defaults.c

   1 /*
   2  * firewall3 - 3rd OpenWrt UCI firewall implementation
   3  *
   4  *   Copyright (C) 2013 Jo-Philipp Wich <jo@mein.io>
   5  *
   6  * Permission to use, copy, modify, and/or distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 #include "defaults.h"
  20
  21
  22 #define C(f, tbl, def, fmt) \
  23         { FW3_FAMILY_##f, FW3_TABLE_##tbl, FW3_FLAG_##def, fmt }
  24
  25 static const struct fw3_chain_spec default_chains[] = {
  26         C(ANY, FILTER, UNSPEC,        "reject"),
  27         C(ANY, FILTER, CUSTOM_CHAINS, "input_rule"),
  28         C(ANY, FILTER, CUSTOM_CHAINS, "output_rule"),
  29         C(ANY, FILTER, CUSTOM_CHAINS, "forwarding_rule"),
  30         C(ANY, FILTER, SYN_FLOOD,     "syn_flood"),
  31
  32         C(V4,  NAT,    CUSTOM_CHAINS, "prerouting_rule"),
  33         C(V4,  NAT,    CUSTOM_CHAINS, "postrouting_rule"),
  34
  35         { }
  36 };
  37
  38 const struct fw3_option fw3_flag_opts[] = {
  39         FW3_OPT("input",               target,   defaults, policy_input),
  40         FW3_OPT("forward",             target,   defaults, policy_forward),
  41         FW3_OPT("output",              target,   defaults, policy_output),
  42
  43         FW3_OPT("drop_invalid",        bool,     defaults, drop_invalid),
  44         FW3_OPT("tcp_reject_code",     reject_code, defaults, tcp_reject_code),
  45         FW3_OPT("any_reject_code",     reject_code, defaults, any_reject_code),
  46
  47         FW3_OPT("syn_flood",           bool,     defaults, syn_flood),
  48         FW3_OPT("synflood_protect",    bool,     defaults, syn_flood),
  49         FW3_OPT("synflood_rate",       limit,    defaults, syn_flood_rate),
  50         FW3_OPT("synflood_burst",      int,      defaults, syn_flood_rate.burst),
  51
  52         FW3_OPT("tcp_syncookies",      bool,     defaults, tcp_syncookies),
  53         FW3_OPT("tcp_ecn",             int,      defaults, tcp_ecn),
  54         FW3_OPT("tcp_window_scaling",  bool,     defaults, tcp_window_scaling),
  55
  56         FW3_OPT("accept_redirects",    bool,     defaults, accept_redirects),
  57         FW3_OPT("accept_source_route", bool,     defaults, accept_source_route),
  58
  59         FW3_OPT("auto_helper",         bool,     defaults, auto_helper),
  60         FW3_OPT("custom_chains",       bool,     defaults, custom_chains),
  61         FW3_OPT("disable_ipv6",        bool,     defaults, disable_ipv6),
  62         FW3_OPT("flow_offloading",     bool,     defaults, flow_offloading),
  63         FW3_OPT("flow_offloading_hw",  bool,     defaults, flow_offloading_hw),
  64
  65         FW3_OPT("__flags_v4",          int,      defaults, flags[0]),
  66         FW3_OPT("__flags_v6",          int,      defaults, flags[1]),
  67
  68         { }
  69 };
  70
  71
  72 static void
  73 check_policy(struct uci_element *e, enum fw3_flag *pol, const char *name)
  74 {
  75         if (*pol == FW3_FLAG_UNSPEC)
  76         {
  77                 warn_elem(e, "has no %s policy specified, defaulting to DROP", name);
  78                 *pol = FW3_FLAG_DROP;
  79         }
  80         else if (*pol > FW3_FLAG_DROP)
  81         {
  82                 warn_elem(e, "has invalid %s policy, defaulting to DROP", name);
  83                 *pol = FW3_FLAG_DROP;
  84         }
  85 }
  86
  87 static void
  88 check_target(struct uci_element *e, bool *available, const char *target, const bool ipv6)
  89 {
  90         const bool b = fw3_has_target(ipv6, target);
  91         if (!b)
  92         {
  93                 warn_elem(e, "requires unavailable target extension %s, disabling", target);
  94         }
  95         *available = b;
  96 }
  97
  98 static void
  99 check_any_reject_code(struct uci_element *e, enum fw3_reject_code *any_reject_code)
 100 {
 101         if (*any_reject_code == FW3_REJECT_CODE_TCP_RESET) {
 102                 warn_elem(e, "tcp-reset not valid for any_reject_code, defaulting to port-unreach");
 103                 *any_reject_code = FW3_REJECT_CODE_PORT_UNREACH;
 104         }
 105 }
 106
 107 static const char*
 108 get_reject_code(enum fw3_family family, enum fw3_reject_code reject_code)
 109 {
 110         switch (reject_code) {
 111         case FW3_REJECT_CODE_TCP_RESET:
 112                 return "tcp-reset";
 113         case FW3_REJECT_CODE_PORT_UNREACH:
 114                 return "port-unreach";
 115         case FW3_REJECT_CODE_ADM_PROHIBITED:
 116                 return family == FW3_FAMILY_V6 ? "adm-prohibited": "admin-prohib";
 117         default:
 118                 return "unknown";
 119         }
