On Mon, Jul 13, 2020 at 01:48:30PM -0300, Bruno Meneguele wrote:
> The IMA_APPRAISE_BOOTPARAM config allows enabling different "ima_appraise="
> modes - log, fix, enforce - at run time, but not when IMA architecture
> specific policies are enabled. This prevents properly labeling the
> filesystem on systems where secure boot is supported, but not enabled on the
> platform. Only when secure boot is actually enabled should these IMA
> appraise modes be disabled.
>
> This patch removes the compile time dependency and makes it a runtime
> decision, based on the secure boot state of that platform.
>
> Test results as follows:
>
> -> x86-64 with secure boot enabled
>
> [ 0.015637] Kernel command line: <...> ima_policy=appraise_tcb
> ima_appraise=fix
> [ 0.015668] ima: Secure boot enabled: ignoring ima_appraise=fix boot
> parameter option
>
> -> powerpc with secure boot disabled
>
> [ 0.000000] Kernel command line: <...> ima_policy=appraise_tcb
> ima_appraise=fix
> [ 0.000000] Secure boot mode disabled
>
> -> Running the system without secure boot and with both options set:
>
> CONFIG_IMA_APPRAISE_BOOTPARAM=y
> CONFIG_IMA_ARCH_POLICY=y
>
> Audit prompts "missing-hash" but still allow execution and, consequently,
> filesystem labeling:
>
> type=INTEGRITY_DATA msg=audit(07/09/2020 12:30:27.778:1691) : pid=4976
> uid=root auid=root ses=2
> subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 op=appraise_data
> cause=missing-hash comm=bash name=/usr/bin/evmctl dev="dm-0" ino=493150
> res=no
>
> Cc: sta...@vger.kernel.org
> Fixes: d958083a8f64 ("x86/ima: define arch_get_ima_policy() for x86")
> Signed-off-by: Bruno Meneguele <bme...@redhat.com>
> ---
> v6:
> - explictly print the bootparam being ignored to the user (Mimi)
> v5:
> - add pr_info() to inform user the ima_appraise= boot param is being
> ignored 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 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 | 6 ++++++
> 2 files changed, 7 insertions(+), 1 deletion(-)
>
> 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..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
> + if (arch_ima_get_secureboot()) {
> + pr_info("Secure boot enabled: ignoring ima_appraise=%s boot
> parameter option",
> + str);
> + return 1;
> + }
> +
> if (strncmp(str, "off", 3) == 0)
> ima_appraise = 0;
> else if (strncmp(str, "log", 3) == 0)
> --
> 2.26.2
> Ping for review. Many thanks. -- bmeneg PGP Key: http://bmeneg.com/pubkey.txt
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