1 /*
2 subnet_parse.c -- handle subnet parsing
3 Copyright (C) 2000-2021 Guus Sliepen <guus@tinc-vpn.org>,
4 2000-2005 Ivo Timmermans
5
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or
9 (at your option) any later version.
10
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License along
17 with this program; if not, write to the Free Software Foundation, Inc.,
18 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
19 */
20
21 #include "system.h"
22
23 #include "logger.h"
24 #include "net.h"
25 #include "netutl.h"
26 #include "subnet.h"
27 #include "utils.h"
28 #include "xalloc.h"
29
30 /* Changing this default will affect ADD_SUBNET messages - beware of inconsistencies between versions */
31 static const int DEFAULT_WEIGHT = 10;
32
33 /* Subnet mask handling */
34
maskcmp(const void * va,const void * vb,int masklen)35 int maskcmp(const void *va, const void *vb, int masklen) {
36 int i, m, result;
37 const char *a = va;
38 const char *b = vb;
39
40 for(m = masklen, i = 0; m >= 8; m -= 8, i++) {
41 result = a[i] - b[i];
42
43 if(result) {
44 return result;
45 }
46 }
47
48 if(m)
49 return (a[i] & (0x100 - (1 << (8 - m)))) -
50 (b[i] & (0x100 - (1 << (8 - m))));
51
52 return 0;
53 }
54
mask(void * va,int masklen,int len)55 void mask(void *va, int masklen, int len) {
56 int i;
57 char *a = va;
58
59 i = masklen / 8;
60 masklen %= 8;
61
62 if(masklen) {
63 a[i++] &= (0x100 - (1 << (8 - masklen)));
64 }
65
66 for(; i < len; i++) {
67 a[i] = 0;
68 }
69 }
70
maskcpy(void * va,const void * vb,int masklen,int len)71 void maskcpy(void *va, const void *vb, int masklen, int len) {
72 int i, m;
73 char *a = va;
74 const char *b = vb;
75
76 for(m = masklen, i = 0; m >= 8; m -= 8, i++) {
77 a[i] = b[i];
78 }
79
80 if(m) {
81 a[i] = b[i] & (0x100 - (1 << (8 - m)));
82 i++;
83 }
84
85 for(; i < len; i++) {
86 a[i] = 0;
87 }
88 }
89
subnetcheck(const subnet_t subnet)90 bool subnetcheck(const subnet_t subnet) {
91 if(((subnet.type == SUBNET_IPV4)
92 && !maskcheck(&subnet.net.ipv4.address, subnet.net.ipv4.prefixlength, sizeof(subnet.net.ipv4.address)))
93 || ((subnet.type == SUBNET_IPV6)
94 && !maskcheck(&subnet.net.ipv6.address, subnet.net.ipv6.prefixlength, sizeof(subnet.net.ipv6.address)))) {
95 return false;
96 }
97
98 return true;
99 }
100
maskcheck(const void * va,int masklen,int len)101 bool maskcheck(const void *va, int masklen, int len) {
102 int i;
103 const char *a = va;
104
105 i = masklen / 8;
106 masklen %= 8;
107
108 if(masklen && a[i++] & (0xff >> masklen)) {
109 return false;
110 }
111
112 for(; i < len; i++)
113 if(a[i] != 0) {
114 return false;
115 }
116
117 return true;
118 }
119
120 /* Subnet comparison */
121
subnet_compare_mac(const subnet_t * a,const subnet_t * b)122 static int subnet_compare_mac(const subnet_t *a, const subnet_t *b) {
123 int result;
124
125 result = memcmp(&a->net.mac.address, &b->net.mac.address, sizeof(a->net.mac.address));
126
127 if(result) {
128 return result;
129 }
130
131 result = a->weight - b->weight;
132
133 if(result || !a->owner || !b->owner) {
134 return result;
135 }
136
137 return strcmp(a->owner->name, b->owner->name);
138 }
139
subnet_compare_ipv4(const subnet_t * a,const subnet_t * b)140 static int subnet_compare_ipv4(const subnet_t *a, const subnet_t *b) {
141 int result;
142
143 result = b->net.ipv4.prefixlength - a->net.ipv4.prefixlength;
144
145 if(result) {
146 return result;
147 }
148
149 result = memcmp(&a->net.ipv4.address, &b->net.ipv4.address, sizeof(ipv4_t));
150
151 if(result) {
152 return result;
153 }
154
155 result = a->weight - b->weight;
156
157 if(result || !a->owner || !b->owner) {
158 return result;
159 }
160
161 return strcmp(a->owner->name, b->owner->name);
162 }
163
subnet_compare_ipv6(const subnet_t * a,const subnet_t * b)164 static int subnet_compare_ipv6(const subnet_t *a, const subnet_t *b) {
165 int result;
166
167 result = b->net.ipv6.prefixlength - a->net.ipv6.prefixlength;
168
169 if(result) {
170 return result;
171 }
172
173 result = memcmp(&a->net.ipv6.address, &b->net.ipv6.address, sizeof(ipv6_t));
