249 lines
7.4 KiB
C
249 lines
7.4 KiB
C
/* $OpenBSD: packet.c,v 1.9 2004/05/04 18:58:50 deraadt Exp $ */
|
|
|
|
/* Packet assembly code, originally contributed by Archie Cobbs. */
|
|
|
|
/*
|
|
* Copyright (c) 1995, 1996, 1999 The Internet Software Consortium.
|
|
* All rights reserved.
|
|
*
|
|
* 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.
|
|
* 3. Neither the name of The Internet Software Consortium nor the names
|
|
* of its contributors may be used to endorse or promote products derived
|
|
* from this software without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM 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 INTERNET SOFTWARE CONSORTIUM 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.
|
|
*
|
|
* This software has been written for the Internet Software Consortium
|
|
* by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
|
|
* Enterprises. To learn more about the Internet Software Consortium,
|
|
* see ``http://www.vix.com/isc''. To learn more about Vixie
|
|
* Enterprises, see ``http://www.vix.com''.
|
|
*/
|
|
|
|
#include <sys/cdefs.h>
|
|
__FBSDID("$FreeBSD$");
|
|
|
|
#include "dhcpd.h"
|
|
|
|
#include <netinet/in_systm.h>
|
|
#include <netinet/ip.h>
|
|
#include <netinet/udp.h>
|
|
#include <netinet/if_ether.h>
|
|
|
|
#define ETHER_HEADER_SIZE (ETHER_ADDR_LEN * 2 + sizeof(u_int16_t))
|
|
|
|
u_int32_t checksum(unsigned char *, unsigned, u_int32_t);
|
|
u_int32_t wrapsum(u_int32_t);
|
|
|
|
u_int32_t
|
|
checksum(unsigned char *buf, unsigned nbytes, u_int32_t sum)
|
|
{
|
|
int i;
|
|
|
|
/* Checksum all the pairs of bytes first... */
|
|
for (i = 0; i < (nbytes & ~1U); i += 2) {
|
|
sum += (u_int16_t)ntohs(*((u_int16_t *)(buf + i)));
|
|
if (sum > 0xFFFF)
|
|
sum -= 0xFFFF;
|
|
}
|
|
|
|
/*
|
|
* If there's a single byte left over, checksum it, too.
|
|
* Network byte order is big-endian, so the remaining byte is
|
|
* the high byte.
|
|
*/
|
|
if (i < nbytes) {
|
|
sum += buf[i] << 8;
|
|
if (sum > 0xFFFF)
|
|
sum -= 0xFFFF;
|
|
}
|
|
|
|
return (sum);
|
|
}
|
|
|
|
u_int32_t
|
|
wrapsum(u_int32_t sum)
|
|
{
|
|
sum = ~sum & 0xFFFF;
|
|
return (htons(sum));
|
|
}
|
|
|
|
void
|
|
assemble_hw_header(struct interface_info *interface, unsigned char *buf,
|
|
int *bufix)
|
|
{
|
|
struct ether_header eh;
|
|
|
|
memset(eh.ether_dhost, 0xff, sizeof(eh.ether_dhost));
|
|
if (interface->hw_address.hlen == sizeof(eh.ether_shost))
|
|
memcpy(eh.ether_shost, interface->hw_address.haddr,
|
|
sizeof(eh.ether_shost));
|
|
else
|
|
memset(eh.ether_shost, 0x00, sizeof(eh.ether_shost));
|
|
|
|
eh.ether_type = htons(ETHERTYPE_IP);
|
|
|
|
memcpy(&buf[*bufix], &eh, ETHER_HEADER_SIZE);
|
|
*bufix += ETHER_HEADER_SIZE;
|
|
}
|
|
|
|
void
|
|
assemble_udp_ip_header(unsigned char *buf, int *bufix, u_int32_t from,
|
|
u_int32_t to, unsigned int port, unsigned char *data, int len)
|
|
{
|
|
struct ip ip;
|
|
struct udphdr udp;
|
|
|
|
ip.ip_v = 4;
|
|
ip.ip_hl = 5;
|
|
ip.ip_tos = IPTOS_LOWDELAY;
|
|
ip.ip_len = htons(sizeof(ip) + sizeof(udp) + len);
|
|
ip.ip_id = 0;
|
|
ip.ip_off = 0;
|
|
ip.ip_ttl = 128;
|
|
ip.ip_p = IPPROTO_UDP;
|
|
ip.ip_sum = 0;
|
|
ip.ip_src.s_addr = from;
|
|
ip.ip_dst.s_addr = to;
|
|
|
|
ip.ip_sum = wrapsum(checksum((unsigned char *)&ip, sizeof(ip), 0));
|
|
memcpy(&buf[*bufix], &ip, sizeof(ip));
|
|
*bufix += sizeof(ip);
|
|
|
|
udp.uh_sport = htons(LOCAL_PORT); /* XXX */
|
|
udp.uh_dport = port; /* XXX */
|
|
udp.uh_ulen = htons(sizeof(udp) + len);
|
|
