From: Casey Schaufler <casey@schaufler-ca.com>
To: Mimi Zohar <zohar@linux.ibm.com>,
casey.schaufler@intel.com, jmorris@namei.org,
linux-security-module@vger.kernel.org, selinux@vger.kernel.org
Cc: john.johansen@canonical.com, linux-kernel@vger.kernel.org,
linux-audit@redhat.com, sds@tycho.nsa.gov
Subject: Re: [PATCH v24 04/25] IMA: avoid label collisions with stacked LSMs
Date: Tue, 16 Feb 2021 07:26:30 -0800 [thread overview]
Message-ID: <ae6dcadf-57d5-cb29-a361-d020f6333f59@schaufler-ca.com> (raw)
In-Reply-To: <693f81d9d2f50a920cafbbc8d1d634598b99081a.camel@linux.ibm.com>
On 2/14/2021 10:21 AM, Mimi Zohar wrote:
> Hi Casey,
>
> On Tue, 2021-01-26 at 08:40 -0800, Casey Schaufler wrote:
>> Integrity measurement may filter on security module information
>> and needs to be clear in the case of multiple active security
>> modules which applies. Provide a boot option ima_rules_lsm= to
>> allow the user to specify an active securty module to apply
>> filters to. If not specified, use the first registered module
>> that supports the audit_rule_match() LSM hook. Allow the user
>> to specify in the IMA policy an lsm= option to specify the
>> security module to use for a particular rule.
> Thanks, Casey.
>
> (This patch description line length seems short.)
>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>> To: Mimi Zohar <zohar@linux.ibm.com>
>> To: linux-integrity@vger.kernel.org
>> ---
>> Documentation/ABI/testing/ima_policy | 8 +++-
>> security/integrity/ima/ima_policy.c | 64 ++++++++++++++++++++++------
>> 2 files changed, 57 insertions(+), 15 deletions(-)
>>
>> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
>> index e35263f97fc1..a7943d40466f 100644
>> --- a/Documentation/ABI/testing/ima_policy
>> +++ b/Documentation/ABI/testing/ima_policy
>> @@ -25,7 +25,7 @@ Description:
>> base: [[func=] [mask=] [fsmagic=] [fsuuid=] [uid=]
>> [euid=] [fowner=] [fsname=]]
>> lsm: [[subj_user=] [subj_role=] [subj_type=]
>> - [obj_user=] [obj_role=] [obj_type=]]
>> + [obj_user=] [obj_role=] [obj_type=] [lsm=]]
> "[lsm=]" either requires all LSM rules types (e.g. {subj/obj}_user,
> role, type) to be exactly the same for multiple LSMs or all of the LSM
> rule types are applicable to only a single LSM. Supporting multiple
> LSMs with exactly the same LSM labels doesn't seem worth the effort.
> Keep it simple - a single rule, containing any LSM rule types, is
> applicable to a single LSM.
Thank you. I will add this.
>
>> option: [[appraise_type=]] [template=] [permit_directio]
>> [appraise_flag=] [keyrings=]
>> base:
>> @@ -114,6 +114,12 @@ Description:
>>
>> measure subj_user=_ func=FILE_CHECK mask=MAY_READ
>>
>> + It is possible to explicitly specify which security
>> + module a rule applies to using lsm=. If the security
>> + modules specified is not active on the system the rule
>> + will be rejected. If lsm= is not specified the first
>> + security module registered on the system will be assumed.
>> +
>> Example of measure rules using alternate PCRs::
>>
>> measure func=KEXEC_KERNEL_CHECK pcr=4
>> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
>> index 8002683003e6..de72b719c90c 100644
>> --- a/security/integrity/ima/ima_policy.c
>> +++ b/security/integrity/ima/ima_policy.c
>> @@ -82,6 +82,7 @@ struct ima_rule_entry {
>> void *rules[LSMBLOB_ENTRIES]; /* LSM file metadata specific */
>> char *args_p; /* audit value */
>> int type; /* audit type */
>> + int which_lsm; /* which of the rules to use */
>> } lsm[MAX_LSM_RULES];
> Even if we wanted to support multiple LSMs within the same rule having
> both "rules[LSMBLOB_ENTRIES]" and "which_lsm" shouldn't be necessary.
> The LSMBLOB_ENTRIES should already identify the LSM.
>
> To support a single LSM per policy rule, "which_lsm" should be defined
> outside of lsm[MAX_LSM_RULES]. This will simplify the rest of the code
> (e.g. matching/freeing rules).
>
> int which_lsm; /* which of the rules to use */
> struct {
> void *rule; /* LSM file metadata specific */
> char *args_p; /* audit value */
> int type; /* audit type */
> } lsm[MAX_LSM_RULES];
You're right, that is better. I'll incorporate the change.
>
>
>> char *fsname;
>> struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */
>> @@ -90,17 +91,15 @@ struct ima_rule_entry {
>>
>> /**
>> * ima_lsm_isset - Is a rule set for any of the active security modules
>> - * @rules: The set of IMA rules to check
>> + * @entry: the rule entry to examine
>> + * @lsm_rule: the specific rule type in question
>> *
>> - * If a rule is set for any LSM return true, otherwise return false.
