Remove hop-by-hop headers from forward auth response

middlewares/auth/forward.go

@@ -73,6 +73,7 @@ func Forward(config *types.Forward, w http.ResponseWriter, r *http.Request, next
 		log.Debugf("Remote error %s. StatusCode: %d", config.Address, forwardResponse.StatusCode)
 
 		utils.CopyHeaders(w.Header(), forwardResponse.Header)
+		utils.RemoveHeaders(w.Header(), forward.HopHeaders...)
 
 		// Grab the location header, if any.
 		redirectURL, err := forwardResponse.Location()

middlewares/auth/forward_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"github.com/urfave/negroni"
+	"github.com/vulcand/oxy/forward"
 )
 
 func TestForwardAuthFail(t *testing.T) {
@@ -122,6 +123,59 @@ func TestForwardAuthRedirect(t *testing.T) {
 	assert.NotEmpty(t, string(body), "there should be something in the body")
 }
 
+func TestForwardAuthRemoveHopByHopHeaders(t *testing.T) {
+	authTs := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		headers := w.Header()
+		for _, header := range forward.HopHeaders {
+			if header == forward.TransferEncoding {
+				headers.Add(header, "identity")
+			} else {
+				headers.Add(header, "test")
+			}
+		}
+
+		http.Redirect(w, r, "http://example.com/redirect-test", http.StatusFound)
+	}))
+	defer authTs.Close()
+
+	authMiddleware, err := NewAuthenticator(&types.Auth{
+		Forward: &types.Forward{
+			Address: authTs.URL,
+		},
+	}, &tracing.Tracing{})
+	assert.NoError(t, err, "there should be no error")
+
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintln(w, "traefik")
+	})
+	n := negroni.New(authMiddleware)
+	n.UseHandler(handler)
+	ts := httptest.NewServer(n)
+	defer ts.Close()
+
+	client := &http.Client{
+		CheckRedirect: func(r *http.Request, via []*http.Request) error {
+			return http.ErrUseLastResponse
+		},
+	}
+	req := testhelpers.MustNewRequest(http.MethodGet, ts.URL, nil)
+	res, err := client.Do(req)
+	assert.NoError(t, err, "there should be no error")
+	assert.Equal(t, http.StatusFound, res.StatusCode, "they should be equal")
+
+	for _, header := range forward.HopHeaders {
+		assert.Equal(t, "", res.Header.Get(header), "hop-by-hop header '%s' mustn't be set", header)
+	}
+
+	location, err := res.Location()
+	assert.NoError(t, err, "there should be no error")
+	assert.Equal(t, "http://example.com/redirect-test", location.String(), "they should be equal")
+
+	body, err := ioutil.ReadAll(res.Body)
+	assert.NoError(t, err, "there should be no error")
+	assert.NotEmpty(t, string(body), "there should be something in the body")
+}
+
 func TestForwardAuthFailResponseHeaders(t *testing.T) {
 	authTs := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		cookie := &http.Cookie{Name: "example", Value: "testing", Path: "/"}