/*
*
* libnet 1.1
* Build a GRE packet
* To view: tcpdump -s 0 -n -X -vvv proto gre
*
* Copyright (c) 2003 Frédéric Raynal <pappy@security-labs.org>
* All rights reserved.
*
*
* KNOWN BUG
* the encapsulated headers have wrong checksums. I guess this is due to
* the one pass libnet_pblock_coalesce() which is really to complicated :(
*
*
* Default packet:
* # ./gre -d 1.2.3.4
* libnet 1.1 packet shaping: GRE 1701 [link]
* Wrote 78 byte GRE packet; check the wire.
*
* 18:58:12.112157 192.168.1.2 > 1.2.3.4: gre 198.35.123.50.1234 > 103.69.139.107.53: S [bad tcp cksum 698a!] 16843009:16843009(0) win 32767 (ttl 64, id 242, len 40, bad cksum 0!) (ttl 255, id 255, len 64)
* 0x0000 4500 0040 00ff 0000 ff2f f4df c0a8 0102 E..@...../......
* 0x0010 0102 0304 0000 0800 4500 0028 00f2 0000 ........E..(....
* 0x0020 4006 0000 c623 7b32 6745 8b6b 04d2 0035 @....#{2gE.k...5
* 0x0030 0101 0101 0202 0202 5002 7fff 6666 0000 ........P...ff..
*
* Packet with a computed checksum
* # ./gre -d 1.2.3.4 -c 0
* libnet 1.1 packet shaping: GRE 1701 [link]
* Wrote 82 byte GRE packet; check the wire.
*
* 18:58:22.587513 192.168.1.2 > 1.2.3.4: gre [Cv0] C:7c62 198.35.123.50.1234 > 103.69.139.107.53: S [bad tcp cksum 698a!] 16843009:16843009(0) win 32767 (ttl 64, id 242, len 40, bad cksum 0!) (ttl 255, id 255, len 68)
* 0x0000 4500 0044 00ff 0000 ff2f f4db c0a8 0102 E..D...../......
* 0x0010 0102 0304 8000 0800 7c62 0000 4500 0028 ........|b..E..(
* 0x0020 00f2 0000 4006 0000 c623 7b32 6745 8b6b ....@....#{2gE.k
* 0x0030 04d2 0035 0101 0101 0202 0202 5002 7fff ...5........P...
* 0x0040 6666 0000 ff..
*
*
* Packet with a forced checksum
* # ./gre -d 1.2.3.4 -c 6666
* libnet 1.1 packet shaping: GRE 1701 [link]
* Wrote 68 byte GRE packet; check the wire.
*
* 19:04:12.108080 192.168.1.2 > 1.2.3.4: gre [Cv0] C:1a0a 198.35.123.50.1234 > 103.69.139.107.53: S [bad tcp cksum 698a!] 16843009:16843009(0) win 32767 (ttl 64, id 242, len 40, bad cksum 0!) (ttl 255, id 255, len 68)
* 0x0000 4500 0044 00ff 0000 ff2f f4db c0a8 0102 E..D...../......
* 0x0010 0102 0304 8000 0800 1a0a 0000 4500 0028 ............E..(
* 0x0020 00f2 0000 4006 0000 c623 7b32 6745 8b6b ....@....#{2gE.k
* 0x0030 04d2 0035 0101 0101 0202 0202 5002 7fff ...5........P...
* 0x0040 6666 0000 ff..
