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From: Casey Schaufler <casey@schaufler-ca.com>
To: Paul Moore <paul@paul-moore.com>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>,
	casey.schaufler@intel.com, James Morris <jmorris@namei.org>,
	LSM List <linux-security-module@vger.kernel.org>,
	SElinux list <selinux@vger.kernel.org>,
	Kees Cook <keescook@chromium.org>,
	John Johansen <john.johansen@canonical.com>,
	penguin-kernel@i-love.sakura.ne.jp,
	Stephen Smalley <sds@tycho.nsa.gov>,
	linux-audit@redhat.com, Steve Grubb <sgrubb@redhat.com>,
	Richard Guy Briggs <rgb@redhat.com>,
	Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [PATCH v17 20/23] Audit: Add a new record for multiple subject LSM attributes
Date: Mon, 18 May 2020 17:16:34 -0700
Message-ID: <774a37e3-3469-d606-a468-a57892b44645@schaufler-ca.com> (raw)
In-Reply-To: <CAHC9VhRGopG0=DbEZArz2X2yfEQ1pOqoSLRMn9ABe5JYZB2Y8Q@mail.gmail.com>

On 5/18/2020 3:21 PM, Paul Moore wrote:
> On Mon, May 18, 2020 at 4:43 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>> On 5/18/2020 11:02 AM, Stephen Smalley wrote:
>>> On Thu, May 14, 2020 at 7:30 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>>>> Create a new audit record type to contain the subject information
>>>> when there are multiple security modules that require such data.
>>>> This record is emitted before the other records for the event, but
>>>> is linked with the same timestamp and serial number.
>>>>
>>>> Reviewed-by: Kees Cook <keescook@chromium.org>
>>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>>> Cc: linux-audit@redhat.com
>>>> ---
>>> With this patch, I see userspace audit records like this one:
>>>
>>> type=SYSTEM_BOOT msg=audit(1589816792.181:103): pid=789 uid=0
>>> auid=4294967295 ses=4294967295 subj=? subj=system_u:system_r:init_t:s0
>>> msg=' comm="systemd-update-utmp"
>>> exe="/usr/lib/systemd/systemd-update-utmp" hostname=? addr=?
>>> terminal=? res=success'
>>>
>>> I'm guessing that userspace is appending the second subj= field when
>>> it sees subj=? or otherwise is missing subj= information?
>> I haven't looked at the userspace code, but I expect you're right.
>> It looks like there will need to be some change in the userspace
>> for the multiple LSM case. The "completion" shown here isn't correct,
>> because it only fills in one of the subject attributes, not both.
> Wait, didn't we agree on a a "subj=? subj_selinux=XXX
> subj_apparmor=YYY subj_smack=ZZZ" format?  It looks like there are two
> 'subj' fields in the record above which is bad, don't do that please.

That's not something that's coming from the kernel.
I'll check again, but I think that everyplace in the kernel that
produces a subj= has been trained to create a type=1420 record
instead.

>
>>> Then we have kernel audit records like this:
>>>
>>> type=PROCTITLE msg=audit(1589816791.959:101): proctitle=2F7362696E2F617564697463
>>> 746C002D52002F6574632F61756469742F61756469742E72756C6573
>>> type=SYSCALL msg=audit(1589816791.959:101): arch=c000003e syscall=44
>>> success=yes exit=1056 a0=3 a1=7fff9ccc98a0 a2=420 a3=0 items=0
>>> ppid=773 pid=783 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0
>>> egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="auditctl"
>>> exe="/usr/sbin/auditctl" subj=? key=(null)
>>> type=UNKNOWN[1420] msg=audit(1589816791.959:101):
>>> subj_selinux=system_u:system_r:unconfined_service_t:s0
>>> subj_apparmor==unconfined
>>> type=CONFIG_CHANGE msg=audit(1589816791.959:101): auid=4294967295
>>> ses=4294967295 subj=? op=add_rule key=(null) list=1 res=1
>>> type=UNKNOWN[1420] msg=audit(1589816791.959:101):
>>> subj_selinux=system_u:system_r:unconfined_service_t:s0
>>> subj_apparmor==unconfined
>>>
>>> where we are getting multiple copies of the new record type, one for
>>> each record type that had subj=?.
>> While obviously wasteful, the type=1420 behavior is consistent with
>> the subj=? behavior, which is to duplicate the subj= value. I know
>> we've got enough hobgoblins in the audit system that we don't need
>> to add any more in the name of a foolish consistency.
> You need to provide a bit more reason why we need byte-for-byte
> duplicate records in a single event.  As it currently stands this
> looks like something we definitely don't want.

The CONFIG_CHANGE record already duplicates the subj= information
in the SYSCALL record. I just maintained the duplication. You're
right, it's silly to have two identical type=1420 records for the event.
I will have to come up with a mechanism to prevent the duplication.
with luck, there's already a similar case for some other record.

>
> --
> paul moore
> www.paul-moore.com


  reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200514221142.11857-1-casey.ref@schaufler-ca.com>
2020-05-14 22:11 ` [PATCH v17 00/23] LSM: Module stacking for AppArmor Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 01/23] LSM: Infrastructure management of the sock security Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 02/23] LSM: Create and manage the lsmblob data structure Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 03/23] LSM: Use lsmblob in security_audit_rule_match Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 04/23] LSM: Use lsmblob in security_kernel_act_as Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 05/23] net: Prepare UDS for security module stacking Casey Schaufler
2020-05-18 17:02     ` Stephen Smalley
2020-05-14 22:11   ` [PATCH v17 06/23] Use lsmblob in security_secctx_to_secid Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 07/23] LSM: Use lsmblob in security_secid_to_secctx Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 08/23] LSM: Use lsmblob in security_ipc_getsecid Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 09/23] LSM: Use lsmblob in security_task_getsecid Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 10/23] LSM: Use lsmblob in security_inode_getsecid Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 11/23] LSM: Use lsmblob in security_cred_getsecid Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 12/23] IMA: Change internal interfaces to use lsmblobs Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 13/23] LSM: Specify which LSM to display Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 14/23] LSM: Ensure the correct LSM context releaser Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 15/23] LSM: Use lsmcontext in security_secid_to_secctx Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 16/23] LSM: Use lsmcontext in security_inode_getsecctx Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 17/23] LSM: security_secid_to_secctx in netlink netfilter Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 18/23] NET: Store LSM netlabel data in a lsmblob Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 19/23] LSM: Verify LSM display sanity in binder Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 20/23] Audit: Add a new record for multiple subject LSM attributes Casey Schaufler
2020-05-18 18:02     ` Stephen Smalley
2020-05-18 20:42       ` Casey Schaufler
2020-05-18 22:21         ` Paul Moore
2020-05-19  0:16           ` Casey Schaufler [this message]
2020-05-19  0:58             ` Casey Schaufler
2020-05-19 15:48             ` Paul Moore
2020-05-14 22:11   ` [PATCH v17 21/23] Audit: Add a new record for multiple object " Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 22/23] LSM: Add /proc attr entry for full LSM context Casey Schaufler
2020-05-14 22:11   ` [PATCH v17 23/23] AppArmor: Remove the exclusive flag Casey Schaufler

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