2023-07-03 12:10:00

by Coiby Xu

Subject: [PATCH] ima: require signed IMA policy when UEFI secure boot is enabled

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 <[email protected]>
Signed-off-by: Coiby Xu <[email protected]>
---
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
};
--
2.41.0

2023-07-04 13:04:49

by Mimi Zohar

Subject: Re: [PATCH] ima: require signed IMA policy when UEFI secure boot is enabled

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 <[email protected]>
> Signed-off-by: Coiby Xu <[email protected]>
> ---
> 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.

--
thanks,

Mimi

2023-07-14 01:39:04

by Coiby Xu

Subject: Re: [PATCH] ima: require signed IMA policy when UEFI secure boot is enabled

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 <[email protected]>
>> Signed-off-by: Coiby Xu <[email protected]>
>> ---
>> 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
>

--
Best regards,
Coiby

2023-07-20 14:45:50

by Mimi Zohar

Subject: Re: [PATCH] ima: require signed IMA policy when UEFI secure boot is enabled

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 <[email protected]>
> >> Signed-off-by: Coiby Xu <[email protected]>

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

2023-07-26 02:58:00

by Coiby Xu

Subject: [PATCH v2] ima: require signed IMA policy when UEFI secure boot is enabled

With commit 099f26f22f58 ("integrity: machine keyring CA
configuration"), users are able to add custom IMA CA keys via
MOK. This allows users to sign their own IMA polices without
recompiling the kernel. For the sake of security, mandate signed IMA
policy when UEFI secure boot is enabled.

Note this change may affect existing users/tests i.e users won't be able
to load an unsigned IMA policy when the IMA architecture specific policy
is configured and UEFI secure boot is enabled.

Suggested-by: Mimi Zohar <[email protected]>
Signed-off-by: Coiby Xu <[email protected]>
---
v2
- improve commit message [Mimi]
- explicitly mention the dependent commit
- add a note that the change will affect user space
- remove "/* CONFIG_INTEGRITY_MACHINE_KEYRING .. */" to improve code
readability
---
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..138029bfcce1 100644
--- a/security/integrity/ima/ima_efi.c
+++ b/security/integrity/ima/ima_efi.c
@@ -57,6 +57,9 @@ static const char * const sb_arch_rules[] = {
"measure func=KEXEC_KERNEL_CHECK",
#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
"measure func=MODULE_CHECK",
NULL
--
2.41.0

2023-07-27 18:47:00

by Mimi Zohar

Subject: Re: [PATCH v2] ima: require signed IMA policy when UEFI secure boot is enabled

On Wed, 2023-07-26 at 10:08 +0800, Coiby Xu wrote:
> With commit 099f26f22f58 ("integrity: machine keyring CA
> configuration"), users are able to add custom IMA CA keys via
> MOK. This allows users to sign their own IMA polices without
> recompiling the kernel. For the sake of security, mandate signed IMA
> policy when UEFI secure boot is enabled.
>
> Note this change may affect existing users/tests i.e users won't be able
> to load an unsigned IMA policy when the IMA architecture specific policy
> is configured and UEFI secure boot is enabled.
>
> Suggested-by: Mimi Zohar <[email protected]>
> Signed-off-by: Coiby Xu <[email protected]>
> ---
> v2
> - improve commit message [Mimi]
> - explicitly mention the dependent commit
> - add a note that the change will affect user space
> - remove "/* CONFIG_INTEGRITY_MACHINE_KEYRING .. */" to improve code
> readability

Thank you for updating the commit message. The patch is now queued in
next-integrity-testing.

--
thanks,

Mimi