auditctl usage for filter lists: "user" , "watch" and "exclude"

auditctl usage for filter lists: "user" , "watch" and "exclude"

[Michael C Thompson]

Hey all,

I'm trying to understand better the user, watch and exclude auditctl 
filter lists. I believe I have a reasonable understanding of exclude 
from some examples Steve gave (see below), but I have very little idea 
of how user is meant to be used, and none about watch.

Any enlightenment will be helpful.

For the exclude list,

exclude,always -F msgtype=SYSCALL

seems to be the only valid structure, where msgtype can be any value 
(XXX) for the type in the audit.log? (where the 1st field in the audit 
log is type=XXX)

Are there more filters that apply? (and does it have any meaning without 
a filter?)

Any examples and/or explanations on "user" and "watch" would be appriciated.

Thanks,
Mike

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Michael C Thompson]

Michael C Thompson wrote:
> Hey all,
> 
> I'm trying to understand better the user, watch and exclude auditctl 
> filter lists. I believe I have a reasonable understanding of exclude 
> from some examples Steve gave (see below), but I have very little idea 
> of how user is meant to be used, and none about watch.
> 
> Any enlightenment will be helpful.
> 
> For the exclude list,
> 
> exclude,always -F msgtype=SYSCALL
> 
> seems to be the only valid structure, where msgtype can be any value 
> (XXX) for the type in the audit.log? (where the 1st field in the audit 
> log is type=XXX)
> 
> Are there more filters that apply? (and does it have any meaning without 
> a filter?)

Question, is it intended for:
auditctl -a exclude,always -F msgtype=CONFIG_CHANGE
   and
auditctl -a exclude,never -F msgtype=CONFIG_CHANGE

(being active at different times) to both block the CONFIG_CHANGE 
messages? I would assume that exclude,never to _not_ block messages of 
that type?

Mike

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Michael C Thompson]

Michael C Thompson wrote:
> Michael C Thompson wrote:
>> Hey all,
>>
>> I'm trying to understand better the user, watch and exclude auditctl 
>> filter lists. I believe I have a reasonable understanding of exclude 
>> from some examples Steve gave (see below), but I have very little idea 
>> of how user is meant to be used, and none about watch.
>>
>> Any enlightenment will be helpful.
>>
>> For the exclude list,
>>
>> exclude,always -F msgtype=SYSCALL
>>
>> seems to be the only valid structure, where msgtype can be any value 
>> (XXX) for the type in the audit.log? (where the 1st field in the audit 
>> log is type=XXX)
>>
>> Are there more filters that apply? (and does it have any meaning 
>> without a filter?)
> 
> Question, is it intended for:
> auditctl -a exclude,always -F msgtype=CONFIG_CHANGE
>   and
> auditctl -a exclude,never -F msgtype=CONFIG_CHANGE
> 
> (being active at different times) to both block the CONFIG_CHANGE 
> messages? I would assume that exclude,never to _not_ block messages of 
> that type?

It also seems to be that:

auditctl -a exclude,always -F msgtype=CWD
auditctl -a exclude,always -F msgtype=PATH

and

auditctl -a exclude,always -F msgtype=CWD -F msgtype=PATH

do not work in the same way, in fact, "auditctl -a exclude,always -F 
msgtype=CWD -F msgtype=PATH" does not remove either the CWD or the PATH 
type from the message. Can the exclude list have only 1 msgtype per rule?

Mike

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Steve Grubb]

On Thursday 18 May 2006 11:41, Michael C Thompson wrote:
> It also seems to be that:
>
> auditctl -a exclude,always -F msgtype=CWD
> auditctl -a exclude,always -F msgtype=PATH
>
> and
>
> auditctl -a exclude,always -F msgtype=CWD -F msgtype=PATH
>
> do not work in the same way, 

This is true. The ones on the same line form an "and" expression. The ones on 
different lines form an "or" expression.

-Steve

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Michael C Thompson]

Steve Grubb wrote:
> On Thursday 18 May 2006 11:41, Michael C Thompson wrote:
>> It also seems to be that:
>>
>> auditctl -a exclude,always -F msgtype=CWD
>> auditctl -a exclude,always -F msgtype=PATH
>>
>> and
>>
>> auditctl -a exclude,always -F msgtype=CWD -F msgtype=PATH
>>
>> do not work in the same way, 
> 
> This is true. The ones on the same line form an "and" expression. The ones on 
> different lines form an "or" expression.

So then it should be safe to say that having two -F msgtype=... is an 
invalid construct for a rule? Since messages have only 1 type?

Mike

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Steve Grubb]

On Thursday 18 May 2006 12:04, Michael C Thompson wrote:
> So then it should be safe to say that having two -F msgtype=... is an
> invalid construct for a rule? Since messages have only 1 type?

