diff mbox series

ima: require signed IMA policy when UEFI secure boot is enabled

Message ID 20230703115442.129725-1-coxu@redhat.com
State New
Headers
Series ima: require signed IMA policy when UEFI secure boot is enabled |

Commit Message

Coiby Xu July 3, 2023, 11:54 a.m. UTC 
  With the introduction of the .machine keyring for UEFI-based systems,
users are able to add custom CAs keys via MOK. This allow users to sign
their own IMA polices. For the sake of security, mandate signed IMA
policy when UEFI secure boot is enabled.

Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
 security/integrity/ima/ima_efi.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Mimi Zohar July 4, 2023, 12:57 p.m. UTC | #1 
On Mon, 2023-07-03 at 19:54 +0800, Coiby Xu wrote:
> With the introduction of the .machine keyring for UEFI-based systems,
> users are able to add custom CAs keys via MOK. This allow users to sign
> their own IMA polices. For the sake of security, mandate signed IMA
> policy when UEFI secure boot is enabled.
> 
> Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
> Signed-off-by: Coiby Xu <coxu@redhat.com>
> ---
>  security/integrity/ima/ima_efi.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/security/integrity/ima/ima_efi.c b/security/integrity/ima/ima_efi.c
> index 9db66fe310d4..bb2881759505 100644
> --- a/security/integrity/ima/ima_efi.c
> +++ b/security/integrity/ima/ima_efi.c
> @@ -58,6 +58,9 @@ static const char * const sb_arch_rules[] = {
>  #if !IS_ENABLED(CONFIG_MODULE_SIG)
>  	"appraise func=MODULE_CHECK appraise_type=imasig",
>  #endif
> +#if IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING) && IS_ENABLED(CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY)
> +	"appraise func=POLICY_CHECK appraise_type=imasig",
> +#endif /* CONFIG_INTEGRITY_MACHINE_KEYRING && IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY */
>  	"measure func=MODULE_CHECK",
>  	NULL
>  };

Thanks, Coiby.

Using IS_ENABLED() is not wrong, but unnecessary.  IS_BUILTIN()
suffices.
Coiby Xu July 14, 2023, 1:29 a.m. UTC | #2 
On Tue, Jul 04, 2023 at 08:57:10AM -0400, Mimi Zohar wrote:
>On Mon, 2023-07-03 at 19:54 +0800, Coiby Xu wrote:
>> With the introduction of the .machine keyring for UEFI-based systems,
>> users are able to add custom CAs keys via MOK. This allow users to sign
>> their own IMA polices. For the sake of security, mandate signed IMA
>> policy when UEFI secure boot is enabled.
>>
>> Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
>> Signed-off-by: Coiby Xu <coxu@redhat.com>
>> ---
>>  security/integrity/ima/ima_efi.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/security/integrity/ima/ima_efi.c b/security/integrity/ima/ima_efi.c
>> index 9db66fe310d4..bb2881759505 100644
>> --- a/security/integrity/ima/ima_efi.c
>> +++ b/security/integrity/ima/ima_efi.c
>> @@ -58,6 +58,9 @@ static const char * const sb_arch_rules[] = {
>>  #if !IS_ENABLED(CONFIG_MODULE_SIG)
>>  	"appraise func=MODULE_CHECK appraise_type=imasig",
>>  #endif
>> +#if IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING) && IS_ENABLED(CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY)
>> +	"appraise func=POLICY_CHECK appraise_type=imasig",
>> +#endif /* CONFIG_INTEGRITY_MACHINE_KEYRING && IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY */
>>  	"measure func=MODULE_CHECK",
>>  	NULL
>>  };
>
>Thanks, Coiby.

You are welcome!

>
>Using IS_ENABLED() is not wrong, but unnecessary.  IS_BUILTIN()
>suffices.