*
*
*
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*/
#if (HAVE_CONFIG_H)
#include "../include/config.h"
#endif
#include "./libnet_test.h"
void
usage(char *prog)
{
fprintf(stderr, "Usage: %s\n", prog);
fprintf(stderr, "\t IP options: -d <dst ip> [-s src ip]\n");
fprintf(stderr, "\t GRE options: [-v] set RFC 2637 mode (PPP in GRE) (default is RFC 1701 for IP in GRE)\n");
fprintf(stderr, "\t\t RFC 1701 options (IP in GRE):\n");
fprintf(stderr, "\t\t [-c sum] [-r routing] [-k key] [-n seqnum]\n");
fprintf(stderr, "\t\t IP in GRE options: [-S src ip] [-D dst ip]\n");
fprintf(stderr, "\t\t RFC 2637 options (PPP in GRE):\n");
fprintf(stderr, "\t\t [-a ack]\n");
exit(1);
}
/*
* ---------------------------------
* | Delivery Header |
* ---------------------------------
* | GRE Header |
* ---------------------------------
* | Payload packet |
* ---------------------------------
*/
int
main(int argc, char *argv[])
{
char c;
libnet_t *l;
char errbuf[LIBNET_ERRBUF_SIZE];
u_long src_ip = 0, dst_ip = 0, gre_src_ip = 0, gre_dst_ip = 0;
u_short checksum = 0, offset = 0;
u_char *routing = NULL;
u_long key = 0, seq = 0;
u_short gre_flags = 0;
u_long len;
u_long size = 0;
libnet_ptag_t t;
printf("libnet 1.1 packet shaping: GRE [link]\n");
/*
* Initialize the library. Root priviledges are required.
*/
l = libnet_init(
LIBNET_LINK, /* injection type */
NULL, /* network interface */
errbuf); /* error buffer */
if (!l)
{
fprintf(stderr, "libnet_init: %s", errbuf);
exit(EXIT_FAILURE);
}
/*
* parse options
*/
while ((c = getopt(argc, argv, "d:s:D:S:c:r:k:n:va:")) != EOF)
{
switch (c)
{
case 'd':
if ((dst_ip = libnet_name2addr4(l, optarg, LIBNET_RESOLVE)) == -1)
{
fprintf(stderr, "Bad destination IP address: %s\n", optarg);
exit(EXIT_FAILURE);
}
break;
case 's':
if ((src_ip = libnet_name2addr4(l, optarg, LIBNET_RESOLVE)) == -1)
{
fprintf(stderr, "Bad source IP address: %s\n", optarg);
exit(EXIT_FAILURE);
}
break;
case 'D':
if ((gre_dst_ip = libnet_name2addr4(l, optarg, LIBNET_RESOLVE)) == -1)
{
fprintf(stderr, "Bad destination IP address (GRE): %s\n", optarg);
exit(EXIT_FAILURE);
}
break;
case 'S':
if ((gre_src_ip = libnet_name2addr4(l, optarg, LIBNET_RESOLVE)) == -1)
{
fprintf(stderr, "Bad source IP address (GRE): %s\n", optarg);
exit(EXIT_FAILURE);
}
break;
case 'c':
checksum = atoi(optarg);
gre_flags|=GRE_CSUM;
break;
case 'r':
routing = optarg;
gre_flags|=GRE_ROUTING;
break;
case 'k':
key = atoi(optarg);
gre_flags|=GRE_KEY;
break;
case 'n':
seq = atoi(optarg);
gre_flags|=GRE_SEQ;
break;
case 'v':
gre_flags|=(GRE_VERSION_1|GRE_KEY);
break;
case 'a':
if (! (gre_flags & GRE_VERSION_1))
usage(argv[0]);
seq = atoi(optarg); /* seq in v0 is ack in v1 */
gre_flags|=GRE_ACK;
break;
default:
exit(EXIT_FAILURE);
}
}
/*
* check options
*/
if (!dst_ip)
{
usage(argv[0]);
}
if (!src_ip)
{
src_ip = libnet_get_ipaddr4(l);
}
if (!gre_dst_ip)
{
gre_dst_ip = libnet_get_prand(LIBNET_PRu32);
}
if (!gre_src_ip)
{
gre_src_ip = libnet_get_prand(LIBNET_PRu32);
}
if ( (gre_flags & GRE_VERSION_MASK) == 0)
{
/*
* Build a TCP/IP packet embedded in GRE message
*/
size = LIBNET_TCP_H;
t = libnet_build_tcp(
1234, /* source port */
53, /* destination port */
0x01010101, /* sequence number */
0x02020202, /* acknowledgement num */
TH_SYN, /* control flags */
32767, /* window size */
0, /* checksum */
0, /* urgent pointer */
