defaults.c

   1 /*
   2  * firewall3 - 3rd OpenWrt UCI firewall implementation
   3  *
   4  *   Copyright (C) 2013 Jo-Philipp Wich <jow@openwrt.org>
   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("custom_chains",       bool,     defaults, custom_chains),
  58         FW3_OPT("disable_ipv6",        bool,     defaults, disable_ipv6),
  59
  60         FW3_OPT("__flags_v4",          int,      defaults, flags[0]),
  61         FW3_OPT("__flags_v6",          int,      defaults, flags[1]),
  62
  63         { }
  64 };
  65
  66
  67 static void
  68 check_policy(struct uci_element *e, enum fw3_flag *pol, const char *name)
  69 {
  70         if (*pol == FW3_FLAG_UNSPEC)
  71         {
  72                 warn_elem(e, "has no %s policy specified, defaulting to DROP", name);
  73                 *pol = FW3_FLAG_DROP;
  74         }
  75         else if (*pol > FW3_FLAG_DROP)
  76         {
  77                 warn_elem(e, "has invalid %s policy, defaulting to DROP", name);
  78                 *pol = FW3_FLAG_DROP;
  79         }
  80 }
  81
  82 void
  83 fw3_load_defaults(struct fw3_state *state, struct uci_package *p)
  84 {
  85         struct uci_section *s;
  86         struct uci_element *e;
  87         struct fw3_defaults *defs = &state->defaults;
  88
  89         bool seen = false;
  90
  91         defs->syn_flood_rate.rate  = 25;
  92         defs->syn_flood_rate.burst = 50;
  93         defs->tcp_syncookies       = true;
  94         defs->tcp_window_scaling   = true;
  95         defs->custom_chains        = true;
  96
  97         uci_foreach_element(&p->sections, e)
  98         {
  99                 s = uci_to_section(e);
 100
 101                 if (strcmp(s->type, "defaults"))
 102                         continue;
 103
 104                 if (seen)
 105                 {
 106                         warn_elem(e, "ignoring duplicate section");
 107                         continue;
 108                 }
 109
 110                 fw3_parse_options(&state->defaults, fw3_flag_opts, s);
 111
 112                 check_policy(e, &defs->policy_input, "input");
 113                 check_policy(e, &defs->policy_output, "output");
 114                 check_policy(e, &defs->policy_forward, "forward");
 115         }
 116 }
 117
 118 void
 119 fw3_print_default_chains(struct fw3_ipt_handle *handle, struct fw3_state *state,
 120                          bool reload)
 121 {
 122         struct fw3_defaults *defs = &state->defaults;
 123         const struct fw3_chain_spec *c;
 124
 125 #define policy(t) \
 126         ((t == FW3_FLAG_REJECT) ? FW3_FLAG_DROP : t)
 127
 128         if (handle->family == FW3_FAMILY_V6 && defs->disable_ipv6)
 129                 return;
 130
 131         if (handle->table == FW3_TABLE_FILTER)
 132         {
 133                 fw3_ipt_set_policy(handle, "INPUT",   policy(defs->policy_input));
 134                 fw3_ipt_set_policy(handle, "OUTPUT",  policy(defs->policy_output));
 135                 fw3_ipt_set_policy(handle, "FORWARD", policy(defs->policy_forward));
 136         }
 137
 138         if (defs->custom_chains)
 139                 set(defs->flags, handle->family, FW3_FLAG_CUSTOM_CHAINS);
 140
 141         if (defs->syn_flood)
 142                 set(defs->flags, handle->family, FW3_FLAG_SYN_FLOOD);
 143
 144         for (c = default_chains; c->format; c++)
 145         {
 146                 /* don't touch user chains on selective stop */
 147                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 148                         continue;
 149
 150                 if (!fw3_is_family(c, handle->family))
 151                         continue;
 152
 153                 if (c->table != handle->table)
 154                         continue;
 155
 156                 if (c->flag &&
 157                     !hasbit(defs->flags[handle->family == FW3_FAMILY_V6], c->flag))
 158                         continue;
 159
 160                 fw3_ipt_create_chain(handle, c->format);
 161         }
 162
 163         set(defs->flags, handle->family, handle->table);
 164 }
 165
 166
 167 struct toplevel_rule {
 168         enum fw3_table table;
 169         const char *chain;
 170         const char *target;
 171 };
 172
 173 void
 174 fw3_print_default_head_rules(struct fw3_ipt_handle *handle,
 175                              struct fw3_state *state, bool reload)
 176 {
 177         int i;
 178         struct fw3_defaults *defs = &state->defaults;
 179         struct fw3_device lodev = { .set = true };
