1/* $OpenBSD: packet.c,v 1.9 2004/05/04 18:58:50 deraadt Exp $ */
2
3/* Packet assembly code, originally contributed by Archie Cobbs. */
4
5/*
6 * Copyright (c) 1995, 1996, 1999 The Internet Software Consortium.
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 *
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of The Internet Software Consortium nor the names
19 * of its contributors may be used to endorse or promote products derived
20 * from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
23 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
24 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
25 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
26 * DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
27 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
29 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
30 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
31 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
32 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
33 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * This software has been written for the Internet Software Consortium
37 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
38 * Enterprises. To learn more about the Internet Software Consortium,
39 * see ``http://www.vix.com/isc''. To learn more about Vixie
40 * Enterprises, see ``http://www.vix.com''.
41 */
42
43#include <sys/cdefs.h>
44__FBSDID("$FreeBSD: head/sbin/dhclient/packet.c 198352 2009-10-21 23:50:35Z philip $");
45
46#include "dhcpd.h"
47
48#include <netinet/in_systm.h>
49#include <netinet/ip.h>
50#include <netinet/udp.h>
51#include <netinet/if_ether.h>
52
53#define ETHER_HEADER_SIZE (ETHER_ADDR_LEN * 2 + sizeof(u_int16_t))
54
55u_int32_t checksum(unsigned char *, unsigned, u_int32_t);
56u_int32_t wrapsum(u_int32_t);
57
58void assemble_ethernet_header(struct interface_info *, unsigned char *,
59 int *, struct hardware *);
60ssize_t decode_ethernet_header(struct interface_info *, unsigned char *,
61 int bufix, struct hardware *);
62
63u_int32_t
64checksum(unsigned char *buf, unsigned nbytes, u_int32_t sum)
65{
66 int i;
67
68 /* Checksum all the pairs of bytes first... */
69 for (i = 0; i < (nbytes & ~1U); i += 2) {
70 sum += (u_int16_t)ntohs(*((u_int16_t *)(buf + i)));
71 if (sum > 0xFFFF)
72 sum -= 0xFFFF;
73 }
74
75 /*
76 * If there's a single byte left over, checksum it, too.
77 * Network byte order is big-endian, so the remaining byte is
78 * the high byte.
79 */
80 if (i < nbytes) {
81 sum += buf[i] << 8;
82 if (sum > 0xFFFF)
83 sum -= 0xFFFF;
84 }
85
86 return (sum);
87}
88
89u_int32_t
90wrapsum(u_int32_t sum)
91{
92 sum = ~sum & 0xFFFF;
93 return (htons(sum));
94}
95
96void
97assemble_hw_header(struct interface_info *interface, unsigned char *buf,
98 int *bufix, struct hardware *to)
99{
100 struct ether_header eh;
101
102 if (to != NULL && to->hlen == 6) /* XXX */
103 memcpy(eh.ether_dhost, to->haddr, sizeof(eh.ether_dhost));
104 else
105 memset(eh.ether_dhost, 0xff, sizeof(eh.ether_dhost));
106 if (interface->hw_address.hlen == sizeof(eh.ether_shost))
107 memcpy(eh.ether_shost, interface->hw_address.haddr,
108 sizeof(eh.ether_shost));
109 else
110 memset(eh.ether_shost, 0x00, sizeof(eh.ether_shost));
111
112 eh.ether_type = htons(ETHERTYPE_IP);
113
114 memcpy(&buf[*bufix], &eh, ETHER_HEADER_SIZE);
115 *bufix += ETHER_HEADER_SIZE;
116}
117
118void
119assemble_udp_ip_header(unsigned char *buf, int *bufix, u_int32_t from,
120 u_int32_t to, unsigned int port, unsigned char *data, int len)
121{
122 struct ip ip;
123 struct udphdr udp;
124
125 ip.ip_v = 4;
126 ip.ip_hl = 5;
127 ip.ip_tos = IPTOS_LOWDELAY;
128 ip.ip_len = htons(sizeof(ip) + sizeof(udp) + len);
129 ip.ip_id = 0;
130 ip.ip_off = 0;
131 ip.ip_ttl = 16;
132 ip.ip_p = IPPROTO_UDP;
133 ip.ip_sum = 0;
134 ip.ip_src.s_addr = from;
135 ip.ip_dst.s_addr = to;
136
137 ip.ip_sum = wrapsum(checksum((unsigned char *)&ip, sizeof(ip), 0));
138
139 /*
140 * While the BPF -- used for broadcasts -- expects a "true" IP header
141 * with all the bytes in network byte order, the raw socket interface
142 * which is used for unicasts expects the ip_len field to be in host
143 * byte order. In both cases, the checksum has to be correct, so this
144 * is as good a place as any to turn the bytes around again.
