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Snort_AIPreproc/alert_parser.c

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/*
* =====================================================================================
*
* Filename: alert_parser.c
*
* Description: Managing the parsing of Snort's alert file
*
* Version: 0.1
* Created: 08/08/2010 09:21:57
* 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 <stdio.h>
#include <unistd.h>
#include <time.h>
#include <sys/inotify.h>
#include <sys/stat.h>
#include <pthread.h>
PRIVATE AI_snort_alert *alerts = NULL;
PRIVATE FILE *alert_fp = NULL;
PRIVATE BOOL lock_flag = false;
/** \defgroup alert_parser Parse the alert log into binary structures
* @{ */
/**
* \brief Thread for parsing Snort's alert file
* \param arg void* pointer to module's configuration
*/
void*
AI_file_alertparser_thread ( void* arg )
{
struct logtime {
unsigned short day;
unsigned short month;
unsigned short year;
unsigned short hour;
unsigned short min;
unsigned short sec;
};
int i;
int ifd;
int wd;
int nmatches = 0;
char line[8192];
char strtime[256];
char **matches = NULL;
time_t stamp;
struct tm *_tm;
struct logtime ltime;
struct stat st;
struct pkt_key key;
struct pkt_info *info;
AI_config *conf = ( AI_config* ) arg;
AI_snort_alert *alert = NULL;
AI_snort_alert *tmp = NULL;
BOOL in_alert = false;
while ( 1 )
{
if (( ifd = inotify_init() ) < 0 )
{
_dpd.fatalMsg ( "Could not initialize an inotify object on the alert log file" );
}
if ( stat ( conf->alertfile, &st ) < 0 )
{
if (( wd = inotify_add_watch ( ifd, conf->alertfile, IN_CREATE )) < 0 )
{
_dpd.fatalMsg ( "Could not initialize a watch descriptor on the alert log file" );
}
read ( ifd, line, sizeof(line) );
inotify_rm_watch ( ifd, wd );
} else {
if ( !alert_fp )
{
if ( ! (alert_fp = fopen ( conf->alertfile, "r" )) )
{
_dpd.fatalMsg ( "Could not open alert log file for reading" );
}
}
}
if (( wd = inotify_add_watch ( ifd, conf->alertfile, IN_MODIFY )) < 0 )
{
_dpd.fatalMsg ( "Could not initialize a watch descriptor on the alert log file" );
}
fseek ( alert_fp, 0, SEEK_END );
read ( ifd, line, sizeof(line) );
inotify_rm_watch ( ifd, wd );
close ( ifd );
/* Set the lock flag to true until it's done with alert parsing */
lock_flag = true;
while ( !feof ( alert_fp ))
{
fgets ( line, sizeof(line), alert_fp );
for ( i = strlen(line)-1;
i >= 0 && ( line[i] == '\n' || line[i] == '\r' || line[i] == '\t' || line[i] == ' ' );
i++ )
{
line[i] = 0;
}
if ( strlen(line) == 0 )
{
if ( in_alert )
{
if ( alert->ip_src_addr && ( alert->ip_proto == IPPROTO_TCP || alert->ip_proto == IPPROTO_UDP ))
{
key.src_ip = alert->ip_src_addr;
key.dst_port = alert->tcp_dst_port;
if ( alert->ip_proto == IPPROTO_TCP )
{
if (( info = AI_get_stream_by_key ( key ) ))
{
AI_set_stream_observed ( key );
alert->stream = info;
}
}
}
if ( alerts == NULL )
{
alerts = alert;
alerts->next = NULL;
} else {
for ( tmp = alerts; tmp->next; tmp = tmp->next );
tmp->next = alert;
}
/* TODO Do something!! */
in_alert = false;
alert = NULL;
}
continue;
}
if ( !in_alert )
{
if ( preg_match ( "^\\[\\*\\*\\]\\s*\\[([0-9]+):([0-9]+):([0-9]+)\\]\\s*(.*)\\s*\\[\\*\\*\\]$", line, &matches, &nmatches ) > 0 )
{
in_alert = true;
if ( !( alert = ( AI_snort_alert* ) malloc ( sizeof( AI_snort_alert ))))
{
_dpd.fatalMsg ( "\nDynamic memory allocation error at %s:%d\n", __FILE__, __LINE__ );
}
memset ( alert, 0, sizeof(AI_snort_alert) );
alert->gid = strtoul ( matches[0], NULL, 10 );
