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SubjectRe: [patch 2.1.97] more capabilities support

Albert D. Cahalan writes:
> > Sorry, I guess I was not clear on this. The only requirement for a
> > process to raise an effective capability is that its Permitted
> > capability (pP' here) is raised. In the case that you cite here,
> > the fact that pP' is 1 implies that the process is permitted to raise
> > its pE' with a system call.
> So "nobody" gets to use the "remove any file" capability.
> IMHO it would be nice to be able to stop that.

The question you originally posed was one of a "setuid" remove script.
In the current non-capability model, there is no protection against
'nobody' running it. None besides straigt forward file
permission/ownership -- as Astor points out.

> Considering users as:
> a. authorized to use the capability as desired
> b. limited by tools & not expected to find holes in the tools
> c. possibly serious crackers who are likely to look for holes

> User "nobody" is in group c, and should not be able to
> execute tools with such power.

> > If your claim is that when the cleanme.tool runs it will fail to
> > execute the unlink() operation on files it doesn't own, I hope I've
> > cleared that up.
> Just the opposite: the user must not have access to tools with
> that kind of power because the tools might be buggy.

The capability model has nothing to say about people's programming

> I'm thinking of the shell removing files. The closest I can imagine
> is with redirection. Would that fail? Maybe it is good, but it
> doesn't seem very compatible.

I have absolutely no idea what you mean by this since I have already
explained how 'rm' can be safely implemented in this model.


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