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DNS FLood Detector 1.10
Dennis Opacki
dopacki@adotout.com
What is DNS Flood Detector?
DNS Flood Detector was developed to detect abusive usage levels on high
traffic nameservers and to enable quick response to the use of one's
nameserver to facilitate spam. DNS Flood Detector is distributed under the
Gnu Public License (see included LICENSE file for details).
How does it work?
DNS Flood Detector uses libpcap (in non-promiscuous mode) to monitor
incoming dns queries to a nameserver. The tool may be run in one of two
modes, either daemon mode or "bindsnap" mode. In daemon mode, the tool
will alarm via syslog. In bindsnap mode, the user is able to get
near-real-time stats on usage to aid in more detailed troubleshooting.
How do I build it?
Execute ./configure.pl to select the appropriate make target. Then simply
type "make".
Why was it written?
I wrote DNS Flood Detector because the fifty or so public recursive
nameservers I am responsible for were being abused by both customers and
non-customers. DNS Flood Detector allows for prompt action when anomalous
conditions are detected.
What do I need to use it?
You need libpcap and a little bit of patience.
What platforms does it work on?
Linux, BSDI, FreeBSD, Mac OSX, Solaris
Will it run under Windows {95,98,NT,2000,XP}?
Maybe. I haven't tried. If it doesn't, feel free to submit a fix.
What does it look like?
Usage: ./dns_flood_detector [OPTION]
-i IFNAME specify interface to listen on
-t N alarm at >N queries per second
-a N reset alarm after N seconds
-w N calculate stats every N seconds
-x N create N buckets
-m N mark total query rate every N seconds
-b run in foreground in bindsnap mode
-d run in background in daemon mode
-v verbose output - use again for more verbosity
-h display this usage information
Sample Output:
dopacki:~$ sudo ./dns_flood_detector -v -v -b -t10
[15:14:56] source [192.168.1.45] - 0 qps tcp : 24 qps udp [8 qps A] [16
qps PTR]
[15:14:56] source [10.0.24.2] - 0 qps tcp : 15 qps udp [15 qps A]
[15:15:06] source [192.168.1.45] - 0 qps tcp : 24 qps udp [8 qps A] [16
qps PTR]
[15:15:06] source [10.0.24.2] - 0 qps tcp : 15 qps udp [14 qps A]
[15:15:16] source [192.168.1.45] - 0 qps tcp : 23 qps udp [7 qps A] [15
qps PTR]
What if I have questions?
You can e-mail me at dopacki@adotout.com

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#!/usr/bin/perl
use strict;
my $os = shift;
# get target listings
opendir(MAKE_TARGETS,'./makefiles');
my @targets = grep { /Makefile/ && -f './makefiles/'.$_ && s/^Makefile-// } readdir(MAKE_TARGETS);
closedir(MAKE_TARGETS);
# display usage
unless ($os && grep{/$os/}@targets) {print<<EOF;exit(0)}
usage: $0 {@targets}
EOF
# link appropriate target
symlink './makefiles/Makefile-'.$os, 'Makefile';
print "type make.\n";

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/********************************************************************************
Program: dns_flood_detector.c
Author: Dennis Opacki <dopacki@adotout.com>
Date: Tue Mar 18 16:46:53 EST 2003
Purpose: Monitor DNS servers for abusive usage levels
and alarm to syslog
compile with:
gcc -o dns_flood_detector -lpcap -lpthread -lm dns_flood_detector.c
command-line options:
-i ifname specify interface to listen on (default lets pcap pick)
