linux-kernel - Re: [PATCH 1/3] IMA: add policy condition to measure duplicate critical data

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Date:   Tue, 9 Feb 2021 10:26:13 -0800
From:   Tushar Sugandhi <tusharsu@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, stephen.smalley.work@...il.com,
        casey@...aufler-ca.com, agk@...hat.com, snitzer@...hat.com,
        gmazyland@...il.com, paul@...l-moore.com
Cc:     tyhicks@...ux.microsoft.com, sashal@...nel.org, jmorris@...ei.org,
        nramas@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        selinux@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: Re: [PATCH 1/3] IMA: add policy condition to measure duplicate
 critical data



On 2021-02-08 12:45 p.m., Mimi Zohar wrote:
> Hi Tushar,
> 
> On Fri, 2021-01-29 at 16:45 -0800, Tushar Sugandhi wrote:
>> IMA needs to support duplicate measurements of integrity
>> critical data to accurately determine the current state of that data
>> on the system.  Further, since measurement of duplicate data is not
>> required for all the use cases, it needs to be policy driven.
>>
>> Define "allow_dup", a new IMA policy condition, for the IMA func
>> CRITICAL_DATA to allow duplicate buffer measurement of integrity
>> critical data.
>>
>> Limit the ability to measure duplicate buffer data when action is
>> "measure" and func is CRITICAL_DATA.
> 
> Why?!
> 
I wasn't sure if it would break any use-case by supporting this for all 
the files / buffers.  That's why I only wanted to address the scenario 
that we discussed in the last series (critical data measurement).
But as you suggested in this series' cover letter response, I am happy 
to extend it to other scenarios (by disabling "htable" using new Kconfig 
(e.g. CONFIG_IMA_DISABLE_HTABLE)
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
>> ---
>>
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index 9b45d064a87d..b89eb768dd05 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -35,6 +35,7 @@
>>   #define IMA_FSNAME	0x0200
>>   #define IMA_KEYRINGS	0x0400
>>   #define IMA_LABEL	0x0800
>> +#define IMA_ALLOW_DUP	0x1000
>>   
>>   #define UNKNOWN		0
>>   #define MEASURE		0x0001	/* same as IMA_MEASURE */
>> @@ -87,6 +88,7 @@ struct ima_rule_entry {
>>   	char *fsname;
>>   	struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */
>>   	struct ima_rule_opt_list *label; /* Measure data grouped under this label */
> 
> Defining a new boolean entry shouldn't be necessary.    The other
> boolean values are just stored in "flags".
> 
Thanks.  Will do the same here.
Thanks,
Tushar
>>   	struct ima_template_desc *template;
>>   };
> 
> thanks,
> 
> Mimi
>