Add logout endpoint (#107)

Add logout endpoint that clears the auth cookie + optional "logout-redirect" config option, to which, when set, the user will be redirected.

Author: thomseddon

Makefile

@@ -2,4 +2,7 @@
 format:
 	gofmt -w -s internal/*.go internal/provider/*.go cmd/*.go
 
-.PHONY: format
+test:
+	go test -v ./...
+
+.PHONY: format test

README.md

@@ -35,6 +35,7 @@ A minimal forward authentication service that provides OAuth/SSO login and authe
   - [Operation Modes](#operation-modes)
     - [Overlay Mode](#overlay-mode)
     - [Auth Host Mode](#auth-host-mode)
+  - [Logging Out](#logging-out)
 - [Copyright](#copyright)
 - [License](#license)
 
@@ -136,6 +137,7 @@ Application Options:
   --default-provider=[google|oidc]                      Default provider (default: google) [$DEFAULT_PROVIDER]
   --domain=                                             Only allow given email domains, can be set multiple times [$DOMAIN]
   --lifetime=                                           Lifetime in seconds (default: 43200) [$LIFETIME]
+  --logout-redirect=                                    URL to redirect to following logout [$LOGOUT_REDIRECT]
   --url-path=                                           Callback URL Path (default: /_oauth) [$URL_PATH]
   --secret=                                             Secret used for signing (required) [$SECRET]
   --whitelist=                                          Only allow given email addresses, can be set multiple times [$WHITELIST]
@@ -243,6 +245,10 @@ All options can be supplied in any of the following ways, in the following prece
 
    Default: `43200` (12 hours)
 
+- `logout-redirect`
+
+   When set, users will be redirected to this URL following logout.
+
 - `url-path`
 
    Customise the path that this service uses to handle the callback following authentication.
@@ -443,6 +449,14 @@ Two criteria must be met for an `auth-host` to be used:
 
 Please note: For Auth Host mode to work, you must ensure that requests to your auth-host are routed to the traefik-forward-auth container, as demonstrated with the service labels in the [docker-compose-auth.yml](https://github.com/thomseddon/traefik-forward-auth/blob/master/examples/traefik-v2/swarm/docker-compose-auth-host.yml) example and the [ingressroute resource](https://github.com/thomseddon/traefik-forward-auth/blob/master/examples/traefik-v2/kubernetes/advanced-separate-pod/traefik-forward-auth/ingress.yaml) in a kubernetes example.
 
+### Logging Out
+
+The service provides an endpoint to clear a users session and "log them out". The path is created by appending `/logout` to your configured `path` and so with the default settings it will be: `/_oauth/logout`.
+
+You can use the `logout-redirect` config option to redirect users to another URL following logout (note: the user will not have a valid auth cookie after being logged out).
+
+Note: This only clears the auth cookie from the users browser and as this service is stateless, it does not invalidate the cookie against future use. So if the cookie was recorded, for example, it could continue to be used for the duration of the cookie lifetime.
+
 ## Copyright
 
 2018 Thom Seddon

internal/auth.go

@@ -144,6 +144,19 @@ func MakeCookie(r *http.Request, email string) *http.Cookie {
 	}
 }
 
+// ClearCookie clears the auth cookie
+func ClearCookie(r *http.Request) *http.Cookie {
+	return &http.Cookie{
+		Name:     config.CookieName,
+		Value:    "",
+		Path:     "/",
+		Domain:   cookieDomain(r),
+		HttpOnly: true,
+		Secure:   !config.InsecureCookie,
+		Expires:  time.Now().Local().Add(time.Hour * -1),
+	}
+}
+
 // MakeCSRFCookie makes a csrf cookie (used during login only)
 func MakeCSRFCookie(r *http.Request, nonce string) *http.Cookie {
 	return &http.Cookie{