memset(&udp.uh_sum, 0, sizeof(udp.uh_sum));
|
|
|
|
udp.uh_sum = wrapsum(checksum((unsigned char *)&udp, sizeof(udp),
|
|
checksum(data, len, checksum((unsigned char *)&ip.ip_src,
|
|
2 * sizeof(ip.ip_src),
|
|
IPPROTO_UDP + (u_int32_t)ntohs(udp.uh_ulen)))));
|
|
|
|
memcpy(&buf[*bufix], &udp, sizeof(udp));
|
|
*bufix += sizeof(udp);
|
|
}
|
|
|
|
ssize_t
|
|
decode_hw_header(unsigned char *buf, int bufix, struct hardware *from)
|
|
{
|
|
struct ether_header eh;
|
|
|
|
memcpy(&eh, buf + bufix, ETHER_HEADER_SIZE);
|
|
|
|
memcpy(from->haddr, eh.ether_shost, sizeof(eh.ether_shost));
|
|
from->htype = ARPHRD_ETHER;
|
|
from->hlen = sizeof(eh.ether_shost);
|
|
|
|
return (sizeof(eh));
|
|
}
|
|
|
|
ssize_t
|
|
decode_udp_ip_header(unsigned char *buf, int bufix, struct sockaddr_in *from,
|
|
unsigned char *data, int buflen)
|
|
{
|
|
struct ip *ip;
|
|
struct udphdr *udp;
|
|
u_int32_t ip_len = (buf[bufix] & 0xf) << 2;
|
|
u_int32_t sum, usum;
|
|
static int ip_packets_seen;
|
|
static int ip_packets_bad_checksum;
|
|
static int udp_packets_seen;
|
|
static int udp_packets_bad_checksum;
|
|
static int udp_packets_length_checked;
|
|
static int udp_packets_length_overflow;
|
|
int len = 0;
|
|
|
|
ip = (struct ip *)(buf + bufix);
|
|
udp = (struct udphdr *)(buf + bufix + ip_len);
|
|
|
|
/* Check the IP header checksum - it should be zero. */
|
|
ip_packets_seen++;
|
|
if (wrapsum(checksum(buf + bufix, ip_len, 0)) != 0) {
|
|
ip_packets_bad_checksum++;
|
|
if (ip_packets_seen > 4 &&
|
|
(ip_packets_seen / ip_packets_bad_checksum) < 2) {
|
|
note("%d bad IP checksums seen in %d packets",
|
|
ip_packets_bad_checksum, ip_packets_seen);
|
|
ip_packets_seen = ip_packets_bad_checksum = 0;
|
|
}
|
|
return (-1);
|
|
}
|
|
|
|
if (ntohs(ip->ip_len) != buflen)
|
|
debug("ip length %d disagrees with bytes received %d.",
|
|
ntohs(ip->ip_len), buflen);
|
|
|
|
memcpy(&from->sin_addr, &ip->ip_src, 4);
|
|
|
|
/*
|
|
* Compute UDP checksums, including the ``pseudo-header'', the
|
|
* UDP header and the data. If the UDP checksum field is zero,
|
|
* we're not supposed to do a checksum.
|
|
*/
|
|
if (!data) {
|
|
data = buf + bufix + ip_len + sizeof(*udp);
|
|
len = ntohs(udp->uh_ulen) - sizeof(*udp);
|
|
udp_packets_length_checked++;
|
|
if (len + data > buf + bufix + buflen) {
|
|
udp_packets_length_overflow++;
|
|
if (udp_packets_length_checked > 4 &&
|
|
(udp_packets_length_checked /
|
|
udp_packets_length_overflow) < 2) {
|
|
note("%d udp packets in %d too long - dropped",
|
|
udp_packets_length_overflow,
|
|
udp_packets_length_checked);
|
|
udp_packets_length_overflow =
|
|
udp_packets_length_checked = 0;
|
|
}
|
|
return (-1);
|
|
}
|
|
if (len + data != buf + bufix + buflen)
|
|
debug("accepting packet with data after udp payload.");
|
|
}
|
|
|
|
usum = udp->uh_sum;
|
|
udp->uh_sum = 0;
|
|
|
|
sum = wrapsum(checksum((unsigned char *)udp, sizeof(*udp),
|
|
checksum(data, len, checksum((unsigned char *)&ip->ip_src,
|
|
2 * sizeof(ip->ip_src),
|
|
IPPROTO_UDP + (u_int32_t)ntohs(udp->uh_ulen)))));
|
|
|
|
udp_packets_seen++;
|
|
if (usum && usum != sum) {
|
|
udp_packets_bad_checksum++;
|
|
if (udp_packets_seen > 4 &&
|
|
(udp_packets_seen / udp_packets_bad_checksum) < 2) {
|
|
note("%d bad udp checksums in %d packets",
|
|
udp_packets_bad_checksum, udp_packets_seen);
|
|
udp_packets_seen = udp_packets_bad_checksum = 0;
|
|
}
|
|
return (-1);
|
|
}
|
|
|
|
memcpy(&from->sin_port, &udp->uh_sport, sizeof(udp->uh_sport));
|
|
|
|
return (ip_len + sizeof(*udp));
|
|
}
|