From 6d33fa5d937be3e33fa9cf14d35fc9ab45712750 Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Wed, 26 Feb 2020 15:59:33 +0100
Subject: [PATCH] Safer ident transform

---
 appservice/util.go | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/appservice/util.go b/appservice/util.go
index 4175fb0..160f492 100644
--- a/appservice/util.go
+++ b/appservice/util.go
@@ -2,7 +2,7 @@ package appservice
 
 import (
 	"fmt"
-	"strings"
+	"unicode"
 
 	log "github.com/sirupsen/logrus"
 
@@ -44,8 +44,15 @@ func userMxId(protocol string, id UserID) string {
 }
 
 func safeStringForId(in string) string {
-	id2 := strings.ReplaceAll(in, "#", "")
-	id2 = strings.ReplaceAll(id2, "@", "__")
-	id2 = strings.ReplaceAll(id2, ":", "_")
+	id2 := ""
+	for _, c := range in {
+		if c == '@' {
+			id2 += "__"
+		} else if c == ':' {
+			id2 += "_"
+		} else if unicode.IsDigit(c) || unicode.IsLetter(c) {
+			id2 += string(c)
+		}
+	}
 	return id2
 }