Re: [PATCH v6] ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime

[Bruno Meneguele]

On Tue, Jul 21, 2020 at 01:26:16PM -0400, Mimi Zohar wrote:
> On Mon, 2020-07-20 at 12:38 -0300, Bruno Meneguele wrote:
> > On Mon, Jul 20, 2020 at 10:56:55AM -0400, Mimi Zohar wrote:
> > > On Mon, 2020-07-20 at 10:40 -0400, Nayna wrote:
> > > > On 7/13/20 12:48 PM, 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
> > > > >
> > > 
> > > Is it common to have two colons in the same line?  Is the colon being
> > > used as a delimiter when parsing the kernel logs?  Should the second
> > > colon be replaced with a hyphen?  (No need to repost.  I'll fix it
> > > up.)
> > >  
> > 
> > AFAICS it has been used without any limitations, e.g:
> > 
> > PM: hibernation: Registered nosave memory: [mem 0x-0x0fff]
> > clocksource: hpet: mask: 0x max_cycles: 0x, max_idle_ns: 
> > 133484873504 ns
> > microcode: CPU0: patch_level=0x08701013
> > Lockdown: modprobe: unsigned module loading is restricted; see man 
> > kernel_lockdown.7
> > ...
> > 
> > I'd say we're fine using it.
> 
> Ok.  FYI, it's now in next-integrity.
> 
> Mimi
> 

Thanks Mimi.

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Re: [PATCH v6] ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime

[Bruno Meneguele]

On Mon, Jul 20, 2020 at 10:56:55AM -0400, Mimi Zohar wrote:
> On Mon, 2020-07-20 at 10:40 -0400, Nayna wrote:
> > On 7/13/20 12:48 PM, 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
> > >
> 
> Is it common to have two colons in the same line?  Is the colon being
> used as a delimiter when parsing the kernel logs?  Should the second
> colon be replaced with a hyphen?  (No need to repost.  I'll fix it
> up.)
>  

AFAICS it has been used without any limitations, e.g:

PM: hibernation: Registered nosave memory: [mem 0x-0x0fff]
clocksource: hpet: mask: 0x max_cycles: 0x, max_idle_ns: 
133484873504 ns
microcode: CPU0: patch_level=0x08701013
Lockdown: modprobe: unsigned module loading is restricted; see man 
kernel_lockdown.7
...

I'd say we're fine using it.

> 
> > > -> powerpc with secure boot disabled
> > >
> > > [0.00] Kernel command line: <...> ima_policy=appraise_tcb 
> > > ima_appraise=fix
> > > [0.00] 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 
> > 
> > 
> > Reviewed-by: Nayna Jain
> > Tested-by: Nayna Jain
> 
> Thanks, Nayna.
> 
> Mimi
> 

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Re: [PATCH v6] ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime

[Bruno Meneguele]

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
> 
> [0.00] Kernel command line: <...> ima_policy=appraise_tcb 
> ima_appraise=fix
> [0.00] 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 
> ---
> 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.

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[PATCH v6] ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime

[Bruno Meneguele]

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

[0.00] Kernel command line: <...> ima_policy=appraise_tcb 
ima_appraise=fix
[0.00] 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 
---
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

Re: [PATCH v5] ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime

[Bruno Meneguele]

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.
> > > > 
> > > > > 
> > > > > 
> > > > > > 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 \"

Re: [PATCH v5] ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime

[Bruno Meneguele]

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.
> > > 
> > > > 
> > > > 
> > > > > 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;
> > +   }
> > +   }
> 
> Providing feedback is probably a good idea.  However, the
> &quo

Re: [PATCH v5] ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime

[Bruno Meneguele]

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.
> 
> > 
> > 
> > > 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



-- 
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Re: [PATCH v5] ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime

[Bruno Meneguele]

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.

> 
> 
> > 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)
> 

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[PATCH v5] ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime

[Bruno Meneguele]

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

[0.00] Kernel command line: <...> ima_policy=appraise_tcb 
ima_appraise=fix
[0.00] 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: sta...@vger.kernel.org
Fixes: d958083a8f64 ("x86/ima: define arch_get_ima_policy() for x86")
Signed-off-by: Bruno Meneguele 
---
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)
-- 
2.26.2