token endpoint requests.
	// The default OAuth2 and OpenID Connect handlers require the session to implement a few methods. Apart from that, the
	// session struct can be anything you want it to be.
	mySessionData := &fosite.DefaultSession{
		Username: req.Form.Get("username"),

	// It's also wise to check the requested scopes, e.g.:
	// if authorizeRequest.GetScopes().Has("admin") {
	//     http.Error(rw, "you're not allowed to do that", http.StatusForbidden)
	//     return
	// }

	// Now we need to get a response. This is the place where the AuthorizeEndpointHandlers kick in and start processing the request.
	// NewAuthorizeResponse is capable of running multiple response type handlers which in turn enables this library
	// to support open id connect.
	response, err := oauth2Provider.NewAuthorizeResponse(ctx, ar, mySessionData)
	if err != nil {
		oauth2Provider.WriteAuthorizeError(ctx, rw, ar, err)

	// Awesome, now we redirect back to the client redirect uri and pass along an authorize code
	oauth2Provider.WriteAuthorizeResponse(ctx, rw, ar, response)

// The token endpoint is usually at ""
func tokenHandlerFunc(rw http.ResponseWriter, req *http.Request) {
	ctx := req.Context()

	// Create an empty session object that will be passed to storage implementation to populate (unmarshal) the session into.
	// By passing an empty session object as a "prototype" to the store, the store can use the underlying type to unmarshal the value into it.
	// For an example of storage implementation that takes advantage of that, see SQL Store (fosite_store_sql.go) from ory/Hydra project.
	mySessionData := new(fosite.DefaultSession)

	// This will create an access request object and iterate through the registered TokenEndpointHandlers to validate the request.
	accessRequest, err := oauth2Provider.NewAccessRequest(ctx, req, mySessionData)
	if err != nil {
		oauth2Provider.WriteAccessError(ctx, rw, accessRequest, err)

	if mySessionData.Username == "super-admin-guy" {
		// do something...

	// Next we create a response for the access request. Again, we iterate through the TokenEndpointHandlers
	// and aggregate the result in response.
	response, err := oauth2Provider.NewAccessResponse(ctx, accessRequest)
	if err != nil {
		oauth2Provider.WriteAccessError(ctx, rw, accessRequest, err)

	// All done, send the response.
	oauth2Provider.WriteAccessResponse(ctx, rw, accessRequest, response)

	// The client has a valid access token now

func someResourceProviderHandlerFunc(rw http.ResponseWriter, req *http.Request) {
	ctx := req.Context()
	requiredScope := "blogposts.create"

	_, ar, err := oauth2Provider.IntrospectToken(ctx, fosite.AccessTokenFromRequest(req), fosite.AccessToken, new(fosite.DefaultSession), requiredScope)
	if err != nil {
		// ...

	// If no error occurred the token + scope is valid and you have access to:
	// ar.GetClient().GetID(), ar.GetGrantedScopes(), ar.GetScopes(), ar.GetSession().UserID, ar.GetRequestedAt(), ...

Code Examples

Fosite provides integration tests as well as a http server example:

  • Fosite ships with an example app that runs in your browser: Example app.
  • If you want to check out how to enable specific handlers, check out the integration tests.

If you have working examples yourself, please share them with us!

Example Storage Implementation

Fosite does not ship a storage implementation. This is intended, because requirements vary with every environment. You can find a reference implementation at storage/memory.go. This storage fulfills requirements from all OAuth2 and OpenID Connect handlers.

Extensible handlers

OAuth2 is a framework. Fosite mimics this behaviour by enabling you to replace existing or create new OAuth2 handlers. Of course, fosite ships handlers for all OAuth2 and OpenID Connect flows.

This section is missing documentation and we welcome any contributions in that direction.

JWT Introspection

Please note that when using the OAuth2StatelessJWTIntrospectionFactory access token revocation is not possible.


You need git and golang installed on your system.

go get -d
cd $GOPATH/src/
git status
git remote add myfork <url-to-your-fork>
go test ./...

Simple, right? Now you are ready to go! Make sure to run go test ./... often, detecting problems with your code rather sooner than later. Please read [] before creating pull requests and issues.

Refresh mock objects

Run ./ in fosite's root directory or run the contents of [] in a shell.

Hall of Fame

This place is reserved for the fearless bug hunters, reviewers and contributors (alphabetical order).

Find out more about the author of Fosite and Hydra, and the Ory Company.

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