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_kmod(struct uci_element *e, bool *module, const char *name)
  89 {
  90         FILE *f;
  91         char buf[128];
  92
  93         if (!*module)
  94                 return;
  95
  96         snprintf(buf, sizeof(buf), "/sys/module/%s/refcnt", name);
  97
  98         f = fopen(buf, "r");
  99
 100         if (f)
 101         {
 102                 fclose(f);
 103                 return;
 104         }
 105
 106         warn_elem(e, sprintf("requires module %s but missing kernel support, disabling", name));
 107         *module = false;
 108 }
 109
 110 static void
 111 check_any_reject_code(struct uci_element *e, enum fw3_reject_code *any_reject_code)
 112 {
 113         if (*any_reject_code == FW3_REJECT_CODE_TCP_RESET) {
 114                 warn_elem(e, "tcp-reset not valid for any_reject_code, defaulting to port-unreach");
 115                 *any_reject_code = FW3_REJECT_CODE_PORT_UNREACH;
 116         }
 117 }
 118
 119 static const char*
 120 get_reject_code(enum fw3_family family, enum fw3_reject_code reject_code)
 121 {
 122         switch (reject_code) {
 123         case FW3_REJECT_CODE_TCP_RESET:
 124                 return "tcp-reset";
 125         case FW3_REJECT_CODE_PORT_UNREACH:
 126                 return "port-unreach";
 127         case FW3_REJECT_CODE_ADM_PROHIBITED:
 128                 return family == FW3_FAMILY_V6 ? "adm-prohibited": "admin-prohib";
 129         default:
 130                 return "unknown";
 131         }
 132 }
 133
 134 void
 135 fw3_load_defaults(struct fw3_state *state, struct uci_package *p)
 136 {
 137         struct uci_section *s;
 138         struct uci_element *e;
 139         struct fw3_defaults *defs = &state->defaults;
 140
 141         bool seen = false;
 142
 143         defs->tcp_reject_code      = FW3_REJECT_CODE_TCP_RESET;
 144         defs->any_reject_code      = FW3_REJECT_CODE_PORT_UNREACH;
 145         defs->syn_flood_rate.rate  = 25;
 146         defs->syn_flood_rate.burst = 50;
 147         defs->tcp_syncookies       = true;
 148         defs->tcp_window_scaling   = true;
 149         defs->custom_chains        = true;
 150         defs->auto_helper          = true;
 151
 152         uci_foreach_element(&p->sections, e)
 153         {
 154                 s = uci_to_section(e);
 155
 156                 if (strcmp(s->type, "defaults"))
 157                         continue;
 158
 159                 if (seen)
 160                 {
 161                         warn_elem(e, "ignoring duplicate section");
 162                         continue;
 163                 }
 164
 165                 if(!fw3_parse_options(&state->defaults, fw3_flag_opts, s))
 166                         warn_elem(e, "has invalid options");
 167
 168                 check_policy(e, &defs->policy_input, "input");
 169                 check_policy(e, &defs->policy_output, "output");
 170                 check_policy(e, &defs->policy_forward, "forward");
 171
 172                 check_any_reject_code(e, &defs->any_reject_code);
 173
 174                 check_kmod(e, &defs->flow_offloading, "xt_FLOWOFFLOAD");
 175         }
 176 }
 177
 178 void
 179 fw3_print_default_chains(struct fw3_ipt_handle *handle, struct fw3_state *state,
 180                          bool reload)
 181 {
 182         struct fw3_defaults *defs = &state->defaults;
 183         const struct fw3_chain_spec *c;
 184
 185 #define policy(t) \
 186         ((t == FW3_FLAG_REJECT) ? FW3_FLAG_DROP : t)
 187
 188         if (handle->family == FW3_FAMILY_V6 && defs->disable_ipv6)
 189                 return;
 190
 191         if (handle->table == FW3_TABLE_FILTER)
 192         {
 193                 fw3_ipt_set_policy(handle, "INPUT",   policy(defs->policy_input));
 194                 fw3_ipt_set_policy(handle, "OUTPUT",  policy(defs->policy_output));
 195                 fw3_ipt_set_policy(handle, "FORWARD", policy(defs->policy_forward));
 196         }
 197
 198         if (defs->custom_chains)
 199                 set(defs->flags, handle->family, FW3_FLAG_CUSTOM_CHAINS);
 200
 201         if (defs->syn_flood)
 202                 set(defs->flags, handle->family, FW3_FLAG_SYN_FLOOD);
 203
 204         for (c = default_chains; c->format; c++)
 205         {
 206                 /* don't touch user chains on selective stop */
 207                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 208                         continue;
 209
 210                 if (!fw3_is_family(c, handle->family))
 211                         continue;
 212
 213                 if (c->table != handle->table)
 214                         continue;
 215
 216                 if (c->flag &&
 217                     !fw3_hasbit(defs->flags[handle->family == FW3_FAMILY_V6], c->flag))
 218                         continue;
 219
 220                 fw3_ipt_create_chain(handle, c->format);