-t n alarm when more than n queries per second are observed
(default 40)
-a n wait for n seconds before alarming again on same source
(default 90)
-w n calculate statistics every n seconds
(default 10)
-x n use n buckets
(default 50)
-m n mark overall query rate every n seconds
(default disabled)
-b run in foreground in "bindsnap" mode
-d run in background in "daemon" mode
-v detailed information (use twice for more detail)
-h usage info
Copyright (C) 2003 Dennis Opacki
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
--- new in v1.05 ---
8/18/2003 - FreeBSD target - Jim Westfall <jwestfall@surrealistic.net>
8/18/2003 - Moved to getopt(3) for compatibility <dopacki@adotout.com>
8/19/2003 - Added OSX/BSDI make targets - <dopacki@adotout.com>
Added ability to specify inteface - <dopacki@adotout.com>
--- new in v1.06 ---
8/20/2003 - Added Solaris9 make target - <dopacki@adotout.com>
8/26/2003 - Fixed tcp qdcount bug - <dopacki@adotout.com>
--- new in v1.07 ---
8/27/2003 - Fixed alarm reset bug - <dopacki@adotout.com>
8/28/2003 - Added malloc_fail function - <dopacki@adotout.com>
8/28/2003 - Added mutex thread locking - <dopacki@adotout.com>
8/30/2003 - Fixed wierd qtype segfault - <jwestfall@surrealistic.net>
<dopacki@adotout.com>
--- new in v1.08 ---
9/02/2003 - Added -v -v output in daemon mode - <dopacki@adotout.com>
--- new in v1.09 ---
10/19/2003 - Added stdout flushing to bindsnap mode - <dopacki@adotout.com>
10/19/2003 - Changed logging priority to LOG_NOTICE - <dopacki@adotout.com>
10/19/2003 - Fixed low traffic verbose logging bugs - <dopacki@adotout.com>
--- new in v1.10 ---
10/22/2003 - Added 'mark status' option via '-m' - <dopacki@adotout.com>
10/23/2003 - Code cleanup in verbose syslogging - <dopacki@adotout.com>
********************************************************************************/
#include <pcap.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <netinet/udp.h>
#ifdef __bsdi__
#include <net/if_ethernet.h>
#else
#ifdef __sun__
#include <sys/ethernet.h>
#else
#include <net/ethernet.h>
#endif
#endif
#include <pthread.h>
#include <unistd.h>
#include <time.h>
#include <math.h>
#include <signal.h>
#include <syslog.h>
#include "dns_flood_detector.h"
// global variables and their defaults
pthread_mutex_t stats_lock;
struct bucket **bb;
int option_t = 60;
int option_a = 90;
int option_w = 10;
int option_x = 50;
int option_m = 0;
int option_b = 0;
int option_d = 0;
int option_v = 0;
int option_h = 0;
int totals = 0;
char VERSION[] = "1.10";
// this is our statistics thread
void *run_stats () {
while (1) {
// check statistical stuff
pthread_mutex_lock(&stats_lock);
calculate_averages();
pthread_mutex_unlock(&stats_lock);
sleep (option_w);
}
}
// calculate the running average within each bucket
int calculate_averages() {
u_int i,j,delta,cursize,newsize,qps;
char st_time[10];
time_t now = time(0);
u_int types[] = {1,2,5,6,12,15,252,0};
u_char *type;
u_char *target;
char *names[] = {"A","NS","CNAME","SOA","PTR","MX","AXFR",""};
struct tm *raw_time = localtime(&now);
snprintf(st_time, 9, "%02d:%02d:%02d",raw_time->tm_hour,raw_time->tm_min,raw_time->tm_sec);
for (i=0; i<option_x; i++) {
// only process valid buckets
if ( bb[i]->ip_addr != NULL ) {
delta = now - bb[i]->first_packet;
// let's try to avoid a divide-by-zero, shall we?