145 */
146 if (to != INADDR_BROADCAST)
147 ip.ip_len = ntohs(ip.ip_len);
148
149 memcpy(&buf[*bufix], &ip, sizeof(ip));
150 *bufix += sizeof(ip);
151
152 udp.uh_sport = htons(LOCAL_PORT); /* XXX */
153 udp.uh_dport = port; /* XXX */
154 udp.uh_ulen = htons(sizeof(udp) + len);
155 memset(&udp.uh_sum, 0, sizeof(udp.uh_sum));
156
157 udp.uh_sum = wrapsum(checksum((unsigned char *)&udp, sizeof(udp),
158 checksum(data, len, checksum((unsigned char *)&ip.ip_src,
159 2 * sizeof(ip.ip_src),
160 IPPROTO_UDP + (u_int32_t)ntohs(udp.uh_ulen)))));
161
162 memcpy(&buf[*bufix], &udp, sizeof(udp));
163 *bufix += sizeof(udp);
164}
165
166ssize_t
167decode_hw_header(unsigned char *buf, int bufix, struct hardware *from)
168{
169 struct ether_header eh;
170
171 memcpy(&eh, buf + bufix, ETHER_HEADER_SIZE);
172
173 memcpy(from->haddr, eh.ether_shost, sizeof(eh.ether_shost));
174 from->htype = ARPHRD_ETHER;
175 from->hlen = sizeof(eh.ether_shost);
176
177 return (sizeof(eh));
178}
179
180ssize_t
181decode_udp_ip_header(unsigned char *buf, int bufix, struct sockaddr_in *from,
182 unsigned char *data, int buflen)
183{
184 struct ip *ip;
185 struct udphdr *udp;
186 u_int32_t ip_len = (buf[bufix] & 0xf) << 2;
187 u_int32_t sum, usum;
188 static int ip_packets_seen;
189 static int ip_packets_bad_checksum;
190 static int udp_packets_seen;
191 static int udp_packets_bad_checksum;
192 static int udp_packets_length_checked;
193 static int udp_packets_length_overflow;
194 int len = 0;
195
196 ip = (struct ip *)(buf + bufix);
197 udp = (struct udphdr *)(buf + bufix + ip_len);
198
199 /* Check the IP header checksum - it should be zero. */
200 ip_packets_seen++;
201 if (wrapsum(checksum(buf + bufix, ip_len, 0)) != 0) {
202 ip_packets_bad_checksum++;
203 if (ip_packets_seen > 4 &&
204 (ip_packets_seen / ip_packets_bad_checksum) < 2) {
205 note("%d bad IP checksums seen in %d packets",
206 ip_packets_bad_checksum, ip_packets_seen);
207 ip_packets_seen = ip_packets_bad_checksum = 0;
208 }
209 return (-1);
210 }
211
212 if (ntohs(ip->ip_len) != buflen)
213 debug("ip length %d disagrees with bytes received %d.",
214 ntohs(ip->ip_len), buflen);
215
216 memcpy(&from->sin_addr, &ip->ip_src, 4);
217
218 /*
219 * Compute UDP checksums, including the ``pseudo-header'', the
220 * UDP header and the data. If the UDP checksum field is zero,
221 * we're not supposed to do a checksum.
