Re: auparse with AUSOURCE_DESCRIPTOR

[Steve Grubb <sgrubb@redhat.com>]

On Thursday, July 30, 2015 12:34:26 PM Satish Chandra Kilaru wrote:
> Thank you. I went through the example code.

There is another example that does not use the feed interface here:
https://fedorahosted.org/audit/browser/trunk/tools/aulast/aulast.c#L531


> I do not see how FEED is better than using descriptor. Probably I am
> missing something.

It decouples processing from collecting events from the descriptor. This makes 
the event processing asynchronous relative to the socket. You just write a 
loop feeding events into the library and another that has the event handed to 
it. Typically, the part that collects the event only needs minor changes 
leaving the event handler as the only place you really need to worry about.

-Steve


> On Thu, Jul 30, 2015 at 12:12 PM, Steve Grubb <sgrubb@redhat.com> wrote:
> > On Thursday, July 30, 2015 10:16:53 AM Satish Chandra Kilaru wrote:
> > > Never mind... I found out why it was not working...
> > 
> > The auparse API expects string formatted events. The binary interface
> > exists
> > in case you completely understand how the audit events are formatted and
> > prefer to take events as they come out.
> > 
> > For anyone not completely familiar with the data structures, its better to
> > just use strings. In thsi way, you can extract portions of the log using
> > ausearch --raw > test.log  and then feed that to your program for
> > debugging.
> > 
> > > 1. auparse_next_event() does not call callback function. I have to call
> > > that function when auparse_next_event() returns.
> > 
> > The next event function is normally used when you are iterating through a
> > file.
> > If you are taking real-time events, its best to use the feed API and then
> > process the event in the call back. There is a sample program here that
> > should
> > make starting an analysis program very simple:
> > 
> > https://fedorahosted.org/audit/browser/trunk/contrib/plugin
> > 
> > > 2. it expects events in string format. I configured the plugin to send
> > > events in binary format. hence auparse_next_event() was not returning.
> > 
> > I'll update the man page to auparse_init to make sure this is clear.
> > 
> > > 3. auparse_next_event() returns only when the parser sees the beginning
> > 
> > of
> > 
> > > the next event.. i.e first event is returned after seeing the beginning
> > 
> > of
> > 
> > > the 2nd event. Is this expected?
> > 
> > Yes. For some types of events, we don't know when the event is complete
> > until
> > we see the next one. They can also be interlaced. Its on the TODO list to
> > fix
> > this second issue. But my suggestion is to look at a couple sample
> > programs
> > and follow how they do things.
> > 
> > -Steve
> > 
> > > On Wed, Jul 29, 2015 at 4:36 PM, Satish Chandra Kilaru <
> > 
> > iam.kilaru@gmail.com
> > 
> > > > wrote:
> > > > 
> > > > Has anyone tried AUSOURCE_DESCRIPTOR with a unix socket as fd?
> > > > 
> > > > I am doing the following.
> > > > 
> > > > int sd_u = socket(AF_UNIX, SOCK_STREAM, 0);
> > > > connect(sd_u, (struct sockaddr *) &sa, sizeof(sa))!=0)
> > > > auparse_state_t *au = auparse_init(AUSOURCE_DESCRIPTOR, (const void
> > > > *)sd_u);
> > > > auparse_add_callback(au, auparse_callback, event_cnt, free);
> > > > ausearch_next_event(au);
> > > > 
> > > > My auparse_callback() is not getting called. My program just blocks in
> > > > ausearch_next_event().
> > > > 
> > > > read(sd_u, buf, sizeof(buf)) gets me events... That means I am using
> > > > correct unix socket.
> > > > How do I make the callback function to get called for each event?
> > > > 
> > > > Am I missing something here?
> > > > 
> > > > Thanks in advance.
> > > > --Satish
> > > > --
> > > > Please Donate to www.wikipedia.org