 180         struct fw3_protocol tcp = { .protocol = 6 };
 181         struct fw3_ipt_rule *r;
 182
 183         const char *chains[] = {
 184                 "INPUT", "input",
 185                 "OUTPUT", "output",
 186                 "FORWARD", "forwarding",
 187         };
 188
 189         switch (handle->table)
 190         {
 191         case FW3_TABLE_FILTER:
 192
 193                 sprintf(lodev.name, "lo");
 194
 195                 r = fw3_ipt_rule_create(handle, NULL, &lodev, NULL, NULL, NULL);
 196                 fw3_ipt_rule_target(r, "ACCEPT");
 197                 fw3_ipt_rule_append(r, "INPUT");
 198
 199                 r = fw3_ipt_rule_create(handle, NULL, NULL, &lodev, NULL, NULL);
 200                 fw3_ipt_rule_target(r, "ACCEPT");
 201                 fw3_ipt_rule_append(r, "OUTPUT");
 202
 203                 if (defs->custom_chains)
 204                 {
 205                         for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 206                         {
 207                                 r = fw3_ipt_rule_new(handle);
 208                                 fw3_ipt_rule_comment(r, "user chain for %s", chains[i+1]);
 209                                 fw3_ipt_rule_target(r, "%s_rule", chains[i+1]);
 210                                 fw3_ipt_rule_append(r, chains[i]);
 211                         }
 212                 }
 213
 214                 for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 215                 {
 216                         r = fw3_ipt_rule_new(handle);
 217                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 218                         fw3_ipt_rule_target(r, "ACCEPT");
 219                         fw3_ipt_rule_append(r, chains[i]);
 220
 221                         if (defs->drop_invalid)
 222                         {
 223                                 r = fw3_ipt_rule_new(handle);
 224                                 fw3_ipt_rule_extra(r, "-m conntrack --ctstate INVALID");
 225                                 fw3_ipt_rule_target(r, "DROP");
 226                                 fw3_ipt_rule_append(r, chains[i]);
 227                         }
 228                 }
 229
 230                 if (defs->syn_flood)
 231                 {
 232                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 233                         fw3_ipt_rule_extra(r, "--syn");
 234                         fw3_ipt_rule_limit(r, &defs->syn_flood_rate);
 235                         fw3_ipt_rule_target(r, "RETURN");
 236                         fw3_ipt_rule_append(r, "syn_flood");
 237
 238                         r = fw3_ipt_rule_new(handle);
 239                         fw3_ipt_rule_target(r, "DROP");
 240                         fw3_ipt_rule_append(r, "syn_flood");
 241
 242                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 243                         fw3_ipt_rule_extra(r, "--syn");
 244                         fw3_ipt_rule_target(r, "syn_flood");
 245                         fw3_ipt_rule_append(r, "INPUT");
 246                 }
 247
 248                 r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 249                 fw3_ipt_rule_target(r, "REJECT");
 250                 fw3_ipt_rule_addarg(r, false, "--reject-with", "tcp-reset");
 251                 fw3_ipt_rule_append(r, "reject");
 252
 253                 r = fw3_ipt_rule_new(handle);
 254                 fw3_ipt_rule_target(r, "REJECT");
 255                 fw3_ipt_rule_addarg(r, false, "--reject-with", "port-unreach");
 256                 fw3_ipt_rule_append(r, "reject");
 257
 258                 break;
 259
 260         case FW3_TABLE_NAT:
 261                 if (defs->custom_chains)
 262                 {
 263                         r = fw3_ipt_rule_new(handle);
 264                         fw3_ipt_rule_comment(r, "user chain for prerouting");
 265                         fw3_ipt_rule_target(r, "prerouting_rule");
 266                         fw3_ipt_rule_append(r, "PREROUTING");
 267
 268                         r = fw3_ipt_rule_new(handle);
 269                         fw3_ipt_rule_comment(r, "user chain for postrouting");
 270                         fw3_ipt_rule_target(r, "postrouting_rule");
 271                         fw3_ipt_rule_append(r, "POSTROUTING");
 272                 }
 273                 break;
 274
 275         default:
 276                 break;
 277         }
 278 }
 279
 280 void
 281 fw3_print_default_tail_rules(struct fw3_ipt_handle *handle,
 282                              struct fw3_state *state, bool reload)
