Re: Linux audit performance impact
On Wed, Feb 18, 2015 at 4:13 PM, Richard Guy Briggs <rgb(a)redhat.com> wrote:
On 15/02/17, Viswanath, Logeswari P (MCOU OSTL) wrote:
> I agree that changing the formatting of the records could break the existing
applications
> that consume them, and I didn't mean changing or eliminating of the formatting
completely.
> We agree that formatting is required for logging the records(as buffers) into the log
files.
> We are wondering if these records can be made available as RAW records so that the
> analytical programs which are capable of reading them for processing can perform
better.
There are tools that completely ignore any of the audit userspace suite
including libaudit, so changing the formatting in the kernel and
deferring to userspace to later do that formatting is not currently an
option.
It is if you take a versioned API approach where the kernel defaults
to the current behavior and switches, per-socket/connection, at the
request of userspace. It's really the only way to have a graceful
transition with audit.
> This option of RAW mode for the events can be an additional
option
> where, kauditd delivers the audit buffer without formatting. Any
> comments on this?
For a transition period if we were to consider it, it would mean
rewriting *all* places in the kernel that generate audit messages and
provide two paths switched on this RAW mode for each one of them, then
copying all that duplication to userspace libaudit.
Your comment is a little vague, so let me mention what I'm currently
considering: we convert all of the in-kernel audit users away from
generating strings in the context of the caller, instead having them
record information in a native/struct/etc. format that would be later
used by the kernel audit subsystem to generate the audit records (in
whatever format(s) is(are) requested). This actually has advantages
beyond the record format work, it moves the issue of record formatting
(always a problem) out of the caller and into audit itself which
should hopefully prevent future audit abuses (a netlink attribute
based record format would likely help further).
According to Linus' decree, it would need to remain that way
until we
were certain that all tools including ones we don't know about had
switched over.
I would imagine a scenario where we introduced the new format in stages:
#1 - Move in-kernel audit record string generation completely into
kernel/audit*.c. Benefits everyone regardless of the audit format.
#2 - Introduce a versioned audit API. The most difficult step for
obvious reasons.
#3 - Deprecate the old/existing audit record format, make it a Kconfig
option that defaults to off and emit a warning when the old formatting
is used. This will be a year, and most likely more, after step #2.
#4 - Remove the old/existing audit record code. Once again, this
would happen a couple of years after step #3.
However, nothing is really determined yet, this is just my current thinking.
--
paul moore
www.paul-moore.com