On 2021-01-16 09:18, Burn Alting wrote:

On Sun, 2021-01-10 at 15:39 +1100, Burn Alting wrote:

On Tue, 2021-01-05 at 07:12 +1100, Burn Alting wrote:

On Mon, 2021-01-04 at 09:46 -0500, Steve Grubb wrote:

On Monday, January 4, 2021 2:55:25 AM EST Burn Alting wrote:

On Sun, 2021-01-03 at 10:41 -0500, Steve Grubb wrote:

On Friday, January 1, 2021 4:22:33 PM EST Burn Alting wrote:

Sometimes, events recorded in /var/log/audit/audit.log appear

someseconds past co- located events which results

inauparse:au_check_events() marking  these events complete before

theyare. An example of this can be seen below with the offending event

id44609.

This has been plaguing me for a year or two and this morning was

thefirst time I still had access to the raw audit.log files (I monitor a

lotof event types and the log files roll over fairly quickly).The

example below is from a fully patched Centos 7 but I have also seenthis

on a patched Fedora 32.

Has this been seen before? Do we need to re-evaluate how

auparse'completes' an event (ie 2 seconds is too quick).

I have never seen this. But on the way to disk, auditd only does

lightprocessing of the event.  If the format is enriched, it looks things

upon a record by record basis. It does not collect events until they

arecomplete - it dumps it to disk as soon as it can tack on the

extrainformation.

So, the question would be, does this delay happen on the way to disk? Oris

this an artifact of post processing the logs with an auparse basedutility?

Can this be observed repeatedly on the same raw logs? If so,then maybe

auparse does have some issue. But if this is a postprocessing issue, then

the wall clock doesn't matter because this eventshould have collected up

together.

I'd say this merits some investigation.

OK. I think this needs to be addressed on two fronts. There may be

more.A.  Within post processing ... a 2 second timeout is not sufficient.

Iwould suggest we modify auparse.c:au_check_events() to i) perform theevent

type checks first, then  ii) increase the timeout of 2 seconds to be a

larger value based onempirical tests.

In the post processing, there are 2 use cases. The first is events that are on

disk. In this usage, the 2 second timeout does not come into effect because

the events are run through probably within nanoseconds or microseconds at the

worst. The only time it would come into effect is if the terminating record is

missing.

In this first case, the 2 second timeout is on the event's time, not the

'processing time'.  See ausearch-lol.c:check_events() and

auparse.c:au_get_ready_event().

And I use the checkpointing code to avoid the incomplete event issue.

In my case, I have not lost records, it's just that an event has arrived on disk

with an event time more than 2 seconds after the previously written event.

Basically,

a. The event was delayed getting to auditd and we look to the kernel for a

solution.

b. The event arrived at a reasonable point in time at auditd and for some reason

auditd delayed it's printing (by the way I tend to use RAW log format, not

enriched.

In either case, I believe ausearch-lol.c:check_events() and

auparse.c:au_get_ready_event() do need to be changed as we have complete events

written by auditd

which these two routines fail to process properly.

Changing the two second timeout in ausearch-lol.c:check_events() and, one assumes

in  auparse.c:au_get_ready_event() (but I have not tested the auparse code) fixes

the processing  of the delayed event.

Changing the value to say 10 seconds fixes my example use case, but given the

kernel or auditd could emit an event with a larger delay, should this be a

configuration item in /etc/audit/auditd.conf?

I have raised both a bugzilla report (

https://bugzilla.redhat.com/show_bug.cgi?id=1914603

) and Issue (

https://github.com/linux-audit/audit-userspace/issues/148

)

How do you want me to proceed ... a simple change to 10 seconds or a more

versatile configuration item in auditd.conf?

I can perform either and issue a PR if so required.

What do people think ... I would point out this currently occurs in both audit-

2.8.5-4.el7.x86_64 and audit-3.0-0.17.20191104git1c2f876.el8.x86_64 and a just

compiled checkout of the audit-userspace code audit-3.0-1.fc33.x86_64.

I have found examples (under audit-3.0-0.17.20191104git1c2f876.el8.x86_64) that I

need a 15 second delay.

