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Snort_AIPreproc
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Snort_AIPreproc/correlation.c

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/*
* =====================================================================================
*
* Filename: correlation.c
*
* Description: Runs the correlation algorithm of the alerts
*
* Version: 0.1
* Created: 07/09/2010 22:04:27
* Revision: none
* Compiler: gcc
*
* Author: BlackLight (http://0x00.ath.cx), <blacklight@autistici.org>
* Licence: GNU GPL v.3
* Company: DO WHAT YOU WANT CAUSE A PIRATE IS FREE, YOU ARE A PIRATE!
*
* =====================================================================================
*/
#include "spp_ai.h"
#include <unistd.h>
#include <sys/stat.h>
#include <pthread.h>
#include <libxml/xmlreader.h>
/** \defgroup correlation Module for the correlation of hyperalerts
* @{ */
#ifndef LIBXML_READER_ENABLED
#error "libxml reader not enabled\n"
#endif
/** Enumeration for the types of XML tags */
enum { inHyperAlert, inSnortIdTag, inPreTag, inPostTag, TAG_NUM };
PRIVATE AI_hyperalert_info *hyperalerts = NULL;
PRIVATE AI_config *conf = NULL;
PRIVATE AI_snort_alert *alerts = NULL;
/**
* \brief Substitute the macros in hyperalert pre-conditions and post-conditions with their associated values
* \param alert Reference to the hyperalert to work on
*/
void
_AI_macro_subst ( AI_snort_alert **alert )
{
/*
* Recognized macros:
* +SRC_ADDR+, +DST_ADDR+, +SRC_PORT+, +DST_PORT+, +ANY_ADDR+, +ANY_PORT+
*/
int i;
char src_addr[INET_ADDRSTRLEN], dst_addr[INET_ADDRSTRLEN];
char src_port[10], dst_port[10];
char *tmp;
for ( i=0; i < (*alert)->hyperalert->n_preconds; i++ )
{
tmp = (*alert)->hyperalert->preconds[i];
(*alert)->hyperalert->preconds[i] = str_replace_all ( (*alert)->hyperalert->preconds[i], " ", "" );
free ( tmp );
if ( strstr ( (*alert)->hyperalert->preconds[i], "+SRC_ADDR+" ))
{
inet_ntop ( AF_INET, &((*alert)->ip_src_addr), src_addr, INET_ADDRSTRLEN );
tmp = (*alert)->hyperalert->preconds[i];
(*alert)->hyperalert->preconds[i] = str_replace ( (*alert)->hyperalert->preconds[i], "+SRC_ADDR+", src_addr );
free ( tmp );
}
if ( strstr ( (*alert)->hyperalert->preconds[i], "+DST_ADDR+" )) {
inet_ntop ( AF_INET, &((*alert)->ip_dst_addr), dst_addr, INET_ADDRSTRLEN );
tmp = (*alert)->hyperalert->preconds[i];
(*alert)->hyperalert->preconds[i] = str_replace ( (*alert)->hyperalert->preconds[i], "+DST_ADDR+", dst_addr );
free ( tmp );
}
if ( strstr ( (*alert)->hyperalert->preconds[i], "+ANY_ADDR+" )) {
tmp = (*alert)->hyperalert->preconds[i];
(*alert)->hyperalert->preconds[i] = str_replace ( (*alert)->hyperalert->preconds[i], "+ANY_ADDR+", "0.0.0.0" );
free ( tmp );
}
if ( strstr ( (*alert)->hyperalert->preconds[i], "+SRC_PORT+" )) {
snprintf ( src_port, sizeof ( src_port ), "%d", ntohs ((*alert)->tcp_src_port) );
tmp = (*alert)->hyperalert->preconds[i];
(*alert)->hyperalert->preconds[i] = str_replace ( (*alert)->hyperalert->preconds[i], "+SRC_PORT+", src_port );
free ( tmp );
}
if ( strstr ( (*alert)->hyperalert->preconds[i], "+DST_PORT+" )) {
snprintf ( dst_port, sizeof ( dst_port ), "%d", ntohs ((*alert)->tcp_dst_port) );
tmp = (*alert)->hyperalert->preconds[i];
(*alert)->hyperalert->preconds[i] = str_replace ( (*alert)->hyperalert->preconds[i], "+DST_PORT+", dst_port );
free ( tmp );
}
