diff mbox series

[v6,7/8] IMA: add a built-in policy rule for critical data measurement

Message ID 20201119232611.30114-8-tusharsu@linux.microsoft.com (mailing list archive)
State New
Headers show
Series IMA: support for measuring kernel integrity critical data | expand

Commit Message

Tushar Sugandhi Nov. 19, 2020, 11:26 p.m. UTC
From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>

The IMA hook to measure kernel critical data, namely
ima_measure_critical_data(), could be called before a custom IMA policy
is loaded. Define a new critical data builtin policy to allow measuring
early kernel integrity critical data before a custom IMA policy is
loaded.

Add critical data to built-in IMA rules if the kernel command line
contains "ima_policy=critical_data".

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---
 security/integrity/ima/ima_policy.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Comments

Mimi Zohar Nov. 20, 2020, 2:30 p.m. UTC | #1
Hi Lakshmi,

On Thu, 2020-11-19 at 15:26 -0800, Tushar Sugandhi wrote:
> From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> 
> The IMA hook to measure kernel critical data, namely
> ima_measure_critical_data(), could be called before a custom IMA policy
> is loaded.
> Define a new critical data builtin policy to allow measuring
> early kernel integrity critical data before a custom IMA policy is
> loaded.

Everything needing to be said seems to be included in the second
sentence.  Does the first sentence add anything?  "Define a new
critical data builtin policy" makes for a good Subject line.

> 
> Add critical data to built-in IMA rules if the kernel command line
> contains "ima_policy=critical_data".

The boot command line parameters are defined in Documentation/admin-
guide/kernel-parameters.txt.  Please update "ima_policy".

> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> ---
>  security/integrity/ima/ima_policy.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index c9e52dab0638..119604a3efa0 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -206,6 +206,10 @@ static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
>  	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
>  };
> 
> +static struct ima_rule_entry critical_data_rules[] __ro_after_init = {
> +	{.action = MEASURE, .func = CRITICAL_DATA, .flags = IMA_FUNC},
> +};
> +
>  /* An array of architecture specific rules */
>  static struct ima_rule_entry *arch_policy_entry __ro_after_init;
>  
> @@ -228,6 +232,7 @@ __setup("ima_tcb", default_measure_policy_setup);
>  
>  static bool ima_use_appraise_tcb __initdata;
>  static bool ima_use_secure_boot __initdata;
> +static bool ima_use_critical_data __ro_after_init;

Unlike ima_fail_unverifiable_sigs, ima_use_critical_data is only used
during __init.  Please change "__ro_after_init" to "__initdata".  (The
critical data policy itself is defined properly as __ro_after_init.)

>  static bool ima_fail_unverifiable_sigs __ro_after_init;
>  static int __init policy_setup(char *str)
>  {
> @@ -242,6 +247,8 @@ static int __init policy_setup(char *str)
>  			ima_use_appraise_tcb = true;
>  		else if (strcmp(p, "secure_boot") == 0)
>  			ima_use_secure_boot = true;
> +		else if (strcmp(p, "critical_data") == 0)
> +			ima_use_critical_data = true;
>  		else if (strcmp(p, "fail_securely") == 0)
>  			ima_fail_unverifiable_sigs = true;
>  		else
> @@ -875,6 +882,11 @@ void __init ima_init_policy(void)
>  			  ARRAY_SIZE(default_appraise_rules),
>  			  IMA_DEFAULT_POLICY);
>  
> +	if (ima_use_critical_data)
> +		add_rules(critical_data_rules,
> +			  ARRAY_SIZE(critical_data_rules),
> +			  IMA_DEFAULT_POLICY);
> +
>  	ima_update_policy_flag();
>  }
>
Lakshmi Ramasubramanian Nov. 20, 2020, 11:33 p.m. UTC | #2
On 11/20/20 6:30 AM, Mimi Zohar wrote:

Hi Mimi,

> 
> On Thu, 2020-11-19 at 15:26 -0800, Tushar Sugandhi wrote:
>> From: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
>>
>> The IMA hook to measure kernel critical data, namely
>> ima_measure_critical_data(), could be called before a custom IMA policy
>> is loaded.
>> Define a new critical data builtin policy to allow measuring
>> early kernel integrity critical data before a custom IMA policy is
>> loaded.
> 
> Everything needing to be said seems to be included in the second
> sentence.  Does the first sentence add anything?  "Define a new
> critical data builtin policy" makes for a good Subject line.

