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
  45         FW3_OPT("syn_flood",           bool,     defaults, syn_flood),
  46         FW3_OPT("synflood_protect",    bool,     defaults, syn_flood),
  47         FW3_OPT("synflood_rate",       limit,    defaults, syn_flood_rate),
  48         FW3_OPT("synflood_burst",      int,      defaults, syn_flood_rate.burst),
  49
  50         FW3_OPT("tcp_syncookies",      bool,     defaults, tcp_syncookies),
  51         FW3_OPT("tcp_ecn",             int,      defaults, tcp_ecn),
  52         FW3_OPT("tcp_window_scaling",  bool,     defaults, tcp_window_scaling),
  53
  54         FW3_OPT("accept_redirects",    bool,     defaults, accept_redirects),
  55         FW3_OPT("accept_source_route", bool,     defaults, accept_source_route),
  56
  57         FW3_OPT("auto_helper",         bool,     defaults, auto_helper),
  58         FW3_OPT("custom_chains",       bool,     defaults, custom_chains),
  59         FW3_OPT("disable_ipv6",        bool,     defaults, disable_ipv6),
  60         FW3_OPT("flow_offloading",     bool,     defaults, flow_offloading),
  61
  62         FW3_OPT("__flags_v4",          int,      defaults, flags[0]),
  63         FW3_OPT("__flags_v6",          int,      defaults, flags[1]),
  64
  65         { }
  66 };
  67
  68
  69 static void
  70 check_policy(struct uci_element *e, enum fw3_flag *pol, const char *name)
  71 {
  72         if (*pol == FW3_FLAG_UNSPEC)
  73         {
  74                 warn_elem(e, "has no %s policy specified, defaulting to DROP", name);
  75                 *pol = FW3_FLAG_DROP;
  76         }
  77         else if (*pol > FW3_FLAG_DROP)
  78         {
  79                 warn_elem(e, "has invalid %s policy, defaulting to DROP", name);
  80                 *pol = FW3_FLAG_DROP;
  81         }
  82 }
  83
  84 static void
  85 check_offloading(struct uci_element *e, bool *offloading)
  86 {
  87         FILE *f;
  88
  89         if (!*offloading)
  90                 return;
  91
  92         f = fopen("/sys/module/xt_FLOWOFFLOAD/refcnt", "r");
  93
  94         if (f)
  95         {
  96                 fclose(f);
  97                 return;
  98         }
  99
 100         warn_elem(e, "enables offloading but missing kernel support, disabling");
 101         *offloading = false;
 102 }
 103
 104 void
 105 fw3_load_defaults(struct fw3_state *state, struct uci_package *p)
 106 {
 107         struct uci_section *s;
 108         struct uci_element *e;
 109         struct fw3_defaults *defs = &state->defaults;
 110
 111         bool seen = false;
 112
 113         defs->syn_flood_rate.rate  = 25;
 114         defs->syn_flood_rate.burst = 50;
 115         defs->tcp_syncookies       = true;
 116         defs->tcp_window_scaling   = true;
 117         defs->custom_chains        = true;
 118         defs->auto_helper          = true;
 119
 120         uci_foreach_element(&p->sections, e)
 121         {
 122                 s = uci_to_section(e);
 123
 124                 if (strcmp(s->type, "defaults"))
 125                         continue;
 126
 127                 if (seen)
 128                 {
 129                         warn_elem(e, "ignoring duplicate section");
 130                         continue;
 131                 }
 132
 133                 if(!fw3_parse_options(&state->defaults, fw3_flag_opts, s))
 134                         warn_elem(e, "has invalid options");
 135
 136                 check_policy(e, &defs->policy_input, "input");
 137                 check_policy(e, &defs->policy_output, "output");
 138                 check_policy(e, &defs->policy_forward, "forward");
 139
 140                 check_offloading(e, &defs->flow_offloading);
 141         }
 142 }
 143
 144 void
 145 fw3_print_default_chains(struct fw3_ipt_handle *handle, struct fw3_state *state,
 146                          bool reload)
