1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <errno.h>
4 #include <fcntl.h>
5
6 #include "dhcp.h"
7 #include "config.h"
8
9 #ifndef DEFAULT_LEASETIME
10 #define DEFAULT_LEASETIME 3600 /* 1 hour */
11 #endif
12
13 #define REQUEST (1 << 0)
14 #define UINT8 (1 << 1)
15 #define UINT16 (1 << 2)
16 #define SINT16 (1 << 3)
17 #define UINT32 (1 << 4)
18 #define SINT32 (1 << 5)
19 #define IPV4 (1 << 6)
20 #define STRING (1 << 7)
21 #define PAIR (1 << 8)
22 #define ARRAY (1 << 9)
23 #define RFC3361 (1 << 10)
24 #define RFC3397 (1 << 11)
25 #define RFC3442 (1 << 12)
26
27 struct dhcp_opt {
28 uint8_t option;
29 int type;
30 const char *var;
31 };
32
33 static const struct dhcp_opt const dhcp_opts[] = {
34 { 1, IPV4 | REQUEST, "subnet_mask" },
35 { 2, UINT32, "time_offset" },
36 { 3, IPV4 | ARRAY | REQUEST, "routers" },
37 { 4, IPV4 | ARRAY, "time_servers" },
38 { 5, IPV4 | ARRAY, "ien116_name_servers" },
39 { 6, IPV4 | ARRAY, "domain_name_servers" },
40 { 7, IPV4 | ARRAY, "log_servers" },
41 { 8, IPV4 | ARRAY, "cookie_servers" },
42 { 9, IPV4 | ARRAY, "lpr_servers" },
43 { 10, IPV4 | ARRAY, "impress_servers" },
44 { 11, IPV4 | ARRAY, "resource_location_servers" },
45 { 12, STRING, "host_name" },
46 { 13, UINT16, "boot_size" },
47 { 14, STRING, "merit_dump" },
48 { 15, STRING, "domain_name" },
49 { 16, IPV4, "swap_server" },
50 { 17, STRING, "root_path" },
51 { 18, STRING, "extensions_path" },
52 { 19, UINT8, "ip_forwarding" },
53 { 20, UINT8, "non_local_source_routing" },
54 { 21, IPV4 | ARRAY, "policy_filter" },
55 { 22, SINT16, "max_dgram_reassembly" },
56 { 23, UINT16, "default_ip_ttl" },
57 { 24, UINT32, "path_mtu_aging_timeout" },
58 { 25, UINT16 | ARRAY, "path_mtu_plateau_table" },
59 { 26, UINT16, "interface_mtu" },
60 { 27, UINT8, "all_subnets_local" },
61 { 28, IPV4 | REQUEST, "broadcast_address" },
62 { 29, UINT8, "perform_mask_discovery" },
63 { 30, UINT8, "mask_supplier" },
64 { 31, UINT8, "router_discovery" },
65 { 32, IPV4, "router_solicitation_address" },
66 { 33, IPV4 | ARRAY | REQUEST, "static_routes" },
67 { 34, UINT8, "trailer_encapsulation" },
68 { 35, UINT32, "arp_cache_timeout" },
69 { 36, UINT16, "ieee802_3_encapsulation" },
70 { 37, UINT8, "default_tcp_ttl" },
71 { 38, UINT32, "tcp_keepalive_interval" },
72 { 39, UINT8, "tcp_keepalive_garbage" },
73 { 40, STRING, "nis_domain" },
74 { 41, IPV4 | ARRAY, "nis_servers" },
75 { 42, IPV4 | ARRAY, "ntp_servers" },
76 { 43, STRING, "vendor_encapsulated_options" },
77 { 44, IPV4 | ARRAY, "netbios_name_servers" },
78 { 45, IPV4, "netbios_dd_server" },
79 { 46, UINT8, "netbios_node_type" },
80 { 47, STRING, "netbios_scope" },
81 { 48, IPV4 | ARRAY, "font_servers" },
82 { 49, IPV4 | ARRAY, "x_display_manager" },
83 { 50, IPV4, "dhcp_requested_address" },
84 { 51, UINT32 | REQUEST, "dhcp_lease_time" },
85 { 52, UINT8, "dhcp_option_overload" },
86 { 53, UINT8, "dhcp_message_type" },
87 { 54, IPV4, "dhcp_server_identifier" },
88 { 55, UINT8 | ARRAY, "dhcp_parameter_request_list" },
89 { 56, STRING, "dhcp_message" },
90 { 57, UINT16, "dhcp_max_message_size" },
91 { 58, UINT32 | REQUEST, "dhcp_renewal_time" },
92 { 59, UINT32 | REQUEST, "dhcp_rebinding_time" },
93 { 64, STRING, "nisplus_domain" },
94 { 65, IPV4 | ARRAY, "nisplus_servers" },
95 { 66, STRING, "tftp_server_name" },
96 { 67, STRING, "bootfile_name" },
97 { 68, IPV4 | ARRAY, "mobile_ip_home_agent" },
98 { 69, IPV4 | ARRAY, "smtp_server" },
99 { 70, IPV4 | ARRAY, "pop_server" },
