util.jid: Fix special escaping of '\' per XEP-0106 From XEP-0106 §2. Requirements: > in certain circumstances, the escaping character itself ("\") might > also be escaped Later in §4.2 Address Transformation Algorithm it is stated that the backslash would only be escaped if it forms an escape sequence. Thus '\foo' is unaltered but '\20' must be escaped into '\5c20'. Thanks to lovetox and jonas’ for brining up.

author: Kim Alvefur <zash@zash.se>
date: Fri, 28 Aug 2020 18:44:02 +0200
parent: 10358:a77d9b3885bb
child: 12190:3616128cd2e3
--- a/util/jid.lua	Fri Aug 28 18:43:37 2020 +0200
+++ b/util/jid.lua	Fri Aug 28 18:44:02 2020 +0200
@@ -22,7 +22,11 @@
 	["@"] = "\\40"; ["\\"] = "\\5c";
 };
 local unescapes = {};
-for k,v in pairs(escapes) do unescapes[v] = k; end
+local backslash_escapes = {};
+for k,v in pairs(escapes) do
+	unescapes[v] = k;
+	backslash_escapes[v] = v:gsub("\\", escapes)
+end
 
 local _ENV = nil;
 -- luacheck: std none
@@ -107,7 +111,7 @@
 	return (select(3, split(jid)));
 end
 
-local function escape(s) return s and (s:gsub(".", escapes)); end
+local function escape(s) return s and (s:gsub("\\%x%x", backslash_escapes):gsub("[\"&'/:<>@ ]", escapes)); end
 local function unescape(s) return s and (s:gsub("\\%x%x", unescapes)); end
 
 return {