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