100 { 71, IPV4 | ARRAY, "nntp_server" },
101 { 72, IPV4 | ARRAY, "www_server" },
102 { 73, IPV4 | ARRAY, "finger_server" },
103 { 74, IPV4 | ARRAY, "irc_server" },
104 { 75, IPV4 | ARRAY, "streettalk_server" },
105 { 76, IPV4 | ARRAY, "streettalk_directory_assistance_server" },
106 { 77, STRING, "user_class" },
107 { 85, IPV4 | ARRAY, "nds_servers" },
108 { 86, STRING, "nds_tree_name" },
109 { 87, STRING, "nds_context" },
110 { 88, STRING | RFC3397, "bcms_controller_names" },
111 { 89, IPV4 | ARRAY, "bcms_controller_address" },
112 { 91, UINT32, "client_last_transaction_time" },
113 { 92, IPV4 | ARRAY, "associated_ip" },
114 { 98, STRING, "uap_servers" },
115 { 112, IPV4 | ARRAY, "netinfo_server_address" },
116 { 113, STRING, "netinfo_server_tag" },
117 { 114, STRING, "default_url" },
118 { 118, IPV4, "subnet_selection" },
119 { 119, STRING | RFC3397, "domain_search" },
120 { 121, RFC3442 | REQUEST, "classless_static_routes" },
121 { 249, RFC3442, "ms-classless_static_routes" },
122 { 0, 0, NULL }
123 };
124
125 struct dhcp_message *
get_lease_from_file(const char * leasefile)126 get_lease_from_file(const char *leasefile)
127 {
128 int fd;
129 struct dhcp_message *dhcp;
130 ssize_t bytes;
131
132 fd = open(leasefile, O_RDONLY);
133 if (fd == -1)
134 return NULL;
135 dhcp = malloc(sizeof(*dhcp));
136 memset(dhcp, 0, sizeof(*dhcp));
137 bytes = read(fd, dhcp, sizeof(*dhcp));
138 close(fd);
139 if (bytes < 0) {
140 free(dhcp);
141 dhcp = NULL;
142 }
143 return dhcp;
144 }
145
146 static uint8_t *dhcp_opt_buffer = NULL;
147
148 static int
valid_length(uint8_t option,int dl,int * type)149 valid_length(uint8_t option, int dl, int *type)
150 {
151 const struct dhcp_opt *opt;
152 ssize_t sz;
153
154 if (dl == 0)
155 return -1;
156
157 for (opt = dhcp_opts; opt->option; opt++) {
158 if (opt->option != option)
159 continue;
160
161 if (type)
162 *type = opt->type;
163
164 if (opt->type == 0 || opt->type & STRING || opt->type & RFC3442)
165 return 0;
166
167 sz = 0;
168 if (opt->type & UINT32 || opt->type & IPV4)
169 sz = sizeof(uint32_t);
170 if (opt->type & UINT16)
171 sz = sizeof(uint16_t);
172 if (opt->type & UINT8)
173 sz = sizeof(uint8_t);
174 if (opt->type & IPV4 || opt->type & ARRAY)
175 return dl % sz;
176 return (dl == sz ? 0 : -1);
177 }
178
179 /* unknown option, so let it pass */
180 return 0;
181 }
182
183 static void
free_option_buffer(void)184 free_option_buffer(void)
185 {
186 free(dhcp_opt_buffer);
187 }
188
189
190 #define get_option_raw(dhcp, opt) get_option(dhcp, opt, NULL, NULL)
191 static const uint8_t *
get_option(const struct dhcp_message * dhcp,uint8_t opt,int * len,int * type)192 get_option(const struct dhcp_message *dhcp, uint8_t opt, int *len, int *type)
193 {
194 const uint8_t *p = dhcp->options;
195 const uint8_t *e = p + sizeof(dhcp->options);
196 uint8_t l, ol = 0;
197 uint8_t o = 0;
198 uint8_t overl = 0;
199 uint8_t *bp = NULL;
200 const uint8_t *op = NULL;
201 int bl = 0;
202
203 while (p < e) {
204 o = *p++;
205 if (o == opt) {
206 if (op) {
207 if (!dhcp_opt_buffer) {
208 dhcp_opt_buffer = malloc(sizeof(struct dhcp_message));
209 atexit(free_option_buffer);
210 }
211 if (!bp)
212 bp = dhcp_opt_buffer;
213 memcpy(bp, op, ol);
214 bp += ol;
215 }
216 ol = *p;
217 op = p + 1;
218 bl += ol;
219 }
220 switch (o) {
221 case DHO_PAD:
222 continue;
223 case DHO_END:
224 if (overl & 1) {
225 /* bit 1 set means parse boot file */
226 overl &= ~1;
227 p = dhcp->bootfile;
