From 1630b1f8a2d6699856702c952e44c7fd9027c046 Mon Sep 17 00:00:00 2001
From: Anant Prakash <anantprakashjsr@gmail.com>
Date: Tue, 10 Apr 2018 19:33:34 +0530
Subject: [PATCH] Refactor username parse function of login

Signed-off-by: Anant Prakash <anantprakashjsr@gmail.com>
---
 .../dendrite/clientapi/routing/login.go       | 25 +++--------
 .../dendrite/clientapi/userutil/userutil.go   | 43 +++++++++++++++++++
 2 files changed, 49 insertions(+), 19 deletions(-)
 create mode 100644 src/github.com/matrix-org/dendrite/clientapi/userutil/userutil.go

diff --git a/src/github.com/matrix-org/dendrite/clientapi/routing/login.go b/src/github.com/matrix-org/dendrite/clientapi/routing/login.go
index e0a4e6327..3804da47e 100644
--- a/src/github.com/matrix-org/dendrite/clientapi/routing/login.go
+++ b/src/github.com/matrix-org/dendrite/clientapi/routing/login.go
@@ -16,13 +16,13 @@ package routing
 
 import (
 	"net/http"
-	"strings"
 
 	"github.com/matrix-org/dendrite/clientapi/auth"
 	"github.com/matrix-org/dendrite/clientapi/auth/storage/accounts"
 	"github.com/matrix-org/dendrite/clientapi/auth/storage/devices"
 	"github.com/matrix-org/dendrite/clientapi/httputil"
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	"github.com/matrix-org/dendrite/clientapi/userutil"
 	"github.com/matrix-org/dendrite/common/config"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
@@ -82,24 +82,11 @@ func Login(
 
 		util.GetLogger(req.Context()).WithField("user", r.User).Info("Processing login request")
 
-		// r.User can either be a user ID or just the localpart... or other things maybe.
-		localpart := r.User
-		if strings.HasPrefix(r.User, "@") {
-			var domain gomatrixserverlib.ServerName
-			var err error
-			localpart, domain, err = gomatrixserverlib.SplitID('@', r.User)
-			if err != nil {
-				return util.JSONResponse{
-					Code: http.StatusBadRequest,
-					JSON: jsonerror.InvalidUsername("Invalid username"),
-				}
-			}
-
-			if domain != cfg.Matrix.ServerName {
-				return util.JSONResponse{
-					Code: http.StatusBadRequest,
-					JSON: jsonerror.InvalidUsername("User ID not ours"),
-				}
+		localpart, err := userutil.ParseUsernameParam(r.User, &cfg.Matrix.ServerName)
+		if err != nil {
+			return util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: jsonerror.InvalidUsername(err.Error()),
 			}
 		}
 
diff --git a/src/github.com/matrix-org/dendrite/clientapi/userutil/userutil.go b/src/github.com/matrix-org/dendrite/clientapi/userutil/userutil.go
new file mode 100644
index 000000000..07f21bd17
--- /dev/null
+++ b/src/github.com/matrix-org/dendrite/clientapi/userutil/userutil.go
@@ -0,0 +1,43 @@
+// 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 userutil
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+// ParseUsernameParam extracts localpart from usernameParam.
+// usernameParam can either be a user ID or just the localpart/username.
+// If serverName is passed, it is verified against the domain obtained from usernameParam (if present)
+// Returns error in case of invalid usernameParam.
+func ParseUsernameParam(userID string, expectedServerName *gomatrixserverlib.ServerName) (string, error) {
+	localpart := userID
+
+	if strings.HasPrefix(userID, "@") {
+		lp, domain, err := gomatrixserverlib.SplitID('@', userID)
+
+		if err != nil {
+			return "", errors.New("Invalid username")
+		}
+
+		if expectedServerName != nil && domain != *expectedServerName {
+			return "", errors.New("User ID does not belong to this server")
+		}
+
+		localpart = lp
+	}
+	return localpart, nil
+}