Sample Code—Punch
The following two source files comprise the Punch codebase. To preserve readability, we richly comment the code but do not display book-text inside the code. You can download the full source files from this book's companion Web site at http://www.wiley.com/compbooks/schiffman.
Punch.h
/*
* $Id: punch.h,v 1.2 2002/03/24 20:06:38 route Exp $
*
* Building Open Source Network Security Tools
* punch.h - libnet example code
*
* Copyright (c) 2002 Mike D. Schiffman <mike@infonexus.com>
* All rights reserved.
*
*/
#include <libnet.h>
/*
* Simple way to subtract timeval based timers. Not every OS has this,
* so we'll just define it here
*/
#define PTIMERSUB(tvp, uvp, vvp) do { (vvp)-> tv_sec = (tvp)-> tv_sec - (uvp)-> tv_sec; (vvp)-> tv_usec = (tvp)-> tv_usec - (uvp)->tv_usec; if ( (vvp)-> tv_usec < 0) { (vvp) -> tv_sec-; (vvp) -> tv_usec += 1000000; } } while (0)
/* Check the OUI table for this one! */
u_char enet_src[6] = {0x00, 0x50, 0x58, 0x0d, 0x0d, 0x0d};
u_char enet_dst[6] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
void usage(char *);
/* EOF */
punch.c
/*
* $Id: punch.c,v 1.2 2002/03/24 20:06:38 route Exp $
*
* Building Open Source Network Security Tools
* punch.c - libnet 1.1.0 example code
*
* Copyright (c) 2002 Mike D. Schiffman <mike@infonexus.com>
* All rights reserved.
*
*/
#include "./punch.h"
int
main(int argc, char **argv)
{
u_short sleep;
libnet_t *1;
char *payload;
libnet_ptag_t t, udp;
int c, fast, timer, build_ip;
u_long src_ip, dst_ip;
struct timeval r, s , e;
struct libnet_stats ls;
char dot = '.', bs = '\b';
libnet_plist_t plist, *plist_p;
char errbuf[LIBNET_ERRBUF_SIZE];
u_short payload_s, bport, eport, cport;
printf("Punch 1.0 [UDP packet shaping/blasting tool] \n");
/*
* Power up libnet using the link-layer interface. We're going to
* rely on libnet to find a device to use and 'errbuf' will hold
* the error if something breaks.
*/
1 = libnet_init(
LIBNET_LINK, /* injection type */
NULL, /* network interface */
errbuf); /* errbuf */
if (l == NULL)
{
fprintf(stderr, "libnet_init() failed: %s", errbuf);
exit(EXIT_FAILURE);
}
fast = 0;
timer = 1;
sleep = 0;
src_ip = 0;
dst_ip = 0;
payload_s = 0;
qpayload = NULL;
plist_p = NULL;
while ((c = getopt(argc, argv, "d:fs:s:p:P:")) != EOF)
{
switch (c)
{
case 'd':
dst_ip = libnet_name2addr4(1, optarg, LIBNET_RESOLVE);
if (dst_ip == -1)
{
fprintf(stderr, "Bad IP address %s\n", optarg);
exit (EXIT_FAILURE);
}
break;
case 'f':
fast = 1;
break;
case 'S' :
sleep = atoi(optarg);
break;
case 's':
src_ip = libnet_name2addr4 (1, optarg, LIBNET_RESOLVE);
if (src_ip == -1)
{
fprintf(stderr, "Bad IP address: %s\n", optarg);
exit(EXIT_FAILURE);
}
break;
case 'P':
/*
* Initialize the port list chain. Libnet's expecting
* the port list to be specified in the format "x - y,
* z" or some combination thereof.
*/
plist_p = &cplist;
if (libnet_plist_chain_new(l, &plist_p, optarg) == -1)
{
fprintf(stderr,
"Bad token: %s\n", libnet_geterror(1));
exit(EXIT_FAILURE);
}
break;
case 'p':
payload = optarg;
payload_s = strlen(payload);
break;
default:
usage(argv[0]);
exit(EXIT_FAILURE);
}
}
if (!src_ip || !dst_ip || !plist_p)
{
usage(argv[0]);
exit(EXIT_FAILURE);
}
/* initialize these guys */
udp = t = LIBNET_PTAG_INITIALIZER;
/* start the loop timer */
if (gettimeofday(&s, NULL) == -1)
{
fprintf(stderr, "Can't set timer\n");
timer = 0;
}
/*
* Only the first time we run through the loop will we need to
* build an IPv4 and an Ethernet header.
