APPRAISE_BOOTPARAM has been marked as dependent on !ARCH_POLICY in compile
time, enforcing the appraisal whenever the kernel had the arch policy option
enabled.
However it breaks systems where the option is set but the system wasn't
booted in a "secure boot" platform. In this scenario, anytime an appraisal
policy (i.e. ima_policy=appraisal_tcb) is used it will be forced, giving no
chance to the user set the 'fix' state (ima_appraise=fix) to actually
measure system's files.
Considering the ARCH_POLICY is only effective when secure boot is actually
enabled this patch remove the compile time dependency and move it to a
runtime decision, based on the secure boot state of that platform.
Cc: [email protected]
Fixes: d958083a8f64 ("x86/ima: define arch_get_ima_policy() for x86")
Signed-off-by: Bruno Meneguele <[email protected]>
---
Changelog:
v4:
- instead of change arch_policy loading code, check secure boot state
at "ima_appraise=" parameter handler (Mimi)
v3:
- extend secure boot arch checker to also consider trusted boot
- enforce IMA appraisal when secure boot is effectively enabled (Nayna)
- fix ima_appraise flag assignment by or'ing it (Mimi)
v2:
- pr_info() message prefix correction
security/integrity/ima/Kconfig | 2 +-
security/integrity/ima/ima_appraise.c | 18 ++++++++++--------
2 files changed, 11 insertions(+), 9 deletions(-)
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index edde88dbe576..62dc11a5af01 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -232,7 +232,7 @@ config IMA_APPRAISE_REQUIRE_POLICY_SIGS
config IMA_APPRAISE_BOOTPARAM
bool "ima_appraise boot parameter"
- depends on IMA_APPRAISE && !IMA_ARCH_POLICY
+ depends on IMA_APPRAISE
default y
help
This option enables the different "ima_appraise=" modes
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index a9649b04b9f1..4fc83b3fbd5c 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -18,14 +18,16 @@
static int __init default_appraise_setup(char *str)
{
-#ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
- if (strncmp(str, "off", 3) == 0)
- ima_appraise = 0;
- else if (strncmp(str, "log", 3) == 0)
- ima_appraise = IMA_APPRAISE_LOG;
- else if (strncmp(str, "fix", 3) == 0)
- ima_appraise = IMA_APPRAISE_FIX;
-#endif
+ if (IS_ENABLED(CONFIG_IMA_APPRAISE_BOOTPARAM) &&
+ !arch_ima_get_secureboot()) {
+ if (strncmp(str, "off", 3) == 0)
+ ima_appraise = 0;
+ else if (strncmp(str, "log", 3) == 0)
+ ima_appraise = IMA_APPRAISE_LOG;
+ else if (strncmp(str, "fix", 3) == 0)
+ ima_appraise = IMA_APPRAISE_FIX;
+ }
+
return 1;
}
--
2.26.2
On Tue, Jul 07, 2020 at 07:56:37PM -0400, Nayna wrote:
>
> On 7/3/20 2:00 PM, Bruno Meneguele wrote:
> > APPRAISE_BOOTPARAM has been marked as dependent on !ARCH_POLICY in compile
> > time, enforcing the appraisal whenever the kernel had the arch policy option
> > enabled.
> >
> > However it breaks systems where the option is set but the system wasn't
> > booted in a "secure boot" platform. In this scenario, anytime an appraisal
> > policy (i.e. ima_policy=appraisal_tcb) is used it will be forced, giving no
> > chance to the user set the 'fix' state (ima_appraise=fix) to actually
> > measure system's files.
>
> "measure" is incorrect. It is appraisal.
>
Yes, of course, sorry.
> How about changing the statement to "without giving the user the opportunity
> to label the filesystem, before enforcing integrity." ?
>
Ack.
That's better :)
> > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> > index a9649b04b9f1..4fc83b3fbd5c 100644
> > --- a/security/integrity/ima/ima_appraise.c
> > +++ b/security/integrity/ima/ima_appraise.c
> > @@ -18,14 +18,16 @@
> > static int __init default_appraise_setup(char *str)
> > {
> > -#ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
> > - if (strncmp(str, "off", 3) == 0)
> > - ima_appraise = 0;
> > - else if (strncmp(str, "log", 3) == 0)
> > - ima_appraise = IMA_APPRAISE_LOG;
> > - else if (strncmp(str, "fix", 3) == 0)
> > - ima_appraise = IMA_APPRAISE_FIX;
> > -#endif
> > + if (IS_ENABLED(CONFIG_IMA_APPRAISE_BOOTPARAM) &&
> > + !arch_ima_get_secureboot()) {
> > + if (strncmp(str, "off", 3) == 0)
> > + ima_appraise = 0;
> > + else if (strncmp(str, "log", 3) == 0)
> > + ima_appraise = IMA_APPRAISE_LOG;
> > + else if (strncmp(str, "fix", 3) == 0)
> > + ima_appraise = IMA_APPRAISE_FIX;
> > + }
> > +
> > return 1;
> > }
>
> If secureboot is enabled, it is silently ignoring the boot parameters. It
> would be helpful if there is a log message notifying user about that.
>
> Can you please Cc powerpc, s390, and x86 mailing list and maintainers, when
> you post the next version ?
>
> I would try to test it sometime in this week.
>
Sure. I'm preparing a new version and will post soon.
> Thanks & Regards,
>
Thank you.
--
bmeneg
PGP Key: http://bmeneg.com/pubkey.txt