if (delta > 1 ) {
// round our average and save it in the bucket
bb[i]->qps = (int)ceil( (float)((((float)bb[i]->tcp_count) + bb[i]->udp_count) / delta));
// handle threshold crossing
if ( bb[i]->qps > option_t ) {
// display detail to either syslog or stdout
if ( option_b ) {
if ( ! option_v ) {
printf("[%s] source [%s] - %d qps\n",st_time,bb[i]->ip_addr,bb[i]->qps);
fflush(stdout);
}
else {
printf("[%s] source [%s] - %d qps tcp : %d qps udp ",st_time,bb[i]->ip_addr,
(int)ceil( (float)(bb[i]->tcp_count/delta)),
(int)ceil( (float)(bb[i]->udp_count/delta))
);
if ( option_v >1 ) {
for (j=0;types[j];j++) {
if ((int)ceil((float)(bb[i]->qstats[types[j]]/delta))){
printf("[%d qps %s] ",(int)ceil((float)(bb[i]->qstats[types[j]]/delta)),names[j]);
}
}
}
printf("\n");
fflush(stdout);
}
}
else {
// if running in background, use alarm reset timer
if ((now-bb[i]->alarm_set)>option_a) {
// display appropriate level of detail via syslog
if ( ! option_v ) {
syslog(LOG_NOTICE,"source [%s] - %d qps\n",bb[i]->ip_addr,bb[i]->qps);
}
else if (option_v > 1) {
target = (char *)malloc(sizeof(char)*MAXSYSLOG);
newsize = MAXSYSLOG;
cursize = snprintf(target,newsize,"source [%s] - %d tcp qps : %d udp qps ",bb[i]->ip_addr,
(int)ceil( (float)(bb[i]->tcp_count/delta)),
(int)ceil( (float)(bb[i]->udp_count/delta))
);
newsize-=cursize;
for (j=0;types[j];j++ ) {
qps = (u_int)ceil((float)(bb[i]->qstats[types[j]]/delta));
if ( ( qps > 0) && ( newsize > 1 ) ) {
cursize = snprintf(target+(MAXSYSLOG-newsize),newsize,"[%d qps %s] ",qps,names[j]);
newsize-=cursize;
}
}
if (newsize <= 0 ) {
target[MAXSYSLOG-1]='\0';
}
syslog(LOG_NOTICE,"%s",target);
free(target);
}
else {
syslog(LOG_NOTICE,"source [%s] - %d tcp qps - %d udp qps\n",bb[i]->ip_addr,
(int)ceil( (float)(bb[i]->tcp_count/delta)),
(int)ceil( (float)(bb[i]->udp_count/delta))
);
}
// reset alarm
bb[i]->alarm_set = now;
}
}
}
}
}
}
// 'mark stats' if required and it is time
delta = now - bb[totals]->first_packet;
if ( (option_m > 0)&&(delta > 1)&&(delta >= option_m) ) {
// handle bindsnap mode
if (option_b) {
printf("[%s] totals - %d qps tcp : %d qps udp ",st_time,(int)ceil( (float)(bb[totals]->tcp_count/delta)),(int)ceil( (float)(bb[totals]->udp_count/delta)));
if (option_v) {
for (j=0;types[j];j++) {
qps = (u_int)ceil((float)(bb[totals]->qstats[types[j]]/delta));
if (qps){
printf("[%d qps %s] ",qps,names[j]);
}
}
}
printf("\n");
fflush(stdout);
}
else {
// agonizing high verbosity code
if (option_v) {
target = (char *)malloc(sizeof(char)*MAXSYSLOG);
newsize = MAXSYSLOG;
cursize = snprintf(target,newsize,"[totals] - %d tcp qps : %d udp qps ",
(int)ceil( (float)(bb[totals]->tcp_count/delta)),
(int)ceil( (float)(bb[totals]->udp_count/delta))
);
newsize-=cursize;
for (j=0;types[j];j++ ) {
qps = (u_int)ceil((float)(bb[totals]->qstats[types[j]]/delta));
if ( ( qps > 0) && ( newsize > 1 ) ) {
cursize = snprintf(target+(MAXSYSLOG-newsize),newsize,"[%d qps %s] ",qps,names[j]);
newsize-=cursize;
}
}
if (newsize <= 0 ) {
target[MAXSYSLOG-1]='\0';
}
syslog(LOG_NOTICE,"%s",target);
free(target);
}
else {
syslog(LOG_NOTICE,"[totals] - %d tcp qps : %d udp qps\n",
(int)ceil( (float)(bb[totals]->tcp_count/delta)),
(int)ceil( (float)(bb[totals]->udp_count/delta))
);
}
}
scour_bucket(totals);
}
return 1;
}
// purge and initialize all buckets
void init_buckets() {
u_int i;
// create bucket brigade (final bucket is for totals)
