If the SSG mandated that the value get set at boot time via a file in /etc/<upstart|systemd|something> wouldn't that be equally easy to validate offline?

You would want to do this anyway if you were going to use UDEV.

Trevor


On Fri, Apr 25, 2014 at 8:40 AM, Jan Lieskovsky <jlieskov@redhat.com> wrote:
Hi Trevor,

----- Original Message -----
> From: "Trevor Vaughan" <tvaughan@onyxpoint.com>
> To: "SCAP Security Guide" <scap-security-guide@lists.fedorahosted.org>
> Sent: Thursday, April 17, 2014 9:37:38 PM
> Subject: Re: [PATCH] [RHEL/6] Search for nousb kernel command line argument in        /etc/grub.conf within
> bootloader_nousb_argument check       case-insensitively
>
> So, wouldn't this be better approached as a udev requirement?

Checking /etc/grub.conf settings instead of udev ones has the advantage,
the system to be scanned doesn't need to run (offline scan of provided VM
image) to be able to decide if the system is configured properly.

>
> I've been avoiding udev for ages just because I don't want to get pummelled
> over the complexity but this is exactly what it can do, isn't it?
>
> Instead of saying that all USB keyboards are allowed, if you know your
> vendor, then you say that exactly the keyboards you expect to be on your
> systems are allowed, etc...
>
> I understand that no USB at the kernel level is safer but this is pushing my
> 'usability vs security' balance warnings.
>
> I.e. if, for whatever reason, I HAVE to use something USB on a system that
> can't have any downtime, you'd better believe that I'm going to leave usb on
> in the kernel. And, realistically, isn't that most of the systems you're
> trying to protect the most?
>
> http://www.irongeek.com/i.php?page=security/plug-and-prey-malicious-usb-devices#3.2_Locking_down_Linux_using_UDEV
>
> As for VMs, if I wanted to plug a USB device into a VM, I would need
> administrative access to the physical host to be able to attach the virtual
> device. If that's the case it doesn't really matter since I can pretty much
> do whatever I like to the VM (including copying its memory and disk) and not
> worry about it.
>
> Yes, I know, whining and no patches....but I'm trying to have constructive
> whining ;-).
>
> Thanks,
>
> Trevor

Thank you && Regards, Jan.
--
Jan iankko Lieskovsky / Red Hat Security Technologies Team