222 */
223 if (!data) {
224 data = buf + bufix + ip_len + sizeof(*udp);
225 len = ntohs(udp->uh_ulen) - sizeof(*udp);
226 udp_packets_length_checked++;
227 if (len + data > buf + bufix + buflen) {
228 udp_packets_length_overflow++;
229 if (udp_packets_length_checked > 4 &&
230 (udp_packets_length_checked /
231 udp_packets_length_overflow) < 2) {
232 note("%d udp packets in %d too long - dropped",
233 udp_packets_length_overflow,
234 udp_packets_length_checked);
235 udp_packets_length_overflow =
236 udp_packets_length_checked = 0;
237 }
238 return (-1);
239 }
240 if (len + data != buf + bufix + buflen)
241 debug("accepting packet with data after udp payload.");
242 }
243
244 usum = udp->uh_sum;
245 udp->uh_sum = 0;
246
247 sum = wrapsum(checksum((unsigned char *)udp, sizeof(*udp),
248 checksum(data, len, checksum((unsigned char *)&ip->ip_src,
249 2 * sizeof(ip->ip_src),
250 IPPROTO_UDP + (u_int32_t)ntohs(udp->uh_ulen)))));
251
252 udp_packets_seen++;
253 if (usum && usum != sum) {
254 udp_packets_bad_checksum++;
255 if (udp_packets_seen > 4 &&
256 (udp_packets_seen / udp_packets_bad_checksum) < 2) {
257 note("%d bad udp checksums in %d packets",
258 udp_packets_bad_checksum, udp_packets_seen);
259 udp_packets_seen = udp_packets_bad_checksum = 0;
260 }
261 return (-1);
262 }
263
264 memcpy(&from->sin_port, &udp->uh_sport, sizeof(udp->uh_sport));
265
266 return (ip_len + sizeof(*udp));
267}
2
3/* Packet assembly code, originally contributed by Archie Cobbs. */
4
5/*
6 * Copyright (c) 1995, 1996, 1999 The Internet Software Consortium.
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 *
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of The Internet Software Consortium nor the names
19 * of its contributors may be used to endorse or promote products derived
20 * from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
23 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
24 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
25 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
26 * DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
27 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
29 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
30 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
31 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
32 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
33 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * This software has been written for the Internet Software Consortium
37 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
38 * Enterprises. To learn more about the Internet Software Consortium,
39 * see ``http://www.vix.com/isc''. To learn more about Vixie
40 * Enterprises, see ``http://www.vix.com''.
41 */
42
43#include <sys/cdefs.h>
44__FBSDID("$FreeBSD: head/sbin/dhclient/packet.c 198352 2009-10-21 23:50:35Z philip $");
45
46#include "dhcpd.h"
47
48#include <netinet/in_systm.h>
49#include <netinet/ip.h>
50#include <netinet/udp.h>
51#include <netinet/if_ether.h>
52
53#define ETHER_HEADER_SIZE (ETHER_ADDR_LEN * 2 + sizeof(u_int16_t))
54
55u_int32_t checksum(unsigned char *, unsigned, u_int32_t);
56u_int32_t wrapsum(u_int32_t);
57
58void assemble_ethernet_header(struct interface_info *, unsigned char *,
59 int *, struct hardware *);
60ssize_t decode_ethernet_header(struct interface_info *, unsigned char *,
61 int bufix, struct hardware *);
62
63u_int32_t
64checksum(unsigned char *buf, unsigned nbytes, u_int32_t sum)
65{
66 int i;
67
68 /* Checksum all the pairs of bytes first... */
69 for (i = 0; i < (nbytes & ~1U); i += 2) {
70 sum += (u_int16_t)ntohs(*((u_int16_t *)(buf + i)));
71 if (sum > 0xFFFF)
72 sum -= 0xFFFF;
73 }
74
75 /*
76 * If there's a single byte left over, checksum it, too.
