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, name) \
  23         { FW3_FAMILY_##f, FW3_TABLE_##tbl, FW3_DEFAULT_##def, name }
  24
  25 struct chain {
  26         enum fw3_family family;
  27         enum fw3_table table;
  28         enum fw3_default flag;
  29         const char *name;
  30 };
  31
  32 static const struct chain default_chains[] = {
  33         C(ANY, FILTER, UNSPEC,        "delegate_input"),
  34         C(ANY, FILTER, UNSPEC,        "delegate_output"),
  35         C(ANY, FILTER, UNSPEC,        "delegate_forward"),
  36         C(ANY, FILTER, CUSTOM_CHAINS, "input_rule"),
  37         C(ANY, FILTER, CUSTOM_CHAINS, "output_rule"),
  38         C(ANY, FILTER, CUSTOM_CHAINS, "forwarding_rule"),
  39         C(ANY, FILTER, UNSPEC,        "reject"),
  40         C(ANY, FILTER, SYN_FLOOD,     "syn_flood"),
  41
  42         C(V4,  NAT,    UNSPEC,        "delegate_prerouting"),
  43         C(V4,  NAT,    UNSPEC,        "delegate_postrouting"),
  44         C(V4,  NAT,    CUSTOM_CHAINS, "prerouting_rule"),
  45         C(V4,  NAT,    CUSTOM_CHAINS, "postrouting_rule"),
  46
  47         C(ANY, MANGLE, UNSPEC,        "mssfix"),
  48         C(ANY, RAW,    UNSPEC,        "notrack"),
  49 };
  50
  51 static const struct chain toplevel_rules[] = {
  52         C(ANY, FILTER, UNSPEC,        "INPUT -j delegate_input"),
  53         C(ANY, FILTER, UNSPEC,        "OUTPUT -j delegate_output"),
  54         C(ANY, FILTER, UNSPEC,        "FORWARD -j delegate_forward"),
  55
  56         C(V4,  NAT,    UNSPEC,        "PREROUTING -j delegate_prerouting"),
  57         C(V4,  NAT,    UNSPEC,        "POSTROUTING -j delegate_postrouting"),
  58
  59         C(ANY, MANGLE, UNSPEC,        "FORWARD -j mssfix"),
  60         C(ANY, RAW,    UNSPEC,        "PREROUTING -j notrack"),
  61 };
  62
  63 const struct fw3_option fw3_default_opts[] = {
  64         FW3_OPT("input",               target,   defaults, policy_input),
  65         FW3_OPT("forward",             target,   defaults, policy_forward),
  66         FW3_OPT("output",              target,   defaults, policy_output),
  67
  68         FW3_OPT("drop_invalid",        bool,     defaults, drop_invalid),
  69
  70         FW3_OPT("syn_flood",           bool,     defaults, syn_flood),
  71         FW3_OPT("synflood_protect",    bool,     defaults, syn_flood),
  72         FW3_OPT("synflood_rate",       limit,    defaults, syn_flood_rate),
  73         FW3_OPT("synflood_burst",      int,      defaults, syn_flood_rate.burst),
  74
  75         FW3_OPT("tcp_syncookies",      bool,     defaults, tcp_syncookies),
  76         FW3_OPT("tcp_ecn",             bool,     defaults, tcp_ecn),
  77         FW3_OPT("tcp_window_scaling",  bool,     defaults, tcp_window_scaling),
  78
  79         FW3_OPT("accept_redirects",    bool,     defaults, accept_redirects),
  80         FW3_OPT("accept_source_route", bool,     defaults, accept_source_route),
  81
  82         FW3_OPT("custom_chains",       bool,     defaults, custom_chains),
  83         FW3_OPT("disable_ipv6",        bool,     defaults, disable_ipv6),
  84
  85         { }
  86 };
  87
  88
  89 static bool
  90 print_chains(enum fw3_table table, enum fw3_family family,
  91              const char *fmt, uint32_t flags,
  92              const struct chain *chains, int n)
  93 {
  94         bool rv = false;
  95         const struct chain *c;
  96
  97         for (c = chains; n > 0; c++, n--)
  98         {
  99                 if (!fw3_is_family(c, family))
 100                         continue;
 101
 102                 if (c->table != table)
 103                         continue;
 104
 105                 if ((c->flag != FW3_DEFAULT_UNSPEC) && !hasbit(flags, c->flag))
 106                         continue;
 107
 108                 fw3_pr(fmt, c->name);
 109
 110                 rv = true;
 111         }
 112
 113         return rv;
 114 }
 115
 116 static void
 117 check_policy(struct uci_element *e, enum fw3_target *pol, const char *name)
 118 {
 119         if (*pol == FW3_TARGET_UNSPEC)
 120         {
 121                 warn_elem(e, "has no %s policy specified, defaulting to DROP", name);
 122                 *pol = FW3_TARGET_DROP;
 123         }
 124         else if (*pol > FW3_TARGET_DROP)
 125         {
 126                 warn_elem(e, "has invalid %s policy, defaulting to DROP", name);
 127                 *pol = FW3_TARGET_DROP;
 128         }
 129 }
 130
 131 void
 132 fw3_load_defaults(struct fw3_state *state, struct uci_package *p)
 133 {
 134         struct uci_section *s;
 135         struct uci_element *e;