>> + * If a rule is set return true, otherwise return false.
>> */
>> -static inline bool ima_lsm_isset(void *rules[])
>> +static inline bool ima_lsm_isset(struct ima_rule_entry *entry, int lsm_rule)
>> {
>> - int i;
>> -
>> - for (i = 0; i < LSMBLOB_ENTRIES; i++)
>> - if (rules[i])
>> - return true;
>> + if (entry->lsm[lsm_rule].rules[entry->lsm[lsm_rule].which_lsm])
>> + return true;
> If each IMA policy rule is limited to a specific LSM, then the test
> would be "entry->which_lsm".
Which would be an improvement.
>
>> return false;
>> }
>>
>> @@ -273,6 +272,20 @@ static int __init default_appraise_policy_setup(char *str)
>> }
>> __setup("ima_appraise_tcb", default_appraise_policy_setup);
>>
>> +static int ima_rule_lsm __ro_after_init;
>> +
>> +static int __init ima_rule_lsm_init(char *str)
>> +{
>> + ima_rule_lsm = lsm_name_to_slot(str);
>> + if (ima_rule_lsm < 0) {
>> + ima_rule_lsm = 0;
>> + pr_err("rule lsm \"%s\" not registered", str);
>> + }
>> +
>> + return 1;
>> +}
>> +__setup("ima_rule_lsm=", ima_rule_lsm_init);
> The patch description refers to "ima_rules_lsm=". Please update one or
> the other.
ima_rules_lsm seem to be more accurate. I'll fix it.
>
> thanks,
>
> Mimi
Thanks for the review and recommendations.
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next prev parent reply other threads:[~2021-02-16 15:27 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210126164108.1958-1-casey.ref@schaufler-ca.com>
2021-01-26 16:40 ` [PATCH v24 00/25] LSM: Module stacking for AppArmor Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 01/25] LSM: Infrastructure management of the sock security Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 02/25] LSM: Add the lsmblob data structure Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 03/25] LSM: provide lsm name and id slot mappings Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 04/25] IMA: avoid label collisions with stacked LSMs Casey Schaufler
[not found] ` <693f81d9d2f50a920cafbbc8d1d634598b99081a.camel@linux.ibm.com>
2021-02-16 15:26 ` Casey Schaufler [this message]
2021-02-22 23:45 ` Casey Schaufler
2021-02-23 0:27 ` Mimi Zohar
2021-01-26 16:40 ` [PATCH v24 05/25] LSM: Use lsmblob in security_audit_rule_match Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 06/25] LSM: Use lsmblob in security_kernel_act_as Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 07/25] LSM: Use lsmblob in security_secctx_to_secid Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 08/25] LSM: Use lsmblob in security_secid_to_secctx Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 09/25] LSM: Use lsmblob in security_ipc_getsecid Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 10/25] LSM: Use lsmblob in security_task_getsecid Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 11/25] LSM: Use lsmblob in security_inode_getsecid Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 12/25] LSM: Use lsmblob in security_cred_getsecid Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 13/25] IMA: Change internal interfaces to use lsmblobs Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 14/25] LSM: Specify which LSM to display Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 15/25] LSM: Ensure the correct LSM context releaser Casey Schaufler
2021-01-26 16:40 ` [PATCH v24 16/25] LSM: Use lsmcontext in security_secid_to_secctx Casey Schaufler
2021-01-26 16:41 ` [PATCH v24 17/25] LSM: Use lsmcontext in security_inode_getsecctx Casey Schaufler
2021-01-26 16:41 ` [PATCH v24 18/25] LSM: security_secid_to_secctx in netlink netfilter Casey Schaufler
2021-01-26 16:41 ` [PATCH v24 19/25] NET: Store LSM netlabel data in a lsmblob Casey Schaufler
2021-01-26 16:41 ` [PATCH v24 20/25] LSM: Verify LSM display sanity in binder Casey Schaufler
2021-01-26 16:41 ` [PATCH v24 21/25] audit: add support for non-syscall auxiliary records Casey Schaufler
2021-01-26 18:42 ` Richard Guy Briggs
2021-01-26 18:58 ` Casey Schaufler
2021-01-26 20:05 ` Paul Moore
2021-01-26 20:22 ` Richard Guy Briggs
2021-01-26 16:41 ` [PATCH v24 22/25] Audit: Add new record for multiple process LSM attributes Casey Schaufler
2021-01-26 16:41 ` [PATCH v24 23/25] Audit: Add a new record for multiple object " Casey Schaufler
2021-01-26 16:41 ` [PATCH v24 24/25] LSM: Add /proc attr entry for full LSM context Casey Schaufler
2021-01-26 16:41 ` [PATCH v24 25/25] AppArmor: Remove the exclusive flag Casey Schaufler
2021-02-02 12:05 ` [PATCH v24 00/25] LSM: Module stacking for AppArmor Topi Miettinen
2021-02-02 15:30 ` Casey Schaufler
2021-02-02 17:12 ` Topi Miettinen
2021-02-02 18:06 ` Casey Schaufler
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