gologin

Package gologin provides chainable login handlers for Google, Github, Twitter, Digits, Facebook, Bitbucket, Tumblr, OAuth1, OAuth2, and other authentication providers.

Choose an auth provider package. Register the LoginHandler and CallbackHandler for web logins and the TokenHandler for (mobile) token logins. Get the verified User/Account and access token from the ctx.

See examples for tutorials with apps you can run from the command line. Visit whoam.io to see a live site running on some Kubernetes clusters.

tldr: Handlers which implement the steps of standard authentication flows to provide access tokens and associated User/Account structs.

Packages

Google - docs · tutorial
Github - docs · tutorial
Facebook - docs · tutorial
Twitter - docs · tutorial
Digits - docs · tutorial
Bitbucket docs
Tumblr - docs
OAuth2 - docs
OAuth1 - docs

Features

LoginHandler and CallbackHandler support web login flows
TokenHandler supports native mobile token login flows
Get the verified User/Account and access token from the ctx
OAuth 2 State Parameter CSRF protection

Flexibility

Handlers work with any mux accepting an http.Handler
Does not attempt to be your session system or token system.
Configurable OAuth 2 state parameter handling
Configurable OAuth 1 request secret handling

Install

go get github.com/quasor/gologin

Docs

Read GoDoc

Goals

Create small, chainable handlers to correctly implement the steps of common authentication flows. Handle provider-specific validation requirements.

Concept

Package gologin provides ContextHandler's which can be chained together to implement authorization flows and pass data (e.g. tokens, users) in a ctx argument.

type ContextHandler interface {
    ServeHTTP(ctx context.Context, w http.ResponseWriter, req *http.Request)
}

For example, oauth2 has handlers which generate a state parameter, redirect users to an AuthURL, or validate a redirectURL callback to exchange for a Token.

gologin handlers generally take success and failure ContextHandlers to be called next if an authentication step succeeds or fails. They populate the ctx with values needed for the next step. If the flow succeeds, the last success ContextHandler ctx should include the access token and (optional) associated User/Account.

ctxh defines a ContextHandler and some convenience functions to convert to a handler which plays well with net/http.

func NewHandler(h ContextHandler) http.Handler

Usage

Choose an auth provider package such as github or twitter. These packages chain together lower level oauth1 and oauth2 ContextHandlers and fetch the Github or Twitter User before calling your success ContextHandler.

Let's walk through Github and Twitter web login examples.

Github OAuth2

config := &oauth2.Config{
    ClientID:     "GithubClientID",
    ClientSecret: "GithubClientSecret",
    RedirectURL:  "http://localhost:8080/callback",
    Endpoint:     githubOAuth2.Endpoint,
}
mux := http.NewServeMux()
stateConfig := gologin.DebugOnlyCookieConfig
mux.Handle("/login", ctxh.NewHandler(github.StateHandler(stateConfig, github.LoginHandler(config, nil))))
mux.Handle("/callback", ctxh.NewHandler(github.StateHandler(stateConfig, github.CallbackHandler(config, issueSession(), nil))))

The StateHandler checks for an OAuth2 state parameter cookie, generates a non-guessable state as a short-lived cookie if missing, and passes the state value in the ctx. The CookieConfig allows the cookie name or expiration (default 60 seconds) to be configured. In production, use a config like gologin.DefaultCookieConfig which sets Secure true to require cookies be sent over HTTPS. If you wish to persist state parameters a different way, you may chain your own ContextHandler. (info)

The github LoginHandler reads the state from the ctx and redirects to the AuthURL (at github.com) to prompt the user to grant access. Passing nil for the failure ContextHandler just means the DefaultFailureHandler should be used, which reports errors. (info)

The github CallbackHandler receives an auth code and state OAuth2 redirection, validates the state against the state in the ctx, and exchanges the auth code for an OAuth2 Token. The github CallbackHandler wraps the lower level oauth2 CallbackHandler to further use the Token to obtain the Github User before calling through to the success or failure handlers.

Next, write the success ContextHandler to do something with the Token and Github User added to the ctx.

func issueSession() goji.Handler {
    fn := func(ctx context.Context, w http.ResponseWriter, req *http.Request) {
        token, _ := oauth2Login.TokenFromContext(ctx)
        githubUser, err := github.UserFromContext(ctx)
        // handle errors and grant the visitor a session (cookie, token, etc.)
    }
    return goji.HandlerFunc(fn)
}

See the Github tutorial for a web app you can run from the command line.