internal/config.go

@@ -34,6 +34,7 @@ type Config struct {
 	DefaultProvider string               `long:"default-provider" env:"DEFAULT_PROVIDER" default:"google" choice:"google" choice:"oidc" description:"Default provider"`
 	Domains         CommaSeparatedList   `long:"domain" env:"DOMAIN" env-delim:"," description:"Only allow given email domains, can be set multiple times"`
 	LifetimeString  int                  `long:"lifetime" env:"LIFETIME" default:"43200" description:"Lifetime in seconds"`
+	LogoutRedirect  string               `long:"logout-redirect" env:"LOGOUT_REDIRECT" description:"URL to redirect to following logout"`
 	Path            string               `long:"url-path" env:"URL_PATH" default:"/_oauth" description:"Callback URL Path"`
 	SecretString    string               `long:"secret" env:"SECRET" description:"Secret used for signing (required)" json:"-"`
 	Whitelist       CommaSeparatedList   `long:"whitelist" env:"WHITELIST" env-delim:"," description:"Only allow given email addresses, can be set multiple times"`

internal/config_test.go

@@ -33,6 +33,7 @@ func TestConfigDefaults(t *testing.T) {
 	assert.Equal("google", c.DefaultProvider)
 	assert.Len(c.Domains, 0)
 	assert.Equal(time.Second*time.Duration(43200), c.Lifetime)
+	assert.Equal("", c.LogoutRedirect)
 	assert.Equal("/_oauth", c.Path)
 	assert.Len(c.Whitelist, 0)
 

internal/server.go

@@ -41,6 +41,9 @@ func (s *Server) buildRoutes() {
 	// Add callback handler
 	s.router.Handle(config.Path, s.AuthCallbackHandler())
 
+	// Add logout handler
+	s.router.Handle(config.Path+"/logout", s.LogoutHandler())
+
 	// Add a default handler
 	if config.DefaultAction == "allow" {
 		s.router.NewRoute().Handler(s.AllowHandler("default"))
@@ -180,6 +183,23 @@ func (s *Server) AuthCallbackHandler() http.HandlerFunc {
 	}
 }
 
+// LogoutHandler logs a user out
+func (s *Server) LogoutHandler() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		// Clear cookie
+		http.SetCookie(w, ClearCookie(r))
+
+		logger := s.logger(r, "Logout", "default", "Handling logout")
+		logger.Info("Logged out user")
+
+		if config.LogoutRedirect != "" {
+			http.Redirect(w, r, config.LogoutRedirect, http.StatusTemporaryRedirect)
+		} else {
+			http.Error(w, "You have been logged out", 401)
+		}
+	}
+}
+
 func (s *Server) authRedirect(logger *logrus.Entry, w http.ResponseWriter, r *http.Request, p provider.Provider) {
 	// Error indicates no cookie, generate nonce
 	err, nonce := Nonce()

internal/server_test.go

@@ -170,6 +170,49 @@ func TestServerAuthCallback(t *testing.T) {
 	assert.Equal("", fwd.Path, "valid request should be redirected to return url")
 }
 
+func TestServerLogout(t *testing.T) {
+	require := require.New(t)
+	assert := assert.New(t)
+	config = newDefaultConfig()
+
+	req := newDefaultHttpRequest("/_oauth/logout")
+	res, _ := doHttpRequest(req, nil)
+	require.Equal(401, res.StatusCode, "should return a 401")
+
+	// Check for cookie
+	var cookie *http.Cookie
+	for _, c := range res.Cookies() {
+		if c.Name == config.CookieName {
+			cookie = c
+		}
+	}
+	require.NotNil(cookie)
+	require.Less(cookie.Expires.Local().Unix(), time.Now().Local().Unix()-50, "cookie should have expired")
+
+	// Test with redirect
+	config.LogoutRedirect = "http://redirect/path"
+	req = newDefaultHttpRequest("/_oauth/logout")
+	res, _ = doHttpRequest(req, nil)
+	require.Equal(307, res.StatusCode, "should return a 307")
+
+	// Check for cookie
+	cookie = nil
+	for _, c := range res.Cookies() {
+		if c.Name == config.CookieName {
+			cookie = c
+		}
+	}
+	require.NotNil(cookie)
+	require.Less(cookie.Expires.Local().Unix(), time.Now().Local().Unix()-50, "cookie should have expired")
+
+	fwd, _ := res.Location()
+	require.NotNil(fwd)
+	assert.Equal("http", fwd.Scheme, "valid request should be redirected to return url")
+	assert.Equal("redirect", fwd.Host, "valid request should be redirected to return url")
+	assert.Equal("/path", fwd.Path, "valid request should be redirected to return url")
+
+}
+
 func TestServerDefaultAction(t *testing.T) {
 	assert := assert.New(t)
 	config = newDefaultConfig()