Add default redirect URL for missing go-parameter

This adds a configuration option to set a default redirect URL for when
no `go` parameter was passed. This allows for users to have bookmarked
the login page and be redirected to the right location instead of seeing
a 404 page.

Signed-off-by: Knut Ahlers <knut@ahlers.me>

config.yaml

@@ -3,6 +3,7 @@
 login:
   title: "luzifer.io - Login"
   default_method: "simple"
+  default_redirect: "https://luzifer.io/"
   hide_mfa_field: false
   names:
     simple: "Username / Password"

main.go

@@ -36,10 +36,11 @@ type mainConfig struct {
 		Port int    `yaml:"port"`
 	} `yaml:"listen"`
 	Login struct {
-		Title         string            `yaml:"title"`
-		DefaultMethod string            `yaml:"default_method"`
-		HideMFAField  bool              `yaml:"hide_mfa_field"`
-		Names         map[string]string `yaml:"names"`
+		Title           string            `yaml:"title"`
+		DefaultMethod   string            `yaml:"default_method"`
+		DefaultRedirect string            `yaml:"default_redirect"`
+		HideMFAField    bool              `yaml:"hide_mfa_field"`
+		Names           map[string]string `yaml:"names"`
 	} `yaml:"login"`
 	Plugins struct {
 		Directory string `yaml:"directory"`
@@ -181,7 +182,7 @@ func handleAuthRequest(res http.ResponseWriter, r *http.Request) {
 }
 
 func handleLoginRequest(res http.ResponseWriter, r *http.Request) {
-	redirURL, err := getRedirectURL(r)
+	redirURL, err := getRedirectURL(r, mainCfg.Login.DefaultRedirect)
 	if err != nil {
 		http.Error(res, "Invalid redirect URL specified", http.StatusBadRequest)
 	}
@@ -254,7 +255,7 @@ func handleLoginRequest(res http.ResponseWriter, r *http.Request) {
 }
 
 func handleLogoutRequest(res http.ResponseWriter, r *http.Request) {
-	redirURL, err := getRedirectURL(r)
+	redirURL, err := getRedirectURL(r, mainCfg.Login.DefaultRedirect)
 	if err != nil {
 		http.Error(res, "Invalid redirect URL specified", http.StatusBadRequest)
 	}

redirect.go

@@ -7,30 +7,45 @@ import (
 	"github.com/pkg/errors"
 )
 
-func getRedirectURL(r *http.Request) (string, error) {
+func getRedirectURL(r *http.Request, fallback string) (string, error) {
 	var (
-		redirURL = r.URL.Query().Get("go")
-		params   = r.URL.Query()
+		redirURL string
+		params   url.Values
 	)
 
-	if redirURL == "" {
+	switch {
+	case r.URL.Query().Get("go") != "":
+		// We have a GET request, use "go" query param
+		redirURL = r.URL.Query().Get("go")
+		params = r.URL.Query()
+
+	case r.FormValue("go") != "":
+		// We have a POST request, use "go" form value
 		redirURL = r.FormValue("go")
 		params = url.Values{} // No need to read other form fields
+
+	default:
+		// No URL specified, use specified fallback URL
+		return fallback, nil
 	}
 
+	// Remove the "go" parameter as it is a parameter for nginx-sso
 	params.Del("go")
 
+	// Parse given URL to extract attached parameters
 	pURL, err := url.Parse(redirURL)
 	if err != nil {
 		return "", errors.Wrap(err, "Unable to parse redirect URL")
 	}
 
+	// Transfer parameters from URL to params set
 	for k, vs := range pURL.Query() {
 		for _, v := range vs {
 			params.Add(k, v)
 		}
 	}
 
+	// Re-add assembled parameters to URL
 	pURL.RawQuery = params.Encode()
 
 	return pURL.String(), nil

redirect_test.go

@@ -14,7 +14,7 @@ func TestGetRedirectGet(t *testing.T) {
 
 	req, _ := http.NewRequest(http.MethodGet, testURL, nil)
 
-	rURL, err := getRedirectURL(req)
+	rURL, err := getRedirectURL(req, "")
 	if err != nil {
 		t.Errorf("getRedirectURL caused an error in GET: %s", err)
 	}
@@ -24,13 +24,13 @@ func TestGetRedirectGet(t *testing.T) {
 	}
 }
 
-func TestGetRedirectGetEmpty(t *testing.T) {
+func TestGetRedirectFallback(t *testing.T) {
 	testURL := "https://example.com/login"
-	expectURL := ""
+	expectURL := "https://example.com/default"
 
 	req, _ := http.NewRequest(http.MethodGet, testURL, nil)
 
-	rURL, err := getRedirectURL(req)
+	rURL, err := getRedirectURL(req, expectURL)
 	if err != nil {
 		t.Errorf("getRedirectURL caused an error in GET: %s", err)
 	}
@@ -51,7 +51,7 @@ func TestGetRedirectPost(t *testing.T) {
 	req, _ := http.NewRequest(http.MethodPost, testURL, nil)
 	req.Form = body // Force-set the form values to emulate parsed form
 
-	rURL, err := getRedirectURL(req)
+	rURL, err := getRedirectURL(req, "")
 	if err != nil {
 		t.Errorf("getRedirectURL caused an error in POST: %s", err)
 	}