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Date:   Fri, 17 Jul 2020 15:40:19 -0300
From:   Bruno Meneguele <bmeneg@redhat.com>
To:     linux-kernel@vger.kernel.org, x86@kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
        linux-integrity@vger.kernel.org
Cc:     zohar@linux.ibm.com, erichte@linux.ibm.com, nayna@linux.ibm.com,
        stable@vger.kernel.org
Subject: Re: [PATCH v6] ima: move APPRAISE_BOOTPARAM dependency on
 ARCH_POLICY to runtime
Message-ID: <20200717184019.GI2984@glitch>
References: <20200713164830.101165-1-bmeneg@redhat.com>
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On Mon, Jul 13, 2020 at 01:48:30PM -0300, Bruno Meneguele wrote:
> The IMA_APPRAISE_BOOTPARAM config allows enabling different "ima_appraise=
=3D"
> modes - log, fix, enforce - at run time, but not when IMA architecture
> specific policies are enabled. =A0This prevents properly labeling the
> filesystem on systems where secure boot is supported, but not enabled on =
the
> platform. =A0Only when secure boot is actually enabled should these IMA
> appraise modes be disabled.
>=20
> This patch removes the compile time dependency and makes it a runtime
> decision, based on the secure boot state of that platform.
>=20
> Test results as follows:
>=20
> -> x86-64 with secure boot enabled
>=20
> [    0.015637] Kernel command line: <...> ima_policy=3Dappraise_tcb ima_a=
ppraise=3Dfix
> [    0.015668] ima: Secure boot enabled: ignoring ima_appraise=3Dfix boot=
 parameter option
>=20
> -> powerpc with secure boot disabled
>=20
> [    0.000000] Kernel command line: <...> ima_policy=3Dappraise_tcb ima_a=
ppraise=3Dfix
> [    0.000000] Secure boot mode disabled
>=20
> -> Running the system without secure boot and with both options set:
>=20
> CONFIG_IMA_APPRAISE_BOOTPARAM=3Dy
> CONFIG_IMA_ARCH_POLICY=3Dy
>=20
> Audit prompts "missing-hash" but still allow execution and, consequently,
> filesystem labeling:
>=20
> type=3DINTEGRITY_DATA msg=3Daudit(07/09/2020 12:30:27.778:1691) : pid=3D4=
976
> uid=3Droot auid=3Droot ses=3D2
> subj=3Dunconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 op=3Dapprais=
e_data
> cause=3Dmissing-hash comm=3Dbash name=3D/usr/bin/evmctl dev=3D"dm-0" ino=
=3D493150
> res=3Dno
>=20
> Cc: stable@vger.kernel.org
> Fixes: d958083a8f64 ("x86/ima: define arch_get_ima_policy() for x86")
> Signed-off-by: Bruno Meneguele <bmeneg@redhat.com>
> ---
> v6:
>   - explictly print the bootparam being ignored to the user (Mimi)
> v5:
>   - add pr_info() to inform user the ima_appraise=3D boot param is being
> =09ignored due to secure boot enabled (Nayna)
>   - add some testing results to commit log
> v4:
>   - instead of change arch_policy loading code, check secure boot state a=
t
> =09"ima_appraise=3D" 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 | 6 ++++++
>  2 files changed, 7 insertions(+), 1 deletion(-)
>=20
> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kcon=
fig
> index edde88dbe576..62dc11a5af01 100644
> --- a/security/integrity/ima/Kconfig
> +++ b/security/integrity/ima/Kconfig
> @@ -232,7 +232,7 @@ config IMA_APPRAISE_REQUIRE_POLICY_SIGS
> =20
>  config IMA_APPRAISE_BOOTPARAM
>  =09bool "ima_appraise boot parameter"
> -=09depends on IMA_APPRAISE && !IMA_ARCH_POLICY
> +=09depends on IMA_APPRAISE
>  =09default y
>  =09help
>  =09  This option enables the different "ima_appraise=3D" modes
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/i=
ma/ima_appraise.c
> index a9649b04b9f1..28a59508c6bd 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -19,6 +19,12 @@
>  static int __init default_appraise_setup(char *str)
>  {
>  #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
> +=09if (arch_ima_get_secureboot()) {
> +=09=09pr_info("Secure boot enabled: ignoring ima_appraise=3D%s boot para=
meter option",
> +=09=09=09str);
> +=09=09return 1;
> +=09}
> +
>  =09if (strncmp(str, "off", 3) =3D=3D 0)
>  =09=09ima_appraise =3D 0;
>  =09else if (strncmp(str, "log", 3) =3D=3D 0)
> --=20
> 2.26.2
>=20

Ping for review.

Many thanks.

--=20
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