Only send WS hello event once authenticated (#4509)

api/web_conn.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/mattermost/platform/model"
+	"github.com/mattermost/platform/utils"
 
 	l4g "github.com/alecthomas/log4go"
 	"github.com/gorilla/websocket"
@@ -142,6 +143,13 @@ func (webCon *WebConn) isAuthenticated() bool {
 	return webCon.SessionToken != ""
 }
 
+func (webCon *WebConn) SendHello() {
+	msg := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_HELLO, "", "", webCon.UserId, nil)
+	msg.Add("server_version", fmt.Sprintf("%v.%v.%v", model.CurrentVersion, model.BuildNumber, utils.CfgHash))
+	msg.DoPreComputeJson()
+	webCon.Send <- msg
+}
+
 func (webCon *WebConn) ShouldSendEvent(msg *model.WebSocketEvent) bool {
 	// IMPORTANT: Do not send event if WebConn does not have a session
 	if !webCon.isAuthenticated() {