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From: Casey Schaufler <casey@schaufler-ca.com>
To: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: 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,
	Paul Moore <paul@paul-moore.com>,
	Stephen Smalley <sds@tycho.nsa.gov>,
	linux-audit@redhat.com, Steve Grubb <sgrubb@redhat.com>,
	Richard Guy Briggs <rgb@redhat.com>
Subject: Re: [PATCH v17 20/23] Audit: Add a new record for multiple subject LSM attributes
Date: Mon, 18 May 2020 13:42:58 -0700
Message-ID: <9cabbb54-69e6-91e6-88f8-e76d53da2a77@schaufler-ca.com> (raw)
In-Reply-To: <CAEjxPJ67cA_A-Oh72EGgmCrP6k9x0PuaU2q7UL9eOc+J6Do0zQ@mail.gmail.com>

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.

> 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.

> Not sure what it is the audit folks want here.

I doubt that redundant type=1420 records are a good idea, but having
seen some of the other active threads about useless fields I am not
going to assume what is most appropriate.

> This is with multiple LSMs enabled; need to confirm that no change
> occurs if only one is enabled.


  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 [this message]
2020-05-18 22:21         ` Paul Moore
2020-05-19  0:16           ` Casey Schaufler
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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