fix(electron): validate external login URL scheme and callback port (#1621)

electron/external-login.cjs

@@ -0,0 +1,20 @@
+/**
+ * The login URL a server hands the desktop app goes to shell.openExternal,
+ * so only web pages pass: any other scheme (file:, smb:, ms-msdt:, ...)
+ * would launch whatever OS handler is registered for it.
+ */
+function isExternalLoginUrl(value) {
+  try {
+    const { protocol } = new URL(value);
+    return protocol === "https:" || protocol === "http:";
+  } catch {
+    return false;
+  }
+}
+
+/** A non-privileged port for the loopback callback listener. */
+function isCallbackPort(value) {
+  return Number.isInteger(value) && value >= 1024 && value <= 65535;
+}
+
+module.exports = { isExternalLoginUrl, isCallbackPort };