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cf597f65 TG |
1 | /*** |
2 | This file is part of systemd. | |
3 | ||
4 | Copyright (C) 2013 Intel Corporation. All rights reserved. | |
5 | Copyright (C) 2014 Tom Gundersen | |
6 | ||
7 | systemd is free software; you can redistribute it and/or modify it | |
8 | under the terms of the GNU Lesser General Public License as published by | |
9 | the Free Software Foundation; either version 2.1 of the License, or | |
10 | (at your option) any later version. | |
11 | ||
12 | systemd is distributed in the hope that it will be useful, but | |
13 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 | Lesser General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU Lesser General Public License | |
18 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
19 | ***/ | |
20 | ||
21 | #include <stdlib.h> | |
22 | #include <errno.h> | |
23 | #include <string.h> | |
24 | #include <stdio.h> | |
25 | #include <net/ethernet.h> | |
26 | #include <net/if_arp.h> | |
27 | #include <sys/param.h> | |
28 | ||
29 | #include "util.h" | |
30 | #include "list.h" | |
31 | ||
32 | #include "dhcp-protocol.h" | |
fe8db0c5 | 33 | #include "dhcp-lease-internal.h" |
cf597f65 | 34 | #include "dhcp-internal.h" |
fe8db0c5 | 35 | #include "sd-dhcp-lease.h" |
cf597f65 TG |
36 | #include "sd-dhcp-client.h" |
37 | ||
38 | #define DHCP_CLIENT_MIN_OPTIONS_SIZE 312 | |
39 | ||
40 | int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid, | |
0a1b6da8 | 41 | uint8_t type, uint8_t **opt, size_t *optlen) { |
cf597f65 TG |
42 | int err; |
43 | ||
0a1b6da8 TG |
44 | assert(op == BOOTREQUEST || op == BOOTREPLY); |
45 | ||
cf597f65 TG |
46 | message->op = op; |
47 | message->htype = ARPHRD_ETHER; | |
48 | message->hlen = ETHER_ADDR_LEN; | |
49 | message->xid = htobe32(xid); | |
3b7ca119 | 50 | message->magic = htobe32(DHCP_MAGIC_COOKIE); |
cf597f65 | 51 | |
3b7ca119 | 52 | *opt = (uint8_t *)(message + 1); |
cf597f65 TG |
53 | |
54 | err = dhcp_option_append(opt, optlen, DHCP_OPTION_MESSAGE_TYPE, 1, | |
55 | &type); | |
56 | if (err < 0) | |
57 | return err; | |
58 | ||
59 | return 0; | |
60 | } | |
61 | ||
d5761274 TG |
62 | uint16_t dhcp_packet_checksum(void *buf, size_t len) { |
63 | uint64_t *buf_64 = buf; | |
64 | uint64_t *end_64 = (uint64_t*)buf + (len / sizeof(uint64_t)); | |
65 | uint32_t *buf_32; | |
66 | uint16_t *buf_16; | |
67 | uint8_t *buf_8; | |
68 | uint64_t sum = 0; | |
69 | ||
70 | while (buf_64 < end_64) { | |
71 | sum += *buf_64; | |
72 | if (sum < *buf_64) | |
73 | sum++; | |
74 | ||
75 | buf_64 ++; | |
76 | } | |
77 | ||
78 | buf_32 = (uint32_t*)buf_64; | |
79 | ||
80 | if (len & sizeof(uint32_t)) { | |
81 | sum += *buf_32; | |
82 | if (sum < *buf_32) | |
83 | sum++; | |
84 | ||
85 | buf_32 ++; | |
86 | } | |
87 | ||
88 | buf_16 = (uint16_t*)buf_32; | |
cf597f65 | 89 | |
d5761274 TG |
90 | if (len & sizeof(uint16_t)) { |
91 | sum += *buf_16; | |
92 | if (sum < *buf_16) | |
93 | sum ++; | |
94 | ||
95 | buf_16 ++; | |
96 | } | |
cf597f65 | 97 | |
d5761274 | 98 | buf_8 = (uint8_t*)buf_16; |
cf597f65 | 99 | |
d5761274 TG |
100 | if (len & sizeof(uint8_t)) { |
101 | sum += *buf_8; | |
102 | if (sum < *buf_8) | |
103 | sum++; | |
cf597f65 TG |
104 | } |
105 | ||
106 | while (sum >> 16) | |
107 | sum = (sum & 0xffff) + (sum >> 16); | |
108 | ||
109 | return ~sum; | |
110 | } | |
111 | ||
63edaa62 TG |
112 | void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr, |
113 | uint16_t source_port, be32_t destination_addr, | |
114 | uint16_t destination_port, uint16_t len) { | |
cf597f65 TG |
115 | packet->ip.version = IPVERSION; |
116 | packet->ip.ihl = DHCP_IP_SIZE / 4; | |