77 * Network byte order is big-endian, so the remaining byte is
78 * the high byte.
79 */
80 if (i < nbytes) {
81 sum += buf[i] << 8;
82 if (sum > 0xFFFF)
83 sum -= 0xFFFF;
84 }
85
86 return (sum);
87}
88
89u_int32_t
90wrapsum(u_int32_t sum)
91{
92 sum = ~sum & 0xFFFF;
93 return (htons(sum));
94}
95
96void
97assemble_hw_header(struct interface_info *interface, unsigned char *buf,
98 int *bufix, struct hardware *to)
99{
100 struct ether_header eh;
101
102 if (to != NULL && to->hlen == 6) /* XXX */
103 memcpy(eh.ether_dhost, to->haddr, sizeof(eh.ether_dhost));
104 else
105 memset(eh.ether_dhost, 0xff, sizeof(eh.ether_dhost));
106 if (interface->hw_address.hlen == sizeof(eh.ether_shost))
107 memcpy(eh.ether_shost, interface->hw_address.haddr,
108 sizeof(eh.ether_shost));
109 else
110 memset(eh.ether_shost, 0x00, sizeof(eh.ether_shost));
111
112 eh.ether_type = htons(ETHERTYPE_IP);
113
114 memcpy(&buf[*bufix], &eh, ETHER_HEADER_SIZE);
115 *bufix += ETHER_HEADER_SIZE;
116}
117
118void
119assemble_udp_ip_header(unsigned char *buf, int *bufix, u_int32_t from,
120 u_int32_t to, unsigned int port, unsigned char *data, int len)
121{
122 struct ip ip;
123 struct udphdr udp;
124
125 ip.ip_v = 4;
126 ip.ip_hl = 5;
127 ip.ip_tos = IPTOS_LOWDELAY;
128 ip.ip_len = htons(sizeof(ip) + sizeof(udp) + len);
129 ip.ip_id = 0;
130 ip.ip_off = 0;
131 ip.ip_ttl = 16;
132 ip.ip_p = IPPROTO_UDP;
133 ip.ip_sum = 0;
134 ip.ip_src.s_addr = from;
135 ip.ip_dst.s_addr = to;
136
137 ip.ip_sum = wrapsum(checksum((unsigned char *)&ip, sizeof(ip), 0));
138
139 /*
140 * While the BPF -- used for broadcasts -- expects a "true" IP header
141 * with all the bytes in network byte order, the raw socket interface
142 * which is used for unicasts expects the ip_len field to be in host
143 * byte order. In both cases, the checksum has to be correct, so this
144 * is as good a place as any to turn the bytes around again.
