Safe compare password (timing attack) (#338)

Author: denji

models/user.go

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"container/list"
 	"crypto/sha256"
+	"crypto/subtle"
 	"encoding/hex"
 	"errors"
 	"fmt"
@@ -368,7 +369,7 @@ func (u *User) EncodePasswd() {
 func (u *User) ValidatePassword(passwd string) bool {
 	newUser := &User{Passwd: passwd, Salt: u.Salt}
 	newUser.EncodePasswd()
-	return u.Passwd == newUser.Passwd
+	return subtle.ConstantTimeCompare([]byte(u.Passwd), []byte(newUser.Passwd)) == 1
 }
 
 // UploadAvatar saves custom avatar for user.