Re: [Xen-devel] XSM permissive by default.

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 10/03/16 17:10, Konrad Rzeszutek Wilk wrote:
> I presume this patch would be to folks +1:
>
> From 3373a50f386b41eea6ecede4b430e4fa09b2fe7e Mon Sep 17 00:00:00 2001
> From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> 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@xxxxxxxxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

> ---
>  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);
>  


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