I accept there may be an issue in the kernel but if it is not simple (I only see

this occasionally), then we need a fix in the userspace. Since I have found varied

times required, do I go down the path of a big value OR a configuration item in

/etc/audit/auditd.conf?

Or we go back to userspace code looking for the EOE record?  This

doesn't help if they arrive out of order.  Do we number the records in

the kernel?  N of M...

The other use case is realtime processing as an audispd plugin. In this use

case the wall clock could matter because records could potentially get lost

due to overflows or another plugin taking too long. This is the use case where

the wall clock matters. And again, it matters when records get lost or delayed

in transit. As long as everything is flowing, it should not factor into event

processing.

B. I will build a temporary auditd daemon to perform some empirical

testingto see how long events can reside within the daemon. I may need

someadvice on this. I assume that the code that sets the timestamp is

insrc/auditd.c:send_audit_event().

This is only for audit daemon's internal events. For all "real" events, it's

set in the kernel.

If that is the case and the kernel is establishing the timestamp, then either

the kernel has delayed the eventsarrival at the daemon or the daemon has delayed

it's writing.

If so, I will see if I can put orchestration debug code in to monitor

anevent's 'time in daemon' until this point. I will then report on this.

I believe given that AUDIT_PROCTITLE and AUDIT_EOE is fairly widespread,then

the testing switch in A. will not be a big issue (time cost wise). Itwill

also mean that if we over compensate the timeout that would causeadditional

memory cost in auparse() then this is mittigated.

I'd suggest breaking up the event completion tests so that an exact collection

termination reason code could be associated to the event.

With respect to 'There may be more' fronts. Are there other points in

the'audit ecosystem' that makes use of the '2 second timeout'.

Ausearch/report has its own special copy of the event collection logic. It

should be nearly identical to what auparse does.

They appear identical  ... ausearch-lol.c:check_events() and

auparse.c:au_get_ready_event().

I will start work on this, this coming weekend if the above makes sense.

One other thought, the current shipping code is audit-3.0, doing a diff

between it and audit-2.8.5 for the auparse directory does show some

differences in event collection/grouping/next_event. A lot of the differences

are cosmetic to fix extra whitespace or indentation. But if you skip all that,

there are some real changes that probably were because of bug reports. For

example,

I will go through these, although this occurs on my Centos 7's (audit-2.8.5-

4.el7.x86_64) as well as my 8's (audit-3.0-0.17.20191104git1c2f876.el8.x86_64).

@@ -259,15 +260,6 @@ static event_list_t *au_get_ready_event(        if

(lowest && lowest->status == EBS_COMPLETE) {                lowest->status =

EBS_EMPTY;                au->au_ready--;-               // Try to consolidate

the array so that we iterate-               // over a smaller portion next

time-               if (lowest == &lol->array[lol->maxi])

{-                       au_lolnode *ptr =

lowest;-                       while (ptr->status == EBS_EMPTY && lol->maxi >

0) {-                               lol->maxi

--;-                               ptr = &lol->array[lol

->maxi];-                       }-               }                return

lowest->l;        }

and

@@ -1536,6 +1550,13 @@ static int

au_auparse_next_event(auparse                aup_list_create(l);              

  aup_list_set_event(l, &e);                aup_list_append(l, au->cur_buf,

au->list_idx, au-

line_number);

+               // Eat standalone EOE - main event was already marked

complete+               if (l->head->type == AUDIT_EOE)

{+                       au->cur_buf =

NULL;+                       aup_list_clear(l);+                       free(l)

;+                       continue;+               }                if

(au_lol_append(au->au_lo, l) == NULL) {                        free((char

*)e.host); #ifdef LOL_EVENTS_DEBUG01

I don't know if those have an effect on what you are seeing. But that is the

only substantial changes that I can see.

-Steve

Burn

- RGB

--

Richard Guy Briggs <

rgb@redhat.com

>

Sr. S/W Engineer, Kernel Security, Base Operating Systems

Remote, Ottawa, Red Hat Canada

IRC: rgb, SunRaycer

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