 136         struct fw3_defaults *defs = &state->defaults;
 137
 138         bool seen = false;
 139
 140         defs->syn_flood_rate.rate  = 25;
 141         defs->syn_flood_rate.burst = 50;
 142         defs->tcp_syncookies       = true;
 143         defs->tcp_window_scaling   = true;
 144         defs->custom_chains        = true;
 145
 146         setbit(defs->flags, FW3_FAMILY_V4);
 147
 148         uci_foreach_element(&p->sections, e)
 149         {
 150                 s = uci_to_section(e);
 151
 152                 if (strcmp(s->type, "defaults"))
 153                         continue;
 154
 155                 if (seen)
 156                 {
 157                         warn_elem(e, "ignoring duplicate section");
 158                         continue;
 159                 }
 160
 161                 fw3_parse_options(&state->defaults, fw3_default_opts, s);
 162
 163                 check_policy(e, &defs->policy_input, "input");
 164                 check_policy(e, &defs->policy_output, "output");
 165                 check_policy(e, &defs->policy_forward, "forward");
 166
 167                 if (!defs->disable_ipv6)
 168                         setbit(defs->flags, FW3_FAMILY_V6);
 169
 170                 if (defs->custom_chains)
 171                         setbit(defs->flags, FW3_DEFAULT_CUSTOM_CHAINS);
 172
 173                 if (defs->syn_flood)
 174                         setbit(defs->flags, FW3_DEFAULT_SYN_FLOOD);
 175         }
 176 }
 177
 178 void
 179 fw3_print_default_chains(enum fw3_table table, enum fw3_family family,
 180                          struct fw3_state *state)
 181 {
 182         struct fw3_defaults *defs = &state->defaults;
 183         uint32_t custom_mask = ~0;
 184
 185 #define policy(t) \
 186         ((t == FW3_TARGET_REJECT) ? "DROP" : fw3_flag_names[t])
 187
 188         if (table == FW3_TABLE_FILTER)
 189         {
 190                 fw3_pr(":INPUT %s [0:0]\n", policy(defs->policy_input));
 191                 fw3_pr(":FORWARD %s [0:0]\n", policy(defs->policy_forward));
 192                 fw3_pr(":OUTPUT %s [0:0]\n", policy(defs->policy_output));
 193         }
 194
 195         /* user chains already loaded, don't create again */
 196         if (hasbit(state->defaults.running_flags, FW3_DEFAULT_CUSTOM_CHAINS))
 197                 delbit(custom_mask, FW3_DEFAULT_CUSTOM_CHAINS);
 198
 199         print_chains(table, family, ":%s - [0:0]\n", defs->flags & custom_mask,
 200                      default_chains, ARRAY_SIZE(default_chains));
 201 }
 202
 203 void
 204 fw3_print_default_head_rules(enum fw3_table table, enum fw3_family family,
 205                              struct fw3_state *state)
 206 {
 207         int i;
 208         struct fw3_defaults *defs = &state->defaults;
 209         const char *chains[] = {
 210                 "input", "input",
 211                 "output", "output",
 212                 "forward", "forwarding",
 213         };
 214
 215         print_chains(table, family, "-A %s\n", 0,
 216                      toplevel_rules, ARRAY_SIZE(toplevel_rules));
 217
 218         switch (table)
 219         {
 220         case FW3_TABLE_FILTER:
 221                 fw3_pr("-A delegate_input -i lo -j ACCEPT\n");
 222                 fw3_pr("-A delegate_output -o lo -j ACCEPT\n");
 223
 224                 if (defs->custom_chains)
 225                 {
 226                         for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 227                         {
 228                                 fw3_pr("-A delegate_%s -m comment "
 229                                        "--comment \"user chain for %s\" -j %s_rule\n",
 230                                            chains[i], chains[i+1], chains[i+1]);
 231                         }
 232                 }
 233
 234                 for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 235                 {
 236                         fw3_pr("-A delegate_%s -m conntrack --ctstate RELATED,ESTABLISHED "
 237                                "-j ACCEPT\n", chains[i]);
 238
 239                         if (defs->drop_invalid)
 240                         {
 241                                 fw3_pr("-A delegate_%s -m conntrack --ctstate INVALID -j DROP\n",
 242                                        chains[i]);
 243                         }
 244                 }
 245
 246                 if (defs->syn_flood)
 247                 {
 248                         fw3_pr("-A syn_flood -p tcp --syn");
 249                         fw3_format_limit(&defs->syn_flood_rate);
 250                         fw3_pr(" -j RETURN\n");
