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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 | ||
cf597f65 | 21 | #include <errno.h> |
cf597f65 TG |
22 | #include <net/ethernet.h> |
23 | #include <net/if_arp.h> | |
cf0fbc49 | 24 | #include <string.h> |
cf597f65 | 25 | |
cf597f65 | 26 | #include "dhcp-internal.h" |
cf0fbc49 | 27 | #include "dhcp-protocol.h" |
cf597f65 TG |
28 | |
29 | #define DHCP_CLIENT_MIN_OPTIONS_SIZE 312 | |
30 | ||
31 | int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid, | |
76253e73 DW |
32 | uint8_t type, uint16_t arp_type, size_t optlen, |
33 | size_t *optoffset) { | |
20b958bf TG |
34 | size_t offset = 0; |
35 | int r; | |
cf597f65 | 36 | |
0a1b6da8 | 37 | assert(op == BOOTREQUEST || op == BOOTREPLY); |
76253e73 | 38 | assert(arp_type == ARPHRD_ETHER || arp_type == ARPHRD_INFINIBAND); |
0a1b6da8 | 39 | |
cf597f65 | 40 | message->op = op; |
76253e73 DW |
41 | message->htype = arp_type; |
42 | message->hlen = (arp_type == ARPHRD_ETHER) ? ETHER_ADDR_LEN : 0; | |
cf597f65 | 43 | message->xid = htobe32(xid); |
3b7ca119 | 44 | message->magic = htobe32(DHCP_MAGIC_COOKIE); |
cf597f65 | 45 | |
04b28be1 | 46 | r = dhcp_option_append(message, optlen, &offset, 0, |
22805d92 | 47 | SD_DHCP_OPTION_MESSAGE_TYPE, 1, &type); |
20b958bf TG |
48 | if (r < 0) |
49 | return r; | |
cf597f65 | 50 | |
20b958bf | 51 | *optoffset = offset; |
cf597f65 TG |
52 | |
53 | return 0; | |
54 | } | |
55 | ||
0bbc2c1f TG |
56 | uint16_t dhcp_packet_checksum(uint8_t *buf, size_t len) { |
57 | uint64_t *buf_64 = (uint64_t*)buf; | |
58 | uint64_t *end_64 = buf_64 + (len / sizeof(uint64_t)); | |
d5761274 TG |
59 | uint64_t sum = 0; |
60 | ||
0bbc2c1f TG |
61 | /* See RFC1071 */ |
62 | ||
d5761274 TG |
63 | while (buf_64 < end_64) { |
64 | sum += *buf_64; | |
65 | if (sum < *buf_64) | |
0bbc2c1f | 66 | /* wrap around in one's complement */ |
d5761274 TG |
67 | sum++; |
68 | ||
69 | buf_64 ++; | |
70 | } | |
71 | ||
0bbc2c1f TG |
72 | if (len % sizeof(uint64_t)) { |
73 | /* If the buffer is not aligned to 64-bit, we need | |
74 | to zero-pad the last few bytes and add them in */ | |
75 | uint64_t buf_tail = 0; | |
cf597f65 | 76 | |
0bbc2c1f | 77 | memcpy(&buf_tail, buf_64, len % sizeof(uint64_t)); |
cf597f65 | 78 | |
0bbc2c1f TG |
79 | sum += buf_tail; |
80 | if (sum < buf_tail) | |
81 | /* wrap around */ | |
d5761274 | 82 | sum++; |
cf597f65 TG |
83 | } |
84 | ||
85 | while (sum >> 16) | |
86 | sum = (sum & 0xffff) + (sum >> 16); | |
87 | ||
88 | return ~sum; | |
89 | } | |
90 | ||
63edaa62 TG |
91 | void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr, |
92 | uint16_t source_port, be32_t destination_addr, | |
93 | uint16_t destination_port, uint16_t len) { | |
cf597f65 TG |
94 | packet->ip.version = IPVERSION; |
95 | packet->ip.ihl = DHCP_IP_SIZE / 4; | |
96 | packet->ip.tot_len = htobe16(len); | |
97 | ||
85923f79 TG |
98 | packet->ip.tos = IPTOS_CLASS_CS6; |
99 | ||
cf597f65 | 100 | packet->ip.protocol = IPPROTO_UDP; |
63edaa62 TG |
101 | packet->ip.saddr = source_addr; |
102 | packet->ip.daddr = destination_addr; | |
cf597f65 | 103 | |
63edaa62 TG |
104 | packet->udp.source = htobe16(source_port); |
105 | packet->udp.dest = htobe16(destination_port); | |
cf597f65 TG |
106 | |