117 | packet->ip.tot_len = htobe16(len); | |
118 | ||
85923f79 TG |
119 | packet->ip.tos = IPTOS_CLASS_CS6; |
120 | ||
cf597f65 | 121 | packet->ip.protocol = IPPROTO_UDP; |
63edaa62 TG |
122 | packet->ip.saddr = source_addr; |
123 | packet->ip.daddr = destination_addr; | |
cf597f65 | 124 | |
63edaa62 TG |
125 | packet->udp.source = htobe16(source_port); |
126 | packet->udp.dest = htobe16(destination_port); | |
cf597f65 TG |
127 | |
128 | packet->udp.len = htobe16(len - DHCP_IP_SIZE); | |
129 | ||
130 | packet->ip.check = packet->udp.len; | |
a838c939 | 131 | packet->udp.check = dhcp_packet_checksum(&packet->ip.ttl, len - 8); |
cf597f65 TG |
132 | |
133 | packet->ip.ttl = IPDEFTTL; | |
134 | packet->ip.check = 0; | |
a838c939 | 135 | packet->ip.check = dhcp_packet_checksum(&packet->ip, DHCP_IP_SIZE); |
cf597f65 TG |
136 | } |
137 | ||
55dab2ed | 138 | int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) { |
cf597f65 TG |
139 | size_t hdrlen; |
140 | ||
5266a81e TG |
141 | assert(packet); |
142 | ||
06b44be7 | 143 | /* IP */ |
cf597f65 | 144 | |
6e34949d | 145 | if (packet->ip.version != IPVERSION) { |
aa6fc9b8 | 146 | log_debug("ignoring packet: not IPv4"); |
6e34949d TG |
147 | return -EINVAL; |
148 | } | |
149 | ||
06b44be7 | 150 | if (packet->ip.ihl < 5) { |
aa6fc9b8 TG |
151 | log_debug("ignoring packet: IPv4 IHL (%u words) invalid", |
152 | packet->ip.ihl); | |
cf597f65 | 153 | return -EINVAL; |
ac4f16ab | 154 | } |
cf597f65 TG |
155 | |
156 | hdrlen = packet->ip.ihl * 4; | |
06b44be7 | 157 | if (hdrlen < 20) { |
aa6fc9b8 TG |
158 | log_debug("ignoring packet: IPv4 IHL (%zu bytes) " |
159 | "smaller than minimum (20 bytes)", hdrlen); | |
06b44be7 TG |
160 | return -EINVAL; |
161 | } | |
162 | ||
163 | if (len < hdrlen) { | |
aa6fc9b8 TG |
164 | log_debug("ignoring packet: packet (%zu bytes) " |
165 | "smaller than expected (%zu) by IP header", len, | |
166 | hdrlen); | |
cf597f65 | 167 | return -EINVAL; |
ac4f16ab | 168 | } |
cf597f65 | 169 | |
06b44be7 TG |
170 | /* UDP */ |
171 | ||
d454a674 | 172 | if (packet->ip.protocol != IPPROTO_UDP) { |
aa6fc9b8 | 173 | log_debug("ignoring packet: not UDP"); |
d454a674 UTL |
174 | return -EINVAL; |
175 | } | |
176 | ||
8fa2eeac | 177 | if (len < hdrlen + be16toh(packet->udp.len)) { |
aa6fc9b8 TG |
178 | log_debug("ignoring packet: packet (%zu bytes) " |
179 | "smaller than expected (%zu) by UDP header", len, | |
180 | hdrlen + be16toh(packet->udp.len)); | |
ac4f16ab TG |
181 | return -EINVAL; |
182 | } | |
cf597f65 | 183 | |
2ad7561f | 184 | if (be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) { |
aa6fc9b8 TG |
185 | log_debug("ignoring packet: to port %u, which " |
186 | "is not the DHCP client port (%u)", | |
187 | be16toh(packet->udp.dest), DHCP_PORT_CLIENT); | |
2ad7561f TG |
188 | return -EINVAL; |
189 | } | |
190 | ||
191 | /* checksums - computing these is relatively expensive, so only do it | |
192 | if all the other checks have passed | |
193 | */ | |
194 | ||
195 | if (dhcp_packet_checksum(&packet->ip, hdrlen)) { | |
aa6fc9b8 | 196 | log_debug("ignoring packet: invalid IP checksum"); |
2ad7561f TG |
197 | return -EINVAL; |
198 | } | |
199 | ||
55dab2ed | 200 | if (checksum && packet->udp.check) { |
cf597f65 TG |
201 | packet->ip.check = packet->udp.len; |
202 | packet->ip.ttl = 0; | |
203 | ||
a838c939 | 204 | if (dhcp_packet_checksum(&packet->ip.ttl, |
ac4f16ab | 205 | be16toh(packet->udp.len) + 12)) { |
aa6fc9b8 | 206 | log_debug("ignoring packet: invalid UDP checksum"); |
cf597f65 | 207 | return -EINVAL; |
ac4f16ab | 208 | } |
cf597f65 TG |
209 | } |
210 | ||
cf597f65 TG |
211 | return 0; |
212 | } |