 147 {
 148         struct fw3_defaults *defs = &state->defaults;
 149         const struct fw3_chain_spec *c;
 150
 151 #define policy(t) \
 152         ((t == FW3_FLAG_REJECT) ? FW3_FLAG_DROP : t)
 153
 154         if (handle->family == FW3_FAMILY_V6 && defs->disable_ipv6)
 155                 return;
 156
 157         if (handle->table == FW3_TABLE_FILTER)
 158         {
 159                 fw3_ipt_set_policy(handle, "INPUT",   policy(defs->policy_input));
 160                 fw3_ipt_set_policy(handle, "OUTPUT",  policy(defs->policy_output));
 161                 fw3_ipt_set_policy(handle, "FORWARD", policy(defs->policy_forward));
 162         }
 163
 164         if (defs->custom_chains)
 165                 set(defs->flags, handle->family, FW3_FLAG_CUSTOM_CHAINS);
 166
 167         if (defs->syn_flood)
 168                 set(defs->flags, handle->family, FW3_FLAG_SYN_FLOOD);
 169
 170         for (c = default_chains; c->format; c++)
 171         {
 172                 /* don't touch user chains on selective stop */
 173                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 174                         continue;
 175
 176                 if (!fw3_is_family(c, handle->family))
 177                         continue;
 178
 179                 if (c->table != handle->table)
 180                         continue;
 181
 182                 if (c->flag &&
 183                     !fw3_hasbit(defs->flags[handle->family == FW3_FAMILY_V6], c->flag))
 184                         continue;
 185
 186                 fw3_ipt_create_chain(handle, c->format);
 187         }
 188
 189         set(defs->flags, handle->family, handle->table);
 190 }
 191
 192 void
 193 fw3_print_default_head_rules(struct fw3_ipt_handle *handle,
 194                              struct fw3_state *state, bool reload)
 195 {
 196         int i;
 197         struct fw3_defaults *defs = &state->defaults;
 198         struct fw3_device lodev = { .set = true };
 199         struct fw3_protocol tcp = { .protocol = 6 };
 200         struct fw3_ipt_rule *r;
 201
 202         const char *chains[] = {
 203                 "INPUT", "input",
 204                 "OUTPUT", "output",
 205                 "FORWARD", "forwarding",
 206         };
 207
 208         switch (handle->table)
 209         {
 210         case FW3_TABLE_FILTER:
 211
 212                 sprintf(lodev.name, "lo");
 213
 214                 r = fw3_ipt_rule_create(handle, NULL, &lodev, NULL, NULL, NULL);
 215                 fw3_ipt_rule_target(r, "ACCEPT");
 216                 fw3_ipt_rule_append(r, "INPUT");
 217
 218                 r = fw3_ipt_rule_create(handle, NULL, NULL, &lodev, NULL, NULL);
 219                 fw3_ipt_rule_target(r, "ACCEPT");
 220                 fw3_ipt_rule_append(r, "OUTPUT");
 221
 222                 if (defs->custom_chains)
 223                 {
 224                         for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 225                         {
 226                                 r = fw3_ipt_rule_new(handle);
 227                                 fw3_ipt_rule_comment(r, "Custom %s rule chain", chains[i+1]);
 228                                 fw3_ipt_rule_target(r, "%s_rule", chains[i+1]);
 229                                 fw3_ipt_rule_append(r, chains[i]);
 230                         }
 231                 }
 232
 233                 if (defs->flow_offloading)
 234                 {
 235                         r = fw3_ipt_rule_new(handle);
 236                         fw3_ipt_rule_comment(r, "Traffic offloading");
 237                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 238                         fw3_ipt_rule_target(r, "FLOWOFFLOAD");
 239                         fw3_ipt_rule_append(r, "FORWARD");
 240                 }
 241
