Add forward authentication option

auth/forward.go

@@ -0,0 +1,60 @@
+package auth
+
+import (
+	"io/ioutil"
+	"net/http"
+
+	"github.com/containous/traefik/log"
+	"github.com/containous/traefik/types"
+)
+
+// Forward the authentication to a external server
+func Forward(forward *types.Forward, w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+	httpClient := http.Client{}
+
+	if forward.TLS != nil {
+		tlsConfig, err := forward.TLS.CreateTLSConfig()
+		if err != nil {
+			log.Debugf("Impossible to configure TLS to call %s. Cause %s", forward.Address, err)
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		httpClient.Transport = &http.Transport{
+			TLSClientConfig: tlsConfig,
+		}
+
+	}
+
+	forwardReq, err := http.NewRequest(http.MethodGet, forward.Address, nil)
+	if err != nil {
+		log.Debugf("Error calling %s. Cause %s", forward.Address, err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	forwardReq.Header = r.Header
+
+	forwardResponse, forwardErr := httpClient.Do(forwardReq)
+	if forwardErr != nil {
+		log.Debugf("Error calling %s. Cause: %s", forward.Address, forwardErr)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	body, readError := ioutil.ReadAll(forwardResponse.Body)
+	if readError != nil {
+		log.Debugf("Error reading body %s. Cause: %s", forward.Address, readError)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	defer forwardResponse.Body.Close()
+
+	if forwardResponse.StatusCode < http.StatusOK || forwardResponse.StatusCode >= http.StatusMultipleChoices {
+		log.Debugf("Remote error %s. StatusCode: %d", forward.Address, forwardResponse.StatusCode)
+		w.WriteHeader(forwardResponse.StatusCode)
+		w.Write(body)
+		return
+	}
+
+	r.RequestURI = r.URL.RequestURI()
+	next(w, r)
+}