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_offloading(struct uci_element *e, bool *offloading)
  89 {
  90         FILE *f;
  91
  92         if (!*offloading)
  93                 return;
  94
  95         f = fopen("/sys/module/xt_FLOWOFFLOAD/refcnt", "r");
  96
  97         if (f)
  98         {
  99                 fclose(f);
 100                 return;
 101         }
 102
 103         warn_elem(e, "enables offloading but missing kernel support, disabling");
 104         *offloading = false;
 105 }
 106
 107 static void
 108 check_any_reject_code(struct uci_element *e, enum fw3_reject_code *any_reject_code)
 109 {
 110         if (*any_reject_code == FW3_REJECT_CODE_TCP_RESET) {
 111                 warn_elem(e, "tcp-reset not valid for any_reject_code, defaulting to port-unreach");
 112                 *any_reject_code = FW3_REJECT_CODE_PORT_UNREACH;
 113         }
 114 }
 115
 116 static const char*
 117 get_reject_code(enum fw3_family family, enum fw3_reject_code reject_code)
 118 {
 119         switch (reject_code) {
 120         case FW3_REJECT_CODE_TCP_RESET:
 121                 return "tcp-reset";
 122         case FW3_REJECT_CODE_PORT_UNREACH:
 123                 return "port-unreach";
 124         case FW3_REJECT_CODE_ADM_PROHIBITED:
 125                 return family == FW3_FAMILY_V6 ? "adm-prohibited": "admin-prohib";
 126         default:
 127                 return "unknown";
 128         }
 129 }
 130
 131 void
 132 fw3_load_defaults(struct fw3_state *state, struct uci_package *p)
 133 {
 134         struct uci_section *s;
 135         struct uci_element *e;
 136         struct fw3_defaults *defs = &state->defaults;
 137
 138         bool seen = false;
 139
 140         defs->tcp_reject_code      = FW3_REJECT_CODE_TCP_RESET;
 141         defs->any_reject_code      = FW3_REJECT_CODE_PORT_UNREACH;
 142         defs->syn_flood_rate.rate  = 25;
 143         defs->syn_flood_rate.burst = 50;
 144         defs->tcp_syncookies       = true;
 145         defs->tcp_window_scaling   = true;
 146         defs->custom_chains        = true;
 147         defs->auto_helper          = true;
 148
 149         uci_foreach_element(&p->sections, e)
 150         {
 151                 s = uci_to_section(e);
 152
 153                 if (strcmp(s->type, "defaults"))
 154                         continue;
 155
 156                 if (seen)
 157                 {
 158                         warn_elem(e, "ignoring duplicate section");
 159                         continue;
 160                 }
 161
 162                 if(!fw3_parse_options(&state->defaults, fw3_flag_opts, s))
 163                         warn_elem(e, "has invalid options");
 164
 165                 check_policy(e, &defs->policy_input, "input");
 166                 check_policy(e, &defs->policy_output, "output");
 167                 check_policy(e, &defs->policy_forward, "forward");
 168
 169                 check_any_reject_code(e, &defs->any_reject_code);
 170
 171                 check_offloading(e, &defs->flow_offloading);
 172         }
 173 }
 174
 175 void
 176 fw3_print_default_chains(struct fw3_ipt_handle *handle, struct fw3_state *state,
 177                          bool reload)
 178 {
 179         struct fw3_defaults *defs = &state->defaults;
 180         const struct fw3_chain_spec *c;
 181
 182 #define policy(t) \
 183         ((t == FW3_FLAG_REJECT) ? FW3_FLAG_DROP : t)
 184
 185         if (handle->family == FW3_FAMILY_V6 && defs->disable_ipv6)
 186                 return;
 187
 188         if (handle->table == FW3_TABLE_FILTER)
 189         {
 190                 fw3_ipt_set_policy(handle, "INPUT",   policy(defs->policy_input));
 191                 fw3_ipt_set_policy(handle, "OUTPUT",  policy(defs->policy_output));
 192                 fw3_ipt_set_policy(handle, "FORWARD", policy(defs->policy_forward));
 193         }
 194
 195         if (defs->custom_chains)
 196                 set(defs->flags, handle->family, FW3_FLAG_CUSTOM_CHAINS);
 197
 198         if (defs->syn_flood)
 199                 set(defs->flags, handle->family, FW3_FLAG_SYN_FLOOD);
 200
 201         for (c = default_chains; c->format; c++)
 202         {
 203                 /* don't touch user chains on selective stop */
 204                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 205                         continue;
 206
 207                 if (!fw3_is_family(c, handle->family))
 208                         continue;
 209
 210                 if (c->table != handle->table)
 211                         continue;
 212
 213                 if (c->flag &&
 214                     !fw3_hasbit(defs->flags[handle->family == FW3_FAMILY_V6], c->flag))
 215                         continue;
 216
 217                 fw3_ipt_create_chain(handle, c->format);
 218         }
 219
 220         set(defs->flags, handle->family, handle->table);
 221 }
 222
 223 void
 224 fw3_print_default_head_rules(struct fw3_ipt_handle *handle,