 120 }
 121
 122 void
 123 fw3_load_defaults(struct fw3_state *state, struct uci_package *p)
 124 {
 125         struct uci_section *s;
 126         struct uci_element *e;
 127         struct fw3_defaults *defs = &state->defaults;
 128
 129         bool flow_offload_avaliable = false;
 130         bool seen = false;
 131
 132         defs->tcp_reject_code      = FW3_REJECT_CODE_TCP_RESET;
 133         defs->any_reject_code      = FW3_REJECT_CODE_PORT_UNREACH;
 134         defs->syn_flood_rate.rate  = 25;
 135         defs->syn_flood_rate.burst = 50;
 136         defs->tcp_syncookies       = true;
 137         defs->tcp_window_scaling   = true;
 138         defs->custom_chains        = true;
 139         defs->auto_helper          = true;
 140
 141         uci_foreach_element(&p->sections, e)
 142         {
 143                 s = uci_to_section(e);
 144
 145                 if (strcmp(s->type, "defaults"))
 146                         continue;
 147
 148                 if (seen)
 149                 {
 150                         warn_elem(e, "ignoring duplicate section");
 151                         continue;
 152                 }
 153
 154                 if(!fw3_parse_options(&state->defaults, fw3_flag_opts, s))
 155                         warn_elem(e, "has invalid options");
 156
 157                 check_policy(e, &defs->policy_input, "input");
 158                 check_policy(e, &defs->policy_output, "output");
 159                 check_policy(e, &defs->policy_forward, "forward");
 160
 161                 check_any_reject_code(e, &defs->any_reject_code);
 162
 163                 /* exists in both ipv4 and ipv6, if at all, so only check ipv4 */
 164                 check_target(e, &flow_offload_avaliable, "FLOWOFFLOAD", false);
 165
 166                 if (!flow_offload_avaliable)
 167                         defs->flow_offloading = false;
 168         }
 169 }
 170
 171 void
 172 fw3_print_default_chains(struct fw3_ipt_handle *handle, struct fw3_state *state,
 173                          bool reload)
 174 {
 175         struct fw3_defaults *defs = &state->defaults;
 176         const struct fw3_chain_spec *c;
 177
 178 #define policy(t) \
 179         ((t == FW3_FLAG_REJECT) ? FW3_FLAG_DROP : t)
 180
 181         if (handle->family == FW3_FAMILY_V6 && defs->disable_ipv6)
 182                 return;
 183
 184         if (handle->table == FW3_TABLE_FILTER)
 185         {
 186                 fw3_ipt_set_policy(handle, "INPUT",   policy(defs->policy_input));
 187                 fw3_ipt_set_policy(handle, "OUTPUT",  policy(defs->policy_output));
 188                 fw3_ipt_set_policy(handle, "FORWARD", policy(defs->policy_forward));
 189         }
 190
 191         if (defs->custom_chains)
 192                 set(defs->flags, handle->family, FW3_FLAG_CUSTOM_CHAINS);
 193
 194         if (defs->syn_flood)
 195                 set(defs->flags, handle->family, FW3_FLAG_SYN_FLOOD);
 196
 197         for (c = default_chains; c->format; c++)
 198         {
 199                 /* don't touch user chains on selective stop */
 200                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 201                         continue;
 202
 203                 if (!fw3_is_family(c, handle->family))
 204                         continue;
 205
 206                 if (c->table != handle->table)
 207                         continue;
 208
 209                 if (c->flag &&
 210                     !fw3_hasbit(defs->flags[handle->family == FW3_FAMILY_V6], c->flag))
 211                         continue;
 212
 213                 fw3_ipt_create_chain(handle, c->format);
 214         }
 215
 216         set(defs->flags, handle->family, handle->table);
 217 }
 218
 219 void
 220 fw3_print_default_head_rules(struct fw3_ipt_handle *handle,
 221                              struct fw3_state *state, bool reload)
 222 {
 223         int i;
 224         struct fw3_defaults *defs = &state->defaults;
 225         struct fw3_device lodev = { .set = true };
 226         struct fw3_protocol tcp = { .protocol = 6 };
 227         struct fw3_ipt_rule *r;
 228
 229         const char *chains[] = {
 230                 "INPUT", "input",
 231                 "OUTPUT", "output",
 232                 "FORWARD", "forwarding",
 233         };
 234
 235         switch (handle->table)
 236         {
 237         case FW3_TABLE_FILTER:
 238
 239                 sprintf(lodev.name, "lo");
 240
 241                 r = fw3_ipt_rule_create(handle, NULL, &lodev, NULL, NULL, NULL);
 242                 fw3_ipt_rule_target(r, "ACCEPT");