pthread_mutex_lock(&stats_lock);
if ( ( bb = malloc( sizeof(struct bucket *) * (option_x+1)) ) == NULL ) malloc_fail("bb", sizeof(struct bucket *) * (option_x+1));
for (i=0; i <=option_x; i++ ) {
if ( ( bb[i] = (struct bucket *)malloc( sizeof(struct bucket) ) ) == NULL) malloc_fail("bb[i]", sizeof(struct bucket) );
bb[i]->ip_addr=NULL;
scour_bucket(i);
}
pthread_mutex_unlock(&stats_lock);
}
// clean out a bucket while avoiding obvious memory leak
int scour_bucket( int i ) {
int j;
if ( bb[i]->ip_addr != NULL ) {
free ( bb[i]->ip_addr );
}
bb[i]->ip_addr=NULL;
bb[i]->tcp_count=0;
bb[i]->udp_count=0;
bb[i]->qps=0;
bb[i]->first_packet=time(0);
bb[i]->last_packet=(time_t)0;
bb[i]->alarm_set=(time_t)0;
for (j=0;j<256;j++) {
bb[i]->qstats[j]=0;
}
return 1;
}
// add a packet to a bucket
int add_to_bucket ( char * ip_src, int ip_proto, int num_queries, u_int8_t qtype) {
int bucket = 0;
// get the bucket to put packet in
pthread_mutex_lock(&stats_lock);
bucket = find_bucket(ip_src);
// set bucket fields
bb[bucket]->last_packet = time(0);
if (ip_proto == 6 ) {
bb[bucket]->tcp_count+=num_queries;
bb[totals]->tcp_count+=num_queries;
}
else {
bb[bucket]->udp_count+=num_queries;
bb[totals]->udp_count+=num_queries;
}
bb[bucket]->qstats[qtype]+=num_queries;
bb[totals]->qstats[qtype]+=num_queries;
pthread_mutex_unlock(&stats_lock);
return 1;
}
// figure out where to put this packet
int find_bucket(char *ip_src) {
int i, bucket=0;
time_t oldest=0;
// look for an existing bucket for this IP
for (i=0; i< option_x; i++ ){
// ip field of bucket is not null and seems to match the ip we are checking
if ((bb[i]->ip_addr != NULL)&&(strncmp(bb[i]->ip_addr, ip_src, strlen(bb[i]->ip_addr))==0)) {
return i;
}
}
// look for unused buckets
for (i=0; i< option_x; i++ ) {
// found an unused one - clean it, init it, and return it
if ( bb[i]->ip_addr == NULL ) {
scour_bucket(i);
if ( ( bb[i]->ip_addr = (char *)strdup(ip_src) ) == NULL) malloc_fail("bb[i]->ip_addr", strlen(ip_src) );
return i;
}
// find the most stagnant bucket in case we need it
// avoids another loop through the buckets
if ( ( bb[i]->last_packet != 0 ) && ((oldest==0)||( bb[i]->last_packet < oldest))) {
oldest = bb[i]->last_packet;
bucket = i;
}
}
// use the most stagnant bucket since all are in use
// clean it, init it, and return it
scour_bucket(bucket);
if ( ( bb[bucket]->ip_addr = (char *)strdup(ip_src) ) == NULL) malloc_fail("bb[bucket]->ip_addr", strlen(ip_src) );
return bucket;
}
// handle all packets we throw at it
void handle_IP(u_char *args, const struct pcap_pkthdr* pkthdr,const u_char* packet){
const struct ip* ip;
const struct my_dns *dns;
const struct tcphdr *tcp;
const struct udphdr *udp;
u_int length = pkthdr->len;
u_int caplen = pkthdr->caplen;
u_int hlen,off,version;
unsigned char dname[NS_MAXDNAME]="";
char *ip_src;
unsigned char *data;
u_int i,len,dpos;
u_int8_t qtype,qclass,tlen;
// skip the ethernet header
length -= sizeof(struct ether_header);
// make sure packet is a valid length
if (length < sizeof(struct ip)) {
return;
}
// snap off the ip portion
ip = (struct ip*)(packet + sizeof(struct ether_header));
// get utility params for sanity checking
len = ntohs(ip->ip_len);
hlen = ip->ip_hl;
version = ip->ip_v;
// let's not do ipv6 just yet
if(version != 4) {
return;
}
// make sure we have a sane header length
if(hlen < 5 ) {
return;
}
// do we have the everything we are supposed to?