 225                              struct fw3_state *state, bool reload)
 226 {
 227         int i;
 228         struct fw3_defaults *defs = &state->defaults;
 229         struct fw3_device lodev = { .set = true };
 230         struct fw3_protocol tcp = { .protocol = 6 };
 231         struct fw3_ipt_rule *r;
 232
 233         const char *chains[] = {
 234                 "INPUT", "input",
 235                 "OUTPUT", "output",
 236                 "FORWARD", "forwarding",
 237         };
 238
 239         switch (handle->table)
 240         {
 241         case FW3_TABLE_FILTER:
 242
 243                 sprintf(lodev.name, "lo");
 244
 245                 r = fw3_ipt_rule_create(handle, NULL, &lodev, NULL, NULL, NULL);
 246                 fw3_ipt_rule_target(r, "ACCEPT");
 247                 fw3_ipt_rule_append(r, "INPUT");
 248
 249                 r = fw3_ipt_rule_create(handle, NULL, NULL, &lodev, NULL, NULL);
 250                 fw3_ipt_rule_target(r, "ACCEPT");
 251                 fw3_ipt_rule_append(r, "OUTPUT");
 252
 253                 if (defs->custom_chains)
 254                 {
 255                         for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 256                         {
 257                                 r = fw3_ipt_rule_new(handle);
 258                                 fw3_ipt_rule_comment(r, "Custom %s rule chain", chains[i+1]);
 259                                 fw3_ipt_rule_target(r, "%s_rule", chains[i+1]);
 260                                 fw3_ipt_rule_append(r, chains[i]);
 261                         }
 262                 }
 263
 264                 if (defs->flow_offloading)
 265                 {
 266                         r = fw3_ipt_rule_new(handle);
 267                         fw3_ipt_rule_comment(r, "Traffic offloading");
 268                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 269                         fw3_ipt_rule_target(r, "FLOWOFFLOAD");
 270                         if (defs->flow_offloading_hw)
 271                                 fw3_ipt_rule_addarg(r, false, "--hw", NULL);
 272                         fw3_ipt_rule_append(r, "FORWARD");
 273                 }
 274
 275                 for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 276                 {
 277                         r = fw3_ipt_rule_new(handle);
 278                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 279                         fw3_ipt_rule_target(r, "ACCEPT");
 280                         fw3_ipt_rule_append(r, chains[i]);
 281
 282                         if (defs->drop_invalid)
 283                         {
 284                                 r = fw3_ipt_rule_new(handle);
 285                                 fw3_ipt_rule_extra(r, "-m conntrack --ctstate INVALID");
 286                                 fw3_ipt_rule_target(r, "DROP");
 287                                 fw3_ipt_rule_append(r, chains[i]);
 288                         }
 289                 }
 290
 291                 if (defs->syn_flood)
 292                 {
 293                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 294                         fw3_ipt_rule_extra(r, "--syn");
 295                         fw3_ipt_rule_limit(r, &defs->syn_flood_rate);
 296                         fw3_ipt_rule_target(r, "RETURN");
 297                         fw3_ipt_rule_append(r, "syn_flood");
 298
 299                         r = fw3_ipt_rule_new(handle);
 300                         fw3_ipt_rule_target(r, "DROP");
 301                         fw3_ipt_rule_append(r, "syn_flood");
 302
 303                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 304                         fw3_ipt_rule_extra(r, "--syn");
 305                         fw3_ipt_rule_target(r, "syn_flood");
 306                         fw3_ipt_rule_append(r, "INPUT");
 307                 }
 308
 309                 r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 310                 fw3_ipt_rule_target(r, "REJECT");
 311                 fw3_ipt_rule_addarg(r, false, "--reject-with", get_reject_code(handle->family, defs->tcp_reject_code));
 312                 fw3_ipt_rule_append(r, "reject");
 313
 314                 r = fw3_ipt_rule_new(handle);
 315                 fw3_ipt_rule_target(r, "REJECT");
 316                 fw3_ipt_rule_addarg(r, false, "--reject-with", get_reject_code(handle->family, defs->any_reject_code));
 317                 fw3_ipt_rule_append(r, "reject");
 318
 319                 break;
 320
 321         case FW3_TABLE_NAT:
 322                 if (defs->custom_chains)
 323                 {
 324                         r = fw3_ipt_rule_new(handle);
 325                         fw3_ipt_rule_comment(r, "Custom prerouting rule chain");
 326                         fw3_ipt_rule_target(r, "prerouting_rule");
 327                         fw3_ipt_rule_append(r, "PREROUTING");
 328
 329                         r = fw3_ipt_rule_new(handle);
 330                         fw3_ipt_rule_comment(r, "Custom postrouting rule chain");