*/
build_ip = 1;
/*
* Start through the packet sending loop pulling out port list
* numbers as we go. This will terminate when we run out of port
* list pairs.
*/
for (; libnet_plist_chain_next_pair (plist_p, &bport, &eport); )
{
while (!(bport > eport) && bport != 0)
{
cport = bport++;
/*
* Start our packet building process. Remember we have to
* the packet in order as it will appear on the wire. We
* go from highest protocol to lowest, so we start with
* our UDP header (and any user supplied payload data).
* Since we're going to be modifying this packet header
* throughout the loop, we'll save the ptag 'udp' and
* reuse it.
*/
udp = libnet_build_udp(
1025, /* source port */
cport, /* destination port */
LIBNET_UDP_H + payload_s, /* packet size */
0, /* checksum */
payload, /* payload */
payload_s, /* payload size */
l, /* libnet context */
udp); /* ptag */
if (udp == -1)
{
fprintf(stderr, "Can't build UDP header (port %d): %s\n",
cport, libnet_geterror(1));
goto bad;
}
/*
* The first time through the loop we'll build an IPv4 and
* an Ethernet header. Since we're not going to modify
* either one of them again, we only need to do this once.
*/
if (build_ip)
{
build_ip = 0;
/*
* Build the IPv4 header. Note that we have to pass in
* the ENTIRE IP packet length, including the IP header
* itself. Previous versions of libnet would assume a
* length of at least 20 bytes and would add to that
* value whatever the app programmer passed in. Also
* note the checksum of 0, which tells libnet to
* compute the checksum before writing the packet to
* the wire. The payload functionality isn't used here
* since we havelibnet functionality to build our UDP
* header. The ptag 't' is thrown away since we're not
* going modify the IP header again.
*/
t = libnet_build_ipv4(
/* total length */
LIBNET_IPV4_H + LIBNET_UDP_H + payload_s,
0, /* type of service */
242, /* identification */
0, /* fragmentation * /
64, /* time to live */
IPPROTO_UDP, /* protocol */
0, /* checksum */
src_ip, /* source */
dst_ip, /* destination */
NULL, /* payload */
0, /* payload size */
1, /* libnet context */
0); /* ptag */
if (t == -1)
{
fprintf(stderr, "Can't build IP header: %s\n",
libnet_geterror(1));
goto bad;
}
/*
* Build the Ethernet header and discard the ptag.
*/
t = libnet_build_ethernet(
enet_dst, /* ethernet destination */
enet_src, /* ethernet source */
ETHERTYPE_IP, /* protocol type */
NULL, /* payload */
0, /* payload size */
1, /* libnet context */
0); /* ptag */
if (t == -1)
{
fprintf(stderr, "Can't build ethernet header: %s\n",
libnet_geterror(1));
goto bad;
}
}
if (sleep)
{
/* even 1 usec makes a huge difference */
usleep(sleep);
}
if (fast)
{
/* this is needed to set up the screen properly */
write(STDERR_FILENO, &dot, 1);
}
/*
* Write the packet to the wire. Libnet will handle the
* checksum calculation here for IP (since we're at the
* link-layer) and UDP.
*/
c = libnet_write(1);
if (c == -1)
{
if (fast)
{
write(STDERR_FILENO, &dot, 1);
}
else
{
fprintf(stderr, "write error: %s\n",
libnet_geterror(1));
}
}
else
{
if (fast)
{
write(STDERR_FILENO, &bs, 1);
}
else
{
fprintf(stderr,
"wrote %d byte UDP packet to port %d\n",
c, cport);
}
}
}
}
if (timer)
{
if (gettimeofday(&e, NULL) == -1)
{
fprintf(stderr, "Can't set timer\n");
}
else
{
PTIMERSUB(&e, &s, &r);
fprintf(stderr, "\nTime spent in loop: %ld.%ld seconds \n",
r.tv_sec, r.tv_usec);
}
}
libnet_stats(1, &ls);
printf("Packets sent: %ld\nPacket errors: %ld\nBytes written:
%ld\n",
ls.packets_sent, ls.packet_errors, ls.bytes_written);
libnet_destroy(l);
return (EXIT_SUCCESS);
bad:
libnet_destroy(l);
return (EXIT_FAILURE);
}
void
usage(char *name)
{
fprintf (stderr,
"usage: %s:\n"
"-s ip\t\tSource IP address\n"
"-d ip\t\tDestination IP address\n"
"-P port list\tUDP port list (x-y,z)\n"
"[-f]\t\tFast mode, minimal screen output\n"
"[-p payload]\tPayload\n"
"[-S usec] \tMicrosecond pause between writing\n", name);
}
/* EOF */
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