 221         }
 222
 223         set(defs->flags, handle->family, handle->table);
 224 }
 225
 226 void
 227 fw3_print_default_head_rules(struct fw3_ipt_handle *handle,
 228                              struct fw3_state *state, bool reload)
 229 {
 230         int i;
 231         struct fw3_defaults *defs = &state->defaults;
 232         struct fw3_device lodev = { .set = true };
 233         struct fw3_protocol tcp = { .protocol = 6 };
 234         struct fw3_ipt_rule *r;
 235
 236         const char *chains[] = {
 237                 "INPUT", "input",
 238                 "OUTPUT", "output",
 239                 "FORWARD", "forwarding",
 240         };
 241
 242         switch (handle->table)
 243         {
 244         case FW3_TABLE_FILTER:
 245
 246                 sprintf(lodev.name, "lo");
 247
 248                 r = fw3_ipt_rule_create(handle, NULL, &lodev, NULL, NULL, NULL);
 249                 fw3_ipt_rule_target(r, "ACCEPT");
 250                 fw3_ipt_rule_append(r, "INPUT");
 251
 252                 r = fw3_ipt_rule_create(handle, NULL, NULL, &lodev, NULL, NULL);
 253                 fw3_ipt_rule_target(r, "ACCEPT");
 254                 fw3_ipt_rule_append(r, "OUTPUT");
 255
 256                 if (defs->custom_chains)
 257                 {
 258                         for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 259                         {
 260                                 r = fw3_ipt_rule_new(handle);
 261                                 fw3_ipt_rule_comment(r, "Custom %s rule chain", chains[i+1]);
 262                                 fw3_ipt_rule_target(r, "%s_rule", chains[i+1]);
 263                                 fw3_ipt_rule_append(r, chains[i]);
 264                         }
 265                 }
 266
 267                 if (defs->flow_offloading)
 268                 {
 269                         r = fw3_ipt_rule_new(handle);
 270                         fw3_ipt_rule_comment(r, "Traffic offloading");
 271                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 272                         fw3_ipt_rule_target(r, "FLOWOFFLOAD");
 273                         if (defs->flow_offloading_hw)
 274                                 fw3_ipt_rule_addarg(r, false, "--hw", NULL);
 275                         fw3_ipt_rule_append(r, "FORWARD");
 276                 }
 277
 278                 for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 279                 {
 280                         r = fw3_ipt_rule_new(handle);
 281                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 282                         fw3_ipt_rule_target(r, "ACCEPT");
 283                         fw3_ipt_rule_append(r, chains[i]);
 284
 285                         if (defs->drop_invalid)
 286                         {
 287                                 r = fw3_ipt_rule_new(handle);
 288                                 fw3_ipt_rule_extra(r, "-m conntrack --ctstate INVALID");
 289                                 fw3_ipt_rule_target(r, "DROP");
 290                                 fw3_ipt_rule_append(r, chains[i]);
 291                         }
 292                 }
 293
 294                 if (defs->syn_flood)
 295                 {
 296                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 297                         fw3_ipt_rule_extra(r, "--syn");
 298                         fw3_ipt_rule_limit(r, &defs->syn_flood_rate);
 299                         fw3_ipt_rule_target(r, "RETURN");
 300                         fw3_ipt_rule_append(r, "syn_flood");
 301
 302                         r = fw3_ipt_rule_new(handle);
 303                         fw3_ipt_rule_target(r, "DROP");
 304                         fw3_ipt_rule_append(r, "syn_flood");
 305
 306                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 307                         fw3_ipt_rule_extra(r, "--syn");
 308                         fw3_ipt_rule_target(r, "syn_flood");
 309                         fw3_ipt_rule_append(r, "INPUT");
 310                 }
 311
 312                 r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 313                 fw3_ipt_rule_target(r, "REJECT");
 314                 fw3_ipt_rule_addarg(r, false, "--reject-with", get_reject_code(handle->family, defs->tcp_reject_code));
 315                 fw3_ipt_rule_append(r, "reject");
 316
 317                 r = fw3_ipt_rule_new(handle);
 318                 fw3_ipt_rule_target(r, "REJECT");
 319                 fw3_ipt_rule_addarg(r, false, "--reject-with", get_reject_code(handle->family, defs->any_reject_code));
 320                 fw3_ipt_rule_append(r, "reject");
 321
 322                 break;
 323
 324         case FW3_TABLE_NAT:
 325                 if (defs->custom_chains)
 326                 {
 327                         r = fw3_ipt_rule_new(handle);
 328                         fw3_ipt_rule_comment(r, "Custom prerouting rule chain");
