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60f067b4 JS |
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 | ||
60f067b4 JS |
21 | #include <errno.h> |
22 | #include <string.h> | |
60f067b4 JS |
23 | #include <net/ethernet.h> |
24 | #include <net/if_arp.h> | |
60f067b4 | 25 | |
60f067b4 JS |
26 | |
27 | #include "dhcp-protocol.h" | |
60f067b4 | 28 | #include "dhcp-internal.h" |
60f067b4 JS |
29 | |
30 | #define DHCP_CLIENT_MIN_OPTIONS_SIZE 312 | |
31 | ||
32 | int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid, | |
5eef597e MP |
33 | uint8_t type, uint16_t arp_type, size_t optlen, |
34 | size_t *optoffset) { | |
60f067b4 JS |
35 | size_t offset = 0; |
36 | int r; | |
37 | ||
38 | assert(op == BOOTREQUEST || op == BOOTREPLY); | |
5eef597e | 39 | assert(arp_type == ARPHRD_ETHER || arp_type == ARPHRD_INFINIBAND); |
60f067b4 JS |
40 | |
41 | message->op = op; | |
5eef597e MP |
42 | message->htype = arp_type; |
43 | message->hlen = (arp_type == ARPHRD_ETHER) ? ETHER_ADDR_LEN : 0; | |
60f067b4 JS |
44 | message->xid = htobe32(xid); |
45 | message->magic = htobe32(DHCP_MAGIC_COOKIE); | |
46 | ||
47 | r = dhcp_option_append(message, optlen, &offset, 0, | |
48 | DHCP_OPTION_MESSAGE_TYPE, 1, &type); | |
49 | if (r < 0) | |
50 | return r; | |
51 | ||
52 | *optoffset = offset; | |
53 | ||
54 | return 0; | |
55 | } | |
56 | ||
e842803a MB |
57 | uint16_t dhcp_packet_checksum(uint8_t *buf, size_t len) { |
58 | uint64_t *buf_64 = (uint64_t*)buf; | |
59 | uint64_t *end_64 = buf_64 + (len / sizeof(uint64_t)); | |
60f067b4 JS |
60 | uint64_t sum = 0; |
61 | ||
e842803a MB |
62 | /* See RFC1071 */ |
63 | ||
60f067b4 JS |
64 | while (buf_64 < end_64) { |
65 | sum += *buf_64; | |
66 | if (sum < *buf_64) | |
e842803a | 67 | /* wrap around in one's complement */ |
60f067b4 JS |
68 | sum++; |
69 | ||
70 | buf_64 ++; | |
71 | } | |
72 | ||
e842803a MB |
73 | if (len % sizeof(uint64_t)) { |
74 | /* If the buffer is not aligned to 64-bit, we need | |
75 | to zero-pad the last few bytes and add them in */ | |
76 | uint64_t buf_tail = 0; | |
60f067b4 | 77 | |
e842803a | 78 | memcpy(&buf_tail, buf_64, len % sizeof(uint64_t)); |
60f067b4 | 79 | |
e842803a MB |
80 | sum += buf_tail; |
81 | if (sum < buf_tail) | |
82 | /* wrap around */ | |
60f067b4 JS |
83 | sum++; |
84 | } | |
85 | ||
86 | while (sum >> 16) | |
87 | sum = (sum & 0xffff) + (sum >> 16); | |
88 | ||
89 | return ~sum; | |
90 | } | |
91 | ||
92 | void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr, | |
93 | uint16_t source_port, be32_t destination_addr, | |
94 | uint16_t destination_port, uint16_t len) { | |
95 | packet->ip.version = IPVERSION; | |
96 | packet->ip.ihl = DHCP_IP_SIZE / 4; | |
97 | packet->ip.tot_len = htobe16(len); | |
98 | ||
99 | packet->ip.tos = IPTOS_CLASS_CS6; | |
100 | ||
101 | packet->ip.protocol = IPPROTO_UDP; | |
102 | packet->ip.saddr = source_addr; | |
103 | packet->ip.daddr = destination_addr; | |
104 | ||