Thanks for the reminding! When I was going to apply this suggestion, I
noticed ima_efi.c uses IS_ENABLED for all configuration items i.e.
CONFIG_MODULE_SIG and CONFIG_KEXEC_SIG which are all of bool type. Would
you like me to switch all IS_ENABLEs to IS_BUILTIN or still use
IS_ENABLED? While IS_BUILTIN is exclusively for bool type, it's not as
intuitive as IS_ENABLED. So it's not easy for me to make a choice.

>
>-- 
>thanks,
>
>Mimi
>
Mimi Zohar July 20, 2023, 2:12 p.m. UTC | #3 
On Fri, 2023-07-14 at 09:29 +0800, Coiby Xu wrote:
> On Tue, Jul 04, 2023 at 08:57:10AM -0400, Mimi Zohar wrote:
> >On Mon, 2023-07-03 at 19:54 +0800, Coiby Xu wrote:
> >> With the introduction of the .machine keyring for UEFI-based systems,
> >> users are able to add custom CAs keys via MOK. This allow users to sign
> >> their own IMA polices. For the sake of security, mandate signed IMA
> >> policy when UEFI secure boot is enabled.
> >>
> >> Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
> >> Signed-off-by: Coiby Xu <coxu@redhat.com>

With commit 099f26f22f58 ("integrity: machine keyring CA
configuration") it is now possible to require signed IMA policies
without having to recompile the kernel.  Please note this change might
affect existing users/tests.

> >> ---
> >>  security/integrity/ima/ima_efi.c | 3 +++
> >>  1 file changed, 3 insertions(+)
> >>
> >> diff --git a/security/integrity/ima/ima_efi.c b/security/integrity/ima/ima_efi.c
> >> index 9db66fe310d4..bb2881759505 100644
> >> --- a/security/integrity/ima/ima_efi.c
> >> +++ b/security/integrity/ima/ima_efi.c
> >> @@ -58,6 +58,9 @@ static const char * const sb_arch_rules[] = {
> >>  #if !IS_ENABLED(CONFIG_MODULE_SIG)
> >>  	"appraise func=MODULE_CHECK appraise_type=imasig",
> >>  #endif
> >> +#if IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING) && IS_ENABLED(CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY)
> >> +	"appraise func=POLICY_CHECK appraise_type=imasig",
> >> +#endif /* CONFIG_INTEGRITY_MACHINE_KEYRING && IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY */
> >>  	"measure func=MODULE_CHECK",
> >>  	NULL
> >>  };
> >
> >Thanks, Coiby.
> 
> You are welcome!
> 
> >
> >Using IS_ENABLED() is not wrong, but unnecessary.  IS_BUILTIN()
> >suffices.
> 
> Thanks for the reminding! When I was going to apply this suggestion, I
> noticed ima_efi.c uses IS_ENABLED for all configuration items i.e.
> CONFIG_MODULE_SIG and CONFIG_KEXEC_SIG which are all of bool type. Would
> you like me to switch all IS_ENABLEs to IS_BUILTIN or still use
> IS_ENABLED? While IS_BUILTIN is exclusively for bool type, it's not as
> intuitive as IS_ENABLED. So it's not easy for me to make a choice.

Sure, for consistency with the other rules IS_ENABLED is fine.

thanks,

Mimi
diff mbox series

Patch

diff --git a/security/integrity/ima/ima_efi.c b/security/integrity/ima/ima_efi.c
index 9db66fe310d4..bb2881759505 100644
--- a/security/integrity/ima/ima_efi.c
+++ b/security/integrity/ima/ima_efi.c
@@ -58,6 +58,9 @@  static const char * const sb_arch_rules[] = {
 #if !IS_ENABLED(CONFIG_MODULE_SIG)
 	"appraise func=MODULE_CHECK appraise_type=imasig",
 #endif
+#if IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING) && IS_ENABLED(CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY)
+	"appraise func=POLICY_CHECK appraise_type=imasig",
+#endif /* CONFIG_INTEGRITY_MACHINE_KEYRING && IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY */
 	"measure func=MODULE_CHECK",
 	NULL
 };