 329                         fw3_ipt_rule_target(r, "prerouting_rule");
 330                         fw3_ipt_rule_append(r, "PREROUTING");
 331
 332                         r = fw3_ipt_rule_new(handle);
 333                         fw3_ipt_rule_comment(r, "Custom postrouting rule chain");
 334                         fw3_ipt_rule_target(r, "postrouting_rule");
 335                         fw3_ipt_rule_append(r, "POSTROUTING");
 336                 }
 337                 break;
 338
 339         default:
 340                 break;
 341         }
 342 }
 343
 344 void
 345 fw3_print_default_tail_rules(struct fw3_ipt_handle *handle,
 346                              struct fw3_state *state, bool reload)
 347 {
 348         struct fw3_defaults *defs = &state->defaults;
 349         struct fw3_ipt_rule *r;
 350
 351         if (handle->table != FW3_TABLE_FILTER)
 352                 return;
 353
 354         if (defs->policy_input == 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, "INPUT");
 363         }
 364
 365         if (defs->policy_output == 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, "OUTPUT");
 374         }
 375
 376         if (defs->policy_forward == FW3_FLAG_REJECT)
 377         {
 378                 r = fw3_ipt_rule_new(handle);
 379
 380                 if (!r)
 381                         return;
 382
 383                 fw3_ipt_rule_target(r, "reject");
 384                 fw3_ipt_rule_append(r, "FORWARD");
 385         }
 386 }
 387
 388 static void
 389 set_default(const char *name, int set)
 390 {
 391         FILE *f;
 392         char path[sizeof("/proc/sys/net/ipv4/tcp_window_scaling\0")];
 393
 394         snprintf(path, sizeof(path), "/proc/sys/net/ipv4/tcp_%s", name);
 395
 396         info(" * Set tcp_%s to %s", name, set ? "on" : "off", name);
 397
 398         if (!(f = fopen(path, "w")))
 399         {
 400                 info("   ! Unable to write value: %s", strerror(errno));
 401                 return;
 402         }
 403
 404         fprintf(f, "%u\n", set);
 405         fclose(f);
 406 }
 407
 408 void
 409 fw3_set_defaults(struct fw3_state *state)
 410 {
 411         set_default("ecn",            state->defaults.tcp_ecn);
 412         set_default("syncookies",     state->defaults.tcp_syncookies);
 413         set_default("window_scaling", state->defaults.tcp_window_scaling);
 414 }
 415
 416 void
 417 fw3_flush_rules(struct fw3_ipt_handle *handle, struct fw3_state *state,
 418                 bool reload)
 419 {
 420         enum fw3_flag policy = reload ? FW3_FLAG_DROP : FW3_FLAG_ACCEPT;
 421         struct fw3_defaults *defs = &state->defaults;
 422         const struct fw3_chain_spec *c;
 423
 424         if (!has(defs->flags, handle->family, handle->table))
 425                 return;
 426
 427         if (handle->table == FW3_TABLE_FILTER)
 428         {
 429                 fw3_ipt_set_policy(handle, "INPUT",   policy);
 430                 fw3_ipt_set_policy(handle, "OUTPUT",  policy);
 431                 fw3_ipt_set_policy(handle, "FORWARD", policy);
 432         }
 433
 434         fw3_ipt_delete_id_rules(handle, "INPUT");
 435         fw3_ipt_delete_id_rules(handle, "OUTPUT");
 436         fw3_ipt_delete_id_rules(handle, "FORWARD");
 437         fw3_ipt_delete_id_rules(handle, "PREROUTING");
 438         fw3_ipt_delete_id_rules(handle, "POSTROUTING");
 439
 440         for (c = default_chains; c->format; c++)
 441         {
 442                 /* don't touch user chains on selective stop */
 443                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 444                         continue;
 445
 446                 if (!fw3_is_family(c, handle->family))
 447                         continue;
 448
 449                 if (c->table != handle->table)
 450                         continue;
 451
 452                 if (c->flag && !has(defs->flags, handle->family, c->flag))
 453                         continue;
 454
 455                 fw3_ipt_flush_chain(handle, c->format);
 456
 457                 /* keep certain basic chains that do not depend on any settings to
 458                    avoid purging unrelated user rules pointing to them */
 459                 if (reload && !c->flag)
 460                         continue;
 461
 462                 fw3_ipt_delete_chain(handle, c->format);
 463         }
 464
 465         del(defs->flags, handle->family, handle->table);
 466 }
 467
 468 void
 469 fw3_flush_all(struct fw3_ipt_handle *handle)
 470 {
 471         if (handle->table == FW3_TABLE_FILTER)
 472         {
 473                 fw3_ipt_set_policy(handle, "INPUT",   FW3_FLAG_ACCEPT);
 474                 fw3_ipt_set_policy(handle, "OUTPUT",  FW3_FLAG_ACCEPT);
 475                 fw3_ipt_set_policy(handle, "FORWARD", FW3_FLAG_ACCEPT);
 476         }
 477
 478         fw3_ipt_flush(handle);
 479 }