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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v5] flask: create unified "flask=" boot parameter
On 09/03/15 17:02, Daniel De Graaf wrote:
> This unifies the flask_enforcing and flask_enabled boot parameters into
> a single parameter with additional states. Defined options are:
>
> enforcing - require policy to be loaded at boot time and enforce it
> permissive - a missing or broken policy does not panic
> disabled - revert to dummy (no XSM) policy. Was flask_enabled=0
> late - bootloader policy is not used; later loadpolicy is enforcing
>
> The default mode remains "permissive" and the flask_enforcing boot
> parameter is retained for compatibility. If flask_enforcing=1 is
> specified and flask= is not, the bootloader policy will be loaded in
> enforcing mode if present, but errors will disable access controls until
> a successful loadpolicy instead of causing a panic at boot.
>
> Suggested-by: Julien Grall <julien.grall@xxxxxxxxxx>
> Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Bonus - we gain more command line documentation!
> ---
> Changes from v4:
> - Use enum and bool_t for parameter globals
> - Remove duplication of flask=force/enforcing
> - Move panic out of command line parsing so it is visible
>
> ---
> docs/man/xl.pod.1 | 4 ++--
> docs/misc/xen-command-line.markdown | 30 +++++++++++++++++++++++++-----
> docs/misc/xsm-flask.txt | 29 -----------------------------
> xen/xsm/flask/flask_op.c | 34 ++++++++++++++++++++++++++++++----
> xen/xsm/flask/hooks.c | 32 +++++++++++++++++++++++---------
> xen/xsm/flask/include/avc.h | 2 +-
> xen/xsm/flask/include/security.h | 10 +++++++++-
> 7 files changed, 90 insertions(+), 51 deletions(-)
>
> diff --git a/docs/man/xl.pod.1 b/docs/man/xl.pod.1
> index cd80ffc..198ee2b 100644
> --- a/docs/man/xl.pod.1
> +++ b/docs/man/xl.pod.1
> @@ -1441,8 +1441,8 @@ Determine if the FLASK security module is loaded and
> enforcing its policy.
> =item B<setenforce> I<1|0|Enforcing|Permissive>
>
> Enable or disable enforcing of the FLASK access controls. The default is
> -permissive and can be changed using the flask_enforcing option on the
> -hypervisor's command line.
> +permissive, but this can be changed to enforcing by specifying
> "flask=enforcing"
> +or "flask=late" on the hypervisor's command line.
>
> =item B<loadpolicy> I<policy-file>
>
> diff --git a/docs/misc/xen-command-line.markdown
> b/docs/misc/xen-command-line.markdown
> index e125212..5044da1 100644
> --- a/docs/misc/xen-command-line.markdown
> +++ b/docs/misc/xen-command-line.markdown
> @@ -638,11 +638,31 @@ hardware domain is architecture dependent.
> Note that specifying zero as domU value means zero, while for dom0 it means
> to use the default.
>
> -### flask\_enabled
> -> `= <integer>`
> -
> -### flask\_enforcing
> -> `= <integer>`
> +### flask
> +> `= permissive | enforcing | late | disabled`
> +
> +> Default: `permissive`
> +
> +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
> +by setting XSM\_ENABLE = y in .config).
> +
> +* `permissive`: This is intended for development and is not suitable for use
> + with untrusted guests. If a policy is provided by the bootloader, it will
> be
> + loaded; errors will be reported to the ring buffer but will not prevent
> + booting. The policy can be changed to enforcing mode using "xl
> setenforce".
> +* `enforcing`: This requires a security policy to be provided by the
> bootloader
> + and will enter enforcing mode prior to the creation of domain 0. If a
> valid
> + policy is not provided, the hypervisor will not continue booting.
> +* `late`: This disables loading of the security policy from the bootloader.
> + FLASK will be enabled but will not enforce access controls until a policy
> is
> + loaded by a domain using "xl loadpolicy". Once a policy is loaded, FLASK
> will
> + run in enforcing mode unless "xl setenforce" has changed that setting.
> +* `disabled`: This causes the XSM framework to revert to the dummy module.
