# Adding custom root certificate authority (secure MQTT)

**URL:** <https://forum.legato.io/t/adding-custom-root-certificate-authority-secure-mqtt/6565>\
**Category:** Legato Application Framework\
**Created:** [August 8, 2023, 3:46pm UTC](https://forum.legato.io/t/adding-custom-root-certificate-authority-secure-mqtt/6565 "2023-08-08T15:46:54Z")\
**Posts on this page:** 1\
**Showing post:** 12

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**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\
**Post date:** [August 10, 2023, 1:12am UTC](https://forum.legato.io/t/adding-custom-root-certificate-authority-secure-mqtt/6565/12 "2023-08-10T01:12:35Z")

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see if these help to create file and access it in sandboxed app

> [@App access to /tmp](https://forum.legato.io/t/app-access-to-tmp/3480/18):
>
> On my side, if I change the unsandboxed application to create a file in /tmp, and then create another symbolic link in /home/root to this file, then the sandboxed application can still access this symbolic link. system("echo hello\_everybody \> /tmp/hello.txt"); system("ln -s /tmp/hello.txt /home/root/hello.txt"); system("chmod o+w /home/root/hello.txt"); system("/mnt/legato/system/bin/xattr set 'security.SMACK64' 'app.hello7rwx' /home/root/hello.txt"); So it seems we can still create the fi…

> [@Opening Files in Sandboxed App](https://forum.legato.io/t/opening-files-in-sandboxed-app/5525):
>
> Quick question: I created a file in /tmp on my WP8548: /tmp/test.txt How do i access it in my Sandboxed app? I tried adding requires: { file: { /tmp/test.txt /tmp } } But i still cannot open it.

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