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                 *available = false;
  95         }
  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 seen = false;
 130
 131         defs->tcp_reject_code      = FW3_REJECT_CODE_TCP_RESET;
 132         defs->any_reject_code      = FW3_REJECT_CODE_PORT_UNREACH;
 133         defs->syn_flood_rate.rate  = 25;
 134         defs->syn_flood_rate.burst = 50;
 135         defs->tcp_syncookies       = true;
 136         defs->tcp_window_scaling   = true;
 137         defs->custom_chains        = true;
 138         defs->auto_helper          = true;
 139
 140         uci_foreach_element(&p->sections, e)
 141         {
 142                 s = uci_to_section(e);
 143
 144                 if (strcmp(s->type, "defaults"))
 145                         continue;
 146
 147                 if (seen)
 148                 {
 149                         warn_elem(e, "ignoring duplicate section");
 150                         continue;
 151                 }
 152
 153                 seen = true;
 154
 155                 if(!fw3_parse_options(&state->defaults, fw3_flag_opts, s))
 156                         warn_elem(e, "has invalid options");
 157
 158                 check_policy(e, &defs->policy_input, "input");
 159                 check_policy(e, &defs->policy_output, "output");
 160                 check_policy(e, &defs->policy_forward, "forward");
 161
 162                 check_any_reject_code(e, &defs->any_reject_code);
 163
 164                 /* exists in both ipv4 and ipv6, if at all, so only check ipv4 */
 165                 check_target(e, &defs->flow_offloading, "FLOWOFFLOAD", false);
 166         }
 167 }
 168
 169 void
 170 fw3_print_default_chains(struct fw3_ipt_handle *handle, struct fw3_state *state,
 171                          bool reload)
 172 {
 173         struct fw3_defaults *defs = &state->defaults;
 174         const struct fw3_chain_spec *c;
 175
 176 #define policy(t) \
 177         ((t == FW3_FLAG_REJECT) ? FW3_FLAG_DROP : t)
 178
 179         if (handle->family == FW3_FAMILY_V6 && defs->disable_ipv6)
 180                 return;
 181
 182         if (handle->table == FW3_TABLE_FILTER)
 183         {
 184                 fw3_ipt_set_policy(handle, "INPUT",   policy(defs->policy_input));
 185                 fw3_ipt_set_policy(handle, "OUTPUT",  policy(defs->policy_output));
 186                 fw3_ipt_set_policy(handle, "FORWARD", policy(defs->policy_forward));
 187         }
 188
 189         if (defs->custom_chains)
 190                 set(defs->flags, handle->family, FW3_FLAG_CUSTOM_CHAINS);
 191
 192         if (defs->syn_flood)
 193                 set(defs->flags, handle->family, FW3_FLAG_SYN_FLOOD);
 194
 195         for (c = default_chains; c->format; c++)
 196         {
 197                 if (!fw3_is_family(c, handle->family))
 198                         continue;
 199
 200                 if (c->table != handle->table)
 201                         continue;
 202
 203                 if (c->flag &&
 204                     !fw3_hasbit(defs->flags[handle->family == FW3_FAMILY_V6], c->flag))
 205                         continue;
 206
 207                 fw3_ipt_create_chain(handle, reload, c->format);
 208         }
 209
 210         set(defs->flags, handle->family, handle->table);
 211 }
 212
 213 void
 214 fw3_print_default_head_rules(struct fw3_ipt_handle *handle,
 215                              struct fw3_state *state, bool reload)
 216 {
 217         int i;
 218         struct fw3_defaults *defs = &state->defaults;
 219         struct fw3_device lodev = { .set = true, .name = "lo" };
 220         struct fw3_protocol tcp = { .protocol = 6 };
 221         struct fw3_ipt_rule *r;
 222
 223         const char *chains[] = {
 224                 "INPUT", "input",
 225                 "OUTPUT", "output",
 226                 "FORWARD", "forwarding",
 227         };
 228
 229         switch (handle->table)
 230         {
 231         case FW3_TABLE_FILTER:
 232
 233                 r = fw3_ipt_rule_create(handle, NULL, &lodev, NULL, NULL, NULL);
 234                 fw3_ipt_rule_target(r, "ACCEPT");
 235                 fw3_ipt_rule_append(r, "INPUT");
 236
 237                 r = fw3_ipt_rule_create(handle, NULL, NULL, &lodev, NULL, NULL);
 238                 fw3_ipt_rule_target(r, "ACCEPT");
 239                 fw3_ipt_rule_append(r, "OUTPUT");
 240
 241                 if (defs->custom_chains)
 242                 {
 243                         for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 244                         {
