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("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                     !fw3_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 void
 167 fw3_print_default_head_rules(struct fw3_ipt_handle *handle,
 168                              struct fw3_state *state, bool reload)
 169 {
 170         int i;
 171         struct fw3_defaults *defs = &state->defaults;
 172         struct fw3_device lodev = { .set = true };
 173         struct fw3_protocol tcp = { .protocol = 6 };
 174         struct fw3_ipt_rule *r;
 175
 176         const char *chains[] = {
 177                 "INPUT", "input",
 178                 "OUTPUT", "output",
 179                 "FORWARD", "forwarding",
 180         };
 181
 182         switch (handle->table)
 183         {
 184         case FW3_TABLE_FILTER:
 185
 186                 sprintf(lodev.name, "lo");
 187
 188                 r = fw3_ipt_rule_create(handle, NULL, &lodev, NULL, NULL, NULL);
 189                 fw3_ipt_rule_target(r, "ACCEPT");
 190                 fw3_ipt_rule_append(r, "INPUT");
 191
 192                 r = fw3_ipt_rule_create(handle, NULL, NULL, &lodev, NULL, NULL);
 193                 fw3_ipt_rule_target(r, "ACCEPT");
 194                 fw3_ipt_rule_append(r, "OUTPUT");
 195
 196                 if (defs->custom_chains)
 197                 {
 198                         for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 199                         {
 200                                 r = fw3_ipt_rule_new(handle);
 201                                 fw3_ipt_rule_comment(r, "user chain for %s", chains[i+1]);
 202                                 fw3_ipt_rule_target(r, "%s_rule", chains[i+1]);
 203                                 fw3_ipt_rule_append(r, chains[i]);
 204                         }
 205                 }
 206
 207                 for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 208                 {
 209                         r = fw3_ipt_rule_new(handle);
 210                         fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED");
 211                         fw3_ipt_rule_target(r, "ACCEPT");
 212                         fw3_ipt_rule_append(r, chains[i]);
 213
 214                         if (defs->drop_invalid)
 215                         {
 216                                 r = fw3_ipt_rule_new(handle);
 217                                 fw3_ipt_rule_extra(r, "-m conntrack --ctstate INVALID");
 218                                 fw3_ipt_rule_target(r, "DROP");
 219                                 fw3_ipt_rule_append(r, chains[i]);
 220                         }
 221                 }
 222
 223                 if (defs->syn_flood)
 224                 {
 225                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 226                         fw3_ipt_rule_extra(r, "--syn");
 227                         fw3_ipt_rule_limit(r, &defs->syn_flood_rate);
 228                         fw3_ipt_rule_target(r, "RETURN");
 229                         fw3_ipt_rule_append(r, "syn_flood");
 230
 231                         r = fw3_ipt_rule_new(handle);
 232                         fw3_ipt_rule_target(r, "DROP");
 233                         fw3_ipt_rule_append(r, "syn_flood");
 234
 235                         r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 236                         fw3_ipt_rule_extra(r, "--syn");
 237                         fw3_ipt_rule_target(r, "syn_flood");
 238                         fw3_ipt_rule_append(r, "INPUT");
 239                 }
 240
 241                 r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL);
 242                 fw3_ipt_rule_target(r, "REJECT");
 243                 fw3_ipt_rule_addarg(r, false, "--reject-with", "tcp-reset");
 244                 fw3_ipt_rule_append(r, "reject");
 245
 246                 r = fw3_ipt_rule_new(handle);
 247                 fw3_ipt_rule_target(r, "REJECT");
 248                 fw3_ipt_rule_addarg(r, false, "--reject-with", "port-unreach");
 249                 fw3_ipt_rule_append(r, "reject");
 250
 251                 break;
 252
 253         case FW3_TABLE_NAT:
 254                 if (defs->custom_chains)
 255                 {
 256                         r = fw3_ipt_rule_new(handle);
 257                         fw3_ipt_rule_comment(r, "user chain for prerouting");
 258                         fw3_ipt_rule_target(r, "prerouting_rule");
 259                         fw3_ipt_rule_append(r, "PREROUTING");
 260
 261                         r = fw3_ipt_rule_new(handle);
 262                         fw3_ipt_rule_comment(r, "user chain for postrouting");
 263                         fw3_ipt_rule_target(r, "postrouting_rule");
 264                         fw3_ipt_rule_append(r, "POSTROUTING");
 265                 }
