Add basic authentication (#1683)

* Add basic authentication

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

https/users.go

@@ -0,0 +1,73 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package https
+
+import (
+	"net/http"
+
+	"github.com/go-kit/kit/log"
+	"golang.org/x/crypto/bcrypt"
+)
+
+func validateUsers(configPath string) error {
+	c, err := getConfig(configPath)
+	if err != nil {
+		return err
+	}
+
+	for _, p := range c.Users {
+		_, err = bcrypt.Cost([]byte(p))
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+type userAuthRoundtrip struct {
+	tlsConfigPath string
+	handler       http.Handler
+	logger        log.Logger
+}
+
+func (u *userAuthRoundtrip) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	c, err := getConfig(u.tlsConfigPath)
+	if err != nil {
+		u.logger.Log("msg", "Unable to parse configuration", "err", err)
+		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+		return
+	}
+
+	if len(c.Users) == 0 {
+		u.handler.ServeHTTP(w, r)
+		return
+	}
+
+	user, pass, ok := r.BasicAuth()
+	if !ok {
+		w.Header().Set("WWW-Authenticate", "Basic")
+		http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
+		return
+	}
+
+	if hashedPassword, ok := c.Users[user]; ok {
+		if err := bcrypt.CompareHashAndPassword([]byte(hashedPassword), []byte(pass)); err == nil {
+			u.handler.ServeHTTP(w, r)
+			return
+		}
+	}
+
+	http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
+}