 331                         fw3_ipt_rule_target(r, "postrouting_rule");
 332                         fw3_ipt_rule_append(r, "POSTROUTING");
 333                 }
 334                 break;
 335
 336         default:
 337                 break;
 338         }
 339 }
 340
 341 void
 342 fw3_print_default_tail_rules(struct fw3_ipt_handle *handle,
 343                              struct fw3_state *state, bool reload)
 344 {
 345         struct fw3_defaults *defs = &state->defaults;
 346         struct fw3_ipt_rule *r;
 347
 348         if (handle->table != FW3_TABLE_FILTER)
 349                 return;
 350
 351         if (defs->policy_input == FW3_FLAG_REJECT)
 352         {
 353                 r = fw3_ipt_rule_new(handle);
 354
 355                 if (!r)
 356                         return;
 357
 358                 fw3_ipt_rule_target(r, "reject");
 359                 fw3_ipt_rule_append(r, "INPUT");
 360         }
 361
 362         if (defs->policy_output == FW3_FLAG_REJECT)
 363         {
 364                 r = fw3_ipt_rule_new(handle);
 365
 366                 if (!r)
 367                         return;
 368
 369                 fw3_ipt_rule_target(r, "reject");
 370                 fw3_ipt_rule_append(r, "OUTPUT");
 371         }
 372
 373         if (defs->policy_forward == FW3_FLAG_REJECT)
 374         {
 375                 r = fw3_ipt_rule_new(handle);
 376
 377                 if (!r)
 378                         return;
 379
 380                 fw3_ipt_rule_target(r, "reject");
 381                 fw3_ipt_rule_append(r, "FORWARD");
 382         }
 383 }
 384
 385 static void
 386 set_default(const char *name, int set)
 387 {
 388         FILE *f;
 389         char path[sizeof("/proc/sys/net/ipv4/tcp_window_scaling\0")];
 390
 391         snprintf(path, sizeof(path), "/proc/sys/net/ipv4/tcp_%s", name);
 392
 393         info(" * Set tcp_%s to %s", name, set ? "on" : "off", name);
 394
 395         if (!(f = fopen(path, "w")))
 396         {
 397                 info("   ! Unable to write value: %s", strerror(errno));
 398                 return;
 399         }
 400
 401         fprintf(f, "%u\n", set);
 402         fclose(f);
 403 }
 404
 405 void
 406 fw3_set_defaults(struct fw3_state *state)
 407 {
 408         set_default("ecn",            state->defaults.tcp_ecn);
 409         set_default("syncookies",     state->defaults.tcp_syncookies);
 410         set_default("window_scaling", state->defaults.tcp_window_scaling);
 411 }
 412
 413 void
 414 fw3_flush_rules(struct fw3_ipt_handle *handle, struct fw3_state *state,
 415                 bool reload)
 416 {
 417         enum fw3_flag policy = reload ? FW3_FLAG_DROP : FW3_FLAG_ACCEPT;
 418         struct fw3_defaults *defs = &state->defaults;
 419         const struct fw3_chain_spec *c;
 420
 421         if (!has(defs->flags, handle->family, handle->table))
 422                 return;
 423
 424         if (handle->table == FW3_TABLE_FILTER)
 425         {
 426                 fw3_ipt_set_policy(handle, "INPUT",   policy);
 427                 fw3_ipt_set_policy(handle, "OUTPUT",  policy);
 428                 fw3_ipt_set_policy(handle, "FORWARD", policy);
 429         }
 430
 431         fw3_ipt_delete_id_rules(handle, "INPUT");
 432         fw3_ipt_delete_id_rules(handle, "OUTPUT");
 433         fw3_ipt_delete_id_rules(handle, "FORWARD");
 434         fw3_ipt_delete_id_rules(handle, "PREROUTING");
 435         fw3_ipt_delete_id_rules(handle, "POSTROUTING");
 436
 437         for (c = default_chains; c->format; c++)
 438         {
 439                 /* don't touch user chains on selective stop */
 440                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 441                         continue;
 442
 443                 if (!fw3_is_family(c, handle->family))
 444                         continue;
 445
 446                 if (c->table != handle->table)
 447                         continue;
 448
 449                 if (c->flag && !has(defs->flags, handle->family, c->flag))
 450                         continue;
 451
 452                 fw3_ipt_flush_chain(handle, c->format);
 453
 454                 /* keep certain basic chains that do not depend on any settings to
 455                    avoid purging unrelated user rules pointing to them */
 456                 if (reload && !c->flag)
 457                         continue;
 458
 459                 fw3_ipt_delete_chain(handle, c->format);
 460         }
 461
 462         del(defs->flags, handle->family, handle->table);
 463 }
 464
 465 void
 466 fw3_flush_all(struct fw3_ipt_handle *handle)
 467 {
 468         if (handle->table == FW3_TABLE_FILTER)
 469         {
 470                 fw3_ipt_set_policy(handle, "INPUT",   FW3_FLAG_ACCEPT);
 471                 fw3_ipt_set_policy(handle, "OUTPUT",  FW3_FLAG_ACCEPT);
 472                 fw3_ipt_set_policy(handle, "FORWARD", FW3_FLAG_ACCEPT);
 473         }
 474
 475         fw3_ipt_flush(handle);
 476 }