Add ability to set authenticated user in request header (#889)

* Add ability to set authenticated user in request header

Some web applications provide the ability to authorize users based on
the authenticated from Basic Auth. This patch provides a way to set a
key to which the authenticated user can be set in the Header.

For example, if I set `HeaderValue = "X-WebAuth-User"` and authenticate,
my application will be able to read my user name from that header and
provide me with the proper access.

This fixes #802

docs/user-guide/examples.md

@@ -115,3 +115,19 @@ defaultEntryPoints = ["http"]
   [entryPoints.http.auth.basic]
   users = ["test:$apr1$H6uskkkW$IgXLP6ewTrSuBkTrqE8wj/", "test2:$apr1$d9hr9HBB$4HxwgUir3HP4EsggP/QNo0"]
 ```
+
+## Pass Authenticated user to application via headers
+
+Providing an authentication method as described above, it is possible to pass the user to the application
+via a configurable header value
+
+```
+defaultEntryPoints = ["http"]
+[entryPoints]
+  [entryPoints.http]
+  address = ":80"
+  [entryPoints.http.auth]
+    headerField = "X-WebAuth-User"
+    [entryPoints.http.auth.basic]
+    users = ["test:$apr1$H6uskkkW$IgXLP6ewTrSuBkTrqE8wj/", "test2:$apr1$d9hr9HBB$4HxwgUir3HP4EsggP/QNo0"]
+```

middlewares/authenticator.go

@@ -31,9 +31,13 @@ func NewAuthenticator(authConfig *types.Auth) (*Authenticator, error) {
 		basicAuth := auth.NewBasicAuthenticator("traefik", authenticator.secretBasic)
 		authenticator.handler = negroni.HandlerFunc(func(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
 			if username := basicAuth.CheckAuth(r); username == "" {
-				log.Debugf("Auth failed...")
+				log.Debugf("Basic auth failed...")
 				basicAuth.RequireAuth(w, r)
 			} else {
+				log.Debugf("Basic auth success...")
+				if authConfig.HeaderField != "" {
+					r.Header[authConfig.HeaderField] = []string{username}
+				}
 				next.ServeHTTP(w, r)
 			}
 		})
@@ -45,8 +49,13 @@ func NewAuthenticator(authConfig *types.Auth) (*Authenticator, error) {
 		digestAuth := auth.NewDigestAuthenticator("traefik", authenticator.secretDigest)
 		authenticator.handler = negroni.HandlerFunc(func(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
 			if username, _ := digestAuth.CheckAuth(r); username == "" {
+				log.Debugf("Digest auth failed...")
 				digestAuth.RequireAuth(w, r)
 			} else {
+				log.Debugf("Digest auth success...")
+				if authConfig.HeaderField != "" {
+					r.Header[authConfig.HeaderField] = []string{username}
+				}
 				next.ServeHTTP(w, r)
 			}
 		})

middlewares/authenticator_test.go

@@ -101,3 +101,33 @@ func TestDigestAuthFail(t *testing.T) {
 	assert.NoError(t, err, "there should be no error")
 	assert.Equal(t, http.StatusUnauthorized, res.StatusCode, "they should be equal")
 }
+
+func TestBasicAuthUserHeader(t *testing.T) {
+	authMiddleware, err := NewAuthenticator(&types.Auth{
+		Basic: &types.Basic{
+			Users: []string{"test:$apr1$H6uskkkW$IgXLP6ewTrSuBkTrqE8wj/"},
+		},
+		HeaderField: "X-WebAuth-User",
+	})
+	assert.NoError(t, err, "there should be no error")
+
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, "test", r.Header["X-WebAuth-User"][0], "auth user should be set")
+		fmt.Fprintln(w, "traefik")
+	})
+	n := negroni.New(authMiddleware)
+	n.UseHandler(handler)
+	ts := httptest.NewServer(n)
+	defer ts.Close()
+
+	client := &http.Client{}
+	req, err := http.NewRequest("GET", ts.URL, nil)
+	req.SetBasicAuth("test", "test")
+	res, err := client.Do(req)
+	assert.NoError(t, err, "there should be no error")
+	assert.Equal(t, http.StatusOK, res.StatusCode, "they should be equal")
+
+	body, err := ioutil.ReadAll(res.Body)
+	assert.NoError(t, err, "there should be no error")
+	assert.Equal(t, "traefik\n", string(body), "they should be equal")
+}

types/types.go

@@ -222,8 +222,9 @@ type Cluster struct {
 
 // Auth holds authentication configuration (BASIC, DIGEST, users)
 type Auth struct {
-	Basic  *Basic
-	Digest *Digest
+	Basic       *Basic
+	Digest      *Digest
+	HeaderField string
 }
 
 // Users authentication users