size, /* TCP packet size */
NULL, /* payload */
0, /* payload size */
l, /* libnet handle */
0); /* libnet id */
if (t == -1)
{
fprintf(stderr, "Can't build TCP header (GRE): %s\n", libnet_geterror(l));
goto bad;
}
size += LIBNET_IPV4_H;
t = libnet_build_ipv4(
size, /* length */
0, /* TOS */
242, /* IP ID */
0, /* IP Frag */
64, /* TTL */
IPPROTO_TCP, /* protocol */
0, /* checksum */
gre_src_ip, /* source IP */
gre_dst_ip, /* destination IP */
NULL, /* payload */
0, /* payload size */
l, /* libnet handle */
0); /* libnet id */
if (t == -1)
{
fprintf(stderr, "Can't build IP header (GRE): %s\n", libnet_geterror(l));
goto bad;
}
}
if ( (gre_flags & GRE_VERSION_MASK) == 1)
{
offset = libnet_get_prand(LIBNET_PRu16);
if (~gre_flags & GRE_ACK)
{
u_char ppp[4] = "\x00\x01"; /* PPP padding */
checksum = 2; /* checksum is in fact payload_s in PPP/GRE (v1) */
size = 2;
gre_flags|=GRE_SEQ;
key = libnet_get_prand(LIBNET_PRu32);
/*
* Build a PPP packet embedded in GRE message
*/
t = libnet_build_data(
ppp,
checksum,
l,
0
);
if (t == -1)
{
fprintf(stderr, "Can't build PPP header (GRE): %s\n", libnet_geterror(l));
goto bad;
}
}
gre_flags&=~(GRE_CSUM|GRE_ROUTING);
}
/*
* Build the GRE message
*/
if (gre_flags & GRE_ROUTING)
{
/* as packet are stacked, start by the last one, ie null sre */
size += LIBNET_GRE_SRE_H;
t = libnet_build_gre_last_sre(l, 0);
if (t == -1)
{
fprintf(stderr, "Can't build GRE last SRE header: %s\n", libnet_geterror(l));
goto bad;
}
size += LIBNET_GRE_SRE_H + strlen(routing);
t = libnet_build_gre_sre(
GRE_IP, /* address family */
0, /* offset */
strlen(routing), /* routing length */
routing, /* routing info */
NULL, /* payload */
0, /* payload size */
l, /* libnet handle */
0); /* libnet id */
if (t == -1)
{
fprintf(stderr, "Can't build GRE last SRE header: %s\n", libnet_geterror(l));
goto bad;
}
}
len = libnet_getgre_length(gre_flags);
size += len;
t = libnet_build_gre(
gre_flags, /* flags & version */
(gre_flags & GRE_VERSION_1 ? GRE_PPP : GRE_IP), /* type */
checksum, /* v0: checksum / v1: payload_s */
offset, /* v0: offset / v1: callID */
key, /* v0: key / v1: seq bum */
seq, /* v0: seq num / v1: ack */
size, /* length */
NULL, /* payload */
0, /* payload size */
l, /* libnet handle */
0); /* libnet id */
if (t == -1)
{
fprintf(stderr, "Can't build GRE header: %s\n", libnet_geterror(l));
goto bad;
}
/*
* Build the "real" IP header
*/
size+=LIBNET_IPV4_H;
t = libnet_build_ipv4(
size, /* length */
0, /* TOS */
255, /* IP ID */
0, /* IP Frag */
255, /* TTL */
IPPROTO_GRE, /* protocol */
0, /* checksum */
src_ip, /* source IP */
dst_ip, /* destination IP */
NULL, /* payload */
0, /* payload size */
l, /* libnet handle */
0); /* libnet id */
if (t == -1)
{
fprintf(stderr, "Can't build IP header (GRE): %s\n", libnet_geterror(l));
goto bad;
}
t = libnet_autobuild_ethernet(
"11:11:11:11:11:11", /* ethernet destination */
ETHERTYPE_IP, /* protocol type */
l); /* libnet handle */
if (t == -1)
{
fprintf(stderr, "Can't build ethernet header: %s\n",
libnet_geterror(l));
goto bad;
}
/*
* Write it to the wire.
*/
c = libnet_write(l);
if (c == -1)
{
fprintf(stderr, "Write error: %s\n", libnet_geterror(l));
goto bad;
}
else
{
fprintf(stderr, "Wrote %d byte GRE packet; check the wire.\n", c);
}
libnet_destroy(l);
return (EXIT_SUCCESS);
bad:
libnet_destroy(l);
return (EXIT_FAILURE);
}