 242                 for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 243                 {
 244                         r = fw3_ipt_rule_new(handle);
 245                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 246                         fw3_ipt_rule_target(r, "ACCEPT");
 247                         fw3_ipt_rule_append(r, chains[i]);
 248
 249                         if (defs->drop_invalid)
 250                         {
 251                                 r = fw3_ipt_rule_new(handle);
 252                                 fw3_ipt_rule_extra(r, "-m conntrack --ctstate INVALID");
 253                                 fw3_ipt_rule_target(r, "DROP");
 254                                 fw3_ipt_rule_append(r, chains[i]);
 255                         }
 256                 }
 257
 258                 if (defs->syn_flood)
 259                 {
 260                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 261                         fw3_ipt_rule_extra(r, "--syn");
 262                         fw3_ipt_rule_limit(r, &defs->syn_flood_rate);
 263                         fw3_ipt_rule_target(r, "RETURN");
 264                         fw3_ipt_rule_append(r, "syn_flood");
 265
 266                         r = fw3_ipt_rule_new(handle);
 267                         fw3_ipt_rule_target(r, "DROP");
 268                         fw3_ipt_rule_append(r, "syn_flood");
 269
 270                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 271                         fw3_ipt_rule_extra(r, "--syn");
 272                         fw3_ipt_rule_target(r, "syn_flood");
 273                         fw3_ipt_rule_append(r, "INPUT");
 274                 }
 275
 276                 r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 277                 fw3_ipt_rule_target(r, "REJECT");
 278                 fw3_ipt_rule_addarg(r, false, "--reject-with", "tcp-reset");
 279                 fw3_ipt_rule_append(r, "reject");
 280
 281                 r = fw3_ipt_rule_new(handle);
 282                 fw3_ipt_rule_target(r, "REJECT");
 283                 fw3_ipt_rule_addarg(r, false, "--reject-with", "port-unreach");
 284                 fw3_ipt_rule_append(r, "reject");
 285
 286                 break;
 287
 288         case FW3_TABLE_NAT:
 289                 if (defs->custom_chains)
 290                 {
 291                         r = fw3_ipt_rule_new(handle);
 292                         fw3_ipt_rule_comment(r, "Custom prerouting rule chain");
 293                         fw3_ipt_rule_target(r, "prerouting_rule");
 294                         fw3_ipt_rule_append(r, "PREROUTING");
 295
 296                         r = fw3_ipt_rule_new(handle);
 297                         fw3_ipt_rule_comment(r, "Custom postrouting rule chain");
 298                         fw3_ipt_rule_target(r, "postrouting_rule");
 299                         fw3_ipt_rule_append(r, "POSTROUTING");
 300                 }
 301                 break;
 302
 303         default:
 304                 break;
 305         }
 306 }
 307
 308 void
 309 fw3_print_default_tail_rules(struct fw3_ipt_handle *handle,
 310                              struct fw3_state *state, bool reload)
 311 {
 312         struct fw3_defaults *defs = &state->defaults;
 313         struct fw3_ipt_rule *r;
 314
 315         if (handle->table != FW3_TABLE_FILTER)
 316                 return;
 317
 318         if (defs->policy_input == FW3_FLAG_REJECT)
 319         {
 320                 r = fw3_ipt_rule_new(handle);
 321
 322                 if (!r)
 323                         return;
 324
 325                 fw3_ipt_rule_target(r, "reject");
 326                 fw3_ipt_rule_append(r, "INPUT");
 327         }
 328
 329         if (defs->policy_output == FW3_FLAG_REJECT)
 330         {
 331                 r = fw3_ipt_rule_new(handle);
 332
 333                 if (!r)