 243                 fw3_ipt_rule_append(r, "INPUT");
 244
 245                 r = fw3_ipt_rule_create(handle, NULL, NULL, &lodev, NULL, NULL);
 246                 fw3_ipt_rule_target(r, "ACCEPT");
 247                 fw3_ipt_rule_append(r, "OUTPUT");
 248
 249                 if (defs->custom_chains)
 250                 {
 251                         for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 252                         {
 253                                 r = fw3_ipt_rule_new(handle);
 254                                 fw3_ipt_rule_comment(r, "Custom %s rule chain", chains[i+1]);
 255                                 fw3_ipt_rule_target(r, "%s_rule", chains[i+1]);
 256                                 fw3_ipt_rule_append(r, chains[i]);
 257                         }
 258                 }
 259
 260                 if (defs->flow_offloading)
 261                 {
 262                         r = fw3_ipt_rule_new(handle);
 263                         fw3_ipt_rule_comment(r, "Traffic offloading");
 264                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 265                         fw3_ipt_rule_target(r, "FLOWOFFLOAD");
 266                         if (defs->flow_offloading_hw)
 267                                 fw3_ipt_rule_addarg(r, false, "--hw", NULL);
 268                         fw3_ipt_rule_append(r, "FORWARD");
 269                 }
 270
 271                 for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 272                 {
 273                         r = fw3_ipt_rule_new(handle);
 274                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 275                         fw3_ipt_rule_target(r, "ACCEPT");
 276                         fw3_ipt_rule_append(r, chains[i]);
 277
 278                         if (defs->drop_invalid)
 279                         {
 280                                 r = fw3_ipt_rule_new(handle);
 281                                 fw3_ipt_rule_extra(r, "-m conntrack --ctstate INVALID");
 282                                 fw3_ipt_rule_target(r, "DROP");
 283                                 fw3_ipt_rule_append(r, chains[i]);
 284                         }
 285                 }
 286
 287                 if (defs->syn_flood)
 288                 {
 289                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 290                         fw3_ipt_rule_extra(r, "--syn");
 291                         fw3_ipt_rule_limit(r, &defs->syn_flood_rate);
 292                         fw3_ipt_rule_target(r, "RETURN");
 293                         fw3_ipt_rule_append(r, "syn_flood");
 294
 295                         r = fw3_ipt_rule_new(handle);
 296                         fw3_ipt_rule_target(r, "DROP");
 297                         fw3_ipt_rule_append(r, "syn_flood");
 298
 299                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 300                         fw3_ipt_rule_extra(r, "--syn");
 301                         fw3_ipt_rule_target(r, "syn_flood");
 302                         fw3_ipt_rule_append(r, "INPUT");
 303                 }
 304
 305                 r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 306                 fw3_ipt_rule_target(r, "REJECT");
 307                 fw3_ipt_rule_addarg(r, false, "--reject-with", get_reject_code(handle->family, defs->tcp_reject_code));
 308                 fw3_ipt_rule_append(r, "reject");
 309
 310                 r = fw3_ipt_rule_new(handle);
 311                 fw3_ipt_rule_target(r, "REJECT");
 312                 fw3_ipt_rule_addarg(r, false, "--reject-with", get_reject_code(handle->family, defs->any_reject_code));
 313                 fw3_ipt_rule_append(r, "reject");
 314
 315                 break;
 316
 317         case FW3_TABLE_NAT:
 318                 if (defs->custom_chains)
 319                 {
 320                         r = fw3_ipt_rule_new(handle);
 321                         fw3_ipt_rule_comment(r, "Custom prerouting rule chain");
 322                         fw3_ipt_rule_target(r, "prerouting_rule");
 323                         fw3_ipt_rule_append(r, "PREROUTING");
 324
 325                         r = fw3_ipt_rule_new(handle);
 326                         fw3_ipt_rule_comment(r, "Custom postrouting rule chain");
 327                         fw3_ipt_rule_target(r, "postrouting_rule");
 328                         fw3_ipt_rule_append(r, "POSTROUTING");
 329                 }
 330                 break;
 331
 332         default:
 333                 break;
 334         }
 335 }
 336
 337 void
 338 fw3_print_default_tail_rules(struct fw3_ipt_handle *handle,
