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)
On Thu, 2020-07-09 at 13:46 -0300, Bruno Meneguele wrote:
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.
Perhaps we could simplify this patch description a bit?
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 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.
<snip>
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(c
har *str) { #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
- if (arch_ima_get_secureboot()) {
pr_info("appraise boot param ignored: secure boot enabled");
Instead of a generic statement, is it possible to include the actual option being denied? Perhaps something like: "Secure boot enabled, ignoring %s boot command line option"
Mimi
return 1;- }
- if (strncmp(str, "off", 3) == 0) ima_appraise = 0; else if (strncmp(str, "log", 3) == 0)
On Fri, Jul 10, 2020 at 01:23:24PM -0400, Mimi Zohar wrote:
On Thu, 2020-07-09 at 13:46 -0300, Bruno Meneguele wrote:
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.
Perhaps we could simplify this patch description a bit?
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 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.
Sounds good to me.
<snip>
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(c
har *str) { #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
- if (arch_ima_get_secureboot()) {
pr_info("appraise boot param ignored: secure boot enabled");Instead of a generic statement, is it possible to include the actual option being denied? Perhaps something like: "Secure boot enabled, ignoring %s boot command line option"
Mimi
Yes, sure.
Thanks!
return 1;- }
- if (strncmp(str, "off", 3) == 0) ima_appraise = 0; else if (strncmp(str, "log", 3) == 0)
On Fri, Jul 10, 2020 at 03:03:38PM -0300, Bruno Meneguele wrote:
On Fri, Jul 10, 2020 at 01:23:24PM -0400, Mimi Zohar wrote:
On Thu, 2020-07-09 at 13:46 -0300, Bruno Meneguele wrote:
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.
Perhaps we could simplify this patch description a bit?
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 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.
Sounds good to me.
<snip>
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(c
har *str) { #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
- if (arch_ima_get_secureboot()) {
pr_info("appraise boot param ignored: secure boot enabled");Instead of a generic statement, is it possible to include the actual option being denied? Perhaps something like: "Secure boot enabled, ignoring %s boot command line option"
Mimi
Yes, sure.
Btw, would it make sense to first make sure we have a valid "str" option and not something random to print?
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index a9649b04b9f1..1f1175531d3e 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -25,6 +25,16 @@ static int __init default_appraise_setup(char *str) ima_appraise = IMA_APPRAISE_LOG; else if (strncmp(str, "fix", 3) == 0) ima_appraise = IMA_APPRAISE_FIX; + else + pr_info("invalid "%s" appraise option"); + + if (arch_ima_get_secureboot()) { + if (!is_ima_appraise_enabled()) { + pr_info("Secure boot enabled: ignoring ima_appraise=%s boot parameter option", + str); + ima_appraise = IMA_APPRAISE_ENFORCE; + } + } #endif return 1; }
The "else" there I think would make sense as well, at least to give the user some feedback about a possible mispelling of him (as a separate patch).
And "if(!is_ima_appraise_enabled())" would avoid to print anything about "ignoring the option" to the user in case he explicitly set "enforce", which we know there isn't any real effect but is allowed and shown in kernel-parameters.txt.
Thanks!
return 1;- }
- if (strncmp(str, "off", 3) == 0) ima_appraise = 0; else if (strncmp(str, "log", 3) == 0)
-- bmeneg PGP Key: http://bmeneg.com/pubkey.txt
On Fri, 2020-07-10 at 15:34 -0300, Bruno Meneguele wrote:
On Fri, Jul 10, 2020 at 03:03:38PM -0300, Bruno Meneguele wrote:
On Fri, Jul 10, 2020 at 01:23:24PM -0400, Mimi Zohar wrote:
On Thu, 2020-07-09 at 13:46 -0300, Bruno Meneguele wrote:
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.
Perhaps we could simplify this patch description a bit?
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 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.
Sounds good to me.
<snip>
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(c
har *str) { #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
- if (arch_ima_get_secureboot()) {
pr_info("appraise boot param ignored: secure boot enabled");Instead of a generic statement, is it possible to include the actual option being denied? Perhaps something like: "Secure boot enabled, ignoring %s boot command line option"
Mimi
Yes, sure.
Btw, would it make sense to first make sure we have a valid "str" option and not something random to print? diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index a9649b04b9f1..1f1175531d3e 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -25,6 +25,16 @@ static int __init default_appraise_setup(char *str) ima_appraise = IMA_APPRAISE_LOG; else if (strncmp(str, "fix", 3) == 0) ima_appraise = IMA_APPRAISE_FIX;
elsepr_info("invalid \"%s\" appraise option");if (arch_ima_get_secureboot()) {if (!is_ima_appraise_enabled()) {pr_info("Secure boot enabled: ignoring ima_appraise=%s boot parameter option",str);ima_appraise = IMA_APPRAISE_ENFORCE;}}
Providing feedback is probably a good idea. However, the "arch_ima_get_secureboot" test can't come after setting "ima_appraise."
Mimi
#endif return 1; }
The "else" there I think would make sense as well, at least to give the user some feedback about a possible mispelling of him (as a separate patch).
And "if(!is_ima_appraise_enabled())" would avoid to print anything about "ignoring the option" to the user in case he explicitly set "enforce", which we know there isn't any real effect but is allowed and shown in kernel-parameters.txt.