Twitter OAuth1

config := &oauth1.Config{
    ConsumerKey:    "TwitterConsumerKey",
    ConsumerSecret: "TwitterConsumerSecret",
    CallbackURL:    "http://localhost:8080/callback",
    Endpoint:       twitterOAuth1.AuthorizeEndpoint,
}
mux := http.NewServeMux()
mux.Handle("/login", ctxh.NewHandler(twitter.LoginHandler(config, nil)))
mux.Handle("/callback", ctxh.NewHandler(twitter.CallbackHandler(config, issueSession(), nil)))

The twitter LoginHandler obtains a request token and secret, adds them to the ctx, and redirects to the AuthorizeURL to prompt the user to grant access. Passing nil for the failure ContextHandler just means the DefaultFailureHandler should be used, which reports errors. (info)

The twitter CallbackHandler receives an OAuth1 token and verifier, reads the request secret from the ctx, and obtains an OAuth1 access token and secret. The twitter CallbackHandler wraps the lower level oauth1 CallbackHandler to further use the access token/secret to obtain the Twitter User before calling through to the success or failure handlers.

Next, write the success ContextHandler to do something with the access token/secret and Twitter User added to the ctx.

func success() goji.Handler {
    fn := func(ctx context.Context, w http.ResponseWriter, req *http.Request) {
        accessToken, accessSecret, _ := oauth1Login.AccessTokenFromContext(ctx)
        twitterUser, err := twitter.UserFromContext(ctx)
        // handle errors and grant the visitor a session (cookie, token, etc.)
    }
    return goji.HandlerFunc(fn)
}

*Note: Some OAuth1 providers (not Twitter), require the request secret be persisted until the callback is received. For this reason, the lower level oauth1 package splits LoginHandler functionality into a LoginHandler and AuthRedirectHandler. Provider packages, like tumblr, chain these together for you, but the lower level handlers are there if needed.

See the Twitter tutorial for a web app you can run from the command line.

State Parameters

OAuth2 StateHandler implements OAuth 2 RFC 6749 10.12 CSRF Protection using non-guessable values in short-lived HTTPS-only cookies to provide reasonable assurance the user in the login phase and callback phase are the same. If you wish to implement this differently, write a ContextHandler which sets a state in the ctx, which is expected by LoginHandler and CallbackHandler.

You may use oauth2.WithState(context.Context, state string) for this. docs

Failure Handlers

If you wish to define your own failure ContextHandler, you can get the error from the ctx using gologin.ErrorFromContext(ctx).

Production Requirements

Use HTTPS.
Never put consumer/client secrets in source control.
Ensure the CookieConfig requires state or temp credential cookies be sent over HTTPS-only.

Going Further

Check out the available auth provider packages. Each has handlers for the web authorization flow and ensures the ctx contains the appropriate type of user/account and the access token.

Mobile

Twitter and Digits include a TokenHandler which can be useful for building APIs for mobile devices which use Login with Twitter or Login with Digits.

Motivations

Package gologin implements authorization flow steps with chained handlers.

Authentication should be performed with chainable handlers to allow customization, swapping, or adding additional steps easily.
Authentication should be orthogonal to the session system. Let users choose their session/token library.
OAuth2 State CSRF should be included out of the box, but easy to customize.
Packages should import only what is required. OAuth1 and OAuth2 packages are separate.
ContextHandlers are flexible and useful for more than just data passing.

Projects goth and gomniauth aim to provide a similar login solution with a different design. Check them out if you decide you don't like the ideas in gologin.

Roadmap

Improve test coverage
OTP Handlers
Per-Provider User types (current) vs one combined gologin User type?

Contributing

Contributions are welcome. Improving documentation and examples is a good way to start. New auth providers can be implemented by composing the oauth1 or oauth2 ContextHandlers.

Also, gologin aims to use the defacto standard API libraries for User/Account models and verify endpoints. Tumblr and Bitbucket don't seem to have good ones yet. Tiny internal API clients are used.

See the Contributing Guide.

Why Contexts?

I originally thought gologin should use only http.Handler handlers and handler(http.Handler) http.Handler chaining. Passing request data becomes messy with many custom handler types. Global request to context mappings are similarly gross.

A while ago, some great materials like this Go blog post, Sameer Ajmani's Gotham talk, and Joe Shaw's article helped convince me that

type ContextHandler interface {
    ServeHTTP(ctx context.Context, w http.ResponseWriter, req *http.Request)
}

is an excellent choice for more advanced handlers. These days I use it a lot.

License

MIT License