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