if ( strstr ( (*alert)->hyperalert->preconds[i], "+ANY_PORT+" )) {
tmp = (*alert)->hyperalert->preconds[i];
(*alert)->hyperalert->preconds[i] = str_replace ( (*alert)->hyperalert->preconds[i], "+ANY_PORT+", "0" );
free ( tmp );
}
}
for ( i=0; i < (*alert)->hyperalert->n_postconds; i++ )
{
tmp = (*alert)->hyperalert->postconds[i];
(*alert)->hyperalert->postconds[i] = str_replace_all ( (*alert)->hyperalert->postconds[i], " ", "" );
free ( tmp );
if ( strstr ( (*alert)->hyperalert->postconds[i], "+SRC_ADDR+" ))
{
inet_ntop ( AF_INET, &((*alert)->ip_src_addr), src_addr, INET_ADDRSTRLEN );
tmp = (*alert)->hyperalert->postconds[i];
(*alert)->hyperalert->postconds[i] = str_replace ( (*alert)->hyperalert->postconds[i], "+SRC_ADDR+", src_addr );
free ( tmp );
}
if ( strstr ( (*alert)->hyperalert->postconds[i], "+DST_ADDR+" )) {
inet_ntop ( AF_INET, &((*alert)->ip_dst_addr), dst_addr, INET_ADDRSTRLEN );
tmp = (*alert)->hyperalert->postconds[i];
(*alert)->hyperalert->postconds[i] = str_replace ( (*alert)->hyperalert->postconds[i], "+DST_ADDR+", dst_addr );
free ( tmp );
}
if ( strstr ( (*alert)->hyperalert->postconds[i], "+ANY_ADDR+" )) {
tmp = (*alert)->hyperalert->postconds[i];
(*alert)->hyperalert->postconds[i] = str_replace ( (*alert)->hyperalert->postconds[i], "+ANY_ADDR+", "0.0.0.0" );
free ( tmp );
}
if ( strstr ( (*alert)->hyperalert->postconds[i], "+SRC_PORT+" )) {
snprintf ( src_port, sizeof ( src_port ), "%d", ntohs ((*alert)->tcp_src_port) );
tmp = (*alert)->hyperalert->postconds[i];
(*alert)->hyperalert->postconds[i] = str_replace ( (*alert)->hyperalert->postconds[i], "+SRC_PORT+", src_port );
free ( tmp );
}
if ( strstr ( (*alert)->hyperalert->postconds[i], "+DST_PORT+" )) {
snprintf ( dst_port, sizeof ( dst_port ), "%d", ntohs ((*alert)->tcp_dst_port) );
tmp = (*alert)->hyperalert->postconds[i];
(*alert)->hyperalert->postconds[i] = str_replace ( (*alert)->hyperalert->postconds[i], "+DST_PORT+", dst_port );
free ( tmp );
}
if ( strstr ( (*alert)->hyperalert->postconds[i], "+ANY_PORT+" )) {
tmp = (*alert)->hyperalert->postconds[i];
(*alert)->hyperalert->postconds[i] = str_replace ( (*alert)->hyperalert->postconds[i], "+ANY_PORT+", "0" );
free ( tmp );
}
}
} /* ----- end of function _AI_macro_subst ----- */
/**
* \brief Parse info about a hyperalert from a correlation XML file, if it exists
* \param key Key (gid, sid, rev) identifying the alert
* \return A hyperalert structure containing the info about the current alert, if the XML file was found
*/
PRIVATE AI_hyperalert_info*
_AI_hyperalert_from_XML ( AI_hyperalert_key key )
{
char hyperalert_file[1024] = {0};
char snort_id[1024] = {0};
BOOL xmlFlags[TAG_NUM] = { false };
struct stat st;
xmlTextReaderPtr xml;
const xmlChar *tagname, *tagvalue;
AI_hyperalert_info *hyp;
if ( !( hyp = ( AI_hyperalert_info* ) malloc ( sizeof ( AI_hyperalert_info ))))
{
_dpd.fatalMsg ( "AIPreproc: Fatal memory allocation error at %s:%d\n", __FILE__, __LINE__ );
}
memset ( hyp, 0, sizeof ( AI_hyperalert_info ));
memset ( hyperalert_file, 0, sizeof ( hyperalert_file ));
hyp->key = key;
snprintf ( hyperalert_file, sizeof ( hyperalert_file ), "%s/%d-%d-%d.xml",
conf->corr_rules_dir, key.gid, key.sid, key.rev );
if ( stat ( hyperalert_file, &st ) < 0 )
return NULL;
LIBXML_TEST_VERSION
if ( !( xml = xmlReaderForFile ( hyperalert_file, NULL, 0 )))
return NULL;
while ( xmlTextReaderRead ( xml ))
{
