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SubjectRe: [PATCH v7 4/8] IMA: add policy rule to measure critical data
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On 2020-12-10 3:10 p.m., Tyler Hicks wrote:
> On 2020-12-09 11:42:08, 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@linux.microsoft.com>
>> ---
>> security/integrity/ima/ima_policy.c | 35 +++++++++++++++++++++++++----
>> 1 file changed, 31 insertions(+), 4 deletions(-)
>>
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index 2a0c0603626e..9a8ee80a3128 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -34,6 +34,7 @@
>> #define IMA_PCR 0x0100
>> #define IMA_FSNAME 0x0200
>> #define IMA_KEYRINGS 0x0400
>> +#define IMA_DATA_SOURCE 0x0800
>
> You introduce data_source= in the next patch. This macro shouldn't be
> added until the next patch.
>
Ok I will move IMA_DATA_SOURCE to the next patch.

>>
>> #define UNKNOWN 0
>> #define MEASURE 0x0001 /* same as IMA_MEASURE */
>> @@ -85,6 +86,7 @@ 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 */
>> struct ima_template_desc *template;
>> };
>>
>> @@ -479,6 +481,12 @@ static bool ima_match_rule_data(struct ima_rule_entry *rule,
>> else
>> opt_list = rule->keyrings;
>> break;
>> + case CRITICAL_DATA:
>> + if (!rule->data_source)
>> + return true;
>> + else
>> + opt_list = rule->data_source;
>
> If you take my suggestions on patch #1, remove the else and simply
> assign opt_list here, too.
>
Yup. Will do.
>> + break;
>> default:
>> break;
>> }
>> @@ -518,13 +526,19 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
>> {
>> int i;
>>
>> - if (func == KEY_CHECK) {
>> - return (rule->flags & IMA_FUNC) && (rule->func == func) &&
>> - ima_match_rule_data(rule, func_data, cred);
>> - }
>> if ((rule->flags & IMA_FUNC) &&
>> (rule->func != func && func != POST_SETATTR))
>> return false;
>> +
>> + switch (func) {
>> + case KEY_CHECK:
>> + case CRITICAL_DATA:
>> + return ((rule->func == func) &&
>> + ima_match_rule_data(rule, func_data, cred));
>> + default:
>> + break;
>> + }
>> +
>> if ((rule->flags & IMA_MASK) &&
>> (rule->mask != mask && func != POST_SETATTR))
>> return false;
>> @@ -1119,6 +1133,19 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
>> if (ima_rule_contains_lsm_cond(entry))
>> return false;
>>
>> + break;
>> + case CRITICAL_DATA:
>> + if (entry->action & ~(MEASURE | DONT_MEASURE))
>> + return false;
>> +
>> + if (!(entry->flags & IMA_DATA_SOURCE) ||
>> + (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR |
>> + IMA_DATA_SOURCE)))
>
> IMA_DATA_SOURCE shouldn't exist in this patch. This isn't the right
> indentation, either. See how IMA_KEYRINGS is indented in the KEY_CHECK
> case above.
>
Will do.
~Tushar
> Tyler
>
>> + return false;
>> +
>> + if (ima_rule_contains_lsm_cond(entry))
>> + return false;
>> +
>> break;
>> default:
>> return false;
>> --
>> 2.17.1
>>

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