alert->sid = strtoul ( matches[1], NULL, 10 );
alert->rev = strtoul ( matches[2], NULL, 10 );
alert->desc = strdup ( matches[3] );
for ( i=0; i < nmatches; i++ )
free ( matches[i] );
free ( matches );
matches = NULL;
} else {
_dpd.fatalMsg ( "Parse error: a line in the alert log cannot be associated to an alert block\n" );
}
} else if ( preg_match ( "\\[Priority:\\s*([0-9]+)\\]", line, &matches, &nmatches) > 0 ) {
alert->priority = (unsigned short) strtoul ( matches[0], NULL, 10 );
for ( i=0; i < nmatches; i++ )
free ( matches[i] );
free ( matches );
matches = NULL;
if ( preg_match ( "\\[Classification:\\s*([^\\]]+)\\]", line, &matches, &nmatches) > 0 )
{
alert->classification = strdup ( matches[0] );
for ( i=0; i < nmatches; i++ )
free ( matches[i] );
free ( matches );
matches = NULL;
}
} else if ( preg_match ( "^([0-9]{2})/([0-9]{2})-([0-9]{2}):([0-9]{2}):([0-9]{2})\\.[0-9]+\\s+([0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}):([0-9]{1,5})\\s*"
"->\\s*([0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}):([0-9]{1,5})",
line, &matches, &nmatches ) > 0 ) {
stamp = time(NULL);
_tm = localtime ( &stamp );
ltime.year = (unsigned short) _tm->tm_year + 1900;
ltime.day = (unsigned short) strtoul ( matches[0], NULL, 10 );
ltime.month = (unsigned short) strtoul ( matches[1], NULL, 10 );
ltime.hour = (unsigned short) strtoul ( matches[2], NULL, 10 );
ltime.min = (unsigned short) strtoul ( matches[3], NULL, 10 );
ltime.sec = (unsigned short) strtoul ( matches[4], NULL, 10 );
snprintf ( strtime, sizeof(strtime), "%02hu/%02hu/%04hu, %02hu:%02hu:%02hu",
ltime.day, ltime.month, ltime.year, ltime.hour, ltime.min, ltime.sec );
strptime ( strtime, "%d/%m/%Y, %H:%M:%S", _tm );
alert->timestamp = mktime ( _tm );
alert->ip_src_addr = inet_addr ( matches[5] );
alert->ip_dst_addr = inet_addr ( matches[7] );
alert->tcp_src_port = htons ( atoi( matches[6] ));
alert->tcp_dst_port = htons ( atoi( matches[8] ));
for ( i=0; i < nmatches; i++ )
free ( matches[i] );
free ( matches );
matches = NULL;
} else if ( preg_match ( "^([0-9]{2})/([0-9]{2})-([0-9]{2}):([0-9]{2}):([0-9]{2})\\.[0-9]+\\s+([0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3})\\s*"
"->\\s*([0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3})",
line, &matches, &nmatches ) > 0 ) {
stamp = time(NULL);
_tm = localtime ( &stamp );
ltime.year = (unsigned short) _tm->tm_year + 1900;
ltime.day = (unsigned short) strtoul ( matches[0], NULL, 10 );
ltime.month = (unsigned short) strtoul ( matches[1], NULL, 10 );
ltime.hour = (unsigned short) strtoul ( matches[2], NULL, 10 );
ltime.min = (unsigned short) strtoul ( matches[3], NULL, 10 );
ltime.sec = (unsigned short) strtoul ( matches[4], NULL, 10 );
snprintf ( strtime, sizeof(strtime), "%02hu/%02hu/%04hu, %02hu:%02hu:%02hu",
ltime.day, ltime.month, ltime.year, ltime.hour, ltime.min, ltime.sec );
strptime ( strtime, "%d/%m/%Y, %H:%M:%S", _tm );
alert->timestamp = mktime ( _tm );
alert->ip_src_addr = inet_addr ( matches[5] );
alert->ip_dst_addr = inet_addr ( matches[6] );
for ( i=0; i < nmatches; i++ )
free ( matches[i] );
free ( matches );
matches = NULL;
} else if ( preg_match ( "^([^\\s+]+)\\s+TTL:\\s*([0-9]+)\\s+TOS:\\s*0x([0-9A-F]+)\\s+ID:\\s*([0-9]+)\\s+IpLen:\\s*([0-9]+)",
line, &matches, &nmatches ) > 0 ) {
if ( !strcasecmp ( matches[0], "tcp" ) ) {
alert->ip_proto = IPPROTO_TCP;
} else if ( !strcasecmp ( matches[0], "udp" ) ) {
alert->ip_proto = IPPROTO_UDP;
} else if ( !strcasecmp ( matches[0], "icmp" ) ) {
alert->ip_proto = IPPROTO_ICMP;