if ( !( tagname = xmlTextReaderConstName ( xml )))
continue;
if ( xmlTextReaderNodeType ( xml ) == XML_READER_TYPE_ELEMENT )
{
if ( !strcasecmp ((const char*) tagname, "hyperalert" ))
{
if ( xmlFlags[inHyperAlert] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': the hyperalert tag was opened twice\n", hyperalert_file );
else
xmlFlags[inHyperAlert] = true;
} else if ( !strcasecmp ((const char*) tagname, "snort-id" )) {
if ( xmlFlags[inSnortIdTag] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': 'snort-id' tag open inside of another 'snort-id' tag\n", hyperalert_file );
else if ( !xmlFlags[inHyperAlert] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': 'snort-id' tag open outside of 'hyperalert' tag\n", hyperalert_file );
else
xmlFlags[inSnortIdTag] = true;
} else if ( !strcasecmp ((const char*) tagname, "pre" )) {
if ( xmlFlags[inPreTag] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': 'pre' tag open inside of another 'pre' tag\n", hyperalert_file );
else if ( !xmlFlags[inHyperAlert] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': 'pre' tag open outside of 'hyperalert' tag\n", hyperalert_file );
else
xmlFlags[inPreTag] = true;
} else if ( !strcasecmp ((const char*) tagname, "post" )) {
if ( xmlFlags[inPostTag] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': 'post' tag open inside of another 'post' tag\n", hyperalert_file );
else if ( !xmlFlags[inHyperAlert] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': 'post' tag open outside of 'hyperalert' tag\n", hyperalert_file );
else
xmlFlags[inPostTag] = true;
} else {
_dpd.fatalMsg ( "AIPreproc: Unrecognized tag '%s' in XML file '%s'\n", tagname, hyperalert_file );
}
} else if ( xmlTextReaderNodeType ( xml ) == XML_READER_TYPE_END_ELEMENT ) {
if ( !strcasecmp ((const char*) tagname, "hyperalert" ))
{
if ( !xmlFlags[inHyperAlert] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': hyperalert tag closed but never opend\n", hyperalert_file );
else
xmlFlags[inHyperAlert] = false;
} else if ( !strcasecmp ((const char*) tagname, "snort-id" )) {
if ( !xmlFlags[inSnortIdTag] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': snort-id tag closed but never opend\n", hyperalert_file );
else
xmlFlags[inSnortIdTag] = false;
} else if ( !strcasecmp ((const char*) tagname, "pre" )) {
if ( !xmlFlags[inPreTag] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': pre tag closed but never opend\n", hyperalert_file );
else
xmlFlags[inPreTag] = false;
} else if ( !strcasecmp ((const char*) tagname, "post" )) {
if ( !xmlFlags[inPostTag] )
_dpd.fatalMsg ( "AIPreproc: Error in XML file '%s': post tag closed but never opend\n", hyperalert_file );
else
xmlFlags[inPostTag] = false;
} else {
_dpd.fatalMsg ( "AIPreproc: Unrecognized tag '%s' in XML file '%s'\n", tagname, hyperalert_file );
}
} else if ( xmlTextReaderNodeType ( xml ) == XML_READER_TYPE_TEXT ) {
if ( !( tagvalue = xmlTextReaderConstValue ( xml )))
continue;
if ( xmlFlags[inSnortIdTag] )
{
snprintf ( snort_id, sizeof ( snort_id ), "%d.%d.%d",
key.gid, key.sid, key.rev );
if ( strcmp ( snort_id, (const char*) tagvalue ))
{
_dpd.errMsg ( "AIPreproc: Found the file associated to hyperalert: '%s', "
"but the 'snort-id' field in there has a different value\n",
hyperalert_file );
return NULL;
}
} else if ( xmlFlags[inPreTag] ) {
if ( !( hyp->preconds = (char**) realloc ( hyp->preconds, (++hyp->n_preconds)*sizeof(char*) )))