Only if they are using the '=' operator. Other operators might be valid to 
have multiple -F msgtype.

-Steve

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Michael C Thompson]

Steve Grubb wrote:
> On Thursday 18 May 2006 12:04, Michael C Thompson wrote:
>> So then it should be safe to say that having two -F msgtype=... is an
>> invalid construct for a rule? Since messages have only 1 type?
> 
> Only if they are using the '=' operator. Other operators might be valid to 
> have multiple -F msgtype.

Ah yes, good point. I'll be sure to properly test the relational 
operators. Other than the source code, is there any place for a user to 
go and get the message types to determine their ordering?

Mike

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Steve Grubb]

On Thursday 18 May 2006 15:01, Michael C Thompson wrote:
> Other than the source code, is there any place for a user to
> go and get the message types to determine their ordering?

Not at this point. I want to update the docs at some point...but until 
then...source code.

-Steve

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Steve Grubb]

On Thursday 18 May 2006 10:59, Michael C Thompson wrote:
> Question, is it intended for:
> auditctl -a exclude,always -F msgtype=CONFIG_CHANGE
>    and
> auditctl -a exclude,never -F msgtype=CONFIG_CHANGE
>
> (being active at different times) to both block the CONFIG_CHANGE
> messages? I would assume that exclude,never to _not_ block messages of
> that type?

I can't see a reason to have both for the same msgtype. The first rule to 
match "wins" though, so the second rule would not apply. I can see that you 
may want to do something like this:

-a exclude,never -F msgtype=DAEMON_END
-a exclude,always -F 'msgtype>=DAEMON_START' -F 'msgtype<=DAEMON_ROTATE'

Together, this means exclude all messages in the DAEMON_* range except the 
DAEMON_END message.

-Steve

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Michael C Thompson]

Steve Grubb wrote:
> On Thursday 18 May 2006 10:59, Michael C Thompson wrote:
>> Question, is it intended for:
>> auditctl -a exclude,always -F msgtype=CONFIG_CHANGE
>>    and
>> auditctl -a exclude,never -F msgtype=CONFIG_CHANGE
>>
>> (being active at different times) to both block the CONFIG_CHANGE
>> messages? I would assume that exclude,never to _not_ block messages of
>> that type?
> 
> I can't see a reason to have both for the same msgtype. The first rule to 
> match "wins" though, so the second rule would not apply.

True, but I didn't mean for you to interpret them as being active 
together. Example:

auditctl -a exclude,always -F msgtype=CONFIG_CHANGE
auditctl -a entry,always -S chmod -- no message logged

auditctl -D

auditctl -a exclude,never -F msgtype=CONFIG_CHANGE
auditctl -a entry,always -S chmod -- no message logged

The 2nd no message logged doesn't make sense to me, as the exclude,never 
is in fact causing the messages to not get logged.

Mike

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Steve Grubb]

On Thursday 18 May 2006 11:58, Michael C Thompson wrote:
> True, but I didn't mean for you to interpret them as being active
> together. Example:
>
> auditctl -a exclude,always -F msgtype=CONFIG_CHANGE
> auditctl -a entry,always -S chmod -- no message logged
>
> auditctl -D
>
> auditctl -a exclude,never -F msgtype=CONFIG_CHANGE
> auditctl -a entry,always -S chmod -- no message logged

> The 2nd no message logged doesn't make sense to me, as the exclude,never
> is in fact causing the messages to not get logged.

Looking at the kernel code...I don't think it takes the action into account. 
If you have exclude list and msgtype matches, it gets excluded.

-Steve

Re: auditctl usage for filter lists: "user" , "watch" and "exclude"

[Steve Grubb]

On Thursday 18 May 2006 10:47, Michael C Thompson wrote:
> but I have very little idea f how user is meant to be used, and none about
> watch.

First, watch doesn't exist. I deleted it from the man pages yesterday.

User is used to filter userspace originating audit messages. For example, you 
can use passwd and a message can be generated saying that a users password 
has been changed. You can filter those events so that they do not hit the 
audit logs.

auditctl -a user,always -F uid=500

> For the exclude list,
>
> exclude,always -F msgtype=SYSCALL
>
> seems to be the only valid structure, where msgtype can be any value
> (XXX) for the type in the audit.log? (where the 1st field in the audit
> log is type=XXX)

Yes. But note that you can also do things like this:

-a exclude,always -F 'msgtype>=DAEMON_START' -F 'msgtype<=DAEMON_ROTATE'

to take out a whole range of message types.


> Are there more filters that apply? (and does it have any meaning without
> a filter?)

No

-Steve