if(length < len) {
return;
}
// make sure we are only processing the first fragment
off = ntohs(ip->ip_off);
if((off & 0x1fff) == 0 ) {
// get the source ip as a string (probably more efficient to use decimal)
ip_src = (char *)inet_ntoa(ip->ip_src);
// process udp packets
if ( ip->ip_p == 17 ) {
udp = (struct udphdr *) ( (char *) packet + sizeof(struct ether_header)+ sizeof (struct ip) );
// try to make sure it is safe to cast packet into dns structure
if ( (sizeof(struct my_dns)+sizeof(struct ether_header)+sizeof(struct ip)+sizeof(struct udphdr)) >= caplen ) {
return;
}
else {
// populate dns header
dns = (struct my_dns *) ( (char *) packet + sizeof(struct ether_header) + sizeof (struct ip) + sizeof (struct udphdr) );
data = (char *) packet +sizeof(struct ether_header) + sizeof (struct ip) + sizeof (struct udphdr) + sizeof(struct my_dns);
}
}
// process tcp packets
else if ( ip->ip_p == 6 ) {
tcp = (struct tcphdr *) ( (char *) packet + sizeof(struct ether_header)+ sizeof (struct ip) );
// ignore packets without push flag set
if (! tcp->th_flags & TH_PUSH) return;
// try to make sure it is safe to cast packet into dns structure
if ( (sizeof(struct my_dns)+sizeof(struct ether_header)+sizeof(struct ip)+(tcp->th_off * sizeof(u_int32_t))) >= caplen ) {
return;
}
else {
// populate dns header
dns = (struct my_dns *) ( (char *) packet + sizeof(struct ether_header)+ sizeof (struct ip) + (tcp->th_off * sizeof(u_int32_t)));
data = (char *) packet + sizeof(struct ether_header) + sizeof (struct ip) + (tcp->th_off * sizeof(u_int32_t)) + sizeof(struct my_dns);
}
}
// hmm.. not tcp, not udp.. move on.
else {
return;
}
// we only want queries, not responses
if ( dns->dns_flags1 & 0x80 ) {
return;
}
// ignore seemingly bogus queries with multiple flags set
if ((ntohs(dns->dns_qdcount)>0)+(ntohs(dns->dns_ancount)>0)+(ntohs(dns->dns_nscount)>0)+(ntohs(dns->dns_arcount)>0)>1 ) {
return;
}
// get the domain name and query type
tlen=dpos=0;
for (;(*data)&&((void *)data<((void *)packet+caplen-1)); data++) {
if (!tlen) tlen=*data;
for (;(tlen&&((void *)data<((void *)packet+caplen-1)));tlen--){
data++;
if (dpos<NS_MAXDNAME) dname[dpos++] = *data;
}
if (dpos<NS_MAXDNAME) dname[dpos++] = '.';
}
dname[dpos]='\0';
// be careful not to walk past the end of the captured data
if ( (void *)data < ((void *)packet+caplen-3) ) {
data+=2;
qtype = *data;
}
else {
return;
}
// add packet to bucket array
if (ntohs(dns->dns_qdcount)&&qtype) {
add_to_bucket( ip_src, ip->ip_p, 1, qtype );
}
}
return;
}
// main logic
// some pcap code borrowed from http://www.cet.nau.edu/~mc8/Socket/Tutorials/section1.html
int main(int argc,char **argv){
char *dev = NULL;
pthread_t thread;
char errbuf[PCAP_ERRBUF_SIZE];
pcap_t* descr;
struct bpf_program fp; /* hold compiled program */
bpf_u_int32 maskp=0; /* subnet mask */
bpf_u_int32 netp=0; /* ip */
char *filter = NULL;
char *dst_addr = NULL;
char *dst_mask = NULL;
struct sigaction sa;
struct in_addr addr;
u_int f_size;
char *args = NULL;
u_int c = 0;
// loop through command line options and get options
while(1) {
int option_index = 0;
c = getopt(argc, argv,"i:t:a:w:x:m:bdvh");
if (c==-1) break;
switch(c) {
case 0:
break;
case 'i':
if (optarg) {
