avc_snap a python tool that grabs Audit messages from the auditd.

avc_snap a python tool that grabs Audit messages from the auditd.

[Daniel J Walsh]

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We are building a tool that will try to diagnose an AVC Message and tell 
the administrator what it means. 

To do this I have written a fairly simple python script that grabs the 
dispatcher message from the audit daemon and then formats
python dictionary which will eventually be handed off to the analyzer 
code. 

Dan


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#!/usr/bin/python
# Copyright (C) 2006 Red Hat, Inc
# Author by Dan Walsh, <dwalsh@redhat.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
# avc_snap - this script is is launched by the auditd and listense on
# stdin for Audit messages. It then searches for AVC Messages and assembles
# them into a python dictionary for later processing by the AVC Plugins
#
#

import os, string, select, struct, syslog
# audit python provided by audit-python package
# avc python provided by policycoreutils package
import audit, avc

#
# Collect a list of audit messages until a timeout or the audit signature changes
# Check to see if the list contains an AUDIT_AVC message
# If yes
#         create the dictionary using serules.
#         For now just syslog the dictionary,
#         eventually will call analyze and process avc message
# else
#         discard
# 
class avc_snap:
	def __init__(self):
		self.audit_list = []
		self.cur_sig = ""

	def is_avc(self):
		for i in self.audit_list:
			if i[0] == audit.AUDIT_AVC:
				return True
		return False
		
	def out(self):
		if self.is_avc():
			rules=avc.SERules()
			l=[]
			for ( type, data_list ) in self.audit_list:
				l  += data_list
				syslog.syslog("data %s" % string.join(data_list, " "))
			rules.translate(l)
			for dict in rules.AVCS:
				for d in dict.keys():
					syslog.syslog("%s->%s" % (d, dict[d]))
		self.audit_list = []

	def process(self, type, data):
		data_list=data.split()
		new_sig=data_list[0]

		if len(self.audit_list) > 0 and new_sig != self.cur_sig:
			self.out()
			self.cur_sig = new_sig

		self.audit_list.append((type, data_list[1:]))

	def run(self):
		while 1:
			input,output, err = select.select([0],[], [], 5)
			try:
				if 0 in input:
					baseformat="iiii"
					theline=os.read(0,16 + audit.MAX_AUDIT_MESSAGE_LENGTH)
					numremain = len(theline)-struct.calcsize(baseformat)
					format = "%s%ds" % (baseformat, numremain)
					version, size, type, length, data = struct.unpack(format, theline)
#					syslog.syslog("append type=%d data %s" % (type,data[:length]))
					self.process(type, data[:length])
				else:
					self.out()

			except struct.error, e:
				syslog.syslog("struct exception %s " % e.args)
			except TypeError, e:
				syslog.syslog("Type exception %s " % e.args)

try:
		snap=avc_snap()
		snap.run()

except IOError,e:
	syslog.syslog("IOError exception %s" % e.args)

except Exception, e:
	syslog.syslog("Unexpected exception %s " % e.args)

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