[PATCH v8 4/8] IMA: add policy rule to measure critical data
Tushar Sugandhi
tusharsu at linux.microsoft.com
Sat Dec 12 01:17:22 UTC 2020
On 2020-12-11 4:25 p.m., Tyler Hicks wrote:
> On 2020-12-11 15:58:03, Tushar Sugandhi wrote:
>> A new IMA policy rule is needed for the IMA hook
>> ima_measure_critical_data() and the corresponding func CRITICAL_DATA for
>> measuring the input buffer. The policy rule should ensure the buffer
>> would get measured only when the policy rule allows the action. The
>> policy rule should also support the necessary constraints (flags etc.)
>> for integrity critical buffer data measurements.
>>
>> Add a policy rule to define the constraints for restricting integrity
>> critical data measurements.
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu at linux.microsoft.com>
>> ---
>> Documentation/ABI/testing/ima_policy | 2 +-
>> security/integrity/ima/ima_policy.c | 34 ++++++++++++++++++++++++----
>> 2 files changed, 31 insertions(+), 5 deletions(-)
>>
>> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
>> index e35263f97fc1..6ec7daa87cba 100644
>> --- a/Documentation/ABI/testing/ima_policy
>> +++ b/Documentation/ABI/testing/ima_policy
>> @@ -32,7 +32,7 @@ Description:
>> func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK]MODULE_CHECK]
>> [FIRMWARE_CHECK]
>> [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
>> - [KEXEC_CMDLINE] [KEY_CHECK]
>> + [KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA]
>> mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
>> [[^]MAY_EXEC]
>> fsmagic:= hex value
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index a09d1a41a290..07116ff35c25 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -85,6 +85,7 @@ struct ima_rule_entry {
>> } lsm[MAX_LSM_RULES];
>> char *fsname;
>> struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */
>> + struct ima_rule_opt_list *data_source; /* Measure data from this source */
>
> Argh, there are still some more instances of data_source sneaking into
> this patch too early instead of waiting until the next patch.
>
I kept it purposefully in this patch so that the
"case CRITICAL_DATA:" could be properly defined.
Also, my impression was rule->data_source is not part of the user facing
policy.
Whereas IMA_DATA_SOURCE, Opt_data_source, data_source=%s are.
That's why they are part of Patch #5.
Patch #5 IMA: limit critical data measurement based on a label
>> struct ima_template_desc *template;
>> };
>>
>> @@ -479,6 +480,12 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule,
>>
>> opt_list = rule->keyrings;
>> break;
>> + case CRITICAL_DATA:
>> + if (!rule->data_source)
>> + return true;
>> +
>> + opt_list = rule->data_source;
>> + break;
>
> I guess this case should unconditionally return true in this patch and
> then the include this additional logic in the next patch.
>
> Sorry, I missed these on my last review.
>
No worries.
As I mentioned above, I kept it purposefully in this patch since
my impression was rule->data_source is not part of the user facing
policy.
But I can simply return true here as you suggested, and move the logic
to the next patch.
+ case CRITICAL_DATA:
+ if (!rule->data_source)
+ return true;
+
+ opt_list = rule->data_source;
+ break;
~Tushar
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