tinc-vpn.org Git - tinc/blob - src/subnet_parse.c

   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
  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
  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
  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
  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
 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
 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
 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
 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
 188 int subnet_compare(const subnet_t *a, const subnet_t *b) {
 189         int result = (int)a->type - (int)b->type;
 190
 191         if(result) {
 192                 return result;
 193         }
 194
 195         switch(a->type) {
 196         case SUBNET_MAC:
 197                 return subnet_compare_mac(a, b);
 198
 199         case SUBNET_IPV4:
 200                 return subnet_compare_ipv4(a, b);
 201
 202         case SUBNET_IPV6:
 203                 return subnet_compare_ipv6(a, b);
 204
 205         default:
 206                 logger(DEBUG_ALWAYS, LOG_ERR, "subnet_compare() was called with unknown subnet type %d, exitting!", a->type);
 207                 exit(1);
 208         }
 209
 210         return 0;
 211 }
 212
 213 /* Ascii representation of subnets */
 214
 215 bool str2net(subnet_t *subnet, const char *subnetstr) {
 216         char str[1024];
 217         strncpy(str, subnetstr, sizeof(str));
 218         str[sizeof(str) - 1] = 0;
 219         int consumed;
 220
 221         int weight = DEFAULT_WEIGHT;
 222         char *weight_separator = strchr(str, '#');
 223
 224         if(weight_separator) {
 225                 char *weight_str = weight_separator + 1;
 226
 227                 if(sscanf(weight_str, "%d%n", &weight, &consumed) < 1) {
 228                         return false;
 229                 }
 230
 231                 if(weight_str[consumed]) {
 232                         return false;
 233                 }
 234
 235                 *weight_separator = 0;
 236         }
 237
 238         int prefixlength = -1;
 239         char *prefixlength_separator = strchr(str, '/');
 240
 241         if(prefixlength_separator) {
 242                 char *prefixlength_str = prefixlength_separator + 1;
 243
 244                 if(sscanf(prefixlength_str, "%d%n", &prefixlength, &consumed) < 1) {
 245                         return false;
 246                 }
 247
 248                 if(prefixlength_str[consumed]) {
 249                         return false;
 250                 }
 251
 252                 *prefixlength_separator = 0;
 253
 254                 if(prefixlength < 0) {
 255                         return false;
 256                 }
 257         }
 258
 259         uint16_t x[8];
 260
 261         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]) {
 262                 /*
 263                    Normally we should check that each part has two digits to prevent ambiguities.
 264                    However, in old tinc versions net2str() will aggressively return MAC addresses with one-digit parts,
 265                    so we have to accept them otherwise we would be unable to parse ADD_SUBNET messages.
 266                 */
 267                 if(prefixlength >= 0) {
 268                         return false;
 269                 }
 270
 271                 subnet->type = SUBNET_MAC;
 272                 subnet->weight = weight;
 273
 274                 for(int i = 0; i < 6; i++) {
 275                         subnet->net.mac.address.x[i] = x[i];
 276                 }
 277
 278                 return true;
 279         }
 280
 281         if(sscanf(str, "%hu.%hu.%hu.%hu%n", &x[0], &x[1], &x[2], &x[3], &consumed) >= 4 && !str[consumed]) {
 282                 if(prefixlength == -1) {
 283                         prefixlength = 32;
 284                 }
 285
 286                 if(prefixlength > 32) {
 287                         return false;
 288                 }
 289
 290                 subnet->type = SUBNET_IPV4;
 291                 subnet->net.ipv4.prefixlength = prefixlength;
 292                 subnet->weight = weight;
 293
 294                 for(int i = 0; i < 4; i++) {
 295                         if(x[i] > 255) {
 296                                 return false;
 297                         }
 298
 299                         subnet->net.ipv4.address.x[i] = x[i];
 300                 }
 301
 302                 return true;
 303         }
 304
 305         /* IPv6 */
 306
 307         char *last_colon = strrchr(str, ':');
 308
 309         if(last_colon && sscanf(last_colon, ":%hu.%hu.%hu.%hu%n", &x[0], &x[1], &x[2], &x[3], &consumed) >= 4 && !last_colon[consumed]) {
 310                 /* Dotted quad suffix notation, convert to standard IPv6 notation */
 311                 for(int i = 0; i < 4; i++)
 312                         if(x[i] > 255) {
 313                                 return false;
 314                         }
 315
 316                 snprintf(last_colon, sizeof(str) - (last_colon - str), ":%02x%02x:%02x%02x", x[0], x[1], x[2], x[3]);
 317         }
 318
 319         char *double_colon = strstr(str, "::");
 320
 321         if(double_colon) {
 322                 /* Figure out how many zero groups we need to expand */
 323                 int zero_group_count = 8;
 324
 325                 for(const char *cur = str; *cur; cur++)
 326                         if(*cur != ':') {
 327                                 zero_group_count--;
 328
 329                                 while(cur[1] && cur[1] != ':') {
 330                                         cur++;
 331                                 }
 332                         }
 333
 334                 if(zero_group_count < 1) {
 335                         return false;
 336                 }
 337
 338                 /* Split the double colon in the middle to make room for zero groups */
 339                 double_colon++;
 340                 memmove(double_colon + (zero_group_count * 2 - 1), double_colon, strlen(double_colon) + 1);
 341
 342                 /* Write zero groups in the resulting gap, overwriting the second colon */
 343                 for(int i = 0; i < zero_group_count; i++) {
 344                         memcpy(&double_colon[i * 2], "0:", 2);