} else {
alert->ip_proto = IPPROTO_NONE;
}
alert->ip_ttl = htons ( (uint16_t) strtoul ( matches[1], NULL, 10 ));
alert->ip_tos = htons ( (uint16_t) strtoul ( matches[2], NULL, 16 ));
alert->ip_id = htons ( (uint16_t) strtoul ( matches[3], NULL, 10 ));
alert->ip_len = htons ( (uint16_t) strtoul ( matches[4], NULL, 10 ));
for ( i=0; i < nmatches; i++ )
free ( matches[i] );
free ( matches );
matches = NULL;
} else if ( preg_match ( "^([\\*CEUAPRSF]{8})\\s+Seq:\\s*0x([0-9A-F]+)\\s+Ack:\\s*0x([0-9A-F]+)\\s+Win:\\s*0x([0-9A-F]+)\\s+TcpLen:\\s*([0-9]+)",
line, &matches, &nmatches ) > 0 ) {
alert->tcp_flags = 0;
alert->tcp_flags |= ( strstr ( matches[0], "C" ) ) ? TCPHEADER_RES1 : 0;
alert->tcp_flags |= ( strstr ( matches[0], "E" ) ) ? TCPHEADER_RES2 : 0;
alert->tcp_flags |= ( strstr ( matches[0], "U" ) ) ? TCPHEADER_URG : 0;
alert->tcp_flags |= ( strstr ( matches[0], "A" ) ) ? TCPHEADER_ACK : 0;
alert->tcp_flags |= ( strstr ( matches[0], "P" ) ) ? TCPHEADER_PUSH : 0;
alert->tcp_flags |= ( strstr ( matches[0], "R" ) ) ? TCPHEADER_RST : 0;
alert->tcp_flags |= ( strstr ( matches[0], "S" ) ) ? TCPHEADER_SYN : 0;
alert->tcp_flags |= ( strstr ( matches[0], "F" ) ) ? TCPHEADER_FIN : 0;
alert->tcp_seq = htonl ( strtoul ( matches[1], NULL, 16 ));
alert->tcp_ack = htonl ( strtoul ( matches[2], NULL, 16 ));
alert->tcp_window = htons ( (uint16_t) strtoul ( matches[3], NULL, 16 ));
alert->tcp_len = htons ( (uint16_t) strtoul ( matches[4], NULL, 10 ));
for ( i=0; i < nmatches; i++ )
free ( matches[i] );
free ( matches );
matches = NULL;
}
}
lock_flag = false;
}
pthread_exit ((void*) 0 );
return (void*) 0;
} /* ----- end of function AI_file_alertparser_thread ----- */
/**
* \brief Create a copy of the alert log struct (this is done for leaving the alert log structure in this file as read-only)
* \param node Starting node (used for the recursion)
* \return A copy of the alert log linked list
*/
PRIVATE AI_snort_alert*
_AI_copy_alerts ( AI_snort_alert *node )
{
AI_snort_alert *current = NULL, *next = NULL;
if ( !node )
{
return NULL;
}
if ( node->next )
{
next = _AI_copy_alerts ( node->next );
}
if ( !( current = ( AI_snort_alert* ) malloc ( sizeof ( AI_snort_alert )) ))
{
_dpd.fatalMsg ( "Fatal dynamic memory allocation failure at %s:%d\n", __FILE__, __LINE__ );
}
memcpy ( current, node, sizeof ( AI_snort_alert ));
current->next = next;
return current;
} /* ----- end of function _AI_copy_alerts ----- */
/**
* \brief Return the alerts parsed so far as a linked list
* \return An AI_snort_alert pointer identifying the list of alerts
*/
AI_snort_alert*
AI_get_alerts ()
{
while ( lock_flag );
return _AI_copy_alerts ( alerts );
} /* ----- end of function AI_get_alerts ----- */
/**
* \brief Deallocate the memory of a log alert linked list
* \param node Linked list to be freed
*/
void
AI_free_alerts ( AI_snort_alert *node )
{
int i;
if ( !node )
return;
if ( node->next )
AI_free_alerts ( node->next );
if ( node->hyperalert )
{
for ( i=0; i < node->hyperalert->n_preconds; i++ )
free ( node->hyperalert->preconds[i] );
free ( node->hyperalert->preconds );
for ( i=0; i < node->hyperalert->n_postconds; i++ )
free ( node->hyperalert->postconds[i] );
free ( node->hyperalert->postconds );
free ( node->hyperalert );
node->hyperalert = NULL;
}
if ( node->derived_alerts )
free ( node->derived_alerts );
free ( node );
node = NULL;
} /* ----- end of function AI_free_alerts ----- */
/** @} */
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