outposts/proxy: make templates more re-usable

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

internal/outpost/proxyv2/application/application.go

@@ -5,6 +5,7 @@ import (
 	"crypto/tls"
 	"encoding/gob"
 	"fmt"
+	"html/template"
 	"net/http"
 	"net/url"
 	"regexp"
@@ -24,6 +25,7 @@ import (
 	"goauthentik.io/internal/outpost/proxyv2/constants"
 	"goauthentik.io/internal/outpost/proxyv2/hs256"
 	"goauthentik.io/internal/outpost/proxyv2/metrics"
+	"goauthentik.io/internal/outpost/proxyv2/templates"
 	"goauthentik.io/internal/utils/web"
 	"golang.org/x/oauth2"
 )
@@ -44,6 +46,8 @@ type Application struct {
 
 	log *log.Entry
 	mux *mux.Router
+
+	errorTemplates *template.Template
 }
 
 func NewApplication(p api.ProxyOutpostConfig, c *http.Client, cs *ak.CryptoStore, ak *ak.APIController) (*Application, error) {
@@ -88,6 +92,7 @@ func NewApplication(p api.ProxyOutpostConfig, c *http.Client, cs *ak.CryptoStore
 		proxyConfig:    p,
 		httpClient:     c,
 		mux:            mux,
+		errorTemplates: templates.GetTemplates(),
 	}
 	a.sessions = a.getStore(p)
 	mux.Use(web.NewLoggingHandler(muxLogger, func(l *log.Entry, r *http.Request) *log.Entry {

internal/outpost/proxyv2/application/error.go

@@ -2,33 +2,38 @@ package application
 
 import (
 	"fmt"
-	"html/template"
 	"net/http"
 
 	log "github.com/sirupsen/logrus"
 )
 
-// NewProxyErrorHandler creates a ProxyErrorHandler using the template given.
-func (a *Application) newProxyErrorHandler(errorTemplate *template.Template) func(http.ResponseWriter, *http.Request, error) {
-	return func(rw http.ResponseWriter, req *http.Request, proxyErr error) {
-		claims, _ := a.getClaims(req)
-		log.WithError(proxyErr).Warning("Error proxying to upstream server")
-		rw.WriteHeader(http.StatusBadGateway)
-		data := struct {
+type ErrorPageData struct {
 	Title       string
 	Message     string
 	ProxyPrefix string
-		}{
+}
+
+func (a *Application) ErrorPage(rw http.ResponseWriter, r *http.Request, err string) {
+	claims, _ := a.getClaims(r)
+	data := ErrorPageData{
 		Title:       "Bad Gateway",
 		Message:     "Error proxying to upstream server",
 		ProxyPrefix: "/akprox",
 	}
-		if claims != nil {
-			data.Message = fmt.Sprintf("Error proxying to upstream server: %s", proxyErr.Error())
+	if claims != nil && len(err) > 0 {
+		data.Message = err
 	}
-		err := errorTemplate.Execute(rw, data)
-		if err != nil {
+	er := a.errorTemplates.Execute(rw, data)
+	if er != nil {
 		http.Error(rw, "Internal Server Error", http.StatusInternalServerError)
 	}
+}
+
+// NewProxyErrorHandler creates a ProxyErrorHandler using the template given.
+func (a *Application) newProxyErrorHandler() func(http.ResponseWriter, *http.Request, error) {
+	return func(rw http.ResponseWriter, req *http.Request, proxyErr error) {
+		log.WithError(proxyErr).Warning("Error proxying to upstream server")
+		rw.WriteHeader(http.StatusBadGateway)
+		a.ErrorPage(rw, req, fmt.Sprintf("Error proxying to upstream server: %s", proxyErr.Error()))
 	}
 }

internal/outpost/proxyv2/application/mode_proxy.go

@@ -13,7 +13,6 @@ import (
 	log "github.com/sirupsen/logrus"
 	"goauthentik.io/internal/outpost/ak"
 	"goauthentik.io/internal/outpost/proxyv2/metrics"
-	"goauthentik.io/internal/outpost/proxyv2/templates"
 	"goauthentik.io/internal/utils/web"
 )
 
@@ -32,7 +31,7 @@ func (a *Application) configureProxy() error {
 	rp := &httputil.ReverseProxy{Director: a.proxyModifyRequest(u)}
 	rsp := sentry.StartSpan(context.TODO(), "authentik.outposts.proxy.application_transport")
 	rp.Transport = ak.NewTracingTransport(rsp.Context(), a.getUpstreamTransport())
-	rp.ErrorHandler = a.newProxyErrorHandler(templates.GetTemplates())
+	rp.ErrorHandler = a.newProxyErrorHandler()
 	rp.ModifyResponse = a.proxyModifyResponse
 	a.mux.PathPrefix("/").HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
 		claims, err := a.getClaims(r)

internal/outpost/proxyv2/templates/templates.go

@@ -10,7 +10,7 @@ import (
 var ErrorTemplate string
 
 func GetTemplates() *template.Template {
-	t, err := template.New("foo").Parse(ErrorTemplate)
+	t, err := template.New("authentik.outpost.proxy.errors").Parse(ErrorTemplate)
 	if err != nil {
 		log.Fatalf("failed parsing template %s", err)
 	}