Re: Capabilities done right [diff against 2.3.1]

Albert D. Cahalan (acahalan@cs.uml.edu)
Sun, 16 May 1999 03:34:46 -0400 (EDT)


Linus Torvalds writes:
> On Sun, 16 May 1999, Albert D. Cahalan wrote:

>> You want to allow shellscripts with special powers?!?!?
>
> I may want to _strip_ shellscripts of power.

I suppose you intend to turn normal user abilities into default
capabilities. (the ability to write to a writable file...)

I think that has the same problem, but nevermind.

It is also dangerous to add default capabilities because apps may drop
unknown capabilities, causing failure at some critical point.

> I may want to give special power to certain Javascripts (assuming I'd ever
> trust the java engine itself). I do _not_ consider it acceptable to give
> all powers to the java interpreter in general, but I _do_ consider it
> acceptable to give special capabilities to certain scripts.

When the interpreter and script both have capabilities marked...?

> The ELF notes way doesn't allow that.

You give capabilities to your trusted interpreter.
It handles the issue according to whatever policy is needed.

> Do you start to see a pattern here now? It's not about ELF. It's about
> everything ELSE. It's about doing something right, and not getting stuck
> with a bad decision forever.

You only get stuck with the existance of the mechanism, which isn't
too bad. The mechanism may be needed anyway for non-native filesystems.

Nothing prevents the creation of an alternate system that overrides the
ELF header. (so there is no need to even look at the ELF notes in that case)

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