 339                              struct fw3_state *state, bool reload)
 340 {
 341         struct fw3_defaults *defs = &state->defaults;
 342         struct fw3_ipt_rule *r;
 343
 344         if (handle->table != FW3_TABLE_FILTER)
 345                 return;
 346
 347         if (defs->policy_input == FW3_FLAG_REJECT)
 348         {
 349                 r = fw3_ipt_rule_new(handle);
 350
 351                 if (!r)
 352                         return;
 353
 354                 fw3_ipt_rule_target(r, "reject");
 355                 fw3_ipt_rule_append(r, "INPUT");
 356         }
 357
 358         if (defs->policy_output == FW3_FLAG_REJECT)
 359         {
 360                 r = fw3_ipt_rule_new(handle);
 361
 362                 if (!r)
 363                         return;
 364
 365                 fw3_ipt_rule_target(r, "reject");
 366                 fw3_ipt_rule_append(r, "OUTPUT");
 367         }
 368
 369         if (defs->policy_forward == FW3_FLAG_REJECT)
 370         {
 371                 r = fw3_ipt_rule_new(handle);
 372
 373                 if (!r)
 374                         return;
 375
 376                 fw3_ipt_rule_target(r, "reject");
 377                 fw3_ipt_rule_append(r, "FORWARD");
 378         }
 379 }
 380
 381 static void
 382 set_default(const char *name, int set)
 383 {
 384         FILE *f;
 385         char path[sizeof("/proc/sys/net/ipv4/tcp_window_scaling\0")];
 386
 387         snprintf(path, sizeof(path), "/proc/sys/net/ipv4/tcp_%s", name);
 388
 389         info(" * Set tcp_%s to %s", name, set ? "on" : "off");
 390
 391         if (!(f = fopen(path, "w")))
 392         {
 393                 info("   ! Unable to write value: %s", strerror(errno));
 394                 return;
 395         }
 396
 397         fprintf(f, "%u\n", set);
 398         fclose(f);
 399 }
 400
 401 void
 402 fw3_set_defaults(struct fw3_state *state)
 403 {
 404         set_default("ecn",            state->defaults.tcp_ecn);
 405         set_default("syncookies",     state->defaults.tcp_syncookies);
 406         set_default("window_scaling", state->defaults.tcp_window_scaling);
 407 }
 408
 409 void
 410 fw3_flush_rules(struct fw3_ipt_handle *handle, struct fw3_state *state,
 411                 bool reload)
 412 {
 413         enum fw3_flag policy = reload ? FW3_FLAG_DROP : FW3_FLAG_ACCEPT;
 414         struct fw3_defaults *defs = &state->defaults;
 415         const struct fw3_chain_spec *c;
 416
 417         if (!has(defs->flags, handle->family, handle->table))
 418                 return;
 419
 420         if (handle->table == FW3_TABLE_FILTER)
 421         {
 422                 fw3_ipt_set_policy(handle, "INPUT",   policy);
 423                 fw3_ipt_set_policy(handle, "OUTPUT",  policy);
 424                 fw3_ipt_set_policy(handle, "FORWARD", policy);
 425         }
 426
 427         fw3_ipt_delete_id_rules(handle, "INPUT");
 428         fw3_ipt_delete_id_rules(handle, "OUTPUT");
 429         fw3_ipt_delete_id_rules(handle, "FORWARD");
 430         fw3_ipt_delete_id_rules(handle, "PREROUTING");
 431         fw3_ipt_delete_id_rules(handle, "POSTROUTING");
 432
 433         for (c = default_chains; c->format; c++)
 434         {
 435                 /* don't touch user chains on selective stop */
 436                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 437                         continue;
 438
 439                 if (!fw3_is_family(c, handle->family))
 440                         continue;
 441
 442                 if (c->table != handle->table)
 443                         continue;
 444
 445                 if (c->flag && !has(defs->flags, handle->family, c->flag))
 446                         continue;
 447
 448                 fw3_ipt_flush_chain(handle, c->format);
 449
 450                 /* keep certain basic chains that do not depend on any settings to
 451                    avoid purging unrelated user rules pointing to them */
 452                 if (reload && !c->flag)
 453                         continue;
 454
 455                 fw3_ipt_delete_chain(handle, c->format);
 456         }
 457
 458         del(defs->flags, handle->family, handle->table);
 459 }
 460
 461 void
 462 fw3_flush_all(struct fw3_ipt_handle *handle)
 463 {
 464         if (handle->table == FW3_TABLE_FILTER)
 465         {
 466                 fw3_ipt_set_policy(handle, "INPUT",   FW3_FLAG_ACCEPT);
 467                 fw3_ipt_set_policy(handle, "OUTPUT",  FW3_FLAG_ACCEPT);
 468                 fw3_ipt_set_policy(handle, "FORWARD", FW3_FLAG_ACCEPT);
 469         }
 470
 471         fw3_ipt_flush(handle);
 472 }