1/*
2 * options.c -- DHCP server option packet tools
3 * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
4 */
5
6#include <stdio.h>
7#include <stdlib.h>
8#include <string.h>
9
10#include "debug.h"
11#include "dhcpd.h"
12#include "files.h"
13#include "options.h"
14#include "leases.h"
15
16
17/* supported options are easily added here */
18struct dhcp_option options[] = {
19	/* name[10]	flags					code */
20	{"subnet",	OPTION_IP | OPTION_REQ,			0x01},
21	{"timezone",	OPTION_S32,				0x02},
22	{"router",	OPTION_IP | OPTION_LIST | OPTION_REQ,	0x03},
23	{"timesvr",	OPTION_IP | OPTION_LIST,		0x04},
24	{"namesvr",	OPTION_IP | OPTION_LIST,		0x05},
25	{"dns",		OPTION_IP | OPTION_LIST | OPTION_REQ,	0x06},
26	{"logsvr",	OPTION_IP | OPTION_LIST,		0x07},
27	{"cookiesvr",	OPTION_IP | OPTION_LIST,		0x08},
28	{"lprsvr",	OPTION_IP | OPTION_LIST,		0x09},
29	{"hostname",	OPTION_STRING | OPTION_REQ,		0x0c},
30	{"bootsize",	OPTION_U16,				0x0d},
31	{"domain",	OPTION_STRING | OPTION_REQ,		0x0f},
32	{"swapsvr",	OPTION_IP,				0x10},
33	{"rootpath",	OPTION_STRING,				0x11},
34	{"ipttl",	OPTION_U8,				0x17},
35	{"mtu",		OPTION_U16,				0x1a},
36	{"broadcast",	OPTION_IP | OPTION_REQ,			0x1c},
37	{"ntpsrv",	OPTION_IP | OPTION_LIST,		0x2a},
38	{"wins",	OPTION_IP | OPTION_LIST | OPTION_REQ,	0x2c},
39	{"requestip",	OPTION_IP,				0x32},
40	{"lease",	OPTION_U32,				0x33},
41	{"dhcptype",	OPTION_U8,				0x35},
42	{"serverid",	OPTION_IP,				0x36},
43	{"message",	OPTION_STRING,				0x38},
44	{"tftp",	OPTION_STRING,				0x42},
45	{"bootfile",	OPTION_STRING,				0x43},
46	{"",		0x00,				0x00}
47};
48
49/* Lengths of the different option types */
50int option_lengths[] = {
51	[OPTION_IP] =		4,
52	[OPTION_IP_PAIR] =	8,
53	[OPTION_BOOLEAN] =	1,
54	[OPTION_STRING] =	1,
55	[OPTION_U8] =		1,
56	[OPTION_U16] =		2,
57	[OPTION_S16] =		2,
58	[OPTION_U32] =		4,
59	[OPTION_S32] =		4
60};
61
62
63/* get an option with bounds checking (warning, not aligned). */
64unsigned char *get_option(struct dhcpMessage *packet, int code)
65{
66	int i, length;
67	unsigned char *optionptr;
68	int over = 0, done = 0, curr = OPTION_FIELD;
69
70	optionptr = packet->options;
71	i = 0;
72	length = 308;
73	while (!done) {
74		if (i >= length) {
75			LOG(LOG_WARNING, "bogus packet, option fields too long.");
76			return NULL;
77		}
78		if (optionptr[i + OPT_CODE] == code) {
79			if (i + 1 + optionptr[i + OPT_LEN] >= length) {
80				LOG(LOG_WARNING, "bogus packet, option fields too long.");
81				return NULL;
82			}
83			return optionptr + i + 2;
84		}
85		switch (optionptr[i + OPT_CODE]) {
86		case DHCP_PADDING:
87			i++;
88			break;
89		case DHCP_OPTION_OVER:
90			if (i + 1 + optionptr[i + OPT_LEN] >= length) {
91				LOG(LOG_WARNING, "bogus packet, option fields too long.");
92				return NULL;
93			}
94			over = optionptr[i + 3];
95			i += optionptr[OPT_LEN] + 2;
96			break;
97		case DHCP_END:
98			if (curr == OPTION_FIELD && over & FILE_FIELD) {
99				optionptr = packet->file;
100				i = 0;
101				length = 128;
102				curr = FILE_FIELD;
103			} else if (curr == FILE_FIELD && over & SNAME_FIELD) {
104				optionptr = packet->sname;
105				i = 0;
106				length = 64;
107				curr = SNAME_FIELD;
108			} else done = 1;
109			break;
110		default:
111			i += optionptr[OPT_LEN + i] + 2;
112		}
113	}
114	return NULL;
115}
116
117
118/* return the position of the 'end' option (no bounds checking) */
119int end_option(unsigned char *optionptr)
120{
