Enable Customization of Auth Request Redirect (#1993)

Adds the 'nginx.ingress.kubernetes.io/auth-request-redirect'
annotation, which allows the customization of the
'X-Auth-Request-Redirect' Header. Fixes: #1979

internal/ingress/controller/template/template.go

@@ -214,7 +214,6 @@ func buildLocation(input interface{}) string {
 	return path
 }
 
-// TODO: Needs Unit Tests
 func buildAuthLocation(input interface{}) string {
 	location, ok := input.(*ingress.Location)
 	if !ok {
@@ -227,7 +226,7 @@ func buildAuthLocation(input interface{}) string {
 	}
 
 	str := base64.URLEncoding.EncodeToString([]byte(location.Path))
-	// avoid locations containing the = char
+	// removes "=" after encoding
 	str = strings.Replace(str, "=", "", -1)
 	return fmt.Sprintf("/_external-auth-%v", str)
 }

internal/ingress/controller/template/template_test.go

@@ -26,6 +26,8 @@ import (
 	"strings"
 	"testing"
 
+	"encoding/base64"
+	"fmt"
 	"k8s.io/ingress-nginx/internal/file"
 	"k8s.io/ingress-nginx/internal/ingress"
 	"k8s.io/ingress-nginx/internal/ingress/annotations/authreq"
@@ -172,6 +174,26 @@ func TestBuildProxyPass(t *testing.T) {
 	}
 }
 
+func TestBuildAuthLocation(t *testing.T) {
+	authURL := "foo.com/auth"
+
+	loc := &ingress.Location{
+		ExternalAuth: authreq.Config{
+			URL: authURL,
+		},
+		Path: "/cat",
+	}
+
+	str := buildAuthLocation(loc)
+
+	encodedAuthURL := strings.Replace(base64.URLEncoding.EncodeToString([]byte(loc.Path)), "=", "", -1)
+	expected := fmt.Sprintf("/_external-auth-%v", encodedAuthURL)
+
+	if str != expected {
+		t.Errorf("Expected \n'%v'\nbut returned \n'%v'", expected, str)
+	}
+}
+
 func TestBuildAuthResponseHeaders(t *testing.T) {
 	loc := &ingress.Location{
 		ExternalAuth: authreq.Config{ResponseHeaders: []string{"h1", "H-With-Caps-And-Dashes"}},