174
175 if(result) {
176 return result;
177 }
178
179 result = a->weight - b->weight;
180
181 if(result || !a->owner || !b->owner) {
182 return result;
183 }
184
185 return strcmp(a->owner->name, b->owner->name);
186 }
187
subnet_compare(const subnet_t * a,const subnet_t * b)188 int subnet_compare(const subnet_t *a, const subnet_t *b) {
189 int result;
190
191 result = a->type - b->type;
192
193 if(result) {
194 return result;
195 }
196
197 switch(a->type) {
198 case SUBNET_MAC:
199 return subnet_compare_mac(a, b);
200
201 case SUBNET_IPV4:
202 return subnet_compare_ipv4(a, b);
203
204 case SUBNET_IPV6:
205 return subnet_compare_ipv6(a, b);
206
207 default:
208 logger(DEBUG_ALWAYS, LOG_ERR, "subnet_compare() was called with unknown subnet type %d, exitting!", a->type);
209 exit(1);
210 }
211
212 return 0;
213 }
214
215 /* Ascii representation of subnets */
216
str2net(subnet_t * subnet,const char * subnetstr)217 bool str2net(subnet_t *subnet, const char *subnetstr) {
218 char str[1024];
219 strncpy(str, subnetstr, sizeof(str));
220 str[sizeof(str) - 1] = 0;
221 int consumed;
222
223 int weight = DEFAULT_WEIGHT;
224 char *weight_separator = strchr(str, '#');
225
226 if(weight_separator) {
227 char *weight_str = weight_separator + 1;
228
229 if(sscanf(weight_str, "%d%n", &weight, &consumed) < 1) {
230 return false;
231 }
232
233 if(weight_str[consumed]) {
234 return false;
235 }
236
237 *weight_separator = 0;
238 }
239
240 int prefixlength = -1;
241 char *prefixlength_separator = strchr(str, '/');
242
243 if(prefixlength_separator) {
244 char *prefixlength_str = prefixlength_separator + 1;
245
246 if(sscanf(prefixlength_str, "%d%n", &prefixlength, &consumed) < 1) {
247 return false;
248 }
249
250 if(prefixlength_str[consumed]) {
251 return false;
252 }
253
254 *prefixlength_separator = 0;
255
256 if(prefixlength < 0) {
257 return false;
258 }
259 }
260
261 uint16_t x[8];
262
263 if(sscanf(str, "%hx:%hx:%hx:%hx:%hx:%hx%n", &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &consumed) >= 6 && !str[consumed]) {
264 /*
265 Normally we should check that each part has two digits to prevent ambiguities.
266 However, in old tinc versions net2str() will aggressively return MAC addresses with one-digit parts,
267 so we have to accept them otherwise we would be unable to parse ADD_SUBNET messages.
268 */
269 if(prefixlength >= 0) {
270 return false;
271 }
272
273 subnet->type = SUBNET_MAC;
274 subnet->weight = weight;
275
276 for(int i = 0; i < 6; i++) {
277 subnet->net.mac.address.x[i] = x[i];
278 }
279
280 return true;
281 }
282
283 if(sscanf(str, "%hu.%hu.%hu.%hu%n", &x[0], &x[1], &x[2], &x[3], &consumed) >= 4 && !str[consumed]) {
284 if(prefixlength == -1) {
285 prefixlength = 32;
286 }
287
288 if(prefixlength > 32) {
289 return false;
290 }
291
292 subnet->type = SUBNET_IPV4;
293 subnet->net.ipv4.prefixlength = prefixlength;
294 subnet->weight = weight;
295
296 for(int i = 0; i < 4; i++) {
297 if(x[i] > 255) {
298 return false;
299 }
300
301 subnet->net.ipv4.address.x[i] = x[i];
302 }
303
304 return true;
305 }
306
307 /* IPv6 */
308
309 char *last_colon = strrchr(str, ':');
310
311 if(last_colon && sscanf(last_colon, ":%hu.%hu.%hu.%hu%n", &x[0], &x[1], &x[2], &x[3], &consumed) >= 4 && !last_colon[consumed]) {
312 /* Dotted quad suffix notation, convert to standard IPv6 notation */
313 for(int i = 0; i < 4; i++)
314 if(x[i] > 255) {
315 return false;
316 }
317
318 snprintf(last_colon, sizeof(str) - (last_colon - str), ":%02x%02x:%02x%02x", x[0], x[1], x[2], x[3]);
319 }
320
321 char *double_colon = strstr(str, "::");
322
323 if(double_colon) {
324 /* Figure out how many zero groups we need to expand */
325 int zero_group_count = 8;
326
327 for(const char *cur = str; *cur; cur++)
328 if(*cur != ':') {
329 zero_group_count--;
330
331 while(cur[1] && cur[1] != ':') {
332 cur++;
333 }
334 }
335
336 if(zero_group_count < 1) {
337 return false;
338 }
339
340 /* Split the double colon in the middle to make room for zero groups */
341 double_colon++;