Agreed - will update.

> 
>>
>> Add critical data to built-in IMA rules if the kernel command line
>> contains "ima_policy=critical_data".
> 
> The boot command line parameters are defined in Documentation/admin-
> guide/kernel-parameters.txt.  Please update "ima_policy".

Will do.

> 
>>
>> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
>> ---
>>   security/integrity/ima/ima_policy.c | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index c9e52dab0638..119604a3efa0 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -206,6 +206,10 @@ static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
>>   	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
>>   };
>>
>> +static struct ima_rule_entry critical_data_rules[] __ro_after_init = {
>> +	{.action = MEASURE, .func = CRITICAL_DATA, .flags = IMA_FUNC},
>> +};
>> +
>>   /* An array of architecture specific rules */
>>   static struct ima_rule_entry *arch_policy_entry __ro_after_init;
>>   
>> @@ -228,6 +232,7 @@ __setup("ima_tcb", default_measure_policy_setup);
>>   
>>   static bool ima_use_appraise_tcb __initdata;
>>   static bool ima_use_secure_boot __initdata;
>> +static bool ima_use_critical_data __ro_after_init;
> 
> Unlike ima_fail_unverifiable_sigs, ima_use_critical_data is only used
> during __init.  Please change "__ro_after_init" to "__initdata".  (The
> critical data policy itself is defined properly as __ro_after_init.)

Will do.

> 
>>   static bool ima_fail_unverifiable_sigs __ro_after_init;
>>   static int __init policy_setup(char *str)
>>   {
>> @@ -242,6 +247,8 @@ static int __init policy_setup(char *str)
>>   			ima_use_appraise_tcb = true;
>>   		else if (strcmp(p, "secure_boot") == 0)
>>   			ima_use_secure_boot = true;
>> +		else if (strcmp(p, "critical_data") == 0)
>> +			ima_use_critical_data = true;
>>   		else if (strcmp(p, "fail_securely") == 0)
>>   			ima_fail_unverifiable_sigs = true;
>>   		else
>> @@ -875,6 +882,11 @@ void __init ima_init_policy(void)
>>   			  ARRAY_SIZE(default_appraise_rules),
>>   			  IMA_DEFAULT_POLICY);
>>   
>> +	if (ima_use_critical_data)
>> +		add_rules(critical_data_rules,
>> +			  ARRAY_SIZE(critical_data_rules),
>> +			  IMA_DEFAULT_POLICY);
>> +
>>   	ima_update_policy_flag();
>>   }
>>   
> 

thanks,
  -lakshmi
diff mbox series

Patch

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index c9e52dab0638..119604a3efa0 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -206,6 +206,10 @@  static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
 	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
 };
 
+static struct ima_rule_entry critical_data_rules[] __ro_after_init = {
+	{.action = MEASURE, .func = CRITICAL_DATA, .flags = IMA_FUNC},
+};
+
 /* An array of architecture specific rules */
 static struct ima_rule_entry *arch_policy_entry __ro_after_init;
 
@@ -228,6 +232,7 @@  __setup("ima_tcb", default_measure_policy_setup);
 
 static bool ima_use_appraise_tcb __initdata;
 static bool ima_use_secure_boot __initdata;
+static bool ima_use_critical_data __ro_after_init;
 static bool ima_fail_unverifiable_sigs __ro_after_init;
 static int __init policy_setup(char *str)
 {
@@ -242,6 +247,8 @@  static int __init policy_setup(char *str)
 			ima_use_appraise_tcb = true;
 		else if (strcmp(p, "secure_boot") == 0)
 			ima_use_secure_boot = true;
+		else if (strcmp(p, "critical_data") == 0)
+			ima_use_critical_data = true;
 		else if (strcmp(p, "fail_securely") == 0)
 			ima_fail_unverifiable_sigs = true;
 		else
@@ -875,6 +882,11 @@  void __init ima_init_policy(void)
 			  ARRAY_SIZE(default_appraise_rules),
 			  IMA_DEFAULT_POLICY);
 
+	if (ima_use_critical_data)
+		add_rules(critical_data_rules,
+			  ARRAY_SIZE(critical_data_rules),
+			  IMA_DEFAULT_POLICY);
+
 	ima_update_policy_flag();
 }