> The
> + dummy module provides the same security policy as is used when compiling
> the
> + hypervisor without support for XSM. The xsm\_op hypercall can also be
> used to
> + switch to this mode after boot, but there is no way to re-enable FLASK once
> + the dummy module is loaded.
>
> ### font
> > `= <height>` where height is `8x8 | 8x14 | 8x16`
> diff --git a/docs/misc/xsm-flask.txt b/docs/misc/xsm-flask.txt
> index 9559028..ab05913 100644
> --- a/docs/misc/xsm-flask.txt
> +++ b/docs/misc/xsm-flask.txt
> @@ -396,32 +396,3 @@ the ranges being denied to more easily determine what
> resources are required.
> When running in permissive mode, only the first denial of a given
> source/destination is printed to the log, so labeling devices using this
> method
> may require multiple passes to find all required ranges.
> -
> -Additional notes on XSM:FLASK
> ------------------------------
> -
> -1) xen command line parameters
> -
> - a) flask_enforcing
> -
> - The default value for flask_enforcing is '0'. This parameter causes
> the
> - platform to boot in permissive mode which means that the policy is
> loaded
> - but not enforced. This mode is often helpful for developing new
> systems
> - and policies as the policy violations are reported on the xen console
> and
> - may be viewed in dom0 through 'xl dmesg'.
> -
> - To boot the platform into enforcing mode, which means that the policy is
> - loaded and enforced, append 'flask_enforcing=1' on the grub line.
> -
> - This parameter may also be changed through the flask hypercall.
> -
> - b) flask_enabled
> -
> - The default value for flask_enabled is '1'. This parameter causes the
> - platform to enable the FLASK security module under the XSM framework.
> - The parameter may be enabled/disabled only once per boot. If the
> parameter
> - is set to '0', only a reboot can re-enable flask. When flask_enabled
> is '0'
> - the DUMMY module is enforced.
> -
> - This parameter may also be changed through the flask hypercall. But may
> - only be performed once per boot.
> diff --git a/xen/xsm/flask/flask_op.c b/xen/xsm/flask/flask_op.c
> index 0e89360..84c7fec 100644
> --- a/xen/xsm/flask/flask_op.c
> +++ b/xen/xsm/flask/flask_op.c
> @@ -24,11 +24,12 @@
> #define _copy_to_guest copy_to_guest
> #define _copy_from_guest copy_from_guest
>
> -int flask_enforcing = 0;
> -integer_param("flask_enforcing", flask_enforcing);
> +enum flask_bootparam_t __read_mostly flask_bootparam =
> FLASK_BOOTPARAM_PERMISSIVE;
> +static void parse_flask_param(char *s);
> +custom_param("flask", parse_flask_param);
>
> -int flask_enabled = 1;
> -integer_param("flask_enabled", flask_enabled);
> +bool_t __read_mostly flask_enforcing = 0;
> +boolean_param("flask_enforcing", flask_enforcing);
>
> #define MAX_POLICY_SIZE 0x4000000
>
> @@ -60,6 +61,26 @@ extern int ss_initialized;
>
> extern struct xsm_operations *original_ops;
>
> +static void __init parse_flask_param(char *s)
> +{
> + if ( !strcmp(s, "enforcing") )
> + {
> + flask_enforcing = 1;
> + flask_bootparam = FLASK_BOOTPARAM_ENFORCING;
> + }
> + else if ( !strcmp(s, "late") )
> + {
> + flask_enforcing = 1;
> + flask_bootparam = FLASK_BOOTPARAM_LATELOAD;
> + }
> + else if ( !strcmp(s, "disabled") )
> + flask_bootparam = FLASK_BOOTPARAM_DISABLED;
> + else if ( !strcmp(s, "permissive") )
> + flask_bootparam = FLASK_BOOTPARAM_PERMISSIVE;
> + else
> + flask_bootparam = FLASK_BOOTPARAM_INVALID;
> +}
> +