if ( ( dev = (char *)strdup(optarg) ) == NULL) malloc_fail("dev", strlen(optarg) );
}
break;
case 't':
if (optarg) {
if ( abs (atoi(optarg)) > 0) {
option_t = abs( atoi(optarg));
}
}
break;
case 'a':
if (optarg) {
if ( abs (atoi(optarg)) > 10) {
option_a = abs( atoi(optarg));
}
}
break;
case 'w':
if (optarg) {
if ( abs (atoi(optarg)) > 1) {
option_w = abs( atoi(optarg));
}
}
break;
case 'x':
if (optarg) {
if ( abs (atoi(optarg)) > 10) {
option_x = abs( atoi(optarg));
}
}
break;
case 'm':
if (optarg) {
if ( abs (atoi(optarg)) > 0) {
option_m = abs( atoi(optarg));
}
}
break;
case 'b':
option_b = 1;
break;
case 'd':
option_d = 1;
break;
case 'v':
option_v++;
break;
case 'h':
option_h = 1;
default:
break;
}
}
// display usage info if needed
if (optind<argc) option_h = 1;
if (option_h) {
fprintf(stderr,"dns_flood_detector, version %s\n",VERSION);
fprintf(stderr,"Usage: %s [OPTION]\n\n",argv[0]);
fprintf(stderr,"-i IFNAME specify device name to listen on\n");
fprintf(stderr,"-t N alarm at >N queries per second\n");
fprintf(stderr,"-a N reset alarm after N seconds\n");
fprintf(stderr,"-w N calculate stats every N seconds\n");
fprintf(stderr,"-x N create N buckets\n");
fprintf(stderr,"-m N report overall stats every N seconds\n");
fprintf(stderr,"-b run in foreground in bindsnap mode\n");
fprintf(stderr,"-d run in background in daemon mode\n");
fprintf(stderr,"-v verbose output - use again for more verbosity\n");
fprintf(stderr,"-h display this usage information\n");
exit(1);
}
if ( ( ! option_d ) && ( ! option_b ) ) {
fprintf(stderr,"%s couldn't start\n",argv[0]);
fprintf(stderr,"You must specify either either -d (daemon) or -b (bindsnap)\n");
exit(1);
}
// set up for daemonized operation unless running in bindsnap mode
if ( ! option_b ) {
openlog("dns_flood_detector",LOG_PID|LOG_CONS,LOG_DAEMON);
syslog(LOG_NOTICE,"dns_flood_detector starting");
// daemonize unless running in bindsnap mode
daemonize();
// set up signal handlers
sa.sa_handler=exit;
sa.sa_flags=0;
if(sigaction(SIGTERM,&sa,NULL)) {
syslog(LOG_ERR,"Unable to set signal handler: %s. Exiting.",
strerror(errno));
}
}
// find a valid device to open
if(dev == NULL && ( (dev=pcap_lookupdev(errbuf)) == NULL ) ){
fprintf(stderr,"unable to bind to valid device\n");
exit(1);
}
// get network address and netmask for device
pcap_lookupnet(dev,&netp,&maskp,errbuf);
// set up filter with local network
addr.s_addr = (unsigned long int)netp;
if ( ( dst_addr = (char *)malloc( strlen((char *)inet_ntoa(addr))+1) ) == NULL ) malloc_fail("dest_addr", strlen((char *)inet_ntoa(addr))+1 );
strncpy(dst_addr,(char*)inet_ntoa(addr),strlen((char *)inet_ntoa(addr)));
dst_addr[strlen((char *)inet_ntoa(addr))]='\0';
addr.s_addr = (unsigned long int)maskp;
if ( ( dst_mask = (char *)malloc( strlen((char *)inet_ntoa(addr))+1) ) == NULL ) malloc_fail("dest_mask", strlen((char *)inet_ntoa(addr))+1 );
strncpy(dst_mask,(char*)inet_ntoa(addr),strlen((char *)inet_ntoa(addr)));
dst_mask[strlen((char *)inet_ntoa(addr))]='\0';
f_size = strlen("port 53 and dst net mask ")+ strlen(dst_mask)+ strlen(dst_addr);
if ( ( filter = (char *) malloc ( f_size+1) ) == NULL ) malloc_fail( "filter", f_size+1 );
snprintf( filter, f_size, "port 53 and dst net %s mask %s", dst_addr, dst_mask);