 345                 }
 346
 347                 /* Remove any leading or trailing colons */
 348                 if(str[0] == ':') {
 349                         memmove(&str[0], &str[1], strlen(&str[1]) + 1);
 350                 }
 351
 352                 if(str[strlen(str) - 1] == ':') {
 353                         str[strlen(str) - 1] = 0;
 354                 }
 355         }
 356
 357         if(sscanf(str, "%hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx%n",
 358                         &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &x[6], &x[7], &consumed) >= 8 && !str[consumed]) {
 359                 if(prefixlength == -1) {
 360                         prefixlength = 128;
 361                 }
 362
 363                 if(prefixlength > 128) {
 364                         return false;
 365                 }
 366
 367                 subnet->type = SUBNET_IPV6;
 368                 subnet->net.ipv6.prefixlength = prefixlength;
 369                 subnet->weight = weight;
 370
 371                 for(int i = 0; i < 8; i++) {
 372                         subnet->net.ipv6.address.x[i] = htons(x[i]);
 373                 }
 374
 375                 return true;
 376         }
 377
 378         return false;
 379 }
 380
 381 bool net2str(char *netstr, int len, const subnet_t *subnet) {
 382         if(!netstr || !subnet) {
 383                 logger(DEBUG_ALWAYS, LOG_ERR, "net2str() was called with netstr=%p, subnet=%p!", (void *)netstr, (void *)subnet);
 384                 return false;
 385         }
 386
 387         int result;
 388         int prefixlength = -1;
 389
 390         switch(subnet->type) {
 391         case SUBNET_MAC:
 392                 result = snprintf(netstr, len, "%02x:%02x:%02x:%02x:%02x:%02x",
 393                                   subnet->net.mac.address.x[0],
 394                                   subnet->net.mac.address.x[1],
 395                                   subnet->net.mac.address.x[2],
 396                                   subnet->net.mac.address.x[3],
 397                                   subnet->net.mac.address.x[4],
 398                                   subnet->net.mac.address.x[5]);
 399                 netstr += result;
 400                 len -= result;
 401                 break;
 402
 403         case SUBNET_IPV4:
 404                 result = snprintf(netstr, len, "%u.%u.%u.%u",
 405                                   subnet->net.ipv4.address.x[0],
 406                                   subnet->net.ipv4.address.x[1],
 407                                   subnet->net.ipv4.address.x[2],
 408                                   subnet->net.ipv4.address.x[3]);
 409                 netstr += result;
 410                 len -= result;
 411                 prefixlength = subnet->net.ipv4.prefixlength;
 412
 413                 if(prefixlength == 32) {
 414                         prefixlength = -1;
 415                 }
 416
 417                 break;
 418
 419         case SUBNET_IPV6: {
 420                 /* Find the longest sequence of consecutive zeroes */
 421                 int max_zero_length = 0;
 422                 int max_zero_length_index = 0;
 423                 int current_zero_length = 0;
 424                 int current_zero_length_index = 0;
 425
 426                 for(int i = 0; i < 8; i++) {
 427                         if(subnet->net.ipv6.address.x[i] != 0) {
 428                                 current_zero_length = 0;
 429                         } else {
 430                                 if(current_zero_length == 0) {
 431                                         current_zero_length_index = i;
 432                                 }
 433
 434                                 current_zero_length++;
 435
 436                                 if(current_zero_length > max_zero_length) {
 437                                         max_zero_length = current_zero_length;
 438                                         max_zero_length_index = current_zero_length_index;
 439                                 }
 440                         }
 441                 }
 442
 443                 /* Print the address */
 444                 for(int i = 0; i < 8;) {
 445                         if(max_zero_length > 1 && max_zero_length_index == i) {
 446                                 /* Shorten the representation as per RFC 5952 */
 447                                 const char *const FORMATS[] = { "%.1s", "%.2s", "%.3s" };
 448                                 const char *const *format = &FORMATS[0];
 449
 450                                 if(i == 0) {
 451                                         format++;
 452                                 }
 453
 454                                 if(i + max_zero_length == 8) {
 455                                         format++;
 456                                 }
 457
 458                                 result = snprintf(netstr, len, *format, ":::");
 459                                 i += max_zero_length;
 460                         } else {
 461                                 result = snprintf(netstr, len, "%x:", ntohs(subnet->net.ipv6.address.x[i]));
 462                                 i++;
 463                         }
 464
 465                         netstr += result;
 466                         len -= result;
 467                 }
 468
 469                 /* Remove the trailing colon */
 470                 netstr--;
 471                 len++;
 472                 *netstr = 0;
 473
 474                 prefixlength = subnet->net.ipv6.prefixlength;
 475
 476                 if(prefixlength == 128) {
 477                         prefixlength = -1;
 478                 }
 479
 480                 break;
 481         }
 482
 483         default:
 484                 logger(DEBUG_ALWAYS, LOG_ERR, "net2str() was called with unknown subnet type %d, exiting!", subnet->type);
 485                 exit(1);
 486         }
 487
 488         if(prefixlength >= 0) {
 489                 result = snprintf(netstr, len, "/%d", prefixlength);
 490                 netstr += result;
 491                 len -= result;
 492         }
 493
 494         if(subnet->weight != DEFAULT_WEIGHT) {
 495                 snprintf(netstr, len, "#%d", subnet->weight);
 496         }
 497
 498         return true;
 499 }