linux-kernel - Re: [patch 1/2] [RFC] Simple tamper-proof device filesystem.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <476738A0.9010601@cs.columbia.edu>
Date:	Mon, 17 Dec 2007 22:04:00 -0500
From:	Oren Laadan <orenl@...columbia.edu>
To:	"Serge E. Hallyn" <serue@...ibm.com>
CC:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	linux-fsdevel@...r.kernel.org,
	Linux Containers <containers@...ts.osdl.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 1/2] [RFC] Simple tamper-proof device filesystem.


Serge E. Hallyn wrote:
> Quoting Oren Laadan (orenl@...columbia.edu):
>> I hate to bring this again, but what if the admin in the container
>> mounts an external file system (eg. nfs, usb, loop mount from a file,
>> or via fuse), and that file system already has a device that we would
>> like to ban inside that container ?
> 
> Miklos' user mount patches enforced that if !capable(CAP_MKNOD),
> then mnt->mnt_flags |= MNT_NODEV.  So that's no problem.

Yes, that works to disallow all device files from a mounted file system.

But it's a black and white thing: either they are all banned or allowed;
you can't have some devices allowed and others not, depending on type
A scenario where this may be useful is, for instance, if we some apps in
the container to execute withing a pre-made chroot (sub)tree within that
container.

> 
> But that's been pulled out of -mm! ?  Crap.
> 
>> Since anyway we will have to keep a white- (or black-) list of devices
>> that are permitted in a container, and that list may change even change
>> per container -- why not enforce the access control at the VFS layer ?
>> It's safer in the long run.
> 
> By that you mean more along the lines of Pavel's patch than my whitelist
> LSM, or you actually mean Tetsuo's filesystem (i assume you don't mean that
> by 'vfs layer' :), or something different entirely?

:)

By 'vfs' I mean at open() time, and not at mount(), or mknod() time.
Either yours or Pavel's; I tend to prefer not to use LSM as it may
collide with future security modules.

Oren.

> 
> thanks,
> -serge
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/