free (dst_mask);
free (dst_addr);
// open device for reading only local traffic
descr = pcap_open_live(dev,1500,0,1,errbuf);
if(descr == NULL) {
fprintf(stderr,"unable to open device %s\n",dev);
exit(1);
}
// compile filter
if(pcap_compile(descr,&fp,filter,0,netp) == -1) {
exit(1);
}
// set filter
if(pcap_setfilter(descr,&fp) == -1){
exit(1);
}
// initialize buckets and mark overall stats bucket
init_buckets();
totals = option_x;
// create mutex lock
if (pthread_mutex_init(&stats_lock, NULL) < 0) {
exit(1);
}
// launch watcher thread
if (pthread_create (&thread, NULL, run_stats, (void *)0)) {
exit(1);
}
// main pcap loop
pcap_loop(descr,-1,handle_IP,args);
// done
closelog();
return 0;
}
// daemonize the process
int daemonize(void) {
pid_t pid;
int fd;
fd=open("/dev/null",O_RDWR);
if(fd<0) {
syslog(LOG_ERR,"Failed to open /dev/null: %s. Exiting.",strerror(errno));
exit(1);
}
dup2(fd,0);
dup2(fd,1);
dup2(fd,2);
if((pid=fork())<0) {
syslog(LOG_ERR,"Fork failed: %s. Exiting.",strerror(errno));
exit(1);
}
else if (pid!=0) {
exit(0);
}
setsid();
chdir("/");
umask(0);
return 0;
}
int malloc_fail( char * var, int size ) {
// print error to stderr if running in bindsnap mode
if (option_b) {
fprintf(stderr, "our OS wouldn't let me malloc %d bytes for a new %s. giving up", size, var);
}
else {
syslog(LOG_ERR, "our OS wouldn't let me malloc %d bytes for a new %s. giving up", size, var);
}
exit(1);
}

65
dns_flood_detector.h Normal file
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/******************************************************************************
Program: dns_flood_detector.h
Author: Dennis Opacki <dopacki@adotout.com>
Date: Tue Mar 18 16:46:53 EST 2003
Purpose: Monitor DNS servers for abusive usage levels
and alarm to syslog
Copyright (C) 2003 Dennis Opacki
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
*******************************************************************************/
// definitions
#ifndef ETHER_HDRLEN
#define ETHER_HDRLEN 14
#endif
#define NS_MAXDNAME 1025
#define MAXSYSLOG 128
// evil Solaris hack
#ifdef __sun__
typedef uint8_t u_int8_t;
typedef uint16_t u_int16_t;
typedef uint32_t u_int32_t;
#endif
// prototypes
void handle_IP(u_char *args,const struct pcap_pkthdr* pkthdr,const u_char* packet);
// data structures
struct my_dns {
u_int16_t dns_id; /* query identification number */
u_int8_t dns_flags1; /* first byte of flags */
u_int8_t dns_flags2; /* second byte of flags */
u_int16_t dns_qdcount; /* number of question entries */
u_int16_t dns_ancount; /* number of answer entries */
u_int16_t dns_nscount; /* number of authority entries */
u_int16_t dns_arcount; /* number of resource entries */
};
struct bucket {
char * ip_addr;
unsigned int tcp_count;
unsigned int udp_count;
unsigned int qps;
int qstats[256];
time_t first_packet;
time_t last_packet;
time_t alarm_set;
};

36
dnsflood Executable file
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@ -0,0 +1,36 @@
#! /bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
test -f /usr/local/sbin/dns_flood_detector || exit 0
case "$1" in
start)
echo -n "Starting DNS flood detector: dns_flood_detector"
start-stop-daemon --start --quiet --exec /usr/local/sbin/dns_flood_detector -- -d
echo "."