 245                                 r = fw3_ipt_rule_new(handle);
 246                                 fw3_ipt_rule_comment(r, "Custom %s rule chain", chains[i+1]);
 247                                 fw3_ipt_rule_target(r, "%s_rule", chains[i+1]);
 248                                 fw3_ipt_rule_append(r, chains[i]);
 249                         }
 250                 }
 251
 252                 if (defs->flow_offloading)
 253                 {
 254                         r = fw3_ipt_rule_new(handle);
 255                         fw3_ipt_rule_comment(r, "Traffic offloading");
 256                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 257                         fw3_ipt_rule_target(r, "FLOWOFFLOAD");
 258                         if (defs->flow_offloading_hw)
 259                                 fw3_ipt_rule_addarg(r, false, "--hw", NULL);
 260                         fw3_ipt_rule_append(r, "FORWARD");
 261                 }
 262
 263                 for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 264                 {
 265                         r = fw3_ipt_rule_new(handle);
 266                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 267                         fw3_ipt_rule_target(r, "ACCEPT");
 268                         fw3_ipt_rule_append(r, chains[i]);
 269
 270                         if (defs->drop_invalid)
 271                         {
 272                                 r = fw3_ipt_rule_new(handle);
 273                                 fw3_ipt_rule_extra(r, "-m conntrack --ctstate INVALID");
 274                                 fw3_ipt_rule_target(r, "DROP");
 275                                 fw3_ipt_rule_append(r, chains[i]);
 276                         }
 277                 }
 278
 279                 if (defs->syn_flood)
 280                 {
 281                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 282                         fw3_ipt_rule_extra(r, "--syn");
 283                         fw3_ipt_rule_limit(r, &defs->syn_flood_rate);
 284                         fw3_ipt_rule_target(r, "RETURN");
 285                         fw3_ipt_rule_append(r, "syn_flood");
 286
 287                         r = fw3_ipt_rule_new(handle);
 288                         fw3_ipt_rule_target(r, "DROP");
 289                         fw3_ipt_rule_append(r, "syn_flood");
 290
 291                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 292                         fw3_ipt_rule_extra(r, "--syn");
 293                         fw3_ipt_rule_target(r, "syn_flood");
 294                         fw3_ipt_rule_append(r, "INPUT");
 295                 }
 296
 297                 r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 298                 fw3_ipt_rule_target(r, "REJECT");
 299                 fw3_ipt_rule_addarg(r, false, "--reject-with", get_reject_code(handle->family, defs->tcp_reject_code));
 300                 fw3_ipt_rule_append(r, "reject");
 301
 302                 r = fw3_ipt_rule_new(handle);
 303                 fw3_ipt_rule_target(r, "REJECT");
 304                 fw3_ipt_rule_addarg(r, false, "--reject-with", get_reject_code(handle->family, defs->any_reject_code));
 305                 fw3_ipt_rule_append(r, "reject");
 306
 307                 break;
 308
 309         case FW3_TABLE_NAT:
 310                 if (defs->custom_chains)
 311                 {
 312                         r = fw3_ipt_rule_new(handle);
 313                         fw3_ipt_rule_comment(r, "Custom prerouting rule chain");
 314                         fw3_ipt_rule_target(r, "prerouting_rule");
 315                         fw3_ipt_rule_append(r, "PREROUTING");
 316
 317                         r = fw3_ipt_rule_new(handle);
 318                         fw3_ipt_rule_comment(r, "Custom postrouting rule chain");
 319                         fw3_ipt_rule_target(r, "postrouting_rule");
 320                         fw3_ipt_rule_append(r, "POSTROUTING");
 321                 }
 322                 break;
 323
 324         default:
 325                 break;
 326         }
 327 }
 328
 329 void
 330 fw3_print_default_tail_rules(struct fw3_ipt_handle *handle,
 331                              struct fw3_state *state, bool reload)
 332 {
 333         struct fw3_defaults *defs = &state->defaults;
 334         struct fw3_ipt_rule *r;
 335
 336         if (handle->table != FW3_TABLE_FILTER)
 337                 return;
 338
 339         if (defs->policy_input == FW3_FLAG_REJECT)
