[Snort-users] yet another unix socket question...

Fyodor fygrave at ...121...
Sun Jan 13 08:32:03 EST 2002


Attach. is README for unix sockets feature, which I have written
quickly. if you have any questions, queries or comments, please let us
know.

-Fyodor
-------------- next part --------------
$Id: README.UNSOCK,v 1.1 2002/01/13 16:27:09 fygrave Exp $

It is possible to send alert messages and some packet releveant data
from snort through a unix socket, to perform additional separate
processing of alert data. 
Snort has to be built with spo_unsock.c/h output plugin is built in and
-A unsock (or its equivalent through the config file) is
used. The unix socket file should be created in /dev/snort_alert. Your
'client' code should act as 'server' listening to this unix socket.
Snort will be sending you Alertpkt structures which contain alert
message, event id. Original datagaram, lipcap pkthdr, and offsets to
datalink, netlayer, and transport layer headers.

Below is an example how unix sockets could be used. If you have any
comments bug reports, and feature requests, please contact
snort-devel at lists.sourceforge.net or drop me an email to fygrave at
tigerteam dot net.

-Fyodor

[for copyright notice, see snort distribution code]

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <signal.h>
#include "snort.h"

int sockfd;

void
sig_term (int sig)
{
  printf ("Exiting!\n");
  close (sockfd);
  unlink (UNSOCK_FILE);
  exit (1);
}

int
main (void)
{
  struct sockaddr_un snortaddr;
  struct sockaddr_un bogus;
  Alertpkt alert;
  Packet *p;
  socklen_t len = sizeof (struct sockaddr_un);

  if ((sockfd = socket (AF_UNIX, SOCK_DGRAM, 0)) < 0)
    {
      perror ("socket");
      exit (1);
    }

  bzero (&snortaddr, sizeof (snortaddr));
  snortaddr.sun_family = AF_UNIX;
  strcpy (snortaddr.sun_path, UNSOCK_FILE);


  if (bind (sockfd, (struct sockaddr *) &snortaddr, sizeof (snortaddr)) < 0)
    {
      perror ("bind");
      exit (1);
    }

  while (recvfrom (sockfd, (void *) &alert, sizeof (alert),
		   0, (struct sockaddr *) &bogus, &len) > 0)
    {

      if (!(alert.val & NOPACKET_STRUCT))
	{
	  if ((p = calloc (1, sizeof (Packet))) == NULL)
	    {
	      perror ("calloc");
	      exit (1);
	    }

	  p->pkt = alert.pkt;
	  p->pkth = &alert.pkth;
	  if (alert.dlthdr)
	    p->eh = (EtherHdr *) (alert.pkt + alert.dlthdr);
	  if (alert.nethdr)
	    {
	      p->iph = (IPHdr *) (alert.pkt + alert.nethdr);
	      if (alert.transhdr)
		{
		  switch (p->iph->ip_proto)
		    {
		    case IPPROTO_TCP:
		      p->tcph = (TCPHdr *) (alert.pkt + alert.transhdr);
		      break;
		    case IPPROTO_UDP:
		      p->udph = (UDPHdr *) (alert.pkt + alert.transhdr);
		      break;
		    case IPPROTO_ICMP:
		      p->icmph = (ICMPHdr *) (alert.pkt + alert.transhdr);
		      break;
		    default:
		      printf ("WTF!\n");
		    }		/* case */
		}		/* thanshdr */
	    }			/* nethdr */
	  if (alert.data)
	    p->data = alert.pkt + alert.data;

	  /*  now  do whatever you want with these packet structures */
	}			/* if (!NOPACKET_STRUCT) */

      printf ("%s [%d]\n", alert.alertmsg, alert.event.event_id);
      if (!(alert.val & NOPACKET_STRUCT))
	if (p->iph && (p->tcph || p->udph || p->icmph))
	  {
	    switch (p->iph->ip_proto)
	      {
	      case IPPROTO_TCP:
		printf ("TCP from: %s:%d ",
			inet_ntoa (p->iph->ip_src),
			ntohs (p->tcph->th_sport));
		printf ("to: %s:%d\n", inet_ntoa (p->iph->ip_dst),
			ntohs (p->tcph->th_dport));
		break;
	      case IPPROTO_UDP:
		printf ("UDP from: %s:%d ",
			inet_ntoa (p->iph->ip_src),
			ntohs (p->udph->uh_sport));
		printf ("to: %s:%d\n", inet_ntoa (p->iph->ip_dst),
			ntohs (p->udph->uh_dport));
		break;
	      case IPPROTO_ICMP:
		printf ("ICMP type: %d code: %d from: %s ",
			p->icmph->type,
			p->icmph->code, inet_ntoa (p->iph->ip_src));
		printf ("to: %s\n", inet_ntoa (p->iph->ip_dst));
		break;
	      }
	  }

    }

  perror ("recvfrom");
  close (sockfd);
  unlink (UNSOCK_FILE);

  return 0;
}


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