228 e = p + sizeof(dhcp->bootfile);
229 } else if (overl & 2) {
230 /* bit 2 set means parse server name */
231 overl &= ~2;
232 p = dhcp->servername;
233 e = p + sizeof(dhcp->servername);
234 } else
235 goto exit;
236 break;
237 case DHO_OPTIONSOVERLOADED:
238 /* Ensure we only get this option once */
239 if (!overl)
240 overl = p[1];
241 break;
242 }
243 l = *p++;
244 p += l;
245 }
246
247 exit:
248 if (valid_length(o, bl, type) == -1) {
249 errno = EINVAL;
250 return NULL;
251 }
252 if (len)
253 *len = bl;
254 if (bp) {
255 memcpy(bp, op, ol);
256 return (const uint8_t *)&dhcp_opt_buffer;
257 }
258 if (op)
259 return op;
260 errno = ENOENT;
261 return NULL;
262 }
263
264 int
get_option_addr32(uint32_t * a,const struct dhcp_message * dhcp,uint8_t option)265 get_option_addr32(uint32_t *a, const struct dhcp_message *dhcp, uint8_t option)
266 {
267 const uint8_t *p = get_option_raw(dhcp, option);
268
269 if (!p)
270 return -1;
271 memcpy(a, p, sizeof(*a));
272 return 0;
273 }
274
275 int
get_option_uint32(uint32_t * i,const struct dhcp_message * dhcp,uint8_t option)276 get_option_uint32(uint32_t *i, const struct dhcp_message *dhcp, uint8_t option)
277 {
278 uint32_t a;
279
280 if (get_option_addr32(&a, dhcp, option) == -1)
281 return -1;
282
283 *i = ntohl(a);
284 return 0;
285 }
286
287 uint32_t
get_netmask(uint32_t addr)288 get_netmask(uint32_t addr)
289 {
290 uint32_t dst;
291
292 if (addr == 0)
293 return 0;
294
295 dst = htonl(addr);
296 if (IN_CLASSA(dst))
297 return ntohl(IN_CLASSA_NET);
298 if (IN_CLASSB (dst))
299 return ntohl(IN_CLASSB_NET);
300 if (IN_CLASSC (dst))
301 return ntohl(IN_CLASSC_NET);
302
303 return 0;
304 }
305
showlease(struct dhcp_lease * lease)306 void showlease(struct dhcp_lease *lease)
307 {
308 printf("addr: %s\n", inet_ntoa(lease->addr));
309 printf("net: %s\n", inet_ntoa(lease->net));
310 printf("leasetime: %d\n", lease->leasetime);
311 printf("renew: %d\n", lease->renewaltime);
312 printf("rebind: %d\n", lease->rebindtime);
313 printf("server: %s\n", inet_ntoa(lease->server));
314 }
315 #define MAX_LEASETIME 2147460
316
317 int
main(int argc,char * argv[])318 main(int argc, char *argv[])
319 {
320 struct dhcp_message *dhcp;
321 struct dhcp_lease *lease;
322 char leasefile[PATH_MAX];
323
324 if (argc < 2) {
325 fprintf(stderr, "Usage: %s <interface>\n", argv[0]);
326 exit(1);
327 }
328 snprintf(leasefile, PATH_MAX, LEASEFILE, argv[1]);
329 if ((dhcp = get_lease_from_file(leasefile)) == NULL) {
330 fprintf(stderr, "Couldn't read lease file: %s\n", strerror(errno));
331 exit(1);
332 }
333 lease = malloc(sizeof(*lease));
334 lease->frominfo = 0;
335 lease->addr.s_addr = dhcp->yiaddr;
336
337 if (get_option_addr32(&lease->net.s_addr, dhcp, DHO_SUBNETMASK) == -1)
338 lease->net.s_addr = get_netmask(dhcp->yiaddr);
339 if (get_option_uint32(&lease->leasetime, dhcp, DHO_LEASETIME) != 0)
340 lease->leasetime = DEFAULT_LEASETIME;
341 get_option_addr32(&lease->server.s_addr, dhcp, DHO_SERVERID);
342 /* Dm: limit lease time value to avoid negative numbers when
343 converting to milliseconds */
344 if ((lease->leasetime != ~0U) && (lease->leasetime > MAX_LEASETIME))
345 lease->leasetime = MAX_LEASETIME;
346 if (get_option_uint32(&lease->renewaltime, dhcp, DHO_RENEWALTIME) != 0)
347 lease->renewaltime = 0;
348 if (get_option_uint32(&lease->rebindtime, dhcp, DHO_REBINDTIME) != 0)
349 lease->rebindtime = 0;
350 showlease(lease);
351 free(lease);
352 return 0;
353 }
354