;;
stop)
echo -n "Stopping DNS flood detector: dns_flood_detector"
start-stop-daemon --stop --quiet --exec /usr/local/sbin/dns_flood_detector
killall dns_flood_detector
echo "."
;;
restart|force-reload)
echo -n "Restarting DNS flood detector: dns_flood_detector... "
start-stop-daemon --stop --quiet --exec /usr/local/sbin/dns_flood_detector
sleep 2
start-stop-daemon --stop --quiet --exec /usr/local/sbin/dns_flood_detector
sleep 4
killall dns_flood_detector
sleep 2
start-stop-daemon --start --quiet --exec /usr/local/sbin/dns_flood_detector -- -d
echo "done."
;;
*)
echo "Usage: /etc/init.d/dnsflood {start|stop|restart|force-reload}"
exit 1
;;
esac
exit 0

11
makefiles/Makefile-BSDI Normal file
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CFLAGS+=-O -g
LDLIBS=-lpcap -pthread -lm
all: dns_flood_detector
strip dns_flood_detector
clean:
rm -rf dns_flood_detector *.o *~
install:
cp dns_flood_detector /usr/local/sbin/
dns_flood_detector: dns_flood_detector.c

11
makefiles/Makefile-FreeBSD Normal file
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@ -0,0 +1,11 @@
CFLAGS+=-O -g
LDLIBS=-lpcap -pthread -lm
all: dns_flood_detector
strip dns_flood_detector
clean:
rm -rf dns_flood_detector *.o *~
install:
cp dns_flood_detector /usr/local/sbin/
dns_flood_detector: dns_flood_detector.c

11
makefiles/Makefile-Linux Normal file
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@ -0,0 +1,11 @@
CFLAGS=-O -D_BSD_SOURCE -g
LDLIBS=-lpcap -lpthread -lm
all: dns_flood_detector
strip dns_flood_detector
clean:
rm -rf dns_flood_detector *.o *~
install:
cp dns_flood_detector /usr/local/sbin/
dns_flood_detector: dns_flood_detector.c

11
makefiles/Makefile-OSX Normal file
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@ -0,0 +1,11 @@
CFLAGS+=-O -g -I/usr/local/include -I/usr/include
LDLIBS=-L/usr/local/lib -lpcap -lpthread -lm
all: dns_flood_detector
strip dns_flood_detector
clean:
rm -rf dns_flood_detector *.o *~
install:
cp dns_flood_detector /usr/local/sbin/
dns_flood_detector: dns_flood_detector.c

11
makefiles/Makefile-Solaris Normal file
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@ -0,0 +1,11 @@
CFLAGS+=-O -g -I/usr/local/include -I/usr/include
LDLIBS=-L/usr/local/lib -L/usr/lib -lpcap -lpthread -lm -lsocket -lnsl
all: dns_flood_detector
strip dns_flood_detector
clean:
rm -rf dns_flood_detector *.o *~
install:
cp dns_flood_detector /usr/local/sbin/
dns_flood_detector: dns_flood_detector.c