 283 {
 284         struct fw3_defaults *defs = &state->defaults;
 285         struct fw3_ipt_rule *r;
 286
 287         if (handle->table != FW3_TABLE_FILTER)
 288                 return;
 289
 290         if (defs->policy_input == FW3_FLAG_REJECT)
 291         {
 292                 r = fw3_ipt_rule_new(handle);
 293
 294                 if (!r)
 295                         return;
 296
 297                 fw3_ipt_rule_target(r, "reject");
 298                 fw3_ipt_rule_append(r, "INPUT");
 299         }
 300
 301         if (defs->policy_output == FW3_FLAG_REJECT)
 302         {
 303                 r = fw3_ipt_rule_new(handle);
 304
 305                 if (!r)
 306                         return;
 307
 308                 fw3_ipt_rule_target(r, "reject");
 309                 fw3_ipt_rule_append(r, "OUTPUT");
 310         }
 311
 312         if (defs->policy_forward == FW3_FLAG_REJECT)
 313         {
 314                 r = fw3_ipt_rule_new(handle);
 315
 316                 if (!r)
 317                         return;
 318
 319                 fw3_ipt_rule_target(r, "reject");
 320                 fw3_ipt_rule_append(r, "FORWARD");
 321         }
 322 }
 323
 324 static void
 325 set_default(const char *name, int set)
 326 {
 327         FILE *f;
 328         char path[sizeof("/proc/sys/net/ipv4/tcp_window_scaling\0")];
 329
 330         snprintf(path, sizeof(path), "/proc/sys/net/ipv4/tcp_%s", name);
 331
 332         info(" * Set tcp_%s to %s", name, set ? "on" : "off", name);
 333
 334         if (!(f = fopen(path, "w")))
 335         {
 336                 info("   ! Unable to write value: %s", strerror(errno));
 337                 return;
 338         }
 339
 340         fprintf(f, "%u\n", set);
 341         fclose(f);
 342 }
 343
 344 void
 345 fw3_set_defaults(struct fw3_state *state)
 346 {
 347         set_default("ecn",            state->defaults.tcp_ecn);
 348         set_default("syncookies",     state->defaults.tcp_syncookies);
 349         set_default("window_scaling", state->defaults.tcp_window_scaling);
 350 }
 351
 352 void
 353 fw3_flush_rules(struct fw3_ipt_handle *handle, struct fw3_state *state,
 354                 bool reload)
 355 {
 356         enum fw3_flag policy = reload ? FW3_FLAG_DROP : FW3_FLAG_ACCEPT;
 357         struct fw3_defaults *defs = &state->defaults;
 358         const struct fw3_chain_spec *c;
 359
 360         if (!has(defs->flags, handle->family, handle->table))
 361                 return;
 362
 363         if (handle->table == FW3_TABLE_FILTER)
 364         {
 365                 fw3_ipt_set_policy(handle, "INPUT",   policy);
 366                 fw3_ipt_set_policy(handle, "OUTPUT",  policy);
 367                 fw3_ipt_set_policy(handle, "FORWARD", policy);
 368         }
 369
 370         fw3_ipt_delete_id_rules(handle, "INPUT");
 371         fw3_ipt_delete_id_rules(handle, "OUTPUT");
 372         fw3_ipt_delete_id_rules(handle, "FORWARD");
 373         fw3_ipt_delete_id_rules(handle, "PREROUTING");
 374         fw3_ipt_delete_id_rules(handle, "POSTROUTING");
 375
 376         for (c = default_chains; c->format; c++)
 377         {
 378                 /* don't touch user chains on selective stop */
 379                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 380                         continue;
 381
 382                 if (!fw3_is_family(c, handle->family))
 383                         continue;
 384
 385                 if (c->table != handle->table)
 386                         continue;
 387
 388                 if (c->flag && !has(defs->flags, handle->family, c->flag))
 389                         continue;
 390
 391                 fw3_ipt_flush_chain(handle, c->format);
 392
 393                 /* keep certain basic chains that do not depend on any settings to
 394                    avoid purging unrelated user rules pointing to them */
 395                 if (reload && !c->flag)
 396                         continue;
 397
 398                 fw3_ipt_delete_chain(handle, c->format);
 399         }
 400
 401         del(defs->flags, handle->family, handle->table);
 402 }
 403
 404 void
 405 fw3_flush_all(struct fw3_ipt_handle *handle)
 406 {
 407         if (handle->table == FW3_TABLE_FILTER)
 408         {
 409                 fw3_ipt_set_policy(handle, "INPUT",   FW3_FLAG_ACCEPT);
 410                 fw3_ipt_set_policy(handle, "OUTPUT",  FW3_FLAG_ACCEPT);
 411                 fw3_ipt_set_policy(handle, "FORWARD", FW3_FLAG_ACCEPT);
 412         }
 413
 414         fw3_ipt_flush(handle);
 415 }