use special multibyte shell escaping to support unicode ssid names with qr code

app/img/wifi-qr-code.php

@@ -42,7 +42,7 @@ $ssid = qr_encode($ssid);
 $password = qr_encode($password);
 
 $data = "WIFI:S:$ssid;T:$type;P:$password;$hidden;";
-$command = "qrencode -t svg -m 0 -o - " . escapeshellarg($data);
+$command = "qrencode -t svg -m 0 -o - " . mb_escapeshellarg($data);
 $svg = shell_exec($command);
 
 $config_mtime  = filemtime(RASPI_HOSTAPD_CONFIG);

includes/functions.php

@@ -518,6 +518,18 @@ function cache($key, $callback)
     }
 }
 
+// insspired by
+// http://markushedlund.com/dev/php-escapeshellarg-with-unicodeutf-8-support
+function mb_escapeshellarg($arg)
+{
+    $isWindows = strtolower(substr(PHP_OS, 0, 3)) === 'win';
+    if ($isWindows) {
+        return '"' . str_replace(array('"', '%'), '', $arg) . '"';
+    } else {
+        return "'" . str_replace("'", "'\\''", $arg) . "'";
+    }
+}
+
 function dnsServers()
 {
     $data = json_decode(file_get_contents("./config/dns-servers.json"));