refactor(handler/error): remove custom redirect

Reduce the risk of exposing oauth query parameters in "dirty dancing" attacks.

README.md

@@ -133,7 +133,6 @@ The following flags are available:
 --auto-login-ignore-paths strings          Comma separated list of absolute paths to ignore when 'auto-login' is enabled. Supports basic wildcard matching with glob-style asterisks. Invalid patterns are ignored.
 --bind-address string                      Listen address for public connections. (default "127.0.0.1:3000")
 --encryption-key string                    Base64 encoded 256-bit cookie encryption key; must be identical in instances that share session store.
---error-path string                        Absolute path to redirect user to on errors for custom error handling.
 --ingress strings                          Comma separated list of ingresses used to access the main application.
 --log-format string                        Log format, either 'json' or 'text'. (default "json")
 --log-level string                         Logging verbosity level. (default "info")

pkg/config/config.go

@@ -22,7 +22,6 @@ type Config struct {
 	AutoLogin            bool     `json:"auto-login"`
 	AutoLoginIgnorePaths []string `json:"auto-login-ignore-paths"`
 	EncryptionKey        string   `json:"encryption-key"`
-	ErrorPath            string   `json:"error-path"`
 	Ingresses            []string `json:"ingress"`
 	Session              Session  `json:"session"`
 	UpstreamHost         string   `json:"upstream-host"`
@@ -73,7 +72,6 @@ const (
 	AutoLogin            = "auto-login"
 	AutoLoginIgnorePaths = "auto-login-ignore-paths"
 	EncryptionKey        = "encryption-key"
-	ErrorPath            = "error-path"
 	Ingress              = "ingress"
 	UpstreamHost         = "upstream-host"
 
@@ -106,7 +104,6 @@ func Initialize() (*Config, error) {
 	flag.Bool(AutoLogin, false, "Automatically redirect all HTTP GET requests to login if the user does not have a valid session for all matching upstream paths.")
 	flag.StringSlice(AutoLoginIgnorePaths, []string{}, "Comma separated list of absolute paths to ignore when 'auto-login' is enabled. Supports basic wildcard matching with glob-style asterisks. Invalid patterns are ignored.")
 	flag.String(EncryptionKey, "", "Base64 encoded 256-bit cookie encryption key; must be identical in instances that share session store.")
-	flag.String(ErrorPath, "", "Absolute path to redirect user to on errors for custom error handling.")
 	flag.StringSlice(Ingress, []string{}, "Comma separated list of ingresses used to access the main application.")
 	flag.String(UpstreamHost, "127.0.0.1:8080", "Address of upstream host.")
 

pkg/handler/error/error.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"net/http"
-	"net/url"
 	"strconv"
 	"strings"
 
@@ -29,7 +28,6 @@ const (
 type Source interface {
 	GetCookieOptsPathAware(r *http.Request) cookie.Options
 	GetCrypter() crypto.Crypter
-	GetErrorPath() string
 	GetPath(r *http.Request) string
 	GetRedirectHandler() redirect.Handler
 }
@@ -112,14 +110,6 @@ func (h Handler) respondError(w http.ResponseWriter, r *http.Request, statusCode
 	}
 
 	logger.Info("errorhandler: maximum retry attempts exceeded; executing error template...")
-
-	if len(h.GetErrorPath()) > 0 {
-		err := h.customErrorRedirect(w, r, statusCode)
-		if err == nil {
-			return
-		}
-	}
-
 	h.defaultErrorResponse(w, r, statusCode)
 }
 
@@ -141,27 +131,6 @@ func (h Handler) defaultErrorResponse(w http.ResponseWriter, r *http.Request, st
 	}
 }
 
-func (h Handler) customErrorRedirect(w http.ResponseWriter, r *http.Request, statusCode int) error {
-	override, err := url.ParseRequestURI(h.GetErrorPath())
-	if err != nil {
-		return err
-	}
-
-	// strip scheme and host to avoid cross-domain redirects
-	override.Scheme = ""
-	override.Host = ""
-
-	query := override.Query()
-	query.Add("correlation_id", middleware.GetReqID(r.Context()))
-	query.Add("status_code", strconv.Itoa(statusCode))
-
-	override.RawQuery = query.Encode()
-
-	errorRedirectURI := override.String()
-	http.Redirect(w, r, errorRedirectURI, http.StatusFound)
-	return nil
-}
-
 func getRetryAttempts(r *http.Request) (int, bool) {
 	c, err := cookie.Get(r, cookie.Retry)
 	if err != nil {

pkg/handler/handler_default.go

@@ -112,10 +112,6 @@ func (d *DefaultHandler) GetErrorHandler() errorhandler.Handler {
 	return errorhandler.New(d)
 }
 
-func (d *DefaultHandler) GetErrorPath() string {
-	return d.Config.ErrorPath
-}
-
 func (d *DefaultHandler) GetIngresses() *ingress.Ingresses {
 	return d.Ingresses
 }