 340         {
 341                 r = fw3_ipt_rule_new(handle);
 342
 343                 if (!r)
 344                         return;
 345
 346                 fw3_ipt_rule_target(r, "reject");
 347                 fw3_ipt_rule_append(r, "INPUT");
 348         }
 349
 350         if (defs->policy_output == FW3_FLAG_REJECT)
 351         {
 352                 r = fw3_ipt_rule_new(handle);
 353
 354                 if (!r)
 355                         return;
 356
 357                 fw3_ipt_rule_target(r, "reject");
 358                 fw3_ipt_rule_append(r, "OUTPUT");
 359         }
 360
 361         if (defs->policy_forward == FW3_FLAG_REJECT)
 362         {
 363                 r = fw3_ipt_rule_new(handle);
 364
 365                 if (!r)
 366                         return;
 367
 368                 fw3_ipt_rule_target(r, "reject");
 369                 fw3_ipt_rule_append(r, "FORWARD");
 370         }
 371 }
 372
 373 static void
 374 set_default(const char *name, int set)
 375 {
 376         FILE *f;
 377         char path[sizeof("/proc/sys/net/ipv4/tcp_window_scaling")];
 378
 379         snprintf(path, sizeof(path), "/proc/sys/net/ipv4/tcp_%s", name);
 380
 381         info(" * Set tcp_%s to %s", name, set ? "on" : "off");
 382
 383         if (!(f = fopen(path, "w")))
 384         {
 385                 info("   ! Unable to write value: %s", strerror(errno));
 386                 return;
 387         }
 388
 389         fprintf(f, "%u\n", set);
 390         fclose(f);
 391 }
 392
 393 void
 394 fw3_set_defaults(struct fw3_state *state)
 395 {
 396         set_default("ecn",            state->defaults.tcp_ecn);
 397         set_default("syncookies",     state->defaults.tcp_syncookies);
 398         set_default("window_scaling", state->defaults.tcp_window_scaling);
 399 }
 400
 401 void
 402 fw3_flush_rules(struct fw3_ipt_handle *handle, struct fw3_state *state,
 403                 bool reload)
 404 {
 405         enum fw3_flag policy = reload ? FW3_FLAG_DROP : FW3_FLAG_ACCEPT;
 406         struct fw3_defaults *defs = &state->defaults;
 407         const struct fw3_chain_spec *c;
 408
 409         if (!has(defs->flags, handle->family, handle->table))
 410                 return;
 411
 412         if (handle->table == FW3_TABLE_FILTER)
 413         {
 414                 fw3_ipt_set_policy(handle, "INPUT",   policy);
 415                 fw3_ipt_set_policy(handle, "OUTPUT",  policy);
 416                 fw3_ipt_set_policy(handle, "FORWARD", policy);
 417         }
 418
 419         fw3_ipt_delete_id_rules(handle, "INPUT");
 420         fw3_ipt_delete_id_rules(handle, "OUTPUT");
 421         fw3_ipt_delete_id_rules(handle, "FORWARD");
 422         fw3_ipt_delete_id_rules(handle, "PREROUTING");
 423         fw3_ipt_delete_id_rules(handle, "POSTROUTING");
 424
 425         /* first flush all the rules ... */
 426         for (c = default_chains; c->format; c++)
 427         {
 428                 /* don't touch user chains on selective stop */
 429                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 430                         continue;
 431
 432                 if (!fw3_is_family(c, handle->family))
 433                         continue;
 434
 435                 if (c->table != handle->table)
 436                         continue;
 437
 438                 if (c->flag && !has(defs->flags, handle->family, c->flag))
 439                         continue;
 440
 441                 fw3_ipt_flush_chain(handle, c->format);
 442         }
 443
 444         /* ... then remove the chains */
 445         for (c = default_chains; c->format; c++)
 446         {
 447                 if (!fw3_is_family(c, handle->family))
 448                         continue;
 449
 450                 if (c->table != handle->table)
 451                         continue;
 452
 453                 if (c->flag && !has(defs->flags, handle->family, c->flag))
 454                         continue;
 455
 456                 fw3_ipt_delete_chain(handle, reload, c->format);
 457         }
 458
 459         del(defs->flags, handle->family, handle->table);
 460 }
 461
 462 void
 463 fw3_flush_all(struct fw3_ipt_handle *handle)
 464 {
 465         if (handle->table == FW3_TABLE_FILTER)
 466         {
 467                 fw3_ipt_set_policy(handle, "INPUT",   FW3_FLAG_ACCEPT);
 468                 fw3_ipt_set_policy(handle, "OUTPUT",  FW3_FLAG_ACCEPT);
 469                 fw3_ipt_set_policy(handle, "FORWARD", FW3_FLAG_ACCEPT);
 470         }
 471
 472         fw3_ipt_flush(handle);
 473 }