Log errors returned from graphql (#3562)

* Add func methods to logger
* Log errors returned from the graphql interface
* Log authentication
* Log when credentials changed

pkg/session/session.go

@@ -34,7 +34,15 @@ const (
 	passwordFormKey = "password"
 )
 
-var ErrInvalidCredentials = errors.New("invalid username or password")
+type InvalidCredentialsError struct {
+	Username string
+}
+
+func (e InvalidCredentialsError) Error() string {
+	// don't leak the username
+	return "invalid credentials"
+}
+
 var ErrUnauthorized = errors.New("unauthorized")
 
 type Store struct {
@@ -63,9 +71,12 @@ func (s *Store) Login(w http.ResponseWriter, r *http.Request) error {
 
 	// authenticate the user
 	if !s.config.ValidateCredentials(username, password) {
-		return ErrInvalidCredentials
+		return &InvalidCredentialsError{Username: username}
 	}
 
+	// since we only have one user, don't leak the name
+	logger.Info("User logged in")
+
 	newSession.Values[userIDKey] = username
 
 	err := newSession.Save(r, w)
@@ -90,6 +101,9 @@ func (s *Store) Logout(w http.ResponseWriter, r *http.Request) error {
 		return err
 	}
 
+	// since we only have one user, don't leak the name
+	logger.Infof("User logged out")
+
 	return nil
 }