GT.M does not implement a security layer itself, and instead uses on access control as implemented by the operating system (user/group/world permissions and layered security such as SELinux). I know that some applications have accomplished what you want using the traditional user/group/world controls, but it does require the application schema to be amenable. Other applications implement access controls at the application layer.
The quote above by @DAiMor is dated. The current quote from the manual is:
Ensure that database file ownership (user and group), UNIX user and group ids, and permissions at the UNIX level match the intended access. If finer grained access controls than those provided by user and group ids and permissions are needed, consider using, where appropriate and available, security products layered on top of the operating system.
In general, we no longer recommend Access Control Lists. I notice that there is a later mention of it in the manual, which we should remove. ACLs work for files, but not for resources like shared memory.