Thanks!
return 1;- }
- if (strncmp(str, "off", 3) == 0) ima_appraise = 0; else if (strncmp(str, "log", 3) == 0)
-- bmeneg PGP Key: http://bmeneg.com/pubkey.txt
On Fri, Jul 10, 2020 at 02:54:48PM -0400, Mimi Zohar wrote:
On Fri, 2020-07-10 at 15:34 -0300, Bruno Meneguele wrote:
On Fri, Jul 10, 2020 at 03:03:38PM -0300, Bruno Meneguele wrote:
On Fri, Jul 10, 2020 at 01:23:24PM -0400, Mimi Zohar wrote:
On Thu, 2020-07-09 at 13:46 -0300, Bruno Meneguele wrote:
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.
Perhaps we could simplify this patch description a bit?
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 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.
Sounds good to me.
<snip>
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(c
har *str) { #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
- if (arch_ima_get_secureboot()) {
pr_info("appraise boot param ignored: secure boot enabled");Instead of a generic statement, is it possible to include the actual option being denied? Perhaps something like: "Secure boot enabled, ignoring %s boot command line option"
Mimi
Yes, sure.
Btw, would it make sense to first make sure we have a valid "str" option and not something random to print? diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index a9649b04b9f1..1f1175531d3e 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -25,6 +25,16 @@ static int __init default_appraise_setup(char *str) ima_appraise = IMA_APPRAISE_LOG; else if (strncmp(str, "fix", 3) == 0) ima_appraise = IMA_APPRAISE_FIX;
elsepr_info("invalid \"%s\" appraise option");if (arch_ima_get_secureboot()) {if (!is_ima_appraise_enabled()) {pr_info("Secure boot enabled: ignoring ima_appraise=%s boot parameter option",str);ima_appraise = IMA_APPRAISE_ENFORCE;}}Providing feedback is probably a good idea. However, the "arch_ima_get_secureboot" test can't come after setting "ima_appraise."
Sorry, but I'm not sure if I got the reason to why it can't be done after: would it be basically to prevent any further processing about ima_appraise as a matter of security principle? Or maybe to keep the dependency between secureboot and bootparam truly strict?
Or are there something else I'm missing?
Mimi
#endif return 1; }
The "else" there I think would make sense as well, at least to give the user some feedback about a possible mispelling of him (as a separate patch).
And "if(!is_ima_appraise_enabled())" would avoid to print anything about "ignoring the option" to the user in case he explicitly set "enforce", which we know there isn't any real effect but is allowed and shown in kernel-parameters.txt.
Thanks!
return 1;- }
- if (strncmp(str, "off", 3) == 0) ima_appraise = 0; else if (strncmp(str, "log", 3) == 0)
-- bmeneg PGP Key: http://bmeneg.com/pubkey.txt
On Fri, Jul 10, 2020 at 04:25:16PM -0300, Bruno Meneguele wrote:
On Fri, Jul 10, 2020 at 02:54:48PM -0400, Mimi Zohar wrote:
On Fri, 2020-07-10 at 15:34 -0300, Bruno Meneguele wrote:
On Fri, Jul 10, 2020 at 03:03:38PM -0300, Bruno Meneguele wrote:
On Fri, Jul 10, 2020 at 01:23:24PM -0400, Mimi Zohar wrote:
On Thu, 2020-07-09 at 13:46 -0300, Bruno Meneguele wrote:
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.
Perhaps we could simplify this patch description a bit?
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 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.
Sounds good to me.
<snip>
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(c
har *str) { #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
- if (arch_ima_get_secureboot()) {
pr_info("appraise boot param ignored: secure boot enabled");Instead of a generic statement, is it possible to include the actual option being denied? Perhaps something like: "Secure boot enabled, ignoring %s boot command line option"
Mimi
Yes, sure.
Btw, would it make sense to first make sure we have a valid "str" option and not something random to print? diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index a9649b04b9f1..1f1175531d3e 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -25,6 +25,16 @@ static int __init default_appraise_setup(char *str) ima_appraise = IMA_APPRAISE_LOG; else if (strncmp(str, "fix", 3) == 0) ima_appraise = IMA_APPRAISE_FIX;
elsepr_info("invalid \"%s\" appraise option");if (arch_ima_get_secureboot()) {if (!is_ima_appraise_enabled()) {pr_info("Secure boot enabled: ignoring ima_appraise=%s boot parameter option",str);ima_appraise = IMA_APPRAISE_ENFORCE;}}Providing feedback is probably a good idea. However, the "arch_ima_get_secureboot" test can't come after setting "ima_appraise."
Sorry, but I'm not sure if I got the reason to why it can't be done after: would it be basically to prevent any further processing about ima_appraise as a matter of security principle? Or maybe to keep the dependency between secureboot and bootparam truly strict?
Or are there something else I'm missing?
I'm going to send a v6 with the pr_info() placed in the beginning directly printing 'str', thus we can have the actual issue solved.
Then later I send another patches to handle the other cases of limiting 'str' printing and also giving the user a feedback about invalid ima_appraise= options. So we can discuss further on that.
Thanks Mimi.
Mimi
#endif return 1; }
The "else" there I think would make sense as well, at least to give the user some feedback about a possible mispelling of him (as a separate patch).
And "if(!is_ima_appraise_enabled())" would avoid to print anything about "ignoring the option" to the user in case he explicitly set "enforce", which we know there isn't any real effect but is allowed and shown in kernel-parameters.txt.
Thanks!
return 1;- }
- if (strncmp(str, "off", 3) == 0) ima_appraise = 0; else if (strncmp(str, "log", 3) == 0)
-- bmeneg PGP Key: http://bmeneg.com/pubkey.txt
-- bmeneg PGP Key: http://bmeneg.com/pubkey.txt
linux-stable-mirror@lists.linaro.org
-
Bruno Meneguele -
Mimi Zohar