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Re: A niche for the Hurd - next step: reality check


From: Arne Babenhauserheide
Subject: Re: A niche for the Hurd - next step: reality check
Date: Thu, 13 Nov 2008 22:13:22 +0100
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Am Donnerstag 13 November 2008 21:13:52 schrieb Michal Suchanek:
> This would require rewriting most of the Hurd in Lisp to allow
> carrying around modifications to even more basic services.

Wouldn't it suffice to have your modifications in lisp? You don't need every 
aspect, just the ones you want different from the provided ones. 

> Still what profile would you assign to Firefox? It does all of the
> above so it can read all your files, make enough copies of them to
> fill your disk, and send them all over the network.

I would provide it basic internet connectivity and have it request my password 
for temporarily getting additional permissions (just adding the correct 
group). 

$ addauth -p firefoxPID -g filewrite

is a crude example for allowing file writing, which would be removed after the 
filewriting operation. 

(I don't know if I currently need sudo for that)

Or a bit more finegrained: firefox would spawn a process for file transfer and 
request filewriting permissions for it. 

> And when you start actually doing something you need an editor - a
> program that can write files. And since it often shares many of the
> bugs of the viewers through use of libraries confining the viewers was
> not that great success.

For most things I view in viewers (images, movies, music) this wouldn't be 
much of a problem (ignoring metadata for the time being). 

Text editors wouldn't be a problem either. 

OpenOffice would be a problem, though. But it still could do the filewriting 
by momentarily requesting additional permissions (I don't write files all the 
time) and save all its temporary saves in its config dir with only its own 
permissions. 

> I do that daily. My ALSA setup scripts are written in Python. I never
> looked at them since Python code makes me want to wander off to the
> right. They are technically signed by Debian but I am not sure how
> much of an assurance that is given the volume of code Debian signs
> daily.

There's quite a difference between getting code from some central place (i.e. 
Debian) or getting it via email. 

Many people just open programs they get via mail ("hey, look, I found a great 
game!"). 

With the Hurd I could then just say "OK, open with game permissions". 

And then it won't be able to access the network or modify files (aside from 
the ones it creates itself in dirs games may affect). 

> And viewing a picture might be as dangerous - there are always bugs in
> some libraries but most people aren't paranoid enough to suspect data.

But these are bugs - they will eventually be fixed. 

> Yes, the critical bugs aren't that common. But good security should
> protect you from most of them, and it can be done.

Ignoring bugs in the security system - yes. 

(there's almost always a catch - but at least this would provide two layers of 
security and would make it considerably harder to exploit a weakness in a 
single library, since weaknesses in the security system would naturally also 
be fixed quite quickly)

> On a secure system I would not have to specifically set up a special
> environment for that.
> The shell would simply assign limited permissions to any process at
> startup, and should it want more it would have to ask me through the
> shell.
> 
> Of course, some processes would be privileged - for example, a browser
> (or better yet a part of a browser)  would be set up with rights to
> access the internet.

Since I don't know enough about the Hurds internals I need to ask: How much 
work would it be to adapt a shell (and the subhurd code) to do just this? 

And would you join in? 

Best wishes, 
Arne
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