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
|
/***
This file is part of systemd.
Copyright (C) 2013 Intel Corporation. All rights reserved.
Copyright (C) 2014 Tom Gundersen
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <net/ethernet.h>
#include <net/if_arp.h>
#include <sys/param.h>
#include "util.h"
#include "list.h"
#include "dhcp-protocol.h"
#include "dhcp-lease.h"
#include "dhcp-internal.h"
#include "sd-dhcp-client.h"
#define DHCP_CLIENT_MIN_OPTIONS_SIZE 312
int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid,
uint8_t type, uint16_t secs, uint8_t **opt,
size_t *optlen) {
int err;
*opt = (uint8_t *)(message + 1);
if (*optlen < 4)
return -ENOBUFS;
*optlen -= 4;
message->op = op;
message->htype = ARPHRD_ETHER;
message->hlen = ETHER_ADDR_LEN;
message->xid = htobe32(xid);
/* Although 'secs' field is a SHOULD in RFC 2131, certain DHCP servers
refuse to issue an DHCP lease if 'secs' is set to zero */
message->secs = htobe16(secs);
(*opt)[0] = 0x63;
(*opt)[1] = 0x82;
(*opt)[2] = 0x53;
(*opt)[3] = 0x63;
*opt += 4;
err = dhcp_option_append(opt, optlen, DHCP_OPTION_MESSAGE_TYPE, 1,
&type);
if (err < 0)
return err;
return 0;
}
static uint16_t dhcp_checksum(void *buf, int len) {
uint32_t sum;
uint16_t *check;
int i;
uint8_t *odd;
sum = 0;
check = buf;
for (i = 0; i < len / 2 ; i++)
sum += check[i];
if (len & 0x01) {
odd = buf;
sum += odd[len - 1];
}
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
return ~sum;
}
void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint8_t op,
uint16_t len) {
assert(op == BOOTREQUEST || op == BOOTREPLY);
packet->ip.version = IPVERSION;
packet->ip.ihl = DHCP_IP_SIZE / 4;
packet->ip.tot_len = htobe16(len);
packet->ip.protocol = IPPROTO_UDP;
packet->ip.saddr = INADDR_ANY;
packet->ip.daddr = INADDR_BROADCAST;
switch (op) {
case BOOTREQUEST:
packet->udp.source = htobe16(DHCP_PORT_CLIENT);
packet->udp.dest = htobe16(DHCP_PORT_SERVER);
break;
case BOOTREPLY:
packet->udp.source = htobe16(DHCP_PORT_SERVER);
packet->udp.dest = htobe16(DHCP_PORT_CLIENT);
break;
}
packet->udp.len = htobe16(len - DHCP_IP_SIZE);
packet->ip.check = packet->udp.len;
packet->udp.check = dhcp_checksum(&packet->ip.ttl, len - 8);
packet->ip.ttl = IPDEFTTL;
packet->ip.check = 0;
packet->ip.check = dhcp_checksum(&packet->ip, DHCP_IP_SIZE);
}
int dhcp_packet_verify_headers(DHCPPacket *packet, uint8_t op, size_t len) {
size_t hdrlen;
assert(op == BOOTREQUEST || op == BOOTREPLY);
if (len < (DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE)) {
log_dhcp_client(client, "ignoring packet: packet too small");
return -EINVAL;
}
hdrlen = packet->ip.ihl * 4;
if (hdrlen < 20 || hdrlen > len) {
log_dhcp_client(client, "ignoring packet: header with wrong size");
return -EINVAL;
}
if (dhcp_checksum(&packet->ip, hdrlen)) {
log_dhcp_client(client, "ignoring packet: invalid ip checksum");
return -EINVAL;
}
if (hdrlen + be16toh(packet->udp.len) > len) {
log_dhcp_client(client, "ignoring packet: packet too small (udp.len=%u)",
be16toh(packet->udp.len));
return -EINVAL;
}
if (packet->udp.check) {
packet->ip.check = packet->udp.len;
packet->ip.ttl = 0;
if (dhcp_checksum(&packet->ip.ttl,
be16toh(packet->udp.len) + 12)) {
log_dhcp_client(client, "ignoring packet: invalid udp checksum");
return -EINVAL;
}
}
if (packet->dhcp.op != op) {
log_dhcp_client(client, "ignoring packet: wrong operation");
return -EINVAL;
}
switch (op) {
case BOOTREQUEST:
if (be16toh(packet->udp.source) != DHCP_PORT_CLIENT ||
be16toh(packet->udp.dest) != DHCP_PORT_SERVER) {
log_dhcp_client(client, "ignoring packet: wrong ports");
return -EINVAL;
}
break;
case BOOTREPLY:
if (be16toh(packet->udp.source) != DHCP_PORT_SERVER ||
be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) {
log_dhcp_client(client, "ignoring packet: wrong ports");
return -EINVAL;
}
break;
}
return 0;
}
|
