use constant time comparison (#3452)

pkg/util/net/http.go

@@ -19,6 +19,9 @@ import (
 	"io"
 	"net/http"
 	"strings"
+	"time"
+
+	"github.com/fatedier/frp/pkg/util/util"
 )
 
 type HTTPAuthWraper struct {
@@ -46,8 +49,9 @@ func (aw *HTTPAuthWraper) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 }
 
 type HTTPAuthMiddleware struct {
-	user   string
-	passwd string
+	user          string
+	passwd        string
+	authFailDelay time.Duration
 }
 
 func NewHTTPAuthMiddleware(user, passwd string) *HTTPAuthMiddleware {
@@ -57,32 +61,28 @@ func NewHTTPAuthMiddleware(user, passwd string) *HTTPAuthMiddleware {
 	}
 }
 
+func (authMid *HTTPAuthMiddleware) SetAuthFailDelay(delay time.Duration) *HTTPAuthMiddleware {
+	authMid.authFailDelay = delay
+	return authMid
+}
+
 func (authMid *HTTPAuthMiddleware) Middleware(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		reqUser, reqPasswd, hasAuth := r.BasicAuth()
 		if (authMid.user == "" && authMid.passwd == "") ||
-			(hasAuth && reqUser == authMid.user && reqPasswd == authMid.passwd) {
+			(hasAuth && util.ConstantTimeEqString(reqUser, authMid.user) &&
+				util.ConstantTimeEqString(reqPasswd, authMid.passwd)) {
 			next.ServeHTTP(w, r)
 		} else {
+			if authMid.authFailDelay > 0 {
+				time.Sleep(authMid.authFailDelay)
+			}
 			w.Header().Set("WWW-Authenticate", `Basic realm="Restricted"`)
 			http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
 		}
 	})
 }
 
-func HTTPBasicAuth(h http.HandlerFunc, user, passwd string) http.HandlerFunc {
-	return func(w http.ResponseWriter, r *http.Request) {
-		reqUser, reqPasswd, hasAuth := r.BasicAuth()
-		if (user == "" && passwd == "") ||
-			(hasAuth && reqUser == user && reqPasswd == passwd) {
-			h.ServeHTTP(w, r)
-		} else {
-			w.Header().Set("WWW-Authenticate", `Basic realm="Restricted"`)
-			http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
-		}
-	}
-}
-
 type HTTPGzipWraper struct {
 	h http.Handler
 }

pkg/util/util/util.go

@@ -17,6 +17,7 @@ package util
 import (
 	"crypto/md5"
 	"crypto/rand"
+	"crypto/subtle"
 	"encoding/hex"
 	"fmt"
 	mathrand "math/rand"
@@ -139,3 +140,7 @@ func RandomSleep(duration time.Duration, minRatio, maxRatio float64) time.Durati
 	time.Sleep(d)
 	return d
 }
+
+func ConstantTimeEqString(a, b string) bool {
+	return subtle.ConstantTimeCompare([]byte(a), []byte(b)) == 1
+}