1/* vi: set sw=4 ts=4: */
2/*
3 * options.c -- DHCP server option packet tools
4 * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
5 */
6
7#include "common.h"
8#include "dhcpd.h"
9#include "options.h"
10
11
12/* supported options are easily added here */
13const struct dhcp_option dhcp_options[] = {
14	/* name[12]     flags                                   code */
15	{"subnet",      OPTION_IP | OPTION_REQ,                 0x01},
16	{"timezone",    OPTION_S32,                             0x02},
17	{"router",      OPTION_IP | OPTION_LIST | OPTION_REQ,   0x03},
18	{"timesvr",     OPTION_IP | OPTION_LIST,                0x04},
19	{"namesvr",     OPTION_IP | OPTION_LIST,                0x05},
20	{"dns",         OPTION_IP | OPTION_LIST | OPTION_REQ,   0x06},
21	{"logsvr",      OPTION_IP | OPTION_LIST,                0x07},
22	{"cookiesvr",   OPTION_IP | OPTION_LIST,                0x08},
23	{"lprsvr",      OPTION_IP | OPTION_LIST,                0x09},
24	{"hostname",    OPTION_STRING | OPTION_REQ,             0x0c},
25	{"bootsize",    OPTION_U16,                             0x0d},
26	{"domain",      OPTION_STRING | OPTION_LIST | OPTION_REQ, 0x0f},
27	{"swapsvr",     OPTION_IP,                              0x10},
28	{"rootpath",    OPTION_STRING,                          0x11},
29	{"ipttl",       OPTION_U8,                              0x17},
30	{"mtu",         OPTION_U16,                             0x1a},
31	{"broadcast",   OPTION_IP | OPTION_REQ,                 0x1c},
32	{"nisdomain",   OPTION_STRING | OPTION_REQ,             0x28},
33	{"nissrv",      OPTION_IP | OPTION_LIST | OPTION_REQ,   0x29},
34	{"ntpsrv",      OPTION_IP | OPTION_LIST | OPTION_REQ,   0x2a},
35	{"wins",        OPTION_IP | OPTION_LIST,                0x2c},
36	{"requestip",   OPTION_IP,                              0x32},
37	{"lease",       OPTION_U32,                             0x33},
38	{"dhcptype",    OPTION_U8,                              0x35},
39	{"serverid",    OPTION_IP,                              0x36},
40	{"message",     OPTION_STRING,                          0x38},
41	{"vendorclass", OPTION_STRING,                          0x3C},
42	{"clientid",    OPTION_STRING,                          0x3D},
43	{"tftp",        OPTION_STRING,                          0x42},
44	{"bootfile",    OPTION_STRING,                          0x43},
45	{"userclass",   OPTION_STRING,                          0x4D},
46#if ENABLE_FEATURE_RFC3397
47	{"search",      OPTION_STR1035 | OPTION_LIST | OPTION_REQ, 0x77},
48#endif
49	/* MSIE's "Web Proxy Autodiscovery Protocol" support */
50	{"wpad",        OPTION_STRING,                          0xfc},
51	{"",            0x00,                                   0x00}
52};
53
54/* Lengths of the different option types */
55const unsigned char option_lengths[] ALIGN1 = {
56	[OPTION_IP] =      4,
57	[OPTION_IP_PAIR] = 8,
58	[OPTION_BOOLEAN] = 1,
59	[OPTION_STRING] =  1,
60#if ENABLE_FEATURE_RFC3397
61	[OPTION_STR1035] = 1,
62#endif
63	[OPTION_U8] =      1,
64	[OPTION_U16] =     2,
65	[OPTION_S16] =     2,
66	[OPTION_U32] =     4,
67	[OPTION_S32] =     4
68};
69
70
71/* get an option with bounds checking (warning, not aligned). */
72uint8_t *get_option(struct dhcpMessage *packet, int code)
73{
74	int i, length;
75	uint8_t *optionptr;
76	int over = 0, done = 0, curr = OPTION_FIELD;
77
78	optionptr = packet->options;
79	i = 0;
80	length = 308;
81	while (!done) {
82		if (i >= length) {
83			bb_error_msg("bogus packet, option fields too long");
84			return NULL;
85		}
86		if (optionptr[i + OPT_CODE] == code) {
87			if (i + 1 + optionptr[i + OPT_LEN] >= length) {
88				bb_error_msg("bogus packet, option fields too long");
89				return NULL;
90			}
91			return optionptr + i + 2;
92		}
93		switch (optionptr[i + OPT_CODE]) {
94		case DHCP_PADDING:
95			i++;
96			break;
97		case DHCP_OPTION_OVER:
98			if (i + 1 + optionptr[i + OPT_LEN] >= length) {
99				bb_error_msg("bogus packet, option fields too long");
100				return NULL;
101			}
102			over = optionptr[i + 3];
103			i += optionptr[OPT_LEN] + 2;
104			break;
105		case DHCP_END:
106			if (curr == OPTION_FIELD && over & FILE_FIELD) {
107				optionptr = packet->file;
108				i = 0;
109				length = 128;
110				curr = FILE_FIELD;
111			} else if (curr == FILE_FIELD && over & SNAME_FIELD) {
112				optionptr = packet->sname;
113				i = 0;
114				length = 64;
115				curr = SNAME_FIELD;
116			} else done = 1;
117			break;
118		default:
119			i += optionptr[OPT_LEN + i] + 2;
120		}
121	}
122	return NULL;
123}
124
125
126/* return the position of the 'end' option (no bounds checking) */
127int end_option(uint8_t *optionptr)
128{
129	int i = 0;
130
131	while (optionptr[i] != DHCP_END) {
132		if (optionptr[i] == DHCP_PADDING) i++;
133		else i += optionptr[i + OPT_LEN] + 2;
134	}
135	return i;
136}
137
138
139/* add an option string to the options (an option string contains an option code,
140 * length, then data) */
141int add_option_string(uint8_t *optionptr, uint8_t *string)
142{
143	int end = end_option(optionptr);
144
145	/* end position + string length + option code/length + end option */
146	if (end + string[OPT_LEN] + 2 + 1 >= 308) {
147		bb_error_msg("option 0x%02x did not fit into the packet",
148				string[OPT_CODE]);
149		return 0;
150	}
151	DEBUG("adding option 0x%02x", string[OPT_CODE]);
152	memcpy(optionptr + end, string, string[OPT_LEN] + 2);
153	optionptr[end + string[OPT_LEN] + 2] = DHCP_END;
154	return string[OPT_LEN] + 2;
155}
156
157
158/* add a one to four byte option to a packet */
159int add_simple_option(uint8_t *optionptr, uint8_t code, uint32_t data)
160{
161	const struct dhcp_option *dh;
162
163	for (dh = dhcp_options; dh->code; dh++) {
164		if (dh->code == code) {
165			uint8_t option[6], len;
166
167			option[OPT_CODE] = code;
168			len = option_lengths[dh->flags & TYPE_MASK];
169			option[OPT_LEN] = len;
170			if (BB_BIG_ENDIAN) data <<= 8 * (4 - len);
171			/* This memcpy is for broken processors which can't
172			 * handle a simple unaligned 32-bit assignment */
173			memcpy(&option[OPT_DATA], &data, 4);
174			return add_option_string(optionptr, option);
175		}
176	}
177
178	bb_error_msg("cannot add option 0x%02x", code);
179	return 0;
180}
181