121	int i = 0;
122
123	while (optionptr[i] != DHCP_END) {
124		if (optionptr[i] == DHCP_PADDING) i++;
125		else i += optionptr[i + OPT_LEN] + 2;
126	}
127	return i;
128}
129
130
131/* add an option string to the options (an option string contains an option code,
132 * length, then data) */
133int add_option_string(unsigned char *optionptr, unsigned char *string)
134{
135	int end = end_option(optionptr);
136
137	/* end position + string length + option code/length + end option */
138	if (end + string[OPT_LEN] + 2 + 1 >= 308) {
139		LOG(LOG_ERR, "Option 0x%02x did not fit into the packet!", string[OPT_CODE]);
140		return 0;
141	}
142	DEBUG(LOG_INFO, "adding option 0x%02x", string[OPT_CODE]);
143	memcpy(optionptr + end, string, string[OPT_LEN] + 2);
144	optionptr[end + string[OPT_LEN] + 2] = DHCP_END;
145	return string[OPT_LEN] + 2;
146}
147
148
149/* add a one to four byte option to a packet */
150int add_simple_option(unsigned char *optionptr, unsigned char code, u_int32_t data)
151{
152	char length = 0;
153	int i;
154	unsigned char option[2 + 4];
155	unsigned char *u8;
156	u_int16_t *u16;
157	u_int32_t *u32;
158	u_int32_t aligned;
159	u8 = (unsigned char *) &aligned;
160	u16 = (u_int16_t *) (void *)&aligned;
161	u32 = &aligned;
162
163	for (i = 0; options[i].code; i++)
164		if (options[i].code == code) {
165			length = option_lengths[options[i].flags & TYPE_MASK];
166		}
167
168	if (!length) {
169		DEBUG(LOG_ERR, "Could not add option 0x%02x", code);
170		return 0;
171	}
172
173	option[OPT_CODE] = code;
174	option[OPT_LEN] = length;
175
176	switch (length) {
177		case 1: *u8 =  data; break;
178		case 2: *u16 = data; break;
179		case 4: *u32 = data; break;
180	}
181	memcpy(option + 2, &aligned, length);
182	return add_option_string(optionptr, option);
183}
184
185
186/* find option 'code' in opt_list */
187struct option_set *find_option(struct option_set *opt_list, char code)
188{
189	while (opt_list && opt_list->data[OPT_CODE] < code)
190		opt_list = opt_list->next;
191
192	if (opt_list && opt_list->data[OPT_CODE] == code) return opt_list;
193	else return NULL;
194}
195
196
197/* add an option to the opt_list */
198void attach_option(struct option_set **opt_list, struct dhcp_option *option, char *buffer, int length)
199{
200	struct option_set *existing, *new, **curr;
201
202	/* add it to an existing option */
203	if ((existing = find_option(*opt_list, option->code))) {
204		DEBUG(LOG_INFO, "Attaching option %s to existing member of list", option->name);
205		if (option->flags & OPTION_LIST) {
206			if (existing->data[OPT_LEN] + length <= 255) {
207				existing->data = realloc(existing->data,
208						existing->data[OPT_LEN] + length + 2);
209				memcpy(existing->data + existing->data[OPT_LEN] + 2, buffer, length);
210				existing->data[OPT_LEN] += length;
211			} /* else, ignore the data, we could put this in a second option in the future */
212		} /* else, ignore the new data */
213	} else {
214		DEBUG(LOG_INFO, "Attaching option %s to list", option->name);
215
216		/* make a new option */
217		new = malloc(sizeof(struct option_set));
218		new->data = malloc(length + 2);
219		new->data[OPT_CODE] = option->code;
220		new->data[OPT_LEN] = length;
221		memcpy(new->data + 2, buffer, length);
222
223		curr = opt_list;
224		while (*curr && (*curr)->data[OPT_CODE] < option->code)
225			curr = &(*curr)->next;
226
227		new->next = *curr;
228		*curr = new;
229	}
230}
231