[ubuntu-hardened] Re: Fixed some bugs in the postinst and postrm
scripts of vSecurity packages, merged amd64 changes
magnus at therning.org
Fri Oct 14 04:44:46 CDT 2005
On Thu, Oct 13, 2005 at 06:48:12PM +0200, Lorenzo Hernández García-Hierro wrote:
>$ sudo apt-get install vsecurity
> Setting up vsecurity-686 (0.3-0ubuntu1) ...
> FATAL: Error inserting vsecurity (/lib/modules/2.6.12-9-686/kernel/security/vsecurity.ko): Invalid argument
> !!! Capabilities module blocks vSecurity. For keeping capabilities set in current processes, a reboot is needed.
> !!! PLEASE, REBOOT.
[.. explanation of fatal error inserting vsecurity ..]
Thanks for the clarification. It looks much worse than it is then :-)
Is there any documentation at all for vsecurity?
In the `documentation` dir there's only one file, on BSD jails. I'm not
sure that doc is worth very much since it seems one needs to know what a
BSD jail is in order to understand the explanation of a BSD jail in
there (I am not that familiar with the term). The examples for setting
up a jail is also a little confusing, they refer to executables I don't
have on my system, not even after installing vsecurity.
I'd also like to see some more details on the other parts of the module.
>BTW, I'm thinking about adding a by-parameter-configured feature
>implementing "kernel sealing". Let's clarify that "sealing" concept.
>I'm sure most of us know that a kernel open for LKMs is a kernel
>providing interfaces for a wide range of malicious or dangerous
>operations (ie. runtime patching, rootkit installation, etc). The
>problem is that we can't cut certain capabilities without affecting
>programs execution flow. CapOver changes (to be merged) will deploy a
>fine-grained control (using a simplistic policy language) over which
>capabilities are granted to each binary, but this may sound still weak
>to security junkies and other people (like myself a few times...),
>hence the need of an extra option. We could try to seal the kernel
>preventing any further modules to be loaded until reboot (think that,
>when you're root in the machine and there's no MAC engine running, but
>only DAC, root can virtually do anything). Also, we could try to limit
>CAP_SYS_RAWIO or even removing it from the
>capabilities-that-can-be-granted ring (return -EPERM when requested
>within the capable() hook). This is not a difficult thing to get done
>but I want to hear your opinion about it, before I work out something
>by myself and commit it to CVS.
I've always been leaning somewhat towards saying that this isn't
necessary. Plugging the loadable-kernel-module hole (be it a security
module or a regular module) is done easiest by simply not compiling in
support for loading kernel modules. :-)
I could see a use for your "sealing" in test systems---adding hardware
requires a reboot rather than a kernel compilation.
Another use, that I might have myself is for the times when I enter my
laptop into a network I don't really trust. Just as an extra precaution
I'd "seal" my kernel before hooking it into the network. I think I could
live with having to reboot to "unseal" it again.
Magnus Therning (OpenPGP: 0xAB4DFBA4)
magnus at therning.org
Software is not manufactured, it is something you write and publish.
Keep Europe free from software patents, we do not want censorship
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rogrammers and programs alike need die gracefully upon failure, and
exit with no system disruption.
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