1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
|
/* $OpenBSD: packet.c,v 1.1 2017/03/17 14:45:16 rzalamena 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/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/udp.h>
#include <netinet/if_ether.h>
#include <string.h>
#include "dhcp.h"
#include "dhcpd.h"
#include "log.h"
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)
{
unsigned 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(unsigned char *buf, int *bufix, struct packet_ctx *pc)
{
struct ether_header eh;
memcpy(eh.ether_shost, pc->pc_smac, ETHER_ADDR_LEN);
memcpy(eh.ether_dhost, pc->pc_dmac, ETHER_ADDR_LEN);
eh.ether_type = htons(pc->pc_ethertype);
memcpy(&buf[*bufix], &eh, ETHER_HDR_LEN);
*bufix += ETHER_HDR_LEN;
}
void
assemble_udp_ip6_header(unsigned char *p, int *off, struct packet_ctx *pc,
unsigned char *payload, int plen)
{
struct ip6_hdr ip6;
struct udphdr uh;
memset(&ip6, 0, sizeof(ip6));
ip6.ip6_vfc = IPV6_VERSION;
ip6.ip6_nxt = IPPROTO_UDP;
ip6.ip6_src = ss2sin6(&pc->pc_src)->sin6_addr;
ip6.ip6_dst = ss2sin6(&pc->pc_dst)->sin6_addr;
ip6.ip6_plen = htons(sizeof(uh) + plen);
ip6.ip6_hlim = 64;
memcpy(&p[*off], &ip6, sizeof(ip6));
*off += sizeof(ip6);
memset(&uh, 0, sizeof(uh));
uh.uh_ulen = ip6.ip6_plen;
uh.uh_sport = ss2sin6(&pc->pc_src)->sin6_port;
uh.uh_dport = ss2sin6(&pc->pc_dst)->sin6_port;
uh.uh_sum = wrapsum(
checksum((unsigned char *)&uh, sizeof(uh),
checksum(payload, plen,
checksum((unsigned char *)&ip6.ip6_src, sizeof(ip6.ip6_src),
checksum((unsigned char *)&ip6.ip6_dst, sizeof(ip6.ip6_dst),
IPPROTO_UDP + ntohs(ip6.ip6_plen)
))))
);
memcpy(&p[*off], &uh, sizeof(uh));
*off += sizeof(uh);
}
ssize_t
decode_hw_header(unsigned char *buf, int bufix, struct packet_ctx *pc)
{
struct ether_header *ether;
ether = (struct ether_header *)(buf + bufix);
memcpy(pc->pc_dmac, ether->ether_dhost, ETHER_ADDR_LEN);
memcpy(pc->pc_smac, ether->ether_shost, ETHER_ADDR_LEN);
pc->pc_ethertype = ntohs(ether->ether_type);
pc->pc_htype = ARPHRD_ETHER;
pc->pc_hlen = ETHER_ADDR_LEN;
return sizeof(struct ether_header);
}
ssize_t
decode_udp_ip6_header(unsigned char *p, int off, struct packet_ctx *pc,
size_t plen)
{
struct ip6_hdr *ip6;
struct udphdr *uh;
struct in6_addr *asrc, *adst;
size_t ptotal, poff = 0;
uint16_t ocksum, cksum;
/* Check the IPv6 header. */
if (plen < sizeof(*ip6)) {
log_debug("package too small (%ld)", plen);
return -1;
}
ip6 = (struct ip6_hdr *)(p + off);
if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
log_debug("invalid IPv6 version");
return -1;
}
poff += sizeof(*ip6);
ptotal = ntohs(ip6->ip6_plen);
if (ptotal > plen) {
log_debug("expected %ld bytes, but got %ld", ptotal, plen);
return (-1);
}
pc->pc_src.ss_len = sizeof(struct sockaddr_in6);
pc->pc_src.ss_family = AF_INET6;
asrc = &ss2sin6(&pc->pc_src)->sin6_addr;
memcpy(asrc, &ip6->ip6_src, sizeof(*asrc));
pc->pc_dst.ss_len = sizeof(struct sockaddr_in6);
pc->pc_dst.ss_family = AF_INET6;
adst = &ss2sin6(&pc->pc_dst)->sin6_addr;
memcpy(adst, &ip6->ip6_dst, sizeof(*adst));
/* Deal with the UDP header. */
if (ip6->ip6_nxt != IPPROTO_UDP) {
/* We don't support skipping extensions yet. */
log_debug("expected UDP header, got %#02X", ip6->ip6_nxt);
return -1;
}
uh = (struct udphdr *)((uint8_t *)ip6 + sizeof(*ip6));
ss2sin6(&pc->pc_src)->sin6_port = uh->uh_sport;
ss2sin6(&pc->pc_dst)->sin6_port = uh->uh_dport;
ocksum = uh->uh_sum;
uh->uh_sum = 0;
poff += sizeof(*uh);
/* Validate the packet. */
cksum = wrapsum(
checksum((unsigned char *)asrc, sizeof(*asrc),
checksum((unsigned char *)adst, sizeof(*adst),
checksum((unsigned char *)uh, sizeof(*uh),
checksum(p + off + poff, ptotal - sizeof(*uh),
IPPROTO_UDP + ntohs(uh->uh_ulen)))))
);
if (ocksum != cksum) {
log_debug("checksum invalid (%#04x != %#04x)",
ocksum, cksum);
return -1;
}
return poff;
}
|
