Anything that can be modified by an attacker can not be used to secure the sudo command. This is a recursive requirementor hierarchy for secure systems.

You can set the permissions so that the attacker can't modify it?

You would need to prevent an attacker from installing shell aliases, or shell config files, or altering any binaries in PATH.

Like, sure you could, but you end up with a very useless system.

Easier to just use VMs for each security context.

Is any of this specific to a link vs tyre original full-pathed sudo?

A simple LD_PRELOAD command can cause your shell to run "rm -rf /" when you type "/sudo".

If your unprivileged user is compromised, you are pretty hosed.

It should be a way to make system env vars (profile.d or simlar) as readonly so every users' shell had these set to empty values and unable to change them.

I have a better idea, not dependent on whether shell is secure (which is endless whack a mole): https://news.ycombinator.com/item?id=48107092

Shell-only, but https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V...

Yes; I'm aware, but for some environments writting a custom shell as the one for SDF would be an easier task. Or maybe a really restricted "ash" called "rash" -because it is- with maybe autocomplete and that's it. Hardcoded $PATH and the like.