 266                 break;
 267
 268         default:
 269                 break;
 270         }
 271 }
 272
 273 void
 274 fw3_print_default_tail_rules(struct fw3_ipt_handle *handle,
 275                              struct fw3_state *state, bool reload)
 276 {
 277         struct fw3_defaults *defs = &state->defaults;
 278         struct fw3_ipt_rule *r;
 279
 280         if (handle->table != FW3_TABLE_FILTER)
 281                 return;
 282
 283         if (defs->policy_input == FW3_FLAG_REJECT)
 284         {
 285                 r = fw3_ipt_rule_new(handle);
 286
 287                 if (!r)
 288                         return;
 289
 290                 fw3_ipt_rule_target(r, "reject");
 291                 fw3_ipt_rule_append(r, "INPUT");
 292         }
 293
 294         if (defs->policy_output == FW3_FLAG_REJECT)
 295         {
 296                 r = fw3_ipt_rule_new(handle);
 297
 298                 if (!r)
 299                         return;
 300
 301                 fw3_ipt_rule_target(r, "reject");
 302                 fw3_ipt_rule_append(r, "OUTPUT");
 303         }
 304
 305         if (defs->policy_forward == FW3_FLAG_REJECT)
 306         {
 307                 r = fw3_ipt_rule_new(handle);
 308
 309                 if (!r)
 310                         return;
 311
 312                 fw3_ipt_rule_target(r, "reject");
 313                 fw3_ipt_rule_append(r, "FORWARD");
 314         }
 315 }
 316
 317 static void
 318 set_default(const char *name, int set)
 319 {
 320         FILE *f;
 321         char path[sizeof("/proc/sys/net/ipv4/tcp_window_scaling\0")];
 322
 323         snprintf(path, sizeof(path), "/proc/sys/net/ipv4/tcp_%s", name);
 324
 325         info(" * Set tcp_%s to %s", name, set ? "on" : "off", name);
 326
 327         if (!(f = fopen(path, "w")))
 328         {
 329                 info("   ! Unable to write value: %s", strerror(errno));
 330                 return;
 331         }
 332
 333         fprintf(f, "%u\n", set);
 334         fclose(f);
 335 }
 336
 337 void
 338 fw3_set_defaults(struct fw3_state *state)
 339 {
 340         set_default("ecn",            state->defaults.tcp_ecn);
 341         set_default("syncookies",     state->defaults.tcp_syncookies);
 342         set_default("window_scaling", state->defaults.tcp_window_scaling);
 343 }
 344
 345 void
 346 fw3_flush_rules(struct fw3_ipt_handle *handle, struct fw3_state *state,
 347                 bool reload)
 348 {
 349         enum fw3_flag policy = reload ? FW3_FLAG_DROP : FW3_FLAG_ACCEPT;
 350         struct fw3_defaults *defs = &state->defaults;
 351         const struct fw3_chain_spec *c;
 352
 353         if (!has(defs->flags, handle->family, handle->table))
 354                 return;
 355
 356         if (handle->table == FW3_TABLE_FILTER)
 357         {
 358                 fw3_ipt_set_policy(handle, "INPUT",   policy);
 359                 fw3_ipt_set_policy(handle, "OUTPUT",  policy);
 360                 fw3_ipt_set_policy(handle, "FORWARD", policy);
 361         }
 362
 363         fw3_ipt_delete_id_rules(handle, "INPUT");
 364         fw3_ipt_delete_id_rules(handle, "OUTPUT");
 365         fw3_ipt_delete_id_rules(handle, "FORWARD");
 366         fw3_ipt_delete_id_rules(handle, "PREROUTING");
 367         fw3_ipt_delete_id_rules(handle, "POSTROUTING");
 368
 369         for (c = default_chains; c->format; c++)
 370         {
 371                 /* don't touch user chains on selective stop */
 372                 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS)
 373                         continue;
 374
 375                 if (!fw3_is_family(c, handle->family))
 376                         continue;
 377
 378                 if (c->table != handle->table)
 379                         continue;
 380
 381                 if (c->flag && !has(defs->flags, handle->family, c->flag))
 382                         continue;
 383
 384                 fw3_ipt_flush_chain(handle, c->format);
 385
 386                 /* keep certain basic chains that do not depend on any settings to
 387                    avoid purging unrelated user rules pointing to them */
 388                 if (reload && !c->flag)
 389                         continue;
 390
 391                 fw3_ipt_delete_chain(handle, c->format);
 392         }
 393
 394         del(defs->flags, handle->family, handle->table);
 395 }
 396
 397 void
 398 fw3_flush_all(struct fw3_ipt_handle *handle)
 399 {
 400         if (handle->table == FW3_TABLE_FILTER)
 401         {
 402                 fw3_ipt_set_policy(handle, "INPUT",   FW3_FLAG_ACCEPT);
 403                 fw3_ipt_set_policy(handle, "OUTPUT",  FW3_FLAG_ACCEPT);
 404                 fw3_ipt_set_policy(handle, "FORWARD", FW3_FLAG_ACCEPT);
 405         }
 406
 407         fw3_ipt_flush(handle);
 408 }