From: Doug Goldstein <cardoe@cardoe.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Daniel De Graaf <dgdegra@tycho.nsa.gov>,
xen-devel@lists.xenproject.org
Subject: Re: XSM permissive by default.
Date: Thu, 10 Mar 2016 11:34:59 -0600 [thread overview]
Message-ID: <56E1B043.2020508@cardoe.com> (raw)
In-Reply-To: <20160310171059.GA32334@char.us.oracle.com>
[-- Attachment #1.1.1: Type: text/plain, Size: 5260 bytes --]
On 3/10/16 11:10 AM, Konrad Rzeszutek Wilk wrote:
> On Wed, Mar 09, 2016 at 08:40:05PM -0600, Doug Goldstein wrote:
>> On 3/9/16 4:09 PM, Daniel De Graaf wrote:
>>> On 03/09/2016 04:17 PM, Konrad Rzeszutek Wilk wrote:
>>>> On Wed, Mar 09, 2016 at 01:24:15PM +0000, Andrew Cooper wrote:
>>>>> On 09/03/16 01:51, Konrad Rzeszutek Wilk wrote:
>>>>>> Hey,
>>>>>>
>>>>>> I was wondering if it we should change the default flask_bootparam
>>>>>> option from permissive to disabled?
>>
>>>>>
>>>>> By the looks of it, "permissive" shouldn't be an available option at
>>>>> all.
>>>
>>> Permissive is meant for developing (or debugging) a disaggregated system,
>>> where the restrictions on non-dom0 would also break the system. However,
>>> I agree that it needs to be harder to end up in this mode by accident.
>>>
>>> The simplest solution in my opinion is to change the boot parameter to
>>> default to "flask=enforcing", which will fail the boot if a policy is
>>> not available prior to dom0 creation. This would require any setup
>>> where the policy is loaded from userspace to explicitly specify
>>> "flask=late", whereas they can currently get away with no parameter.
>>>
>>> Another solution would be to default to "flask=late" and either deny the
>>> creation of domains if a policy is not present, or automatically revert
>>> to the dummy module on domain creation with no loaded policy. The latter
>>> probably deserves a different name ("flask=auto"?).
>>>
>>
>> Honestly I'm in favor of secure by default approach. Since Xen is not
>> built with flask by default to me the sane approach would be to default
>> the system to "flask=enforcing".
>>
>> "flask=late" not allowing the creation of domains sounds good but what
>> if you're using a disaggregated dom0 with some domDs and one of them
>> needs to be up to fetch your policy? Just a hypothetical.
>>
>> XSMs like LSMs just aren't meant to be swapped around at runtime and
>> like Daniel points out if go down the road of swapping to the dummy
>> module there could be further dragons and whose to say someone won't
>> look at that and put something in that allows you to switch to another
>> later on (yes I know there's only really 1 but I'm speaking of the
>> hypothetical).
>
>
> I presume this patch would be to folks +1:
>
> From 3373a50f386b41eea6ecede4b430e4fa09b2fe7e Mon Sep 17 00:00:00 2001
> From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Date: Thu, 10 Mar 2016 12:05:29 -0500
> Subject: [PATCH] flask: By default be in FLASK_BOOTPARAM_ENFORCING mode.
>
> By default the mode was 'permissive' which is "meant for
> developing (or debugging) a disaggregated system,
> where the restrictions on non-dom0 would also break the system."
>
> However this default mode made it possible to boot an machine
> in this state if a policy file during bootup was not provided.
>
> The end was less secure than with XSM-enabled - any guest
> could do any operation (including rebooting the machine).
>
> Alternative solutions such as switching from flask to dummy.
> However "The main issue with starting with dummy and then
> switching to FLASK is that any domains created while using
> the dummy policy won't have flask_domain_alloc_security called
> to populate domain->ssid, and the rest of the flask code relies
> on this being non-NULL. The same would be true for event channels,
> but inlining the field to save space makes that a non-issue."
>
> (both excerpts are from Daniel De Graaf emails).
>
> This is a much easier fix.
>
> Suggested-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
> docs/misc/xen-command-line.markdown | 2 +-
> xen/xsm/flask/flask_op.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
> index ca77e3b..9e77f8a 100644
> --- a/docs/misc/xen-command-line.markdown
> +++ b/docs/misc/xen-command-line.markdown
> @@ -662,7 +662,7 @@ to use the default.
> ### flask
> > `= permissive | enforcing | late | disabled`
>
> -> Default: `permissive`
> +> Default: `enforcing`
>
> Specify how the FLASK security server should be configured. This option is only
> available if the hypervisor was compiled with XSM support (which can be enabled
> diff --git a/xen/xsm/flask/flask_op.c b/xen/xsm/flask/flask_op.c
> index f4f5dd1..aaed75d 100644
> --- a/xen/xsm/flask/flask_op.c
> +++ b/xen/xsm/flask/flask_op.c
> @@ -25,7 +25,7 @@
> #define _copy_to_guest copy_to_guest
> #define _copy_from_guest copy_from_guest
>
> -enum flask_bootparam_t __read_mostly flask_bootparam = FLASK_BOOTPARAM_PERMISSIVE;
> +enum flask_bootparam_t __read_mostly flask_bootparam = FLASK_BOOTPARAM_ENFORCING;
> static void parse_flask_param(char *s);
> custom_param("flask", parse_flask_param);
>
>
+1
You also found a spot that I didn't find when doing the Kconfig
conversion of CONFIG_XSM / CONFIG_FLASK. My search didn't catch
XSM\_ENABLE so follow on patch from me for that will be coming.
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>
--
Doug Goldstein
[-- Attachment #1.2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 959 bytes --]
[-- Attachment #2: Type: text/plain, Size: 126 bytes --]
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-03-10 17:35 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-09 1:51 XSM permissive by default Konrad Rzeszutek Wilk
2016-03-09 2:11 ` Doug Goldstein
2016-03-09 13:24 ` Andrew Cooper
2016-03-09 21:17 ` Konrad Rzeszutek Wilk
2016-03-09 22:09 ` Daniel De Graaf
2016-03-10 2:40 ` Doug Goldstein
2016-03-10 17:10 ` Konrad Rzeszutek Wilk
2016-03-10 17:34 ` Doug Goldstein [this message]
2016-03-10 17:44 ` Andrew Cooper
2016-03-10 18:30 ` [PATCH] flask: change default state to enforcing Daniel De Graaf
2016-03-10 19:12 ` Konrad Rzeszutek Wilk
2016-03-10 19:37 ` Daniel De Graaf
2016-03-15 14:48 ` Anshul Makkar
2016-03-11 9:07 ` Jan Beulich
2016-03-11 14:58 ` Konrad Rzeszutek Wilk
2016-03-11 15:39 ` Daniel De Graaf
2016-03-11 15:43 ` Jan Beulich
2016-03-11 15:51 ` Daniel De Graaf
2016-04-04 17:12 ` XSM permissive by default Ian Jackson
2016-04-05 8:03 ` Jan Beulich
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=56E1B043.2020508@cardoe.com \
--to=cardoe@cardoe.com \
--cc=andrew.cooper3@citrix.com \
--cc=dgdegra@tycho.nsa.gov \
--cc=konrad.wilk@oracle.com \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).