>
>
> On Thu, Apr 17, 2014 at 3:20 PM, Trey Henefield <
> trey.henefield@ultra-ats.com > wrote:
>
>
>
>
>
>
>
> We have a mix a systems to which some require USB and some do not. While it’s
> not feasible to know the need of every system when applying this
> requirement, I have found some logic that seems to work:
>
>
>
> USB_DEVICE=$(grep 'Product=' /proc/bus/usb/devices | egrep -ic '(ps2 to usb
> adapter|keyboard|kvm|sc reader)')
>
>
>
> If [ $USB_DEVICE = 0 ]; then
>
> DO SOME ACTION
>
> fi
>
>
>
> The above will check for a USB keyboard, a PS2 to USB adapter (needed for a
> USB keyboard in some cases), a USB KVM, and a CAC reader (only approved
> versions are USB).
>
>
>
> It may be useful to add that logic to your fix.
>
>
>
> Best regards,
>
>
>
>
>
> Trey Henefield, CISSP
>
> Senior IAVA Engineer
>
>
>
> Ultra Electronics
>
> Advanced Tactical Systems, Inc.
>
> 4101 Smith School Road
>
> Building IV, Suite 100
>
> Austin, TX 78744 USA
>
>
>
> Trey.Henefield@ultra-ats.com
>
> Tel: +1 512 327 6795 ext. 647
>
> Fax: +1 512 327 8043
>
> Mobile: +1 512 541 6450
>
>
>
> www.ultra-ats.com
>
>
>
> From: scap-security-guide-bounces@lists.fedorahosted.org [mailto:
> scap-security-guide-bounces@lists.fedorahosted.org ] On Behalf Of Trevor
> Vaughan
> Sent: Thursday, April 17, 2014 7:11 AM
> To: SCAP Security Guide
> Subject: Re: [PATCH] [RHEL/6] Search for nousb kernel command line argument
> in /etc/grub.conf within bootloader_nousb_argument check case-insensitively
>
>
>
>
>
> Just out of curiosity, is adding nousb to the grub command line actually
> feasible for enforcement?
>
>
>
>
>
> I can't remember the last time I used a system where I didn't need a USB
> keyboard at some point (can you even buy server class systems with PS/2
> support any more?)
>
>
>
>
>
> Trevor
>
>
>
>
>
> On Wed, Apr 16, 2014 at 8:23 PM, Shawn Wells < shawn@redhat.com > wrote:
>
>
>
>
> On 4/16/14, 5:08 PM, Kayse, Josh wrote:
>
>
>
>
>
>
>
>
> On Apr 16, 2014, at 8:06 PM, Kayse, Josh < Joshua.Kayse@gtri.gatech.edu >
> wrote:
>
>
>
>
>
>
>
>
>
>
>
>
> On Apr 16, 2014, at 7:59 PM, Shawn Wells < shawn@redhat.com > wrote:
>
>
>
>
>
>
>
>
>
> On 4/16/14, 5:44 AM, Jan Lieskovsky wrote:
>
>
>
> Patch summary:
> * check for 'nousb' argument on kernel command line in /etc/grub.conf
> within the bootloader_nousb_argument check in a case-insensitive way
> * update comments where appropriate
> * add test attestation timestamp
> * replace path + filename ind construct with filepath one
> Testing report:
> * Tested on RHEL-6. Works fine.
>
>
>
> I wasn't sure if nousb was case insensitive, so I checked
> https://www.kernel.org/doc/Documentation/kernel-parameters.txt
>
> And found this:
>
>
>
>
> Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
> a trailing = on the name of any parameter states that that parameter will
> be entered as an environment variable, whereas its absence indicates that
> it will appear as a kernel argument readable via /proc/cmdline by programs
> running once the system is up.
>
>
>
> "nousb" was in the list as case sensitive.
>
> Applied your patch (RHEL 6.5), added "nOuSB," and things seem to check out.
> Should we follow the kernel docs (which say case sensitive), or allow
> insensitivity since it actually works?
>
>
> _______________________________________________
> scap-security-guide mailing list
> scap-security-guide@lists.fedorahosted.org
> https://lists.fedorahosted.org/mailman/listinfo/scap-security-guide
>
>
>
>
>
> I’d like to point out that the selinux parameter is also within that list. I
> vote we should follow what actually works and assume the kernel docs are out
> of date.
>
>
>
>
>
> -josh
>
>
>
>
>
> Also, according to
> https://github.com/torvalds/linux/blame/master/Documentation/kernel-parameters.txt
> that line was last changed 2005. Perhaps someone should brave lkml and
> submit a patch.
>
>
>
>
>
> -josh
>
>
>
> Thanks for that link!
>
> Ack to Jan's patch.
>
>
>
>
> _______________________________________________
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>
>
>
>
>
>
>
>
>
> --
> Trevor Vaughan
> Vice President, Onyx Point, Inc
> (410) 541-6699
> tvaughan@onyxpoint.com
>
> -- This account not approved for unencrypted proprietary information --
>
>
>
>
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>
>
>
>
> --
> Trevor Vaughan
> Vice President, Onyx Point, Inc
> (410) 541-6699
> tvaughan@onyxpoint.com
>
> -- This account not approved for unencrypted proprietary information --
>
> _______________________________________________
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--
Trevor Vaughan
Vice President, Onyx Point, Inc
(410) 541-6699
tvaughan@onyxpoint.com

-- This account not approved for unencrypted proprietary information --