107 | packet->udp.len = htobe16(len - DHCP_IP_SIZE); | |
108 | ||
109 | packet->ip.check = packet->udp.len; | |
0bbc2c1f | 110 | packet->udp.check = dhcp_packet_checksum((uint8_t*)&packet->ip.ttl, len - 8); |
cf597f65 TG |
111 | |
112 | packet->ip.ttl = IPDEFTTL; | |
113 | packet->ip.check = 0; | |
0bbc2c1f | 114 | packet->ip.check = dhcp_packet_checksum((uint8_t*)&packet->ip, DHCP_IP_SIZE); |
cf597f65 TG |
115 | } |
116 | ||
55dab2ed | 117 | int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) { |
cf597f65 TG |
118 | size_t hdrlen; |
119 | ||
5266a81e TG |
120 | assert(packet); |
121 | ||
06b44be7 | 122 | /* IP */ |
cf597f65 | 123 | |
6e34949d | 124 | if (packet->ip.version != IPVERSION) { |
aa6fc9b8 | 125 | log_debug("ignoring packet: not IPv4"); |
6e34949d TG |
126 | return -EINVAL; |
127 | } | |
128 | ||
06b44be7 | 129 | if (packet->ip.ihl < 5) { |
aa6fc9b8 TG |
130 | log_debug("ignoring packet: IPv4 IHL (%u words) invalid", |
131 | packet->ip.ihl); | |
cf597f65 | 132 | return -EINVAL; |
ac4f16ab | 133 | } |
cf597f65 TG |
134 | |
135 | hdrlen = packet->ip.ihl * 4; | |
06b44be7 | 136 | if (hdrlen < 20) { |
aa6fc9b8 TG |
137 | log_debug("ignoring packet: IPv4 IHL (%zu bytes) " |
138 | "smaller than minimum (20 bytes)", hdrlen); | |
06b44be7 TG |
139 | return -EINVAL; |
140 | } | |
141 | ||
142 | if (len < hdrlen) { | |
aa6fc9b8 TG |
143 | log_debug("ignoring packet: packet (%zu bytes) " |
144 | "smaller than expected (%zu) by IP header", len, | |
145 | hdrlen); | |
cf597f65 | 146 | return -EINVAL; |
ac4f16ab | 147 | } |
cf597f65 | 148 | |
06b44be7 TG |
149 | /* UDP */ |
150 | ||
d454a674 | 151 | if (packet->ip.protocol != IPPROTO_UDP) { |
aa6fc9b8 | 152 | log_debug("ignoring packet: not UDP"); |
d454a674 UTL |
153 | return -EINVAL; |
154 | } | |
155 | ||
8fa2eeac | 156 | if (len < hdrlen + be16toh(packet->udp.len)) { |
aa6fc9b8 TG |
157 | log_debug("ignoring packet: packet (%zu bytes) " |
158 | "smaller than expected (%zu) by UDP header", len, | |
159 | hdrlen + be16toh(packet->udp.len)); | |
ac4f16ab TG |
160 | return -EINVAL; |
161 | } | |
cf597f65 | 162 | |
2ad7561f | 163 | if (be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) { |
aa6fc9b8 TG |
164 | log_debug("ignoring packet: to port %u, which " |
165 | "is not the DHCP client port (%u)", | |
166 | be16toh(packet->udp.dest), DHCP_PORT_CLIENT); | |
2ad7561f TG |
167 | return -EINVAL; |
168 | } | |
169 | ||
170 | /* checksums - computing these is relatively expensive, so only do it | |
171 | if all the other checks have passed | |
172 | */ | |
173 | ||
0bbc2c1f | 174 | if (dhcp_packet_checksum((uint8_t*)&packet->ip, hdrlen)) { |
aa6fc9b8 | 175 | log_debug("ignoring packet: invalid IP checksum"); |
2ad7561f TG |
176 | return -EINVAL; |
177 | } | |
178 | ||
55dab2ed | 179 | if (checksum && packet->udp.check) { |
cf597f65 TG |
180 | packet->ip.check = packet->udp.len; |
181 | packet->ip.ttl = 0; | |
182 | ||
0bbc2c1f | 183 | if (dhcp_packet_checksum((uint8_t*)&packet->ip.ttl, |
ac4f16ab | 184 | be16toh(packet->udp.len) + 12)) { |
aa6fc9b8 | 185 | log_debug("ignoring packet: invalid UDP checksum"); |
cf597f65 | 186 | return -EINVAL; |
ac4f16ab | 187 | } |
cf597f65 TG |
188 | } |
189 | ||
cf597f65 TG |
190 | return 0; |
191 | } |