1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
2 /***
3 Copyright © 2013 Intel Corporation. All rights reserved.
4 ***/
5
6 #include <errno.h>
7 #include <net/ethernet.h>
8 #include <net/if_arp.h>
9 #include <string.h>
10
11 #include "dhcp-internal.h"
12 #include "dhcp-protocol.h"
13 #include "memory-util.h"
14
15 #define DHCP_CLIENT_MIN_OPTIONS_SIZE 312
16
dhcp_message_init(DHCPMessage * message,uint8_t op,uint32_t xid,uint8_t type,uint16_t arp_type,uint8_t hlen,const uint8_t * chaddr,size_t optlen,size_t * optoffset)17 int dhcp_message_init(
18 DHCPMessage *message,
19 uint8_t op,
20 uint32_t xid,
21 uint8_t type,
22 uint16_t arp_type,
23 uint8_t hlen,
24 const uint8_t *chaddr,
25 size_t optlen,
26 size_t *optoffset) {
27
28 size_t offset = 0;
29 int r;
30
31 assert(IN_SET(op, BOOTREQUEST, BOOTREPLY));
32 assert(chaddr || hlen == 0);
33
34 message->op = op;
35 message->htype = arp_type;
36
37 /* RFC2131 section 4.1.1:
38 The client MUST include its hardware address in the ’chaddr’ field, if
39 necessary for delivery of DHCP reply messages.
40
41 RFC 4390 section 2.1:
42 A DHCP client, when working over an IPoIB interface, MUST follow the
43 following rules:
44 "htype" (hardware address type) MUST be 32 [ARPPARAM].
45 "hlen" (hardware address length) MUST be 0.
46 "chaddr" (client hardware address) field MUST be zeroed.
47 */
48 message->hlen = (arp_type == ARPHRD_INFINIBAND) ? 0 : hlen;
49 memcpy_safe(message->chaddr, chaddr, message->hlen);
50
51 message->xid = htobe32(xid);
52 message->magic = htobe32(DHCP_MAGIC_COOKIE);
53
54 r = dhcp_option_append(message, optlen, &offset, 0,
55 SD_DHCP_OPTION_MESSAGE_TYPE, 1, &type);
56 if (r < 0)
57 return r;
58
59 *optoffset = offset;
60
61 return 0;
62 }
63
dhcp_packet_checksum(uint8_t * buf,size_t len)64 uint16_t dhcp_packet_checksum(uint8_t *buf, size_t len) {
65 uint64_t *buf_64 = (uint64_t*)buf;
66 uint64_t *end_64 = buf_64 + (len / sizeof(uint64_t));
67 uint64_t sum = 0;
68
69 /* See RFC1071 */
70
71 while (buf_64 < end_64) {
72 sum += *buf_64;
73 if (sum < *buf_64)
74 /* wrap around in one's complement */
75 sum++;
76
77 buf_64++;
78 }
79
80 if (len % sizeof(uint64_t)) {
81 /* If the buffer is not aligned to 64-bit, we need
82 to zero-pad the last few bytes and add them in */
83 uint64_t buf_tail = 0;
84
85 memcpy(&buf_tail, buf_64, len % sizeof(uint64_t));
86
87 sum += buf_tail;
88 if (sum < buf_tail)
89 /* wrap around */
90 sum++;
91 }
92
93 while (sum >> 16)
94 sum = (sum & 0xffff) + (sum >> 16);
95
96 return ~sum;
97 }
98
dhcp_packet_append_ip_headers(DHCPPacket * packet,be32_t source_addr,uint16_t source_port,be32_t destination_addr,uint16_t destination_port,uint16_t len,int ip_service_type)99 void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr,
100 uint16_t source_port, be32_t destination_addr,
101 uint16_t destination_port, uint16_t len, int ip_service_type) {
102 packet->ip.version = IPVERSION;
103 packet->ip.ihl = DHCP_IP_SIZE / 4;
104 packet->ip.tot_len = htobe16(len);
105
106 if (ip_service_type >= 0)
107 packet->ip.tos = ip_service_type;
108 else
109 packet->ip.tos = IPTOS_CLASS_CS6;
110
111 packet->ip.protocol = IPPROTO_UDP;
112 packet->ip.saddr = source_addr;
113 packet->ip.daddr = destination_addr;
114
115 packet->udp.source = htobe16(source_port);
116 packet->udp.dest = htobe16(destination_port);
117
118 packet->udp.len = htobe16(len - DHCP_IP_SIZE);
119
120 packet->ip.check = packet->udp.len;
121 packet->udp.check = dhcp_packet_checksum((uint8_t*)&packet->ip.ttl, len - 8);
122
123 packet->ip.ttl = IPDEFTTL;
124 packet->ip.check = 0;
125 packet->ip.check = dhcp_packet_checksum((uint8_t*)&packet->ip, DHCP_IP_SIZE);
126 }
127
dhcp_packet_verify_headers(DHCPPacket * packet,size_t len,bool checksum,uint16_t port)128 int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum, uint16_t port) {
129 size_t hdrlen;
130
131 assert(packet);
132 assert(len >= sizeof(DHCPPacket));
133
134 /* IP */
135
136 if (packet->ip.version != IPVERSION)
137 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
138 "ignoring packet: not IPv4");
139
140 if (packet->ip.ihl < 5)
141 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
142 "ignoring packet: IPv4 IHL (%u words) invalid",
143 packet->ip.ihl);
144
145 hdrlen = packet->ip.ihl * 4;
146 if (hdrlen < 20)
147 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
148 "ignoring packet: IPv4 IHL (%zu bytes) smaller than minimum (20 bytes)",
149 hdrlen);
150
151 if (len < hdrlen)
152 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
153 "ignoring packet: packet (%zu bytes) smaller than expected (%zu) by IP header",
154 len, hdrlen);
155
156 /* UDP */
157
158 if (packet->ip.protocol != IPPROTO_UDP)
159 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
160 "ignoring packet: not UDP");
161
162 if (len < hdrlen + be16toh(packet->udp.len))
163 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
164 "ignoring packet: packet (%zu bytes) smaller than expected (%zu) by UDP header",
165 len, hdrlen + be16toh(packet->udp.len));
166
167 if (be16toh(packet->udp.dest) != port)
168 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
169 "ignoring packet: to port %u, which is not the DHCP client port (%u)",
170 be16toh(packet->udp.dest), port);
171
172 /* checksums - computing these is relatively expensive, so only do it
173 if all the other checks have passed
174 */
175
176 if (dhcp_packet_checksum((uint8_t*)&packet->ip, hdrlen))
177 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
178 "ignoring packet: invalid IP checksum");
179
180 if (checksum && packet->udp.check) {
181 packet->ip.check = packet->udp.len;
182 packet->ip.ttl = 0;
183
184 if (dhcp_packet_checksum((uint8_t*)&packet->ip.ttl,
185 be16toh(packet->udp.len) + 12))
186 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
187 "ignoring packet: invalid UDP checksum");
188 }
189
190 return 0;
191 }
192