_dpd.fatalMsg ( "AIPreproc: Fatal allocation memory error at %s:%d\n",
__FILE__, __LINE__ );
hyp->preconds[hyp->n_preconds-1] = strdup ((const char*) tagvalue );
} else if ( xmlFlags[inPostTag] ) {
if ( !( hyp->postconds = (char**) realloc ( hyp->postconds, (++hyp->n_postconds)*sizeof(char*) )))
_dpd.fatalMsg ( "AIPreproc: Fatal allocation memory error at %s:%d\n",
__FILE__, __LINE__ );
hyp->postconds[hyp->n_postconds-1] = strdup ((const char*) tagvalue );
}
}
}
xmlFreeTextReader ( xml );
xmlCleanupParser();
return hyp;
} /* ----- end of function _AI_hyperalert_from_XML ----- */
/**
* \brief Thread for correlating clustered alerts
* \param arg Void pointer to module's configuration
*/
void*
AI_alert_correlation_thread ( void *arg )
{
int i;
struct stat st;
AI_hyperalert_key key;
AI_hyperalert_info *hyp = NULL;
AI_snort_alert *tmp = NULL;
FILE *fp;
conf = (AI_config*) arg;
while ( 1 )
{
sleep ( conf->correlationGraphInterval );
if ( stat ( conf->corr_rules_dir, &st ) < 0 )
{
_dpd.errMsg ( "AIPreproc: Correlation rules directory '%s' not found, the correlation thread won't be active\n",
conf->corr_rules_dir );
pthread_exit (( void* ) 0 );
return ( void* ) 0;
}
if ( !( alerts = AI_get_clustered_alerts() ))
continue;
for ( tmp = alerts; tmp; tmp = tmp->next )
{
/* Check if my hash table of hyperalerts already contains info about this alert */
key.gid = tmp->gid;
key.sid = tmp->sid;
key.rev = tmp->rev;
HASH_FIND ( hh, hyperalerts, &key, sizeof ( AI_hyperalert_key ), hyp );
/* If not, try to read info from the XML file, if it exists */
if ( !hyp )
{
/* If there is no hyperalert knowledge on XML for this alert, ignore it and get the next one */
if ( !( hyp = _AI_hyperalert_from_XML ( key )))
continue;
/* If the XML file exists and it's valid, add the hypertalert to the hash table */
HASH_ADD ( hh, hyperalerts, key, sizeof ( AI_hyperalert_key ), hyp );
}
/* Fill the hyper alert info for the current alert */
if ( !( tmp->hyperalert = ( AI_hyperalert_info* ) malloc ( sizeof ( AI_hyperalert_info ))))
_dpd.fatalMsg ( "AIPreproc: Fatal memory allocation error at %s:%d\n", __FILE__, __LINE__ );
tmp->hyperalert->key = hyp->key;
tmp->hyperalert->n_preconds = hyp->n_preconds;
tmp->hyperalert->n_postconds = hyp->n_postconds;
if ( !( tmp->hyperalert->preconds = ( char** ) malloc ( tmp->hyperalert->n_preconds * sizeof ( char* ))))
_dpd.fatalMsg ( "AIPreproc: Fatal memory allocation error at %s:%d\n", __FILE__, __LINE__ );
for ( i=0; i < tmp->hyperalert->n_preconds; i++ )
tmp->hyperalert->preconds[i] = strdup ( hyp->preconds[i] );
if ( !( tmp->hyperalert->postconds = ( char** ) malloc ( tmp->hyperalert->n_postconds * sizeof ( char* ))))
_dpd.fatalMsg ( "AIPreproc: Fatal memory allocation error at %s:%d\n", __FILE__, __LINE__ );
for ( i=0; i < tmp->hyperalert->n_postconds; i++ )
tmp->hyperalert->postconds[i] = strdup ( hyp->postconds[i] );
_AI_macro_subst ( &tmp );
fp = fopen ( "/home/blacklight/LOG", "a" );
fprintf ( fp, "pre: %s\n", (tmp->hyperalert->n_preconds > 0) ? tmp->hyperalert->preconds[0] : "()" );
fprintf ( fp, "post: %s\n", (tmp->hyperalert->n_postconds > 0) ? tmp->hyperalert->postconds[0] : "()" );
fclose ( fp );
}
AI_free_alerts ( alerts );
}
pthread_exit (( void* ) 0 );
return (void*) 0;
} /* ----- end of function AI_alert_correlation_thread ----- */
/** @} */
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