145 */
146 if (to != INADDR_BROADCAST)
147 ip.ip_len = ntohs(ip.ip_len);
148
149 memcpy(&buf[*bufix], &ip, sizeof(ip));
150 *bufix += sizeof(ip);
151
152 udp.uh_sport = htons(LOCAL_PORT); /* XXX */
153 udp.uh_dport = port; /* XXX */
154 udp.uh_ulen = htons(sizeof(udp) + len);
155 memset(&udp.uh_sum, 0, sizeof(udp.uh_sum));
156
157 udp.uh_sum = wrapsum(checksum((unsigned char *)&udp, sizeof(udp),
158 checksum(data, len, checksum((unsigned char *)&ip.ip_src,
159 2 * sizeof(ip.ip_src),
160 IPPROTO_UDP + (u_int32_t)ntohs(udp.uh_ulen)))));
161
162 memcpy(&buf[*bufix], &udp, sizeof(udp));
163 *bufix += sizeof(udp);
164}
165
166ssize_t
167decode_hw_header(unsigned char *buf, int bufix, struct hardware *from)
168{
169 struct ether_header eh;
170
171 memcpy(&eh, buf + bufix, ETHER_HEADER_SIZE);
172
173 memcpy(from->haddr, eh.ether_shost, sizeof(eh.ether_shost));
174 from->htype = ARPHRD_ETHER;
175 from->hlen = sizeof(eh.ether_shost);
176
177 return (sizeof(eh));
178}
179
180ssize_t
181decode_udp_ip_header(unsigned char *buf, int bufix, struct sockaddr_in *from,
182 unsigned char *data, int buflen)
183{
184 struct ip *ip;
185 struct udphdr *udp;
186 u_int32_t ip_len = (buf[bufix] & 0xf) << 2;
187 u_int32_t sum, usum;
188 static int ip_packets_seen;
189 static int ip_packets_bad_checksum;
190 static int udp_packets_seen;
191 static int udp_packets_bad_checksum;
192 static int udp_packets_length_checked;
193 static int udp_packets_length_overflow;
194 int len = 0;
195
196 ip = (struct ip *)(buf + bufix);
197 udp = (struct udphdr *)(buf + bufix + ip_len);
198
199 /* Check the IP header checksum - it should be zero. */
200 ip_packets_seen++;
201 if (wrapsum(checksum(buf + bufix, ip_len, 0)) != 0) {
202 ip_packets_bad_checksum++;
203 if (ip_packets_seen > 4 &&
204 (ip_packets_seen / ip_packets_bad_checksum) < 2) {
205 note("%d bad IP checksums seen in %d packets",
206 ip_packets_bad_checksum, ip_packets_seen);
207 ip_packets_seen = ip_packets_bad_checksum = 0;
208 }
209 return (-1);
210 }
211
212 if (ntohs(ip->ip_len) != buflen)
213 debug("ip length %d disagrees with bytes received %d.",
214 ntohs(ip->ip_len), buflen);
215
216 memcpy(&from->sin_addr, &ip->ip_src, 4);
217
218 /*
219 * Compute UDP checksums, including the ``pseudo-header'', the
220 * UDP header and the data. If the UDP checksum field is zero,
221 * we're not supposed to do a checksum.
222 */
223 if (!data) {
224 data = buf + bufix + ip_len + sizeof(*udp);
225 len = ntohs(udp->uh_ulen) - sizeof(*udp);
226 udp_packets_length_checked++;
227 if (len + data > buf + bufix + buflen) {
228 udp_packets_length_overflow++;
229 if (udp_packets_length_checked > 4 &&
230 (udp_packets_length_checked /
231 udp_packets_length_overflow) < 2) {
232 note("%d udp packets in %d too long - dropped",
233 udp_packets_length_overflow,
234 udp_packets_length_checked);
235 udp_packets_length_overflow =
236 udp_packets_length_checked = 0;
237 }
238 return (-1);
239 }
240 if (len + data != buf + bufix + buflen)
241 debug("accepting packet with data after udp payload.");
242 }
243
244 usum = udp->uh_sum;
245 udp->uh_sum = 0;
246
247 sum = wrapsum(checksum((unsigned char *)udp, sizeof(*udp),
248 checksum(data, len, checksum((unsigned char *)&ip->ip_src,
249 2 * sizeof(ip->ip_src),
250 IPPROTO_UDP + (u_int32_t)ntohs(udp->uh_ulen)))));
251
252 udp_packets_seen++;
253 if (usum && usum != sum) {
254 udp_packets_bad_checksum++;
255 if (udp_packets_seen > 4 &&
256 (udp_packets_seen / udp_packets_bad_checksum) < 2) {
257 note("%d bad udp checksums in %d packets",
258 udp_packets_bad_checksum, udp_packets_seen);
259 udp_packets_seen = udp_packets_bad_checksum = 0;
260 }
261 return (-1);
262 }
263
264 memcpy(&from->sin_port, &udp->uh_sport, sizeof(udp->uh_sport));
265
266 return (ip_len + sizeof(*udp));
267}