linux-kernel - Re: [PATCH v7 5/8] IMA: limit critical data measurement based on a label

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Message-ID: <730f52ec-4b78-9aac-6c2e-c1ca63c929f1@linux.microsoft.com>
Date:   Thu, 10 Dec 2020 19:28:58 -0800
From:   Tushar Sugandhi <tusharsu@...ux.microsoft.com>
To:     Tyler Hicks <tyhicks@...ux.microsoft.com>
Cc:     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, 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 v7 5/8] IMA: limit critical data measurement based on a
 label



On 2020-12-10 3:15 p.m., Tyler Hicks wrote:
> On 2020-12-09 11:42:09, Tushar Sugandhi wrote:
>> System administrators should be able to limit which kernel subsystems
>> they want to measure the critical data for. To enable that, an IMA policy
>> condition to choose specific kernel subsystems is needed. This policy
>> condition would constrain the measurement of the critical data based on
>> a label for the given subsystems.
>>
>> Add a new IMA policy condition - "data_source:=" to the IMA func
>> CRITICAL_DATA to allow measurement of various kernel subsystems. This
>> policy condition would enable the system administrators to restrict the
>> measurement to the labels listed in "data_source:=".
>>
>> Limit the measurement to the labels that are specified in the IMA
>> policy - CRITICAL_DATA+"data_source:=". If "data_sources:=" is not
>> provided with the func CRITICAL_DATA, the data from all the
>> supported kernel subsystems is measured.
>>
>> Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
> 
> This patch will look good once all the IMA_DATA_SOURCE stuff is moved
> over from patch #4.
> 
> Tyler
> 
Sounds good. Will do.
~Tushar

>> ---
>>   Documentation/ABI/testing/ima_policy |  2 ++
>>   security/integrity/ima/ima_policy.c  | 26 +++++++++++++++++++++++++-
>>   2 files changed, 27 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
>> index 6ec7daa87cba..0f4ee9e0a455 100644
>> --- a/Documentation/ABI/testing/ima_policy
>> +++ b/Documentation/ABI/testing/ima_policy
>> @@ -52,6 +52,8 @@ Description:
>>   			template:= name of a defined IMA template type
>>   			(eg, ima-ng). Only valid when action is "measure".
>>   			pcr:= decimal value
>> +			data_source:= [label]
>> +			label:= a unique string used for grouping and limiting critical data.
>>   
>>   		  default policy:
>>   			# PROC_SUPER_MAGIC
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index 9a8ee80a3128..7486d09a3f60 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -934,7 +934,7 @@ enum {
>>   	Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt,
>>   	Opt_appraise_type, Opt_appraise_flag,
>>   	Opt_permit_directio, Opt_pcr, Opt_template, Opt_keyrings,
>> -	Opt_err
>> +	Opt_data_source, Opt_err
>>   };
>>   
>>   static const match_table_t policy_tokens = {
>> @@ -971,6 +971,7 @@ static const match_table_t policy_tokens = {
>>   	{Opt_pcr, "pcr=%s"},
>>   	{Opt_template, "template=%s"},
>>   	{Opt_keyrings, "keyrings=%s"},
>> +	{Opt_data_source, "data_source=%s"},
>>   	{Opt_err, NULL}
>>   };
>>   
>> @@ -1350,6 +1351,23 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
>>   
>>   			entry->flags |= IMA_KEYRINGS;
>>   			break;
>> +		case Opt_data_source:
>> +			ima_log_string(ab, "data_source", args[0].from);
>> +
>> +			if (entry->data_source) {
>> +				result = -EINVAL;
>> +				break;
>> +			}
>> +
>> +			entry->data_source = ima_alloc_rule_opt_list(args);
>> +			if (IS_ERR(entry->data_source)) {
>> +				result = PTR_ERR(entry->data_source);
>> +				entry->data_source = NULL;
>> +				break;
>> +			}
>> +
>> +			entry->flags |= IMA_DATA_SOURCE;
>> +			break;
>>   		case Opt_fsuuid:
>>   			ima_log_string(ab, "fsuuid", args[0].from);
>>   
>> @@ -1730,6 +1748,12 @@ int ima_policy_show(struct seq_file *m, void *v)
>>   		seq_puts(m, " ");
>>   	}
>>   
>> +	if (entry->flags & IMA_DATA_SOURCE) {
>> +		seq_puts(m, "data_source=");
>> +		ima_show_rule_opt_list(m, entry->data_source);
>> +		seq_puts(m, " ");
>> +	}
>> +
>>   	if (entry->flags & IMA_PCR) {
>>   		snprintf(tbuf, sizeof(tbuf), "%d", entry->pcr);
>>   		seq_printf(m, pt(Opt_pcr), tbuf);
>> -- 
>> 2.17.1
>>