Fix Logout Redirection (#375)

- a minor fix to the logout redirection, defaulting to the hostname if no redirect param is given

CHANGELOG.md

 
+#### **2.2.1**
+
+FIX
+- a minor fix to the logout handler, when logout redirection is enable if no redirect param is given we default to the hostname [#PR375](https://github.com/gambol99/keycloak-proxy/pull/375)
+
 #### **2.2.0**
 
 FEATURES:

doc.go

@@ -27,7 +27,7 @@ import (
 )
 
 var (
-	release  = "v2.2.0"
+	release  = "v2.2.1"
 	gitsha   = "no gitsha provided"
 	compiled = "0"
 	version  = ""

handlers.go

@@ -327,10 +327,12 @@ func (r *oauthProxy) logoutHandler(w http.ResponseWriter, req *http.Request) {
 	// @check if we should redirect to the provider
 	if r.config.EnableLogoutRedirect {
 		sendTo := fmt.Sprintf("%s/protocol/openid-connect/logout", strings.TrimSuffix(r.config.DiscoveryURL, "/.well-known/openid-configuration"))
-		if redirectURL != "" {
-			sendTo = fmt.Sprintf("%s?redirect_uri=%s", sendTo, url.QueryEscape(redirectURL))
+		// @step: if not redirect uri is set we default back to the hostname
+		if redirectURL == "" {
+			redirectURL = getRequestHostURL(req)
 		}
-		r.redirectToURL(sendTo, w, req)
+
+		r.redirectToURL(fmt.Sprintf("%s?redirect_uri=%s", sendTo, url.QueryEscape(redirectURL)), w, req)
 
 		return
 	}

utils.go

@@ -62,6 +62,21 @@ var (
 	symbolsFilter = regexp.MustCompilePOSIX("[_$><\\[\\].,\\+-/'%^&*()!\\\\]+")
 )
 
+// getRequestHostURL returns the hostname from the request
+func getRequestHostURL(r *http.Request) string {
+	hostname := r.Host
+	if r.Header.Get("X-Forwarded-Host") != "" {
+		hostname = r.Header.Get("X-Forwarded-Host")
+	}
+
+	scheme := "http"
+	if r.TLS != nil {
+		scheme = "https"
+	}
+
+	return fmt.Sprintf("%s://%s", scheme, hostname)
+}
+
 // readConfigFile reads and parses the configuration file
 func readConfigFile(filename string, config *Config) error {
 	content, err := ioutil.ReadFile(filename)