105 | packet->udp.source = htobe16(source_port); | |
106 | packet->udp.dest = htobe16(destination_port); | |
107 | ||
108 | packet->udp.len = htobe16(len - DHCP_IP_SIZE); | |
109 | ||
110 | packet->ip.check = packet->udp.len; | |
e842803a | 111 | packet->udp.check = dhcp_packet_checksum((uint8_t*)&packet->ip.ttl, len - 8); |
60f067b4 JS |
112 | |
113 | packet->ip.ttl = IPDEFTTL; | |
114 | packet->ip.check = 0; | |
e842803a | 115 | packet->ip.check = dhcp_packet_checksum((uint8_t*)&packet->ip, DHCP_IP_SIZE); |
60f067b4 JS |
116 | } |
117 | ||
118 | int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) { | |
119 | size_t hdrlen; | |
120 | ||
121 | assert(packet); | |
122 | ||
123 | /* IP */ | |
124 | ||
125 | if (packet->ip.version != IPVERSION) { | |
126 | log_debug("ignoring packet: not IPv4"); | |
127 | return -EINVAL; | |
128 | } | |
129 | ||
130 | if (packet->ip.ihl < 5) { | |
131 | log_debug("ignoring packet: IPv4 IHL (%u words) invalid", | |
132 | packet->ip.ihl); | |
133 | return -EINVAL; | |
134 | } | |
135 | ||
136 | hdrlen = packet->ip.ihl * 4; | |
137 | if (hdrlen < 20) { | |
138 | log_debug("ignoring packet: IPv4 IHL (%zu bytes) " | |
139 | "smaller than minimum (20 bytes)", hdrlen); | |
140 | return -EINVAL; | |
141 | } | |
142 | ||
143 | if (len < hdrlen) { | |
144 | log_debug("ignoring packet: packet (%zu bytes) " | |
145 | "smaller than expected (%zu) by IP header", len, | |
146 | hdrlen); | |
147 | return -EINVAL; | |
148 | } | |
149 | ||
150 | /* UDP */ | |
151 | ||
152 | if (packet->ip.protocol != IPPROTO_UDP) { | |
153 | log_debug("ignoring packet: not UDP"); | |
154 | return -EINVAL; | |
155 | } | |
156 | ||
157 | if (len < hdrlen + be16toh(packet->udp.len)) { | |
158 | log_debug("ignoring packet: packet (%zu bytes) " | |
159 | "smaller than expected (%zu) by UDP header", len, | |
160 | hdrlen + be16toh(packet->udp.len)); | |
161 | return -EINVAL; | |
162 | } | |
163 | ||
164 | if (be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) { | |
165 | log_debug("ignoring packet: to port %u, which " | |
166 | "is not the DHCP client port (%u)", | |
167 | be16toh(packet->udp.dest), DHCP_PORT_CLIENT); | |
168 | return -EINVAL; | |
169 | } | |
170 | ||
171 | /* checksums - computing these is relatively expensive, so only do it | |
172 | if all the other checks have passed | |
173 | */ | |
174 | ||
e842803a | 175 | if (dhcp_packet_checksum((uint8_t*)&packet->ip, hdrlen)) { |
60f067b4 JS |
176 | log_debug("ignoring packet: invalid IP checksum"); |
177 | return -EINVAL; | |
178 | } | |
179 | ||
180 | if (checksum && packet->udp.check) { | |
181 | packet->ip.check = packet->udp.len; | |
182 | packet->ip.ttl = 0; | |
183 | ||
e842803a | 184 | if (dhcp_packet_checksum((uint8_t*)&packet->ip.ttl, |
60f067b4 JS |
185 | be16toh(packet->udp.len) + 12)) { |
186 | log_debug("ignoring packet: invalid UDP checksum"); | |
187 | return -EINVAL; | |
188 | } | |
189 | } | |
190 | ||
191 | return 0; | |
192 | } |