 251
 252                         fw3_pr("-A syn_flood -j DROP\n");
 253                         fw3_pr("-A delegate_input -p tcp --syn -j syn_flood\n");
 254                 }
 255
 256                 fw3_pr("-A reject -p tcp -j REJECT --reject-with tcp-reset\n");
 257                 fw3_pr("-A reject -j REJECT --reject-with port-unreach\n");
 258
 259                 break;
 260
 261         case FW3_TABLE_NAT:
 262                 if (defs->custom_chains)
 263                 {
 264                         fw3_pr("-A delegate_prerouting "
 265                                "-m comment --comment \"user chain for prerouting\" "
 266                                "-j prerouting_rule\n");
 267
 268                         fw3_pr("-A delegate_postrouting "
 269                                "-m comment --comment \"user chain for postrouting\" "
 270                                "-j postrouting_rule\n");
 271                 }
 272                 break;
 273
 274         default:
 275                 break;
 276         }
 277 }
 278
 279 void
 280 fw3_print_default_tail_rules(enum fw3_table table, enum fw3_family family,
 281                              struct fw3_state *state)
 282 {
 283         struct fw3_defaults *defs = &state->defaults;
 284
 285         if (table != FW3_TABLE_FILTER)
 286                 return;
 287
 288         if (defs->policy_input == FW3_TARGET_REJECT)
 289                 fw3_pr("-A delegate_input -j reject\n");
 290
 291         if (defs->policy_output == FW3_TARGET_REJECT)
 292                 fw3_pr("-A delegate_output -j reject\n");
 293
 294         if (defs->policy_forward == FW3_TARGET_REJECT)
 295                 fw3_pr("-A delegate_forward -j reject\n");
 296 }
 297
 298 static void
 299 set_default(const char *name, bool set)
 300 {
 301         FILE *f;
 302         char path[sizeof("/proc/sys/net/ipv4/tcp_window_scaling\0")];
 303
 304         snprintf(path, sizeof(path), "/proc/sys/net/ipv4/tcp_%s", name);
 305
 306         info(" * Set tcp_%s to %s", name, set ? "on" : "off", name);
 307
 308         if (!(f = fopen(path, "w")))
 309         {
 310                 info("   ! Unable to write value: %s", strerror(errno));
 311                 return;
 312         }
 313
 314         fprintf(f, "%u\n", set);
 315         fclose(f);
 316 }
 317
 318 void
 319 fw3_set_defaults(struct fw3_state *state)
 320 {
 321         info("Setting sysctl values");
 322
 323         set_default("ecn",            state->defaults.tcp_ecn);
 324         set_default("syncookies",     state->defaults.tcp_syncookies);
 325         set_default("window_scaling", state->defaults.tcp_window_scaling);
 326 }
 327
 328 static void
 329 reset_policy(enum fw3_table table, enum fw3_target policy)
 330 {
 331         if (table != FW3_TABLE_FILTER)
 332                 return;
 333
 334         fw3_pr(":INPUT %s [0:0]\n", fw3_flag_names[policy]);
 335         fw3_pr(":OUTPUT %s [0:0]\n", fw3_flag_names[policy]);
 336         fw3_pr(":FORWARD %s [0:0]\n", fw3_flag_names[policy]);
 337 }
 338
 339 void
 340 fw3_flush_rules(enum fw3_table table, enum fw3_family family,
 341                 bool pass2, struct fw3_state *state, enum fw3_target policy)
 342 {
 343         struct fw3_defaults *defs = &state->defaults;
 344         uint32_t custom_mask = ~0;
 345
 346         if (!hasbit(defs->running_flags, family))
 347                 return;
 348
 349         /* don't touch user chains on selective stop */
 350         delbit(custom_mask, FW3_DEFAULT_CUSTOM_CHAINS);
 351
 352         if (!pass2)
 353         {
 354                 reset_policy(table, policy);
 355
 356                 print_chains(table, family, "-D %s\n",
 357                              defs->running_flags & custom_mask,
 358                                          toplevel_rules, ARRAY_SIZE(toplevel_rules));
 359
 360                 print_chains(table, family, "-F %s\n",
 361                              defs->running_flags & custom_mask,
 362                                          default_chains, ARRAY_SIZE(default_chains));
 363         }
 364         else
 365         {
 366                 print_chains(table, family, "-X %s\n",
 367                              defs->running_flags & custom_mask,
 368                                          default_chains, ARRAY_SIZE(default_chains));
 369
 370                 delbit(defs->flags, family);
 371         }
 372 }
 373
 374 void
 375 fw3_flush_all(enum fw3_table table)
 376 {
 377         reset_policy(table, FW3_TARGET_ACCEPT);
 378
 379         fw3_pr("-F\n");
 380         fw3_pr("-X\n");
 381 }