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Re: Future Direction of GNU Hurd?

From: William ML Leslie
Subject: Re: Future Direction of GNU Hurd?
Date: Thu, 18 Mar 2021 19:35:26 +1100

On Mon, 15 Mar 2021 at 19:58, William ML Leslie
<william.leslie.ttg@gmail.com> wrote:
> To a first approximation, I guess.  The constructor can take on a
> similar role to a setuid binary in that it may have access to things
> the user does not, but that is not unique to constructors really (it's
> true of most running system services, also).  What a constructor
> enables is local secure collaboration.  If we use the same machine,
> then I can run a program that you've shared with me, and if you have
> provided it as a constructor then I can check that it cannot leak any
> data or capabilities I provide it back to you (or anyone else).
> Similarly, you can know that I can't open your program up in the
> debugger and force it to leak or misuse your authority.  The process
> is "mine" in the sense that I have the authority to reclaim its
> resources.
> I don't imagine that this feature will be used that much between
> different users on the same system, but more likely between two
> different processes.  The *default* should be not to leak information
> that isn't necessary to other applications.  For example, windowed
> clients shouldn't by default get to learn about what other processes
> are visible, or what brand of GPU is rendering them, or what
> keybindings are not passed on by the window manager.  The aim should
> be to limit any surveilance or fingerprinting to the level where it
> must be explicitly operated on, namely, at the express request of the
> user, not a random process running on their behalf or a broad root
> user that is misused by everything under the sun.

I feel it's worth saying that constructors aren't super useful anyway,
as far as I can tell.  They can only attenuate read authority, and so
aren't really a substitute for the setuid mechanism.

They aren't really an essential part of the system, they require no
kernel support (unless you *really* squint at Descrim), the truly
special part is the attestation about non-leakage, which isn't very
useful for system services or for most kinds of collaboration, anyway.

It's easy enough to ignore them, at least as far as the GNU is
concerned; leaving only the missing facilities for debugging and
inspection that aren't so difficult to add.

William Leslie

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A: "Authentication", clearly

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