 334                         return;
 335
 336                 fw3_ipt_rule_target(r, "reject");
 337                 fw3_ipt_rule_append(r, "OUTPUT");
 338         }
 339
 340         if (defs->policy_forward == FW3_FLAG_REJECT)
 341         {
 342                 r = fw3_ipt_rule_new(handle);
 343
 344                 if (!r)
 345                         return;
 346
 347                 fw3_ipt_rule_target(r, "reject");
 348                 fw3_ipt_rule_append(r, "FORWARD");
 349         }
 350 }
 351
 352 static void
 353 set_default(const char *name, int set)
 354 {
 355         FILE *f;
 356         char path[sizeof("/proc/sys/net/ipv4/tcp_window_scaling\0")];
 357
 358         snprintf(path, sizeof(path), "/proc/sys/net/ipv4/tcp_%s", name);
 359
 360         info(" * Set tcp_%s to %s", name, set ? "on" : "off", name);
 361
 362         if (!(f = fopen(path, "w")))
 363         {
 364                 info("   ! Unable to write value: %s", strerror(errno));
 365                 return;
 366         }
 367
 368         fprintf(f, "%u\n", set);
 369         fclose(f);
 370 }
 371
 372 void
 373 fw3_set_defaults(struct fw3_state *state)
 374 {
 375         set_default("ecn",            state->defaults.tcp_ecn);
 376         set_default("syncookies",     state->defaults.tcp_syncookies);
 377         set_default("window_scaling", state->defaults.tcp_window_scaling);
 378 }
 379
 380 void
 381 fw3_flush_rules(struct fw3_ipt_handle *handle, struct fw3_state *state,
 382                 bool reload)
 383 {
 384         enum fw3_flag policy = reload ? FW3_FLAG_DROP : FW3_FLAG_ACCEPT;
 385         struct fw3_defaults *defs = &state->defaults;
 386         const struct fw3_chain_spec *c;
 387
 388         if (!has(defs->flags, handle->family, handle->table))
 389                 return;
 390
 391         if (handle->table == FW3_TABLE_FILTER)
 392         {
 393                 fw3_ipt_set_policy(handle, "INPUT",   policy);
 394                 fw3_ipt_set_policy(handle, "OUTPUT",  policy);
 395                 fw3_ipt_set_policy(handle, "FORWARD", policy);
 396         }
 397
 398         fw3_ipt_delete_id_rules(handle, "INPUT");
 399         fw3_ipt_delete_id_rules(handle, "OUTPUT");
 400         fw3_ipt_delete_id_rules(handle, "FORWARD");
 401         fw3_ipt_delete_id_rules(handle, "PREROUTING");
 402         fw3_ipt_delete_id_rules(handle, "POSTROUTING");
 403
 404         for (c = default_chains; c->format; c++)
 405         {
 406                 /* don't touch user chains on selective stop */
 407                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 408                         continue;
 409
 410                 if (!fw3_is_family(c, handle->family))
 411                         continue;
 412
 413                 if (c->table != handle->table)
 414                         continue;
 415
 416                 if (c->flag && !has(defs->flags, handle->family, c->flag))
 417                         continue;
 418
 419                 fw3_ipt_flush_chain(handle, c->format);
 420
 421                 /* keep certain basic chains that do not depend on any settings to
 422                    avoid purging unrelated user rules pointing to them */
 423                 if (reload && !c->flag)
 424                         continue;
 425
 426                 fw3_ipt_delete_chain(handle, c->format);
 427         }
 428
 429         del(defs->flags, handle->family, handle->table);
 430 }
 431
 432 void
 433 fw3_flush_all(struct fw3_ipt_handle *handle)
 434 {
 435         if (handle->table == FW3_TABLE_FILTER)
 436         {
 437                 fw3_ipt_set_policy(handle, "INPUT",   FW3_FLAG_ACCEPT);
 438                 fw3_ipt_set_policy(handle, "OUTPUT",  FW3_FLAG_ACCEPT);
 439                 fw3_ipt_set_policy(handle, "FORWARD", FW3_FLAG_ACCEPT);
 440         }
 441
 442         fw3_ipt_flush(handle);
 443 }