> static int domain_has_security(struct domain *d, u32 perms)
> {
> struct domain_security_struct *dsec;
> @@ -502,6 +523,7 @@ static int flask_security_load(struct xen_flask_load
> *load)
> {
> int ret;
> void *buf = NULL;
> + bool_t is_reload = ss_initialized;
>
> ret = domain_has_security(current->domain, SECURITY__LOAD_POLICY);
> if ( ret )
> @@ -526,6 +548,10 @@ static int flask_security_load(struct xen_flask_load
> *load)
> if ( ret )
> goto out;
>
> + if ( !is_reload )
> + printk(XENLOG_INFO "Flask: Policy loaded, continuing in %s mode.\n",
> + flask_enforcing ? "enforcing" : "permissive");
> +
> xfree(bool_pending_values);
> bool_pending_values = NULL;
> ret = 0;
> diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
> index dad5deb..05dafed 100644
> --- a/xen/xsm/flask/hooks.c
> +++ b/xen/xsm/flask/hooks.c
> @@ -1628,15 +1628,23 @@ static struct xsm_operations flask_ops = {
>
> static __init void flask_init(void)
> {
> - int ret = 0;
> + int ret = -ENOENT;
>
> - if ( !flask_enabled )
> + switch ( flask_bootparam )
> {
> - printk("Flask: Disabled at boot.\n");
> + case FLASK_BOOTPARAM_DISABLED:
> + printk(XENLOG_INFO "Flask: Disabled at boot.\n");
> return;
> - }
>
> - printk("Flask: Initializing.\n");
> + case FLASK_BOOTPARAM_PERMISSIVE:
> + case FLASK_BOOTPARAM_ENFORCING:
> + case FLASK_BOOTPARAM_LATELOAD:
> + break;
> +
> + case FLASK_BOOTPARAM_INVALID:
> + default:
> + panic("Flask: Invalid value for flask= boot parameter.\n");
> + }
>
> avc_init();
>
> @@ -1644,12 +1652,18 @@ static __init void flask_init(void)
> if ( register_xsm(&flask_ops) )
> panic("Flask: Unable to register with XSM");
>
> - ret = security_load_policy(policy_buffer, policy_size);
> + if ( policy_size && flask_bootparam != FLASK_BOOTPARAM_LATELOAD )
> + ret = security_load_policy(policy_buffer, policy_size);
> +
> + if ( ret && flask_bootparam == FLASK_BOOTPARAM_ENFORCING )
> + panic("Unable to load FLASK policy");
>
> - if ( flask_enforcing )
> - printk("Flask: Starting in enforcing mode.\n");
> + if ( ret )
> + printk(XENLOG_INFO "Flask: Access controls disabled until policy is
> loaded.\n");
> + else if ( flask_enforcing )
> + printk(XENLOG_INFO "Flask: Starting in enforcing mode.\n");
> else
> - printk("Flask: Starting in permissive mode.\n");
> + printk(XENLOG_INFO "Flask: Starting in permissive mode.\n");
> }
>
> xsm_initcall(flask_init);
> diff --git a/xen/xsm/flask/include/avc.h b/xen/xsm/flask/include/avc.h
> index a00a6eb..c7a99fc 100644
> --- a/xen/xsm/flask/include/avc.h
> +++ b/xen/xsm/flask/include/avc.h
> @@ -17,7 +17,7 @@
> #include "av_permissions.h"
> #include "security.h"
>
> -extern int flask_enforcing;
> +extern bool_t flask_enforcing;
>
> /*
> * An entry in the AVC.
> diff --git a/xen/xsm/flask/include/security.h
> b/xen/xsm/flask/include/security.h
> index dea0143..d07bae0 100644
> --- a/xen/xsm/flask/include/security.h
> +++ b/xen/xsm/flask/include/security.h
> @@ -35,7 +35,15 @@
> #define POLICYDB_VERSION_MIN POLICYDB_VERSION_BASE
> #define POLICYDB_VERSION_MAX POLICYDB_VERSION_BOUNDARY
>
> -extern int flask_enabled;
> +enum flask_bootparam_t {
> + FLASK_BOOTPARAM_PERMISSIVE,
> + FLASK_BOOTPARAM_ENFORCING,
> + FLASK_BOOTPARAM_LATELOAD,
> + FLASK_BOOTPARAM_DISABLED,
> + FLASK_BOOTPARAM_INVALID,
> +};
> +
> +extern enum flask_bootparam_t flask_bootparam;
> extern int flask_mls_enabled;
>
> int security_load_policy(void * data, size_t len);
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