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 didn't boot in a "secure boot" platform. In this scenario, anytime an appraisal policy (i.e. ima_policy=appraisal_tcb) is used it will be forced, without giving the user the opportunity to label the filesystem, before enforcing integrity.
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.
With this patch:
- x86-64 with secure boot enabled
[ 0.004305] Secure boot enabled ... [ 0.015651] Kernel command line: <...> ima_policy=appraise_tcb ima_appraise=fix [ 0.015682] ima: appraise boot param ignored: secure boot enabled
- powerpc with secure boot disabled
[ 0.000000] Kernel command line: <...> ima_policy=appraise_tcb ima_appraise=fix [ 0.000000] Secure boot mode disabled ... < nothing about boot param ignored >
System working fine without secure boot and with both options set:
CONFIG_IMA_APPRAISE_BOOTPARAM=y CONFIG_IMA_ARCH_POLICY=y
Audit logs pointing to "missing-hash" but still being able to execute due to ima_appraise=fix:
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: stable@vger.kernel.org Fixes: d958083a8f64 ("x86/ima: define arch_get_ima_policy() for x86") Signed-off-by: Bruno Meneguele bmeneg@redhat.com --- Changelog: 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 | 5 +++++ 2 files changed, 6 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..884de471b38a 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -19,6 +19,11 @@ static int __init default_appraise_setup(char *str) { #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM + if (arch_ima_get_secureboot()) { + pr_info("appraise boot param ignored: secure boot enabled"); + return 1; + } + if (strncmp(str, "off", 3) == 0) ima_appraise = 0; else if (strncmp(str, "log", 3) == 0)