342 memmove(double_colon + (zero_group_count * 2 - 1), double_colon, strlen(double_colon) + 1);
343
344 /* Write zero groups in the resulting gap, overwriting the second colon */
345 for(int i = 0; i < zero_group_count; i++) {
346 memcpy(&double_colon[i * 2], "0:", 2);
347 }
348
349 /* Remove any leading or trailing colons */
350 if(str[0] == ':') {
351 memmove(&str[0], &str[1], strlen(&str[1]) + 1);
352 }
353
354 if(str[strlen(str) - 1] == ':') {
355 str[strlen(str) - 1] = 0;
356 }
357 }
358
359 if(sscanf(str, "%hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx%n",
360 &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &x[6], &x[7], &consumed) >= 8 && !str[consumed]) {
361 if(prefixlength == -1) {
362 prefixlength = 128;
363 }
364
365 if(prefixlength > 128) {
366 return false;
367 }
368
369 subnet->type = SUBNET_IPV6;
370 subnet->net.ipv6.prefixlength = prefixlength;
371 subnet->weight = weight;
372
373 for(int i = 0; i < 8; i++) {
374 subnet->net.ipv6.address.x[i] = htons(x[i]);
375 }
376
377 return true;
378 }
379
380 return false;
381 }
382
net2str(char * netstr,int len,const subnet_t * subnet)383 bool net2str(char *netstr, int len, const subnet_t *subnet) {
384 if(!netstr || !subnet) {
385 logger(DEBUG_ALWAYS, LOG_ERR, "net2str() was called with netstr=%p, subnet=%p!", (void *)netstr, (void *)subnet);
386 return false;
387 }
388
389 int result;
390 int prefixlength = -1;
391
392 switch(subnet->type) {
393 case SUBNET_MAC:
394 result = snprintf(netstr, len, "%02x:%02x:%02x:%02x:%02x:%02x",
395 subnet->net.mac.address.x[0],
396 subnet->net.mac.address.x[1],
397 subnet->net.mac.address.x[2],
398 subnet->net.mac.address.x[3],
399 subnet->net.mac.address.x[4],
400 subnet->net.mac.address.x[5]);
401 netstr += result;
402 len -= result;
403 break;
404
405 case SUBNET_IPV4:
406 result = snprintf(netstr, len, "%u.%u.%u.%u",
407 subnet->net.ipv4.address.x[0],
408 subnet->net.ipv4.address.x[1],
409 subnet->net.ipv4.address.x[2],
410 subnet->net.ipv4.address.x[3]);
411 netstr += result;
412 len -= result;
413 prefixlength = subnet->net.ipv4.prefixlength;
414
415 if(prefixlength == 32) {
416 prefixlength = -1;
417 }
418
419 break;
420
421 case SUBNET_IPV6: {
422 /* Find the longest sequence of consecutive zeroes */
423 int max_zero_length = 0;
424 int max_zero_length_index = 0;
425 int current_zero_length = 0;
426 int current_zero_length_index = 0;
427
428 for(int i = 0; i < 8; i++) {
429 if(subnet->net.ipv6.address.x[i] != 0) {
430 current_zero_length = 0;
431 } else {
432 if(current_zero_length == 0) {
433 current_zero_length_index = i;
434 }
435
436 current_zero_length++;
437
438 if(current_zero_length > max_zero_length) {
439 max_zero_length = current_zero_length;
440 max_zero_length_index = current_zero_length_index;
441 }
442 }
443 }
444
445 /* Print the address */
446 for(int i = 0; i < 8;) {
447 if(max_zero_length > 1 && max_zero_length_index == i) {
448 /* Shorten the representation as per RFC 5952 */
449 const char *const FORMATS[] = { "%.1s", "%.2s", "%.3s" };
450 const char *const *format = &FORMATS[0];
451
452 if(i == 0) {
453 format++;
454 }
455
456 if(i + max_zero_length == 8) {
457 format++;
458 }
459
460 result = snprintf(netstr, len, *format, ":::");
461 i += max_zero_length;
462 } else {
463 result = snprintf(netstr, len, "%x:", ntohs(subnet->net.ipv6.address.x[i]));
464 i++;
465 }
466
467 netstr += result;
468 len -= result;
469 }
470
471 /* Remove the trailing colon */
472 netstr--;
473 len++;
474 *netstr = 0;
475
476 prefixlength = subnet->net.ipv6.prefixlength;
477
478 if(prefixlength == 128) {
479 prefixlength = -1;
480 }
481
482 break;
483 }
484
485 default:
486 logger(DEBUG_ALWAYS, LOG_ERR, "net2str() was called with unknown subnet type %d, exiting!", subnet->type);
487 exit(1);
488 }
489
490 if(prefixlength >= 0) {
491 result = snprintf(netstr, len, "/%d", prefixlength);
492 netstr += result;
493 len -= result;
494 }
495
496 if(subnet->weight != DEFAULT_WEIGHT) {
497 snprintf(netstr, len, "#%d", subnet->weight);
498 }
499
500 return true;
501 }
502