Deno.mainModule should not require permissions

[nayeemrmn]

The value of Deno.mainModule is visible in call stacks. In general, we should make it a non-goal to hide information about "calling" code. You can currently hide it from call stacks by moving calls to untrusted code to the top-level of some other insignificant imported module. But the same technique could most likely be used to make sure your Deno.mainModule is insignificant.

This leaves future opportunities to remove import.meta.main in favour of import.meta.url == Deno.mainModule, as was intended by the spec: https://github.com/tc39/proposal-import-meta#am-i-the-main-module. But that means we have to statically substitute Deno.mainModule in bundles, leaving no way to get the "true" main module which some people won't like (#6344 (comment)). Anyway, that discussion can wait.

[kitsonk]

Hmmm...

The one "problem" with this is that any module could get information about the local system. We have import.meta.main which provides this information, and we have "fixed" what happens with bundles. This means each module can know itself and if it is the main module.

So personally, I think the permissions should stay, taking the conservative viewpoint, until there is a compelling use case we can't work around reasonably.

Actually the point about the stack traces is interesting from a security exploit perspective. I wonder if throwing an error and trapping the trace would expose information about the local file system?

[bartlomieju]

I hit this problem as well working on Node compatibility - accessing process.argv (which uses Deno.mainModule internally) requires to open full FS read sandbox. I think it's hindering DX in this case, and unless users gave --allow-write there's no harm in allowing to inspect Deno.mainModule without a permission.

[jsejcksn]

and unless users gave --allow-write there's no harm in allowing to inspect Deno.mainModule without a permission

Network access would allow for exfiltrating this information.

[bartlomieju]

Discussed with other team members, we are going to remove requirement for allow read permission on Deno.mainModule.

[alexandrubau]

Any updates regarding this topic? Thanks